Patent Publication Number: US-9884427-B2

Title: Compact robotic wrist

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/388,208, filed Sep. 25, 2014, which is a U.S. national phase filing of PCT Application No. PCT/US2014/026721, filed Mar. 13, 2014, which claims the priority benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/781,092 filed Mar. 14, 2013, and U.S. Provisional Application No. 61/791,248 filed Mar. 15, 2013. The disclosures of the PCT Application and the Provisional Applications are each hereby incorporated by reference in their entirety and should be considered a part of this specification. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED R&amp;D 
     This invention was made with Government support under Government contract number HSHQDC-10-C-00118, awarded by the Department of Homeland Security. The Government has certain rights in this invention. 
    
    
     BACKGROUND 
     Field 
     Robotic end effectors allow robots to manipulate objects. The present application relates to robotic tools, end effectors of the tools, and methods of operating the same. 
     Description of the Related Art 
     Robots are used for various purposes including industrial, research, medical and non-medical purposes. Each different type of robot may have its own set of unique features and characteristics in addition to features and characteristics that are common among most robots. One common characteristic of most robots is the use of tools. Tools controlled by robots are used to perform a variety of tasks. Each tool controlled by a robot may be specially designed for the task to be performed. Typically, robotic tools are elongate in shape and have an end effector (e.g., grasper). 
     With respect to surgical systems, typical on-market robotic systems use straight rigid tools or flexible tools (e.g., curved tools) controlled by cables or other mechanisms. Straight rigid tools are insufficient in some surgical settings, for example when an organ or anatomical structure is between the incision point or port (e.g., the location the tool enters into the body) and the tissue to be operated upon, because the straight shaft is unable to reach around the organ or anatomical structure to access the tissue. Another deficiency of straight rigid tools is that they are not well suited for use in what is referred to as single port surgery, where more than one tool is introduced through a single surgical incision or port, which is sometimes desirable to limit trauma to the patient. In such single port surgeries, cooperative interaction between the multiple tools is needed for tasks such as suturing. To interact cooperatively, the tools need to converge on the operative space from different angles, which straight rigid tools are not well suited for. 
     With respect to flexible tools, such as curved or bent tools, these tools overcome some of the access and maneuverability issues of straight rigid tools discussed above, but also have deficiencies. One shortcoming of flexible tools is that they typically are not rigid enough to resist bending loads during surgical procedures. Commonly, to improve rigidity, the curved or bent profile of the tools is pre-formed outside the body, either by the manufacturer or by the user using a bending tool, and is therefore unable to be bent within the body to accommodate operative geometry in situ. Other flexible tools are available that are segmented or have flexible shafts, and can be controlled for example by cables. These flexible tools also have shortcomings, such as being unable to achieve sufficient rigidity to withstand bending loads once bent during a surgical procedure. 
     Straight rigid tools and curved or bent tools are also used in non-medical applications and have the same deficiencies noted above when used in said non-medical applications. 
     SUMMARY 
     Accordingly, there is a need for improved robotic tools and end effectors that address the deficiencies noted above with on-market tools. There is a need for improved robotic tools and end effectors that provide for less occlusion of a worksite, enhanced ability to perform complex operations, and enhanced ability to work in areas where access is limited, relative to on-market robotic tools. 
     In accordance with one aspect of the invention, a tool is provided with a wrist coupled to an end effector. The wrist can include four independent cable ends. The four independent cable ends can be arranged such that each independent cable end may be driven independently. In one embodiment, the four independent cable ends are defined by four independent cables. In another embodiment, the four independent cable ends are defined by two cables, where each end of each cable defines an independent cable end. 
     The tool can be arranged in one embodiment such that it includes four motors to control each cable end independently. 
     In accordance with one aspect of the invention, a tool with a wrist coupled to an end effector can have one or more twisted strings instead of cables. A single string may be arranged to behave like a twisted string. The tool can have one or more twisted strings that drive the end effector. 
     The tool with the wrist and end effector can be arranged to have three or more sets of pulleys. Each cable can be arranged such that each cable winds around the three or more sets of pulleys in two orthogonal directions. Each cable can be arranged such that the relative tension between the two sides of each cable may result in a yaw motion. Each cable can be arranged such that the relative tension between two cables may result in a pitch motion. 
     The tool with the wrist and end effector can be arranged to have three sets of pulleys and two additional sets of pulleys. Each cable can be arranged such that each cable winds around the three sets of pulleys in two orthogonal directions. The two additional sets of pulleys can be angled relative to the three sets of pulleys. The two additional sets of pulleys can be arranged between the three sets of pulleys. 
     In accordance with one aspect of the invention, three sets of pulleys are provided and three additional sets of pulleys are provided. Each cable can be arranged such that each cable winds around the three sets of pulleys in two orthogonal directions. The three additional sets of pulleys can be arranged between the three sets of pulleys. The two sets of pulleys and the two additional sets of pulleys can be arranged in first direction, and the one set of pulleys and the one additional set of pulleys can be arranged an orthogonal direction to the first direction. 
     In accordance with one aspect of the invention, three sets of pulleys are provided and two additional sets of pulleys are provided. Each cable can be arranged such that each cable winds around the three sets of pulleys in two orthogonal directions. The two additional sets of pulleys can be arranged between the three sets of pulleys. The two sets of pulleys and the two additional sets of pulleys can be arranged in first direction, and the one set of pulleys can be arranged an orthogonal direction to the first direction. 
     The tool can be arranged such that the two cable loops are controlled with three motors. The third motor can be arranged to control a mechanism. The mechanism can be arranged such that the mechanism applies tension to both sides of the same cable. The mechanism can be arranged such that the mechanism enables a pitch motion. 
     The tool can be arranged such that the mechanism is a rocker member that increases the tension on one cable relative to a tension on another cable. The rocker mechanism can be arranged such that the rocker mechanism rotates (e.g., rocks back and forth) about an axis to move one pulley distally and one pulley proximally to thereby increase tension on one of the two cables and relax tension on the other of the two cables. 
     The tool can be arranged such that the mechanism is a shuttle mechanism that increases the tension on one cable relative to a tension on another cable. The shuttle mechanism can be arranged to linearly translate along the axis of the tool shaft to move the orientation of shuttle pulleys to thereby increase the distance one cable must travel relative to the distance the other cable must travel. The shuttle mechanism can be arranged such that the motion of the shuttle mechanism applies tension to one of the two cables and relaxes tension on the other of the two cables. 
     In accordance with another aspect of the invention, a tool has a wrist coupled to an end effector. The wrist can include one or more vertebra, where each vertebra is controllable with one or more independent cables. The one or more cables can be arranged to affect a bend in yaw and pitch. The tool can be arranged such that each vertebra is controllable with two or more cables, where the two or more cables can be arranged to affect a bend in yaw and pitch. 
     In accordance with another aspect of the invention, a tool is provided that includes one or more rigid sections and one or more flexible sections. The one or more flexible sections can be controllable and selectively locked and unlocked, for example in a bent configuration. 
     The tool with one or more rigid sections and one or more flexible sections can be arranged such that the one or more flexible sections are passively controlled. The one or more flexible sections can be passively controlled by one or more vertebra. In one embodiment the one or more flexible sections can be controlled by one or more vertebra to rigidize a sheath of the tool to, for example, provide a joint proximal of a wrist of the tool. The joint and wrist can provide redundant mechanisms to effect a motion of the distal end of the tool (e.g., the end effector of the tool). In one embodiment, a configuration (e.g., position, angle) of the joint can be controlled by the same mechanism that controls the actuation of the wrist distal of the joint. In one embodiment, the mechanism can be a locking mechanism, such as one employing a low melting point solid. In another embodiment, the mechanism can be a set of cables actuated to effect movement of the wrist and the joint proximal of the wrist. 
     The tool with one or more rigid sections and one or more flexible sections can be arranged such that the one or more flexible sections are actively controlled. The one or more flexible sections can be actively controlled by one or more cables. In one embodiment, the one or more flexible sections can be actively controlled by two or more cables. 
     The tool with one or more rigid sections and one or more flexible sections can be arranged such that the one or more flexible sections are selectively locked with a locking mechanism. The locking mechanism can be arranged to include a low melting point solid. In one embodiment, the melting point solid can be a polymer. The one or more flexible sections can be arranged to include a sheath. The sheath can include a braid of conductive material with filaments impregnated with a matrix of said low melting point solid that can change state from solid to liquid. The locking mechanism can include an activating element actuatable such that the low melting point solid becomes pliable, thereby allowing the one or more flexible sections to bend. The locking mechanism can be arranged so that the activating element includes a heater and/or heater wires. In other embodiments, rigidizing mechanisms based on electrostatic effect or magnetic effects may be used instead of, or in addition to, using low melting point solids. 
     The tool with one or more rigid sections and one or more flexible sections can be arranged such that the one or more flexible sections can include one or more sensors. The one or more sensors can be one or more strain sensors, one or more position sensors, and/or one or more pressure sensors. 
     The tool with one or more rigid sections and one or more flexible sections can be arranged such that the one or more flexible sections can be monitored. In one embodiment, the one or more flexible sections can be monitored on a periodic basis. In another embodiment, the one or more flexible sections can be monitored on a continuous basis. The one or more flexible sections can be monitored by one or more cameras. The cameras can be endoscopic cameras. The one or more cameras can produce images, and the images can be processed to obtain the bend parameters of the tool and/or wrist. The bend parameters can further inform the user and/or the control system of a system regarding the control of the tool, such that once the location of the bends are known, this information can be fed into a control loop of the control system to control the tool. 
     In accordance with another aspect of the invention, a tool has a wrist coupled to an end effector, where one or more cables control the wrist and the end effector. The end effector is arranged such that the one or more cables that control end effector are independent from the one or more cables that control the wrist. 
     The wrist can include three sets of pulleys. The first set of pulleys can include four pulleys. The four pulleys can be arranged in two sets of two pulleys. In one embodiment, the four pulleys can be arranged so that the first set of two pulleys is parallel to the second set of two pulleys. The second set of pulleys is arranged such that the second set of pulleys is angled relative to the first set of pulleys. The third set of pulleys is arranged such that the third set of pulleys is orthogonal to the first set of pulleys. The third set of pulleys can be coupled to the end effector. 
     The wrist can include three sets of pulleys. The first set of pulleys can include four pulleys. The four pulleys can be arranged in two sets of two pulleys. The four pulleys can be arranged parallel in two sets of two pulleys. The second set of pulleys is arranged such that the second set of pulleys is not angled relative to the first set of pulleys. The third set of pulleys is arranged such that the third set of pulleys is not orthogonal to the first set of pulleys. The third set of pulleys is arranged such that the third set of pulleys is not orthogonal to the second set of pulleys. The third set of pulleys is arranged such a cable from the second set of pulleys follows a straight path to the third set of pulleys to thereby minimize friction between the cable and pulleys. 
     The tool with the wrist and end effector can be arranged to have three sets of pulleys and two additional sets of pulleys. The two sets of pulleys and the two additional sets of pulleys can be arranged in first direction, and the one set of pulleys can be arranged in another direction, angled to the first direction. The two additional sets of pulleys can be arranged between the three sets of pulleys. The third set of pulleys is arranged such that a cable from the two additional sets follows a straight path to the third set of pulleys to thereby minimize friction between the cable and pulleys. 
     The tool with the wrist and end effector can be arranged to have three sets of pulleys and three additional sets of pulleys. The two sets of pulleys and the two additional sets of pulleys can be arranged in first direction, and the one set of pulleys and the one additional set of pulleys can be arranged in an orthogonal direction to the first direction. The three additional sets of pulleys can be arranged between the three sets of pulleys. The two additional sets of pulleys arranged in first direction can have pulleys with offset centers of rotation. The two additional sets of pulleys arranged in first direction can have pulleys with different diameters. 
     The tool with the wrist and end effector can be arranged to have three sets of pulleys and four additional sets of pulleys. The two sets of pulleys and the four additional sets of pulleys can be arranged in first direction, and the one set of pulleys can be arranged in an orthogonal direction to the first direction. The four additional sets of pulleys can be arranged between the three sets of pulleys. The center of rotation of the first additional set of pulleys is offset from the center of rotation of the second additional set of pulleys. The center of rotation of the third additional set of pulleys is aligned with the center of rotation of the fourth additional set of pulleys. 
     In accordance with one aspect, a minimally-invasive surgical tool is provided. The tool comprises a tool shaft, an end effector and a multi-axial wrist disposed between the tool shaft and the end effector, the wrist comprising three or more sets of pulleys arranged in two orthogonal directions. The tool further comprises a drive mechanism comprising four electric motors configured to effect movement of one or both of the wrist and the end effector. Each of the four electric motors is configured to independently control one of four independent cables that wind at least partially around one or more of the three or more sets of pulleys. The motors are configured to vary relative tension between the four independent cables to effect a yaw or pitch motion. 
     In accordance with another aspect, a minimally-invasive surgical tool is provided. The tool comprises a tool shaft, an end effector and a multi-axial wrist disposed between the tool shaft and the end effector, the wrist comprising three or more sets of pulleys arranged in two orthogonal directions. The tool further comprises a drive mechanism configured to effect movement of one or both of the wrist and the end effector. The drive mechanism is configured to independently control four independent cables that wind at least partially around one or more of the three or more sets of pulleys to vary relative tension between the four independent cables to effect a yaw or pitch motion. 
     In accordance with another aspect, a minimally-invasive surgical tool is provided. The tool comprises a tool shaft, an end effector and a multi-axial wrist disposed between the tool shaft and the end effector, the wrist comprising three or more sets of pulleys arranged in two orthogonal directions. The tool further comprises a drive mechanism comprising three electric motors configured to effect movement of one or both of the wrist and the end effector. The drive mechanism is configured to independently control two cable loops that wind at least partially around one or more of the three or more sets of pulleys to vary relative tension between the two cable loops and between two ends of each cable loop to effect a yaw or pitch motion. One of the three motors is coupled to a mechanism configured to tension two sides of the same cable loop to effect a pitch motion. 
     In accordance with another aspect, a minimally-invasive surgical tool is provided. The tool comprises a tool shaft, an end effector and a multi-axial wrist disposed between the tool shaft and the end effector, the wrist comprising three or more sets of pulleys arranged in two orthogonal directions. The tool further comprises means for effecting movement of one or both of the wrist and the end effector via independent control of four independent cables that wind at least partially around one or more of the three or more sets of pulleys to vary relative tension between the four independent cables to effect a yaw or pitch motion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a distal end of one embodiment of a tool including a wrist and an end effector. 
