Abstract:
A radio transmitter used to transmit an activation signal for radio tags held by individuals or the like provides multi-dimensional polarization to an activation signal so as to allow more consistent range detection of an individual with a tag having a single axis of sensitivity. Circular or spherical polarization can be obtained using the system which may include an antenna design permitting decoupling of antennas necessary for the polarization, a quadrature locking system simplifying proper phase control of the necessary signals and a system for tuning the same.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     CROSS REFERENCE TO RELATED APPLICATION 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     The present invention relates to security systems, for example, for tracking patients in a hospital or medical care facility, and in particular to a security system providing improved range discrimination when wirelessly interrogating patient-held transponders. 
     Security systems may be used m institutions such as hospital for monitoring patients, for example in pediatrics to deter infant abductions, and in nursing homes or neurological centers to reduce the likelihood of an Alzheimer&#39;s or head trauma patient wandering out of the facility. 
     Wireless security systems equip each patient with a small, wearable transponder (transmitter and receiver). The transponder monitors a selected frequency to detect an activation signal and is activated when an activation signal on the selected frequency is detected at a predetermined threshold amplitude. The activation signal originates from a control unit with an antenna typically located near a door or other exit. In this way, as the patient approaches the door exit, the amplitude of the received activation signal rises until the transponder is activated. 
     Upon activation, the transponder transmits an identification signal to a receiver connected to the control unit and a control unit decodes the identification signal to lock or unlock the door. 
     One disadvantage to such a wireless system is that it can be hard to localize the wireless identification signal to a particular door. One reason for this difficulty is that the receiving antenna on the patient transponder may have a variety of different orientations which significantly change its sensitivity as it varies from the orientation of the activation signal. As a result of this variation in practical sensitivity, the activation signal needs to be set to a power level that ensures activation of the patient transponder even with the worst-case transponder antenna orientation. As a result, the activation signal can activate some transponders at a substantial distance from the door including, for example, in rooms or corridors so far removed from the door so as not to warrant activation of the control unit. The difficulty of precise localization of a region of activation can limit the use of such security systems in many important applications where such false triggering cannot be tolerated. 
     SUMMARY OF THE INVENTION 
     The present invention provides a control unit that produces an activation signal having circular or spherical polarization. This polarization provides rapid and uniform activation of simple single-axis transponders in a variety of orientations allowing the region of activation to be more precisely defined. The ability to provide accurate circular or spherical polarization is facilitated by a quadrature lock circuit which provides the desired phase relationship between antenna driving signals regardless of antenna mis-tuning or changes in temperature or mounting location and at a variety of frequencies to produce the desired circular polarization. In addition, one embodiment of the invention provides an antenna design and adjustment method that permits precise decoupling of the antennas necessary for the polarization process. Specifically, in one embodiment, the present invention provides a control unit for a wirelessly activated security tag. The control unit has a first and second antenna having mutually perpendicular transmission axes, a first radiofrequency amplifier communicating with the first antenna to provide a first activation signal at a first center frequency; and a second radiofrequency amplifier communicating with the second antenna to provide a second activation signal at the first center frequency and having a 90 degrees phase shift with respect to the first activation signal. A radiofrequency receiver in the control unit receives an identification signal from a security tag activated by one of the first and second activation signals to provide an output control signal. 
     It is thus a feature of at least one embodiment of the invention to provide more consistent range sensitivity for wireless security systems through multidimensional polarization of an activation signal used for activating security tags. A benefit of spherical polarization is that it provides field uniformity such that a tag held in any orientation will be detected within a defined area. This allows, for example, that the strength of the activation field may be reduced to cover a small area around a door without bleeding activation signal into nearby patient rooms. 
     The control unit may include a lockable pivot supporting the first antenna to allow it to pivot about an axis perpendicular to the first and a second axes when unlocked and to be retained against pivoting in a locked state. 
     It is thus a feature of at least one embodiment of the invention to provide an antenna design that facilitates multidimensional polarization by reducing cross-coupling between antennas oriented along the different dimensions. 
     The control unit may also include a visual indicator circuit discriminating among variations in electrical energy induced in the first antenna from the second antenna. 
     It is thus a feature of at least one embodiment of the invention to provide a method of field adjustment of the antennas for minimizing cross coupling; thus achieving “null” positioning. 
