Patent Publication Number: US-11660153-B2

Title: Active drive mechanism with finite range of motion

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 15/229,639, filed Aug. 5, 2016, issued as U.S. Pat. No. 10,792,112 on Oct. 6, 2020, and entitled “ACTIVE DRIVE MECHANISM WITH FINITE RANGE OF MOTION,” which is a continuation of U.S. patent application Ser. No. 13/838,777, filed Mar. 15, 2013, issued as U.S. Pat. No. 9,408,669 on Aug. 9, 2016, and entitled “ACTIVE DRIVE MECHANISM WITH FINITE RANGE OF MOTION,” the entirety of each application is herein incorporated by reference for all purposes 
    
    
     BACKGROUND 
     Robotic interventional systems and devices are well suited for performing minimally invasive medical procedures as opposed to conventional techniques wherein the patient&#39;s body cavity is open to permit the surgeon&#39;s hands access to internal organs. However, advances in technology have led to significant changes in the field of medical surgery such that less invasive surgical procedures, in particular, minimally invasive surgery (MIS), are increasingly popular. 
     MIS is generally defined as a surgery that is performed by entering the body through the skin, a body cavity, or an anatomical opening utilizing small incisions rather than large, open incisions in the body. With MIS, it is possible to achieve less operative trauma for the patient, reduced hospitalization time, less pain and scarring, reduced incidence of complications related to surgical trauma, lower costs, and a speedier recovery. 
     Special medical equipment may be used to perform MIS procedures. Typically, a surgeon inserts small tubes or ports into a patient and uses endoscopes or laparoscopes having a fiber optic camera, light source, or miniaturized surgical instruments. Without a traditional large and invasive incision, the surgeon is not able to see directly into the patient. Thus, the video camera serves as the surgeon&#39;s eyes. The images of the interior of the body are transmitted to an external video monitor to allow a surgeon to analyze the images, make a diagnosis, visually identify internal features, and perform surgical procedures based on the images presented on the monitor. 
     MIS devices and techniques have advanced to the point where an insertion and rolling motion of components of an elongated component such as a catheter instrument, e.g., a catheter sheath and associated guidewire, are generally controllable by selectively operating rollers or other mechanisms for generally gripping the component. Some known mechanisms use gripping devices capable of infinite motion for insertion of a catheter, e.g., a roller, may require more complex catheter component loading procedures, or may not be compatible with replaceable components adapted for a sterile operating environment. 
     Accordingly, there is a need in the art for systems and methods for inserting and rolling catheter components that address or solve the above problems. 
     SUMMARY 
     Various exemplary drive apparatuses and associated methods are disclosed for driving an elongated member, e.g., a catheter, sheath, or guidewire. An exemplary drive apparatus may include a first component and a moveable component, each configured to selectively grip the elongated member. In some examples, the first and moveable components may each include a gripping device. The moveable component may be configured to selectively move axially and rotationally with respect to a support surface to effect axial movement and rotation movement, respectively, of the elongated member with respect to the support surface within a range of motion of the moveable component. The moveable component may be configured to move the elongated member across a predetermined movement having a magnitude greater than the range of motion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the claims are not limited to the illustrated embodiments, an appreciation of various aspects is best gained through a discussion of various examples thereof. Referring now to the drawings, illustrative embodiments are shown in detail. Although the drawings represent the embodiments, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain an innovative aspect of an embodiment. Further, the embodiments described herein are not intended to be exhaustive or otherwise limiting or restricting to the precise form and configuration shown in the drawings and disclosed in the following detailed description. Exemplary embodiments of the present invention are described in detail by referring to the drawings as follows. 
         FIG.  1    is an illustration of a robotically controlled surgical system, according to one exemplary illustration; 
         FIG.  2    is an illustration of an exemplary catheter assembly of the surgical system of  FIG.  1   ; 
         FIG.  3    is another exemplary illustration of an exemplary catheter assembly of the surgical system of  FIG.  1   ; 
         FIG.  4    is an illustration of an exemplary drive apparatus for an elongated member, e.g., a guidewire for a catheter; 
         FIG.  5    is a top view of the exemplary drive apparatus of  FIG.  4   ; 
         FIG.  6    is a side view of the exemplary drive apparatus of  FIG.  4   ; 
         FIG.  7    is a rear view of the exemplary drive apparatus of  FIG.  4   ; 
         FIG.  8    is a perspective view of the exemplary drive apparatus of  FIG.  4   , with the dynamic gripper rotated to a maximum rotation in a clockwise direction; 
         FIG.  9    is a perspective view of the exemplary drive apparatus of  FIG.  4   , with the dynamic gripper rotated to a maximum rotation in a counter-clockwise direction; 
         FIG.  10    is an illustration of another exemplary drive apparatus for an elongated member, e.g., a guidewire for a catheter; 
         FIG.  11    is another perspective view of the exemplary drive apparatus of  FIG.  10   ; 
         FIG.  12    is a front view of the exemplary drive apparatus of  FIG.  10   ; 
         FIG.  13    is a rear view of the exemplary drive apparatus of  FIG.  10   ; 
         FIG.  14    is another perspective view of the exemplary drive apparatus of  FIG.  10   , with the grippers placed in an open position; 
         FIG.  15    is a front view of an exemplary instrument with a sterile drape assembly; 
         FIG.  16    is a graph illustrating an exemplary proxy command for a drive apparatus; 
         FIG.  17    is a graph illustrating insert joint position for the exemplary proxy command illustrated in  FIG.  16   ; 
         FIG.  18    is a process flow diagram for an exemplary method of providing a generally continuous motion using a discontinuous drive system, e.g., the exemplary drive apparatus illustrated in  FIGS.  4 - 9    and/or  FIGS.  10 - 14   ; and 
         FIG.  19    is a top view of an exemplary pivotable pad for a gripper. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, illustrative embodiments are shown in detail. Although the drawings represent the embodiments, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain an innovative aspect of an embodiment. Further, the embodiments described herein are not intended to be exhaustive or otherwise limit or restrict the invention to the precise form and configuration shown in the drawings and disclosed in the following detailed description. 
     Exemplary System and Drive Apparatuses 
     Referring to  FIG.  1   , a robotically controlled surgical system  100  is illustrated in which an apparatus, a system, and/or method may be implemented according to various exemplary illustrations. System  100  may include a robotic catheter assembly  102  having a robotic or first or outer steerable complement, otherwise referred to as a sheath instrument  104  (generally referred to as “sheath” or “sheath instrument”) and/or a second or inner steerable component, otherwise referred to as a robotic catheter or guide or catheter instrument  106  (generally referred to as “catheter” or “catheter instrument”). Catheter assembly  102  is controllable using a robotic instrument driver  108  (generally referred to as “instrument driver”). During use, a patient is positioned on an operating table or surgical bed  110  (generally referred to as “operating table”) to which robotic instrument driver  108  may be coupled or mounted. In the illustrated example, system  100  includes an operator workstation  112 , an electronics rack  114  and associated bedside electronics box (not shown), a setup joint mounting brace  116 , and instrument driver  108 . A surgeon is seated at operator workstation  112  and can monitor the surgical procedure, patient vitals, and control one or more catheter devices. Operator workstation  112  may include a computer monitor to display a three dimensional object, such as a catheter instrument or component thereof, e.g., a guidewire, catheter sheath. Moreover, catheter instrument  502  may be displayed within or relative to a three dimensional space, such as a body cavity or organ, e.g., a chamber of a patient&#39;s heart. In one example, an operator uses a computer mouse to move a control point around the display to control the position of catheter instrument. 
