Patent Publication Number: US-2023147049-A1

Title: Infusion pump assembly

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. application Ser. No. 14/323,636 filed Jul. 3, 2014, which claims the benefit of U.S. Provisional Application Ser. No. 61/842,449 filed Jul. 3, 2013 and entitled Infusion Pump Assembly (Attorney Docket No. K80), which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This application relates generally to fluid delivery systems, and more particularly to infusion pump assemblies. 
     BACKGROUND 
     Many potentially valuable medicines or compounds, including biologicals, are not orally active due to poor absorption, hepatic metabolism or other pharmacokinetic factors. Additionally, some therapeutic compounds, although they can be orally absorbed, are sometimes required to be administered so often it is difficult for a patient to maintain the desired schedule. In these cases, parenteral delivery is often employed or could be employed. 
     Effective parenteral routes of drug delivery, as well as other fluids and compounds, such as subcutaneous injection, intramuscular injection, and intravenous (IV) administration include puncture of the skin with a needle or stylet. Insulin is an example of a therapeutic fluid that is self-injected by millions of diabetic patients. Users of parenterally delivered drugs may benefit from a wearable device that would automatically deliver needed drugs/compounds over a period of time. 
     To this end, there have been efforts to design portable and wearable devices for the controlled release of therapeutics. Such devices are known to have a reservoir such as a cartridge, syringe, or bag, and to be electronically controlled. These devices suffer from a number of drawbacks including the malfunction rate. Reducing the size, weight and cost of these devices is also an ongoing challenge. Additionally, these devices often apply to the skin and pose the challenge of frequent re-location for application. 
     SUMMARY OF THE INVENTION 
     In accordance with one implementation, a fluid connector assembly is disclosed. The fluid connector assembly includes a tab portion including a slot; a plug portion slidably connected to the tab portion the plug portion comprising a fluid path and a disc, the disc configured to seat within the slot; a catch feature located on a first end of the tab portion and configured to interact with a reservoir; and a latching feature located on a second end of the tab portion, the latching feature configured to interact and lock onto the reservoir, wherein force applied to the plug portion may overcome a threshold force and unseat the disc from the slot wherein the plug portion moves with respect to the tab portion. 
     Some embodiments of this implementation may include one or more of the following features. Wherein the tab portion further comprising an indent wherein the indent configured to interact with a reusable housing assembly. Wherein the connector includes a tubing connected to the plug Wherein the catch feature comprising a ramp. Wherein the second end of the tubing connected to a cannula assembly. Wherein the tab portion further comprising a tapered tubing opening, the first end of the tubing connecting to the tapered tubing opening. Wherein the underside of the tab portion comprising a core. Wherein the core comprising an identification tag. Wherein the tab portion comprising an identification tag. Wherein the identification tag is an RFID tag. Wherein the identification tag is a near-field communication readable RFID. 
     In accordance with one implementation a fluid connector assembly is disclosed. The fluid connector assembly includes a fluid connector assembly including a tab portion including a tubing side and a reservoir side; a plug portion slidably connected to the tab portion, the plug portion comprising a fluid path; a catch feature located on a first end of the tab portion and configured to interact with a reservoir; and a latching feature located on a second end of the tab portion, the latching feature configured to interact and lock onto the reservoir, wherein force applied to the plug portion causes the plug portion to move with respect to the tab portion from an initial position to a final position in the direction of the tubing side of the tab portion. 
     Some embodiments of this implementation may include one or more of the following features. Wherein the tab portion further comprising an indent wherein the indent configured to interact with a reusable housing assembly. Wherein the connector includes a tubing connected to the plug Wherein the catch feature comprising a ramp. Wherein the second end of the tubing connected to a cannula assembly. Wherein the tab portion further comprising a tapered tubing opening, the first end of the tubing connecting to the tapered tubing opening. Wherein the underside of the tab portion comprising a core. Wherein the core comprising an identification tag. Wherein the tab portion comprising an identification tag. Wherein the identification tag is an RFID tag. Wherein the identification tag is a near-field communication readable RFID. 
     In accordance with one implementation, a connector. The connector includes a body portion, a plug, and a tubing in communication with the plug, wherein the plug is configured to attach to an exit in a disposable housing assembly. 
     In accordance with first implementation, a wearable infusion pump assembly is disclosed. The wearable infusion pump assembly includes a reservoir for receiving an infusible fluid and a fluid delivery system configured to deliver the infusible fluid from the reservoir to an external infusion set. The fluid delivery system includes a controller, a pump assembly for extracting a quantity of infusible fluid from the reservoir and providing the quantity of infusible fluid to the external infusion set, the pump assembly comprising a pump plunger, the pump plunger having distance of travel, the distance of travel having a starting position and an ending position, at least one optical sensor assembly for sensing the starting position and ending position of the pump plunger distance of travel and sending sensor output to the controller, and a first valve assembly configured to selectively isolate the pump assembly from the reservoir, wherein the controller receives the sensor output and determines the total displacement of the pump plunger. 
     Some embodiments of this implementation may include one or more of the following features. Wherein the wearable infusion pump assembly includes wherein the controller correlates the displacement of the pump plunger to a volume of fluid delivered. Wherein the wearable infusion pump assembly includes wherein the controller, based on the volume of fluid delivered, commands an actuator to actuate the pump plunger to a target position. Wherein the wearable infusion pump assembly further includes a second valve assembly configured to selectively isolate the pump assembly from the external infusion set. Wherein the wearable infusion pump assembly further includes at least one optical sensor assembly for sensing the position of the second valve assembly. Wherein the wearable infusion pump assembly further includes a disposable housing assembly including the reservoir and a first portion of the fluid delivery system, and a reusable housing assembly including a second portion of the fluid delivery system. Wherein the wearable infusion pump assembly includes wherein a first portion of the pump assembly is positioned within the disposable housing assembly, and a second portion of the pump assembly is positioned within the reusable housing assembly. Wherein the wearable infusion pump assembly includes wherein a first portion of the first valve assembly is positioned within the disposable housing assembly, and a second portion of the first valve assembly is positioned within the reusable housing assembly. Wherein the wearable infusion pump assembly includes wherein a first portion of the second valve assembly is positioned within the disposable housing assembly, and a second portion of the second valve assembly is positioned within the reusable housing assembly. Wherein the wearable infusion pump assembly includes wherein the external infusion set is a detachable external infusion set configured to releasably engage the fluid delivery system. 
     In accordance with first implementation, a disposable housing assembly for an infusion pump assembly is disclosed. The disposable housing assembly includes a reservoir portion fluidly connected to a fluid path, the reservoir portion including a bubble trap wherein the bubble trap prevents air from moving from the reservoir portion to the fluid path. The bubble trap further includes an outlet portion and a non-outlet portion, the non-outlet portion including a tapered portion that tapers to a bottom portion, the tapered portion of the non-outlet portion ending at the outlet portion. The bubble trap also includes wherein the outlet portion including the bottom portion in communication with an upward ramped portion in fluid communication with a reservoir outlet, wherein the bottom portion configured whereby fluid congregates in the bottom portion and the tapered portion configured whereby air bubbles congregate in the tapered portion. 
     Some embodiments of this implementation may include one or more of the following features. Wherein the disposable housing assembly further includes a membrane assembly, the membrane assembly connected to the reservoir wherein the membrane assembly forms a portion of the reservoir. Wherein the disposable housing assembly further includes a septum assembly, the septum assembly formed on the membrane assembly. Wherein the disposable housing assembly further includes a septum assembly, the septum assembly connected to the reservoir. Wherein the disposable housing assembly further includes a vent, wherein the vent further comprising a filter. 
     In accordance with one implementation, a fluid connector assembly is disclosed. The fluid connector assembly includes a body portion, a plug receiver portion located on the body portion, the plug receiver portion including a fluid path and configured to receive a plug on a reservoir, and a tubing, a first end of the tubing fluidly connected to the plug receiver portion fluid path. 
     Some embodiments of this implementation may include one or more of the following features. Wherein the body portion further includes an indent wherein the indent configured to interact with a reusable portion of an infusion pump. Wherein a second end of the tubing connected to a cannula assembly. Wherein the body portion further includes a tapered tubing opening, the first end of the tubing connecting to the tapered tubing opening. Wherein a first end of the body portion further comprising a locked icon. Wherein the underside of the body portion comprising a core. Wherein the core comprising an identification tag. Wherein the body portion comprising an identification tag. Wherein the identification tag is an RFID tag. Wherein the identification tag is a near-field communication readable RFID. 
     In accordance with one implementation, a clip assembly is disclosed. The clip assembly includes a clip portion and a clip housing portion. The clip housing portion includes a front portion and a back portion. The back portion includes at least one protrusion and at least one clip feature, wherein the at least one clip feature secures the clip portion onto the back portion of the housing portion. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will become apparent from the description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of an infusion pump assembly; 
         FIG.  2    is a perspective view of the infusion pump assembly of  FIG.  1   ; 
         FIG.  3    is an exploded view of various components of the infusion pump assembly of  FIG.  1   ; 
         FIG.  4    is a cross-sectional view of the disposable housing assembly of the infusion pump assembly of  FIG.  1   ; 
         FIGS.  5 A- 5 C  are cross-sectional views of an embodiment of a septum access assembly; 
         FIGS.  6 A- 6 B  are cross-sectional views of another embodiment of a septum access assembly; 
         FIGS.  7 A- 7 B  are partial top views of another embodiment of a septum access assembly; 
         FIGS.  8 A- 8 B  are cross-sectional views of another embodiment of a septum access assembly; 
         FIG.  9    is a perspective view of the infusion pump assembly of  FIG.  1    showing an external infusion set; 
         FIGS.  10 A- 10 E  depict a plurality of hook-and-loop fastener configurations; 
         FIG.  11 A  is an isometric view of a remote control assembly and an alternative embodiment of the infusion pump assembly of  FIG.  1   ; 
         FIGS.  11 B- 11 R  depicts various views of high level schematics and flow charts of the infusion pump assembly of  FIG.  1   ; 
         FIGS.  12 A- 12 F  is a plurality of display screens rendered by the remote control assembly of  FIG.  11 A ; 
         FIG.  13    is an isometric view of an alternative embodiment of the infusion pump assembly of  FIG.  1   ; 
         FIG.  14    is an isometric view of the infusion pump assembly of  FIG.  13   ; 
         FIG.  15    is an isometric view of the infusion pump assembly of  FIG.  13   ; 
         FIG.  16    is an isometric view of an alternative embodiment of the infusion pump assembly of  FIG.  1   ; 
         FIG.  17    is an plan view of the infusion pump assembly of  FIG.  16   ; 
         FIG.  18    is a plan view of the infusion pump assembly of  FIG.  16   ; 
         FIG.  19 A  is an exploded view of various components of the infusion pump assembly of  FIG.  16   ; 
         FIG.  19 B  is an isometric view of a portion of the infusion pump assembly of  FIG.  16   ; 
         FIG.  20    is a cross-sectional view of the disposable housing assembly of the infusion pump assembly of  FIG.  16   ; 
         FIG.  21    is a diagrammatic view of a fluid path within the infusion pump assembly of  FIG.  16   ; 
         FIGS.  22 A- 22 C  are diagrammatic views of a fluid path within the infusion pump assembly of  FIG.  16   ; 
         FIG.  23    is an exploded view of various components of the infusion pump assembly of  FIG.  16   ; 
         FIG.  24    is a cutaway isometric view of a pump assembly of the infusion pump assembly of  FIG.  16   ; 
         FIGS.  25 A- 25 D  are other isometric views of the pump assembly of  FIG.  24   ; 
         FIG.  26 A- 26 B  are isometric views of a measurement valve assembly of the infusion pump assembly of  FIG.  16   ; 
         FIG.  27 A- 27 B  are side views of the measurement valve assembly of  FIGS.  26 A- 26 B ; 
         FIGS.  28 A- 28 D  are views of a measurement valve assembly of the infusion pump assembly of  FIG.  16   ; 
         FIG.  29    is an isometric view of an alternative embodiment of the infusion pump assembly of  FIG.  1   ; 
         FIG.  30    is an isometric view of an alternative embodiment of the infusion pump assembly of  FIG.  1   ; 
         FIG.  31    is another view of the alternative embodiment infusion pump assembly of  FIG.  9   ; 
         FIG.  32    is an exploded view of another embodiment of an infusion pump assembly; 
         FIG.  33    is another exploded view of the infusion pump assembly of  FIG.  32   ; 
         FIGS.  34 A- 34 B  depict another embodiment of an infusion pump assembly; 
         FIGS.  35 A- 35 C  are a top view, side view, and bottom view of a reusable housing assembly of the infusion pump assembly of  FIG.  32   ; 
         FIG.  36    is an exploded view of the reusable housing assembly of  FIGS.  35 A- 35 C ; 
         FIG.  37    is an exploded view of the reusable housing assembly of  FIGS.  35 A- 35 C ; 
         FIG.  38 A  is an exploded view of the reusable housing assembly of  FIGS.  35 A- 35 C ; 
         FIG.  38 B- 38 D  are top, side and bottom views of one embodiment of a dust cover; 
         FIGS.  39 A- 39 C  are a top view, side view, and bottom view of an electrical control assembly of the reusable housing assembly of  FIGS.  35 A- 35 C ; 
         FIGS.  40 A- 40 C  are a top view, side view, and bottom view of a base plate of the reusable housing assembly of  FIGS.  35 A- 35 C ; 
         FIGS.  41 A- 41 B  are a perspective top view and a perspective bottom view of the base plate of  FIGS.  40 A- 40 C ; 
         FIGS.  42 A- 42 C  are a top view, side view, and bottom view of a base plate of the reusable housing assembly of  FIGS.  35 A- 35 C ; 
         FIGS.  43 A- 43 B  depict a mechanical control assembly of the reusable housing assembly of  FIGS.  35 A- 35 C ; 
         FIGS.  44 A- 44 C  depict the mechanical control assembly of the reusable housing assembly of  FIGS.  35 A- 35 C ; 
         FIGS.  45 A- 45 B  depict the pump plunger and reservoir valve of the mechanical control assembly of the reusable housing assembly of  FIGS.  35 A- 35 C ; 
         FIGS.  46 A- 46 E  depict various views of the plunger pump and reservoir valve of the mechanical control assembly of the reusable housing assembly of  FIGS.  35 A- 35 C ; 
         FIGS.  47 A- 47 B  depict the measurement valve of the mechanical control assembly of the reusable housing assembly of  FIGS.  35 A- 35 C ; 
         FIG.  48    is an exploded view of the disposable housing assembly of the infusion pump assembly of  FIG.  32   ; 
         FIG.  49 A  is a plan view of the disposable housing assembly of  FIG.  48   ; 
         FIG.  49 B  is a sectional view of the disposable housing assembly of  FIG.  49 A  taken along line B-B; 
         FIG.  49 C  is a sectional view of the disposable housing assembly of  FIG.  49 A  taken along line C-C; 
         FIGS.  50 A- 50 C  depict the base portion of the disposable housing assembly of  FIG.  48   ; 
         FIGS.  51 A- 51 C  depict the fluid pathway cover of the disposable housing assembly of  FIG.  48   ; 
         FIGS.  52 A- 52 C  depict the membrane assembly of the disposable housing assembly of  FIG.  48   ; 
         FIGS.  53 A- 53 C  depict the top portion of the disposable housing assembly of  FIG.  48   ; 
         FIGS.  54 A- 54 C  depict the valve membrane insert of the disposable housing assembly of  FIG.  48   ; 
         FIGS.  55 A- 55 B  depict the locking ring assembly of the infusion pump assembly of  FIG.  32   ; 
         FIG.  56 A- 56 C  depict the locking ring assembly of the infusion pump assembly of  FIG.  32   ; 
         FIGS.  57 - 58    is an isometric view of an infusion pump assembly and a fill adapter; 
         FIGS.  59 - 64    are various views of the fill adapter of  FIG.  57   ; 
         FIG.  65    is an isometric view of another embodiment of a fill adapter; 
         FIGS.  66 - 67    depict an infusion pump assembly and another embodiment of a fill adapter; 
         FIGS.  68 - 74    are various views of the fill adapter of  FIG.  66   ; 
         FIGS.  75 - 80    depict various views of an embodiment of a battery charger; 
         FIGS.  81 - 89 B  depict various embodiments of battery chargers/docking stations; 
         FIGS.  90 A- 90 C  are various views of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIGS.  91 A- 91 I  are various views of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIGS.  92 A- 92 I  are various views of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIGS.  93 A- 93 I  are various views of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIGS.  94 A- 94 F  are various views of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  95    is an exploded view of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  96    is a diagrammatic view of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  97    is a two-dimensional graph of a performance characteristic of the volume sensor assembly of  FIG.  96   ; 
         FIG.  98    is a two-dimensional graph of a performance characteristic of the volume sensor assembly of  FIG.  96   ; 
         FIG.  99    is a two-dimensional graph of a performance characteristic of the volume sensor assembly of  FIG.  96   ; 
         FIG.  100    is a diagrammatic view of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  101    is a two-dimensional graph of a performance characteristic of the volume sensor assembly of  FIG.  100   ; 
         FIG.  102    is a two-dimensional graph of a performance characteristic of the volume sensor assembly of  FIG.  100   ; 
         FIG.  103    is a diagrammatic view of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  104    is a two-dimensional graph of a performance characteristic of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  105    is a two-dimensional graph of a performance characteristic of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  106    is a two-dimensional graph of a performance characteristic of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  107    is a two-dimensional graph of a performance characteristic of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  108    is a two-dimensional graph of a performance characteristic of a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  109    is a diagrammatic view of a control model for a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  110    is a diagrammatic view of an electrical control assembly for the volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  111    is a diagrammatic view of a volume controller for the volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  112    is a diagrammatic view of a feed forward controller of the volume controller of  FIG.  111   ; 
         FIGS.  113 - 114    diagrammatically depicts an implementation of an SMA controller of the volume controller of  FIG.  111   ; 
         FIG.  114 A- 114 B  is an alternate implementation of an SMA controller; 
         FIG.  115    diagrammatically depicts a multi-processor control configuration that may be included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  116    is a diagrammatic view of a multi-processor control configuration that may be included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  117 A- 117 B  diagrammatically depicts multi-processor functionality; 
         FIG.  118    diagrammatically depicts multi-processor functionality; 
         FIG.  119    diagrammatically depicts multi-processor functionality; 
         FIG.  120 A  graphically depicts various software layers; 
         FIGS.  120 B- 120 C  depict various state diagrams; 
         FIG.  120 D  graphically depicts device interaction; 
         FIG.  120 E  graphically depicts device interaction; 
         FIG.  121    diagrammatically depicts a volume sensor assembly included within the infusion pump assembly of  FIG.  1   ; 
         FIG.  122    diagrammatically depicts an inter-connection of the various systems of the infusion pump assembly of  FIG.  1   ; 
         FIG.  123    diagrammatically depicts basal—bolus infusion events; 
         FIG.  124    diagrammatically depicts basal—bolus infusion events; 
         FIG.  125 A- 125 G  depicts a hierarchal state machine; 
         FIG.  126 A- 126 M  depicts a hierarchal state machine; 
         FIG.  127    is an exemplary diagram of a split ring resonator antenna; 
         FIG.  128    is an exemplary diagram of a medical device configured to utilize a split ring resonator antenna; 
         FIG.  129    is an exemplary diagram of a split ring resonator antenna and transmission line from a medical infusion device; 
         FIG.  130    is a graph of the return loss of a split ring resonator antenna prior to contact with human skin; 
         FIG.  130 A  is a graph of the return loss of a split ring resonator antenna during contact with human skin; 
         FIG.  131    is an exemplary diagram of a split ring resonator antenna integrated into a device which operates within close proximity to dielectric material; 
         FIG.  132    is a diagram of the dimensions of the inner and outer portion of the exemplary embodiment; 
         FIG.  133    is a graph of the return loss of a non-split ring resonator antenna prior to contact with human skin; 
         FIG.  133 A  is a graph of the return loss of a non-split ring resonator antenna during contact with human skin; 
         FIGS.  134 A- 134 C  shows a top, cross sectional, taken at cross section “B”, and isometric view of one embodiment of a top portion of a disposable housing assembly; 
         FIGS.  135 A- 135 B  shows top and cross sectional views, taken at cross section “B”, of one embodiment of a top portion of a disposable housing assembly; 
         FIG.  136    shows a partially exploded view of one embodiments of the reusable housing assembly together with one embodiment of the disposable housing assembly with icons; 
         FIG.  137    shows a cross sectional view taken along “A” showing the reusable housing assembly orientated above the disposable housing assembly in an unlocked orientation; 
         FIG.  138    shows a cross sectional view taken along “A” showing the reusable housing assembly attached to the disposable housing assembly in an unlocked position; 
         FIG.  139    shows a cross sectional view taken along “A” showing the reusable housing assembly attached to the disposable housing assembly in a locked position; 
         FIG.  140 A  shows an isometric view of one embodiment of the reusable housing assembly and one embodiment of the dust cover; 
         FIG.  140 B  is a top view of one embodiment of the dust cover; 
         FIG.  140 C  is a cross sectional view taken at “C” as shown in  FIG.  140 B ; 
         FIG.  140 D  is a cut-away cross-sectional view of section “D” as shown in  FIG.  140 C ; 
         FIG.  141 A  is a view of one embodiment of a disposable housing assembly; 
         FIG.  141 B  is a magnified cut away view of  FIG.  141 A  as indicated by “B”; 
         FIG.  142 A  is a top view of one embodiments of a disposable housing assembly; 
         FIG.  142 B  is a magnified cut away view of  FIG.  142 A  as indicated by “B”; 
         FIG.  142 C  is a magnified cut away view of  FIG.  142 A  as indicated by “C”; 
         FIG.  143 A  is a top view of one embodiment of the disposable housing assembly; 
         FIG.  143 B  is a cross sectional view of one embodiment of the disposable housing assembly, taken at “B” as indicated on  FIG.  143 A ; 
         FIG.  144 A  is an isometric view of one embodiment of the disposable housing assembly; 
         FIG.  144 B  is a magnified cut away sectional view of section “B” as indicated in  FIG.  144 A ; 
         FIG.  144 C  is a top view of one embodiment of the disposable housing assembly; 
         FIG.  144 D  is a magnified cut away sectional view of section “D” as indicated in  FIG.  144 C ; 
         FIG.  144 E  is an illustrated view of a cross section of the bubble trap according to one embodiment; 
         FIG.  145    is a graph of delivery volume versus pump actuation time for an embodiment of the pump system; 
         FIG.  146    is a graph of one embodiment of the optical sensor output as a function of reflector distance; 
         FIG.  147    is an illustration of various locations of optical sensors in one embodiment of an infusion pump assembly; 
         FIG.  148 A- 148 B  is an embodiment of an optical sensor assembly where  148 B is a magnified section view according to section “B” in  FIG.  148 A ; 
         FIG.  149 A- 149 B  is an embodiment of an optical sensor assembly where  149 B is a magnified section view according to section “B” in  FIG.  149 A ; 
         FIG.  150    is a schematic of one embodiment of the pump system; 
         FIG.  151    is a schematic of the pump plunger drive electronics according to one embodiment; 
         FIG.  152    is a graph of pump plunger target position versus volume delivered according to one embodiment; 
         FIG.  153    is a schematic of a model of the pump plunger as a gain element with a dead band and saturation limit according to one embodiment; 
         FIG.  154 A  is a schematic of the SMA power controller according to one embodiment; 
         FIG.  154 B  is a graph of time versus pump plunger position according to one embodiment; 
         FIG.  154 C  is a graph of time versus duty cycle according to one embodiment; 
         FIG.  155    is a schematic representation of sampling time; 
         FIG.  156    is a graph of time versus pump plunger position according to one embodiment; 
         FIG.  157    is a graph of time versus measurement valve position according to one embodiment; 
         FIG.  158    is a schematic SMA switch monitoring according to one embodiment; 
         FIG.  159 A  is a graph of delivery number versus position according to one embodiment; 
         FIG.  159 B  is a graph of delivery number versus trajectory error according to one embodiment; 
         FIG.  160    is a flow chart of the delivery controller according to one embodiment; 
         FIG.  161    is a flow chart of the inner voltage and outer volume feedback controller according to one embodiment; 
         FIG.  162    is a flow chart of the volume controller architecture according to one embodiment; 
         FIG.  163    is a flow chart of one embodiment of the volume delivery controller feed-forward; 
         FIG.  164    is a flow chart of one embodiment of the discontinuous leak check; 
         FIG.  165    is a flow chart of one embodiment of at least a portion of a start-up integrity test; 
         FIG.  166    is a flow chart of one embodiment of at least a portion of a start-up integrity test; 
         FIG.  167    is a flow chart of one embodiment of at least a portion of a start-up integrity test; 
         FIG.  168    is a graph of the pump plunger target position versus the volume delivered according to one embodiment; 
         FIG.  169    is a graph of valve position versus the volume pumped according to one embodiment; 
         FIG.  170    is a graph of a pump plunger target position versus the volume delivered according to one embodiment; 
         FIG.  171    is a flow chart of the volume controller architecture according to one embodiment; 
         FIG.  172    is a flow chart of the inner voltage and outer volume feedback controller according to one embodiment; 
         FIGS.  173 A- 173 B  are views of a reservoir membrane according to one embodiment; 
         FIGS.  174 A- 174 D  are sections views of a reservoir membrane according to one embodiment; 
         FIG.  175    is a view of the actuator assembly according to one embodiment; 
         FIG.  176 A  is a view of the actuator assembly according to one embodiment; 
         FIG.  176 B  is a view of the actuator assembly according to one embodiment; 
         FIGS.  177 A- 177 B  are views of the actuator assembly according to one embodiment; 
         FIGS.  178 A- 178 B  are views of the actuator assembly according to one embodiment; 
         FIGS.  179 A- 179 B  are views of the actuator assembly according to one embodiment; 
         FIG.  180    is a view of the actuator assembly according to one embodiment; 
         FIGS.  181 - 184    show various views of various embodiments of the configuration of the measurement valve and the shape memory alloy configurations; 
         FIGS.  185 A- 185 B  show views of one embodiment of the disposable packaging according to one embodiment; 
         FIGS.  186 A- 186 B  show views of one embodiment of the disposable packaging according to one embodiment; 
         FIGS.  187 A- 187 J  show views of one embodiment of the disposable packaging according to one embodiment; 
         FIG.  188    is one embodiment of a two pump system; 
         FIG.  189 A  is an illustration of the resting state of one embodiment of a pump system; 
         FIG.  189 B  is an illustration of the fill state of one embodiment of a pump system; 
         FIG.  189 C  is an illustration of the delivery state of one embodiment of a pump system; 
         FIG.  190    shows one embodiments of a disposable housing assembly having a luer connector; 
         FIG.  191    shows one embodiment of a locking ring on a disposable housing assembly; 
         FIG.  192    shows one embodiment of a charger with charging pins; 
         FIG.  193 A  shows one embodiment of a pump assembly; 
         FIG.  193 B  shows an illustration of the embodiment shown in  FIG.  193 A ; 
         FIG.  194    shows an illustration of one embodiment of a locking ring spring latch; 
         FIG.  195    shows an illustration of one embodiment of disposable detection system; 
         FIG.  196    is an illustrative view of one embodiment of a system to determine initial reservoir volume after fill; 
         FIG.  197    is an illustrative view of one embodiment of a reservoir; 
         FIG.  198    is an illustrative view of one embodiment of a tubing connection to the disposable housing assembly; 
         FIG.  199    is an illustrative view of one embodiment of a tubing connector to the disposable housing assembly; 
         FIGS.  200 A- 200 B  are illustrative views of one embodiment of a tubing connector to the disposable housing assembly; 
         FIGS.  201 A- 201 B  are illustrative views of one embodiment of a tubing connector to the disposable housing assembly; 
         FIG.  202    is an illustrative view of one embodiment of a tubing connector to the disposable housing assembly; 
         FIGS.  203 A- 203 B  are illustrative views of one embodiment of a tubing connector to the disposable housing assembly; 
         FIGS.  204 A- 204 C  are illustrative views of one embodiment of a tubing connector to the disposable housing assembly; 
         FIG.  205    is an illustrative view of an embodiment of a tubing connection to a connector; 
         FIG.  206    is a view of one embodiment of a connector attached to a tubing; 
         FIG.  207    is a view of one embodiment of a connector attached to a tubing, which is attached to a cannula; 
         FIG.  208    is a view of one embodiment of a connector attached to a tubing, which is attached to a cannula, and a disposable housing assembly, according to one embodiment; 
         FIG.  209    is a view of one embodiment of the connector shown in  FIGS.  206 - 208   , connected to an embodiment of a disposable housing assembly; 
         FIG.  210    is a view of one embodiment of the connector shown in  FIGS.  206 - 208   , connected to an embodiment of a disposable housing assembly; 
         FIGS.  211 - 217    are illustrative views of various embodiments of plugs; 
         FIGS.  218 A- 218 C  are various views of an embodiment of a connector; 
         FIGS.  219 A- 219 M  are views of an embodiment of a connector in various stages of interacting with an embodiment of the disposable housing assembly such that the connector is attached to the disposable housing assembly; 
         FIGS.  220 A- 220 J  are views of an embodiment of the connector which is connected to a disposable housing assembly, and an embodiment of a reusable housing assembly in various stages of rotatably connecting to the disposable housing assembly; 
         FIG.  221    is a partial view of one embodiment of a disposable housing assembly; 
         FIG.  222    is a partial view of one embodiment of a disposable housing assembly including a finger cut-out; 
         FIG.  223 A  is a exploded view of the swivel connector and the stopcock style valve, according to one embodiment; 
         FIG.  223 B  is an assembled view of the swivel connector and the stopcock style valve, according to one embodiment; 
         FIG.  224    is a view of the latching connector attached to a disposable housing assembly according to one embodiment; 
         FIG.  225 A  is a view of one embodiment of a perimeter connector attached to a disposable housing assembly, according to one embodiment; 
         FIG.  225 B  is an illustrated exploded view of a perimeter connector and a disposable housing assembly, according to one embodiment; 
         FIG.  226    is an illustrated partially exploded view of a perimeter connector and a disposable housing assembly, according to one embodiment; 
         FIGS.  227 A- 227 C  are views of the assembly of one embodiment of a folding snap connector being attached to one embodiments of the disposable housing assembly; 
         FIG.  228 A  is an exploded view of one embodiment of a perimeter connector and one embodiment of a disposable housing assembly; 
         FIG.  228 B  is a view of one embodiments of the perimeter connector shown in  FIG.  228 A  attaching to the disposable housing assembly shown in  FIG.  228 A ; 
         FIG.  229    shows one embodiment of a connected being attached to an embodiment of a disposable housing assembly; 
         FIG.  230    shows one embodiment of a connected being attached to an embodiment of a disposable housing assembly; 
         FIG.  231 A- 231 D  are various views of an embodiment of a pinch connector, tubing set and a disposable housing assembly, according to one embodiment; 
         FIG.  231 E  is a cross sectional view of one embodiment of a pinch connector connected to an embodiment of the disposable housing assembly; 
         FIG.  232 A- 232 D  are various views of an embodiment of a top down connector, tubing set and a disposable housing assembly, according to one embodiment; 
         FIG.  232 E  is a cross sectional view of one embodiment of a top down connector connected to an embodiment of the disposable housing assembly; 
         FIG.  233 A- 233 F  are various views of an embodiment of a connector, tubing set and a disposable housing assembly, according to one embodiment; 
         FIG.  233 G  is a cross sectional view of one embodiment of a connector connected to an embodiment of the disposable housing assembly; 
         FIG.  234 A- 234 F  are various views of an embodiment of a connector, tubing set and a disposable housing assembly, according to one embodiment; 
         FIG.  234 G  is a cross sectional view of one embodiment of a connector connected to an embodiment of the disposable housing assembly; 
         FIGS.  235 A- 235 C  are views of an embodiment of a connector; 
         FIG.  235 D  is a view of an embodiment of a disposable housing assembly; 
         FIG.  235 E  is a sectional view of section “A” from  FIG.  235 D ; 
         FIGS.  236 A- 236 H  are various views of an embodiment of a connector, tubing set and a disposable housing assembly, according to one embodiment; 
         FIGS.  236 I- 236 K  are various views of an embodiment of a connector; 
         FIG.  236 L  is a cut-away views of a connector connected to a disposable housing assembly according to one embodiment; 
         FIGS.  236 M- 236 P  are various views of a connector connected to a disposable housing assembly according to one embodiment; 
         FIGS.  236 Q- 236 R  are views of a connector partially connected to a disposable housing assembly according to one embodiment; 
         FIGS.  236 S- 236 T  are views of a connector connected to a disposable housing assembly according to one embodiment; 
         FIG.  237    is a bottom view of one embodiment of a connector connected to one embodiment of a disposable housing assembly, the connector including an RFID tag; 
         FIG.  238    is an exploded view of an embodiment of a disposable housing assembly and an embodiment of connector, tubing and cannula assembly; 
         FIG.  239    is a cross sectional view of one section of the reusable housing assembly connected with the disposable housing assembly, according to one embodiment; 
         FIG.  240    is an exploded view of one embodiment of the volume measurement sensor; 
         FIGS.  241 A and  241 B  are views of the actuator assembly according to one embodiment; 
         FIGS.  242  and  243    are views of the measurement valve assembly according to one embodiment; 
         FIG.  244 A  is a top view of one embodiment of the disposable housing assembly; 
         FIG.  244 B  is a sectional view, taken from section “B” shown on  FIG.  244 A , of one embodiment of the disposable housing assembly; 
         FIG.  245 A  is a partial cross sectional view of the disposable housing assembly according to one embodiment; 
         FIG.  245 B  is a partial cross section view of the disposable housing assembly and reusable housing assembly engaged, according to one embodiment; 
         FIG.  246 A  is a view of the inside of the reusable housing assembly cover according to one embodiment; 
         FIG.  246 B  is a section view of section “A” of  FIG.  246 A ; 
         FIGS.  247 A- 247 C  are various views of one embodiment of a clip assembly; 
         FIG.  248    is a bottom view of one embodiment of the housing of a clip assembly; 
         FIGS.  249 A- 249 D  are various views of one embodiment of the clip portion; 
         FIG.  250    is a view of one embodiment of the disposable housing assembly; 
         FIG.  251    is a detail view of one section of the disposable housing assembly shown in  FIG.  250   ; 
         FIG.  252    is a view of one embodiment of the disposable housing assembly; 
         FIG.  253    is a cross-sectional view of section “B” shown in  FIG.  252   ; 
         FIG.  254    is a view of one embodiment of the disposable housing assembly; 
         FIG.  255    is a detail view of one section of the disposable housing assembly shown in  FIG.  254   ; 
         FIGS.  256 A- 256 C  are various views of embodiments of a plug; 
         FIG.  256 D  is a partial view of one embodiment of the exit of a disposable housing assembly; 
         FIG.  257 A  is a views of one embodiments of a connector; 
         FIG.  257 B  is a cross sectional view of one embodiment of the plug shown in  FIG.  257 A ; 
         FIG.  258 A  is a views of one embodiments of a connector; 
         FIG.  258 B  is a cross sectional view of one embodiment of the plug shown in  FIG.  258 A ; 
         FIG.  259 A  is a view of one embodiment of a connector; 
         FIG.  258 B  is a cross sectional view of one embodiment of the plug shown in  FIG.  259 A ; 
         FIG.  259 C  is a partial view of an embodiment of a connector; 
         FIGS.  260 A- 260 G  are various views of one embodiment of a connector; 
         FIGS.  261 A- 262 K  are various views of one embodiment of a connector; 
         FIGS.  263 A- 263 I  are various views of one embodiment of a connector together with one embodiment of a disposable housing assembly; 
         FIGS.  264 A- 264 B  are various views of an embodiment of a clip assembly; and 
         FIG.  265    is an exploded view of one embodiment of a clip assembly. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     Referring to  FIGS.  1 - 3   , an infusion pump assembly  100  may include a reusable housing assembly  102 . Reusable housing assembly  102  may be constructed from any suitable material, such as a hard or rigid plastic, that will resist compression. For example, use of durable materials and parts may improve quality and reduce costs by providing a reusable portion that lasts longer and is more durable, providing greater protection to components disposed therein. 
     Reusable housing assembly  102  may include mechanical control assembly  104  having a pump assembly  106  and at least one valve assembly  108 . Reusable housing assembly  102  may also include electrical control assembly  110  configured to provide one or more control signals to mechanical control assembly  104  and effectuate the basal and/or bolus delivery of an infusible fluid to a user. Disposable housing assembly  114  may include valve assembly  108  which may be configured to control the flow of the infusible fluid through a fluid path. Reusable housing assembly  102  may also include pump assembly  106  which may be configured to pump the infusible fluid from the fluid path to the user. 
     Electrical control assembly  110  may monitor and control the amount of infusible fluid that has been and/or is being pumped. For example, electrical control assembly  110  may receive signals from volume sensor assembly  148  and calculate the amount of infusible fluid that has just been dispensed and determine, based upon the dosage required by the user, whether enough infusible fluid has been dispensed. If enough infusible fluid has not been dispensed, electrical control assembly  110  may determine that more infusible fluid should be pumped. Electrical control assembly  110  may provide the appropriate signal to mechanical control assembly  104  so that any additional necessary dosage may be pumped or electrical control assembly  110  may provide the appropriate signal to mechanical control assembly  104  so that the additional dosage may be dispensed with the next dosage. Alternatively, if too much infusible fluid has been dispensed, electrical control assembly  110  may provide the appropriate signal to mechanical control assembly  104  so that less infusible fluid may be dispensed in the next dosage. 
     Mechanical control assembly  104  may include at least one shape-memory actuator  112 . Pump assembly  106  and/or valve assembly  108  of mechanical control assembly  104  may be actuated by at least one shape-memory actuator, e.g., shape-memory actuator  112 , which may be a shape-memory wire in wire or spring configuration. Shape memory actuator  112  may be operably connected to and activated by electrical control assembly  110 , which may control the timing and the amount of heat and/or electrical energy used to actuate mechanical control assembly  104 . Shape memory actuator  112  may be, for example, a conductive shape-memory alloy wire that changes shape with temperature. The temperature of shape-memory actuator  112  may be changed with a heater, or more conveniently, by application of electrical energy. Shape memory actuator  112  may be a shape memory wire constructed of nickel/titanium alloy, such as NITINOL™ or FLEXINOL®. 
     Infusion pump assembly  100  may include a volume sensor assembly  148  configured to monitor the amount of fluid infused by infusion pump assembly  100 . For example, volume sensor assembly  148  may employ, for example, acoustic volume sensing. Acoustic volume measurement technology is the subject of U.S. Pat. Nos. 5,575,310 and 5,755,683 assigned to DEKA Products Limited Partnership, as well as U.S. patent application Publication Nos. US 2007/0228071 A1, US 2007/0219496 A1, US 2007/0219480 A1, US 2007/0219597 A1, the entire disclosures of all of which are incorporated herein by reference. Other alternative techniques for measuring fluid flow may also be used; for example, Doppler-based methods; the use of Hall-effect sensors in combination with a vane or flapper valve; the use of a strain beam (for example, related to a flexible member over a fluid reservoir to sense deflection of the flexible member); the use of capacitive sensing with plates; or thermal time of flight methods. One such alternative technique is disclosed in U.S. patent application Ser. No. 11/704,899 filed Feb. 9, 2007, now U.S. Publication No. US-2007-0228071-A1 published Oct. 4, 2007 and entitled Fluid Delivery Systems and Methods (Attorney Docket No. E70), the entire disclosure of which is incorporated herein by reference. Infusion pump assembly  100  may be configured so that the volume measurements produced by volume sensor assembly  148  may be used to control, through a feedback loop, the amount of infusible fluid that is infused into the user. 
     Infusion pump assembly  100  may further include a disposable housing assembly  114 . For example, disposable housing assembly  114  may be configured for a single use or for use for a specified period of time, e.g., three days or any other amount of time. Disposable housing assembly  114  may be configured such that any components in infusion pump assembly  100  that come in contact with the infusible fluid are disposed on and/or within disposable housing assembly  114 . For example, a fluid path or channel including a reservoir, may be positioned within disposable housing assembly  114  and may be configured for a single use or for a specified number of uses before disposal. The disposable nature of disposable housing assembly  114  may improve sanitation of infusion pump assembly  100 . 
     Referring also to  FIG.  4   , disposable housing assembly  114  may be configured to releasably engage reusable housing assembly  102 , and includes a cavity  116  that has a reservoir  118  for receiving an infusible fluid (not shown), e.g., insulin. Such releasable engagement may be accomplished by a screw-on, a twist-lock or a compression fit configuration, for example. Disposable housing assembly  114  and/or reusable housing assembly  102  may include an alignment assembly configured to assist in aligning disposable housing assembly  114  and reusable housing assembly  102  for engagement in a specific orientation. Similarly, base nub  120  and top nub  122  may be used as indicators of alignment and complete engagement. 
     Cavity  116  may be at least partially formed by and integral to disposable housing assembly  114 . Cavity  116  may include a membrane assembly  124  for at least partially defining reservoir  118 . Reservoir  118  may be further defined by disposable housing assembly  114 , e.g., by a recess  126  formed in base portion  128  of disposable housing assembly  114 . For example, membrane assembly  124  may be disposed over recess  126  and attached to base portion  128 , thereby forming reservoir  118 . Membrane assembly  124  may be attached to base portion  128  by conventional means, such as gluing, heat sealing, and/or compression fitting, such that a seal  130  is formed between membrane assembly  124  and base portion  128 . Membrane assembly  124  may be flexible and the space formed between membrane assembly  124  and recess  126  in base portion  128  may define reservoir  118 . Reservoir  118  may be non-pressurized and in fluid communication with a fluid path (not shown). Membrane assembly  124  may be at least partially collapsible and cavity  116  may include a vent assembly, thereby advantageously preventing the buildup of a vacuum in reservoir  118  as the infusible fluid is delivered from reservoir  118  to the fluid path. In a preferred embodiment, membrane assembly  124  is fully collapsible, thus allowing for the complete delivery of the infusible fluid. Cavity  116  may be configured to provide sufficient space to ensure there is always some air space even when reservoir  118  is filled with infusible fluid. 
     The membranes and reservoirs described herein may be made from materials including but not limited to silicone, NITRILE, butyl rubber, SANTOPRENE, thermal plastic elastomers (TPE), styrene ethylene butylene styrene (SEBS) and/or any other material having desired resilience and properties for functioning as described herein. Additionally, other structures could serve the same purpose. 
     The use of a partially collapsible non pressurized reservoir may advantageously prevent the buildup of air in the reservoir as the fluid in the reservoir is depleted. Air buildup in a vented reservoir could prevent fluid egress from the reservoir, especially if the system is tilted so that an air pocket intervenes between the fluid contained in the reservoir and the septum of the reservoir. Tilting of the system is expected during normal operation as a wearable device. 
     Reservoir  118  may be conveniently sized to hold an insulin supply sufficient for delivery over one or more days. For example, reservoir  118  may hold about 1.00 to 3.00 ml of insulin. A 3.00 ml insulin reservoir may correspond to approximately a three day supply for about 90% of potential users. In other embodiments, reservoir  118  may be any size or shape and may be adapted to hold any amount of insulin or other infusible fluid. In some embodiments, the size and shape of cavity  116  and reservoir  118  is related to the type of infusible fluid that cavity  116  and reservoir  118  are adapted to hold. 
     Disposable housing assembly  114  may include a support member  132  ( FIG.  3   ) configured to prevent accidental compression of reservoir  118 . Compression of reservoir  118  may result in an unintentional dosage of infusible fluid being forced through the fluid path to the user. In a preferred embodiment, reusable housing assembly  102  and disposable housing assembly  114  may be constructed of a rigid material that is not easily compressible. However, as an added precaution, support member  132  may be included within disposable housing assembly  114  to prevent compression of infusion pump assembly  100  and cavity  116  therein. Support member  132  may be a rigid projection from base portion  128 . For example, support member  132  may be disposed within cavity  116  and may prevent compression of reservoir  118 . 
     As discussed above, cavity  116  may be configured to provide sufficient space to ensure there is always some air space even when reservoir  118  is filled with infusible fluid. Accordingly, in the event that infusion pump assembly  100  is accidentally compressed, the infusible fluid may not be forced through cannula assembly  136  (e.g., shown in  FIG.  9   ). 
     Cavity  116  may include a septum assembly  146  ( FIG.  3   ) configured to allow reservoir  118  to be filled with the infusible fluid. Septum assembly  146  may be a conventional septum made from rubber or plastic and have a one-way fluid valve configured to allow a user to fill reservoir  118  from a syringe or other filling device. In some embodiments, septum  146  may be located on the top of membrane assembly  124 . In these embodiments, cavity  116  may include a support structure (e.g., support member  132  in  FIG.  3   ) for supporting the area about the back side of the septum so as to maintain the integrity of the septum seal when a needle is introducing infusible fluid into cavity  116 . The support structure may be configured to support the septum while still allowing the introduction of the needle for introducing infusible fluid into cavity  116 . 
     Referring also to  FIGS.  134 A- 135 B , embodiments of a top portion  2962  of the disposable housing assembly are shown. Top portion  2962  is shown in  FIG.  134 A , with the cross sectional view, taken at “B”, shown in  FIG.  134 B . Septum assembly  2964  is shown. In some embodiments, the septum assembly  2964  includes a tunnel feature which may, in some embodiments, serves as a feature to press a needle (e.g., filling needle) against while not pressing full force directly onto the septum  2966 . In some embodiments, as shown in  FIGS.  134 A- 134 C , the septum  2966  may be a separately molded part attached to the disposable housing assembly portion  2962 , but separate from the membrane assembly  902 . 
     Referring now to  FIGS.  135 A- 135 B , another embodiment of a septum assembly  2968 , part of a top portion  2962  of the disposable housing assembly is shown. In this embodiment, the septum  2970  may be molded into the membrane assembly  902 . 
     In some embodiments of the various embodiments of the septum assembly  2964 ,  2968 , the septum  2970 ,  2976  may be at a forty-five degree angle relative to the top portion  2962 . In some embodiments, the septum  2970 ,  2976  may be made from the same material as the membrane assembly  902 . 
     Infusion pump assembly  100  may include an overfill prevention assembly (not shown) that may e.g., protrude into cavity  116  and may e.g., prevent the overfilling of reservoir  118 . 
     In some embodiments, reservoir  118  may be configured to be filled a plurality of times. For example, reservoir  118  may be refillable through septum assembly  146 . As infusible fluid may be dispensed to a user, electronic control assembly  110  may monitor the fluid level of the infusible fluid in reservoir  118 . When the fluid level reaches a low point, electronic control assembly  110  may provide a signal, such as a light or a vibration, to the user that reservoir  118  needs to be refilled. A syringe, or other filling device, may be used to fill reservoir  118  through septum  146 . 
     Reservoir  118  may be configured to be filled a single time. For example, a refill prevention assembly (not shown) may be utilized to prevent the refilling of reservoir  118 , such that disposable housing assembly  114  may only be used once. The refill prevention assembly (not shown) may be a mechanical device or an electro-mechanical device. For example, insertion of a syringe into septum assembly  146  for filling reservoir  118  may trigger a shutter to close over septum  146  after a single filling, thus preventing future access to septum  146 . Similarly, a sensor may indicate to electronic control assembly  110  that reservoir  118  has been filled once and may trigger a shutter to close over septum  146  after a single filling, thus preventing future access to septum  146 . Other means of preventing refilling may be utilized and are considered to be within the scope of this disclosure. 
     As discussed above, disposable housing assembly  114  may include septum assembly  146  that may be configured to allow reservoir  118  to be filled with the infusible fluid. Septum assembly  146  may be a conventional septum made from rubber or any other material that may function as a septum, or, in other embodiments, septum assembly  146  may be, but is not limited to, a plastic, or other material, one-way fluid valve. In various embodiments, including the exemplary embodiment, septum assembly  146  is configured to allow a user to fill reservoir  118  from a syringe or other filling device. Disposable housing assembly  114  may include a septum access assembly that may be configured to limit the number of times that the user may refill reservoir  118 . 
     For example and referring also to  FIGS.  5 A- 5 C , septum access assembly  152  may include shutter assembly  154  that may be held in an “open” position by a tab assembly  156  that is configured to fit within a slot assembly  158 . Upon penetrating septum  146  with filling syringe  160 , shutter assembly  154  may be displaced downward, resulting in tab assembly  156  disengaging from slot assembly  158 . Once disengaged, spring assembly  162  may displace shutter assembly  154  in the direction of arrow  164 , resulting in septum  146  no longer being accessible to the user. 
     Referring also to  FIG.  6 A , an alternative-embodiment septum access assembly  166  is shown in the “open” position. In a fashion similar to that of septum access assembly  152 , septum access assembly  166  includes shutter assembly  168  and spring assembly  170 . 
     Referring also to  FIG.  6 B , an alternative-embodiment of septum access assembly  172  is shown in the “open” position where tab  178  may engage slot  180 . In a fashion similar to that of septum access assembly  166 , septum access assembly  172  may include shutter assembly  174  and spring assembly  176 . Once shutter assembly  172  moves to the “closed” position (e.g., which may prevent further access of septum  146  by the user), tab  178  may at least partially engage slot  180   a . Engagement between tab  178  and slot  180   a  may lock shutter assembly  172  in the “closed” position to inhibit tampering and reopening of shutter assembly  172 . Spring tab  182  of shutter assembly  172  may bias tab  178  into engagement with slot  180   a.    
     However, in various embodiments, septum access assemblies may not be actuated linearly. For example and referring also to  FIGS.  7 A- 7 B , there is shown alternative embodiment septum access assembly  184  that includes shutter assembly  186  that is configured to pivot about axis  188 . When positioned in the open position (as shown in  FIG.  7 A ), septum  146  may be accessible due to passage  190  (in shutter assembly  186 ) being aligned with passage  192  in e.g., a surface of disposable housing assembly  114 . However, in a fashion similar to septum access assemblies  166 ,  172 , upon penetrating septum  146  with filling syringe  160  (See  FIG.  6 B ), shutter assembly  186  may be displaced in a clockwise fashion, resulting in passage  190  (in shutter assembly  186 ) no longer being aligned with passage  192  in e.g., a surface of disposable housing assembly  114 , thus preventing access to septum  146 . 
     Referring also to  FIGS.  8 A- 8 B , an alternative-embodiment septum access assembly  194  is shown. In a fashion similar to that of septum access assemblies  166 ,  172 , septum access assembly  194  includes shutter assembly  196  and spring assembly  198  that is configured to bias shutter assembly  196  in the direction of arrow  200 . Filling assembly  202  may be used to fill reservoir  118 . Filling assembly  202  may include shutter displacement assembly  204  that may be configured to displace shutter assembly  196  in the direction of arrow  206 , which in turn aligns passage  208  in shutter assembly  196  with septum  146  and passage  210  in septum access assembly  194 , thus allowing filling syringe assembly  212  to penetrate septum  146  and fill reservoir  118 . 
     Infusion pump assembly  100  may include a sealing assembly  150  ( FIG.  3   ) configured to provide a seal between reusable housing assembly  102  and disposable housing assembly  114 . For example, when reusable housing assembly  102  and disposable housing assembly  114  are engaged by e.g. rotational screw-on engagement, twist-lock engagement or compression engagement, reusable housing assembly  102  and disposable housing assembly  114  may fit together snuggly, thus forming a seal. In some embodiments, it may be desirable for the seal to be more secure. Accordingly, sealing assembly  150  may include an o-ring assembly (not shown). Alternatively, sealing assembly  150  may include an over molded seal assembly (not shown). The use of an o-ring assembly or an over molded seal assembly may make the seal more secure by providing a compressible rubber or plastic layer between reusable housing assembly  102  and disposable housing assembly  114  when engaged thus preventing penetration by outside fluids. In some instances, the o-ring assembly may prevent inadvertent disengagement. For example, sealing assembly  150  may be a watertight seal assembly and, thus, enable a user to wear infusion pump assembly  100  while swimming, bathing or exercising. 
     Referring also to  FIG.  9   , infusion pump assembly  100  may include an external infusion set  134  configured to deliver the infusible fluid to a user. External infusion set  134  may be in fluid communication with cavity  118 , e.g. by way of the fluid path. External infusion set  134  may be disposed adjacent to infusion pump assembly  100 . Alternatively, external infusion set  134  may be configured for application remote from infusion pump assembly  100 , as discussed in greater detail below. External infusion set  134  may include a cannula assembly  136 , which may include a needle or a disposable cannula  138 , and tubing assembly  140 . Tubing assembly  140  may be in fluid communication with reservoir  118 , for example, by way of the fluid path, and with cannula assembly  138  for example, either directly or by way of a cannula interface  142 . 
     External infusion set  134  may be a tethered infusion set, as discussed above regarding application remote from infusion pump assembly  100 . For example, external infusion set  134  may be in fluid communication with infusion pump assembly  100  through tubing assembly  140 , which may be of any length desired by the user (e.g., 3-18 inches). Though infusion pump assembly  100  may be worn on the skin of a user with the use of adhesive patch  144 , the length of tubing assembly  140  may enable the user to alternatively wear infusion pump assembly  100  in a pocket. This may be beneficial to users whose skin is easily irritated by application of adhesive patch  144 . Similarly, wearing and/or securing infusion pump assembly  100  in a pocket may be preferable for users engaged in physical activity. 
     In addition to/as an alternative to adhesive patch  144 , a hook and loop fastener system (e.g. such as hook and loop fastener systems offered by Velcro USA Inc. of Manchester, N.H.) may be utilized to allow for easy attachment/removal of an infusion pump assembly (e.g., infusion pump assembly  100 ) from the user. Accordingly, adhesive patch  144  may be attached to the skin of the user and may include an outward facing hook or loop surface. Additionally, the lower surface of disposable housing assembly  114  may include a complementary hook or loop surface. Depending upon the separation resistance of the particular type of hook and loop fastener system employed, it may be possible for the strength of the hook and loop connection to be stronger than the strength of the adhesive to skin connection. Accordingly, various hook and loop surface patterns may be utilized to regulate the strength of the hook and loop connection. 
     Referring also to  FIGS.  10 A- 10 E , five examples of such hook and loop surface patterns are shown. Assume for illustrative purposes that the entire lower surface of disposable housing assembly  114  is covered in a “loop” material. Accordingly, the strength of the hook and loop connection may be regulated by varying the pattern (i.e., amount) of the “hook” material present on the surface of adhesive patch  144 . Examples of such patterns may include but are not limited to: a singular outer circle  220  of “hook” material (as shown in  FIG.  10 A ); a plurality of concentric circles  222 ,  224  of “hook” material (as shown in  FIG.  10 B ); a plurality of radial spokes  226  of “hook” material (as shown in  FIG.  10 C ); a plurality of radial spokes  228  of “hook” material in combination with a single outer circle  230  of “hook” material (as shown in  FIG.  10 D ); and a plurality of radial spokes  232  of “hook” material in combination with a plurality of concentric circles  234 ,  236  of “hook” material (as shown in  FIG.  10 E ). 
     Additionally and referring also to  FIG.  11 A , in one exemplary embodiment of the above-described infusion pump assembly, infusion pump assembly  100 ′ may be configured via a remote control assembly  300 . In this particular embodiment, infusion pump assembly  100 ′ may include telemetry circuitry (not shown) that allows for communication (e.g., wired or wireless) between infusion pump assembly  100 ′ and e.g., remote control assembly  300 , thus allowing remote control assembly  300  to remotely control infusion pump assembly  100 ′. Remote control assembly  300  (which may also include telemetry circuitry (not shown) and may be capable of communicating with infusion pump assembly  100 ′) may include display assembly  302  and input assembly  304 . Input assembly  304  may include slider assembly  306  and switch assemblies  308 ,  310 . In other embodiments, the input assembly may include a jog wheel, a plurality of switch assemblies, or the like. 
     Remote control assembly  300  may include the ability to pre-program basal rates, bolus alarms, delivery limitations, and allow the user to view history and to establish user preferences. Remote control assembly  300  may also include a glucose strip reader. 
     During use, remote control assembly  300  may provide instructions to infusion pump assembly  100 ′ via wireless communication channel  312  established between remote control assembly  300  and infusion pump assembly  100 ′. Accordingly, the user may use remote control assembly  300  to program/configure infusion pump assembly  100 ′. Some or all of the communication between remote control assembly  300  and infusion pump assembly  100 ′ may be encrypted to provide an enhanced level of security. 
     Communication between remote control assembly  300  and infusion pump assembly  100 ′ may be accomplished utilizing a standardized communication protocol. Further, communication between the various components included within infusion pump assembly  100 ,  100 ′ may be accomplished using the same protocol. One example of such a communication protocol is the Packet Communication Gateway Protocol (PCGP) developed by DEKA Research &amp; Development of Manchester, N.H. As discussed above, infusion pump assembly  100 ,  100 ′ may include electrical control assembly  110  that may include one or more electrical components. For example, electrical control assembly  110  may include a plurality of data processors (e.g. a supervisor processor and a command processor) and a radio processor for allowing infusion pump assembly  100 ,  100 ′ to communicate with remote control assembly  300 . Further, remote control assembly  300  may include one or more electrical components, examples of which may include but are not limited to a command processor and a radio processor for allowing remote control assembly  300  to communicate with infusion pump assembly  100 ,  100 ′. A high-level diagrammatic view of one example of such a system is shown in  FIG.  11 B . 
     Each of these electrical components may be manufactured from a different component provider and, therefore, may utilize native (i.e. unique) communication commands. Accordingly, through the use of a standardized communication protocol, efficient communication between such disparate components may be accomplished. 
     PCGP may be a flexible extendable software module that may be used on the processors within infusion pump assembly  100 ,  100 ′ and remote control assembly  300  to build and route packets. PCGP may abstract the various interfaces and may provide a unified application programming interface (API) to the various applications being executed on each processor. PCGP may also provide an adaptable interface to the various drivers. For illustrative purposes only, PCGP may have the conceptual structure illustrated in  FIG.  11 C  for any given processor. 
     PCGP may ensure data integrity by utilizing cyclic redundancy checks (CRCs). PCGP may also provide guaranteed delivery status. For example, all new messages should have a reply. If such a reply isn&#39;t sent back in time, the message may time out and PCGP may generate a negative acknowledge reply message for the application (i.e., a NACK). Accordingly, the message-reply protocol may let the application know whether the application should retry sending a message. 
     PCGP may also limit the number of messages in-flight from a given node, and may be coupled with a flow-control mechanism at the driver level to provide a deterministic approach to message delivery and may let individual nodes have different quantities of buffers without dropping packets. As a node runs out of buffers, drivers may provide back pressure to other nodes and prevent sending of new messages. 
     PCGP may use a shared buffer pool strategy to minimize data copies, and may avoid mutual exclusions, which may have a small affect on the API used to send/receive messages to the application, and a larger affect on the drivers. PCGP may use a “Bridge” base class that provides routing and buffer ownership. The main PCGP class may be sub-classed from the bridge base class. Drivers may either be derived from a bridge class, or talk to or own a derived bridge class. 
     PCGP may be designed to work in an embedded environment with or without an operating system by using a semaphore to protect shared data such that some calls can be re-entrant and run on a multiple threads. One illustrative example of such an implementation is shown in  FIG.  11 D . PCGP may operate the same way in both environments, but there may be versions of the call for specific processor types (e.g., the ARM 9/OS version). So while the functionality may be the same, there may be an operating system abstraction layer with slightly different calls tailored for e.g., the ARM 9 Nucleus OS environment. 
     Referring also to  FIG.  11 E , PCGP may:
         allow multiple Send/Reply calls to occur (on Pilot&#39;s ARM 9 on multiple tasks re-entrant);   have multiple drivers running asynchronously for RX and TX on different interfaces; and   provide packet ordering for send/receive, and deterministic timeout on message send.       

     Each software object may ask the buffer manager for the next buffer to use, and may then give that buffer to another object. Buffers may pass from one exclusive owner to another autonomicly, and queues may occur automatically by ordering buffers by sequence number. When a buffer is no longer in use, the buffer may be recycled (e.g., object attempts to give the buffer to itself, or frees it for the buffer manager to re-allocate later). Accordingly, data generally doesn&#39;t need to be copied, and routing simply writes over the buffer ownership byte. 
     Such an implementation of PCGP may provide various benefits, examples of which may include but are not limited to:
         dropping a message due to lack of buffers may be impossible, as once a message is put into a buffer, the message may live there until it is transferred or received by the application;   data may not need to be copied, as offsets are used to access driver, PCGP and payload sections of a buffer;   drivers may exchange ownership of message data by writing over one byte (i.e., the buffer ownership byte);   there may be no need for multiple exclusions except for re-entrant calls, as a mutual exclusion may be needed only when a single buffer owner could simultaneously want to use a buffer or get a new sequence number;   there may be fewer rules for application writers to follow to implement a reliable system;   drivers may use ISR/push/pull and polled data models, as there are a set of calls provided to push/pull data out of the buffer management system from the drivers;   drivers may not do much work beyond TX and RX, as drivers may not copy, CRC or check anything but the destination byte and CRC and other checks may be done off of the ISR hot path later;   as the buffer manager may order access by sequence number, queue ordering may automatically occur; and   a small code/variable foot print may be utilized; hot path code may be small and overhead may be low.       

     As shown in  FIG.  11 F , when a message needs to be sent, the PCGP may build the packet quickly and may insert it into the buffer management system. Once in the buffer management system, a call to “packetProcessor” may apply protocol rules and may give the messages to the drivers/application. 
     To send a new message or send a reply, PCGP may:
         check the call arguments to e.g., make sure the packet length is legal, destination is ok, etc.;   avoid trying to send a message across a link that is down unless the down link is the radio node, which may allow PCGP to be used by the radio processors to establish a link, pair, etc. and may notify the application when PCGP is trying to talk across a link that is not functional (instead of timing out);   obtain a sequence number for a new message or utilize an existing sequence number for an existing message;   build the packet, copy the payload data and write in the CRC, wherein (from this point forward) the packet integrity may be protected by the CRC; and   either give the message to the buffer manager as a reply or as a new message, and check to see if putting this buffer into the buffer manager would exceed the maximum number of en-queued send messages.       

     Referring also to  FIGS.  11 G- 11 H , PCGP may work by doing all of the main work on one thread to avoid mutual exclusions, and to avoid doing considerable work on the send/reply or driver calls. The “packetProcessor” call may have to apply protocol rules to replies, new sent messages, and received messages. Reply messages may simply get routed, but new messages and received messages may have rules for routing the messages. In each case, the software may loop while a message of the right type is available to apply protocol rules until it cannot process the packets. 
     Sending a new message may conform to the following rules:
         only two messages may be allowed “in-flight” on the network; and   enough data about an in-flight message may be stored to match the response and handle timeout.       

     Receiving a message may conform to the following rules:
         responses that match may clear out the “in-flight” information slot so a new packet can be sent;   responses that do not match may be dropped;   new messages may be for the protocol (e.g., getting/clearing network statistics for this node);   to receive a message, the buffer may be given up to the application and may use a call back; and   the buffer may be freed or left owned by the application.       

     Accordingly, PCGP may be configured such that:
         the call back function may copy the payload data out or may use it completely before returning;   the call back function owns the buffer and may reference the buffer and the buffer&#39;s payload by the payload address, wherein the message may be processed later;   applications may poll the PCGP system for received messages; and   applications may use the call back to set an event and then poll for received messages.       

     The communication system may have a limited number of buffers. When PCGP runs out of buffers, drivers may stop receiving new packets and the application may be told that the application cannot send new packets. To avoid this and maintain optimal performance, the application may try to perform one or more procedures, examples of which may include but are not limited to:
         a) The application should keep PCGP up to date with radio status: Specifically, if the link goes down and PCGP doesn&#39;t know, PCGP may accept and queue new messages to send (or not timeout messages optimally), which may jam the send queue and delay the application from using the link optimally.   b) The application should call “decrement timeouts” regularly: Optimally, every 20-100 milliseconds unless the processor is asleep. In general, a message moves fast (milliseconds) slow (seconds) or not at all. Timeouts are an attempt to remove “in-flight” messages that should be dropped to free up buffers and bandwidth. Doing this less often may delay when a new message gets sent, or when the application can queue a new message.   c) The application should ask PCGP if it has work to do that is pending before going to sleep: If PCGP has nothing to do, driver activity may wake up the system and thus PCGP, and then PCGP won&#39;t need a call to “packetProcessor” or “decrement timeouts” until new packets enter the system. Failure to do this may cause messages that could have been sent/forwarded/received successfully to be dropped due to a timeout condition.   d) The application should not hold onto received messages indefinitely: The message system relies on prompt replies. If the application is sharing PCGP buffers, then holding onto a message means holding onto a PCGP buffer. The receiving node doesn&#39;t know if the sending node has timeout configured for slow or fast radio. This means when a node receives a message it should assume the network&#39;s fast timeout speed.   e) The application should call the “packetProcessor” often: The call may cause new messages queued by the application to get sent and may handle receipt of new messages. The call may also cause buffers to re-allocate and calling it infrequently may delay message traffic.       

     As shown in  FIG.  11 I , at some point the RX driver may be asked to receive a message from the other side of the interface. To ensure a message does not get dropped, the RX driver may ask the buffer manager if there is an available buffer for storing a new message. The driver may then ask for a buffer pointer and may start filling the buffer with received data. When a complete message is received, the RX driver may call a function to route the packet. The route function may examine the destination byte in the packet header and may change the owner to either the other driver, or the application, or may detect that the packet is bad and may drop the packet by freeing the buffer. 
     PCGP RX overhead may consist of asking for the next available buffer and calling the route function. An example of code that performs such a function is as follows: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                   
                 @ Receive request 
               
               
                   
                   
                 uint8 i=0, *p; 
               
               
                   
                   
                 if (Bridge::canReceiveFlowControl( ) ) 
               
               
                   
                   
                 { 
               
               
                   
                   
                  p = Bridge::nextBufferRX( ); 
               
               
                   
                   
                  while (not done) { p[i] = the next byte; } 
               
               
                   
                   
                  Bridge::route(p); 
               
               
                   
                   
                 } 
               
               
                   
                   
               
            
           
         
       
     
     A driver may perform a TX by asking the buffer manager for the pointer to the next buffer to send. The TX driver may then ask the other side of the interface if it can accept a packet. If the other side denies the packet, the TX driver may do nothing to the buffer, as its status has not changed. Otherwise, the driver may send the packet and may recycle/free the buffer. An example of code that performs such a function is as follows: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                   
                 uint8 *p = Bridge::nextBufferTX( ); 
               
               
                   
                   
                 if (p != (uint8 *)0) 
               
               
                   
                   
                 { 
               
               
                   
                   
                  send the buffer p; 
               
               
                   
                   
                  Bridge::recycle(p); 
               
               
                   
                   
                 } 
               
               
                   
                   
               
            
           
         
       
     
     To avoid forwarding packets that are past the maximum message system timeout time, asking for the nextBuffer may call the BufferManager::first(uint8 owner) function that may scan for buffers to free. Accordingly, full TX buffers with no hope of making a timeout may be freed on the thread that owns the buffer. A bridge that is doing TX (i.e., while looking for the next TX buffer) may free all of the TX buffers that are expired before receiving the next TX buffer for processing. 
     As shown in  FIG.  11 J- 11 L , during the buffer allocation process, buffers marked free may be transferred to the drivers to receive new packets, or to PCGP to receive new payloads for TX. Allocation from “free” may be done by the “packetProcessor” function. The number of sends and receives between “packetProcessor” calls may dictate how many LT_Driver_RX, GT_Driver_RX and PCGP_Free buffers need to be allocated. LT_Driver may represent drivers that handle addresses that are less than the node address. GT_Driver may represent drivers that handle addresses that are greater than the node address. 
     When a driver receives a packet, the driver may put the data into an RX buffer that gets handed to the router. The router may then reassign the buffer to PCGP_Receive or to the other driver&#39;s TX (not shown). If the buffer contains obviously invalid data, the buffer may transition to free. 
     After a router marks a buffer for TX, the driver may discover the buffer is TX and may send the message. After sending the message, the buffer may immediately become an RX buffer if the driver was low in RX buffers, or the buffer may be freed for re-allocation. 
     During the “packetProcessor” call, PCGP may process all buffers that the router marked as PCGP_Receive. At this point, data may be acted upon, so the CRC and other data items may be checked. If the data is corrupted, a statistic may be incremented and the buffer may be freed. Otherwise, the buffer may be marked as owned by the application. Buffers marked as owned by the application may be either recycled for the use of PCGP or freed for reallocation by the buffer manager. 
     When the application wants to send a new message, it may be done in a re-entrant friendly/mutual exclusion manner. If the buffer may be allocated, PCGP may mark the buffer as busy. Once marked busy, no other thread calling the send or reply functions may grab this buffer, as it is owned by this function call&#39;s invocation. The remainder of the process of error checking and building the message may be done outside the isolated race condition mutual exclusion guarded code. The buffer may either transition to free or may become a valid filled CRC-checked buffer and passed to the router. These buffers may not be routed immediately and may be queued so that messages can be sent later (assuming that protocol rules allow). Reply messages may be marked differently than new send messages because reply messages may be routed with a higher priority than regular send messages and reply messages may have no rules limiting how many/when they can be sent. 
     PCGP was designed to work with flow control, and flow control may negotiate the transfer of messages from one node to another node so that a buffer is never dropped because the other side of an interface lacks a buffer (which may cause back pressure on the sending node). 
     Flow control may be apart of the shared buffer format. The first two bytes may be reserved for the driver so that the driver never needs to shift the packet bytes. Two bytes may be used so that one byte is the DMA length—1, and the second byte is to control the flow of messages. These same two bytes may be synchronizing bytes if a PCGP message is transmitted over RS232. 
     When a packet is “in-flight”, the packet may be in the process of being sent by a driver on the way to its destination, being processed by the destination, or being sent back as a response. 
     Typical delays are as follows: 
     
       
         
           
               
               
               
             
               
                   
               
               
                 Interface/Delay 
                   
                   
               
               
                 cause 
                 Delay (seconds) 
                 Notes 
               
               
                   
               
             
            
               
                 SPI 
                 &lt;3 
                 Roughly 400 kbps 
               
               
                 I2C 
                 &lt;1 
                   
               
               
                 Waking a CC2510 
                 &lt;6 ? 
                 Clock calibration, min. sleep 
               
               
                   
                   
                 time. 
               
               
                 Flow control 
                 &lt;0.2 
                   
               
               
                 RF link 
                 20 to 2000 
                   
               
               
                 Interference/ 
                 Minutes, never 
                   
               
               
                 separation 
               
               
                   
               
            
           
         
       
     
     Accordingly, messages tend to complete the round trip either: quickly (e.g., &lt;50 ms); slowly (e.g., one or more seconds); or not at all. 
     PCGP may use two different times (set at initialization) for all timeouts, one for when the RE link is in fast heartbeat mode, and another for when the RE link is in slow mode. If a message is in-flight and the link status changes from fast to slow, the timeout may be adjusted and the difference between fast and slow may be added to the time-to-live counter for the packet. No additional transitions back and forth may affect the time-to-live time for the message. 
     There is a second timeout that may be twice as long as the slow timeout that is used to monitor buffer allocation inside PCGP. Accordingly, if a message is “stuck” inside a driver and hasn&#39;t been sent due to e.g., flow control or hardware damage, the buffer may be freed by the buffer manager, resulting in the buffer being dropped. For a “new” message, this may mean that the packet already timed out and the application was already given a reply saying the message wasn&#39;t delivered, resulting in the buffer being freed. Since the driver polls the buffer manager for buffers that need to be sent, the buffer is freed up so that a message that could be sent is handed to the driver the next time that it unblocks. For a reply message, the reply may simply get dropped and the sending node may time out. 
     The PCGP messaging system may pass messages that contain header information and payload. Outside of PCGP, the header may be a set of data items in a call signature. However, internal to PCGP, there may be a consistent, driver friendly byte layout. Drivers may insert bytes either into the PCGP packet or before the PCGP packet such:
         DE, CA: Synch bytes for use with RS232, nominal value of 0xDE, 0xCA or 0x5A, 0xA5.   LD: Driver DMA length byte, equals amount driver is pushing in this DMA transfer, which is the total size, not including the size byte or synch bytes.   Cmd: Driver command and control byte used for flow control.   LP: PCGP packet length, always the total header+payload size in bytes+CRC size. LD=LP+1.   Dst: Destination address.   Src: Source address   Cmd: Command byte   Scd: Sub command byte   AT: Application Tag is defined by the application and has no significance to PCGP. It allows the application to attach more information to a message e.g., the thread from which the message originated.   SeqNum: thirty-two bit sequence number is incremented by PCGP for a new message sent, guarantees the number will not wrap, acts as a token, endianess isn&#39;t relevant.   CRC16: A sixteen bit CRC of the PCGP header and payload.       

     An example of a message with no payload, cmd=1, subcmd=2 is as follows: 
     0xDE, 0xCA, 0xC, 0x5, 0x14, 1, 2, 0, 0, 0, 0, 0x1, crchigh, crclow. 
     0x0D, cmd, 0xC, 0x5, 0x14, 1, 2, 0, 0, 0, 0, 0x1, crchigh, crclow. 
     There may be several advantages to this methodology, examples of which may include but are not limited to:
         Most of our hardware DMA engines may use the first byte to define how many additional bytes to move, so in this methodology, drivers and PCGP may share buffers.   A byte may be provided right after the DMA length to pass flow control information between drivers.   Driver length and “Cmd” byte may be outside the CRC region so they may be altered by the driver, may be owned by the driver transport mechanism, and the driver may guard for invalid lengths.   There may be a separate PGCP packet length byte that is CRC protected. Accordingly, the application may trust the that payload length is correct.   The endianness of the sequence number may not be relevant, as it is just a byte pattern that may be matched that happens to also be a thirty-two bit integer.   The sequence number may be four bytes aligned to the edge of the shared buffer pool length.   There may be optional RS232 synchronizing bytes so that users may move cables around while debugging a message stream and both sides of the interface may resynchronize.   The application, driver and PCGP may share buffers and may release them by pointer.       

     PCGP may not be an event driven software design, but may be used in event driven architectures by how the sub-classes are written. Data may be exchanged between the classes conceptually (as shown in  FIG.  11 M- 11 N ). 
     Some event model in the driver may wake the driver, may receive a message and may pass the message through the bridge into the buffer manager that routes the message to new owner of the new message (through a bridge to either a driver or PCGP). 
     The following summarizes some exemplary events: 
     
       
         
           
               
               
               
             
               
                   
               
               
                   
                   
                 Where this  
               
               
                 Event: 
                 Possible use: 
                 occurs: 
               
               
                   
               
             
            
               
                 When a new send or reply is 
                 Decide to run  
                 Inside 
               
               
                 queued, or decTimeouts 
                 packetProcessor. 
                 PCGP::sendInternal 
               
               
                 generates a timeout reply. 
                   
                   
               
               
                 When a messages is received  
                 Decide to run 
                 BufferManager::give 
               
               
                 for PCGP. 
                 packetProcessor. 
                   
               
               
                 When a driver has something  
                 Wake driver for  
                 BufferManager::give 
               
               
                 new to send. 
                 TX. 
                   
               
               
                 When a Driver RX buffer  
                 Turn off flow 
                 BufferManager::give 
               
               
                 becomes available. 
                 control. 
               
               
                   
               
            
           
         
       
     
     The following illustrative example shows how the PCGP event model may work with Nucleus to wakeup the PCGP task after every message send, reply, or decTimeout that generated a NACK: 
     
       
         
           
               
               
             
               
                   
               
             
            
               
                   
                 class PcgpOS : public Pcgp 
               
               
                   
                 { 
               
               
                   
                  virtual void schedulePacketProcessor(void) 
               
               
                   
                  { 
               
               
                   
                   OS_EventGrp_Set(g_RCVEvGrps[EVG_RF_TASK].pEvgHandle, 
               
               
                   
                    RfRadioTxEvent, OS_EV_OR_NO_CLEAR); 
               
               
                   
                  } 
               
               
                   
                 } 
               
               
                   
               
            
           
         
       
     
     The following is a pseudo code driver that is event based, illustrating how driver events work. The Driver subclasses Bridge and overrides hasMessagesToSend and flowControlTumedOff to schedule the TX and RX functions to run if they aren&#39;t already running. 
     
       
         
           
               
               
             
               
                   
               
             
            
               
                   
                 class SPI_Driver : public Bridge 
               
               
                   
                 {  
               
               
                   
                  virtual void hasMessagesToSend( ) 
               
               
                   
                  {  
               
               
                   
                   Trigger_ISR(TX_ISR, this); 
               
               
                   
                  } 
               
               
                   
                  virtual void flowControlTurnedOff( ) 
               
               
                   
                  {  
               
               
                   
                   Trigger_ISR(RX_ISR, this); 
               
               
                   
                  } 
               
               
                   
                  static void TX_RetryTimer( ) 
               
               
                   
                  {  
               
               
                   
                   Trigger_ISR(TX_ISR, this); 
               
               
                   
                  } 
               
               
                   
                  static void TX_ISR(Bridge *b) 
               
               
                   
                  {  
               
               
                   
                   DisableISRs( ); 
               
               
                   
                    do 
               
               
                   
                   {  
               
               
                   
                    uint8 *p = b-&gt;nextBufferTX( ); 
               
               
                   
                    if (p == null) break; 
               
               
                   
                    if (b-&gt;_bufferManager-&gt;bufferTimedOut(p)==false) 
               
               
                   
                    { 
               
               
                   
                     if (OtherSideSPI_FlowControl( ) == false) 
               
               
                   
                     {  
               
               
                   
                      Trigger TX_RetryTimer in 20 msec. 
               
               
                   
                      break; 
               
               
                   
                     } 
               
               
                   
                     send(p); 
               
               
                   
                    } 
               
               
                   
                    free(p); 
               
               
                   
                   } while (true) ; 
               
               
                   
                   EnableISRs( ); 
               
               
                   
                  } 
               
               
                   
                  static void RX_ISR(Bridge *b) 
               
               
                   
                  { 
               
               
                   
                   DisableISRs( ); 
               
               
                   
                   do 
               
               
                   
                   { 
               
               
                   
                    uint8* p = b-&gt;nextBufferRX( ); 
               
               
                   
                    if (p == null) break; 
               
               
                   
                    uint i; 
               
               
                   
                    while (not done receiving) 
               
               
                   
                     p[i++] = getChar ( ); 
               
               
                   
                    b-&gt;route(p); 
               
               
                   
                   } while (true) ; 
               
               
                   
                   EnableISRs( ); 
               
               
                   
                  } 
               
               
                   
                 } 
               
               
                   
               
            
           
         
       
     
     The following statistics may be supported by PCGP:
         Number of packets sent;   Number of packets received;   CRC errors;   Timeouts; and   Buffer unavailable (ran out of buffers)       

     PCGP may be designed to run in multiple processing environments. Most parameters may be run time configured because it facilitates testing, and any run time fine tuning for performance. Other parameters may be compile time e.g., anything that alters memory allocation must be done statically at compile time. 
     The following may be compile time configuration # defines that may vary where PCGP is implemented:
         # driver bytes: may be two bytes reserved in the common buffer scheme for the driver, but this may be a compile time option to accommodate other drivers such as RE protocol.   # RX driver buffers: may be tuned to how many buffers would be good for that processor/traffic flow, etc.   # PCGP RX buffers: may be tuned to how many buffers would be good for that processor/traffic flow, etc.   Total # of buffers: may be tuned to how many buffers should be at that processor.       

     The CRC may be used to ensure data integrity. If a CRC is invalid, it may not be delivered to the application and the CRC error may be tracked. The message may eventually timeout and may be retried by the originator. 
     Likewise, if the messaging system informs the application that a message was delivered when it was not, this may be a hazard to the system. The Stop Bolus Command is an example of such a command. This may be mitigated by the Request/Action sequence of messages which may be required by the application to change therapy. The Controller may receive a matching command from the Pump application to consider the message delivered. 
     DEKA may provide a reference way of interfacing PCGP into the Nucleus OS system on the ARM 9 (as shown in  FIG.  11 O ). 
     As shown in  FIG.  11 P , the pcgpOS.cpp file may instantiate a PCGP node instance (Pcgp, a Bridge, etc.) and may provide through pcgpOS.h a ‘C’ linkable set of function calls that provide a ‘C’ language interface to the C++ code. This may simplify the ‘C’ code as the objects acted upon are implicit. 
     The following general rules may be applied:
         PCGP may run on all nodes: any driver may support a generic driver interface.   Race conditions may not be permitted.   May support half duplex on the SPI port between slave processor and master processor.   Data transfer may not be attempted; as it either succeeds or returns fail/false.   May require low overhead (time, processing, bandwidth wasted).   May support CC2510 operating at DMA (fast) SPI clock rates.       