         FIG. 1B  illustrates the tool of  FIG. 1A . 
         FIG. 2  illustrates a yoke of  FIG. 1A . 
         FIG. 3A  illustrates the routing of a first cable of the tool of  FIG. 1A . 
         FIG. 3B  illustrates the routing of a second cable of the tool of  FIG. 1A . 
         FIG. 4A  schematically illustrates an embodiment of a twisted string based drive mechanism for a tool. 
         FIG. 4B  schematically illustrates an embodiment of a transition block of a twisted string based drive mechanism. 
         FIG. 4C  schematically illustrates an embodiment of a twisted string based drive mechanism. 
         FIG. 4D  schematically illustrates an embodiment of a cable based drive mechanism. 
         FIG. 5A  illustrates an embodiment of a tool including a wrist and an end effector. 
         FIG. 5B  illustrates a rocker mechanism of the tool of  FIG. 5A   
         FIG. 5C  schematically illustrates the cable routing of a first cable for the tool of  FIG. 5A . 
         FIG. 5D  schematically illustrates the cable routing of a second cable for the tool of  FIG. 5A . 
         FIG. 5E  schematically illustrates the rocker mechanism. 
         FIG. 6A  illustrates a distal portion of a tool having a shuttle mechanism. 
         FIG. 6B  schematically illustrates the cable routing of a first cable for the tool of  FIG. 6A . 
         FIG. 6C  schematically illustrates the cable routing of a second cable for the tool of  FIG. 6A . 
         FIG. 6D  schematically illustrates the shuttle mechanism. 
         FIG. 7A  illustrates an embodiment of a wrist. 
         FIG. 7B  illustrates a front view of the wrist of  FIG. 7A . 
         FIG. 8A  illustrates embodiment of a tool with a flexible section. 
         FIG. 8B  illustrates the flexible section of  FIG. 8A . 
         FIG. 8C  illustrates an embodiment of a flexible section. 
         FIG. 8D  illustrates an embodiment of a flexible section. 
         FIG. 9A  illustrates an embodiment of a flexible section. 
         FIG. 9B  illustrates the flexible section of  FIG. 9A . 
         FIG. 9C  illustrates a vertebra of a flexible section. 
         FIG. 10  illustrates a hyperdexterous surgical system. 
         FIG. 11  illustrates a hyperdexterous surgical arm coupled to a hyperdexterous surgical tool. 
         FIG. 12A  illustrates a distal end of an embodiment of a tool including a wrist and an end effector. 
         FIG. 12B  illustrates the tool of  FIG. 12A . 
         FIG. 12C  illustrates an angled wedge that supports the angled pulleys of the tool of  FIG. 12A . 
         FIG. 13A  illustrates the routing of a first cable of the tool of  FIG. 12A . 
         FIG. 13B  illustrates the routing of a second cable of the tool of  FIG. 12A . 
         FIG. 14A  illustrates an embodiment of the proximal end of a tool. 
         FIG. 14B  illustrates a coupling unit that couples to the proximal end of  FIG. 14A . 
         FIG. 14C  illustrates the distal end of the coupling unit of  FIG. 14B . 
         FIG. 14D  illustrates the coupling unit of  FIG. 14B . 
         FIG. 14E  illustrates a partial view of the coupling unit of  FIG. 14B . 
         FIG. 15  schematically illustrates an embodiment of a tool including a wrist and an end effector. 
         FIG. 16  schematically illustrates an embodiment of a tool including a wrist and an end effector. 
         FIG. 17A  illustrates a distal portion of an embodiment of a tool including a wrist and an end effector. 
         FIG. 17B  illustrates the tool of  FIG. 17A . 
         FIG. 17C  illustrates the tool of  FIG. 17A . 
         FIG. 17D  illustrates the cable routing of a first cable for the tool of  FIG. 17A . 
         FIG. 17E  illustrates the cable routing of a second cable for the tool of  FIG. 17A . 
         FIG. 18A  illustrates a distal end of an embodiment of a tool including a wrist and an end effector. 
         FIG. 18B  illustrates the tool of  FIG. 18A . 
         FIG. 18C  illustrates the tool of  FIG. 18A . 
         FIG. 18D  illustrates the cable routing of a first cable for the tool of  FIG. 18A . 
         FIG. 18E  illustrates the cable routing of a second cable for the tool of  FIG. 18A . 
     
    
    
     DETAILED DESCRIPTION 
     Described below are embodiments of tools, such as surgical tools, that have various advantages over on-market tools. At least some of the embodiments of tools described herein advantageously provide for less occlusion of the worksite, thereby allowing the operator improved visualization of the worksite. At least some of the embodiments of tools described herein provide for enhanced ability (e.g., of an operator of the tool, of a surgeon operating a tool) to perform complex operations by, for example, reducing the diameter of the wrist of the tool. At least some embodiments of tools describe herein provide enhanced ability to work in areas where access is limited (e.g., a smaller workspace), which can be made possible at least in part by a reduction in the diameter of the wrist of the tool. 
     In some embodiments disclosed below, a tool can include an end effector coupled to a tool shaft via a wrist, where the wrist allows for multi-axial motion (e.g., movement in pitch and yaw). The size of the wrist may be advantageously optimized by using a reduced number of cables to affect the control of the end effector of the tool. Tools so optimized can be used, for example, in minimally invasive surgical procedures due to such a feature of the wrist. However it should be understood that a general wrist described below can also be used in la large number of non-surgical and non-medical applications. 
     In several of the embodiments described below, the motion of the wrist and/or end effector of the tool is controlled by controlling four cable ends, which provides several advantages. One advantage is a reduction of the number of cables that extend to the wrist of the tool, which allows for minimizing the size and complexity of the mechanical assembly of the wrist. Another advantage is that the four cable arrangement allows independent control of tension on each cable of the wrist, without the need for pre-tensioning of the cables and the resulting friction in the joints of the tool wrist. The independent control of tension of each cable also enables variable compliance in the joints of the wrist and increased sensitivity to external loads. The independent control of tension of the cables further allows increased robustness to wear of the tool since tension can be readjusted. Further, the independent control of the tension of each cable allows the use of non-linear transmissions such as twisted strings since each cable can change length in different amounts. Independent control of each cable additionally enables wrist designs that do not require the sum of all cable lengths to be constant over the range of motion of the wrist, as is required when using fixed cable loops. Other advantages of the tools described herein will become apparent to persons of skill in the art based on the detailed description provided below. 
       FIGS. 1A-1B  show one embodiment of a tool  30  having a proximal end (not shown) and a distal end  31 , where the configuration of the wrist of the tool and cable routing of the tool  30 , as discussed below, advantageously allows for a reduction in the size of the wrist of the tool. In some embodiments, the reduction in the size of the wrist is enabled by cable routing that is simpler, which allows for a reduction in the complexity of the wrist assembly of the tool and allows for a shorted radius of curvature for the wrist. In some embodiments, the reduction in the size of the wrist of the tool  30  can include a reduction in the diameter of the wrist. 
     As shown in  FIG. 1A , the distal end  31  of the tool  30  can have a yoke  360  coupled to a shaft  30 A of the tool  30 . The yoke  360  is movably coupled to a second yoke  330  via an extended axle  332  that extends along an axis  380  (as shown in  FIG. 2 ). In one embodiment, the extended axle  332  can be removable or integrally formed with the second yoke  330 . In other embodiments, the extended axle  332  can be removable or integrally formed with the yoke  360 , such that portions of the axle  332  are attached to the arms of the yoke  360  and the yoke  330  can be inserted between said portions of the axle  332 . In one embodiment, the tool  30  can be a surgical tool. In another embodiment, the tool  30  can be a non-surgical tool. 
     As shown in  FIG. 1B , the extended axle  332  of the second yoke  330  is coupled with pulleys  340 A,  340 B,  350 A,  350 B such that the pulleys  340 A,  340 B,  350 A,  350 B are arranged along the axis  380  of the extended axle  332 . The pulleys  340 A,  340 B,  350 A,  350 B are arranged into a first set of pulleys  340 B,  350 B and a second set of pulleys  340 A,  350 A. The first set of pulleys  340 B,  350 B are on one side of the yoke  330 , and the second set of pulley  340 A,  350 A are on the other side of the yoke  330 . The pulleys  340 A,  340 B are outer pulleys and the pulleys  350 A,  350 B are inner pulleys. 
     The terms “inner” and “outer” indicate the orientation of the pulleys as shown in the Figures. As used herein, a “set” of pulleys can include any number of pulleys. A set of pulleys can include one pulley. A set of pulleys can include more than one pulley (e.g., two, three, four, five, six pulleys etc.). 
     With continued reference to  FIGS. 1A-1B , the second yoke  330  is coupled to a third set of pulleys  320 A,  320 B. The third set of pulleys  320 A,  320 B can be spaced a distance (e.g., distally) from the axis  380 . The third set of pulleys  320 A,  320 B are coupled to arms  330 A,  330 B of the second yoke  330  and arranged along an axis  370  defined through the arms  330 A,  330 B. In one embodiment, the second yoke  330  can include an extended axle that extends along the axis  370 . In one embodiment, the extended axle can be removably coupled with the second yoke  330 . In another embodiment, the extended axle can be integrally formed with the second yoke  330  such that portions of the axle are attached to the arms of the second yoke  330  and the pulleys  320 A,  320 B can be inserted between said portions of the axle. In one embodiment, the axis  370  can be angled relative to the axis  380 . In another embodiment, the axis  370  can be orthogonal to the axis  380 . The first set of pulleys  340 B,  350 B can be orthogonal to the third set of pulleys  320 A,  320 B. The second set of pulleys  340 A,  350 A can also be orthogonal to the third set of pulleys  320 A,  320 B. 
     A pair of jaws  310 A,  310 B of a grasper  310  can be coupled to the second yoke  330  via the third set of pulleys  320 A,  320 B, so that the jaws  310 A,  310 B can rotate about the axis  370 . In one embodiment, the jaw  310 A is coupled to the pulley  320 A. In another embodiment, the jaw  310 A can be integrally formed with the pulley  320 A. Similarly, in one embodiment, the jaw  310 B is coupled to the pulley  320 B. In another embodiment, the jaw  310 B can be integrally formed with the pulley  320 B. The jaw  310 A and the pulley  320 A can rotate about the axis  370 . Similarly, the jaw  310 B and the pulley  320 B can rotate the about axis  370 . In the illustrated embodiment, the grasper  310  is an end effector of the tool  30 . However, in other embodiments, the end effector can be other suitable mechanisms, such as mechanisms used in surgical procedures (e.g., percutaneous surgical procedures). 
     The tool  30  can be actuated to move one of both of the jaws  310 A,  310 B in a variety of ways around the axis  370 . For example, the jaws  310 A,  310 B may open and close relative to each other. The jaws  310 A,  310 B may also be actuated to rotate together as a pair to provide a yaw motion of the grasper  310 . Additionally, the tool  30  can be actuated to affect various types of motions of the jaws  310 A,  310 B around the axis  380 . For example, the second yoke  330 , the pulleys  320 A,  320 B, and the jaws  310 A,  310 B can rotate about the axis  380  to provide a pitch motion of the grasper  310 . 
       FIGS. 3A-3B  show an embodiment of the orientation of the cables of the tool  30 . Advantageously, as described below, the routing of the cables allows the motion of the grasper  310  to be controlled via the actuation of four independent cable ends or two cable loops, which allows the number of cables used to control the grasper  310  to be reduced relative to on-market tools (which typically use three cable loops with six cable ends), thereby advantageously allowing the size and complexity of the wrist of the tool  30  to be reduced, as discussed above. This advantageous feature (e.g., ability to control movement of an end effector via the actuation of only four independent cable ends or two cable loops) is present in tools described in embodiments of this disclosure. 
     With reference to  FIGS. 3A-3B , the third set of pulleys  320 A,  320 B can each include a pocket or recess. In one embodiment, the pocket is sized to at least partially retain a bead  315 A,  315 B. The bead  315 B is not shown in  FIGS. 3A-3B  but can be similar to bead  315 A as shown in these figures. The bead  315 A can be affixed to a first cable  390 A and the bead  315 B can be affixed to a second cable  390 B, where the cables  390 A,  390 B each have two independent cable ends. The beads  315 A,  315 B are affixed to the cables  390 A,  390 B in such a way as to inhibit (e.g., prevent) the cables  390 A,  390 B from slipping or sliding relative to the pulleys  320 A,  320 B. The cables  390 A,  390 B are coupled immovably to the beads  315 A,  315 B. In one embodiment, the beads  315 A,  315 B can be integrally formed with the cables  390 A,  390 B. In another embodiment, the beads  315 A,  315 B can be crimped on to the cables  390 A,  390 B. 
       FIG. 3A  shows the cable routing of a first cable  390 A, which is shown in dashed lines in  FIG. 3A . The first cable  390 A originates in the proximal end of the tool  30  and extends through the tool shaft  30 A. The first cable  390 A extends through a hole or aperture  30 C (see  FIG. 1A ) in the yoke  360 . The first cable  390 A winds at least partially around one pulley in the first set of pulleys  340 B,  350 B. The first cable  390 A winds at least partially around one pulley in the third set of pulleys  320 A,  320 B. The first cable  390 A winds at least partially around one pulley in the second set of pulleys  340 A,  350 B. In some embodiments, the first cable  390 A winds at least partially around the pulley  340 B, the pulley  320 A, and the pulley  340 A, as shown in  FIG. 3A . The first cable  390 A then passes through another hole or aperture  30 B (see  FIG. 1A ) in the yoke  360  and returns to the proximal end of the tool  30  via the tool shaft  30 A. 
     In some embodiments, the first cable  390 A can be replaced by two cables  390 A′ and  390 A″ (not shown) that may be coupled to the pulley  320 A (e.g., where the cable  390 A is replaced with two separate cable portions  390 A′,  390 A″). The cable  390 A′ winds at least partially around one pulley in the first set of pulleys  340 B,  350 B and the cable  390 A″ winds at least partially around one pulley in the second set of pulleys  340 A,  350 A. In this embodiment, the cables  390 A′,  390 A″ traverse only one side of one pulley in the third set of pulleys  320 A,  320 B. In one embodiment, each of the cables  390 A′,  390 A″ traverse only one side of the pulley  320 A. In some embodiments, the cables  390 A′,  390 A″ are coupled immovably to the pulley  320 A (e.g., via bead  315 A). For example, the bead  315 A can be crimped onto an end of each of the cables  390 A′,  390 A″, and the bead  315 A retained in the pocket of the pulley  320 A, as discussed above, to thereby immovably couple the cables  390 A′,  390 A″ to the pulley  320 A. The effect of having two independent cables  390 A′,  390 A″ affixed to a pulley  320 A or having one cable  390 A affixed to the pulley  320 A is the same. 
