Patent Publication Number: US-2019167369-A1

Title: Cable tensioning in a robotic surgical system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/339,244, filed Oct. 31, 2016, which is a continuation of U.S. patent application Ser. No. 14/708,797, filed May 11, 2015, issued as U.S. Pat. No. 9,486,288; which is a continuation of U.S. patent application Ser. No. 11/613,578, filed Dec. 20, 2006, issued as U.S. Pat. No. 9,050,119; which claims the benefit of U.S. Provisional Application No. 60/752,755, filed Dec. 20, 2005, the full disclosures of which (including all references incorporated by reference therein) are incorporated by reference herein for all purposes. 
     This application is related to U.S. application Ser. No. 11/613,800, filed Dec. 20, 2006, entitled “Telescopic Insertion Axis of A Robotic Surgical System”, U.S. application Ser. No. 11/556,484, filed Nov. 3, 2006, entitled “Indicator For Tool State and Communication In A Multi-Arm Robotic Telesurgery”, U.S. application Ser. No. 11/613,695, filed Dec. 20, 2006, entitled “Instrument Interface In A Robotic Surgical System”, and U.S. application Ser. No. 11/613,915, filed Dec. 20, 2006, entitled “Wireless Communication In A Robotic Surgical System”, the full disclosures of which (including all references incorporated by reference therein) are incorporated by reference herein for all purposes. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to surgical robot systems and, more particularly, to an apparatus, system, and method for cable tensioning in a robotic surgical system. 
     BACKGROUND 
     Minimally invasive robotic surgical or telesurgical systems have been developed to increase a surgeon&#39;s dexterity and to avoid some of the limitations on traditional minimally invasive techniques. In telesurgery, the surgeon uses some form of remote control, e.g., a servomechanism or the like, to manipulate surgical instrument movements, rather than directly holding and moving the instruments by hand. In telesurgery systems, the surgeon can be provided with an image of the surgical site at the surgical workstation. While viewing a two or three dimensional image of the surgical site on a display, the surgeon performs the surgical procedures on the patient by manipulating master control devices, which in turn control motion of the servomechanically operated instruments. 
     In robotically-assisted surgery, the surgeon typically operates a master controller to control the motion of surgical instruments at the surgical site from a location that may be remote from the patient (e.g., across the operating room, in a different room, or a completely different building from the patient). The master controller usually includes one or more hand input devices, such as hand-held wrist gimbals, joysticks, exoskeletal gloves or the like, which are operatively coupled to the surgical instruments that are releasably coupled to a patient side surgical manipulator (“the slave”). The master controller controls the instruments&#39; position, orientation, and articulation at the surgical site. The slave is an electromechanical assembly which includes a plurality of arms, joints, linkages, servo motors, etc. that are connected together to support and control the surgical instruments. In a surgical procedure, the surgical instruments (including an endoscope) may be introduced directly into an open surgical site or more typically through trocar sleeves into a body cavity. Depending on a surgical procedure, there are available a variety of surgical instruments, such as tissue graspers, needle drivers, electrosurgical cautery probes, etc., to perform various functions for the surgeon, e.g., holding or driving a needle, suturing, grasping a blood vessel, or dissecting, cauterizing or coagulating tissue. 
     A surgical manipulator assembly may be said to be divided into three main components that include a non-sterile drive and control component, a sterilizable end effector or surgical tool/instrument, and an intermediate connector component. The intermediate connector component includes mechanical elements for coupling the surgical tool with the drive and control component, and for transferring motion from the drive component to the surgical tool. Cables (also referred to as wire rope) and pulleys in conjunction with motors have been used to actuate carriages, the surgical instrument, and other apparatus of the surgical system. Prior telerobotic surgical systems with such pulley systems are described for example in U.S. application Ser. Nos. 08/517,053 and 11/314,040, the complete disclosures of which are incorporated herein by reference for all purposes. 
     Setting and maintaining cable tension is of prime importance for accurately and precisely moving the various apparatus and instruments during surgery. Previously, cable tension was set by screw clamps at the termination points of the cables. Setting the cable tension using these screw clamps required skill beyond that of standard field personnel. 
     What is needed, therefore, are improved apparatus and methods for setting cable tension in a telerobotic surgical system for remotely controlling surgical instruments at a surgical site on a patient. In particular, these apparatus and methods should allow for easily adjusting cable tension using standard tools. Accordingly, a cable tensioning apparatus, system, and method having improved efficiency and cost-effectiveness is highly desirable. 
     SUMMARY 
     The present invention provides an apparatus, system, and method for setting, maintaining, and adjusting cable tension in a telerobotic surgical system. In particular, an adjustable cable tensioning apparatus, a termination block, and a method cable tensioning in a closed loop cable scheme are provided. 