     System components may be coupled together via a plurality of cables or other suitable connectors  118  to provide for data communication, or one or more components may be equipped with wireless communication components to reduce or eliminate cables  118 . Communication between components may also be implemented over a network or over the internet. In this manner, a surgeon or other operator may control a surgical instrument while being located away from or remotely from radiation sources, thereby decreasing radiation exposure. Because of the option for wireless or networked operation, the surgeon may even be located remotely from the patient in a different room or building. 
     Referring now to  FIG.  2   , an exemplary instrument assembly  200  is shown, including sheath instrument  104  and the associated guide or catheter instrument  106  mounted to mounting plates  202 ,  204  on a top portion of instrument driver  108 . During use, catheter instrument  106  is inserted within a central lumen of sheath instrument  104  such that instruments  104 ,  106  are arranged in a coaxial manner. Although instruments  104 ,  106  are arranged coaxially, movement of each instrument  104 ,  106  can be controlled and manipulated independently. For this purpose, motors within instrument driver  108  are controlled such that carriages coupled to each of the instruments  104 ,  160  may allow the instruments  104 ,  106  to be driven forwards and backwards along the driver  108 , e.g., with mounting plates securing the instruments to the driver  108  on bearings. As a result, a catheter  300  coupled to guide catheter instrument  106  and sheath instrument  104  can be controllably manipulated while inserted into the patient, as will be further illustrated. Additional instrument driver  108  motors (not shown in  FIG.  2   ) may be activated to control bending of the catheter as well as the orientation of the distal tips thereof, including tools mounted at the distal tip. Sheath catheter instrument  106  is configured to move forward and backward for effecting an axial motion of the catheter, e.g., to insert and withdraw the catheter from a patient, respectively. 
     Referring now to  FIG.  3   , another exemplary instrument  109  is illustrated mounted on the exemplary instrument driver  108 . The instrument  109  includes a cover  111  and a drive apparatus, e.g., drive apparatus  400  or drive apparatus  1000 , as will be described further below. During use the instrument  109  may be used to manipulate an elongate member included in the catheter assembly  102 , e.g., a catheter guidewire (not shown in  FIG.  3   ). Alternatively, the instrument  109  may be employed to manipulate a catheter sheath (not shown in  FIG.  3   ). Although a single instrument  109  is illustrated in  FIG.  3   , in another exemplary illustration two instruments  109  may be employed in which a first instrument  109  is used to insert and roll a guidewire, which guidewire is inserted within a central lumen of a second instrument  109  (not shown in  FIG.  3   ) such that the two instruments  109  are arranged in a coaxial manner, substantially as described above regarding the instruments  104 ,  106 . Additionally, the instruments  109  may generally insert and rotate the associated elongate member, i.e., the guidewire and catheter sheath, independently, as described above regarding the instruments  104 ,  106 . Accordingly, while the exemplary illustrations herein may generally focus on the insertion and rotation of a guidewire for a catheter, the instrument  109  may be used for insertion and rotation of any elongate member that is convenient. 
     Turning now to  FIGS.  4 - 9   , exemplary drive apparatus  400  is illustrated in further detail. As noted above, and as will be described further below, the drive apparatus  400  may generally include a moveable component  440 . In the illustrated example, the moveable component  440  is a dynamic gripper  440 . The drive apparatus may further comprise a first component  442 . As illustrated in  FIGS.  4 - 9   , the first component  442  may be a static gripper  442 , and in some exemplary approaches the static gripper  442  may be generally fixed with respect to the support surface  401 . Each of the grippers  440 ,  442  may comprise a clamp  445 ,  447  having a pair of opposing pads  444   a ,  444   b  and  446   a ,  446   b , respectively. Accordingly, the grippers  440 ,  442  may each selectively clamp an elongate member, e.g., a guidewire or catheter, between their respective opposing pads  444   a ,  444   b  and  446   a ,  446   b.    
     The moveable component or dynamic gripper  440  may have a range of motion to which it is confined. For example, as will be described further below, the dynamic gripper  440  may be capable of axial movement in a direction A along a distance D. Additionally, the dynamic gripper  440  may be capable of limited rotational movement about an axis parallel to the direction of axial movement, e.g., to a range of plus or minus a predetermined angle with respect to a normal or center position. Nevertheless, the as described further below the dynamic gripper  440  may move an elongated component across a predetermined movement, e.g., an axial or rotational movement that may be provided by a user, that is greater than the axial or rotational range of motion. 
     The pads  444  may each generally define a length L D  in the axial direction associated with the elongate member, as best seen in  FIG.  5   . Similarly, the pads  446  may each generally define a length L S  in the axial direction associated with the elongate member. As best seen in  FIG.  6   , the pads  444  may also each define a height H D  in a direction perpendicular to the axial direction, i.e., in a direction corresponding to a direction of top loading the elongate member, as will be described further below. Moreover, the pads  446  may similarly each define a height H S  in a direction perpendicular to the axial direction, i.e., in a direction corresponding to a direction of top loading the elongate member, as will be described further below. 
     An elongated member, e.g., a guidewire, may be wrapped about a slip detection wheel  406  that passively rotates in response to a length of the guidewire being moved by the dynamic grippers  440 . The slip detection wheel  406  may be mounted on a rotatable member  405 . Moreover, as will be described further below the wheel  406  may include optical marks allowing for tracking of the wheel  406  rotation, thereby allowing measurement of movement and/or slippage of the elongate member. 
     As shown in  FIG.  4   , the grippers may each be mounted to a support structure  401 , e.g., a top surface or support structure associated with the driver  108 . The grippers  440 ,  432  are each configured to selectively grip an elongate member such as a catheter guidewire or sheath, merely as examples. Moreover, the dynamic gripper  440  is configured to generally move axially and rotationally with respect to the support structure  401  to effect a corresponding axial and rotational movement of the elongated member. By contrast, the static gripper  442  is generally not movable axially or rotationally with respect to the support structure  401 . The static gripper  442  selectively closes and opens to grip and release the elongate member. 
