Abstract:
The present invention provides a robotic surgical tool for use in a robotic surgical system to perform a surgical operation. The robotic surgical tool includes a wrist mechanism disposed near the distal end of a shaft which connects with an end effector. The wrist mechanism includes a distal member configured to support the end effector, and a plurality of rods extending generally along an axial direction within the shaft and movable generally along this axial direction to adjust the orientation of the distal member with respect to the shaft. Advancement or retraction of a first rod generally along the axial direction tips the base through a first angle. The addition of a second angle allows the distal member to direct the end effector in essentially a compound angle. The robotic surgical tool may also include provisions for roll movement.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 10/758,050, filed on Jan. 14, 2004, now U.S. Pat. No. 7,066,926, which is a continuation of U.S. patent application Ser. No. 10/186,176, filed on Jun. 28, 2002, now U.S. Pat. No. 6,699,235, which was based on and claimed the benefit of U.S. Provisional Patent Application No. 60/301,967, filed Jun. 29, 2001, and U.S. Provisional Patent Application No. 60/327,702, filed Oct. 5, 2001, the entire disclosures of which are incorporated herein by reference. 
     This application is related to the following patents and patent applications, the full disclosures of which are incorporated herein by reference: 
     PCT International Application No. PCT/US98/19508, entitled “Robotic Apparatus”, filed on Sep. 18, 1998, and published as WO99/50721; 
     U.S. patent application Ser. No. 09/418,726, entitled “Surgical Robotic Tools, Data Architecture, and Use”, filed on Oct. 15, 1999; 
     U.S. Patent Application No. 60/111,711, entitled “Image Shifting for a Telerobotic System”, filed on Dec. 8, 1998; 
     U.S. patent application Ser. No. 09/378,173, entitled “Stereo Imaging System for Use in Telerobotic System”, filed on Aug. 20, 1999; 
     U.S. patent application Ser. No. 09/398,507, entitled “Master Having Redundant Degrees of Freedom”, filed on Sep. 17, 1999; 
     U.S. application Ser. No. 09/399,457, entitled “Cooperative Minimally Invasive Telesurgery System”, filed on Sep. 17, 1999; 
     U.S. patent application Ser. No. 09/373,678, entitled “Camera Referenced Control in a Minimally Invasive Surgical Apparatus”, filed on Aug. 13, 1999; 
     U.S. patent application Ser. No. 09/398,958, entitled “Surgical Tools for Use in Minimally Invasive Telesurgical Applications”, filed on Sep. 17, 1999; and 
     U.S. Pat. No. 5,808,665, entitled “Endoscopic Surgical Instrument and Method for Use”, issued on Sep. 15, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to surgical tools and, more particularly, to various wrist mechanisms in surgical tools for performing robotic surgery. 
     Robotic surgery has developed to improve and expand the use of minimally invasive surgical (MIS) techniques in the treatment of patients. Minimally invasive techniques are aimed at reducing the amount of extraneous tissue that is damaged during diagnostic or surgical procedures, thereby reducing patient recovery time, discomfort, and deleterious side effects. The average length of a hospital stay for a standard surgery may also be shortened significantly using MIS techniques. Thus, an increased adoption of minimally invasive techniques could save millions of hospital days and millions of dollars annually in hospital residency costs alone. Patient recovery times, patient discomfort, surgical side effects and time away from work may also be reduced with minimally invasive surgery. 
     The most common form of minimally invasive surgery may be endoscopy. And, probably the most common form of endoscopy is laparoscopy, which is minimally invasive inspection and surgery inside the abdominal cavity. In standard laparoscopic surgery, a patient&#39;s abdomen is insufflated with gas, and cannula sleeves are passed through small (approximately ½ inch) incisions to provide entry ports for laparoscopic surgical instruments. The laparoscopic surgical instruments generally include a laparoscope (for viewing the surgical field) and working tools. The working tools are similar to those used in conventional (open) surgery, except that the working end or end effector of each tool is separated from its handle by an extension tube. As used herein, the term “end effector” means the actual working part of the surgical instrument and can include clamps, graspers, scissors, staplers, and needle holders, for example. To perform surgical procedures, the surgeon passes these working tools or instruments through the cannula sleeves to an internal surgical site and manipulates them from outside the abdomen. The surgeon monitors the procedure by means of a monitor that displays an image of the surgical site taken from the laparoscope. Similar endoscopic techniques are employed in, e.g., arthroscopy, retroperitoneoscopy, pelviscopy, nephroscopy, cystoscopy, cisternoscopy, sinoscopy, hysteroscopy, urethroscopy and the like. 
     There are many disadvantages relating to current MIS technology. For example, existing MIS instruments deny the surgeon the flexibility of tool placement found in open surgery. Most current laparoscopic tools have rigid shafts, so that it can be difficult to approach the worksite through the small incision. Additionally, the length and construction of many endoscopic instruments reduces the surgeon&#39;s ability to feel forces exerted by tissues and organs on the end effector of the associated tool. The lack of dexterity and sensitivity of endoscopic tools is a major impediment to the expansion of minimally invasive surgery. 