     The visual indicator circuit may also discriminate among variations in electrical energy induced in the first antenna from the first radiofrequency amplifier or the second antenna from the second radiofrequency amplifier. 
     The first and second antennas may be wound antennas or solenoids providing windings about respective transmission axes. 
     It is thus a feature of at least one embodiment of the invention to provide a multidimensional polarization using simple solenoid-type antenna designs in combination. 
     The control unit may include a radiofrequency oscillator communicating with the first and second radiofrequency amplifiers and further including a phase comparator comparing phases of signals of the first and second antennas to detect a deviation from a 90 degrees phase relationship and to dynamically adjust the phase of at least one signal from the radiofrequency oscillator to the first and second radiofrequency amplifier to hold a phase of the signals of the first and second antennas at a phase difference of 90 degrees. 
     It is thus a feature of at least one embodiment of the invention to provide feedback control of the phase between the signals from the first and second antenna to maintain “quadrature” phasing for improved uniformity in the circular polarization plane. 
     The radiofrequency oscillator may communicate with the first and second radiofrequency amplifier through a first and second phase shift adjuster and the phase comparator may communicate with the first and second phase shift adjuster to provide for the adjustment of either of the phases of the signals of the first and second antennas. 
     It is thus a feature of at least one embodiment of the invention to permit bidirectional phase adjustment using unidirectional phase adjusters. 
     The control unit may also include a third antenna orthogonal to the first and second antennas and a third radiofrequency amplifier communicating with the third antenna to provide a third activation signal deviating from the first center frequency to provide a varying phase shift with respect to the first and second activation signals. 
     It is thus a feature of at least one embodiment of the invention to provide a “spherical” polarization for improved reception uniformity beyond that provided by circular polarization. 
     The third activation signal may be frequency modulated at a modulating frequency at least 100 times less than the first center frequency. 
     It is thus a feature of at least one embodiment of the invention to permit spherical polarization which has the effectiveness of generating a field as though produced by an isotropic radiator; without substantial distortion of the activation signal&#39;s perimeter as received by the security tag. 
     The antenna may further include a lockable pivot supporting the third antenna to allow it to pivot about a first pivot axis parallel with the first transmission axis and a second pivot axis parallel to the second transmission axes. 
     It is thus a feature of at least one embodiment of the invention to provide an antenna that allows tuning of the spatial orthogonality of each of three antennas for minimized antenna coupling. 
     The third antenna may be implemented as copy traces on a printed circuit board having multiple layers producing a set of windings about an axis perpendicular to a broad face of the printed circuit board. 
     It is thus a feature of at least one embodiment of the invention to provide a simplified third antenna design that may be easily integated with wound core material of the first and second antennas. 
     The control unit may also include a visual indicator indicating electrical energy induced in the third antenna from at least one of the first and second antennas. 
     It is thus a feature of at least one embodiment of the invention to permit field positional “nulling” of the third antenna for minimize coupling with the first and second antennas. 
     The visual indicator circuit may further discriminate among variations in electrical energy induced in the third antenna from the third radiofrequency amplifier for tuning purposes. 
     It is thus a feature of at least one embodiment of the invention to permit spatial and frequency tuning of the third antenna. 
     The control unit may further include a radiofrequency oscillator communicating with the third radiofrequency amplifier and further including a phase lock loop providing a phase comparator and a voltage controlled oscillator, the latter providing an output to the third radiofrequency amplifier frequency locked to the radiofrequency oscillator. 
     It is thus a feature of at least one embodiment of the invention to provide frequency locking between three antennas. 
     The phase lock loop may include a phase comparator and a voltage controlled oscillator and a summing junction summing a phase modulation signal to the output of the phase comparator. 
     It is thus a feature of at least one embodiment of the invention to provide a circuit for stably locking signals in phase while allowing circular polarization by slight frequency perturbations. 
     The control unit may further include a processor for controlling the first, second, and third radiofrequency amplifiers to vary a power output provided by each of the first, second, and third amplifiers to modulate an activation region and to monitor the radiofrequency receiver for receiving an identification signal from the security tag with at least two different power outputs provided, to each of the first, second, and third amplifiers to deduce a range of an activated security tag. 
     It is thus a feature of at least one embodiment of the invention to exploit the improved range consistency provided by circular or spherical polarization to extract range information about the security tag. 