     In accordance with an embodiment of the present invention, an apparatus for cable tensioning comprises an arm, a pulley rotatably coupled to the arm, and a base operably coupled to the arm, the base including a translation mechanism for changing the position of the pulley to control a tension of a cable movable along the pulley. 
     In accordance with another embodiment of the present invention, a robotic surgical system is provided, the system comprising a drive assembly, a surgical instrument, and a manipulator arm operably coupling the surgical instrument to the drive assembly, the manipulator arm having a cable tensioning apparatus as described above. The system further includes a cable running along the pulley for transmitting motion from the drive assembly to the manipulator arm, the tension of the cable being controlled in part by the cable tensioning apparatus. 
     In accordance with another embodiment of the present invention, a method of cable tensioning is provided, the method comprising providing a drive assembly, providing a surgical instrument, providing a manipulator arm as described above operably coupling the surgical instrument to the drive assembly. The method further includes moving a cable along the pulley for transmitting motion from the drive assembly to the manipulator arm, and changing the position of the pulley to control the tension of the cable. 
     In accordance with yet another embodiment, a termination block of a cabling system in a robotic surgical manipulator is provided, the termination block comprising a block including two cable pathways, each cable pathway including a retaining means for a ball fitting, and a support for moving a cable along the two cable pathways, the cable including a ball fitting in each of the cable pathways. 
     Advantageously, the present invention provides for easily adjusting cable tension in a robotic surgical arm and system, for example using standard tools and/or a processor, and also provides for a safety feature based upon cable redundancy in a termination block. 
     The scope of the invention is defined by the claims, which are incorporated into this section by reference. A more complete understanding of embodiments of the present invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a portion of an operating theater illustrating a robotic surgical system, including a master surgeon console or workstation for inputting a surgical procedure and a robotic manipulator system for robotically moving surgical instruments at a surgical site within a patient. 
         FIGS. 2A and 2B  illustrate a perspective view and a front view, respectively, of an embodiment of a manipulator system, including positioning linkages or set up joints which allow a patient side robotic manipulator and/or an endoscope or camera robotic manipulator to be pre-configured for surgery. 
         FIG. 3  is a perspective view of an example of a surgical instrument for use in the system of  FIG. 1 . 
         FIG. 4  is a perspective from above of an alternative manipulator system including a plurality of positioning linkages, each supporting a manipulator arm. 
         FIGS. 5A through 5E  are perspective views of a manipulator including a telescopic insertion axis and cable tensioning means in accordance with an embodiment of the present invention. FIG.  5 A 1  is a close-up view of a carriage link of the telescopic insertion axis in accordance with an embodiment of the present invention. 
         FIGS. 6A through 6C  are perspective views of the insertion axis, an accessory mount (e.g., a cannula mount), and an accessory (e.g., a cannula), the insertion axis being telescoped from a retracted position in  FIG. 6A , to an intermediate position in  FIG. 6B , and to a fully extended position in  FIG. 6C . 
         FIGS. 7A and 78  illustrate a side view and a perspective view, respectively, of a closed loop cable tensioning scheme for a wrist axis of a manipulator arm in accordance with an embodiment of the present invention. 
         FIGS. 8A and 8B  illustrate a side view and a perspective view, respectively, of a closed loop cable tensioning scheme for an insertion axis of a manipulator arm in accordance with another embodiment of the present invention. 
         FIG. 9A  is a view of a cable running through a manipulator arm and insertion axis in accordance with an embodiment of the present invention. 
         FIGS. 9B and 9C  illustrate a perspective view and a side view, respectively, of the cable and pulleys of  FIG. 9A  in accordance with an embodiment of the present invention. 
         FIGS. 10A and 10B  illustrate views of a linear tensioning apparatus within a manipulator arm of a telerobotic surgical system in accordance with an embodiment of the present invention. 
         FIGS. 11A through 11D  are different views of a dual linear tensioning apparatus in accordance with another embodiment of the present invention. 
         FIGS. 12A through 12C  are different views of a quad linear tensioning apparatus in accordance with another embodiment of the present invention. 
         FIGS. 13A through 13C  are different views of a rotational tensioning apparatus in accordance with an embodiment of the present invention. 
         FIGS. 13D and 13E  are side views of other rotational tensioning apparatus in accordance with other embodiments of the present invention. 
         FIGS. 14A through 14D  are different views of a termination block in accordance with an embodiment of the present invention. 
     
    
    
     Embodiments of the present invention and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures. It should also be appreciated that the figures may not be necessarily drawn to scale. 
     DETAILED DESCRIPTION 
     The present invention provides an apparatus and method for setting, maintaining, and/or adjusting cable tension in a telerobotic surgical system, the cable tensioning apparatus in one embodiment including an arm having a first end and a second end, a pulley rotatably coupled to the first end of the arm, and a base operably coupled to the second end of the arm, the base including a translation mechanism for changing the position of the pulley. The term “pulley” as used throughout this document is defined as including a rotatable wheel along which a cable may move. 