     Minimally invasive telesurgical robotic systems are being developed to increase a surgeon&#39;s dexterity when working within an internal surgical site, as well as to allow a surgeon to operate on a patient from a remote location. In a telesurgery system, the surgeon is often provided with an image of the surgical site at a computer workstation. While viewing a three-dimensional image of the surgical site on a suitable viewer or display, the surgeon performs the surgical procedures on the patient by manipulating master input or control devices of the workstation. The master controls the motion of a servomechanically operated surgical instrument. During the surgical procedure, the telesurgical system can provide mechanical actuation and control of a variety of surgical instruments or tools having end effectors such as, e.g., tissue graspers, needle drivers, or the like, that perform various functions for the surgeon, e.g., holding or driving a needle, grasping a blood vessel, or dissecting tissue, or the like, in response to manipulation of the master control devices. 
     Manipulation and control of these end effectors is a critical aspect of robotic surgical systems. For these reasons, it is desirable to provide surgical tools which include mechanisms to provide three degrees of rotational movement of an end effector around three perpendicular axes to mimic the natural action of a surgeon&#39;s wrist. Such mechanisms should be appropriately sized for use in a minimally invasive procedure and relatively simple in design to reduce possible points of failure. In addition, such mechanisms should provide adequate degree of rotation to allow the end effector to be manipulated in a wide variety of positions. At least some of these objectives will be met by the inventions described hereinafter. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a robotic surgical tool for use in a robotic surgical system to perform a surgical operation. Robotic surgical systems perform surgical operations with tools which are robotically operated by a surgeon. Such systems generally include master controllers and a robotic arm slave cart. The robotic arm slave cart is positioned adjacent to the patient&#39;s body and moves the tools to perform the surgery. The tools have shafts which extend into an internal surgical site within the patient body via minimally invasive access openings. The robotic arm slave cart is connected with master controllers which are grasped by the surgeon and manipulated in space while the surgeon views the procedure on a stereo display. The master controllers are manual input devices which preferably move with six degrees of freedom, and which often further have an actuatable handle for actuating the tools (for example, for closing grasping saws, applying an electrical potential to an electrode, or the like). Robotic surgery systems and methods are further described in co-pending U.S. patent application Ser. No. 08/975,617, filed Nov. 21, 1997, the full disclosure of which is incorporated herein by reference. 
     As described, robotic surgical tools comprise an elongated shaft having a surgical end effector disposed near the distal end of the shaft. As used herein, the terms “surgical instrument”, “instrument”, “surgical tool”, or “tool” refer to a member having a working end which carries one or more end effectors to be introduced into a surgical site in a cavity of a patient, and is actuatable from outside the cavity to manipulate the end effector(s) for effecting a desired treatment or medical function of a target tissue in the surgical site. The instrument or tool typically includes a shaft carrying the end effector(s) at a distal end, and is preferably servomechanically actuated by a telesurgical system for performing functions such as holding or driving a needle, grasping a blood vessel, and dissecting tissue. In addition, as used herein, “end effector” refers to the actual working part that is manipulable for effecting a predetermined treatment of a target tissue. For instance, some end effectors have a single working member such as a scalpel, a blade, or an electrode. Other end effectors have a pair or plurality of working members such as forceps, graspers, scissors, or clip appliers, for example. 
     In a first aspect of the present invention, the robotic surgical tool includes a wrist mechanism disposed near the distal end of the shaft which connects with the end effector. The wrist mechanism includes a distal member, configured to support the end effector, and a plurality of rods extending generally along an axial direction within the shaft and movable generally along this axial direction to adjust the orientation of the distal member with respect to the axial direction or shaft. The distal member may have any form suitable for supporting an end effector. In most embodiments, the distal member has the form of a clevis. In any case, the distal member has a base to which the rods are rotatably connected. 
     Advancement or retraction of a first rod generally along the axial direction tips the base through a first angle so that the distal member faces a first articulated direction. The first angle may be any angle in the range of 0-90 degrees and oriented so that the first articulated direction is any direction that is not parallel to the axial direction. This would allow the distal member to direct an end effector in any direction in relation to the shaft of the surgical tool. In most embodiments, the first angle is greater than approximately 30 degrees. In some embodiments, the first angle is greater than approximately 60 degrees and in other embodiments the first angle is greater than approximately 70 degrees. This first angle may represent the pitch or the yaw of the wrist mechanism. 
     In some embodiments, advancement or retraction of a second rod generally along the axial direction tips the base through a second angle so that the distal member faces a second articulated direction. The second angle may also be any angle in the range of 0-90 degrees and oriented so that the second articulated direction is any direction that is not parallel to the axial direction. The addition of a second angle would allow the distal member to direct an end effector in essentially a compound angle or in a second articulated direction in relation to the shaft of the surgical tool. In most embodiments, the second angle is greater than approximately 30 degrees. In some embodiments, the second angle is greater than approximately 60 degrees and in other embodiments the second angle is greater than approximately 70 degrees. If the first angle represents the pitch of the wrist mechanism, the second angle may represent the yaw of the wrist mechanism and vice versa. 
     The plurality of rods may comprise two, three, four or more rods. In preferred embodiments, three or four rods are used to provide both pitch and yaw angulation. When four rods are used, the first and second rods are positioned adjacent to each other and the remaining two rods are located in positions diametrically opposite to the first and second rods. The four rods are generally arranged symmetrically around a central axis of the shaft or the axial direction. When the first rod is advanced, the diametrically opposite rod is simultaneously retracted. Likewise, when the first rod is retracted, the diametrically opposite rod is simultaneously advanced. This is similarly the case with the second rod and its diametrically opposite rod. Thus, the rods actuate in pairs. Such actuation will be further described in a later section. 