       FIG. 3B  shows a second cable  390 B in dashed lines. The second cable  390 B originates in the proximal end of the tool  30  and extends through the tool shaft  30 A. The second cable  390 B extends through the hole or aperture  30 C (see  FIG. 1A ) in the yoke  360 . The second cable  390 B winds at least partially around one pulley in the first set of pulleys  340 B,  350 B. The second cable  390 B winds at least partially around one pulley in the third set of pulleys  320 A,  320 B. The second cable  390 B winds at least partially around one pulley in the second set of pulleys  340 A,  350 A. In some embodiments, the second cable  390 B winds at least partially around the pulley  350 B, the pulley  320 B, and the pulley  350 A, as shown in  FIG. 3B . The second cable  390 B then passes through the hole or aperture  30 B (see  FIG. 1A ) in the yoke  360  and returns to the proximal end of the tool  30  via the tool shaft  30 A. 
     In some embodiments, the second cable  390 B can be replaced by two cables  390 B′ and  390 B″ (not shown) that may be coupled to the pulley  320 B in a similar manner as described above for cables  390 A′,  390 A″. Therefore, in some embodiments, four independent cables  390 A′,  390 A″,  390 B′ and  390 B″ can be used. For example, in one embodiment, the cable  390 B′ winds at least partially around one pulley in the first set of pulleys  340 B,  350 B and the cable  390 B″ winds at least partially around one pulley in the second set of pulleys  340 A,  350 A. In this embodiment, the cables  390 B′,  390 B″ traverse only one side of one pulley in the third set of pulleys  320 A,  320 B. In one embodiment, each of the cables  390 A′,  390 A″ traverse only one side of the pulley  320 B. In some embodiments, the cables  390 B′,  390 B″ are coupled immovably to the pulley  320 B (e.g., via bead  315 B, not shown). For example, the bead  315 B can be crimped onto an end of each of the cables  390 B′,  390 B″, and the bead  315 B retained in the pocket of the pulley  320 B, as discussed above, to thereby immovably couple the cables  390 B′,  390 B″ to the pulley  320 B. The effect of having two independent cables  390 B′,  390 B″ affixed to a pulley  320 B or having one cable  390 B affixed to the pulley  320 B is the same. 
     The tool  30  can be actuated to move the jaws  310 A,  310 B in a variety of ways such as grasping (e.g., jaws rotating independently about axis  370 ), yaw (e.g., jaws rotating together about axis  370 ), and pitch (e.g., jaws rotating about axis  380 ) by imparting motion to one or more of the pulleys  340 A,  340 B,  350 A,  350 B,  320 A,  320 B to thereby impart motion on the yoke  330  and/or one or both of the jaws  310 A,  310 B. In one embodiment, where the tool  30  has two cables  390 A,  390 B that effect the movement of the grasper  310 , each cable  390 A,  390 B has two independent cable ends which may be independently controlled or tensioned to impart motion on the third set of pulleys  320 A,  320 B and the jaws  310 A,  310 B. For example, motion of the pulley  320 A and the jaw  310 A can be controlled with the two cable ends of cable  390 A. Similarly, motion of the pulley  320 B and the jaw  310 B can be controlled with the two cable ends of cable  390 B. The system of  FIGS. 1A-3B  has four cable ends. The four cable ends may be controlled to impart motion on one or more of the pulleys,  340 A,  340 B,  350 A,  350 B,  320 A,  320 B. The four cable ends (a pair for each cable  390 A,  390 B) can be coupled to motors near the proximal end  32  (not shown) of the tool  30 , as further described below. In other embodiments, the four cable ends (a pair for each cable  390 A,  390 B) are coupled to motors located at any distance along the tool shaft  30 A. 
     In another embodiment, where the tool  30  has four cables  390 A′,  390 A″,  390 B′,  390 B″ that effect the movement of the grasper  310 , each cable  390 A′,  390 A″,  390 B′,  390 B″ has one independent cable end which may be independently controlled or tensioned to impart motion on the yoke  330  and/or one or both of the third set of pulleys  320 A,  320 B. Independent cable ends can be considered free cable ends (e.g., the ends not coupled to the bead  315 A,  315 B). Motion of the pulley  320 A can be controlled by the independent cable ends of cables  390 A′,  390 A″. Motion of the pulley  320 B can be controlled by the independent cable ends of cables  390 B′,  390 B″. The system of  FIGS. 1A-3B  has four independent cable ends. The four cable ends may be controlled to impart motion on one or more of the pulleys,  340 A,  340 B,  350 A,  350 B,  320 A,  320 B to thereby impart motion on the yoke  330  and/or one or both of the jaws  310 A,  310 B. The four cable ends (an end for each cable  390 A′,  390 ″,  390 B′,  390 B″) can be located near the proximal end (not shown) of the tool  30  or at any distance along the tool shaft  30 A. 
     In some embodiments, a pitch motion of the yoke  330  and the jaws  310 A,  310 B about the axis  380  is achieved by tensioning both ends of one cable (e.g.,  390 A) and relaxing both ends of the other cable (e.g.,  390 B). For example, referring to  FIGS. 3A-3B , to pitch the jaws  310 A,  310 B out of the plane of the paper, both ends of cable  390 A are tensioned and both ends of cable  390 B are relaxed. To pitch the jaws into the plane of the paper, both ends of cable  390 A are relaxed and both ends of cable  390 B are tensioned. 
     In some embodiments, a yaw motion of the jaws  310 A,  310 B of the grasper  310  about the axis  370  is achieved by moving the pulleys  320 A,  320 B in the same direction. For example, referring to  FIG. 3A , to yaw the jaws  310 A,  310 B upward, both pulleys  320 A,  320 B have to move in a counterclockwise direction. The end of the cable  390 A coupled to one pulley in the first set of pulleys  340 B,  350 B is tensioned and the end of the cable  390 B coupled to one pulley in the first set of pulleys  340 B,  350 B is tensioned. In  FIG. 3A , the end of the cable  390 A coupled to  340 B, and the end of the cable  390 B coupled to  350 B are tensioned. The other ends of the cables  390 A,  390 B are relaxed. The jaws  310 A,  310 B will therefore rotate about axis  370  upward. To yaw the jaws  310 A,  310 B downward, both pulleys  320 A,  320 B have to move in a clockwise direction. The end of the cable  390 A coupled to one pulley in the second set of pulleys  340 A,  350 A and the end of the cable  390 B coupled to one pulley in the second set of pulleys  340 A,  350 A are tensioned. In  FIGS. 3A-3B , the end of the cable  390 A coupled to  340 A, and the end of the cable  390 B coupled to  350 A are tensioned. The other ends of the cables  390 A,  390 B are relaxed. Such a combination of tensioning and relaxation of the cables  390 A,  390 B will cause the jaws  310 A,  310 B to rotate about axis  370  downward. 
     The jaws  310 A,  310 B can be moved relative to each other, for example to effect a grasping action, a release action, or a scissoring motion. To move the jaws  310 A,  310 B toward each other, the pulley  320 A can move in a counterclockwise direction and the pulley  320 B can move in a clockwise direction. To achieve such motion, the end of the cable  390 A coupled to one pulley in the first set of pulleys  340 B,  350 B and the end of the cable  390 B coupled to one pulley in the second set of pulleys  340 A,  350 A are tensioned. In  FIGS. 3A-3B , the end of the cable  390 A coupled to  340 B, and the end of the cable  390 B coupled to  350 A are tensioned. The other ends of the cables  390 A,  390 B are relaxed. Such a combination of tensioning and relaxation of the cables  390 A,  390 B will cause the jaws  310 A,  310 B to rotate about axis  370  toward each other. 
     To move jaws  310 A,  310 B apart, the pulley  320 A can move in a clockwise direction and the pulley  320 B can move in a counterclockwise direction. The end of the cable  390 A coupled to one pulley in the second set of pulleys  340 A,  350 A and the end of the cable  390 B coupled to one pulley in the first set of pulleys  340 B,  350 B are tensioned. In  FIGS. 3A-3B , the end of the cable  390 A coupled to  340 A, and the end of the cable  390 B coupled to  350 B are tensioned. The other ends of the cables  390 A,  390 B are relaxed. Such a combination of the tensioning and relaxing of the cables  390 A,  390 B will cause the jaws  310 A,  310 B to rotate about axis  370  away from each other. 
     The jaws  310 A,  310 B can be moved toward or away from each other by applying different amounts of tension to each cable end. By applying varying amounts of tension, the jaws  310 A,  310 B will yaw differently, effectively emulating a grasping or release action. All three modes of movement (pitch, yaw and grasping action) can be obtained by varying the cable ends that are being tensioned and relaxed, and/or by varying the amount of tension and relaxation applied to each cable end. Although a specific routing configuration is described in  FIGS. 1A-3B , other routing configurations are possible. For example, cable  390 A may wind around the inner pulley  350 B instead of winding around outer pulley  340 B as described above. 
     In some embodiments, motion of a wrist and/or end effector of a tool can be effected with one or more twisted strings. A twisted string pair works on the principle of twisting two component strings around each other so that the length of the twisted string pair can be shortened, thus creating tension along the twisted string pair. Similarly, as the component strings of a twisted string pair unwind, the length of the twisted string pair approaches the natural length of each component string.  FIGS. 4A-4D  show embodiments of drive mechanisms and methods of controlling a tool, such as tool  30 , with twisted strings and cables.  FIG. 4A  schematically shows a drive mechanism  500 A for controlling cables of a tool. The system includes two cables  521 ,  522 . Each cable  521 ,  522  is associated with a pulley  510 A,  510 B. The pulleys  510 A,  510 B are the objects being driven. The cable  521  may be associated with multiple pulleys, although one pulley  510 B is shown. Similarly, the cable  522  may be associated with multiple pulleys, although one pulley  510 A is shown. Each cable  521 ,  522  has two cable ends. Each cable end is coupled to a transition block  530 A,  530 B,  530 C,  530 D. Each transition block  530 A,  530 B,  530 C,  530 D is coupled to a twisted string pair  520 A,  520 B,  520 C,  520 D. Each twisted string pair  520 A,  520 B,  520 C,  520 D is coupled to a motor  515 A,  515 B,  515 C,  515 D. 
     With continued reference to  FIG. 4A , each twisted string pair  520 A,  520 B,  520 C,  520 D is driven by an axial motor  515 A,  515 B,  515 C,  515 D. For example, twisted string pair  520 A is driven by axial motor  515 A and twisted string pair  520 B is driven by axial motor  515 B. 
     The transition blocks  530 A,  530 B,  530 C,  530 D provide a transition between the twisted string pairs  520 A,  520 B,  520 C,  520 D and the cables  521 ,  522 . As shown in  FIG. 4A , the cable  521  extends between transition blocks  530 B and  530 C. The cable  522  extends between transition blocks  530 A and  530 D. The twisted strings pairs  520 A,  520 B,  520 C,  520 D may exhibit unpredictable behavior when contacting a surface over which the twisted strings pairs need to bend (e.g., a curved surface of the pulleys  510 A,  510 B), so the transition blocks  530 A,  530 B,  530 C,  530 D provide a transition between the twisted string pairs  520 A,  520 B,  520 C,  520 D and the cables  521 ,  522  so that only the cables  521 ,  522  contact the curved surfaces of the pulleys  510 A,  510 B. 
       FIG. 4B  shows the transition block  530 A. In one embodiment, all four transition blocks  530 A,  530 B,  530 C and  530 D have similar features to the transition block  530 A. The twisted string pair  520 A is coupled to a termination block  531 A. The cable  522  is also coupled to the termination block  531 A. The termination block  531 A is coupled immovably to a peg  532 A. In one embodiment, the termination block  531 A can be integrally formed with the peg  532 A. 
     The peg  532 A can slide within a slot  535 A in a base block  533 A along arrow  534 A to allow the twisted string pair  520 A to shorten or increase in length. In the illustrated embodiment, the peg  532 A and slot  535 A are both internal structures of the base block  533 A, and shown in dashed line form. The peg  532 A and slot  535 A advantageously prevent the termination block  531 A from rotating or spinning due to the influence of the twisted string pair  520 A. When the length of the twisted string pair  520 A is decreased, the peg  532 A coupled to the termination block  531 A slides within the slot  535 A in the base block  533 A, and the termination block  531 A in turn pulls the cable  522 . The cable  522  transmits this tension to the pulley  510 A to rotate the pulley  510 A. 
     With continued reference to  FIG. 4A , the twisted string pair  520 A is moved relative to the twisted string pair  520 C. The motor  515 A may wind the twisted string pair  520 A attached to the motor  515 A, thereby shortening the length of the twisted string pair  520 A. The motor  515 C may unwind the twisted string pair  520 C attached to the motor  515 C, thereby extending the length of the twisted string pair  520 C. These two actions cause the cable  522  to be pulled towards motor  515 A, causing the pulley  510 A to rotate in a counterclockwise direction. To move the pulley  510 A in the clockwise direction, the motor  515 A would unwind the twisted string pair  520 A and the motor  515 C would wind the twisted string pair  520 C. The motors  515 B,  515 D can move the cable  521  and the pulley  510 B in a similar manner. The cables  521 ,  522  can be coupled to a bead, similar to beads  315 A,  315 B, and the bead can be coupled to the pulleys  510 A,  510 B (e.g., retained in pockets of the pulleys  510 A,  510 B, in the manner discussed above). Additionally, in other embodiments, each of the cables  521 ,  522  can be replaced by two independent cables so that four cables extend between the transition blocks  530 A,  530 B,  530 C,  530 D and beads on the pulleys  510 A,  510 B. 
     In another mode of driving the pulleys  510 A,  510 B, both twisted string pairs can be wound equally. For example, motors  515 A,  515 C may both wind the twisted string pairs  520 A and  520 C, while motors  515 B,  515 D are not actuated. Pulley  510 A will not rotate in this case but experience a pulling force in the direction of the motors  515 A,  515 C, causing a yaw motion into the page along arrow  523 . If instead motors  515 B,  515 D are actuated to wind the twisted string pairs  520 B,  530 D, while motors  512 A,  515 C are not actuated, pulley  510 B will not rotated but experience a pulling force in the direction of motors  515 B,  515 D, thereby causing a yaw motion out of the page in a direction opposite to arrow  523 . Further to the description above, the amount of yaw motion can be controlled by the amount the twisted string pairs are wound. 