     SPI flow control may prevent data from being sent if the receiving side does not currently have an empty buffer to place the packet. This may be accomplished by asking for permission to send and waiting for a response indicating that you have been cleared to do so. There may also be a way to tell the other side that there are currently no free buffers and the transfer should be attempted at a later time. 
     All transmission may begin with a length byte that indicates the number of bytes to be sent, not including the length byte itself. Following the length may be a single byte indicating the command being sent. 
     The actual transmission of a packet may be the length of packet plus one for the command byte, followed by the command byte for a message appended and finally the packet itself. 
     In addition to the command bytes that will be sent, an additional hardware line called the FlowControl line may be added to the traditional four SPI signals. The purpose of this line is to allow the protocol to run as quickly as possible without a need for preset delays. It also allows the slave processor to tell the master processor that it has a packet waiting to be sent, thus eliminating the need for the master processor to poll the slave processor for status. 
     The following exemplary command values may be used: 
     Commands to be Sent by the Master Processor: 
       
     
       
         
           
               
               
               
             
               
                   
               
               
                 Command 
                 Value 
                 Description 
               
               
                   
               
             
            
               
                 M_RTS 
                 0xC1 
                 Master is requesting to send a packet 
               
               
                 M_MSG_APPENDED 
                 0xC2 
                 Master is sending a packet 
               
               
                 M_CTS 
                 0xC3 
                 Master is tell slave it is Cleared to 
               
               
                   
                   
                 Send 
               
               
                 M_ERROR 
                 0xC4 
                 An Error condition has been  
               
               
                   
                   
                 encountered 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
               
               
                 Command 
                 Value 
                 Description 
               
               
                   
               
             
            
               
                 S_PREPARING_FOR_RX 
                 0xA1 
                 Slave is prepare the dma to receive  
               
               
                   
                   
                 a packet 
               
               
                 S_RX_BUFF_FULL 
                 0xA2 
                 Slave is currently out of RX  
               
               
                   
                   
                 buffers, retry later 
               
               
                 S_MSG_APPENDED 
                 0xA3 
                 Slave is sending a packet 
               
               
                 S_ERROR 
                 0xA4 
                 An Error condition has been  
               
               
                   
                   
                 encountered 
               
               
                   
               
            
           
         
       
     
     As illustrated in  FIG.  11 Q , when the slave processor has a packet to send to the master processor, the slave processor may notify the master processor (by asserting the FlowControl line) that it has a pending packet that is waiting to be sent. Doing so may result in an IRQ on the master processor at which time the master processor may decide when to go retrieve the message from the slave processor. Retrieving the packet may be delayed at the discretion of the master processor, and the master processor may even decide to attempt to send a packet to the slave processor before retrieving from the slave processor. 
     The master processor may begin the retrieval by sending the slave processor M_CTS commands; this shall be repeated until the slave processor responds by sending the S_MSG_APPENDED command along with the packet itself. The FlowControl line may be cleared after the packet has been sent. If a M_CTS command is received by the slave processor when one is not expected, the M_CTS command may be ignored. 
     As illustrated in  FIG.  11 R , when the master processor has a packet to send to the slave processor, the master processor may initiate the transfer by sending a M_RTS command. Upon receiving the M_RTS command, if the slave processor currently has a send packet pending, the slave processor will lower the FlowControl line so that it may be re-used as a Cleared To Send signal. The slave processor may then tell the master processor that it is in the process of preparing the SPI DMA to receive the packet, during which time the master processor may stop clocking bytes onto the bus and may allow the slave processor to finish preparing for the receive. 
     The slave processor may then indicate it is ready to receive the full packet by raising the FlowControl line (which is now used as the CTS signal). Upon receiving the CTS signal, the master processor may proceed to send the M_MSG_APPENDED command along with the packet itself. 
     After the completion of the transfer, the slave processor may lower the FlowControl line. If a packet was pending at the start of the transfer, or a send occurred on the slave processor when the packet was being received, the slave processor may reassert the FlowControl line now indicating that it has a pending packet. 
     Referring again to  FIG.  11 A , infusion pump assembly  100 ,  100 ′ may include switch assembly  318  coupled to electrical control assembly  110  ( FIG.  3   ) that may allow a user (not shown) to perform at least one, and in some embodiments, a plurality of tasks. One illustrative example of such a task is the administration of a bolus dose of the infusible fluid (e.g., insulin) without the use of a display assembly. Remote control assembly  300  may allow the user to enable/disable/configure infusion pump assembly  100 ,  100 ′ to administer the bolus dose of insulin. 
     Referring also to  FIG.  12 A , slider assembly  306  may be configured, at least in part, to enable the user to manipulate the menu-based information rendered on display assembly  302 . An example of slider assembly  306  may include a capacitive slider assembly, which may be implemented using a CY8C21434-24LFXI PSOC offered by Cypress Semiconductor of San Jose, Calif., the design an operation of which are described within the “CSD User Module” published by Cypress Semiconductor. For example, via slider assembly  306 , the user may slide their finger in the direction of arrow  314 , resulting in the highlighted portion of the information included within main menu  350  (shown in  FIG.  12 A ) rendered on display assembly  302  scrolling upward. Alternatively, the user may slide their finger in the direction of arrow  316 , resulting in the highlighted portion of the information included within main menu  350  rendered on display assembly  302  scrolling downward. 
     Slider assembly  306  may be configured so that the rate at which e.g. the highlighted portion of main menu  350  scrolls “upward” or “downward” varies depending upon the displacement of the finger of the user with respect to point of origin  320 . Therefore, if the user wishes to quickly scroll “upward”, the user may position their finger near the top of slider assembly  306 . Likewise, if the user wishes to quickly scroll “downward”, the user may position their finger near the bottom of slider assembly  306 . Additionally, if the user wishes to slowly scroll “upward”, the user may position their finger slightly “upward” with respect to point of origin  320 . Further, if the user wishes to slowly scroll “downward”, the user may position their finger slightly “downward” with respect to point of origin  320 . Once the appropriate menu item is highlighted, the user may select the highlighted menu item via one or more switch assemblies  308 ,  310 . 
     Referring also to  FIGS.  12 B- 12 F , assume for illustrative purposes that infusion pump assembly  100 ,  100 ′ is an insulin pump and the user wishes to configure infusion pump assembly  100 ,  100 ′ so that when switch assembly  318  is depressed by the user, a 0.20 unit bolus dose of insulin is administered. Accordingly, the user may use slider assembly  306  to highlight “Bolus” within main menu  350  rendered on display assembly  302 . The user may then use switch assembly  308  to select “Bolus”. Once selected, processing logic (not shown) within remote control assembly  300  may then render submenu  352  on display assembly  302  (as shown in  FIG.  12 B ). 
     The user may then use slider assembly  306  to highlight “Manual Bolus” within submenu  352 , which may be selected using switch assembly  308 . Processing logic (not shown) within remote control assembly  300  may then render submenu  354  on display assembly  302  (as shown in  FIG.  12 C ). 
     The user may then use slider assembly  306  to highlight “Bolus: 0.0 Units” within submenu  354 , which may be selected using switch assembly  308 . Processing logic (not shown) within remote control assembly  300  may then render submenu  356  on display assembly  302  (as shown in  FIG.  12 D ). 
     The user may then use slider assembly  306  to adjust the “Bolus” insulin amount to “0.20 units”, which may be selected using switch assembly  308 . Processing logic (not shown) within remote control assembly  300  may then render submenu  358  on display assembly  302  (as shown in  FIG.  12 E ). 
     The user  14  may then use slider assembly  306  to highlight “Confirm”, which may be selected using switch assembly  308 . Processing logic (not shown) within remote control assembly  300  may then generate the appropriate signals that may be sent to the above-described telemetry circuitry (not shown) included within remote control assembly  300 . The telemetry circuitry (not shown) included within the remote control assembly may then transmit, via wireless communication channel  312  established between remote control assembly  300  and infusion pump assembly  100 ′, the appropriate configuration commands to configure infusion pump assembly  100 ′ so that whenever switch assembly  318  is depressed by the user, a 0.20 unit bolus dose of insulin is administered. 
     Once the appropriate commands are successfully transmitted, processing logic (not shown) within remote control assembly  300  may once again render submenu  350  on display assembly  302  (as shown in  FIG.  12 F ). 
     Specifically and once programmed via remote control assembly  300 , the user may depress switch assembly  318  of infusion pump assembly  100 ′ to administer the above-described 0.20 unit bolus dose of insulin. Via the above-described menuing system included within remote control assembly  300 , the user may define a quantity of insulin to be administered each time that the user depresses switch assembly  318 . While this particular example specifies that a single depression of switch assembly  318  is equivalent to 0.20 units of insulin, this is for illustrative purposes only and is not intended to be a limitation of this disclosure, as other values (e.g. 1.00 units of insulin per depression) are equally applicable. 
     Assume for illustrative purposes that the user wishes to administer a 2.00 unit bolus dose of insulin. To activate the above-describe bolus dose administration system, the user may be required to press and hold switch assembly  318  for a defined period of time (e.g. five seconds), at which point infusion pump assembly  100 ,  100 ′ may generate an audible signal indicating to the user that infusion pump assembly  100 ,  100 ′ is ready to administer a bolus does of insulin via switch assembly  318 . Accordingly, the user may depress switch assembly  318  ten times (i.e., 2.00 units is ten 0.20 unit doses). After each time that switch assembly  318  is depressed, infusion pump assembly  100 ,  100 ′ may provide on audible response to the user via an internal speaker/sound generation device (not shown). Accordingly, the user may depress switch assembly  318  the first time and infusion pump assembly  100 ,  100 ′ may generate a confirmation beep in response, thus indicating to the user that infusion pump assembly  100 ,  100 ′ received the command for (in this particular example) 0.20 units of insulin. As the desired bolus dose is 2.00 units of insulin, the user may repeat this procedure nine more times in order to effectuate a bolus dose of 2.00 units, wherein infusion pump assembly  100 ,  100 ′ generates a confirmation beep after each depression of switch assembly  318 . 
     While in this particular example, infusion pump assemblies  100 ,  100 ′ are described as providing one beep after each time the user depresses switch assembly  318 , this is for illustrative purposes only and is not intended to be a limitation of this disclosure. Specifically, infusion pump assembly  100 ,  100 ′ may be configured to provide a single beep for each defined quantity of insulin. As discussed above, a single depression of switch assembly  318  may be equivalent to 0.20 units of insulin. Accordingly, infusion pump assembly  100 ,  100 ′ may be configured to provide a single beep for each 0.10 units of insulin. Accordingly, if infusion pump assembly  100 ,  100 ′ is configured such that a single depression of switch assembly  318  is equivalent to 0.20 units of insulin, each time switch assembly  318  is depressed, infusion pump assembly  100 ,  100 ′ may provide the user with two beeps (i.e. one for each 0.10 units of insulin). 
     Once the user has depressed switch assembly  318  on infusion pump assembly  100 ′ a total of ten times, the user may simply wait for infusion pump assembly  100 ,  100 ′ to acknowledge receipt of the instructions to administer a 2.00 unit bolus dose of insulin (as opposed to the confirmation beep received at each depression of switch assembly  318 ). Once a defined period of time (e.g., two seconds) passes, infusion pump assembly  100 ,  100 ′ may provide an audible confirmation to the user concerning the quantity of units to be administered via the bolus insulin dose that the user just requested. For example, as (in this example) infusion pump assembly  100 ,  100 ′ was programmed by the user so that a single depression of switch assembly  318  is equivalent to 0.20 units of insulin, infusion pump assembly  100 ,  100 ′ may beep ten times (i.e., 2.00 units is ten 0.20 unit doses). 
     When providing feedback to the user concerning the quantity of units to be administered via the bolus insulin dose, infusion pump assembly  100 ,  100 ′ may provide a multifrequency audible confirmation. For example and continuing with the above-stated example in which ten beeps are to be provided to the user, infusion pump assembly  100 ,  100 ′ may group the beeps into groups of five (to facilitate easier counting by the user) and the beeps within each group of five may be rendered by infusion pump assembly  100 ,  100 ′ so that each subsequent beep has a higher frequency than the preceding beep (in a manner similar to a musical scale). Accordingly and continuing with the above-stated example, infusion pump assembly  100 ,  100 ′ may render a 1,000 Hz beep, followed by an 1,100 Hz beep, followed by a 1,200 Hz beep, followed by a 1,300 Hz beep, followed by a 1,400 Hz beep (thus completing a group of five beeps), followed by a short pause, and then a 1,000 Hz beep, followed by an 1,100 Hz beep, followed by a 1,200 Hz beep, followed by a 1,300 Hz beep, followed by a 1,400 Hz beep (thus completing the second group of five beeps). According to various additional/alternative embodiments the multifrequency audible confirmation may utilize various numbers of tones incrementing in frequency. For example, an embodiment may utilize twenty different tones incrementing in frequency. However, the number of tones should not be construed as a limitation of the present disclosure as number of tones may vary according to design criteria and user need. 
     Once infusion pump assembly  100 ,  100 ′ completes the rendering of the multifrequency audible confirmation (i.e. the ten beeps described above), the user may, within a defined period of time (e.g. two seconds), depress switch assembly  318  to provide a confirmation signal to infusion pump assembly  100 ,  100 ′, indicating that the multifrequency audible confirmation was accurate and indicative of the size of the bolus dose of insulin to be administered (i.e. 2.00 units). Upon receiving this confirmation signal, infusion pump assembly  100 ,  100 ′ may render a “confirmation received” audible tone and effectuate the delivery of (in this particular example) the 2.00 unit bolus dose of insulin. In the event that infusion pump assembly  100 ,  100 ′ fails to receive the above-described confirmation signal, infusion pump assembly  100 ,  100 ′ may render a “confirmation failed” audible tone and will not effectuate the delivery of the bolus dose of insulin. Accordingly, if the multifrequency audible confirmation was not accurate/indicative of the size of the bolus dose of insulin to be administered, the user may simply not provide the above-described confirmation signal, thereby canceling the delivery of the bolus dose of insulin. 
     As discussed above, in one exemplary embodiment of the above-described infusion pump assembly, infusion pump assembly  100 ′ may be used to communicate with a remote control assembly  300 . When such a remote control assembly  300  is utilized, infusion pump assembly  100 ′ and remote control assembly  300  may routinely contact each other to ensure that the two devices are still in communication with each other. For example, infusion pump assembly  100 ′ may “ping” remote control assembly  300  to ensure that remote control assembly  300  is present and active. Further, remote control assembly  300  may “ping” infusion pump assembly  100 ′ to ensure that infusion pump assembly  100 ′ is still present and active. In the event that one of infusion pump assembly  100 ′ and remote control assembly  300  fails to establish communication with the other assembly, the assembly that is unable to establish communication may sound a “separation” alarm. For example, assume that remote control assembly  300  is left in the car of the user, while infusion pump assembly  100 ′ is in the pocket of the user. Accordingly and after a defined period of time, infusion pump assembly  100 ′ may begin sounding the “separation” alarm, indicating that communication with remote control assembly  300  cannot be established. Using switch assembly  318 , the user may acknowledge/silence this “separation” alarm. 
     As the user may define and administer a bolus insulin dose via switch assembly  318  of infusion pump assembly  100 ′ while remote control assembly  300  is not in communication with infusion pump assembly  100 ′, infusion pump assembly  100 ′ may store information concerning the administered bolus insulin dose within a log file (not shown) stored within infusion pump assembly  100 ′. This log file (not shown) may be stored within nonvolatile memory (not shown) included within infusion pump assembly  100 ′. Upon communication being reestablished between infusion pump assembly  100 ′ and remote control assembly  300 , infusion pump assembly  100 ′ may provide the information concerning the administered bolus insulin dose stored within the log file (not shown) of infusion pump assembly  100 ′ to remote control assembly  300 . 
     Further, if the user anticipates separating remote control assembly  300  from infusion pump assembly  100 ′, the user (via the above-described menuing system) may configure infusion pump assembly  100 ′ and remote control assembly  300  to be in “separation” mode, thus eliminating the occurrence of the above-described “separation” alarms. However, the devices may continue to “ping” each other so that when they come back into communication with each other, infusion pump assembly  100 ′ and remote control assembly  300  may automatically exit “separation” mode. 
     Further, if the user anticipates traveling in an airplane, the user (via the above-described menuing system of remote control assembly  300 ) may configure infusion pump assembly  100 ′ and remote control assembly  300  to be in “airplane” mode, in which each of infusion pump assembly  100 ′ and remote control assembly  300  suspend any and all data transmissions. While in “airplane” mode, infusion pump assembly  100 ′ and remote control assembly  300  may or may not continue to receive data. 
     Switch assembly  318  may be used to perform additional functions, such as: checking the battery life of reusable housing assembly  102 ; pairing reusable housing assembly  102  with remote control assembly  300 ; and aborting the administration of a bolus does of infusible fluid. 
     Checking Battery Life: Reusable housing assembly  102  may include a rechargeable battery assembly that may be capable of powering infusion pump assembly  100 ,  100 ′ for approximately three days (when fully charged). Such a rechargeable battery assembly may have a usable life of a predetermined number of usable hours, for example, or years, or other predetermined length of usage. However, the predetermined life may depend on many factors, including but not limited to, one or more of the following: climate, daily usage, and number of recharges. Whenever reusable housing assembly  102  is disconnected from disposable housing assembly  114 , infusion pump assembly  100 ,  100 ′ may perform a battery check on the above-described rechargeable battery assembly whenever switch assembly  318  is depressed for a defined period of time (e.g. in excess of two seconds). In the event that the above-described rechargeable battery assembly is determined to be charged above a desired threshold, infusion pump assembly  100 ,  100 ′ may render a “battery pass” tone. Alternatively, in the event that the above-described rechargeable battery assembly is determined to be charged below a desired threshold, infusion pump assembly  100 ,  100 ′ may render a “battery fail” tone. Infusion pump assembly  100 ,  100 ′ may include components and/or circuitry to determine whether reusable housing assembly  102  is disconnected from disposable housing assembly  114 . 
     Pairing: As discussed above and in one exemplary embodiment of the above-described infusion pump assembly, infusion pump assembly  100 ′ may be used to communicate with remote control assembly  300 . In order to effectuate communication between infusion pump assembly  100 ′ and remote control assembly  300 , a paring process may be performed. During such a pairing process, one or more infusion pump assemblies (e.g. infusion pump assembly  100 ′) may be configured to communicate with remote control assembly  300  and (conversely) remote control assembly  300  may be configured to communicate with one or more infusion pump assemblies (e.g. infusion pump assembly  100 ′). Specifically, the serial numbers of the infusion pump assemblies (e.g. infusion pump assembly  100 ′) may be recorded within a pairing file (not shown) included within remote control assembly  300  and the serial number of remote control assembly  300  may be recorded within a pairing file (not shown) included within the infusion pump assemblies (e.g. infusion pump assembly  100 ′). 
     According to an embodiment, in order to effectuate such a pairing procedure, the user may simultaneously hold down one or more switch assemblies on both remote control assembly  300  and infusion pump assembly  100 ′. For example, the user may simultaneously hold down switch assembly  310  included within remote control assembly  300  and switch assembly  318  included within infusion pump assembly  100 ′ for a defined period exceeding e.g. five seconds. Once this defined period is reached, one or more of remote control assembly  300  and infusion pump assembly  100 ′ may generate an audible signal indicating that the above-described pairing procedure has been effectuated. 
     According to another embodiment, prior to performing the pairing process, the user may uncouple reusable housing assembly  102  from disposable housing assembly  114 . By requiring this initial step, further assurance is provided that an infusion pump assembly being worn by a user may not be surreptitiously paired with a remote control assembly. 
     Once uncoupled, the user may enter pairing mode via input assembly  304  of remote control assembly  300 . For example, the user may enter pairing mode on remote control assembly  300  via the above-described menuing system in combination with e.g., switch assembly  310 . The user may be prompted on display assembly  302  of remote control assembly  300  to depress and hold switch assembly  318  on infusion pump assembly  100 ′. Additionally, remote control assembly  304  may switch to a low power mode to e.g., avoid trying to pair with distant infusion pump assemblies. The user may then depress and hold switch assembly  318  on infusion pump assembly  100 ′ so that infusion pump assembly  100 ′ enters a receive mode and waits for a pairing command from remote control assembly  300 . 
     Remote control assembly  300  may then transmit a pairing request to infusion pump assembly  100 ′, which may be acknowledged by infusion pump assembly  100 ′. Infusion pump assembly  100 ′ may perform a security check on the pairing request received from remote control assembly  300  and (if the security check passes) infusion pump assembly  100 ′ may activate a pump pairing signal (i.e., enter active pairing mode). Remote control assembly  300  may perform a security check on the acknowledgment received from infusion pump assembly  100 ′. 
     The acknowledgment received from infusion pump assembly  100 ′ may define the serial number of infusion pump assembly  100 ′ and remote control assembly  300  may display that serial number on display assembly  302  of remote control assembly  300 . The user may be asked if they wish to pair with the pump found. If the user declines, the pairing process may be aborted. If the user agrees to the pairing process, remote control assembly  300  may prompt the user (via display assembly  302 ) to depress and hold switch assembly  318  on infusion pump assembly  100 ′. 
     The user may then depress and hold switch assembly  318  on infusion pump assembly  100 ′ and depress and hold e.g. switch assembly  310  on remote control assembly  300 . 
     Remote control assembly  300  may confirm that remote switch assembly  310  was held (which may be reported to infusion pump assembly  100 ′). Infusion pump assembly  100 ′ may perform a security check on the confirmation received from remote control assembly  300  to confirm the integrity of same. If the integrity of the confirmation received is not verified, the pairing process is aborted. If the integrity of the confirmation received is verified, any existing remote pair configuration file is overwritten to reflect newly-paired remote control assembly  300 , the pump pairing completed signal is activated, and the pairing process is completed. 
     Additionally, infusion pump assembly  100 ′ may confirm that switch assembly  318  was held (which may be reported to remote control assembly  300 ). Remote control assembly  300  may perform a security check on the confirmation received from infusion pump assembly  100 ′ to confirm the integrity of same. If the integrity of the confirmation received is not verified, the pairing process is aborted. If the integrity of the confirmation received is verified, a pair list file within remote control assembly  300  may be modified to add infusion pump assembly  100 ′. Typically, remote control assembly  300  may be capable of pairing with multiple infusion pump assemblies, while infusion pump assembly  100 ′ may be capable of only pairing with a single remote control assembly. The pairing completed signal may be activated and the pairing process may be completed. 
     When the pairing process is completed, one or more of remote control assembly  300  and infusion pump assembly  100 ′ may generate an audible signal indicating that the above-described pairing procedure has been successfully effectuated. 
     Aborting Bolus Dose: in the event that the user wishes to cancel a bolus dose of e.g. insulin being administered by infusion pump assembly  100 ′, the user may depress switch assembly  318  (e.g., shown in  FIGS.  1  &amp;  2   ) for a defined period exceeding e.g. five seconds. Once this defined period is reached, infusion pump assembly  100 ′ may render an audible signal indicating that the above-described cancellation procedure has been effectuated. 
     While switch assembly  318  is shown as being positioned on the top of infusion pump assembly  100 ,  100 ′, this is for illustrative purposes only and is not intended to be a limitation of this disclosure, as other configurations are possible. For example, switch assembly  318  may be positioned about the periphery of infusion pump assembly  100 ,  100 ′. 
     Referring also to  FIGS.  13 - 15   , there is shown an alternative-embodiment infusion pump assembly  400 . As with pump assembly  100 ,  100 ′, infusion pump assembly  400  may include reusable housing assembly  402  and disposable housing assembly  404 . 
     In a fashion similar to reusable housing assembly  102 , reusable housing assembly  402  may include a mechanical control assembly (that includes at least one pump assembly and at least one valve assembly). Reusable housing assembly  402  may also include an electrical control assembly that is configured to provide control signals to the mechanical control assembly and effectuate the delivery of an infusible fluid to a user. The valve assembly may be configured to control the flow of the infusible fluid through a fluid path and the pump assembly may be configured to pump the infusible fluid from the fluid path to the user 
     In a fashion similar to disposable housing assembly  114 , disposable housing assembly  404  may be configured for a single use or for use for a specified period of time, e.g., e.g., three days or any other amount of time. Disposable housing assembly  404  may be configured such that any components in infusion pump assembly  400  that come in contact with the infusible fluid are disposed on and/or within disposable housing assembly  404 . 
     In this particular embodiment of the infusion pump assembly, infusion pump assembly  400  may include switch assembly  406  positioned about the periphery of infusion pump assembly  400 . For example, switch assembly  406  may be positioned along a radial edge of infusion pump assembly  400 , which may allow for easier use by a user. Switch assembly  406  may be covered with a waterproof membrane configured to prevent the infiltration of water into infusion pump assembly  400 . Reusable housing assembly  402  may include main body portion  408  (housing the above-described mechanical and electrical control assemblies) and locking ring assembly  410  that may be configured to rotate about main body portion  408  (in the direction of arrow  412 ). 
     In a fashion similar to reusable housing assembly  102  and disposable housing assembly  114 , reusable housing assembly  402  may be configured to releasably engage disposable housing assembly  404 . Such releasable engagement may be accomplished by a screw-on, a twist-lock or a compression fit configuration, for example. In an embodiment in which a twist-lock configuration is utilized, the user of infusion pump assembly  400  may first properly position reusable housing assembly  402  with respect to disposable housing assembly  404  and may then rotate locking ring assembly  410  (in the direction of arrow  412 ) to releasably engage reusable housing assembly  402  with disposable housing assembly  404 . 
     Through the use of locking ring assembly  410 , reusable housing assembly  402  may be properly positioned with respect to disposable housing assembly  404  and then releasably engaged by rotating locking ring assembly  410 , thus eliminating the need to rotate reusable housing assembly  402  with respect to disposable housing assembly  404 . Accordingly, reusable housing assembly  402  may be properly aligned with disposable housing assembly  404  prior to engagement, and such alignment may not be disturbed during the engagement process. Locking ring assembly  410  may include a latching mechanism (not shown) that may prevent the rotation of locking ring assembly  410  until reusable housing assembly  402  and disposable housing assembly  404  are properly positioned with respect to each other. 
     Referring also to  FIGS.  16 - 18   , there is shown an alternative-embodiment infusion pump assembly  500 . As with pump assembly  100 ,  100 ′, infusion pump assembly  500  may include reusable housing assembly  502  and disposable housing assembly  504 . 
     In a fashion similar to reusable housing assembly  402 , reusable housing assembly  502  may include a mechanical control assembly (that includes at least one pump assembly and at least one valve assembly). Reusable housing assembly  502  may also include an electrical control assembly that is configured to provide control signals to the mechanical control assembly and effectuate the delivery of an infusible fluid to a user. The valve assembly may be configured to control the flow of the infusible fluid through a fluid path and the pump assembly may be configured to pump the infusible fluid from the fluid path to the user 
     In a fashion similar to disposable housing assembly  404 , disposable housing assembly  504  may be configured for a single use or for use for a specified period of time, e.g., e.g., three days or any other amount of time. Disposable housing assembly  504  may be configured such that any components in infusion pump assembly  500  that come in contact with the infusible fluid are disposed on and/or within disposable housing assembly  504 . 
     In this particular embodiment of the infusion pump assembly, infusion pump assembly  500  may include switch assembly  506  positioned about the periphery of infusion pump assembly  500 . For example, switch assembly  506  may be positioned along a radial edge of infusion pump assembly  500 , which may allow for easier use by a user. Switch assembly  506  may be covered with a waterproof membrane and/or an o-ring or other sealing mechanism may be included on the stem  507  of the switch assembly  506  configured to prevent the infiltration of water into infusion pump assembly  500 . However, in some embodiments, switch assembly  506  may include an overmolded rubber button, thus providing functionality as a waterproof seal without the use of a waterproof membrane or an o-ring. However, in still other embodiments, the overmolded rubber button may additionally be covered by a waterproof membrane and/or include an o-ring. Reusable housing assembly  502  may include main body portion  508  (housing the above-described mechanical and electrical control assemblies) and locking ring assembly  510  that may be configured to rotate about main body portion  508  (in the direction of arrow  512 ). 
     In a fashion similar to reusable housing assembly  402  and disposable housing assembly  404 , reusable housing assembly  502  may be configured to releasably engage disposable housing assembly  504 . Such releasable engagement may be accomplished by a screw-on, a twist-lock or a compression fit configuration, for example. In an embodiment in which a twist-lock configuration is utilized, the user of infusion pump assembly  500  may first properly position reusable housing assembly  502  with respect to disposable housing assembly  504  and may then rotate locking ring assembly  510  (in the direction of arrow  512 ) to releasably engage reusable housing assembly  502  with disposable housing assembly  404 . 
     As locking ring assembly  510  included within infusion pump assembly  500  may be taller (i.e., as indicated by arrow  514 ) than locking ring assembly  410 , locking ring assembly  510  may include a passage  516  through which button  506  may pass. Accordingly, when assembling reusable housing assembly  502 , locking ring assembly  510  may be installed onto main body portion  508  (in the direction of arrow  518 ). Once locking ring assembly  510  is installed onto main body portion  508 , one or more locking tabs (not shown) may prevent locking ring assembly  510  from being removed from main body portion  508 . The portion of switch assembly  506  that protrudes through passage  516  may then be pressed into main body portion  508  (in the direction of arrow  520 ), thus completing the installation of switch assembly  506 . 
     Although button  506  is shown in various locations on infusion pump assembly  500 , button  506 , in other embodiments, may be located anywhere desirable on infusion pump assembly  500 . 
     Through the use of locking ring assembly  510 , reusable housing assembly  502  may be properly positioned with respect to disposable housing assembly  504  and then releasably engaged by rotating locking ring assembly  510 , thus eliminating the need to rotate reusable housing assembly  502  with respect to disposable housing assembly  504 . Accordingly, reusable housing assembly  502  may be properly aligned with disposable housing assembly  504  prior to engagement, and such alignment may not be disturbed during the engagement process. Locking ring assembly  510  may include a latching mechanism (not shown) that prevents the rotation of locking ring assembly  510  until reusable housing assembly  502  and disposable housing assembly  504  are properly positioned with respect to each other. Passage  516  may be elongated to allow for the movement of locking ring  510  about switch assembly  506 . 
     Referring also to  FIGS.  19 A- 19 B &amp;  20 - 21   , there are shown various views of infusion pump assembly  500 , which is shown to include reusable housing assembly  502 , switch assembly  506 , and main body portion  508 . As discussed above, main body portion  508  may include a plurality of components, examples of which may include but are not limited to volume sensor assembly  148 , printed circuit board  600 , vibration motor assembly  602 , shape memory actuator anchor  604 , switch assembly  506 , battery  606 , antenna assembly  608 , pump assembly  106 , measurement valve assembly  610 , volume sensor valve assembly  612  and reservoir valve assembly  614 . To enhance clarity, printed circuit board  600  has been removed from  FIG.  19 B  to allow for viewing of the various components positioned beneath printed circuit board  600 . 
     The various electrical components that may be electrically coupled with printed circuit board  600  may utilize spring-biased terminals that allow for electrical coupling without the need for soldering the connections. For example, vibration motor assembly  602  may utilize a pair of spring-biased terminals (one positive terminal and one negative terminal) that are configured to press against corresponding conductive pads on printed circuit board  600  when vibration motor assembly  602  is positioned on printed circuit board  600 . However, in the exemplary embodiment, vibration motor assembly  602  is soldered directly to the printed circuit board. 
     As discussed above, volume sensor assembly  148  may be configured to monitor the amount of fluid infused by infusion pump assembly  500 . For example, volume sensor assembly  148  may employ acoustic volume sensing, which is the subject of U.S. Pat. Nos. 5,575,310 and 5,755,683 assigned to DEKA Products Limited Partnership, as well as the U.S. Patent Application Publication Nos. US 2007/0228071 A1, US 2007/0219496 A1, US 2007/0219480 A1, US 2007/0219597 A1, the entire disclosures of all of which are incorporated herein by reference. 
     Vibration motor assembly  602  may be configured to provide a vibration-based signal to the user of infusion pump assembly  500 . For example, in the event that the voltage of battery  606  (which powers infusion pump assembly  500 ) is below the minimum acceptable voltage, vibration motor assembly  602  may vibrate infusion pump assembly  500  to provide a vibration-based signal to the user of infusion pump assembly  500 . Shape memory actuator anchor  604  may provide a mounting point for the above-described shape memory actuator (e.g. shape memory actuator  112 ). As discussed above, shape memory actuator  112  may be, for example, a conductive shape-memory alloy wire that changes shape with temperature. The temperature of shape-memory actuator  112  may be changed with a heater, or more conveniently, by application of electrical energy. Accordingly, one end of shape memory actuator  112  may be rigidly affixed (i.e., anchored) to shape memory actuator anchor  604  and the other end of shape memory actuator  112  may be applied to e.g. a valve assembly and/or a pump actuator. Therefore, by applying electrical energy to shape memory actuator  112 , the length of shape memory actuator  112  may be controlled and, therefore, the valve assembly and/or the pump actuator to which it is attached may be manipulated. 
     Antenna assembly  608  may be configured to allow for wireless communication between e.g. infusion pump assembly  500  and remote control assembly  300  ( FIG.  11   ). As discussed above, remote control assembly  300  may allow the user to program infusion pump assembly  500  and e.g. configure bolus infusion events. As discussed above, infusion pump assembly  500  may include one or more valve assemblies configured to control the flow of the infusible fluid through a fluid path (within infusion pump assembly  500 ) and pump assembly  106  may be configured to pump the infusible fluid from the fluid path to the user. In this particular embodiment of infusion pump assembly  500 , infusion pump assembly  500  is shown to include three valve assemblies, namely measurement valve assembly  610 , volume sensor valve assembly  612 , and reservoir valve assembly  614 . 
     As discussed above and referring also to  FIG.  21   , the infusible fluid may be stored within reservoir  118 . In order to effectuate the delivery of the infusible fluid to the user, the processing logic (not shown) included within infusion pump assembly  500  may energize shape memory actuator  112 , which may be anchored on one end using shape memory actuator anchor  604 . Referring also to  FIG.  22 A , shape memory actuator  112  may result in the activation of pump assembly  106  and reservoir valve assembly  614 . Reservoir valve assembly  614  may include reservoir valve actuator  614 A and reservoir valve  614 B, and the activation of reservoir valve assembly  614  may result in the downward displacement of reservoir valve actuator  614 A and the closing of reservoir valve  614 B, resulting in the effective isolation of reservoir  118 . Further, pump assembly  106  may include pump plunger  106 A and pump chamber  106 B and the activation of pump assembly  106  may result in pump plunger  106 A being displaced in a downward fashion into pump chamber  106 B and the displacement of the infusible fluid (in the direction of arrow  616 ). 
     Volume sensor valve assembly  612  may include volume sensor valve actuator  612 A and volume sensor valve  612 B. Referring also to  FIG.  22 B , volume sensor valve actuator  612 A may be closed via a spring assembly that provides mechanical force to seal volume sensor valve  612 B. However, when pump assembly  106  is activated, if the displaced infusible fluid is of sufficient pressure to overcome the mechanical sealing force of volume sensor valve assembly  612 , the displacement of the infusible fluid occurs in the direction of arrow  618 . This may result in the filling of volume sensor chamber  620  included within volume sensor assembly  148 . Through the use of speaker assembly  622 , port assembly  624 , reference microphone  626 , spring diaphragm  628 , invariable volume microphone  630 , volume sensor assembly  148  may determine the volume of infusible fluid included within volume sensor chamber  620 . 
     Referring also to  FIG.  22 C , once the volume of infusible fluid included within volume sensor chamber  620  is calculated, shape memory actuator  632  may be energized, resulting in the activation of measurement valve assembly  610 , which may include measurement valve actuator  610 A and measurement valve  610 B. Once activated and due to the mechanical energy asserted on the infusible fluid within volume sensor chamber  620  by spring diaphragm  628 , the infusible fluid within volume sensor chamber  620  may be displaced (in the direction of arrow  634 ) through disposable cannula  138  and into the body of the user. 
     Referring also to  FIG.  23   , there is shown an exploded view of infusion pump assembly  500 . Shape memory actuator  632  may be anchored (on a first end) to shape memory actuator anchor  636 . Additionally, the other end of shape memory actuator  632  may be used to provide mechanical energy to valve assembly  638 , which may activate measurement valve assembly  610 . Volume sensor assembly spring retainer  642  may properly position volume sensor assembly  148  with respect to the various other components of infusion pump assembly  500 . Valve assembly  638  may be used in conjunction with shape memory actuator  112  to activate pump plunger  106 A. Measurement valve  610 B, volume sensor valve  612 B and/or reservoir valve  614 B may be self-contained valves that are configured to allow for installation during assembly of infusion pump assembly  500  by pressing the valves upward into the lower surface of main body portion  508 . 
     Referring also to  FIG.  24    &amp;  FIGS.  25 A- 25 D , there is shown a more-detailed view of pump assembly  106 . Pump actuator assembly  644  may include pump actuator support structure  646 , bias spring  648 , and lever assembly  650 . 
     Referring also to  FIGS.  26 A- 26 B  &amp;  FIGS.  27 A- 27 B , there is shown a more-detailed view of measurement valve assembly  610 . As discussed above, valve assembly  638  may activate measurement valve assembly  610 . 
     Referring also to  FIGS.  28 A- 28 D , infusion pump assembly  500  may include measurement valve assembly  610 . As discussed above, valve assembly  638  may be activated via shape memory actuator  632  and actuator assembly  640 . Accordingly, to infuse the quantity of infusible fluid stored within volume sensor chamber  620 , shape memory actuator  632  may need to activate valve assembly  638  for a considerable period of time (e.g. one minute or more). As this would consume a considerable amount of power from battery  606 , measurement valve assembly  610  may allow for the temporary activation of valve assembly  638 , at which point measurement valve latch  656  may prevent valve assembly  638  from returning to its non-activated position. Shape memory actuator  652  may be anchored on a first end using electrical contact  654 . The other end of shape memory actuator  652  may be connected to a valve latch  656 . When shape memory actuator  652  is activated, shape memory actuator  652  may pull valve latch  656  forward and release valve assembly  638 . As such, measurement valve assembly  610  may be activated via shape memory actuator  632 . Once measurement valve assembly  610  has been activated, valve latch  656  may automatically latch valve assembly  638  in the activated position. Actuating shape memory actuator  652  may pull valve latch  656  forward and release valve assembly  638 . Assuming shape memory actuator  632  is no longer activated, measurement valve assembly  610  may move to a de-activated state once valve latch  656  has released valve assembly  638 . Accordingly, through the use of measurement valve assembly  610 , shape memory actuator  632  does not need to be activated during the entire time that it takes to infuse the quantity of infusible fluid stored within volume sensor chamber  620 . 
     As discussed above, the above-described infusion pump assemblies (e.g., infusion pumps assemblies  100 ,  100 ′,  400 ,  500 ) may include an external infusion set  134  configured to deliver the infusible fluid to a user. External infusion set  134  may include a cannula assembly  136 , which may include a needle or a disposable cannula  138 , and tubing assembly  140  which may be also referred to as a tubing set. Tubing assembly  140  may be in fluid communication with reservoir  118 , for example, by way of the fluid path, and with cannula assembly  138  for example, either directly or by way of a cannula interface  142 . 
     Referring also to  FIG.  29   , there is shown an alternative embodiment infusion pump assembly  700  that is configured to store a portion of tubing assembly  140 . Specifically, infusion pump assembly  700  may include peripheral tubing storage assembly  702  that is configured to allow the user to wind a portion of tubing assembly  140  about the periphery of infusion pump assembly  700  (in a manner similar to that of a yoyo). Peripheral tubing storage assembly  702  may be positioned about the periphery of infusion pump assembly  700 . Peripheral tubing storage assembly  702  may be configured as an open trough into which a portion of tubing assembly  140  may be wound. Alternatively, peripheral tubing storage assembly  702  may include one or more divider portions  704 ,  706  that form a plurality of narrower troughs that may be sized to generate an interference fit between the walls of the narrower trough and the exterior surface of the portion of tubing  140 . When peripheral tubing storage assembly  705  includes plurality of divider portions  704 ,  706 , the resulting narrower troughs may be wound in a spiral fashion about the periphery of infusion pump assembly  700  (in a manner similar to the thread of a screw). 
     Referring also to  FIGS.  30 - 31   , there is shown an alternative embodiment infusion pump assembly  750  that is configured to store a portion of tubing assembly  140 . Specifically, infusion pump assembly  750  may include peripheral tubing storage assembly  752  that is configured to allow the user to wind a portion of tubing assembly  140  about the periphery of infusion pump assembly  750  (again, in a manner similar to that of a yoyo). Peripheral tubing storage assembly  752  may be positioned about the periphery of infusion pump assembly  750 . Peripheral tubing storage assembly  752  may be configured as an open trough into which a portion of tubing assembly  140  is wound. Alternatively, peripheral tubing storage assembly  752  may include one or more divider portions  754 ,  756  that form a plurality of narrower troughs that may be sized to generate an interference fit between the walls of the narrower trough and the exterior surface of the portion of tubing  140 . When peripheral tubing storage assembly  752  includes plurality of divider portions  754 ,  756 , the resulting narrower trough may be wound in a spiral fashion about the periphery of infusion pump assembly  750  (again, in a manner similar to the thread of a screw). 
     Infusion pump assembly  750  may include tubing retainer assembly  758 . Tubing retainer assembly  758  may be configured to releasably secure tubing assembly  140  so as to prevent tubing assembly  140  from unraveling from around infusion pump assembly  750 . In one embodiment of tubing retainer assembly  758 , tubing retainer assembly  758  may include downward facing pin assembly  760  positioned above upward facing pin assembly  762 . The combination of pin assemblies  760 ,  762  may define a “pinch point” through which tubing assembly  140  may be pushed. Accordingly, the user may wrap tubing assembly  140  around the periphery of infusion pump assembly  750 , wherein each loop of tubing assembly  140  is secured within peripheral tubing storage assembly  752  via tubing retainer assembly  758 . In the event that the user wishes to lengthen the unsecured portion of tubing assembly  140 , the user may release one loop of tubing assembly  140  from tubing retainer assembly  758 . Conversely, in the event that the user wishes to shorten the unsecured portion of tubing assembly  140 , the user may secure one additional loop of tubing assembly  140  within tubing retainer assembly  758 . 
     Referring also to  FIGS.  32 - 33   , there is shown an exemplary embodiment of infusion pump assembly  800 . As with infusion pump assemblies  100 ,  100 ′,  400 , and  500 , infusion pump assembly  800  may include reusable housing assembly  802  and disposable housing assembly  804 . 
     With reference also to  FIGS.  34 A- 34 B , in a fashion similar to infusion pump assembly  100 , reusable housing assembly  802  may be configured to releasably engage disposable housing assembly  804 . Such releasable engagement may be effectuated by a screw-on, twist-lock, or compression fit configuration, for example. Infusion pump assembly  800  may include locking ring assembly  806 . For example, reusable housing assembly  802  may be properly positioned relative to disposable housing assembly, and locking ring assembly  806  may be rotated to releasable engage reusable housing assembly  802  and disposable housing assembly  804 . 
     Locking ring assembly  806  may include nub  808 , having a spring actuated tab  2980 , that may facilitate rotation of locking ring assembly  806 . Additionally, the position of nub  808 , e.g., relative to tab  810  of disposable housing assembly  804 , may provide verification that reusable housing assembly  802  is fully engaged with disposable housing assembly  804 . For example, as shown in  FIG.  34 A , when reusable housing assembly  802  is properly aligned with disposable housing assembly  804 , nub  808  may be aligned in a first position relative to tab  810 . Upon achieving a fully engaged condition, by rotation locking ring assembly  806 , nub  808  may be aligned in a second position relative to tab  810 , as shown in  FIG.  34 B . 
     Referring also to  FIGS.  35 A- 35 C  and  FIGS.  36 - 38 A , in a fashion similar to reusable housing assembly  102 , reusable housing assembly  802  may include mechanical control assembly  812  (e.g., which may include valve assembly  814 , shown in  FIG.  36   , including one or more valves and one or more pumps for pumping and controlling the flow of the infusible fluid). Reusable housing assembly  802  may also include an electrical control assembly  816  that may be configured to provide control signals to the mechanical control assembly  812  to effectuate the delivery of an infusible fluid to the user. Valve assembly  814  may be configured to control the flow of the infusible fluid through a fluid path and the pump assembly may be configured to pump the infusible fluid from the fluid path to the user. 
     Mechanical control assembly  812  and electrical control assembly  816  may be contained within a housing defined by base plate  818 , body  820 . In some embodiments one or more of base plate  818  and body  820  may provide electromagnetic shielding. In such an embodiment, the electromagnetic shielding may prevent and/or reduce electromagnetic interference received by electrical control assembly  816  and/or created by electrical control assembly  816 . Additionally/alternatively, EMI shield  822  may be included, as shown in  FIG.  36    and  FIG.  37   . EMI shield  822  may provide shielding against generated and/or received electromagnetic interference. 
     Reusable housing assembly  802  may include a switch assembly that may be configured to receive user commands (e.g., for bolus delivery, pairing with a remote control assembly, or the like). The switch assembly may include button  824  that may be disposed in opening  826  of body  820 . As shown, e.g., in  FIG.  35 B , locking ring assembly  806  may include radial slot  828  that may be configured to allow locking ring assembly  806  to be rotated relative to body  820  while still providing facile access to button  824 . 
     Referring also to  FIGS.  39 A- 39 C , electrical control assembly  816  may include printed circuit board  830  as well as battery  832 . Printed circuit board  830  may include the various control electronics for monitoring and controlling the amount of infusible fluid that has been and/or is being pumped. For example, electrical control assembly  816  may measure the amount of infusible fluid that has just been dispensed, and determine, based upon the dosage required by the user, whether enough infusible fluid has been dispensed. If not enough infusible fluid has been dispensed, electrical control assembly  816  may determine that more infusible fluid should be pumped. Electrical control assembly  816  may provide the appropriate signal to mechanical control assembly  812  so that any additional necessary dosage may be pumped or electrical control assembly  816  may provide the appropriate signal to mechanical control assembly  812  so that the additional dosage may be dispensed with the next dosage. Alternatively, if too much infusible fluid has been dispensed, electrical control assembly  816  may provide the appropriate signal to mechanical control assembly  812  so that less infusible fluid may be dispensed in the next dosage. Electrical control assembly  816  may include one or more microprocessors. In an exemplary embodiment, electrical control assembly  816  may include three microprocessors. One processor (e.g., which may include, but is not limited to a CC2510 microcontroller/RF transceiver, available from Chipcon AS, of Oslo, Norway) may be dedicated to radio communication, e.g., for communicating with a remote control assembly. Two additional microprocessors (example of which may include, but is not limited to an MSP430 microcontroller, available from Texas Instruments Inc. of Dallas, Tex.) may be dedicated to issuing and carrying out commands (e.g., to dispense a dosage of infusible fluid, process feedback signals from a volume measurement device, and the like). 
     As shown in  FIG.  35 C , base plate  818  may provide access to electrical contacts  834 , e.g., which may be electrically coupled to electrical control assembly  816  for recharging battery  832 . Base plate  818  may include one or more features (e.g., openings  836 ,  838 ) which may be configured to facilitate proper alignment with disposable housing assembly  804  by way of cooperating features (e.g., tabs) of disposable housing assembly  804 . Additionally, as shown in  FIGS.  40 A- 40 C,  41 A- 41 B, and  42 A- 42 C , base plate  818  may include various features for mounting valve assembly  814  and electrical control assembly  816 , as well as providing access to disposable housing assembly  804  by valve assembly  814 . 
     Locking ring assembly  806  may include grip inserts  840 ,  842 , e.g., which may include an elastomeric or textured material that may facilitate gripping and twisting locking ring assembly  806 , e.g., for engaging/disengaging reusable housing assembly  802  and disposable housing assembly  804 . Additionally, locking ring assembly  806  may include a sensing component (e.g., magnet  844 ) that may interact with a component of reusable housing assembly  802  (e.g., a Hall Effect sensor), e.g., to provide an indication of the nature of a mating component (e.g., which in some embodiments may include, but is not limited to, one or more of disposable housing assembly  804 , a charging station, or a filling station) and/or of whether reusable housing assembly  802  is properly engaged with the mating component. In the exemplary embodiment, a Hall Effect sensor (not shown) may be located on the pump printed circuit board. The Hall Effect sensor may detect when the locking ring has been rotated to a closed position. Thus, the Hall Effect sensor together with magnet  844  may provide a system for determining whether the locking ring has been rotated to a closed position. 
     The sensing component (magnet)  844  together with the reusable housing assembly components, i.e., in the exemplary embodiment, the Hall Effect sensor, may work to provide for a determination of whether the reusable housing assembly is properly attached to the intended component or device. Locking ring assembly  806  may not turn without being attached to a component, i.e., disposable housing assembly  804 , a dust cover or a charger. Thus, the sensing component together with the reusable housing assembly component may function to provide many advantageous safety features to the infusion pump system. These features may include, but are not limited to, one or more of the following. Where the system does not detect being attached to a disposable assembly, a dust cover or a charger, the system may notify, alert or alarm the user as the reusable portion, e.g., the valves and pumping components, may be vulnerable to contamination or destruction which may compromise the integrity of the reusable assembly. Thus, the system may provide for an integrity alarm to alert the user of potential reusable integrity threats. Also, where the system senses the reusable assembly is attached to a dust cover, the system may power off or reduce power to conserve power. This may provide for more efficient use of power where the reusable assembly is not connecting to a component in which it needs to interact. 
     Referring also now to  FIGS.  136 - 139   , in some embodiments, in addition to the sensing component, a mechanical audible, or “click”, indication may indicate that the reusable housing assembly  2972  is fully attached to the disposable housing assembly  2976 . In some embodiments, the latching mechanism shown and described above, for example, with respect to  FIG.  38 A , may include a spring  2982  actuated tab  2980  assembly. In some embodiments, the tab  2980  includes the sensing component, which, in some embodiments, may be a magnetic  2986 . Referring now also to  FIG.  137   , a cross section view at “A” is shown of the reusable housing assembly  2972  above the disposable housing assembly  2974  in the “unlocked” position. In some embodiments, the “locked” and “unlocked” position may also be visually indicated to a user/patient using icons  2976 ,  2978  that may be molded, etched and/or printed on the disposable housing assembly  2974 , indicating whether the reusable housing assembly  2972 , or, in some embodiments, a fill adapter, is in a locked or unlocked relationship with the disposable housing assembly  2974  (or, in some embodiments, the same or similar icons may appear on the dust cover). In various embodiments, the icons  2976 ,  2978  may be any form that may indicate “locked” and “unlocked”, or a similar indication, to aid in the user/patient&#39;s understanding of the orientation/position between the reusable housing assembly  2972  and the disposable housing assembly  2974  (or the dust cover). As shown, the reusable housing assembly  2972  is aligned about the disposable housing assembly  2974  in an unlocked orientation. Referring now also to  FIG.  138   , a cross section view at “A” is shown of the reusable housing assembly  2972  attached to the disposable housing assembly  2974  in the unlocked orientation/position is shown. The tab  2080  is in the unlocked position. Referring now to  FIG.  139   , a cross section view at “A” is shown of the reusable housing assembly  2972  attached to the disposable housing assembly  2974  in the locked orientation/position is shown. As may be seen, the tab  2980  has moved towards the disposable housing assembly  2974 , leaving a space  2984  above the tab  2980  in the reusable housing assembly  2972 . When the tab  2980  moves from the unlocked position (shown in  FIG.  138   ) to the locked position (shown in  FIG.  139   ) in some embodiments, an audible “click” sound, and tactile “click”, may be detected by the user/patient. This may be beneficial for many reasons including that the user/patient may only hear the audible “click” sound if the reusable housing assembly  2972  and the disposable housing assembly  2974  (or, the dust cover or charger in various embodiments) are in the correct orientation and fully locked arrangement. This may ensure the user/patient that the infusion pump assembly is in the correct and fully locked position. Thus, in various embodiments where an audible “click” may be heard upon the disposable housing assembly  2974  and reusable housing assembly  2972  being attached, the infusion pump assembly will include two safety checks that they are fully locked: 1) the sensing component described and discussed above; and 2) the audible “click” mechanical component. In various embodiments the disposable housing assembly  2974  may include a ramp feature that the tab  2980  assembly rides on as the reusable housing assembly  2972  is rotated from an unlocked to a locked position with respect to the disposable housing assembly  2974 . At the end of the ramp, in some embodiments, an indentation or relief in the disposable housing assembly  2974  allows the tab  2980 , actuated by the spring  2982 , to “click” into the indentation/relief Other embodiments allowing for an audible and or tactile indication to the user/patient may be used in various embodiments. 
     Reusable housing assembly  802  may attach to a number of different components, including but not limited to, a disposable housing assembly, a dust cover or a battery charger/battery charging station. In each case, the Hall Effect sensor may detect that the locking ring is in the closed position, and therefore, that reusable housing assembly  802  is releasably engaged to a disposable housing assembly, a dust cover, or a battery charger/battery charging station (or, another component). The infusion pump system may determine the component to which it is attached by using the AVS system (which may also be referred to as the volume measurement sensor) described in more detail below or by an electronic contact. Referring now also to  FIGS.  38 B- 38 D , one embodiment of a dust cover (e.g., dust cover  839 ) is shown. In the exemplary embodiment, dust cover  839  may include features  841 ,  843 ,  845 ,  847  such that the locking ring of reusable housing assembly  802  may releasably engage dust cover  839 . In addition, dust cover  839  may further include recess region  849  for accommodating the valving and pumping features of reusable housing assembly  804 . Referring also to  FIGS.  140 A- 140 D , in some embodiments, various embodiments of the dust cover  839 ,  2988  may include a sealing assembly  2990  that may be over molded to provide for a complete seal of the dust cover  839 ,  2988  to the reusable housing assembly  2972 . As shown in  FIG.  140 D , where a cut-away cross-sectional view of section D in  FIG.  140 C , the sealing assembly  2990  is over molded. Additionally, as may be seen in  FIGS.  140 A and  140 B , in some embodiments of the dust cover  2988 , the dust cover  2988  may include icons  2976 ,  2978 . As discussed above, the icons  2976 ,  2978 , may be molded, etched and/or printed onto the dust cover  2988  and may be any form that may indicate “locked” and “unlocked”, or a similar indication, to aid in the user/patient&#39;s understanding of the orientation/position between the reusable housing assembly  2972  and the dust cover  2988  and/or indicating whether the reusable housing assembly  2972  is in a locked or unlocked position with respect to the dust cover  2988 . For example, with respect to the dust cover, the AVS system may determine that a dust cover, and not a disposable housing assembly, is connected to the reusable housing assembly. The AVS system may distinguish using a look-up table or other comparative data and comparing the measurement data with characteristic dust cover or empty disposable housing assembly data. With respect to the battery charger, the battery charger, in the exemplary embodiments, may include electric contacts. When the reusable housing assembly is attached to the battery charger, the infusion pump assembly electronic system may sense that the contacts have been made, and will thus indicate that the reusable housing assembly is attached to a battery charger. 
     Referring also to  FIGS.  43 A- 45 B  and  FIGS.  44 A- 44 C  an embodiment of valve assembly  814 , which may include one or more valves and one or more pumps, is shown. As with infusion pump assemblies  100 ,  100 ′,  400 , and  500 , valve assembly  814  may generally include reservoir valve  850 , plunger pump  852 , volume sensor valve  854 , and measurement valve  856 . Similar to the previous description, reservoir valve  850  and plunger pump  852  may be actuated by shape memory actuator  858 , which may be anchored (on a first end) to shape memory actuator anchor  860 . Additionally, measurement valve  856  may be actuated, via valve actuator  862 , by shape memory actuator  864 , which may be anchored (on a first end) to shape memory actuator anchor  866 . In a similar manner as discussed above, measurement valve may be maintained in an open position via measurement valve latch assembly  868 . Measurement valve  856  may be released via actuation of shape memory actuator  870 , which may be anchored (on a first end) by shape memory actuator anchor  872 . In some embodiments, shape memory actuator anchor  860  may be potted onto the reusable housing assembly. Using this process during manufacture ensures shape memory length actuator  858  is installed and maintains the desired length and tension/strain. 
     Referring also to  FIGS.  45 A- 45 B  and  FIGS.  46 A- 46 E , shape memory actuator  858  (e.g., which may include one or more shape memory wires) may actuate plunger pump  852  via actuator assembly  874 . Actuator assembly  874  may include bias spring  876  and lever assembly  878 . Actuator assembly  874  may actuate both plunger pump  852  and measurement valve  850 . 
     Referring also to  FIGS.  47 A- 47 B , measurement valve  856  may be actuated by shape memory actuator  864 , via valve actuator  862  and lever assembly  878 . Once actuated, measurement valve latch assembly  868  may maintain measurement valve  856  in an open position. Measurement valve latch assembly  868  actuated by shape memory actuator  870  to release measurement valve  856 , allowing it to return to a closed position. 
     Disposable housing assembly  804  may be configured for a single use or for use for a specified period of time, e.g., e.g., three days or any other amount of time. Disposable housing assembly  804  may be configured such that any of the component of infusion pump assembly  800  that come in contact with the infusible fluid may be disposed on and/or within disposable housing assembly  804 . As such, the risk of contaminating the infusible fluid may be reduced. 
     Referring also to  FIG.  48    and  FIGS.  49 A- 49 C , disposable housing assembly  804  may include base portion  900 , membrane assembly  902 , and top portion  904 . Base portion  900  may include recess  906  that together with membrane assembly  902  defines reservoir  908  for receiving an infusible fluid (not shown), e.g., insulin. Referring also to  FIGS.  50 A- 50 C , recess  906  may be at least partially formed by and integral with base portion  900 . Membrane assembly  902  may be sealingly engaged with base portion  900 , e.g., by being compressively pinched between base portion  900  and top portion  904 . Top portion  904  may be attached to base portion  900  by conventional means, such as gluing, heat sealing, ultrasonic welding, and compression fitting. Additionally/alternatively, membrane assembly  902  may be attached to base portion  900 , e.g., via gluing, ultrasonic welding, heat sealing, and the like, to provide a seal between membrane assembly  902  and base portion  900 . 
     Referring also to  FIGS.  141 A- 141 B , an embodiment of the disposable housing assembly  2974  is shown without the top portion or membrane assembly. Referring to  FIG.  141 B , a magnified cut away view of the pump chamber  106 B as indicated by “B” in  FIG.  141 A  is shown. In some embodiments, a groove  2992  is included on the wall of the pump chamber. In some embodiments, the groove may allow fluid to flow while the pump plunger  106 A is fully actuated, thus, preventing the pump plunger  106 A from sealing flow out of the pump chamber  106 B.  FIGS.  142 B and  142 C  are cross sectional views of  FIG.  142 A  taken at section “B” and “C” respectively. The groove  2992  may be seen in the pump chamber  106 B. 
     Referring also to  FIGS.  143 A- 143 B , in some embodiments of the disposable housing assembly  2974 , the disposable housing assembly  2974  may include at least one vent  2994  which, in some embodiments, may include a filter  2996 , which may, in some embodiments, be a hydrophobic filter, which may be, in some embodiments, be a 10 micron filter made from POREX PM 1020 MUPOR micro porous PTFE membrane, however, in other embodiments may be a different sized or type of filter for example, a 5 micron, 15 microns, filter and/or a GORTEX filter. 
     Still referring to  FIGS.  48  and  50 A , recess  906 , in the exemplary embodiment, includes raised portion  901  which includes area  903  about fluid openings  905  leading to the fluid line. Raised portion  901 , in the exemplary embodiment, extends about the perimeter of recess  906 . However, in other embodiments, raised portion  901  may not extend the entire perimeter, but may be partially about the perimeter. Area  903  about fluid openings  905  may be shaped as shown in the exemplary embodiment, including an angled portion, which in some embodiments, includes 45 degree angles, however in other embodiments, the angle may be greater or lesser. In some embodiments, the pump may not generate a sufficient enough vacuum to collapse the reservoir so as to eliminate the entire volume of fluid that may be stored in the reservoir. Raised portion  901  may act to minimize wasted fluid. 
     Fluid openings  905 , which, in the exemplary embodiment, may include three openings, however, in other embodiments may include more openings or fewer openings, may be surrounded by area  903  of the raised portion. In the exemplary embodiment, fluid openings  905  may be narrow in the center, thus creating a surface tension that may prevent the air from being drawn into the opening. In the exemplary embodiment, this area may be designed to encourage any air that is present in the reservoir to be drawn above one of fluid openings  905  rather than be pulled through fluid openings  905  and into the fluid line. Additionally, because there may be more than one fluid opening  905 , where an air bubble is caught above one, the air may not prevent fluid from flowing through the other two openings. 
     Referring also to  FIGS.  144 A- 144 E , another embodiment of the disposable housing assembly  2974  is shown. In these embodiments, and as may be seen in  FIG.  144 B , showing a magnified sectional view of section “B” as indicated in  FIG.  144 A , and as may be seen in  FIG.  144 D , showing a magnified sectional view of section “D” as indicated in  FIG.  144 C , and  FIG.  144 E  is an illustration of the bubble trap, a bubble trap  2998  and raised area  3000 , as well as a radius  3006  and a relief for the septum  3016  are included in the reservoir  3002 . In this embodiment, the bubble trap  2998  is located about the perimeter of the reservoir  3002  wall and the radius  3006 . However, in the area of the raised area  3000 , the bubble trap  2998  includes an outlet section. In the non-outlet section of the perimeter of the reservoir  3002 , the bubble trap  2998  includes essentially two portions, a taper portion  3008 , which tapers to a bottom portion  3010 . In the outlet section, the taper portion  3008  ends, shown as the end of the taper portion  3014 , and the bottom portion  3010  continues in an upward ramp portion  3012  to the reservoir outlet  3004 . The reservoir  3002  includes a membrane (not shown) which forms, together with the raised area  3000  and the upward ramp portion  3012 , essentially a “tunnel” between the membrane and the fluid outlet. 
     As the fluid in the reservoir is pumped out of the reservoir, the membrane (not shown) moves towards the reservoir wall  3002 . In the embodiments shown in  FIGS.  144 A- 144 D , the fluid tends to congregate in bottom portion  3010  of the bubble trap  2998  and air bubbles do not. Rather, to the extent air is present, air bubbles tend to congregate in taper portion  3008  of the bubble trap  2998 . At the raised area  3000 , where the taper portion  3008  of the bubble trap  2998  ends at the end of the taper portion  3014 , bubbles, to the extent present, will not likely enter into the upward ramp portion  3012 , and thus, will not likely be pumped through the exit of the reservoir  3004 . 
     Thus, as the fluid is pumped through the exit of the reservoir  3004 , air is not pulled through the exit of the reservoir  3004 . The embodiments shown in  FIGS.  144 A- 144 D  may be beneficial for many reasons, including but not limited to, decreasing air that is pumped from the reservoir  3002  and into the fluid path in the disposable housing assembly  2974 . As air bubbles have a greater surface tension than fluid, the bubbles will not tend to congregate in the bottom portion  3010  of the bubble trap  2998 , and further, will not tend to flow passed the end of the taper portion  3014  and onto the upward ramp portion  3012  and through the exit of the reservoir  3004 . 
     Referring also to  FIGS.  51 A- 51 C , disposable housing assembly  804  may also include fluid pathway cover  910 . Fluid pathway cover  910  may be received in cavity  912  formed on/within base portion  900 . Fluid pathway cover  910  may, in some embodiments, include at least a portion of one or more channels (e.g., channel  914 ). The channels included in fluid pathway cover  910  may fluidly couple one or more volcano valve features (e.g. volcano valves  916 ) included on base portion  900 . Volcano valves  916  may include a protrusion having an opening extending through it. Additionally, fluid pathway cover  910  and base portion  900  may each define a portion of recess (e.g., recess portions  918 ,  920  included in base portion  900  and fluid pathway cover  910  respectively) for fluidly coupling to an infusion set (e.g., including cannula  922 ). Cannula  922  may be coupled to disposable housing assembly  804  by conventional means (e.g., gluing, heat sealing, compression fit, or the like). The fluid pathways defined by fluid pathway cover  910  and the volcano valves (e.g., volcano valves  916 ) of base portion  900  may define a fluid pathway between reservoir  908  and cannula  922  for the delivery of the infusible fluid to the user via the infusion set. However, in some embodiments, fluid path cover  910  may include at least a portion of the fluid path, and in some embodiments, fluid path cover  910  may not include at least a portion of the fluid path. In the exemplary embodiment, fluid pathway cover  910  may be laser welded to base portion  900 . However, in other embodiments, fluid pathway cover  910  may also be connected to base portion  900  by conventional means (e.g., gluing, heat sealing, ultrasonic welding, compression fit, or the like) to achieve a generally fluid tight seal between fluid pathway cover  910  and base portion  900 . 
     With reference also to  FIGS.  54 A- 54 C , disposable housing assembly  804  may further include valve membrane cover  924 . Valve membrane cover  924  may be at least partially disposed over the volcano valves (e.g., volcano valve  916 ) and pumping recess  926  included on/within base portion  900 . Valve membrane cover  924  may include a flexible material, e.g., which may be selectively engaged against the volcano valves by reservoir valve  850 , volume sensor valve  854 , and measurement valve  856  of reusable housing assembly  802 , e.g., for controlling the flow of the infusible fluid. Additionally, valve membrane cover  924  may be resiliently deformed into pumping recess  926  by plunger pump  852  to effectuate pumping of the infusible fluid. Valve membrane cover  924  may be engaged between base portion  900  and top portion  904  of disposable housing assembly  804  to form seal  928  between valve membrane cover  924  and base portion  900 . For example, in the exemplary embodiment, valve membrane cover  924  may be overmolded onto base portion  900 . In other embodiment, valve membrane cover  924  may be compressively pinched between base portion  900  and top portion  904  to form seal  928 . Additionally/alternatively, valve membrane insert may be connected to one or more of base portion  900  and top portion  904 , e.g., by gluing, heat sealing, or the like. 
     Referring also to  FIGS.  53 A-C , top portion  904  may include alignment tabs  930 ,  932  that may be configured to be at least partially received in openings  836 ,  838  of base plate  818  of reusable housing assembly  802  to ensure proper alignment between reusable housing assembly  802  and disposable housing assembly  804 . Additionally, top portion  904  may include one or more radial tabs  934 ,  936 ,  938 ,  940  configured to be engaged by cooperating tabs  942 ,  944 ,  946 ,  948  of locking ring assembly  806 . The one or more radial tabs (e.g., radial tab  940 ) may include stops (e.g., alignment tab stop  950 , which may be used for welding, it&#39;s the tab that fits in the recess to locate and ultrasonically weld), e.g., which may prevent further rotation of locking ring assembly  806  once reusable housing assembly  802  and disposable housing assembly  804  are fully engaged. 
     As discussed above, valve membrane insert  924  may allow for pumping and flow of the infusible fluid by reservoir valve  850 , plunger pump  852 , volume sensor valve  854 , and measurement valve  856 . Accordingly, top portion  904  may include one or more openings (e.g., openings  952 ,  954 ,  956 ) that may expose at least a portion of valve membrane insert  924  for actuation by reservoir valve  850 , plunger pump  852 , volume sensor valve  854 , and measurement valve  856 . Additionally, top portion  904  may include one or more openings  958 ,  960 ,  962  which may be configured to allow the fill volume to be controlled during filling of reservoir  908 , as will be discussed in greater detail below. Reservoir assembly  902  may include ribs  964 ,  966 ,  968  (e.g., as shown in  FIG.  52 A ), which may be at least partially received in respective openings  958 ,  960 ,  962 . As will be described in greater detail below, a force may be applied to one or more of ribs  964 ,  966 ,  968  to, at least temporarily, reduce the volume of reservoir  908 . 
     In some embodiments, it may be desirable to provide a seal between reusable housing assembly  802  and disposable housing assembly  804 . Accordingly, disposable housing assembly  804  may include sealing assembly  970 . Sealing assembly  970  may include, for example, an elastomeric member that may provide a compressible rubber or plastic layer between reusable housing assembly  802  and disposable housing assembly  804  when engaged, thus preventing inadvertent disengagement and penetration by outside fluids. For example, sealing assembly  970  may be a watertight seal assembly and, thus, enable a user to wear infusion pump assembly  800  while swimming, bathing or exercising. 
     In a fashion similar to, e.g., disposable housing assembly  114 , disposable housing assembly  802  may, in some embodiments, be configured to have reservoir  908  filled a plurality of times. However, in some embodiments, disposable housing assembly  114  may be configured such that reservoir  908  may not be refilled. Referring also to  FIGS.  57 - 64   , fill adapter  1000  may be configured to be coupled to disposable housing assembly  804  for refilling reservoir  908  using a syringe (not shown). Fill adapter  1000  may include locking tabs  1002 ,  1004 ,  1006 ,  1008  that may be configured to engage radial tabs  934 ,  936 ,  938 ,  940  of disposable housing assembly  804  in a manner generally similar to tabs  942 ,  944 ,  946 ,  948  of locking ring assembly  806 . Accordingly, fill adapter  1000  may be releasably engaged with disposable housing assembly  804  by aligning fill adapter  1000  with disposable housing assembly  804  and rotating fill adapter  1000  and disposable housing assembly  804  relative to one another to releasably engage locking tabs  1002 ,  1004 ,  1006 ,  1008  with radial tabs  934 ,  936 ,  938 ,  940 . 
     Fill adapter  1000  may further include filling aid  1010 , which may include guide passage  1012 , e.g., which may be configured to guide a needle of a syringe (not shown) to a septum of disposable housing assembly  804  to allow reservoir  908  of disposable housing assembly  804  to be filled by the syringe. In some embodiments, guide passage  1012  may be an angled bevel or other gradual angled bevel to further guide a syringe to a septum. Fill adapter  1000  may facilitate filling reservoir  908  by providing a relatively large insertion area, e.g., at the distal opening of guide passage  1012 . Guide passage  1012  may generally taper to a smaller proximal opening that may be properly aligned with the septum of disposable housing assembly  804 , when fill adapter  1000  is engaged with disposable housing assembly  804 . Accordingly, fill adapter  1000  may reduce the dexterity and aim necessary to properly insert a needle through the septum of disposable housing assembly  804  for the purpose of filling reservoir  908 . 
     As discussed above, disposable housing assembly  804  may configured to facilitate controlling the quantity of infusible fluid delivered to reservoir  908  during filling. For example, membrane assembly  902  of disposable housing assembly  804  may include ribs  964 ,  966 ,  968  that may be depressed and at least partially displaced into reservoir  908 , thereby reducing the volume of reservoir  908 . Accordingly, when infusible fluid is delivered to reservoir  908 , the volume of fluid that may be accommodated by reservoir  908  may be correspondingly reduced. Ribs  964 ,  966 ,  968  may be accessible via openings  958 ,  960 ,  962  in top portion  904  of disposable housing assembly  804 . 
     Fill adapter  1000  may include one or more button assemblies (e.g., button assemblies  1014 ,  1016 ,  1018 ) corresponding to ribs  964 ,  966 ,  968 . That is, when fill adapter  1000  is releasably engaged with disposable housing assembly  804 , buttons  1014 ,  1016 ,  1018  may be aligned with ribs  964 ,  966 ,  968 . Button assemblies  1014 ,  1016 ,  1018  may be, for example, cantilever members capable of being depressed. When fill adapter  1000  is releasably engaged with disposable housing assembly  804 , one or more of button assemblies  1014 ,  1016 ,  1018  may be depressed, and may correspondingly displace a respective one of ribs  964 ,  966 ,  698  into reservoir  908 , causing an attendant reduction in the volume of reservoir  908 . 
     For example, assume for illustrative purposes that reservoir  908  has a maximum capacity of 3.00 mL. Further, assume that button assembly  1014  is configured to displace rib  964  into disposable housing assembly  804 , resulting in a 0.5 mL reduction in the 3.00 mL capacity of disposable housing assembly  804 . Further, assume that button assembly  1016  is configured to displace rib  966  into disposable housing assembly  804 , also resulting in a 0.5 mL reduction in the 3.00 mL capacity of disposable housing assembly  804 . Further, assume that button assembly  1018  is configured to displace slot assembly  968  into disposable housing assembly  804 , also resulting in a 0.5 mL reduction in the 3.00 mL capacity of disposable housing assembly  804 . Therefore, if the user wishes to fill reservoir  908  within disposable housing assembly  804  with 2.00 mL of infusible fluid, in some embodiments, the user may first fill the reservoir to the 3.00 mL capacity and then depresses button assemblies  1016  and  1014  (resulting in the displacement of rib  966  into disposable housing assembly  804 ), effectively reducing the 3.00 mL capacity of reservoir  908  within disposable housing assembly  804  to 2.00 mL. In some embodiments, the user may first depress a respective number of button assemblies, effectively reducing the capacity of reservoir  908 , and then fill reservoir  908 . Although a particular number of button assemblies are shown, representing the exemplary embodiment, in other embodiments, the number of button assemblies may vary from a minimum of 1 to as many as is desired. Additionally, although for descriptive purposes, and in the exemplary embodiment, each button assembly may displace 0.5 mL, in other embodiments, the volume of displacement per button may vary. Additionally, the reservoir may be, in various embodiments, include a larger or smaller volume than described in the exemplary embodiment. 
     According to the above-described configuration, the button assemblies (e.g., button assemblies  1014 ,  1016 ,  108 ) may employed, at least in part, to control the fill volume of reservoir  908 . By not depressing any of the button assemblies, the greatest fill volume of reservoir  908  may be achieved. Depressing one button assembly (e.g., button assembly  1014 ) may allow the second greatest fill volume to be achieved. Depressing two button assemblies (e.g., button assemblies  1014 ,  1016 ) may achieve the third greatest fill volume. Depressing all three button assemblies (e.g., button assemblies  1014 ,  1016 ,  1018 ) may allow the smallest fill volume to be achieve. 
     Further, in an embodiment button assemblies  1014 ,  1016 ,  1018  may be utilized, at least in part, to facilitate filling of reservoir  908 . For example, once a filling needle (e.g., which may be fluidly coupled to a vial of infusible fluid) has been inserted into reservoir  908 , button assemblies  1014 ,  1016 ,  1018  may be depressed to pump at least a portion of any air that may be contained within reservoir into the vial of infusible fluid. Button assemblies  1014 ,  1016 ,  1018  may subsequently be released to allow infusible fluid to flow from the vial into reservoir  908 . Once reservoir  908  has been filled with the infusible fluid, one or more button assemblies (e.g., one or more of button assemblies  1014 ,  1016 ,  1018 ) may be depressed, thereby squeezing at least a portion of the infusible fluid from reservoir  908  (e.g., via a needle used to fill reservoir  908  and back into the vial of infusible fluid). As discussed above, the volume of infusible fluid contained within reservoir  908  may be controlled, e.g., depending upon how many button assemblies are depressed (e.g., which may control how much infusible fluid is squeezed back into the vial of infusible fluid). 
     With particular reference to  FIGS.  62 - 64   , filling aid  1010  may be pivotally coupled to fill adapter base plate  1020 . For example, filling aid  1010  may include pivot members  1022 ,  1024  that may be configured to be received in pivot supports  1026 ,  1028 , thereby allowing filling aid to pivot between an open position (e.g., as shown in  FIGS.  57 - 61   ) and a closed position (e.g., as shown in  FIGS.  63 - 64   ). The closed position may be suitable, e.g., for packaging fill adapter  1000 , storage of fill adapter  1000 , or the like. In order to ensure that filling aid  1010  is properly oriented for filling reservoir  908 , fill adapter  1000  may include support member  1030 . To properly orient filling aid  1010 , a user may pivot filling aid  1010  to a fully open position, wherein filling aid  1010  may contact support member  1030 . 
     According to an alternative embodiment, and referring also to  FIG.  65   , fill adapter  1050  may be configured to releasably engage disposable housing assembly  804  via a plurality of locking tabs (e.g., locking tabs  1052 ,  1054 ). Additionally, fill adapter  1050  may include a plurality of button assemblies (e.g., button assemblies  1056 ,  1058 ,  1060 ) that may interact with ribs  964 ,  966 ,  968  of disposable housing assembly  804  to adjust a fill volume of reservoir  908 . Fill adapter  1050  may further include filling aid  1062 , having guide passage  1064  configured to align a needle of a syringe with the septum of disposable housing  804 , e.g., for accessing reservoir  908  for the purpose of filling reservoir  908  with an infusible fluid. Filling aid  1062  may be connected to base plate  1066 , e.g., as an integral component therewith, by gluing, heat sealing, compression fit, or the like. 
     Referring also to  FIGS.  66 - 74   , vial fill adapter  1100  may be configured to facilitate filling reservoir  908  of disposable housing assembly  804  directly from a vial. Similar to fill adapter  1000 , vial fill adapter  1100  may include locking tabs  1102 ,  1104 ,  1106 ,  1108  that may be configured to engage radial tabs  934 ,  936 ,  938 ,  940  of disposable housing assembly in a manner generally similar to tabs  942 ,  944 ,  946 ,  948  of locking ring assembly  806 . Accordingly, vial fill adapter  1100  may be releasably engaged with disposable housing assembly  804  by aligning vial fill adapter  1100  with disposable housing assembly  804  and rotating vial fill adapter  1100  and disposable housing assembly  804  relative to one another to releasably engage locking tabs  1102 ,  1104 ,  1106 ,  1108  with radial tabs  934 ,  936 ,  938 ,  940 . 
     As discussed above, disposable housing assembly  804  may be configured to facilitate controlling the quantity of infusible fluid delivered to reservoir  908  during filling. For example, membrane assembly  902  of disposable housing assembly  804  may include ribs  964 ,  966 ,  968  that may be depressed and at least partially displaced into reservoir  908 , thereby reducing the volume of reservoir  908 . Accordingly, when infusible fluid is delivered to reservoir  908 , the volume of fluid that may be accommodated by reservoir  908  may be correspondingly reduced. Ribs  964 ,  966 ,  968  may be accessible via openings  958 ,  960 ,  962  in top portion  904  of disposable housing assembly  804 . 
     Vial fill adapter  1100  may include one or more button assemblies (e.g., button assemblies  1110 ,  1112 ,  1114 ) corresponding to ribs  964 ,  966 ,  968  (e.g., shown in  FIG.  52 A ). That is, when vial fill adapter  1100  is releasably engaged with disposable housing assembly  804 , buttons  1110 ,  1112 ,  1114  may be aligned with ribs  964 ,  966 ,  968 . Button assemblies  1110 ,  1112 ,  1114  may be, for example, cantilever members capable of being depressed. When vial fill adapter  1100  is releasably engaged with disposable housing assembly  804 , one or more of button assemblies  1110 ,  1112 ,  1114  may be depressed, and may correspondingly displace a respective one of ribs  964 ,  966 ,  698  into reservoir  908 , thereby reducing the volume of reservoir  908 . 
     For example, assume for illustrative purposes that reservoir  908  has a maximum capacity of 3.00 mL. Further, assume that button assembly  1110  is configured to displace rib  964  into disposable housing assembly  804 , resulting in a 0.5 mL reduction in the 3.00 mL capacity of disposable housing assembly  804 . Further, assume that button assembly  1112  is configured to displace rib  966  into disposable housing assembly  804 , also resulting in a 0.5 mL reduction in the 3.00 mL capacity of disposable housing assembly  804 . Further, assume that button assembly  1114  is configured to displace rib  968  into disposable housing assembly  804 , also resulting in a 0.50 mL reduction in the 3.00 mL capacity of disposable housing assembly  804 . Therefore, if the user wishes to fill reservoir  908  within disposable housing assembly  804  with 2.00 mL of infusible fluid, the user may depress button assemblies  1112  and  1114  (resulting in the displacement of ribs  966  and  968  into disposable housing assembly  804 ), effectively reducing the 3.00 mL capacity of reservoir  908  within disposable housing assembly  804  to 2.0 mL. 
     Vial fill adapter  1100  may further include vial filling aid assembly  1116  that may be configured to fluidly couple a vial of infusible fluid to reservoir  908  of disposable housing assembly  804  via a septum. With particular reference to  FIG.  71   , vial filling aid assembly may include double ended needle assembly  1118 . Double ended needle assembly  1118  may include first needle end  1120  configured to penetrate the septum of a vial (not shown) and second needle end  1122  configured to penetrate the septum of disposable housing assembly  804 . As such, the vial and reservoir  908  may be fluidly coupled allowing infusible fluid to be transferred from the vial to reservoir  908 . Double ended needle assembly  1118  may include vial engagement portion  1124  adjacent first end  1120 . Vial engagement arms  1124 ,  1126  may be configured to releasably engage, e.g., a vial cap, to assist in maintaining the fluid connection between double ended needle assembly  1118  and the vial. Additionally, double ended needle assembly  1118  may include body  1128  that may be slidably received in opening  1130  of vial filling aid body  1132 . Vial filling aid body  1132  may include stabilizer arms  1134 ,  1136 , e.g., which may be configured to stabilize the vial during filling of disposable housing assembly  804 . In one embodiment, the vial may be engaged with double ended needle assembly  1118  e.g., such that first end  1120  may penetrate the septum of the vial and the cap of the vial may be engaged by engagement arms  1124 ,  1126 . Body  1128  may be slidably inserted into opening  1130  such that second end  1122  of double ended needle assembly  1118  may penetrate the septum of disposable body assembly  804 . 
     Similar to fill adapter  1000 , vial filling aid assembly  1116  may be configured to be pivotally coupled to vial fill adapter base plate  1138 . For example, vial filling aid  1116  may include pivot members  1140 ,  1142  that may be configured to be received in pivot supports  1144 ,  1146  (e.g., shown in  FIG.  71   ), thereby allowing vial filling aid  1116  to pivot between an open position (e.g., as shown in  FIGS.  66 - 70   ) and a closed position (e.g., as shown in  FIGS.  72 - 74   ). The closed position may be suitable, e.g., for packaging vial fill adapter  1100 , storage of vial fill adapter  1100 , or the like. In order to ensure that vial filling aid  1116  is properly oriented for filling reservoir  908 , vial fill adapter  1100  may include support member  1148 . To properly orient vial filling aid  1116 , a user may pivot vial filling aid  1116  to a fully open position, wherein vial filling aid  1116  may contact support member  1148 . Additionally, vial fill adapter base plate  1138  may include one or more locking features (e.g., locking tabs  1150 ,  1152 ) that may engage vial filing aid  1116 , and may maintain vial filling aid  1116  in the closed position. Vial fill adapter base plate  1138  may also include features (e.g., tabs  1154 ,  1156 ) that may be configured to assist in retaining double ended needle assembly  1118 , e.g., by preventing slidable separation of double ended needle assembly  1118  from vial filling aid body  1132 . 
     As shown in  FIGS.  72 - 74   , filling aid assembly  1116  is in a closed position. In this configuration, support member  1148  may additionally function as a needle guard. When removing filling aid assembly  1116  from disposable housing assembly  804 , support member  1148  may function to safely allow a user to squeeze the ends and rotate filling aid assembly  1116  for removal. As shown in  FIG.  70   , in the open position, support member  1148  may function as a stop to maintain proper orientation. 
     Referring again to  FIGS.  57 - 73   , the exemplary embodiments of the fill adapter include a grip feature (e.g.,  1166  in  FIG.  72   ). Grip feature  1166  may provide a grip interface for removal of the fill adapter from disposable housing assembly  804 . Although shown in one configuration in these figures, in other embodiments, the configuration may vary. In still other embodiments, a grip feature may not be included. 
     According to one embodiment, fill adapter base plate  1020  and vial fill adapter base plate  1138  may be interchangeable components. Accordingly, a single base plate (e.g., either fill adapter base plate  1020  or vial fill adapter base plate  1138  may be used with either filling aid  1010  or vial filling aid  1116 . Accordingly, the number of distinct components that are required for both filling adapters may be reduced, and a user may have the ability to select the filling adapter that may be the most suitable for a given filling scenario. 
     The various embodiments of the fill adapters may provide many safely benefits, including but not limited to: providing a system for filling the reservoir without handling a needle; protecting the reservoir from unintentional contact with the needle, i.e., destruction of the integrity of the reservoir through unintentional puncture; designed to be ambidextrous; in some embodiments, may provide a system for maintaining air in the reservoir. 
     As discussed above, reusable housing assembly  802  may include battery  832 , e.g., which may include a rechargeable battery. Referring also to  FIGS.  75 - 80   , battery charger  1200  may be configured to recharge battery  832 . Battery charger  1200  may include housing  1202  having top plate  1204 . Top plate  1204  may include one or more electrical contacts  1206 , generally, configured to be electrically coupled to electrical contacts  834  of reusable housing assembly  802 . Electrical contacts  1206  may include, but are not limited to, electrical contact pads, spring biased electrical contact members, or the like. Additionally, top plate  1204  may include alignment tabs  1208 ,  1210 , which may be configured to mate with openings  836 ,  838  in base plate  818  of reusable housing assembly  802  (e.g., as shown in  FIG.  35 C ). The cooperation of alignment tabs  1208 ,  1210  and openings  836 ,  838  may ensure that reusable housing assembly  802  is aligned with battery charger  1200  such that electrical contacts  1206  of battery charger  1200  may electrically couple with electrical contacts  834  of reusable housing assembly  802 . 
     With reference also to  FIGS.  77  and  78   , battery charger  1200  may be configured to releasably engage reusable housing assembly  802 . For example, in a similar manner as disposable housing assembly  804 , battery charger  1200  may include one or more locking tabs (e.g., locking tabs  1212 ,  1214  shown in  FIG.  76   ). The locking tabs (e.g., locking tabs  1212 ,  1214 ) may be engaged by tabs  942 ,  944 ,  946 ,  948  of locking ring assembly  806 . As such, reusable housing assembly  802  may be aligned with battery charger  1200  (via alignment tabs  1208 ,  1210 ) with locking ring  806  in a first, unlocked position, as shown in  FIG.  77   . Locking ring  806  may be rotated relative to battery charger  1200  in the direction of arrow  1216  to releasably engage tabs  942 ,  944 ,  946 ,  948  of locking ring  806  with the locking tabs (e.g., locking tabs  1212 ,  1214 ) of battery charger  1200 , as shown in  FIG.  78   . 
     In an embodiment, battery charger  1200  may include recessed region  1218 , e.g., which may, in the exemplary embodiments, provide clearance to accommodate reusable housing assembly  802  pumping and valving components. Referring also to  FIGS.  79  &amp;  80   , battery charger  1200  may provide electrical current to electrical contacts  1206  (and thereby to reusable housing assembly  802  via electrical contacts  834 ) for recharging battery  832  of reusable housing assembly  802 . In some embodiments, when a signal indicative of a fully engaged reusable housing is not provided, current may not be provided to electrical contacts  1206 . According to such an embodiment, the risk associated with an electrical short circuit (e.g., resulting from foreign objects contacting electrical contacts  1206 ) and damage to reusable housing assembly  802  (e.g., resulting from improper initial alignment between electrical contacts  1206  and electrical contacts  834 ) may be reduced. Additionally, battery charger  1200  may not unnecessarily draw current when battery charger is not charging reusable housing assembly  802 . 
     Still referring to  FIGS.  79  and  80   , battery charger  1200  may include a lower housing portion  1224  and top plate  1204 . Printed circuit board  1222  (e.g., which may include electrical contacts  1206 ) may be disposed within a cavity included between top plate  1204  and lower housing portion  1224 . 
     Referring also to  FIGS.  81 - 89   , various embodiments of battery charger/docking stations are shown.  FIGS.  81  and  82    depicts desktop charger  1250  including recess  1252  configured to mate with and recharge a reusable housing assembly (e.g., reusable housing assembly  802 ). The reusable housing assembly may rest in recess  1252  and or may be releasably engaged in recess  1252 , in a similar manner as discussed above. Additionally, desktop charger  1250  may include recess  1254  configured to mate with a remote control assembly (e.g., remote control assembly  300 ). Recess  1254  may include a USB plug  1256 , e.g., which may be configured to couple with the remote control assembly when the remote control assembly is disposed within recess  1254 . USB plug  1256  may allow for data transfer to/from the remote control assembly, as well as charging of remote control assembly. Desktop charger  1250  may also include USB port  1258  (e.g., which may include a mini-USB port), allowing desktop charger to receive power (e.g., for charging the reusable housing assembly and/or the remote control assembly). Additionally/alternatively USB port  1258  may be configured for data transfer to/from remote control assembly and/or reusable housing assembly, e.g., by connection to a computer (not shown). 
     Referring to  FIGS.  83 A- 83 B , similar to the previous embodiment, desktop charger  1260  may include recess  1262  for mating with a reusable housing assembly (e.g., reusable housing assembly  1264 ). Desktop charger may also include recess  1266  configured to receive a remote control assembly (e.g., remote control assembly  1268 ). One or more of recess  1262 ,  1266  may include electrical and/or data connections configure to charge and/or transfer data to/from reusable housing assembly  1262  and/or remote control assembly  1268 , respectively. 
     Referring to  FIGS.  84 A- 84 B , another embodiment of a desktop charger is shown. Similar to desktop charger  1260 , desktop charger  1270  may include recesses (not shown) for respectively mating with reusable housing assembly  1272  and remote control assembly  1274 . As shown, desktop charger  1270  may hold reusable housing assembly  1272  and remote control assembly  1274  in a side-by-side configuration. Desktop charger  1270  may include various electrical and data connection configured to charge and/or transfer data to/from reusable housing assembly  1272  and/or remote control assembly  1274 , as described in various embodiments above. 
     Referring to  FIG.  85 A- 85 D , collapsible charger  1280  may include recess  1282  for receiving reusable housing assembly  1284  and remote control assembly  1286 . Collapsible charger  1280  may include various electrical and data connection configured to charge and/or transfer data to/from reusable housing assembly  1284  and/or remote control assembly  1286 , as described in various embodiments above. Additionally, as shown in  FIGS.  85 B- 85 D , collapsible charger  1280  may include pivotable cover  1288 . Pivotable cover  1288  may be configured to pivot between an open position (e.g., as shown in  FIG.  85 B ), in which reusable housing assembly  1284  and remote control assembly  1286  may be docked in collapsible charger  1280 , and a closed position (e.g., as shown in  FIG.  85 D ), in which recess  1282  may be covered by pivotable cover  1288 . In the closed position, recess  1282 , as well as any electrical and/or data connections disposed therein, may be protected from damage. 
     Referring to  FIG.  86   , wall charger  1290  may include recess  1292  configured to receive reusable housing assembly  1294 . Additionally, wall charger  1290  may include recess  1296  configured to receive remote control assembly  1298 . Reusable housing assembly  1294  and remote control assembly  1298  may be positioned in a stacked configuration, e.g., thereby providing a relatively slim profile. A rear portion of wall charger  1290  may include an electrical plug, configured to allow wall charger to be plugged into an electrical receptacle. As such, wall charger  1290 , while plugged into the electrical receptacle, may achieve a wall mounted configuration. Additionally, while plugged into the electrical receptacle, wall charger  1290  may be provided with power for charging reusable housing assembly  1294  and/or remote control assembly  1298 . 
     Referring to  FIG.  87   , wall charger  1300  may include recess  1302  configured to receive remote control assembly  1304 . Additionally, wall charger may include a recess (not shown) configured to receive reusable housing assembly  1306 . Wall charger  1300  may be configured to position remote control assembly  1304  and reusable housing assembly  1306  in a back-to-back configuration, which may provide a relatively thin profile. Additionally, wall charger  1300  may include an electrical plug  1308  configured to be plugged into an electrical receptacle. Electrical plug  1308  may include a stowable configuration, in which electrical plug  1308  may be pivotable between a deployed position (e.g., as shown), and a stowed position. In the deployed position, electrical plug  1308  may be oriented to be plugged into an electrical receptacle. In the stowed position electrical plug  1308  may be disposed within recess  1310 , which may protect electrical plug  1308  from damage and/or from damaging other items. 
     Referring to  FIG.  88   , charger  1320  may include recess  1322  configured to receive reusable housing assembly  1324 . Charger  1320  may additionally include a recess (not shown) configured to receive remote control assembly  1326 . Charger  1320  may additionally include cover  1328 . Cover  1328  may be configured to pivot between an open position (as shown) and a closed position. When cover  1328  is in the open position, reusable housing assembly  1324  and remote control assembly  1326  may be accessible (e.g., allowing a user to remove/install reusable housing assembly  1324  and/or remote control assembly  1326  from/into charger  1320 . When cover  1324  is in the closed position, cover  1328  and charger body  1330  may substantially enclose reusable housing assembly  1324  and/or remote control assembly  1326  and/or recess  1322  and the recess configured to receive remote control assembly  1326 , thereby providing damage and/or tamper protection for reusable housing assembly  1324 , remote control assembly  1326  and/or any electrical and/or data connection associated with charger  1320 . 
     Referring to  FIGS.  89 A- 89 B , wall charger  1350  may include recess  1352  configured to receive remote control assembly  1354 . Wall charger  1350  may also include recess  1356  configured to receive reusable housing assembly  1358 . Wall charger  1350  may be configured to position remote control assembly  1354  and reusable housing assembly  1358  in a generally side-by-side configuration, thereby providing a relatively slim profile. Charger  1350  may additionally include electrical plug  1360 , e.g., which may be configured to be plugged into an electrical receptacle. Electrical plug  1360  may include a stowable configuration, in which electrical plug  1360  may be pivotable between a deployed position (e.g., as shown), and a stowed position. In the deployed position, electrical plug  1360  may be oriented to be plugged into an electrical receptacle. In the stowed position electrical plug  1360  may be disposed within recess  1362 , which may protect electrical plug  1308  from damage and/or from damaging other items. 
     Infusion pump therapy may include volume and time specifications. The amount of fluid dispensed together with the dispense timing may be two critical factors of infusion pump therapy. As discussed in detail below, the infusion pump apparatus and systems described herein may provide for a method of dispensing fluid together with a device, system and method for measuring the amount of fluid dispensed. However, in a circumstance where the calibration and precision of the measurement device calibration is critical, there may be advantages to determining any compromise in the precision of the measurement device as soon as possible. Thus, there are advantages to off-board verification of volume and pumping. 
     As discussed above, infusion pump assembly  100  may include volume sensor assembly  148  configured to monitor the amount of fluid infused by infusion pump assembly  100 . Further and as discussed above, infusion pump assembly  100  may be configured so that the volume measurements produced by volume sensor assembly  148  may be used to control, through a feedback loop, the amount of infusible fluid that is infused into the user. 
     Referring also to  FIGS.  90 A- 90 C , there is shown one diagrammatic view and two cross-sectional views of volume sensor assembly  148 . Referring also to  FIGS.  91 A- 91 I , there is shown various isometric and diagrammatic views of volume sensor assembly  148  (which is shown to include upper housing  1400 ). Referring also to  FIGS.  92 A- 92 I , there is shown various isometric and diagrammatic views of volume sensor assembly  148  (with upper housing  1400  removed), exposing speaker assembly  622 , reference microphone  626 , and printed circuit board assembly  830 . Referring also to  FIGS.  93 A- 93 I , there is shown various isometric and diagrammatic views of volume sensor assembly  148  (with printed circuit board assembly  830  removed), exposing port assembly  624 . Referring also to  FIGS.  94 A- 94 F , there is shown various isometric and diagrammatic cross-sectional views of volume sensor assembly  148  (with printed circuit board assembly  830  removed), exposing port assembly  624 . Referring also to  FIG.  95   , there are shown an exploded view of volume sensor assembly  148 , exposing upper housing  1400 , speaker assembly  622 , reference microphone  626 , seal assembly  1404 , lower housing  1402 , port assembly  624 , spring diaphragm  628 , and retaining ring assembly  1406 . 
     The following discussion concerns the design and operation of volume sensor assembly  148  (which is shown in a simplified form in  FIG.  96   ). For the following discussion, the following nomenclature may be used 
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 Symbols 
                   
               
               
                   
               
               
                 P 
                 Pressure 
               
               
                 p 
                 Pressure Perturbation 
               
               
                 V 
                 Volume 
               
               
                 ν 
                 Volume Perturbation 
               
               
                 γ 
                 Specific Heat Ratio 
               
               
                 R 
                 Gas Constant 
               
               
                 ρ 
                 Density 
               
               
                 Z 
                 Impedance 
               
               
                 ƒ 
                 Flow friction 
               
               
                 A 
                 Cross sectional Area 
               
               
                 L 
                 Length 
               
               
                 ω 
                 Frequency 
               
               
                 ζ 
                 Damping ratio 
               
               
                 α 
                 Volume Ratio 
               
               
                   
               
               
                 Subscripts 
               
               
                   
               
               
                 0  
                 Speaker Volume 
               
               
                 1 
                 Reference Volume 
               
               
                 2 
                 Variable Volume 
               
               
                 k 
                 Speaker 
               
               
                 r 
                 Resonant Port 
               
               
                 z 
                 Zero 
               
               
                 p 
                 Pole 
               
               
                   
               
            
           
         
       
     
     Derivation of the Equations for Volume Sensor Assembly  148 : 
     Modeling the Acoustic Volumes 
     The pressure and volume of an ideal adiabatic gas may be related by: 
         PV   γ   =K   [EQ #1]
 
     where K is a constant defined by the initial conditions of the system. 
     EQ #1 may be written in terms of a mean pressure, P, and volume, V, and a small time-dependent perturbation on top of those pressures, p(t), v(t) as follows: 
       ( P+p ( t ))( V+v ( t )) γ   =K   [EQ #2]
 
     Differentiating this equation may result in: 
           p   ( t )( V+v ( t )) γ +γ( V+v ( t )) γ-1 ( P+p ( t ))   v   ( t )=0  [EQ #3]
 
     which may simplify to: 
     
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         ‐ 
                       
                       ( 
                       t 
                       ) 
                     
                     + 
                     
                       γ 
                       ⁢ 
                       
                         
                           P 
                           + 
                           
                             p 
                             ⁡ 
                             ( 
                             t 
                             ) 
                           
                         
                         
                           V 
                           + 
                           
                             v 
                             ⁡ 
                             ( 
                             t 
                             ) 
                           
                         
                       
                       ⁢ 
                       
                         
                           v 
                           ‐ 
                         
                         ( 
                         t 
                         ) 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #4 
                   
                   ] 
                 
               
             
           
         
       
     
     If the acoustic pressure levels are much less than the ambient pressure, the equation may be further simplified to: 
     
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         ‐ 
                       
                       ( 
                       t 
                       ) 
                     
                     + 
                     
                       
                         
                           γ 
                           ⁢ 
                           P 
                         
                         V 
                       
                       ⁢ 
                       
                         
                           v 
                           ‐ 
                         
                         ( 
                         t 
                         ) 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #5 
                   
                   ] 
                 
               
             
           
         
       
     
     How good is this assumption? Using the adiabatic relation it may be shown that: 
     
       
         
           
             
               
                 
                   
                     P 
                     V 
                   
                   = 
                   
                     
                       ( 
                       
                         
                           P 
                           + 
                           
                             p 
                             ⁡ 
                             ( 
                             t 
                             ) 
                           
                         
                         
                           V 
                           + 
                           
                             v 
                             ⁡ 
                             ( 
                             t 
                             ) 
                           
                         
                       
                       ) 
                     
                     ⁢ 
                     
                       
                         ( 
                         
                           
                             P 
                             + 
                             
                               p 
                               ⁡ 
                               ( 
                               t 
                               ) 
                             
                           
                           P 
                         
                         ) 
                       
                       
                         
                           γ 
                           + 
                           1 
                         
                         γ 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #6 
                   
                   ] 
                 
               
             
           
         
       
     
     Accordingly, the error in the assumption would be: 
     
       
         
           
             
               
                 
                   error 
                   = 
                   
                     1 
                     - 
                     
                       
                         ( 
                         
                           
                             P 
                             + 
                             
                               p 
                               ⁡ 
                               ( 
                               t 
                               ) 
                             
                           
                           P 
                         
                         ) 
                       
                       
                         
                           γ 
                           + 
                           1 
                         
                         γ 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #7 
                   
                   ] 
                 
               
             
           
         
       
     
     A very loud acoustic signal (120 dB) may correspond to pressure sine wave with amplitude of roughly 20 Pascal. Assuming air at atmospheric conditions (γ=1.4, P=101325 Pa), the resulting error is 0.03%. The conversion from dB to Pa is as follows: 
     
       
         
           
             
               
                 
                   λ 
                   = 
                   
                     
                       20 
                       ⁢ 
                       
                         
                           log 
                           10 
                         
                         ( 
                         
                           
                             p 
                             rms 
                           
                           
                             p 
                             ref 
                           
                         
                         ) 
                       
                       ⁢ 
                       or 
                       ⁢ 
                           
                       
                         p 
                         rms 
                       
                     
                     = 
                     
                       
                         p 
                         res 
                       
                       ⁢ 
                       
                         10 
                         
                           λ 
                           20 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #8 
                   
                   ] 
                 
               
             
           
         
       
     
     where p ref =20·μPa. 
     Applying the ideal gas law, P=ρRT, and substituting in for pressure may result in the following: 
     
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         ‐ 
                       
                       ( 
                       t 
                       ) 
                     
                     + 
                     
                       
                         
                           γ 
                           ⁢ 
                           RT 
                           ⁢ 
                           ρ 
                         
                         V 
                       
                       ⁢ 
                       
                         
                           v 
                           ‐ 
                         
                         ( 
                         t 
                         ) 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #9 
                   
                   ] 
                 
               
             
           
         
       
     
     EQ #9 may be written in terms of the speed of sound, a=√{square root over (γRT)} as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         ‐ 
                       
                       ( 
                       t 
                       ) 
                     
                     + 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         V 
                       
                       ⁢ 
                       
                         
                           v 
                           ‐ 
                         
                         ( 
                         t 
                         ) 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #10 
                   
                   ] 
                 
               
             
           
         
       
     
     Acoustic impedance for a volume may be defined as follows: 
     
       
         
           
             
               
                 
                   
                     Z 
                     v 
                   
                   = 
                   
                     
                       
                         p 
                         ⁡ 
                         ( 
                         t 
                         ) 
                       
                       
                         
                           v 
                           ‐ 
                         
                         ( 
                         t 
                         ) 
                       
                     
                     = 
                     
                       - 
                       
                         1 
                         
                           
                             ( 
                             
                               V 
                               
                                 ρ 
                                 ⁢ 
                                 
                                   a 
                                   2 
                                 
                               
                             
                             ) 
                           
                           ⁢ 
                           s 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #11 
                   
                   ] 
                 
               
             
           
         
       
     
     Modeling the Acoustic Port 
     The acoustic port may be modeled assuming that all of the fluid in the port essentially moves as a rigid cylinder reciprocating in the axial direction. All of the fluid in the channel is assumed to travel at the same velocity, the channel is assumed to be of constant cross section, and the “end effects” resulting from the fluid entering and leaving the channel are neglected. 
     If we assume laminar flow friction of the form Δp=f ρ v , the friction force acting on the mass of fluid in the channel may be written as follows: 
         F=fρA   2     x     [EQ #12]
 
     A second order differential equation may then be written for the dynamics of the fluid in the channel: 
       ρ LA{umlaut over (x)}=ΔpA−fρA   2     x     [EQ #13]
 
     or, in terms of volume flow rate: 
     
       
         
           
             
               
                 
                   
                     v 
                     
                       ‐ 
                       ⁢ 
                       ‐ 
                     
                   
                   = 
                   
                     
                       - 
                       
                         fA 
                         L 
                       
                       ⁢ 
                       
                         v 
                         ‐ 
                       
                     
                     + 
                     
                       Δ 
                       ⁢ 
                       p 
                       ⁢ 
                       
                         A 
                         
                           ρ 
                           ⁢ 
                           L 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #14 
                   
                   ] 
                 
               
             
           
         
       
     
     The acoustic impedance of the channel may then be written as follows: 
     
       
         
           
             
               
                 
                   
                     Z 
                     p 
                   
                   = 
                   
                     
                       
                         Δ 
                         ⁢ 
                         p 
                       
                       
                         v 
                         ‐ 
                       
                     
                     = 
                     
                       
                         
                           ρ 
                           ⁢ 
                           L 
                         
                         A 
                       
                       ⁢ 
                       
                         ( 
                         
                           s 
                           + 
                           
                             fA 
                             L 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #15 
                   
                   ] 
                 
               
             
           
         
       
     
     System Transfer Functions 
     Using the volume and port dynamics defined above, volume sensor assembly  148  may be described by the following system of equations: (k=speaker, r=resonator) 
     
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         ‐ 
                       
                       0 
                     
                     - 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           0 
                         
                       
                       ⁢ 
                       
                         
                           v 
                           ‐ 
                         
                         k 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #16 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         ‐ 
                       
                       1 
                     
                     + 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           1 
                         
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             
                               v 
                               ‐ 
                             
                             k 
                           
                           - 
                           
                             
                               v 
                               ‐ 
                             
                             r 
                           
                         
                         ) 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #17 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         ‐ 
                       
                       2 
                     
                     + 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           2 
                         
                       
                       ⁢ 
                       
                         
                           v 
                           ‐ 
                         
                         r 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #18 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       v 
                       
                         ‐ 
                         ⁢ 
                         ‐ 
                       
                     
                     r 
                   
                   = 
                   
                     
                       - 
                       
                         fA 
                         L 
                       
                       ⁢ 
                       
                         
                           v 
                           ‐ 
                         
                         r 
                       
                     
                     + 
                     
                       
                         A 
                         
                           ρ 
                           ⁢ 
                           L 
                         
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             p 
                             2 
                           
                           - 
                           
                             p 
                             1 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   
                     [ 
                     
                       EQ 
                       ⁢ 
                           
                       #19 
                     
                     ] 
                   
                 
               
             
           
         
       
     
     One equation may be eliminated if p 0  is treated as the input substituting in 
     
       
         
           
             
               
                 v 
                 . 
               
               k 
             
             = 
             
               
                 
                   V 
                   0 
                 
                 
                   ρ 
                   ⁢ 
                   
                     a 
                     2 
                   
                 
               
               ⁢ 
               
                 
                   
                     p 
                     . 
                   