     To maintain desired positioning of the rods, some embodiments include a guide tube having a plurality of guide slots. Each guide slot is shaped for receiving and guiding one of the plurality of rods substantially along the axial direction. In some embodiments, the rods are shaped so as to have a rectangular cross-section. In these instances, the corresponding guide slots also rectangular in shape to receive and maintain proper orientation of the rods. 
     In a second aspect of the present invention, the robotic surgical tool includes a tool base disposed near the proximal end of the shaft. The tool base includes mechanisms for actuating the wrist mechanism and often mechanisms for actuating the end effector. Mechanisms for actuating the wrist mechanism includes mechanisms for advancing or retracting the first rod. In some embodiments, such mechanisms comprises a first rotational actuation member to which the first rod is attached so that rotation of the first rotational actuation member advances or retracts the first rod. Typically, another rod is attached to the first rotational actuation member in a position diametrically opposite to the first rod so that rotation of the first rotational actuation member simultaneously advances the first rod and retracts the diametrically opposite rod. In some embodiments, the tool base further comprises a second rotational actuation member to which the second rod is attached so that rotation of the second rotational actuation member advances or retracts the second rod substantially along the axial direction. Again, another rod is often attached to the second rotational actuation member in a position diametrically opposite to the second rod so that rotation of the second rotational actuation member simultaneously advances the second rod and retracts the diametrically opposite rod. Thus, by rotating the first and second rotational actuation members, the distal member is tipped through two angles, or a compound angle, so that the distal member faces any desired direction. This allows refined control of the end effector throughout three dimensions. 
     The robotic surgical tool of the present invention may also include provisions for roll movement. Roll movement is achieved by rotating the shaft around its central axis. Since the shaft is connected to a guide tube through which the plurality of rods pass, rotation of the shaft rotates guide tube which in turn rotates the rods around the central axis which is parallel to the axial direction. To actuate such roll, the above described tool base comprises a roll pulley which rotates the shaft. Since the rods extend through the roll pulley and attach to the rotational actuation members, such rotation is possible by flexing of the rods. Due to the length, thickness and flexibility of the rods, 360 degree rotation is possible. Thus, pitch, yaw and roll movement can be individually actuated by the tool base, particularly by manipulation of the rotational actuation members and roll pulley. 
     Although actuation of the wrist mechanism is achieved by manipulation of the rods, it is the connection of the rods to the base which allows tipping and manipulation of the distal member to face a desired direction. Such connection is achieved with the use of a plurality of linkages, each linkage connecting one of the plurality of rods with the base. In some embodiments, the linkages comprise orthogonal linkage assemblies. Each orthogonal linkage assembly rotatably connects one of the plurality of rods with the base to allow the base to be rotated in at least two directions with respect to the axial direction. In some embodiments, each orthogonal linkage assembly comprises an orthogonal linkage having a first link portion which is rotatably connectable with the one of the plurality of rods and a second link portion which is rotatably connectable with the base and wherein the first link portion and the second link portion lie in orthogonal planes. In other embodiments, each orthogonal linkage assembly comprises a linkage fastener having a link base portion which is rotatably connectable with one of the plurality of rods and a cylindrical fastening end portion which is rotatably connectable with the base. The different orthogonal linkage assemblies allow the base to be rotated to different degrees of angularity relative to the axial direction. 
     Such rotation is assisted by flexibility of the rods. Generally, each rod is flexible in at least one direction. For example, when each rod has a rectangular cross-section, having a wide side and a narrow side, the rod may be flexible along the wide side yet rigid along the narrow side. When the rods are arranged so that the wide sides are parallel to the perimeter of the shaft, flexibility along the wide sides allows each rod to bend slightly inward, toward the center of the shaft or the longitudinal axis. This allows greater rotation of the distal member and flexibility in design parameters. 
     In a third aspect of the present invention, methods of actuating the robotic surgical tool are provided. In some embodiments, methods include providing a robotic surgical tool comprising a wrist mechanism, which includes a distal member coupleable with a surgical end effector and having a base and a plurality of rods rotatably connected to the base and extending along an axial direction, and actuating the wrist by manipulating a first rod of the plurality of rods to tip the base through a first angle so that the distal member faces a first articulated direction. Manipulating typically comprises advancing or retracting the first rod. As previously mentioned, advancing or retracting may comprise rotating a first rotational actuation member to which the first rod is attached. Likewise, actuating the wrist may further comprises manipulating a second rod of the plurality of rods to tip the base through a second angle so that the distal member faces a second articulated direction. Again, advancing or retracting may comprise rotating a second rotational actuation member to which the second rod is attached. 
     In some embodiments, methods further comprise actuating the wrist by rotating the plurality of rods around a longitudinal axis parallel to the axial direction to rotate the base. In some embodiments, rotating the plurality of rods comprises rotating a roll pulley through which the plurality of rods extend. And, lastly, methods may further comprise coupling the end effector to the base and actuating the end effector. 
     Other objects and advantages of the present invention will become apparent from the detailed description to follow, together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective overall view of an embodiment of the surgical tool of the present invention. 
         FIGS. 2A-2B  illustrate exemplary surgical end effectors. 
         FIG. 3  illustrates an embodiment of a wrist mechanism. 