     The apparatus, system, and method of the present invention is particularly useful for performing neurosurgical procedures, such as stereotaxy, and endoscopic procedures, such as laparoscopy, arthroscopy, thoracoscopy and the like. 
     Furthermore, the present invention is particularly useful as part of a telerobotic surgical system that allows the surgeon to manipulate the surgical instruments through a servomechanism at a location remote from the patient. One example of a robotic surgical system is the da Vinci® S™ surgical system available from Intuitive Surgical, Inc. of Sunnyvale, Calif. A User&#39;s Guide for the da Vinci® S™ surgical system is available from Intuitive Surgical, Inc. and is incorporated by reference herein for all purposes. 
       FIGS. 1-3  illustrate components of a robotic surgical system  1  for performing minimally invasive robotic surgery. System  1  is similar to that described in more detail in U.S. Pat. No. 6,246,200, the full disclosure of which is incorporated herein by reference. A system operator  0  (generally a surgeon) performs a minimally invasive surgical procedure on a patient P lying on an operating table T. The system operator  0  sees images presented by display  12  and manipulates one or more input devices or masters  2  at a surgeon&#39;s console  3 . In response to the surgeon&#39;s input commands, a computer processor  4  of console  3  directs movement of surgical instruments or tools  5 , effecting servomechanical movement of the instruments via a robotic patient-side manipulator system  6  (a cart-based system in this example) including joints, linkages, and manipulator arms each having a telescopic insertion axis. In one embodiment, processor  4  correlates the movement of the end effectors of tools  5  so that the motions of the end effectors follow the movements of the input devices in the hands of the system operator  0 . 
     Processor  4  will typically include data processing hardware and software, with the software typically comprising machine-readable code. The machine-readable code will embody software  25  programming instructions to implement some or all of the methods described herein. While processor  4  is shown as a single block in the simplified schematic of  FIG. 1 , the processor may comprise a number of data processing circuits, with at least a portion of the processing optionally being performed adjacent an input device, a portion being performed adjacent a manipulator, and the like. Any of a wide variety of centralized or distributed data processing architectures may be employed. Similarly, the programming code may be implemented as a number of separate programs or subroutines, or may be integrated into a number of other aspects of the robotic systems described herein. 
     In one example, manipulator system  6  includes at least four robotic manipulator assemblies. Three linkages  7  (mounted at the sides of the cart in this example) support and position manipulators  8  with linkages  7  in general supporting a base of the manipulators  8  at a fixed location during at least a portion of the surgical procedure. Manipulators  8  move surgical tools  5  for robotic manipulation of tissues. One additional linkage  9  (mounted at the center of the cart in this example) supports and positions manipulator  10  which controls the motion of an endoscope/camera probe  11  to capture an image (preferably stereoscopic) of the internal surgical site. The fixable portion of positioning linkages  7 ,  9  of the patient-side system is sometimes referred to herein as a “set-up arm”. 
     In one example, the image of the internal surgical site is shown to operator  0  by a stereoscopic display  12  in surgeon&#39;s console  3 . The internal surgical site is simultaneously shown to assistant A by an assistance display  14 . 
     Assistant A assists in pre-positioning manipulator assemblies  8  and  10  relative to patient P using set-up linkage arms  7 ,  9 ; in swapping tools  5  from one or more of the surgical manipulators for alternative surgical tools or instruments  5 ′; in operating related non-robotic medical instruments and equipment; in manually moving a manipulator assembly so that the associated tool accesses the internal surgical site through a different aperture, and the like. 
     In general terms, the linkages  7 ,  9  are used primarily during set-up of patient-side system  6 , and typically remain in a fixed configuration during at least a portion of a surgical procedure. Manipulators  8 ,  10  each comprise a driven linkage which is actively articulated under the direction of surgeon&#39;s console  3 . Although one or more of the joints of the set-up arm may optionally be driven and robotically controlled, at least some of the set-up arm joints may be configured for manual positioning by assistant A. 
     Some of the manipulators include a telescopic insertion axis  100  in accordance with an embodiment of the present invention, although in other embodiments, all of the manipulators may include a telescopic insertion axis  100 . Telescopic insertion axis  100  allows for movement of mounted instrument  5 , via three operably coupled links in one example. 
     For convenience, a manipulator such as manipulator  8  that is supporting a surgical tool used to manipulate tissues is sometimes referred to as a patient-side manipulator (PSM), while a manipulator  10  which controls an image capture or data acquisition device such as endoscope  11  may be referred to as an endoscope-camera manipulator (ECM). The manipulators may optionally actuate, maneuver and control a wide variety of instruments or tools, image capture devices, and the like which are useful for surgery. 