       FIG. 4C  schematically shows another drive mechanism  500 B for controlling a tool, such as tool  30 . The system includes a cable  570  associated with a pulley  580 . In the illustrated embodiment, the cable  570  defines one or more twisted string pairs, as discussed further below. Although only one pulley  580  is shown, the cable can be associated with multiple pulleys, as discussed above. Additionally, the system can include a second cable (not shown) associated with a second pulley (not shown). In the illustrated embodiment, the pulley  580  is the object being driven. As described in previous embodiments, the cable  570  is coupled to two transition blocks  565 A,  565 B. 
     Each transition block  565 A,  565 B is coupled to a twisted string pair  560 A,  560 B. Each twisted string pair  560 A,  560 B forms a loop  555 A,  555 B. Each loop  555 A,  555 B is coupled to a motor  550 A,  550 B. The twisted string pair  560 A is defined by the cable  570  doubled onto itself. In other words, the cable  570  couples to transition block  565 A (e.g., couples to the peg of the transition block  565 A so the peg can slide on the base block of the transition block  565 A and not rotate, similar to transition block  530 A), extends past the transition block  565 A to define the twisted string pair  560 A and loop  555 A, and couples back to transition block  565 A. Similarly, the twisted string pair  560 B is defined by the cable  570  doubled onto itself. In other words, the cable  570  couples to transition block  565 B and extends past the transition block  565 B to define the twisted string pair  560 B and loop  555 B, and couples back to transition block  565 B. 
     The motors  550 A and  550 B can wind or unwind the loops  555 A,  555 B and consequently wind or unwind the twisted string pair  560 A,  560 B. The cable  570  therefore extends from both sides of the termination block of the transition blocks  565 A,  565 B. The cable  570  can be attached to a bead  575 , which can be similar to the attachment of cables to bead  315 A in  FIG. 3A . The drive mechanism  500 B advantageously has fewer parts (e.g., one cable) compared to the drive mechanism  500 A in  FIG. 4A . 
       FIG. 4D  schematically shows another drive mechanism  500 C for controlling cables of a tool, such as tool  30 . The system includes two cables  595 A,  595 B. Each cable  595 A,  595 B is associated with a pulley  597 A,  597 B. The pulleys  597 A,  597 B are the objects being driven. Each cable  595 A,  595 B has two cable ends. Each cable end is driven by a motor,  590 A,  590 B,  590 C,  590 D. The motors can be flat, high torque motors (electrical motors). In other embodiments, other types of motors can be used. The spools that wind and unwind the cables  595 A,  595 B are not shown. 
       FIGS. 5A-6D  show embodiments of mechanisms that can be incorporated with the tools described herein, including the drive mechanisms described above.  FIG. 5A  shows another embodiment of a tool. The tool  600  includes a distal end  670  and a proximal end  680 . The distal end  670  can be substantially similar to the distal end  31  of the tool  30  shown in  FIGS. 1A-3B . For clarity, the cables that drive the distal end  670  are not shown in  FIG. 5A . As with the embodiments described previously, two cable loops having four cable ends are controlled to effect motion of a wrist and/or end effector of the tool  600 . In the illustrated embodiment, the tool  600  can include four motors  660 A,  660 B,  660 C,  660 D. However, only three motors are required to drive the cables and control the four cable ends. In one embodiment, the fourth motor can provide roll or rotation of the distal end  670  of the tool  600  about its axis. In some embodiments, the tool  600  includes only three motors. 
     The tool  600  can include four pulleys  630 A,  630 B,  640 A,  640 B. The pulleys  630 A,  630 B can be located distally in relation to the pulleys  640 A,  640 B. The pulleys  630 A,  630 B can be considered front pulleys, and the pulleys  640 A,  640 B can be considered rear pulleys. The front pulleys  630 A,  630 B are each driven by a motor  660 A,  660 B, respectively. The rear pulleys  640 A,  640 B are coupled to a rocker mechanism  650 . 
       FIG. 5B  shows the rocker mechanism  650 . The motors  660 A,  660 B are not shown in  FIG. 5B  to more clearly illustrate the rocker mechanism  650 . The rocker mechanism  650  can rock back and forth (in a clockwise and counterclockwise direction) about an axis  668 . The axes of the pulleys  640 A,  640 B are coupled to the ends of rocker mechanism  650 , as shown. In one embodiment, a plane defined by the axes of the pulleys  640 A,  640 B (e.g., a plane transverse to the longitudinal axis of the tool) can be axially offset from the axis  668  such that the axis  668  does not lie on said plane (e.g., so that planes defined by the axes of the rocker mechanism  650  and pulleys  640   a ,  640 B define a triangle). In another embodiment, the axes of the pulleys  640 A,  640 B and the axis  668  can be on the same plane transverse to the longitudinal axis of the tool  600 . 
     As the rocker mechanism  650  rotates counterclockwise, the pulley  640 B is moved toward the distal end  670  of the tool  600  and the pulley  640 A is moved toward the proximal end  680  of the tool  600 . As the rocker mechanism  650  rotates clockwise, the pulley  640 B is moved toward the proximal end  680  of the tool  600  and the pulley  640 A is moved toward the distal end  670  of the tool  600 . The position of the rocker mechanism  650  is determined by a motor (e.g., motor  660 D). The motor  660 D may be coupled to a lead screw. The lead screw may be coupled with a lead screw nut, which translates along the length of the lead screw. The lead screw nut may be coupled to a pushrod. The pushrod may be coupled to the rocker mechanism  650 . As the motor  660 D turns, the pushrod translates over the lead screw and alters the position of the rocker mechanism  150 . The rocker mechanism  150  adjusts the position of the pulleys  640 A,  640 B, as discussed above, which in turn adjusts the tension imparted on the cables coupled to the pulleys  640 A,  640 B. 
       FIG. 5C  illustrates the routing of a first cable  690 A of the tool  600 . The cable routing in the distal section  670  can be substantially similar to the cable routing illustrated in  FIGS. 3A-3B . The pulleys  615 A,  615 B can be substantially similar to pulleys  320 A,  320 B. The pulleys  615 A,  615 B can be coupled to jaws  610 A,  610 B, as shown in  FIG. 5A . The pulley  620  is similar to pulleys  340 A,  340 B,  350 A,  350 B. Both sides of the cable  690 A wind around the pulley  620 in the same direction Proximal to pulley  620 , the two sides of the cable  690 A travel through the tool shaft  605  (see  FIG. 5A ) and wind at least partially around the pulley  640 A, as shown in  FIG. 5C . After exiting the pulley  640 A, the free ends of the cable  690 A are attached to the opposite sides of a spool  630 A. The free ends of the cable  690 A are at least partially wound around the spool  630 A in opposite directions. The spool  630 A is actuated by a motor (e.g., motor  660 A). The speed with which spool  630 A rotates can be controlled via gearboxes coupled to the motor  660 A. As motor  660 A turns, spool  630 A turns, applying tension to one end of the cable  690 A and releasing the tension on the other end of the same cable  690 A. The cable  690 A can couple to a bead retained in a pocket or recess of pulley  615 A, in a manner similar to how cable  390 A couples to the bead  315 A in  FIG. 3A . 
     As the spool  630 A is rotated, a first cable end unwinds and the second cable end winds around spool  630 A. The effect of this type of motion is that the pulley  620  will not rotate but the pulley  615 A will rotate, which will cause the jaw  610 A attached to the pulley  615 A to move. For example, to yaw the jaw  610 A upward, the pulley  615 A has to move in a counterclockwise direction. To yaw the jaw  610  upward, the top cable end would need to be tensioned by winding the cable end around the spool  630 A. To yaw the jaw downward, the bottom cable end would need to be tensioned. The rocker mechanism  650  can be in a neutral position (e.g., the pulleys  640 A,  640 B aligned along a plane orthogonal to the longitudinal axis of the tool  600 ). 
     The tool  600  can be actuated to move the jaws  610 A,  610 B in a variety of ways such as grasping (e.g., jaws rotating independently via pulleys  615 A,  615 B), yaw (e.g., jaws rotating together via pulleys  615 A,  615 B), and pitch (e.g., jaws rotating about pulley  620 ).  FIG. 5D  illustrates the routing of a second cable in the tool  600 . The routing is similar to that described in  FIG. 5C . The cable  690 B winds around pulley  620 , around pulley  640 B, and terminates at spool  630 B. The spool  630 B is driven by a motor (e.g., motor  660 B). As the spool  630 B rotates, tension is applied to one side of the cable  690 B while tension on the other side of the cable  690 B is relaxed. The effect of this rotation is to move the jaw  610 B attached to the pulley  615 B. 
     To move both of the jaws  610 A,  610 B upward at the same time, the spools  630 A,  630 B are driven by the motors to move pulleys  615 A,  615 B counterclockwise. This motion will provide yaw to the jaws  610 A,  610 B. To move both the jaws  610 A,  610 B downward at the same time, the spools  630 A,  630 B are driven by the motors to move pulleys  615 A,  615 B clockwise. 
     To provide pitch, the rocker mechanism  650  is manipulated, changing the position of the pulleys  640 A,  640 B relative to the longitudinal axis of the tool  600 .  FIG. 5E  shows the rocker mechanism  650  rotated clockwise, moving the pulley  640 A toward the distal end  670  of the tool  600  and the pulley  640 B toward the proximal end  680  of the tool  600 . In this embodiment, the position of the rocker mechanism  650  increases the tension on both sides of the cable  690 B. This tension causes the pulley  620  to rotate in the clockwise direction, which causes the wrist of the tool  600  and jaws  610 A,  610 B to pitch in the clockwise direction, as shown by the arrow  695 . To rotate the pulley  620  in the opposite direction, the rocker mechanism  650  is rotated in the counterclockwise direction, moving the pulley  640 A toward the proximal end  680  of the tool  600  and the pulley  640 B toward the distal end  670  of the tool  600 . This increases the tension on cable  690 A, which causes the pulley  620  to rotate in the counterclockwise direction, which in turn causes the wrist of the tool  600  and jaws  610 A,  610   b  to pitch in the counterclockwise direction (opposite to the direction shown by arrow  695 ). The implementation of the lead screw and the pushrod as describe herein can allow a pitch of up to +/−90° or greater (e.g., up to a total of 180° or greater). The use of the rocker mechanism  650  results in increasing the tension of one cable (e.g., lengthening the distance one cable must travel to reach pulleys  615 A,  615 B), while decreasing or relaxing the tension of another cable (e.g., shortening the distance one cable must travel to reach pulleys  615 A,  615 B). 
       FIG. 6A  shows another embodiment of a tool. The tool  700  includes a distal end  770  and a proximal end  780 . The distal end  770  can be substantially similar to the distal end  31  of the tool  30  shown in  FIGS. 1A-3B . The tool  700  can be actuated to move the jaws  710 A,  710 B in a variety of ways such as grasping (e.g., jaws rotating independently via pulleys  715 A,  715 B), yaw (e.g., jaws rotating together via pulleys  715 A,  715 B), and pitch (e.g., jaws rotating about pulley  720 ). The tool  700  includes a shuttle mechanism  730  which provides the pitch motion of the jaws, instead of the rocker mechanism  650  described in  FIG. 5B . For clarity, the cable routing for the tool  700  is not shown in  FIG. 6A . In one embodiment, the tool  700  can also include the rocker mechanism  650  to hold the rear pulleys (similar to pulleys  640 A  640 B) of the tool  700 , and to reverse the cable routing in the proximal end (e.g., in a manner similar to how pulleys  640 A,  640 B reverse the cable routing toward pulleys  630 A,  630 B). That is, in one embodiment the proximal end of the tool  700  can have the same structure as the proximal end of the tool  600 . 
     Referring now to  FIG. 6B , the top view and the bottom view of the shuttle mechanism  730  with the cable routing for a first cable  760 A is shown. In the illustrated embodiment, the axle of a central pulley  735  of the shuttle mechanism  730  is immovably coupled to the body of the tool shaft  705 . The shuttle mechanism  730  can slide linearly back and forth along the longitudinal axis of the tool shaft  705 . 
     Looking at the top view in  FIG. 6B , the cable  760 A enters the tool shaft body from the proximal end  780 . The cable  760 A winds at least partially around the central pulley  735 . The cable  760 A extends back toward the proximal end  780  and winds at least partially around shuttle pulley  755 . The cable  760 A then extends toward the distal end  770  and winds at least partially around a pulley  720 . The pulley  720  can be substantially similar to pulley  620 , described above, and can function as a wrist of the tool  700 . The pulley  720  is coupled to a yoke  790  which is coupled to the jaws  710 A,  710 B, as shown in  FIG. 6A . Looking at the bottom view in  FIG. 6B , the cable  760 A enters the tool shaft body from the distal end  770  after winding around the pulley  720 . The cable  760 A extends back toward the proximal end  780  and winds at least partially around the shuttle pulley  755 . The cable  760 A then extends toward the distal end  770  and winds at least partially around the central pulley  735 , after which the cable  760 A extends toward proximal end  780 . 
       FIG. 6C  illustrates the top view and the bottom view of the shuttle  730  with the cable routing for a second cable  760 B. Looking at the top view in  FIG. 6C , the cable  760 B enters the tool shaft body  705  from the proximal end  780 . The cable  760 B winds at least partially around the shuttle pulley  750 . The cable  760 A extends back toward the proximal end  780  and winds at least partially around the central pulley  735 . The cable  760 A extends toward the distal end  770  and winds at least partially around the pulley  720 . The pulley  720  is coupled to the yoke  790  which is coupled to the jaws  710 A,  710 B, as shown in  FIG. 6A . Looking at the bottom view in  FIG. 6C , the cable  760 B enters the tool shaft body  705  from the distal end  770  after winding around the pulley  720 . The cable  760 B extends back toward the proximal end  780  and winds at least partially around the central pulley  735 . The cable  760 B then extends toward the distal end  770  and winds at least partially around the shuttle pulley  750 , after which the cable  760 B extends toward proximal end  780 . 