     These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top-down perspective view of a door monitored by a security system of a type that may be implemented by the present invention using at least one transponder tag and a control unit and showing a localized region of activation obtained with spherical polarization in comparison with a range of activation that may occur in prior art unpolarized units; 
         FIG. 2  is an exploded view of an antenna assembly for the control unit of  FIG. 1  providing three orthogonal antennas and at adjustment mechanism for nulling the antennas for spherical polarization; 
         FIG. 3  is an orthogonal view of the assembled antenna system of  FIG. 2  along three axes illustrating the nulling process; 
         FIG. 4  is a block diagram of radiofrequency amplifiers attached to the antennas of the system of  FIGS. 2 and 3  as locked together by means of a primary driving oscillator and two phase locked loops, the latter of which receive a dithering modulation; 
         FIG. 5  is a perspective representation of a radiofrequency vector as modulated by the system of the present invention; 
         FIG. 6  is a block diagram of a power monitoring system suitable for use with the present invention for tuning and nulling the control unit and antenna and showing a processor such as may control the amplifiers of  FIG. 4  for range control; and 
         FIG. 7  is a side elevational view of the door of  FIG. 1  showing a sweeping of range of the activation region for tag discrimination by range. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , an access control system  10  for an access region may provide a control unit  12 , for example, mounted above a door  14  for detecting a tag  16 , for example, on a patient  18  or the like. 
     Generally, the control unit  12  transmits an activation signal  20  that will activate the tag  16  when that activation signal  20  is detected by the tag  16  at a predetermined threshold amplitude. As is generally understood in the art, tag  16  may include a radio transponder (transceiver) and battery system and may monitor a predetermined frequency for the activation, signal  20  and in response to receiving the activation signal  20  at the predetermined amplitude, may return an identification signal  22  to be received by the control unit  12 . 
     The control unit  12 , receiving the identification signal  22 , may compare the information of the identification signal to a stored authorization list to provide a control output, for example, locking or unlocking the door  14  through the use of electro-mechanically activated locks such as are well known in the art. Alternatively, an alarm signal may be generated as may be appropriate if the patient  18  is not authorized to be in a particular region. 
     A system of this type is described in U.S. Pat. No. 6,084,513 issued Jul. 4, 2007, and U.S. Pat. No. 7,132,944 issued Nov. 7, 2006, both assigned to the assignee of the present invention and hereby incorporated by reference. 
     The location at which the tag  16  is activated by the activation signal  20  defines an activation region  24 . In the prior art, the activation region  24  is highly dependent on the orientation of an internal antenna of the tag  16  and can vary between a larger region of activation  24  and a small region of activation  24 ″ whose difference in size can cause unwanted variation in the activation for different patients  18  or a given patient  18  at different times. Simple and low-cost implementations of the tag  16  include an antenna having a reception sensitivity that is dominant along a single axis. 
     In order to provide certainty in protecting a given door  14 , the smallest activation region  24 ″ must be made large enough to fully encompass the door  14  such as can result in the largest activation region  24 ′ straying into unwanted zones, for example, through walls and into rooms outside of a given corridor. As will be discussed in greater detail below, the present invention provides a circular or spherical polarization to the activation signal  20  that provides substantially more uniformity in the activation region  24  because the internal antenna of the tag  16  will be aligned with the orientation of the activation signal  20  at some point during the circular or spherical polarization to have a reception that is substantially constant at a given distance regardless of the orientation of the tag  16 . 
     Referring now to  FIGS. 2 and 3 , in the present invention, the control unit  12  may include an antenna system  26  providing a base plate  29  that may be mounted, for example, against the wall above a door to lie in a generally vertical plane extending upward along a y-axis  28 . A center of the plate  29  may support a y-axis antenna  30  being generally a solenoid of conductive wire  32  wrapped around a high permittivity core  34  where the axis of the solenoid extends along the y-axis  28 . In one embodiment the solenoid may be a ferrite loop stick. 
     Positioned below the y-axis antenna  30  and coplanar therewith is an x-axis antenna  36  also providing a solenoid of conductive wire  38  wrapped about a high permittivity core  40 . In this case, the axis of the solenoid of conductive wire  38  extends parallel to the x-axis  42  (termed a transmission axis) perpendicular to and coplanar with the y-axis  28 . The x-axis antenna  36  is mounted on a pivot axle  44  extending into a corresponding socket  46  on the plate  29  allowing the x-axis antenna  36  to rotate about an axis perpendicular to both the x-axis  42  and y-axis  28 , as indicated by arrows  45  parallel to the plane of the plate  29 . To align the x-axis antenna  36  with the x-axis  42 , a locking screw fastener  47  interfacing between the pivot axle  44  and the plate  29  is loosened to allow moving then re-locks the position of the x-axis antenna  36  once it is properly aligned. 