                   0 
                 
                 . 
               
             
           
         
       
     
     
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         . 
                       
                       1 
                     
                     + 
                     
                       
                         
                           V 
                           0 
                         
                         
                           V 
                           1 
                         
                       
                       ⁢ 
                       
                         
                           p 
                           . 
                         
                         0 
                       
                     
                     - 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           1 
                         
                       
                       ⁢ 
                       
                         
                           v 
                           . 
                         
                         r 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #20 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         . 
                       
                       2 
                     
                     + 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           2 
                         
                       
                       ⁢ 
                       
                         
                           v 
                           . 
                         
                         r 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #21 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       v 
                       ¨ 
                     
                     r 
                   
                   = 
                   
                     
                       
                         - 
                         
                           fA 
                           L 
                         
                       
                       ⁢ 
                       
                         
                           v 
                           . 
                         
                         r 
                       
                     
                     + 
                     
                       
                         A 
                         
                           ρ 
                           ⁢ 
                           L 
                         
                       
                       ⁢ 
                       
                         p 
                         2 
                       
                     
                     - 
                     
                       
                         A 
                         
                           ρ 
                           ⁢ 
                           L 
                         
                       
                       ⁢ 
                       
                         p 
                         1 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #22 
                   
                   ] 
                 
               
             
           
         
       
     
     Cross System Transfer Function 
     The relationship between the speaker volume and the variable volume may be referred to as the Cross System transfer function. This transfer function may be derived from the above equations and is as follows: 
     
       
         
           
             
               
                 
                   
                     
                       p 
                       2 
                     
                     
                       p 
                       0 
                     
                   
                   = 
                   
                     
                       - 
                       
                         
                           V 
                           0 
                         
                         
                           
                             V 
                             1 
                           
                             
                         
                       
                     
                     ⁢ 
                     
                       
                         ω 
                         n 
                         2 
                       
                       
                         
                           s 
                           2 
                         
                         + 
                         
                           2 
                           ⁢ 
                           
                             ζω 
                             n 
                           
                           ⁢ 
                           s 
                         
                         + 
                         
                           αω 
                           n 
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #23 
                   
                   ] 
                 
               
             
           
         
       
     
     where 
     
       
         
           
             
               
                 
                   
                     
                       ω 
                       n 
                       2 
                     
                     = 
                     
                       
                         
                           
                             a 
                             2 
                           
                           ⁢ 
                           A 
                         
                         L 
                       
                       ⁢ 
                       
                         1 
                         
                           V 
                           2 
                         
                       
                     
                   
                   , 
                   
                     ζ 
                     = 
                     
                       
                         
                           fA 
                           
                             2 
                             ⁢ 
                             L 
                             ⁢ 
                             
                               ω 
                               n 
                             
                           
                         
                         ⁢ 
                             
                         and 
                         ⁢ 
                             
                         α 
                       
                       = 
                       
                         ( 
                         
                           1 
                           + 
                           
                             
                               V 
                               2 
                             
                             
                               V 
                               1 
                             
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #24 
                   
                   ] 
                 
               
             
           
         
       
     
     Referring also to  FIG.  97   , a bode plot of EQ #23 is shown. 
     The difficulty of this relationship is that the complex poles depend on both the variable volume, V 2 , and the reference volume, V 1 . Any change in the mean position of the speaker may result in an error in the estimated volume. 
     Cross Port Transfer Function 
     The relationship between the two volumes on each side of the acoustic port may be referred to as the Cross Port transfer function. This relationship is as follows: 
     
       
         
           
             
               
                 
                   
                     
                       p 
                       2 
                     
                     
                       p 
                       1 
                     
                   
                   = 
                     
                   
                     
                       ω 
                       n 
                       2 
                     
                     
                       
                         s 
                         2 
                       
                       + 
                       
                         2 
                         ⁢ 
                         
                           ζω 
                           n 
                         
                         ⁢ 
                         s 
                       
                       + 
                       
                         ω 
                         n 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #25 
                   
                   ] 
                 
               
             
           
         
       
     
     which is shown graphically in  FIG.  98   . 
     This relationship has the advantage that the poles are only dependent on the variable volume and not on the reference volume. It does, however, have the difficulty that the resonant peak is actually due to the inversion of the zero in the response of the reference volume pressure. Accordingly, the pressure measurement in the reference chamber will have a low amplitude in the vicinity of the resonance, potentially increasing the noise in the measurement. 
     Cross Speaker Transfer Function 
     The pressures may also be measured on each side of the speaker. This is referred to as the cross speaker transfer function: 
     
       
         
           
             
               
                 
                   
                     
                       p 
                       1 
                     
                     
                       p 
                       0 
                     
                   
                   = 
                   
                     
                       - 
                       
                         
                           V 
                           0 
                         
                         
                           
                             V 
                             1 
                           
                             
                         
                       
                     
                     ⁢ 
                     
                       
                         
                           s 
                           2 
                         
                         + 
                         
                           2 
                           ⁢ 
                           
                             ζω 
                             n 
                           
                           ⁢ 
                           s 
                         
                         + 
                         
                           ω 
                           n 
                           2 
                         
                       
                       
                         
                           s 
                           2 
                         
                         + 
                         
                           2 
                           ⁢ 
                           
                             ζω 
                             n 
                           
                           ⁢ 
                           s 
                         
                         + 
                         
                           αω 
                           n 
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #26 
                   
                   ] 
                 
               
             
           
         
       
     
     which is shown graphically in  FIG.  99   . 
     This transfer function has a set of complex zeros in addition to the set of complex poles. 
     Looking at the limits of this transfer function: as 
     
       
         
           
             
               s 
               → 
               0 
             
             , 
             
               
                 
                   
                     p 
                     1 
                   
                   
                     p 
                     0 
                   
                 
                 → 
                 
                   - 
                   
                     
                       V 
                       0 
                     
                     
                       
                         V 
                         1 
                       
                       + 
                       
                         V 
                         2 
                       
                     
                   
                 
               
               ; 
                   
               
                 
                   and 
                   ⁢ 
                       
                   as 
                   ⁢ 
                       
                   s 
                 
                 → 
                 ∞ 
               
             
             , 
             
               
                 
                   p 
                   1 
                 
                 
                   p 
                   0 
                 
               
               → 
               
                 - 
                 
                   
                     
                       V 
                       0 
                     
                     
                       V 
                       1 
                     
                   
                   . 
                 
               
             
           
         
       
     
     Resonance Q Factor and Peak Response 
     The quality of the resonance is the ratio of the energy stored to the power loss multiplied by the resonant frequency. For a pure second-order system, the quality factor may be expressed as a function of the damping ratio: 
     
       
         
           
             
               
                 
                   Q 
                   = 
                   
                     1 
                     
                       2 
                       ⁢ 
                       ζ 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #27 
                   
                   ] 
                 
               
             
           
         
       
     
     The ratio of the peak response to the low-frequency response may also be written as a function of the damping ratio: 
     
       
         
           
             
               
                 
                   
                     
                       
                         ❘ 
                         &#34;\[LeftBracketingBar]&#34; 
                       
                       G 
                       
                         ❘ 
                         &#34;\[RightBracketingBar]&#34; 
                       
                     
                     
                       ω 
                       d 
                     
                   
                   = 
                   
                     1 
                     
                       ζ 
                       ⁢ 
                       
                         
                           5 
                           - 
                           
                             4 
                             ⁢ 
                             ζ 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #28 
                   
                   ] 
                 
               
             
           
         
       
     
     This may occur at the damped natural frequency: 
       ω d =ω n √{square root over (1−ζ)}  [EQ #29]
 
     Volume Estimation 
     Volume Estimation using Cross-Port Phase 
     The variable volume (i.e., within volume sensor chamber  620 ) may also be estimated using the cross-port phase. The transfer function for the pressure ratio across the resonant port may be as follows: 
     
       
         
           
             
               
                 
                   
                     
                       p 
                       2 
                     
                     
                       p 
                       1 
                     
                   
                   = 
                   
                     
                       ω 
                       n 
                       2 
                     
                     
                       
                         s 
                         2 
                       
                       + 
                       bs 
                       + 
                       
                         ω 
                         n 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #30 
                   
                   ] 
                 
               
             
           
         
       
     
     At the 90° phase point, ω=ω n ; where 
     
       
         
           
             
               ω 
               n 
               2 
             
             = 
             
               
                 1 
                 
                   V 
                   2 
                 
               
               ⁢ 
               
                 
                   
                     a 
                     2 
                   
                   ⁢ 
                   A 
                 
                 L 
               
             
           
         
       
     
     The resonant frequency may be found on the physical system using a number of methods. A phase-lock loop may be employed to find the 90° phase point—this frequency may correspond to the natural frequency of the system. Alternatively, the resonant frequency may be calculated using the phase at any two frequencies: 
     The phase, ϕ, at any given frequency will satisfy the following relation: 
     
       
         
           
             
               
                 
                   
                     tan 
                     ⁢ 
                     ϕ 
                   
                   = 
                   
                     
                       b 
                       ⁢ 
                       ω 
                     
                     
                       
                         ω 
                         2 
                       
                       - 
                       
                         ω 
                         n 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #31 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               where 
               ⁢ 
               
                   
                    
               
               ⁢ 
               b 
             
             = 
             
               
                 fA 
                 L 
               
               . 
             
           
         
       
     
     Solving for V 2  results in: 
     
       
         
           
             
               
                 
                   
                     V 
                     2 
                   
                   = 
                   
                     
                       
                         
                           a 
                           2 
                         
                         ⁢ 
                         A 
                       
                       L 
                     
                     
                       
                         ω 
                         2 
                       
                       - 
                       
                         f 
                         ⁢ 
                         ω 
                         ⁢ 
                         cot 
                         ⁢ 
                         ϕ 
                           
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #32 
                   
                   ] 
                 
               
             
           
         
       
     
     Accordingly, the ratio of the phases at two different frequencies ω 1  and ω 2  can be used to compute the natural frequency of the system: 
     
       
         
           
             
               
                 
                   
                     αω 
                     n 
                     2 
                   
                   = 
                   
                     
                       ω 
                       1 
                     
                     ⁢ 
                     
                       ω 
                       2 
                     
                     ⁢ 
                     
                       
                         ( 
                         
                           
                             
                               ω 
                               1 
                             
                             ⁢ 
                             
                               
                                 tan 
                                 ⁢ 
                                 
                                   ϕ 
                                   1 
                                 
                               
                               
                                 tan 
                                 ⁢ 
                                 
                                   ϕ 
                                   2 
                                 
                               
                             
                           
                           - 
                           
                             ω 
                             2 
                           
                         
                         ) 
                       
                       
                         ( 
                         
                           
                             
                               ω 
                               2 
                             
                             ⁢ 
                             
                               
                                 tan 
                                 ⁢ 
                                 
                                   ϕ 
                                   1 
                                 
                               
                               
                                 tan 
                                 ⁢ 
                                 
                                   ϕ 
                                   2 
                                 
                               
                             
                           
                           - 
                           
                             ω 
                             1 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #33 
                   
                   ] 
                 
               
             
           
         
       
     
     For computational efficiency, the actual phase does not need to be calculated. All that is needed is the ratio of the real and imaginary parts of the response (tan ϕ). 
     Re-writing EQ #33 in terms of the variable volume results in: 
     
       
         
           
             
               
                 
                   
                     1 
                     
                       V 
                       2 
                     
                   
                   = 
                   
                     
                       1 
                       
                         a 
                         2 
                       
                     
                     ⁢ 
                     
                       L 
                       A 
                     
                     ⁢ 
                     
                       ω 
                       1 
                     
                     ⁢ 
                     
                       ω 
                       2 
                     
                     ⁢ 
                     
                       
                         ( 
                         
                           
                             
                               ω 
                               1 
                             
                             ⁢ 
                             
                               
                                 tan 
                                 ⁢ 
                                 
                                   ϕ 
                                   1 
                                 
                               
                               
                                 tan 
                                 ⁢ 
                                 
                                   ϕ 
                                   2 
                                 
                               
                             
                           
                           - 
                           
                             ω 
                             2 
                           
                         
                         ) 
                       
                       
                         ( 
                         
                           
                             
                               ω 
                               2 
                             
                             ⁢ 
                             
                               
                                 tan 
                                 ⁢ 
                                 
                                   ϕ 
                                   1 
                                 
                               
                               
                                 tan 
                                 ⁢ 
                                 
                                   ϕ 
                                   2 
                                 
                               
                             
                           
                           - 
                           
                             ω 
                             1 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #34 
                   
                   ] 
                 
               
             
           
         
       
     
     Volume Estimation using Swept Sine 
     The resonant frequency of the system may be estimated using swept-sine system identification. In this method, the response of the system to a sinusoidal pressure variation may be found at a number of different frequencies. This frequency response data may then used to estimate the system transfer function using linear regression. 
     The transfer function for the system may be expressed as a rational function of s. The general case is expressed below for a transfer function with an n th  order numerator and an m th  order denominator. N and D are the coefficients for the numerator and denominator respectively. The equation has been normalized such that the leading coefficient in the denominator is 1. 
     
       
         
           
             
               
                 
                   
                     G 
                     ⁡ 
                     ( 
                     s 
                     ) 
                   
                   = 
                   
                     
                       
                         
                           N 
                           n 
                         
                         ⁢ 
                         
                           s 
                           n 
                         
                       
                       + 
                       
                         
                           N 
                           
                             n 
                             - 
                             1 
                           
                         
                         ⁢ 
                         
                           s 
                           
                             n 
                             - 
                             1 
                           
                         
                       
                       + 
                       … 
                       + 
                       
                         N 
                         0 
                       
                     
                     
                       
                         s 
                         m 
                       
                       + 
                       
                         
                           D 
                           
                             m 
                             - 
                             1 
                           
                         
                         ⁢ 
                         
                           s 
                           
                             m 
                             - 
                             1 
                           
                         
                       
                       + 
                       
                         
                           D 
                           
                             m 
                             - 
                             2 
                           
                         
                         ⁢ 
                         
                           s 
                           
                             m 
                             - 
                             2 
                           
                         
                       
                       + 
                       … 
                       + 
                       
                         D 
                         0 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #35 
                   
                   ] 
                 
               
             
           
         
       
       
         
           or 
         
       
       
         
           
             
               
                 
                   
                     G 
                     ⁡ 
                     ( 
                     s 
                     ) 
                   
                   = 
                   
                     
                       
                         ∑ 
                         
                           k 
                           = 
                           0 
                         
                         n 
                       
                       
                         
                           N 
                           k 
                         
                         ⁢ 
                         
                           s 
                           k 
                         
                       
                     
                     
                       
                         s 
                         m 
                       
                       + 
                       
                         
                           ∑ 
                           
                             k 
                             = 
                             0 
                           
                           
                             m 
                             - 
                             1 
                           
                         
                         
                           
                             D 
                             k 
                           
                           ⁢ 
                           
                             s 
                             k 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #36 
                   
                   ] 
                 
               
             
           
         
       
     
     This equation may be re-written as follows: 
     
       
         
           
             
               
                 
                   
                     Gs 
                     m 
                   
                   = 
                   
                     
                       
                         ∑ 
                         
                           k 
                           = 
                           0 
                         
                         n 
                       
                         
                       
                         
                           N 
                           k 
                         
                         ⁢ 
                         
                           s 
                           k 
                         
                       
                     
                     - 
                     
                       G 
                       ⁢ 
                       
                         
                           ∑ 
                           
                             k 
                             = 
                             0 
                           
                           
                             m 
                             - 
                             1 
                           
                         
                           
                         
                           
                             D 
                             k 
                           
                           ⁢ 
                           
                             s 
                             k 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #37 
                   
                   ] 
                 
               
             
           
         
       
     
     Representing this summation in matrix notation resulting in the following: 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             
                               G 
                               1 
                             
                             ⁢ 
                             
                               s 
                               1 
                               m 
                             
                           
                         
                       
                       
                         
                           ⋮ 
                         
                       
                       
                         
                           
                             
                               G 
                               k 
                             
                             ⁢ 
                             
                               s 
                               k 
                               m 
                             
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             
                               s 
                               1 
                               n 
                             
                           
                           
                             … 
                           
                           
                             
                               s 
                               1 
                               0 
                             
                           
                           
                             
                               - 
                               
                                 G 
                                 1 
                               
                               ⁢ 
                               
                                 s 
                                 1 
                                 
                                   m 
                                   - 
                                   1 
                                 
                               
                             
                           
                           
                             … 
                           
                           
                             
                               - 
                               
                                 G 
                                 1 
                               
                               ⁢ 
                               
                                 s 
                                 1 
                                 0 
                               
                             
                           
                         
                         
                           
                             ⋮ 
                           
                           
                               
                           
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                           
                               
                           
                           
                             ⋮ 
                           
                         
                         
                           
                             
                               S 
                               k 
                               n 
                             
                           
                           
                             … 
                           
                           
                             
                               s 
                               k 
                               0 
                             
                           
                           
                             
                               - 
                               
                                 G 
                                 k 
                               
                               ⁢ 
                               
                                 s 
                                 k 
                                 
                                   m 
                                   - 
                                   1 
                                 
                               
                             
                           
                           
                             … 
                           
                           
                             
                               - 
                               
                                 G 
                                 k 
                               
                               ⁢ 
                               
                                 s 
                                 k 
                                 0 
                               
                             
                           
                         
                       
                       ] 
                     
                     [ 
                     
                       
                         
                           
                             N 
                             n 
                           
                         
                       
                       
                         
                           ⋮ 
                         
                       
                       
                         
                           
                             N 
                             0 
                           
                         
                       
                       
                         
                           
                             D 
                             
                               m 
                               - 
                               1 
                             
                           
                         
                       
                       
                         
                           ⋮ 
                         
                       
                       
                         
                           
                             D 
                             0 
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #38 
                   
                   ] 
                 
               
             
           
         
       
     
     where k is the number of data points collected in the swept sine. To simplify the notation, this equation may be summarized using the vectors: 
         y=Xc   [EQ #39]
 
     where y is k by 1, x is k by (m+n−1) and c is (m+n−1) by 1. The coefficients may then be found using a least square approach. The error function may be written as follows: 
         e=y−Xc   [EQ #40]
 
     The function to be minimized is the weighted square of the error function; W is a k×k diagonal matrix. 
         e   T   We =( y−Xc ) T   W ( y−Xc )  [EQ #41]
 
         e   T   We=y   T   Wy −( y   T   WXc ) T   −y   T   WXc+c   T   x   T   WXc   [EQ #42]
 
     As the center two terms are scalars, the transpose may be neglected. 
     
       
         
           
             
               
                 
                   
                     
                       e 
                       T 
                     
                     ⁢ 
                     We 
                   
                   = 
                   
                     
                       
                         y 
                         T 
                       
                       ⁢ 
                       Wy 
                     
                     - 
                     
                       2 
                       ⁢ 
                       
                         y 
                         T 
                       
                       ⁢ 
                       WXc 
                     
                     + 
                     
                       
                         c 
                         T 
                       
                       ⁢ 
                       
                         x 
                         T 
                       
                       ⁢ 
                       WXc 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #43 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       
                         ∂ 
                         
                           e 
                           T 
                         
                       
                       ⁢ 
                       We 
                     
                     
                       ∂ 
                       c 
                     
                   
                   = 
                   
                     
                       
                         - 
                         2 
                         ⁢ 
                         
                           X 
                           T 
                         
                         ⁢ 
                         Wy 
                       
                       + 
                       
                         2 
                         ⁢ 
                         
                           X 
                           T 
                         
                         ⁢ 
                         WXc 
                       
                     
                     = 
                     0 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #44 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   c 
                   = 
                   
                     
                       
                         ( 
                         
                           
                             X 
                             T 
                           
                           ⁢ 
                           WX 
                         
                         ) 
                       
                       
                         - 
                         1 
                       
                     
                     ⁢ 
                     
                       X 
                       T 
                     
                     ⁢ 
                     Wy 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #45 
                   
                   ] 
                 
               
             
           
         
       
     
     It may be necessary to use the complex transpose in all of these cases. This approach may result in complex coefficients, but the process may be modified to ensure that all the coefficients are real. The least-square minimization may be modified to give only real coefficients if the error function is changed to be 
         e   T   We =Re( y−Xc ) T   W  Re( y−Xc )+Im( y−Xc ) T   W  Im( y−Xc )  [EQ #46]
 
     Accordingly, the coefficients may be found with the relation: 
         c =(Re( X ) T   W  Re( X )+Im( X ) T   W  Im( X )) −1 (Re( X ) T   W  Re( y )+Im( X ) T   W  Im( y ))  [EQ #47]
 
     Solution for a 2nd Order System 
     For a system with a 0 th  order numerator and a second order denominator as shown in the transfer function: 
     
       
         
           
             
               
                 
                   
                     G 
                     ⁡ 
                     ( 
                     s 
                     ) 
                   
                   = 
                   
                     
                       N 
                       0 
                     
                     
                       
                         s 
                         2 
                       
                       + 
                       
                         
                           D 
                           1 
                         
                         ⁢ 
                         s 
                       
                       + 
                       
                         D 
                         0 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #48 
                   
                   ] 
                 
               
             
           
         
       
     
     The coefficients in this transfer function may be found based on the expression found in the previous section: 
     
       
         
           
             
               
                 
                   c 
                   = 
                   
                     
                       
                         ( 
                         
                           
                             
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 X 
                                 ) 
                               
                               T 
                             
                             ⁢ 
                             W 
                             ⁢ 
                             
                               Re 
                               ⁡ 
                               ( 
                               X 
                               ) 
                             
                           
                           + 
                           
                             
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 X 
                                 ) 
                               
                               T 
                             
                             ⁢ 
                             W 
                             ⁢ 
                             
                               Im 
                               ⁡ 
                               ( 
                               X 
                               ) 
                             
                           
                         
                         ) 
                       
                       
                         - 
                         1 
                       
                     
                     ⁢ 
                     
                       ( 
                       
                         
                           
                             
                               Re 
                               ⁡ 
                               ( 
                               X 
                               ) 
                             
                             T 
                           
                           ⁢ 
                           W 
                           ⁢ 
                           
                             Re 
                             ⁡ 
                             ( 
                             y 
                             ) 
                           
                         
                         + 
                         
                           
                             
                               Im 
                               ⁡ 
                               ( 
                               X 
                               ) 
                             
                             T 
                           
                           ⁢ 
                           W 
                           ⁢ 
                           
                             Im 
                             ⁡ 
                             ( 
                             y 
                             ) 
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #49 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             	 
             
               where 
               : 
             
           
         
       
       
         
           
             
               
                 
                   	 
                   
                     
                       y 
                       = 
                       
                         [ 
                         
                           
                             
                               
                                 
                                   G 
                                   1 
                                 
                                 ⁢ 
                                 
                                   s 
                                   1 
                                   2 
                                 
                               
                             
                           
                           
                             
                               ⋮ 
                             
                           
                           
                             
                               
                                 
                                   G 
                                   k 
                                 
                                 ⁢ 
                                 
                                   s 
                                   k 
                                   2 
                                 
                               
                             
                           
                         
                         ] 
                       
                     
                     , 
                     
                       X 
                       = 
                       
                         [ 
                         
                           
                             
                               1 
                             
                             
                               
                                 - 
                                 
                                   G 
                                   1 
                                 
                                 ⁢ 
                                 
                                   s 
                                   1 
                                 
                               
                             
                             
                               
                                 - 
                                 
                                   G 
                                   1 
                                 
                               
                             
                           
                           
                             
                               ⋮ 
                             
                             
                               ⋮ 
                             
                             
                               ⋮ 
                             
                           
                           
                             
                               1 
                             
                             
                               
                                 - 
                                 
                                   G 
                                   k 
                                 
                                 ⁢ 
                                 
                                   s 
                                   k 
                                 
                               
                             
                             
                               
                                 - 
                                 
                                   G 
                                   k 
                                 
                               
                             
                           
                         
                         ] 
                       
                     
                     , 
                     
                       
                         and 
                         ⁢ 
                             
                         c 
                       
                       = 
                       
                         [ 
                         
                           
                             
                               
                                 N 
                                 0 
                               
                             
                           
                           
                             
                               
                                 D 
                                 1 
                               
                             
                           
                           
                             
                               
                                 D 
                                 0 
                               
                             
                           
                         
                         ] 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #50 
                   
                   ] 
                 
               
             
           
         
       
     
     To simplify the algorithm, we may combine some of terms: 
         c=D   −1   b   [EQ #51]
 
       where: 
         D =Re( X ) T   W  Re( X )+Im( X ) T   W  Im( X )  [EQ #52]
 
         b =Re( X ) T   W  Re( y )+Im( X ) T   W  Im( y )  [EQ #53]
 
     To find an expression for D in terms of the complex response vector G and the natural frequency s=jω, X may be split into its real and imaginary parts: 
     
       
         
           
             
               
                 
                   
                     
                       Re 
                       ⁡ 
                       ( 
                       X 
                       ) 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             1 
                           
                           
                             
                               
                                 ω 
                                 k 
                               
                               ⁢ 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   1 
                                 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   1 
                                 
                                 ) 
                               
                             
                           
                         
                         
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                         
                         
                           
                             1 
                           
                           
                             
                               
                                 ω 
                                 k 
                               
                               ⁢ 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   k 
                                 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   k 
                                 
                                 ) 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
 
                   
                     
                       Im 
                       ⁡ 
                       ( 
                       X 
                       ) 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             0 
                           
                           
                             
                               - 
                               
                                 ω 
                                 k 
                               
                               ⁢ 
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   1 
                                 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   1 
                                 
                                 ) 
                               
                             
                           
                         
                         
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                         
                         
                           
                             0 
                           
                           
                             
                               - 
                               
                                 ω 
                                 k 
                               
                               ⁢ 
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   k 
                                 
                                 ) 
                               
                             
                           
                           
                             
                               - 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   k 
                                 
                                 ) 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #54 
                   
                   ] 
                 
               
             
           
         
       
     
     The real and imaginary portions of the expression for D above may then become: 
     
       
         
           
             
               
                 
                   
                     
                       
                         Re 
                         ⁡ 
                         ( 
                         X 
                         ) 
                       
                       T 
                     
                     ⁢ 
                     W 
                     ⁢ 
                     
                       Re 
                       ⁡ 
                       ( 
                       X 
                       ) 
                     
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               w 
                               i 
                             
                           
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   i 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 ω 
                                 i 
                               
                             
                           
                         
                         
                           
                             - 
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                                 
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 
                                   Re 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                               
                             
                           
                         
                       
                       
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   i 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 ω 
                                 i 
                               
                             
                           
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 
                                   Im 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 2 
                               
                               ⁢ 
                               
                                 ω 
                                 i 
                                 2 
                               
                             
                           
                         
                         
                           
                             - 
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                                 
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 
                                   Im 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   Re 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                 
                               
                             
                           
                         
                       
                       
                         
                           
                             - 
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                                 
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 
                                   Re 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                               
                             
                           
                         
                         
                           
                             - 
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                                 
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 
                                   Im 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   Re 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                 
                               
                             
                           
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 
                                   Re 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 2 
                               
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #55 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       
                         Im 
                         ⁡ 
                         ( 
                         X 
                         ) 
                       
                       T 
                     
                     ⁢ 
                     W 
                     ⁢ 
                     
                       Im 
                       ⁡ 
                       ( 
                       X 
                       ) 
                     
                   
                   = 
                   
                     [ 
                     
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 
                                   Re 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 2 
                               
                               ⁢ 
                               
                                 ω 
                                 i 
                                 2 
                               
                             
                           
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   i 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   i 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 ω 
                                 i 
                               
                             
                           
                         
                       
                       
                         
                           0 
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   i 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   i 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 ω 
                                 i 
                               
                             
                           
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 
                                   Im 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 2 
                               
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #56 
                   
                   ] 
                 
               
             
           
         
       
     
     Combining these terms results in the final expression for the D matrix, which may contain only real values. 
     
       
         
           
             
               
                 
                   D 
                   = 
                   
                     [ 
                     
                       
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               w 
                               i 
                             
                           
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   i 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 ω 
                                 i 
                               
                             
                           
                         
                         
                           
                             - 
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                                 
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 
                                   Re 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                               
                             
                           
                         
                       
                       
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   i 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 ω 
                                 i 
                               
                             
                           
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 
                                   w 
                                   i 
                                 
                                 ( 
                                 
                                   
                                     
                                       Re 
                                       ⁡ 
                                       ( 
                                       
                                         G 
                                         i 
                                       
                                       ) 
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                       Im 
                                       ⁡ 
                                       ( 
                                       
                                         G 
                                         i 
                                       
                                       ) 
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 ω 
                                 i 
                                 2 
                               
                             
                           
                         
                         
                           0 
                         
                       
                       
                         
                           
                             - 
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                                 
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 
                                   Re 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     
                                       i 
                                         
                                     
                                   
                                   ) 
                                 
                               
                             
                           
                         
                         
                           0 
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                               
                             
                               
                                 w 
                                 i 
                               
                               ( 
                               
                                 
                                   
                                     Re 
                                     ⁡ 
                                     ( 
                                     
                                       G 
                                       
                                         i 
                                           
                                       
                                     
                                     ) 
                                   
                                   2 
                                 
                                 + 
                                 
                                   
                                     Im 
                                     ⁡ 
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   2 
                                 
                               
                               ) 
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #57 
                   
                   ] 
                 
               
             
           
         
       
     
     The same approach may be taken to find an expression for the b vector in terms of G and ω. The real and imaginary parts of y are as follows: 
     
       
         
           
             
               
                 
                   
                     
                       Re 
                       ⁡ 
                       ( 
                       y 
                       ) 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               - 
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   1 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 ω 
                                 1 
                                 2 
                               
                             
                           
                         
                         
                           
                             ⋮ 
                           
                         
                         
                           
                             
                               - 
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   k 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 ω 
                                 k 
                                 2 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
                       Im 
                       ⁡ 
                       ( 
                       y 
                       ) 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               - 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   1 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 ω 
                                 1 
                                 2 
                               
                             
                           
                         
                         
                           
                             ⋮ 
                           
                         
                         
                           
                             
                               - 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   k 
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 ω 
                                 k 
                                 2 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #58 
                   
                   ] 
                 
               
             
           
         
       
     
     Combining the real and imaginary parts results in the expression for the b vector as follows: 
     
       
         
           
             
               
                 
                   b 
                   = 
                   
                     
                       
                         
                           
                             Re 
                             ⁡ 
                             ( 
                             X 
                             ) 
                           
                           T 
                         
                         ⁢ 
                         W 
                         ⁢ 
                         
                           Re 
                           ⁡ 
                           ( 
                           y 
                           ) 
                         
                       
                       + 
                       
                         
                           
                             Im 
                             ⁡ 
                             ( 
                             X 
                             ) 
                           
                           T 
                         
                         ⁢ 
                         W 
                         ⁢ 
                         
                           Im 
                           ⁡ 
                           ( 
                           y 
                           ) 
                         
                       
                     
                     = 
                       
                     
                       [ 
                       
                         
                           
                             
                               - 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     1 
                                   
                                   k 
                                 
                                   
                                 
                                   
                                     w 
                                     i 
                                   
                                   ⁢ 
                                   
                                     Re 
                                     ⁡ 
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ω 
                                     i 
                                     2 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             0 
                           
                         
                         
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                                 
                               
                                 
                                   
                                     w 
                                     i 
                                   
                                   ( 
                                   
                                     
                                       
                                         Re 
                                         ⁡ 
                                         ( 
                                         
                                           G 
                                           i 
                                         
                                         ) 
                                       
                                       2 
                                     
                                     + 
                                     
                                       
                                         Im 
                                         ⁡ 
                                         ( 
                                         
                                           G 
                                           i 
                                         
                                         ) 
                                       
                                       2 
                                     
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   2 
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #59 
                   
                   ] 
                 
               
             
           
         
       
     
     The next step is to invert the D matrix. The matrix is symmetric and positive-definite so the number of computations needed to find the inverse will be reduced from the general 3×3 case. The general expression for a matrix inverse is: 
     
       
         
           
             
               
                 
                   
                     D 
                     
                       - 
                       1 
                     
                   
                   = 
                   
                     
                       1 
                       
                         det 
                         ⁡ 
                         ( 
                         D 
                         ) 
                       
                     
                     ⁢ 
                     
                       adj 
                       ⁡ 
                       ( 
                       D 
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #60 
                   
                   ] 
                 
               
             
           
         
       
     
     If D is expressed as follows: 
     
       
         
           
             
               
                 
                   D 
                   = 
                   
                     [ 
                     
                       
                         
                           
                             d 
                             11 
                           
                         
                         
                           
                             d 
                             12 
                           
                         
                         
                           
                             d 
                             13 
                           
                         
                       
                       
                         
                           
                             d 
                             12 
                           
                         
                         
                           
                             d 
                             22 
                           
                         
                         
                           0 
                         
                       
                       
                         
                           
                             d 
                             13 
                           
                         
                         
                           0 
                         
                         
                           
                             d 
                             33 
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #61 
                   
                   ] 
                 
               
             
           
         
       
     
     then the adjugate matrix may be written as follows: 
     
       
         
           
             
               
                 
                   
                     adj 
                     ⁡ 
                     ( 
                     D 
                     ) 
                   
                   = 
                     
                   
                     
                       [ 
                       
                         
                           
                             
                               
                                 ❘ 
                                 &#34;\[LeftBracketingBar]&#34; 
                               
                               
                                 
                                   
                                     
                                       d 
                                       22 
                                     
                                   
                                   
                                     0 
                                   
                                 
                                 
                                   
                                     0 
                                   
                                   
                                     
                                       d 
                                       33 
                                     
                                   
                                 
                               
                               
                                 ❘ 
                                 &#34;\[RightBracketingBar]&#34; 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   ❘ 
                                   &#34;\[LeftBracketingBar]&#34; 
                                 
                                 
                                   
                                     
                                       
                                         d 
                                         12 
                                       
                                     
                                     
                                       0 
                                     
                                   
                                   
                                     
                                       
                                         d 
                                         13 
                                       
                                     
                                     
                                       
                                         d 
                                         33 
                                       
                                     
                                   
                                 
                                 
                                   ❘ 
                                   &#34;\[RightBracketingBar]&#34; 
                                 
                               
                             
                           
                           
                             
                               
                                 ❘ 
                                 &#34;\[LeftBracketingBar]&#34; 
                               
                               
                                 
                                   
                                     
                                       d 
                                       12 
                                     
                                   
                                   
                                     
                                       d 
                                       22 
                                     
                                   
                                 
                                 
                                   
                                     
                                       d 
                                       13 
                                     
                                   
                                   
                                     0 
                                   
                                 
                               
                               
                                 ❘ 
                                 &#34;\[RightBracketingBar]&#34; 
                               
                             
                           
                         
                         
                           
                             
                               - 
                               
                                 
                                   ❘ 
                                   &#34;\[LeftBracketingBar]&#34; 
                                 
                                 
                                   
                                     
                                       
                                         d 
                                         12 
                                       
                                     
                                     
                                       
                                         d 
                                         13 
                                       
                                     
                                   
                                   
                                     
                                       0 
                                     
                                     
                                       
                                         d 
                                         33 
                                       
                                     
                                   
                                 
                                 
                                   ❘ 
                                   &#34;\[RightBracketingBar]&#34; 
                                 
                               
                             
                           
                           
                             
                               
                                 ❘ 
                                 &#34;\[LeftBracketingBar]&#34; 
                               
                               
                                 
                                   
                                     
                                       d 
                                       11 
                                     
                                   
                                   
                                     
                                       d 
                                       13 
                                     
                                   
                                 
                                 
                                   
                                     
                                       d 
                                       13 
                                     
                                   
                                   
                                     
                                       d 
                                       33 
                                     
                                   
                                 
                               
                               
                                 ❘ 
                                 &#34;\[RightBracketingBar]&#34; 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   ❘ 
                                   &#34;\[LeftBracketingBar]&#34; 
                                 
                                 
                                   
                                     
                                       
                                         d 
                                         11 
                                       
                                     
                                     
                                       
                                         d 
                                         12 
                                       
                                     
                                   
                                   
                                     
                                       
                                         d 
                                         13 
                                       
                                     
                                     
                                       0 
                                     
                                   
                                 
                                 
                                   ❘ 
                                   &#34;\[RightBracketingBar]&#34; 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 ❘ 
                                 &#34;\[LeftBracketingBar]&#34; 
                               
                               
                                 
                                   
                                     
                                       d 
                                       12 
                                     
                                   
                                   
                                     
                                       d 
                                       13 
                                     
                                   
                                 
                                 
                                   
                                     
                                       d 
                                       22 
                                     
                                   
                                   
                                     0 
                                   
                                 
                               
                               
                                 ❘ 
                                 &#34;\[RightBracketingBar]&#34; 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   ❘ 
                                   &#34;\[LeftBracketingBar]&#34; 
                                 
                                 
                                   
                                     
                                       
                                         d 
                                         11 
                                       
                                     
                                     
                                       
                                         d 
                                         13 
                                       
                                     
                                   
                                   
                                     
                                       
                                         d 
                                         12 
                                       
                                     
                                     
                                       0 
                                     
                                   
                                 
                                 
                                   ❘ 
                                   &#34;\[RightBracketingBar]&#34; 
                                 
                               
                             
                           
                           
                             
                               
                                 ❘ 
                                 &#34;\[LeftBracketingBar]&#34; 
                               
                               
                                 
                                   
                                     
                                       d 
                                       11 
                                     
                                   
                                   
                                     
                                       d 
                                       12 
                                     
                                   
                                 
                                 
                                   
                                     
                                       d 
                                       12 
                                     
                                   
                                   
                                     
                                       d 
                                       22 
                                     
                                   
                                 
                               
                               
                                 ❘ 
                                 &#34;\[RightBracketingBar]&#34; 
                               
                             
                           
                         
                       
                       ] 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               a 
                               11 
                             
                           
                           
                             
                               a 
                               12 
                             
                           
                           
                             
                               a 
                               13 
                             
                           
                         
                         
                           
                             
                               a 
                               12 
                             
                           
                           
                             
                               a 
                               22 
                             
                           
                           
                             
                               a 
                               23 
                             
                           
                         
                         
                           
                             
                               a 
                               13 
                             
                           
                           
                             
                               a 
                               32 
                             
                           
                           
                             
                               a 
                               33 
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #62 
                   
                   ] 
                 
               
             
           
         
       
     
     Due to symmetry, only the upper diagonal matrix may need to be calculated. 
     The Determinant may then be computed in terms of the adjugate matrix values, taking advantage of the zero elements in the original array: 
       det( D )= a   12   d   12   +a   22   d   22   [EQ #63]
 
     Finally, the inverse of D may be written as follows: 
     
       
         
           
             
               
                 
                   
                     D 
                     
                       - 
                       1 
                     
                   
                   = 
                   
                     
                       1 
                       
                         det 
                         ⁡ 
                         ( 
                         D 
                         ) 
                       
                     
                     ⁢ 
                     
                       adj 
                       ⁡ 
                       ( 
                       D 
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #64 
                   
                   ] 
                 
               
             
           
         
       
     
     Since we are trying to solve: 
     
       
         
           
             
               
                 
                   c 
                   = 
                   
                     
                       
                         D 
                         
                           - 
                           1 
                         
                       
                       ⁢ 
                       b 
                     
                     = 
                     
                       
                         1 
                         
                           det 
                           ⁡ 
                           ( 
                           D 
                           ) 
                         
                       
                       ⁢ 
                       
                         adj 
                         ⁡ 
                         ( 
                         D 
                         ) 
                       
                       ⁢ 
                       b 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                         
                     #65 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             then 
             : 
           
         
       
       
         
           
             
               
                 
                   
                     c 
                     = 
                     
                       
                         
                           
                             1 
                             
                               det 
                               ⁡ 
                               ( 
                               D 
                               ) 
                             
                           
                           [ 
                           
                             
                               
                                 
                                   a 
                                   11 
                                 
                               
                               
                                 
                                   a 
                                   12 
                                 
                               
                               
                                 
                                   a 
                                   13 
                                 
                               
                             
                             
                               
                                 
                                   a 
                                   12 
                                 
                               
                               
                                 
                                   a 
                                   22 
                                 
                               
                               
                                 
                                   a 
                                   23 
                                 
                               
                             
                             
                               
                                 
                                   a 
                                   13 
                                 
                               
                               
                                 
                                   a 
                                   32 
                                 
                               
                               
                                 
                                   a 
                                   33 
                                 
                               
                             
                           
                           ] 
                         
                         [ 
                         
                           
                             
                               
                                 b 
                                 1 
                               
                             
                           
                           
                             
                               0 
                             
                           
                           
                             
                               
                                 b 
                                 3 
                               
                             
                           
                         
                         ] 
                       
                       = 
                       
                         
                           1 
                           
                             det 
                             ⁡ 
                             ( 
                             D 
                             ) 
                           
                         
                         [ 
                         
                           
                             
                               
                                 
                                   
                                     a 
                                     11 
                                   
                                   ⁢ 
                                   
                                     b 
                                     1 
                                   
                                 
                                 + 
                                 
                                   
                                     a 
                                     13 
                                   
                                   ⁢ 
                                   
                                     b 
                                     3 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   
                                     a 
                                     12 
                                   
                                   ⁢ 
                                   
                                     b 
                                     1 
                                   
                                 
                                 + 
                                 
                                   
                                     a 
                                     23 
                                   
                                   ⁢ 
                                   
                                     b 
                                     3 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   
                                     a 
                                     13 
                                   
                                   ⁢ 
                                   
                                     b 
                                     1 
                                   
                                 
                                 + 
                                 
                                   
                                     a 
                                     33 
                                   
                                   ⁢ 
                                   
                                     b 
                                     3 
                                   
                                 
                               
                             
                           
                         
                         ] 
                       
                     
                   
                 
                 
                   
                     [ 
                     
                       EQ 
                       ⁢ 
                           
                       #66 
                     
                     ] 
                   
                 
               
             
           
         
       
     
     The final step is to get a quantitative assessment of how well the data fits the model. Accordingly, the original expression for the error is as follows: 
         e   T   We =Re( y−Xc ) T   W  Re( y−Xc )+Im( y−Xc ) T   W  Im( y−Xc )  [EQ #67]
 
     This may be expressed in terms of the D matrix and the b and c vectors as follows: 
     
       
         
           
             
               
                 
                   
                     
                       e 
                       T 
                     
                     ⁢ 
                     We 
                   
                   = 
                   
                     h 
                     - 
                     
                       2 
                       ⁢ 
                       
                         c 
                         T 
                       
                       ⁢ 
                       b 
                     
                     + 
                     
                       
                         c 
                         T 
                       
                       ⁢ 
                       Dc 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #68 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             where 
             : 
           
         
       
       
         
           
             
               
                 
                   h 
                   = 
                   
                     
                       
                         Re 
                         ⁡ 
                         ( 
                         
                           y 
                           T 
                         
                         ) 
                       
                       ⁢ 
                       W 
                       ⁢ 
                       
                         Re 
                         ⁡ 
                         ( 
                         y 
                         ) 
                       
                     
                     + 
                     
                       
                         Im 
                         ⁡ 
                         ( 
                         
                           y 
                           T 
                         
                         ) 
                       
                       ⁢ 
                       W 
                       ⁢ 
                       
                         Im 
                         ⁡ 
                         ( 
                         y 
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #69 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   h 
                   = 
                   
                     
                       ∑ 
                       
                         i 
                         = 
                         1 
                       
                       k 
                     
                     
                       
                         
                           w 
                           i 
                         
                         ( 
                         
                           
                             
                               Re 
                               ⁡ 
                               ( 
                               
                                 G 
                                 i 
                               
                               ) 
                             
                             2 
                           
                           + 
                           
                             
                               Im 
                               ⁡ 
                               ( 
                               
                                 G 
                                 i 
                               
                               ) 
                             
                             2 
                           
                         
                         ) 
                       
                       ⁢ 
                       
                         ω 
                         i 
                         4 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #70 
                   
                   ] 
                 
               
             
           
         
       
     
     The model fit error may also be used to detect sensor failures. 
     Alternate Solution for a 2nd Order System 
     
       
         
           
             
               
                 
                   
                     G 
                     ⁡ 
                     ( 
                     s 
                     ) 
                   
                   = 
                   
                     
                       
                         
                           N 
                           n 
                         
                         ⁢ 
                         
                           s 
                           n 
                         
                       
                       + 
                       
                         
                           N 
                           
                             n 
                             - 
                             1 
                           
                         
                         ⁢ 
                         
                           s 
                           
                             n 
                             - 
                             1 
                           
                         
                       
                       + 
                       … 
                       + 
                       
                         N 
                         0 
                       
                     
                     
                       
                         s 
                         m 
                       
                       + 
                       
                         
                           D 
                           
                             m 
                             - 
                             1 
                           
                         
                         ⁢ 
                         
                           s 
                           
                             m 
                             - 
                             1 
                           
                         
                       
                       + 
                       
                         
                           D 
                           
                             m 
                             - 
                             2 
                           
                         
                         ⁢ 
                         
                           s 
                           
                             m 
                             - 
                             2 
                           
                         
                       
                       + 
                       … 
                       + 
                       
                         D 
                         0 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #71 
                   
                   ] 
                 
               
             
           
         
       
       
         
           or 
         
       
       
         
           
             
               
                 
                   
                     G 
                     ⁡ 
                     ( 
                     s 
                     ) 
                   
                   = 
                   
                     
                       
                         ∑ 
                         
                           k 
                           = 
                           0 
                         
                         n 
                       
                       
                         
                           N 
                           k 
                         
                         ⁢ 
                         
                           s 
                           k 
                         
                       
                     
                     
                       
                         s 
                         m 
                       
                       + 
                       
                         
                           ∑ 
                           
                             k 
                             = 
                             0 
                           
                           
                             m 
                             - 
                             1 
                           
                         
                         
                           
                             D 
                             k 
                           
                           ⁢ 
                           
                             s 
                             k 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #72 
                   
                   ] 
                 
               
             
           
         
       
     
     This equation may be re-written as follows: 
     
       
         
           
             
               
                 
                   G 
                   = 
                   
                     
                       
                         ∑ 
                         
                           k 
                           = 
                           0 
                         
                         n 
                       
                       
                         
                           N 
                           k 
                         
                         ⁢ 
                         
                           s 
                           
                             k 
                             - 
                             m 
                           
                         
                       
                     
                     - 
                     
                       G 
                       ⁢ 
                       
                         
                           ∑ 
                           
                             k 
                             = 
                             0 
                           
                           
                             m 
                             - 
                             1 
                           
                         
                         
                           
                             D 
                             k 
                           
                           ⁢ 
                           
                             s 
                             
                               k 
                               - 
                               m 
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #73 
                   
                   ] 
                 
               
             
           
         
       
     
     Putting this summation into matrix notation results in the following: 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             G 
                             1 
                           
                         
                       
                       
                         
                           ⋮ 
                         
                       
                       
                         
                           
                             G 
                             k 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             
                               s 
                               1 
                               
                                 n 
                                 - 
                                 m 
                               
                             
                           
                           
                             … 
                           
                           
                             
                               s 
                               1 
                               
                                 - 
                                 m 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   G 
                                   1 
                                 
                               
                               ⁢ 
                               
                                 s 
                                 1 
                                 
                                   - 
                                   1 
                                 
                               
                             
                           
                           
                             … 
                           
                           
                             
                               
                                 - 
                                 
                                   G 
                                   1 
                                 
                               
                               ⁢ 
                               
                                 s 
                                 1 
                                 
                                   - 
                                   m 
                                 
                               
                             
                           
                         
                         
                           
                             ⋮ 
                           
                           
                               
                           
                           
                             ⋮ 
                           
                           
                             
                                 
                               ⋮ 
                             
                           
                           
                               
                           
                           
                             ⋮ 
                           
                         
                         
                           
                             
                               s 
                               k 
                               
                                 n 
                                 - 
                                 m 
                               
                             
                           
                           
                             … 
                           
                           
                             
                               s 
                               k 
                               
                                 - 
                                 m 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                   G 
                                   k 
                                 
                               
                               ⁢ 
                               
                                 s 
                                 k 
                                 
                                   - 
                                   1 
                                 
                               
                             
                           
                           
                             … 
                           
                           
                             
                               
                                 - 
                                 
                                   G 
                                   k 
                                 
                               
                               ⁢ 
                               
                                 s 
                                 k 
                                 
                                   - 
                                   m 
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                     [ 
                     
                       
                         
                           
                             N 
                             n 
                           
                         
                       
                       
                         
                           ⋮ 
                         
                       
                       
                         
                           
                             N 
                             0 
                           
                         
                       
                       
                         
                           
                             D 
                             
                               m 
                               - 
                               1 
                             
                           
                         
                       
                       
                         
                           ⋮ 
                         
                       
                       
                         
                           
                             D 
                             0 
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #74 
                   
                   ] 
                 
               
             
           
         
       
     
     For a system with a 0 th  order numerator and a second order denominator as shown in the transfer function: 
     
       
         
           
             
               
                 
                   
                     G 
                     ⁡ 
                     ( 
                     s 
                     ) 
                   
                   = 
                   
                     
                       N 
                       0 
                     
                     
                       
                         s 
                         2 
                       
                       + 
                       
                         
                           D 
                           1 
                         
                         ⁢ 
                         s 
                       
                       + 
                       
                         D 
                         0 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #75 
                   
                   ] 
                 
               
             
           
         
       
     
     The coefficients in this transfer function may be found based on the expression found in the previous section: 
     
       
         
           
             
               
                 
                   c 
                   = 
                   
                     
                       
                         ( 
                         
                           
                             
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 X 
                                 ) 
                               
                               T 
                             
                             ⁢ 
                             W 
                             ⁢ 
                             
                               Re 
                               ⁡ 
                               ( 
                               X 
                               ) 
                             
                           
                           + 
                           
                             
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 X 
                                 ) 
                               
                               T 
                             
                             ⁢ 
                             W 
                             ⁢ 
                             
                               Im 
                               ⁡ 
                               ( 
                               X 
                               ) 
                             
                           
                         
                         ) 
                       
                       
                         - 
                         1 
                       
                     
                     ⁢ 
                     
                       ( 
                       
                         
                           
                             
                               Re 
                               ⁡ 
                               ( 
                               X 
                               ) 
                             
                             T 
                           
                           ⁢ 
                           W 
                           ⁢ 
                           
                             Re 
                             ⁡ 
                             ( 
                             y 
                             ) 
                           
                         
                         + 
                         
                           
                             
                               Im 
                               ⁡ 
                               ( 
                               X 
                               ) 
                             
                             T 
                           
                           ⁢ 
                           W 
                           ⁢ 
                           
                             Im 
                             ⁡ 
                             ( 
                             y 
                             ) 
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #76 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             	 
             where 
           
         
       
       
         
           
             
               
                 
                                    
                   
                     
                       y 
                       = 
                       
                         [ 
                         
                           
                             
                               
                                 G 
                                 1 
                               
                             
                           
                           
                             
                               ⋮ 
                             
                           
                           
                             
                               
                                 G 
                                 k 
                               
                             
                           
                         
                         ] 
                       
                     
                     , 
                     
                       X 
                       - 
                       
                         [ 
                         
                           
                             
                               
                                 s 
                                 1 
                                 
                                   - 
                                   2 
                                 
                               
                             
                             
                               
                                 
                                   - 
                                   
                                     G 
                                     1 
                                   
                                 
                                 ⁢ 
                                 
                                   s 
                                   1 
                                   
                                     - 
                                     1 
                                   
                                 
                               
                             
                             
                               
                                 
                                   - 
                                   
                                     G 
                                     1 
                                   
                                 
                                 ⁢ 
                                 
                                   s 
                                   1 
                                   
                                     - 
                                     2 
                                   
                                 
                               
                             
                           
                           
                             
                               ⋮ 
                             
                             
                               ⋮ 
                             
                             
                               ⋮ 
                             
                           
                           
                             
                               
                                 s 
                                 k 
                                 
                                   - 
                                   2 
                                 
                               
                             
                             
                               
                                 
                                   - 
                                   
                                     G 
                                     k 
                                   
                                 
                                 ⁢ 
                                 
                                   s 
                                   k 
                                   
                                     - 
                                     1 
                                   
                                 
                               
                             
                             
                               
                                 
                                   - 
                                   
                                     G 
                                     k 
                                   
                                 
                                 ⁢ 
                                 
                                   s 
                                   k 
                                   
                                     - 
                                     2 
                                   
                                 
                               
                             
                           
                         
                         ] 
                       
                     
                     , 
                     
                       
                         and 
                         ⁢ 
                             
                         c 
                       
                       = 
                       
                         [ 
                         
                           
                             
                               
                                 N 
                                 0 
                               
                             
                           
                           
                             
                               
                                 D 
                                 1 
                               
                             
                           
                           
                             
                               
                                 D 
                                 0 
                               
                             
                           
                         
                         ] 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #77 
                   
                   ] 
                 
               
             
           
         
       
     
     To simplify the algorithm, some terms may be combined: 
         c=D   −1   b   [EQ #78]
 
       where: 
         D =Re( X ) T   W  Re( X )+Im( X ) T   W  Im( X )  [EQ #79]
 
         b =Re( X ) T   W  Re( y )+Im( X ) T   W  Im( y )  [EQ #80]
 
     To find an expression for D in terms of the complex response vector G and the natural frequency s=jω, split X may be split into its real and imaginary parts: 
     
       
         
           
             
               
                 
                   
                     Re 
                     ⁡ 
                     ( 
                     X 
                     ) 
                   
                   = 
                   
                     [ 
                     
                       
                         
                           
                             - 
                             
                               ω 
                               1 
                               2 
                             
                           
                         
                         
                           
                             
                               - 
                               
                                 ω 
                                 1 
                                 
                                   - 
                                   1 
                                 
                               
                             
                             ⁢ 
                             
                               Im 
                               ⁡ 
                               ( 
                               
                                 G 
                                 1 
                               
                               ) 
                             
                           
                         
                         
                           
                             
                               ω 
                               1 
                               2 
                             
                             ⁢ 
                             
                               Re 
                               ⁡ 
                               ( 
                               
                                 G 
                                 1 
                               
                               ) 
                             
                           
                         
                       
                       
                         
                           ⋮ 
                         
                         
                           ⋮ 
                         
                         
                           ⋮ 
                         
                       
                       
                         
                           
                             - 
                             
                               ω 
                               k 
                               
                                 - 
                                 2 
                               
                             
                           
                         
                         
                           
                             
                               - 
                               
                                 ω 
                                 k 
                                 
                                   - 
                                   1 
                                 
                               
                             
                             ⁢ 
                             
                               Im 
                               ⁡ 
                               ( 
                               
                                 G 
                                 k 
                               
                               ) 
                             
                           
                         
                         
                           
                             
                               ω 
                               k 
                               
                                 - 
                                 2 
                               
                             
                             ⁢ 
                             
                               Re 
                               ⁡ 
                               ( 
                               
                                 G 
                                 k 
                               
                               ) 
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #81 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     Im 
                     ⁡ 
                     ( 
                     X 
                     ) 
                   
                   = 
                   
                     [ 
                     
                       
                         
                           0 
                         
                         
                           
                             
                               - 
                               
                                 ω 
                                 1 
                                 
                                   - 
                                   1 
                                 
                               
                             
                             ⁢ 
                             
                               Re 
                               ⁡ 
                               ( 
                               
                                 G 
                                 1 
                               
                               ) 
                             
                           
                         
                         
                           
                             
                               ω 
                               1 
                               2 
                             
                             ⁢ 
                             
                               Im 
                               ⁡ 
                               ( 
                               
                                 G 
                                 1 
                               
                               ) 
                             
                           
                         
                       
                       
                         
                           ⋮ 
                         
                         
                           ⋮ 
                         
                         
                           ⋮ 
                         
                       
                       
                         
                           0 
                         
                         
                           
                             
                               - 
                               
                                 ω 
                                 k 
                                 
                                   - 
                                   1 
                                 
                               
                             
                             ⁢ 
                             
                               Re 
                               ⁡ 
                               ( 
                               
                                 G 
                                 k 
                               
                               ) 
                             
                           
                         
                         
                           
                             
                               ω 
                               k 
                               
                                 - 
                                 2 
                               
                             
                             ⁢ 
                             
                               Im 
                               ⁡ 
                               ( 
                               
                                 G 
                                 k 
                               
                               ) 
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #82 
                   
                   ] 
                 
               
             
           
         
       
     
     The real and imaginary portions of the expression for D above may then become: 
     
       
         
           
             
               
                 
                   
                     
                       
                         Re 
                         ⁡ 
                         ( 
                         X 
                         ) 
                       
                       T 
                     
                     ⁢ 
                     W 
                     ⁢ 
                     
                       Re 
                       ⁡ 
                       ( 
                       X 
                       ) 
                     
                   
                   = 
                   
                      
                     
                       [ 
                       
                         
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     4 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 
                                   Im 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     3 
                                   
                                 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     1 
                                   
                                   k 
                                 
                                 
                                   
                                     w 
                                     i 
                                   
                                   ⁢ 
                                   
                                     Re 
                                     ⁡ 
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ω 
                                     i 
                                     
                                       - 
                                       4 
                                     
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 Im 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     3 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 Im 
                                 ⁢ 
                                 
                                   
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   2 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     2 
                                   
                                 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     1 
                                   
                                   k 
                                 
                                 
                                   
                                     w 
                                     i 
                                   
                                   ⁢ 
                                   
                                     Im 
                                     ⁡ 
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     Re 
                                     ⁡ 
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ω 
                                     i 
                                     
                                       - 
                                       3 
                                     
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               - 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     1 
                                   
                                   k 
                                 
                                 
                                   
                                     w 
                                     i 
                                   
                                   ⁢ 
                                   Re 
                                   ⁢ 
                                   
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ω 
                                     i 
                                     
                                       - 
                                       4 
                                     
                                   
                                 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     1 
                                   
                                   k 
                                 
                                 
                                   
                                     w 
                                     i 
                                   
                                   ⁢ 
                                   Im 
                                   ⁢ 
                                   
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   Re 
                                   ⁢ 
                                   
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ω 
                                     i 
                                     
                                       - 
                                       3 
                                     
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 
                                   
                                     Re 
                                     ⁡ 
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   2 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     4 
                                   
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #83 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       
                         Im 
                         ⁡ 
                         ( 
                         X 
                         ) 
                       
                       T 
                     
                     ⁢ 
                     W 
                     ⁢ 
                     
                       Im 
                       ⁡ 
                       ( 
                       X 
                       ) 
                     
                   
                   = 
                   
                     [ 
                     
                       
                         
                           0 
                         
                         
                           0 
                         
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 
                                   Re 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 2 
                               
                               ⁢ 
                               
                                 ω 
                                 i 
                                 
                                   - 
                                   2 
                                 
                               
                             
                           
                         
                         
                           
                             - 
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 Im 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 Re 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     3 
                                   
                                 
                               
                             
                           
                         
                       
                       
                         
                           0 
                         
                         
                           
                             - 
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 Im 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 Re 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     3 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               k 
                             
                             
                               
                                 w 
                                 i 
                               
                               ⁢ 
                               
                                 
                                   Im 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 2 
                               
                               ⁢ 
                               
                                 ω 
                                 i 
                                 
                                   - 
                                   4 
                                 
                               
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #84 
                   
                   ] 
                 
               
             
           
         
       
     
     Combining these terms results in the final expression for the D matrix, which may contain only real values. 
     
       
         
           
             
               
                 
                   D 
                   = 
                   
                      
                     
                       [ 
                       
                         
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     4 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 Im 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     3 
                                   
                                 
                               
                             
                           
                           
                             
                               - 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     1 
                                   
                                   k 
                                 
                                 
                                   
                                     w 
                                     i 
                                   
                                   ⁢ 
                                   Re 
                                   ⁢ 
                                   
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ω 
                                     i 
                                     
                                       - 
                                       4 
                                     
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 Im 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     3 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   
                                     w 
                                     i 
                                   
                                   ( 
                                   
                                     
                                       
                                         Re 
                                         ⁡ 
                                         ( 
                                         
                                           G 
                                           i 
                                         
                                         ) 
                                       
                                       2 
                                     
                                     + 
                                     
                                       
                                         Im 
                                         ⁡ 
                                         ( 
                                         
                                           G 
                                           i 
                                         
                                         ) 
                                       
                                       2 
                                     
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     2 
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 2 
                               
                               ⁢ 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     1 
                                   
                                   k 
                                 
                                 
                                   
                                     w 
                                     i 
                                   
                                   ⁢ 
                                   
                                     Im 
                                     ⁡ 
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     Re 
                                     ⁡ 
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ω 
                                     i 
                                     
                                       - 
                                       3 
                                     
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               - 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     1 
                                   
                                   k 
                                 
                                 
                                   
                                     w 
                                     i 
                                   
                                   ⁢ 
                                   Re 
                                   ⁢ 
                                   
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ω 
                                     i 
                                     
                                       - 
                                       4 
                                     
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 - 
                                 2 
                               
                               ⁢ 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     1 
                                   
                                   k 
                                 
                                 
                                   
                                     w 
                                     i 
                                   
                                   ⁢ 
                                   Im 
                                   ⁢ 
                                   
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   Re 
                                   ⁢ 
                                   
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ω 
                                     i 
                                     
                                       - 
                                       3 
                                     
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   w 
                                   i 
                                 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     
                                       
                                         Re 
                                         ⁡ 
                                         ( 
                                         
                                           G 
                                           i 
                                         
                                         ) 
                                       
                                       2 
                                     
                                     + 
                                     
                                       
                                         Im 
                                         ⁡ 
                                         ( 
                                         
                                           G 
                                           i 
                                         
                                         ) 
                                       
                                       2 
                                     
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     4 
                                   
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #85 
                   
                   ] 
                 
               
             
           
         
       
     
     The same approach may be taken to find an expression for the b vector in terms of G and ω. The real and imaginary parts of y areas follows: 
     
       
         
           
             
               
                 
                   
                     
                       Re 
                       ⁡ 
                       ( 
                       y 
                       ) 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               - 
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   1 
                                 
                                 ) 
                               
                             
                           
                         
                         
                           
                             ⋮ 
                           
                         
                         
                           
                             
                               - 
                               
                                 Re 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   k 
                                 
                                 ) 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
                       Im 
                       ⁡ 
                       ( 
                       y 
                       ) 
                     
                     = 
                     
                       [ 
                       
                         
                           
                             
                               - 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   1 
                                 
                                 ) 
                               
                             
                           
                         
                         
                           
                             ⋮ 
                           
                         
                         
                           
                             
                               - 
                               
                                 Im 
                                 ⁡ 
                                 ( 
                                 
                                   G 
                                   k 
                                 
                                 ) 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #86 
                   
                   ] 
                 
               
             
           
         
       
     
     Combining the real and imaginary parts results in the expression for the b vector as follows: 
     
       
         
           
             
               
                 
                   b 
                   = 
                   
                     
                       
                         
                           
                             Re 
                             ⁡ 
                             ( 
                             X 
                             ) 
                           
                           T 
                         
                         ⁢ 
                         W 
                         ⁢ 
                         
                           Re 
                           ⁡ 
                           ( 
                           y 
                           ) 
                         
                       
                       + 
                       
                         
                           
                             Im 
                             ⁡ 
                             ( 
                             X 
                             ) 
                           
                           T 
                         
                         ⁢ 
                         W 
                         ⁢ 
                         
                           Im 
                           ⁡ 
                           ( 
                           y 
                           ) 
                         
                       
                     
                     = 
                     
                       [ 
                       ⁠ 
                       
                         
                           
                             
                               - 
                               
                                 
                                   ∑ 
                                   
                                     i 
                                     = 
                                     1 
                                   
                                   k 
                                 
                                 
                                   
                                     w 
                                     i 
                                   
                                   ⁢ 
                                   Re 
                                   ⁢ 
                                   
                                     ( 
                                     
                                       G 
                                       i 
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     ω 
                                     i 
                                     
                                       - 
                                       2 
                                     
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 - 
                                 
                                   
                                     ∑ 
                                     
                                       i 
                                       = 
                                       1 
                                     
                                     k 
                                   
                                   
                                     
                                       w 
                                       i 
                                     
                                     ⁢ 
                                     Im 
                                     ⁢ 
                                     
                                       ( 
                                       
                                         G 
                                         i 
                                       
                                       ) 
                                     
                                   
                                 
                               
                               + 
                               
                                 
                                   Re 
                                   ⁡ 
                                   ( 
                                   
                                     G 
                                     i 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     1 
                                   
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 k 
                               
                               
                                 
                                   
                                     w 
                                     i 
                                   
                                   ( 
                                   
                                     
                                       
                                         Re 
                                         ⁡ 
                                         ( 
                                         
                                           G 
                                           i 
                                         
                                         ) 
                                       
                                       2 
                                     
                                     + 
                                     
                                       
                                         Im 
                                         ⁡ 
                                         ( 
                                         
                                           G 
                                           i 
                                         
                                         ) 
                                       
                                       2 
                                     
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   i 
                                   
                                     - 
                                     2 
                                   
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #87 
                   
                   ] 
                 
               
             
           
         
       
     
     Implementing Acoustic Volume Sensing 
     Collecting the Frequency Response Data and Computing the Complex Response 
     To implement volume sensor assembly  148 , volume sensor assembly  148  should determine the relative response of reference microphone  626  and invariable volume microphone  630  to the acoustic wave set up by speaker assembly  622 . This may be accomplished by driving speaker assembly  622  with a sinusoidal output at a known frequency; the complex response of microphones  626 ,  630  may then be found at that driving frequency. Finally, the relative response of microphones  626 ,  630  may be found and corrected for alternating sampling by e.g., an analog-to-digital convertor (i.e., ADC). 
     Additionally, the total signal variance may be computed and compared to the variance of pure tone extracted using the discrete Fourier transform (i.e., DFT). This may result in a measure of how much of the signal power comes from noise sources or distortion. This value may then be used to reject and repeat bad measurements. 
     Computing the Discrete Fourier Transform 
     The signal from the microphone may be sampled synchronously with the output to speaker assembly  622  such that a fixed number of points, N, are taken per wavelength. The measured signal at each point in the wavelength may be summed over an integer number of wavelengths, M, and stored in an array x by the ISR for processing after all the data for that frequency has been collected. 
     A DFT may be performed on the data at the integer value corresponding to the driven frequency of the speaker. The general expression for the first harmonic of a DFT is as follows: 
     
       
         
           
             
               
                 
                   
                     x 
                     k 
                   
                   = 
                   
                     
                       2 
                       MN 
                     
                     ⁢ 
                     
                       
                         ∑ 
                         
                           n 
                           = 
                           0 
                         
                         
                           N 
                           - 
                           1 
                         
                       
                       
                         
                           x 
                           n 
                         
                         ⁢ 
                         
                           e 
                           
                             
                               - 
                               
                                 
                                   2 
                                   ⁢ 
                                   π 
                                   ⁢ 
                                   i 
                                 
                                 N 
                               
                             
                             ⁢ 
                             kn 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #88 
                   
                   ] 
                 
               
             
           
         
       
     
     The product MN may be the total number of points and the factor of two may be added such that the resulting real and imaginary portions of the answer match the amplitude of the sine wave: 
     
       
         
           
             
               
                 
                   
                     x 
                     n 
                   
                   = 
                   
                     
                       
                         re 
                         ⁡ 
                         ( 
                         
                           x 
                           n 
                         
                         ) 
                       
                       ⁢ 
                       
                         cos 
                         ⁡ 
                         ( 
                         
                           
                             
                               2 
                               ⁢ 
                               π 
                             
                             N 
                           
                           ⁢ 
                           kn 
                         
                         ) 
                       
                     
                     + 
                     
                       
                         im 
                         ⁡ 
                         ( 
                         
                           x 
                           k 
                         
                         ) 
                       
                       ⁢ 
                       
                         sin 
                         ⁡ 
                         ( 
                         
                           
                             
                               2 
                               ⁢ 
                               π 
                             
                             N 
                           
                           ⁢ 
                           kn 
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #89 
                   
                   ] 
                 
               
             
           
         
       
     
     This real part of this expression may be as follows: 
     
       
         
           
             
               
                 
                   
                     re 
                     ⁡ 
                     ( 
                     x 
                     ) 
                   
                   = 
                   
                     
                       2 
                       MN 
                     
                     ⁢ 
                     
                       
                         ∑ 
                         
                           n 
                           = 
                           0 
                         
                         
                           N 
                           - 
                           1 
                         
                       
                       
                         
                           x 
                           n 
                         
                         ⁢ 
                         
                           cos 
                           ⁡ 
                           ( 
                           
                             
                               
                                 2 
                                 ⁢ 
                                 π 
                               
                               N 
                             
                             ⁢ 
                             n 
                           
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #90 
                   
                   ] 
                 
               
             
           
         
       
     
     We may take advantage of the symmetry of the cosine function to reduce the number of computations needed to compute the DFT. The expression above may be equivalent to: 
     
       
         
           
             
               
                 
                   
                     re 
                     ⁡ 
                     ( 
                     x 
                     ) 
                   
                   = 
                   
                     
                       2 
                       MN 
                     
                     ⁢ 
                     
                        
                       
                         [ 
                         
                           
                             ( 
                             
                               
                                 x 
                                 0 
                               
                               - 
                               
                                 x 
                                 
                                   
                                     1 
                                     2 
                                   
                                   ⁢ 
                                   N 
                                 
                               
                             
                             ) 
                           
                           + 
                           
                             
                               ∑ 
                               
                                 n 
                                 = 
                                 1 
                               
                               
                                 
                                   
                                     1 
                                     4 
                                   
                                   ⁢ 
                                   N 
                                 
                                 - 
                                 1 
                               
                             
                             
                               
                                 sin 
                                 ⁡ 
                                 ( 
                                 
                                   
                                     π 
                                     2 
                                   
                                   - 
                                   
                                     
                                       
                                         2 
                                         ⁢ 
                                         π 
                                       
                                       N 
                                     
                                     ⁢ 
                                     n 
                                   
                                 
                                 ) 
                               
                               [ 
                               
                                 
                                   ( 
                                   
                                     
                                       x 
                                       n 
                                     
                                     - 
                                     
                                       x 
                                       
                                         
                                           
                                             1 
                                             2 
                                           
                                           ⁢ 
                                           N 
                                         
                                         + 
                                         n 
                                       
                                     
                                   
                                   ) 
                                 
                                 - 
                                 
                                   ( 
                                   
                                     
                                       x 
                                       
                                         
                                           
                                             1 
                                             2 
                                           
                                           ⁢ 
                                           N 
                                         
                                         + 
                                         n 
                                       
                                     
                                     - 
                                     
                                       x 
                                       
                                         N 
                                         - 
                                         n 
                                       
                                     
                                   
                                   ) 
                                 
                               
                               ] 
                             
                           
                         
                         ] 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #91 
                   
                   ] 
                 
               
             
           
         
       
     
     Similarly, for the imaginary portion of the equation: 
     
       
         
           
             
               
                 
                   
                     im 
                     ( 
                     x 
                     ) 
                   
                   = 
                   
                     
                       - 
                       
                         2 
                         MN 
                       
                     
                     ⁢ 
                     
                       
                         ∑ 
                         
                           n 
                           = 
                           0 
                         
                         
                           N 
                           - 
                           1 
                         
                       
                       
                         
                           x 
                           n 
                         
                         ⁢ 
                         
                           sin 
                           ⁡ 
                           ( 
                           
                             
                               
                                 2 
                                 ⁢ 
                                 π 
                               
                               N 
                             
                             ⁢ 
                             n 
                           
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #92 
                   
                   ] 
                 
               
             
           
         
       
     
     which may be expressed as follows: 
     
       
         
           
             
               
                 
                   
                     im 
                     ( 
                     x 
                     ) 
                   
                   = 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #93 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             - 
             
               
                 2 
                 MN 
               
               [ 
               
                 
                   ( 
                   
                     
                       x 
                       
                         
                           1 
                           4 
                         
                         ⁢ 
                         N 
                       
                     
                     - 
                     
                       x 
                       
                         
                           3 
                           4 
                         
                         ⁢ 
                         N 
                       
                     
                   
                   ) 
                 
                 + 
                 
                   
                     ∑ 
                     
                       n 
                       = 
                       1 
                     
                     
                       
                         
                           1 
                           4 
                         
                         ⁢ 
                         N 
                       
                       - 
                       1 
                     
                   
                   
                     
                       sin 
                       ⁡ 
                       ( 
                       
                         
                           
                             2 
                             ⁢ 
                             π 
                           
                           N 
                         
                         ⁢ 
                         n 
                       
                       ) 
                     
                     [ 
                     
                       
                         ( 
                         
                           
                             x 
                             n 
                           
                           - 
                           
                             x 
                             
                               
                                 
                                   1 
                                   2 
                                 
                                 ⁢ 
                                 N 
                               
                               + 
                               n 
                             
                           
                         
                         ) 
                       
                       + 
                       
                         ( 
                         
                           
                             x 
                             
                               
                                 
                                   1 
                                   2 
                                 
                                 ⁢ 
                                 N 
                               
                               + 
                               n 
                             
                           
                           - 
                           
                             x 
                             
                               N 
                               - 
                               n 
                             
                           
                         
                         ) 
                       
                     
                     ] 
                   
                 
               
               ] 
             
           
         
       
     
     The variance of this signal may be calculated as follows: 
       σ 2 =½(re( x ) 2 +im( x ) 2 )  [EQ #94]
 
     The maximum possible value of the real and imaginary portions of x may be 2 11 ; which corresponds to half the AD range. The maximum value of the tone variance may be 2 21 ; half the square of the AD range. 
     Computing the Signal Variance 
     The pseudo-variance of the signal may be calculated using the following relation: 
     
       
         
           
             
               
                 
                   
                     σ 
                     2 
                   
                   = 
                   
                     
                       
                         1 
                         
                           NM 
                           2 
                         
                       
                       ⁢ 
                       
                         
                           ∑ 
                           
                             n 
                             = 
                             0 
                           
                           
                             N 
                             - 
                             1 
                           
                         
                         
                           x 
                           n 
                           2 
                         
                       
                     
                     - 
                     
                       
                         1 
                         
                           
                             N 
                             2 
                           
                           ⁢ 
                           
                             M 
                             2 
                           
                         
                       
                       ⁢ 
                       
                         
                           ( 
                           
                             
                               ∑ 
                               
                                 n 
                                 = 
                                 0 
                               
                               
                                 N 
                                 - 
                                 1 
                               
                             
                             
                               x 
                               n 
                             
                           
                           ) 
                         
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #95 
                   
                   ] 
                 
               
             
           
         
       
     
     The result may be in the units of AD counts squared. It may only be the “pseudo-variance” because the signal has been averaged over M periods before the variance is calculated over the N samples in the “averaged” period. This may be a useful metric, however, for finding if the “averaged” signal looks like a sinusoid at the expected frequency. This may be done by comparing the total signal variance to that of the sinusoid found in the discrete Fourier transform. 
     The summation may be on the order of 
     
       
         
           
             
               
                 ∑ 
                 
                   n 
                   = 
                   0 
                 
                 
                   N 
                   - 
                   1 
                 
               
               
                 x 
                 n 
                 2 
               
             
             = 
             
               O 
               ⁡ 
               ( 
               
                 
                   NM 
                   2 
                 
                 ⁢ 
                 
                   2 
                   24 
                 
               
               ) 
             
           
         
       
     
     for a 12-bit ADC. If N&lt;2 7 =128 and M&lt;2 6 =64, then the summation will be less than 24 3  and may be stored in a 64-bit integer. The maximum possible value of the variance may result if the ADC oscillated between a value of 0 and 2 12  on each consecutive sample. This may result in a peak variance of ¼(2 12 ) 2 =2 22  so the result may be stored at a maximum of a ½ 9  resolution in a signed 32-bit integer. 
     Computing the Relative Microphone Response 
     The relative response (G) of microphones  626 ,  630  may be computed from the complex response of the individual microphones: 
     
       
         
           
             
               
                 
                   G 
                   = 
                   
                     
                       
                         x 
                         var 
                       
                       
                         x 
                         ref 
                       
                     
                     = 
                     
                       
                         
                           x 
                           var 
                         
                         
                           x 
                           ref 
                         
                       
                       ⁢ 
                       
                         
                           x 
                           ref 
                           * 
                         
                         
                           x 
                           ref 
                           * 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #96 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     Re 
                     ⁡ 
                     ( 
                     G 
                     ) 
                   
                   = 
                   
                     
                       
                         
                           Re 
                           ⁡ 
                           ( 
                           
                             x 
                             var 
                           
                           ) 
                         
                         ⁢ 
                         
                           Re 
                           ⁡ 
                           ( 
                           
                             x 
                             ref 
                           
                           ) 
                         
                       
                       + 
                       
                         
                           Im 
                           ⁡ 
                           ( 
                           
                             x 
                             var 
                           
                           ) 
                         
                         ⁢ 
                         
                           Im 
                           ⁡ 
                           ( 
                           
                             x 
                             ref 
                           
                           ) 
                         
                       
                     
                     
                       
                         
                           Re 
                           ⁡ 
                           ( 
                           
                             x 
                             ref 
                           
                           ) 
                         
                         2 
                       
                       + 
                       
                         
                           Im 
                           ⁡ 
                           ( 
                           
                             x 
                             ref 
                           
                           ) 
                         
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #97 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     Im 
                     ⁡ 
                     ( 
                     G 
                     ) 
                   
                   = 
                   
                     
                       
                         
                           Re 
                           ⁡ 
                           ( 
                           
                             x 
                             ref 
                           
                           ) 
                         
                         ⁢ 
                         
                           Im 
                           ⁡ 
                           ( 
                           
                             x 
                             var 
                           
                           ) 
                         
                       
                       - 
                       
                         
                           Re 
                           ⁡ 
                           ( 
                           
                             x 
                             var 
                           
                           ) 
                         
                         ⁢ 
                         
                           Im 
                           ⁡ 
                           ( 
                           
                             x 
                             ref 
                           
                           ) 
                         
                       
                     
                     
                       
                         
                           Re 
                           ⁡ 
                           ( 
                           
                             x 
                             ref 
                           
                           ) 
                         
                         2 
                       
                       + 
                       
                         
                           Im 
                           ⁡ 
                           ( 
                           
                             x 
                             ref 
                           
                           ) 
                         
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #98 
                   
                   ] 
                 
               
             
           
         
       
     
     The denominator of either expression may be expressed in terms of the reference tone variance computed in the previous section as follows: 
       Re( x   ref ) 2 +Im( x   ref ) 2 =2σ ref   2   [EQ #99]
 
     Correcting for A/D Skew 
     The signals from microphones  626 ,  630  may not be sampled simultaneously; the A/D ISR alternates between microphones  626 ,  630 , taking a total of N samples per wavelength for each of microphones  626 ,  630 . The result may be a phase offset between two microphones  626 ,  630  of 
     
       
         
           
             
               π 
               N 
             
             . 
           
         
       
     
     To correct for this phase offset, a complex rotation may be applied to the relative frequency response computed in the previous section: 
     
       
         
           
             
               
                 
                   
                     G 
                     rotated 
                   
                   = 
                   
                     G 
                     · 
                     
                       ( 
                       
                         
                           cos 
                           ⁡ 
                           ( 
                           
                             π 
                             N 
                           
                           ) 
                         
                         + 
                         
                           i 
                           ⁢ 
                           
                             sin 
                             ⁡ 
                             ( 
                             
                               π 
                               N 
                             
                             ) 
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #100 
                   
                   ] 
                 
               
             
           
         
       
     
     Reference Models 
     Second and Higher Order Models 
     Leakage through the seals (e.g., seal assembly  1404 ) of volume sensor chamber  620  may be modeled as a second resonant port (e.g., port  1504 ,  FIG.  100   ) connected to an external volume (e.g., external volume  1506 ,  FIG.  100   ). 
     The system of equations describing the three-chamber configuration may be as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         . 
                       
                       1 
                     
                     + 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           1 
                         
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             
                               v 
                               . 
                             
                             k 
                           
                           - 
                           
                             
                               v 
                               . 
                             
                             
                               r 
                               ⁢ 
                               12 
                             
                           
                         
                         ) 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #101 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         . 
                       
                       2 
                     
                     + 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           2 
                         
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             
                               v 
                               . 
                             
                             
                                 
                               12 
                             
                           
                           - 
                           
                             
                               v 
                               . 
                             
                             
                               r 
                               ⁢ 
                               23 
                             
                           
                         
                         ) 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #102 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       v 
                       ¨ 
                     
                     
                       r 
                       ⁢ 
                       12 
                     
                   
                   = 
                   
                     
                       
                         - 
                         
                           
                             
                               f 
                               12 
                             
                             ⁢ 
                             
                               A 
                               12 
                             
                           
                           
                             L 
                             12 
                           
                         
                       
                       ⁢ 
                       
                         
                           v 
                           . 
                         
                         
                           r 
                           ⁢ 
                           12 
                         
                       
                     
                     + 
                     
                       
                         
                           A 
                           12 
                         
                         
                           ρ 
                           ⁢ 
                           
                             L 
                             12 
                           
                         
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             p 
                             2 
                           
                           - 
                           
                             p 
                             1 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #103 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         . 
                       
                       3 
                     
                     + 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           3 
                         
                       
                       ⁢ 
                       
                         
                           v 
                           . 
                         
                         
                           r 
                           ⁢ 
                           23 
                         
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #104 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       v 
                       ¨ 
                     
                     
                       r 
                       ⁢ 
                       23 
                     
                   
                   = 
                   
                     
                       
                         - 
                         
                           
                             
                               f 
                               23 
                             
                             ⁢ 
                             
                               A 
                               23 
                             
                           
                           
                             L 
                             23 
                           
                         
                       
                       ⁢ 
                       
                         
                           v 
                           . 
                         
                         
                           r 
                           ⁢ 
                           23 
                         
                       
                     
                     + 
                     
                       
                         
                           A 
                           23 
                         
                         
                           ρ 
                           ⁢ 
                           
                             L 
                             23 
                           
                         
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             p 
                             3 
                           
                           - 
                           
                             p 
                             2 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #105 
                   
                   ] 
                 
               
             
           
         
       
     
     Putting these equations into state-space results in the following: 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             
                               p 
                               . 
                             
                             1 
                           
                         
                       
                       
                         
                           
                             
                               p 
                               . 
                             
                             2 
                           
                         
                       
                       
                         
                           
                             
                               p 
                               . 
                             
                             3 
                           
                         
                       
                       
                         
                           
                             
                               v 
                               ¨ 
                             
                             12 
                           
                         
                       
                       
                         
                           
                             
                               v 
                               ¨ 
                             
                             23 
                           
                         
                       
                     
                     ] 
                   
                   = 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #106 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 [ 
                 
                   
                     
                       0 
                     
                     
                       0 
                     
                     
                       0 
                     
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           1 
                         
                       
                     
                     
                       0 
                     
                   
                   
                     
                       0 
                     
                     
                       0 
                     
                     
                       0 
                     
                     
                       
                         - 
                         
                           
                             ρ 
                             ⁢ 
                             
                               a 
                               2 
                             
                           
                           
                             V 
                             2 
                           
                         
                       
                     
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           2 
                         
                       
                     
                   
                   
                     
                       0 
                     
                     
                       0 
                     
                     
                       0 
                     
                     
                       0 
                     
                     
                       
                         - 
                         
                           
                             ρ 
                             ⁢ 
                             
                               a 
                               2 
                             
                           
                           
                             V 
                             3 
                           
                         
                       
                     
                   
                   
                     
                       
                         - 
                         
                           
                             A 
                             12 
                           
                           
                             ρ 
                             ⁢ 
                             
                               L 
                               12 
                             
                           
                         
                       
                     
                     
                       
                         
                           A 
                           12 
                         
                         
                           ρ 
                           ⁢ 
                           
                             L 
                             12 
                           
                         
                       
                     
                     
                       0 
                     
                     
                       
                         - 
                         
                           b 
                           12 
                         
                       
                     
                     
                       0 
                     
                   
                   
                     
                       0 
                     
                     
                       
                         - 
                         
                           
                             A 
                             23 
                           
                           
                             ρ 
                             ⁢ 
                             
                               L 
                               23 
                             
                           
                         
                       
                     
                     
                       
                         
                           A 
                           23 
                         
                         
                           ρ 
                           ⁢ 
                           
                             L 
                             23 
                           
                         
                       
                     
                     
                       0 
                     
                     
                       
                         - 
                         
                           b 
                           23 
                         
                       
                     
                   
                 
                 ] 
               
               [ 
               
                 
                   
                     
                       p 
                       1 
                     
                   
                 
                 
                   
                     
                       p 
                       2 
                     
                   
                 
                 
                   
                     
                       p 
                       3 
                     
                   
                 
                 
                   
                     
                       v 
                       12 
                     
                   
                 
                 
                   
                     
                       v 
                       23 
                     
                   
                 
               
               ] 
             
             + 
             
               
                 [ 
                 
                   
                     
                       
                         - 
                         
                           
                             ρ 
                             ⁢ 
                             
                               a 
                               2 
                             
                           
                           
                             V 
                             1 
                           
                         
                       
                     
                   
                   
                     
                       0 
                     
                   
                   
                     
                       0 
                     
                   
                   
                     
                       0 
                     
                   
                   
                     
                       0 
                     
                   
                 
                 ] 
               
               [ 
               
                 
                   v 
                   . 
                 
                 k 
               
               ] 
             
           
         
       
     
     the frequency response of which may be represented graphically in the Bode diagram shown in  FIG.  101    and which may also be written in transfer function form: 
     
       
         
           
             
               
                 
                   
                     
                       p 
                       2 
                     
                     
                       p 
                       1 
                     
                   
                   = 
                   
                     
                       
                         ω 
                         12 
                         2 
                       
                       ( 
                       
                         
                           s 
                           2 
                         
                         + 
                         
                           
                             b 
                             23 
                           
                           ⁢ 
                           s 
                         
                         + 
                         
                           ω 
                           23 
                           2 
                         
                       
                       ) 
                     
                     
                       
                         
                           ( 
                           
                             
                               s 
                               2 
                             
                             + 
                             
                               
                                 b 
                                 12 
                               
                               ⁢ 
                               s 
                             
                             + 
                             
                               ω 
                               12 
                               2 
                             
                           
                           ) 
                         
                         ⁢ 
                         
                           ( 
                           
                             
                               s 
                               2 
                             
                             + 
                             
                               
                                 b 
                                 23 
                               
                               ⁢ 
                               s 
                             
                             + 
                             
                               ω 
                               23 
                               2 
                             
                           
                           ) 
                         
                       
                       + 
                       
                         
                           
                             V 
                             3 
                           
                           
                             V 
                             2 
                           
                         
                         ⁢ 
                         
                           
                             ω 
                             23 
                             2 
                           
                           ( 
                           
                             s 
                             + 
                             
                               b 
                               12 
                             
                           
                           ) 
                         
                         ⁢ 
                         s 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #107 
                   
                   ] 
                 
               
             
           
         
       
     
     Expanding the denominator results in the following: 
     
       
         
           
             
               
                 
                   
                     
                       p 
                       2 
                     
                     
                       p 
                       1 
                     
                   
                   = 
                   
                     
                       
                         ω 
                         12 
                         2 
                       
                       ( 
                       
                         
                           s 
                           2 
                         
                         + 
                         
                           
                             b 
                             23 
                           
                           ⁢ 
                           s 
                         
                         + 
                         
                           ω 
                           23 
                           2 
                         
                       
                       ) 
                     
                     
                       
                         
                           
                             
                               s 
                               4 
                             
                             + 
                             
                               
                                 ( 
                                 
                                   
                                     b 
                                     12 
                                   
                                   + 
                                   
                                     b 
                                     23 
                                   
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 s 
                                 3 
                               
                             
                             + 
                             
                               
                                 ( 
                                 
                                   
                                     
                                       b 
                                       12 
                                     
                                     ⁢ 
                                     
                                       b 
                                       23 
                                     
                                   
                                   + 
                                   
                                     ω 
                                     12 
                                     2 
                                   
                                   + 
                                   
                                     
                                       ω 
                                       23 
                                       2 
                                     
                                     ( 
                                     
                                       1 
                                       + 
                                       
                                         
                                           V 
                                           3 
                                         
                                         
                                           V 
                                           2 
                                         
                                       
                                     
                                     ) 
                                   
                                 
                                 ) 
                               
                               ⁢ 
                               
                                 s 
                                 2 
                               
                             
                             + 
                           
                         
                       
                       
                         
                           
                             
                               
                                 ( 
                                 
                                   
                                     
                                       b 
                                       23 
                                     
                                     ⁢ 
                                     
                                       ω 
                                       12 
                                       2 
                                     
                                   
                                   + 
                                   
                                     
                                       b 
                                       12 
                                     
                                     ⁢ 
                                     
                                       
                                         ω 
                                         23 
                                         2 
                                       
                                       ( 
                                       
                                         1 
                                         + 
                                         
                                           
                                             V 
                                             3 
                                           
                                           
                                             V 
                                             2 
                                           
                                         
                                       
                                       ) 
                                     
                                   
                                 
                                 ) 
                               
                               ⁢ 
                               s 
                             
                             + 
                             
                               
                                 ω 
                                 12 
                                 2 
                               
                               ⁢ 
                               
                                 ω 
                                 23 
                                 2 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #108 
                   
                   ] 
                 
               
             
           
         
       
     
     A bubble underneath the diaphragm material in the variable volume will follow the same dynamic equations as a leakage path. In this case, the diaphragm material may act as the resonant mass rather than the leakage port. Accordingly, the equation may be as follows: 
         m{umlaut over (x)}=ΔpA−b   m     x     [EQ #109]
 
     wherein m is the mass of the diaphragm, A is the cross sectional area of the diaphragm that can resonate, and b m  is the mechanical damping. EQ #106 may be written in terms of the volume flow rate: 
     
       
         
           
             
               
                 
                   
                     v 
                     ¨ 
                   
                   = 
                   
                     
                       
                         - 
                         
                           b 
                           m 
                         
                       
                       ⁢ 
                       
                         v 
                         . 
                       