     Generally, the static gripper  442  cooperates with the dynamic gripper  440  to effect axial movement (i.e., for insertion) along a direction A as illustrated in  FIG.  4   , and rotational movement R about the direction A of the elongate member. The grippers  440 ,  432  may generally work in sequence such that at least one of the grippers  440 ,  432  is gripping the elongate member at any given time. More specifically, during any movement of the guidewire, e.g., insertion, retraction, or rotational movement in either direction, the dynamic grippers  440  are closed, and static grippers  442  are open. 
     A range of axial motion associated with the dynamic grippers  440  may be finite, and in particular be limited to a predetermined axial distance D, as seen in  FIG.  6   . Accordingly, upon reaching a limit to the range of motion, i.e., at an axially furthest position in one direction, the dynamic grippers  440  generally release the elongate member, move back in an opposite direction, and re-grip the elongated member for continued axial movement. While the dynamic grippers  440  are not gripping the elongated member, the static grippers  442  may hold the elongated member in place to prevent movement or loss of position. 
     Axial and rotational motion of the elongated member may be governed by independent drive systems associated with the drive apparatus  400 . For example, the dynamic gripper  440  may have separate motors or mechanisms controlling axial motion on the one hand and rotational motion on the other. Accordingly, insertion and rotation of the elongated member may be accomplished completely independently of the other. More specifically, the elongated member may be inserted axially while it is being rotated, or the elongated member may be inserted without any rotation. Moreover, the elongate member may be rotated without requiring any insertion motion at the same time. 
     Turning now to  FIGS.  8  and  9   , rotational motion of the dynamic grippers  440  is described and shown in further detail. A rotation drive motor  423 , as best seen in  FIG.  8   , may rotate a gear  424  engaging a carriage or swing platform  425  configured to rotate about an axis of rotation, e.g., in a rotational motion R about the direction of insertion A. The carriage  425  may be located by a pair of rolling posts  422  supported by a base structure  434 . The base structure  434  may in turn be secured to the support structure  401 . The carriage or swing platform  425  may be capable of rolling from a nominal or center position to any degree that is convenient. In one exemplary illustration, the carriage or swing platform  425  may be capable of rolling 30 degrees in either direction from a nominal or center position. More specifically, as illustrated in  FIG.  8   , swing platform  425  is rotated in a clock-wise direction thirty degrees away from a nominal or center position, i.e., as shown in  FIG.  4   . Moreover, as illustrated in  FIG.  9   , swing platform  425  is illustrated rotated in a counter-clock-wise direction away from the nominal position. 
     Turning now to  FIGS.  6  and  8   , axial motion of the dynamic gripper  440  is illustrated in further detail. The dynamic gripper  440  may be axially moved by a shaft  426  which is linked to an axial drive motor  431  by way of cam  430 , as best seen in  FIG.  6   . The cam  430  may be connected to the motor  431  via gears  432 ,  433 . The opposite end of the shaft  426  may be connected to an axially movable platform  428  via a cam follower  427 . Accordingly, the dynamic gripper  440  may be independently driven in an axial direction, e.g., for insertion, by the axial drive motor  431 , and may be rotated independently by a rotation drive motor  423 . 
     The static and dynamic grippers  442 ,  440  may each be configured to open to allow loading of an elongated member, e.g., a guidewire or catheter. Moreover, the grippers  440 ,  442  may generally allow “top loading” of the drive apparatus  400  in a direction perpendicular to the axial motion of the gripper  440 . More specifically, the grippers  440 ,  442  may each generally open to allow the guidewire to be laid between the open grippers, e.g., from above the apparatus  400 , without needing to “thread” the elongated member into the grippers  440 ,  442  axially. The ability to load the elongated member without requiring the catheter to be threaded through the drive apparatus  400  advantageously saves time, and also facilitates use of a sterile drape as will be described further below. 
     Turning now to  FIGS.  5 - 7   , the opening and closing of the static gripper  442  and dynamic gripper  440  will now be explained in further detail. The dynamic gripper  440  may be opened by a grip open motor  407 . For example, as best seen in  FIGS.  5  and  6   , a grip open motor  407  may be provided which drives a cam  408 , which in turn actuates shaft  9 . The shaft  9  has a cam follower  410  that provides axial motion to movable platform  411  and cam follower  412 , which is attached to the lever  413  (see  FIG.  6   ). The lever  13 , as seen in  FIG.  5   , provides lateral motion through a rotation over shaft  414  to a dynamic gripper bracket  416  by way of cam follower  415 . Cam  408  thus may generally provide only one way motion, to open the dynamic grippers  440 . On the other hand, the dynamic grippers may be urged toward a closed position by a set of springs  417 . For example, the springs  417  may act between the opposing pads included in the dynamic grippers  440 , thereby urging the grippers  440  into a closed position absent a force applied by the grip open motor  407  to counteract the closing force of the springs  417 . 
     As noted above, the static gripper  442  may be selectively opened and closed, independent of the opening and closing of the dynamic gripper  440 . Nevertheless, the same cam  408  employed to open the dynamic grippers  440  may be used to selectively open the static grippers  442 . For example, as best seen in  FIG.  7   , the cam  408  may include two separate profiles, with one configured to open the dynamic grippers  440 , and another configured to open the static grippers  442 . More specifically, the cam  408  as seen in  FIG.  7    may be in proximity to a cam follower  418  that is connected to static gripper platform  419 . The static gripper platform  419  may urge the opposing pads of the static grippers  442  apart. One or more compliant elements, e.g., spring  420 , may generally urge the static gripper platform  419  toward a closed position where the static grippers  442  are clasped together, e.g., about a guidewire or catheter. 
     The platform  425  on which the dynamic grippers  440  are mounted may generally move in relation to the support surface  401 , as noted above. The platform  425  thus may also be moving in relation to the cam follower  410 , shaft  409 , and cam  408  used to effect opening and closing movement of the dynamic grippers  440 . Accordingly, the movement of the shaft  409  is in relation to the moving platform  425 , and thus the opening movement of the cam  408  may need to account for this additional relative movement in order to open the dynamic grippers  440 . 
     As briefly described above, the grippers  440 ,  442  generally allow a top loading of the elongated member, e.g., a guidewire, thereby increasing the speed with which the guidewire may be loaded into the drive apparatus  400 . Additionally, the positioning of the grippers  440 ,  442  and the opposing pads  444 ,  446  may also facilitate the use of a sterile drape that generally maximizes the potential for reusing components of the drive apparatus  400 . In other words, the sterile drape may allow for keeping nearly the entire drive apparatus  400  out of the sterile environment, defining in part a disposable portion of the system  100  that is within the sterile environment. 