         FIGS. 3A-3B  illustrate possible arrangements of guide slots within the guide tube. 
         FIGS. 3C-3D  illustrate connection of rods to the distal member via orthogonal linkages. 
         FIG. 4  illustrates movement of the wrist mechanism through a compound angle. 
         FIG. 5  illustrates tipping in a variety of directions including a combinations of pitch and yaw. 
         FIGS. 6A-6F  illustrate three different embodiments of the wrist mechanism of the present invention. 
         FIG. 7  illustrates assemblage of the first main embodiment of the wrist mechanism. 
         FIGS. 8-9  illustrate joining of a rod with an orthogonal linkage and then joining of the linkage with a foot on the distal clevis. 
         FIG. 10  illustrates joining of additional rods to the distal clevis. 
         FIG. 11A  illustrates the first main embodiment of the wrist mechanism wherein four rods are attached.  FIG. 11B  is a cross-sectional view of  FIG. 11A . 
         FIG. 12  illustrates assemblage of the second main embodiment of the wrist mechanism. 
         FIG. 13  illustrates joining of a rod with a linkage fastener and for later joining with a distal clevis half. 
         FIG. 14  illustrates joining rods with corresponding apertures on the first and second clevis halves with the use of linkage fasteners. 
         FIGS. 15-16  show mating of the clevis halves and joining with a clevis tip. 
         FIG. 17A  illustrates the second main embodiment of the wrist mechanism wherein four rods are attached.  FIG. 17B  is a cross-sectional view of  FIG. 17A . 
         FIG. 18  is a perspective view of an embodiment of the wrist mechanism showing rods inserted through a guide tube. 
         FIG. 19  illustrates tipping of the distal clevis in response to advancement and/or retraction of one or more rods. 
         FIG. 20  illustrates assemblage of the third main embodiment of the wrist mechanism. 
         FIGS. 21-22  illustrate joining of a rod with an linkage fastener and then joining linkage fastener with a foot on the distal clevis. 
         FIG. 23A  illustrates the third main embodiment of the wrist mechanism wherein four rods are attached.  FIG. 23B  is a cross-sectional view of  FIG. 23A . 
         FIG. 24  illustrates tipping of the distal clevis in response to advancement and/or retraction of one or more rods. 
         FIG. 25  illustrates joining of a rod with a wire to create a wire/rod assembly. 
         FIG. 26  illustrates inserting the wire/rod assembly through a roll pulley within the tool base. 
         FIG. 27  illustrates additional features of the tool base, including rotational actuation members. 
         FIG. 28  is a side view illustrating insertion of the wire through a crosshole in a pivot pin which is mounted in a sector gear. 
         FIG. 29  is a side view illustrating crimping of a crimp onto the wire to maintain positioning of the rod against the pivot pin. 
         FIG. 30  is a top perspective view of the tool base, including mechanisms to manipulate the rods to actuate the wrist mechanism. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a surgical tool  50  of the present invention which is used in robotic surgery systems. The surgical tool  50  includes a rigid shaft  52  having a proximal end  54 , a distal end  56  and a longitudinal axis therebetween. The proximal end  54  is coupled to a tool base  62 . The tool base  62  includes an interface  64  which mechanically and electrically couples the tool  50  to a manipulator on the robotic arm cart. A distal member, in this embodiment a distal clevis  58 , is coupled to shaft  52  by a wrist joint or wrist mechanism  10 , the wrist mechanism  10  providing the distal clevis  58  with at least 1 degree of freedom and ideally providing at least 3 degrees of freedom. The distal clevis  58  supports a surgical end effector  66 , the actual working part that is manipulable for effecting a predetermined treatment of a target tissue. Exemplary surgical end effectors  66  are illustrated in  FIGS. 2A-2B . Grasping jaws  70  are illustrated in  FIG. 2A , while a cautery isolation effector  72  is illustrated in  FIG. 2B . It may be appreciated however that any suitable end effector  66  may be used, such as DeBakey forceps, microforceps, Potts scissors, clip appliers, scalpels or electrocautery probes, to name a few. The end effectors  66  can be permanently attached or be removable and optionally replaceable with a different type of end effector  66  depending on the surgical need. 
     The end effector  66  is manipulated by the wrist mechanism  10  to provide the ability of continuous movement in a wide range of angles (in roll, pitch and yaw) relative to an axial direction or the longitudinal axis  51  of the shaft  52 . An embodiment of the wrist mechanism  10  is illustrated in  FIGS. 3 ,  3 A- 3 D. Referring to  FIG. 3 , the wrist joint or mechanism  10  comprises a distal member  12  connected with a plurality of rods  14  via a plurality of orthogonal linkages  16 . Movement of the distal member  12  is directly translated to the surgical end effector  66 . In this embodiment, the distal member  12  has the shape of a disk and includes a plurality of feet  18  with apertures  17  which are connected to the orthogonal linkages  16 . There are at least three rods, and more desirably four rods  14  as shown in  FIG. 3 . The rods  14  extend through a guide tube  20  within the shaft  52  (not shown in  FIG. 3 ) which guides and supports the rods  14 .  FIG. 3A  shows the guide tube  20  having four guide slots  30  for receiving the four rods  14 .  FIG. 3B  shows a guide tube  20 ′ having three guide slots  30 ′ for receiving three rods in a different embodiment. The guide slots  30  or  30 ′ are evenly distributed in a generally circular pattern to allow the rods  14  to manipulate and orient the distal member  12  in different directions in a generally continuous manner. 