     To provide pitch to the wrist and jaws  710 A,  710 B of the tool  700 , the shuttle mechanism  730  is adjusted, changing the position of the shuttle mechanism  730  along the longitudinal axis of the tool  700 .  FIG. 6D  shows the shuttle mechanism  730  shifted toward the distal end  770  of the tool  700 . The position of the shuttle mechanism  730  is adjusted by a mechanism (e.g., a pushrod, lead screw, cable transmission) attached to a motor (e.g., motor  660 D shown in  FIG. 5A ).  FIG. 6D  shows the effect of linearly translating the shuttle mechanism  730  towards the distal end  770 . The top two diagrams in  FIG. 6D  illustrate the cable routing for cable  760 B and the bottom two diagram illustrates the cable routing for cable  760 A. The position of the shuttle mechanism  730  increases the tension on both sides of the cable  760 B. The distance that the cable  760 B has to travel to reach the pulley  720  has increased (e.g., the distance between the shuttle pulley  750  and central pulley  735  has increased), while the distance that the cable  760 A has to travel to reach pulley  720  has decreased (e.g., the distance between the central pulley  735  and the shuttle pulley  755  has decreased). As a result, the tension imparted by cable  760 B onto the pulley  720  increases and the tension imparted to the pulley  720  by cable  760 A decreases. This tension rotates the pulley  720  in the counterclockwise direction in the direction of arrow  765 . The cable routing described above can in other embodiments use alternate sets of pulleys than those described, but the use of the shuttle mechanism  730  results in increasing the tension of one cable (e.g., lengthening the distance one cable must travel to reach pulleys  715 A,  715 B), while decreasing or relaxing the tension of another cable (e.g., shortening the distance one cable must travel to reach pulleys  715 A,  715 B). 
     To rotate the pulley  720  (e.g., wrist pulley) in the opposite direction, the shuttle mechanism  730  is translated toward the proximal end  780  of the tool  700 . This tension rotates the pulley  720  in the clockwise direction. With the shuttle positions towards the proximal end  780 , the tension on cable  760 A increases and the wrist (e.g., pulley  720 ) will pitch in the opposite direction as the arrow  765 . The implementation of the shuttle mechanism  730  as describe herein can allow a pitch of up to +/−90° or greater (e.g., up to a total of 180° or greater). 
     As described above, the rocker mechanism  650  and shuttle mechanism  730  increase the tension on a first cable and release the tension on a second cable. The rocker mechanism  650  and shuttle mechanism  730  can be used to effect movement of one pulley  620 ,  720  or any combination of pulleys (e.g., the pulleys shown in  FIG. 1A ). 
       FIG. 7A  shows another embodiment of a tool. The tool  1000  has ten pulleys,  1010 A,  1010 B,  1020 A,  1020 B,  1030 A,  1030 B,  1040 A,  1040 B,  1050 A,  1050 B. The pulleys  1010 A,  1020 A are arranged in a first set. The pulleys  1010 B,  1020 B are arranged in a second set. The pulleys  1050 A,  1050 B are arranged in a third set. The third set of pulleys can be angled relative the first set of pulleys and/or the second set of pulleys. 
     The pulleys  1030 A,  1040 A are arranged in a fourth set. The pulleys  1030 B,  1040 B are arranged in a fifth set. The third set of pulleys can be angled relative the fourth set of pulleys and/or the fifth set of pulleys. In the illustrated embodiment, the first set of pulleys  1010 A,  1020 A can be in series with the fourth set of pulleys  1030 A,  1040 A. The second set of pulley  1010 B,  1020 B can be in series with the fifth set of pulley  1030 B,  1040 B. The first set of pulleys  1010 A,  1020 A can be arranged along an axis of rotation with the second set of pulleys  1010 B,  1020 B. The fourth set of pulleys  1030 A,  1040 A can be arranged along an axis of rotation with the fifth set of pulleys  1030 B,  1040 B. Other arrangements of the pulleys  1010 A,  1010 B,  1020 A,  1020 B,  1030 A,  1030 B,  1040 A,  1040 B are possible. 
     Referring to  FIG. 7B , the third set of pulleys  1050 A,  1050 B can be arranged along an axis of rotation  1060 . The fourth set of pulleys  1030 A,  1040 A and the fifth set of pulleys  1030 B,  1040 B can be arranged along an axis of rotation  1070 . The axis of rotation  1060  of third set of pulleys  1050 A,  1050 B can be angled relative to the axis of rotation  1070  of the fourth set of pulleys  1030 A,  1040 A and the fifth set of pulleys  1030 B,  1040 B such that the grooves on pulleys  1030 B and  1040 A are aligned with the grooves on pulleys  1050 A and  1050 B, respectively, thereby allowing the cables to follow a straight path between the pulleys  1030 B and  1040 A and the pulleys  1050 A,  1050 B to reduce cable bending and friction between the cables and pulleys. 
     The first set of pulleys  1010 A,  1020 A and the second set of pulleys  1010 B,  1020 B can be arranged along an axis of rotation  1070 ′, shown in  FIG. 7A . The axis of rotation  1060  of the third set of pulleys  1050 A,  1050 B can be angled relative to the axis of rotation  1070 ′ of the first set of pulleys  1010 A,  1020 A and the second set of pulleys  1010 B,  1020 B. 
     The routing of a first cable and a second cable is shown in  FIG. 7A . The pulleys  1050 A,  1050 B are coupled to a yoke  1055 . The yoke  1055  can have two attachments  1055 A,  1055 B extending from a surface of the yoke  1055 . In one embodiment, the jaws of the tool  1000  can be coupled to the pulleys  1050 A,  1050 B via the attachments  1055 A,  1055 B. The cable routing can be similar to the routing described with respect to  FIGS. 1A-3B . Each cable winds at least partially around one pulley in the fourth set of pulleys  1030 A,  1040 A, and one pulley in the fifth set of pulleys  1030 B,  1040 B, as shown. In some embodiments, the angle of the third set of pulleys  1050 A,  1050 B is arranged such that the cables from and to the fourth set of pulleys  1030 A,  1040 A and the fifth set of pulleys  1030 B,  1040 B follow a straight path to the third set of pulleys  1050 A, 1050 B. The tool  1000  can be actuated to move the jaws (not shown) in a variety of ways such as grasping (e.g., jaws rotating independently via pulleys  1050 A,  1050 B), yaw (e.g., jaws rotating together via pulleys  1050 A,  1050 B), and pitch (e.g., jaws rotating about pulleys  1030 A,  1040 A,  1030 B,  1040 B). 
     In other embodiments, a tool can include a rigid portion and a flexible portion, where the flexible portion can selectively be made rigid and/or locked into place to thereby effect a bent configuration to at least a portion of the tool. In some embodiments, said flexible portion that can be selectively made rigid can be disposed proximal of a wrist of the tool, where the wrist of the tool can have any configuration disclosed in the embodiments herein. Accordingly, in some embodiments, a tool can have a wrist and a flexible portion proximal of the wrist that provides another joint that can be actuated to position an end effector of the tool at different orientations, thereby advantageously increasing the range of motion of the distal end of the tool. 
       FIGS. 8A-9C  show embodiments of a flexible section which may be incorporated into tools described herein.  FIG. 8A  shows another embodiment of a tool. The tool  1300  can include a bend or elbow along a portion of the tool shaft  1302 . The tool  1300  can include one or more rigid sections  1310 . The tool  1300  includes one or more flexible sections  1305 . The flexible section  1305  can include a sheath  1320 , which is shown in cross-hatching. The tool  1300  can include an end effector  1340  (e.g., a grasper). The tool  1300  can be bent or otherwise manipulated to attain a nonlinear configuration, such as to reach around obstacles to a desired position or object. Further, the tool  1300  can be arranged such that the flexible section  1305  can selectively be made rigid and/or locked in place (e.g., to maintain said bent configuration). 
     In some embodiments, when used in surgical applications, the tool  1300  can be inserted through a trocar. Since trocars generally have a straight configuration, the tool  1300  can be arranged to extend along a longitudinal axis (e.g., straight, rigid) for insertion through the trocar. The tool  1300  can be bent or manipulated after exiting the trocar and into the body (e.g., when the tool is used in percutaneous surgery) to assume a shape other than straight. Once the desired shape has been obtained, the tool  1300  can be locked into position in order to rigidly maintain the bent shape. The locking of the tool  1300  may prevent the user from losing control of the position of the tool  1300 . 
       FIG. 8B  shows the flexible section  1305  in greater detail. In one embodiment, the flexible section  1305  can include a flexible core (e.g., a braid)  1370 . The flexible section  1305  can include a container  1360  which can be flexible. The container  1360  can include a low-melting point material (e.g., wax, polymer) which has both a solid state and a liquid state. In one embodiment, the flexible core (e.g., braid)  1370  can include a conductive material of filaments impregnated with a matrix of the low-melting point material. The transition between the solid state and the liquid state occurs at a low-temperature (e.g. less than 150 degrees F., less than 140 degrees F., less than 130 degrees F., less than 120 degrees F., less than 110 degrees F., less than 100 degrees F., less than 90 degrees F., etc.). The container  1360  can be surrounded by a sheath  1320 . The arrow  1380  represents the cables to actuate the end effector, such as the electrical wire to actuate the flexible sheath  1320  that travel toward the proximal end of the tool  1300 . 
     With continued reference to  FIGS. 8A-8B , the low-melting point material can become fluid when activated by an activation mechanism. The low-melting point material can become solid when not activated. The activation mechanism can include a heating element  1330 , which applies heat to the low melting point material. In one embodiment, the heating element  1330  can apply heat when an electric current is passed through the heating element (e.g., the heating element can be a resistive heater). In other embodiments, other rigidizing mechanisms based on electrostatic effect or magnetic effects may be used instead of, or in addition to, low melting point solids. 
     When the heating element  1330  is turned on, the low-melting point material transitions to a fluid state and becomes flexible. The tool  1300  can be bent or manipulated. When the heating element  1330  is turned off, the low-melting point material transitions to a solid state and becomes rigid. The tool  1300  can maintain its bent position. 
       FIG. 8C  shows an embodiment of the flexible section  1305  of a tool  1300 ′. This configuration can be considered an active elbow configuration. The tool  1300 ′ can include a cable  1380 . The cable  1380  can be enclosed by a housing  1382 . The housing  1382  can be flexible to bend with the flexible section  1305 . The tool  1300 ′ can include one or more cables. The tool  1300 ′ can include two or more cables. The cable  1380  can be attached to the one or more rigid sections  1310 , the one or more flexible sections  1305 , and/or the end effector  1340 . The cable  1380  can be coupled to the distal end of the flexible section  1305 , (e.g., to a distal location  1385 ). In some embodiments, the heating element  1330  is actuated and the flexible section  1305  becomes malleable. The cable  1380  is tensioned and the flexible section  1305  is tensioned to form a bend via the cable  1380  pulling on the distal location  1385  of the flexible section  1305 , thereby providing an active elbow. When an appropriate or desired bend of the flexible section  1305  is obtained, the activation element may be deactivated. The flexible section  1305  becomes rigid and the bend would be locked into position. The low-melting point material would harden and maintain the position of the flexible section  1305 . 
       FIG. 8D  shows an embodiment of the flexible section  1305  of a tool  1300 ″. This configuration can be considered a passive elbow configuration. The flexible section  1305  can include one or more vertebra  1391  (e.g., one, two, three, four, five, six vertebrae, etc.). The vertebrae  1391  can be any cross-sectional shape (e.g., circular, disc). The vertebra  1391  are retained within or covered by the sheath  1320 . The flexible section  1305  can include a flexible core (e.g., a braid), such as braid  1370  in  FIG. 8B . Similar to the tool  1300  in  FIG. 8B , the flexible section  1305  can include a container  1360  which can be flexible and can include a low-melting point material (e.g., wax, polymer) which has both a solid state and a liquid state and can transition between the solid state and the liquid state occurs at a low-temperature, such as the temperatures noted above. 
     The tool  1300 ″ can include a cable  1392 . The cable  1392  can be enclosed by a housing (not shown). The tool  1300 ″ can include one or more cables  1392 . The tool  1300 ″ can include two or more cables  1392 . The cable  1392  can be attached to the one or more rigid sections  1310 , the one or more flexible sections  1305 , one or more vertebra  1391  and/or the end effector  1340 . The cable  1392  can extend within the tool  1300 ″, as shown in  FIG. 8D . 
     In some embodiments, the heating element  1330  is actuated and the flexible section  1305  becomes malleable. The cable  1392  is tensioned, which changes the orientation of the one or more vertebra  1391  to form a bend in the flexible section  1305 . The bending of the flexible section  1305  originates from the one or more vertebrae  1391  which form part of the flexible section  1305 . The flexible section  1305  and/or flexible sheath  1320  simply follow the bend of the one or more vertebrae  1391 , thereby providing a passive elbow. When an appropriate or desired bend of the flexible section  1305  is obtained, the activation element  1330  may be deactivated. The flexible section  1305  becomes rigid and the bend would be locked into position. The low-melting point material would harden and maintain the position of the flexible section  1305 . 
       FIG. 9A  shows another embodiment of a tool. The tool  1600  includes a sheath  1610 . The sheath  1610  can be formed from a flexible material (e.g., cast silicon rubber). The tool  1600  can include one or more control cables  1620 A,  1620 B,  1620 C. Three control cables are shown in  FIG. 9A , but any number of control cables can be utilized (e.g., one, two, three, four, five, six cables, etc.). The control cables  1620 A,  1620 B,  1620 C are coupled to a mechanism (not shown) for manipulating the curvature of the flexible section  1605 . The three control cables  1620 A,  1620 B,  1620 C can extend through the flexible section  1605  and exit the proximal end of the flexible section  1605 . The tool  1600  can include an instrument channel  1630 . The instrument channel  1630  can extend along a longitudinal axis of the tool  1600 . The instrument channel  1630  can extend along then entire tool  1600  or a portion of the length of the tool  1600 . The instrument channel  1630  can include a control mechanism (not shown) for manipulating the end effector and/or other components (e.g., electrical wires, safety wires). 
     In one embodiment, the sheath  1610  can be disposed proximal of a wrist of the tool  1600 , where the wrist can have one of the configurations disclosed herein (e.g., the pulley system in  FIGS. 1A-3B ). The sheath  1610  can thus provide an additional joint to increase a range of motion of a distal end of the tool  1600 . In some embodiments, the control cables that manipulate the curvature of the flexible section  1605  of the sheath  1610  can also effect movement of the wrist of the tool (e.g., the distal end  31  of tool  30  in  FIGS. 1A-3B ). 
       FIG. 9B  shows the tool  1600  with the sheath  1610  removed. The tool  1600  can include one or more vertebrae  1635  (e.g., one, two, three, four, five, six vertebrae, etc.). The one or more control cables  1620 A,  1620 B,  1620 C can extend through the one or more vertebrae  1635 . The orientation of each vertebra  1635  may be controlled by the control cables  1620 A,  1620 B,  1620 C. 