     Turning now to  FIGS.  10 - 14   , another exemplary drive apparatus  1000  is illustrated in further detail. The drive apparatus  1000  may generally include a moveable component such as a dynamic gripper  1050 . The drive apparatus may further comprise a fixed component. In the example illustrated in  FIGS.  10 - 14   , the fixed component includes at least one static gripper. As illustrated in  FIGS.  10 - 14    the fixed component includes two static grippers  1052   a ,  1052   b . More specifically, the fixed component includes a first static gripper  1052   a , and a second static gripper  1052   b . The dynamic gripper  1050  may comprise a pair of opposing pads  1003 ,  1004 . Similarly, a first one of the static grippers  1052   a  may comprise a pair of opposing pads  1005   a ,  1006   a , and the other static gripper  1052   b  may also comprise a pair of opposing pads  1005   b ,  1006   b . Accordingly, the grippers  1050 ,  1052   a , and  1052   b  may each selectively clamp an elongate member, e.g., a guidewire or catheter, between their respective opposing pads  1003 / 1004 ,  1005   a / 1006   a , and  1005   b / 1006   b . The pads  1003 / 1004 ,  1005   a / 1006   a , and  1005   b / 1006   b  may each be relatively soft with respect to the particular elongate member being employed, in order to more securely grip the elongate member and minimize potential damage to the elongate member, e.g., by spreading grip load across an increased surface area of the elongate member. 
     As best seen in  FIGS.  12  and  13   , the pads  1003 ,  1004  of the dynamic gripper  1050  each define generally arcuate profiles for engaging the elongate member (not shown in  FIGS.  12  and  13   ). More specifically, the pads  1003 ,  1004  each have curved pad surfaces  1098 ,  1099 , respectively. Accordingly, the pads  1003 ,  1004  may engage an elongate member along a longitudinal line extending parallel to the elongate member, i.e., axially with respect to the dynamic gripper  1050 . In other exemplary approaches, the surfaces of the pads  1003 ,  1004  may be generally flat. The pads  1005   a / 1006   a  and  1005   b / 1006   b  of the static grippers  1052   a ,  1052   b , respectively, may similarly define either curved or flat engagement surfaces for engaging an elongate member. 
     Turning now to  FIG.  19   , in another exemplary approach one of the pads  1003 ′ of a dynamic gripper  1050 ′ may be pivotable about a substantially vertical axis A-A with respect to an opposing pad  1004 ′. While the pads  1003 / 1004 ,  1005   a / 1006   a , and  1005   b / 1006   b  described in regard to  FIGS.  10 - 14    are illustrated as being generally fixed rotationally with respect to one another, a pivotable pad  1003 ′ may be employed in place of any of the rotationally fixed pads. The pivotable pad  1003 ′ may generally improve grip of an elongate member by minimizing any loss of grip due to misalignment of the pad  1003 ′ or  1004 ′. More specifically, to any extent the pad  1004 ′ is possibly misaligned, the pad  1003 ′ will generally automatically rotate about the vertical axis A-A as the associated gripper, e.g., dynamic gripper  1050 , closes upon the elongate member. The pivoting pad  1003 ′ may thereby ensure a substantially parallel alignment of the two pads  1003 ′,  1004 ′ as the gripper  1050 ′ closes upon the elongate member. Moreover, the pivotable pad concept may be applied not only to a dynamic gripper  1050 ′, but also to a static gripper, e.g., static grippers  1052   a ,  1052   b.    
     Similar to the drive apparatus  400 , the moveable component or dynamic gripper  1050  of the drive apparatus  1000  may have a predetermined range of motion which it is confined to. For example, as will be described further below, the dynamic gripper  1050  may be capable of axial movement in a direction A along a predetermined distance D 2  (see  FIG.  10   ). Additionally, the dynamic gripper  1050  may be capable of imparting a limited rotational movement to the elongate member about an axis parallel to the direction of axial movement, e.g., to a range of plus or minus a predetermined angle with respect to a normal position. More specifically, as will be described further below the pads  1003 ,  1004  of the dynamic gripper  1050  may generally translate vertically with respect to one another across a limited range of translational motion, e.g., as defined by a gear and rack system. Nevertheless, the dynamic gripper  1050  may move an elongated component across a movement, e.g., an axial or rotational movement, for example as commanded by a user or surgeon, that is greater than the predetermined axial or rotational motion capable of the dynamic gripper  1050  in a single vertical stroke of the dynamic grippers  1050 . 
     The pads  1003 ,  1004  of the dynamic gripper  1050  may generally define a length L D  in the axial direction associated with the elongate member, as best seen in  FIG.  14   . Similarly, the pads  1005   a ,  1006   a  and  1005   b ,  1006   b  of the first and second static grippers  1052   a ,  1052   b , respectively, may generally define respective lengths L S1 , L S2  in the axial direction associated with the elongate member. Similar to the heights HD and Hs described above regarding drive apparatus  400 , the pads  1003 / 1004 ,  1005   a / 1006   a , and  1005   b / 1006   b  may each generally define an axial height, i.e., in a direction perpendicular to the direction of axial insertion A and corresponding to a direction from which an elongated member may be placed in between the pads. For example, as best seen in  FIG.  12   , the pads  1003 ,  1004  of the dynamic grippers  1050  may define respective axial heights H 2  and H 1 , which may be equal. The pads  1003 / 1004 ,  1005   a / 1006   a , and  1005   b / 1006   b  may each generally be open to a space above the pads when opened, e.g., as shown in regard to the dynamic pads  1003 ,  1004  in  FIG.  12   , allowing an elongated member extending across the pads axially to be laid in between the pads  1003 / 1004 ,  1005   a / 1006   a , and  1005   b / 1006   b.    
     An elongated member, e.g., a guidewire, may be wrapped about slip detection wheel  1002  that passively rotates in response to a length of the guidewire being moved by the dynamic grippers  1050 . The slip detection wheel  1002  may be mounted on a support  1001 . Moreover, as will be described further below the wheel  1002  may include optical marks allowing for tracking of the wheel  1002  rotation, thereby allowing measurement of movement of the elongate member. It should be noted that for stiffer elongate members, it may not be necessary to wrap the elongate member about the slip detection wheel. Instead, the wheel may be configured to just contact the elongate member and rotation is imparted to the passive wheel via friction between the wheel and the surface of the elongate member. 
     As shown in  FIG.  10   , the static grippers  1052   a ,  1052   b  and dynamic gripper  1050  may each be mounted to a support structure  999 , e.g., a top surface or support structure associated with the driver  108 . The grippers  1050 ,  1052  are may each be configured to selectively grip an elongate member such as a catheter guidewire or sheath, merely as examples. Moreover, the dynamic gripper  1050  is configured to generally move axially with respect to the support structure  999  to effect a corresponding axial movement of the elongated member. The pads  1003 ,  1004  of the dynamic gripper  1050  are also configured to translate in a vertical direction across a fixed range of motion to impart rotational motion to the elongate member with respect to the support structure  999 . By contrast, the static grippers  1052   a  and  1052   b  are generally not movable axially or rotationally with respect to the support structure  401 . The static grippers  1052   a  and  1052   b  selectively close and open to grip and release the elongate member. 
