Abstract:
Instrument device with an elongated, flexible shaft that is configured to both roll and articulate in a controllable manner. The claimed system and apparatus provides endoscopic rolling and articulating capabilities with minimal tradeoffs in control, allowing for greater ease of use and clinical efficacy.

Description:
CROSS-REFERENCE 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 15/072,072, filed Mar. 16, 2016, which claims the benefit of U.S. Provisional Application No. 62/134,366, filed Mar. 17, 2015, which applications are incorporated herein by reference. 
         [0002]    The present invention relates to medical instruments, tools, and methods that may be incorporated into a robotic system, such as those disclosed in U.S. patent application Ser. No. 14/523,760, filed Oct. 24, 2014, U.S. Provisional Patent Application No. 62/019,816, filed Jul. 1, 2014, U.S. Provisional Patent Application No. 62/037,520, filed Aug. 14, 2014, and U.S. Provisional Patent Application No. 62/057,936, filed Sep. 30, 2014, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The field of the present invention relates to flexible endoscopic tools that may be used in a number of endolumenal procedures. More particularly, the field of the invention pertains to flexible endoscopic tools that have roll capabilities for use during endolumenal procedures. 
         [0005]    2. Description of the Background Art 
         [0006]    The spread of robotic surgery has precipitated the development of novel technologies. For example, in order to enable robotically-driven endoscopes, robotically-driven tools are more useful when they are able to both articulate in a desired linear direction and roll in a desired angular direction. In current elongated medical devices, roll in the device shafts is often achieved at the expense of pull-cable management. For example, in some laparoscopic devices on the market, roll of the rigid shaft may be accomplished by simply twisting the actuation pull wires (used for manipulation of the device&#39;s end effectors and/or wrist) around each other at the same rate as the shaft. Due to mechanically-limited revolutions in either direction, the twist in the cables show little to no adverse effect on either roll or grasper manipulation. Nevertheless, this lack of pull-wire management results in noticeably varying levels of friction throughout the shaft rotations. The accumulated friction steadily increases with each rotation until the pull wires are tightly bound around one another. 
         [0007]      FIG. 1  illustrates the physical limitations of current elongated devices arising from the implementation of roll capabilities. Specifically,  FIG. 1  illustrates how the implementation of roll capabilities in a prior art device creates undesirable friction and winding of the articulation pull wires. As shown in  FIG. 1 , the pull wires  104  in prior art device  100  extend from the distal tip  102  and at the proximal end  101  of the device  100 . Rotation of the shaft  103  forces the pull wires  104  to twist amongst one another along the entire length of the hollow shaft  103 . As the shaft  103  rotates beyond a full rotation, the tensioned wires start to tightly wrap around one another much like a wire-rope. Eventually, the pull-wires  104  would not be able to overcome the resulting friction to exert tension on the elements on the distal end  102 . 
         [0008]    In competing products, such as the TransEnterix SurgiBot, articulation and roll are de-coupled using a robotic outer “sheath” to enable pitch and yaw articulation, while a flexible laparoscopic tool controls insertion roll and end-effector actuation. However, this results in an unnecessarily large system with two separate modules controlling different degrees of freedom. Separate modules complicate the pre-operative workflow because the operator must now register two sets of devices relative to the patient. 
         [0009]    In manual endoscopes, knobs and dials actuate the distal tip of the scope while rotation of the shaft is achieved by twisting the entire proximal end of the tool. As a result, when rolling the scope, the operator is forced to contort into an uncomfortable, compensatory position in order to operate the knobs and dials. These contortions are undesirable; thus, necessitating a different approach. 
         [0010]    Accordingly, there is a need for an endoscopic tool that is capable of rolling without compromise to its actuation and articulation capabilities, while also being ergonomically ease to use. 