     Instruments  5  and endoscope  11  may be manually positioned when setting up for a surgical procedure, when reconfiguring the manipulator system  6  for a different phase of a surgical procedure, when removing and replacing an instrument with an alternate instrument  5 ′, and the like. During such manual reconfiguring of the manipulator assembly by assistant A, the manipulator assembly may be placed in a different mode than is used during master/slave telesurgery, with the manually repositionable mode sometimes being referred to as a clutch mode. The manipulator assembly may change between the tissue manipulation mode and the clutch mode in response to an input such as pushing a button or switch on manipulator  8  (e.g., a clutch button/switch  103  in  FIGS. 6A-6C ), or some other component to the manipulator assembly, thereby allowing assistant A to change the manipulator mode. 
     As can be seen in  FIGS. 1 and 2A-2B , indicators  20  may be disposed on a manipulator assembly. In this embodiment, indicators  20  are disposed on manipulators  8  near the interface between the manipulators and their mounted tools  5 . In alternative embodiments, indicators  20  may instead be disposed on set-up joints  7 ,  9 , on tools  5 , elsewhere on manipulators  8 ,  10 , or the like. An example of an indicator is disclosed in U.S. application Ser. No. 11/556,484, filed Nov. 3, 2006, the full disclosure of which (including all references incorporated by reference therein) is incorporated by reference herein for all purposes. 
       FIG. 3  illustrates a perspective view of an articulated surgical tool or instrument  5 . Tool  5  has a proximal housing  24  which interfaces with a tool holder or instrument interface of the manipulator, generally providing a quick release mounting engagement through a sterile adapter or interface, an example of which is disclosed in U.S. patent application Ser. No. 11/314,040, filed Dec. 20, 2005, and U.S. patent application Ser. No. 11/395,418, filed Mar. 31, 2006, which are incorporated by reference herein for all purposes. Tool  5  includes an elongated shaft  23  supporting an end effector  28  relative to proximal housing  24 . Proximal housing  24  accepts and transmits drive signals or drive motion between the manipulator  8  and the end effector  28 . An articulated wrist  29  may provide two degrees of freedom of motion between end effector  28  and shaft  23 , and the shaft may be rotatable relative to proximal housing  24  about the axis of the shaft so as to provide the end effector  28  with three orientational degrees of freedom within the patient&#39;s body. 
     The surgical tool may include a variety of articulated end effectors, such as jaws, scissors, graspers, needle holders, micro-dissectors, staple appliers, tackers, suction irrigation tools, and clip appliers, that may be driven by wire links, eccentric cams, push-rods, or other mechanisms. In addition, the surgical tool may comprise a non-articulated instrument, such as cutting blades, probes, irrigators, catheters or suction orifices. Alternatively, the surgical tool may comprise an electrosurgical probe for ablating, resecting, cutting or coagulating tissue. Examples of applicable adaptors, tools or instruments, and accessories are described in U.S. Pat. Nos. 6,331,181, 6,491,701, and 6,770,081, the full disclosures of which (including disclosures incorporated by reference therein are incorporated by reference herein for all purposes. Applicable surgical instruments are also commercially available from Intuitive Surgical, Inc. of Sunnyvale, Calif. 
     Referring now to  FIG. 4 , a perspective view is illustrated of an alternative modular manipulator support assembly  30  that may be mounted to a ceiling of an operating room. The modular manipulator support  30  aligns and supports a robotic manipulator system relative to a set of desired surgical incision sites in a patient&#39;s body. Modular manipulator support  30  generally includes an orientating platform  36  and a plurality of configurable set-up linkage arms  38 ,  40 ,  42 ,  44  that may be coupled to the orienting platform. Each arm movably supports an associated manipulator  32 ,  34 , which in turn movably supports an associated tool or an image capture device. Orienting platform  36  also supports an assistant display  104 , which may be used for set-up, instrument changes, viewing of the procedure, and the like. The structures and use of any of the components of modular manipulator support assembly  30  are analogous to those described above regarding manipulator system  6 , and are more fully described in co-pending U.S. patent application Ser. No. 11/043,688, filed on Jan. 24, 2005, and entitled “Modular Manipulator Support For Robotic Surgery”, the full disclosure which is incorporated herein by reference. As generally described above, each manipulator  32 ,  34  of modular manipulator support  30  may also include an insertion axis  100 . 
     Referring now to  FIGS. 5A-5E , manipulator  8  including a telescopic insertion axis  100  and a cable tensioning apparatus is shown in more detail in accordance with embodiments of the present invention. The insertion axis of the present invention is comprised of a 3-stage telescopic linear axis including three links, in one example, movably coupled to one another via rails, pulleys, and cables, with the links narrowing in width or form factor moving from the proximal link toward the distal link. Advantageously, the present invention provides for one-handed port and instrument clutching, a larger range of motion, narrower insertion arm, and greater insertion axis stiffness and strength with reduced inertia as a function of insertion depth, thereby helping to enable a two-quadrant surgery with a single setup (e.g., a colorectal surgery), and providing for more space and visibility near the surgical field. 