     As the rods  14  are slid up and down the guide slots  30  of the guide tube  20 , the orthogonal linkages  16  transfer the motion to the distal member  12 . The rods  14  are configured to flex in one plane and be stiff in another plane. In the embodiment shown, the rods  14  are flattened to have a rectangular cross-section with a wide face and a narrow width. The rods  14  can flex along the wide face and remain stiff along the narrow width. Referring to  FIGS. 3A-3B , the rods  14  can flex toward or away from the center or central axis of the guide tube  20 ,  20 ′ but remain stiff in terms of side-to-side movement along the perimeter of the guide tube  20 ,  20 ′. 
     The rods  14  include apertures  19  near their distal ends which connect the rods  14  to the distal member  12  via orthogonal linkages  16 . Each orthogonal linkage  16  has a first link portion  22  and a second link portion  24  which are oriented in an orthogonal manner, as illustrated in  FIGS. 3C-3D . The first link portion  22  includes a first aperture and the second link portion  24  includes a second aperture which is perpendicular in orientation with respect to the first aperture. The second link portion  24  is rotatably coupled to the distal end of the rod  14  by a fastener  26  extending through the apertures of the second link portion  24  and the distal end of the rod  14 . The first link portion  22  is rotatably coupled to the feet  18  of the distal member  12  by a fastener  28  extending through the apertures of the first link portion  22  and the feet  18 . Because each orthogonal linkage  16  allows relative movement between the rod  14  and the distal member  12  in two orthogonal directions, the distal member  12  can be articulated to move continuously to have orientation in a wide range of angles (in roll, pitch, and yaw) relative to the axial direction of the guide tube  20 . 
     When a first rod is extended generally along the axial direction, the distal member or clevis will be tipped through a first angle. Likewise, when a second rod is extended generally along the axial direction, the distal member or clevis will be tipped through a second angle creating a compound angle. An example of this movement is shown in a simplified illustration in  FIG. 4 . Here, distal clevis  58  is shown in dashed line having been tipped through a first angle  39  so that the clevis  58  faces a first articulated direction  41 . For clarity, the axial direction  37  is aligned with the y-axis and the first articulated direction  41  aligned with the z-axis so that the first angle  39  is formed in a y-z plane. The distal clevis  58  is then tipped through a second angle  43  so that the clevis  58  faces a second articulated direction  45 . The second angle  43  is formed in an x-z plane. In this illustration, the first angle  39  represents the pitch and the second angle  43  represents the yaw. 
     Generally, the range of angles through which the distal member  12  can be articulated varies depending on the combination of pitch and yaw movement. For example,  FIG. 5  illustrates a top view of the distal member  12  showing a first rod connection point  500 , a second rod connection point  502 , a third rod connection point  504  and a fourth rod connection point  506 . In this example, a movement of pure pitch would involve rotating the distal member  12  around the y-axis or tipping the distal member toward the x direction or −x direction. This is achieved by advancement of a second rod and corresponding second rod connection point  502  and retraction of a fourth rod and corresponding fourth rod connection point  506 , or vice versa. Likewise, in this example, a movement of pure yaw would involve rotating the distal member  12  around the x-axis or tipping the distal member toward the y direction or −y direction. This is achieved by advancement of a first rod and corresponding first rod connection point  500  and retraction of a third rod and corresponding third rod connection point  504 , or vice versa. In pure pitch or pure yaw, the distal member  12  can be tipped through angles up to approximately 90 degrees. 
     However, when the distal member  12  is oriented to face a direction between pure pitch and pure yaw, additional challenges arise in achieving full rotation. In particular, the most challenging position occurs when tipping the distal member toward an m direction midway between the x direction and the y direction which would involve approximately equal portions of pitch and yaw. This would similarly be the case for tipping toward an m′, m″ or m′″ direction as shown in  FIG. 5 . In these positions, different variations in the wrist mechanism  10  design allow movement of the distal member through different ranges of angles. For example, three different embodiments of the wrist mechanism  10  are shown in  FIGS. 6A-6F  wherein each wrist mechanism  10  design provides a different range of motion in this most challenging position.  FIG. 6A  is an illustration of a first main embodiment of the wrist mechanism  10  which allows movement in the approximate range of ±40 degrees, as illustrated in corresponding  FIG. 6B . In  FIG. 6B , a plurality of rods are shown wherein a first rod and a second rod are extended generally along an axial direction  37  which tips the clevis  58  through a combination of a first angle and a second angle (forming a compound angle  39 ) so that the clevis  58  faces an articulated direction  41 . In this example, the angle  39  is approximately 39.2 degrees. This wrist mechanism embodiment was introduced above and will be further described herein below.  FIG. 6C  is an illustration of a second main embodiment of the wrist mechanism  10  which allows movement in the approximate range of ±64 degrees, as illustrated in corresponding  FIG. 6D . Again, a plurality of rods are shown wherein a first rod and a second rod are extended generally along an axial direction  37  which tips the clevis  58  through a first angle and a second angle (forming a compound angle  39 ) so that the clevis  58  faces a articulated direction  41 . In this example, the angle  39  is approximately 63.5 degrees.  FIG. 6E  is an illustration of a third main embodiment of the wrist mechanism  10  which allows movement in the approximate range of ±74 degrees, as illustrated in corresponding  FIG. 6F . Likewise, a plurality of rods are shown wherein a first rod and a second rod are extended generally along an axial direction  37  which tips the clevis  58  through a first angle and a second angle (forming a compound angle  39 ) so that the clevis  58  faces a articulated direction  41 . In this example, the angle  39  is approximately 73.7 degrees. 