       SUMMARY OF THE INVENTION 
       [0011]    In general, the present invention provides a flexible endoscopic tool that has both articulation and roll capabilities. In one aspect, the present invention provides for a medical instrument comprising an elongated member, and an instrument base located at the proximal end of the elongated member, the base comprising a pull wire configured to spiral along the shaft at a helical pitch and a helical angle, and a translating redirect member configured to direct the pull wire to begin spiraling along the elongated member at a consistent angular position on the elongated member. 
         [0012]    In another aspect, the instrument base further comprises a lead screw configured to longitudinally translate the redirect member relative to the elongated member in response to rotating the lead screw. In another aspect, the lead screw is further configured to roll the elongated member. In another aspect, longitudinal translation of the redirect member relative to the shaft maintains the helical pitch of the pull wire around the shaft it rolls. In another aspect, longitudinal translation of the redirect member relative to the shaft maintains the helical angle of the pull wire around the shaft it rolls. 
         [0013]    In yet another aspect, the medical instrument further comprises a rotatable spool configured to rotate in response to longitudinal translation by the redirect member. In another aspect, the spool rotates in order to either collect or pull wire length. In another aspect, the lead screw is coupled to a transmission gear that is configured to transmit angular motion from the lead screw to the elongated member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention will be described, by way of example, and with reference to the accompanying diagrammatic drawings, in which: 
           [0015]      FIG. 1  illustrates the physical limitations in current elongated devices arising from the implementation of roll capabilities, consistent with the current state of the art; 
           [0016]      FIGS. 2A-2C  illustrates the physical limitations arising from use of a central shaft to capture the winding pull wires arising from rotations, in accordance with an embodiment of the present invention; 
           [0017]      FIG. 3  illustrates an endoscopic device with an instrument base comprising multiple rolling structures, in accordance with an embodiment of the present invention; 
           [0018]      FIGS. 4A-4B  illustrates how the helical angle of the pull wire wrap around the elongated shaft may be controlled by rolling the articulation shaft in concert with rolling the elongated shaft, in accordance with an embodiment of the present invention; 
           [0019]      FIG. 5A  illustrates an endoscopic device with an instrument base that utilizes a lead screw and angled idlers to ensure a consistent helical pitch around an elongated shaft, in accordance with an embodiment of the present invention; 
           [0020]      FIG. 5B  illustrates a frontal view of idler carriage  504  and elongated shaft  502  in endoscopic device  501  from  FIG. 5A ; 
           [0021]      FIG. 5C  illustrates a top view that shows the configuration of the key components of endoscopic device  501  from  FIG. 5A ; 
           [0022]      FIG. 5D  illustrates a rear view of the elongated shaft idler carriage  FIGS. 5A, 5B and 5C ; 
           [0023]      FIG. 6A  illustrates how a single pull wire may be tensioned in order to generate articulation in the elongated shaft; 
           [0024]      FIG. 6B  illustrates how the elongated shaft, pull wire, angled idler, and spool components from  FIG. 6A  maintain a consistent helical pitch when rolling the elongated shaft clockwise; and 
           [0025]      FIG. 6C  illustrates how the elongated shaft, pull wire, angled idler, and spool from  FIGS. 6A, 6B  maintain a consistent helical pitch when rolling the elongated shaft counter-clockwise. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    Although certain preferred embodiments and examples are disclosed below, inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses, and to modifications and equivalents thereof. Thus, the scope of the claims appended hereto is not limited by any of the particular embodiments described below. For example, in any method or process disclosed herein, the acts or operations of the method or process may be performed in any suitable sequence and are not necessarily limited to any particular disclosed sequence. Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding certain embodiments; however, the order of description should not be construed to imply that these operations are order dependent. Additionally, the structures, systems, and/or devices described herein may be embodied as integrated components or as separate components. 
         [0027]    In clinical applications, the design of the instrument base, which includes the robotic interface and the mechanical assembly to enable articulation and roll, is often constrained in size and design. For example, in a robotically-driven system, the design of the instrument base may be limited by both the lifting power of the robotic appendages and the necessity of maintaining a sterile barrier. Moreover, the use of pull wires to actuate the endoscopic shaft further complicates attempts to implement roll into the endoscopic shaft design. 