       FIG. 9C  shows an exploded view of a vertebra  1635 . The vertebra  1635  can include one or more printed circuit boards  1640 A,  1640 B. The vertebra  1635  can include two printed circuit boards  1640 A,  1640 B disposed on either side of the vertebra  1635 . The two printed circuit boards  1640 A,  1640 B can be identical. The two printed circuit boards  1640 A,  1640 B can include a heating element  1641  on one side of the printed circuit boards, as shown on printed circuit board  1640 B. The two printed circuit boards  1640 A,  1640 B can include components on other side of the printed circuit boards, as shown on printed circuit board  1640 A. The components can include a switch  1655  (e.g., an addressable micro-switch). The switch  1655  selects which vertebra to turn on. The components can include a relay or FET  1660  for turning the heating element  1641  on and off. The relay of FET  1660  provides the power source for the heating elements  1641 . In other embodiments, other rigidizing mechanisms based on electrostatic effect or magnetic effects may be used instead of, or in addition to, low melting point solids. One or more electrical wires (not shown) connect the two printed circuit boards  1640 A,  1640 B to other components for various functions (e.g. power, data transmission). The switch  1655  and the relay  1660  may be combined into one component. The switch  1655  and/or the relay or FET  1660  can be replaced with other mechanism for activating/deactivating an element known in the art. 
     The vertebra  1635  can include a spherical spacer ball  1646 . The spherical spacer ball  1646  can be retained in ball seats  1645 A,  1645 B. The ball seats  1645 A,  1645 B can be coupled with the printed circuit boards  1640 A,  1640 B. The ball seats  1645 A,  1645 B can maintain a pre-determined distance between each other. The vertebra  1635  can include a spacer  1650 . The spacer  1650  can be formed from a low-melting point material (e.g., metal) which has both a solid state and a liquid state. The transition between the solid state and the liquid state occurs at a low-temperature (e.g. less than 150 degrees F., less than 140 degrees F., less than 130 degrees F., less than 120 degrees F., less than 110 degrees F., less than 100 degrees F., less than 90 degrees F., etc.). At room temperature, the spacer  1650  can be solid. The low-melting point material can be encapsulated by a container (e.g. silicon cast around the low-melting point material). The spacer  1650  is positioned between the two printed circuit boards  1640 A,  1640 B. The spherical spacer ball  1646  is retained within the spacer  1650 . 
     To position the tool  1600 , a data signal is sent to the two printed circuit boards  1640 A,  1640 B of a selected vertebra. The data signal can be sent to one selected vertebra  1635  or more than one selected vertebra  1635 . The data signal causes the pair of heating elements  1641  of the selected vertebra  1635  to be activated. The control cables  1620 A,  1620 B,  1620 C can be tensioned to create a bend and/or any angular orientation between the two printed circuit boards  1640 A,  1640 B in the selected vertebra  1635  may be obtained. 
     The data signal can cause the pair of heating elements  1641  of the selected vertebra  1635  to be deactivated. This turns off the heating elements  1641 , allowing the low-melting point material to solidify at an orientation (e.g., position and/or angle) set by the control cables  1620 A,  1620 B,  1620 C. In one embodiment, control cables  1620 A,  1620   b ,  1620 C can maintain the position and/or angle of the selected vertebra  1635  until the low-melting point material solidifies. In some embodiments, a coolant may be directed through the instrument channel  1630  to accelerate solidification and/or cooling of the low-melting point material. By activating and setting the angles of selected vertebra  1635  and groups of selected vertebra  1635 , compound curves can be achieved as shown in  FIG. 9B . 
     Several concepts are now described that are advantageous for surgical systems, although these concepts can also provide advantages in non-surgical and non-medical applications.  FIG. 10  shows an embodiment of a hyperdexterous surgical system  5  that can be used to perform surgical procedures (e.g., percutaneous minimally invasive surgical procedures). The hyperdexterous surgical system  5  can include one or more hyperdexterous surgical arms  10 . In some embodiments, a surgical procedure is performed by manipulating a tool (e.g., any of the tools described herein), for example by manipulating a tool held by the hyperdexterous surgical arm  10 . 
       FIG. 11  shows an embodiment of the hyperdexterous surgical arm  10 . The hyperdexterous surgical arm  10  can be coupled to a hyperdexterous surgical tool  30 ′. The tool will be variably called a “hyperdexterous surgical tool” or simply the “tool”. The hyperdexterous surgical tool  30 ′ includes a distal end  31 ′ and a proximal end  32 ′. In one embodiment, the hyperdexterous surgical tool  30 ′ and distal end  31 ′ can be similar to the tool  30  and distal end  31  in  FIGS. 1A-3B . In use, the distal end  31 ′ may be placed within the body of a patient through an incision (e.g., in a percutaneous minimally invasive surgical procedure). The distal end  31 ′ of the tool  30 ′ can include an end-effector (e.g., a grasper, such as the grasper  310  in  FIG. 1A ). The end-effector may be selected based on the surgical procedure or task to be performed. The distal end  31 ′ of the tool  30 ′ can include a wrist, the details of which are further described herein. Several concepts for improved design of the wrist of a tool, such as tool  310  in  FIG. 1A , have been discussed above. Several concepts are now described that are advantageous for surgical systems, but that could also apply to non-surgical systems as well. 
     The hyperdexterous surgical system  5  and the hyperdexterous surgical arm  10  are further described in commonly owned, co-pending applications PCT/US2014/26115 filed Mar. 13, 2014, U.S. Provisional Application No. 61/791,248 filed Mar. 15, 2013, U.S. Provisional Application No. 61/906,802 filed Nov. 20, 2013, U.S. Provisional Application No. 61/908,888 filed Nov. 26, 2013, U.S. Provisional Application No. 61/915,403 filed Dec. 12, 2013, and U.S. Provisional Application No. 61/935,966 filed Feb. 5, 2014, all of which are hereby incorporated by reference in their entirety and should be considered a part of this specification. 
       FIG. 12A  shows another embodiment of a tool. The tool  400  can be substantially similar to the tool  30  shown in  FIGS. 1A-3B . The tool  400  can have a wrist  402  at a distal end  31 ′ of the tool  400 , where the wrist  402  couples an end effector  410  to a shaft  30 A of the tool  400 . In the illustrated embodiment, the wrist  402  can include pulleys  440 A,  440 B,  450 A,  450 B,  425 A,  427 A,  425 B,  427 B,  420 A and  420 B. The pulleys  440 A,  450 A are arranged in a first set. The pulleys  440 B,  450 B are arranged in a second set. The pulleys  420 A,  420 B are arranged in a third set. The pulleys  425 A,  427 A are arranged in a fourth set. The pulleys  425 B,  427 B are arranged in a fifth set. The third set of pulleys  420 A,  420 B are substantially similar to the third set of pulleys  320 A,  320 B discussed above with respect to  FIG. 3A , and couple to jaws  410 A,  410 B of the end effector  410 , respectively. Similarly, the first set of pulleys  440 A,  450 A and the second set of pulleys  440 B,  450 B are substantially similar to the first set of pulleys  340 B,  350 B and the second set of pulleys  340 A,  340 B discussed above with respect to  FIG. 3A . The tool  400  differs from the tool  30  in  FIG. 3A  in that it includes two additional sets of pulleys, the fourth set of pulleys  425 A,  427 A and the fifth set of pulleys  425 B,  427 B. 
     As shown in  FIG. 12B , the fourth set of pulleys  425 A,  427 A and the fifth set of pulleys  425 B,  427 B are angled relative to the first set of pulley  440 A,  450 A and the second set of pulleys  440 B,  450 B. The rotational axis of pulley  425 A is angled relative to the rotational axis of the pulley  440 A. The rotational axis of pulley  427 A is angled relative to the rotational axis of the pulley  450 A. The rotational axis of pulley  425 B is angled relative to the rotational axis of the pulley  440 B. The rotational axis of pulley  427 B is angled relative to the rotational axis of the pulley  450 B. 
     With reference to  FIG. 12C , the fourth set of pulleys  425 A,  427 A is maintained at an angle by an angled wedge  426 A, which can include two axles  452 A,  452 B that extend at an angle relative to each other (e.g., 15 degrees, 30 degrees, 45 degrees, etc.). The angled axles  452 A,  452 B support the fourth set of pulleys  425 A,  427 A thereon so that the pulleys  425 A,  427 A can rotate about the axles  452 A,  452 B. In a similar manner, the fifth set of pulleys  425 B,  427 B can be maintained at an angle by an angled wedge  426 B, as best shown in  FIG. 12B . The angled wedge  426 B is substantially similar to the angled wedge  426 A. The design of the wrist  402 , as illustrated in  FIGS. 12A-12C  and discussed above, decreases the cross over and friction between the cables that are routed around the pulleys of the wrist  402 , thus making the routing of the cables more advantageous. The routing of the cables of the wrist  402  is further described below. 
     The tool  400  can be actuated to move the jaws  410 A,  410 B in a variety of ways such as grasping (e.g., jaws rotating independently via pulleys  420 A,  420 B), yaw (e.g., jaws rotating together via pulleys  420 A,  420 B), and pitch (e.g., jaws rotating about pulleys  440 A,  450 A,  440 B,  450 B).  FIG. 13A  shows the routing of a first cable  490 A in the wrist  402  of the tool  400 . The first cable  490 A originates in the proximal end (not shown) of the tool  400  and extends through the tool shaft  30 A and out of the tool shaft  30 A (e.g., through a yoke attached to the end of the shaft  30 A, such as through an aperture or hole), in a similar manner as described previously in connection with the tool  30  illustrated in  FIG. 3A . In the illustrated embodiment, the first cable  490 A winds at least partially around one pulley in the first set of pulleys  440 A,  450 A. The first cable  490 A then winds at least partially around one pulley in the fourth set of pulleys  425 A,  427 A. The first cable  490 A then winds at least partially around one pulley in the third set of pulleys  420 A,  420 B. As discussed in previous embodiments, the first cable  490 A can couple to a bead (e.g., immovably coupled to a bead, like bead  315 A in  FIG. 3A ) that is retained within one pulley in the third set of pulleys  420 A,  420 B. The first cable  490 A then winds at least partially around one pulley in the fifth set of pulleys  425 B,  427 B, after which the first cable  490 A winds at least partially around one pulley in the second set of pulleys  440 B,  450 B. The first cable  490 A then extends toward the proximal end of the tool  400  and through the tool shaft. In some embodiments, the first cable  490 A winds at least partially around pulleys  450 A,  427 A,  420 A,  425 B and  440 B, as shown in  FIG. 13A . 
     In the illustrated embodiment, the pulleys  440 A,  440 B,  425 A,  425 B are considered outer pulleys and the pulleys  450 A,  450 B,  427 A,  427 B are considered inner pulleys. In some embodiments, the first cable  490 A winds around two outer pulleys (e.g., pulleys  440 B,  425 B) and two inner pulleys (e.g., pulleys  450 A,  427 A). The first cable  490 A is shown in  FIG. 13A  slightly displaced from the pulleys to more clearly illustrate the routing of the first cable  490 A. 
       FIG. 13B  shows the routing of a second cable  490 B in the wrist  402  of the tool  400 . The second cable  490 B winds at least partially around one pulley in the first set of pulleys  440 A,  450 A. The second cable  490 B then winds at least partially around one pulley in the fourth set of pulleys  425 A,  427 A. The second cable  490 B then winds at least partially around one pulley in the third set of pulleys  420 A,  420 B. The second cable  490 B can couple to a bead (e.g., immovably coupled to a bead, like bead  315 A) that is retained within one pulley in the third set of pulleys  420 A,  420 B, as described in previous embodiments. The second cable  490 B then winds at least partially around one pulley in the fifth set of pulleys  425 B,  427 B, after which the second cable  490 B winds at least partially around one pulley in the second set of pulleys  440 B,  450 B. The second cable  490 B then extends toward the proximal end of the tool  400  and through the tool shaft  30 A. In some embodiments, the second cable  490 B winds at least partially around pulleys  450 B,  427 B,  420 B,  425 A and  440 A, as shown in  FIG. 13B . 
     In some embodiments, the second cable  490 B winds at least partially around two outer pulleys (e.g., pulleys  440 A,  425 A) and two inner pulleys (e.g., pulleys  450 B,  427 B). The second cable  490 B is shown in  FIG. 13B  slightly displaced from the pulleys to more clearly illustrate the routing of the second cable  490 B. 
       FIG. 14A  shows an embodiment of the proximal end of a tool that can be incorporated into tools described herein. The proximal end includes a motor pack  800 . In the illustrated embodiment, the motor pack  800  includes four motors (e.g., electric motors) which drive four independent cables, as previously discussed above. 
     In some embodiments, each of the four cables is controlled independently by a motor of the motor pack  800 . Advantageously, a tool with the motor pack  800 , where each of four cables is controlled by a motor of the pack  800  does not require pre-tensioning because the motors can take out any slack in the cable. Pre-tensioning is required due to the elastic properties of the cables which may cause slippage as the cables interact with pulleys in a cable-pulley system. Pre-tensioning is therefore compensated for by the design or by other methodologies in on-market tools. While the method of driving cables described in  FIGS. 5A-6D  requires only three motors to drive the cables, the systems utilize cable loops that may require pre-tensioning. 
     With continued reference to  FIG. 14A , the motor pack  800  can include a motor housing  840 . The motor pack  800  can include four motors retained within the motor housing  840 , only two of the motors  810 A,  810 B visible in  FIG. 14A . The four motors  810 A,  810 B,  810 C (not shown),  810 D (not shown) can be associated with gearboxes  815 A,  815 B,  815 C (not shown),  815 D (not shown), respectively. Each motor  810 A,  810 B,  810 C,  810 D can be associated with a spindle, such as spindle  820 , and each spindle  820  can have a mating interface  830  (e.g., a square aperture, hexagonal aperture, a slot). The motors  810 A,  810 B,  810 C,  810 D are driven under software control by drive units (not shown). The motor pack  840  can be attached to a proximal end of a tool, such as the proximal end  32  of the tool  30  shown in  FIG. 11 , or any other tool described herein. 