                     
                     + 
                     
                       Δ 
                       ⁢ 
                       p 
                       ⁢ 
                       
                         
                           A 
                           2 
                         
                         m 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #110 
                   
                   ] 
                 
               
             
           
         
       
     
     wherein the volume of the air bubble is V 3 . If the bubble volume is substantially smaller than the acoustic volume V 3 &lt;&lt;V 2  than the transfer function may be simplified to: 
     
       
         
           
             
               
                 
                   
                     
                       p 
                       2 
                     
                     
                       p 
                       1 
                     
                   
                   = 
                   
                     
                       
                         ω 
                         12 
                         2 
                       
                       ( 
                       
                         
                           s 
                           2 
                         
                         + 
                         
                           
                             b 
                             23 
                           
                           ⁢ 
                           s 
                         
                         + 
                         
                           ω 
                           23 
                           2 
                         
                       
                       ) 
                     
                     
                       
                         ( 
                         
                           
                             s 
                             2 
                           
                           + 
                           
                             
                               b 
                               12 
                             
                             ⁢ 
                             s 
                           
                           + 
                           
                             ω 
                             12 
                             2 
                           
                         
                         ) 
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             s 
                             2 
                           
                           + 
                           
                             
                               b 
                               23 
                             
                             ⁢ 
                             s 
                           
                           + 
                           
                             
                               ω 
                               23 
                               2 
                             
                             ( 
                             
                               1 
                               + 
                               
                                 
                                   V 
                                   3 
                                 
                                 
                                   V 
                                   2 
                                 
                               
                             
                             ) 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #111 
                   
                   ] 
                 
               
             
           
         
       
     
     Second Order with Time Delay 
     The volume sensor assembly  148  equations derived above assume that the pressure is the same everywhere in the acoustic volume. This is only an approximation, as there are time delays associated with the propagation of the sound waves through the volume. This situation may look like a time delay or a time advance based on the relative position of the microphone and speakers. 
     A time delay may be expressed in the Laplace domain as: 
         G ( s )= e   −ΔTs   [EQ #112]
 
     which makes for a non-linear set of equations. However, a first-order Pade approximation of the time delay may be used as follows: 
     
       
         
           
             
               
                 
                   
                     G 
                     ⁡ 
                     ( 
                     s 
                     ) 
                   
                   = 
                   
                     - 
                     
                       
                         s 
                         + 
                         
                           2 
                           
                             Δ 
                             ⁢ 
                             T 
                           
                         
                       
                       
                         s 
                         - 
                         
                           2 
                           
                             Δ 
                             ⁢ 
                             T 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #113 
                   
                   ] 
                 
               
             
           
         
       
     
     which is shown graphically in  FIG.  102   . 
     Three Chamber Volume Estimation 
     Volume sensor assembly  148  may also be configured using a third reference volume (e.g., reference volume  1508 ;  FIG.  103   ) connected with a separate resonant port (e.g., port  1510 ;  FIG.  103   ). This configuration may allow for temperature-independent volume estimation. 
     The system of equations describing the three-chamber configuration are as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         . 
                       
                       1 
                     
                     + 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           1 
                         
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             
                               v 
                               . 
                             
                             k 
                           
                           - 
                           
                             
                               v 
                               . 
                             
                             
                               r 
                               ⁢ 
                               12 
                             
                           
                           - 
                           
                             
                               v 
                               . 
                             
                             
                               r 
                               ⁢ 
                               13 
                             
                           
                         
                         ) 
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #114 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         . 
                       
                       2 
                     
                     + 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           2 
                         
                       
                       ⁢ 
                       
                         
                           v 
                           . 
                         
                         
                           r 
                           ⁢ 
                           12 
                         
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #115 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       v 
                       ¨ 
                     
                     
                       r 
                       ⁢ 
                       12 
                     
                   
                   = 
                   
                     
                       
                         - 
                         
                           
                             
                               f 
                               12 
                             
                             ⁢ 
                             
                               A 
                               12 
                             
                           
                           
                             L 
                             12 
                           
                         
                       
                       ⁢ 
                       
                         
                           v 
                           . 
                         
                         
                           r 
                           ⁢ 
                           12 
                         
                       
                     
                     + 
                     
                       
                         
                           A 
                           12 
                         
                         
                           ρ 
                           ⁢ 
                           
                             L 
                             12 
                           
                         
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             p 
                             2 
                           
                           - 
                           
                             p 
                             1 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #116 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       
                         p 
                         . 
                       
                       3 
                     
                     + 
                     
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           3 
                         
                       
                       ⁢ 
                       
                         
                           v 
                           . 
                         
                         
                           r 
                           ⁢ 
                           13 
                         
                       
                     
                   
                   = 
                   0 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #117 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       v 
                       ¨ 
                     
                     
                       r 
                       ⁢ 
                       13 
                     
                   
                   = 
                   
                     
                       
                         - 
                         
                           
                             
                               f 
                               13 
                             
                             ⁢ 
                             
                               A 
                               13 
                             
                           
                           
                             L 
                             13 
                           
                         
                       
                       ⁢ 
                       
                         
                           v 
                           . 
                         
                         
                           r 
                           ⁢ 
                           13 
                         
                       
                     
                     + 
                     
                       
                         
                           A 
                           13 
                         
                         
                           ρ 
                           ⁢ 
                           
                             L 
                             13 
                           
                         
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             p 
                             2 
                           
                           - 
                           
                             p 
                             1 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #118 
                   
                   ] 
                 
               
             
           
         
       
     
     Using these equations and solving for the transfer function across each of the resonant ports results in the following: 
     
       
         
           
             
               
                 
                   
                     
                       p 
                       2 
                     
                     
                       p 
                       1 
                     
                   
                   = 
                   
                     
                       
                         ω 
                         
                           n 
                           ⁢ 
                           12 
                         
                         2 
                       
                       
                         
                           s 
                           2 
                         
                         + 
                         
                           2 
                           ⁢ 
                           
                             ζ 
                             12 
                           
                           ⁢ 
                           
                             ω 
                             
                               n 
                               ⁢ 
                               12 
                             
                           
                           ⁢ 
                           s 
                         
                         + 
                         
                           ω 
                           
                             n 
                             ⁢ 
                             12 
                           
                           2 
                         
                       
                     
                     ⁢ 
                         
                     where 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #119 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     ω 
                     
                       n 
                       ⁢ 
                       12 
                     
                     2 
                   
                   = 
                   
                     
                       
                         1 
                         
                           V 
                           2 
                         
                       
                       ⁢ 
                       
                         
                           
                             a 
                             2 
                           
                           ⁢ 
                           
                             A 
                             12 
                           
                         
                         
                           L 
                           12 
                         
                       
                       ⁢ 
                           
                       and 
                       ⁢ 
                           
                       ζ 
                     
                     = 
                     
                       
                         
                           f 
                           12 
                         
                         ⁢ 
                         
                           A 
                           12 
                         
                       
                       
                         2 
                         ⁢ 
                         
                           L 
                           12 
                         
                         ⁢ 
                         
                           ω 
                           
                             n 
                             ⁢ 
                             12 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #120 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       p 
                       3 
                     
                     
                       p 
                       1 
                     
                   
                   = 
                   
                     
                       
                         ω 
                         
                           n 
                           ⁢ 
                           13 
                         
                         2 
                       
                       
                         
                           s 
                           2 
                         
                         + 
                         
                           2 
                           ⁢ 
                           
                             ζ 
                             13 
                           
                           ⁢ 
                           
                             ω 
                             
                               n 
                               ⁢ 
                               13 
                             
                           
                           ⁢ 
                           s 
                         
                         + 
                         
                           ω 
                           
                             n 
                             ⁢ 
                             13 
                           
                           2 
                         
                       
                     
                     ⁢ 
                         
                     where 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #121 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     ω 
                     
                       n 
                       ⁢ 
                       13 
                     
                     2 
                   
                   = 
                   
                     
                       
                         1 
                         
                           V 
                           3 
                         
                       
                       ⁢ 
                       
                         
                           
                             a 
                             2 
                           
                           ⁢ 
                           
                             A 
                             13 
                           
                         
                         
                           L 
                           13 
                         
                       
                       ⁢ 
                           
                       and 
                       ⁢ 
                           
                       ζ 
                     
                     = 
                     
                       
                         
                           f 
                           13 
                         
                         ⁢ 
                         
                           A 
                           13 
                         
                       
                       
                         2 
                         ⁢ 
                         
                           L 
                           13 
                         
                         ⁢ 
                         
                           ω 
                           
                             n 
                             ⁢ 
                             13 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #122 
                   
                   ] 
                 
               
             
           
         
       
     
     The volume of volume sensor chamber  620  may be estimated using the ratio of the natural frequency of the two resonant ports as follows: 
     
       
         
           
             
               
                 
                   
                     
                       ω 
                       
                         n 
                         ⁢ 
                         13 
                       
                       2 
                     
                     
                       ω 
                       
                         n 
                         ⁢ 
                         12 
                       
                       2 
                     
                   
                   = 
                   
                     
                       
                         V 
                         2 
                       
                       
                         V 
                         3 
                       
                     
                     ⁢ 
                     
                       
                         A 
                         13 
                       
                       
                         A 
                         12 
                       
                     
                     ⁢ 
                     
                       
                         L 
                         12 
                       
                       
                         L 
                         13 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #123 
                   
                   ] 
                 
               
             
           
         
       
     
     EQ #120 illustrates that the volume of volume sensor chamber  620  may be proportional to reference volume  1508 . The ratio of these two volumes (in the ideal model) may only depend on the geometry of the resonant port (e.g., port  1510 ;  FIG.  103   ) and has no dependence upon temperature. 
     Exponential Volume Model 
     Assume the flow out through the flow resistance has the following form: 
     
       
         
           
             
               
                 
                   
                     
                       V 
                       . 
                     
                     out 
                   
                   = 
                   
                     
                       V 
                       avs 
                     
                     τ 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #124 
                   
                   ] 
                 
               
             
           
         
       
     
     Assuming a fixed input flow rate from the pump chamber, the volume of volume sensor chamber  620  is based upon the following differential equation: 
     
       
         
           
             
               
                 
                   
                     
                       V 
                       . 
                     
                     avs 
                   
                   = 
                   
                     
                       
                         
                           V 
                           . 
                         
                         in 
                       
                       - 
                       
                         
                           V 
                           . 
                         
                         out 
                       
                     
                     = 
                     
                       
                         
                           V 
                           . 
                         
                         in 
                       
                       - 
                       
                         
                           V 
                           avs 
                         
                         τ 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #125 
                   
                   ] 
                 
               
             
           
         
       
     
     which gives the following solution assuming a zero initial volume: 
     
       
         
           
             
               
                 
                   
                     V 
                     avs 
                   
                   = 
                   
                     
                       
                         V 
                         . 
                       
                       in 
                     
                     ⁢ 
                     
                       τ 
                       ⁡ 
                       ( 
                       
                         1 
                         - 
                         
                           e 
                           
                             - 
                             
                               t 
                               τ 
                             
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #126 
                   
                   ] 
                 
               
             
           
         
       
     
     Accordingly, the output flow rate flows: 
     
       
         
           
             
               
                 
                   
                     
                       V 
                       . 
                     
                     out 
                   
                   = 
                   
                     
                       
                         V 
                         . 
                       
                       in 
                     
                     ( 
                     
                       1 
                       - 
                       
                         e 
                         
                           - 
                           
                             t 
                             τ 
                           
                         
                       
                     
                     ) 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #127 
                   
                   ] 
                 
               
             
           
         
       
     
     The volume delivered during the pump phase may be written: 
     
       
         
           
             
               
                 
                   
                     V 
                     out 
                   
                   = 
                   
                     
                       
                         V 
                         . 
                       
                       in 
                     
                     [ 
                     
                       t 
                       - 
                       
                         τ 
                         ⁡ 
                         ( 
                         
                           1 
                           - 
                           
                             e 
                             
                               - 
                               
                                 t 
                                 τ 
                               
                             
                           
                         
                         ) 
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #128 
                   
                   ] 
                 
               
             
           
         
       
     
     Device Calibration 
     The model fit allows the resonant frequency of the port to be extracted from the sine sweep data. The next step is to relate this value to the delivered volume. The ideal relationship between the resonant frequency and the delivered volume to be expressed as follows: 
     
       
         
           
             
               
                 
                   
                     ω 
                     n 
                     2 
                   
                   = 
                   
                     
                       
                         
                           a 
                           2 
                         
                         ⁢ 
                         A 
                       
                       L 
                     
                     ⁢ 
                     
                       1 
                       
                         V 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #129 
                   
                   ] 
                 
               
             
           
         
       
     
     The speed of sound will vary with temperature, so it may be useful to split out the temperature effects. 
     
       
         
           
             
               
                 
                   
                     ω 
                     n 
                     2 
                   
                   = 
                   
                     
                       
                         γ 
                         ⁢ 
                         RA 
                       
                       L 
                     
                     ⁢ 
                     
                       T 
                       
                         V 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #130 
                   
                   ] 
                 
               
             
           
         
       
     
     The volume may then be expressed as a function of the measured resonant frequency and the temperature: 
     
       
         
           
             
               
                 
                   
                     V 
                     2 
                   
                   = 
                   
                     C 
                     ⁢ 
                     
                       T 
                       
                         ω 
                         n 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #131 
                   
                   ] 
                 
               
             
           
         
       
     
     Where c is the calibration constant 
     
       
         
           
             C 
             = 
             
               
                 γ 
                 ⁢ 
                 RA 
               
               L 
             
           
         
       
     
     Implementation Details 
     End Effects 
     The air resonating in the port (e.g., port assembly  624 ) may extend out into the acoustic volumes at the end of each oscillation. The distance the air extends may be estimated based on the fundamental volume sensor assembly equations. For any given acoustic volume, the distance the air extends into the volume may be expressed as a function of the pressure and port cross-sectional area: 
     
       
         
           
             
               
                 
                   x 
                   = 
                   
                     
                       V 
                       
                         ρ 
                         ⁢ 
                         
                           a 
                           2 
                         
                         ⁢ 
                         A 
                       
                     
                     ⁢ 
                     p 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #132 
                   
                   ] 
                 
               
             
           
         
       
     
     If we assume the following values: 
     
       
         
           
             
               
                 
                   V 
                   = 
                   
                     28.8 
                     × 
                     
                       10 
                       
                         - 
                         6 
                       
                     
                     ⁢ 
                     L 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #133 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   ρ 
                   = 
                   
                     1.292 
                     
                       kg 
                       
                         m 
                         3 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #134 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   a 
                   = 
                   
                     340 
                     ⁢ 
                     
                       m 
                       s 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #135 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   d 
                   = 
                   
                     0.5 
                     · 
                     mm 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #136 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   p 
                   = 
                   
                     
                       1 
                       · 
                       Pa 
                     
                     ⁢ 
                         
                     
                       ( 
                       
                         Approximately 
                         ⁢ 
                             
                         100 
                         ⁢ 
                             
                         dB 
                       
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #137 
                   
                   ] 
                 
               
             
           
         
       
     
     Accordingly, the air will extend roughly 1.9 mm in to the acoustic chamber. 
     Sizing V1 (i.e., the Fixed Volume) Relative to V2 (i.e., the Variable Volume) 
     Sizing V 1  (e.g., fixed volume  1500 ) may require trading off acoustic volume with the relative position of the poles and zeros in the transfer function. The transfer function for both V 1  and V 2  (e.g., variable volume  1502 ) are shown below relative to the volume displacement of speaker assembly  622 . 
     
       
         
           
             
               
                 
                   
                     
                       p 
                       2 
                     
                     
                       v 
                       k 
                     
                   
                   = 
                   
                     
                       - 
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           1 
                         
                       
                     
                     ⁢ 
                     
                       
                         ω 
                         
                           n 
                             
                         
                         2 
                       
                       
                         
                           s 
                           2 
                         
                         + 
                         
                           2 
                           ⁢ 
                           
                             ζ 
                             12 
                           
                           ⁢ 
                           
                             ω 
                             
                               n 
                                 
                             
                           
                           ⁢ 
                           s 
                         
                         + 
                         
                           αω 
                           
                             n 
                               
                           
                           2 
                         
                       
                     
                       
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #138 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       p 
                       1 
                     
                     
                       v 
                       k 
                     
                   
                   = 
                   
                     
                       - 
                       
                         
                           ρ 
                           ⁢ 
                           
                             a 
                             2 
                           
                         
                         
                           V 
                           1 
                         
                       
                     
                     ⁢ 
                     
                       
                         
                           s 
                           2 
                         
                         + 
                         
                           2 
                           ⁢ 
                           
                             ζω 
                             n 
                           
                           ⁢ 
                           s 
                         
                         + 
                         
                           αω 
                           
                             n 
                               
                           
                           2 
                         
                       
                       
                         
                           s 
                           2 
                         
                         + 
                         
                           2 
                           ⁢ 
                           
                             ζω 
                             
                               n 
                                 
                             
                           
                           ⁢ 
                           s 
                         
                         + 
                         
                           ω 
                           
                             n 
                               
                           
                           2 
                         
                       
                     
                     ⁢ 
                         
                     where 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #139 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       ω 
                       n 
                       2 
                     
                     = 
                     
                       
                         
                           
                             a 
                             2 
                           
                           ⁢ 
                           A 
                         
                         L 
                       
                       ⁢ 
                       
                         1 
                         
                           V 
                           2 
                         
                       
                     
                   
                   , 
                   
                     ζ 
                     = 
                     
                       
                         
                           fA 
                           
                             2 
                             ⁢ 
                             L 
                             ⁢ 
                             
                               ω 
                               n 
                             
                           
                         
                         ⁢ 
                             
                         and 
                         ⁢ 
                             
                         α 
                       
                       = 
                       
                         ( 
                         
                           1 
                           + 
                           
                             
                               V 
                               2 
                             
                             
                               V 
                               1 
                             
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #140 
                   
                   ] 
                 
               
             
           
         
       
     
     As V 1  is increased the gain may decrease and the speaker may be driven at a higher amplitude to get the same sound pressure level. However, increasing V 1  may also have the benefit of moving the complex zeros in the p 1  transfer function toward the complex poles. In the limiting case where V 1 →∞, α→1 and you have pole-zero cancellation and a flat response. Increasing V 1 , therefore, may have the benefit of reducing both the resonance and the notch in the p 1  transfer function, and moving the p 2  poles toward ω n ; resulting in a lower sensitivity to measurement error when calculating the p 2 /p 1  transfer function. 
       FIG.  104    is a graphical representation of: 
     
       
         
           
             
               
                 
                   
                     p 
                     1 
                   
                   
                     v 
                     k 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #141 
                   
                   ] 
                 
               
             
           
         
       
     
       FIG.  105    is a graphical representation of 
     
       
         
           
             
               
                 
                   
                     p 
                     2 
                   
                   
                     v 
                     k 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #142 
                   
                   ] 
                 
               
             
           
         
       
     
     Aliasing 
     Higher frequencies may alias down to the frequency of interest, wherein the aliased frequency may be expressed as follows: 
         f=|f   n   −nf   s |  [EQ #143]
 
     where f s  is the sampling frequency, f n  is the frequency of the noise source, n is a positive integer, and f is the aliased frequency of the noise source. 
     The demodulation routine may effectively filter out noise except at the specific frequency of the demodulation. If the sample frequency is set dynamically to be a fixed multiple of the demodulation frequency, then the frequency of the noise that can alias down to the demodulation frequency may be a fixed set of harmonics of that fundamental frequency. 
     For example, if the sampling frequency is eight times the demodulation frequency, then the noise frequencies that can alias down to that frequency are as follows: 
     
       
         
           
             
               
                 
                   
                     
                       f 
                       n 
                     
                     f 
                   
                   = 
                   
                     
                       { 
                       
                         
                           1 
                           
                             
                               n 
                               ⁢ 
                               β 
                             
                             + 
                             1 
                           
                         
                         , 
                         
                           1 
                           
                             
                               n 
                               ⁢ 
                               β 
                             
                             - 
                             1 
                           
                         
                       
                       } 
                     
                     = 
                     
                       { 
                       
                         
                           1 
                           7 
                         
                         , 
                         
                           1 
                           9 
                         
                         , 
                         
                           1 
                           15 
                         
                         , 
                         
                           1 
                           17 
                         
                         , 
                         
                           1 
                           23 
                         
                         , 
                         
                           1 
                           25 
                         
                         , 
                         … 
                       
                       } 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #144 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               where 
               ⁢ 
                   
               β 
             
             = 
             
               
                 
                   f 
                   s 
                 
                 f 
               
               = 
               8. 
             
           
         
       
     
     For β=16, the following series would result: 
     
       
         
           
             
               
                 
                   
                     
                       f 
                       n 
                     
                     f 
                   
                   = 
                   
                     { 
                     
                       
                         1 
                         15 
                       
                       , 
                       
                         1 
                         17 
                       
                       , 
                       
                         1 
                         31 
                       
                       , 
                       
                         1 
                         33 
                       
                       , 
                       … 
                     
                     } 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #145 
                   
                   ] 
                 
               
             
           
         
       
     
     Performance 
     Sensitivity to Temperature 
     The sensitivity to temperature may be split into a gain change and a noise change. If the temperature is off by a factor of dT, the resulting gain error may be: 
     
       
         
           
             
               
                 
                   
                     V 
                     2 
                   
                   = 
                   
                     c 
                     ⁡ 
                     ( 
                     
                       
                         
                           T 
                           2 
                         
                         
                           ω 
                           2 
                           2 
                         
                       
                       - 
                       
                         
                           T 
                           1 
                         
                         
                           ω 
                           1 
                           2 
                         
                       
                     
                     ) 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #147 
                   
                   ] 
                 
               
             
           
         
       
     
     Accordingly, if the same temperature is used for both sine sweeps, any error in the temperature measurement may look like a gain change to the system. 
     
       
         
           
             
               
                 
                   
                     e 
                     gain 
                   
                   = 
                   
                     1 
                     - 
                     
                       
                         T 
                         measured 
                       
                       
                         T 
                         actual 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #148 
                   
                   ] 
                 
               
             
           
         
       
     
     Therefore, for a 1° K temperature error, the resulting volume error may be 0.3% at 298° K. This error may include both the error in the temperature sensor and the difference between the sensor temperature and the temperature of the air within volume sensor assembly  148 . 
     The measurement, however, may be more susceptible to noise in the temperature measurement. A temperature change during the differential sine sweeps may result in an error that looks more like an offset rather than a gain change: 
     
       
         
           
             
               
                 
                   
                     V 
                     error 
                   
                   = 
                   
                     
                       c 
                       
                         ω 
                         2 
                       
                     
                     ⁢ 
                     Δ 
                     ⁢ 
                     T 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #149 
                   
                   ] 
                 
               
             
           
         
       
     
     Accordingly, if the measurement varies by 0.1 K during the two measurement sine sweeps, the difference may be 0.012 uL. Therefore, it may be better to use a consistent temperature estimate for each delivery rather than taking a separate temperature measurement for each sine sweep (as shown in  FIG.  107   ). 
     The LM73 temperature sensor has a published accuracy of +/−1° C. and a resolution of 0.03 C. Further, the LM73 temperature sensor seems to consistently have a startup transient of about 0.3° C. that takes about five sine sweeps to level out (as shown in  FIG.  108   ). 
     Since the above-described infusion pump assemblies (e.g., infusion pump assembly  100 ,  100 ′,  400 ,  500 ) provides discrete deliveries of infusible fluid, the above-described infusion pump assemblies may be modeled entirely in the discrete domain (in the manner shown in  FIG.  109   ), which may be reduced to the following: 
     
       
         
           
             
               
                 
                   
                     
                       G 
                       p 
                     
                     ( 
                     z 
                     ) 
                   
                   = 
                   
                     Kz 
                     
                       z 
                       - 
                       1 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #150 
                   
                   ] 
                 
               
             
           
         
       
     
     A discrete-time PI regulator may perform according to the following: 
     
       
         
           
             
               
                 
                   
                     
                       G 
                       c 
                     
                     ( 
                     z 
                     ) 
                   
                   = 
                   
                     
                       K 
                       p 
                     
                     ( 
                     
                       1 
                       + 
                       
                         
                           
                             T 
                             s 
                           
                           
                             T 
                             I 
                           
                         
                         ⁢ 
                         
                           z 
                           
                             z 
                             - 
                             1 
                           
                         
                       
                     
                     ) 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #151 
                   
                   ] 
                 
               
             
           
         
       
     
     The AVS system described above works by comparing the acoustic response in fixed volume  1500  and variable volume  1502  to a speaker driven input and extracting the volume of the variable volume  1502 . As such, there is a microphone in contact with each of these separate volumes (e.g., microphones  626 ,  630 ). The response of variable volume microphone  630  may also be used in a more gross manner to detect the presence or absence of disposable housing assembly  114 . Specifically, if disposable housing assembly  114  is not attached to (i.e., positioned proximate) variable volume  1502 , essentially no acoustic response to the speaker driven input should be sensed. The response of fixed volume  1500 , however, should remain tied to the speaker input. Thus, the microphone data may be used to determine whether disposable housing assembly  114  by simply ensuring that both microphones exhibit an acoustic response. In the event that microphone  626  (i.e., the microphone positioned proximate fixed volume  1500 ) exhibits an acoustic response and microphone  630  (i.e., the microphone positioned proximate variable volume  1502 ) does not exhibit an acoustic response, it may be reasonably concluded that disposable housing assembly  114  is not attached to reusable housing assembly  102 . It should be noted that a failure of variable volume microphone  630  may also appear to be indicative of disposable housing assembly  114  not being attached, as the failure of variable volume microphone  630  may result in a mid-range reading that is nearly indistinguishable from the microphone response expected when disposable housing assembly  114  is not attached. 
     For the following discussion, the following nomenclature may be used: 
     
       
         
           
               
               
             
               
                   
                   
               
             
            
               
                   
                 Symbols 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 α max  (ƒ) 
                 maximum read at a given frequency 
               
               
                   
                 α min  (ƒ) 
                 minimum read at a given frequency 
               
               
                   
                 δ 
                 difference between max and min sums 
               
               
                   
                 ƒ 
                 individual frequency 
               
               
                   
                 F 
                 set of sine sweep frequencies 
               
               
                   
                 N 
                 number of frequencies in each sine sweep, F 
               
               
                   
                 ϕ 
                 boolean disposable attached flag 
               
               
                   
                 σmax 
                 sum of maximum ADC reads 
               
               
                   
                 σmin 
                 sum of minimum ADC reads 
               
               
                   
                 T 
                 max/min ADC difference threshold 
               
               
                   
                   
               
            
           
           
               
               
            
               
                   
                 Subscripts 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 i 
                 sweep number 
               
               
                   
                 ref 
                 reference volume 
               
               
                   
                 var 
                 variable volume 
               
               
                   
                   
               
            
           
         
       
     
     As part of the demodulation routine employed in each frequency response calculation, the minimum and maximum readings of both fixed volume microphone  626  and variable volume microphone  630  may be calculated. The sum of these maximum and minimum values may be calculated over the entire sine-sweep (as discussed above) for both microphone  626  and microphone  630  as follows. 
     
       
         
           
             
               
                 
                   
                     σ 
                     ⁢ 
                     max 
                   
                   = 
                   
                     
                       ∑ 
                       
                         f 
                         ∈ 
                         F 
                       
                     
                     
                       
                         α 
                         max 
                       
                       ( 
                       F 
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #152 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     σ 
                     ⁢ 
                     min 
                   
                   = 
                   
                     
                       ∑ 
                       
                         f 
                         ∈ 
                         F 
                       
                     
                     
                       
                         α 
                         min 
                       
                       ( 
                       F 
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #153 
                   
                   ] 
                 
               
             
           
         
       
     
     and the difference between these two summations may be simplified as follows: 
       δ=δ max−δ min  [EQ #154]
 
     While δ may be divided by the number of sine sweeps to get the average minimum/maximum difference for the sine sweep (which is then compared to a threshold), the threshold may equivalently be multiplied by N for computational efficiency. Accordingly, the basic disposable detection algorithm may be defined as follows: 
     
       
         
           
             
               
                 
                   
                     ϕ 
                     i 
                   
                   = 
                   
                     { 
                     
                       
                         
                           1 
                         
                         
                           
                             
                               if 
                               ⁢ 
                                   
                               
                                 δ 
                                 var 
                               
                             
                             &gt; 
                             
                               N 
                               * 
                               T 
                             
                           
                         
                       
                       
                         
                           0 
                         
                         
                           
                             
                               
                                 
                                   
                                     if 
                                     ⁢ 
                                         
                                     
                                       δ 
                                       var 
                                     
                                   
                                   &lt; 
                                   
                                     N 
                                     * 
                                     T 
                                   
                                 
                                 &amp; 
                               
                               ⁢ 
                                  
                               
                                 δ 
                                 ref 
                               
                             
                             &gt; 
                             
                               N 
                               * 
                               T 
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #155 
                   
                   ] 
                 
               
             
           
         
       
     
     The additional condition that the maximum/minimum difference be greater than the threshold is a check performed to ensure that a failed speaker is not the cause of the acoustic response received. This algorithm may be repeated for any sine-sweep, thus allowing a detachment of disposable housing assembly  114  to be sensed within e.g., at most two consecutive sweeps (i.e., in the worst case scenario in which disposable housing assembly  114  is removed during the second half of an in-progress sine sweep). 
     Thresholding for the above-described algorithm may be based entirely on numerical evidence. For example, examination of typical minimum/maximum response differences may show that no individual difference is ever less than five hundred ADC counts. Accordingly, all data examined while disposable housing assembly  114  is detached from reusable housing assembly  102  may show that all minimum/maximum response differences as being well under five hundred ADC counts. Thus, the threshold for S may be set at T=500. 
     While volume sensor assembly  148  is described above as being utilized within an infusion pump assembly (e.g., infusion pump assembly  100 ), this is for illustrative purposes only and is not intended to be a limitation of this disclosure, as other configurations are possible and are considered to be within the scope of this disclosure. For example, volume sensor assembly  148  may be used within a process control environment for e.g., controlling the quantity of chemicals mixed together. Alternatively, volume sensor assembly  148  may be used within a beverage dispensing system to control e.g., the quantity of ingredients mixed together. 
     While volume sensor assembly  148  is described above as utilizing a port (e.g., port assembly  624 ) as a resonator, this is for illustrative purposes only, as other configurations are possible and are considered to be within the scope of this disclosure. For example, a solid mass (not shown) may be suspended within port assembly  624  and may function as a resonator for volume sensor assembly  148 . Specifically, the mass (not shown) for the resonator may be suspended on a diaphragm (not shown) spanning port assembly  624 . Alternatively, the diaphragm itself (not shown) may act as the mass for the resonator. The natural frequency of volume sensor assembly  148  may be a function of the volume of variable volume  1502 . Accordingly, if the natural frequency of volume sensor assembly  148  can be measured, the volume of variable volume  1502  may be calculated. 
     The natural frequency of volume sensor assembly  148  may be measured in a number of different ways. For example, a time-varying force may be applied to the diaphragm (not shown) and the relationship between that force and the motion of the diaphragm (not shown) may be used to estimate the natural frequency of volume sensor assembly  148 . Alternately the mass (not shown) may be perturbed and then allowed to oscillate. The unforced motion of the mass (not shown) may then be used to calculate the natural frequency of volume sensor assembly  148 . 
     The force applied to the resonant mass (not shown) may be accomplished in various ways, examples of which may include but are not limited to:
         speaker assembly  622  may create a time-varying pressure within fixed volume  1500 ;   the resonant mass (not shown) may be a piezoelectric material responding to a time-varying voltage/current; and   the resonant mass (not shown) may be a voice coil responding to a time-varying voltage/current       

     The force applied to the resonant mass may be measured in various ways, examples of which may include but are not limited to:
         measuring the pressure in the fixed volume;   the resonant mass (not shown) may be a piezoelectric material; and   a strain gauge may be connected to the diaphragm (not shown) or other structural member supporting the resonant mass (not shown).       

     Similarly, the displacement of the resonant mass (not shown) may be estimated by measuring the pressure in the variable volume, or measured directly in various ways, examples of which may include but are not limited to:
         via piezoelectric sensor;   via capacitive sensor;   via optical sensor;   via Hall-effect sensor;   via a potentiometer (time varying impedance) sensor;   via an inductive type sensor; and   via a linear variable differential transformer (LVDT)       

     Further, the resonant mass (not shown) may be integral to either the force or displacement type sensor (i.e. the resonant mass (not shown) may be made of piezoelectric material). 
     The application of force and measurement of displacement may be accomplished by a single device. For example, a piezoelectric material may be used for the resonant mass (not shown) and a time-varying voltage/current may be applied to the piezoelectric material to create a time-varying force. The resulting voltage/current applied to the piezoelectric material may be measured and the transfer function between the two used to estimate the natural frequency of volume sensor assembly  148 . 
     As discussed above, the resonant frequency of volume sensor assembly  148  may be estimated using swept-sine system identification. Specifically, the above-described model fit may allow the resonant frequency of the port assembly to be extracted from the sine sweep data, which may then be used to determine the delivered volume. The ideal relationship between the resonant frequency and the delivered volume may be expressed as follows: 
     
       
         
           
             
               
                 
                   
                     ω 
                     n 
                     2 
                   
                   = 
                   
                     
                       
                         
                           a 
                           2 
                         
                         ⁢ 
                         A 
                       
                       L 
                     
                     ⁢ 
                     
                       1 
                       
                         V 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #129 
                   
                   ] 
                 
               
             
           
         
       
     
     The speed of sound will vary with temperature, so it may be useful to split out the temperature effects. 
     
       
         
           
             
               
                 
                   
                     ω 
                     n 
                     2 
                   
                   = 
                   
                     
                       
                         γ 
                         ⁢ 
                         RA 
                       
                       L 
                     
                     ⁢ 
                     
                       T 
                       
                         V 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #130 
                   
                   ] 
                 
               
             
           
         
       
     
     The volume may then be expressed as a function of the measured resonant frequency and the temperature: 
     
       
         
           
             
               
                 
                   
                     V 
                     2 
                   
                   = 
                   
                     C 
                     ⁢ 
                     
                       T 
                       
                         ω 
                         n 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #131 
                   
                   ] 
                 
               
             
           
         
       
     
     Where c is the calibration constant 
     
       
         
           
             C 
             = 
             
               
                 
                   γ 
                   ⁢ 
                   RA 
                 
                 L 
               
               . 
             
           
         
       
     
     Infusion pump assembly  100  may then compare this calculated volume V 2  (i.e., representative of the actual volume of infusible fluid delivered to the user) to the target volume (i.e., representative of the quantity of fluid that was supposed to be delivered to the user). For example, assume that infusion pump assembly  100  was to deliver a 0.100 unit basal dose of infusible fluid to the user every thirty minutes. Further, assume that upon effectuating such a delivery, volume sensor assembly  148  indicates a calculated volume V 2  (i.e., representative of the actual volume of infusible fluid delivered to the user) of 0.095 units of infusible fluid. 
     When calculating volume V 2 , infusion pump assembly  100  may first determine the volume of fluid within volume sensor chamber  620  prior to the administration of the dose of infusible fluid and may subsequently determine the volume of fluid within volume sensor chamber  620  after the administration of the dose of infusible fluid, wherein the difference of those two measurements is indicative of V 2  (i.e., the actual volume of infusible fluid delivered to the user). Accordingly, V 2  is a differential measurement. 
     V2 may be the total air space over the diaphragm in the variable volume chamber. The actual fluid delivery to the patient may be the difference in V2 from when the chamber was full to after the measurement valve was opened and the chamber was emptied. V2 may not directly be the delivered volume. For example, the air volume may be measured and a series of differential measurements may be taken. For occlusion, an empty measurement may be taken, the chamber may be filed, a full measurement may be taken, and then a final measurement may be taken after the exit valve is open. Accordingly, the difference between the first and second measurement may be the amount pumped and the difference between the second and third is the amount delivered to the patient. 
     Accordingly, electrical control assembly  110  may determine that the infusible fluid delivered is 0.005 units under what was called for. In response to this determination, electrical control assembly  110  may provide the appropriate signal to mechanical control assembly  104  so that any additional necessary dosage may be pumped. Alternatively, electrical control assembly  110  may provide the appropriate signal to mechanical control assembly  104  so that the additional dosage may be dispensed with the next dosage. Accordingly, during administration of the next 0.100 unit dose of the infusible fluid, the output command for the pump may be modified based on the difference between the target and amount delivered. 
     Referring also to  FIG.  110   , there is shown one particular implementation of a control system for controlling the quantity of infusible fluid currently being infused based, at least in part, on the quantity of infusible fluid previously administered. Specifically and continuing with the above-stated example, assume for illustrative purposes that electrical control assembly  110  calls for the delivery of a 0.100 unit dose of the infusible fluid to the user. Accordingly, electrical control assembly  110  may provide a target differential volume signal  1600  (which identifies a partial basal dose of 0.010 units of infusible fluid per cycle of shape memory actuator  112 ) to volume controller  1602 . Accordingly and in this particular example, shape memory actuator  112  may need to be cycled ten times in order to achieve the desired basal dose of 0.100 units of infusible fluid (i.e., 10 cycles×0.010 units per cycle=0.100 units). Volume controller  1602  in turn may provide “on-time” signal  1606  to SMA (i.e., shape memory actuator) controller  1608 . Also provided to SMA controller  1608  is battery voltage signal  1610 . 
     Specifically, shape-memory actuator  112  may be controlled by varying the amount of thermal energy (e.g., joules) applied to shape-memory actuator  112 . Accordingly, if the voltage level of battery  606  is reduced, the quantity of joules applied to shape-memory actuator  112  may also be reduced for a defined period of time. Conversely, if the voltage level of battery  606  is increased, the quantity of joules applied to shape memory actuator  112  may also be increased for a defined period of time. Therefore, by monitoring the voltage level of battery  606  (via battery voltage signal  1610 ), the type of signal applied to shape-memory actuator  112  may be varied to ensure that the appropriate quantity of thermal energy is applied to shape-memory actuator  112  regardless of the battery voltage level. 
     SMA controller  1608  may process “on-time” signal  1606  and battery voltage signal  1610  to determine the appropriate SMA drive signal  1612  to apply to shape-memory actuator  112 . One example of SMA drive signal  1612  may be a series of binary pulses in which the amplitude of SMA drive signal  1612  essentially controls the stroke length of shape-memory actuator  112  (and therefore pump assembly  106 ) and the duty cycle of SMA drive signal  1612  essentially controls the stroke rate of shape-memory actuator  112  (and therefore pump assembly  106 ). Further, since SMA drive signal  1612  is indicative of a differential volume (i.e., the volume infused during each cycle of shape memory actuator  112 ), SMA drive signal  1612  may be integrated by discrete time integrator  1614  to generate volume signal  1616  which may be indicative of the total quantity of infusible fluid infused during a plurality of cycles of shape memory actuator  112 . For example, since (as discussed above) it may take ten cycles of shape memory actuator  112  (at 0.010 units per cycle) to infuse 0.100 units of infusible fluid, discrete time integrator  1614  may integrate SMA drive signal  1612  over these ten cycles to determine the total quantity infused of infusible fluid (as represented by volume signal  1616 ). 
     SMA drive signal  1612  may actuate pump assembly  106  for e.g. one cycle, resulting in the filling of volume sensor chamber  620  included within volume sensor assembly  148 . Infusion pump assembly  100  may then make a first measurement of the quantity of fluid included within volume sensor chamber  620  (as discussed above). Further and as discussed above, measurement valve assembly  610  may be subsequently energized, resulting in all or a portion of the fluid within volume sensor chamber  620  being delivered to the user. Infusion pump assembly  100  may then make a measurement of the quantity of fluid included within volume sensor chamber  620  (as described above) and use those two measurements to determine V 2  (i.e., the actual volume of infusible fluid delivered to the user during the current cycle of shape memory actuator  112 ). Once determined, V 2  (i.e., as represented by signal  1618 ) may be provided (i.e., fed back) to volume controller  1602  for comparison to the earlier-received target differential volume. 
     Continuing with the above-stated example in which the differential target volume was 0.010 units of infusible fluid, assume that V 2  (i.e., as represented by signal  1618 ) identifies 0.009 units of infusible fluid as having been delivered to the user. Accordingly, infusion pump assembly  100  may increase the next differential target volume to 0.011 units to offset the earlier 0.001 unit shortage. Accordingly and as discussed above, the amplitude and/or duty cycle of SMA drive signal  1612  may be increased when delivering the next basal dose of the infusible fluid to the user. This process may be repeated for the remaining nine cycles of shape memory actuator  112  (as discussed above) and discrete time integrator  1614  may continue to integrate SMA drive signal  1612  (to generate volume signal  1616 ) which may define the total quantity of infusible fluid delivered to the user. 
     Referring also to  FIG.  111   , there is shown one possible embodiment of volume controller  1602 . In this particular implementation, volume controller  1602  may include PI (proportional-integrator) controller  1650 . Volume controller  1602  may include feed forward controller  1652  for setting an initial “guess” concerning “on-time” signal  1606 . For example, for the situation described above in which target differential volume signal  1600  identifies a partial basal dose of 0.010 units of infusible fluid per cycle of shape memory actuator  112 , feed forward controller  1652  may define an initial “on-time” of e.g., one millisecond. Feed forward controller  1652  may include e.g., a lookup table that define an initial “on-time” that is based, at least in part, upon target differential volume signal  1600 . Volume controller  1602  may further include discrete time integrator  1654  for integrating target differential volume signal  1600  and discrete time integrator  1656  for integrating V 2  (i.e., as represented by signal  1618 ). 
     Referring also to  FIG.  112   , there is shown one possible embodiment of feed forward controller  1652 . In this particular implementation, feed forward controller  1652  may define a constant value signal  1658  and may include amplifier  1660  (e.g., a unity gain amplifier), the output of which may be summed with constant value signal  1658  at summing node  1662 . The resulting summed signal (i.e., signal  1664 ) may be provided to as an input signal to e.g., lookup table  1666 , which may be processed to generate the output signal of feed forward controller  1652 . 
     As discussed above, pump assembly  106  may be controlled by shape memory actuator  112 . Further and as discussed above, SMA controller  1608  may process “on-time” signal  1606  and battery voltage signal  1610  to determine the appropriate SMA drive signal  1612  to apply to shape-memory actuator  112 . 
     Referring also to  FIGS.  113 - 114   , there is shown one particular implementation of SMA controller  1608 . As discussed above, SMA controller  1608  may be responsive to “on-time” signal  1606  and battery voltage signal  1610  and may provide SMA drive signal  1612  to shape-memory actuator  112 . SMA controller  1608  may include a feedback loop (including unit delay  1700 ), the output of which may be multiplied with battery voltage signal  1610  at multiplier  1702 . The output of multiplier  1702  may be amplified with e.g., unity gain amplifier  1704 . The output of amplifier  1704  may be applied to the negative input of summing node  1706  (to which “on-time” signal  1606  is applied). The output of summing node  1706  may be amplified (via e.g., unity gain amplifier  1708 ). SMA controller may also include feed forward controller  1710  to provide an initial value for SMA drive signal  1612  (in a fashion similar to feed forward controller  1652  of volume controller  1602 ; See  FIG.  112   ). The output of feed forward controller  1710  may be summed at summing node  1712  with the output of amplifier  1708  and an integrated representation (i.e., signal  1714 ) of the output of amplifier  1708  to form SMA drive signal  1612 . 
     SMA drive signal  1612  may be provided to control circuitry that effectuates the application of power to shape-memory actuator  112 . For example, SMA drive signal  1612  may be applied to switching assembly  1716  that may selectively apply current signal  1718  (supplied from battery  606 ) and/or fixed signal  1720  to shape-memory actuator. For example, SMA drive signal  1612  may effectuate the application of energy (supplied from battery  606  via current signal  1718 ) via switching assembly  1716  in a manner that achieves the duty cycle defined by SMA drive signal  1612 . Unit delay  1722  may generate a delayed version of the signal applied to shape-memory actuator  112  to form battery voltage signal  1610  (which may be applied to SMA controller  1608 ). 
     When applying power to shape-memory actuator  112 , voltage may be applied for a fixed amount of time and: a) at a fixed duty cycle with an unregulated voltage; b) at a fixed duty cycle with a regulated voltage; c) at a variable duty cycle based upon a measured current value; d) at a variable duty cycle based upon a measured voltage value; and e) at a variable duty cycle based upon the square of a measured voltage value. Alternatively, voltage may be applied to shape-memory actuator  112  for a variable amount of time based upon a measured impedance. 
     When applying an unregulated voltage for a fixed amount of time at a fixed duty cycle, inner loop feedback may not be used and shape memory actuator may be driven at a fixed duty cycle and with an on-time determined by the outer volume loop. 
     When applying a regulated voltage for a fixed amount of time at a fixed duty cycle, inner loop feedback may not be used and shape memory actuator  112  may be driven at a fixed duty cycle and with an on-time determined by the outer volume loop. 
     When applying an unregulated voltage at a variable duty cycle based upon a measured current value, the actual current applied to shape-memory actuator  112  may be measured and the duty cycle may be adjusted during the actuation of shape-memory actuator  112  to maintain the correct mean current. 
     When applying an unregulated voltage at a variable duty cycle based upon a measured voltage value, the actual voltage applied to shape-memory actuator  112  may be measured and the duty cycle may be adjusted during the actuation of shape-memory actuator  112  to maintain the correct mean voltage. 
     When applying an unregulated voltage at a variable duty cycle based upon the square of a measured voltage value, the actual voltage applied to shape-memory actuator  112  may be measured and the duty cycle may be adjusted during the actuation of shape-memory actuator  112  to maintain the square of the voltage at a level required to provide the desired level of power to shape-memory actuator  112  (based upon the impedance of shape-memory actuator  112 ). 
     Referring also to  FIG.  114 A- 114 B , there is shown other implementations of SMA controller  1608 . Specifically,  FIG.  114 A  is an electrical schematic that includes a microprocessor and various control loops that may be configured to provide a PWM signal that may open and close the switch assembly. The switch assembly may control the current that is allowed to flow through the shape memory actuator. The battery may provide the current to the shape memory actuator. Further,  114 B discloses a volume controller and an inner shape memory actuator controller. The shape memory actuator controller may provide a PWM signal to the pump, which may be modified based on the battery voltage. This may occur for a fixed ontime, the result being a volume that may be measured by volume sensor assembly  148  and fed back into the volume controller. 
     In our preferred embodiment, we vary the duty cycle based on the measured battery voltage to give you approximately consistent power. We adjust the duty cycle to compensate for a lower battery voltage. Battery voltage may change for two reasons: 1) as batteries are discharged, the voltage slowly decreases; and 2) when you apply a load to a battery it has an internal impedance so its voltage dips. This is something that happens in any type of system, and we compensate for that by adjusting the duty cycle, thus mitigating the lower or varying battery voltage. Battery voltage may be measured by the microprocessor. In other systems: 1) voltage may be regulated (put a regulator to maintain the voltage at a steady voltage); 2) feedback based on something else (i.e., speed or position of a motor, not necessarily measuring the battery voltage). 
     Other configurations may be utilized to control the shape memory actuator. For example: A) the shape memory actuator may be controlled at fixed duty cycle with unregulated voltage. As voltage varies, the repeatability of heating the shape memory actuator is reduced. B) a fixed duty cycle, regulated voltage may be utilized which compensate for changes in battery voltage. However, regulate the voltage down is less efficient due to energy of energy. C) the duty cycle may be varied based on changes in current (which may required more complicated measurement circuitry. D) The duty cycle may be varied based on measured voltage. E) The duty cycle may be varied based upon the square of the current or the square of the voltage divided by resistance. F) the voltage may be applied for a variable amount of time based on the measured impedance (e.g., may measure impedance using Wheatstone gauge (not shown)). The impedance of the shape memory actuator may be correlated to strain (i.e., may correlate how much the SMA moves based on its impedance). 
     Referring also to  FIG.  115    and as discussed above, to enhance the safety of infusion pump assembly  100 , electrical control assembly  110  may include two separate and distinct microprocessors, namely supervisor processor  1800  and command processor  1802 . Specifically, command processor  1802  may perform the functions discussed above (e.g., generating SMA drive signal  1612 ) and may control relay/switch assemblies  1804 ,  1806  that control the functionality of (in this example) shape memory actuators  112 ,  632  (respectively). Command processor  1802  may receive feedback from signal conditioner  1808  concerning the condition (e.g., voltage level) of the voltage signal applied to shape memory actuators  112 ,  632 . Command processor  1800  may control relay/switch assembly  1810  independently of relay/switch assemblies  1804 ,  1806 . Accordingly, when an infusion event is desired, both of supervisor processor  1800  and command processor  1802  must agree that the infusion event is proper and must both actuate their respective relays/switches. In the event that either of supervisor processor  1800  and command processor  1802  fails to actuate their respective relays/switches, the infusion event will not occur. Accordingly through the use of supervisor processor  1800  and command processor  1802  and the cooperation and concurrence that must occur, the safety of infusion pump assembly  100  is enhanced. 
     The supervisor processor may prevent the command processor from delivering when it is not supposed and also may alarm if the command processor does not deliver when it should be delivering. The supervisor processor may deactivate the relay/switch assembly if the command processor actuates the wrong switch, or if the command processor it tries to apply power for too long. 
     The supervisor processor may redundantly doing calculations for how much insulin should be delivered (i.e., double checking the calculations of the command processor). Command processor may decide the delivery schedule, and the supervisor processor may redundantly check those calculations. 
     Supervisor also redundantly holds the profiles (delivery profiles) in RAM, so the command processor may be doing the correct calculations, but if is has bad RAM, would cause the command to come up with the wrong result. The Supervisor uses its local copy of the basal profile, etc., to double check. 
     Supervisor can double check AVS measurements, looks at the AVS calculations and applies safety checks. Every time AVS measurement is taken, it double checks. 
     Referring also to  FIG.  116   , one or more of supervisor processor  1800  and command processor  1802  may perform diagnostics on various portions of infusion pump assembly  100 . For example, voltage dividers  1812 ,  1814  may be configured to monitor the voltages (V1 &amp; V2 respectively) sensed at distal ends of e.g., shape memory actuator  112 . The value of voltages V1 &amp; V2 in combination with the knowledge of the signals applied to relay/switch assemblies  1804 ,  1810  may allow for diagnostics to be performed on various components of the circuit shown in  FIG.  116    (in a manner similar to that shown in illustrative diagnostic table  1816 ). 
     As discussed above and as illustrated in  FIGS.  115 - 116   , to enhance the safety of infusion pump assembly  100 , electrical control assembly  110  may include a plurality of microprocessors (e.g., supervisor processor  1800  and command processor  1802 ), each of which may be required to interact and concur in order to effectuate the delivery of a dose of the infusible fluid. In the event that the microprocessors fail to interact/concur, the delivery of the dose of infusible fluid may fail and one or more alarms may be triggered, thus enhancing the safety and reliability of infusion pump assembly  100 . 
     A master alarm may be utilized that tracks the volume error over time. Accordingly, if the sum of the errors becomes too large, the master alarm may be initiated, indicating that something may be wrong with the system. Accordingly, the master alarm may be indicative of a total volume comparison being performed and a discrepancy being noticed. A typical value of the discrepancy required to initiate the master alarm may be 1.00 milliliters. The master alarm may monitor the sum in a leaky fashion (i.e., Inaccuracies have a time horizon). 
     Referring also to  FIGS.  117 A- 117 B , there is shown one such illustrative example of such interaction amongst multiple microprocessors during the delivery of a dose of the infusible fluid. Specifically, command processor  1802  may first determine  1900  the initial volume of infusible fluid within volume sensor chamber  620 . Command processor  1802  may then provide  1902  a “pump power request” message to supervisor processor  1800 . Upon receiving  1904  the “pump power request” message, supervisor processor  1800  may e.g., energize  1906  relay/switch  1810  (thus energizing shape memory actuator  112 ) and may send  1908  a “pump power on” message to command processor  1802 . Upon receiving  1910  the “pump power on” message, command processor  1802  may actuate  1912  e.g., pump assembly  106  (by energizing relay/switch  1804 ), during which time supervisor processor  1800  may monitor  1914  the actuation of e.g., pump assembly  106 . 
     Once actuation of pump assembly  106  is complete, command processor  1802  may provide  1914  a “pump power off” message to supervisor processor  1800 . Upon receiving  1916  the “pump power off” message, supervisor processor  1800  may deenergize  1918  relay/switch  1810  and provide  1920  a “pump power off” message to command processor  1802 . Upon receiving  1922  the “pump power off” message, command processor  1802  may measure  1924  the quantity of infusible fluid pumped by pump assembly  106 . This may be accomplished by measuring the current quantity of fluid within volume sensor chamber  620  and comparing it with the quantity determined above (in step  1900 ). Once determined  1924 , command processor  1802  may provide  1926  a “valve open power request” message to supervisor processor  1800 . Upon receiving  1928  the “valve open power request” message, supervisor processor  1800  may energize  1930  relay/switch  1810  (thus energizing shape memory actuator  632 ) and may send  1932  a “valve open power on” message to command processor  1802 . Upon receiving  1934  the “valve open power on” message, command processor  1802  may actuate  1936  e.g., measurement valve assembly  610  (by energizing relay/switch  1806 ), during which time supervisor processor  1800  may monitor  1938  the actuation of e.g., measurement valve assembly  610 . 
     Once actuation of measurement valve assembly  610  is complete, command processor  1802  may provide  1940  a “valve power off” message to supervisor processor  1800 . Upon receiving  1942  the “valve power off” message, supervisor processor  1800  may deenergize  1944  relay/switch  1810  and provide  1946  a “valve power off” message to command processor  1802 . 
     Upon receiving  1948  the “valve power off” message, command processor  1802  may provide  1950  a “valve close power request” message to supervisor processor  1800 . Upon receiving  1952  the “valve close power request” message, supervisor processor  1800  may energize  1954  relay/switch  1810  (thus energizing shape memory actuator  652 ) and may send  1956  a “power on” message to command processor  1802 . Upon receiving  1958  the “power on” message, command processor  1802  may actuate  1960  an energizing relay/switch (not shown) that is configured to energize shape memory actuator  652 , during which time supervisor processor  1800  may monitor  1962  the actuation of e.g., shape memory actuator  652 . 
     As discussed above (and referring temporarily to  FIGS.  26 A,  26 B,  27 A,  27 B &amp;  28   ), shape memory actuator  652  may be anchored on a first end using electrical contact  654 . The other end of shape memory actuator  652  may be connected to bracket assembly  656 . When shape memory actuator  652  is activated, shape memory actuator  652  may pull bracket assembly  656  forward and release valve assembly  634 . As such, measurement valve assembly  610  may be activated via shape memory actuator  632 . Once measurement valve assembly  610  has been activated, bracket assembly  656  may automatically latch valve assembly  610  in the activated position. Actuating shape memory actuator  652  may pull bracket assembly  656  forward and release valve assembly  634 . Assuming shape memory actuator  632  is no longer activated, measurement valve assembly  610  may move to a de-activated state once bracket assembly  656  has released valve assembly  634 . Accordingly, by actuating shape memory actuator  652 , measurement valve assembly  610  may be deactivated. 
     Once actuation of shape memory actuator  652  is complete, command processor  1802  may provide  1964  a “power off” message to supervisor processor  1800 . Upon receiving  1966  the “power off” message, supervisor processor  1800  may deenergize  1968  relay/switch  1810  and may provide  1970  a “power off” message to command processor  1802 . Upon receiving  1972  the “power off” message, command processor  1802  may determine the quantity of infusible fluid within volume sensor chamber  620 , thus allowing command processor  1802  to compare this measured quantity to the quantity determined above (in step  1924 ) to determine  1974  the quantity of infusible fluid delivered to the user. 
     In the event that the quantity of infusible fluid delivered  1974  to the user is less than the quantity of infusible fluid specified for the basal/bolus infusion event, the above-described procedure may be repeated (via loop  1976 ). 
     Referring also to  FIG.  118   , there is shown another illustrative example of the interaction amongst processors  1800 ,  1802 , this time during the scheduling of a dose of infusible fluid. Command processor  1802  may monitor  2000 ,  2002  for the receipt of a basal scheduling message or a bolus request message (respectively). Upon receipt  2000 ,  2002  of either of these messages, command processor  1802  may set  2004  the desired delivery volume and may provide  2006  a “delivery request” message to supervisor processor  1800 . Upon receiving  2008  the “delivery request” message, supervisor processor  1800  may verify  2010  the volume defined  2004  by command processor  1802 . Once verified  2010 , supervisor processor  1800  may provide  2012  a “delivery accepted” message to command processor  1802 . Upon receipt  2014  of the “delivery accepted” message, command processor  1802  may update  2016  the controller (e.g., the controller discussed above and illustrated in  FIG.  110   ) and execute  2018  delivery of the basal/bolus dose of infusible fluid. Command processor  1808  may monitor and update  2022  the total quantity of infusible fluid delivered to the user (as discussed above and illustrated in  FIGS.  117 A- 117 B ). Once the appropriate quantity of infusible fluid is delivered to the user, command processor  1802  may provide  2024  a “delivery done” message to supervisor processor  1800 . Upon receipt  2026  of the “delivery done” message, supervisor processor  1800  may update  2028  the total quantity of infusible fluid delivered to the user. In the event that the total quantity of infusible fluid delivered  2018  to the user is less than the quantity defined above (in step  2004 ), the infusion process discussed above may be repeated (via loop  2030 ). 
     Referring also to  FIG.  119   , there is shown an example of the manner in which supervisor processor  1800  and command processor  1802  may interact while effectuating a volume measurements via volume sensor assembly  148  (as described above). 
     Specifically, command processor  1802  may initialize  2050  volume sensor assembly  148  and begin collecting  2052  data from volume sensor assembly  148 , the process of which may be repeated for each frequency utilized in the above-described sine sweep. Each time that data is collected for a particular sweep frequency, a data point message may be provided  2054  from command processor  1802 , which may be received  2056  by supervisor processor  1800 . 
     Once data collection  2052  is completed for the entire sine sweep, command processor  1802  may estimate  2058  the volume of infusible fluid delivered by infusion pump assembly  100 . Command processor  1802  may provide  2060  a volume estimate message to supervisor processor  1800 . Upon receiving  2062  this volume estimate message, supervisor processor  1800  may check (i.e., confirm)  2064  the volume estimate message. Once checked (i.e., confirmed), supervisor processor  1800  may provide  2066  a verification message to command processor  1802 . Once received  2068  from supervisor processor  1800 , command processor  1802  may set the measurement status for the dose of infusible fluid delivered by volume sensor assembly  148 . 
     As discussed above and referring temporarily to  FIG.  11   ), the various embodiments of the infusion pump assembly (e.g., infusion pump assembly  100 ,  100 ′,  400 ,  500 ) discussed above may be configured via a remote control assembly  300 . When configurable via remote control assembly  300 , the infusion pump assembly may include telemetry circuitry (not shown) that allows for communication (e.g., wired or wireless) between the infusion pump assembly and e.g., remote control assembly  300 , thus allowing remote control assembly  300  to remotely control the infusion pump assembly. Remote control assembly  300  (which may also include telemetry circuitry (not shown) and may be capable of communicating with the infusion pump assembly) may include display assembly  302  and input assembly  304 . Input assembly  304  may include slider assembly  306  and switch assemblies  308 ,  310 . In other embodiments, the input assembly may include a jog wheel, a plurality of switch assemblies, or the like. Remote control assembly  300  may allow the user to program basal and bolus delivery events. 
     Remote control assembly  300  may include two processors, one processor (e.g., which may include, but is not limited to a CC2510 microcontroller/RF transceiver, available from Chipcon AS, of Oslo, Norway) may be dedicated to radio communication, e.g., for communicating with infusion pump assembly  100 ,  100 ′,  400 ,  500 . The second processor included within remote control assembly (which may include but are not limited to an ARM920T and an ARM922T manufactured by ARM Holdings PLC of the United Kingdom) may be a command processor and may perform data processing tasks associated with e.g., configuring infusion pump assembly  100 ,  100 ′,  400 ,  500 . 
     Further and as discussed above, one embodiment of electrical control assembly  816  may include three microprocessors. One processor (e.g., which may include, but is not limited to a CC2510 microcontroller/RF transceiver, available from Chipcon AS, of Oslo, Norway) may be dedicated to radio communication, e.g., for communicating with a remote control assembly  300 . Two additional microprocessors (e.g., supervisor processor  1800  and command processor  1802 ) may effectuate the delivery of the infusible fluid (as discussed above). Examples of supervisor processor  1800  and command processor  1802  may include, but is not limited to an MSP430 microcontroller, available from Texas Instruments Inc. of Dallas, Tex. 
     The OS may be a non-preemptive scheduling system, in that all tasks may run to completion before the next task is allowed to run regardless of priority. Additionally, context switches may not be performed. When a task completes executing, the highest priority task that is currently scheduled to run may then be executed. If no tasks are scheduled to execute, the OS may place the processor (e.g., supervisor processor  1800  and/or command processor  1802 ) into a low power sleep mode and may wake when the next task is scheduled. The OS may only be used to manage main loop code and may leave interrupt-based functionality unaffected. 
     The OS may be written to take advantage of the C++ language. Inheritance as well as virtual functions may be key elements of the design, allowing for easy creation, scheduling and managing of tasks. 
     At the base of the OS infrastructure may be the ability to keep track of system time and controlling the ability to place the processor in Low Power Mode (LPM; also known as sleep mode). This functionality along with the control and configuration of all system clocks, may be encapsulated by the SysClocks class. 
     The SysClocks class may contain the functionality to place the processor (e.g., supervisor processor  1800  and/or command processor  1802 ) into LPM to reduce energy consumption. While in LPM, the slow real time clock may continue to run while the fast system clock that runs the CPU core and most peripherals may be disabled. 
     Placing the processor into LPM may always be done by the provided SysClocks function. This function may contain all required power down and power up sequences resulting in consistency whenever entering or exiting LPM. Waking from LPM may be initiated by any interrupts based on the slow clock. 
     The OS may keep track of three aspects of time: seconds, milliseconds and the time of day. Concerning seconds, SysClocks may count seconds starting when the processor comes out of reset. The second counter may be based on the slow system clocks and, therefore, may increment regardless of whether the processor is in LPM or at full power. As a result, it is the boundary at which the processor may wake from sleep to execute previously scheduled tasks. If a task is scheduled to run immediately from an interrupt service routine (ISR), the ISR may wake the processor from LPM on exit and the task may be executed immediately. Concerning milliseconds, in addition to counting the seconds since power on, SysClocks may also count milliseconds while the processor is in full power mode. Since the fast clock is stopped during LPM, the millisecond counter may not increment. Accordingly, whenever a task is scheduled to execute based on milliseconds, the processor may not enter LPM. Concerning time of day, the time of day may be represented within SysClocks as seconds since a particular point time (e.g., seconds since 1 Jan. 2004). 
     The SysClocks class may provide useful functionality to be used throughout the Command and Supervisor project code base. The code delays may be necessary to allow hardware to settle or actions to be completed. SysClocks may provide two forms of delays, a delay based on seconds or a delay based on milliseconds. When a delay is used, the processor may simply wait until the desired time has passed before continue with its current code path. Only ISRs may be executed during this time. SysClocks may provide all of the required functionality to set or retrieve the current time of day. 
     The word “task” may be associated with more complex scheduling systems; therefore within the OS, task may be represented by and referred to as Managed Functions. The ManagedFunc class may be an abstract base class that provides all the necessary control members and functionality to manage and schedule the desired functionality. 
     The ManagedFunc base class may have five control members, two scheduling manipulation member functions, and one pure virtual execute function that may contain the managed functionality. All of the ManagedFunc control members may be hidden from the derived class and may only be directly set by the derived class during creation, thus simplifying the use and enhancing the safety of infusion pump assembly  100 ,  100 ′,  400 ,  500 . 
     The Function ID may be set at the time of creation and may never be changed. All Function IDs may be defined within a single .h file, and the base ManagedFunc constructor may strongly enforce that the same ID may not be used for more than one managed function. The ID may also define the priority of a function (with respect to other functions) based upon the function ID assigned, wherein higher priority functions are assigned lower function IDs. The highest priority task that is currently scheduled to execute may execute before lower priority tasks. 
     All other control members may be used to represent the function&#39;s current scheduled state, when it should be executed, and if (upon execution) the function should be rescheduled to execute in a previously set amount of time. Manipulation of these controls and states may be allowed but only through the public member functions (thus enforcing safety controls on all settings). 
     To control the scheduling of a managed function, the set start and set repeat functions may be used. Each of these member functions may be a simple interface allowing the ability to configure or disable repeat settings as well as control whether a managed function is inactive, scheduled by seconds, milliseconds, or time of day. 
     Through inheritance, creating a Managed Function may be done by creating a derived class and defining the pure virtual ‘execute’ function containing the code that needs to be under scheduling control. The ManagedFunc base class constructor may be based upon the unique ID of a function, but may also be used to set default control values to be used at start up. 
     For example to create a function that runs thirty seconds after start up and every 15 seconds thereafter, the desired code is placed into the virtual execute function and the function ID, scheduled by second state, thirty second start time, and repeat setting of fifteen seconds is provided to the constructor. 
     The following is an illustrative code example concerning the creation of a managed function. In this particular example, a “heartbeat” function is created that is scheduled to execute for the first time one second after startup of infusion pump assembly  100 ,  100 ′,  400 ,  500  and execute every ten seconds thereafter: 
     
       
         
           
               
             
               
                   
               
             
            
               
                 #include “ManagedFunc.h” 
               
               
                 // The SendGoodFunc is a “heartbeat” status message 
               
               
                 class SendGoodFunc : public ManagedFunc 
               
               
                 { 
               
               
                 public: 
               
               
                  // Initialize the managed func to run 2 seconds 
               
               
                  after start up 
               
               
                  // and repeat every second. 
               
               
                  SendGoodFunc( ) : 
               
               
                   ManagedFunc(IPC_SEND_GOOD, SCHEDULED_SEC, 1, true, 10) { }; 
               
               
                  ~SendGoodFunc( ) { }; 
               
               
                  protected: 
               
               
                   void execute(void); 
               
               
                 }; 
               
               
                 void SendGoodFunc::execute(void) 
               
               
                 {  
               
               
                  // &lt;&lt; code to send the heartbeat &gt;&gt; 
               
               
                 } 
               
               
                 SendGoodFunc g_sendGoodFunc; 
               
               
                 // to manipulate the heartbeat timing simply call: 
               
               
                 //    g_sendGoodFunc.setFuncStart(...) or g_sendGoodFunc.setRepeat( ... ) 
               
               
                   
               
            
           
         
       
     
     The actual execution of the Managed Functions may be controlled and performed by the SleepManager class. The SleepManager may contain the actual prioritized list of managed functions. This prioritized list of functions may automatically be populated by the managed function creation process and may ensure that each function is created properly and has a unique ID. 
     The main role of the SleepManager class may be to have its ‘manage’ function called repeatedly from the processors main loop and/or from a endless while loop. Upon each call of manage, the SleepManager may execute all functions that are scheduled to run until the SleepManager has exhausted all scheduled functions; at which time the SleepManager may place the processor in LPM. Once the processor wakes from LPM, the manage function may be reentered until the processor is again ready to enter LPM (this process may be repeated until stopped, e.g., by a user or by the system). 
     If the processor has to be kept in full power mode for an extended period of time (e.g., while an analog-to-digital conversion is being sampled), the SleepManager may provide functionality to disable entering LPM. While LPM is disabled, the manage function may continuously search for a scheduled task. 
     The SleepManager may also provide an interface to manipulate the scheduling and repeat settings of any managed function through the use of the unique ID of the function, which may allow any section of code to perform any required scheduling without having direct access to or unnecessary knowledge of the desired ManagedFunc object. 
     Radio circuitry included within each of infusion pump assembly  100 ,  100 ′,  400 ,  500  and remote control assembly  300  may effectuate wireless communication between remote control assembly  300  and infusion pump assembly  100 ,  100 ′,  400 ,  500 . A 2.4 GHz radio communications chip (e.g., a Texas Instruments CC2510 radio transceiver) with an internal 8051 microcontroller may be used for radio communications. 
     The radio link may balance the following three objectives: link availability; latency; and energy. 
     Concerning link availability, remote control assembly  300  may provide the primary means for controlling the infusion pump assembly  100 ,  100 ′,  400 ,  500  and may provide detailed feedback to the user via the graphical user interface (GUI) of remote control assembly  300 . Concerning latency, the communications system may be designed to provide for low latency to deliver data from remote control assembly  300  to the infusion pump assembly  100 ,  100 ′,  400 ,  500  (and vice versa). Concerning energy, both remote control assembly  300  and infusion pump assembly  100 ,  100 ′,  400 ,  500  may have a maximum energy expenditure for radio communications. 
     The radio link may support half-duplex communications. Remote control assembly  300  may be the master of the radio link, initiating all communications. Infusion pump assembly  100 ,  100 ′,  400 ,  500  may only respond to communications and may never initiate communications. The use of such a radio communication system may provide various benefits, such as: increased security: a simplified design (e.g., for airplane use); and coordinated control of the radio link. 
     Referring also to  FIG.  120 A , there is shown one illustrative example of the various software layers of the radio communication system discussed above. 
     The radio processors included within remote control assembly  300  and infusion pump assembly  100 ,  100 ′,  400 ,  500  may transfer messaging packets between an SPI port and a 2.4 GHz radio link (and vice versa). The radio may always be the SPI slave. On infusion pump assembly  100 ,  100 ′,  400 ,  500 , radio processor (PRP)  1818  (See  FIGS.  115 - 116   ) may service two additional nodes over the SPI port that are upstream (namely command processor  1800  and supervisor processor  1802 . In some embodiments, on remote control assembly  300 , the radio processor (CRP) may service at least one additional node over the SPI port that may be either upstream or down stream, for example, in some embodiments, the above-described remote control processor (UI) and the Continuous Glucose Engine (CGE). 
     A messaging system may allow for communication of messages between various nodes in the network. The UI processor of remote control assembly  300  and e.g., supervisor processor  1800  may use the messaging system to configure and initiate some of the mode switching on the two system radios. It may be also used by the radios to convey radio and link status information to other nodes in the network. 
     When the radio of remote control assembly  300  wishes to gather channel statistics from the infusion pump assembly  100 ,  100 ′,  400 ,  500  or update the master channel list of the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500 , the radio of remote control assembly  300  may use system messages. Synchronization for putting the new updated list into effect may use indicators in the heartbeat messages to remove timing uncertainty. 
     The radio communication system may be written in C++ to be compatible with the messaging software. A four byte radio serial number may be used to address each radio node. A hash table may be used to provide a one-to-one translation between the device “readable” serial number string and the radio serial number. The hash table may provide a more randomized 8-bit logical address so that pumps (e.g., infusion pump assembly  100 ,  100 ′,  400 ,  500 ) or controllers with similar readable serial numbers are more likely to have unique logical addresses. Radio serial numbers may not have to be unique between pumps (e.g., infusion pump assembly  100 ,  100 ′,  400 ,  500 ) and controllers due to the unique roles each has in the radio protocol. 
     The radio serial number of remote control assembly  300  and the radio serial number of infusion pump assembly  100 ,  100 ′,  400 ,  500  may be included in all radio packets except for the RE Pairing Request message that may only include the radio serial number of remote control assembly  300 , thus ensuring that only occur with the remote control assembly/infusion pump assembly to which it is paired. The CC2510 may support a one byte logical node address and it may be advantageous to use one byte of the radio serial number as the logical node address to provide a level of filtering for incoming packets. 
     The Quiet_Radio signal may be used by the UI processor of remote control assembly  300  to prevent noise interference on the board of remote control assembly  300  by other systems on the board. When Quiet_Radio is asserted, the radio application of remote control assembly  300  may send a message to the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  asserting Radio Quiet Mode for a pre-determined period of time. The Quiet_Radio feature may not be required based on noise interference levels measured on the PC board of remote control assembly  300 . During this period of time, the radio of remote control assembly  300  may stay in Sleep Mode 2 for up to a maximum of 100 ms. The radio of remote control assembly  300  may come out of Sleep Mode 2 when the Quiet_Radio signal is de-asserted or the maximum time period has expired. The UI processor of remote control assembly  300  may assert Quiet_Radio at least one radio communication&#39;s interval before the event needs to be asserted. The radio of remote control assembly  300  may inform the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  that communications will be shutdown during this quiet period. The periodic radio link protocol may have status bits/bytes that accommodate the Quiet_Radio feature unless Quiet_Radio is not required. 
     The radio software may integrate with the messaging system and radio bootloader on the same processor, and may be verified using a throughput test. The radio software may integrate with the messaging system, SPI Driver using DMA, and radio bootloader, all on the same processor (e.g., the TI CC2510). 
     The radio of remote control assembly  300  may be configured to consume no more than 32 mAh in three days (assuming one hundred minutes of fast heartbeat mode communications per day). The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may be configured to consume no more than 25 mAh in three days (assuming one hundred minutes of fast heartbeat mode communications per day). 
     The maximum time to reacquire communications may be ≤6.1 seconds including connection request mode and acquisition mode. The radio of remote control assembly  300  may use the fast heartbeat mode or slow heartbeat mode setting to its advantage in order to conserve power and minimize latency to the user. The difference between the infusion pump assembly  100 ,  100 ′,  400 ,  500  and remote control assembly  300  entering acquisition mode may be that the infusion pump assembly  100 ,  100 ′,  400 ,  500  needs to enter acquisition mode often enough to ensure communications may be restored within the maximum latency period. However, the remote control assembly  300  may change how often to enter acquisition mode with the infusion pump assembly  100 ,  100 ′,  400 ,  500  when in slow heartbeat mode and heartbeats are lost. The radio of remote control assembly  300  may have knowledge of the user GUI interaction, but the infusion pump assembly  100 ,  100 ′,  400 ,  500  may not. 
     The radio of remote control assembly  300  may set the heartbeat period for both radios. The period may be selectable in order to optimize power and link latency depending on activity. The desired heartbeat period may be communicated in each heartbeat from the radio of remote control assembly  300  to the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500 . This may not exclusively establish the heartbeat rate of infusion pump assembly  100 ,  100 ′,  400 ,  500  due to other conditions that determine what mode to be in. When in fast heartbeat mode, the radio of remote control assembly  300  may set the heartbeat period to 20 ms if data packets are available to send or receive, thus providing low link latency communications when data is actively being exchanged. 
     When in fast heartbeat mode, the radio of remote control assembly  300  may set the heartbeat period to 60 ms four heartbeats after a data packet was last exchanged in either direction on the radio. Keeping the radio heartbeat period short after a data packet has been sent or received may assure that any data response packet may be also serviced using a low link latency. When in slow heartbeat mode, the heartbeat rate may be 2.00 seconds or 6.00 second, depending upon online or offline status respectively. 
     The infusion pump assembly  100 ,  100 ′,  400 ,  500  may use the heartbeat rate set by the radio of remote control assembly  300 . The radio of remote control assembly  300  may support the following mode requests via the messaging system:
         Pairing Mode   Connection Mode   Acquisition Mode (includes the desired paired infusion pump assembly  100 ,  100 ′,  400 ,  500  radio serial number)   Sync Mode—Fast Heartbeat   Sync Mode—Slow Heartbeat   RF Off Mode       

     The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may support the following mode requests via the messaging system:
         Pairing Mode   Acquisition Mode   RF Off Mode       

     The radio may use a system message to obtain the local radio serial number. On remote control assembly  300 , the radio may get the serial number from the UI processor of remote control assembly  300 . The radio may use a system message to store the paired radio serial number. 
     Remote control assembly  300  and the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may issue a status message using the messaging system to the UI processor of remote control assembly  300  and command processor  1802  whenever the following status changes:
         Online Fast: Successful connection   Online Fast: Change from Acquisition Mode to Fast Heartbeat Mode   Online Slow: Successful request change from Fast Heartbeat to Slow Heartbeat   Offline: Automatic change to Search Sync mode due to lack of heartbeat exchanges.   Online Fast: Successful request change from Slow Heartbeat to Fast Heartbeat   Offline: Bandwidth falls below 10% in Sync Mode   Online: Bandwidth rises above 10% in Search Sync mode   Offline: Successful request change to RF Off Mode       

     The radio configuration message may be used to configure the number of radio retries. This message may be sent over the messaging system. The UI processor of remote control assembly  300  will send this command to both the radio of remote control assembly  300  and the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  to configure these radio settings. 
     There may be two parameters in the radio configuration message: namely the number of RF retries (e.g., the value may be from 0 to 10); and the radio offline parameters (e.g., the value may be from 1 to 100 in percent of bandwidth). 
     The radio application on both the remote control assembly  300  and infusion pump assembly  100 ,  100 ′,  400 ,  500  may have an API that allows the messaging system to configure the number of RF retries and radio offline parameters. 
     The following parameters may be recommended for the radio hardware configuration:
         Base Radio Specifications   MSK   250 kbps over air baud rate   Up to 84 channels   Channel spacing 1000 kHz   Filter bandwidth 812 kHz   No Manchester encoding   Data whitening   4 byte preamble   4 byte sync (word)   CRC appended to packet   LQI (Link Quality Indicator) appended to packet   Automatic CRC filtering enabled       

     Forward Error Correction (FEC) may or may not be utilized. Although Forward Error Correction (FEC) may be used to increase the effective signal dynamic range by approximately 3 dB, FEC requires fixed packet sizes and doubles the number of over the air bits for the same fixed size message. 
     The radio may function within 1.83 meters distance under nominal operating conditions (except in pairing mode). It may be a goal that the radio function within 7.32 meters distance under nominal operating conditions. The transmit power level may be 0 dBm (except in pairing mode) and the transmit power level in pairing mode may be −22 dBm. Since the desired radio node address of infusion pump assembly  100 ,  100 ′,  400 ,  500  may be not known by the remote control assembly  300  in pairing mode, both infusion pump assembly  100 ,  100 ′,  400 ,  500  and remote control assembly  300  may use a lower transmit power to reduce the likelihood of inadvertently pairing with another infusion pump assembly. 
     AES Encryption may be used for all packets but may not be required, as the Texas Instruments CC2510 radio transceiver includes this functionality. If AES encryption is used, fixed keys may be utilized, as fixed keys provide a quick way to enable encryption without passing keys. However, key exchange may be provided for in future versions of infusion pump assembly  100 ,  100 ′,  400 ,  500 . The fixed keys may be contained in one separate header source file with no other variables but the fixed keys data, thus allowing for easier management of read access of the file. 
     The radio software may support the following eight modes:
         Pairing Mode   RF Off Mode   Connection Mode   Acquisition Mode   Fast Heartbeat Mode   Slow Heartbeat Mode   Search Sync Mode   Sync&#39;ed Acquisition Mode       

     which are graphically depicted in  FIGS.  120 B- 120 C . 
     Pairing may be the process of exchanging radio serial numbers between remote control assembly  300  and infusion pump assembly  100 ,  100 ′,  400 ,  500 . Remote control assembly  300  may be “paired” with infusion pump assembly  100 ,  100 ′,  400 ,  500  when infusion pump assembly  100 ,  100 ′,  400 ,  500  knows its serial number. Infusion pump assembly  100 ,  100 ′,  400 ,  500  may be “paired” with remote control assembly  300  when remote control assembly  300  knows its serial number. 
     Pairing mode (which is graphically depicted in  FIG.  120 D ) may require that four messages to be exchanged over the RF link:
         RF Pairing Request (broadcast from Remote control assembly  300  to any Infusion pump assembly  100 ,  100 ′,  400 ,  500 )   RF Pairing Acknowledge (from Infusion pump assembly  100 ,  100 ′,  400 ,  500  to Remote control assembly  300 )   RF Pairing Confirm Request (from Remote control assembly  300  to Infusion pump assembly  100 ,  100 ′,  400 ,  500 )   RF Pairing Confirm Acknowledge (from Infusion pump assembly  100 ,  100 ′,  400 ,  500  to Remote control assembly  300 )       

     Additionally, remote control assembly  300  may cancel the pairing process at any time via the RF pairing abort message (from remote control assembly  300  to infusion pump assembly  100 ,  100 ′,  400 ,  500 . Pairing mode may not support messaging system data transfers. 
     The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may enter pairing mode upon receiving a pairing mode request message. It may be the responsibility of supervisor processor  1800  on infusion pump assembly  100 ,  100 ′,  400 ,  500  to request the radio to enter pairing mode if there is no disposable attached to infusion pump assembly  100 ,  100 ′,  400 ,  500  and the user has pressed the button of infusion pump assembly  100 ,  100 ′,  400 ,  500  for six seconds. The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may set the appropriate transmit power level for pairing mode. Infusion pump assembly  100 ,  100 ′,  400 ,  500  may only be paired with one remote control assembly  300  at a time. 
     Upon receiving the first valid RE pairing request message while in pairing mode, the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may use the serial number of remote control assembly  300  for the duration of pairing mode and respond with an RF pairing acknowledge message containing the radio serial number infusion pump assembly  100 ,  100 ′,  400 ,  500 . 
     The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may timeout of pairing mode automatically after 2.0±0.2 seconds if no RF pairing request is received. The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may issue a pairing request received message after transmitting the RF pairing acknowledge. This message to supervisor processors will allow feedback to the user during the pairing confirm process. The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may automatically timeout of pairing mode in 1.0±0.1 minutes after sending an RF pairing acknowledge unless an RF pairing confirm request is received. The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may issue a store paired radio serial number message if an RE pairing confirm request message is received after receiving a RE pairing request message. This action may store the radio serial number of remote control assembly  300  in the non-volatile memory of infusion pump assembly  100 ,  100 ′,  400 ,  500  and may overwrite the existing pairing data for the infusion pump assembly  100 ,  100 ′,  400 ,  500 . 
     The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may transmit an RE pairing confirm acknowledge and exit pairing mode after the acknowledgment from the store paired radio serial number message is received. This may be the normal exit of pairing mode on infusion pump assembly  100 ,  100 ′,  400 ,  500  and may result in infusion pump assembly  100 ,  100 ′,  400 ,  500  powering down until connection mode or paring mode entered by the user. 
     If the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  exits pairing mode upon successfully receiving a pairing confirm request message, then the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may revert to the newly paired remote control assembly  300  and may send a pairing completion success message to command processor  1802 . The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may exit pairing mode upon receiving an RF pairing abort message. The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may exit pairing mode upon receiving a pairing abort request message addressed to it. This may allow command processor  1802  or supervisor processor  1800  to abort the pairing process locally on the infusion pump assembly  100 ,  100 ′,  400 ,  500 . 
     The radio of remote control assembly  300  may enter pairing mode upon receiving a pairing mode request message. It may be the responsibility of the UI processor of remote control assembly  300  to request that the radio enter pairing mode under the appropriate conditions. The radio of remote control assembly  300  may set the appropriate transmit power level for pairing mode. The radio of remote control assembly  300  may transmit RE pairing requests until an RE pairing acknowledge is received or pairing is aborted. 
     The radio of remote control assembly  300  may automatically abort pairing mode if the RF pairing acknowledge message is not received within 30.0±1.0 seconds after entering pairing mode. Upon receiving the first valid RE pairing acknowledge message while in pairing mode, the radio of remote control assembly  300  may send a pairing success message to the UI processor of remote control assembly  300  that includes the serial number of infusion pump assembly  100 ,  100 ′,  400 ,  500  and may use that serial number for the duration of pairing mode. This message may provide a means for the UI processor of remote control assembly  300  to have the user confirm the serial number of the desired infusion pump assembly  100 ,  100 ′,  400 ,  500 . If the radio of remote control assembly  300  receives multiple responses (concerning a single pairing request) from infusion pump assembly  100 ,  100 ′,  400 ,  500 , the first valid one may be used. 
     The Radio of remote control assembly  300  may only accept an RE pairing confirm acknowledge messages after an RE pairing acknowledge is received while in pairing mode. The radio of remote control assembly  300  may transmit the RE pairing confirm message upon receiving a pair confirm request message from the UI processor of remote control assembly  300 . 
     The radio of remote control assembly  300  may check that infusion pump assembly  100 ,  100 ′,  400 ,  500  confirms the pairing before adding infusion pump assembly  100 ,  100 ′,  400 ,  500  to the pairing list. The radio of remote control assembly  300  may issue a store paired radio serial number message if an RF pairing complete message is received. This action may allow the UI processor of remote control assembly  300  to store the new serial number of infusion pump assembly  100 ,  100 ′,  400 ,  500  and provide user feedback of a successful pairing. It may be the responsibility of the UI processor of remote control assembly  300  to manage the list of paired infusion pump assemblies. 
     The radio of remote control assembly  300  may send an RE pairing abort message and exit pairing mode upon receiving a pairing abort request message. This may allow the UI processor of the remote control assembly  300  to abort the pairing process on both the remote control assembly  300  and acknowledged infusion pump assembly  100 ,  100 ′,  400 ,  500 . 
     In connection request mode, the radio of remote control assembly  300  may attempt to acquire each infusion pump assembly  100 ,  100 ′,  400 ,  500  in its paired infusion pump assembly list and retrieve its “connection ready” status. The “connection” process (which is graphically depicted in  FIG.  120 E ) may allow remote control assembly  300  to quickly identify one of its paired infusion pump assemblies that may be ready to be used. The radio of remote control assembly  300  may be capable of performing the connection request mode with up to six paired infusion pump assemblies. Connection request mode may be only supported on remote control assembly  300  and may be a special form of acquisition mode. In connection request mode, remote control assembly  300  may connect with the first infusion pump assembly to respond. However, each message may be directed to a specific infusion pump assembly serial number. 
     The radio of remote control assembly  300  may obtain the latest paired infusion pump assembly serial number list upon entering connection mode. The radio of remote control assembly  300  may enter connection mode upon receiving a connection mode request message. It may be the responsibility of the UI processor of remote control assembly  300  to request that the radio enter connection mode when it desires communications with a paired infusion pump assembly. The radio of remote control assembly  300  may issue a connection assessment message to the UI processor of remote control assembly  300  containing the radio serial number of the first infusion pump assembly, if any, that is “connection ready”. The radio of remote control assembly  300  may generate the connection assessment message within thirty seconds of entering connection request mode. The radio of remote control assembly  300  may exit connection request mode upon receipt of the connection assessment acknowledgement and transition to fast heartbeat mode. The radio of remote control assembly  300  may exit connection request mode upon receipt of a connection request abort message from the UI processor of remote control assembly  300 . 
     On remote control assembly  300 , acquisition mode may be used to find a particular paired infusion pump assembly. The radio of remote control assembly  300  may send RE RUT (aRe yoU There) packets to the desired paired infusion pump assembly. If the infusion pump assembly receives the RE RUT message, it may respond to the radio of remote control assembly  300 . Multiple channels may be used in the acquisition mode algorithm to improve the opportunity for the radio of remote control assembly  300  to find the paired infusion pump assembly. 
     The radio of remote control assembly  300  may enter acquisition mode upon receiving an acquisition mode request or fast heartbeat mode request message while in RE Off Mode. The radio of remote control assembly  300  may enter sync&#39;ed acquisition mode upon receiving an acquisition mode request or fast heartbeat mode request message while in search sync mode. It may be the responsibility of the UI processor of remote control assembly  300  to request that the radio enter acquisition mode when the RE link is off-line and remote control assembly  300  desires communications with infusion pump assembly  100 ,  100 ′,  400 ,  500 . 
     The radio of remote control assembly  300  may only communicate with one paired infusion pump assembly  100 ,  100 ′,  400 ,  500  (except in pairing and connection modes). When communications are lost, the UI processor of remote control assembly  300  may use acquisition mode (at some periodic rate limited by the power budget) to attempt to restore communications. 
     Infusion pump assembly  100 ,  100 ′,  400 ,  500  may enter acquisition mode under the following conditions:
         When in Radio Off Mode and Acquisition Mode may be requested   When Search Sync Mode times out due to lack of heartbeats       

     Upon entering acquisition mode, the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may obtain the serial number of the last stored paired remote control assembly  300 . The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may only communicate with the remote control assembly to which it has been “paired” (except while in the “pairing request” mode). The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may transition from acquisition mode to fast heartbeat mode upon successfully acquiring synchronization with the remote control assembly  300 . The acquisition mode of infusion pump assembly  100 ,  100 ′,  400 ,  500  may be capable of acquiring synchronization within 6.1 seconds, which may implies that the infusion pump assembly  100 ,  100 ′,  400 ,  500  may always be listening at least every ˜6 seconds when in acquisition mode. 
     Data packets may be sent between two paired devices when the two devices are in sync mode and online. The two devices may sync via a heartbeat packet before data packets are exchanged. Each radio may send data packets at known time intervals after the heartbeat exchange. The infusion pump assembly  100 ,  100 ′,  400 ,  500  may adjust its timing to anticipate reception of a packet. The radio may support one data packet in each direction on each heartbeat. The radio may provide a negative response to a fast heartbeat mode request if the radio if offline. The radio of remote control assembly  300  may change to fast heartbeat mode if a system request for fast heartbeat mode is received while in slow heartbeat mode and the radio is online. 
     Upon transitioning to fast heartbeat mode from acquisition mode, the radio of remote control assembly  300  may send the master channel list message. The master channel list may be built by the radio of remote control assembly  300  and sent to the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  to allow a selection of frequency hopping channels based on historical performance. When in fast heartbeat mode or slow heartbeat mode, periodic heartbeat messages may be exchanged between the radio of remote control assembly  300  and the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500 . The periodicity of these messages may be at the heartbeat rate. The heartbeat messages may allow data packet transfers to take place and may also exchange status information. The two radios may exchange the following status information: Quiet Mode, data availability, buffer availability, heartbeat rate, and prior channel performance. It may be a goal to keep the packet size of the heartbeat messages small in order to conserve power. The radio may provide for a maximum data packet size of eighty-two bytes when in Sync Mode. The messaging system may be designed to support packet payload sizes up to sixty-four bytes. This maximum size was selected as an optimal trade-off between minimum messages types and non-fragmented messages. The eighty-two bytes may be the maximum packet size of the messaging system including packet overhead. 
     The messaging system has an API that may allow the radio protocol to send an incoming radio packet to it. The messaging system may also have an API that allows the radio protocol to get a packet for transmission over the radio network. The messaging system may be responsible for packet routing between the radio protocol and the SPI port. Data packets may be given to the messaging system for processing. The messaging system may have an API that allows the radio protocol to obtain a count of the number of data packets waiting to be sent over the radio network. The radio protocol may query the messaging system on each heartbeat to determine if data packets are available to send over the radio network. It may be desirable for the software to check the availability of a message just before the heartbeat is sent to minimize round trip message latency. 
     The radio protocol may be capable of buffering one incoming radio data packet and passing the packet to the messaging system. The radio protocol may send the data packet to the messaging system upon receipt of the data packet. The message system may be responsible for routing radio data packets to the proper destination node. The radio protocol may be capable of buffering one packet from the messaging system. 
     The radio protocol may be responsible for acknowledging receipt of valid data packets over the RF link via an RF ACK reply packet to the sending radio. The RF ACK packet may contain the source and destination radio serial numbers, RF ACK command identification, and sequence number of the data packet being acknowledged. 
     The radio transmitting a radio data packet may retransmit that radio data packet on the next heartbeat with the same sequence number if an RF ACK is not received and the retry count is within the maximum RF retries allowed. It may be expected that, from time to time, interference will corrupt a transmission on a particular frequency. An RF retry allows the same packet to be retransmitted at the next opportunity at a different frequency. The sequence number provides a means of uniquely identifying the packet over a short time window. The number of radio packet retries may be configurable using the radio configuration command. Allowing more retries may increase the probability of a packet being exchanged but introduces more latency for a round trip messages. The default number of radio retries at power up may be ten (i.e., the maximum transmission attempts before dropping the message). 
     A one byte (modulo 256) radio sequence number may be included in all radio data packets over the RE link. Since the radio may be responsible for retrying data packet transmission if not acknowledged, the sequence number may provide a way for the two radios to know if a data packet is a duplicate. The transmitted sequence number may be incremented for each new radio data packet and may be allowed to rollover. When a data packet is successfully received with the same sequence number as the previous successfully received data packet (and in the same direction), the data packet may be ACK&#39;d and the received data packet discarded. This may remove duplicate packets generated by the RF protocol before they are introduced into the network. Note that it may be possible that multiple data packets in a row may need to be dropped with the same sequence number under extreme situations. 
     If a heartbeat is missed, the radio of remote control assembly  300  and the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may attempt to send and listen respectively for subsequent heartbeats. The radio of remote control assembly  300  and the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may automatically change from fast heartbeat mode or slow heartbeat mode to search sync mode if heartbeats are missed for two seconds. This may minimize power consumption when the link is lost by allowing the radios to continue to use their synchronization information, as two seconds allows sufficient time to hop through all channels. 
     The radio may be considered online while in the following modes:
         Fast Heartbeat mode   Slow Heartbeat mode       

     as these are the only conditions where messaging system traffic may be exchanged. All other conditions may be considered offline. 
     The radio may initialize to radio off mode at the start of code execution from reset. When code first executes on the radio processor, the initial state may be the radio off mode to allow other processors to perform self-tests before requesting the radio to be active. This requirement does not intend to define the mode when waking from sleep mode. The radio may cease RF communications when set to radio off mode. On remote control assembly  300 , this mode may be intended for use on an airplane to suppress RF emissions. Since infusion pump assembly  100 ,  100 ′,  400 ,  500  only responds to transmissions from remote control assembly  300  (which will have ceased transmitting in airplane mode), radio off mode may only be used on infusion pump assembly  100 ,  100 ′,  400 ,  500  when charging. 
     Command processor  1802  may be informed of airplane mode and that, therefore, the RE was intentionally turned off on remote control assembly  300  so that it does not generate walk-away alerts. However, this may be completely hidden from the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500 . 
     The radio of remote control assembly  300  and the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may periodically attempt to exchange heartbeats in order to reestablish data bandwidth while in search sync mode. The radio of remote control assembly  300  may transition to radio off mode after twenty minutes of search sync mode with no heartbeats successfully exchanged. 
     The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may transition to acquisition mode after twenty minutes of search sync mode with no heartbeats successfully exchanged. Listening during pre-agreed time slots may be the most efficient use of power for infusion pump assembly  100 ,  100 ′,  400 ,  500  to re-establish the RF link. After a loss of communications, the crystal tolerance and temperature drift may make it necessary to expand the receive window of infusion pump assembly  100 ,  100 ′,  400 ,  500  over time. Staying in search sync mode for extended periods (e.g., 5-20 minutes) after communications loss may cause the instantaneous power consumed to exceed the average power budgeted for the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500 . The radio of remote control assembly  300  may not be forced to expand its window, so staying in search sync mode may be very power efficient. Acquisition mode may consume more power for remote control assembly  300 . Twenty minutes may be used as a compromise to balance power consumption on both the radio of remote control assembly  300  and the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500 . 
     The radio of remote control assembly  300  and the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may transition to slow heartbeat mode if they successfully exchange three of the last five heartbeats. Approximately every six seconds, a burst of five heartbeats may be attempted. If three of these are successful, the bandwidth may be assumed to be sufficient to transition to slow heartbeat mode. The radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  may be acquirable while in search sync mode with a latency of 6.1 seconds. This may imply that the infusion pump assembly  100 ,  100 ′,  400 ,  500  may always be listening at least every ˜6 seconds when in search sync mode. 
     Radio protocol performance statistics may be necessary to promote troubleshooting of the radio and to assess radio performance. The following radio performance statistics may be maintained by the radio protocol in a data structure: 
     
       
         
           
               
               
               
             
               
                   
               
               
                 NAME 
                 SIZE 
                 DESCRIPTION 
               
               
                   
               
             
            
               
                 TX Heartbeat Count 
                 32 Bits 
                 Total transmitted heartbeats 
               
               
                 RX Heartbeat Count 
                 32 bits 
                 Total valid received heartbeats 
               
               
                 CRC Errors 
                 16 bits 
                 Total packets received over the RF  
               
               
                   
                   
                 link which were dropped due to bad  
               
               
                   
                   
                 CRC. This may be a subset of RX 
               
               
                   
                   
                 Packets Nacked. 
               