         [0028]    Accordingly, the present invention provides an efficient, compact design for a robotically-driven tool that accomplishes both articulation and roll in its shaft with minimal design compromises. 
         [0029]    An improvement on current devices, use of an internal shaft within the elongated shaft may be used to interrupt the wire-on-wire wrapping by introducing a low-friction surface upon which the wire can wrap around. Merely adding an internal shaft to the current art, however, creates a number of engineering challenges.  FIGS. 2A-2C  illustrates the physical limitations arising from use of a central shaft to capture the winding pull wires arising from rotations, in accordance with an embodiment of the present invention. In  FIG. 2A , the device  200  remains at rest with respect to roll, revealing that the pull wires  202  within the instrument base  201  in device  200  extend from the spools  203  to the distal end of the internal shaft  204 . The outer shaft  205  is configured with a concentrically aligned internal shaft  204  that is designed to act as a low-friction surface upon which the wires may wrap around. 
         [0030]    In  FIG. 2B , the outer shaft  205  has been slightly rotated, resulting in the pull wires  202  winding around the internal shaft  204 . The pull wire  202  winding and twisting around internal shaft  204  results in the pull wires  202  spiraling into a wrap  206  around the internal shaft  204  at particular helical angle  207  and helical pitch as the outer shaft  205  rolls. 
         [0031]    In  FIG. 2C , the outer shaft  205  has been heavily rotated, resulting the pull wires  202  further winding around the internal shaft  204 . As the outer shaft  205  is rotated, the pull wires  202  “crawl” along the internal shaft  204  in order to compensate for their changed angular position with respect to the internal shaft  204 . The resulting wrap  208  of the pull wires  202 , however, causes the helical angle  209  of the wrap  208  to grow progressively aggressive, i.e., the helical angles of the wrap  208  grow steeper and steeper relative to the internal shaft  204 . 
         [0032]    The change in the helical angles of wrap  208  are largely the result of the changing “takeoff angle”  210 , i.e., the angle at which the pull wires  202  begin to wrap around the internal shaft  204 , as the external shaft  205  rolls. As the internal shaft  204  rotates, the static position of the spools  202  relative to internal shaft  204  and wrap  208  creates a steeper and steeper takeoff angle  210  as the wrap  208  crawls along the internal shaft  204 . Additionally, since the spools are at different locations relative to the wrap  208 , the takeoff angles at each spool may be different. At the extreme, the wrap  208  around the internal shaft  204  would lock due to friction, a phenomenon that reflects Capstan&#39;s principle, wherein the helical pitch  209  would be orthogonal to the internal shaft  204 , resulting in the wrap  208  completely wrapping about itself, i.e., where the helical pitch would be zero. At that point, the pull-wire  202  would not be able to overcome the friction and serve its purpose. 
         [0033]    The “crawl” of the wrap  208  also transmits tension in the pull wires  202 . When pull wires are used in flexible devices, such as catheters, the resulting tension from roll is undesirable and can lead to shaft compression, unwanted stiffness, and hindered steering performance. Moreover, the resulting tension is non-linear and unpredictable, leading to an unpredictable mathematical model for controlling the device. Given that a changing helical angle and helical pitch creates controls and engineering challenges, additional embodiments are needed that incorporate internal shaft roll mechanisms to accommodate. 
         [0034]      FIG. 3  illustrates an endoscopic device with an instrument base comprising multiple rolling structures, in accordance with an embodiment of the present invention. In  FIG. 3 , the device  300  comprises an elongated shaft  301  and instrument base  302 . The instrument base  302  comprises four articulation shafts  303 ,  304 ,  305 , and  306  that act as redirect surfaces for pull wires  307 ,  308 ,  309 , and  310  respectively. Each of the aforementioned pull wires are wrapped in spiral fashion around their respective articulation shafts before being wrapped in spiral fashion around the elongated shaft  301 . 