       FIG. 14B  shows one embodiment of a coupling unit  900  that can removably couple to the motor pack  800 . The coupling unit  900  can include a proximal end  906  and a distal end  905 . The mating interface  830  of each spindle  820  of the motor pack  800  shown in  FIG. 14A  can couple and/or mate with corresponding spindles in the coupling unit  900 , such as spindle  910 A. In  FIG. 14B , though only one spindle  910 A is visible, the coupling unit  900  can have a corresponding spindle for each of the mating interfaces  830  of the motor pack  800  (e.g., four spindles  910 A,  910 B,  910 C,  910 D, as shown in  FIG. 14C ) In one embodiment, the coupling unit  900  can be disposable. In another embodiment, any component distal to the motor pack  800 , including coupling unit  900 , tool shaft, wrist and end effector, can be disposable. Therefore, the motor pack  800 , which is typically the more expensive part of a tool, can be reusable since the coupling unit  900 , which can be incorporated into the proximal portion of the tool, can be easily detached and replaced with a new coupling unit  900  and associated tool shaft, wrist and end effector. This design advantageously provides for a sterile barrier. In other words, everything distal to the motor housing  840  including the coupling unit  900  may be sterile, and the coupling unit  900  can at least partially provide a sterile barrier. The motor housing  840 , the motors  810 A,  810 B,  810 C,  810 D and/or any component located within the motor pack  800  can be non-sterile. 
       FIGS. 14B-14D  further illustrate the coupling unit  900 . In one embodiment, the spindles  910 A,  910 B,  910 C,  910 D extend through the coupling unit  900  from the proximal end  906  to the distal end  905 . The coupling unit  900  can include four pulleys  940 A,  940 B,  940 C,  940 D. The coupling unit  900  can include four spools  945 A,  945 B,  945 C,  945 D mounted on the spindles  910 A,  910 B,  910 C,  910 D, as shown in  FIG. 14C . The pulleys  940 A,  940 B,  940 C,  940 D can feed cable to the spools  945 A,  945 B,  945 C,  945 D. The spools  945 A,  945 B,  945 C,  945 D can feed the cables to other components that drive the wrist and/or jaws of the tool, such as the wrist  402  and jaws  410 A,  410 B in  FIG. 12A . The spools  945 A,  945 B,  945 C,  945 D can also take up the slack in the cables. The pulleys  940 A,  940 B,  940 C,  940 D can be mounted to yokes  950 A,  950 B (not shown),  950 C (not shown),  950 D (not shown), as best shown in  FIG. 14D . 
     Referring now to  FIG. 14D , only yoke  950 A is shown, though as discussed above each of the pulleys  940 A,  940 B,  940 C,  940 D can be mounted to a yoke that is similar to the yoke  950 A. The yoke  950 A can couple to the pulley  940 A. The yokes  950 B,  950 C and  950 D can couple to the pulleys  940 B,  940 C and  940 D. The yokes  940 A,  940 B,  940 C,  940 D can be coupled to load cells  960 A,  960 B,  960 C,  960 D, and the load cells  960 A,  960 B,  960 C,  960 D can be coupled to the coupling unit  900 . 
     Each cable end is routed around one of the pulleys  940 A,  940 B,  940 C,  940 D and wound at least partially around a spool  945 A,  945 B,  945 C,  945 D. After winding around the spool  945 A,  945 B,  945 C,  945 D, the cable ends are secured to the spool  945 A,  945 B,  945 C,  945 D. In one embodiment, the spools  945 A,  945 B,  945 C,  945 D can each include a termination feature (e.g., a notch), such as the termination feature  975 A best shown in  FIG. 14E . Though only one termination feature  975 A is shown in  FIG. 14E , each of the spools  945 A,  945 B,  945 C,  945 D can have a termination feature (e.g., spools  945 B,  945 C,  945 D can have termination features  975 B,  975 C,  975 D, not shown, similar to termination feature  975 A). Each cable end may be retained within the termination feature  975 A,  975 B,  975 C,  975 D to prevent the cable end from disengaging the corresponding spool  945 A,  945 B,  945 C,  945 D. In one embodiment, the cable end can have a shape corresponding to a shape of the termination feature. 
     With reference to  FIG. 14D , the load cells  960 A,  960 B,  960 C,  960 D can include one or more sensors. For example, in one embodiment each load cell  960 A,  960 B,  960 C,  960 D can include a force sensor  970 A,  970 B,  970 C,  970 D. The force sensors  970 A,  970 B,  970 C,  970 D can measure the tension of the cable. When the cables are tensioned, the pulleys  940 A,  940 B,  940 C and  940 D transfer a force to the load cells  960 A,  960 B,  960 C,  960 D. This force can bend the load cells  960 A,  960 B,  960 C,  960 D, and said bending can be measured and converted to a measurement of tension. The measurements output by the force sensors  970 A,  970 B,  970 C,  970 D can provide haptic feedback to the operator of the tool. For example, the measurements output by the force sensors can be converted to haptic feedback for a surgeon giving him or her sense of the gripping force of the jaws of the tool (e.g., jaws  410 A,  410 B of tool  400 ). 
       FIG. 15  shows another embodiment of a tool. The tool  1200  can include a wrist  1202  that utilizes vertebrae instead of pulleys. On-market tools that utilize vertebrae utilize cable loops to control the bend of the wrist of the tool. In contrast, the tool  1200  can utilize independent cables instead of cable loops to control the position of the wrist  1202 . The advantages of this arrangement of the tool  1200  include that pre-tensioning and exact control of the length of the cable is not necessary. 
     The wrist  1202  of the tool  1200  can include one or more vertebra  1220 A,  1220 B,  1220 C. Although three vertebrae  1220 A,  1220 B,  1220 C are shown, the tool  1200  can have more or fewer vertebrae (e.g., one, two, three, four, five, six vertebrae etc.). The vertebra  1220 A can be coupled to the tool shaft  1210 . The vertebrae  1220 A,  1220 B,  1220 C can be coupled to other vertebrae and/or components of the tool  1200  via one or more joints  1240  (e.g., ball and socket joint). In the illustrated embodiment, the vertebrae  1220 A,  1220 B,  1220 C can be coupled to the distal end of the tool  1200 , as shown in  FIG. 15 . However, in other embodiments, one or more vertebra  1220 A,  1220 B,  1220 C can be located at any position along the longitudinal length of the tool  1200 . 
     With continued reference to  FIG. 15 , the tool  1200  can include one or more independent cables  1230 A,  1230 B,  1230 C, which can extend through the tool shaft  1210 . Although three cables  1230 A,  1230 B,  1230 C are shown, the tool  1200  can have more or fewer cables (e.g., one, two, three, four, five, six cables etc.). In one embodiment, additional cables can be used to drive the end effector  1250 . Each cable  1230 A,  1230 B,  1230 C is independently driven by a motor  1260 A,  1260 B,  1260 C. Since cable loops are not utilized in the tool  1200 , this design has the benefits described previously (e.g., no need for pre-tensioning of the cables). 
     The cables  1230 A,  1230 B,  1230 C can extend through the one or more vertebra  1220 A,  1220 B,  1220 C. In the illustrated embodiment, the cables  1230 A,  1230 B,  1230 C can couple to the vertebra  1220 A,  1220 B,  1220 C via one or more engagement mechanism  1270  (e.g. a bead, similar to bead  315 A in  FIG. 3A , that is crimped onto the cable and positioned inside a pocket in the vertebra). When a cable  1230 A,  1230 B,  1230 C is tensioned, the tension is transferred to the vertebra  1220 A,  1220 B,  1220 C) via the engagement mechanism  1270 . The components of the tools (e.g., vertebra  1220 A,  1220 B,  1220 C can be covered by a sheath (not shown)). Various other vertebrae and cable designs are possible. With the independent control of each cable end, it is possible to manipulate the end effector  1250  in any combination of pitch and yaw. 
       FIG. 16  shows another embodiment of a tool. The tool  1700  is similar to the tool shown  30  in  FIGS. 1A-3B . In some embodiments, it may be advantageous to uncouple the actuation of the jaws from the wrist of the tool. For example, decoupling the actuation of an end effector from the actuation of a wrist of a tool can inhibit transfer of loads from the end effector to the wrist (e.g., from the jaws of a grasper to pulleys of a wrist of a tool). Such loading of the wrist by the end effector may cause control of the wrist to become much more difficult and/or result in unpredictable movements of the wrist. 
     The tool  1700  can have a wrist  1702  and include one or more pulleys  1740  and one or more pulleys  1750 . The pulleys  1740  can be substantially similar to pulleys  340 A,  340 B,  350 A,  350 B shown in  FIG. 3A . The pulleys  1750  can be substantially similar to pulleys  320 A,  320 B shown in  FIG. 3A . For clarity, the cable routing for the pulleys  1740 ,  1750  is not shown. 
     In addition to the cables (not shown) that wind at least partially around the pulleys  1740 ,  1750 , the tool  1700  can include one or more additional cables  1730  for controlling the jaws  1760 A,  1760 B of an end effector  1760 , (e.g., grasper). Although one cable  1730  is shown, the tool  1700  can include any number of cables (e.g., one two, three, four, five, six cables, etc.). The cable  1730  can be retained within a sheath  1720 , which in one embodiment can be a flexible sheath. In the illustrated embodiment, the end effector  1760  (e.g., the jaws, the grasper) is coupled to the pulley  1750 . The cable  1730  can at least partially wind around the pulley  1750  and can control the end effector  1760  via the motion of the pulley  1750 . The cable  1730  can be coupled to an actuation mechanism for controlling the end effector  1760  via the pulley  1750 . The actuation mechanism that actuates the cable  1730  may be one or more pulleys (e.g., pulleys located near the base of the end effector  1760 ). In the illustrated embodiment, the end effector  1760 , including the jaws  1760 A,  1760 B, is decoupled from the pulleys  1740 , and therefore the end effector  1760  advantageously does not transfer a load to the pulleys  1740 . That is, the motion of the end effector  1760  is independent of the motion imparted on the pulleys  1740  by cables that wind about the pulleys  1740 . 
     As described in embodiments herein, the tool may have an elbow or bend. In order to maintain control of the tool, it may be important for the user (e.g., an operator, a surgeon) to know the shape of the tool. The flexible section of the tools described herein (e.g., flexible section  1305 ) can be coupled to one or more sensors (e.g., a plurality of sensors), where the sensors can transmit data based on the shape of the tool. In one embodiment, the data may be in real time. The data may be transmitted through a wired or wireless connection. 
     The one or more sensors can include various types of sensors (e.g., strain sensors, position sensors). The one or more sensors can be placed at any location on or within the tool and/or flexible section (e.g. coupled along the length of the tool, coupled to the flexible core, coupled to the vertebra). The sensors may be coupled to the tool using various techniques (e.g. biocompatible glue or adhesive). 
     In some embodiments, indirect ways of calculating the shape of the flexible section may be utilized. For example, the tension of the cables causing the bend may be monitored. If the relative tension of each of the cables responsible for causing the bend is known, then the bend may be estimated. Where no external forces pushing against the flexible section are present while the flexible section is bent, such monitoring of the tension on the cables causing the bend can provide an estimate of the shape of the bend. The estimate may be combined with data from the sensors to improve the estimation of the shape of the tool (e.g., the bend). 
     In some embodiments, a camera may monitor the shape of the tool. The camera may be a camera inserted into the body cavity of a patient. The camera may be positioned at any location to aid the user. The camera can send data related to the tool (e.g., images) to a processing unit (e.g., a processing unit of the hyperdexterous surgical system  5 ). The processing unit may further process the images and use pattern recognition techniques to recognize the flexible section of the tool. Once the flexible section is recognized, the parameters of the bend may be calculated based on the image. These parameters may be transmitted to a main processing unit responsible for maintaining control of the tool. 
       FIG. 17A  shows another embodiment of a tool. The tool  1800  can have a wrist  1802  and can include a housing  1811 .  FIGS. 17B-17C  shows the tool  1800  with the housing  1811  removed. The tool  1800  can include an end effector  1810  with a pair of jaws  1810 A,  1810 B. Other embodiments of end effectors can be utilized. The tool  1800  can include various pulleys, as shown in  FIG. 17B . 
     The pulleys  1845 A,  1845 B are arranged as a first set of pulleys. The pulleys  1850 A,  1850 B are arranged as a second set of pulleys. The first set of pulleys  1845 A,  1845 B and the second set of pulleys  1850 A,  1850 B can be coupled to a yoke  1812 , which can couple to a tool shaft (not shown). The tool can also include pulleys  1820 A,  1820 B,  1815 A,  1815 B arranged as a third set of pulleys. The jaws  1810 A,  1810 B can be coupled to the third set of pulleys  1815 A,  1815 B,  1820 A,  1820 B. In the illustrated embodiment, the jaw  1810 A is coupled to the pulleys  1815 A,  1815 B and the jaw  1810 B is coupled to the pulleys  1820 A,  1820 B. 
     The tool  1800  can also include pulleys  1835 A,  1835 B arranged as a fourth set of pulleys. The center of rotation of pulley  1835 A can be offset from the center of rotation of pulley  1835 B. In one embodiment, the pulley  1835 A can have a smaller diameter than the pulley  1835 B. The tool  1800  can also include pulleys  1840 A,  1840 B arranged as a fifth set of pulleys. The center of rotation of pulley  1840 A can be offset from the center of rotation of pulley  1840 B. The pulley  1840 A can have a smaller diameter than the pulley  1840 B. The pulleys  1835 A,  1840 B can be located on the same axis of rotation. The pulleys  1835 B,  1840 A can be located on the same axis of rotation. The center of rotation of the pulleys  1835 A,  1840 B can be offset from the center of rotation of the first set of pulleys  1845 A,  1845 B and the second set of pulleys  1850 A,  1850 B. The center of rotation of the pulleys  1835 B,  1840 A can be offset from the center of rotation of the first set of pulleys  1845 A,  1845 B and the second set of pulleys  1850 A,  1850 B. 
     With reference to  FIG. 17C , the pulleys  1825 A,  1825 B are arranged as a sixth set of pulleys. The pulleys  1830 A,  1830 B are arranged as a seventh set of pulleys. In the illustrated embodiment, the pulleys  1825 A,  1830 A are outer pulleys and the pulleys  1825 B,  1830 B are inner pulleys. The outer pulleys  1825 A,  1830 A can be smaller in diameter than the inner pulleys  1825 B,  1830 B. 