       FIGS. 5A through 5E  illustrate a perspective view of manipulator  8  including a manipulator arm  50 , and telescopic insertion axis  100  operably coupled to a distal end of arm  50  in accordance with an embodiment of the present invention. Telescopic insertion axis  100  includes a first link or base link  102 , a second link or idler link  104  operably coupled to base link  102 , and a third link or carriage link  106  operably coupled to idler link  104 . FIG.  5 A 1  illustrates a closer view of carriage link  106 . 
     Base link  102  is operably coupled to a distal end of a manipulator arm  50 , and in one example has an accessory clamp  108  attached to a distal end of base link  102 . An accessory  110 , such as a cannula, may be mounted onto accessory clamp  108 . An example of applicable accessory clamps and accessories are disclosed in pending U.S. application Ser. No. 11/240,087, filed Sep. 30, 2005, the full disclosure of which is incorporated by reference herein for all purposes. An example of applicable sterile adaptors and instrument housings are disclosed in U.S. application Ser. No. 11/314,040, filed Dec. 20, 2005 and in U.S. application Ser. No. 11/395,418, filed Mar. 31, 2006, the full disclosures of which are incorporated by reference herein for all purposes. 
     Carriage link  106  includes an instrument interface  101  for operably coupling to a sterile adaptor  109 , that is capable of being operably coupled to a housing of an instrument (e.g., housing  24  of  FIG. 3 ). In one embodiment, the sterile adaptor is part of a drape that may be draped over the robotic surgical system, and in particular the manipulator system, to establish a sterile barrier between the non-sterile PSM arms and the sterile field of the surgical procedure. An example of an applicable drape and adaptor is disclosed in pending U.S. application Ser. No. 11/240,113, filed Sep. 30, 2005, the full disclosure of which is incorporated by reference herein for all purposes. 
     Idler link  104  is movably coupled between base link  102  and carriage link  106  to allow the links  102 ,  104 , and  106  to move relative to one another along a lengthwise axis in a telescoping fashion. 
       FIGS. 6A through 6C  are perspective views of the insertion axis  100 , accessory mount  108  (e.g., a cannula mount), and an accessory  110  (e.g., a cannula) but not including an instrument or an instrument adaptor, the insertion axis  100  being telescoped from a retracted position in  FIG. 6A , to an intermediate position in  FIG. 6B , and to a fully extended position in  FIG. 6C . A pulley bank  112  is located on an underside of base link  102  for passing cables and electrical wires between insertion axis  100  and manipulator arm  50  of manipulator system  6 . 
     Motion along axes C through G in manipulator  8 , as shown in  5   FIGS. 5A  and  5 A 1 , are provided by cables extending between the proximal and distal links in accordance with the present invention. The robotic arm can then control a tool operably coupled to the arm. The cables are a component of a transmission system also including drive pulleys, idler pulleys, and output pulleys, which are driven by electric motors. A pulley bank is located on an underside of base link  102  for passing cables between insertion axis  100  and manipulator arm  50  of manipulator system  6 . A plurality of motion feed-throughs, in addition to other elements, may also be provided for transferring motion. 
     The drive assembly may further include a plurality of drive motors coupled to the arm for rotation therewith. Yaw and pitch motors control the motion of the arm about the A axis and the B axis ( FIG. 5A ), respectively, and drive motors control the motion of the wrist unit and surgical tool. In one embodiment, four drive motors are mounted proximally in the arm to control four degrees of freedom to the tool mounted distally on the arm (the D, E, F, and G axes). Also, a proximally mounted motor controls the insertion position of the tool distally on the arm (along the C axis). The drive motors will preferably be coupled to encoders and potentiometers (not shown) to enable the servomechanism. Embodiments of the drive assembly, arm, and other applicable parts are described for example in U.S. Pat. Nos. 6,331,181, 6,491,701, and 6,770,081, the full disclosures of which (including disclosures incorporated by reference therein) are incorporated herein by reference for all purposes. The manipulator arm and the drive assembly may also be used with a broad range of positioning devices. A more complete description of a remote center positioning device can be found in U.S. patent application Ser. No. 08/504,301, filed Jul. 20, 1995, now U.S. Pat. No. 5,931,832, the complete disclosure of which is incorporated herein by reference for all purposes. 