         [0035]    The use of parallel articulation shafts provides for controlled wrapping of the pull wires around the elongated shaft due to roll by coordinating roll among the articulation shafts.  FIGS. 4A-4B  illustrates how the helical angle of the pull wire wrap around the elongated shaft may be controlled by rolling the articulation shaft in concert with rolling the elongated shaft, in accordance with an embodiment of the present invention. Specifically,  FIG. 4A  illustrates how roll of the elongated shaft  301  from device  300  may be accomplished without creating an unstable helical pitch and angle and undesirable tension. In  FIG. 4A , view  400  isolates and focuses on pull wire  307  wrapped around both articulation shaft  303  and elongated shaft  301  within instrument base  302  of device  300  from  FIG. 3 . When elongated shaft  301  is rolled in the direction shown by arrow  401 , in the absence of any corresponding roll in articulation shaft  303 , undesirable tension  402  would result in pull wire  307 . Accordingly, to compensate for that rise in tension  402 , articulation shaft  303  may be rolled in the (same) direction as the elongated shaft  301  as shown by arrow  403 . In effect, as the elongated shaft  301  “wraps” up the pull wire  307 , additional length of pull wire  307  is “unwrapped” from articulation shaft  303 . When the rate of roll  401  and  403  are matched, there is no tension or slack in the pull wire  307 . This ensures that the helical pitch and angle of the wrap  404  on elongated shaft  301  and the helical pitch and angle of the wrap  405  on the articulation shaft  303  is consistent and predictable. This results in a linear mathematical model for calculating control of the pull wire  307 . 
         [0036]      FIG. 4B  illustrates how tension on pull wire  307  may be generated by rolling the articulation shaft  303  relative to the elongated shaft  301 , in accordance with an embodiment of the present invention. In  FIG. 4B , view  406  shows rotation of the articulation shaft  303  in the direction indicated by arrow  407 . If elongated shaft  301  rolls at a slower rate in the same direction, rolls in the opposite direction, or is held in place rotationally, pull wire  307  will experience tension in the direction indicated by arrow  408 . Accordingly, tension along the pull wire  307  conveys axial compression force down the elongated shaft  301  of the device, resulting in articulation of the device. In circumstances when used in combination with an end effector, the axial compression results in actuation of the end effector element. 
         [0037]    As shown in  FIGS. 4A and 4B , providing secondary structures that assist with the wrap may accommodate the wrapping of the pull wires around the central shaft. The coordinated rolling of both the elongated shaft  301  in combination with the articulation shaft  303 , which wraps pull wires at a precise helical pitch and angle, allows for a consistent helical pitch and angle on the elongated shaft  301 , regardless of whether the operator desires roll in the elongated shaft  301  or tension in the pull wires. In practice, maintaining a consistent helical pitch generally results in a consistent helical angle. 
         [0038]    While embodiments with multiple rolling structures resolve several of the design challenges arising from incorporating articulation and roll, in practice, the use of multiple rolling structures may create issues when attempting to interface the instrument with the robotic drive mechanism. 
         [0039]      FIG. 5A  illustrates an endoscopic device with an instrument base that utilizes a lead screw and angled idlers to ensure a consistent helical angle and pitch around an elongated shaft, in accordance with an embodiment of the present invention. As shown in isometric transparent view  500 , endoscopic device  501  principally comprises an elongated shaft  502  and an instrument base  503 . Within instrument base  503 , an idler carriage  504  is disposed along the elongated shaft  502 , and configured to longitudinally translate and slide along the elongated shaft  502 . 