     The three different main embodiments of  FIGS. 6A-6F  will now be more fully described and illustrated. The wrist mechanism  10  of the first main embodiment is illustrated in  FIGS. 7-10 ,  11 A- 11 B,  12 ,  13  and provides motion in the approximate range of ±40 degrees, under the conditions described above. Referring to  FIG. 7 , the distal member is in the form of a distal clevis  58  which has a plurality of feet  18  with apertures  17 . In this view, two feet  18  are visible, however four feet  18  are present in this embodiment positioned symmetrically around a base  59  of the distal clevis  58 , as partially shown. Each rod  14  is connected with one of the feet  18  by an orthogonal linkage assembly. In this embodiment, the orthogonal linkage assembly comprises an orthogonal linkage  16  which has a first link portion  22  with a first aperture  23  and a second link portion  24  with a second aperture  25 , wherein the first link portion  22  and second link portion  24  lie in perpendicular planes. Consequently, the apertures  23 ,  25  face directions which are 90 degrees apart. A rod  14  is connected to the second link portion  24  by inserting fastener  26  through second aperture  25  and through aperture  19  located near the distal end  15  of the rod  14 . As shown, aperture  19  passes through the wide side  14   a  of the rod  14 . The fastener  26  may be of any suitable type, for example the fastener  26  may include a head  27  and a body  29  as shown. In this case, the body  29  is inserted through the appropriate apertures. Once inserted, the fastener  26  is then held in place by altering the body  29 , such as by swaging, to create a flange, lip, hook or crimp. Thus, the second link portion  24  and distal end  15  of the rod  14  may be held together between the head  27  and the swaged end of the body  29 . This allows free rotation of the rod  14  in the plane of the second link portion  24 . Such joining of the second link portion  24  and distal end  15  of the rod  14  is illustrated in  FIG. 8 . 
     Similarly, the first link portion  22  is connected with one of the feet  18  by inserting fastener  28  through aperture  17  of foot  18  and through first aperture  23  of the first link portion  22 . Again, once inserted, fastener  28  can be held in place by altering the body  29 , such as by swaging. Thus, the first link portion  22  and foot  18  may be held together between the head  27  and the swaged end of the body  29 . This allows free rotation of the first link portion  22  in the plane of the foot  18 . Such joining of the first link portion  22  and foot  18  is illustrated in  FIG. 9 . Due to the shape of the orthogonal linkage  16  and the perpendicular orientation of the apertures  23 ,  25 , the foot  18  is able to be translated in the plane of second link portion  24  or wide side  14   a  of the rod  14 , offset from aperture  19 , while being rotated in a plane perpendicular to the plane of second link portion  24 , or parallel to the narrow side  14   b  of the rod  14 . Consequently, the distal clevis  58  attached to the foot  18  may be tipped to various degrees along two axes simultaneously. 
     As shown in  FIG. 10 , each of the four rods  14  are connected with a corresponding foot  18  as described above.  FIG. 11A  illustrates the wrist mechanism  10  wherein all four rods  14  are attached to the feet  18  of the distal clevis  58 .  FIG. 11B  is a cross-sectional view of  FIG. 11A . When four rods  14  are present, advancement of one rod tips the distal clevis  58  to face away from the advanced rod. In some embodiments, this simultaneously retracts the rod attached to the distal clevis  58  in the diametrically opposite position. When a rod adjacent to the advanced rod is advanced, the distal clevis  58  is tipped to face away from the newly advanced rod simultaneously retracting the diametrically opposite rod. By varying which rods are advanced and the amount by which they are advanced, the distal clevis can be tipped through a continuous series of angles. 
     The wrist mechanism  110  of the second main embodiment is illustrated in  FIGS. 12-16 ,  17 A- 17 B,  18 ,  19 , and provides motion in the approximate range of ±64 degrees, under the conditions described above. In this embodiment, the distal clevis  158  is comprised of a first clevis half  102  and a second clevis half  104  which are then mated by a clevis mater  106  and joined with a clevis tip  108 . This arrangement allows ease of assembly, reduction of parts and an increased range of motion. 
     Referring to  FIG. 12 , the first clevis half  102  is illustrated. Rather than having feet as in the first main embodiment, apertures  117  are formed directly in the first clevis half  102 . The rod  114  is then attached to the first clevis half  102  with the use of linkage fastener  116 . The linkage fastener  116  comprises a link base portion  124  with an aperture  125  and a fastening end portion  128  which extends in the same plane as the link base portion  124 . A rod  114  is connected to the link base portion  124  by inserting fastener  126  through aperture  125  and through aperture  119  located near the distal end  115  of the rod  114 . As shown, aperture  119  passes through the narrow side  114   b  of the rod  114 . The fastener  126  may be of any suitable type, for example the fastener  126  is shown to include a head  127  and a body  129 . In this case, the body  129  is inserted through the appropriate apertures. Once inserted, the fastener  126  is then held in place by altering the body  129 , such as by swaging, to create a flange, lip, hook or crimp. Thus, the link base portion  124  and distal end  115  of the rod  114  may be held together between the head  127  and the swaged end of the body  129 . This allows free rotation of the rod  114  in the plane of the link base portion  124 . Such joining of the link base portion  124  and distal end  115  of the rod  114  is illustrated in  FIG. 13 . 