     Generally, similar to the drive apparatus  400  described above, the static grippers  1052   a  and  1052   b  of the drive apparatus  1000  each cooperate with the dynamic gripper  1050  to effect axial movement (i.e., for insertion or retraction) along a direction A as illustrated in  FIG.  10   , and rotational movement R about the direction A of the elongate member. The static grippers  1052   a ,  1052   b  may generally work in sequence with the dynamic grippers  1050  such that at least one of the grippers  1050 ,  1052   a , and  1052   b  is gripping the elongate member at any given time. More specifically, during any movement of the guidewire, e.g., insertion, retraction, or rotational movement in either direction, the dynamic grippers  1050  are closed, and the static grippers  1052   a  and  1052   b  are open. Moreover, the static grippers  1052   a ,  1052   b  may generally work in concert, such that the static grippers  1052   a ,  1052   b  are either both open or both closed together. 
     A range of axial motion associated with the dynamic grippers  1050  may be finite, and in particular be limited to a predetermined axial distance D 2 , as seen in  FIG.  10   . In the illustrated example having two static grippers  1052   a ,  1052   b , a range of motion of the dynamic gripper  1050  may be limited by the static gripper  1052   a  on one end and the other static gripper  1052   b  on the other end. However, as noted above, in other exemplary approaches only one static gripper  1052  may be present, and thus the axial motion of the dynamic gripper  1050  may be limited by other factors. Nevertheless, the dynamic gripper  1050  may have some predetermined range of axial motion. Accordingly, upon reaching a limit to the range of motion, i.e., at an axially furthest position in one direction, the dynamic grippers  1050  generally release the elongate member, move back in an opposite direction, and re-grip the elongated member for continued axial movement. While the dynamic grippers  1050  are not gripping the elongated member, the static grippers  1052   a  and/or  1052   b  may hold the elongated member in place to prevent movement of the elongated member or loss of position. 
     Axial and rotational motion of the elongated member may be governed by independent drive systems associated with the drive apparatus  1000 , as with drive apparatus  400 . For example, the dynamic gripper  1050  may have separate motors or mechanisms controlling axial motion on the one hand and rotational motion on the other. Accordingly, insertion and rotation of the elongated member may be accomplished completely independently of the other. More specifically, the elongated member may be inserted axially while it is being rotated, or the elongated member may be inserted without any rotation. Moreover, the elongate member may be rotated without requiring any insertion motion at the same time. 
     Referring now to  FIGS.  10 ,  13 , and  14   , opening and closing of the grippers is described and shown in further detail. The drive apparatus  1000  may be generally closed initially. In order to open the grippers, lever  1011  may be manually moved to a vertical position, e.g., as illustrated in  FIG.  14   . The movement of the lever  1011  may rotate a shaft  1012  that is configured to move a static pad bracket  1013  which in turn opens the static pads  1005   a  and  1005   b  with respect to their corresponding static pads  1006   a  and  1006   b , respectively. A dynamic pad bracket  1014  may open the dynamic pads  1003 ,  1004  of the dynamic gripper  1050  in a similar manner. In one exemplary illustration, cams may be positioned on the shaft  1012  for urging the brackets  1013 ,  1014  in a direction opening the pads of each of the static grippers  1052   a ,  1052   b  and the dynamic grippers  1050 , respectively. Moreover, the pads of the static grippers  1052   a ,  1052   b  and the dynamic grippers  1050  may be opened in sequence, i.e., separately from one another. For example, as best seen in  FIGS.  10 ,  13 , and  14   , cams  1015  and  1016  may be connected by a coupling  1017  that is driven by motor  1010 . The cams  1015 ,  1016  may act upon the static pad bracket  1013  and dynamic pad bracket  1014 , respectively, thereby opening each. The static pad bracket  1013  may be urged into a closing position by a spring  1030 , while the dynamic pad bracket  1014  may be urged into a closing position by a spring  1031 . Accordingly, the static pad bracket  1013  and dynamic pad bracket  1014  generally may remain closed in the absence of a force applied to the brackets  1013 ,  1014  tending to open either of the brackets  1013 ,  1014 . 
     Turning now to  FIGS.  10 ,  11 , and  12   , axial motion of the drive apparatus  1000 , e.g., for insertion or retraction of an elongate member, is described in further detail. Axial movement of the dynamic gripper  1050 , i.e., to effect an insertion or refraction motion of the dynamic gripper  1050 , may be driven by a cam  1007  that is turned by motor  1008 , as best seen in  FIG.  11   . More specifically, cam follower  1018  may follow the cam, e.g., within a groove  1060  defined by the cam  1007 , thereby imparting axial motion to dynamic gripper  1050 , including both of the opposing pads  1003 ,  1004 . 
     Turning now to  FIGS.  10  and  12    a mechanism for imparting a rotational motion to an elongate member using the drive apparatus  1000  is described in further detail. As best seen in  FIG.  12   , which is a cross section of the apparatus  1000 , a gear shaft  1020  may be connected through a coupling to a dedicated motor  1009  (see  FIG.  10   ). The gear shaft  1020  may provide relative vertical motion to a first gear rack  1019  that is opposed by a second gear rack  1021 . The relative vertical motion is transferred to the dynamic gripper  1050 . More specifically, a first one of the pads  1003  of the dynamic gripper  1050  translates upward and downward with the first gear rack  1019 , while the other pad  1004  translates upward and downward with the second gear rack  1021 . Accordingly, the relative vertical movement between the pads  1003 ,  1004  imparts a rolling motion to an elongate member held between the pads  1003 ,  1004 . 
     Pads  1003  and  1004  may be designed to optimize the gripping and rolling performance of the elongate member. For example, in one exemplary illustration, a high durometer material that does not engulf the elongate member is used, which may generally prevent pads  1003  and  1004  from contacting each other. This ensures that the spring force closing the grippers is substantially entirely applied to the elongate member and is not transferred from one gripper to the other, ensuring reliable grip on the elongate member. In another exemplary illustration, the contact surface of the pads  1003  and  1004  is beveled in a convex shape such that there is less chance that the pads will contact each other due to any misalignment or non parallelism in the gripper mechanism. 