         [0040]    The idler carriage  504  holds four angled idlers  505 ,  506 ,  507 , and  508  at a fixed angle relative to the elongated shaft  502 . The angle of the angled idlers may be chosen for a particular purpose.  FIG. 5B  illustrates a frontal view of idler carriage  504  and elongated shaft  502  in endoscopic device  501  from  FIG. 5A . In  FIG. 5B , cross-sectional frontal view  522  shows how the idler carriage  504  positions angled idlers  505 ,  506 ,  507 , and  508  deliver the pull wires  518 ,  519 ,  520 , and  521  to the elongated shaft  502  at a consistent and predictable location. In contrast to the previously disclosed embodiments, the angled idlers in endoscopic device  501  wrap and un-wrap the pull wires at the same longitudinal position along the elongated shaft  502 , which assists in maintaining a consistent takeoff angle for all of the pull wires regardless of the length of pull wire wrap around shaft  502 . 
         [0041]    As shown in  FIG. 5A , the instrument base  503  also incorporates a pair of rotating structures  510  and  511 . Rotating structures  510  and  511  comprise two concentrically-aligned, co-radial spools, such as spools  512 ,  513  from rotating structure  510 , and spools  514 ,  515  from rotating structure  511 . The rotating structures  510  and  511  incorporate output shafts  516  and  517  that interface with robotic drive and control mechanisms. Given that spools  512  and  513  and spools  514  and  515  are co-radial, output shaft  516  and  517  each includes both an inner and outer sub-shaft that drives each spool per rotating structure. 
         [0042]    In some embodiments, the output shafts may be replaced by “female” or receiving interfaces rather “male” or protruding interfaces. As shown in isometric view  500 , pull wires  518 ,  519 ,  520 , and  521  are coiled around spools  512 ,  513 ,  514 , and  515  and run around the angled idlers  505 ,  506 ,  507 , and  508  before spiraling around the elongated shaft  502 . 
         [0043]      FIG. 5C  illustrates a top view that shows the configuration of the key components of endoscopic device  501  from  FIG. 5A . Specifically, top view  527  provides a view of the direct alignment of a tangential path between rotation structures  510  and  511  and angled idlers  505  and  507  on idler carriage  504 . As shown in top view  527 , pull wire  518  is coiled around spool  512  and fed around angled idler  505  before spiraling around elongated shaft  502 . The tangential path of the pull wires  518 ,  520  around the idlers  505 ,  507  are aligned with the spools  512 ,  514 . Thus, in some embodiments, the spools  513  and  515  are also aligned with the angled idlers  506  and  508  in order for pull wires  519  and  521  to have a direct transmission path between the spools and idlers. In some embodiments, the idlers  505 ,  506 ,  507 , and  508  may rotate in order to reduce friction as the pull wires  518 ,  519 ,  520 , and  521  wind around them. While the idlers  505 ,  506 ,  507 , and  508  operate similar to rotatable spools or pulleys, other embodiments may use other types of redirect members, such as surfaces. 
         [0044]    Maintaining a consistent wrapping and unwrapping position and takeoff angle helps ensure that the pull wires spiral around the elongated shaft  502  at a consistent helical pitch. The consistency in the helical pitch greatly increases the ability of the robotic system to control and predict the tension on the pull wires. 
         [0045]    In some embodiments, the elongated shaft  502  may be fixedly coupled to a concentric internal shaft that solely resides within the instrument base and is designed for wrapping pull wires around itself. Rolling the internal shaft would effectively roll the elongated shaft while potentially providing other advantages. For example, a distinct internal shaft may be adopted in order to take advantage of different coefficients of friction, different pull wire guiding features, such as grooves or lumens, different diameters, and potentially reduced manufacturing complexity and/or costs. 
         [0046]    Angular motion from the robotic interface may create, for example, rotational motion in spool  512  through output shaft  516 . Rotational motion in spool  512  may then exert compressive tension in pull wire  518 . Tension in pull wire  518  may be carried around angled idler  505  and exerted on the pull wire  518  as it wraps onto elongated shaft  502 . Where the pull wires  518  are fixedly coupled to the distal end of the shaft  502 , the transmission of the compressive tension along pull wire  518  may then articulate the shaft  502 . Thus, the angular motion in the robotic interface may generate articulation in shaft  502 . 