     The linkage fastener  116  is then connected with first clevis half  102  by inserting fastening end portion  128  through aperture  117 . Once inserted, the linkage fastener  116  can be held in place by altering the fastening end portion  128 , such as by swaging, to create a flange, lip, hook or crimp on the inside of the first clevis half  102 . Thus, the first clevis half  102  may be held between the link base portion  124  and the swaged end of the fastening end portion  128 . This allows free rotation of the first clevis half  102  in the plane perpendicular to the link base portion  124 . Due to the shape of the linkage fastener  116  and the orientation of the apertures  119 .  125 ,  117 , the first clevis half  102  is able to be translated in the plane of link base portion  124  or narrow side  114   b  of the rod  114 , offset from aperture  119 , while being rotated in a plane perpendicular to the plane of link base portion  124 , or parallel to the wide side  114   a  of the rod  114 . Consequently, the first clevis half  102  attached may be tipped to various degrees along two axes simultaneously. 
     As shown in  FIG. 14 , rods  114  are connected with corresponding apertures  119  on the first clevis half  102  and the second clevis half  104  with the use of linkage fasteners  116  as described above. In this embodiment, two rods  114  are attached to each half  102 ,  104  for a total of four symmetrically placed rods. Again, it may be appreciated that any number of rods  114  may be used and attached to the clevis halves  102 ,  103  in any arrangement. As shown in  FIG. 15 , the clevis halves  102 ,  103  are then mated by insertion into the clevis mater  106 . The clevis mater  106  may be a ring, as shown, wherein the halves  102 ,  103  are press fit within. Referring now to  FIG. 16 , the clevis mater  106  is then joined with the clevis tip  108 , typically by a threaded fit or press fit. 
       FIG. 17A  illustrates the wrist mechanism  110  wherein all four rods  114  are attached to distal clevis  158 .  FIG. 17B  is a cross-sectional view of  FIG. 17A .  FIG. 18  provides a perspective view of the wrist mechanism  110  showing the rods  114  inserted through guide tube  120  in shaft  152  of the tool  50 . The guide tube  120  includes guide slots  121  through which the rods  114  pass to hold rods  114  in the desired orientation. Advancement (indicated by arrow  130 ) of one rod  114 ′ tips the distal clevis  158  to face away from the advanced rod  114 ′, as illustrated in  FIG. 19 . In some embodiments, this simultaneously retracts the rod  114 ″ attached to the distal clevis  158  in the diametrically opposite position. When a rod adjacent to the advanced rod is advanced, the distal clevis  158  is tipped to face away from the newly advanced rod simultaneously retracting the diametrically opposite rod. By varying which rods are advanced and the amount by which they are advanced, the distal clevis can be tipped through a continuous series of angles. 
     The wrist mechanism  210  of the third main embodiment is illustrated in  FIGS. 20-22 ,  23 A- 23 B,  24 , and provides motion in the approximate range of ±74 degrees, under the conditions described above. Referring to  FIG. 20 , the distal member is in the form of a distal clevis  258 , which has a plurality of feet  218  with apertures  217  and a clevis tip  208 . In this view, three feet  218  are visible, however four feet  218  are present in this embodiment positioned symmetrically around a base  259  of the distal clevis  258 , as partially shown. Each rod  214  is connected with one of the feet  218  by an linkage fastener  216 . This arrangement allows ease of assembly, reduction of parts and an increased range of motion. 
     The linkage fastener  216  comprises a link base portion  224  with an aperture  225  and a fastening end portion  228  which extends in the same plane as the link base portion  224 . A rod  214  is connected to the link base portion  224  by inserting fastener  226  through aperture  219 , located near the distal end  215  of the rod  214  and passes through the wide side  214   b  of the rod  214 , and through aperture  225 . The fastener  226  may be of any suitable type, for example the fastener  226  is shown to include a head  227  and a body  229 . In this case, the body  229  is inserted through the appropriate apertures. Once inserted, the fastener  226  is then held in place by altering the body  229 , such as by swaging, to create a flange, lip, hook or crimp. Thus, the link base portion  224  and distal end  215  of the rod  214  may be held together between the head  227  and the swaged end of the body  229 . This allows free rotation of the rod  214  in the plane of the link base portion  224 . Such joining of the link base portion  224  and distal end  215  of the rod  214  is illustrated in  FIG. 21 . 
     The linkage fastener  216  is then connected with the distal clevis  258  by inserting fastening end portion  228  through aperture  117 , as illustrated in  FIG. 22 . Once inserted, the linkage fastener  216  can be held in place by altering the fastening end portion  228 , such as by swaging. Thus, the foot  218  may be held between the link base portion  224  and the swaged end of the fastening end portion  228 . This allows free rotation of the foot  218  in the plane perpendicular to the link base portion  224 . Due to the shape of the linkage fastener  216  and the orientation of the apertures  219 ,  225 ,  217 , the foot  218  is able to be translated in the plane of the link base portion  224  or wide side  214   a  of the rod  214 , offset from aperture  219 , while being rotated in a plane perpendicular to the plane of link base portion  224 , or parallel to the narrow side  214   b  of the rod  214 . Consequently, the attached distal clevis  258  may be tipped to various degrees along two axes simultaneously. 