     Initially, the pads  1003 ,  1004  of the dynamic grippers  1050  and the pads  1005   a ,  1006   a ,  1005   b ,  1006   b  of the static grippers  1052   a ,  1052   b  may be manually opened with the lever  1011 , as best seen in  FIG.  10   . An elongate member, e.g., a guidewire, may be top loaded into the apparatus  1000 . More specifically, a guidewire may be loaded around wheel  1002  and laid in between the pads  1005   a  and  1006   a  of the first static gripper  1052   a , the pads  1003  and  1004  of the dynamic gripper  1050 , and the pads  1005   b  and  1006   b  of the second static gripper  1052   b . More specifically, the elongate member may generally be laid between the pads  1003 / 1004 ,  1005   a / 1006   a , and  1005   b / 1006   b  from above, allowing the elongate member to be extended and laid in between the pads instead of requiring that the elongate member be threaded axially through the pads. During axial motion, e.g., insertion or retraction, an elongate member such as a guide wire or catheter will be pulled off of or pushed onto wheel  1002 , which may passively rotate according to the insertion motion driven by the dynamic gripper  1050  with respect to a wheel support  1001  of the drive apparatus  1000 . As noted above, rotation of the wheel  1002  may be monitored, e.g., by an optical sensor, to allow for measurement of any axial movement of the elongate member. During axial movement of the elongate member, e.g., insertion or retraction, and also during rotational movement, the dynamic pads  1003  and  1004  are generally closed, thereby trapping the elongate member therebetween as a result of a grip imparted to the elongate member or guidewire. Additionally, during axial or rotational motion of the elongate member, the pads  1005   a ,  1006   a  of the first static gripper  1052   a  and the pads  1005   b ,  1006   b  of the second static gripper  1052   b  remain open, thereby generally freely allowing relative movement of the elongate member with respect to the static grippers  1052   a ,  1052   b . Upon reaching a limit of rotational or axial motion, the pads  1005   a ,  1006   a  of the first static gripper  1052   a  and the pads  1005   b ,  1006   b  of the second static gripper  1052   b  may be closed. The pads  1003  and  1004  of the dynamic gripper  1050  may then be opened, and moved within its range of motion (i.e., along distance D) to allow regripping of the elongated member, while the static grippers  1052   a ,  1052   b  maintain the axial and rotational position of the elongated member. The cycle may then be repeated to allow further axial and/or rotational movement of the elongated member. 
     Turning now to  FIG.  15   , an exemplary sterile drape assembly is illustrated. An exemplary drape assembly may include a sterile drape  500  generally positioned over the instrument  109 . The sterile environment may thereby be confined to the area above the drape  500 , allowing use and reuse of the instrument  109  and essentially all components thereof that are positioned beneath the drape. The drape  500  may be positioned over a set of grippers  504   a ,  504   b  using associated caps  501   a ,  501   b . For purposes of the illustration shown in  FIG.  15   , the grippers  504   a ,  504   b  may correspond to any of the static grippers  1052   a ,  1052   b  or dynamic grippers  1050  of the apparatus  1000 , or the static gripper  442  or dynamic gripper  440  of the apparatus  400 . For example, the caps  501  may be molded into the drape  500 , and may be fitted to the grippers  504 , thereby securing the drape  500  in place over the grippers  504 . Moreover, the caps  501  may generally allow for gripping of an elongated member, e.g., a guidewire or catheter, using the caps  500 , thereby allowing the elongated member to be in the sterile environment. The drape  500  and caps  501  may be included in a disposable portion of the system  100 , i.e., which must be disposed of after a procedure, while substantially all components of the system  100 , and in particular the drive apparatus  400  or drive apparatus  1000 , is kept out of the sterile environment and therefore may be reused. 
     It should be understood that the designs presented here are merely exemplary. For example, while apparatus  400  and apparatus  1000  are both described as having one set of fixed grippers and one set of dynamic grippers, alternative approaches may have two pairs of dynamic grippers instead of one static pair and one dynamic pair. The second pair of dynamic grippers may perform similar duties as the static grippers described herein with respect to the first set of dynamic grippers (i.e., hold the elongate member while the first dynamic gripper is returning). Moreover, the second dynamic gripper may also apply axial and rotation movement just like the first dynamic gripper. 
     It should also be understood that the stroke length and gripper length shown for apparatuses  400  and  1000  are also merely exemplary. For example, the distance between the grippers which is approximately equal to the stroke length is shown to be approximately the same length as each of the grippers. This may not be true in all cases. For example, for stiffer elongate members that have greater buckling strength, there may be a significantly longer length between the grippers, or effectively a significantly longer stroke. In addition, if the elongate member that is being manipulated has a high friction surface, then shorter grippers may be appropriate. Also, the length of the static and dynamic grippers are shown to be equal. It is likely that the static gripper length may be shorter than the dynamic gripper since the static gripper just needs to hold the device. 
     The rotational mechanism of apparatus  400  is shown to have approximately 60° of rotation in both directions. Again, this is merely an exemplary illustration. the 60 degrees of rotation may generally permit a doctor to intervene manually and remove the robotic system if the robotic system is stopped at any point during a procedure, and the guidewire will always be presentable towards the top of the mechanism for removal. If for example, there was 180° of rotational movement on this mechanism, there may be times when the grippers are inverted making it difficult to remove the guidewire. In addition, large rotational strokes make it more difficult to manage the sterile barrier because it may lead to more winding up of the drape. Nevertheless, any angle of rotation may be employed that is convenient. 
     It should also be noted that even though most of the descriptions used here describe the elongate member as a guidewire, it may also be a catheter, a sheath, a microcatheter, a therapeutic device such as a stent or balloon or artherectomy device for example. 
     Control of Discontinuous/Finite Drive Apparatus to Provide Continuous/Infinite Movement 
     As noted above, the dynamic gripper  440  of the apparatus  400  and the dynamic gripper  1050  of the apparatus  1000  generally may have a finite range of motion in the axial direction, i.e., a range of motion across an axial distance D as best seen in  FIGS.  6  and  10   , respectively. Additionally, the dynamic grippers  440  and  1050  have a finite range of rotational motion, i.e., a maximum angle from a nominal position as dictated by the configuration of the swing platform  425  seen in  FIGS.  8  and  9    and the geared rack system  1019 ,  1021  illustrated in  FIG.  12   . Accordingly, to provide an axial insertion across a distance greater than distance D, the dynamic grippers  440  and  1050  generally must release the guidewire as it reaches a position toward or at an end of its range of motion, move axially rearward and then re-grip the guidewire, and continue the axial insertion. Similarly, to provide a rotation to an angle greater than the maximum angle capability of the swing platform  425  or the geared rack system  1019 ,  1021 , the dynamic grippers  440 ,  1050  generally must release the guidewire as the swing platform  425  and geared rack system  1019 ,  1021  reaches a maximum angular travel, allowing the respective systems to move in the opposite rotational direction and re-grip the guidewire to continue rotating the guidewire. The process of gripping and re-gripping an elongate member may occur many times during a given axial or rotational movement command. 
     Accordingly, it may be necessary to track a user command associated with the drive apparatus  400  and  1000 , and selectively adjust the movement of the drive apparatus  400  and  1000  to generally keep a resulting movement of the drive apparatus  400  and  1000  and associated elongated member as close as possible to the commanded movement. In this sense, the challenge is to track a continuous command, i.e., to move or rotate a certain amount, with a discontinuous mechanism having a maximum axial stroke length D or maximum angular rotation that is a smaller magnitude than the commanded movement. 