               
                 First Retry Count 
                 32 bits 
                 Total number of packets which were  
               
               
                   
                   
                 successfully acknowledged after 1  
               
               
                   
                   
                 retry 
               
               
                 Second Retry Count 
                 32 bits 
                 Total number of packets which were  
               
               
                   
                   
                 successfully acknowledged after 2  
               
               
                   
                   
                 retries 
               
               
                 Third Retry Count 
                 32 bits 
                 Total number of packets which were  
               
               
                   
                   
                 successfully acknowledged after 3  
               
               
                   
                   
                 retries 
               
               
                 Fourth Retry Count 
                 32 bits 
                 Total number of packets which were  
               
               
                   
                   
                 successfully acknowledged after 4  
               
               
                   
                   
                 retries 
               
               
                 Fifth Retry Count 
                 16 bits 
                 Total number of packets which were  
               
               
                   
                   
                 successfully acknowledged after 5  
               
               
                   
                   
                 retries 
               
               
                 Sixth Retry Count 
                 16 bits 
                 Total number of packets which were  
               
               
                   
                   
                 successfully acknowledged after 6  
               
               
                   
                   
                 retries 
               
               
                 Seventh Retry Count 
                 16 bits 
                 Total number of packets which were  
               
               
                   
                   
                 successfully acknowledged after 7  
               
               
                   
                   
                 retries 
               
               
                 Eighth Retry Count 
                 16 bits 
                 Total number of packets which were  
               
               
                   
                   
                 successfully acknowledged after 8  
               
               
                   
                   
                 retries 
               
               
                 Ninth Retry Count 
                 16 bits 
                 Total number of packets which were  
               
               
                   
                   
                 successfully acknowledged after 9  
               
               
                   
                   
                 retries 
               
               
                 Tenth Retry Count 
                 16 bits 
                 Total number of packets which were  
               
               
                   
                   
                 successfully acknowledged after 10  
               
               
                   
                   
                 retries 
               
               
                 Dropped Retry Count 
                 16 bits 
                 Total number of packets which were  
               
               
                   
                   
                 dropped after maximum retries  
               
               
                   
                   
                 attempts 
               
               
                 Duplicate Packet Count 
                 16 bits 
                 Total number of received packets  
               
               
                   
                   
                 dropped due to duplicate packet 
               
               
                 1 to 5 Missed Fast Mode  
                 16 bits 
                 Count of 1 to 5 consecutive missed  
               
               
                 Hops 
                   
                 hops in Fast mode (i.e. not received) 
               
               
                 6 to 16 Missed Fast Mode  
                 16 bits 
                 Count of 6 to 16 consecutive missed  
               
               
                 Hops 
                   
                 hops in Fast mode. 
               
               
                 17 to 33 Missed Fast  
                 16 bits 
                 Count of 17 to 33 consecutive missed  
               
               
                 Mode Hops 
                   
                 hops in Fast mode 
               
               
                 34+ Missed Fast Mode  
                 16 bits 
                 Count of 34 or more consecutive  
               
               
                 Hops 
                   
                 missed hops in Fast mode 
               
               
                 1 to 2 Missed Slow Mode  
                 16 bits 
                 Count of 1 to 2 consecutive missed  
               
               
                 Hops 
                   
                 hops in Slow mode (i.e. not received) 
               
               
                 3 to 5 Missed Slow Mode  
                 16 bits 
                 Count of 3 to 5 consecutive missed  
               
               
                 Hops 
                   
                 hops in Slow mode 
               
               
                 5 to 7 Missed Slow Mode  
                 16 bits 
                 Count of 5 to 7 consecutive missed  
               
               
                 Hops 
                   
                 hops in Slow mode 
               
               
                 8+ Missed Slow Mode  
                 16 bits 
                 Count of 8 or more consecutive  
               
               
                 Hops 
                   
                 missed hops in Slow mode 
               
               
                 Destination Radio Serial  
                 16 bits 
                 Count of received packets in which  
               
               
                 Number Mismatch 
                   
                 the destination made it past the  
               
               
                   
                   
                 hardware filtering but does not match 
               
               
                   
                   
                 this radio&#39;s serial number. This may  
               
               
                   
                   
                 be not an error but indicates that the  
               
               
                   
                   
                 radio may be waking up and  
               
               
                   
                   
                 receiving (but not processing) packets  
               
               
                   
                   
                 intended for other radios 
               
               
                 Total Walkaway Time  
                 16 bits 
                   
               
               
                 (minutes) 
                   
                   
               
               
                 Total Walkaway Events 
                 16 bits 
                 Together with total walkaway time  
               
               
                   
                   
                 provides an average walkaway time 
               
               
                 Number of Pairing  
                 16 bits 
                   
               
               
                 Attempts 
                   
                   
               
               
                 Total Time in Acquisition  
                 16 bits 
                   
               
               
                 Mode (Infusion pump  
                   
                   
               
               
                 assembly 100, 100&#39;, 400,  
                   
                   
               
               
                 500 Only) 
                   
                   
               
               
                 Total Acquisition Mode  
                 16 bits 
                 Successful Acquisition Count 16 bits  
               
               
                 Attempts (Remote control  
                   
                 Count of transitions from Connect or  
               
               
                 assembly 300 Only) 
                   
                 Acquisition Mode to Fast Heartbeat  
               
               
                   
                   
                 Mode 
               
               
                 Requested Slow Heartbeat  
                 16 bits 
                   
               
               
                 Mode Transitions 
                   
                   
               
               
                 Automatic Slow Heartbeat  
                 16 bits 
                   
               
               
                 Mode Transitions 
                   
                   
               
               
                 Radio offline messages  
                 16 bits 
                   
               
               
                 sent 
                   
                   
               
               
                 Radio online messages  
                 16 bits 
                   
               
               
                 sent 
               
               
                   
               
            
           
         
       
     
     A # define DEBUG option (compiler option) may be used to gather the following additional radio performance statistics per each channel (16 bit numbers):
         Number of missed hops   CCA good count   CCA bad count   Average RSSI (accumulated for good RX packets only)   Dropped from Frequency Hop List count   Acquisition Mode count (found pair on this channel)       

     The debug option may be used to gather engineering only statistics. If processor performance, power, and memory allow, it may be desirable to keep this information at runtime. The radio statistics may be made available to the messaging system. 
     Link quality may be intended to be used on remote control assembly  300  to provide a bar indicator, similar to a cell phone, of the radio link quality. Link quality may be made available to both remote control assembly  300  and infusion pump assembly  100 ,  100 ′,  400 ,  500 . It may be anticipated that the link quality status will consist of a one byte indicator of the quality of the radio link. 
     The radio may change frequency for each heartbeat. An adaptive pseudo random frequency hopping algorithm may be used for sync mode and heartbeat attempts in search sync mode. It may be a goal to use sixty-four channels for frequency hopping. An algorithm may be developed to adaptively generate a channel list on remote control assembly  300  for frequency hopping. The radio of remote control assembly  300  may build, maintain, and distribute the master channel list. Prior channel statistics and historical performance information may be obtained from the radio of infusion pump assembly  100 ,  100 ′,  400 ,  500  by the radio of remote control assembly  300  using the messaging system as needed to meet performance requirements. By building the channel list from the perspective of both units, the radio interference environment of both units may be considered. The radios may adaptively select hopping channels to meet the round trip message latency, while operating in a desirable RF environment. 
     Occlusions and/or leaks may occur anywhere along the fluid delivery path of infusion pump assembly  100 . For example and referring to  FIG.  121   , occlusions/leaks may occur: in the fluid path between reservoir  118  and reservoir valve assembly  614 ; in the fluid path between reservoir valve assembly  614  and pump assembly  106 ; in the fluid path between pump assembly  106  and volume sensor valve assembly  612 ; in the fluid path between volume sensor valve assembly  612  and volume sensor chamber  620 ; in the fluid path between volume sensor chamber  620  and measurement valve assembly  610 ; and in the fluid path between measurement valve assembly  610  and the tip of disposable cannula  138 . Infusion pump assembly  100  may be configured to execute one or more occlusion/leak detection algorithms that detect and locate such occlusions/leaks and enhance the safety/reliability of infusion pump assembly  100 . 
     As discussed above, when administering the infusible fluid, infusion pump assembly  100  may first determine the volume of infusible fluid within volume sensor chamber  620  prior to the administration of the dose of infusible fluid and may subsequently determine the volume of infusible fluid within volume sensor chamber  620  after the administration of the dose of infusible fluid. By monitoring these values, the occurrence of occlusions/leaks may be detected. 
     Occlusion Type—Total: When a total occlusion is occurring, the difference between the initial measurement prior to the administration of the dose of infusible fluid and the final measurement after the administration of the dose of infusible fluid will be zero (or essentially zero), indicating a large residual quantity of infusible fluid within volume sensor chamber  620 . Accordingly, no fluid may be leaving volume sensor chamber  620 . 
     Specifically, if the tip of disposable cannula is occluded, the fluid path down stream of volume sensor chamber  620  will fill with fluid and eventually become pressurized to a level equivalent to the mechanical pressure exerted by spring diaphragm  628 . Accordingly, upon measurement valve assembly  610  opening, zero (or essentially zero) fluid will be dispensed and, therefore, the value of the initial and final measurements (as made by volume sensor assembly  148 ) will essentially be equal. 
     Upon detecting the occurrence of such a condition, a total occlusion indicator may be set and infusion pump assembly  100  may e.g., trigger an alarm, thus indicating that the user needs to seek alternative means for receiving their therapy. 
     Occlusion Type—Partial: When a partial occlusion is occurring, the difference between the initial measurement prior to the administration of the dose of infusible fluid and the final measurement after the administration of the dose of infusible fluid will indicate that less than a complete dose of infusible fluid was delivered. For example, assume that at the end of a particular pumping cycle, volume sensor assembly  148  indicated that 0.10 microliters of infusible fluid were present in volume sensor chamber  620 . Further, assume that measurement value assembly  610  is subsequently closed and pump assembly  106  is subsequently actuated, resulting in volume sensor chamber  620  being filed with the infusible fluid. Further assume that volume sensor assembly  148  determines that volume sensor chamber  620  is now filled with 1.00 microliters of infusible fluid (indicating a pumped volume of 0.90 microliters). 
     Accordingly, upon the opening of measurement valve assembly  610 , the quantity of infusible fluid included within volume sensor chamber would be expected to drop to 0.10 microliters (or reasonably close thereto). However, in the event of a partial occlusion, due to a slower-than-normal flow rate from volume sensor chamber  620 , the quantity of infusible fluid within volume sensor chamber  620  may only be reduced to 0.40 microliters (indicating a delivered volume of 0.60 microliters). Accordingly, by monitoring the difference between the pumped volume (0.90 microliters) and the delivered volume (0.60 microliters), the residual volume may be defined and the occurrence of a partial occlusion may be detected. 
     Upon detecting the occurrence of such a condition, a partial occlusion indicator may be set and infusion pump assembly  100  may e.g., trigger an alarm, thus indicating that the user needs to seek alternative means for receiving their therapy. However, as this is indicative of a partial occlusion (as opposed to a complete occlusion), the issuance of an alarm may be delayed, as the partial occlusion may clear itself. 
     Alternatively, infusion pump assembly  100  may: calculate a pump ontime to volume delivered ratio; track it through time; and track by using a fast moving and a slow moving exponential average of the pump ontime. The exponential average may be tracked, in a fashion similar to the leaky sum integrator. The infusion pump assembly  100  may filter signal and look for a fast change. The rate of fluid outflow and/or residual volume may be monitored. If the residual volume does not change, then there may be a total occlusion. If the residual volume changed, they may be a partial occlusion. Alternatively still, the residual values may be summed. If the number of valve actuations or the latch time is being varied, the fluid flow rate may be examined, even if you build up pressure in volume sensor assembly  148 . 
     Total/Partial Empty Reservoir: When reservoir  118  is becoming empty, it will become more difficult to fill volume sensor chamber  620  to the desired level. Typically, pump assembly  106  is capable of pumping 1.0 microliters per millisecond. For example, assume that an “empty” condition for volume sensor chamber  620  is 0.10 microliters and a “full” condition for volume sensor chamber  620  is 1.00 microliters. However, as reservoir  118  begins to empty, it may become harder for pump assembly  106  to fill volume sensor chamber  620  to the “full” condition and may consistently miss the goal. Accordingly, during normal operations, it may take one second for pump assembly  106  to fill volume sensor chamber  620  to the “full” condition and, as reservoir  118  empties, it may take three seconds to fill volume sensor chamber  620  to the “full” condition. Eventually, if reservoir  118  completely empties, volume sensor chamber  620  may never be able to achieve a “full condition”. Accordingly, the inability of pump assembly  106  to fill volume sensor chamber  620  to a “full” condition may be indicative of reservoir  118  being empty. Alternatively, the occurrence of such a condition may be indicative of other situations (e.g., the failure of pump assembly  106  or an occlusion in the fluid path prior to volume sensor chamber  620 ). Infusion pump assembly  100  may determine the difference between the “full” condition and the amount actually pumped. These differences may be summed and the made up for once the reservoir condition is addressed. 
     Upon detecting the occurrence of such a condition, an empty indicator may be set and infusion pump assembly  100  may e.g., trigger an alarm, thus indicating that the user needs to e.g., replace disposable housing assembly  114 . 
     Additionally, as reservoir  118  empties, reservoir  118  will eventually result in a “vacuum” condition and the ability of pump assembly  106  to deliver fluid to volume sensor chamber  620  may be compromised. As discussed above, volume controller  1602  may include feed forward controller  1652  for setting an initial “guess” concerning “on-time” signal  1606 , wherein this initial guess is based upon a pump calibration curve. For example, in order for pump assembly  106  to deliver 0.010 units of infusible fluid, feed forward controller  1652  may define an initial “on-time” of e.g., one millisecond. However, as reservoir  118  begins to empty, due to compromised pumping conditions, it may take two milliseconds to deliver 0.010 units of infusible fluid. Further, as reservoir  118  approaches a fully empty condition, it make take ten milliseconds to deliver 0.010 units of infusible fluid. Accordingly, the occurrence of reservoir  118  approaching an empty condition may be detected by monitoring the level at which the actual operation of pump assembly  106  (e.g., two milliseconds to deliver 0.010 units of infusible fluid) differs from the anticipated operation of pump assembly  106  (e.g., one millisecond to deliver 0.010 units of infusible fluid). 
     Upon detecting the occurrence of such a condition, a reserve indicator may be set and infusion pump assembly  100  may e.g., trigger an alarm, thus indicating that the user will need to e.g., replace disposable housing assembly  114  shortly. 
     Leak Detection: In the event of a leak (e.g., a leaky valve or a rupture/perforation) within the fluid path, the ability of the fluid path to retain fluid pressure may be compromised. Accordingly, in order to check for leaks within the fluid path, a bleed down test may be performed in which pump assembly  106  is used to pressurize volume sensor chamber  620 . Volume sensor assembly  148  may then perform a first volume measurement (as described above) to determine the volume of infusible fluid within volume sensor chamber  620 . Infusion pump assembly  100  may then wait a defined period of time to allow for bleed down in the event of a leak. For example, after a sixty second bleed down period, volume sensor assembly  148  may perform a second volume measurement (as described above) to determine the volume of infusible fluid within volume sensor chamber  620 . If there are no leaks, the two volume measurements should be essentially the same. However, in the event of a leak, the second measurement may be less then the first measurement. Additionally, depending on the severity of the leak, pump assembly  106  may be incapable of filling volume sensor chamber  620 . Typically, a leak check may be performed as part of a delivery of infusible fluid. 
     In the event that the difference between the first volume measurement and the second volume measurement exceeds an acceptable threshold, a leak indicator may be set and infusion pump assembly  100  may e.g., trigger an alarm, thus indicating that the user needs to seek alternative means for receiving their therapy 
     As discussed above, infusion pump assembly  100  may include supervisor processor  1800 , command processor  1802 , and radio processor  1818 . Unfortunately, once assembled, access to electrical control assembly  110  within infusion pump assembly  100  very limited. Accordingly, the only means to access electrical control assembly  110  (e.g., for upgrading flash memories) may be through the communication channel established between infusion pump assembly  100 ,  100 ′,  400 ,  500  and remote control assembly  300 , or via electrical contacts  834  used by battery charger  1200 . 
     Electrical contacts  834  may be directly coupled to radio processor  1818  and may be configured to provide I2C communication capability for erasing/programming any flash memory (not shown) included within radio processor  1818 . The process of loading a program into radio processor  1818  may provide a means for erasing/programming of the flash memories in both the supervisor processor  1800  and command processor  1802 . 
     When programming supervisor processor  1800  or command processor  1802 , the program (i.e., data) to be loaded into flash memory accessible by supervisor processor  1800  or command processor  1802  may be provided in a plurality of data blocks. This is because the radio processor  1818  may not have enough memory to hold the entire flash image of the software as one block. 
     Referring also to  FIG.  122   , there is shown one illustrative example of the manner in which the various systems within infusion pump assembly  100 ,  100 ′,  400 ,  500  may be interconnected. For example, battery charger  1200  may be coupled to computing device  2100  (e.g., a personal computer) via bus translator  2102 , which converts e.g., RS232 formatted data to e.g., I2C formatted data. Bus translator  2102  may execute a pass-through program that effectuates the above-described translation. Battery charger  1200  may be coupled to radio processor  181  via electrical contacts  834  (described above). Radio processor  1818  may then be coupled to supervisor processor  1800  and command processor  1802  via e.g., an RS232 bus. Radio processor  1818  may execute an update program that allows radio processor  1818  to control/orchestrate the updating of the flash memories accessible by supervisor processor  1800  and command processor  1802 . Accordingly, through the use of the above-described coupling, software updates obtained by computing device  2100  may be uploaded to flash memory (not shown) accessible by supervisor processor  1800  and command processor  1802 . The above-described software updates may be command line program that may be automatically invoked by a script process. 
     As discussed above, infusion pump assembly  100 ,  100 ′  400 ,  500  may be configured to deliver an infusible fluid to a user. Further and as discussed above, infusion pump assembly  100 ,  100 ′  400 ,  500  may deliver the infusible fluid via sequential, multi-part, infusion events (that may include a plurality of discrete infusion events) and/or one-time infusion events. However, in some embodiments, infusion pump assembly  100 ,  100 ′  400 ,  500  may deliver stacking bolus infusion events. For example, a user may request the delivery of a bolus, e.g., 6 units. While the 6 units are in the process of being delivered to the user, the user may request a second bolus, e.g., 3 units. In some embodiments of infusion pump assembly  100 ,  100 ′  400 ,  500  may deliver the second bolus at the completion of the first bolus. 
     Examples of other such sequential, multi-part, infusion events may include but are not limited to a basal infusion event and an extended-bolus infusion event. As is known in the art, a basal infusion event refers to the repeated injection of small (e.g. 0.05 unit) quantities of infusible fluid at a predefined interval (e.g. every three minutes) that may be repeated until stopped, e.g., by a user or by the system. Further, the basal infusion rates may be pre-programmed and may include specified rates for pre-programmed time-frames, e.g., a rate of 0.50 units per hour from 6:00 am-3:00 pm; a rate of 0.40 units per hour from 3:00 pm-10:00 pm; and a rate of 0.35 units per hour from 10:00 pm-6:00 am. However, the basal rate may be 0.025 units per hour, and may not change according to pre-programmed time-frames. The basal rates may be repeated regularly/daily until otherwise changed. 
     Further and as is known in the art, an extended-bolus infusion event may refer to the repeated injection of small (e.g. 0.05 unit) quantities of infusible fluid at a predefined interval (e.g. every three minutes) that is repeated for a defined number of intervals (e.g., three intervals) or for a defined period of time (e.g., nine minutes). An extended-bolus infusion event may occur simultaneously with a basal infusion event. 
     If multiple infusion events conflict with each other, infusion pump assembly  100 ,  100 ′  400 ,  500  may prioritize the infusion event in the follow manner. 
     Referring also to  FIG.  123   , assume for illustrative purposes only that the user configures infusion pump assembly  100 ,  100 ′  400 ,  500  to administer a basal dose (e.g. 0.05 units) of infusible fluid every three minutes. The user may utilize remote control assembly  300  to define a basal infusion event for the infusible fluid (e.g., 1.00 units per hour). 
     Infusion pump assembly  100 ,  100 ′  400 ,  500  may then determine an infusion schedule based upon the basal infusion event defined. Once determined, infusion pump assembly  100 ,  100 ′  400 ,  500  may administer the sequential, multi-part, infusion event (e.g., 0.05 units of infusible fluid every three minutes). Accordingly, while administering the sequential, multi-part, infusion event, infusion pump assembly  100 ,  100 ′  400 ,  500 : may infuse a first 0.05 unit dose  2200  of the infusible fluid at t=0:00 (i.e., a first discrete infusion event), may infuse a second 0.05 unit dose  2202  of the infusible fluid at t=3:00 (i.e., a second discrete infusion event); may infuse a third 0.05 unit dose  2204  of the infusible fluid at t=6:00 (i.e., a third discrete infusion event); may infuse a fourth 0.05 unit dose  2206  of the infusible fluid at t=9:00 (i.e., a fourth discrete infusion event); and may infuse a fifth 0.05 unit dose  2208  of the infusible fluid at t=12:00 (i.e., a fifth discrete infusion event). As discussed above, this pattern of infusing 0.05 unit doses of the infusible fluid every three minutes may be repeated until stopped, e.g., by a user or by the system, in this example, as this is an illustrative example of a basal infusion event. 
     Further, assume for illustrative purposes that the infusible fluid is insulin and sometime after the first 0.05 unit dose  2200  of infusible fluid is administered (but before the second 0.05 unit dose  2202  of infusible fluid is administered), the user checks their blood glucose level and realizes that their blood glucose level is running a little higher than normal. Accordingly, the user may define an extended bolus infusion event via remote control assembly  300 . An extended bolus infusion event may refer to the continuous infusion of a defined quantity of infusible fluid over a finite period of time. However, as such an infusion methodology is impractical/undesirable for an infusion pump assembly, when administered by such an infusion pump assembly, an extended bolus infusion event may refer to the infusion of additional small doses of infusible fluid over a finite period of time. 
     Accordingly, the user may utilize remote control assembly  300  to define an extended bolus infusion event for the infusible fluid (e.g., 0.20 units over the next six minutes), which may be confirmed in a manner discussed above. While, in this example, the extended bolus infusion event is described as 0.20 units over the next six minutes, this is for illustrative purposes only and is not intended to be a limitation of this disclosure, as either or both of the unit quantity and total time interval may be adjusted upward or downward. Once defined and/or confirmed, infusion pump assembly  100 ,  100 ′  400 ,  500  may determine an infusion schedule based upon the extended bolus infusion event defined; and may administer the infusible fluid. For example, infusion pump assembly  100 ,  100 ′  400 ,  500  may deliver 0.10 units of infusible fluid every three minutes for the next two interval cycles (or six minutes), resulting in the delivery of the extended bolus dose of infusible fluid defined by the user (i.e., 0.20 units over the next six minutes). 
     Accordingly, while administering the second, sequential, multi-part, infusion event, infusion pump assembly  100 ,  100 ′  400 ,  500  may infuse a first 0.10 unit dose  2210  of the infusible fluid at t=3:00 (e.g., after administering the second 0.05 unit dose  2202  of infusible fluid). Infusion pump assembly  100 ,  100 ′  400 ,  500  may also infuse a second 0.10 unit dose  2212  of the infusible fluid at t=6:00 (e.g., after administering the third 0.05 unit dose  2204  of infusible fluid). 
     Assume for illustrative purposes only that after the user programs infusion pump assembly  100 ,  100 ′  400 ,  500  via remote control assembly  300  to administer the first sequential, multi-part, infusion event (i.e., 0.05 units infused every three minute interval repeated continuously) and administer the second sequential, multi-part, infusion event (i.e., 0.10 units infused every three minute interval for two intervals), the user decides to eat a very large meal. Predicting that their blood glucose level might increase considerably, the user may program infusion pump assembly  100 ,  100 ′  400 ,  500  (via remote control assembly  300 ) to administer a one-time infusion event. An example of such a one-time infusion event may include but is not limited to a normal bolus infusion event. As is known in the art, a normal bolus infusion event refers to a one-time infusion of the infusible fluid. 
     For illustrative purposes only, assume that the user wishes to have infusion pump assembly  100 ,  100 ′  400 ,  500  administer a bolus dose of thirty-six units of the infusible fluid. Infusion pump assembly  100 ,  100 ′  400 ,  500  may monitor the various infusion events being administered to determine whether a one-time infusion event is available to be administered. If a one-time infusion event is available for administration, infusion pump assembly  100 ,  100 ′  400 ,  500  may delay the administration of at least a portion of the sequential, multi-part, infusion event. 
     Continuing with the above-stated example, once the user completes the programming of infusion pump assembly  100 ,  100 ′  400 ,  500  to deliver one-time infusion event  2214  (i.e., the thirty-six unit bolus dose of the infusible fluid), upon infusion pump assembly  100 ,  100 ′  400 ,  500  determining that the one-time infusion event is available for administration, infusion pump assembly  100 ,  100 ′  400 ,  500  may delay the administration of each sequential, multi-part infusion event and administer the available one-time infusion event. 
     Specifically and as discussed above, prior to the user programming infusion pump assembly  100 ,  100 ′  400 ,  500  to deliver one-time infusion event  2214 , infusion pump assembly  100 ,  100 ′  400 ,  500  was administering a first sequential, multi-part, infusion event (i.e., 0.05 units infused every three minute interval repeated continuously) and administering a second sequential, multi-part, infusion event (i.e., 0.10 units infused every three minute interval for two intervals). 
     For illustrative purposes only, the first sequential, multi-part, infusion event may be represented within  FIG.  123    as 0.05 unit dose  2200  @ t=0:00, 0.05 unit dose  2202  @ t=3:00, 0.05 unit dose  2204  @ t=6:00, 0.05 unit dose  2206  @ t=9:00, and 0.05 unit dose  2208  @ t=12:00. As the first sequential, multi-part, infusion event as described above is a basal infusion event, infusion pump assembly  100 ,  100 ′  400 ,  500  may continue to infuse 0.05 unit doses of the infusible fluid at three minute intervals indefinitely (i.e., until the procedure is cancelled by the user). 
     Further and for illustrative purposes only, the second sequential, multi-part, infusion event may be represented within  FIG.  123    as 0.10 unit dose  2210  @ t=3:00 and 0.10 unit dose  2212  @ t=6:00. As the second sequential, multi-part, infusion event is described above as an extended bolus infusion event, infusion pump assembly  100 ,  100 ′  400 ,  500  may continue to infuse 0.10 unit doses of the infusible fluid at three minute intervals for exactly two intervals (i.e., the number of intervals defined by the user). 
     Continuing with the above-stated example, upon infusion pump assembly  100 ,  100 ′  400 ,  500  determining that the thirty-six unit normal bolus dose of the infusible fluid (i.e., one-time infusion event  2214 ) is available for administration, infusion pump assembly  100 ,  100 ′  400 ,  500  may delay the administration of each sequential, multi-part infusion event and may start administering one-time infusion event  2214  that is available for administration. 
     Accordingly and for illustrative purposes only, assume that upon completion of the programming of infusion pump assembly  100 ,  100 ′  400 ,  500  to deliver the thirty-six unit normal bolus does of the infusible fluid (i.e., the one-time infusion event), infusion pump assembly  100 ,  100 ′  400 ,  500  begins administering one-time infusion event  2214 . Being that one-time infusion event  2214  is comparatively large, it may take longer than three minutes (i.e., the time interval between individual infused doses of the sequential, multi-part, infusion events) and one or more of the individual infused doses of the sequential, multi-part, infusion events may need to be delayed. 
     Specifically, assume that it will take infusion pump assembly  100 ,  100 ′  400 ,  500  greater than six minutes to infuse thirty-six units of the infusible fluid. Accordingly, infusion pump assembly  100 ,  100 ′  400 ,  500  may delay 0.05 unit dose  2202  (i.e., scheduled to be infused @ t=3:00), 0.05 unit dose  2204  (i.e., scheduled to be infused @ t=6:00), and 0.05 unit dose  2206  (i.e., scheduled to be infused @ t=9:00) until after one-time infusion event  2214  (i.e., the thirty-six unit normal bolus dose of the infusible fluid) is completely administered. Further, infusion pump assembly  100 ,  100 ′  400 ,  500  may delay 0.10 unit dose  2210  (i.e., scheduled to be infused @ t=3:00 and 0.10 unit dose  2212  (i.e., scheduled to be infused @ t=6:00) until after one-time infusion event  2214 . 
     Once administration of one-time infusion event  2214  is completed by infusion pump assembly  100 ,  100 ′  400 ,  500 , any discrete infusion events included within the sequential, multi-part, infusion event that were delayed may be administered by infusion pump assembly  100 ,  100 ′  400 ,  500 . Accordingly, once one-time infusion event  2214  (i.e., the thirty-six unit normal bolus dose of the infusible fluid) is completely administered, infusion pump assembly  100 ,  100 ′  400 ,  500  may administer 0.05 unit dose  2202 , 0.05 unit dose  2204 , 0.05 unit dose  2206 , 0.10 unit dose  2210 , and 0.10 unit dose  2212 . 
     While infusion pump assembly  100 ,  100 ′  400 ,  500  is shown to administer 0.05 unit dose  2202 , then 0.10 unit dose  2210 , then 0.05 unit dose  2204 , then 0.10 unit dose  2212 , and then 0.05 unit dose  2206 , this is for illustrative purposes only and is not intended to be a limitation of this disclosure, as other configurations are possible and are considered to be within the scope of this disclosure. For example, upon infusion pump assembly  100 ,  100 ′  400 ,  500  completing the administration of one-time infusion event  2214  (i.e., the thirty-six unit normal bolus dose of the infusible fluid), infusion pump assembly  100 ,  100 ′  400 ,  500  may administer all of the delayed discrete infusion events associated with the first sequential, multi-part infusion event (i.e., namely 0.05 unit dose  2202 , 0.05 unit dose  2204 , and 0.05 unit dose  2206 ). Infusion pump assembly  100 ,  100 ′  400 ,  500  may then administer all of the delayed discrete infusion events associated with the second sequential, multi-part infusion event (i.e., 0.10 unit dose  2210 , and 0.10 unit dose  2212 ). 
     While one-time infusion event  2214  (i.e., the thirty-six unit normal bolus dose of the infusible fluid) is shown as being infused beginning at t=3:00, this is for illustrative purposes only and is not intended to be a limitation of this disclosure. Specifically, infusion pump assembly  100 ,  100 ′  400 ,  500  may not need to begin infusing one-time infusion event  2214  at one of the three-minute intervals (e.g., t=0:00, t=3:00, t=6:00, t=9:00, or t=12:00) and may begin administering one-time infusion event  2214  at any time. 
     While each discrete infusion event (e.g., 0.05 unit dose  2202 , 0.05 unit dose  2204 , 0.05 unit dose  2206 , 0.10 unit dose  2210 , and 0.10 unit dose  2212 ) and one-time infusion event  2214  are shown as being a single event, this is for illustrative purposes only and is not intended to be a limitation of this disclosure. Specifically, at least one of the plurality of discrete infusion events e.g., 0.05 unit dose  2202 , 0.05 unit dose  2204 , 0.05 unit dose  2206 , 0.10 unit dose  2210 , and 0.10 unit dose  2212 ) may include a plurality of discrete infusion sub-events. Further, one-time infusion event  2214  may include a plurality of one-time infusion sub-events. 
     Referring also to  FIG.  124    and for illustrative purposes, 0.05 unit dose  2202  is shown to include ten discrete infusion sub-events (e.g., infusion sub-events  2216   1-10 ), wherein a 0.005 unit dose of the infusible fluid is infused during each of the ten discrete infusion sub-events. Additionally, 0.10 unit dose  2210  is shown to include ten discrete infusion sub-events (e.g., infusion sub-events  2218   1-10 ), wherein a 0.01 unit dose of the infusible fluid is delivered during each of the ten discrete infusion sub-events. Further, one-time infusion event  2214  may include e.g., three-hundred-sixty one-time infusion sub-events (not shown), wherein a 0.1 unit dose of the infusible fluid is delivered during each of the three-hundred-sixty one-time infusion sub-events. The number of sub-events defined above and the quantity of the infusible fluid delivered during each sub-event is solely for illustrative purposes only and is not intended to be a limitation of this disclosure, as the number of sub-events and/or the quantity of the infusible fluid delivered during each sub-event may be increased or decreased depending upon e.g., the design criteria of infusion pump assembly  100 ,  100 ′  400 ,  500 . 
     Before, after, or in between the above-described infusion sub-events, infusion pump assembly  100 ,  100 ′  400 ,  500  may confirm the proper operation of infusion pump assembly  100 ,  100 ′  400 ,  500  through the use of any of the above-described safety features (e.g., occlusion detection methodologies and/or failure detection methodologies). 
     In the exemplary embodiments, the infusion pump assembly may be wirelessly controlled by a remote control device. In the exemplary embodiments, a split ring resonator antenna may be used for wireless communication between the infusion pump assembly and the remote control device (or other remote device). The term “wirelessly controlled” refers to any device that may receive input, instructions, data, or other, wirelessly. Further, a wirelessly controlled insulin pump refers to any insulin pump that may wirelessly transmit and/or receive data from another device. Thus, for example, an insulin pump may both receive instructions via direct input by a user and may receive instructions wirelessly from a remote controller. 
     Referring to  FIG.  127    and  FIG.  131   , an exemplary embodiment of a split ring resonator antenna adapted for use in a wirelessly controlled medical device, and is used in the exemplary embodiment of the infusion pump assembly, includes at least one split ring resonator antenna (hereinafter “SRR antenna”)  2508 , a wearable electric circuit, such as a wirelessly controlled medical infusion apparatus (hereinafter “infusion apparatus”)  2514 , capable of powering the antenna, and a control unit  2522 . 
     In various embodiments, a SRR antenna  2508  may reside on the surface of a non-conducting substrate base  2500 , allowing a metallic layer (or layers) to resonate at a predetermined frequency. The substrate base  2500  may be composed of standard printed circuit board material such as Flame Retardant 2 (FR-2), FR-3, FR-4, FR-5, FR-6, G-10, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5, Polyimide, Teflon, ceramics, or flexible Mylar. The metallic resonating bodies comprising a SRR antenna  2508  may be made of two rectangular metallic layers  2502 ,  2504 , made of, for example, platinum, iridium, copper, nickel, stainless steel, silver or other conducting materials. In other various embodiments, a SRR antenna  2508  may contain only one metallic resonating body. 
     In the exemplary embodiment, a gold-plated copper outer layer  2502 , surrounds, without physically contacting, a gold-plated copper inner ring  2504 . That is, the inner ring  2504  resides in the cavity  2510  (or aperture) formed by the outer layer  2502 . The inner ring  2504  may contain a gap, or split  2506 , along its surface completely severing the material to form an incomplete ring shape. Both metallic resonating bodies  2502 ,  2504  may reside on the same planar surface of the substrate base  2500 . In such a configuration, the outer layer  2502  may by driven via a transmission line  2512  coupled to the outer layer  2502 , for example. Additionally, in various other embodiments, a transmission line  2512  may be coupled to the inner ring  2504 . 
     Antenna design software, such as AWR Microwave Office, capable of simulating electromagnetic geometries, such as, antenna performance, may significantly decrease the time required to produce satisfactory dimensions compared to physically fabricating and testing antennas. Accordingly, with aid of such software, the SRR antenna  2508  may be designed such that the geometric dimensions of the resonant bodies  2502 ,  2504  facilitate an operational frequency of 2.4 GHz.  FIG.  132    depicts the exemplary dimensions of the inner ring  2504  and outer layer  2502 , and the positioning of the cavity  2510  in which the inner ring  2504  resides. The distance in between the outer layer  2502  and the inner ring  2504  is a constant 0.005 inches along the perimeter of the cavity  2510 . However, in other embodiments, the distance between the outer layer and the inner ring may vary and in some embodiments, the operational frequency may vary. 
     In various embodiments, a SRR antenna  2508  may have dimensions such that it could be categorized as electrically small, that is, the greatest dimension of the antenna being far less than one wavelength at operational frequency. 
     In various other embodiments, a SRR antenna  2508  may be composed of one or more alternatively-shaped metallic outer layers, such as circular, pentagonal, octagonal, or hexagonal, surrounding one or more metallic inner layers of similar shape. Further, in various other embodiments, one or more metallic layers of a SRR antenna  2508  may contain gaps in the material, forming incomplete shapes. 
     Referring to  FIG.  130   , a SRR antenna  2508  having the exemplary geometry exhibits acceptable return loss and frequency values when placed in contact with human skin. As shown in  FIG.  130   , focusing on the band of interest denoted by markers 1 and 2 on the graph, return loss prior to contact with human skin is near −15 dB while monitoring a frequency band centered around 2.44 GHz. Return loss during contact with human skin, as shown in  FIG.  130 A , remains a suitable value near −25 dB at the same frequency, yielding approximately 97% transmission power. 
     These results are favorable especially as compared with a non-split ring resonator antenna type, such as the Inverted-F. Return loss of an Inverted-F antenna may exhibit a difference when the antenna contacts human skin, resulting in a low percentage of power transmitted outward from the antenna. By way of example, as shown in  FIG.  133   , and again focusing on the band of interest denoted by markers 1 and 2 on the graph, return loss of an Inverted-F antenna prior to contact with human skin is near −25 dB at a frequency centered around 2.44 GHz. Return loss during contact with human skin is nearly −2 dB at the same frequency, yielding approximately 37% power transmission. 
     Integration with a Wireless Medical Device 
     In the exemplary embodiment, referring to  FIG.  132    and  FIG.  128   , one application of a SRR antenna  2508  may be integration into a wearable infusion apparatus  2514  capable of delivering fluid medication to a user/patient  2524 . In such an application, the safety of the user/patient is dependent on fluid operation between these electrical components, thus reliable wireless transmission to and from a control unit  2522  is of great importance. 
     An infusion apparatus  2514  may be worn directly on the human body. By way of example, such a device may be attached on or above the hip joint in direct contact with human skin, placing the SRR antenna  2508  at risk of unintended dielectric loading causing a frequency shift in electrical operation. However, in such an application, electrical characteristics of the SRR antenna  2508  which allow it to be less sensitive to nearby parasitic objects are beneficial in reducing or eliminating degradation to the performance. A controlling component, such as a control unit  2522  (generally shown in  FIG.  131   ), may be paired with an infusion apparatus  2514 , and may be designed to transmit and receive wireless signals to and from the infusion apparatus  2514  at a predetermined frequency, such as 2.4 GHz. In the exemplary embodiment, the control unit  2522  serves as the main user interface through which a patient or third party may manage insulin delivery. In other embodiments, infusion apparatus  2514  may utilize a SRR antenna  2508  to communicate with one or more control units  2522 . 
     In various embodiments, a number of different wireless communication protocols may be used in conjunction with the SRR antenna  2508 , as the protocol and data types to be transferred are independent of the electrical characteristics of the antenna. However, in the exemplary embodiment, a bi-directional master/slave means of communication organizes the data transfer through the SRR antenna  2508 . The control unit  2522  may act as the master by periodically polling the infusion apparatus  2514 , or slave, for information. In the exemplary embodiment, only when the slave is polled, the slave may send signals to the control unit  2522  only when the slave is polled. However, in other embodiments, the slave may send signals before being polled. Signals sent by way of this system may include, but are not limited to, control, alarm, status, patient treatment profile, treatment logs, channel selection and negotiation, handshaking, encryption, and check-sum. In some embodiments, transmission through the SRR antenna  2508  may also be halted during certain infusion operations as an added precaution against electrical disruption of administration of insulin to the patient. 
     In the exemplary embodiment, the SRR antenna  2508  may be coupled to electrical source circuitry via one or more pins  2516  on a transmission line  2512 . In various other embodiments a transmission line may comprise a wire, pairs of wire, or other controlled impedance methods providing a channel by which the SRR antenna  2508  is able to resonate at a certain frequency. The transmission line  2512  may reside on the surface of the substrate base  2500  and may be composed of the same material as the SRR antenna  2508 , such as gold-plated copper. Additionally, a ground plane may be attached to the surface of the substrate base opposite the transmission line  2512 . 
     The electrical circuitry coupled to the SRR antenna  2508  may apply an RE signal to the end of the transmission line  2512  nearest the circuitry, creating an electromagnetic field throughout, and propagating from, the SRR antenna  2508 . The electrical circuitry coupled to the SRR antenna  2508  facilitates resonance at a predetermined frequency, such as 2.4 GHz. Preferably, transmission line  2512  and SRR antenna  2508  both have impedances of 50 Ohms to simplify circuit simulation and characterization. However, in other various embodiments, the transmission line and split ring resonator antenna may have other impendence values, or a different resonating frequency. 
     Referring to  FIG.  129   , a signal processing component(s)  2518 , such as, a filter, amplifier, or switch, may be integrated into the transmission line  2512 , or at some point between the signal source connection pins  2516  and the SRR antenna  2508 . In the exemplary embodiment, the signal processing component  2518  is a band-pass filter to facilitate desired signal processing, such as, allowing only the exemplary frequency to be transmitted to the antenna, and rejecting frequencies outside that range. In the exemplary embodiment, a Combline band-pass filter  2518  may be included in the transmission line  2512  between the antenna and the signal source. However in other embodiments, any other signal processing device, for example, but not limited to, filters, amplifiers, or any other signal processing devices known in the art. 
     In various embodiments, a SRR antenna  2508  may be composed of metallic bodies capable of resonating on a flexible or rigid substrate. As shown in  FIG.  128    and  FIG.  3   , the exemplary embodiment incorporates a curved SRR antenna on a flexible Polyimide substrate  2520 . Polyimide may be the exemplary material because it tends to be more flexible than alternative substrates. This configuration may allow for simplified integration into circular-shaped devices (such as a wirelessly controlled medical infusion apparatus  2514 ), devices with irregular-shaped external housing, or devices in which saving space is paramount. 
     In various embodiments, both control unit  2522  and base unit  2514  may incorporate a split SRR antenna  2508 . This configuration may prove beneficial where the control unit is meant to be handheld, in close proximity to human skin, or is likely to be in close proximity to a varying number of materials with varying dielectric constants. 
     In various other embodiments, a SRR antenna  2508  may be integrated into a human or animal limb replacement. As prosthetic limbs are becoming more sophisticated the electrical systems developed to control and simulate muscle movements require much more wiring and data transfer among subsystems. Wireless data transfer within a prosthetic limb may reduce weight through reduced physical wiring, conserve space, and allow greater freedom of movement. However, common antennas in such a system may be susceptible to dielectric loading. Similar to the previously mentioned benefits of integrating a SRR antenna  2508  into a wirelessly controlled medical infusion apparatus, a prosthetic limb, such as a robotic arm, may also come into contact with human skin or other dielectric materials and benefit from the reduction of electrical disturbances associated with such an antenna. In other various embodiments, the SRR antenna  2508  may be integrated into any device comprised of the electrical components capable of powering and transmitting/receiving data to an antenna and susceptible to electrical disturbances associated with proximity to dielectric materials. 
     In various embodiments, a SRR antenna  2508  may be integrated into a configuration of medical components in which one or more implantable medical devices, operating within the human body, communicate wirelessly to a handheld, body-mounted, or remote control unit. In certain embodiments, both body-mounted and in-body wireless devices may utilize a SRR antenna  2508  for wireless communication. Additionally, one or more of the components utilizing a SRR antenna  2508  may be completely surrounded by human skin, tissue or other dielectric material. By way of example, such a configuration may be used in conjunction with a heart monitoring/control system where stability and consistency of wireless data transmission are of fundamental concern. 
     In various other embodiments, a SRR antenna  2508  may be integrated into the embodiments of the infusion pump assembly. Configuration of medical components in which one or more electrical sensors positioned on, or attached to, the human body wirelessly communicate to a remote transceiving unit. By way of example, a plurality of electrodes positioned on the body may be coupled to a wireless unit employing a SRR antenna  2508  for wireless transmission to a remotely located electrocardiogram machine. By way of further example, a wireless temperature sensor in contact with human skin may employ SRR antenna  2508  for wireless communication to a controller unit for temperature regulation of the room in which the sensor resides. 
     As discussed and described above, in some embodiments of the infusion pump system the SMA may control both the pump assembly (including the pump assembly  106 , however, in various other embodiments, the SMA may also control of various embodiments of the pump assembly), and the various embodiments shown and described herein of the measurement valve assembly. However, in some embodiments, the SMA may be controlled using at least one optical position sensor assembly (“optical sensor”) wherein the position of the pump assembly plunger (“pump plunger”) and the measurement valve plunger is measured using at least one optical position sensor, and in the exemplary embodiments, at least one pump assembly plunger optical sensor and at least one measurement valve plunger optical position sensor. Thus, in these embodiments, the command processor provides closed-loop control of the pump plunger position and measurement valve plunger position by comparing the optical sensor output to a target position and then modifying the PWM of the low-side field effect transistors (“FET”). In addition, voltages are measured at various positions such the SMA controller may detect various conditions of the system including, but not limited to, one or more of the following: a broken SMA wire, failed FET and/or a depleted battery assembly and/or power source. Thus, the actual plunger position may be determined for, in some embodiments, both the pump plunger and the measurement valve plunger, and target plunger positions may be established. 
     Referring now to  FIGS.  145 - 149 B  various embodiments of the optical position sensor in the infusion pump system is shown. Some embodiments of the apparatus, methods and systems will be described below with reference to an exemplary embodiment. The exemplary embodiment is described with respect to a medical infusion pump, which in some embodiments may be an infusion pump, which may, in some embodiments, be an insulin pump, as shown and described herein, however, the optical position sensor described herein may also be used with various other infusion pumps and/or medical delivery devices and/or medical systems including, but not limited to, those described in U.S. Pat. No. 7,498,563 issued Mar. 3, 2009 and entitled Optical Displacement Sensor for Infusion Devices (Attorney Docket No. D78), U.S. Pat. No. 7,306,578 issued Dec. 11, 2007 and entitled Loading Mechanism for Infusion Pump (Attorney Docket No. C54), U.S. patent application Ser. No. 11/704,899 filed Feb. 9, 2007, now U.S. Publication No. US-2007-0228071-A1, and entitled Fluid Delivery Systems and Methods (Attorney Docket No. E70), U.S. patent application Ser. No. 11/704,896 filed Feb. 9, 2007, now U.S. Publication No. US-2007-0219496-A1, published Sep. 20, 2007 and entitled Pumping Fluid Delivery Systems and Methods Using Force Application Assembly (Attorney Docket No. E71), U.S. patent application Ser. No. 11/704,886 filed Feb. 9, 2007, now U.S. Publication No. US-2007-0219480-A1, published Sep. 20, 2007 and entitled Patch-Sized Fluid Delivery Systems and Methods (Attorney Docket No. E72), U.S. patent application Ser. No. 11/704,897 filed Feb. 9, 2007, now U.S. Publication No. US-2007-0219597-A1, published Sep. 20, 2007 and entitled Adhesive and Peripheral Systems and Methods for Medical Devices (Attorney Docket No. E73), U.S. patent application Ser. No. 12/560,106 filed Sep. 15, 2009, now U.S. Publication No. US-2010-0185142-A1, published Jul. 22, 2010 and entitled Systems and Methods for Fluid Delivery (Attorney Docket No. G47), and U.S. patent application Ser. No. 12/649,681 filed Dec. 30, 2009, now U.S. Publication No. US-2010-0198182-A1, published Aug. 5, 2010 and entitled Method, System and Apparatus for Verification of Volume and Pumping (Attorney Docket No. G85), which are each hereby incorporated herein by reference in their entireties. Reference herein to a disposable may refer to, in some embodiments, the disposable housing assembly and/or disposable portion and/or reservoir portion of the various infusion pumps described in any of the above-discussed infusion pumps. 
     However, the apparatus, systems and methods described herein may be used in any infusion pump or apparatus. Further, the apparatus, systems and methods described herein may be used to verify the movement of any plunger, pump actuator, valve and/or other moveable part within any medical device to confirm that movement and/or displacement occurred. Further, in addition to confirmation of movement, the determination of the distance of movement, i.e. the total displacement, may also be used in some embodiments. 
     Referring also to  FIG.  150   , the various embodiments of the infusion pump apparatus, methods and systems include the control of the pump and one or more active valves by contraction of a SMA wire, which, in the exemplary embodiments, is NITINOL wire. The SMA wire works by applying current through the wire, which induces heating the wire, and causes a phase change that result in a contraction of the wire length. The change in wire length may be exploited by e.g. lever and/or pulley mechanisms to actuate the pump plunger  2902  and measurement valve  2908 . 
     The infusion pump system  2900  drives the SMA wires, which may include two,  2910 ,  2912  as shown in the exemplary embodiment shown in  FIG.  150   , directly from the battery voltage by switching the battery voltage across the wire to cause a contraction/actuation of the respective component and then switches off the battery voltage to stop the contraction. The wire/component starting position is, in some embodiments, restored by spring forces that oppose the SMA wire contraction force. 
     In the exemplary embodiment, each of the SMA wires  2910 ,  2912  provides proportional control, i.e. the SMA wire contracts over time and displaces the respective component over time. Despite this implementation, the valve components  2904 ,  2906 ,  2908  act to occlude or un-occlude fluid flow, which is a discrete, non-proportional and binary function. However, the pump piston is operated over a range of stroke lengths, so proportional control of the pump plunger  2902  is a functional goal in the exemplary embodiment. 
     In some embodiments, proportional control of the pump plunger  2902  may be achieved by monitoring the volume delivered into the volume measurement chamber  2920  and measured by the volume measurement sensor assembly/system  2946  and adjusting the amount of time that the pump plunger  2902  SMA wire  2910  is activated, i.e., adjusting the ontime. This may result in a closed-loop control of aliquot pumping volume as a function of SMA wire activation time on a stroke by stroke basis. The controller scheme in some embodiments also includes additional control variables which may increase the accuracy of the aliquot pumping volume to converge on a given target delivery volume. 
     Several factors may affect SMA activation including, but not limited to, one or more of the following: energy into the wire (voltage, current, time), ambient temperature, heat sinking, pre-tension, SMA wire variations (diameter, alloy composition, electrical resistance), and/or assembly variations. Changes in physical parameters, such as the ones listed above, may result in an inter-pump and intra-pump variation in the ontime of the pump plunger SMA  2910  that may be expected to result in a given pumped volume per stroke of the pump plunger  2902  (which may also be referred to as a given pump delivery volume). As a result, both an offset in time and a change in the slope of the on-time versus pump aliquot volume relationship may occur. 
     Referring nw also to  FIG.  145   , a graph that shows the same pump system  2900  tested over a temperature range of 18 to 38 degrees Celsius results in a SMA actuation onset time from about 180 to about 310 ms. As may be seen, the slope is also aggravated at lower temperatures. Variation in the offset and slope of ontime versus pump delivery volume may add complexity to the pump system  2900  as compensation for the variation(s) may be necessary to achieve accurate pump delivery volume. This phenomenon may also affect the components, e.g., valves and plungers, actuated by SMA wire in a similar fashion, though valve function is not proportional. 
     At least in part due to the sensitivity of SMA actuation time to multiple physical variations it may be desirable, in some embodiments, to directly control one or more components, e.g., the pump plunger  2902  and/or measurement valve  2908  actuator position. This may be beneficial for many reasons, including, but not limited to, as the position of the pump plunger  2902  and measurement valve actuator  2908  may be a closer indication of proportional performance than SMA on-time. Various embodiments of methods, systems and apparatus for achieving this goal are described below. 
     The ability to sense the position of the pump plunger  2902  and/or the measurement valve actuator  2908  in the infusion pump system  2900  may be desired. Although as has been discussed herein, SMA wire may be used in the exemplary embodiments to actuate the pump plunger and the measurement valves  2940 , in other embodiments, various motors may be used to actuate the pump and/or the valve(s) including but not limited to a peristaltic pump, a rotary pump and a piezoelectric actuator. Thus, disclosed herein, irrespective of the pump actuator, are methods, apparatus and systems for sensing the position of various components in the infusion pump system, including but not limited to, sensing the position of one or more components which may include, but are not limited to, the pump or displacement component, and one or more active valves and/or passive valves. Thus, in some embodiments, it may be desirable to sense the position of inactive valves, e.g., the reservoir valve  2904  and/or the volume measurement chamber inlet valve  2906 . 
     There are various devices that may be used to sense the position of the pump plunger  2902  and/or measurement valve actuator  2908 . These include, but are not limited to, one or more of the following: ultrasonic, optical (reflective, laser interferometer, camera, etc), linear caliper, magnetic, mechanical contact switch, infrared might measurement, etc. However, in the exemplary embodiment, due to the small structure of the infusion pump assembly and/or pump system  2900 , it may be desirable to use a small component so as to utilize a small space with the sensing component(s). In various embodiments, the device battery life also may also be considered since the battery size may be limited by the overall size of the device and battery capacity may be a premium. Sensing distance may also be a consideration in various embodiments. For example, where the displacement of the one or more components, e.g., the pump plunger  2902  and/or the measurement valve actuator  2908  component may be very small (for example, in the exemplary embodiment, a full displacement of the pump plunger  2902  may be about 1 mm and a full displacement of the measurement valve actuator may be about 0.2 mm). The displacement distances are examples for some embodiments, in other embodiments, the displacement distances may vary. 
     In the exemplary embodiment, a small reflective optical sensor assembly (hereinafter “optical sensor”) that fits into the exemplary embodiments of the infusion pump system  2900  hardware, as shown and described, for example, herein, may be used. In some embodiments, the at least one optical sensor is located in the reusable housing assembly. However, in other embodiments, part of the at least one optical sensor may be located in the disposable housing assembly and another part of the at least one optical sensor may be located in the reusable housing assembly. The optical sensor, in the various embodiments, has a sensing range that accommodates the components for which the optical sensor may be sensing, e.g., in some embodiments, the pump plunger  2902  and/or measurement valve actuator  2908  displacements. In the exemplary embodiment any optical sensor may be used, including, but not limited to a Sharp GP2S60, manufactured by Sharp Electronics Corporation which is a U.S. subsidiary of Sharp Corporation of Osaka, Japan. In these embodiments, this optical sensor contains an infra red emitting diode and infra red sensing detector in a single component package. Light from the emitter is unfocused and bounces off the sensing surface, some of which is reflected to the detector. This results in a sensed intensity of light by the detector that varies as a function of distance/angle to the reflector. Referring now to  FIG.  146   , the curve illustrates the sensitivity of the optical sensor to displacement of a reflective surface. 
     Referring also to  FIG.  147   , in various embodiments, one or more optical sensors may be used in the pump system  2900 . The one or more optical sensors may be included in the pump system  2900  such that they may detect the movement and distance of movement/displacement of one or more valves  2904 , 2906 ,  2908  and/or the pump plunger  2902 . With respect to the pump system  2900 ,  FIG.  147    represents various embodiments of the location for one or more optical sensors  2956 ,  2958  to sense the pump plunger  2902 , as well as an embodiment of the location of an optical sensor  2954  to sense the measurement valve  2908 . 
     With respect to the embodiments of the location of the optical sensors  2956 ,  2958  to sense the pump plunger  2902 , although both of these locations may sense the pump plunger  2902 , the distance from the respective sensor  2956 ,  2958  to the component, e.g. pump plunger  2902  in this example, varies the sensitivity of the optical sensor  2956 ,  2958 . Thus, it may be beneficial to use one or the other optical sensor location  256 ,  2958 , depending on, for example, but not limited to, the desired data. In some embodiments, the optical sensors may be placed on the underneath of the printed circuit board. The placement of the optical sensors on the underneath of the circuit board allows for independent sensing of the various components desired in the pump system  2900 , for example, but not limited to, the pump plunger  2902  head, measurement valve actuating arm  2952  and/or the measurement valve  2908 . 
     Still referring the  FIG.  147   , the embodiment shown includes three optical sensors  2954 ,  2956 ,  2958 , placed, in some embodiments, on the bottom of the PCB (not shown) over both pump plunger and valve components to detect motion of the respective components. The optical sensor  2958  shown over the pump plunger  2902  and the optical sensor  2956  of the pump plunger actuator arm  2960  essentially sense the same motion, i.e., the movement of the pump plunger  2902 , however, each of the optical sensor  2956 ,  2958  are a different distance from the respective component being sensed, i.e., the pump plunger  2902 , and thus, each optical sensor  2956 ,  2958 , may result in a different sensitivity of detection. In some embodiments, one of the optical sensors, e.g.,  2956 ,  2958 , may be preferred for detecting onset motion, i.e., the start of the pump plunger  2902  motion towards the pump chamber  2916 , due to the starting distance from the optical sensor. Both the pump plunger  2902  head and the pump plunger actuator arm  2960 , in some embodiments, are made from white DELRIN. Thus, in these embodiments, the surface is naturally reflective. In various embodiments, various materials may be used to manufacture these components such that they include a naturally reflective surface. However, in some embodiments, coatings may be added to the surface of the various components to increase reflection, if desired. In some embodiments, changes to the geometry of the surfaces may also be made to modify the reflection. 
     In some embodiments, the optical sensor  2954  positioned over the measurement valve actuator arm  2952  senses rotation. Thus, the change in reflective intensity is due to a rotational change of the reflecting surface. In the some embodiments, the measurement valve actuator arm  2952  may be made from a metallic MEMS part. However, in other embodiments, the measurement valve actuator arm and/or other parts to be sensed, including the tab discussed below, by the optical sensor may be made from DELRIN or other materials. In other embodiments, features may be added to change or modify the reflective pattern. These changes may include, but are not limited to, adding a tab that extends under the optical sensor  2954 . Additionally, in some embodiments, optical coatings or polishing of the metal surface, or other treatments/methods, may be used to increase the refection intensity. 
     Referring now also to  FIGS.  148 A- 149 B , various embodiments of an optical sensor are shown. Although in various embodiments, for illustration purposes, the optical sensor arrangement may be shown with respect to a measurement valve actuator  2908  or a pump plunger  2902 , this is for illustration purposes only, other embodiments of the various embodiments of the optical sensor arrangements may include where the optical sensor arrangement is used with any component, including, but not limited to, one or more valves and/or one or more pump plungers. 
     Referring now to  FIGS.  148 A- 148 B , an optical sensor detector  2962  is shown with an LED, and/or light source  2964  and a slot wheel  2966 . In some embodiments, the optical sensor detector  2962  may include one or more detectors, and depending on the rotation of the slot wheel  2966 , which, in some embodiments, may indicate the position of either a valve and/or a pump plunger, the LED  2964  will shine through a different slot in the slot wheel  2966  and the one of the detectors  2962  will detect the light, indicating the position of the slot wheel  2966 . 
     Referring now to  FIGS.  149 A- 149 B , another embodiments of an optical sensor, similar to the embodiments shown and described above with respect to  FIGS.  148 A- 148 B , is shown. In this embodiment, the slot wheel  2966  includes a variation in the slots. 
     In various embodiments, the optical sensors  2954 ,  2956 ,  2958 , utilize infrared light, thus ambient light may not be a variable. In some embodiments, each optical sensor&#39;s light emitting source may be controlled independently, which may be beneficial for many reasons, including but not limited to, so that optical cross-talk between the sensors may be avoided (e.g., in some embodiments, raster through the sensors one at a time). Optical sensors may be sensitive to drift and temperature over time, thus, in some embodiments, a “dark” sensor reading, and/or a temperature sensor reading (in some embodiments, at least one temperature sensor may be incorporated into the pump system, and in some embodiments, at least one temperature sensor may be included in the optical sensor system) may be taken before turning on the respective emitting light source in order to compensate for offset. In some embodiments, normalizing the starting reading before inducing motion may be used to compensate for a change in gain. 
     In various embodiments, sensing the pump plunger  2902  may be used in a number of ways, including but not limited to, onset of motion detection and determination of pump plunger  2902  position. 
     Sensing when the pump plunger  2902  has started to move may be beneficial for many reasons, including but not limited to, one or more of the following: removing the offset variation in the SMA wire activation on-time, in embodiments where ontime is used to control the SMA wire. Also, in some embodiments the closed-loop controller compensation may be less confounded because it may be compensating only for variation in slope of ontime versus volume. This may reduce the pump aliquot volume variability and result in more accurate fluid delivery versus time. 
     Since the pump plunger  2902  moves fluid by displacement, the position of the pump plunger  2902  may be correlated with the amount/volume of fluid displaced/pumped. Controlling the position of the pump piston has many benefits, some of which are discussed below. 
     Correlation of the pumped volume with the position of the pump plunger  2902  may enable the pump system  2900 /infusion device to deliver a desired volume of fluid. Additionally, correlation of pump volume may reduce delivery variation. A more precise infusion pump, combined, in some embodiments, with an accurate measurement system, for example, various embodiments of the volume measurement sensor assembly described herein, may improve volume delivery consistency. 
     Improved correlation of pumping volume to pump plunger  2902  position may enable more accurate transitions from low volume to high volume delivery. In some embodiments, the pump controller may pump fluid as a function of SMA wire activation time. Thus, pumping fluid at a fixed volume may be beneficial. However, in some embodiments, to temporarily increase the delivery volume, the pump system  2900  may increase the aliquot delivery rate and hold the volume constant. With more accurate pumping volume the pump may temporarily aliquot higher volumes to meet e.g., a bolus delivery, and return to the basal delivery, which, in some embodiments, may be a lower pumping volume, without losing accuracy of either basal rate or bolus volume in the process. 
     Another benefit may include where, in some embodiments, aliquot pumping time is a variable used to promote fixed volume aliquot delivery; aliquot delivery time may be more independent and possibly speed up bolus volume delivery. Also, determining the pump plunger  2902  position may also enable a direct determination of malfunction. If, for example, a failure occurs with the pump plunger  2902  actuator  2960 , the control system having determined the position of the pump plunger  2902 , may, in some embodiments, alert the pump system that the pump has failed, e.g., failed open, closed, and/or somewhere in between. In some embodiments, this may promote safety for the user/patient as the system may identify failure at a faster rate, preventing over and/or under delivery. 
     In the various embodiments where SMA wire is used for pump actuation and/or active valve actuation, SMA wire activation ontime may be monitored as a function of pump plunger  2902  position to determine if the SMA wire is “wearing out” prematurely, i.e., if the SMA wire expected “life” is being effected. This may be determined, in some embodiments, by monitoring the ontime necessary to achieve a given pump position over time. 
     In some embodiments, sensing when the pump plunger  2902  has stopped moving may impart greater certainty to the pump system  2900  regarding when the pump plunger  2902  has bottomed out and prevent over-driving the pump plunger  2902 . Over driving the SMA wire may reduce the “life” of the SMA wire and continuing to drive either the pump or a valve after reaching the desired position is also a waste of electrical/battery power. Thus, identifying when the pump plunger  2902  has stopped moving, and or, identifying when the measurement valve actuator  2908  has reached the desired location, may increase battery life and/or reduce the power needs of the system, and/or prevent premature SMA wire failure. 
     Similarly as with the pump piston, the various valve pistons may be optically sensed to detect motion of the valve and/or the position of the valve, either of which may have benefits, including but not limited to, one or more of the following. 
     In some embodiments, where one or more valves is controlled by SMA wire, sensing when the valve piston has started to move may remove the offset variation in the SMA wire activation ontime and may give greater certainty to when the valve starts to open and/or close. Additionally, sensing when the valve has stopped moving may give greater certainty to when the valve has opened/closed and prevent over-driving the valve actuator. As over driving the SMA wire may reduce the “life” of the wire and continuing to drive any actuator after the valve state is reached is a waste of electrical power. Thus, identifying when a valve has stopped moving may increase battery life and/or reduce the power needs of the system, and/or prevent premature SMA failure. Also, sensing the valve position may enable the determination of a valve being stuck in an undesirable position, for example, but not limited to, the measurement valve actuator  2908  being stuck in the open position. 
     Optical Position Sensor Control of Infusion Pump System 
     Although described herein as an infusion pump system, the optical sensor control of pumping may be used in various medical devices. For purposes of this description, the term “pump” broadly refers to valves and actuators used to move fluid from the reservoir to the user. 
     In some embodiments, the pump may be used to move the fluid from the reservoir to the volume measurement chamber and then to the user. Referring to  FIG.  150   , a schematic of an embodiment of an infusion pump system  2900  is shown. In some embodiments, pumping may be accomplished using a pump plunger  2902  and three separate valves  2904 ,  2906 ,  2908 , where the pump plunger  2902  is controlled by an independently actuated SMA  2910 , and one valve, the measurement valve  2908 , is controlled by an independently actuated SMA wire  2912 . As discussed herein, SMA may be actuated by changing its temperature (in this case by applying an electrical current) which changes its crystalline structure and causes the SMA to contract. In the infusion pump system  2900 , the SMA wires  2910 ,  2912  are attached to linkages used to move the valve and pump plungers. The positions of the pump plunger  2902  and the measurement valve  2908  are measured using optical sensors (as shown and discussed above with respect to  FIGS.  145 - 149 B ). The current applied to the SMA is modified based on the optical sensor measurements to provide proportional control of the pump plunger  2902  and measurement valve  2908  positions. 
     In some embodiments, the pump sequence is as follows. First, the pump plunger SMA  2902  is actuated which simultaneously moves the reservoir valve plunger  2914 , which occludes the flow path between the pump chamber  2916  and the reservoir  2918 . The pump plunger  2902  forces the fluid in the pump chamber  2916  past the passive volume measurement sensor chamber inlet check valve  2906  and into the volume measurement sensor chamber  2920 . The fluid is held in the volume measurement sensor chamber  2920  by the measurement valve  2908  while a volume measurement taken. Once the volume measurement is completed, the measurement valve SMA  2912  is actuated, which opens the measurement valve  2908  and the fluid is released from the volume measurement sensor chamber  2920  to the tubing set  2922 , which may, in some embodiments, lead to a user/patient which may, in some embodiments, lead to the delivery of medical fluid to the user/patient. 
     Referring now also to  FIG.  151   , the actuation of each SMA wire  2910 ,  2912  is accomplished using two field effect transistors (FET). A high side FET, which, in some embodiments, is controlled by the supervisor processor  2926  (described above), and provides an on/off switch between the battery supply voltage and the SMA wires  2910 ,  2912 . In some embodiments, the high side FET is normally off and may prevent or reduce the occurrence of a single-point electrical fault from actuating the pump. A low-side FET, which, in some embodiments, is pulse-width modulated (PWM), is controlled by the command processor  2924  and provides control of the amount of current flowing through the SMA wire  2910 ,  2912 . 
     In some embodiments, both the position of the pump plunger  2902  and measurement valve plunger  2908  is measured using at least two optical position sensors. However, in some embodiments, a single optical sensor may be used to measure both the pump plunger  2902  and the measurement valve plunger  2908 . This allows the command processor  2924  to provide closed-loop control of the plunger pump  2902  and measurement valve plunger  2908  position by comparing the optical sensor output to a target position and modifying the PWM of the low-side FET. In addition, in some embodiments, voltages are measured at various positions. This enables, in some embodiments, the SMA controller to detect various conditions of the system including, but not limited to, one or more of the following: a broken SMA wire, a failed FET, and/or a depleted battery. 
     For the following discussion, the following nomenclature may be used: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 m 
                 Total mass of the nitinol wire 
               
               
                   
                 T n   
                 Current nitinol temperature 
               
               
                   
                 T i   
                 Initial nitinol temperature 
               
               
                   
                 T a   
                 Ambient temperature 
               
               
                   
                 I 
                 Current 
               
               
                   
                 V 
                 Applied voltage 
               
               
                   
                 R 
                 Electrical Resistance 
               
               
                   
                 h 
                 Heat transfer coefficient [W/K] 
               
               
                   
                 C 
                 Heat capacity [J/kg/K] 
               
               
                   
                 η 
                 Duty cycle 
               
               
                   
                   
               
            
           
         
       
     
     SMA Modeling 
     A thermal model of the SMA wires and a linear model of the pump plunger  2902  is described below. As discussed below, the position of the pump plunger  2902  is measured. In some embodiments, the displacement of the pump plunger  2902  is measurement, i.e., the distance travelled from the starting point to the ending point may be measured. 
     Modeling the SMA Wire 
     The basic heat transfer equation for a constant current going through a wire with resistance R may be as follows. This neglects any of the thermal effects of the phase change in the SMA. 
     
       
         
           
             
               
                 
                   
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     Solving this equation gives the expression: 
     
       
         
           
             
               
                 
                   
                     
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                     ⁢ 
                     #157 
                   
                   ] 
                 
               
             
           
         
       
     
     Thus, at time 0 the SMA temperature will be T i , and at t→∞ a the temperature will approach a steady state value of 
     
       
         
           
             
               
                 
                   
                     ( 
                     
                       
                         T 
                         a 
                       
                       + 
                       
                         
                           
                             I 
                             2 
                           
                           ⁢ 
                           R 
                         
                         h 
                       
                     
                     ) 
                   
                   . 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #158 
                   
                   ] 
                 
               
             
           
         
       
     
     Solving for the required on time to get the SMA to a given temperature: 
     
       
         
           
             
               
                 
                   
                     t 
                     τ 
                   
                   = 
                   
                     ln 
                     ⁡ 
                     ( 
                     
                       
                         1 
                         - 
                         
                           
                             h 
                             
                               
                                 I 
                                 2 
                               
                               ⁢ 
                               R 
                             
                           
                           ⁢ 
                           
                             ( 
                             
                               
                                 T 
                                 i 
                               
                               - 
                               
                                 T 
                                 a 
                               
                             
                             ) 
                           
                         
                       
                       
                         1 
                         - 
                         
                           
                             h 
                             
                               
                                 I 
                                 2 
                               
                               ⁢ 
                               R 
                             
                           
                           ⁢ 
                           
                             ( 
                             
                               
                                 T 
                                 N 
                               
                               - 
                               
                                 T 
                                 a 
                               
                             
                             ) 
                           
                         
                       
                     
                     ) 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #159 
                   
                   ] 
                 
               
             
           
         
       
     
     This may be approximated using a Taylor&#39;s Expansion as: 
     
       
         
           
             
               
                 
                   t 
                   ≈ 
                   
                     
                       mC 
                       
                         
                           I 
                           2 
                         
                         ⁢ 
                         R 
                       
                     
                     [ 
                     
                       
                         ( 
                         
                           
                             T 
                             N 
                           
                           - 
                           
                             T 
                             i 
                           
                         
                         ) 
                       
                       - 
                       
                         
                           1 
                           2 
                         
                         ⁢ 
                         
                           
                             h 
                             
                               
                                 I 
                                 2 
                               
                               ⁢ 
                               R 
                             
                           
                           [ 
                           
                             
                               
                                 ( 
                                 
                                   
                                     T 
                                     a 
                                   
                                   - 
                                   
                                     T 
                                     N 
                                   
                                 
                                 ) 
                               
                               2 
                             
                             - 
                             
                               
                                 ( 
                                 
                                   
                                     T 
                                     a 
                                   
                                   - 
                                   
                                     T 
                                     i 
                                   
                                 
                                 ) 
                               
                               2 
                             
                           
                           ] 
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #160 
                   
                   ] 
                 
               
             
           
         
       
     
     This may also be written in terms of the applied voltage: 
     
       
         
           
             
               
                 
                   t 
                   ≈ 
                   
                     
                       mCR 
                       
                         V 
                         2 
                       
                     
                     [ 
                     
                       
                         ( 
                         
                           
                             T 
                             N 
                           
                           - 
                           
                             T 
                             i 
                           
                         
                         ) 
                       
                       - 
                       
                         
                           1 
                           2 
                         
                         ⁢ 
                         
                           
                             hR 
                             
                               V 
                               2 
                             
                           
                           [ 
                           
                             
                               
                                 ( 
                                 
                                   
                                     T 
                                     a 
                                   
                                   - 
                                   
                                     T 
                                     N 
                                   
                                 
                                 ) 
                               
                               2 
                             
                             - 
                             
                               
                                 ( 
                                 
                                   
                                     T 
                                     a 
                                   
                                   - 
                                   
                                     T 
                                     i 
                                   
                                 
                                 ) 
                               
                               2 
                             
                           
                           ] 
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #161 
                   
                   ] 
                 
               
             
           
         
       
     
     Thus, the ontime needed to produce a given strain in the SMA will be inversely proportional to the square of the applied voltage. In some embodiments, unregulated voltage is applied to the SMA for energy efficiency, thus, the applied voltage may vary with the battery voltage. 
     The internal battery impedance causes a voltage drop as the load is applied during each cycle of the PWM. In addition, the battery open circuit voltage drops over the course of the actuation. Both the battery open circuit voltage and impedance will change as the battery is discharged. The net result is that the electrical power applied to the SMA for a fixed duty cycle is variable. The repeatability of the SMA actuator may be improved by, in some embodiments, measuring the battery voltage and adjusting the duty cycle to provide power that is more consistent. In some embodiments, however, the position of the measurement valve plunger  2908  and the pump plunger  2902  may be measured directly and incorporated into a feedback loop. This may minimize any effects of the battery voltage variation. 
     Pulse Pump Modeling 
     An example of a relationship between the linear displacement of the pump plunger  2902  (as measured by the optical sensor) and the delivered volume is shown in  FIG.  152   . In some embodiments, the pump plunger  2902  may exhibit a dead zone where the pump plunger  2902  may not be in contact with the membrane covering the pump chamber  2906 . Once the pump plunger  2902  reaches the pump chamber  2916  membrane there may be a relatively linear relationship between pump plunger  2902  displacement and volume until the pump plunger  2902  contacts the bottom of the pump chamber  2906 . 
     A model of the pump plunger  2902  is shown in  FIG.  153    as a gain  2930  element with a dead zone  2928  and saturation  2932  limit. The idealized linear model of a pump plunger  2902  that neglects the dead zone  2928  and saturation  2932  is then a static gain element  2930 : 
       Δ v ( k )= Kδ   target ( k )  [EQ #162]
 
     where Δv(k) is the change in volume during a single pump pulse, which refers to one actuation of the pump plunger  2902  by the SMA, the pump plunger  2902  moving from a starting point towards the pump chamber  2916  and reaching an end point, then returning to a stopping point. The total volume delivered may be the sum of the individual pulses: 
     
       
         
           
             
               
                 
                   
                     v 
                     ⁡ 
                     ( 
                     n 
                     ) 
                   
                   = 
                   
                     
                       ∑ 
                       
                         k 
                         = 
                         0 
                       
                       n 
                     
                     
                       K 
                       ⁢ 
                       
                         
                           δ 
                           target 
                         
                         ( 
                         k 
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #163 
                   
                   ] 
                 
               
             
           
         
       
     
     This may be expressed as a transfer function in the discrete domain: 
     
       
         
           
             
               
                 
                   
                     
                       G 
                       p 
                     
                     ( 
                     z 
                     ) 
                   
                   = 
                   
                     
                       
                         v 
                         ⁡ 
                         ( 
                         z 
                         ) 
                       
                       
                         
                           δ 
                           target 
                         
                         ( 
                         z 
                         ) 
                       
                     
                     = 
                     
                       K 
                       ⁢ 
                       
                         z 
                         
                           z 
                           - 
                           1 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #164 
                   
                   ] 
                 
               
             
           
         
       
     
     SMA Controller 
     Feedback Controller 
     Referring now to  FIGS.  154 B and  154 C , during a typical actuation, as shown in the FIGS., target position as a function of time and actual position as measured by the optical sensor as a function of time are shown in  FIG.  154 B .  FIG.  154 C  shows the controlled variable, the duty cycle  2902  is the duty cycle that may be changed in response to errors in following the position trajectory. It should be noted that the term “ADC counts” refer to the counts as read by the analog to digital converter (“ADC”) on the MSP  430  command processor. The ADC counts are proportional to the voltage of the at least one optical sensor. Thus, the output of the at least one optical sensor will be a voltage which is read by the ADC (analog to digital converter). 
     In some embodiments, and referring also to  FIGS.  154 A,  154 B and  154 C , the SMA controller may use a proportional controller  2936  with a fixed feed-forward  2934  to control the position of the pump plunger  2902  or measurement valve plunger  2908 . The heating of the SMA wire  2910 ,  2912  may be an integrating process, thus, uses a proportional controller  2936  for controlling the position of the plungers  2902 ,  2908 . In some embodiments, a fixed duty-cycle feed forward  2934  term may be used to provide fast initial heating of the SMA wire  2910 ,  2912 . The output of the controller is limited to a valid PWM range (0% to 100%), where valid may be, in some embodiments, referring to a combination of that which the system may perform together with potential SMA stress and/or strain and/or saturation factors which may contribute to overall SMA wire life. In some embodiments, the signal from the one or more optical sensor is low passed filtered  2938  with, in some embodiments, a single-pole discrete filter. In some embodiments, the PWM frequency is 20 kHz, which moves it outside the audible range, which may be beneficial for many reasons, including, but not limited to, one or more of the following: user comfort and improving the user experience while pumping as the PWM frequency is outside the audible range. In some embodiments, the PWM output is updated at a frequency of 5 kHz, but in other embodiments, the frequency may vary. 
     Voltage Sensing and Timing 
     In some embodiments, the battery voltage sensing is done through a resistor-divider to an ADC input on the MSP430. The minimum time needed to sample the voltage may be represented in EQ #165: 
         t   sample &gt;( R   s +2 k Ω)ln 2 13 (40 pF)+800 ns  [EQ #165]
 
     where R s  is the source impedance. The minimum sampling time may therefore be 1.77 microseconds. A sampling time of 2 microseconds may be used in some embodiments, however, in other embodiments the sampling time may be greater than or less than 2 microseconds. In some embodiments the minimum sampling time may be less than 1.77 microseconds or greater than 1.77 microseconds depending on the value of R s . In some embodiments, the sampling is done synchronous with the PWM and timed to be a fixed interval from the end of the high cycle of the PWM. Referring now to  FIG.  155   , in some embodiments, as presented in  FIG.  155   , the ontime of the PWM duty cycle cannot be/should not be less than the ADC sampling time. As a result, in this embodiment, the voltage measurement will be higher than the actual battery voltage for duty cycles under 4%. In the exemplary embodiment, the control algorithm is updated every 4 th  PWM period to give time for the Interrupt Service Routine (“ISR”): to complete. However, in various embodiments, the control algorithm may be updated using intervals other than every 4 th  PWM period. 
     SMA Target Trajectory 
     In some embodiments, the outer “volume” loop (described in more detail below with respect to the volume controller) provides a target final pump plunger  2902  position to the inner pump plunger  2902  position control loop. The inner pump plunger  2902  position controller, in some embodiments, brings the pump plunger  2902  to this target position with minimum overshoot because once fluid is moved past the measurement valve  2940  it may not be brought back to the pump chamber  2916 . Thus, it may be desirable in some embodiments to minimize and/or prevent overshoot, and this may be desirable for many reasons, including, but not limited to, safety to the user as it may be beneficial to prevent an “overdelivery” of medical fluid. In some embodiments, this may be accomplished where the pump plunger  2902  position controller generates a position trajectory, i.e., a series of pump plunger  2902  target positions as a function of time that may be followed by the SMA actuator. This may be compared with other embodiments including a step change in target position which may increase the incidence of overshoot in some instances. 
     Referring also to  FIG.  156   , the pump plunger  2902  target position, in some embodiments, has two parts, which are shown: an initial flat region and a linear region. The initial flat region  2942  is where the pump plunger  2902  position is not changing to allow the SMA  2910  to reach the transition temperature. The linear region  2944  is where the pump plunger  2902  is brought to its final position over a fixed time interval. Because the time interval is fixed, the target pump plunger velocity may be less for smaller actuations. In some embodiments, this may be beneficial for many reasons, including, but not limited to, improved controller accuracy for small volume deliveries. 
     Referring to  FIG.  157   , the measurement valve plunger  2908 , in some embodiments, may be controlled differently from the pump plunger  2902  (as described above) because it is binary in its operation, i.e., the measurement valve  2940  is either in an open position or a closed position. The measurement valve plunger  2908  position controller, therefore, in some embodiments, moves the measurement valve plunger  2908  to the “open” position and then, in some embodiments, holds the measurement valve plunger  2908  in the open position which may allow the fluid ample time to fully drain from the measurement chamber  2920 . This method may be beneficial for many reasons, including, but not limited to, adding the “open and hold” phase to the measurement valve plunger  2908  trajectory which may require less strain on the SMA wire  2912 , which may increase the SMA wire  2912  “life”/duration of useful/usable performance for actuation. Thus, adding the “open and hold” phase, rather than, in some embodiments, continuing to move the measurement valve plunger  2908 , may require less strain on the SMA wire  2912 , thus, increasing the SMA wire  2912  “life”. 
     Safety Check and Fault Handling 
     The pump controller in various embodiments includes a number of safety checks designed to provide greater safety to the pump system  2900  operation. These including, but are not limited to, preventing the SMA actuator from “browning out” the electrical system if the battery voltage is too low and guarding against electrical failures in the SMA drive circuit. Thus, the pump controller monitors and ensures that the SMA wire and the drive circuit, or source of electrical energy, functions so as to allow for function of the pump system  2900 . 
     In some embodiments, these safety checks include supply voltage monitoring. In some embodiments, the supply voltage is measured once during each period of the low-side switch PWM and is used in the feedback controller. However, in other embodiments, the pump controller may measure the supply voltage more or less often. However, this measurement is also checked, in some embodiments, to verify that the supply voltage is within the range of expected battery voltages. Where the measurement is outside this range, the actuation may be stopped and in some embodiments, an alarm may be posted by the command processor. The failure of this integrity check could indicate one or more, but not limited to, the following: a failure of voltage sensing circuit, a failure of the battery, and/or a depleted battery. Although supply voltage monitoring is not the primary mechanism for detecting a depleted battery—that may also be done by the battery gauge—in the event of a failure of the battery gauge, supply voltage monitoring allows the pump system  2900  to terminate the high-current SMA actuation before actuating same may deplete or “pull down” the battery voltage to a level below a threshold needed for the processor voltage regulators. 
     The integrity of the switches and SMA wires  2910 ,  2912 , are also monitored during each actuation. This safety routine verifies the safety of the system which may, in some embodiments, may including, but are not limited to, one or more of the following: verification that the switches are functioning correctly; and verification that the measurement valve plunger  2908  and the pump plunger  2902  are not actuated simultaneously. These verifications may provide greater safety to the pump system  2900  for many reasons, including, but limited to, actuating the pump plunger  2902 , i.e., pumping fluid from the reservoir, while the measurement valve plunger  2908  is in the open position, thereby pumping fluid to the tubing set  2922  without holding the fluid in the measurement chamber  2920 . In some embodiments, this may be desirable and beneficial, e.g., in those embodiments where the volume measurement sensor  2946  includes a method for determining the volume of the fluid in the measurement chamber  2020  which includes holding the fluid in the measurement chamber  2020  during the actual volume measurement. Some embodiments of the volume measurement sensor  2946  may not require the measurement valve  2940 , but for those that do, the safety routine described above ensures the volume measurement sensor  2946  may perform measurements according to the method. In some embodiments, to perform these safety-checks the supervisor processor monitors the voltage above the low-side switches using three digital inputs. Referring also to  FIG.  158   , the electrical architecture is shown for a single strand of SMA wire. However, in some embodiments, the SMA wires share the same high-side switch, but have their own low-side switch and voltage monitor line. 
     Still referring to  FIG.  158   , in some embodiments, the safety-check routine proceeds as follows. The command processor  2924  requests SMA power from the supervisor processor  2926 . The supervisor processor  2926  receives the message and proceeds to perform the following: the supervisor processor  2926  verifies that the high-side SMA voltage is low. If the voltage is high, the supervisor processor  2926  may indicates that the power FET has failed closed. The supervisor processor  2926  closes the SMA power switch  2948  and the supervisor processor  2926  verifies that the high-side SMA voltage is high. If it is low the supervisor processor  2926  indicates that the high-side FET has failed open. The supervisor processor  2926  verifies that the low-side SMA voltage is high. If the voltage is low the supervisor processor  2926  indicates that the SMA wire is broken or the low side FET has failed closed. The supervisor processor  2926  then sends a message to the command Processor  2924  that the SMA power is on. The command processor  2924  receives the SMA power on message and starts the SMA actuation. At the same time, the supervisor processor  2926  monitors the SMA monitor lines verifying that only the designated SMA wire is being actuated and that the low-side FET has not failed open. The command processor  2924  completes the actuation and sends a SMA power-off message to the supervisor processor  2926 . At this point, the supervisor processor  2926  turns off the SMA power and sends a confirmation message. 
     In various embodiments, the pump system  2900  may include additional safety checks and/or, the process for the above-described safety checks may vary. In some embodiments, in addition to the safety checks described above, the supervisor processor  2926  may turn off the SMA power switch  2948  and alarm if the supervisor processor  2926  does not receive a “power off” request from the command processor  2924  within a fixed period of time. Thus, in some embodiments, if the command processor  2924 , for example, freezes mid-SMA actuation, and continues to actuate the SMA, and thus, does not command the SMA power switch  2948  to turn off, the supervisor processor  2926  may determine that the command processor  2924  has not turned off the SMA power switch, and the supervisor processor  2926  may post an alarm. This protects the pump system  2900  from command processor  2924  faults which may provide another safety layer to the pump system  2900 . 
     Optical Sensor Monitoring 
     In the exemplary embodiment, the command processor  2924  checks the integrity of each of the at least two optical sensors during every actuation. However, as discussed above, in some embodiments, the pump system  2900  may include at least one optical sensor where the optical sensor is used to determine the position of the pump plunger  2902  but not the measurement valve plunger  2908 . In some embodiments, the pump plunger  2902  may include at least two optical sensors determining the position of the pump plunger  2902 . Further, and as discussed above, in some embodiments, the pump system  2900  may include additional optical sensor to determine the position of additional valves and or membrane position. Thus, for purposes of the discussion, the term “optical sensor” is not meant to be limited to a single optical sensor, rather, applies to the at least one optical sensor that may be included in the pump system  2900  in some embodiments. Where more than one optical sensor is included in the pump system  2900 , in some embodiments, the discussion below may apply to each optical sensor. 
     In some embodiments, the command processor  2924  may check the optical sensor signal output, which, in some embodiments, may include confirming that the optical sensor is within an expected range at the start of actuation: Sensor Check: range check, looking at the optical sensor and if not within the expected range at the start of the actuation, then it may conclude it&#39;s broken] before each actuation. In some embodiments, if the output of the optical sensor is outside the normal operating range the command processor  2924  may post an alarm. 
     The command processor may, in some embodiments, post an alarm if the output of the optical sensor does not change significantly during an actuation. This may be beneficial for this optical sensor output may indicate, e.g., an electrical fault which may produce an optical sensor output that is in range but not related to the plunger displacement for which the optical sensor is determining. Also, in some embodiments, allowances may be made for optical sensor noise and/or drift. 
     Saturation 
     Referring also to  FIGS.  159 A and  159 B , in some embodiments, to maximize the “life” of the SMA wire (which include at least one SMA wire, and in some embodiments, may be more than one SMA wire), it may be desirable to minimize the number of times the pump plunger/measurement valve plunger (and/or any valve/plunger that is being actuated by a SMA) “bottoms out” at the end of its travel. When the plunger reaches the end of its travel, it cannot move any further so it falls behind the target position. If the tracking error (the difference between the target position and actual position) exceeds a fixed threshold, the plunger is assumed to have “bottomed out” and the power to the SMA wire is turned off. Allowances are made to prevent false detects. 
     If the plunger is detected to have “bottomed out” twice in a row, the maximum allowed target position may be reduced to prevent the plunger from bottoming out again. In some embodiments, the maximum target position may not be reduced the first time the plunger is detected to have “bottomed out” to prevent any false detections of plunger saturation from limiting the plunger travel. 
     Delivery Controller 
     The delivery controller delivers a discrete dose of fluid (which in some embodiments, as discussed above, may be any fluid, including, but not limited to, a medical fluid, e.g., insulin) each time it is commanded by the therapy layer. The delivery controller, in some embodiments, does not track nor control the therapy, e.g., basal programs, boluses, or the timing of the delivery; rather, the therapy is controlled by the therapy layer. The delivery controller, in some embodiments, has a primary responsibility to deliver a dose of fluid when commanded and to measure the actual fluid delivered (using the volume measurement sensor  2946 ), and also, to adjust the pump plunger  2902  command to minimize any volume delivery error. Thus, where the pump plunger  2902  target position is met, the delivery controller determines whether the volume of fluid delivered is as expected and if not, to adjust the pump plunger  2902  command. 
     In addition, in some embodiments, the delivery controller may confirm and process a variety of system checks including, but not limited to, detecting occlusions, detecting an empty reservoir, and/or system faults that may affect the delivery of fluid to the tubing set  2922 , which, in some embodiments, may be connected by way of a cannula to the patient/user of the system. If one or more faults are detected by the delivery controller, the delivery controller may, and in some embodiments, will always, enter a failsafe state preventing further delivery until and unless the at least one detected fault is resolved. The delivery controller reports faults detected to the therapy layer. The term failsafe may refer to a state of non-delivery in response to a determined failure, following alerting the user/patient that the system is entering a failsafe mode. 
     For the following discussion, the following nomenclature may be used: 
     Term Definition 
     G p (z) Pulse pump discrete transfer function 
     G c (z) Controller discrete transfer function 
     K p  Controller loop gain 
     T 1  Controller Integrator time constant 
     z Complex argument for the discrete transform 
     
       
         
           
             
               x 
               ⁡ 
               ( 
               z 
               ) 
             
             = 
             
               
                 Z 
                 ⁢ 
                 
                   { 
                   
                     x 
                     ⁡ 
                     ( 
                     n 
                     ) 
                   
                   } 
                 
               
               = 
               
                 
                   ∑ 
                   
                     n 
                     = 
                     0 
                   
                   ∞ 
                 
                 
                   
                     x 
                     ⁡ 
                     ( 
                     n 
                     ) 
                   
                   ⁢ 
                   
                     z 
                     
                       - 
                       n 
                     
                   
                 
               
             
           
         
       
     
     e Delivery error 
     r(z) Target volume trajectory 
     K Pulse pump gain 
     Volume Controller 
     Referring also now to  FIG.  160   , in some embodiments, the primary function of the delivery controller may be to provide closed-loop control of the delivered fluid volume. The delivery controller accomplishes this function, in some embodiments, by taking the measured volume change (this is the difference between the AVS/volume measurement sensor measurement with the AVS/volume measurement sensor chamber full and the AVS measurement with the chamber empty), comparing it to the target volume, and setting the pump plunger  2902  target displacement accordingly. Referring also to  FIG.  161   , the schematic shows the outer volume loop as well as the inner voltage loop described above. 
     As shown in  FIGS.  161 - 162   , the volume controller architecture on the total delivered volume and a feed-forward term based on the target volume for the current delivery is shown. As shown in this embodiment, the target volume and measured volume changes (dV AVS) are integrated before being passed into the feedback controller; there is no direct feedback on the error from an individual delivery. 
     Feedback Controller 
     Referring now to  FIG.  162   , in some embodiments, the volume controller may include the architecture, as shown, with integrator saturation and anti-windup. The discrete transfer function is shown below for the region where the integrator is active. A unit time delay is included to account for the 1-frame delay between the volume measurement and its use in the feedback loop. 
     