     The sixth set of pulleys  1825 A,  1825 B and the seventh set of pulleys  1830 A,  1830 B can align with the pair of jaws  1810 A,  1810 B and/or the third set of pulleys  1820 A,  1820 B,  1815 A,  1815 B. In some embodiments, the pulleys  1820 A,  1820 B,  1815 B,  1815 A aligns with the pulleys  1825 A,  1825 B,  1830 B,  1830 A, respectively, to thereby allow cables to extend along a straight path between the pulleys  1820 A,  1820 B,  1815 B,  1815 A and the pulleys  1825 A,  1825 B,  1830 B,  1830 A, respectively, thus advantageously reducing bends in the cables and friction between the cables and the pulleys. Other advantages of this arrangement are explained below. 
     The third set of pulleys  1815 A,  1815 B,  1820 A,  1820 B can have a large diameter (e.g., relative to the other pulleys in the tool  1800 ). In one embodiment, the diameter of the third set of pulleys  1815 A,  1815 B,  1820 A,  1820 B can have a diameter as large as (e.g., substantially equal to) the diameter of the tool shaft (not shown). The third set of pulleys  1815 A,  1815 B,  1820 A,  1820 B can be arranged close to each other and/or closer to the central axis of the tool shaft than the pulleys  320 A,  320 B of tool  30  shown in  FIG. 1A . The placement and the diameter size of the third set of pulleys  1815 A,  1815 B,  1820 A,  1820 B can advantageously increase the reliability and usable lifetime (e.g., less wear and tear) of the cables. Since larger pulleys have a larger diameter, cables that traverse larger pulleys bend less thus affecting the reliability in a positive way. The placement of the third set of pulleys  1815 A,  1815 B,  1820 A,  1820 B along with the placement of the other sets of pulleys ensures that the one or more cables of the tool  1800  experience fewer and less tight turns, again affecting the reliability and usable lifetime of the cables in a positive way. The placement and the diameter size of the third set of pulleys  1815 A,  1815 B,  1820 A,  1820 B is arranged to apply a larger force on jaws than the pulleys  320 A,  320 B shown in  FIG. 1A , since the cables experience fewer bends and less tight turns, thereby being able to apply larger forces on the jaws. 
     The tool  1800  can be actuated to move the jaws  1810 A,  1810 B in a variety of ways such as grasping (e.g., jaws rotating independently via pulleys  1815 A,  1815 B,  1820 A,  1820 B), yaw (e.g., jaws rotating together via pulleys  1815 A,  1815 B,  1820 A,  1820 B), and pitch (e.g., jaws rotating about axis  1813  through yoke  1812 ).  FIGS. 17D-17E  shows the cable routing of a first cable  1855 A of the tool  1800 . As discussed previously in other embodiments, four cables can be controlled independently to effect motion on the yoke  1812  and/or one or both of the jaws  1810 A,  1810 B. The independent control of each cable end may provide more accurate movement of the wrist  1802  (see  FIG. 17A ) and the end effector  1810 . The cable routing for  FIGS. 17D-17E  control jaw  1810 A. The tool  1800  utilizes four cables with four cable ends (similar to cables  390 A′,  390 A″,  390 B′,  390 B″ described herein). 
     Referring to  FIG. 17D , the first cable  1855 A originates from the tool shaft (not shown). The first cable  1855 A winds at least partially around one pulley in the first set of pulleys  1845 A,  1845 B. The first cable  1855 A then winds at least partially around one pulley in the fourth set of pulleys  1835 A,  1835 B. The first cable  1855 A then winds at least partially around one pulley in the sixth set of pulleys  1825 A,  1825 B. The first cable  1855 A then winds at least partially around one pulley in the third set of pulleys  1815 A,  1815 B,  1820 A,  1820 B. In some embodiments, the first cable  1855 A winds at least partially around the pulleys  1845 A,  1835 A,  1825 B,  1820 B, as shown in  FIG. 17D . The cable  1855 A can be immovably coupled to the pulley  1820 B (e.g., via crimping to a bead retained in a pocket of the pulley, such as the bead  315 A in  FIG. 3A ). In some embodiments, the first cable  1855 A winds at least partially around the inner pulleys  1820 B,  1825 B, and the outer pulley  1835 A,  1845 A. 
     Referring to  FIG. 17E , a second cable  1855 B originates from the tool shaft (not shown). The second cable  1855 B winds at least partially around one pulley in the second set of pulleys  1850 A,  1850 B. The second cable  1855 B then winds at least partially around one pulley in the fifth set of pulleys  1840 A,  1840 B. The second cable  1855 B then winds at least partially around one pulley in the sixth set of pulleys  1825 A,  1825 B. The second cable  1855 B then winds at least partially around one pulley in the third set of pulleys  1815 A,  1815 B,  1820 A,  1820 B. In some embodiments, the second cable  1855 B winds at least partially around the pulleys  1850 B,  1840 B,  1825 A,  1820 A, as shown in  FIG. 17E . In some embodiments, the second cable  1855 B winds at least partially around the outer pulleys  1820 A,  1825 A and the inner pulleys  1840 B,  1850 B. 
     With reference to  FIGS. 17D-17E , if only one cable is actuated or tensioned, the jaw will rotate in one direction, and if the other cable is actuated or tensioned, the jaw will rotate in an opposite direction. Additionally, the amount of tension placed on the cables can control the position of the jaws  1810 A,  1810 B. For example, the cable  1855 A shown in  FIG. 17D  is tensioned in the direction of arrow  1860  and the cable  1855 B is relaxed. The jaw  1810 A will thus move in the direction of the arrow  1862 . If instead the cable  1855 B is tensioned in the direction of arrow  1865 , the jaw  1810 A will move in the direction of the arrow  1867 . If both cables are tensioned at the same time, the third set of pulleys  1815 A,  1815 B,  1820 A,  1820 B do not rotate. Rather, the third set of pulleys  1815 A,  1815 B,  1820 A,  1820 B move in a motion as shown by the arrow  1870 , into the plane of the paper (i.e., about axis  1813  of yoke  1812 , as shown in  FIG. 17A ). 
     Another pair of cables can be coupled to the jaw  1810 B in a similar manner as cables  1855 A,  1855 B are coupled to jaw  1810 A. The action of pulling said other set of cables attached to the jaw  1810 B is not explained as it is similar to the above explanation for cables  1855 A,  1855 B. From the above explanation it can be seen how the motion of the jaws  1810 A,  1810 B can in one embodiment be controlled with four independent cables. 
       FIG. 18A  shows another embodiment of a tool. The tool  1900  can have a wrist  1902  and end effector  1901  that includes two jaws  1901 A,  1901 B. The tool  1900  can include a yoke  1910  coupled to a tool shaft  1915 .  FIG. 18B  shows the yoke  1910  removed. The tool  1900  can include a first set of pulleys  1930 A,  1930 B. The tool  1900  can also include a second set of pulleys  1935 A,  1935 B. The axis of rotation of the first set of pulleys  1930 A,  1930 B can be aligned with the axis of rotation of the second set of pulleys  1935 A,  1935 B. The tool  1900  can include a third set of pulleys  1905 A,  1905 B. The jaws  1901 A,  1901 B can be coupled third set of pulleys  1905 A,  1905 B. 
     The tool  1900  can include a fourth set of pulleys  1920 A,  1920 B, and can include a fifth set of pulleys  1925 A,  1925 B. The fourth set of pulleys  1920 A,  1920 B can be located on one side of the tool  1900  and fifth set of pulleys  1925 A,  1925 B can be located on the other side of the tool  1900 . The axis of rotation of the fourth set of pulleys  1920 A,  1920 B can be aligned with the axis of rotation of the fifth set of pulleys  1925 A,  1925 B. 
     The tool  1900  can additionally include a sixth set of pulleys  1910 A,  1910 B and a seventh set of pulleys  1915 A,  1915 B. The sixth set of pulleys  1910 A,  1910 B can be located on one side of the tool  1900  and seventh set of pulleys  1915 A,  1915 B can be located on the other side of the tool  1900 . The sixth and seventh sets of pulleys are offset pulleys because the center of rotation of the sixth set of pulleys  1910 A,  1910 B is offset from the center of rotation of the seventh set of pulleys  1915 A,  1915 B. 
     The tool  1900  can be actuated to move the jaws  1905 A,  1905 B in a variety of ways such as grasping (e.g., jaws rotating independently via pulleys  1905 A,  1905 B), yaw (e.g., jaws rotating together via pulleys  1905 A,  1905 B), and pitch (e.g., jaws rotating about axis  1913  of yoke  1910  shown into plane of paper in  FIG. 18A ).  FIG. 18D  shows the routing of a first cable  1950 A and a second cable  1950 B. For clarity, the first cable  1950 A is shown in a dashed line and the second cable  1950 B is shown in a solid line. The first cable  1950 A originates from the tool shaft  1915 . The first cable  1950 A winds at least partially around one pulley in the first set of pulleys  1930 A,  1930 B. The first cable  1950 A then winds at least partially around one pulley in the fourth set of pulleys  1920 A,  1920 B. The first cable  1950 A then winds at least partially around one pulley in the sixth set of pulleys  1910 A,  1910 B. The first cable  1950 A then winds at least partially around one pulley in the third set of pulleys  1905 A,  1905 B. In some embodiments, the first cable  1950 A winds at least partially around the pulley  1905 A, the outer pulley  1910 A, the outer pulley  1920 A, and the outer pulley  1930 A. The cable  1950 A can be immovably coupled to the pulley  1905 A (e.g., via crimping to a bead retained in a pocket of the pulley, such as the bead  315 A in  FIG. 3A ). 
     The second cable  1950 B also originates from the tool shaft  1915 . The second cable  1950 B winds at least partially around one pulley in the first set of pulleys  1930 A,  1930 B. The second cable  1950 B then winds at least partially around one pulley in the fourth set of pulleys  1920 A,  1920 B. The second cable  1950 B then winds at least partially around one pulley in the third set of pulleys  1905 A,  1905 B. In some embodiments, the second cable  1950 B winds at least partially around the pulley  1905 B, inner pulley  1920 B, and inner pulley  1930 B. The second cable  1950 B does not wind around one pulley in the sixth set of pulleys  1910 A,  1910 B. The cable  1950 B can be immovably coupled to the pulley  1905 B (e.g., via crimping to a bead retained in a pocket of the pulley, such as the bead  315 A in  FIG. 3A ). The cables  1950 A,  1950 B extend toward the proximal end of the tool  1900 . 
     The jaw  1910 A is coupled to pulley  1905 A, and the jaw  1901 B is coupled to pulley  1905 B. The first cable  1905 A can couple to the pulley  1905 A and control jaw  1901 A. The second cable can couple to the pulley  1905 B and control the jaw  1901 B. Another pair of cables ( 1905 C,  1905 D) can extend along the opposite side of the pulleys and can couple to the pulleys  1905 A and  1905 B, and the cable routing would have the same configuration shown in  FIGS. 18D-18E , except the cables would wind at least partially around pulleys  1915 A,  1915 B. In some embodiments, the cables  1905 A and  1905 C are integral and form a single cable. In some embodiments, the cables  1905 B and  1905 D are integral and form a single cable. The action of pulling said other set of cables (e.g.,  1905 C,  1905 D) is not explained as it is similar to the above explanation for cables  1950 A,  1950 B. 
     From the above explanation it can now be seen how the motion of the jaws  1901 A,  1901 B may be controlled with four independent cables (e.g., four independent cable ends). The cables  1950 A,  1950 B,  1950 C,  1950 D, can be coupled to the pulleys  1905 A,  1905 B with an engagement mechanism (e.g. via crimping to a bead retained in a pocket of the pulley, such as the bead  315 A in  FIG. 3A ). 
     For example, the cable  1950 A is tensioned and the other cables are relaxed. The jaw  1901 A will move according to the tension that is experienced by the third set of pulleys  1905 A,  1905 B. When both sides of the pulley  1905 A are tensioned (e.g., if there are two independent cables, when both cables are tensioned at the same time), the wrist moves in the direction of arrow  1960  as shown in  FIG. 18E . When both sides of pulley  1905 B are tensioned (e.g., if there are two independent cables, when both cables are tensioned at the same time), the wrist moves in the direction of arrow  1965  as shown in  FIG. 18D . From the above explanation it can now be seen how the motion of the jaws  1901 A,  1901 B may be controlled with four cables (e.g., four independent cables having four independent cable ends, or two cables having four independent cable ends). 
     While certain embodiments have been described herein, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the systems and methods described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure. Accordingly, the scope of the present inventions is defined only by reference to the appended claims. 
     Features, materials, characteristics, or groups described in conjunction with a particular aspect, embodiment, or example are to be understood to be applicable to any other aspect, embodiment or example described in this section or elsewhere in this specification unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The protection is not restricted to the details of any foregoing embodiments. The protection extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 
     Furthermore, certain features that are described in this disclosure in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations, one or more features from a claimed combination can, in some cases, be excised from the combination, and the combination may be claimed as a subcombination or variation of a subcombination. 
     Moreover, while operations may be depicted in the drawings or described in the specification in a particular order, such operations need not be performed in the particular order shown or in sequential order, or that all operations be performed, to achieve desirable results. Other operations that are not depicted or described can be incorporated in the example methods and processes. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the described operations. Further, the operations may be rearranged or reordered in other implementations. Those skilled in the art will appreciate that in some embodiments, the actual steps taken in the processes illustrated and/or disclosed may differ from those shown in the figures. Depending on the embodiment, certain of the steps described above may be removed, others may be added. Furthermore, the features and attributes of the specific embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure. Also, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described components and systems can generally be integrated together in a single product or packaged into multiple products. 
     For purposes of this disclosure, certain aspects, advantages, and novel features are described herein. Not necessarily all such advantages may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the disclosure may be embodied or carried out in a manner that achieves one advantage or a group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein. 
     Conditional language, such as “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and/or steps are included or are to be performed in any particular embodiment. 
     Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z. Thus, such conjunctive language is not generally intended to imply that certain embodiments require the presence of at least one of X, at least one of Y, and at least one of Z. 
     Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, “generally,” and “substantially” may refer to an amount that is within less than 10% of, within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of the stated amount. As another example, in certain embodiments, the terms “generally parallel” and “substantially parallel” refer to a value, amount, or characteristic that departs from exactly parallel by less than or equal to 15 degrees, 10 degrees, 5 degrees, 3 degrees, 1 degree, 0.1 degree, or otherwise. 
     The scope of the present disclosure is not intended to be limited by the specific disclosures of preferred embodiments in this section or elsewhere in this specification, and may be defined by claims as presented in this section or elsewhere in this specification or as presented in the future. The language of the claims is to be interpreted broadly based on the language employed in the claims and not limited to the examples described in the present specification or during the prosecution of the application, which examples are to be construed as non-exclusive.