     To get power and signals to and from a printed circuit assembly (PCA) in carriage link  106 , a wire harness may be used. In one embodiment, the remote PCA may have inputs and outputs for providing power and/or communicating with LEDs, Hall effect sensors, a sterile adaptor, an instrument, and a user interface button (e.g., for a clutch operation). The remote PCA may also include an input for receiving power and an input/output for communicating with a main PCA (e.g., processor  4  of  FIG. 1 ). In one embodiment, the main PCA may have inputs and outputs for providing power and/or communicating with motors (e.g., the main PCA transmits position controls to the motors and processes potentiometer and encoder signals), sensors, the user interface button, the remote PCA, and other printed circuit boards on a patient side cart system via a serial communication bus. An example of the inputs and outputs of applicable PCAs are described in U.S. application Ser. No. 11/613,915, filed Dec. 20, 2006, entitled “Wireless Communication In A Robotic Surgical System”, the complete disclosure of which has been previously incorporated herein by reference for all purposes. The remote PCA may include, in one example, an Embedded Serializer for Instrument Interface (ESII) PCA, and the main PCA may include, in one example, an Embedded Serializer Patient Manipulator (ESPM) PCA, both available from Intuitive Surgical, Inc. of Sunnyvale, Calif. 
     Referring now to  FIGS. 7A-7B and 8A-8B , tensioning schemes for a closed loop cable drive used for a wrist axis and an insertion axis of the manipulator arm, respectively, are illustrated in accordance with an embodiment of the present invention. 
     In  FIGS. 7A and 7B , cables may extend from a pulley  202  coupled to a motor, which will be referred to as a capstan throughout this document, and over an adjustable idler pulley set  300  including two pulleys  302  and  304  within the manipulator arm (pulleys  302  and  304  are positioned in parallel along an axis perpendicular to the page and therefore appear as one pulley in  FIG. 7A ). Cables  201  and  203  each extend around an output pulley  204  at the distal end of the arm, and over idler pulleys  302  and  304 , respectively, back to the capstan  202 . In one embodiment, cables  201  and  203  are anchored to the capstan  202  as well as the output pulley  204  via ball crimps on the cable and slots in the pulleys. One cable is used to form each side of the closed loop (e.g., cable  201  on top and cable  203  on the bottom), and thus two cables are required for a single closed loop axis drive. In one example, cables  201  and  203  run from capstan  202  to output pulley  204 , passing over idler pulleys  302  and  304 , respectively, to route the cables through the joints and internal cavities of the manipulator arm. It is noted that cables  201  and  203  may pass over a plurality of idler pulleys  300  in some embodiments. 
     In one embodiment, the method of tensioning the cables is achieved by altering the position of two of the idler pulleys between the anchor points: one idler pulley on each side of the closed loop. These idler pulleys can be moved in either a linear or rotary fashion, or both, relative to their mounting, as long as the overall length of the closed loop cable path changes as a function of their position. Examples of applicable idler pulleys are further discussed below with respect to  FIGS. 11A-11C and 13A-13C . 
     Referring now to  FIGS. 8A and 8B  in accordance with another embodiment (e.g., in the insertion axis), cables  205 ,  207 ,  209 , and  211  are anchored to capstan  202  and a termination block  600  that is fastened to one of the links (e.g., idler link  104 ) that comprises the linear carriage on the distal end of the arm. Similar to the embodiment described above with respect to  FIG. 7 , one continuous cable is used to form each side of the closed loop, and thus two cables are required for a single closed loop axis drive. One difference between this embodiment and that described above with respect to  FIGS. 7A and 7B  is that this embodiment uses two parallel cables in each direction of the closed loop to provide a safety feature. Utilizing parallel cables provides redundancy and load sharing, and the termination block  600  is instrumental to enable these safety features. An example of termination block  600  is further discussed below with regard to  FIGS. 14A-14D . 
     Between capstan  202  and termination block  600 , cables  205  and  207  in parallel, and cables  209  and  211  in parallel, pass over fixed idler pulleys  210 ,  212  and  214 ,  216 , respectively, and over an adjustable idler pulley set  400  including four pulleys  401 ,  402 ,  403 , and  404 , used to route the cables through the joints and internal cavities of the robots links. It is noted that cables  205 ,  207 ,  209 , and  211  may pass over a plurality of idler pulleys  400  in some embodiments. 
     In one embodiment, a method of tensioning the cables is achieved by altering the position of four of these idler pulleys between the anchor points: two idler pulleys on each side of the closed loop. These idler pulleys can be moved in either a linear or rotary fashion relative to their mounting, as long as the overall length of the closed loop cable path changes as a function of their position. An example of an applicable idler pulley  400  is further discussed below with respect to  FIGS. 12A-12C . 
     Referring now to  FIGS. 9A-9C and 10A-10B , cables  201  and  203  are illustrated running through manipulator  8  in accordance with one embodiment of the present invention.  FIG. 9A  is a view of cables  201  and  203  running through manipulator arm  50  and insertion axis  100  of a telerobotic surgical system.  FIGS. 9B and 9C  illustrate a perspective view and a side view, respectively, of the cable and pulleys of  FIG. 9A .  FIGS. 10A   10  and  10 B illustrate closer views of an adjustable idler pulley  300  within manipulator arm  50 . 