         [0047]    The instrument base  503  also comprises a lead screw  509  that runs parallel to the elongated shaft  502 . Rotation of lead screw  509  is operated by a right angle gear transmission  525 , which is visible in isometric view  500  from  FIG. 5A . Rotational force in right angle gear transmission  525  originates from lead screw output shaft  526  which interfaces with external robotic drive and control mechanisms. Thus, angular motion in the robotic interface may rotate lead screw output shaft  526  to generate angular motion that ultimately rotates lead screw  509 . As with the rotational structures  510  and  511 , rotation motion from the robotic interface may also be transmitted to right angle gear transmission  525  using “female” or receiving connectors, rather than lead screw output shaft  526 , which is considered a “male” connector. 
         [0048]      FIG. 5D  illustrates a rear view of the elongated shaft and idler carriage from  FIGS. 5A, 5B , and  5 C. As shown in rear view  524  from  FIG. 5D , lead screw  509  is operatively coupled to elongated shaft  502  through a shaft transmission gear  523 . Shaft transmission gear  525  transmits angular motion from the lead screw  509  that rotates the shaft  502 . In different embodiments, the shaft transmission gear  523  may be selected from various gear and transmission ratios to ensure the desired rotational motion in the elongated shaft  502  relative to the lead screw  509 . 
         [0049]    The combination of the shaft  502 , lead screw  509 , and the idler carriage  504  manages the linear translation of the idler carriage  504  (and thus angled idlers  505 ,  506 ,  507 , and  508 ) that helps preserve the helical pitch of the pull wires when rolling of shaft  502 . In practice, elongated shaft  502  rotates at a relative speed determined by the angular motion transmitted by shaft transmission gear  523  which is proportional to the rotation of lead screw  509 . As the lead screw  509  rotates itself and the elongated shaft  502 , the idler carriage  504  acts as a nut on lead screw  509 . This “lead screw nut” engagement advances the idler carriage  504  at a rate proportional to the rotation of both the lead screw  509  and elongated shaft  502 . Thus, idler carriage  504  translates along the lead screw  509  while sliding freely along the elongated shaft  502  as lead screw  509  rotates itself and elongated shaft  502 . The pitch and angle of the thread on lead screw  509  determines the direction and speed at which the idler carriage  504  advances relative to the elongated shaft  502 . Similarly, the rate of rotation of elongated shaft  502  is dependent on at least the size of shaft transmission gear  523 . Accordingly, careful calibration and selection of those components ensures that they properly coordinate in unison in order to keep consistent the helical pitch and angle of the pull wires about the elongated shaft  502 . 
         [0050]    Given that the idler carriage  504  translates along the length of the shaft  502  during roll operations, the length and pitch of the lead screw  509  may limit the number of elongated shaft roll revolutions allowed by the device  501 . Consequently, longer devices with longer lead screws will generally allow greater shaft roll revolutions than shorter devices with shorter lead screws. Accordingly there may be a longer instrument base  503  to accommodate more rotations from a given lead screw with a specific pitch. Moreover, since wraps around the shaft  502  are directly proportional to the revolutions the shaft  502  may roll, an excessive number of wraps may heavily influence friction. Alternatively, a tighter pitch or steeper angle in the grade of the lead screw  509  may also affect roll revolutions and thus the length of the instrument base. 
         [0051]      FIGS. 6A-6C  illustrates roll and articulation operations of endoscopic device  501  with respect to a single pull wire, single angled idler, and single spool. Specifically,  FIG. 6A  illustrates how a single pull wire may be tensioned in order to generate articulation in the elongated shaft. As shown in isolated top view  600 , exemplar elongated shaft  601  may already be wrapped with a single pull wire  602 . Similar to the earlier embodiments, pull wire  602  may be directed to spiral onto a portion of the elongated shaft  601  by angled idler  603 . The pull wire  602  may also be controlled via spool  604 , whose rotational motion may generate compressive force along the length of the pull wire  602 . Thus, in order to tension pull wire  602  and articulate the distal tip of shaft  601 , shaft  601  and idler  603  remain static while spool  604  rotates in the direction indicated by arrow  606  to create compression tension along pull wire  602  in the direction indicated by arrow  605 . That “pulling” force is then transferred along the length of pull wire around idler  603 , along shaft  601  until reaching the distal tip, where the pull wire  602  is fixedly coupled. As the pull wire  602  is fixedly coupled to the end of the distal end of the elongated shaft  601 , compressive tension results in bending or articulating of the elongated shaft  601 . 