     As best seen in  FIG. 3( c )  when the x-axis antenna  36  is properly aligned parallel with the x-axis  42 , it is bisected by the y-axis  28  and as a result is decoupled from the y-axis antenna  30  whose flux lines  48  are generally perpendicular to the axis of the x-axis antenna  36  and symmetric in their deviation about the y-axis  28  so as to induce no current in the x-axis antenna  36 . Only these antennas are required if circular polarization is preferred. 
     A printed circuit board  50  having a center cut-out  52  fitting around the y-axis antenna  30  may be supported against the plate  29  separated therefrom by helical compression springs  54  and retained by four machine screws  56  passing through holes  59  in the corners of the printed circuit board  50  to be received by threaded sockets  57 . The machine screws  56  place these helical compression springs  54  into slight compression captivating plate  29  between heads of the machine screws  56  and the helical compression springs  54 . Alternatively, it will be appreciated that the screws may be fixed with respect to the plate  29  and one or more threaded nuts or spacers rotated along the screws to provide the necessary adjustment. By changing the relative compression of each of the helical compression springs  54 , the printed circuit board  50  may be adjusted in angle with respect to both the y-axis  28  and x-axis  42  as indicated by arrows  58 . This adjustment may be such as to bring a normal of the surface of the printed circuit board  50  into alignment with the z-axis  62  being orthogonal to the y-axis  28  and x-axis  42  and for a plane defined by that surface to bisect the x-axis antenna  36  and y-axis antenna  30 . 
     The surface of the printed circuit board  50  may support a helically wound z-axis antenna  60  that is coplanar with the surface formed by multiple layers of traces constructed using standard printed circuit board techniques. As best seen in  FIGS. 3( a ) and ( b ) , the surface of the printed circuit board  50  is aligned as described above, and flux lines  48  from the z-axis antenna  60  are substantially perpendicular to the extent of the y-axis antenna  30  and x-axis antenna  36  and symmetric to induce no current in those antennas. By similar analysis, it can be seen that each of the y-axis antenna  30 , x-axis antenna  36 , and z-axis antenna  60  may be decoupled from the others when they are properly adjusted using the pivot axle  44  and the machine screws  56 . A tuning aid for this adjustment will be described further below. 
     Referring now to  FIG. 4 , the antenna system  26  may communicate with a radiofrequency driver circuit  64  generally providing periodic waveforms to each of the x-axis antenna  36 , y-axis antenna  30 , and z-axis antenna  60  to create a spherically polarized activation signal  20  produced by providing three separate waveforms. 
     In this regard, each of y-axis antenna  30 , x-axis antenna  36 , and z-axis antenna  60  may comprise a tank circuit including inductor  66  shunted by capacitor  70   a , and tapped along its length at an input point  68  to act like an auto transformer stepping up the voltage applied at the input point  68 . The capacitor  70   a  provides a parallel resonance of the tank circuit near a desired transmission frequency. It will be understood that the solenoid of the antennas  30 ,  36 , and  60  may also provide double duty as part of the inductor  66  forming the parallel resonance. A radiating portion  72 , respectively, may be attached to this tank circuit of each of the antennas  30 ,  36 , or  60 . Tuned antennas are advantageous when using Class C amplifiers to drive the antennas, and provide good power efficiency. 
     A tunable oscillator  74  may be set to a desired frequency for the activation signal  20  to provide an input signal to a voltage controlled phase lag circuit  75  and then to class-C amplifier  76  operating in switching mode to provide a series of pulses to the input point  68  of y-axis antenna  30 . The tank circuit smooths these pulses to provide substantially sinusoidal radiated radiofrequency in the range of a few hundred kilohertz. 
     The tunable oscillator  74  may provide for a second output having a 90 degrees phase lag with respect to the signal provided to the voltage controlled phase lag circuit  75 . This second output is provided to voltage controlled phase lag circuit  77  and then to class-C amplifier  84  whose output connects to the input point  68  of the x-axis antenna  36 . 