     Referring now to  FIGS. 11A-11D , different views of an adjustable linear tensioner  300  are shown in accordance with an embodiment of the present invention. Tensioner  300  includes an arm  306 , pulleys  302  and  304  rotatably coupled to a first end of arm  306 , and a base  308  operably coupled to a second end of arm  306 . Pulleys  302  and  304  may rotate independently of each other. In one embodiment, tensioner  300  includes a translation mechanism for changing the position of the pulleys  302 ,  304  to control a tension of a cable movable along the pulleys. In one example, the translation mechanism includes a threaded cavity  310  for mating with a screw  312  (shown by dashed lines) along which the base  308  may translate, as shown by the double-sided arrow. In other embodiments, base  308  may include a cavity for sliding along a rod. The axial position of screw  312  (or a rod) is fixedly mounted within the manipulator in one embodiment (but may spin along the lengthwise axis of the screw or rod in one example). Tensioner  300  further includes a locking mechanism for maintaining the position of the base  308  relative to screw  312  and therefore to the arm of the robot, thereby maintaining the cable tension of a cable(s) (not shown) running along pulleys  302  and/or  304 . The locking mechanism may include in one example a screw  316  or similar fastener for coupling to a threaded cavity  314  in base  308 . As shown in the exploded view of tensioner  300  in  FIG. 11D , various bearings, shafts, and spacers may be used for allowing pulleys  302  and  304  to rotate. 
     In this embodiment, two pulleys  302  and  304  are included with either side of a closed loop cable transmission passing over them. The position of these pulleys  302  and  304  are constrained to a linear path and movable by a translation mechanism, in this embodiment threaded cavity  310  and screw  312 . Turning screw  312  (in one example with an ordinary screw driver) adjusts the linear position of the pulleys  302 ,  304  along screw  312 . The position of the pulleys in turn adjusts the tension of the cables because the linear path along which the pulleys move is not parallel to the path of the cables (see, for example,  FIGS. 10A and 10B ). In this design, an end of the closed loop can be around an output pulley (e.g., output pulley  204  of  FIG. 7 ) that is free to spin. The spinning of such an output pulley will eliminate tension imbalance between the two sides of the closed loop. Advantageously, the present invention provides a means to easily adjust the cable tension of a closed loop transmission using two pulleys that move linearly. It is noted that although two pulleys are illustrated as an integrated cable tensioner  300 , one or other various numbers of pulleys are within the scope of the present invention. 
     Referring now to  FIGS. 12A-12C , different views of an adjustable linear tensioner  400  are shown in accordance with an embodiment of the present invention. Similar to tensioner  300 , tensioner  400  includes an arm  406  having a first end and a second end, pulleys  401 ,  402 ,  403 , and  404  rotatably coupled to the first end of arm  406 , and a base  408  operably coupled to the second end of arm  406 . Pulleys  401 - 404  may rotate independently of each other. In one embodiment, tensioner  400  includes a translation mechanism for changing the position of the pulleys  401 - 404  to control a tension of a cable(s) movable along the pulleys. In one example, the translation mechanism includes a threaded cavity  410  for mating with a screw  412  (shown by dashed 5 lines) along which the base  408  may translate, as shown by the double-sided arrow. In other embodiments, base  408  may include a cavity for sliding along a rod. The axial position of screw  412  (or rod) is fixedly mounted within the manipulator in one embodiment (but may spin along the lengthwise axis of the screw or rod in one example). Turning screw  412  (in one example with an ordinary screw driver) adjusts the linear position of the pulleys  401 - 404  along screw  412 . The position of the pulleys in turn adjusts the tension of the cables because the linear path along which the pulleys move is not parallel to the path of the cables (see, for example,  FIGS. 10A and 10B ). 
     Tensioner  400  further includes a locking mechanism for maintaining the position of the base  408  relative to screw  412  and therefore to the arm of the robot, thereby maintaining the cable tension of a cable(s) (not shown) running along pulleys  401 - 404 . The locking mechanism may include in one example a screw  416  or similar fastener for coupling to a threaded cavity  414  in base  408 . It is noted that although four pulleys are illustrated as an integrated cable tensioner  400 , one or other various numbers of pulleys are within the scope of the present invention. 
     Referring now to  FIGS. 13A-13C , different views of an adjustable rotational tensioner  500  are shown in accordance with an embodiment of the present invention. Tensioner  500  includes a base  508 , two arms  506  and  506 ′ with each arm having a first end movably coupled to base  508 , and two pulleys  502  and  504  operably coupled to a second end of arm  506  and  506 ′, respectively. In one embodiment, pulleys  502  and  504  may rotate independently of each other and arms  506  and  506 ′ may move independently of each other with respect to base  508 . Base  508  is fixedly coupled to a position within the manipulator, and arms  506  and  506 ′ are rotatable about base  508  as shown by the double-sided arrow. In one embodiment, arms  506  and  506 ′ are spring loaded by torsion springs in such a way that the spring force is balanced against the cable tension through the pulleys. Therefore, the cable tension is proportional to the strength of the spring. 