         [0052]      FIG. 6B  illustrates how the elongated shaft, pull wire, angled idler, and spool components from  FIG. 6A  maintain a consistent helical pitch when rolling the elongated shaft clockwise. In order to roll the elongated shaft  601 , the angled idler  603  may be moved simultaneously to maintain a consistent takeoff angle in the pull wire  602 . When rolling the elongated shaft  601  in the clockwise direction indicated by arrow  607 , in order to maintain the helical pitch, the angled idler  603  may be translated longitudinally relative to the shaft  601  in the direction indicated by arrow  608 . Translating the idler  603  while shaft  601  rotates ensures that the pull wire  602  is wrapped around shaft  601  with a consistent helix by ensuring that the pull wire  602  always has the same takeoff angle from angled idler  603 . Put differently, translating the idler  603  in the direction of arrow  608  ensures that the pull wire  602  is “wrapped” around unwrapped portions of the shaft  601  at an even pitch, rather than wrapping in an uneven pitch or even on already-wrapped portions of the shaft  601 . Due to the translation of the idler tension in the pull wire  602  requires that the spool  604  be rotated in direction indicated by arrow  609  in order to allow additional length of the pull wire  602  to be wrapped around shaft  601  at a consistent takeoff angle. In effect, the spool  604  must unwrap additional length of the pull wire  602  from itself in order to accommodate the additional wrapping of the pull wire  602  around the shaft  601  and the translation of the idler  603 . The rate at which idler  603  advances in direction  608  relative to the rotation of  601  in direction  607  ensures that pull wire  602  is always encounters shaft  601  at the same takeoff angle, which maintains a consistent helical pitch and angle around the shaft  601 . 
         [0053]      FIG. 6C  illustrates how the elongated shaft, pull wire, angled idler, and spool from  FIGS. 6A, 6B  maintain a consistent helical pitch when rolling the elongated shaft counter-clockwise. When rolling the elongated shaft  601  in the counter-clockwise direction indicated by arrow  610 , in order to maintain the helical pitch, the angled idler  603  may be translated longitudinally relative to the shaft  601  in the direction indicated by arrow  611 . Translating the idler  603  while shaft  601  rotates ensures that the pull wire  602  has the same takeoff angle as it unwraps from shaft  601 . Put differently, translating the idler  603  in the direction of arrow  611  ensures that the pull wire  602  is “unwrapped” with the same takeoff angle from the shaft  601  preserving the helical pitch and angle of the pull wire  602  still wrapped about the shaft  601 . Due to the translation of the idler  603 , the formation of slack in the pull wire  602  requires that the spool  604  be rotated in direction indicated by arrow  612  in order to collect the loose length of pull wire  602 . In effect, the spool  604  must wrap and collect additional length of the pull wire  602  to accommodate the “unwrapping” of the pull wire  602  from the shaft  601  and the translation of the idler  603 . The angle of the idler  603  ensures that pull wire  602  is always unwrapped from the shaft  601  at the same point, helping ensure a consistent helical pitch and angle about shaft  601 . 
         [0054]    The embodiments in  FIGS. 5A-5D, 6A-6C  enable three-degrees of freedom at the tip of a flexible, articulating device while maintaining a static instrument base ( 503 ). By constraining the pull wire helical pitch on the elongated shaft during roll operations, tension variability is minimized and articulation controls are simplified. Furthermore, the design allows for functional adjustments and fine-tuning of features, such as shaft revolutions and relative carriage speed, merely by altering the features of the lead screw and transmission gears. Different configurations of helical wire pitches and the number of revolutions can be attained simply by varying the length of the lead screw, pitch of the threads, and its associated drivetrain to the main shaft. Moreover, the compact design also allows for electronics (such as circuit board  527  in  FIG. 5A ) and other internal features to be placed within the instrument base. 