     In one exemplary illustration, an intermediate or proxy command is employed that is internal to a control system, e.g., included in operator workstation  112  or electronics rack  114  of the system  100 , or incorporated as part of the drive apparatus  400  or  1000 . The controller may generally be aware of the above movement limitations of the mechanism, and may accordingly determine an appropriate movement in response to a given command. Referring now to  FIG.  16   , an exemplary proxy command is illustrated for an exemplary drive apparatus  400 . In this example, the thicker line represents a commanded position provided by the user of the system, while the thinner line illustrates an exemplary proxy command. The proxy command is generally developed internally by the controller based on the user command and the physical realities of the mechanism. 
     Generally, when the drive apparatus  400 ,  1000  is away from the end of its range of motion (either axially or rotationally), the proxy command may track the user command tightly. Once the drive apparatus  400 ,  1000  gets to the end of its range of motion, however, the proxy command may freeze while the mechanism clutches and resets to allow continued driving. When the mechanism is finished with its clutching motion, the proxy command then catches up with the drive command such that the deviation between the commanded position of the wire and the actual wire position is as small as possible for as short a period of time as possible. 
     Accordingly, the motion of the proxy command may be controlled by a process using two general states for the proxy command: a “freeze” state and a “tracking” state. More specifically, the proxy command may enter the “freeze” state whenever the mechanism under control, i.e., the drive apparatus  400 ,  1000  indicates that it cannot currently drive. For example, when a user is commanding an insertion motion of 40 millimeters and there is only 20 millimeters remaining the axial range of motion of the drive apparatus  400 ,  1000 , the proxy command may enter the freeze state. Additionally, the freeze state associated with the proxy command may be employed for other purposes, such as when the drive mechanism is deactivated or taken off line, e.g., for diagnostics. 
     The proxy command spends most of the time in the tracking state. In the tracking state, the proxy command follows the user command with dynamics that generally dictate how the proxy command catches up with the user command when it leaves the freeze state. The dynamics can generally be tuned to achieve whatever behavior is desired for the particular drive apparatus  400 ,  1000 . Depending on the application, the dynamics may provide as smooth and slow a transition as possible, e.g., for procedures where insertion of an elongated member is necessarily very slow; alternatively, the dynamics may provide for as fast and abrupt a transition as possible, or any blend of the two extremes. 
     In one exemplary illustration, the proxy command is a filtered version of the user command. When the proxy command leaves the freeze state, the filter is reset such that the filter naturally follows a smooth trajectory connecting the proxy command with the user command. Merely as examples, a first order or second order low-pass filter may be employed. In another example, a non-linear filter that includes features such as limiting the maximum speed of the proxy may be employed. A second order filter may advantageously mimic, in terms of the proxy command dynamics, a mass-spring-damper system, i.e., where the proxy can be thought of as a mass which is connected to the user command by a spring and a damper. 
     A proxy command may be mapped to the actual joint commands of the mechanism in any manner that is convenient. In one exemplary illustration of the drive apparatus  400 ,  1000 , the joint command may be reset at the end of every clutching cycle, i.e., when the dynamic grippers  440 ,  1050  release, move to accommodate additional insertion or rotational motion, and re-grip the elongated member, to be at either the front or the end of the range of motion. The joint command may be incremented by the same amount as the proxy command was incremented every cycle. For example as illustrated in  FIG.  17   , an actual joint position command that was sent to the drive apparatus  400 ,  1000  for the same data set as shown in  FIG.  16   . 
     In another exemplary illustration, the drive apparatus  400 ,  1000  may be configured to track a user command for axial motion or rotation of the elongate member by increasing actual velocity of components of the drive apparatus  400 ,  1000  relative to a velocity expected were releasing/re-gripping not necessary. For example, when there is an expectation that the dynamic grippers  440 ,  1050  will need to re-grip the elongate member, e.g., due to a commanded motion being beyond the range of motion of the dynamic grippers  440 ,  1050 , the grippers  440 ,  1050  may increase a velocity of the movement, even in some cases “getting ahead” of the commanded motion. Accordingly, the movement of the elongate member may be preventing from falling behind or falling undesirably far behind a commanded motion. In other words, a drive apparatus  400 ,  1000  or associated control system may generally compensate for the need to release and re-grip the elongate member by increasing a velocity of a component associated with a commanded motion. In another exemplary illustration, an actual position of an elongated member may be kept within a predetermined range of a commanded movement, i.e., slightly ahead or behind a commanded position, to account for the periodic releasing and re-gripping of the elongate member. Moreover, any velocity or positional adjustments may be performed without intervention by the surgeon, such that the process of releasing and re-gripping the elongate member is generally undetected. In some exemplary approaches, control of any buffer between the commanded position/velocity and actual position/velocity may be quick enough that any positional difference or velocity different resulting from the need to start and stop movement of the elongated member to allow release and re-gripping may generally be imperceptible by the user, e.g., the surgeon. 
     Turning now to  FIG.  18   , an exemplary process  1300  for a proxy command is illustrated. The process  1300  is generally begins at block  1302 , where the process may query whether a commanded movement of the drive apparatus is within an associated limit to the range of motion. 
     If a commanded movement is within the range of motion, process  1300  proceeds to block  1304 , where the tracking state is set. In other words, if a movement of 40 millimeters is requested by an operator, and 60 millimeters of travel remain in the axial insertion range of the drive apparatus, the proxy command may be equal to the user command. 
     On the other hand, if the commanded movement is outside the range of motion, then the process  1300  proceeds to block  1306 , where the proxy command may enter the freeze state. As noted above the freeze state may allow the drive apparatus  400 ,  1000  to release and re-grip the elongated member in order to reduce or eliminate the shortfall between the commanded motion and the capability of the drive apparatus  400 ,  1000 . For example, if a rotational movement of 45 degrees is commanded by the user and the maximum rotation available from the current position of the dynamic gripper  440 ,  1050  is only 35 degrees, then the proxy command may enter the freeze state to allow the dynamic grippers  440 ,  1050  to be released and rotated to allow greater range of rotational movement. 
     Proceeding to block  1308 , the dynamic grippers  440 ,  1050  are opened to release the elongate member from their grip, and the dynamic grippers  440 ,  1050  are then moved to allow greater range of motion and re-grip the elongate member to reduce or eliminate the shortfall between the proxy command and the user command. Process  1300  may then proceed to block  1310 . 
     At block  1310 , the commanded position may be compared with the proxy command position, i.e., to determine any shortfall between the new position of the dynamic grippers  440 ,  1050  and the desired or commanded position. 
     Proceeding to block  1312 , the proxy command may be adjusted with the difference determined at block  1310 . As noted above, in some examples the proxy command may be a filtered version of the comparison between the proxy command and the user command, in order to “smooth” the response of the system to differences between the commanded position and the current position of the dynamic grippers. Moreover, the transition may be tuned according to the desired response. A relatively slower transition may be employed in situations where any relatively sudden or relative large movement is especially problematic, while a faster transition may be employed where speed or responsiveness is more essential. Process  1300  may then terminate. 