       
         
           
             
               
                 
                   
                     
                       G 
                       c 
                     
                     ( 
                     z 
                     ) 
                   
                   = 
                   
                     
                       
                         K 
                         p 
                       
                       ( 
                       
                         1 
                         + 
                         
                           
                             1 
                             
                               T 
                               I 
                             
                           
                           ⁢ 
                           
                             z 
                             
                               z 
                               - 
                               1 
                             
                           
                         
                       
                       ) 
                     
                     ⁢ 
                     
                       1 
                       z 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #166 
                   
                   ] 
                 
               
             
           
         
       
     
     The pump plunger  2902  displacement versus volume delivered transfer function (input is the pump plunger position, and the output is the volume delivered) between total volume delivered and pump plunger  2902  may be modeled as a simple discrete integrator. 
     
       
         
           
             
               
                 
                   
                     
                       G 
                       p 
                     
                     ( 
                     z 
                     ) 
                   
                   = 
                   
                     
                       
                         v 
                         ⁡ 
                         ( 
                         z 
                         ) 
                       
                       
                         
                           t 
                           on 
                         
                         ( 
                         z 
                         ) 
                       
                     
                     = 
                     
                       K 
                       ⁢ 
                       
                         z 
                         
                           z 
                           - 
                           1 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #167 
                   
                   ] 
                 
               
             
           
         
       
     
     The forward path transfer function may then be written as follows. An additional unit time delay may be added to account for the fact that the AVS measurement/volume measurement sensor measurement will be from the previous delivery. A corresponding unit delay was also added to the target input. 
     
       
         
           
             
               
                 
                   
                     
                       
                         G 
                         c 
                       
                       ( 
                       z 
                       ) 
                     
                     ⁢ 
                     
                       
                         G 
                         p 
                       
                       ( 
                       z 
                       ) 
                     
                   
                   = 
                   
                     
                       
                         
                           K 
                           p 
                         
                         ( 
                         
                           1 
                           + 
                           
                             
                               1 
                               
                                 T 
                                 I 
                               
                             
                             ⁢ 
                             
                               z 
                               
                                 z 
                                 - 
                                 1 
                               
                             
                           
                         
                         ) 
                       
                       ⁢ 
                       
                         K 
                         ⁡ 
                         ( 
                         
                           z 
                           
                             z 
                             - 
                             1 
                           
                         
                         ) 
                       
                       ⁢ 
                       
                         1 
                         z 
                       
                     
                     = 
                     
                       
                         K 
                         p 
                       
                       ⁢ 
                       K 
                       ⁢ 
                       
                         
                           
                             
                               ( 
                               
                                 1 
                                 + 
                                 
                                   1 
                                   
                                     T 
                                     I 
                                   
                                 
                               
                               ) 
                             
                             ⁢ 
                             z 
                           
                           - 
                           1 
                         
                         
                           
                             ( 
                             
                               z 
                               - 
                               1 
                             
                             ) 
                           
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #168 
                   
                   ] 
                 
               
             
           
         
       
     
     The steady-state volume error for this type of controller when following an input r(z) is shown below: 
     
       
         
           
             
               
                 
                   
                     
                       e 
                       ⁡ 
                       ( 
                       z 
                       ) 
                     
                     
                       r 
                       ⁡ 
                       ( 
                       z 
                       ) 
                     
                   
                   = 
                   
                     
                       1 
                       
                         1 
                         + 
                         
                           
                             G 
                             c 
                           
                           ⁢ 
                           
                             G 
                             p 
                           
                         
                       
                     
                     = 
                     
                       
                         
                           ( 
                           
                             1 
                             - 
                             
                               z 
                               
                                 - 
                                 1 
                               
                             
                           
                           ) 
                         
                         2 
                       
                       
                         
                           
                             ( 
                             
                               1 
                               - 
                               
                                 z 
                                 
                                   - 
                                   1 
                                 
                               
                             
                             ) 
                           
                           2 
                         
                         + 
                         
                           
                             
                               KK 
                               p 
                             
                             [ 
                             
                               
                                 ( 
                                 
                                   
                                     1 
                                     
                                       T 
                                       I 
                                     
                                   
                                   + 
                                   1 
                                 
                                 ) 
                               
                               - 
                               
                                 z 
                                 
                                   - 
                                   1 
                                 
                               
                             
                             ] 
                           
                           ⁢ 
                           
                             z 
                             
                               - 
                               1 
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #169 
                   
                   ] 
                 
               
             
           
         
       
     
     The pump system  2900  may typically be following a ramp target volume trajectory (piecewise constant delivery rate). This input may be described in the discrete domain as follows: 
     
       
         
           
             
               
                 
                   
                     r 
                     ⁡ 
                     ( 
                     z 
                     ) 
                   
                   = 
                   
                     C 
                     ⁢ 
                     
                       z 
                       
                         
                           ( 
                           
                             z 
                             - 
                             1 
                           
                           ) 
                         
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #170 
                   
                   ] 
                 
               
             
           
         
       
     
     The steady state flowing error can then be found using the discrete final value theorem applied to the plant and controller derived above: 
     
       
         
           
             
               
                 
                   
                     
                       lim 
                       
                         t 
                         
                           → 
                           &#34;\[Rule]&#34; 
                         
                         ∞ 
                       
                     
                     
                       ( 
                       t 
                       ) 
                     
                   
                   = 
                   
                     
                       
                         lim 
                         
                           z 
                           
                             → 
                             &#34;\[Rule]&#34; 
                           
                           1 
                         
                       
                       
                         [ 
                         
                           
                             ( 
                             
                               1 
                               - 
                               
                                 z 
                                 
                                   - 
                                   1 
                                 
                               
                             
                             ) 
                           
                           ⁢ 
                           
                             e 
                             ⁡ 
                             ( 
                             z 
                             ) 
                           
                         
                         ] 
                       
                     
                     = 
                     
                       
                         
                           lim 
                           
                             z 
                             
                               → 
                               &#34;\[Rule]&#34; 
                             
                             1 
                           
                         
                         
                           [ 
                           
                             
                               ( 
                               
                                 
                                   
                                     ( 
                                     
                                       1 
                                       - 
                                       
                                         z 
                                         
                                           - 
                                           1 
                                         
                                       
                                     
                                     ) 
                                   
                                   3 
                                 
                                 
                                   
                                     
                                       ( 
                                       
                                         1 
                                         - 
                                         
                                           z 
                                           
                                             - 
                                             1 
                                           
                                         
                                       
                                       ) 
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                       
                                         KK 
                                         p 
                                       
                                       [ 
                                       
                                         
                                           ( 
                                           
                                             
                                               1 
                                               
                                                 T 
                                                 I 
                                               
                                             
                                             + 
                                             1 
                                           
                                           ) 
                                         
                                         - 
                                         
                                           z 
                                           
                                             - 
                                             1 
                                           
                                         
                                       
                                       ] 
                                     
                                     ⁢ 
                                     
                                       z 
                                       
                                         - 
                                         1 
                                       
                                     
                                   
                                 
                               
                               ) 
                             
                             ⁢ 
                             
                               ( 
                               
                                 
                                   z 
                                   
                                     - 
                                     1 
                                   
                                 
                                 
                                   
                                     ( 
                                     
                                       1 
                                       - 
                                       
                                         z 
                                         
                                           - 
                                           1 
                                         
                                       
                                     
                                     ) 
                                   
                                   2 
                                 
                               
                               ) 
                             
                           
                           ] 
                         
                       
                       = 
                       0 
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #171 
                   
                   ] 
                 
               
             
           
         
       
     
     So a PI controller will theoretically have zero steady state error when following a ramp input in volume. 
     Controller Feed-Forward 
     Referring also to  FIG.  163   , in some embodiments, to improve the trajectory following of the controller, a non-linear feed-forward term may be added to, e.g., compensate for the pulse pump dead-band. In some embodiments, this feed-forward term provides a “best guess” of the pump plunger  2902  displacement for a given target volume by inverting the idealized pump plunger  2902  model described above with respect to the delivery controller. Pump system  2900  characteristics are different for different reusable housing assemblies, disposable housing assemblies, and reservoir fill volumes, i.e., the volume of fluid in the reservoir. Thus, this feed-forward term may generally produce some error that may need to be corrected by the feedback controller. 
     Initialization of the Feed-Forward Parameters 
     The gain and offset used in the feed forward controller, shown in  FIG.  164   , are initialized during the start-up test based on the measured pump characteristics. 
     Least Square Recursive Filter 
     The gain and offset parameters of the feed-forward controller are adjusted as the pump is operating. Thus, the slope and offset of the model are continuously updated based on the AVS measurements/volume measurement sensor measurements to improve the accuracy of the feed-forward model. The “learning” algorithm may be based on a linear exponentially forgetting least square recursive filter. The time constant is set such that it adapts slowly compared to the feedback controller ( FIG.  162   ) and the two do not have significant interaction. If the feed-forward term was never changed, it would have no effect on the stability of the feedback controller. 
     The feed-forward model is updated using a recursive least-square estimator. The function we are fitting is as follows: 
         y ( n )= mx ( n )+ b   [EQ #172]
 
     The dependent variable x is the delivered volume and the independent variable, y, is the pump plunger  2902  target position/displacement. In vector form, this may be written: 
     
       
         
           
             
               
                 
                   
                     
                       y 
                       ⁡ 
                       ( 
                       n 
                       ) 
                     
                     = 
                     
                       
                         w 
                         T 
                       
                       ⁢ 
                       
                         x 
                         ⁡ 
                         ( 
                         n 
                         ) 
                       
                     
                   
                   ⁢ 
                   
 
                   
                     w 
                     = 
                     
                       
                         
                           [ 
                           
                             
                               
                                 
                                   m 
                                   n 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   n 
                                 
                               
                             
                           
                           ] 
                         
                         ⁢ 
                             
                         and 
                         ⁢ 
                             
                         
                           x 
                           n 
                         
                       
                       = 
                       
                         [ 
                         
                           
                             
                               
                                 x 
                                 
                                   n 
                                   , 
                                   11 
                                 
                               
                             
                           
                           
                             
                               1 
                             
                           
                         
                         ] 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #173 
                   
                   ] 
                 
               
             
           
         
       
     
     It may be noted that x n  is the vector x at time step n, and x n,11  is the 1 st  element of the vector x at the time step n. The function being optimized is: 
     
       
         
           
             
               
                 
                   
                     y 
                     n 
                   
                   = 
                   
                     
                       
                         
                           m 
                           n 
                         
                         ⁢ 
                         
                           x 
                           n 
                         
                       
                       + 
                       
                         b 
                         n 
                       
                     
                     = 
                     
                       
                         
                           w 
                           T 
                         
                         ⁢ 
                         x 
                       
                       = 
                       
                         
                           [ 
                           
                             
                               
                                 
                                   m 
                                   n 
                                 
                               
                               
                                 
                                   b 
                                   n 
                                 
                               
                             
                           
                           ] 
                         
                         [ 
                         
                           
                             
                               
                                 x 
                                 
                                   n 
                                   , 
                                   11 
                                 
                               
                             
                           
                           
                             
                               1 
                             
                           
                         
                         ] 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     #174 
                   
                   ] 
                 
               
             
           
         
       
     
     The error for a given time step, n may be written: 
         e   n   =y   n −( m   n-1   x   n   +b   n-1 )  [EQ #175]
 
     To update the w vector based on the error signal, the gain matrix is first updated: 
     
       
         
           
             
               
                 
                   
                     g 
                     n 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             
                               
                                 
                                   p 
                                   
                                     
                                       n 
                                       - 
                                       1 
                                     
                                     , 
                                     11 
                                   
                                 
                                 ⁢ 
                                 
                                   x 
                                   
                                     n 
                                     , 
                                     11 
                                   
                                 
                               
                               + 
                               
                                 p 
                                 
                                   
                                     n 
                                     - 
                                     1 
                                   
                                   , 
                                   12 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   p 
                                   
                                     
                                       n 
                                       - 
                                       1 
                                     
                                     , 
                                     21 
                                   
                                 
                                 ⁢ 
                                 
                                   x 
                                   
                                     n 
                                     , 
                                     11 
                                   
                                 
                               
                               + 
                               
                                 p 
                                 
                                   
                                     n 
                                     - 
                                     1 
                                   
                                   , 
                                   22 
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                     ⁢ 
                     
                       
                         { 
                         
                           λ 
                           + 
                           
                             
                               p 
                               
                                 
                                   n 
                                   - 
                                   1 
                                 
                                 , 
                                 11 
                               
                             
                             ⁢ 
                             
                               x 
                               2 
                             
                           
                           + 
                           
                             
                               ( 
                               
                                 
                                   p 
                                   
                                     
                                       n 
                                       - 
                                       1 
                                     
                                     , 
                                     12 
                                   
                                 
                                 + 
                                 
                                   p 
                                   
                                     
                                       n 
                                       - 
                                       1 
                                     
                                     , 
                                     21 
                                   
                                 
                               
                               ) 
                             
                             ⁢ 
                             
                               x 
                               
                                 n 
                                 , 
                                 11 
                               
                             
                           
                           + 
                           
                             p 
                             
                               
                                 n 
                                 - 
                                 1 
                               
                               , 
                               22 
                             
                           
                         
                         } 
                       
                       
                         - 
                         1 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     176 
                   
                   ] 
                 
               
             
           
         
       
     
     The inverse is of a scalar so no matrix inversion is required. The covariance matrix may then be updated for the next time step: 
     
       
         
           
             
               
                 
                   
                     P 
                     n 
                   
                   = 
                   
                     
                       λ 
                       
                         - 
                         1 
                       
                     
                     [ 
                     
                       
                         
                           
                             
                               
                                 p 
                                 
                                   
                                     n 
                                     - 
                                     1 
                                   
                                   , 
                                   11 
                                 
                               
                               ( 
                               
                                 1 
                                 - 
                                 
                                   
                                     g 
                                     
                                       n 
                                       , 
                                       11 
                                     
                                   
                                   ⁢ 
                                   
                                     x 
                                     
                                       n 
                                       , 
                                       11 
                                     
                                   
                                 
                               
                               ) 
                             
                             - 
                             
                               
                                 p 
                                 
                                   
                                     n 
                                     - 
                                     1 
                                   
                                   , 
                                   12 
                                 
                               
                               ⁢ 
                               
                                 g 
                                 
                                   n 
                                   , 
                                   11 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 p 
                                 
                                   
                                     n 
                                     - 
                                     1 
                                   
                                   , 
                                   21 
                                 
                               
                               ⁢ 
                               
                                 ( 
                                 
                                   1 
                                   - 
                                   
                                     
                                       g 
                                       
                                         n 
                                         , 
                                         11 
                                       
                                     
                                     ⁢ 
                                     
                                       x 
                                       
                                         n 
                                         , 
                                         11 
                                       
                                     
                                   
                                 
                                 ) 
                               
                             
                             - 
                             
                               
                                 p 
                                 
                                   
                                     n 
                                     - 
                                     1 
                                   
                                   , 
                                   22 
                                 
                               
                               ⁢ 
                               
                                 g 
                                 
                                   n 
                                   , 
                                   11 
                                 
                               
                             
                           
                         
                       
                       
                         
                           
                             
                               
                                 p 
                                 
                                   
                                     n 
                                     - 
                                     1 
                                   
                                   , 
                                   12 
                                 
                               
                               ⁢ 
                               
                                 ( 
                                 
                                   1 
                                   - 
                                   
                                     g 
                                     
                                       n 
                                       , 
                                       12 
                                     
                                   
                                 
                                 ) 
                               
                             
                             - 
                             
                               
                                 p 
                                 
                                   
                                     n 
                                     - 
                                     1 
                                   
                                   , 
                                   11 
                                 
                               
                               ⁢ 
                               
                                 g 
                                 
                                   n 
                                   , 
                                   12 
                                 
                               
                               ⁢ 
                               
                                 x 
                                 
                                   n 
                                   , 
                                   11 
                                 
                               
                             
                           
                         
                         
                           
                             
                               
                                 p 
                                 
                                   
                                     n 
                                     - 
                                     1 
                                   
                                   , 
                                   22 
                                 
                               
                               ⁢ 
                               
                                 ( 
                                 
                                   1 
                                   - 
                                   
                                     g 
                                     
                                       n 
                                       , 
                                       12 
                                     
                                   
                                 
                                 ) 
                               
                             
                             - 
                             
                               
                                 p 
                                 
                                   
                                     n 
                                     - 
                                     1 
                                   
                                   , 
                                   21 
                                 
                               
                               ⁢ 
                               
                                 g 
                                 
                                   n 
                                   , 
                                   12 
                                 
                               
                               ⁢ 
                               
                                 x 
                                 
                                   n 
                                   , 
                                   11 
                                 
                               
                             
                           
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     177 
                   
                   ] 
                 
               
             
           
         
       
     
     The coefficients can then be updated based on the gain vector and the error: 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             m 
                             n 
                           
                         
                       
                       
                         
                           
                             b 
                             n 
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             
                               m 
                               
                                 n 
                                 - 
                                 1 
                               
                             
                           
                         
                         
                           
                             
                               b 
                               
                                 n 
                                 - 
                                 1 
                               
                             
                           
                         
                       
                       ] 
                     
                     + 
                     
                       
                         e 
                         n 
                       
                       ⁢ 
                       
                         g 
                         n 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     178 
                   
                   ] 
                 
               
             
           
         
       
     
     Taking advantage that the covariance matrix is symmetric, the method and/or algorithm may be written more computationally efficiently. This may, in some embodiments, be beneficial for many reasons, including, but not limited to, efficient implementation in software. 
     In some embodiments, the filter is only valid if the pump plunger  2902  is operating in its linear range, so the value may only be updated if the measured volume is in the range of 0.1 uL to 2.1 uL, for example, where this range is in the linear range. In some embodiments, the recursive filter may not be effective if the measurements are not sufficiently “signal rich”, i.e., where too many deliveries are performed at a single operating point the linear fit may converge to a solution that may not be valid once the pump plunger  2902  being operation over the full range. To guard against this possible “localized” solution, the algorithm, in some embodiments, may not be updated where the diagonal terms of the covariance matrix exceed a set threshold. 
     Delivery Fault Detection 
     In addition to providing closed-loop control of the volume delivered by the pump system  2900 , the delivery controller, in some embodiments, may also detect fault conditions associated with fluid delivery. A variety of fault detection methods are described below, one or more of which may be included in various embodiments of the delivery controller. 
     In some embodiments, the delivery controller monitors, amongst possible additional functions, the total volume error, which may be defined as the cumulative volume error of all the deliveries since the delivery controller was last reset. If the delivered volume exceeds the target volume by more than a specified amount, which indicates an over-delivery, the delivery controller, in some embodiments, may post a pump fault and switch to a failsafe mode, which is described above. Conversely, if the target volume exceeds the measured volume by a specified amount, which indicates under-delivery, the delivery controller, in some embodiments, may post a pump fault and switch the pump system  2902  to a failsafe mode, which is described above. In some embodiments, the under-delivery tolerance may be programmable by the user/patient and further, in some embodiments, the tolerance may include a high and low sensitivity setting. 
     Thus, where the delivery controller determines that the cumulative volume error is such that a either an over-delivery or under-delivery threshold has been met, which threshold may be set based on safety to the user/patient, the delivery controller may signal a pump fault condition and the pump system  2902  may be shut down, with at least one indication to the user/patient, such that the pump system  2902  avoids over delivery and under delivery at unsafe levels. Thus, in various embodiments, the pump system  2902  includes a determination of the volume of over delivery and/or under delivery and a threshold tolerance of same where when the threshold is reached, the pump system  2902  may enter failsafe mode. 
     Occlusion Detection 
     In some embodiments, the deliver controller monitors the volume of fluid that both flows into and out of the volume measurement chamber  2920  and, in some embodiments, may determine whether the tubing set  2922  may be occluded. In some embodiments, there are two parallel methods used for detecting an occlusion, which may be termed the total occlusion method and the partial occlusion method. The total occlusion detection method monitors the flow into and out of the volume measurement chamber  2920  during a single delivery of fluid. The partial occlusion detection method monitors for a gradual build-up of fluid in the volume measurement chamber  2920 . 
     The residual volume for an individual delivery may be defined as the difference between the volume flow into the volume measurement chamber  2920 , which may be referred to as the “pumped volume” and the volume flowing out of the volume measurement chamber  2920 , which may be referred to as the “delivered volume”: 
       Δ v   res   =Δv   pump   −Δv   delivered   [EQ #179]
 
     This is equivalent to the difference between the final and initial variable volume estimates: 
       Δ v   res   =ΔV   final   −ΔV   initial   [EQ #180]
 
     Under normal operation, in some embodiments, the residual volume may be close to zero at steady state. In some embodiments, the residual volume may be the fundamental metric for detecting both total and partial occlusions. 
     Total Occlusion 
     In the event of a total occlusion of the fluid exit path, which may also be referred to as the tubing set  2922  and the cannula as well as the fluid path in the disposable housing assembly downstream from the volume measurement chamber  2920 , the residual volume in the volume measurement chamber  2920  may be approximately the same size as the volume pumped, i.e., the volume of fluid pumped into the volume measurement chamber  2920 . Thus, in these circumstances, fluid has been pumped into the volume measurement chamber  2920 , however, little or no fluid may have left the volume measurement chamber  2920 . In these circumstances, in some embodiments, a threshold residual volume may be used as an indicator of a total occlusion. In some embodiments, the total occlusion detection threshold may be set based on the cumulative pumped volume, i.e., the total volume of fluid pumped. A linearized model of the fluid flow out of the volume measurement chamber  2920  may have the form: 
     
       
         
           
             
               
                 
                   
                     
                       V 
                       . 
                     
                     avs 
                   
                   ∝ 
                   
                     
                       V 
                       avs 
                     
                     τ 
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     181 
                   
                   ] 
                 
               
             
           
         
       
     
     Where V avs  is the volume of the variable volume chamber  2950 . 
     Larger pumped volumes/larger volumes of fluid pumped into the volume measurement chamber  2920 , may result in larger delivered volumes for the same measurement valve  2940  open time and tubing set  2922  flow impedance. In some embodiments, therefore, the residual volume threshold for occlusion is therefore calculated as a fraction of the total volume pumped: 
         T   O =ρ o   Δv   pump   [EQ #182]
 
     where ρ o  is a value less than one. An exemplary value for ρ o  is 0.15, which means the delivery controller may detect a total occlusion if less than 85% of the fluid pumped into the volume measurement chamber  2920  is delivered/pumped out of the volume measurement chamber  2920  (and in some embodiments to the tubing set  2922  and to the user/patient). Determination of a total occlusion may be as follows: 
     
       
         
           
             
               
                 
                   
                     Φ 
                     o 
                   
                   = 
                   
                     { 
                     
                       
                         
                           
                             
                               1 
                               ⁢ 
                                   
                               if 
                               ⁢ 
                                   
                               
                                 v 
                                 res 
                               
                             
                             &gt; 
                             
                               T 
                               o 
                             
                           
                         
                       
                       
                         
                           
                             0 
                             ⁢ 
                                 
                             otherwise 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     183 
                   
                   ] 
                 
               
             
           
         
       
     
     Where Φ o  is the total occlusion detection indicator. In some embodiments, the pump system  2902  may not alarm immediately after the total occlusion detection indicator has been set to “1”, rather in some embodiments, an alarm may be posted once the total occlusion detection indicator remains positive for a preset number of consecutive deliveries to allow time for the occlusion to clear through regular operation of the pump system  2902 , which, in some circumstances, may be accomplished. In various embodiments, the number of occluded deliveries permitted is variable and may, in some embodiments, be pre-set/preprogrammed and/or may be based on a user/patient configurable occlusion sensitivity setting. 
     In some embodiments, in the event that an occlusion clears on its own, the fluid may once again flow out of the volume measurement chamber  2920 . Thus, in some embodiments, the logic for clearing the total occlusion is related to the delivered volume, v del  being greater than a given threshold. This cleared-occlusion threshold may be, in some embodiments, calculated as a fraction of the total volume pumped for a given delivery plus the accumulated residual volume, if any, from previous deliveries, which may be represented as follows: 
     
       
         
           
             
               
                 
                   
                     
                       T 
                       u 
                     
                     = 
                     
                       
                         ρ 
                         u 
                       
                       ( 
                       
                         
                           Δ 
                           ⁢ 
                           
                             v 
                             pump 
                           
                         
                         + 
                         
                           v 
                           
                             residual 
                             , 
                             total 
                           
                         
                       
                       ) 
                     
                   
                   ⁢ 
                   
 
                   Or 
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     184 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     Φ 
                     o 
                   
                   = 
                   
                     { 
                     
                       
                         
                           
                             
                               1 
                               ⁢ 
                                   
                               if 
                               ⁢ 
                                 
                               
                                 v 
                                 del 
                               
                             
                             &gt; 
                             
                               T 
                               u 
                             
                           
                         
                       
                       
                         
                           
                             1 
                             ⁢ 
                                 
                             otherwise 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     185 
                   
                   ] 
                 
               
             
           
         
       
     
     Combining these two, the total occlusion update logic is as follows: 
     
       
         
           
             
               
                 
                   
                     
                       Φ 
                       o 
                     
                     [ 
                     
                       n 
                       + 
                       1 
                     
                     ] 
                   
                   = 
                   
                     { 
                     
                       
                         
                           
                             
                               1 
                               ⁢ 
                                   
                               if 
                               ⁢ 
                                   
                               
                                 
                                   v 
                                   res 
                                 
                                 [ 
                                 
                                   n 
                                   + 
                                   1 
                                 
                                 ] 
                               
                             
                             &gt; 
                             
                               T 
                               o 
                             
                           
                         
                       
                       
                         
                           
                             
                               0 
                               ⁢ 
                                   
                               if 
                               ⁢ 
                                   
                               
                                 
                                   v 
                                   del 
                                 
                                 [ 
                                 
                                   n 
                                   + 
                                   1 
                                 
                                 ] 
                               
                             
                             &lt; 
                             
                               T 
                               u 
                             
                           
                         
                       
                       
                         
                           
                             otherwise 
                             ⁢ 
                                 
                             
                               
                                 Φ 
                                 o 
                               
                               [ 
                               n 
                               ] 
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     186 
                   
                   ] 
                 
               
             
           
         
       
     
     In some embodiments, an increase in the residual volume may be an indication that an occlusion has occurred, however, the residual volume returning to zero may not necessarily be an indication that an occlusion has cleared. This is because the pump plunger  2902  may, in some instances, only be able to pump one or two deliveries following an occlusion due to the build up of back-pressure in the volume measurement chamber  2920 . Thus, once the pump system  2900  has reached this condition, the change in residual volume becomes close to zero, thus, no fluid flows into the volume measurement chamber  2920  and no fluid volume flows out of the volume measurement chamber  2920 . As a result, in some embodiments, the delivered volume, instead of the residual volume, may be used for the condition to clear a total occlusion indication. 
     In various embodiments, partial occlusions result in an accumulation of residual volume in the volume measurement chamber  2920 , but this accumulation may occur over time at a low enough rate that the total occlusion detection logic may not detect the accumulation. As a result, in some embodiments, a second method, i.e., partial occlusion method, may be used which integrates the residual volume of individual deliveries and uses this sum to detect a slow build-up of volume characteristic of a partial occlusion. Additionally, any volume that leaks from the volume measurement chamber  2920  between deliveries may be subtracted out of the total of the residual volume of individual deliveries so as to prevent confusing an inter-delivery leak with a partial occlusion. A “leaky” integration, as shown in EQ #187 and EQ #188 may be performed so that the cumulative effect of measurement error may be minimized. 
     The Integrator 
         S   var =γ var   *S   var +( v   res   −v   interleak )  [EQ #187]
 
     The partial occlusion indicator, Φ var , is then set based on the following logic: 
     
       
         
           
             
               
                 
                   
                     Φ 
                     var 
                   
                   = 
                   
                     { 
                     
                       
                         
                           
                             
                               1 
                               ⁢ 
                                   
                               if 
                               ⁢ 
                                   
                               
                                 S 
                                 var 
                               
                             
                             &gt; 
                             
                               T 
                               var 
                             
                           
                         
                       
                       
                         
                           
                             0 
                             ⁢ 
                                 
                             otherwise 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     188 
                   
                   ] 
                 
               
             
           
         
       
     
     As with the total occlusion detection and occlusion alarm, a partial occlusion detection may not trigger an occlusion alarm until a minimum number of consecutive deliveries are detected/determined to be occluded. This allows time for partial occlusions to clear through regular operation of the pump system  2902 , which, in some circumstances, may be accomplished. Additionally, in some embodiments, the partial occlusion alarm may not be posted unless the total trajectory error exceeds a certain threshold. 
     In some embodiments, the partial occlusion threshold may be a limit on how much fluid volume may remain in the volume measurement chamber  2920  between deliveries. If there is too much residual volume in the volume measurement chamber  2920  the pump plunger  2902  may be unable to deliver a full pump-stroke due to the increased back pressure. In some embodiments, this sets an upper limit for the allowed residual volume. Thus, if the maximum target delivery volume for a single delivery is Δv max  and the maximum total volume of the volume measurement chamber  2920  before the pack-pressure prevents further pumping is v max  then the maximum partial occlusion threshold is: 
         T   var,max   =ΔV   max   −Δv   max   [EQ #189]
 
     This threshold is on the order of T var =1.0 μL. If a cumulative total of more than 1.0 μL of volume remains in the volume measurement chamber  2920  a partial occlusion may be detected. Again, an alarm may not be posted unless the under-delivery and number of consecutive occluded delivery conditions have also been met. 
     Empty Reservoir Detection 
     The empty reservoir detection algorithm, may, in some embodiments, evaluate the ability of the pump plunger  2902  to deliver fluid from the reservoir  2918  to the volume measurement chamber  2920 . The pump system  2902 , in some embodiments, may use two parameters for this evaluation, which may include, but is not limited to, the pumping error and the total trajectory error. The pumping error may be the difference between the target and actual pumped volumes. An internal “empty reservoir indicator”, which may be set if the pump is under-delivering. In some embodiments, if under-delivery occurs two consecutive deliveries while the pump plunger  2902  is at its maximum actuation, the maximum target volume may be decreased, allowing pumping to continue with smaller and more frequent deliveries. If the maximum target volume is reduced by this method below a minimum threshold, an empty reservoir alarm may be posted. Alternatively, in some embodiments, if the difference between the measured volume delivered and the total target volume requested exceeds a threshold, an empty reservoir may be assumed by the pump system  2902  and an alarm may be posted. In some embodiments, empty reservoir alarms may also be posted due to an up-stream occlusion, leak, or possibly a faulty pump plunger shape memory actuator  2910 . 
     Maximum Target Volume Reduction Empty Reservoir Alarm 
     In some embodiments, as the reservoir  2918  empties, the maximum volume that the pump chamber  2916  membrane restoring force may pull from the reservoir  2918  may decrease. Consequently, the maximum volume that the pump plunger  2902  may deliver to the measurement chamber  2920  and then to the tubing set  2922  may also decrease. To minimize the volume left in the reservoir  2918  when the disposable housing assembly may be discarded, the delivery controller may dynamically decrease the maximum target volume as this occurs. Thus, in some embodiments, this may allow the pump system  2900  to continue administering fluid/therapy by delivering smaller deliveries more frequently. 
     The basis for this empty reservoir detection maximum volume reduction, in some embodiments, may be the difference between the goal/target volume for each delivery, v target , and the volume pumped into the volume measurement chamber  2920 , v pump . This difference may be defined as the pumped volume error, v error : 
         v   error   =v   target   −v   pump   [EQ #190]
 
     An internal indicator may be set whenever this difference is greater than zero, v error &gt;0 and the pump plunger  2902  is either saturating or at its maximum allowed value. If this occurs in two consecutive deliveries, the maximum target delivery volume may be decremented and the therapy layer may be called to reschedule the next delivery. In some embodiments, an exception to this method may be made during a bolus. When bolusing, the target delivery volume for the entire bolus may be, in some embodiments, calculated at the start of the bolus. Therefore, the maximum target volume may not decrement during a bolus. 
     In some embodiments, once the maximum target volume has been reduced to the minimum delivery volume, any further saturated under-delivering may result in an empty reservoir alarm. 
     Under Delivery Empty Reservoir Alarm 
     In some embodiments, the pump system  2900  may alarm for an empty reservoir when either the maximum allowed target volume is reduced below a minimum by way of a dynamic reduction, as described above, or, in some embodiments, whenever the pump system  2900  is under-delivering by more than a given amount/threshold. The basis for the under-delivery empty reservoir detection algorithm may be the difference between the total target volume, V target , and the measured volume, V measured . This difference may be defined as the total trajectory error, V error : 
         V   error   =V   target   −V   pumped   [EQ #191]
 
     The under delivery empty reservoir metric therefore may be: 
     
       
         
           
             
               
                 
                   
                     Φ 
                     empty 
                   
                   = 
                   
                     { 
                     
                       
                         
                           1 
                         
                         
                           
                             
                               V 
                               error 
                             
                             &gt; 
                             
                               V 
                               threshold 
                             
                           
                         
                       
                       
                         
                           0 
                         
                         
                           otherwise 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     192 
                   
                   ] 
                 
               
             
           
         
       
     
     In some embodiments, additional conditions are not placed on this metric for alarming. The pump system  2900  may alarm in this way if the reservoir  2918  is emptying while a bolus is in progress and hence, no maximum volume reduction may be possible. In some embodiments, the pump system  2900  may also/rather alarm in this way when the ability of the pump chamber  2916  is reduced faster than the maximum volume reduction algorithm may reduce the maximum volume. 
     Acoustic Leak and Bubble Detection 
     In some embodiments of the pump system  2900 , the delivery controller may include an algorithm for detecting acoustic leaks and resonant air bubbles in the volume measurement chamber  2920 . The detection algorithm may be based on the premise that the volume measurement sensor damping ratio for the second-order resonance may, in some embodiments, remain substantially constant during all the sine-sweeps of an individual delivery. 
     In some embodiments, therefore, the comparison of the model fit calculated damping ratios in the pumped and un-pumped states may be used as a metric for the detection of, for example, gross acoustic leaks or large air bubbles. This metric may be separate from the absolute check on damping ratio performed, in some embodiments, as a volume measurement sensor level integrity check. 
     In some embodiments, the method for detecting acoustic leaks and bubbles in the volume measurement chamber  2920  may include the following steps. First, define the maximum and minimum damping ratios from a single set of sine sweep data: 
     
       
         
           
             
               
                 
                   
                     
                       ζ 
                       max 
                     
                     = 
                     
                       max 
                       ⁢ 
                          
                       
                         ( 
                         
                           
                             ζ 
                             1 
                           
                           , 
                           
                             ζ 
                             2 
                           
                           , 
                           
                             ζ 
                             3 
                           
                         
                         ) 
                       
                     
                   
                   ⁢ 
                   
 
                   
                     
                       ζ 
                       min 
                     
                     = 
                     
                       min 
                       ⁢ 
                          
                       
                         ( 
                         
                           
                             ζ 
                             1 
                           
                           , 
                           
                             ζ 
                             2 
                           
                           , 
                           
                             ζ 
                             3 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     193 
                   
                   ] 
                 
               
             
           
         
       
     
     The differential damping metric may then be defined as the percent difference between these two values: 
     
       
         
           
             
               
                 
                   
                     S 
                     diffDamp 
                   
                   = 
                   
                     100 
                     * 
                     
                       
                         
                           ζ 
                           min 
                         
                         - 
                         
                           ζ 
                           max 
                         
                       
                       
                         
                           ζ 
                           min 
                         
                         + 
                         
                           ζ 
                           max 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     194 
                   
                   ] 
                 
               
             
           
         
       
     
     And the differential damping acoustic leak indicator may be set as a threshold on this value: 
     
       
         
           
             
               
                 
                   
                     Φ 
                     diffDamp 
                   
                   = 
                   
                     { 
                     
                       
                         
                           
                             
                               1 
                               ⁢ 
                                   
                               if 
                               ⁢ 
                                   
                               
                                 S 
                                 diffDamp 
                               
                             
                             &gt; 
                             
                               T 
                               diffDamp 
                             
                           
                         
                       
                       
                         
                           
                             0 
                             ⁢ 
                                 
                             otherwise 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     195 
                   
                   ] 
                 
               
             
           
         
       
     
     As differentiated from the occlusion and empty reservoir indicators, described above, a differential damping indicator may be, in some embodiments, sufficient to trigger an acoustic leak alarm and thus the differential damping indicator may always, in some embodiments, result in an acoustic leak alarm. 
     The thresholds for this metric may be based entirely on experimental evidence. In some embodiments, a very conservative threshold of, e.g., a ten percent difference between the damping ratios of any two sine sweeps from a single delivery may be set, or T diffDamp =5. However, in various embodiments, the threshold may be higher or lower. 
     Leak Detection 
     In some embodiments, the delivery controller may check for leaking fluid leaking out of the volume measurement chamber  2920  either, for example, but not limited to, upstream past the measurement valve  2940  or downstream past the measurement valve  2940 . It may be beneficial for many reasons to perform checks and detect leaks as, for example, leaks may generate issues both during a delivery and between delivery if residual volume leaks out of the volume measurement chamber  2920 . Thus, in some embodiments, two different leak tests may be performed by the pump system  2900 , including, but not limited to, an inter-delivery leak test to check for leaks during a delivery and an intra-delivery leak test to check for loss of residual volume between deliveries. 
     The intra-delivery leak test may be performed, in some embodiments, when the volume measurement chamber  2920  is full of fluid. A first volume measurement may be taken after the pump plunger  2902  has been actuated. The fluid may be left in the volume measurement chamber  2920  for a fixed period of time, e.g., 1 second, and then a second volume measurement may be taken. In some embodiments, in general, these two volume measurements should be the same. Thus, any difference between these measurements, that is, above the expected measurement noise, which, in some embodiments, may be approximately 1 nL, may generally be attributed to a leaking valve. The intra-delivery leak test, in some embodiments, may be performed during each delivery, i.e., each basal or bolus delivery, however, in various embodiments, the intra-delivery test may be performed more, or less, often. 
     The inter-delivery leak test, in some embodiments, may be performed when the measurement chamber  2920  is empty except for the normally generally small amount of residual volume that may persist in the chamber between deliveries. For the inter-delivery leak test, the last volume estimate of the previous delivery is compared to the first volume estimate of the new delivery. As in the case of the intra-delivery leak test, these measurements should generally be the same. The expected measurement noise, in some embodiments, may be marginally higher than in the case of the intra-delivery leak test. Still, any volume change outside this expected noise floor may also generally be attributed to a leaking valve. The inter-delivery leak test may be performed before each basal delivery. In some embodiments, the intra-delivery test may not be performed during a bolus delivery because there is a minimal delay between consecutive deliveries. However, in some embodiments, the intra-delivery test may be performed during a bolus delivery. 
     Generalized Leak Algorithm 
     A similar algorithm may be used to detect both inter and intra delivery leaks. The basis for the detection algorithms is the leaked volume defined as the difference between the consecutive volume estimates: 
         v   leak   =v   avs,2   −v   avs,1   [EQ #196]
 
     This leaked volume may be integrated over consecutive deliveries using a leaky integrator. In this case, the metric for leak detection, S leak , will be defined as follows. 
         S   leak =γ leak   S   leak   +v   leak   [EQ #197]
 
     where γ leak &lt;1.0 is the rate of decay. The leak detection logic is then: 
     
       
         
           
             
               
                 
                   
                     Φ 
                     
                       ℓ 
                       ⁢ 
                       eak 
                     
                   
                   = 
                   
                     { 
                     
                       
                         
                           
                             
                               1 
                               ⁢ 
                                   
                               if 
                               ⁢ 
                                   
                               
                                 S 
                                 
                                   ℓ 
                                   ⁢ 
                                   eak 
                                 
                               
                             
                             &gt; 
                             
                               T 
                               
                                 ℓ 
                                 ⁢ 
                                 eak 
                               
                             
                           
                         
                       
                       
                         
                           
                             0 
                             ⁢ 
                                 
                             otherwise 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     198 
                   
                   ] 
                 
               
             
           
         
       
     
     In some embodiments, the leak thresholds for the inter-delivery leak algorithm may be set whereby the measured leaked volume is the volume that was over-delivered in the case of a leaking measurement valve. In the case of a leaking measurement chamber inlet valve  2906 , there may be no over-delivery but, in some embodiments, the leak measurement may not differentiate between this and a measurement valve leak. In the case of an inter-delivery leak, in some embodiments, the potential over-delivery will generally be bounded by the amount of residual volume. 
     In some embodiments, the intra-leak detection threshold may be set by taking into account that the actual leaked volume may be greater than the volume measured during the leak test. In some embodiments, the leak test may be performed/completed over a short interval, for example, approximately 1 second, but where the fluid is pressurized in the volume measurement chamber  2920  for a longer period of time, this may allow for additional volume to leak out. 
     Exit Valve Fail Detection 
     In some embodiments, as described above, the pump system  2900  includes a measurement valve  2940  which maintains the fluid in the measurement chamber  2920  unless and until the measurement has been completed by the volume measurement sensor. Thus, in some embodiments, it may be beneficial to determine if a leak is present in the measurement valve  2940 , i.e., where fluid is leaking from the volume measurement chamber  2920  prior to the completion of the volume measurement, thus, detecting possibly inaccurate volume measurements as soon as they occur. The measurement valve  2940  fail detection metric, in some embodiments, compares the expected outcome of an actuation to the observed outcome. In the event of a full measurement valve  2940  failure, for example, the volume pumped may appear to be near zero, as the fluid exits nearly as fast or as fast as it is pumped into the measurement chamber  2920 . Using a feed forward model estimate for the actuator response, in some embodiments, measurement valve  2940  failures may be guarded against in the following manner, where slope, m, and offset, b, are the actuator model: 
         v   buffer =3* v   target    
       δ threshold =( V   buffer   *m )+ b  
 
         V   threshold =0.1* v   target    
       Φ noMeasuredVolume   =v   pumped   &lt;v   threshold  
 
       Φ highControllerEfort =δ target &gt;δ threshold  
 
       Φ plungerSaturated =true if the plunger is saturated
 
     Note: both δ threshold  and v threshold  are limited to a reasonable range of values 
     
       
         
           
             
               
                 
                   
                     Φ 
                     exitValueFail 
                   
                   = 
                   
                     { 
                     
                       
                         
                           
                             1 
                             ⁢ 
                                 
                             if 
                             ⁢ 
                                 
                             
                               Φ 
                               noMeasuredVolume 
                             
                             ⁢ 
                                 
                             and 
                             ⁢ 
                                 
                             either 
                             ⁢ 
                                
                             
                               ( 
                               
                                 
                                   Φ 
                                   highControllerEffort 
                                 
                                 ⁢ 
                                     
                                 or 
                                 ⁢ 
                                     
                                 
                                   Φ 
                                   plungerSaturated 
                                 
                               
                               ) 
                             
                           
                         
                       
                       
                         
                           
                             0 
                             ⁢ 
                                 
                             otherwise 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     EQ 
                     ⁢ 
                     # 
                     ⁢ 
                         
                     199 
                   
                   ] 
                 
               
             
           
         
       
     
     Thus, in some embodiments, following this method, where the delivery controller commands an actuation that the current model predicts should result in three times the target volume pumped, but where the volume observed to be pumped is less than a tenth of the targeted pumped volume, then in some embodiments, a measurement valve  2940  failure may be assumed and an alarm may be posted. 
     In some embodiments, the intra-leak method assumes that a leak is continuous. However, discontinuous leaks, i.e., where this assumption would not hold true, may occur. Thus, in some embodiments, to detect a leak of this type, the local relationship between the target pump plunger  2902  position commanded and the subsequent volume pumped may be monitored. An indication of a discontinuous leak may be that a change in the target position does not necessarily correspond to a change in the volume pumped. Thus, if the relationship between the target position of the plunger and the volume pumped becomes uncorrelated, a discontinuous leak may be suspected by the pump system  2900 . Referring now also to  FIG.  164   , in these cases, in some embodiments, a double pump plunger  2902  stroke delivery may be performed. If the measurement valve  2940  is operating normally, a second actuation of the pump plunger  2902  would result in additional volume measured in the measurement chamber  2920 . However, if the measurement valve  2940  performs like a pressure relief valve, the additional pumped volume is expected to leak discontinuously and the volume in the measurement chamber  2920  may remain substantially unchanged. In some embodiments, while performing a discontinuous leak check, the pump plunger  2902  position change targeted for each of the two strokes may be one that should, during regular pump system  2900  function, result in one-half the targeted volume pumped for each stroke, based on the current actuator model. 
     In some embodiments, in addition to the various safety-checks performed by the command processor  2924 , there are a set of secondary checks performed by the supervisor processor  2926 . In some embodiments, the supervisor processor  2926  may control the power to the pump system  2900  so the active participation of both processors  2924 ,  2926  is needed for the pump system  2900  to deliver fluid. The supervisor processor  2926  may provide oversight at a number of different levels and, in some embodiments, may not turn on power to the pump system  2900  unless all of the integrity checks pass. Some of the secondary checks performed by the supervisor processor  2926  may include, but are not limited to, one or more of the following. 
     In some embodiments, a therapy monitor on the supervisor processor  2926  may determine the volume and timing of fluid delivery independent of the command processor  2924 . Thus, in some embodiments, the supervisor processor  2926  may prevent the command processor  2924  from delivering fluid if both the timing and volume are not in agreement. 
     In some embodiments, the delivery monitor provides oversight of the volume measurement sensor using a redundant temperature sensor, redundant storage of the calibration parameter, and independent range-checking of the results and back-calculation of the volume measurement sensor model-fit errors. 
     In some embodiments, the delivery controller checks for failed switches (open or closed) and broken SMA, and also guards against simultaneous or out-of-sequence actuation of the pump plunger  2902  and measurement valve  2940 . The delivery controller may also limit the time the power is applied to SMA. In some embodiments, the delivery controller may independently track the target fluid volume and delivered fluid volume. In some embodiments, the delivery controller may post an alarm and prevent further delivery if it detects a substantial over or under delivery. 
     Verifying the integrity of a system or device prior to use is desirable. With respect to medical devices, the integrity of the system or device may be verified to, for example, but not limited to, ensure the safety of the user/patient. The detection of fault conditions is at least one method of verifying the integrity of the system or device. In many embodiments, detecting fault conditions at start-up is desirable to avoid downstream errors and failures while the medical device is delivering therapy or otherwise medically serving a user or patient. 
     Some embodiments of the infusion device methods and systems will be described below with reference to an exemplary embodiment. The exemplary embodiment is described with respect to a medical infusion pump, which in some embodiments may be an insulin pump, as shown and described in herein. Reference herein to a disposable may refer to, in some embodiments, the various embodiments of the disposable housing assembly and/or reservoir portion of the infusion pump described herein. 
     Although the term “start-up test” may be used herein, the systems and methods described herein may be used at any time. However, in many embodiments, the systems and methods are used at start-up as well as at various other times during the use of the medical device. These include, but are not limited to, when various faults are detected by the system during operation. The start-up test may be beneficial for many reasons, including but not limited to, identifying defective or faulty disposables prior to their use in administering a medical therapy, and/or detecting a fault condition with a medical device that is in ongoing use. Thus, the start-up test may increase the safety of medical devices. 
     In some embodiments of the method and system, the method and system may be used to determine whether a disposable housing assembly has faults prior to use for delivering therapy. Thus, in some embodiments, the start-up test/procedure/method may be performed each time a disposable housing assembly is attached to a reusable housing assembly. The faults may include, but are not limited to, one or more of the following: disposable leaks, disposable valve malfunction, disposable reservoir malfunction, and/or pump/reusable/disposable malfunction. In some embodiments of the systems and methods, where the integrity of the disposable is not verified for two sequential disposable housing assemblies, the lack of integrity of the reusable pump may be confirmed/assumed. In some embodiments, the system may indicate that a new pump/reusable may be recommended, and once another reusable is attached to a disposable, the start-up test may be repeated on a disposable, which may include, repeating the start-up test on one or more previously failed disposable housing assemblies. In some embodiments, this method may be used to consistently verify the integrity of the pump. 
     Referring now to  FIGS.  165 - 166   , in some embodiments, after a priming function has been completed, which may be performed for many reasons, including, but not limited to, initial priming of a new disposable housing assembly and/or priming after disconnect of a tubing set  2922  from a cannula. However, in any case, once a priming function has been completed, and before a cannula is attached to administer therapeutic medications, the system may, in some embodiments, perform a verification of the measurement valve  2940  integrity. This may be completed by actuating the pump plunger  2902  to deliver a threshold volume of fluid. This may be done by actuating the pump plunger  2902  with increasingly longer ontime, taking a volume measurements sensor  2946  measurement, and following, determining the volume pumped, and if the volume pumped is less than a threshold volume, actuating the pump plunger  2902  again using an increasingly longer ontime. However, where the pump system  2900 , after repeating this process, reaches the maximum ontime (which, in some embodiments, is a preprogrammed time) and has not reached the threshold volume, i.e., pumped more than the minimum for a measurement valve  2908 ,  2940  failure detection but less than the minimum to pass the start-up test. Thus, in these circumstances, in some embodiments, the pump system  2900  may conclude that the pump plunger  2902  SMA actuator  2910  and the reservoir may be faulty. 
     With respect to measurement valve  2908 ,  2940  integrity, there are many benefits to confirming the integrity prior to administering therapy to a user/patient. These benefits include, but are not limited to, preventing over delivery. Thus, confirming the integrity of the pump system  2900  prior to administering therapy to a user/patient, safety of the system may be maintained. 
     With respect to the increasing ontime, in various embodiments using ontime to control the delivery of the medical fluid, this may be performed to verify a measurement valve  2940  failure versus a pump plunger  2902 /pump plunger SMA actuator  2910  failure. The maximum ontime, in some embodiments, may be determined using many variables, including, but not limited to, the ontime that a reasonable pump plunger  2902 /pump plunger SMA actuator  2910  requires to actuate. Thus, where the system is experiencing the maximum ontime and there is no volume measured by the volume measurement sensor assembly  2946 , i.e., the volume measured is less than the measurement valve  2908 ,  2940  failure detection threshold, than it may be determined and/or confirmed that the measurement valve  2940 ,  2908  may have failed. 
     In some embodiments, however, the pump may be functioning, however, is weakened. Thus, in some embodiments, this differentiation may be confirmed by removing the disposable housing assembly, and attaching a new/another disposable housing assembly. Where the same results are repeated, it may be determined and/or confirmed that the pump plunger  2902  and/or pump plunger SMA actuator  2910  is weak and may be replaced. In some embodiments, the controller may recommend the reusable housing assembly of the pump system  2900  be replaced. In some embodiments, the controller may include a safety system that prevents the continued use of the reusable housing assembly that has been determined to be weak, thus, ensuring the potentially failed reusable housing assembly is not reused. 
     Additionally, where the system is confirming whether the pump is weak or the disposable is faulty, replacing the disposable with a new disposable may also confirm whether the reservoir  2918  in the first disposable housing assembly included a faulty reservoir which may indicate for example, but not limited, one or more of the following: that the reservoir valve  2904  is not functioning properly, e.g., is not able to be opened, i.e., is stuck in the closed position, and/or that the reservoir  2918  is not filled enough. Thus, where a fault is found with one disposable housing assembly, in some embodiments, the pump system  2900  may require the user/patient to replace the disposable housing assembly with another disposable housing assembly. In some embodiments, where a fault is found with the second disposable housing assembly, the pump system  2900 , in some embodiments, may require another reusable housing assembly. Thus, in some embodiments, this system reduces the need of the system to determine whether the fault was caused by a leaking measurement valve  2940  or a faulty reservoir  2910  and/or faulty reservoir valve  2904 . In either case, the reusable housing assembly is replaced. However, the system and methods described herein ensure that a faulty reusable housing assembly is detected and confirmed prior to continued use for providing therapy to a user/patient. 
     In some embodiments, when the threshold volume has been met as determined by the volume measurement sensor assembly  2947 , in some embodiments, a leak test is performed. The threshold volume may be any volume preprogrammed into the system. In the exemplary embodiment, this volume may be 1 microliter, however, in other embodiments, the volume may be less than or greater than 1 microliter. The leak test, in some embodiments, includes holding the volume of fluid in the volume measurement chamber  2920  for a predetermined time, e.g., a number of seconds, which are preprogrammed/predetermined, and in the exemplary embodiments, may be approximately 2 to 5 seconds, however, in other embodiments, may be less than or greater than this time. The volume measurement sensor assembly  2947  then completes another volume measurement to determine whether any volume leaked from the volume measurement chamber  2920 . Thus, in some embodiments, this leak test may determine and/or detect a slow leak as opposed to a fast leak (which may be determined/detected as discussed above). 
     In some embodiments, once the leak test is completed, the pump system  2900  opens the measurement valve  2940  to empty the volume of fluid from the volume measurement chamber  2920 . In some embodiments, the pump system  2900  may alert the user/patient to shake the volume of fluid off the tubing set  2922  prior to connection to the cannula. 
     Following, in some embodiments, the system confirms the integrity of the battery, the volume measurement sensor assembly  2946 , and the temperature before signaling to the user/patient that they may connect to the device, i.e., connecting the tubing set  2922  to the cannula. Thus, the start-up test presents an opportunity for the pump system  2900  to perform a delivery, conform the integrity of the disposable housing assembly and the reusable housing assembly. Additionally, the pump system executes  2900  all of the standard run-time integrity tests, i.e., the integrity tests performed after each delivery in the normal course of the therapy, providing an opportunity to detect other failures before therapy has started. 
     Additionally, in some embodiments, prior to any start-up test, the pump system  2900  may alert and/or alarm the user/patient of the start-up test and that the user/patient should ensure they are not connected to the medical device. In some embodiments, a user interface and/or controller device (e.g., remote control assembly) may require the user/patient to verify that they are disconnected, and thus, this may contribute to increased safety and prevention of inadvertent and/or accidental over delivery/delivery. 
     The start-up test, in some embodiments, may provide an initial data point for modeling the ontime versus volume delivered (in embodiments where this system of pump control is used). Thus, in some embodiments, the final volume pumped into the volume measurement chamber  2920  may be determined and be used as an initial model data point. From this initial data point, the slope and offset for the ontime may be determined or estimated. Thus, although the slope and offset may be adjusted through the ongoing operation of the pump, the start-up test may present an initial slope and offset which is a more valuable and useful starting point for the estimator as compared with no initial data. This may improve the accuracy of the estimator and the accuracy of the initial deliveries of the pump. In various embodiments, for example, those described above and below where an ontime control system is not used, the start-up procedure and method may be used to provide the initial date point for the embodiment of the control system. 
     In some embodiments, the infusion pump may perform a start-up test each time the user changes the infusion set/tubing set  2922 . In some embodiments, the start-up test may be performed before the user connects the infusion set/tubing set  2922  to the cannula. This may be beneficial for many reasons, including but not limited to, detecting faults before there is any potential for over or under delivery to the user. Thus, in some embodiments, the start-up test may have one or more of the following benefits: detects measurement valve  2940  failures and may update the pump model to improve the start-up transient. In addition, the start-up method may also execute all of the standard run-time integrity tests which may provide an opportunity for the pump system  2900  to detect other failures before the fluid delivery/therapy has started. 
     In the exemplary embodiment, the start-up may accomplish many tasks, including, but not limited to, initializing the feed forward actuator model offset, initializing the target measurement valve  2040  position near minimum, and performing pump system  2900  integrity checks. In practice, the start-up method may be similar to a standard delivery but with a few key differences outlined in detail below. Referring now to  FIG.  167   , a schematic of one embodiment of the start-up test method is shown. The start-up method may be broken into three distinct phases, namely, a pumping phase, a leak check phase and a valving phase. The pumping phase includes collecting data for the pump plunger  2902  modeling by way of pump SMA actuator  2910  re-actuation. The leak check phase includes checking pumped volumes against expected values after pumping fluid into the measurement chamber  2920  and after a delay. The valving phase includes releasing the pumped fluid from the measurement chamber  2929  and the measurement valve  2908  actuation target position is set by way of re-actuation of the measurement valve SMA actuator  2908 . 
     Referring now also to  FIGS.  168 - 170   , where the pump plunger  2902  target position is plotted against the volume of fluid pumped to the volume measurement chamber  2920 , during a start-up, the pump plunger  2902  may be re-actuated multiple times without actuation of the measurement valve  2940 . At each re-actuation, the pump plunger  2902  target position change may be incremented. The size of this increment may vary based on the total volume that has already been pumped into the volume measurement chamber  2920  by previous re-actuations. 
     Initially, the goal of the start-up procedure is to accurately set the actuator model offset. In some embodiments, the target position may be initialized at a value which is low enough to ensure that the pump will not move fluid. The increment for re-actuation, δ 1 , in some embodiments, is set at a small value so that when the pump plunger  2902  moves from the dead band into its linear region, the first delivery will be small. In order to estimate the offset, based on this single first pumped volume, a default pump slope is assumed. The offset may be therefore: 
       δ offset =δ target   −m   default   v   pumped   [EQ #200]
 
     Where m default  is the default slope, δ target  is the target position change for the first pumped volume delivery, and v pumped  is the first pumped volume. The error in this estimate is directly proportional to the error in the slope, ε, and the size of v pumped . 
     
       
         
           
             
               
                 
                   
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     Referring to  FIG.  168   , thus, the smaller v pumped  is, the less susceptible the offset calculation is to deviation from the average slope, m default , used for the calculation. As such, the pumped volume limit for this phase, V 1 , is close to zero. Once an actuation has moved any fluid, an accurate offset may be calculated. The offset may be calculated for every actuation which results in a pumped volume less than V 1 , even those which move no fluid. In the event that no non-zero volumes are pumped which are less than V 1 , the last zero volume data point is used to determine the offset. This result may be within δ 1  of the actual offset. 
     Referring now to  FIG.  170   , after the first non-zero volume has been pumped and the initial pump offset calculated, the goal of re-actuation, in some embodiments, is to model the slope of the actuator using the least squares estimator described above. The increment of position change, δ 2 , in this phase is set so that multiple points may be collected for the regression analysis, therefore, improving the model. 
     Referring now to  FIG.  169   , as the volume measurement chamber  2920  fills with fluid, the dynamics of pumping may begin to change. Once a certain volume, V 2 , has been achieved, the pumped volume for a given pump plunger  2902  position change (i.e., pump plunger  2902  displacement) may no longer reflect the normal empty chamber actuator response. After this point, the actuator model may no longer be updated. The third position change increment for re-actuation, δ 3 , is based on the normal pump controls described above. The goal of this phase, in some embodiments, is to fill the volume measurement chamber  2920  to the minimum hold volume, V min,startup . 
     During the start-up procedure, integrity checks may also be completed in some embodiments. These may include, but are not limited to, one or more of the following. For example, if the pump target position reaches saturation, and the pumped volume remains close to zero, in some embodiments, the measurement valve  2940  is assumed to have failed in the open position. As may be determined from inspection, this is slightly different from the regular delivery for measurement valve  2940  failure because it is based solely on saturation rather than either saturation or the pump feed-forward model. 
     If the volume delivered to the volume measurement chamber  2920  for a pre-determined pump plunger  2902  position change, i.e., displacement, is substantially less than the expected volume, in some embodiments, it may be determined that the pump is experiencing a “weak pump” fault. 
     At the conclusion of the pump plunger  2902  actuation phase of the start-up test, the total volume pumped into the volume measurement chamber  2920  is determined. Where the minimum threshold for alarm is not met, the start-up procedure may conclude that both the measurement valve  2940  and the measurement chamber inlet check valve  2906  are functioning normally. 
     During start-up, the pump system  2900  tests for inter-delivery leaks using a similar procedure as performed for the run-time tests. In some embodiments, during the start-up procedure, after fluid has been pumped to the volume measurement chamber  2920  and a baseline “pumped” fluid measurement is taken/completed, a second measurement is taken after a fixed delay. If there is any volume change between these two measurements (outside the measurement noise), it may be concluded in some embodiments that it is likely due to fluid leaking past the measurement valve  2940  and/or the measurement chamber inlet check valve  2906 . The start-up test leak-check procedure, in some embodiments, is the same as the run-time leak detection, however, the test parameters, e.g., waiting time between measurements, leak alarm thresholds, may be different. 
     In some embodiments, as with the pump plunger  2902 , the measurement valve SMA  2912  is re-actuated multiple times during the start up test. In some embodiments, following each actuation, the volume in the volume measurement chamber  2920  may be compared to the volume in the volume measurement chamber  2920  before the pump plunger  2902  was actuated. In some embodiments, where there is still a residual volume in the volume measurement chamber  2920 , the measurement valve SMA  2910  may be re-actuated. In some embodiments, the measurement valve  2940  target position change may be incremented from its default value with each re-actuation. When an actuation results in the residual volume dropping to near zero, the re-actuations may be stopped, and, in some embodiments, the last targeted measurement valve  2920  position change becomes the new default position change for future deliveries. In some embodiments, this may be beneficial for one or more reasons, including, by making the increment small, a near minimum measurement valve  2920  target position may be achieved. This may be desirable in some embodiments, for many reasons, including, but not limited to, it reducing the strain on the measurement valve SMA  2912  for each actuation, which may potentially increase the SMA time to failure/shorten the “life” of the SMA. 
     In some embodiments, the start-up occlusion detection may be the same or similar to the run time occlusion detection as described above. However, in some embodiments, the start-up occlusion detection may not require the occlusion detection criteria to be met for consecutive deliveries before alarming. As discussed above, the occlusion detection criteria is that the volume delivered, as determined by the volume measurement sensor, is greater than some fraction of the volume pumped. 
     In some embodiments, for each measurement valve  2940  re-actuation of the start-up test, the measurement valve  2940  target position may be incremented. In some embodiments, when the start-up test is complete, the last targeted measurement valve  2940  position may become the starting target measurement valve  2940  position for the first subsequent run time delivery. 
     In some embodiments, rather than the infusion pump system including a volume measurement sensor assembly, the pump system may include one or more optical sensors used as a feedback measurement. For example, referring also to  FIGS.  171 - 172   , in some embodiments, rather than a delivered volume determination from a volume measurement sensor assembly (see  FIGS.  161 - 162   ), the volume delivered may be presumed/assumed from at least one pump plunger  2902  optical sensor input which may be correlated to a volume delivered based on a model of the pump assembly. In some embodiments, the pump assembly, which may be integrated into a reusable housing assembly, may be calibrated at manufacture, and therefore, a model of pump plunger  2902  displacement versus volume of fluid pumped, may be generated. In some embodiments, additional modeling may be completed with respect to disposable housing assemblies, thus, in some embodiments, each disposable housing assembly may be calibrated with a reusable housing assembly, and, in some embodiments, each disposable housing assembly may include, e.g., a calibration code, for example, which may either be input manually into e.g., a remote control assembly and/or read by the reusable housing assembly and/or remote control assembly, for example, using an RFID reader and writer and/or a bar code scanner. In some embodiments, each reusable housing assembly may include one or more disposable housing assemblies that have been calibrated with the reusable housing assembly. In some embodiments, each disposable housing assembly may be calibrated at manufacture. 
     The code, in some embodiments, may indicate the model for the controller to follow. Thus, variations in disposable housing assemblies may be input into the controller and pump predictive model; therefore, the model may be substantially accurate with respect to predicting an assumed volume delivered. 
     However, in some embodiments of the infusion pump system, a series of one or more models may be established. For example, in some embodiments, for each disposable housing assembly, a code, or indication of the model, may be assigned based on a calibration procedure at manufacture. In these embodiments, therefore, each disposable housing assembly may not be explicitly calibrated to a specific reusable housing assembly, however, the calibration procedure may fit the disposable housing assembly into a category or code that most closely represents the expected performance based on the calibration procedure. 
     Thus, in some embodiments of these embodiments of the infusion pump system, the displacement of the pump plunger  2902 , as discussed above, may follow a trajectory. The at least one optical sensor may determine the actual displacement of the pump plunger  2902  and the volume delivered may be assumed/predicted based on a model. In various embodiments, the pump plunger  2902  may include one or more optical sensors to determine the displacement of the pump plunger  2902 . Examples of the optical sensors and the placement of these optical sensors may include those described above with respect to  FIGS.  145 - 149 B   
     In some embodiments, variations in the disposable housing assembly, for example, SMA wire actuation and membrane spring back/return to starting position following pump, etc., may be accounted for in a predictive model. Thus, in some embodiments, the number of actuations of the pump plunger  2902  may translate to a variation in the feed forward term to compensate for a change in the prediction of the ADC counts to pump plunger  2902  displacement. In some embodiments, the SMA wire may vary upon use, and/or the membrane of the pump chamber  2916  may vary upon use, and therefore, the assumed volume of fluid pumped from the reservoir  2918  for a pump plunge  2902  displacement may vary with the number of pump actuations. In some embodiments, as the volume in the reservoir is depleted, the expected volume delivered for ADC count may vary, and therefore, the volume in the reservoir at the start of the pump may be factored into the one or more models. 
     In some embodiments, the actual displacement of the pump plunge  2902  upon actuation may vary from the trajectory. The volume controller may feed back the actual pump plunger  2902  displacement information, sensed by the at least one optical sensor. The difference between the displacement requested and the actual displacement may be fed into one or more of the upcoming deliveries, therefore, compensating for a displacement error. 
     Thus, the displacement of the pump plunger  2902  may, in some embodiments, essentially be translated into an assumed/presumed volume delivery. Using the at least one optical sensor, the actual displacement of the pump plunger  2902  for each actuation of the pump plunger  2902  may be determined. The displacement may be fed back to the target pump plunger  2902  displacement, and the volume controller may determine whether and how to compensate for the actual displacement, if determined necessary. In some embodiments, as discussed above, the pump plunger  2902  displacement, and in some embodiments, taken together with the number of actuations of the pump plunger  2902  for a given disposable housing assembly, as well as the reservoir volume, may determine the volume delivered based on a model. 
     In some embodiments, whether and how to compensate for the determined actual displacement of the pump plunger  2902  may depend on one or more factors. These may include the size of the difference, whether the difference may indicate an over delivery or an under delivery, the number of consecutive actual displacement readings that may show error, etc. Thus, in some embodiments, a threshold error may be required prior to the controller adjusting the displacement trajectory. 
     In some embodiments of these embodiments of the infusion pump system, the system may include additional optical sensors to sense the movement of valves. For example, in some embodiments, the pump system may include at least one optical sensor to sense the movement of the reservoir valve  2904  and/or a pump chamber exit valve  2906 , which may be similar to the valves described and shown above, for example, with respect to  FIG.  150   . The pump chamber exit valve  2906  may function in a similar manner to the volume measurement chamber valve  2906 , only the pump chamber exit valve  2906 , once opened, may allow fluid to flow from the pump chamber  2916  to the tubing set  2922 . Thus, as discussed above, in these embodiments, the volume measurement sensor assembly  2946 , together with the measurement valve, may be removed from the pump system  2900 . 
     Thus, in these embodiments, confirmation of the valves  2904 ,  2906  opening and closing may confirm fluid was pumped from the reservoir  2918  and fluid was pumped out of the pump chamber  2916  and to the tubing set  2922 . Following, where the optical sensors do not sense the opening and/or closing of one or more valves, the system may post an alarm. However, as discussed above with respect to various alarms posted to the system, in some embodiments, the alarms may be posted after a threshold is met. For example, in some embodiments, an alarm may be posted if the optical sensor determines that two consecutive pump plunger  2902  actuations occurred and two consecutive errors were detected on one or more of the valves  2904 ,  2906 . 
     As discussed above with respect to the at least one optical sensor for the pump plunger  2902 , in some embodiments, greater than one optical sensor may be used to collect sensor input from redundant optical sensors. In some embodiments, for example, as shown in  FIG.  147   , the two optical sensors for the pump plunger  2902  may be located in two different locations in the pump system  2900  thereby collecting sensor data from two different angles which may provide, in some embodiments, a more developed determination of the pump plunger  2902  displacement. 
     In some embodiments, the two or more optical sensors may be used for redundancy and also, to determine whether one of the optical sensors may have an error. Thus, in some embodiments, upon collection of optical sensor data from two or more optical sensors, the system may, comparing the two sets of data, determine that one of the sensors may have an error as the data points vary more than a preset threshold. However, in some embodiments, where the optical sensor data collected by the at least one optical sensor is so far away from the expected value, i.e., exceeds one or more thresholds, the system may post an alarm and conclude the at least one optical sensor has failed and/or is in error. 
     In various embodiments, the various membranes in the disposable housing assembly, including, but not limited to, the membrane assembly and the reservoir membrane, may include a coating, for example, in some embodiments, the coating may be parylene and the membrane may be SANTOPRENE, a thermoplastic elastomer made by ExxonMobil Corporation, Irving, Tex., U.S.A. However, in various other embodiments, the coating may vary and may include any form of parylene, for example, or other coating materials. In various embodiments parylene C may be used. In various embodiments, the parylene coating may be 3 microns in thickness, however in some embodiments the parylene coating may be 1 micron thick and in some embodiments, the reservoir membrane may include a different thickness of coating than the fluid pathway membrane. In some embodiments, the reservoir membrane may include a 3 micron thickness parylene coating and the fluid pathway membranes may include a 1 micron parylene coating. In carious embodiments, the thickness of the parylene may vary and may be less than 1 micron and/or greater than 3 microns. 
     In some embodiments, the coating may be applied using a tumble method, and in various embodiments, the membranes are coated on both sides (i.e., the fluid side and the dry side/non fluid side of the membrane). In various embodiments, various methods may be used to apply the coating to the membrane. 
     In various embodiments, the reservoir in the disposable housing assembly may be a 3 cc volume reservoir. However, in other embodiments, the volume of the reservoir may be less than or greater than 3 cc. 
     Referring now also to  FIGS.  173 A and  173 B , in some embodiments, the parylene coating of the membrane may change the durometer of the membrane material and therefore, in some embodiments, the reservoir membrane may be designed to compensate for this change. In some embodiments, the reservoir membrane  4000  may be “inverted”, that is, may be biased such that it collapses onto the bottom of the reservoir. In these embodiments, the reservoir membrane  4000  includes a perimeter seal  4002  (which in some embodiments may be a bead seal) that allows for the assembly of the reservoir membrane  4000  such that two plates may “pinch seal” the reservoir membrane  4000 . 
     In various embodiments, the reservoir membrane  4000  may also include a septum  4004 . In various embodiments, the septum  4004  may be made from SANTOPRENE and may be parylene coated. The septum  4004 , in these embodiments, is configured such that the septum  4004  is substantially rounded, thus, when the disposable housing assembly is assembled (which, in some embodiments, may include laser welding) the septum  4004  may be pushed into a mating hole that is smaller than the septum  4004  diameter, thus, placing a compression force on the septum  4004 . In addition, in some embodiments, there is axial compression. This compression may seal the septum  4004 . In some embodiments, this configuration of the septum  4004  may be desirable when using a parylene coating as the parylene may make the septum more difficult to seal. In these embodiments of the septum  4004 , the septum  4004  is configured such that the filling needle (e.g., a needle used to fill the reservoir with fluid) enters the septum  4004  at approximately a 45 degree angle. 
     In various embodiments, the reservoir membrane  4000  may include a bump feature  4008  approximate to the septum  4004  location. The bump feature  4008  may be shaped as shown, or may be a different shape. The bump feature  4008  may prevent and/or reduce the likelihood of accidental/unintentional piercing of the membrane  4000  by the filling needle which may reduce the likelihood of leaks in the reservoir. The bump feature  4008  may, in some embodiments, also serve as an air trap such that the filling needle may remove air after filling the reservoir to a desired volume with fluid. 
     Referring now also to  FIGS.  174 A- 174 D , in some embodiments the reservoir membrane  4000  may include one or more features that minimize and/or reduce and/or remove positive pressure from being exerted onto the contents of the reservoir. In some embodiments, one or more notches may be introduced onto the reservoir membrane  4000 . Referring now to  FIG.  174 D , showing the sectional view of  FIG.  174 A  taken at “A”, is an enlarged view of the section “C” shown in  FIG.  174 B , the notches  4010 ,  4012 ,  4014  essentially “weaken” the elastomeric properties of the reservoir membrane  4000  and these features allow the reservoir membrane  4000  to unfold completely or substantially completely when the reservoir is filled to capacity. The notches  4010 ,  4012 ,  4014  may also lessen the force on the fluid at these points. Thus, in some embodiments, the one or more notches may be located at one or more points where the force is greatest and/or in some embodiments, may be located to reduce the force to a maximum threshold amount. In various embodiments, the number, size and or location of the notches may vary. 
     In some embodiments the reservoir membrane  4000  may include features that reduce the dead volume of the reservoir such that air and/or fluid are not trapped in the reservoir. Referring now to  FIG.  174 C , which is an enlarged sectional view of section “B” in  FIG.  174 B  (which is a cross sectional view of  FIG.  174 A  taken at “A”). In some embodiments, a feature  4016  may be included and in some embodiments, the feature  4016  may be located near the septum  4004 . In some embodiments, this feature is configured to ensure air is not “stuck” in the corner of the reservoir. In various embodiments, the features  4016  may be configured differently and/or located differently. 
     Referring now to  FIG.  175   , another embodiment of the actuator assembly  4018  is shown. In this embodiment, the crimp assembly  4020 , which anchors the shape memory alloy wires  4022 ,  4024  may include post assemblies  4026 ,  4028 . In some embodiments, the crimp assembly  4020  may include glue to anchor the memory shape alloy wires  4022 ,  4024  to the crimp assembly  4020 . In some embodiments, glue may be advantageous for many reasons, including, but not limited to, limiting the thermal change of the shape memory alloy wires  4022 ,  4024  (i.e., serving as a thermal heat sink) and/or may serve as an additional mechanical attachment and/or may provide strain relief. In various embodiments, glue of various durometers may be selected to aid in strain relief. In some embodiments, the post assemblies  4026 ,  4028  may be used with and/or without glue at the crimp assembly  4020 . In some embodiments, the post assemblies  4026 ,  4028  may be advantageous, for example, for they maintain the shape memory alloy wires  4022 ,  4024  and prevent and/or minimize and/or reduce lateral rotation and/or angular deflection. 
     Referring now to  FIGS.  176 A and  176 B , another embodiment of the actuator assembly  4030  is shown. In this embodiment, the crimp assembly  4032 , which anchors the shape memory alloy wires  4036 ,  4038  may include dove tail assembly  4034 . In some embodiments, the crimp assembly  4032  may include glue to anchor the memory shape alloy wires  4036 ,  4038  to the crimp assembly  4032 . In some embodiments, the glue may be applied over the crimp assembly  4032  and over the shape memory alloy wires  4036 ,  4038  connection to the crimp assembly  4032 . In some embodiments, glue may be advantageous for many reasons, including, but not limited to, limiting the thermal change of the shape memory alloy wires  4036 ,  4038  and/or may serve as an additional mechanical attachment and/or may provide strain relief. In various embodiments, glue of various durometers may be selected to aid in strain relief. In some embodiments, the dove tail assembly  4034  may be used with and/or without glue at the crimp assembly  4032 . In some embodiments, the dove tail assembly  4034  may be advantageous, for example, for it maintains the shape memory alloy wires  4036 ,  4038  and allows for lateral rotation and/or angular deflection. 
     Referring now to  FIGS.  177 A and  177 B , a partial rendition of another embodiment of the actuator assembly  4046  is shown. In this embodiment, a hook  4040  is added to the crimp assembly  4048 . As the actuator assembly  4046  rotates, the hook  4040  rotates and therefore, the shape memory alloy wires  4042 ,  4044  receive reduced/minimum bending stress. In some embodiments of this embodiment, the crimp assembly  4048  may be used with glue and/or without glue. 
     Referring now to  FIGS.  178 A and  178 B , a partial rendition of another embodiment of the actuator assembly  4050  is shown. In this embodiment, a hook  4052  is added to the actuator assembly  4050 . The shape memory alloy wire  4054  forms a single wire that wraps around a hook  4052 . In some embodiments, the hook  4052  may be shaped differently and may include, for example, a holder to hold the shape memory alloy wire  4054 . In some embodiments of this embodiment, the hook  4052  may be used with glue and/or without glue, and in some embodiments, the shape memory alloy wire  4054  may be glued approximately at the entire contact point between the shape memory alloy wire  4054  and the hook  4052 . In some embodiments, the shape memory alloy wire  4054  may be glued at the entire contact point between the shape memory alloy wire  4054  and the actuator assembly  4050 . In some embodiments, the glue may not be applied as extensively. 
     Referring now to  FIGS.  179 A and  179 B , a partial rendition of another embodiment of the actuator assembly  4056  is shown. In this embodiment, a hook  4058  is added to the actuator assembly  4056 . The shape memory alloy wire  4060 ,  4062  includes either two single strands or a strand that may wrap around the anchor. The shape memory alloy wire  4060 ,  4062  connects to connectors  4064 ,  4068 . Connectors  4064 ,  4068  also connect to a strand of non-shape memory alloy wire  4060 , which, in some embodiments, may be a strand of KEVLAR wire, or an electrically conductive wire. The strand of non-shape memory alloy wire  4060  wraps around the hook  4058 . In some embodiments, the hook  4058  may be shaped differently and may include, for example, a holder to hold the non-shape memory alloy wire  4060 . In some embodiments of this embodiment, the hook  4058  may be used with glue and/or without glue, and in some embodiments, the non-shape memory alloy wire  4060  may be glued approximately at the entire contact point between the non-shape memory alloy wire  4060  and the hook  4058 . In some embodiments, the non-shape memory alloy wire  4060  may be glued at the entire contact point between the non-shape memory alloy wire  4060  and the actuator assembly  4056 . In some embodiments, the glue may not be applied as extensively. In these embodiments, the bend and flex would occur on the non-shape memory alloy wire  4060 . In various embodiments described above, there is an electrical connection between the connectors shown. In some embodiments, an electrically conductive wire may be included. 
     Referring now also to  FIG.  180   , another embodiment of the dove tail crimp embodiment is shown. 
     Referring now also to  FIGS.  241 A and  241 B , another embodiment of the shape memory alloy  7016  and the actuator assembly  4056  are shown. In this embodiment, the shape memory alloy includes a crimp  7018  rather than, for example, an electrical contact. Thus, in this embodiment, a single shape memory alloy  7016  wire is used that is crimped, which mechanically fastens the shape memory alloy  7016  to the actuator assembly  4056 . 
     In some embodiments, the actuator assembly  4056  may include additional material in various sections to impart additional stiffness to the actuator assembly  4056 . This may be beneficial/desirable for many reasons, including, but not limited to, reducing the distance that the shape memory alloy wire travels. 
     In various embodiments, a torsion spring may be included in the actuator assembly. In some embodiments, the actuator assembly may include a pocket for the torsion spring, therefore, stopping the torsion spring during its upward position, therefore, the torsion spring, at this position, does not apply force to the actuator assembly, including the shape memory alloy. 
     In some embodiments, the actuator assembly may be made from plastic. In other embodiments, the actuator assembly may be made from metal and in these embodiments may serve as a heat sink. In the embodiments where the non-shape memory alloy wire or the shape memory alloy wire wraps around a hook, in some of these embodiments, the wire may wrap more than once around the hook. In some embodiments, the crimp may be an inline crimp and may float in space, where one piece of shape-memory alloy wire is attached to the crimp and a second, non-shape memory alloy wire is attached to the crimp. In some embodiments, the second, non-shape memory alloy wire may be a shape-memory alloy wire that has been “deactivated” such that the actuation properties of the shape memory alloy wire are no longer present in the wire. In some embodiments, the non-shape memory alloy wire may be KEVLAR or platinum, for example, but other materials may be used. In some embodiments, one shape-memory alloy wire may be used to pull the plunger pump down and one shape-memory alloy wire may be used to pull the plunger pump up. In some embodiments, the shape-memory alloy wire (and/or the non-shape memory alloy wire) may be potted, for example, in some embodiments by using glue, to the electrical contacts. 
     Referring now to  FIGS.  181 - 184   , various embodiments of the configuration of the measurement valve and the shape memory alloy configurations are shown. 
     Referring now to  FIGS.  242  and  243   , views of the measurement valve assembly  7020  are shown. The plunger assembly includes an optical flag  7022 , and the bell crank assembly  7026  includes an optical flag  7024 . In various embodiments, one or both of these optical flag  7022 ,  7024  may be monitored, however, in some embodiments, one of these optical flags  7022 ,  7024  are monitored. For example, in some embodiments, the optical flag  7022  may be monitored therefore monitoring the movement of the plunger  7032 . In this embodiment of the bell crank  7026 , two arms  7028 ,  7030  that lift the plunger  7032 . 
     Referring now to  FIGS.  185 A and  185 B , one embodiment of a packaging for the disposable housing assembly  4072  is shown. In some embodiments of this embodiment, the housing  4070  includes formed areas for the disposable housing assembly  4072 , fill adapter  4076  and the tubing assembly (tubing and cannula contact assembly)  4074 , which, in various embodiments, is bonded to the disposable housing assembly  4072 . In various embodiments, the housing  4070  is made from PET (polyethylene terephthalate). In some embodiments, the housing  4070  may be formed using other materials. In some embodiments, the housing  4070  may be formed using thermoforming, and, in some embodiment, using thermoforming with vacuum assist. In some embodiments, plug assist may also be used. In various other embodiments, the housing  4070  may be formed using other techniques. In various embodiments the packaging may be designed to accommodate the disposable housing assembly  4072  and/or the disposable housing assembly attached to a fill adapter  4076 , as well as the tubing assembly  7074 . The housing  4070  may therefore include compartments  4078 ,  4080  to accommodate the various disposables. In various embodiments, once the disposable housing assembly  4072  and the cannula assembly  4074  are loaded into the housing  4070 , a cover (not shown) is placed onto the housing  4070 . In some embodiments, the cover may be made from TYVEK, in other embodiments; the cover may be made from another material. In various embodiments, the cover removably bonds to the housing  4070  and provides a barrier to maintain sterility inside the housing  4070 . 
     Referring now to  FIGS.  186 A and  186 B , another embodiment of a disposable packaging is shown. In some embodiments of this embodiment, the housing  4086  includes formed areas  4082 ,  4084  for the disposable housing assembly  4072 , fill adapter  4076  and the tubing assembly (tubing and cannula contact assembly)  4074 , which, in various embodiments, is bonded to the disposable housing assembly  4072 . In various embodiments, the housing  4086  may be made from PET (polyethylene terephthalate). In some embodiments, the housing  4086  may be formed using other materials. In some embodiments, the housing  4086  may be formed using thermoforming, and, in some embodiment, using thermoforming with vacuum assist. In some embodiments, plug assist may also be used. In various other embodiments, the housing  4086  may be formed using other techniques. In various embodiments the packaging may be designed to accommodate the disposable housing assembly  4072  and/or the disposable housing assembly attached to a fill adapter  4076 , as well as the tubing assembly  7074 . The housing  4086  may therefore include compartments  4082 ,  4084  to accommodate the various disposables. In various embodiments, once the disposable housing assembly  4072  and the cannula assembly  4074  are loaded into the housing  4086 , a cover (not shown) is placed onto the housing  4086 . In some embodiments, the cover may be made from TYVEK, in other embodiments; the cover may be made from another material. In various embodiments, the cover removably bonds to the housing  4086  and provides a barrier to maintain sterility inside the housing  4086 . As shown in  FIG.  186 B , in some embodiments, the housing  4086  may include features in the compartments, for example, in compartment  4084 , that provide additional functionality to the housing  4086 . For example, in  FIG.  186 B , the compartment  4084  in the housing  4086  functions to maintain the fill adapter  4076  in a position that may be beneficial/desirable for filling the disposable housing assembly  4072  reservoir. 
     In various embodiments, the shape of the housing of the packaging may vary. Some embodiments may include additional compartments and or features to accommodate additional disposables, which may include, but are not limited to, a filling syringe and/or a filling syringe and a filling needle. 
     Referring now to  FIGS.  187 A- 187 J , various views of another embodiment of disposable packing are shown. In these embodiments, a cover assembly  4088  may be included that is configured to mateably attach to the base assembly  4090  in a removable fashion and may be made from the same material as the base assembly  4090 . However, in various other embodiments, the cover may be different from that shown in  FIGS.  187 A- 187 J  and may be made from TYVEK, in other embodiments; the cover may be made from another material. In various embodiments of this embodiment, the cover may removably bond to the base assembly  4090  and provide a barrier to maintain sterility inside the base assembly  4090 . In various embodiments, the base assembly  4090  is configured to receive the disposable assembly  4092 , which, in various embodiments, may include a disposable housing assembly  4094 , a fill adapter  4096  and a cannula assembly  4098 . 
     In some embodiments of this embodiment, the base assembly  4090  and the cover assembly  4088  include formed areas that are configured to receive the disposable housing assembly  4094 , fill adapter  4096  and the tubing assembly (tubing and cannula contact assembly)  4098 , which, in various embodiments, is bonded to the disposable housing assembly  4094 . In various embodiments, the base assembly  4090  and cover assembly  4088  may be made from PET (polyethylene terephthalate). In some embodiments, the base assembly  4090  and cover assembly  4088  may be formed using other materials. In some embodiments, the base assembly  4090  and cover assembly  4088  may be formed using thermoforming, and, in some embodiment, using thermoforming with vacuum assist. In some embodiments, plug assist may also be used. In various other embodiments, the base assembly  4090  and cover assembly  4088  may be formed using other techniques. 
     In various embodiments the packaging may be designed to accommodate the disposable housing assembly  4094  and/or the disposable housing assembly attached to a fill adapter  4096 , as well as the cannula assembly  4098 . The packaging may therefore include various compartments and features to accommodate the various disposables. In various embodiments, once the disposable housing assembly  4094  and the cannula assembly  4098  are loaded into the base assembly  4090 , the cover assembly  4088  is placed onto the base assembly  4090 . In some embodiments, the cover assembly  4088  may include a TYVEK cover. In some embodiments the cover assembly  4088  may be made from the same material as the base assembly  4090  or, of a different material. In various embodiments, the cover assembly  4088  removably attaches and/or mates to the base assembly  4090  and, together with the TYVEX, provides a barrier to maintain sterility inside the base assembly  4090 . 
     As shown in  FIGS.  187 A- 187 J , in some embodiments, the base assembly  4090  and the cover assembly  4088  may include various features in the compartments, which may provide additional functionality to the base assembly  4090  and the cover assembly  4088 . For example, as shown in  FIG.  187 B , the compartment in the base assembly  4090  functions to maintain the fill adapter  4096  in a position that may be beneficial/desirable for filling the disposable housing assembly  4094  reservoir. In some embodiments, the compartment features maintain the fill adapter  4096  and disposable housing assembly  4094  at a 45 degree angle for filling the reservoir in the disposable housing assembly  4094 . In various embodiments of the cover assembly  4088 , compartments may be included to assist in maintaining the position of the fill adapter  4096  inside the base assembly  4090 . In some embodiments, the cover assembly  4088  may include a well or other to accommodate the cannula connector during priming of the disposable housing assembly  4094 . 
     In various embodiments, the base assembly  4090  may be configured to be self standing and this may be desirable/advantageous for many reason, including, but not limited to, the filling of the disposable housing assembly  4094  may be accomplished by a user using one hand, the packaging itself provides for a sterile work surface and maintains the disposable housing assembly  4094  inside the sterile work surface while filling to reduce/avoid contamination. 
     In some embodiments, the packaging may include user instructions for use wrapped around the outside of the packaging. In some embodiments, the shape and dimensions of the packaging may vary. Some embodiments may include additional compartments and or features to accommodate additional disposables or other devices, which may include, but are not limited to, a filling syringe and/or a filling syringe and a filling needle. 
     Many medical devices are subject to an ethylene oxide (EO) sterilization process to kill potentially harmful pathogens prior to use on or in a human or other animal. The process involves placing the parts to be sterilized in a chamber and subjecting them to phases of vacuum, humidification, heat and EO gas. The EO gas permeates through the packaging materials and comes in contact with the component&#39;s/device&#39;s surface(s). However, the EO gas also permeates and is absorbed by the materials during this process. Due to the volatility of EO, it is harmful to human tissue/biological processes and may have harmful interaction with substances, e.g. drugs, that come into contact with the components (e.g. insulin or other therapeutics), thus, the EO gas must be sufficiently removed from the sterilized parts before they may be used. 
     EO removal may be done using, for example, one of the following two processes. One includes using several vacuum cycles at the end of the sterilization cycle to purge the airspace of EO. Another is where the sterilized components are subject to an “aeration” process whereby the parts may be quarantined for a period of time that has been shown to provide sufficiently low levels of EO and EO variant “residues” (hereby referred to simply as “EO”) exhausting from the components/devices. The vacuum cycle is effective in removing residual EO from the airspace and likely drawing some EO out of materials. During aeration, the EO residuals come out of the sterilized materials by diffusion. The EO is gaseous in nature, so the molecules must make their way to the surface of the component/device and then exhaust into the atmosphere. This process may take hours to days to weeks depending upon the EO dosing and material properties (which may include, but are not limited to, one or more of the following: affinity to absorb/hold onto the EO). Below is described a process to expedite the aeration process to allow sterilized components/devices to be used sooner and to better ensure that the components/devices are sufficiently aerated and EO residues are low enough to be considered safe for general human/animal use and/or drug interaction. 
     Many factors may affect the amount of time elapsed before a sufficiently low EO residual level is reached, these may include, but are not limited to, material used, temperature and packaging. With respect to material, the material density may play a role, thus, a more dense plastic may absorb less EO than, for example, rubber, but less dense rubber may more quickly release the EO/variants as compared with a plastic. With respect to temperature, temperature directly affects the rate of diffusion and raising the temperature raises the energy level of the gas molecules making them more mobile to exhaust from the material. With respect to packaging, on many cases, sterilized components reside in packages that allow them to be handled which indicates that, in many cases, there is an inherent barrier to prevent de-sterilization. In some instances, packaging may include a non-permeable barrier, for example, a plastic sheet and/or shell, and a removable semi-permeable barrier, for example, TYVEK. This packaging may also be enclosed in other packaging, for example, for shipment, such as cardboard boxes or multiple boxes. EO may readily penetrate the packaging during the sterilization process in part because of the motive vacuum force used at the onset of the process to actively move the EO particles into all airspace within the chamber. The EO then permeates the component material as it dwells due to the nature of diffusion (for example, particles move from a higher density volume into a lower density volume). During the vacuum flush cycles, any air born EO may be evacuated from the air space and the vacuum may draw an amount of absorbed gas from the component/device materials. During aeration, the higher concentration of the EO gas in the materials diffuses out into the lower EO concentration air space around the components, eventually making its way out of the packaging and into the atmosphere. 
     In some embodiments, for any device/component configuration or material, an impediment to driving EO levels down quickly may be the packaging. Diffusion rate for any gas is maximized when the density of molecules in the reference space (i.e., where the dense molecules are headed) is kept low. Diffusion acts to homogenize the density of gas in a volume and the large the gradient (density discrepancy) the more quickly the volume of higher density will reduce. In some cases, the aeration takes place in a well ventilated volume, for example, a room or chamber with moving air/ventilation, but the packaging acts to trap exhausted EO and reduce the diffusion gradient. There are often multiple trapped volumes around the sterilized components including the product packaging and one or more bulk packaging containers, for example, cardboard boxes. This results, in many cases, in the EO having to not only diffuse out of the sterilized parts, but the packaging itself. The produce packaging is unavoidable, but the bulk packing boxes act to block convection offered by the ventilated volume around the packaging. 
     In some embodiments, to decrease the EO levels more quickly, ventilating the sterilizer bulk packaging may allow convection to increase the EO gradient. Convection, in some embodiments, may inherently assist with equalization of the temperature throughout the packaging more efficiently since there may be less insulated airspace. In some embodiments, this process/method may include, but is not limited to, one or more of the following: 
     In some embodiments, a sterilizer bulk package may be used that contains individually packed components to be sterilized. A sterilizer bulk package containing slots, holes, mesh, etc., to provide a containment structure that may be ventilated form the space within the bulk pack to the atmosphere in the chamber/room where the aeration is taking place. A sterilizer bulk package may be disposable or reusable. In some embodiments, place the sterilizer bulk package into a standard cardboard box for shipping after aeration. Next, transfer the individually paced components to a standard cardboard box for shipping after aeration. The sterilizer bulk package may, in some embodiments, contain features that leave airspace between the individually packed components (i.e., spacer) to promote airflow around all sides of the components/devices/parts. 
     Sterilizer bulk package, in some embodiments, may incorporate features to mate the packaging directly to a duct that pushes air through the packaging. In some embodiments, this may include modification of a typical aeration chamber to duct air through the parts directly, in addition to moving through the airspace around the packaging. 
     The sterilizer bulk pack may, in some embodiments, contain a built in fan or multiple fans for increasing convection directly within the box. In some embodiments, this may be used with respect to a reusable device/pack/component. 
     The sterilizer bulk pack may contain, in some embodiments, elements to locally apply heat to the parts and expedite the process. This could be combined, in some embodiments, with direct convection within the box to increase the efficiently of the heating process. In some embodiments, this may be used with respect to a reusable device/pack/component. 
     While the process/methods described herein may be applicable to anything that is EO sterilized, in some embodiments, the process/methods may be used in critical applications where the residual EO levels must be significantly lower than what it considered “safe” for a human, for example, devices that come into contact with infused drugs that will be infused into a human, which may include, but is not limited to, insulin. Insulin and other drugs containing amino acid chains are highly sensitive to EO and exposure results in conversion of therapeutic molecules into non-therapeutic or perhaps harmful molecules. The residual EO levels in some cases may be required to be less than 1 part per million (PPM) in order to avoid having a significant impact on the drug potency. Driving the EO residual concentration down into the 1 PPM range implies the impact of the EO gradient (i.e., airspace must be &lt;&lt;1 PPM to maximize the diffusion potential). 
     Referring now also to  FIG.  188   , in some embodiments, it may be desirable to, rather than the pump architecture described and shown herein, include a pump architecture that includes two pumps and the pumps include inverted pump mechanisms. Therefore, rather than the pump actuator actuating in a manner such that the pump chamber gets smaller, the pump actuator starts in the down position, i.e., the pump actuator is in the pump chamber. When pumping fluid from the reservoir is desired, in this configuration, the plunger pump is pulled up, out of the pump chamber, and therefore, if there is air in the pump chamber, there is zero volume remaining in the pump chamber at the end of the pump stroke and the air will be pumped past the 1 way valve. In addition, in this configuration, the AVS/measurement chamber does not store pressure when performing the reading, therefore, the first/beginning and second/end reading are performed at the same pressure. Thus, if there is air in the measurement chamber, because the first and second readings are performed at the same pressure, the air is not compressed and therefore, the readings will be accurate despite the air present in the measurement chamber, the air is not part of the calculation. In some embodiments, there is a second inverted pump actuator/pump mechanism downstream the AVS/measurement chamber. 
     In various embodiments, a reverse pumping sequence may be used as the pump architecture. Thus, rather than having the Pump Piston and Reservoir Valve “normally open”, the two components could be “normally closed”. With the Pump Piston bottomed out in the Pump Chamber, the variable volume delivered to the AVS chamber/measurement chamber may drawn in from the Reservoir and be fully delivered on each Pump stroke, which affords the opportunity for maximum hydraulic force on each stroke. Air would not accumulate in the chamber because there would be minimal residual volume in the Pump Chamber between strokes and the Pump Piston would be in continuous contact with the Pump Chamber Membrane, thus minimizing the air interface with the membrane and the effect of air permeation through the membrane. 
     This could be implemented in several ways including but not limited to, one or more of the following: 
     System 1: Single Actuator, Active Pump/Active Valve 
     In some embodiments, this system would be essentially the same as the embodiments described above, but the mechanism may be designed to operate in reverse. 
     System 2: Dual Actuator, Active Pump/Active Valve 
     In some embodiments, this system would require separating the common articulating mechanism that drives the Pump and Valve pistons into just a Pump Piston/bellcrank and would require a second Reservoir Valve/bellcrank. It would also require adding an additional shape-memory alloy/NITINOL actuator to move the independent Reservoir Valve bellcrank/piston. This method would impart a lower load on the existing Pump NITINOL for actuating the Pump Piston alone. 
     System 3: Single Actuator, Active Pump/Passive Valve 
     In some embodiments, this system may involve removing the entire existing Reservoir Valve actuator functionality from the reusable Pump and placing this functionality in the Disposable Base. As with system 2, the common articulating mechanism that drives the Pump and Valve pistons would be separated into just a Pump Piston/bellcrank and the existing shape-memory allow/NITINOL actuator would drive the Pump Piston. The valve function may become a passive check valve that is part of the disposable Vase. Because the Reservoir must be open when there is a vacuum in the Pump Chamber (in order to draw fluid from the Reservoir) this functionality cannot be implemented in the reusable Pump, as is done with the AVS check valve. 
     Some aspects of this passive check-valve concept:
         Positive pressure in the Pump Chamber may close the valve.   Negative pressure in the Pump Chamber may open the valve.   The valve may be biased normally closed to lessen the chance of reduced efficiency from the valve leaking during small volume/low rate strokes.   The flow restriction when the valve is may be minimized to reduce the fill time of the Pump Chamber.       