         [0055]    The embodiments in  FIGS. 5A-5D, 6A-6C  allow the ability to rotate or “roll” the flexible shaft after a long journey through a tortuous path in the patient&#39;s anatomy. For example, after traversing through a long and tortuous path, endoscopic device  501  may articulate elongated shaft  502  and roll elongated shaft  502  in order to reach to an operative site. In some circumstances, it may be useful to first roll elongated shaft  502  and then articulate elongated shaft  502  in order to reach certain locations with the patient&#39;s anatomy. Use of roll may also provide improved access to operative sites where robotically-driven articulation may be insufficient and ineffective, a circumstance that may occur as a result of traversing through tortuous paths. 
         [0056]    In addition to improved reach, the disclosed embodiments may also enable roll to reduce braking static friction when traversing through a tortuous path. For example, rolling elongated shaft  502  while simultaneously extending into an anatomical lumen may reduce friction caused from contact with the lumen walls. Furthermore, rolling the elongated shaft  502  may also reduce friction caused by contact at anatomical transitions. 
         [0057]    In practice, rolling and subsequently articulating endoscopic device  501  within an anatomical lumen involves several mechanical steps. For example, the instrument interface would first rotate lead screw output shaft  526  in order to rotate right angle gear transmission  525 . In response to rotating right angle gear transmission  525 , lead screw  509  would rotate. The rotation of the lead screw  509  would result in the motion of several components within the instrument base  503 . Firstly, the rotation of the lead screw  509  would transmit angular motion to shaft transmission gear  523  which would cause shaft  502  to rotate. 
         [0058]    Secondly, rotation of the lead screw  509  would also cause idler carriage  504  to laterally move along the shaft  502 . Depending on the direction of rotation and the thread of lead screw  509 , the idler carriage  504  may either move forward towards the distal tip of the elongated shaft  502  or back towards the proximal end of the elongated shaft  502 . 
         [0059]    The roll of elongated shaft  502  creates tension on pull wires  518 ,  519 ,  520 ,  521 . To compensate and alleviate the tension, instrument interface would rotate output shafts  516  and  517  (and their associated concentrically-aligned sub-shafts) in order to reduce tension in the pull wires as explained in  FIGS. 6B and 6C . Once the roll is complete, the tension-compensation process may terminate. After rotating the shaft  502 , the distal tip of the shaft  502  may then be articulated in order to reach the desired operative site. Tensioning the appropriate pull wire in order to articulate may be executed using the technique described in  FIG. 6A . 
         [0060]    The aforementioned embodiments of the present invention may be designed to interface with robotics platform such as those disclosed in the aforementioned patent applications that are incorporated by reference. For example, the embodiments in  FIGS. 5A-5D, 6A-6D  may be configured to be driven by an instrument drive mechanism or an instrument device manipulator that is attached to the distal end of a robotic arm through a sterile interface, such as a drape. As part of a larger robotics system, robotic control signals may be communicated from a remotely-located user interface, down the robotic arm, and to the instrument device manipulator to control the instrument or tool. 
         [0061]    For purposes of comparing various embodiments, certain aspects and advantages of these embodiments are described. Not necessarily all such aspects or advantages are achieved by any particular embodiment. Thus, for example, various embodiments may be carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may also be taught or suggested herein. 
         [0062]    Elements or components shown with any embodiment herein are exemplary for the specific embodiment and may be used on or in combination with other embodiments disclosed herein. While the invention is susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. The invention is not limited, however, to the particular forms or methods disclosed, but to the contrary, covers all modifications, equivalents and alternatives thereof.