     Operator workstation  112 , electronics rack  114 , drive apparatus  400 , and/or drive apparatus  1000  may include a computer or a computer readable storage medium implementing the operation of drive and implementing the various methods and processes described herein, e.g., process  1300 . In general, computing systems and/or devices, such as the processor and the user input device, may employ any of a number of computer operating systems, including, but by no means limited to, versions and/or varieties of the Microsoft Windows® operating system, the Unix operating system (e.g., the Solaris® operating system distributed by Oracle Corporation of Redwood Shores, Calif.), the AIX UNIX operating system distributed by International Business Machines of Armonk, N.Y., the Linux operating system, the Mac OS X and iOS operating systems distributed by Apple Inc. of Cupertino, Calif., and the Android operating system developed by the Open Handset Alliance. 
     Computing devices generally include computer-executable instructions, where the instructions may be executable by one or more computing devices such as those listed above. Computer-executable instructions may be compiled or interpreted from computer programs created using a variety of programming languages and/or technologies, including, without limitation, and either alone or in combination, Java™, C, C++, Visual Basic, Java Script, Perl, etc. In general, a processor (e.g., a microprocessor) receives instructions, e.g., from a memory, a computer-readable medium, etc., and executes these instructions, thereby performing one or more processes, including one or more of the processes described herein. Such instructions and other data may be stored and transmitted using a variety of computer-readable media. 
     A computer-readable medium (also referred to as a processor-readable medium) includes any non-transitory (e.g., tangible) medium that participates in providing data (e.g., instructions) that may be read by a computer (e.g., by a processor of a computer). Such a medium may take many forms, including, but not limited to, non-volatile media and volatile media. Non-volatile media may include, for example, optical or magnetic disks and other persistent memory. Volatile media may include, for example, dynamic random access memory (DRAM), which typically constitutes a main memory. Such instructions may be transmitted by one or more transmission media, including coaxial cables, copper wire and fiber optics, including the wires that comprise a system bus coupled to a processor of a computer. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASH-EEPROM, any other memory chip or cartridge, or any other medium from which a computer can read. 
     Databases, data repositories or other data stores described herein may include various kinds of mechanisms for storing, accessing, and retrieving various kinds of data, including a hierarchical database, a set of files in a file system, an application database in a proprietary format, a relational database management system (RDBMS), etc. Each such data store is generally included within a computing device employing a computer operating system such as one of those mentioned above, and are accessed via a network in any one or more of a variety of manners. A file system may be accessible from a computer operating system, and may include files stored in various formats. An RDBMS generally employs the Structured Query Language (SQL) in addition to a language for creating, storing, editing, and executing stored procedures, such as the PL/SQL language mentioned above. 
     In some examples, system elements may be implemented as computer-readable instructions (e.g., software) on one or more computing devices (e.g., servers, personal computers, etc.), stored on computer readable media associated therewith (e.g., disks, memories, etc.). A computer program product may comprise such instructions stored on computer readable media for carrying out the functions described herein. 
     Slip Detection and Correction 
     As noted above, an elongated member being used in connection with the drive apparatus  400  may be fed from a feed wheel  406 . Similarly, an elongated member associated with drive apparatus  1000  may be fed from a wheel  1002 . The feed wheels  406 ,  1002  may be configured to generally determine whether, when, and/or to what degree the elongated member slips, e.g., axially, during axial motion imparted by the dynamic grippers  440 ,  1050 . For example, while the pads  444   a, b  of the dynamic gripper  440  and the pads  1003 ,  1004  of the dynamic gripper  1050  may include relatively high friction surfaces to prevent slippage of the elongated member, at times slippage may nonetheless occur, resulting in inaccuracies in the measured and commanded movements of the drive apparatuses  400  and  1000 , respectively. Accordingly, the feed wheels  406 ,  1002  may be used as a comparison with the movement of the dynamic grippers  440 ,  1050  to determine when slippage occurs, and to what degree. For example, the feed wheel  406 ,  1050  may include an optical reader that measures actual rotation of the feed wheels  406 ,  1002  ultimately determining a length of the elongated member that is actually deployed from the feed wheel  406  at any given time. The actual movement of the elongated member may be compared with the commanded axial movement to determine whether any slippage has occurred, and may subsequently adjust movement of the dynamic grippers  440  accordingly. 
     In one example, a sensor (not shown in  FIGS.  4 - 14   ) is within view of the feed wheels  406 ,  1002  and is outside of the sterile environment such that it need not be replaced after a procedure. More specifically, if the feed wheels  406 ,  1002  are within the sterile environment, a sensor may be placed on an opposite side of an optically clear section of a sterile drape (not shown in  FIGS.  4 - 14   ), thereby allowing the sensor to remain outside the sterile environment and reduce the frequency with which the sensor itself must be sterilized or replaced. In another exemplary illustration, both the sensor and the feed wheels  406 ,  1002  are outside the sterile environment. Merely as examples, a textured surface (not shown) may be positioned on the feed wheels  406 ,  1002  that is detectable via the sensor. As such, a linear position of an elongate member may be detected using the sensor in any manner that is convenient. 
     In another exemplary illustration, a sensor outside the sterile field is configured to detect motion of the elongate member and a feed wheel is not necessary. This may be suitable for elongate devices such as catheters that have a braided surface or guidewires that have stripes on the outer extrusion. This detail on the surface of the elongate member may be detected by the sensor to detect motion. 
     In another exemplary illustration of a slip detection system, one or more idle rollers may be in communication with the elongated member, such that the rollers provide a measure of the length of the elongated member supplied. The measured length may then be compared with the commanded length in order to determine whether any slippage has occurred, allowing the system to adjust subsequent commands from the system. 
     CONCLUSION 
     The exemplary illustrations are not limited to the previously described examples. Rather, a plurality of variants and modifications are possible, which also make use of the ideas of the exemplary illustrations and therefore fall within the protective scope. Accordingly, it is to be understood that the above description is intended to be illustrative and not restrictive. 
     With regard to the processes, systems, methods, heuristics, etc. described herein, it should be understood that, although the steps of such processes, etc. have been described as occurring according to a certain ordered sequence, such processes could be practiced with the described steps performed in an order other than the order described herein. It further should be understood that certain steps could be performed simultaneously, that other steps could be added, or that certain steps described herein could be omitted. In other words, the descriptions of processes herein are provided for the purpose of illustrating certain embodiments, and should in no way be construed so as to limit the claimed invention. 
     Accordingly, it is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments and applications other than the examples provided would be upon reading the above description. The scope of the invention should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future embodiments. In sum, it should be understood that the invention is capable of modification and variation and is limited only by the following claims. 
     All terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary in made herein. In particular, use of the singular articles such as “a,” “the,” “the,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.