     Referring now to  FIGS. 13D and 13E , tensioners  500 ′ and  500 ″ are shown further including a locking mechanism for maintaining or locking the position of the first end of arms  506  and  506 ′ with respect to base  508 , thereby maintaining the cable tension of a cable(s) (not shown) running along pulleys  502  and/or  504 . Once the cable and spring tensions have come to equilibrium, the arms may be locked in place with the locking mechanism (e.g., a screw  514  or similar fastener within an arcuate slot  512  ( FIG. 13D ) that locks the arms in place and an optional spring washer that may be used for disengaging the locking mechanism and adjusting the cable tension). Alternatively, as shown in  FIG. 13E , an electrically engaged brake  510  may be used to lock the arms  506  and  506 ′ automatically, by a processor, such as computer processor  4  of console  3 . In one example, brake  510  may be operational when not electrically engaged, and not operational when electrically engaged (or vice versa). The brake could also be engaged pneumatically, or by other means. Advantageously, the present invention allows cable tension to be re-calibrated automatically by a processor. Advantageously, the present invention simplifies the process of setting, maintaining, and adjusting cable tension. It is noted that although two pulleys and arms are illustrated as an integrated cable tensioner  500 , one or other various numbers of pulleys and arms are within the scope of the present invention. 
     Referring now to  FIGS. 14A-14D , different views of a termination block assembly  600  are shown in accordance with an embodiment of the present invention. Termination block assembly  600  includes a pin  602 , a pulley  604 A, a mount  612 , slots  610 A, and ball fittings  608  crimped on a cable  606  that runs through slots  610 A. Pulley  604 A is used to equalize the tension in parallel cable paths, and slots  610 A are used to catch ball fittings  608  if one side of the transmission should break or lose tension. Mount  612  is used for fixedly attaching the termination block assembly  600  to a position within the manipulator. Ball fittings  608  are crimped onto each parallel path of cable  606  that move in slots  610 A machined into termination block assembly  600 . Under normal operation, these ball fittings  608  are free to move in their respective slots  610 A. If the cable on either side of the parallel path were to break, the ball on the opposite side would catch on the bottom of its slot and maintain its ability to control the axis. Therefore, the termination block assembly  600  enables the parallel cables to provide redundant actuation of the insertion axis. 
     Pulley  604 A on the termination block allows the cable to wrap 180° around its midpoint. This enables a load on only one side of the parallel path to equalize with the other side of the parallel path, thus enabling load sharing between the two parallel paths. This is important because the ability to equally share loading will reduce the maximum load any one length of the cable sees. Furthermore, enabling differential movement between the two sides of the parallel cable eliminates small length differences potentially resulting from tolerance stack ups. 
     In one embodiment of the present invention, termination block assembly  600  may be used in conjunction with a standard fixed pulley transmission or in conjunction with cable tensioners  300 ,  400 , and  500  as described above to form a closed loop. On one end of the transmission, cables may be terminated into a capstan  202 , and on the other end the cables may terminate into block assembly  600 . 
     In alternative embodiments of termination block assembly  600 , a second pulley  604 B and a second set of slots  610 B may be included for receiving another cable to pull in the opposite direction, as shown in  FIGS. 14A-14D . In addition, a rotatable or stationary post around which a cable may move can be used instead of a pulley in one example. Furthermore, the termination block assembly is not limited to slots but various apertures may be used to provide cable pathways that can also retain the ball fittings (e.g., holes large enough to fit the cables and counterbores small enough to retain the ball fittings). In yet another example, the cable pathway through the termination block assembly is not limited to running in a parallel plane to the lengthwise axis of the pulley or pin, but may be along a perpendicular plane from the lengthwise axis of the pulley or pin. In other words, the cables would move along one plane through the termination block assembly. 
     Advantageously, the present invention provides a redundant cable transmission system thereby providing safe and redundant actuation to a critical axis of a manipulator arm such that if a cable breaks or loses tension, the insertion axis is prevented from falling. Furthermore, an advantageous adjustable tensioner is provided for adjusting the tension of cables in a closed loop. The tensioners, termination blocks, systems, and methods of the present invention provide for the improved setting, maintaining, and adjusting of cables used in a robotic surgical system, thus resulting in greater efficiency and improved accuracy of the system. 
     Embodiments described above illustrate but do not limit the invention. It should also be understood that numerous modifications and variations are possible in accordance with the principles of the present invention. For example, different numbers of arms and pulleys than that provided in the above embodiments of an adjustable cable tensioner is within the scope of the present invention. Furthermore, the system is not limited to four robotic manipulator assemblies, but may include two or more in other examples. Accordingly, the scope of the invention is defined only by the following claims.