     The output from the class-C amplifier  76  and the class-C amplifier  84  also may be input to a phase comparator  80  which provides an output voltage that equals a reference voltage  81  when the inputs are perfectly locked to a 90 degrees phase difference, moving positive with respect to the reference voltage  81  when the output of amplifier  84  is more than 90 degrees ahead of the output of amplifier  88  and moving negative with respect to the reference voltage  81  when the output of amplifier  84  is less than 90 degrees ahead of the output of amplifier  88 . This output voltages received by a comparator  83  that provides a voltage to voltage controlled phase lag circuit  75  in the former case increasing a phase lag in the output of amplifier  84  and provides a voltage to phase lag circuit  77  in the latter case providing relative phase lag in the output of amplifier  88 . The voltage controlled phase lag circuits  75  and  77  may for example switch in a capacitive phase lag network to produce the desired phase lag as is understood in the art. 
     Optimal circular polarization of the activation field requires maintenance of a 90° phase relationship between two of the antennas  30  and  36 . This becomes difficult when driving tuned antennas since a slight mis-tune, or variation of temperature or mounting location, may alter the phase relationship and diminish the effectiveness of circular polarization. The operation of the phase comparator  80  and comparator  83  and voltage controlled phase lag circuit  75  and  77  on the other hand, holds the desired phase relationship despite mis-tuning, variation of temperature, or mounting location. 
     The above described circuit ensures that the waveform applied to the y-axis antenna  30  and the x-axis antenna  36  will be equal in frequency and that the phase between these frequencies will differ by 90 degrees in a self-correcting “quadrature lock”. It will be appreciated that this quadrature lock provides a circularly polarized activation signal that alone will provide for a more consistent activation region  24  in that it will better match with different orientations of the tag  16  in the x-y plane. Spherical polarization is obtained by a frequency lock, phase wobble used with the z-axis antenna  60  as will now be described. 
     Referring still to  FIG. 4 , the output of the voltage controlled phase lag circuit  75  for the y-antenna  30  may be provided to the input of the phase comparator  82  that also receives the output of a voltage controlled oscillator  85 . The output of the voltage controlled oscillator  85  also provides an input to a class-C amplifier  76  whose output connects to the input point  68  of the z-axis antenna  60 . The output of the phase comparator  82  passes through a summing junction  92 , which will be discussed below, to the input of a voltage controlled oscillator  85 . In this way the phase comparator  82  and voltage controlled oscillator  85  provides a signal to amplifier  76  that is loosely phase locked to the frequency originating from the oscillator  74  via phase comparator  75 , but with an arbitrarily changing phase offset that deviates from a truly locked state due to low frequency oscillator  94 . This “dither signal” practically randomizes the phase of z relative to x and y. 
     Referring also to  FIG. 5 , if the phase comparator  82  were to provide a 90 degrees phase lag, this locking system would produce a circular polarization within a polarization plane  90  tipped slightly with respect to the x, y, and z axes if the output of the phase comparator  82  were connected directly to the input of the voltage controlled oscillator  85 . However, as mentioned, the invention routes the output of the phase comparator  82  through summing junction  92 , for example, implemented with an operational amplifier, and sums to that output a low-frequency dither signal produced by dither oscillator  94 . Dither oscillator  94  may have an output frequency, for example a sine wave or other continuous wave, on the order of ten hertz. 
     The sum of these two signals from the summing junction  92  is then provided as the input to the voltage controlled oscillator  85  which provides the output to the class-C amplifier  76 . The result (shown in  FIG. 5 ) is that the polarization plane  90  wobbles as indicated by arrow  95  to sweep through a spherical volume  96  at a ten hertz rate or about ten times per second. In this way, the activation signal will align with an arbitrarily angled antenna of the tag  16  ten times per second effectively producing an extremely uniform activation region  24 . 
     It will be appreciated from the above description that although the oscillator  74  is tunable, each of the antennas  72   a ,  72   b , and  72   c  will operate at substantially the same frequency being driven by the same frequency source. 