       FIG. 23A  illustrates the wrist mechanism  210  wherein all four rods  214  are attached to distal clevis  258 .  FIG. 23B  is a cross-sectional view of  FIG. 23A .  FIG. 24  provides a perspective view of the wrist mechanism  210 . Advancement (indicated by arrow  230 ) of one rod  214 ′ tips the distal clevis  258  to face away from the advanced rod  214 ′. In some embodiments, this simultaneously retracts the rod  214 ″ attached to the distal clevis  258  in the diametrically opposite position. When a rod adjacent to the advanced rod is advanced, the distal clevis  258  is tipped to face away from the newly advanced rod simultaneously retracting the diametrically opposite rod. By varying which rods are advanced and the amount by which they are advanced, the distal clevis can be tipped through a continuous series of angles. 
     Actuation of any of the wrist mechanism embodiments described above is achieved with the use of the tool base  62  schematically depicted in  FIG. 1 . As shown, the proximal end  54  of the shaft  52  is coupled to the tool base  62 . Rods extend through the shaft  52  from the wrist mechanism  10  to the tool base  62  wherein the rods are manipulated to actuate the wrist mechanism. For ease of manipulation, each rod  300  is joined with a cable or wire  302 , as illustrated in  FIG. 25 . The wire  302  has a smaller diameter than the rod  300  and mates concentrically with the center  304  of the rod  300 . Referring to  FIG. 26 , the wire/rod assembly  305  is then inserted through a roll pulley  310  within the tool base  62 . The tool base  62  further includes rotational actuation member, such as a sector gear  312 , mounted on a sector pivot pin  314 , as shown in  FIG. 27 . Inserted into each sector gear  312  are two pivot pins  320 , one on each side of the gear  312 . Each pivot pin  320  has a flat surface  322  and a crosshole  324 . When inserted into a sector gear  312 , the pivot pins  320  can freely rotate to allow maximum roll angle articulation. 
     After the wire/rod assembly is advanced through the roll pulley  310 , the wire  302  is inserted through the crosshole  324  of a pivot pin  320  as illustrated in  FIG. 28 . As shown, crossholes  324  of each of the four pivot pins  320  are arranged between the sector gears  312  facing the roll pulley  310 . Thus, each of the four rods  300  may be inserted through a separate crosshole  324 . It may be appreciated that the number and arrangement of the pivot pins  320  is dependent on the design of the wrist mechanism. Wrist mechanisms having greater or fewer numbers of rods or rods in different arrangements would have corresponding pivot pins  320  to which the rods would be connected. Each crosshole  324  is sized to allow passage of the wire  302  but not the rod  300 . Therefore, the rod  300  abuts the flat surface  322  of the pivot pin  320 . To maintain position of the wire/rod assembly and abutment of the rod  300  against the flat surface  322 , a crimp  330  is slid onto the wire  302 , as shown in  FIG. 29 , and crimped in place. 
       FIG. 30  is a top perspective view of the tool base  62 . Rods  300  emerge from the roll pulley  310  and connect with the pins  320  between the sector gears  312  as described above. Manipulation of the rods  300  actuates the wrist mechanism to position the distal clevis in a desired orientation. For example, the sector gears  312  can be individually rotated clockwise or counterclockwise by action of gears  400 , as indicated by circular arrows. Such rotation either advances or retracts each rod  300  depending on the position of the rods  300 . For example, by rotating the sector gear  312  clockwise, rod  300 ′ is advanced while rod  300 ″ is retracted. As described above, advancement of one rod tips the distal clevis to face away from the advanced rod while, in this embodiment, the rod attached to the distal clevis in the diametrically opposite position is simultaneously retracted. Typically, the one rod is advanced and the diametrically opposite rod is retracted by the same amount. However, it may be appreciated the advancement and retraction of these rods may vary, usually by attaching the rods at different locations on a particular sector gear. In any case, advancement and retraction of the rods provides for the pitch and yaw movements of the distal clevis and attached end effector. The rods  300  can also be rotated by action of gear  420  which rotates the roll pulley  310 , as indicated by a curved arrow. The roll pulley  310  rotates the shaft  54  around its central axis  51 . This in turn rotates the guide tube  20  to which the shaft  54  is connected. Since the rods  300  pass through guide slots  30  in the guide tube  20  yet are fixed to rotational actuation members at their backends, the guide slots  30  translate the distal ends of the rods  300  in a circular fashion around the central axis  51  while the backends are fixed in place. This is possible by flexing of the rods  300 . Due to the length, thickness and flexibility of the rods, 360 degree rotation is possible. This provides for the roll movement of the distal clevis and attached end effector. It may be appreciated that other back end mechanisms may be used to actuate and manipulate the rods  300 . For instance, the rods  300  may be independently controlled without the use of rotational actuation members  312 . 
     Although the foregoing invention has been described in some detail by way of illustration and example, for purposes of clarity of understanding, it will be obvious that various alternatives, modifications and equivalents may be used and the above description should not be taken as limiting in scope of the invention which is defined by the appended claims.