     An example of an implementation of this system is shown in  FIGS.  189 A- 189 C . 
     In some embodiments, an o-ring seal may be added to the inlet valve as an additional sealing method to prevent ingress of fluid, from the reservoir, from entering the pump chamber. In some embodiments, the o-ring seal may be made from SANTOPRENE or another material and in some embodiments, the SANTOPRENE may not include a parylene coating. In some embodiments, the SANTOPRENE does include a parylene coating. 
     In some embodiments, silicone oil, or another type of oil or hydrophobic compound, may be added to the fluid lines in the disposable housing assembly at manufacture. In some embodiments, the silicone oil may enhance air bubble removal, where air bubbles develop in the fluid lines. 
     Tubing Connection to Disposable Housing Assembly 
     Referring now also to  FIG.  190   , in some embodiments, the disposable housing assembly  5000 , which may include any of the various embodiments of the disposable housing assembly described herein, may, rather than a cannula (or tubing) assembly attached to the exit, include a luer connector  5002 . In some embodiments, this may be advantageous for the luer connector  5002  may attach to any number of cannula assemblies/tubing assemblies by a standard connector  5004 . 
     In some embodiments, the disposable housing assembly  5000  may be configured such that tubing, which, in some embodiments may be connected to a cannula assembly, may be introduced directly into the exit. In some embodiments, the tubing may be fastened with adhesive or another mechanism. However, in some embodiments, the tubing may be inserted and the reusable housing assembly, together with the disposable housing assembly, may maintain the tubing connected to the disposable housing assembly and maintain the tubing communication with the fluid path in the disposable housing assembly. In various other embodiments, the tubing may be inserted with an overmold that snaps into the exit. In some embodiments, the tubing may be inserted with an overmold that glues or otherwise adheres to the exit. 
     Referring now to  FIG.  198   , a disposable housing assembly  6000  which, in various embodiments, may include any of the various embodiments of the disposable housing assembly  6000  described herein is shown with tubing  6002  that has been inserted into the exit of the disposable housing assembly  6000 . In some embodiments, the disposable housing assembly  6000  includes a tapered exit, tapered in either direction. In some embodiments, the disposable housing assembly  6000  exit includes a compliant seal  6006 , which, in some embodiments, may be a face seal or radial seal. Thus, in some embodiments, the tapered entry and the compliant seal  6006  form a tubing  6002  interface in the disposable housing assembly  6000 . In some embodiments, the tubing  6002  slides into the compliant seal  6006 . Referring also to  FIG.  48   , in some embodiments, the tubing interface may be located in the base portion of the disposable housing assembly, however, in some embodiments, the tubing interface may be located between the base portion of the disposable housing assembly and the fluid pathway cover. 
     Referring now also to  FIGS.  55 A- 56 C , the reusable housing assembly is shown and, when rotated about the disposable housing assembly and connected to the disposable housing assembly, a nub  808 , having a spring actuated tab  2980 , on the locking ring assembly catches the tubing and pushes the tubing into a recess in the disposable housing assembly. In some embodiments, before the reusable housing assembly is rotated about the disposable housing assembly, there may include sufficient friction between the disposable housing assembly and the tubing to maintain the position of the tubing. 
     In various embodiments, the disposable housing assembly includes a tube recess that may be configured to maintain the tubing such that kinking is prevented and/or minimized. This may be desirable for many reasons, including, but not limited to, prevention and/or minimizing occlusions/restricted flow within the tubing. 
     In various embodiments, once the reusable housing assembly is rotated about the disposable housing assembly, the tubing is locked in position and therefore, a force on the tubing, for example, where the tubing is being pulled in a direction opposite the disposable housing assembly, may not dislodge and/or separate the tubing from being fluidly connected to the fluid path. 
     In various embodiments, the seal, which, as discussed above, may include a face seal, may form a hydraulic seal between the fluid path of the disposable housing assembly and the inner lumen of the tubing. 
     Referring now also to  FIG.  199    and  FIG.  136   , in some embodiments, a plug  6008  or an at least partially compliant part may be connected to the tubing  6002 . In some embodiments, the plug  6008  may be overmolded onto the tubing  6002 . In some embodiments, the plug  6008  may be inserted into the exit of the disposable housing assembly  6000  which, in some embodiments, may include a mating recess. A face seal may be formed between the tubing/plug and the fluid path in the disposable housing assembly  6000 . When the reusable housing assembly  6004  is connected to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000  a nub, having a spring actuated tab  2980 , on the locking ring assembly pushes down and secures the plug in place. As described above in greater detail, in some embodiments, the locking ring assembly may include a tab  2980  which includes a spring loaded plunger that may apply a load to the plug. Displacement of the plug when the tab pushes on the plug reinforces the hydraulic seal between the fluid path in the disposable housing assembly and the inner lumen of the tubing. 
     In some embodiments, the plug  6008  may include a rigid plate or rigid part and/or a portion of the plug  6008  may be rigid, which may, in some embodiments, distribute the loading across the compliant plug when the tab exerts force onto the plug  6008 . In some embodiments, there may be a feature between the disposable housing assembly  6000  and the rigid portion of the plug  6008  to hold the plug  6008  in place before the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 . 
     Referring now also to  FIG.  200 A  and  FIG.  200 B  in some embodiments, a rigid plug  6008  may be connected to the tubing  6002 . In some embodiments, the plug  6008  may be overmolded onto the tubing  6002 . In some embodiments, the plug  6008  may be adhered to the tubing  6002 , e.g., glued to the tubing  6002 . In some embodiments, the plug  6008  may be inserted into the exit of the disposable housing assembly  6000  which, in some embodiments, may include a mating recess. In some embodiments, the plug  6008  may be inserted through the top of the “tab” on the disposable housing assembly  6000 . An o-ring seal  6006  may be located between the plug  6008  and the base portion of the disposable housing assembly  6000 . A face seal or radial seal may be formed between the tubing/plug and the fluid path in the disposable housing assembly  6000 . When the reusable housing assembly  6004  is connected to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000  a nub, having a spring actuated tab  2980 , on the locking ring assembly pushes down and secures the plug in place. Thus, in this embodiment, the plug  6008  is attached to the disposable housing assembly  6000  from the top, but the tubing  6002  will be connected into the exit of the disposable housing assembly  6000 . As described above in greater detail, in some embodiments, the locking ring assembly may include a tab  2980  which includes a spring loaded plunger that may apply a load to the plug. Displacement of the plug when the tab pushes on the plug reinforces the hydraulic seal between the fluid path in the disposable housing assembly and the inner lumen of the tubing. 
     In some embodiments, there may be a feature between the disposable housing assembly  6000  and the rigid plug  6008  to hold the plug  6008  in place before the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 . 
     Referring now also to  FIGS.  201 A and  201 B , in some embodiments, a connector  6010  may be attached to the tubing  6002 . In various embodiments of various embodiments of the connector  6010 , the tubing  6002  may be connected to a cannula assembly (not shown). In some embodiments, the connector  6010  may be configured for both handling by a user and for interaction with the disposable housing assembly  6000 . In some embodiments, as shown in  FIGS.  201 A and  201 B , the connector  6010  may be “butterfly” shaped. In some embodiments, the connector  6010  is rigid and/or partially rigid and is overmolded onto the tubing  6002 . The connector  6010  may include a plug portion and a tab or wing portion. However, in some embodiments, the disposable housing assembly includes the tab or wing portion. The connector  6010  mates with the exit of the disposable housing assembly  6000 , e.g., in some embodiments, the plug portion of the connector  6010  is inserted into the disposable housing portion  6000  exit. In some embodiments, a compliant component may be located on the connector  6010 , however in other embodiments, the compliant component  6006 , e.g., a seal, may be in the disposable housing portion  6000 . When the connector  6010  is connected to the disposable housing component  6000 , the compliant component  6006  forms a hydraulic seal e.g., radial seal or face-seal. In some embodiments, the connector  6010  may bend and flip, i.e., butterfly, relative to the disposable housing assembly  6000  and, in some embodiments; the connector  6010  may include one or more features that connect the connector  6010  to the disposable housing assembly  6000 . For example, in the butterfly embodiment, the wings of the butterfly may snap onto the disposable housing assembly  6000 . In some embodiments, the wings of the butterfly and/or the connector  6010  may be adhesively connected to the disposable housing assembly  6000 . In some embodiments, one side of the butterfly connector may include an adhesive strip with an adhesive covering. Before bending and flipping the wings, the adhesive covering may be removed. The wings may then be bent such that they adhere to the disposable housing assembly  6000 . 
     When the reusable housing assembly  6004  is connected to the disposable housing assembly  6000  by being rotated about the disposable housing assembly a nub, having a spring actuated tab  2980 , on the locking ring assembly pushes down and secures the plug in place. As described above in greater detail, in some embodiments, the locking ring assembly may include a tab  2980  which includes a spring loaded plunger that may apply a load to the plug portion of the connector. In some embodiments, displacement of the plug when the tab pushes on the plug reinforces the hydraulic seal between the fluid path in the disposable housing assembly and the inner lumen of the tubing. 
     Referring now also to  FIG.  202   , in some embodiments, a connector  6010  may be attached to the tubing  6002 . In some embodiments, the connector  6010  may be configured for both handling by a user and for interaction with the disposable housing assembly  6000 . In some embodiments, as shown in  FIG.  202   , the connector  6010  may be “L” shaped. However, in other embodiments, the shape of the connector  6010  may vary, shapes include, but are not limited to, “T” shapes, “L” shapes, and others as well as variations of “L” and “T” shapes. In some embodiments, the connector  6010  is rigid and/or partially rigid and is overmolded onto the tubing  6002 . In some embodiments, the tubing  6002  is adhered to the connector  6010 , e.g., the tubing  6002  may be glued to an opening in the connector  6010 . In some embodiments, the connector  6010  may include a plug portion and a tab or wing portion. The connector  6010  mates with the exit of the disposable housing assembly  6000 , e.g., in some embodiments, the plug portion of the connector  6010  is inserted into the disposable housing portion  6000  exit. In some embodiments, a compliant component  6006  may be located on the connector  6010 , however in other embodiments, the compliant component  6006 , e.g., a seal, may be in the disposable housing portion  6000 . When the connector  6010  is connected to the disposable housing assembly  6000 , the compliant component  6006  forms a hydraulic seal e.g., radial seal or face-seal. In some embodiments, the connector  6010  may be rotated relative to the disposable housing assembly  6000  and, in some embodiments; the connector  6010  may include one or more features that connect the connector  6010  to the disposable housing assembly  6000 . For example, in the “L” shape embodiment, the bottom part of the “L” may snap onto the disposable housing assembly  6000 . In some embodiments, the connector  6010  may be adhesively connected to the disposable housing assembly  6000 . Connecting the connector  6010  to the disposable housing assembly  6000  prior to the connection of the reusable housing assembly  6004  to the disposable housing assembly  6000  may be desirable for maintaining the position of the connector  6010  during filling and priming of the disposable housing assembly  6000 . Once the connector  6010  is connected to the disposable housing assembly  6000 , the tubing  6002  is fluidly connected to the fluid pathway in the disposable housing assembly  6000  through the connector  6010 . 
     When the reusable housing assembly  6004  is connected to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000  a nub, having a spring actuated tab  2980 , on the locking ring assembly pushes down and secures the plug in place. As described above in greater detail, in some embodiments, the locking ring assembly may include a tab  2980  which includes a spring loaded plunger that may apply a load to the connector. Displacement of the plug when the tab pushes on the connector  6010  reinforces the hydraulic seal between the fluid path in the disposable housing assembly  6000  and the inner lumen of the tubing  6002 . 
     Referring now also to  FIGS.  203 A and  203 B , in some embodiments, a rigid plug  6008  may be connected to the tubing  6002 . In some embodiments, the plug  6008  may be overmolded onto the tubing  6002 . In some embodiments, the plug  6008  may be adhered to and/or glued to the tubing  6002 , however, in various embodiments; any mechanism for attaching the plug  6008  to the tubing  6002  may be used. In some embodiments, the plug  6008  may be inserted into the exit of the disposable housing assembly  6000  which, in some embodiments, may include a mating recess. A compliant face-seal or radial seal (seal  6008 ) may be located between the plug  6008  and the base portion of the disposable housing assembly  6000  or between the base portion and the fluid pathway of the disposable housing assembly  6000 . A face seal or radial seal may be formed between the tubing/plug and the fluid path in the disposable housing assembly. In some embodiments, a complaint face-seal or radial seal may be located on the rigid plug. As shown in  FIG.  203 A , in some embodiments, the locking ring assembly may include a tab with a slot  6012 . When the reusable housing assembly  6004  is connected to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000  the slot  6012  in the tab goes around the tubing but captures the plug on the tubing. In some embodiments, the locking ring assembly may include a cam-like feature between the tab and the locking ring and the plug to compress/secure the plug. In these embodiments, the tubing may be maintained in place and the hydraulic seal may be reinforced. 
     In some embodiments, there may be a feature between the disposable housing assembly  6000  and the rigid plug  6008  to hold the plug  6008  in place before the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 . In some embodiments, a snap-like feature is included between the disposable housing assembly and the plug  6008  to hold the plug  6008  in place before the reusable housing assembly  6004  is connected to the disposable housing assembly  6000 . In other embodiments, the feature may include, but is not limited to, adhesive, catches, snaps, loops, hooks, and any other feature that maintains the connector on the disposable housing assembly before the reusable housing assembly  6000  is connected. 
     In various embodiments, an embodiment of a connector may be used. These embodiments may include one or more of the various embodiments discussed above with respect to connectors. However, below, various embodiments of connectors are discussed. The descriptions of these embodiments are not limiting, each may additionally include one or more features described above with respect to connectors. Additionally, in various embodiments, one or more features from one or more embodiments may be combined with one or more features from one or more different embodiments, to form additional embodiments. 
     Referring now also to  FIGS.  204 A,  204 B and  204 C , in some embodiments, a rigid push and rotate connector  6010  may be used. In some embodiments, the location of the exit may be modified to be located on the opposite side of the disposable housing assembly “tab”. In some embodiments, the shape of the connector  6010  may be similar to that of the surface adjacent to the exit of the disposable housing assembly (“tab”), however, in various other embodiments, the shape of the connector  6010  may be any shape. In some embodiments, the connector  6010  is attached to the tubing  6002  by adhering the connector  6010  to the tubing  6002 , e.g., gluing, or overmolding the connector to the tubing. In various embodiments, the connector  6010  may include a plug portion and a top portion connected to the plug portion. 
     In various embodiments, a compliant component  6006  is either attached to the connector  6010  or located in the disposable housing assembly  6000 . The compliant component  6006  forms a face or radial seal when the connector  6010  is mated/connected to the disposable housing assembly  6000 . In various embodiments, the disposable housing assembly  6000  includes a taper or snap interface for the connector  6010 . 
     In various embodiments, the plug  6008  of the connector  6010  is inserted into the disposable housing assembly  6000  with the tab  6018  portion pointing upward. Once the plug  6008  portion is inside the disposable housing assembly  6000 , the tab  6018  portion may be rotated to rest above the disposable housing portion  6000  adjacent to the exit (i.e., adjacent to the “tab portion” on the disposable housing assembly). In some embodiments, mating locking features  6016 ,  6020  ( 6020  not shown) may be included on the tab  6018  portion of the connector  6010  and the disposable housing assembly  6000  such that the connector  6010  is held in place before the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 . In some embodiments, the mating locking features  6016 ,  60120  may include, but are not limited to, snap buttons and/or catch features. In some embodiments, a hook or other feature may be located on the opposite end of the tab  6018  portion of the connector  6010  such that it loops over the end of the tab  6018  portion of the disposable housing assembly  6000  and maintains the position of the connector  6010 . 
     When the reusable housing assembly  6004  is connected to the disposable housing assembly  6000 , by being rotated about the disposable housing assembly  6000 , a nub, having a spring actuated tab  2980 , on the locking ring assembly pushes down and secures the connector  6010  to the disposable housing assembly  6000 . 
     In some embodiments, the connector  6010  may include a feature for example, a finger relief  6022 , for removing the connector  6010  from the disposable housing assembly  6000 . In some embodiments, translation of force on the finger relief  6022  in a direction away from the disposable housing assembly  6000  releases the connector  6010  latching and allows for rotation of the connector  6010  away from the disposable housing assembly  6000 . 
     In the various embodiments, the connector is shown attached to a tubing. In various embodiments, the other end of the tubing may be attached to a cannula. In some embodiments, the tubing may be removably attached to the connector by attachment using a standard or other luer connection. However, in some embodiments, the tubing may be non-removably attached to the connector. In some embodiments, the connector may be attached to the disposable housing assembly and the tubing may then be attached to the connector while the connector is attached to the disposable housing assembly. In some embodiments, including exemplary embodiments shown and described herein, the tubing may be bonded or attached to the connector and the connector is then attached to the disposable housing assembly. In some embodiments, a user may attach the tubing to the connector, however, in other embodiments, the tubing may be attached during manufacture, and the user attaches the connector to the disposable housing assembly. 
     The connector may be any shape, including, but not limited to, the shape shown in herein. In various embodiments, the connector may be various shapes and sizes and may include one or more of the features 
     Referring now also to  FIG.  205   , in various embodiments, the tubing  6002  may be connected to the various embodiments of the connector  6010  or plug  6008  using glue  6024  or adhesive. In various embodiments, the connector  6010  and/or plug  6008  may include an opening configured to receive the tubing  6002 . In various embodiments, the opening in the connector  6010  may include a taper to maintain a minimum bend radius with respect to the tubing  6002 . An example of an opening on a connector  6010  is shown in  FIG.  205   . This configuration may be desirable and beneficial for many reasons, including but not limited to, minimizing and/or preventing kinking of the tubing and or minimizing and/or preventing occlusions/flow restrictions in the tubing. 
     Referring now also to  FIGS.  206 - 210   , another embodiment of a connector is shown. In some embodiments, the connector includes a tab  6018  and a plug  6008 . Tubing  6002  is connected to the connector  6010 . In some embodiments, the other end of the tubing  6002  is connected to a cannula  6026 . This embodiment is shown in  FIG.  207   . Referring now also to  FIG.  208   , the plug  6008  may be any of the embodiments shown and described herein. Other plug embodiments are also contemplated. The plug  6008  is inserted into the exit  6028  of the disposable housing assembly  6000 . In some embodiments, the disposable housing assembly  6000  may include an interlocking feature, disposable housing assembly interlocking feature  6020 , that mates with an interlocking feature, connector interlocking feature  6016 , on the connector  6010 . Upon insertion of the plug  6008  and rotation of the connector  6010 , the interlocking features  6016 ,  6020  may mate and removably lock and/or attach. In some embodiments, once the plug  6008  is inserted and the connector  6010  rotated, the connector  6010  may not be removed unless and until the connector  6010  is rotated. In some embodiments, the connector  6010  may have additional locking/interlocking features and or different interlocking features than those shown herein. 
     Once the reusable housing assembly is rotated about the disposable housing assembly and connected to the disposable housing assembly, the connector, in this embodiment, will be unable to be removed from the disposable housing assembly as the connector will be prevented from rotating by the nub, having a spring actuated tab  2980 , in the locking ring assembly of the reusable housing assembly. 
     In various embodiments, the connector includes a plug and in some embodiments, the connector is a plug  6008 . Various embodiments of the plug  6008  are described with reference to  FIGS.  211 - 217   . Referring now also to  FIG.  211 - 217   , these embodiments of the plug are shown as examples of various embodiments that may be used with any of the embodiments of the connector shown and/or described herein. Further, embodiments contemplated include any connector that may accomplish that which is described herein. Any of these embodiments of the connector may include one or more of the embodiments of the plug shown and/or described herein. 
     Referring to  FIG.  211   , an embodiment of a plug  6008  is shown with an embodiment of an exit  6028  to the disposable housing assembly. In some embodiments, the plug may include a luer-type feature which may, in some embodiments, be modified with a latch mechanism. In these embodiments, the plug  6008  may be made from rigid material. In some embodiments, the plug  6008  may include a shallow taper having shallow clearance. 
     Referring now to  FIG.  212   , in some embodiments, the disposable housing assembly  6000  may include a needle fixture  6032 . In these embodiments, the plug  6008  may include a captured septum  6034 . In these features, additional compliant materials, e.g., seals, may not be desired in the disposable housing assembly  6000 , as discussed in various embodiments above. However, in some embodiments, the use of seals, as described in above-embodiments, may be used. 
     Referring now to  FIG.  213   , in some embodiments, the plug  6008  may be an elastomeric material with one or more integrated o-rings  6036 . In some embodiments of this embodiment of the plug  6008 , the plug  6008  may be overmolded, solvent bonded or adhesively bonded to the tubing. In some embodiments, the plug  6008  may be made from polyurethane, however, in other embodiments; the plug  6008  may be made from other materials. In some embodiments, the plug  6008  may be glued and/or adhered to the tubing. In some embodiments, the plug  6008  may be overmolded to the tubing  6002 . 
     Referring now to  FIG.  214   , in some embodiments, the disposable housing assembly may include a tapered exit  6028 . In some embodiments, the plug  6008  may include a tapered feature. In some embodiments, the plug  6008  may be made from polyurethane, however, in other embodiments; the plug  6008  may be made from other materials. In some embodiments, the plug  6008  may be glued and/or adhered to the tubing. In some embodiments, the plug  6008  may be overmolded to the tubing. 
     Referring now to  FIG.  215   , in some embodiments, the disposable housing assembly exit  6028  may include a minimal taper port. The plug  6008  may include at least one o-ring  6006 . In some embodiments, the plug  6008  may be made from rigid plastic and the o-ring may be made from an elastomeric material for sealing. In some embodiments, the plug  6008  may be glued and/or adhered to the tubing  6002 . In some embodiments, the plug  6008  may be overmolded to the tubing  6002 . 
     Referring now to  FIG.  216   , in some embodiments, the plug  6008  may include at least one seal  6006  feature which may include, but is not limited to, one or more of the following: a lip seal, a wiper seal, a radial seal, a face-seal and/or an X seal. Various other seals may be used. Referring now also to  FIG.  217   , in some embodiments, the plug  6008  may include a face-seal  6006 . In some embodiments, the plug  6008  may be glued and/or adhered to the tubing. In some embodiments, the plug  6008  may be overmolded to the tubing  6002 . 
     In various embodiments, the plug may be made from a rigid material or from a compliant and/or semi-compliant material. In some embodiments, the plug may be made from an elastomeric material or any combination thereof. 
     In various other embodiments, the shape and size of the connector may vary, and/or, in various other embodiments, other types of mating locking features may be used, which include, but are not limited to, latches, catches, snap fits, adhesives, and other mechanisms for securing a connector to the tab of the disposable housing assembly. 
     Referring now also to  FIGS.  218 A- 218 C , another embodiment of a connector  6010  is shown. The connector  6010  may include a tab portion  6018 , a protrusion portion  6038 , and a plug  6008 . In some embodiments, the tab portion  6018  of the connector  6010  may include mating locking features that interact with the tab portion of the disposable housing assembly  6030 . As shown, in some embodiments, the mating locking features may include a catch  6014  on the end of the tab portion  6018  of the connector  6010 . In some embodiments, the catch  6014  may be a snap fit and/or a loose snap fit and may include features such that the tab portion  6018  of the connector  6010  snaps onto the side/end of the tab portion  6018  of the disposable housing assembly  6000  and may, in some embodiments, include a portion that secures underneath the end of the tab portion  6018  of the disposable housing assembly  6000 . In various other embodiments, the shape and size of the connector  6010  may vary, and/or, in various other embodiments, other types of mating locking features may be used, which include, but are not limited to, latches, catches, snap fits, adhesives, and other mechanisms for securing a connector  6010  to the tab  6030  of the disposable housing assembly  6000 . 
     In some embodiments, the connector  6010  includes a protrusion  6038  on the underside. The protrusion  6010  may be tapered in some embodiments. In some embodiments, the protrusion  6038  may be at least slightly curved. Referring now also to  FIG.  219 B  and  FIG.  221   , in various embodiments, the protrusion  6038  is configured to interact with a groove portion  6042  on the tab portion  6030  of the disposable housing assembly  6000 . Referring now also to  FIGS.  219 A- 219 M , when the connector  6010  is being attached to the disposable housing assembly  6000 , the protrusion  6038  on the connector  6030  rests on the groove  6042 . The protrusion  6038  is configured to cam/interfere with the tab portion  6018  of the disposable housing assembly  6000 . Thus, in some embodiments, the protrusion  6038  and groove  6042  work together to assist in the insertion of the plug  6008  into the exit  6028 . Additionally, in various embodiments, the protrusion  6038  and groove  6042  may contribute to maintaining the plug  6008  in the exit  6028 . Thus, the protrusion  6038  and groove  6042 , together with the catch  6014 , contribute to maintaining and/or enforcing both the insertion of the plug  6008  into the exit  6028  and maintaining and/or enforcing the position of the connector  6010  such that after the plug  6008  is inserted into the exit  6028 , the plug  6008  is maintained in the exit  6028  unless and until a user desires to remove the plug  6008  from the exit  6028 . Additionally, once the protrusion  6038  and groove  6042  are mated, the plug  6008  is fully inserted and therefore, may, in some embodiments, serve as an indication that the plug  6008  has been fully inserted into the exit  6028 . 
     In some embodiments, the connector  6010  may be made from rigid plastic. In some embodiments, the protrusion  6038  may be overmolded with a thin layer of compliant materials. In some embodiments, as discussed below, the plug  6008  may include an overmold of compliant material and/or be made from compliant material. In some embodiments, the protrusion  6038  may be made from compliant material. In some embodiments, the groove  6042  on the tab portion  6030  of the disposable housing assembly  6000  may include a compliant material. In embodiments where either the groove  6042  includes compliant material and/or the protrusion  6038  includes compliant material, use of compliant material may increase the “squish” between the protrusion  6038  and the groove  6042  and therefore, resulting in a highly compressed and/or tight fit between the protrusion  6038  and the groove  6042 . 
     Referring now also to  FIG.  136   , in some embodiments, the connector  6010  may include icons that indicate “locked” and “unlocked”, similar to those shown and described above with respect to  FIG.  136   . Thus, in some embodiments, the “locked” and “unlocked” position may also be visually indicated to a user/patient using icons that may be molded, silk-screened, pad printed, injection molded, etched, printed and/or cut-out, e.g., translucent cut-outs of icons, on the connector. In some embodiments using translucent cut-outs, the tab portion  6030  of the disposable housing may be a contrasting color to the connector for visually viewing the tab portion color through the cut-outs. Thus, the icons may indicate whether the reusable housing assembly  6004  is in a locked or unlocked relationship with the disposable housing assembly  6000 . In various embodiments, the icons may be any form that may indicate “locked” and “unlocked”, or a similar indication, to aid in the user/patient&#39;s understanding of the orientation/position between the reusable housing assembly  6004  and the disposable housing assembly  6000 . In some embodiments, an arrow icon may also appear between the “locked” and “unlocked” icons. 
     The plug  6008  may include any embodiment described herein, however, in some embodiments; the plug  6008  may be tapered and may either be rigid with an overmold of elastomeric/compliant material or be made from elastomeric/compliant material. In some embodiments, the tubing  6002  attaches to the connector  6010  as described above. In some embodiments, the tubing  6002  may attach to the connector  6010  and there may be a rigid plastic channel within the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend into the connector  6010  and in some embodiments; the tubing  6002  may extend all the way through the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend past the end of the plug  6008 . 
     In these various embodiments, there is maintained a continuous flow lumen from the exit  6028  to the cannula  6026 . This may be desirable and/or beneficial for many reasons, including, but not limited to, minimizing and/or eliminating dead volume, minimizing priming volume and/or prevention of or minimizing the occurrence of air traps. 
     Referring again to  FIG.  222   , in some embodiments, the tab portion  6030  of the disposable housing assembly  6000  may include a cut-out which may be referred to as a finger cut-out  6044 . This cut-out  6044  may be used to assist in removing the connector  6010  from the disposable housing assembly  6000 . In some embodiments, the user may grab the connector  6010  at the area of the cut-out  6044 , with a thumb and forefinger and pull up on the connector  6010  to remove the connector  6010  from the disposable housing assembly  6000 . Thus, any embodiment of the disposable housing assembly  6000  may include a cut-out  6044  on the tab portion  6030 . 
     Referring now also to  FIGS.  219 A- 219 M , various views of the embodiment of the connector shown in  FIGS.  218 A- 218 C  are shown, where the connector  6010  is being attached to the disposable housing assembly  6000 . As shown in  FIGS.  219 A- 219 M , the connector  6010 , including a tab portion  6018  and a plug  6008 , may be attached to the disposable housing portion  6000  either by being releasably attached or non-releasably attached. In various embodiments, the connector  6010  may be attached to the disposable housing assembly  6000  as shown in  FIGS.  219 A- 219 M . 
     As discussed above, in various embodiments, the plug of the connector is inserted into the exit of the disposable housing assembly with the tab portion pointing in the general upward direction. Once the plug portion is inside the disposable housing assembly, the tab portion of the connector may be rotated to rest above the tab portion of the disposable housing portion, which is adjacent to the exit. In some embodiments, mating locking features may be included on the tab portion of the connector and the disposable housing assembly such that the connector is held in place before the reusable housing assembly is attached to the disposable housing assembly. In some embodiments, the mating locking features may include, but are not limited to, snap buttons and/or catch features. In some embodiments, a hook or other feature may be located on the opposite end of the tab portion of the connector such that it loops over the end of the tab portion of the disposable housing assembly and maintains the position of the connector. 
     In various embodiments, once the connector  2010  is attached to the disposable housing assembly  6000 , the connector  2010  may only be removed when intended, i.e., the connector  6010  is maintained on the disposable housing assembly  6000  unless and until a user desires to remove the connector  6010 . As discussed above, in some embodiments, the connector  6010  may be non-removably attached, however, in some embodiments; the connector  6010  may be removably attached. 
     Referring now also to  FIGS.  220 A- 220 J , once the connector  6010  is attached to the tab portion  6030  of the disposable housing assembly  6000 , the reusable housing assembly  6040  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As shown, as the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the nub  808 , having a spring actuated tab  2980  (not shown), on the reusable housing assembly  6004  interacts with the tab portion  6018  of the connector. As shown in  FIG.  220 E , in some embodiments, the connector  6010  may include an indent portion  6040  which may be configured to interact with the nub  808  and/or spring plunger/tab of the locking ring assembly of the reusable housing assembly  6004 . As shown in  FIG.  2201   , once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808 , having a spring actuated tab  2980 , may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , rests on the tab portion  6018  of the connector  6010 , and in some embodiments, the nub  808 , having a spring actuated tab  2980 , may rest on the indent portion  6040  of the tab portion  6018  of the connector  6010 . The nub  808 , having a spring actuated tab  2980 , presses downward on the connector  6010 , maintaining the connector  6010  in an attached position. In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     Referring now also to  FIGS.  223 A and  223 B , in some embodiments, a stopcock valve  6046  may be non-removably, or in some embodiments, removably, connected to the tab section  6030  of the disposable housing assembly  6000 . Once the connector  6010  is inserted into the stopcock style valve  6046 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  interacts with the swivel connector  6048 , activating the stopcock style valve  6046 , and, in some embodiments, the rotation of the reusable housing assembly  6000  about the disposable housing assembly  6004  prevents the swivel connector  6048  from being removed from the stopcock style valve  6046 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808 , having a spring actuated tab  2980 , may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the swivel connector  6048  is connected such that it will be maintained in the stopcock valve  6046  until and unless the user wishes to remove the connection. In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the swivel connector  6048 , maintaining the swivel connector  6048  in an attached position. In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the swivel connector  6048  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the swivel connector  6048  may be removed from the disposable housing assembly  6000 . In some embodiments, once the swivel connector  6048  is attached to the disposable housing assembly  6000 , it may not be removed. 
     Referring now to  FIG.  224   , in some embodiments, the connector may be a latching connector  6010  that attaches to the tab  6030  of the disposable housing assembly  6000 . In some embodiments, the latching connector  6010  may include a radial or a face seal, and in some embodiments, the latching connector  6010  may include a septum/needle interface. For example, in some embodiments, the latching connector  6010  may include a needle portion and the tab of the disposable housing assembly  6030  may include a septum. In some embodiments, the latching connector  6010  may attach to the disposable housing assembly  6000  from the side, as shown, however, in other embodiments, the latching connector  6010  may attach to the disposable housing assembly  6000  from the top and or from the bottom. In some embodiments, once the latching connector  6010  is connected to the disposable housing assembly  6000 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the latching connector  6010 , such that the rotation of the reusable housing assembly  6004  about the disposable housing assembly  6000  prevents the latching connector  6010  from being removed from the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the latching connector  6010  is connected such that it will be maintained connected to the disposable housing assembly  6000  until and unless the user wishes to remove the latching connector  6010 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the latching connector  6010 , maintaining the latching connector  6010  in an attached position. In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the latching connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the latching connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the latching connector  6010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     Referring now also to  FIGS.  225 A and  225 B , in some embodiments, the connector  6010  may be a perimeter connector  6010  that attaches to the perimeter of the disposable housing assembly  6000 . In some embodiments, the perimeter connector  6010  may be attached to the disposable housing assembly  6000  by being connected to the disposable housing assembly  6000  from the bottom of the disposable housing assembly  6000 . However, in some embodiments, the perimeter connector  6010  may be connected to the disposable housing assembly  6000  by being connected to the disposable housing assembly  6000  from the top, as shown in  FIG.  225 B . Referring now to  FIG.  226   , in some embodiments, the perimeter connector  6010  may be connected to the disposable housing assembly  6000  by first being connected to the tab of the disposable housing assembly  6000  and then being applied over the top of the disposable housing assembly  6000 . 
     Referring now also to  FIG.  136   , in some embodiments, the connector  6010  may include icons that indicate “locked” and “unlocked”, similar to those shown and described above with respect to  FIG.  136   . Thus, in some embodiments, the “locked” and “unlocked” position may also be visually indicated to a user/patient using icons that may be molded, silk-screened, pad printed, injection molded, etched, printed and/or cut-out, e.g., translucent cut-outs of icons, on the connector  6010 . In some embodiments using translucent cut-outs, the tab portion  6030  of the disposable housing assembly  6000  may be a contrasting color to the connector  6010  for visually viewing the tab portion  6030  color through the cut-outs. Thus, the icons may indicate whether the reusable housing assembly  6004  is in a locked or unlocked relationship with the disposable housing assembly  6000 . In various embodiments, the icons may be any form that may indicate “locked” and “unlocked”, or a similar indication, to aid in the user/patient&#39;s understanding of the orientation/position between the reusable housing assembly  6004  and the disposable housing assembly  6000 . In some embodiments, an arrow icon may also appear between the “locked” and “unlocked” icons. 
     In various embodiments of the perimeter connector  6010 , once the perimeter connector  6010  is connected to the disposable housing assembly  6000 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the perimeter connector  6010 , such that the rotation of the reusable housing assembly  6003  about the disposable housing assembly  6000  prevents the perimeter connector  6010  from being removed from the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the perimeter connector  6010  is connected such that it will be maintained connected to the disposable housing assembly  6000  until and unless the user wishes to remove the connector  6010 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the perimeter connector, maintaining the perimeter connector  6010  in an attached position. In some embodiments, features in the locking ring interact with the perimeter connector  6010  and maintain the perimeter connector  6010  in position with respect to the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the perimeter connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the perimeter connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the perimeter connector  6010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     In some embodiments of the various embodiments of the perimeter connector  6010 , the disposable housing assembly  6000  inserts into the perimeter connector  6010  which, in some embodiments, may include guides to align the perimeter connector  6010  with the disposable housing assembly  6000 . In some embodiments, a fluid seal, which, in various embodiments, may be a face seal or a radial seal, connects the fluid path in the disposable housing assembly  6000  to the perimeter connector  6010 /tubing  6002 . In various embodiments, the perimeter connector  6010  is removably attached to the disposable housing assembly  6000 , however, in some embodiments; the perimeter connector  6010  is non-removably attached to the disposable housing assembly  6000 . 
     Referring now to  FIGS.  227 A- 227 C , in some embodiments the connector  6010  may be a folding snap connector  6010 . As shown in  FIG.  227 A , in some embodiments, the folding snap connector  6010  may attach to the tab of the disposable housing assembly  6000  and fold under the tab  6030  such that the folding snap connector  6010  is attached to the disposable housing assembly  6000 . In some embodiments, the folding snap connector  6010  includes a fluid interface sealed with a face or radial seal. In various embodiments, the folding snap connector  6010  is removably attached to the disposable housing assembly  6000 , however, in some embodiments; the folding snap connector  6010  is non-removably attached to the disposable housing assembly  6000 . 
     In various embodiments of the folding snap connector  6010 , once the folding snap connector  6010  is connected to the disposable housing assembly  6000 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the folding snap connector  6010 , such that the rotation of the reusable housing assembly  6004  about the disposable housing assembly  6000  prevents the folding snap connector  6010  from being removed from the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the folding snap connector  6010  is connected such that it will be maintained connected to the disposable housing assembly  6000  until and unless the user wishes to remove the folding snap connector  6010 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the folding snap connector  6010 , maintaining the folding snap connector  6010  in an attached position. In some embodiments, features in the locking ring interact with the folding snap connector  6010  and maintain the folding snap connector  6010  in position with respect to the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the folding snap connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the folding snap connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the folding snap connector  6010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     Referring now to  FIG.  228 A , in some embodiments, the connector  6010  may be a perimeter connector  6010  which may include a plug  6008  which attaches to the fluid path through a tab feature  6030  on the disposable housing assembly. In some embodiments, the perimeter connector  6010  may connect by rotatably connecting to the disposable housing assembly  6000 , as shown in  FIG.  228 B . In various embodiments, the perimeter connector  6010  is removably attached to the disposable housing assembly  6000 , however, in some embodiments; the perimeter connector  6010  is non-removably attached to the disposable housing assembly. 
     In various embodiments of the perimeter connector  6010 , once the perimeter connector  6010  is connected to the disposable housing assembly  6000 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the perimeter connector  6010 , such that the rotation of the reusable housing assembly  6004  about the disposable housing assembly  6000  prevents the perimeter connector  6010  from being removed from the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the perimeter connector  6010  is connected such that it will be maintained connected to the disposable housing assembly  6000  until and unless the user wishes to remove the perimeter connector  6010 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the perimeter connector  6010 , maintaining the perimeter connector  6010  in an attached position. In some embodiments, features in the locking ring interact with the perimeter connector  6010  and maintain the perimeter connector  6010  in position with respect to the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the perimeter connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the perimeter connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the perimeter connector  6010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     Referring now to  FIG.  229   , in some embodiments, the connector  6010  may include a plug  6008  and may fit into a tab portion  6030  on the disposable housing assembly  6000 . In various embodiments, the plug  6008  attaches to the fluid path through a tab feature  6030  on the disposable housing assembly  6000 . Referring now to  FIG.  230   , in some embodiments, the tab  6030  and plug  6008  on the disposable housing assembly  6000  may connect to the connector  6010  through movement as shown by the arrows. In various embodiments, the connector  6010  is removably attached to the disposable housing assembly  6000 , however, in some embodiments; the connector  6010  is non-removably attached to the disposable housing assembly  6000 . As discussed above with respect to various other embodiments, the plug  6008  in this embodiment may include any embodiment described herein, however, in some embodiments; the plug  6008  may be tapered and may either be rigid with an overmold of elastomeric/compliant material or be made from elastomeric/compliant material. In some embodiments, the tubing  6002  attaches to the connector  6010  as described above. In some embodiments, the tubing  6002  may attach to the connector  6010  and there may be a rigid plastic channel within the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend into the connector  6010  and in some embodiments; the tubing  6002  may extend all the way through the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend past the end of the plug  6008 . 
     In these various embodiments, there is maintained a continuous flow lumen from the exit  6028  to the cannula  6026 . This may be desirable and/or beneficial for many reasons, including, but not limited to, minimizing and/or eliminating dead volume, minimizing priming volume and/or prevention of or minimizing the occurrence of air traps. 
     In various embodiments of the connector  6010 , once the connector  6010  is connected to the disposable housing assembly  6010 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the connector  6010 , such that the rotation of the reusable housing assembly  6004  about the disposable housing assembly  6000  prevents the connector  6010  from being removed from the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the connector  6010  is connected such that it will be maintained connected to the disposable housing assembly  6000  until and unless the user wishes to remove the connector  6010 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the connector  6010 , maintaining the connector  6010  in an attached position. In some embodiments, features in the locking ring interact with the connector  6010  and maintain the connector  6010  in position with respect to the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     Referring now also to  FIGS.  231 A- 231 E  another embodiment of a connector  6010  is shown. In some embodiments, the connector  6010  may be a pinch connector  6010 . In various embodiments, the pinch connector  6010  may include fingers  6058 ,  6060 , clips  6052 ,  6066 , grips  6050 , a plug  6008  and/or a post  6054 . The tubing  6002  is fluidly connected to the connector  6010  using any of the embodiments described herein. In various embodiments of the pinch connector  6010  embodiment, the corresponding disposable housing assembly  6000  tab  6030  includes an opening  6064  for receiving the fingers  6058 ,  6060 , an indent  6040 , as described above, an exit  6028  for receiving the plug  6008 , a clip receiver  6056  on each end for receiving the clips  6052 ,  6066  and an opening  6064  for receiving the post  6054 . 
     In various embodiments, the pinch connector  6010  may include grips  6050 , and in various embodiments, grips  6050  are included on both the top side and bottom side of the pinch connector  6010 . In the embodiments shown, the grips  6050  are ribs, however, in various other embodiments, the grips  6050  may include a textured surface, bumps, lumps, protrusions or indentations in any size, shape and/or number. The fingers  6058 ,  6060  are actuated by pressure being applied to both the top side and bottom side grips  6050 . 
     In various embodiments, the fingers  6058 ,  6060  include a lip  6062 . Upon pressure being exerted onto the grips  6050 , the fingers  6058 ,  6060  move towards one another and the fingers  6058 ,  6060  may be inserted into the opening  6064  in the tab  6030  of the disposable housing assembly  6000 . Upon pressure being removed from the grips  6050 , the fingers  6058 ,  6060  move away from one another and the lips  6062  rest against a surface such that the lips  6062  aid in maintaining the fingers  6058 ,  6060  inside the opening  6064 . Once inside the opening  6064 , the fingers  6058 ,  6060  may be viewed from the bottom of the tab  6030  of the disposable housing assembly  6000  through the tab window  6066 . This may be beneficial for many reasons, including, but not limited to, the user may view and ensure that the fingers  6058 ,  6060  have been inserted into the disposable housing assembly  6000 . In various embodiments, the fingers  6058 ,  6060  interlock with the disposable housing assembly  6000  and this may be desirable for many reasons, including, but not limited to, limiting and/or preventing the pinch connector  6010  from rocking while attached to the disposable housing assembly  6000 . 
     Inserting the fingers  6058 ,  6060  into the opening  6064  also inserts the plug  6008  into the exit of the disposable housing assembly  6000  as well as the post  6054  into the tab  6030 . In some embodiments, the post  6054  and plug  6008  together provide lateral stability to the pinch connector  6010  while attached to the disposable housing assembly  6000 . 
     The plug  6008  may be any of the embodiments as described above. In some embodiments, the plug  6008  includes a radial seal. In some embodiments, the radial seal may provide resistance while the plug  6008  is being inserted into the exit. This may be desirable for many reasons, including, but not limited to, that this may ensure the plug  6008  has been inserted into the exit a desirable distance before the radial seal begins. 
     In some embodiments, the pinch connector  6010  includes a clip  6052 ,  6066  on each end which is received by the clip receiver  6056  on each end of the tab of the disposable housing assembly. In some embodiments, the clips including a spring quality and snap into place on the clip receiver. In some embodiments, the “snap” produces an audio indication to the user that the pinch connector has been connected to the disposable housing assembly. The “snap” may also produce a tactile feedback that may be perceived by the user/patient. In some embodiments, the clips  6052 ,  6066  may be beneficial for providing added stability to the connection between the pinch connector  6010  and the disposable housing assembly  6000 . 
     In various embodiments, the pinch connector  6010  is removably attached to the disposable housing assembly  6000 , however, in some embodiments; the pinch connector  6010  is non-removably attached to the disposable housing assembly  6000   
     In various embodiments of the pinch connector  6010 , once the pinch connector  6010  is connected to the disposable housing assembly  6000 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the pinch connector  6010 , such that the rotation of the reusable housing assembly  6003  about the disposable housing assembly  6000  prevents the pinch connector  6010  from being removed from the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the pinch connector  6010  is connected such that it will be maintained connected to the disposable housing assembly  6000  until and unless the user wishes to remove the pinch connector  6010 . In some embodiments, the nub, having a spring actuated tab  2980 , presses downward on the pinch connector  6010 , maintaining the pinch connector  6010  in an attached position. In some embodiments, features in the locking ring interact with the pinch connector  6010  and maintain the pinch connector in position with respect to the disposable housing assembly  6000 . In some embodiments, the pinch connector  6010  may include an indent portion  6040  which may be configured to interact with the nub  808  and/or spring plunger/tab of the locking ring assembly of the reusable housing assembly  6004 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the pinch connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the pinch connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the pinch connector  6010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     Referring now also to  FIGS.  232 A- 232 E , another embodiment of a connector  6010  is shown. In this embodiment, the connector  6010  is a top down connector  6010 . In various embodiments of the top down connector  6010 , the plug  6008  may be located on the disposable housing assembly  6000  and the top down connector  6010  may include a plug receiver  6068 , i.e., an opening configured to receive the plug  6008 . Although this embodiment is shown in the above-referenced figures, in some embodiments, the plug  6008  may be located on the top down connector  6010  and the disposable housing assembly  6000  may include a plug receiver  6068 , or an exit  6028 , as referred to in various other embodiments described herein. 
     In various embodiments, the plug  6008  may be any embodiment of a plug  6008  described herein. For example, in some embodiments, the plug  6008  may include a radial seal. 
     In various embodiments of this embodiment of the top down connector  6010 , the disposable housing assembly  6000  may include a tab  6030  wherein a portion of the tab includes a cut-out portion for receiving the top down connector  6010 . In various embodiments of this embodiment, when the top down connector  6010  is connected to the disposable housing assembly  6000 , the tab  6030  and the top down connector  6010  may be flush with one another. 
     In various embodiments of the top down connector  6010 , the top down connector  6010  may include an indent  6040 , as described in various embodiments of connectors herein. However, in some embodiments of the top down connector  6010 , an indent  6040  may not be included. In those embodiments including an indent  6040 , the size and shape of the indent may vary and be any size and/or shape. 
     The top down connector  6010  may be any shape and size, however, in some embodiments, the top down connector  6010  includes a grip tab  6070  which may be sized and shaped to accommodate a “pinch grip” from a user, i.e., a grip using the thumb and index finger. In various embodiments, the size and shape of the grip tab  6070  may vary. In some embodiments, the grip tab  6070  may include an overmold and in some embodiments, the overmold may be a flexible overmold. This may be beneficial for many reasons, including, but not limited to, the overmold and/or flexible overmold may be preferable for wearing against the skin of a user, for example, the overmold and/or flexible overmold may be more comfortable against a user&#39;s skin. 
     In some embodiments, the size and shape of the tab portion  6030  of the disposable housing assembly  6000  may vary. Additionally, in embodiments where there is a cut-out portion of the tab portion  6030  of the disposable housing assembly  6000 , the size and shape of the cut-out portion may vary and may be any size and/or shape. 
     As discussed above, in various embodiments, the disposable housing assembly  6000  may include the plug  6008  and the top down connector  6010  may include a plug receiver  6068 . This embodiment may be included in any one or more of the various embodiments of connectors  6010  described herein and is not limited to the top down connector  6010 . In these embodiments, the plug  6008  and the plug receiver  6068  may include any of the various embodiments of the plug  6008  and plug receiver  6068  described herein. 
     In some embodiments of the top down connector  6010 , the top down connector may include male interlock features  6016  on both ends of the top down connector  6010 . These male interlock features  6016  are configured to be received by female interlock features  6020  on the disposable housing assembly  6000  tab  6030 . Once the male interlock features  6016  are placed within the female interlock features  6020 , the top down connector  6010  is secured onto the disposable housing assembly  6000 . In some embodiment, the top down connector  6010  may not include interlock features and may be secured by other means. In various embodiments, the top down connector  6010  is removably attached to the disposable housing assembly  6000 , however, in some embodiments; the connector  6010  is non-removably attached to the disposable housing assembly  6000  by various means, some which are discussed herein. In some embodiments, once the male interlock features  6016  are received by the female interlock features  6020 , a “click” and or a tactile feedback may result. This may be beneficial for many reasons, including, but not limited to, providing an indication to the user that the top down connector  6010  is connected to the disposable housing assembly  6000 . 
     In some embodiments, the tab portion  6030  may include a side-cut for accommodation of the grip tab  6070 . In some embodiments, the side-cut may be made on the cut-out portion of the tab  6030 . In some embodiments, the side-cut accommodates the grip tab  6070  such that, when the top down connector  6010  is attached to the disposable housing assembly  6000 , the grip tab  6070  does not overlap with the tab  6030  on the disposable housing assembly  6000 . This may be beneficial for many reasons, including, but not limited to, the ease of connection of the top down connector  6010  to the disposable housing assembly  6000  by pinch gripping the grip tab  6070 . 
     In various embodiments of the top down connector  6010 , once the top down connector  6010  is connected to the disposable housing assembly  6000 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the top down connector  6010 , such that the rotation of the reusable housing assembly  6004  about the disposable housing assembly  6000  prevents the top down connector  6010  from being removed from the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the top down connector  6010  is connected such that it will be maintained connected to the disposable housing assembly  6000  until and unless the user wishes to remove the top down connector  6010 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the top down connector  6010 , maintaining the connector in an attached position. In some embodiments, features in the locking ring interact with the top down connector  6010  and maintain the top down connector  6010  in position with respect to the disposable housing assembly  6000 . In some embodiments, the top down connector  6010  may include an indent portion  6040  which may be configured to interact with the nub  808  and/or spring plunger/tab of the locking ring assembly of the reusable housing assembly  6004 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the top down connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the top down connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the top down connector  60010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     In some embodiments of the top down connector  6010 , the tab  6030  of the disposable housing assembly  6000  may include a post and the top down connector  6010  may include an opening for receiving the post. Placing the top down connector  6010  onto the disposable housing assembly  6000  also places the plug  6008  into the plug receiver  6068  as well as the post into the opening for receiving the post. In some embodiments, the post and plug  6008  together may provide lateral stability to the top down connector while attached to the disposable housing assembly. In some embodiments, the top down connector  6010  may include a post and the disposable housing connector  6000  may include an opening for receiving the post. 
     Referring now also to  FIGS.  233 A- 233 G , another embodiment of a connector  6010  is shown. The connector  6010  may include a body portion/tab  6018 , a post  6054 , and a plug receiver  6068 . In some embodiments, the body portion  6018  of the connector  6010  may include mating locking features that interact with the tab portion  6030  of the disposable housing assembly  6000 . In some embodiments, the body portion  6018  may include features that interact with other portions of the disposable housing assembly  6000 . As shown, in some embodiments, the connector  6010  may include a post  6054  on the end of the body portion  6018  of the connector  6010 . In some embodiments, the post  6054  may be a removably secure fit, and/or a snap fit and/or a loose snap fit and may include features such that the post  6054  portion of the connector  6010  snaps and/or rests onto the opening on the disposable housing assembly  6000 . In various other embodiments, the shape and size of the connector  6010  may vary, and/or, in various other embodiments, other types of features such as mating locking features may be used, which include, but are not limited to, latches, catches, snap fits, adhesives, and other mechanisms for securing a connector to the tab of the disposable housing assembly  6000 . 
     In some embodiments, the connector  6010  may include a locking ring feature  6072  on the underside. The locking ring feature  6072  in some embodiments may be tapered and/or in some embodiments, the locking ring feature  6072  may be at least slightly curved. In some embodiments, the locking ring feature  6072  may interact with the locking ring of the reusable housing assembly  6004  and may act together with the locking ring to secure the connector  6010  to the disposable housing assembly  6000 . 
     As discussed above, in various embodiments, the plug  6008  of the disposable housing assembly  6000  is inserted into the plug receiver  6068  of the connector  6010  with the body portion  6018  pointing in the general upward direction. Once the plug  6008  is inside the connector  6010 , the body portion  6018  of the connector  6010  may be rotated to rest adjacent to the tab portion  6030  of the disposable housing portion. In some embodiments, mating locking features (for example, in some embodiments, a catch feature  6014 ) may be included on the body portion  6018  of the connector  6010  and the disposable housing assembly  6000  such that the connector  6010  is held in place before the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 . In some embodiments, the mating locking features may include, but are not limited to, post and opening, snap, buttons and/or catch features  6014 . In some embodiments, a hook or other feature may be located on the opposite end of the body portion  6018  of the connector  6010  such that it loops over the end of the tab portion  6030  of the disposable housing assembly  6000  and maintains the position of the connector  6010 . In the embodiment shown in  FIGS.  233 A- 233 G , the mating locking features include a post  6054  on the connector  6010  and an opening  6064  on the disposable housing assembly  6000 . 
     In various embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , the connector  6010  may only be removed when intended, i.e., the connector  6010  is maintained on the disposable housing assembly  6000  unless and until a user desires to remove the connector  6010 . As discussed above, in some embodiments, the connector  6010  may be non-removably attached, however, in some embodiments; the connector  6010  may be removably attached. 
     While the connector  6010  is being attached to the disposable housing assembly  6000 , the post  6054  on the connector  6010  rests on the opening  6064 . In some embodiments, the post  6054  and opening  6010  may work together to further stabilize the connection of the connector  6010  to the disposable housing assembly  6000 . Additionally, in various embodiments, the post  6054  and opening may contribute to maintaining the plug  6008  in the plug receiver  6068 . Thus, in some embodiments, the post  6054  and opening may contribute to maintaining and/or enforcing both the insertion of the plug  6008  into the opening and/or maintaining and/or enforcing the position of the connector  6010  such that after the plug  6008  is inserted into the plug receiver  6068 , the plug  6008  is maintained in the plug receiver  6068  unless and until a user desires to remove the plug  6008  from the plug receiver  6068 . Additionally, once the post  6054  and opening  6064  are mated, the plug  6008  is fully inserted and therefore, may, in some embodiments, serve as an indication that the plug  6008  has been fully inserted into the plug receiver  6068 . 
     As shown in, for example,  FIGS.  233 A and  233 B , in some embodiments, the disposable housing assembly  6000  may include a plug  6008 . In some embodiments, as shown in the embodiments in  FIGS.  233 A and  233 B , the plug  6008  may be positioned such that the connector  6010  approaches the plug  6008  from the side (rather than the top, as shown in the top down connector embodiments). Also, in some embodiments, the tab  6030  of the disposable housing assembly  6000  may be shaped as shown in  FIGS.  233 A and  233 B . In some embodiments, the connector  6010 , once attached to the disposable housing assembly  6000 , may extend the tab portion  6030  of the disposable housing assembly  6000 . In some embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , the connector  6010  and tab  6030  may be flush and continuous. 
     In some embodiments, the connector  6010  may include an indent  6040 , as shown. The indent  6040  may be shaped as shown or, in various embodiments, may be shaped and sized differently. 
     In various embodiments, the opening  6064  on the disposable housing assembly  6000  may be located adjacent to the tab portion  6030 . In some embodiments, for example, as shown in  FIGS.  233 A and  233 B , the opening  6064  may be configured such that it receives the post  6054  on the connector  6010  from the top. Some embodiments may not include a post  6054  and opening  6064 . In some embodiments, the location and/or orientation of the opening  6064  may vary. In some embodiments, the location and/or orientation of the post  6054  may vary. 
     In some embodiments, the connector  6010  may be made from rigid plastic. In some embodiments, the locking ring feature and/or the post may be overmolded with a thin layer of compliant materials. In some embodiments, as discussed above, the plug  6008  may include an overmold of compliant material and/or be made from compliant material. In some embodiments, the locking ring feature and/or the post  6054  may be made from compliant material. In embodiments where the post  6054  includes compliant material, use of compliant material may increase the “squish” between the post  6054  and the opening  6064  and therefore, resulting in a highly compressed and/or tight fit between the post  6054  and the opening  6064 . 
     Referring now also to  FIG.  136   , in some embodiments, the connector  6010  may include icons that indicate “locked” and “unlocked”, similar to those shown and described above with respect to  FIG.  136   . Thus, in some embodiments, the “locked” and “unlocked” position may also be visually indicated to a user/patient using icons that may be molded, silk-screened, pad printed, injection molded, etched, printed and/or cut-out, e.g., translucent cut-outs of icons, on the connector. In some embodiments using translucent cut-outs, the tab portion  6030  of the disposable housing assembly  6000  may be a contrasting color to the connector for visually viewing the tab portion  6030  color through the cut-outs. Thus, the icons may indicate whether the reusable housing assembly  6004  is in a locked or unlocked relationship with the disposable housing assembly  6000 . In various embodiments, the icons may be any form that may indicate “locked” and “unlocked”, or a similar indication, to aid in the user/patient&#39;s understanding of the orientation/position between the reusable housing assembly  6004  and the disposable housing assembly  6000 . In some embodiments, an arrow icon may also appear between the “locked” and “unlocked” icons. 
     The plug  6008  may include any embodiment described herein, however, in some embodiments; the plug  6008  may be tapered and may either be rigid with an overmold of elastomeric/compliant material or be made from elastomeric/compliant material. In some embodiments, the tubing  6002  attaches to the connector  6010  as described above. In some embodiments, the tubing  6002  may attach to the connector  6010  and there may be a rigid plastic channel within the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend into the connector  6010  and in some embodiments; the tubing  6002  may extend all the way through the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend past the end of the plug  6008 . 
     In these various embodiments, there is maintained a continuous flow lumen from the exit  6028  to the cannula  6026 . This may be desirable and/or beneficial for many reasons, including, but not limited to, minimizing and/or eliminating dead volume, minimizing priming volume and/or prevention of or minimizing the occurrence of air traps. 
     Some embodiments of the connector  6010  may also include a catching feature  6014  on the opposite side as the post  6054 . The catching feature  6014 , when the connector  6010  is connected to the disposable housing assembly  6000 , interferes with the disposable housing assembly  6000  and prevents the connector  6000  from rotating further. Thus, in some embodiments, the connector  6010  and the disposable housing assembly  6000  form an interference fit in at least one location. Together with the post  6054  and opening  6064  feature, in some embodiments, once the connector  6010  is attached, the connector  6010  may be held in place by these mating features. 
     The connector body portion  6018  may include gripping features, however, in the some embodiments; the connector  6010  is sized such that a user may grip the connector  6010  for insertion/attachment with the disposable housing assembly  6000 . In some embodiments including grip features which, in various embodiments, may include, but are not limited to, one or more of the following: a textured surface, bumps, lumps, protrusions or indentations in any size, shape and/or number. 
     In various embodiments of the connector  6010 , once the connector  6010  is connected to the disposable housing assembly  6000 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the connector  6010 , such that the rotation of the reusable housing assembly  6004  about the disposable housing assembly  6000  prevents the connector  6010  from being removed from the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the connector  6010  is connected such that it will be maintained connected to the disposable housing assembly  6000  until and unless the user wishes to remove the connector  6010 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the connector  6010 , maintaining the connector  6010  in an attached position. In some embodiments, features in the locking ring interact with the locking ring feature on the connector  6010  and contribute to maintain the connector  6010  in position with respect to the disposable housing assembly  6000 . In some embodiments, the body portion  6018  of the connector  6010  may include an indent portion  6040  which may be configured to interact with the nub  808  and/or spring plunger/tab of the locking ring assembly of the reusable housing assembly  6004 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     In the embodiment shown in  FIGS.  233 A- 233 G , the connector  6010  connects to the disposable housing assembly  6000  by the connector  6010  being rotated clockwise with respect to the disposable housing assembly  6000 . In other embodiments, the various features described may be configured differently and the connector  6010  may be connected to the disposable housing assembly  6000  by the connector  6010  being rotated counter-clockwise with respect to the disposable housing assembly  6000 . 
     In some embodiments, the disposable housing assembly may include a plug according to the various embodiment described herein, however, in some embodiments, the plug may be located in a different location and/or orientation than is shown herein. In various embodiments, the disposable housing assembly may include one or more mating features that correspond to one or more mating features on a connector. In some embodiments, these mating features may be located and/or orientated differently than is shown herein. 
     Referring now also to  FIGS.  234 A- 234 G , another embodiment of a connector  6010  is shown. The connector  6010  may include a body portion  6018 , a catch feature  6014 , a latching feature  6016 , and a plug  6008 . In some embodiments, the body portion  6018  of the connector  6010  may include mating locking features that interact with corresponding features in the disposable housing assembly. In some embodiments, the body portion  6018  may include features that interact with other portions of the disposable housing assembly  6000 . As shown, in some embodiments, the connector  6010  may include a male latching feature  6016  on the end of the body portion  6018  of the connector  6010 . In some embodiments, the latching feature  6016  may mate with a corresponding latching feature (a female latching feature  6020 ) on the disposable housing assembly  6000 . In some embodiments, the latch may be a removably secure fit, and/or a snap fit and/or a loose snap fit and in some embodiments may include a spring latch portion. In various other embodiments, the shape and size of the connector  6010  may vary, and/or, in various other embodiments, other types of features such as mating locking features may be used, which include, but are not limited to, latches, catches, snap fits, adhesives, and other mechanisms for securing a connector  6010  to the tab of the disposable housing assembly  6000 . 
     In some embodiments, the connector  6010  may include a locking ring feature on the underside. The locking ring feature in some embodiments may be tapered and/or in some embodiments, the locking ring feature may be at least slightly curved. In some embodiments, the locking ring feature may interact with the locking ring of the reusable housing assembly and may act together with the locking ring to secure the connector to the disposable housing assembly. 
     As discussed above, in various embodiments, the plug  6008  of the connector  6010  is inserted into the exit  6028  of the disposable housing portion  6000  with the body portion  6018  pointing in the general upward direction. Once the plug  6008  is inside the exit, the body portion  6018  of the connector  6010  may be rotated to rest adjacent to the tab portion of the disposable housing portion  6000 . In some embodiments, mating locking features may be included on the body portion  6018  of the connector  6010  and the disposable housing assembly  6000  such that the connector  6010  is held in place before the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 . In some embodiments, the mating locking features may include, but are not limited to, post and opening, snap, buttons, latch features and/or catch features. In some embodiments, a hook or other feature may be located on the opposite end of the body portion of the connector such that it loops over the end of the tab portion of the disposable housing assembly and maintains the position of the connector. In the embodiment shown in FIGS.  234 A- 234 F, the mating locking features include a male latching feature  6016  on the connector  6010  and a female latching feature  6020  on the disposable housing assembly  6000 . 
     In various embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , the connector  6010  may only be removed when intended, i.e., the connector  6010  is maintained on the disposable housing assembly  6000  unless and until a user desires to remove the connector  6010 . As discussed above, in some embodiments, the connector  6010  may be non-removably attached, however, in some embodiments; the connector  6010  may be removably attached. 
     While the connector  6010  is being attached to the disposable housing assembly  6000 , the male latching feature  6016  is mated with the female latching feature  6020 . In some embodiments, male and female latching features  6016 ,  6020  may work together to further stabilize the connection of the connector  6010  to the disposable housing assembly  6000 . Additionally, in various embodiments, the male and female latching features  6016 ,  6020  may contribute to maintaining the plug  6008  in the exit  6028 . Thus, in some embodiments, the male and female latching features  6016 ,  6020  may contribute to maintaining and/or enforcing both the insertion of the plug  6008  into the exit  6028  and/or maintaining and/or enforcing the position of the connector  6010  such that after the plug  6008  is inserted into the exit  6028 , the plug  6008  is maintained in the exit  6028  unless and until a user desires to remove the plug  6008  from the exit  6028 . Additionally, once the male and female latching features  6016 ,  6020  are mated, the plug  6008  is fully inserted and therefore, may, in some embodiments, serve as an indication that the plug  6008  has been fully inserted into the exit  6028 . 
     As shown in  FIGS.  234 A and  234 B , in some embodiments, the connector  6010  may include a plug  6008 . In some embodiments, as shown in the embodiments in  FIGS.  234 A and  234 B , the plug  6008  may be positioned such that the connector  6010  approaches the disposable housing assembly  6000  exit  6028  from the side. Also, in some embodiments, the tab  6030  of the disposable housing portion  6000  may be shaped as shown in  FIGS.  234 A and  234 B . In some embodiments, the connector  6010 , once attached to the disposable housing assembly  6000 , may extend the tab portion  6030  of the disposable housing assembly  6000 . In some embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , the connector  6010  and tab  6030  may be flush and continuous. 
     In some embodiments, the connector  6010  may include an indent  6040 , as shown. The indent  6040  may be shaped as shown or, in various embodiments, may be shaped and sized differently. 
     In various embodiments, the female latching feature  6020  on the disposable housing assembly  6000  may be located adjacent to the tab portion  6030 . In some embodiments, for example, as shown in  FIGS.  234 A- 234 D , the female latching feature  6020  may be configured such that it receives the male latching feature  6016  on the connector  6010  from the top. Some embodiments may not include mating latching features  6016 . In some embodiments, the location and/or orientation of the female latching feature  6020  may vary. In some embodiments, the location and/or orientation of the male latching feature  6016  may vary. 
     In some embodiments, the connector  6010  may be made from rigid plastic. In some embodiments, the locking ring feature and/or the latching features may be overmolded with a thin layer of compliant materials. In some embodiments, as discussed above, the plug  6008  may include an overmold of compliant material and/or be made from compliant material. In some embodiments, the locking ring feature and/or the latching feature may be made from compliant material. In embodiments where the male or female latching features  6016 ,  6020  include compliant material, use of compliant material may increase the “squish” between the male latching feature  6016  and the female latching feature  6020  and therefore, resulting in a highly compressed and/or tight fit between the male and female latching features  6016 ,  6020 . 
     Referring now also to  FIG.  136   , in some embodiments, the connector  6010  may include icons that indicate “locked” and “unlocked”, similar to those shown and described above with respect to  FIG.  136   . Thus, in some embodiments, the “locked” and “unlocked” position may also be visually indicated to a user/patient using icons that may be molded, silk-screened, pad printed, injection molded, etched, printed and/or cut-out, e.g., translucent cut-outs of icons, on the connector  6010 . In some embodiments using translucent cut-outs, the tab portion  6030  of the disposable housing assembly  6000  may be a contrasting color to the connector  6010  for visually viewing the tab portion  6030  color through the cut-outs. Thus, the icons may indicate whether the reusable housing assembly  6004  is in a locked or unlocked relationship with the disposable housing assembly  6000 . In various embodiments, the icons may be any form that may indicate “locked” and “unlocked”, or a similar indication, to aid in the user/patient&#39;s understanding of the orientation/position between the reusable housing assembly  6004  and the disposable housing assembly  6000 . In some embodiments, an arrow icon may also appear between the “locked” and “unlocked” icons. 
     The plug  6008  may include any embodiment described herein, however, in some embodiments; the plug  6008  may be tapered and may either be rigid with an overmold of elastomeric/compliant material or be made from elastomeric/compliant material. In various embodiments, the plug  6008  may include a seal, for example, in some embodiments, the plug  6008  may include a radial seal. 
     In some embodiments, the tubing  6002  attaches to the connector  6010  as described above. In some embodiments, the tubing  6002  may attach to the connector  6010  and there may be a rigid plastic channel within the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend into the connector  6010  and in some embodiments; the tubing  6002  may extend all the way through the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend past the end of the plug  6008 . 
     In these various embodiments, there is maintained a continuous flow lumen from the exit to the cannula  6026 . This may be desirable and/or beneficial for many reasons, including, but not limited to, minimizing and/or eliminating dead volume, minimizing priming volume and/or prevention of or minimizing the occurrence of air traps. 
     Some embodiments of the connector  6010  may also include a catch/catching feature  6014  on the opposite side as the male latching feature  6016 . The catch feature  6014 , when the connector  6010  is connected to the disposable housing assembly  6000 , interferes with the disposable housing assembly  6000  and prevents the connector  6010  from rotating further. Thus, in some embodiments, the connector  6010  and the disposable housing assembly  6000  form an interference fit in at least one location. Together with the male and female latching features  6016 ,  6020 , in some embodiments, once the connector  6010  is attached, the connector  6010  may be held in place by these mating features  6016 ,  6020 . 
     The connector body portion  6018  may include gripping features, however, in the some embodiments; the connector  6010  is sized such that a user may grip the connector  6010  for insertion/attachment with the disposable housing assembly  6000 . In some embodiments including grip features which, in various embodiments, may include, but are not limited to, one or more of the following: a textured surface, bumps, lumps, protrusions or indentations in any size, shape and/or number. 
     In various embodiments of the connector  6010 , once the connector  6010  is connected to the disposable housing assembly  6000 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly is rotatably connected to the disposable housing assembly  6000 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the connector  6010 , such that the rotation of the reusable housing assembly  6004  about the disposable housing assembly  6000  prevents the connector  6010  from being removed from the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the connector  6010  is connected such that it will be maintained connected to the disposable housing assembly  6000  until and unless the user wishes to remove the connector  6010 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the connector  6010 , maintaining the connector  6010  in an attached position. In some embodiments, features in the locking ring interact with a locking ring feature on the connector  6010  and contribute to maintain the connector  6010  in position with respect to the disposable housing assembly  6000 . In some embodiments, the body portion  6018  of the connector  6010  may include an indent portion which may be configured to interact with the nub  808  and/or spring plunger/tab of the locking ring assembly of the reusable housing assembly  6004 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     In the embodiment shown in  FIGS.  234 A- 234 G , the connector  6010  connects to the disposable housing assembly  6000  by the connector  6010  being rotated clockwise with respect to the disposable housing assembly  6000 . In other embodiments, the various features described may be configured differently and the connector  6010  may be connected to the disposable housing assembly  6000  by the connector  6010  being rotated counter-clockwise with respect to the disposable housing assembly  6000 . 
     In some embodiments, the disposable housing assembly  6000  may include a plug  6008  and the connector  6010  may include a plug receiver  6068  according to the various embodiment described herein. In some embodiments, the plug  6008  may be located in a different location and/or orientation than is shown herein. In various embodiments, the disposable housing assembly  6000  may include one or more mating features that correspond to one or more mating features on a connector  6010 . In some embodiments, these mating features may be located and/or orientated differently than is shown herein. 
     Referring now also to  FIGS.  235 A- 235 E , another embodiment of a connector  6010  and a disposable housing assembly  6000  are shown. The connector  6010  may include a body portion  6018 , a catch feature  6015 , a latching feature  6016 , and a plug  6008 . In some embodiments, the body portion  6018  of the connector  6010  may include mating locking features that interact with corresponding features in the disposable housing assembly  6000 . In some embodiments, the body portion  6018  may include features that interact with other portions of the disposable housing assembly  6000 . As shown, in some embodiments, the connector  6010  may include a male latching feature  6016  on the end of the body portion  6018  of the connector  6010 . In some embodiments, the male latching feature  6016  may mate with a corresponding female latching feature  6020  on the disposable housing assembly  6000 . In some embodiments, the latch may be a removably secure fit, and/or a snap fit and/or a loose snap fit and in some embodiments may include a spring latch portion. In various other embodiments, the shape and size of the connector  6010  may vary, and/or, in various other embodiments, other types of features such as mating locking features may be used, which include, but are not limited to, latches, catches, snap fits, adhesives, and other mechanisms for securing a connector to the tab of the disposable housing assembly  6000 . 
     In some embodiments, the connector  6010  may include a locking ring feature on the underside. The locking ring feature in some embodiments may be tapered and/or in some embodiments, the locking ring feature may be at least slightly curved. In some embodiments, the locking ring feature may interact with the locking ring of the reusable housing assembly  6004  and may act together with the locking ring to secure the connector to the disposable housing assembly  6000 . 
     As discussed above, in various embodiments, the plug  6008  of the connector  6010  is inserted into the exit  6028  of the disposable housing assembly  6000  with the body portion  6018  pointing in the general upward direction. Once the plug  6008  is inside the exit  6028 , the body portion  6018  of the connector  6010  may be rotated to rest adjacent to the tab portion  6030  of the disposable housing portion  6000 . In some embodiments, mating locking features may be included on the body portion  6018  of the connector  6010  and the disposable housing assembly  6000  such that the connector  6010  is held in place before the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 . In some embodiments, the mating locking features may include, but are not limited to, post and opening, snap, buttons, latch features and/or catch features. In some embodiments, a hook or other feature may be located on the opposite end of the body portion  6018  of the connector  6010  such that it loops over the end of the tab portion  6030  of the disposable housing assembly  6000  and maintains the position of the connector  6010 . In the embodiment shown in  FIGS.  235 A- 235 E , the mating locking features include a male latching feature  6016  on the connector  6010  and a female latching feature  6020  on the disposable housing assembly  6000 . The male latching feature  6016  is a bump and the female latching feature  6020  is an opening that accommodates the bump. 
     In various embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , the connector  6010  may only be removed when intended, i.e., the connector  6010  is maintained on the disposable housing assembly  6000  unless and until a user desires to remove the connector  6010 . As discussed above, in some embodiments, the connector  6010  may be non-removably attached, however, in some embodiments; the connector  6010  may be removably attached. 
     While the connector  6010  is being attached to the disposable housing assembly  6000 , the male latching feature  6016  is mated with the female latching feature  6020 . In some embodiments, male and female latching features  6016 ,  6020  may work together to further stabilize the connection of the connector  6010  to the disposable housing assembly  6000 . Additionally, in various embodiments, the male and female latching features  6016 ,  6020  may contribute to maintaining the plug  6008  in the exit  6028 . Thus, in some embodiments, the male and female latching features  6016 ,  6020  may contribute to maintaining and/or enforcing both the insertion of the plug  6008  into the exit  6028  and/or maintaining and/or enforcing the position of the connector  6010  such that after the plug  6008  is inserted into the exit  6028 , the plug  6008  is maintained in the exit  6028  unless and until a user desires to remove the plug  6008  from the exit  6028 . Additionally, once the male and female latching features  6016 ,  6020  are mated, the plug  6008  is fully inserted and therefore, may, in some embodiments, serve as an indication that the plug  6008  has been fully inserted into the exit  6028 . 
     As shown in  FIGS.  235 A- 235 C , in some embodiments, the connector  6010  may include a plug  6008 . In some embodiments, as shown in the embodiments in  FIGS.  235 A- 235 C , the plug  6008  may be positioned such that the connector  6010  approaches the disposable housing assembly  6000  exit  6028  from the side. Also, in some embodiments, the tab  6030  of the disposable housing portion  6000  may be shaped as shown in  FIGS.  235 D and  235 E . In some embodiments, the connector  6010 , once attached to the disposable housing assembly  6000 , may extend the tab portion  6030  of the disposable housing assembly  6000 . In some embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , the connector  6010  and tab  6030  may be flush and continuous. 
     In some embodiments, the connector  6010  may include an indent  6040 , as shown. The indent  6040  may be shaped as shown or, in various embodiments, may be shaped and sized differently. 
     In various embodiments, the female latching feature  6020  on the disposable housing assembly  6000  may be located adjacent to the tab portion  6030 . In some embodiments, for example, as shown in  FIGS.  235 D- 235 E , the female latching feature  6020  may be configured such that it receives the male latching feature  6016  on the connector  6010  from the top. Some embodiments may not include mating latching features  6016 ,  6020 . In some embodiments, the location and/or orientation of the female latching feature  6020  may vary. In some embodiments, the location and/or orientation of the male latching feature  6016  may vary. 
     In some embodiments, the connector  6010  may be made from rigid plastic. In some embodiments, the locking ring feature and/or the latching features may be overmolded with a thin layer of compliant materials. In some embodiments, as discussed above, the plug  6008  may include an overmold of compliant material and/or be made from compliant material. In some embodiments, the locking ring feature and/or the latching feature may be made from compliant material. In embodiments where the male or female latching feature  6016 ,  6020  includes compliant material, use of compliant material may increase the “squish” between the male latching feature  6016  and the female latching feature  6020  and therefore, resulting in a highly compressed and/or tight fit between the male and female latching features  6016 ,  6020 . 
     Referring now also to  FIG.  136   , in some embodiments, the connector  6010  may include icons that indicate “locked” and “unlocked”, similar to those shown and described above with respect to  FIG.  136   . Thus, in some embodiments, the “locked” and “unlocked” position may also be visually indicated to a user/patient using icons that may be molded, silk-screened, pad printed, injection molded, etched, printed and/or cut-out, e.g., translucent cut-outs of icons, on the connector  6010 . In some embodiments using translucent cut-outs, the tab portion  6030  of the disposable housing assembly  6000  may be a contrasting color to the connector  6010  for visually viewing the tab portion  6030  color through the cut-outs. Thus, the icons may indicate whether the reusable housing assembly  6004  is in a locked or unlocked relationship with the disposable housing assembly  6000 . In various embodiments, the icons may be any form that may indicate “locked” and “unlocked”, or a similar indication, to aid in the user/patient&#39;s understanding of the orientation/position between the reusable housing assembly  6004  and the disposable housing assembly  6000 . In some embodiments, an arrow icon may also appear between the “locked” and “unlocked” icons. 
     The plug  6008  may include any embodiment described herein, however, in some embodiments; the plug  6008  may be tapered and may either be rigid with an overmold of elastomeric/compliant material or be made from elastomeric/compliant material. In various embodiments, the plug  6008  may include a seal, for example, in some embodiments; the plug  6008  may include a radial seal. 
     In some embodiments, the tubing  6002  attaches to the connector  6010  as described above. In some embodiments, the tubing  6002  may attach to the connector  6010  and there may be a rigid plastic channel within the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend into the connector  6010  and in some embodiments; the tubing  6002  may extend all the way through the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend past the end of the plug  6008 . 
     In these various embodiments, there is maintained a continuous flow lumen from the exit  6028  to the cannula  6026 . This may be desirable and/or beneficial for many reasons, including, but not limited to, minimizing and/or eliminating dead volume, minimizing priming volume and/or prevention of or minimizing the occurrence of air traps. 
     Some embodiments of the connector  6010  may also include a catch feature  6014  on the opposite side as the male latching feature  6016 . The catch feature  6014 , when the connector  6010  is connected to the disposable housing assembly  6000 , interferes with the disposable housing assembly  6000  and prevents the connector  6010  from rotating further. Thus, in some embodiments, the connector  6010  and the disposable housing assembly  6000  form an interference fit in at least one location. Together with the male and female latching features  6016 ,  6020 , in some embodiments, once the connector  6010  is attached, the connector  6010  may be held in place by these mating features. In some embodiments, the catch feature  6014  may be ramped and therefore, may, in some embodiments, aid in the attaching of the connector  6014  to the disposable housing assembly  6000 . 
     The connector body portion  6018  may include gripping features, however, in the some embodiments; the connector is sized such that a user may grip the connector  6010  for insertion/attachment with the disposable housing assembly  6000 . In some embodiments including grip features which, in various embodiments, may include, but are not limited to, one or more of the following: a textured surface, bumps, lumps, protrusions or indentations in any size, shape and/or number. 
     In various embodiments of the connector  6010 , once the connector  6010  is connected to the disposable housing assembly  6000 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the connector  6010 , such that the rotation of the reusable housing assembly  6004  about the disposable housing assembly  6000  prevents the connector  6010  from being removed from the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the connector  6010  is connected such that it will be maintained connected to the disposable housing assembly  6000  until and unless the user wishes to remove the connector  6010 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the connector, maintaining the connector  6010  in an attached position. In some embodiments, features in the locking ring interact with a locking ring feature on the connector  6010  and contribute to maintain the connector  6010  in position with respect to the disposable housing assembly  6000 . In some embodiments, the body portion  6018  of the connector  6010  may include an indent portion  6040  which may be configured to interact with the nub  808  and/or spring plunger/tab of the locking ring assembly of the reusable housing assembly  6004 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     In the embodiment shown in  FIGS.  235 A- 235 E , the connector  6010  connects to the disposable housing assembly  6000  by the connector  6010  being rotated clockwise with respect to the disposable housing assembly  6000 . In other embodiments, the various features described may be configured differently and the connector may be connected to the disposable housing assembly  6000  by the connector  6010  being rotated counter-clockwise with respect to the disposable housing assembly  6000 . 
     In some embodiments, the disposable housing assembly  6000  may include a plug  6008  and the connector  6010  may include a plug receiver  6068  according to the various embodiment described herein. In some embodiments, the plug  6008  may be located in a different location and/or orientation than is shown herein. In various embodiments, the disposable housing assembly  6000  may include one or more mating features that correspond to one or more mating features on a connector  6010 . In some embodiments, these mating features may be located and/or orientated differently than is shown herein. 
     In various embodiments, the tubing  6002 , whether connected to a connector  6010  or directly to the disposable housing assembly  6000 , may connect to a cannula assembly  6026  on the opposite end. The cannula assembly  6026  may be any cannula assembly  6026  known in the art and may include a cannula, whether plastic or metal, and/or an interface between the tubing  6002  and a cannula which, in some embodiments, may include a septum or a needle interface. In some embodiments, the cannula assembly  6026  includes all of these elements. 
     Referring now also to  FIGS.  236 A- 236 X , together with  FIG.  238   , another embodiment of a connector  6010  and a disposable housing assembly  6000  are shown. The connector  6010  may include a body portion  6018 , a catch feature  6014 , a male latching feature  6016 , and a plug  6008 . In some embodiments, the body portion  6018  of the connector  6010  may include one or more mating locking features that interact with corresponding features in the disposable housing assembly  6000 . In some embodiments, the body portion  6018  may include features that interact with other portions of the disposable housing assembly  6000 . As shown, in some embodiments, the connector  6010  may include a male latching feature  6016  on the end of the body portion  6018  of the connector  6010 . In some embodiments, the male latching feature  6016  may mate with a corresponding latching feature, for example, in some embodiments, the corresponding latching feature may be a female latching feature  6020 , on the disposable housing assembly  6000 . In some embodiments, the latch may be a removably secure fit, and/or a snap fit and/or a loose snap fit and in some embodiments may include a spring latch portion. In various other embodiments, the shape and size of the connector  6010  may vary, and/or, in various other embodiments, other types of features such as mating locking features may be used, which include, but are not limited to, latches, catches, snap fits, adhesives, and other mechanisms for securing a connector to the tab of the disposable housing assembly. 
     In some embodiments, the connector  6010  may include a locking ring feature on the underside. The locking ring feature in some embodiments may be tapered and/or in some embodiments, the locking ring feature may be at least slightly curved. In some embodiments, the locking ring feature may interact with the locking ring of the reusable housing assembly  6004  and may act together with the locking ring to secure the connector  6010  to the disposable housing assembly  6000 . 
     In some embodiments, the connector  6010  may include icons that indicate “locked”  6076  and “unlocked”  6078 . Thus, in some embodiments, the “locked” and “unlocked” position may also be visually indicated to a user/patient using icons  6076 ,  6078  that may be molded, silk-screened, pad printed, injection molded, etched, printed and/or cut-out, e.g., translucent cut-outs of icons, on the connector. In some embodiments using translucent cut-outs, the tab portion  6030  of the disposable housing assembly  6000 , or another portion of the disposable housing assembly  6000 , may be a contrasting color to the connector  6010  for visually viewing the tab  6030  portion color through the cut-outs. Thus, the icons  6076 ,  6078  may indicate whether the reusable housing assembly  6004  is in a locked or unlocked relationship with the disposable housing assembly  6000 . In various embodiments, the icons may be any form that may indicate “locked” and “unlocked”, or a similar indication, to aid in the user/patient&#39;s understanding of the orientation/position between the reusable housing assembly  6004  and the disposable housing assembly  6000 . In some embodiments, an arrow icon  6080  may also appear between the “locked” and “unlocked” icons. 
     In various embodiments, the connector  6010  is attached to a length of tubing  6002 . In some embodiments, the tubing  6002  attaches to the connector  6010  through the tubing opening  6082 . In some embodiments, the tubing opening  6082  may be a tapered opening which may be larger on the outside. This may be beneficial for many reasons, including, but not limited to, gluing the tubing  6002  into the tubing opening  6002 . The larger opening on the outside may maintain or aid to maintain the glue at the outer portion of the tubing opening  6082  such that the amount of glue is reduced, minimized and/or prevented from wicking up along the tubing  6002  inside the tubing opening 6-82. This is beneficial for many reasons, including, but not limited to, preventing or reduction of the potential for glue to induce a kink in the tubing  6002 . 
     As discussed above, in various embodiments, the plug  6008  of the connector  6010  is inserted into the exit  6028  of the disposable housing portion  6000  with the body portion  6018  pointing in the general upward direction. Once the plug  6008  is inside the exit  6028 , the body portion  6010  of the connector  6010  may be rotated to rest adjacent to the tab portion  6030  of the disposable housing portion  6000 . In some embodiments, mating locking features may be included on the body portion  6018  of the connector  6010  and the disposable housing assembly  6000  such that the connector  6010  is held in place before the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 . In some embodiments, the mating locking features may include, but are not limited to, post and opening, snap, buttons, latch features and/or catch features. In some embodiments, a hook or other feature may be located on the opposite end from the post of the body portion of the connector such that it loops over the end of the tab portion of the disposable housing assembly  6000  and maintains the position of the connector  6010 . In the embodiment shown in  FIGS.  236 A- 236 D  and  FIGS.  236 I- 236 M , the mating locking features include a male latching feature  6016  on the connector  6010  and a female latching feature  6020  on the disposable housing assembly  6000 . 
     In various embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , the connector  6010  may only be removed when intended, i.e., the connector  6010  is maintained on the disposable housing assembly  6000  unless and until a user desires to remove the connector  6000 . As discussed above, in some embodiments, the connector  6010  may be non-removably attached, however, in some embodiments; the connector  6010  may be removably attached. In some embodiments, one or more mating locking features may include one or more frangible portions such that once the connector  6010  is connected to the disposable housing assembly  6000 , if the connector  6010  is removed, one or more frangible portions will break and prevent reuse. 
     While the connector  6010  is being attached to the disposable housing assembly  6000 , the male latching feature  6016  is mated with the female latching feature  6020 . In some embodiments, male and female latching features  6016 ,  6020  may work together to further stabilize the connection of the connector  6010  to the disposable housing assembly  6000 . Additionally, in various embodiments, the male and female latching features  6016 ,  6020  may contribute to maintaining the plug  6008  in the exit  6028 . Thus, in some embodiments, the male and female latching features  6016 ,  6020  may contribute to maintaining and/or enforcing both the insertion of the plug  6008  into the exit  6028  and/or maintaining and/or enforcing the position of the connector  6010  such that after the plug  6008  is inserted into the exit  6028 , the plug  6008  is maintained in the exit  6028  unless and until a user desires to remove the plug  6008  from the exit  6028 . Additionally, once the male and female latching features  6016 ,  6020  are mated, the plug  6008  is fully inserted and therefore, may, in some embodiments, serve as an indication that the plug  6008  has been fully inserted into the exit  6028 . 
     As shown in  FIGS.  236 A and  236 B , in some embodiments, the connector  6010  may include a plug  6008 . In some embodiments, as shown in the embodiments in  FIGS.  236 A and  236 B , the plug  6008  may be positioned such that the connector  6010  approaches the disposable housing assembly  6000  exit from the side. Also, in some embodiments, the tab  6030  of the disposable housing assembly  6000  may be shaped as shown in  FIGS.  236 A and  236 C . In some embodiments, the connector  6010 , once attached to the disposable housing assembly  6000 , may extend the tab portion  6030  of the disposable housing assembly  6000 . In some embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , the connector  6010  and tab  6030  may be flush and continuous. 
     In some embodiments, the connector  6010  may include an indent  6040 , as shown. The indent  6040  may be shaped as shown or, in various embodiments, may be shaped and sized differently. As shown in the embodiments in  FIGS.  236 A- 236 E , the indent  6040 , in some embodiments, may include one or more icons. In some embodiments the connector  6010  may include at least one indent  6040 , and in some embodiments, the connector  6010  may include greater than one indent  6040 . In some embodiments, the connector  6010  may include at least one indent  6040  and/or at least one feature including, but not limited to, an indent, bump, rib, textured surface, lumps, protrusions or indentations in any size, shape and/or number. 
     In various embodiments, the female latching feature  6020  on the disposable housing assembly  6000  may be located adjacent to the tab portion  6030 . In some embodiments, for example, as shown in  FIGS.  236 C- 236 D  and  FIGS.  236 I- 236 L , the female latching feature  6020  may be configured such that it receives the male latching feature  6016  on the connector  6010  from the top. Some embodiments may not include mating latching features. In some embodiments, the location and/or orientation of the female latching feature may vary. In some embodiments, the location and/or orientation of the male latching feature may vary. In some embodiments, the male latching feature may interlock with the female latching feature such that a portion of the male latching feature clips under the female latching feature. 