     Referring now to  FIG. 6 , the output of the amplifiers  76 ,  84 , and  88  may connect to respective antennas  30 ,  36  and  60  through the switches  100 ,  102 , and  104 , respectively, so that the antennas  30 ,  36  and  60  may be temporarily disconnected from their respective amplifiers  76 ,  84 , and  88  for nulling purposes. Alternatively, because the amplifier  76 ,  84 , and  88  are preferably class-C amplifiers having infinite output impedance when they receive no input signal, the switches  100 ,  102 , and  104  may be placed before the amplifier  76 ,  84 , and  88 . The input points  68  of each of the antennas  30 ,  36  and  60  may also be connected to a voltage display  106 ,  108 , or  110 , respectively, so that the voltage at the respective input points  68   a ,  68   b , and  68   c  can be measured. It will be appreciated that switches  100 ,  102 , and  104  may be conventional mechanical switches, jumpers, shunts, or computer-controlled solid-state switches as desired. 
     Referring to  FIGS. 4 and 6 , the tuning process may proceed by first individually dosing a respective one of the switches  100 ,  102 , and  104  (e.g. opening the other switches) and tuning the capacitor  70   a ,  70   b , or  70   c  to produce the maximum voltage reading on respective displays  106 ,  108 , or  110 . Thus, for example, switch  100  is closed while switch  102  and switch  104  are open and capacitor  70   a  tuned to provide a maximum output reading on display  106 . This process is repeated for each capacitor  70   a ,  70   b , and  70   c.    
     After this tuning of antennas  30 ,  36  and  60  is complete, switch  102  of antenna  30  is closed with switch  100  and  104  open, and fastener  47  (shown in  FIG. 2 ) loosened and x-axis antenna  36  rotated about the pivot axle  44  to produce a slight dip in output voltage on display  108  as a function of that rotation. The x-axis antenna  30  is locked in the position that produces the greatest dip or null. This provides a mechanism of properly aligning x-axis antenna  36  with y-axis antenna  30  to minimize inductive coupling therebetween. 
     Next switch  104  is closed and switches  102 ,  100  are opened. At this point the machine screws  56  (shown in  FIG. 2 ) are loosened and tightened to tip the printed circuit board  50  to minimize the reading visible on display  110 . 
     The invention contemplates the inclusion of a processor system  120  having a processor  122  communicating with an electronic memory  124  such as may hold data and a variety of programs including an operating system  126 , a security monitoring routine  128 , and a tuning routine  130 . The processor system  120  may also communicate with a tag interrogation transmitter  132  used for receiving information from a tag  16  after it has been activated by activation signal  20  (shown in  FIG. 1 ) according to methods generally known in the art. 
     The processor system  120  may also communicate with each of the switches  100 ,  102 . and  104  and the displays  106 ,  108 , and  110 , to assist in the tuning procedure described above by cycling the user through the various steps possibly including written or spoken cues. The processor system  120  may also assist in the detection of the dips, for example, by an audible tone or the like when the dip is arrived at. 
     The processor system  120  may also communicate with each of the amplifiers  76 ,  84 , and  88  to control their gain. Referring now to  FIG. 7 , this gain control may be used to change the relative size of the uniform activation region  24  during operation of the system. The improved accuracy obtained with respect to the size of the uniform activation region  24  may then be used to provide a ranging function to determine the distance between a patient  18  and the control unit  12  according to the size of the activation region (controlled by controlling the gain of amplifier  76 ,  84 . and  88 ) necessary to receive a signal back from a tag on the patient  18 . In this way, the present invention enables a ranging function that may provide additional information about the patient  18  which may be used to fence off particular locations, for example, in an adjacent room  134 , away from the door  14  to prevent nuisance activations. 
     Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “front.”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. It will be appreciated that the particular orientation of the x, y, and z axes is arbitrary and invention is not limited to particular orientation of the control unit. 
     When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may he additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     References to “a microprocessor” and “a processor” or “the microcontroller” can be understood to include one or more processors and similar circuitry such as FPGAs, microprocessors, microcontrollers, etc., that can communicate in a stand-alone and/or a distributed environment(s), and can thus be configured to communicate via wired or wireless communications with other processors, where such one or more processor can be configured to operate on one or more processor-controlled devices that can be similar or different devices. Furthermore, references to memory, unless otherwise specified, can include one or more processor-readable and accessible memory elements and/or components that can be internal to the processor-controlled device, external to the processor-controlled device, and can be accessed via a wired or wireless network. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. All of the publications described herein, including patents and non-patent publications, are hereby incorporated herein by reference in their entireties.