     In some embodiments, the connector  6010  may be made from rigid plastic and in some embodiments, the connector  6010  may be made from TERLUX, however, in various other embodiments, the connector  6010  may be made from other materials, including, but not limited to, polycarbonate, TOPAS or other various plastics. In some embodiments, the locking ring feature and/or the latching features may be overmolded with a thin layer of compliant materials. In some embodiments, as discussed above, the plug  6008  may include an overmold of compliant material and/or be made from compliant material. In some embodiments, the locking ring feature and/or the latching feature may be made from compliant material. In embodiments where the male or female latching feature includes compliant material, use of compliant material may increase the “squish” between the male latching feature and the female latching feature and therefore, resulting in a highly compressed and/or tight fit between the male and female latching features. 
     The plug  6008  may include any embodiment described herein, however, in some embodiments; the plug  6008  may be tapered and may either be rigid with an overmold of elastomeric/compliant material or be made from elastomeric/compliant material. In various embodiments, the plug  6008  may include a seal, for example, in some embodiments; the plug may include a radial seal. In some embodiments, the seal may be made from medical grade silicone. 
     In some embodiments, the tubing  6002  attaches to the connector  6010  as described above. In some embodiments, the tubing  6002  may attach to the connector  6010  and there may be a rigid plastic channel within the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend into the connector  6010  and in some embodiments; the tubing  6002  may extend all the way through the connector  6010  and through the plug  6008 . In some embodiments, the tubing  6002  may extend past the end of the plug  6008 . 
     In these various embodiments, there is maintained a continuous flow lumen from the exit  6028  to the cannula assembly  6026 . This may be desirable and/or beneficial for many reasons, including, but not limited to, minimizing and/or eliminating dead volume, minimizing priming volume and/or prevention of or minimizing the occurrence of air traps. 
     Referring now still to  FIGS.  236 A- 236 H and  236 L- 236 T , some embodiments of the connector  6010  may also include a catch feature  6014  on the opposite side as the male latching feature  6016 . The catch feature  6014 , when the connector  6010  is connected to the disposable housing assembly  6000 , interferes with the disposable housing assembly  6000  and prevents the connector  6010  from rotating further. Thus, in some embodiments, the connector  6010  and the disposable housing assembly  6000  form an interference fit in at least one location. Together with the male and female latching features  6016 ,  6020 , in some embodiments, once the connector  6010  is attached, the connector  6010  may be held in place by these mating features. In some embodiments, the catch feature  6014  may include a ramp  6084  and therefore, may, in some embodiments, aid in the attaching of the connector  6010  to the disposable housing assembly  6000 . Referring now to  FIG.  236 Q  and  FIG.  236 R , in some embodiments, the catch  6014  of the connector  6010  may interfere with a disposable housing assembly interference feature  6086 . As shown, if the plug  6008  is not mostly inserted into the exit  6028 , the catch  6014  and the disposable housing assembly interference feature  6086  meet and this prevents the connector  6010  from being fully connected to the disposable housing assembly  6000 . This configuration additionally prevents the reusable housing assembly  6004  from attaching to the disposable housing assembly  6000 . This may be beneficial for many reasons, including, but not limited to, ensuring that the plug  6008  is fully inserted into the exit  6028  before the reusable housing assembly  6004  is attached and before any delivery by the pump begins. Additionally, the ramp  6084  of the catch  6014  aids in ensuring that the plug  6008  is fully inserted. In some embodiments, where the plug  6008  is mostly inserted into the exit  6028 , but not completely inserted, when the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , pressure from the reusable housing assembly  6004 , together with the ramp  6084  of the catch  6014 , inserts the plug  6008  fully. Thus, while the plug  6008  is almost fully inserted, the plug  6008  may be fully inserted by the motion of the reusable housing assembly  6004  being attached to the disposable housing assembly  6000  due, in part, to the ramp  6084  of the catch  6014  (which acts as a cam). Thus, if a user inserts the plug  6008  of the connector  6010 , even if the plug  6008  is not fully seeded in the exit  6028 , once the reusable housing assembly  6004  is attached, the plug  6008  will be pushed into the exit  6028  and fully seeded. This is beneficial for many reasons, including, but not limited to, preventing or decreasing the incidences of leakage due to a less than fully sealed interface between the connector  6010  and the exit  6028 . 
     The connector body portion  6018  may include gripping features, however, in the some embodiments; the connector  6010  is sized such that a user may grip the connector  6010  for insertion/attachment with the disposable housing assembly  6000 . In some embodiments including grip features which, in various embodiments, may include, but are not limited to, one or more of the following: a textured surface, bumps, lumps, protrusions or indentations in any size, shape and/or number. 
     In various embodiments of the connector  6010 , once the connector  6010  is connected to the disposable housing assembly  6000 , the reusable housing assembly  6004  may be connected/attached to the disposable housing assembly  6000  by being rotated about the disposable housing assembly  6000 . As the reusable housing assembly  6004  is rotatably connected to the disposable housing assembly  6000 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the connector  6010 , such that the rotation of the reusable housing assembly  6004  about the disposable housing assembly  6000  prevents the connector  6010  from being removed from the disposable housing assembly  6000 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  6000 , and, that the connector  6010  is connected such that it will be maintained connected to the disposable housing assembly  6000  until and unless the user wishes to remove the connector  6010 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the connector  6010 , maintaining the connector  6010  in an attached position. In some embodiments, features in the locking ring interact with a locking ring feature on the connector  6010  and contribute to maintain the connector  6010  in position with respect to the disposable housing assembly  6000 . In some embodiments, the body portion  6018  of the connector  6018  may include an indent portion  6040  which may be configured to interact with the nub  808  and/or spring plunger/tab of the locking ring assembly of the reusable housing assembly  6004 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  6000 , the connector  6010  may not be removed from the disposable housing assembly  6000 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  6000  before the connector  6010  may be removed from the disposable housing assembly  6000 . In some embodiments, once the connector  6010  is attached to the disposable housing assembly  6000 , it may not be removed. 
     In some embodiments, for example, referring to  FIG.  36   , the tactile and audio feedback from the “click”, referenced above, may be sensed using the AVS. In some embodiments, as described above, the locking ring assembly  806  may include a sensing component (e.g., magnet  844 ) that may interact with a component of reusable housing assembly  802  (e.g., a Hall Effect sensor) to provide an indication of whether reusable housing assembly  802  is properly engaged with the mating component. The Hall Effect sensor may detect when the locking ring has been rotated to a closed position. Thus, the Hall Effect sensor together with magnet  844  may provide a system for determining whether the locking ring has been rotated to a closed position. 
     In some embodiments, once the system determines that the sensing component has come into proximate contact with the Hall Effect sensor, the system may turn on the AVS microphone to listen for the “click” sounds from the indent. In some embodiments, the AVS microphone may be turned on for a predetermined period of time, for example, 20 seconds, to listen for the “click”. Thus, the system detects that a rotation is occurring before the “click” occurs and may turn on the AVS microphone to listen for a predetermined audio fingerprint. In some embodiments, the system may recognize the “click” sounds based on one or more, but not limited to, the following: frequency, amplitude, duration, and/or width. Once the system determines that the “click” sound has been made, the reusable housing assembly/pump and/or the remote control assembly may beep or otherwise indicate to the user that a successful attachment of the disposable housing assembly  6000  to the reusable housing assembly  6004  has been made. In some embodiments, where the “click” has not been recognized by the system, the reusable housing assembly  6004 /pump and/or remote control assembly may alert and/or alarm. In some embodiments, where the “click” is not heard, the reusable housing assembly  6004 /pump may not begin basal or other delivery programs. 
     In some embodiments, once the attachment has been successfully made, the infusion pump system may start a timer from when the reusable housing assembly/pump/system recognizes that the disposable housing assembly  6000  is attached to the reusable house assembly  6004  and could notify the user in a predetermined period of time, for example, 3 days, that the disposable housing assembly  6000  should be changed. 
     In some embodiments, the connector  6010  could include one or more indents or bumps or other types of texture that, when heard by the AVS microphone, may indicate a code to tell the system various pieces of information, for example, but not limited to, that the connector  6010  is different from the connector  6010  previously used, and or other information about the connector, for example, the lot number, etc. In some embodiments, each connector  6010  may include a unique identification indicator that may be heard by the AVS microphone when the disposable housing assembly  6000  and reusable housing assembly  6004  are attached. This may be beneficial for many reasons, including, but not limited to, the system may be able to differentiate between connectors  6010  and may determine not to pump/deliver if, for example, a new/different connector  6010  is not connected to a disposable housing assembly  6000 , e.g., 3 days after a connector  6010  is connected to a disposable housing assembly  6000 . In some embodiments, the system may recognize whether a connector  6010  is being reused and inform the user/patient that the connector  6010  was previously used and/or prevent the connector  6010  from being reused by alerting/alarming and not beginning delivery until and unless a new connector  6010  is connected. Also, in some embodiments, this may be beneficial to track the manufacturing lot and/or the expiration date of the connector  6010  to inform the user/patient that a recalled and/or expired connector has been attached to the disposable housing assembly  6000 . In some embodiments, the system may prevent a recalled and/or expired and/or previously used connector  6010  from being used for patient/user safety. 
     In the embodiment shown in  FIGS.  236 A- 236 T , the connector  6010  connects to the disposable housing assembly  6000  by the connector  6010  being rotated clockwise with respect to the disposable housing assembly  6000 . In other embodiments, the various features described may be configured differently and the connector  6010  may be connected to the disposable housing assembly  6000  by the connector  6010  being rotated counter-clockwise with respect to the disposable housing assembly  6000 . 
     In some embodiments, the disposable housing assembly  6000  may include a plug  6008  and the connector  6010  may include a plug receiver  6068  according to the various embodiment described herein. In some embodiments, the plug  6008  may be located in a different location and/or orientation than is shown herein. In various embodiments, the disposable housing assembly  6000  may include one or more mating features that correspond to one or more mating features on a connector  6010 . In some embodiments, these mating features may be located and/or orientated differently than is shown herein. 
     In various embodiments, the tubing  6002 , whether connected to a connector  6010  or directly to the disposable housing assembly  6000 , may connect to a cannula assembly  6026  on the opposite end. The cannula assembly  6026  may be any cannula assembly known in the art and may include a cannula, whether plastic or metal, and/or an interface between the tubing  6002  and a cannula which, in some embodiments, may include a septum or a needle interface. In some embodiments, the cannula assembly  6026  includes all of these elements. 
     Referring now to  FIG.  237   , in some embodiments, the connector  6010  may include a “core”  6090  on the bottom. The core  6090  may be an opening in the connector  6010 . In some embodiments, an identification tag  6092  may be located in the core  6090 , however, in various other embodiments, the identification tag  6092  may be located in another location on the connector  6010  (and in some embodiments, the identification tag  6092  may be located on the disposable housing assembly  6000  and/or on the cannula assembly  6026 ). In some embodiments it may be desired to include a method of the system identifying the connector  6010  (and/or disposable housing assembly  6000  and/or cannula assembly  6026 ) and/or a device for the system to identify the connector  6010 . In some embodiments, the identification tag  6092  may be an RFID tag. In some embodiments, the identification tag  6092  may be a near-field communication (“NFC”) readable RFID tag. In some embodiments, the identification tag  6092  may be a 2D or 3D bar code. In some embodiments, the identification tag  6092  may be a QR code. 
     In various embodiments, either before the connector  6010  is connected to the disposable housing assembly  6000  or after the reusable housing assembly  6004  has been connected to the disposable housing assembly  6000 , the reusable housing assembly  6004  and/or the remote control unit may read the identification tag  6092 . The identification tag  6092  may include various information, including, but not limited to, one or more of the following: unique identification number, date of manufacture, date of expiration, part number, lot number, and/or date of sale. Once the system reads the identification tag  6092 , the system may recognize the connector  6010  by its unique identification number or other, and thus, be able to recognize that the connector  6010  is either a new connector  6010 , i.e., has not been used previously, or is an old connector  6010 , i.e., the connector  6010  has been used previously. In some embodiments, once the connector  6010  is attached, the system may start a timer and the infusion pump may alert/alarm and/or turn off after a predetermined period of time where the connector  6010  has been used by the system. In some embodiments, this predetermined time may be the maximum time that the manufacturer recommends using the connector  6010  and/or cannula assembly  6026  attached to the connector  6010 . In some embodiments, this predetermined time may be the maximum time that the manufacturer recommends using the disposable housing assembly  6000 . 
     In some embodiments, the information conveyed by the identification tag  6092  may include information to authenticate the connector  6010 , i.e., to ensure that the connector  6010  is not a counterfeit part. In some embodiments, the remote control unit and/or reusable housing assembly  6004 /pump may include a listing of authentic identification information such that the system may “authenticate” the connector  6010  based on information received from the manufacturer. 
     In various embodiments, the identification tag  6092  may be a “peel and stick” RFID tag, which may be attached to the connector  6010 , for example, in the core  6090  area of the connector  6010 . In some embodiments, the identification tag  6092  may be glued and/or potted and/or another part may be pressed over the identification tag  6092  to sandwich the identification tag  6092 . In some embodiments, the identification tag  6092  may be taped to the connector  6010 . In some embodiments, where the identification tag  6092  is a bar code and/or QR code, the identification tag  6092  may be embossed, printed and/or molded onto the connector  6010 . 
     In some embodiments, the identification tag  6092  may be an RFID tag. In some embodiments, the RFID tag may be a tag that includes an antenna and chip. In some embodiments, the connector  6010  may be manufactured with a conductive ring and a chip could be electrically connected to the conductive ring. In some embodiments, the RFID tag could be on the label which could include additional information, for example, but not limited to, text, for example, part number, label, instructions, expiration date. 
     In some embodiments, the reusable housing assembly  6004  may include hardware to read the identification tag  6092 , which may include an RFID chip and/or a bar code, for example, 2D or 3D, or a QR code. For example, in some embodiments, the hardware may be an antenna which may be a copper trace on a board. In some embodiments the hardware may include a camera and/or a bar code scanner. In some embodiments, the remote control until may include hardware to read the identification tag  6092 , for example, in some embodiments, the remote control until may include an RFID transceiver and/or a near-field communication transceiver which may read the identification tag in those embodiments where the identification tag is an RFID tag. In some embodiments, the RFID tag may be one that may be read by an NFC transceiver. In some embodiments the remote control until may include a camera and/or a bar code scanner. 
     In some embodiments, using NFC may be desirable for many reasons, including, but not limited to, the reusable housing assembly  6004  and the remote control unit could both include NFC transceivers and the reusable housing assembly  6004  and the remote control unit may be paired in this fashion. This provides that the reusable housing assembly  6004  and the remote control unit come into physical contact with one another. This may be beneficial for many reasons including, but not limited to, the devices being paired are both in control of the user/patient and therefore, this may provide additional localized security when pairing the devices, i.e., to ensure that a non-intended device is not paired with either the remote control unit or the reusable housing assembly. 
     In some embodiments, the cannula assembly  6026 , connector  6010  and/or the disposable housing assembly  6000  may include identification tags  6092  and may include one or more of the features discussed above with respect to identification tags  6092  and/or may be used in one or more of the methods discussed above. 
     In various embodiments, the reusable housing assembly  6004  may begin pumping fluid only after either the reusable housing assembly  6004  or the remote control unit has received the information from the one or more identification tags  6092  in the system (e.g., disposable housing assembly  6000 , cannula assembly  6026  and/or connector  6010 ) and has determined that the information received is acceptable. For example, in some embodiments, if the information received does not convey to the system that a “new” and/or “acceptable” (i.e., is not expired, has not been recalled) connector  6010  and/or disposable housing assembly  6000  and/or cannula assembly  6026  is being connected to the system, then the system may not pump fluid and or may alert/alarm. 
     Various embodiments of the connector  6010  may be made from any color desired. In some embodiments, the connector  6010  may be made from a different color than the disposable housing assembly  6000 . In some embodiments, the connector  6010  may be made from the same color as the disposable housing assembly  6000 . 
     In some embodiments the connector  6010 , after being connected/attached to the disposable housing assembly  6000 , may not be removed from the disposable housing assembly  6000 . In some embodiments, once connected/attached to the disposable housing assembly  6000 , it may be difficult for a user to remove the connector  6010  from the disposable housing assembly  6000 . In some embodiments, this may be beneficial and/or desirable for once the tubing has been primed; the tubing  6002  is full of fluid, which, in some embodiments, may include a therapeutic fluid. If the connector  6010  were removed from the disposable housing assembly  6000 , and a cannula assembly  6026 , in fluid communication with the connector  6010 , was already inserted into a user, and if the connector  6010  were to be elevated such that it was higher than the cannula assembly  6026 , the fluid in the tubing  6002  may be delivered through the cannula assembly  6026  to the user. In some circumstances, this may not be desirable for many reasons, including, but not limited to, unintentional delivery of a volume of fluid. Therefore, prevention of this circumstance may be desirable. 
     In some embodiments, the disposable housing assembly  6000  may include fluid membranes that are not over molded, but rather molded separately then attached between the two layers of the disposable housing assembly  6000  and the layers may retain the membranes by affecting a seal through laser welding, however, in some embodiments, we may affect the seal through other processes, which may include, but are not limited to, one or more of the following: ultrasonic welding, heat staking, gluing, bonding or other processes. 
     Referring now also to  FIGS.  191 ,  192 ,  193 A and  193 B , in some embodiments, an alternative to having the locking ring on the reusable housing assembly  5010 /pump housing, as described herein, is to move the locking ring to the disposable housing assembly. In some embodiments this may be desirable for many reasons, including, but not limited to, preventing potential build up of dirt and debris in the interface; allowing the charger to seat further into the reusable housing assembly, protecting the charger pins; removing significant volume since the ring makes up approximately 10% volume; allows for the housing to be used as a big button by using compliant material around its base and a magnet and sensor to detect its displacement, both angular and y axis (pressing down). For example, as shown in  FIG.  191   , in some embodiments, the locking ring on the disposable housing assembly  5006  may be a sliding interface  5008 . A charger  5012 , shown in  FIG.  192   , may include an interlocking interface with the disposable housing assembly  5006  sliding interface  5008 . As shown in  FIG.  193 A- 193 B , in some embodiments, the reusable housing assembly  5010  may include a magnet  5012  that may be sensed by a sensor  5014  that may sense proximity and/or angle, on the disposable housing assembly  5006 . In some embodiments, the locking ring  5008  may be made from a compliant material and in some embodiments, this allows for twisting and depressing of the reusable housing assembly  5010  with respect to the disposable housing assembly  5006  when being attached. 
     In some embodiments, rather than a sliding screw style latch, the locking ring may use a spring latch, for example, as shown in  FIG.  194   . In some embodiments, the spring latch requires that the disposable housing assembly and the reusable housing assembly be aligned and pressed together with a spring, circular in shape, to be compressed while engaging and that snaps to lock in place as shown by the arrows in  FIG.  194   . 
     Referring now also to  FIG.  195   , regarding disposable housing assembly  5018  detection, in some embodiments, a flexible strip  5016  may be used which changes its resistance based on the amount it is bent to determine if the AVS module  5022  has been displaced by an installed/attached disposable housing assembly  5018 . 
     Referring now also to  FIG.  196   , it is desirable to measure the initial reservoir  5028  volume of the disposable housing assembly  5018  after fill. One method to measure this volume, in some embodiments, includes the use of a flat plate  5026  on the top of the reservoir  5028  with a flexible membrane around the edges. Once filled, the flat plate  5026  distance may be measured at a number of points, for example, in some embodiments; the number of points may be from one to three points, using an optical sensor or, in some embodiments, using a magnetic sensor on a spring loaded protrusion from the pump. To measure 20 units, for example, in some embodiments, may require approximately 0.01 mm to 0.25 mm resolution in height. In some embodiments, standard triangulation may be used to estimate the distance using a linear array and LED, for example. Additionally, a flat plate  5026  may be beneficial for the reservoir  5028  to start with no air. 
     Referring now also to  FIG.  197   , in some embodiments, a serpentine reservoir, such as the one shown, may be used. In some embodiments, the serpentine reservoir shown may be a tube-like structure with a hydrophobic filter  5030  on the end. The passages, in some embodiments, may be rounded or square and, in some embodiments, constructed of welded TOPAS or polycarbonate plastic. In some embodiments, the reservoir may be filled from one end through a septum  5032 . As fluid is drawn out of the reservoir by the pump, aid is drawn in through the filter  5030 . The filter  5030  may be configured to allow the passage of air but inhibit the passage of fluid or water vapor (in some embodiments, the filter may be a polypropylene filter and/or a filter made from PTFE). In various embodiments, it is desirable to prevent water vapor from passing through the filter/membrane  5030  to avoid concentrating the fluid through evaporation. In various embodiments, the fluid in the passage may be kept in place by the reservoir valve on one end and by surface tension on the other end. In various embodiments, the small diameter of the passage and surface tension at one end may prevent the fluid from “sloshing” which may degrade the fluid, for example, where the fluid is insulin or another therapeutic fluid. 
     In some embodiments of the various embodiments of the infusion pump assembly described herein, the pump chamber inlet valve may be an active valve, for example, actuated using shape-memory allow or other actuated. 
     Alarm and Alerts 
     In various embodiments, the remote control assembly and/or the infusion pump assembly and/or both may include at least one speaker and in some embodiments, the remote control assembly and/or the infusion pump assembly and/or both may include at least one graphical user interface and/or indicator lights. In some embodiments, the remote control assembly and/or the infusion pump assembly and/or both may include reminders and/or alarms and/or alerts to signal to the user either a critical or non-critical condition. The critical or non-critical condition may include, but is not limited to, an occlusion, low battery, low reservoir, change cannula reminder, reminder to check blood glucose, reminder to change glucose and/or interstitial sensor. Therefore, some reminders and/or alarms and/or alerts to signal to the user that a critical, i.e., therapeutically critical, situation is occurring that requires immediate action and/or a situation is occurring that requires the user to be immediately informed. In some embodiments, there situations are those that may or have the ability to immediately cause a negative outcome, medically, to the user. However, some reminders and/or alarms and/or alerts to signal to the user that a non-critical, i.e., therapeutically non-critical, situation is occurring that does not require immediate action and/or a situation is occurring that does not require the user to be immediately informed. In some embodiments, these situations are those that may not or may not have the ability to immediately cause a negative outcome, medically, to the user. 
     Thus, in some embodiments, for reminders and/or alarms and/or alerts that signal to the user that a non-critical situation is occurring, the user may program and/or select the mode of notification. In some embodiments, depending on the non-critical situation, a different mode of notification may be used. In some embodiments, all non-critical situations may include the same mode of notification. Thus, in some embodiments, user may select, but are not limited to, one or more of the following modes for one or more of non-critical situations giving rise to notifications: 
     1) “turn on mode” where the graphical user interface lights up and displays a message for a predetermined and/or preselected and/or preprogrammed duration or until the user confirms (e.g., user presses a button or other to indicate they confirm); 2) vibration only mode (vibration for a predetermined and/or preselected and/or preprogrammed duration or until the user confirms (e.g., user presses a button or other to indicate they confirm); 3) vibration then alarm mode (vibrate for a duration and if no confirmation (e.g., user presses a button or other to indicate they confirm), then alarm until confirmation by the user and/or alarm for a predetermined and/or preselected and/or preprogrammed duration); 4) alarm only (alarm for a predetermined and/or preselected and/or preprogrammed duration or until user confirms (e.g., user presses a button or other to indicate they confirm) in some embodiments, after confirmation but no further action, the sequence may repeat; 5) silent until turn on (no indication until the user wakes up the device and then the device indicates, for example, on the graphical user interface, the condition/situation); 6) vibrate only (vibrate for a predetermined and/or preselected and/or preprogrammed duration or until user confirms (e.g., user presses a button or other to indicate they confirm), in some embodiments, after confirmation but no further action, the sequence may repeat; 7) wake up/turn on (i.e., graphical interface/screen lights up/turns on and displays the situation/alarm/alert/reminder) until confirmation, then silent/sleep and/or may repeat sequence if anticipated action not taken in predetermined/preprogrammed/preselected duration). In some embodiments, a silent until wake up may refer to where there is a non-critical condition, the system may not remind and/or alarm and/or alert until the user wakes up the graphical user interface and/or device and, in some embodiments, upon first “wake up” the screen displays the reminder and/or alarm and/or alert. 
     In some embodiments, it may be desirable for the user to have the option to preselect/preprogram/predetermine when a non-critical reminder/alarm/alert is given, regardless of the type of reminder/alarm/alert. For example, in some embodiments, the user may request that no non-critical reminder/alarm/alert be given between 11 pm and 6 am, i.e., while the user is sleeping. In some embodiments, this may be termed a timeout. In some embodiments, the user may request a “temporary” timeout for non-critical reminders/alarms/alerts, for example, between 6 pm-8 pm, while, for example, attending a quiet event. Thus, in some embodiments, for non-critical reminder/alarms/alerts the user may do one or more, but not limited to, the following: preselect/predetermine/preprogram the duration of the reminder/alarm/alert; reselect/predetermine/preprogram the type of the reminder/alarm/alert; reselect/predetermine/preprogram timeout or quiet times where no reminder/alarm/alert is given (and in some embodiments, where this is selected by the user, upon wake up, the device may display the reminder/alarm/alert, and/or in some embodiments, at the end of the preselected/predetermined/preprogrammed time-out, any reminder/alarm/alert may be given). 
     In some embodiments where, for example, the system may remind the user to change their cannula, for example, 3 days after filling the cannula. The user may request, for these reminders, that for this reminder, a reminder timeout between 10 pm and 6 am. Thus, the user will not be awoken to remind them to change the cannula. In some embodiments, when the user wakes up the device, for example, at 7 am, the reminder, if applicable, may be indicated, which, in some embodiments, may be indicated by the method reselected/preprogrammed/predetermined by the user. 
     Referring now also to  FIGS.  239  and  240   , another embodiment of the AVS assembly  7000  is shown. With respect to  FIG.  240   , the AVS assembly  7000  includes a speaker  7002  and two microphones, one shown as  7008 . The AVS assembly  7000  includes a “figure eight” seal  7010 . The AVS assembly  7000  includes a top housing  7004  and a bottom housing  7006 . 
     Referring now also to  FIG.  239   , the AVS membrane  7012 , which, in the exemplary embodiment, is located in the disposable housing assembly  6000 , and an acoustic seal  7014  is shown. In some embodiments, the acoustic seal is overmolded onto the reusable housing assembly  6004  portion and is therefore located between the disposable housing assembly  6000  and the reusable housing assembly  6004 . When the reusable housing assembly  6004  is engaged with the disposable housing assembly  6000 , the acoustic seal  7014  comes into contact with surfaces on the disposable housing assembly  6000  and a seal is made. 
     In this embodiment of the AVS assembly, a spring is not included; however, in various other embodiments of this embodiment of the AVS assembly, a spring may be included. In the embodiments without a spring, the AVS membrane  7012  may be made from SEBS and may include properties that are desirable for the AVS membrane  7012 . 
     The membrane in the disposable housing assembly  6000  may be made from plastic and in some embodiments, more than one type of plastic. For example, in some embodiments, the membrane may be made from SEBS and SANTOPRENE. In some embodiments, the AVS membrane  7012  is made from SEBS and the remainder of the membranes is made from SANTOPRENE. In various embodiments of the membrane, the membrane may be at least partially coated with parylene, and in some embodiments, the entire membrane is coated with parylene. 
     Referring now also to  FIGS.  244 A and  244 B , another embodiment of the disposable housing assembly  7000  is shown. The disposable housing assembly  7000  includes a tubing  7034  and a cannula assembly  7026 , similar to those describe above. With respect to the disposable housing assembly  7000 , in some embodiments, the disposable housing assembly  7000  includes a fluid path  7038  that may, in some embodiments, include a chevron path  7040 . This may be desirable/beneficial for many reasons, including, but not limited to, minimizing the amount of air that may become trapped in the fluid path  7038 . 
     Referring now also to  FIGS.  245 A and  245 B , in some embodiments of the disposable housing assembly  7000 , the pump chamber membrane  7042  may be shaped as a pre-formed dome like structure. In some embodiments this may be beneficial/desirable for many reasons, including, but not limited to, providing a higher vacuum force on the reservoir to pump greater volumes of fluid per pump stroke and moving more fluid from the reservoir to the pump chamber with less displacement. In some embodiments, and as shown in  FIG.  245 B , the pump plunger  7044  may be pre-engaged with the pump chamber membrane  7042 . Thus, as the pump plunger  7044  is actuated by the actuator assembly, the pump plunger  7044 , already engaged with the pump chamber member  7042 , may travel less distance to pump fluid from the reservoir  908 . This may be beneficial for many reasons, including, but not limited to, exerting less wear and tear on the shape memory alloy and therefore, increasing the longevity of the shape memory alloy. Thus, the pump may move more fluid using less force, i.e., the pump is more efficient. 
     Referring now also to  FIGS.  246 A and  246 B , in some embodiments, the cover  7046  of the reusable housing assembly, which may include at least some of the features described above with respect to the reusable housing assembly, may include a speaker  7048 . The speaker  7048  may be heat staked in the cover  7036 . A printed circuit board (“PCB”)  7050  may also be located adjacent to the speaker  7048 , in some embodiments, which may include, in some embodiments, spring loaded contacts  7052  such that the speaker  7048  may be connected to the PCB through spring loaded electrical contracts. Placement of the speaker  7048  in the cover  7046  of the reusable housing assembly may be desirable/beneficial for many reasons, including, but not limited to, providing louder/better sound quality to the user by placement of the speaker  7048  closer to the “outside” of the infusion pump system. 
     Clip Assembly 
     In various embodiments, a clip assembly may be attached to one of the various embodiments of the infusion pump assembly described herein. In various embodiments, the reusable housing assembly, attached to the disposable housing assembly and connector, may be inserted into a clip assembly. 
     Referring now also to an embodiment of the clip assembly in  FIGS.  247 A- 247 C . The clip assembly  8000  includes a clip housing portion  8002  and a clip portion  8004 . In various embodiment, the clip housing portion  8002  may be made from plastic, but in various embodiments, the clip housing portion  8002  may be made from any material, including, but not limited to, one or more of the following: metal, plastic, metal-plastic combinations. In various embodiments, the clip housing portion  8002  may include finger tabs  8006 ,  8008  which may be beneficial and/or used to aid in the removal of the infusion pump assembly from the clip housing portion  8002 . In various embodiments, the finger tabs  8006 ,  8008  may be shaped differently than shown. 
     In various embodiments, the clip housing portion  8002  includes retaining ribs  8010 ,  8012 ,  8014 ,  8016  that are attached to clip housing portion sections  8020 ,  8022 ,  8024 ,  8026 . In various embodiments, the clip housing portion sections  8020 ,  8022 ,  8024 ,  8026  may be separated by slots. In various embodiments, the clip housing portion sections  8020 ,  8022 ,  8024 ,  8026  and slots may be beneficial/desirable for many reasons, including, but not limited to, providing appropriate flexibility to provide a desirable amount of spring to the clip housing portion  8002  for attachment to, and removal from, the infusion housing assembly. Thus, in various embodiments, that clip housing portion sections  8020 ,  8022 ,  8024 ,  8026  may expand, allowing for the capture of the infusion pump assembly, and then contract to hold the infusion pump assembly inside the clip housing portion  8002 . 
     The retaining ribs  8010 ,  8012 ,  8014 ,  8016  hold the infusion pump assembly by interacting with the groove where the reusable housing assembly and disposable housing assembly meet when attached. 
     As shown in this embodiment of the clip assembly  8000 , the clip housing portion  8002  includes an opening to accommodate the connector/tab portion of the disposable housing assembly (not shown). 
     In various embodiments, the clip housing portion  8002  includes a recessed area  8028  to accommodate a hook or loop surface, described in more detail above, that, in some embodiments, may be attached to the bottom of the disposable housing assembly. 
     In various embodiments, the clip portion  8004  is attached to the back portion of the clip housing portion  8002 . In various embodiments, the clip portion  8004  may be removable attached to the back portion of the clip housing portion  8002  by clipping into clip features  8032 . In various embodiments, the clip features  8032  are features which hold the clip portion  8004  onto the back of the clip housing portion  8002 . 
     In various embodiments, the clip features  8032  hold the clip portion  8004  such that the clip portion  8004  may rotate about the clip housing portion  8002 . In various embodiments, the back of the clip housing portion  8002  may include features, such as protrusions  8030 , and in various embodiments, a plurality of protrusions, which interact with the clip portion  8004 , such that when the clip portion  8004  rotates with respect to the clip housing portion  8002 , the clip portion  8004  may be captured between two of the protrusions  8030 . The protrusion  8030  and clip  8004  arrangement may be desirable for many reasons, including, but not limited to, the ability to provide both audio and tactile feedback to a user who is turning the clip housing portion  8002  about the clip portion  8004 , such that a “click” sound may be heard as the clip portion  8004  advances from protrusion  8030  to the next protrusion. This system also may be beneficial for providing an ability to rotate the clip housing portion  8002  without rotating or moving the clip portion  8004   
     In various embodiments, different protrusion may be used, and in some embodiments, the clip portion  8004  may include protrusions and the clip housing portion  8002  may include indentations to provide for tactile feedback as the protrusions on the clip portion  8004  rotate from one groove to the next. 
     Referring now also to  FIGS.  249 A- 249 D , an embodiment of the clip portion  8004  is shown. In various embodiments, the clip portion  8004  may be made from any materials, including, but not limited to, plastic and/or metal. In various embodiments, the clip portion  8004  may be overmolded with powder coat, or other materials, which may be desirable/beneficial for many reasons, including, but not limited to, maintaining the temperature of the clip portion  8004  such that, for example, in embodiments where the clip portion  8004  is metal, the clip portion  8004  is not cold to the touch against the user&#39;s skin. 
     The clip portion  8004  includes a rounded portion  8034  that clips into the clip feature  8032 . The rounded portion  8034  also allows for the clip portion  8004  to rotate within the clip features  8032  with respect to the clip housing portion  8002 . In various embodiments, the shape of the clip portion  8004  may vary. 
     Referring now also to  FIGS.  264 A- 264 B , another embodiment of the clip assembly is shown. The clip assembly  26400  includes a clip housing portion  26402  and a clip portion  26404 . In various embodiment, the clip housing portion  26402  may be made from plastic, but in various embodiments, the clip housing portion  26402  may be made from any material, including, but not limited to, one or more of the following: metal, plastic, metal-plastic combinations. In various embodiments, the clip housing portion  26402  may include finger tabs  26406 ,  26408  which may be beneficial and/or used to aid in the removal of the infusion pump assembly from the clip housing portion  26402 . In various embodiments, the finger tabs  26406 ,  26408  may be shaped differently than shown. 
     In various embodiments, the clip housing portion  26402  includes retaining ribs, similar to those shown and described above with respect to  FIGS.  247 A- 247 C  that are attached to clip housing portion sections (as describe above with respect to  FIGS.  247 A- 247 C ). In various embodiments, the clip housing portion sections may be separated by slots. In various embodiments, the clip housing portion sections and slots may be beneficial/desirable for many reasons, including, but not limited to, providing appropriate flexibility to provide a desirable amount of spring to the clip housing portion  26402  for attachment to, and removal from, the infusion housing assembly. Thus, in various embodiments, that clip housing portion sections may expand, allowing for the capture of the infusion pump assembly, and then contract to hold the infusion pump assembly inside the clip housing portion  26402 . 
     The retaining ribs hold the infusion pump assembly by interacting with the groove where the reusable housing assembly and disposable housing assembly meet when attached. 
     As shown in this embodiment of the clip assembly  26400 , the clip housing portion  26402  includes an opening to accommodate the connector/tab portion of the disposable housing assembly (not shown). 
     In various embodiments, the clip housing portion  26402  includes a recessed area  26410  to accommodate a hook or loop surface, described in more detail above, that, in some embodiments, may be attached to the bottom of the disposable housing assembly. 
     In various embodiments, the clip portion  26404  is attached to the back portion of the clip housing portion  26402 . In various embodiments, the clip portion  26404  may be removably attached to the back portion of the clip housing portion  26402  by clipping into clip feature  26412 . In various embodiments, the clip feature  26412  is a feature which holds the clip portion  26404  onto the back of the clip housing portion  26402 . 
     In various embodiments, the clip features  26412  hold the clip portion  26404  such that the clip portion  26404  may rotate about the clip housing portion  26402 . In various embodiments, the back of the clip housing portion  26402  may include features, such as indentations and or dimples  26414 , and in various embodiments, a plurality of dimples (shown), which interact with the clip portion  26404 , such that when the clip portion  26404  rotates with respect to the clip housing portion  26402 , the clip portion  26404  may be captured between two of the dimples  26414 . The dimples  26414  and clip  26404  arrangement may be desirable for many reasons, including, but not limited to, the ability to provide both audio and tactile feedback to a user who is turning the clip housing portion  26402  about the clip portion  26404 , such that a “click” sound may be heard as the clip portion  26404  advances from dimple  26414  to the next dimple. This system also may be beneficial for providing an ability to rotate the clip housing portion  26402  without rotating or moving the clip portion  26404   
     In various embodiments, different dimples or features may be used, and in some embodiments, the clip portion  26404  may include dimples and the clip housing portion  26402  may include protrusions to provide for tactile feedback as the protrusions on the clip portion  26404  rotate from one groove to the next. 
     Still referring to  FIGS.  264 A- 264 B , an embodiment of the clip portion  26404  is shown. In various embodiments, the clip portion  26404  may be made from any materials, including, but not limited to, plastic and/or metal. In various embodiments, the clip portion  26404  may be overmolded with powder coat, or other materials, which may be desirable/beneficial for many reasons, including, but not limited to, maintaining the temperature of the clip portion  26404  such that, for example, in embodiments where the clip portion  26404  is metal, the clip portion  26404  is not cold to the touch against the user&#39;s skin. In various embodiments, the shape of the clip portion  26404  may vary. 
     Referring now also to  FIG.  265   , another embodiment of the clip assembly is shown. The clip assembly  26500  includes a clip housing portion  26502  and a clip portion  26504 . In various embodiment, the clip housing portion  26502  may be made from plastic, but in various embodiments, the clip housing portion  26502  may be made from any material, including, but not limited to, one or more of the following: metal, plastic, metal-plastic combinations. In various embodiments, the clip housing portion  26502  includes retaining ribs  26506 ,  26508 ,  26510 , similar to those shown and described above with respect to  FIGS.  247 A- 247 C  that are attached to the clip housing portion  26502 . The retaining ribs  26506 ,  26508 ,  26510  hold the infusion pump assembly by interacting with the groove where the reusable housing assembly and disposable housing assembly meet when attached. 
     An various embodiments, the clip assembly portion  26502  includes an opening to accommodate the connector/tab portion of the disposable housing assembly (not shown). 
     In various embodiments, the clip housing portion  26502  may include a recessed area to accommodate a hook or loop surface, described in more detail above, that, in some embodiments, may be attached to the bottom of the disposable housing assembly. 
     Still referring to  FIG.  265   , an embodiment of the clip portion  26504  is shown. In various embodiments, the clip portion  26504  may be made from any materials, including, but not limited to, plastic and/or metal. In various embodiments, the clip portion  26504  may be overmolded with powder coat, or other materials, which may be desirable/beneficial for many reasons, including, but not limited to, maintaining the temperature of the clip portion  26504  such that, for example, in embodiments where the clip portion  26504  is metal, the clip portion  26504  is not cold to the touch against the user&#39;s skin. In various embodiments, the shape of the clip portion  26504  may vary. 
     Referring now also to  FIGS.  250  and  251   , in some embodiments of the disposable housing assembly  8040 , the valve areas may include clearance areas  8042 ,  8044 ,  8046  to decrease or eliminate interference between the reusable housing portion and the membrane assembly of the disposable housing assembly  8040 . 
     Referring now also to  FIGS.  252  and  253   , in some embodiments, a hole  8048  may be included in the disposable housing assembly  8040 . This may be beneficial/desirable for many reasons, including, but not limited to, preventing the membrane assembly material from extruding into the exit of the reservoir and restriction flow of fluid from the reservoir to the fluid line. 
     Referring now also to  FIGS.  254  and  255   , in various embodiments of the disposable housing assembly  8040 , a seal bead  8050  may be included about the valves and pumping chamber. In various embodiments, this may be beneficial/desirable for many reasons, including, but not limited to, creating a tortuous path. The seal bead also presents a more robust seal for the disposable housing assembly. 
     As discussed above, the various embodiments of the connector (or fluid connector, said terms may be used interchangeably) may include a plug (or post, namely which may be used interchangeably throughout this specification) that may include one or more features. In various embodiments, the plug may connect to the disposable housing assembly through a luer connection. Referring now to  FIGS.  256 A- 256 C , in various embodiments, any one or more embodiments of the plug  25600  may include (either in addition to one or more features described above or instead of one or more features described above) one more tab features  25602 ,  25604 . In some embodiments, for example, as shown in  FIGS.  256 C- 256 C , various embodiments of the plug  25600  may include two tab features  25606 ,  25608  on either side of the plug  25600 . In various embodiments, the tab features  24602 ,  25604 ,  25606 ,  25608  may take up “play” or “wiggle” between the plug  25600  and the disposable housing assembly exit. In various embodiments, and referring also to  FIG.  256 D , the disposable housing assembly  25610  may include slots  25612 ,  25614  at the exit  25616  to accommodate the tab features  24602 ,  25604 ,  25606 ,  25608 . In some embodiments, the slots  25612 ,  25614  may be ramped, which may be desirable/beneficial for many reasons, including, but not limited to, the ramped slots  25612 ,  25614  may assist in the plug  25600  moving further into the disposable housing assembly  25610 . Once inside the disposable housing assembly  25610 , the tabs with bend such that the plug  25600  and the exit  25616  form a luer connection. In some embodiments the tab features  24602 ,  25604 ,  25606 ,  25608  therefore may drive the plug  25600  as far into the exit  25616  as it may go. In some embodiments, the tab features  24602 ,  25604 ,  25606 ,  25608  are angled with respect to the plug  25600  such that the angle is smaller than 180 degrees, upon entry into the exit  25616 . As the plug  25600  enters further into the exit  25616 , the tab features  24602 ,  25604 ,  25606 ,  25608  move such that they are flattened against the plug  25600 . This may be desirable/beneficial for many reasons, including, but not limited to, the plug  25600  may only rotate with respect to the disposable housing assembly  25610  when the tab features  24602 ,  25604 ,  25606 ,  25608  are flattened, thus ensuring that the plug  25600  is all the way inside the exit  25616  of the disposable housing assembly  25610  before the connector is locked to the disposable housing assembly  25610 . This may be desirable/beneficial for many reasons, including, but not limited to, preventing leaks. In various embodiments of this embodiment of the plug  25600 , the plug  25600  may be rigid, i.e. not include an elastomer, and the tab features  24602 ,  25604 ,  25606 ,  25608  may be made from a rigid material that is thin enough to bend as described above. However, in various other embodiments, the plug  25600  may be made from any one or more of the various materials described herein with respect to the various embodiments of the plug. In some embodiments, the plug  25600  may be made from TERLUX® and/or another ABS material. 
     Referring now also to  FIGS.  257 A- 257 B , in various embodiments, the connector  25700  may include a plug  25700  that may include one or more seals. In some embodiments, as discussed above, the seals may be any type of seal, including, but not limited to, a face seal and or a radial seal. In some embodiments, such as those shown in  FIGS.  257 A- 257 B , the plug  25700  may include a radial seal  25702  and a face seal  25706 . Thus, in some embodiments, the plug  25700  may include two seals, one having a larger diameter than the other. 
     Referring now also to  FIGS.  258 A- 258 B , in various embodiments, the connector  25800  may include a plug  25800  that includes a single elastomer seal  25804  including a radial seal portion  25806  and a face seal portion  25810  separated by an elastomer portion. These embodiment may be beneficial/desirable for many reasons, including, but not limited to, this embodiment allows for the removal of all parting lines on the plug  25802  and the elastomer seal  25804 . This may be beneficial/desirable for many reasons, including, but not limited to, removing the leak paths that may be present due to parting lines. 
     Referring now to  FIGS.  259 A- 259 C , in various embodiments, the connector  25900  may include a plug  25902  that includes a seal  25904  that may be an elastomer and includes two rings  25906 ,  25908  separated by an elastomer section. Various embodiments of the plug may include a double seal. The plug  25902  is shown without the seal in  FIG.  259 C . In this embodiment of the plug  25902 , there are no parting lines on the surface of the plug  2590 . This may be beneficial/desirable for many reasons, including, but not limited to, removing the leak paths that may be present due to parting lines. 
     Referring now also to  FIGS.  260 A- 260 G , some embodiments of the connector  26000  include a plug  26002  that is rigid and forms a luer connection with the exit of the disposable housing assembly. In various embodiments, the plug  26002  may be tapered, and the percentage of tapering may vary. In some embodiments, the taper may be 6%, however, in various other embodiments, the taper may be greater or less than 6%. In some embodiments, including the one shown in  FIGS.  260 A- 260 G , the plug  26002  is removably attached to the connector  26000  and, in addition, is slidably connected to the connector  26000 . Thus, as shown in  FIGS.  260 B and  260 C , the plug  26002  may slide from an initial position, shown in  FIG.  260 B , to a final position, shown in  FIG.  260 D  with respect to the tab portion of the connector  26008 . In various embodiments, the tab portion has a first side or reservoir side and a second side or tubing side and the plug may slide in the direction of the tubing side. In various embodiments, the plug  26002  is configured such that it includes at least one stop feature wherein the exit end portion  26004  of the plug  26002  includes a first stop feature, for example, a lip, that limits the travel of the plug  26004  in one direction. The plug  26002  tubing end portion  26006  in various embodiments also includes a second stop feature, for example, a lip, that limits the travel of the plug  26002  in the other direction. In various embodiments, the plug  26002  may be made from any material, for example, but not limited to, TERLUX® and/or another ABS material. Although not shown in the embodiments shown in  FIGS.  260 A- 260 D , the plug  26002  includes a length of tubing attached to the tubing end portion  26006 , which tubing and attachment may be any one or more of the various embodiments described in more detail above with respect to various embodiments of the plug and the connector. The length of tubing may be any length desired, including, but not limited to, any length between 1 inch and 10 feet, and in some embodiments may be either 4 inches or 23 inches, however, in various embodiments, the length may be greater or less than 4 inches or 23 inches. 
     In various embodiments, the connector  26000  includes a tab portion  26008  including a mating locking feature  26010 , which may be, in various embodiments, the mating locking feature described above with respect to various other embodiments of the connector  26000 . In various embodiments, the mating locking feature  26010  is configured to mate with a corresponding feature on the disposable housing assembly  26012 . 
     In various embodiments, the plug  26002  of the connector  26000  is inserted into the disposable housing assembly  26012  with the tab portion  26008  (or body portion, which may be used interchangeably with the term tab portion) pointing upward. Once the plug  26002  portion is inside the disposable housing assembly  26012 , the tab portion  26008  may be rotated about the plug  26002  to rest above the disposable housing assembly  26012  adjacent to the exit (i.e., adjacent to the tab portion  26016  on the disposable housing assembly). In some embodiments, mating locking features  26010 ,  26014  may be included on the tab portion  26008  of the connector  26000  and the disposable housing assembly  26012  such that the connector  26000  is held in place before the reusable housing assembly (not shown, shown and described as  6004  above) is attached to the disposable housing assembly  26012 . In some embodiments, the mating locking features  26010 ,  26014  may include, but are not limited to, snap buttons and/or catch features. In some embodiments, a hook or other feature may be located on the opposite end of the tab  26008  portion of the connector  26000  such that it loops over the end of the tab portion  26016  of the disposable housing assembly  26012  and maintains the position of the connector  26000 . 
     Still referring also to  FIGS.  260 A- 260 G , another embodiment of a connector  26000  is shown. The connector  26000  may include a tab portion  26008 , a catch feature  26018 , a latching feature  26010 , and a plug  26002 . In some embodiments, the tab portion  26008  of the connector  26000  may include mating locking features that interact with corresponding features in the disposable housing assembly  26012 . In some embodiments, the tab portion  26008  may include features that interact with other portions of the disposable housing assembly  26012 . As shown, in some embodiments, the connector  26000  may include a male latching feature  26010  on the end of the tab portion  26008  of the connector  26000 . In some embodiments, the latching feature  26010  may mate with a corresponding latching feature (a female latching feature  26014 ) on the disposable housing assembly  26012 . In some embodiments, the latch may be a removably secure fit and/or a snap fit and/or a loose snap fit and in some embodiments may include a spring latch portion. In various other embodiments, the shape and size of the connector  26000  may vary and/or in various other embodiments, other types of features such as mating locking features may be used, which include, but are not limited to, latches, catches, snap fits, adhesives, and other mechanisms for securing a connector  26000  to the tab  26016  of the disposable housing assembly  26012 . 
     In some embodiments, the connector  26000  may include a locking ring feature on the underside. The locking ring feature in some embodiments may be tapered and/or in some embodiments, the locking ring feature may be at least slightly curved. In some embodiments, the locking ring feature may interact with the locking ring of the reusable housing assembly and may act together with the locking ring to secure the connector to the disposable housing assembly. 
     As discussed above, in various embodiments, the plug  26002  of the connector  26000  is inserted into the exit of the disposable housing assembly  26012  with the tab portion  26008  pointing in the general upward direction. Once the plug  26002  is inside the exit, the tab portion  26008  of the connector  26000  may be rotated to rest adjacent to the tab portion  26016  of the disposable housing assembly  26012 . In some embodiments, mating locking features may be included on the tab portion  26008  of the connector  26000  and the disposable housing assembly  26012  such that the connector  26000  is held in place before the reusable housing assembly is attached to the disposable housing assembly  26012 . In some embodiments, the mating locking features may include, but are not limited to, post and opening, snap, buttons, latch features and/or catch features. In some embodiments, a hook or other feature may be located on the opposite end of the tab portion  26008  of the connector  26000  such that it loops over the end of the tab portion  26016  of the disposable housing assembly  26012  and maintains the position of the connector  26000 . In the embodiment shown in  FIGS.  260 A- 260 G , the mating locking features include a male latching feature  26010  on the connector  26000  and a female latching feature  26014  on the disposable housing assembly  26012 . 
     In various embodiments, once the connector  26000  is attached to the disposable housing assembly  26012 , the connector  26000  may only be removed when intended, i.e., the connector  26000  is maintained on the disposable housing assembly  26012  unless and until a user desires to remove the connector  26000 . As discussed above, in some embodiments, the connector  26000  may be non-removably attached, however, in some embodiments; the connector  26000  may be removably attached. 
     While the connector  26000  is being attached to the disposable housing assembly  26012 , the male latching feature  26010  is mated with the female latching feature  26014 . In some embodiments, male and female latching features  26010 ,  26014  may work together to further stabilize the connection of the connector  26000  to the disposable housing assembly  26012 . Additionally, in various embodiments, the male and female latching features  26010 ,  26014  may contribute to maintaining the plug  26002  in the exit of the disposable housing assembly  26012 . Thus, in some embodiments, the male and female latching features  26010 ,  26014  may contribute to maintaining and/or enforcing both the insertion of the plug  26002  into the exit and/or maintaining and/or enforcing the position of the connector  26000  such that after the plug  26002  is inserted into the exit, the plug  26002  is maintained in the exit unless and until a user desires to remove the plug  26002  from the exit. Additionally, once the male and female latching features  26010 ,  26014  are mated, the plug  26002  is fully inserted and therefore, may, in some embodiments, serve as an indication that the plug  26002  has been fully inserted into the exit. 
     As discussed above, in the embodiment shown in  FIGS.  260 A- 260 G , the plug  26002  in the connector  26000  is slidably attached to the connector  26000  such that the plug  26002  may move forward or back and the connector tab portion  26008  may move independent from the plug  26002 . This may be beneficial/desirable for many reasons, including, but not limited to, the mating of the luer (i.e., mating between the plug  26002  and the exit of the disposable housing assembly  26012 ) may be completed before the tab portion  26008  of the connector  26000  is rotated and attached to the disposable housing assembly  26012 . Thus, the rotation of the tab portion  26008  about the plug  26002  is to connect the tab portion  26008  to the disposable housing assembly  26012 , but the luer connection of the plug  26002  to the exit is completed by pushing the plug  26002  into the exit of the disposable housing assembly  26012 . The plug  26002  being slidable within the tab portion  26008  of the connector  26000  is beneficial/desirable for many reasons, including, but not limited to, the depth in which the plug  26002  travels within the exit of the disposable housing assembly  26012  to form a luer connection may vary due to variances, for example, tolerances due to manufacturing. Thus, the plug  26002  may move deeper into the exit if the plug is smaller in comparison with the exit, or the exit is larger in comparison with the plug  26002 ; and the plug  26002  may form a connection shallower in the exit if the plug  26002  is large in comparison with the exit or the exit is smaller in comparison with the plug  26002 . Thus, variances in tolerances will not prevent a luer connection from being made between the plug  26002  and the exit/disposable housing assembly  26012 . 
     In some embodiments, the tab portion  26016  of the disposable housing portion  26012  may be shaped as shown in  FIGS.  260 E- 260 G . In some embodiments, the connector  26000 , once attached to the disposable housing assembly  26012 , may extend the tab portion  26016  of the disposable housing assembly  26012 . In some embodiments, once the connector  26000  is attached to the disposable housing assembly  26012 , the connector  26000  and tab portion  26016  may be flush and continuous. 
     In some embodiments, the connector  26000  may include an indent  26020 , as shown. The indent  26020  may be shaped as shown or, in various embodiments, may be shaped and sized differently. 
     In various embodiments, the female latching feature  26014  on the disposable housing assembly  26012  may be located adjacent to the tab portion  26016 . In some embodiments, for example, as shown in  FIGS.  260 E- 260 G , the female latching feature  26014  may be configured such that it receives the male latching feature  26010  on the connector  26000  from the top. Some embodiments may not include mating latching features  26010 ,  26014 . In some embodiments, the location and/or orientation of the female latching feature  26014  may vary. In some embodiments, the location and/or orientation of the male latching feature  26010  may vary. 
     In some embodiments, the connector  26000  may be made from rigid plastic. In some embodiments, the locking ring feature and/or the latching features may be overmolded with a thin layer of compliant materials. In some embodiments, as discussed above, the plug  26002  may include an overmold of compliant material and/or be made from compliant material. In some embodiments, the locking ring feature and/or the latching feature may be made from compliant material. In embodiments where the male or female latching features  26010 ,  26014  include compliant material, use of compliant material may increase the “squish” between the male latching feature  26010  and the female latching feature  26014  and therefore, resulting in a highly compressed and/or tight fit between the male and female latching features  26010 ,  26014 . 
     Referring now also to  FIG.  136   , in some embodiments, the connector  26000  may include icons that indicate “locked” and “unlocked”, similar to those shown and described above with respect to  FIG.  136   . Thus, in some embodiments, the “locked” and “unlocked” position may also be visually indicated to a user/patient using icons that may be molded, silk-screened, pad printed, injection molded, etched, printed and/or cut-out, e.g., translucent cut-outs of icons, on the connector  26000 . In some embodiments using translucent cut-outs, the tab portion  26016  of the disposable housing assembly  26012  may be a contrasting color to the connector  26000  for visually viewing the tab portion  26016  of the disposable housing assembly  26012  color through the cut-outs. Thus, the icons may indicate whether the reusable housing assembly is in a locked or unlocked relationship with the disposable housing assembly  26012 . In various embodiments, the icons may be any form that may indicate “locked” and “unlocked”, or a similar indication, to aid in the user/patient&#39;s understanding of the orientation/position between the reusable housing assembly and the disposable housing assembly  26012 . In some embodiments, an arrow icon may also appear between the “locked” and “unlocked” icons. 
     Although not shown in  FIGS.  260 A- 260 G , in various embodiments, the reusable housing assembly may be any one or more of the various embodiments of the reusable housing assembly described herein, including, but not limited to, the reusable housing assembly shown and described above as  6004 . 
     The plug  26002  may include any embodiment described herein, however, in some embodiments; the plug  26002  may be tapered and may either be rigid without any overmolding, be rigid with an overmold of elastomeric/compliant material or be made from elastomeric/compliant material. In various embodiments, the plug  26002  may include a seal, for example, in some embodiments; the plug  26002  may include one or more of: a radial seal and/or a face seal and/or both. 
     In some embodiments, tubing attaches to the connector  26000  as described above. In some embodiments, the tubing may attach to the connector  26000  and there may be a rigid plastic channel within the connector  26000  and through the plug  26002 . In some embodiments, the tubing may extend into the connector  26000  and in some embodiments; the tubing may extend all the way through the connector  26000  and through the plug  26002 . In some embodiments, the tubing may extend past the end of the plug  26002 . Although not shown in  FIGS.  260 A- 260 G , the various embodiments of the connector may include any of the embodiments of the tubing and tubing connection as shown and described above with respect to various other embodiments of the connector. 
     In various embodiments, there is maintained a continuous flow lumen from the exit to the cannula (not shown). This may be desirable and/or beneficial for many reasons, including, but not limited to, minimizing and/or eliminating dead volume, minimizing priming volume and/or prevention of or minimizing the occurrence of air traps. 
     Some embodiments of the connector  26000  may also include a catch/catching feature  26018  on the opposite side as the male latching feature  26010 . The catch feature  26018 , when the connector  26000  is connected to the disposable housing assembly  26012 , interferes with the disposable housing assembly  26012  and prevents the connector  26000  from rotating further. Thus, in some embodiments, the connector  26000  and the disposable housing assembly  26012  form an interference fit in at least one location. Together with the male and female latching features  26010 ,  26014 , in some embodiments, once the connector  26000  is attached, the connector  26002  may be held in place by these mating features  26010 ,  26014 . 
     The connector tab portion  26008  may include gripping features, however, in the some embodiments; the connector  26000  is sized such that a user may grip the connector  26000  for insertion/attachment with the disposable housing assembly  26012 . Some embodiments including grip features, may include, but are not limited to, one or more of the following: a textured surface, bumps, lumps, protrusions or indentations in any size, shape and/or number. 
     In various embodiments of the connector  26000 , once the connector  26000  is connected to the disposable housing assembly  26012 , the reusable housing assembly  6004  (which may also be one or more of the various reusable housing assemblies described herein or incorporated herein by reference) may be connected/attached to the disposable housing assembly  26012  by being rotated about the disposable housing assembly  26012 . As the reusable housing assembly is rotatably connected to the disposable housing assembly  26012 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the connector  26000 , such that the rotation of the reusable housing assembly  6004  about the disposable housing assembly  26012  prevents the connector  26000  from being removed from the disposable housing assembly  26012 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  26012 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  26012 , and, that the connector  26000  is connected such that it will be maintained connected to the disposable housing assembly  26012  until and unless the user wishes to remove the connector  26000 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the connector  26000 , maintaining the connector  26000  in an attached position. In some embodiments, features in the locking ring interact with a locking ring feature on the connector  26000  and contribute to maintain the connector  26000  in position with respect to the disposable housing assembly  26012 . In some embodiments, the tab portion  26008  of the connector  26000  may include an indent portion  26020  which may be configured to interact with the nub  808  and/or spring plunger/tab of the locking ring assembly of the reusable housing assembly  6004 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  26012 , the connector  26000  may not be removed from the disposable housing assembly  26012 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  26012  before the connector  26000  may be removed from the disposable housing assembly  26012 . In some embodiments, once the connector  26000  is attached to the disposable housing assembly  26012 , it may not be removed. 
     In the embodiment shown in  FIGS.  260 A- 260 G , the connector  26000  connects to the disposable housing assembly  26012  by the connector  26000  being rotated clockwise with respect to the disposable housing assembly  26012 . In other embodiments, the various features described may be configured differently and the connector  26000  may be connected to the disposable housing assembly  26012  by the connector  26000  being rotated counter-clockwise with respect to the disposable housing assembly  26012 . 
     In some embodiments, the disposable housing assembly  26012  may include a plug and the connector  26000  may include a plug receiver according to the various embodiment described herein. In some embodiments, the plug  26002  on the connector  26000  may be located in a different location and/or orientation than is shown herein. In various embodiments, the disposable housing assembly  26012  may include one or more mating features that correspond to one or more mating features on a connector  26000 . In some embodiments, these mating features may be located and/or orientated differently than is shown herein. 
     The embodiment of the connector  26000  shown in  FIGS.  260 A- 260 G  may vary in various embodiments and may include one or more features from any one or more embodiments of the connector and/or disposable housing assembly shown herein. 
     Referring now also to  FIGS.  261 A- 263 I , some embodiments of the connector  26100  include a plug  26102  that is rigid and forms a luer connection with the exit of the disposable housing assembly  26112 . In various embodiments, the plug  26102  may be tapered, and the percentage of tapering may vary. In some embodiments, the taper may be 6%, however, in various other embodiments; the taper may be greater or less than 6%. In some embodiments, including the one shown in  FIGS.  261 A- 261 K , the plug  26102  is removably attached to the connector  26100  and, in addition, is slidably connected to the connector  26100 . Additionally, in some embodiments, the plug  26102  may include a disc  26118  that, together with a slot  26120  control the movement of the plug  26102  with respect to the tab portion  26108  of the connector  26100 . Thus, as shown in  FIGS.  262 A through  262 J , the plug  26102  may slide from an initial position, shown in  FIGS.  262 A- 262 B  and  FIG.  263 G , to a second position, shown in  FIGS.  262 C- 262 E  and  FIG.  263 H , to a third position, shown in  FIGS.  262 F- 262 H , to a final position, shown in  FIGS.  262 I- 262 K  and  FIG.  263 I . As may be seen from  FIGS.  263 G- 263 I , in the various positions of the plug as the plug moves from the initial position to the final position, the plug  26102  occupies less of the exit region  26138  of the disposable housing assembly  26112 . As discussed above, this is due to the tolerance variations of the plug and/or the disposable housing assembly exit region  26138  or both. In various embodiments, the disc and slot may be configured wherein twice the force required to complete the luer connection is required to unseat the disc from the slot. This may be beneficial/desirable for many reasons, including, but not limited to, in various embodiments, if the disc is unseated from the slot, this ensures the luer connection has been made. 
     In various embodiments, the plug  26102  is configured such that it includes at least one stop feature wherein the exit end portion  26104  of the plug  26102  includes a first stop feature, for example, a lip, that limits the travel of the plug  26104  in one direction. The plug  26102  tubing end portion  26106  in various embodiments also includes a second stop feature, for example, a lip, that limits the travel of the plug  26102  in the other direction. In various embodiments, the plug  26102  may be made from any material, for example, but not limited to, TERLUX® and/or another ABS material. Although not shown in the embodiments shown in  FIGS.  261 A- 263 I , the plug  26102  includes a length of tubing attached to the tubing end portion  26106 , which tubing and attachment may be any one or more of the various embodiments described in more detail above with respect to various embodiments of the plug and the connector. The length of tubing may be any length desired, including, but not limited to, any length between 1 inch and 10 feet, and in some embodiments may be either 4 inches or 23 inches, however, in various embodiments, the length may be greater or less than 4 inches or 23 inches. 
     In various embodiments, the connector  26100  includes a tab portion  26108  including a mating locking feature  26110 , which may be, in various embodiments, the mating locking feature described above with respect to various other embodiments of the connector. In various embodiments, the mating locking feature  26110  is configured to mate with a corresponding mating locking feature  26114  on the disposable housing assembly  26112 . In various embodiments, the mating locking feature  26110  on the connector  26100  including a hook that latches to the corresponding mating locking feature  26114  on the disposable housing assembly  26112 . 
     In various embodiments, the plug  26102  of the connector  26100  is inserted into the disposable housing assembly  26112  with the tab  26108  portion pointing upward. Once the plug  26102  portion is inside the disposable housing assembly  26112 , the tab  26108  portion may be rotated about the plug  26102  to rest above the disposable housing assembly  26112  adjacent to the exit (i.e., rest on the tab portion  26116  on the disposable housing assembly  26112 ). In some embodiments, mating locking features  26110 ,  26114  may be included on the tab portion  26108  of the connector  26100  and the disposable housing assembly  26112 , respectively, such that the connector  26100  is held in place before the reusable housing assembly  6004  is attached to the disposable housing assembly  26112 . In some embodiments, the mating locking features  26110 ,  26114  may include, but are not limited to, snap buttons and/or catch features. In some embodiments, a hook or other feature may be located on the opposite end of the tab  26108  portion of the connector  26100  such that it loops over the end of the tab portion  26116  of the disposable housing assembly  26112  and maintains the position of the connector  26100 . 
     Still referring also to  FIGS.  261 A- 263 I , the connector  26100  may include a tab portion  26108 , a catch feature  26118 , a latching feature  26110 , and a plug  26102 . In some embodiments, the tab portion  26108  of the connector  26100  may include mating locking features that interact with corresponding features in the disposable housing assembly  26112 . In some embodiments, the tab portion  26108  may include features that interact with other portions of the disposable housing assembly  26112 . As shown, in some embodiments, the connector  26100  may include a male latching feature  26110  on the end of the tab portion  26108  of the connector  26100 . In some embodiments, the latching feature  26110  may mate with a corresponding latching feature (a female latching feature  26114 ) on the disposable housing assembly  26112 . In some embodiments, the latch may be a removably secure fit, and/or a snap fit and/or a loose snap fit and in some embodiments may include a spring latch portion. In various other embodiments, the shape and size of the connector  26100  may vary, and/or, in various other embodiments, other types of features such as mating locking features may be used, which include, but are not limited to, latches, catches, snap fits, adhesives, and other mechanisms for securing a connector  26100  to the tab  26116  of the disposable housing assembly  26112 . 
     In some embodiments, the connector  26100  may include a locking ring feature on the underside. The locking ring feature in some embodiments may be tapered and/or in some embodiments, the locking ring feature may be at least slightly curved. In some embodiments, the locking ring feature may interact with the locking ring of the reusable housing assembly and may act together with the locking ring to secure the connector to the disposable housing assembly. 
     As discussed above, in various embodiments, the plug  26102  of the connector  26100  is inserted into the exit of the disposable housing assembly  26112  with the tab portion  26108  pointing in the general upward direction. Once the plug  26102  is inside the exit, the tab portion  26108  of the connector  26100  may be rotated to rest adjacent to the tab portion  26116  of the disposable housing assembly  26112 . In some embodiments, mating locking features may be included on the tab portion  26108  of the connector  26100  and the disposable housing assembly  26112  such that the connector  26100  is held in place before the reusable housing assembly is attached to the disposable housing assembly  26112 . In some embodiments, the mating locking features may include, but are not limited to, post and opening, snap, buttons, latch features and/or catch features. In some embodiments, a hook or other feature may be located on the opposite end of the tab portion  26108  of the connector  26100  such that it loops over the end of the tab portion  26116  of the disposable housing assembly  26112  and maintains the position of the connector  26100 . In the embodiment shown in  FIGS.  261 A- 263 I , the mating locking features include a male latching feature  26110  on the connector  26100  and a female latching feature  26114  on the disposable housing assembly  26112 . 
     In various embodiments, once the connector  26100  is attached to the disposable housing assembly  26112 , the connector  26100  may only be removed when intended, i.e., the connector  26100  is maintained on the disposable housing assembly  26112  unless and until a user desires to remove the connector  26100 . As discussed above, in some embodiments, the connector  26100  may be non-removably attached, however, in some embodiments; the connector  26100  may be removably attached. 
     While the connector  26100  is being attached to the disposable housing assembly  26112 , the male latching feature  26110  is mated with the female latching feature  26114 . In some embodiments, male and female latching features  26110 ,  26114  may work together to further stabilize the connection of the connector  26100  to the disposable housing assembly  26112 . Additionally, in various embodiments, the male and female latching features  26110 ,  26114  may contribute to maintaining the plug  26102  in the exit of the disposable housing assembly  26112 . Thus, in some embodiments, the male and female latching features  26110 ,  26114  may contribute to maintaining and/or enforcing both the insertion of the plug  26102  into the exit and/or maintaining and/or enforcing the position of the connector  26100  such that after the plug  26102  is inserted into the exit, the plug  26102  is maintained in the exit unless and until a user desires to remove the plug  26102  from the exit. Additionally, once the male and female latching features  26110 ,  26114  are mated, the plug  26102  is fully inserted and therefore, may, in some embodiments, serve as an indication that the plug  26102  has been fully inserted into the exit. 
     As discussed above, in the embodiment shown in  FIGS.  261 A- 263 I , the plug  26102  in the connector  26100  is slidably attached to the connector  26100  such that the plug  26102  may move forward or back and the connector tab portion  26108  may move independent from the plug  26002 . In addition, in this embodiments of the slidably attached connector plug  26102 , the plug  26102  is biased forward with respect to the tab portion  26108  of the connector  26100 . This may be beneficial/desirable for many reasons, including, but not limited to, the mating of the luer (i.e., mating between the post  26002  and the exit of the disposable housing assembly  26012 ) may be completed before the tab portion  26008  of the connector  26000  is rotated and attached to the disposable housing assembly  26012 . Thus, the rotation of the tab portion  26008  about the plug  26002  is to connect the tab portion  26008  to the disposable housing assembly  26012 , but the luer connection of the plug  26002  to the exit is completed by pushing the plug  26002  into the exit of the disposable housing assembly  26012 . The plug  26002  being slidable within the tab portion  26008  of the connector  26000  is beneficial/desirable for many reasons, including, but not limited to, the depth in which the plug  26002  travels within the exit of the disposable housing assembly  26012  to form a luer connection may vary due to variances, for example, tolerances due to manufacturing. Thus, the plug  26002  may move deeper into the exit if the plug is smaller in comparison with the exit, or the exit is large in comparison with the plug  26002  and the plug  26002  may form a connection shallower in the exit if the plug  26002  is large in comparison with the exit or the exit is smaller in comparison with the plug  26002 . Thus, variances in tolerances will not prevent a luer connection from being made between the plug  26002  and the exit/disposable housing assembly  26012 . Also, the embodiment shown in  FIGS.  261 A- 263 I  may be beneficial/desirable for many reasons, including, but not limited to, ensuring that the luer connection is successful between the plug  26102  and the disposable housing assembly  26112  and that the plug  26102  is prevented from moving away from the disposable housing assembly  26112  unless tolerances dictate that the plug  26102  moves away from the disposable housing assembly  26112  in order to form the luer connection. Thus, the disc  26122 , in the initial position with respect to the tab portion  26108  (shown, for example, in  FIGS.  261 D- 261 H ) is in the slot  26120  and is therefore prevented from sliding either backwards (away from the disposable housing assembly  26112 ) with respect to the tab portion  26108  unless tolerances between the plug  26102  and the exit portion of the disposable housing assembly are such that the disc moves away from the disposable housing assembly. 
     Thus, still referring to  FIGS.  261 A- 263 I , the plug  26102  is inserted into the exit portion of the disposable housing assembly and if, due to tolerances, the plug  26102  is not fully inside the exit, additional force applied to the plug  26102  (via the tab portion  26108  of the connector  26100 ) bends the disc  26122  such that the plug  26102  moves away from the disposable housing assembly  26112 . This moves the plug  26102  from the initial position to a second position. The second position may be seen in  FIGS.  262 A- 262 C . If the plug  26102  is still not fully inside the exit, additional force applied to the plug  26102  detaches the disc  26122  from the slot  26120  and the plug  26102  slides further away from the disposable housing assembly  26112 . This moves the plug  26102  from the second position to the third position. The third position may be seen in  FIGS.  262 G- 262 I . If the plug  26102  is still not fully inside the exit, additional force applied to the plug  26102  causes the plug  26102  to slide further away from the disposable housing assembly  26112 . This moves the plug  26102  from the third position to the final position. The final position may be seen in  FIGS.  262 J- 262 K . As may be seen in  FIGS.  262 J- 262 K , the exit end portion  26104  of the plug  26102  includes a feature, for example, a lip, that limits the travel of the plug  26102  in the direction moving away from the disposable housing assembly  26112 . As may be seen in  FIGS.  262 J- 262 K , once the exit end portion  26104  reaches the tab portion  26108  of the connector  26100 , the plug  26102  is prevented from moving further away from the disposable housing assembly  26112  and is in the final position with respect to the tab potion  26108  of the connector  26100 . 
     Referring now also to  FIGS.  261 A- 263 I , in some embodiments, the tab portion  26116  of the disposable housing portion  26112  may be shaped as shown. In some embodiments, the connector  26100 , once attached to the disposable housing assembly  26112 , may extend the tab portion  26116  of the disposable housing assembly  26112 . In some embodiments, once the connector  26100  is attached to the disposable housing assembly  26112 , the connector  26100  and tab portion  26116  may be flush and continuous. 
     In some embodiments, the connector  26100  may include an indent  26124 , as shown. The indent  26124  may be shaped as shown or, in various embodiments, may be shaped and sized differently. 
     In various embodiments, the female latching feature  26114  on the disposable housing assembly  26112  may be located adjacent to the tab portion  26116 . In some embodiments, for example, as shown in  FIGS.  263 A- 263 C , the female latching feature  26114  may be configured such that it receives the male latching feature  26110  on the connector  26100  from the top. Some embodiments may not include mating latching features  26110 ,  26114 . In some embodiments, the location and/or orientation of the female latching feature  26114  may vary. In some embodiments, the location and/or orientation of the male latching feature  26110  may vary. 
     In some embodiments, the connector  26100  may be made from rigid plastic. In some embodiments, the locking ring feature and/or the latching features may be overmolded with a thin layer of compliant materials. In some embodiments, as discussed above, the plug  26102  may include an overmold of compliant material and/or be made from compliant material. In some embodiments, the locking ring feature and/or the latching feature may be made from compliant material. In embodiments where the male or female latching features  26110 ,  26114  include compliant material, use of compliant material may increase the “squish” between the male latching feature  26110  and the female latching feature  26114  and therefore, resulting in a highly compressed and/or tight fit between the male and female latching features  26110 ,  26114 . 
     Referring now also to  FIGS.  261 A- 263 I  and  FIG.  136   , in some embodiments, the connector  26100  may include icons  26126 ,  26128  that indicate “locked” ( 26126 ) and “unlocked” ( 26128 ), similar to those shown and described above with respect to  FIG.  136   . Thus, in some embodiments, the “locked” and “unlocked” position may also be visually indicated to a user/patient using icons  26126 ,  26128  that may be molded, silk-screened, pad printed, injection molded, etched, printed and/or cut-out, e.g., translucent cut-outs of icons, on the connector  26000 . In some embodiments using translucent cut-outs, the tab portion  26116  of the disposable housing assembly  26112  may be a contrasting color to the connector  26100  for visually viewing the tab portion  26116  of the disposable housing assembly  26112  color through the cut-outs. Thus, the icons  26126 ,  26128  may indicate whether the reusable housing assembly  6004  is in a locked or unlocked relationship with the disposable housing assembly  26112 . In various embodiments, the icons  26126 ,  26128  may be any form that may indicate “locked” and “unlocked”, or a similar indication, to aid in the user/patient&#39;s understanding of the orientation/position between the reusable housing assembly  6004  and the disposable housing assembly  26012 . In some embodiments, an arrow icon  26130  may also appear between the locked icon  26126  and unlocked icon  26128 . 
     Although not shown in  FIGS.  261 A- 263 I , in various embodiments, the reusable housing assembly may be any one or more of the various embodiments of the reusable housing assembly described herein, including, but not limited to, the reusable housing assembly described above as  6004 . 
     The plug  26102  may include any embodiment described herein, however, in some embodiments; the plug  26102  may be tapered and may either be rigid without any overmolding, be rigid with an overmold of elastomeric/compliant material or be made from elastomeric/compliant material. In various embodiments, the plug  26102  may include a seal, for example, in some embodiments, the plug  26102  may include a radial seal, and in some embodiments, the plug  26102  may include a face seal and in some embodiments, the plug  26102  may include a radial and a face seal. In some embodiments, the plug  26102  may include one or more seals, including, but not limited to, a face seal and/or a radial seal. 
     In some embodiments, tubing  26134  attaches to the connector  26100  as described above and as shown in  FIG.  261 G . In some embodiments, the tubing  26134  may attach to the connector  26100  and there may be a rigid plastic channel  26132  within the connector  26100  and through the plug  26102 . In some embodiments, the tubing  26134  may extend into the connector  26100  and in some embodiments; the tubing  26134  may extend all the way through the connector  26200  and through the plug  26202 . In some embodiments, the tubing  26134  may extend past the end of the plug  26102 . Although not shown in  FIGS.  261 A- 263 I , the various embodiments of the connector  26100  may include any of the embodiments of the tubing and tubing connection as shown and described above with respect to various other embodiments of the connector. 
     In various embodiments, there is maintained a continuous flow lumen from the exit of the disposable housing assembly to the cannula (not shown). This may be desirable and/or beneficial for many reasons, including, but not limited to, minimizing and/or eliminating dead volume, minimizing priming volume and/or prevention of or minimizing the occurrence of air traps. As may be seen in  FIGS.  263 G- 263 I , once the plug  26102  is connected to the disposable housing assembly  26112 , and a luer connection is made between the plug  26102  and the exit of the disposable housing assembly  26112 , the fluid line  26136  within the disposable housing assembly  26102  is in fluid and continuous connection with the rigid plastic channel  26132  in the plug  26102 . Where tubing is attached to the plug  26102 , the fluid line  26136  within the disposable housing assembly  26102  is in fluid and continuous connection with the rigid plastic channel  26132  in the plug  26102  and the tubing. 
     Referring still also to FIGS.  261 A 0   263 I, some embodiments of the connector  26100  may also include a catch/catching feature  26118  on the opposite side as the male latching feature  26110 . The catch feature  26118 , when the connector  26100  is connected to the disposable housing assembly  26112 , interferes with the disposable housing assembly  26112  and prevents the connector  26100  from rotating further. Thus, in some embodiments, the connector  26100  and the disposable housing assembly  26112  form an interference fit in at least one location. Together with the male and female latching features  26110 ,  26114 , in some embodiments, once the connector  26100  is attached, the connector  26102  may be held in place by these mating features  26110 ,  26114 . The catch feature  26118  in various embodiments also aids in catching the disposable housing assembly and the ramp portion of the catch feature  26118  assists in pulling the connector  26100  towards the disposable housing assembly  26112 . 
     The connector tab portion  26108  may include gripping features, however, in the some embodiments; the connector  26100  is sized such that a user may grip the connector  26100  for insertion/attachment with the disposable housing assembly  26112 . Some embodiments including grip features, may include, but are not limited to, one or more of the following: a textured surface, bumps, lumps, protrusions or indentations in any size, shape and/or number. 
     In various embodiments of the connector  26100 , once the connector  26100  is connected to the disposable housing assembly  26112 , the reusable housing assembly  6004  (which may also be one or more of the various reusable housing assemblies described herein or incorporated herein by reference) may be connected/attached to the disposable housing assembly  26112  by being rotated about the disposable housing assembly  26112 . As the reusable housing assembly is rotatably connected to the disposable housing assembly  26112 , the locking ring and/or nub  808 , having a spring actuated tab  2980 , on the reusable housing assembly  6004  may interact with the connector  26100 , such that the rotation of the reusable housing assembly  6004  about the disposable housing assembly  26112  prevents the connector  26100  from being removed from the disposable housing assembly  26112 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  26112 , the spring plunger/tab in the nub  808  may be released, making a “click” sound. The “click” may also produce a tactile feedback that may be perceived by the user/patient. This tactile and audio feedback is indicative to the user that the reusable housing assembly  6004  is fully connected to the disposable housing assembly  26112 , and, that the connector  26100  is connected such that it will be maintained connected to the disposable housing assembly  26112  until and unless the user wishes to remove the connector  26100 . In some embodiments, the nub  808 , having a spring actuated tab  2980 , presses downward on the connector  26100 , maintaining the connector  26100  in an attached position. In some embodiments, features in the locking ring interact with a locking ring feature on the connector  26100  and contribute to maintain the connector  26100  in position with respect to the disposable housing assembly  26112 . In some embodiments, the tab portion  26108  of the connector  26100  may include an indent portion  26124  which may be configured to interact with the nub  808  and/or spring plunger/tab of the locking ring assembly of the reusable housing assembly  6004 . In some embodiments, once the reusable housing assembly  6004  is attached to the disposable housing assembly  26112 , the connector  26100  may not be removed from the disposable housing assembly  26112 . Rather, in these embodiments, the reusable housing assembly  6004  must first be detached from the disposable housing assembly  26112  before the connector  26100  may be removed from the disposable housing assembly  26112 . In some embodiments, once the connector  26100  is attached to the disposable housing assembly  26112 , it may not be removed. 
     In the embodiment shown in  FIGS.  261 A- 263 I , the connector  26100  connects to the disposable housing assembly  26112  by the connector  26100  being rotated clockwise with respect to the disposable housing assembly  26112 . In other embodiments, the various features described may be configured differently and the connector  26100  may be connected to the disposable housing assembly  26112  by the connector  26100  being rotated counter-clockwise with respect to the disposable housing assembly  26112 . In various embodiments, the plug  26102  remains stationary as the connector tab portion  26102  is rotated about the plug  26102 . However, in some embodiments, the plug  26102  may be rotated together with the connector  26100 . 
     In some embodiments, the disposable housing assembly may include a plug and the connector may include a plug receiver according to the various embodiment described herein. In some embodiments, the plug  26102  on the connector  26100  may be located in a different location and/or orientation than is shown herein. In various embodiments, the disposable housing assembly  26112  may include one or more mating features that correspond to one or more mating features on a connector  26100 . In some embodiments, these mating features may be located and/or orientated differently than is shown herein. 
     The embodiment of the connector  26100  shown in  FIGS.  261 A- 263 I  may vary in various embodiments and may include one or more features from any one or more embodiments of the connector and/or disposable housing assembly shown herein. 
     Referring now also to  FIGS.  260 A- 262 I , in various embodiments, as described herein, the plug may form a luer connection with the exit of the disposable housing assembly. In various embodiments, the luer connection may be formed between the plug and disposable housing assembly by the plug being inserted into the exit of the disposable housing assembly and in some embodiments, the luer connection is formed between the plug being inserted in the exit of the disposable housing assembly and upon connection of the tab portion of the connector to the disposable housing assembly. As discussed above, in some embodiments the catch feature aids in completing the seal between the plug and the disposable housing assembly by pushing the plug further into the exit of the disposable housing assembly. Therefore, the luer connection may be formed without any rotation of the plug within the disposable housing assembly/exit of the disposable housing assembly. In various embodiments, therefore, the luer connection may be formed between the plug and disposable housing assembly before the tab portion of the connector is rotated about the plug and connected to the disposable housing assembly. This may be beneficial/desirable for many reasons, including but not limited to, forming a luer connection without rotation and then independently rotating a portion attached to the plug prevents the plug from breaking, which would likely occur if the plug were rotated together with the tab portion of the connector. This is beneficial/desirable for many reasons, including but not limited to, forming a luer connection without rotation allows for movement of other portions of an assembly that are not involved in the luer connection whilst the luer connection is maintained. Therefore, in some embodiments, the connector shown and described in, for example,  FIGS.  260 A- 262 I , is an assembly including a luer connection between one or more first portions and a second portion that may rotate independent of the luer connection first portion(s). This is beneficial/desirable for many reasons, including, but not limited to, where the tab portion of the connector could not rotate independent of the plug, once the luer binds, the motion of the tab portion would have to stop and would not rotate sufficiently for the latching features to meet and the connector to attach to the disposable housing assembly. Where the connector is not rotated sufficiently, the reusable housing assembly would not be able to be attached to the disposable housing assembly. The embodiments described with respect to, for example,  FIGS.  260 A- 262 I , may also be beneficial/desirable for many reasons, including but not limited to, the plug and the tab portion of the connector may be made from different materials as they are separate parts and the absence of o-rings, radial seals, facial seals, etc. is beneficial/desirable for many reasons, including, but not limited to, seals may have parting lines and other manufacturing introduced features that may degrade the seal, and luer connections are more reliable seals. 
     Still referring to  FIGS.  260 A- 263 I , in various embodiments, the connector may be connected to tubing (for example, as shown in  FIG.  261 G ) and the tubing may be connected to a cannula assembly, such as one described above and shown in, for example,  FIGS.  236 G and  236 H , however, various embodiments of a cannula assembly may be used together with the connectors described herein. 
     Still referring also to  FIGS.  260 A- 263 I  and  FIG.  237   , in some embodiments, the connector may include a “core”  26040  on the bottom. The core  26040  may be an opening in the connector. In some embodiments, an identification tag (similar to one shown in  FIG.  237   ) may be located in the core  26040 , however, in various other embodiments, the identification tag may be located in another location on the connector (and in some embodiments, the identification tag may be located on the disposable housing assembly and/or on the cannula assembly). In some embodiments it may be desired to include a method of the system identifying the connector (and/or disposable housing assembly and/or cannula assembly) and/or a device for the system to identify the connector. In some embodiments, the identification tag may be an RFID tag. In some embodiments, the identification tag may be a near-field communication (“NFC”) readable RFID tag. In some embodiments, the identification tag may be a 2D or 3D bar code. In some embodiments, the identification tag may be a QR code. 
     In various embodiments, either before the connector is connected to the disposable housing assembly or after the reusable housing assembly has been connected to the disposable housing assembly, the reusable housing assembly  6004  and/or the remote control unit may read the identification tag. The identification tag  6092  may include various information, including, but not limited to, one or more of the following: unique identification number, date of manufacture, date of expiration, part number, lot number, and/or date of sale. Once the system reads the identification tag, the system may recognize the connector by its unique identification number or other, and thus, be able to recognize that the connector is either a new connector  6010 , i.e., has not been used previously, or is an old connector, i.e., the connector has been used previously. In some embodiments, once the connector is attached, the system may start a timer and the infusion pump may alert/alarm and/or turn off after a predetermined period of time where the connector has been used by the system. In some embodiments, this predetermined time may be the maximum time that the manufacturer recommends using the connector and/or cannula assembly attached to the connector. In some embodiments, this predetermined time may be the maximum time that the manufacturer recommends using the disposable housing assembly. 
     In some embodiments, the information conveyed by the identification tag may include information to authenticate the connector, i.e., to ensure that the connector is not a counterfeit part. In some embodiments, the remote control unit and/or reusable housing assembly/pump may include a listing of authentic identification information such that the system may “authenticate” the connector based on information received from the manufacturer. 
     In various embodiments, the identification tag may be a “peel and stick” RFID tag, which may be attached to the connector, for example, in the core  26040  area of the connector. In some embodiments, the identification tag may be glued and/or potted and/or another part may be pressed over the identification tag to sandwich the identification tag. In some embodiments, the identification tag may be taped to the connector. In some embodiments, where the identification tag is a bar code and/or QR code, the identification tag may be embossed, printed and/or molded onto the connector. 
     In some embodiments, the identification tag may be an RFID tag. In some embodiments, the RFID tag may be a tag that includes an antenna and chip. In some embodiments, the connector may be manufactured with a conductive ring and a chip could be electrically connected to the conductive ring. In some embodiments, the RFID tag could be on the label which could include additional information, for example, but not limited to, text, for example, part number, label, instructions, expiration date. 
     In some embodiments, the reusable housing assembly may include hardware to read the identification tag, which may include an RFID chip and/or a bar code, for example, 2D or 3D, or a QR code. For example, in some embodiments, the hardware may be an antenna which may be a copper trace on a board. In some embodiments the hardware may include a camera and/or a bar code scanner. In some embodiments, the remote control until may include hardware to read the identification tag, for example, in some embodiments, the remote control until may include an RFID transceiver and/or a near-field communication transceiver which may read the identification tag in those embodiments where the identification tag is an RFID tag. In some embodiments, the RFID tag may be one that may be read by an NFC transceiver. In some embodiments the remote control until may include a camera and/or a bar code scanner. 
     In some embodiments, using NFC may be desirable for many reasons, including, but not limited to, the reusable housing assembly and the remote control unit could both include NFC transceivers and the reusable housing assembly and the remote control unit may be paired in this fashion. This provides that the reusable housing assembly and the remote control unit come into physical contact with one another. This may be beneficial for many reasons including, but not limited to, the devices being paired are both in control of the user/patient and therefore, this may provide additional localized security when pairing the devices, i.e., to ensure that a non-intended device is not paired with either the remote control unit or the reusable housing assembly. 
     In some embodiments, the cannula assembly, connector and/or the disposable housing assembly may include identification tags and may include one or more of the features discussed above with respect to identification tags and/or may be used in one or more of the methods discussed above. 
     In various embodiments, the reusable housing assembly may begin pumping fluid only after either the reusable housing assembly or the remote control unit has received the information from the one or more identification tags in the system (e.g., disposable housing assembly, cannula assembly and/or connector) and has determined that the information received is acceptable. For example, in some embodiments, if the information received does not convey to the system that a “new” and/or “acceptable” (i.e., is not expired, has not been recalled) connector and/or disposable housing assembly and/or cannula assembly is being connected to the system, then the system may not pump fluid and or may alert/alarm. 
     Various embodiments of the connector may be made from any color desired. In some embodiments, the connector may be made from a different color than the disposable housing assembly. In some embodiments, the connector may be made from the same color as the disposable housing assembly. 
     In some embodiments the connector, after being connected/attached to the disposable housing assembly, may not be removed from the disposable housing assembly. In some embodiments, once connected/attached to the disposable housing assembly, it may be difficult for a user to remove the connector from the disposable housing assembly. In some embodiments, this may be beneficial and/or desirable for once the tubing has been primed; the tubing is full of fluid, which, in some embodiments, may include a therapeutic fluid. If the connector were removed from the disposable housing assembly, and a cannula assembly, in fluid communication with the connector, was already inserted into a user, and if the connector were to be elevated such that it was higher than the cannula assembly, the fluid in the tubing may be delivered through the cannula assembly to the user. In some circumstances, this may not be desirable for many reasons, including, but not limited to, unintentional delivery of a volume of fluid. Therefore, prevention of this circumstance may be desirable. 
     In various embodiments, these methods may be used with respect to any device and/or medical device and/or any controller and/or remote controller for any device and/or medical device and/or any device used in conjunction with or in association with any device and/or medical device. 
     A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other embodiments are within the scope of the following claims. 
     While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention.