Patent Publication Number: US-2022226050-A1

Title: Surgical tool end effectors with wire routing distal wedge

Description:
TECHNICAL FIELD 
     The systems and methods disclosed herein are directed to robotic surgical tools and, more particularly to, vessel sealers with bifurcating jaws and a strain relieved conductor wire. 
     BACKGROUND 
     Minimally invasive surgical (MIS) instruments are often preferred over traditional open surgical devices due to the reduced post-operative recovery time and minimal scarring. The most common MIS procedure may be endoscopy, and the most common form of endoscopy is laparoscopy, in which one or more small incisions are formed in the abdomen of a patient and a trocar is inserted through the incision to form a pathway that provides access to the abdominal cavity. The cannula and sealing system of the trocar are used to introduce various instruments and tools into the abdominal cavity, as well as to provide insufflation to elevate the abdominal wall above the organs. The instruments can be used to engage and/or treat tissue in a number of ways to achieve a diagnostic or therapeutic effect. 
     Each surgical tool typically includes an end effector arranged at its distal end. Example end effectors include clamps, graspers, scissors, staplers, suction irrigators, blades (i.e., RF), and needle holders, and are similar to those used in conventional (open) surgery except that the end effector of each tool is separated from its handle by an approximately 12-inch long shaft. A camera or image capture device, such as an endoscope, is also commonly introduced into the abdominal cavity to enable the surgeon to view the surgical field and the operation of the end effectors during operation. The surgeon is able to view the procedure in real-time by means of a visual display in communication with the image capture device. 
     Various robotic systems have recently been developed to assist in MIS procedures. Robotic systems can allow for more intuitive hand movements by maintaining natural eye-hand axis. Robotic systems can also allow for more degrees of freedom in movement by including a “wrist” joint that creates a more natural hand-like articulation and allows for access to hard to reach spaces. The instrument&#39;s end effector can be articulated (moved) using motors and actuators forming part of a computerized motion system. A user (e.g., a surgeon) is able to remotely operate an instrument&#39;s end effector by grasping and manipulating in space one or more controllers that communicate with an instrument driver coupled to the surgical instrument. User inputs are processed by a computer system incorporated into the robotic surgical system and the instrument driver responds by actuating the motors and actuators of the motion system. Moving drive cables, rods, and/or other mechanical mechanisms causes the end effector to articulate to desired positions and configurations. 
     Improvements to robotically-enabled medical systems will provide physicians with the ability to perform endoscopic and laparoscopic procedures more effectively and with improved ease. 
     SUMMARY OF DISCLOSURE 
     Various details of the present disclosure are hereinafter summarized to provide a basic understanding. This summary is not an extensive overview of the disclosure and is neither intended to identify certain elements of the disclosure, nor to delineate the scope thereof. Rather, the primary purpose of this summary is to present some concepts of the disclosure in a simplified form prior to the more detailed description that is presented hereinafter. 
     Embodiments disclosed herein include a robotic surgical tool that includes an elongate shaft, an end effector arranged at a distal end of the shaft and including opposing first and second jaws, an articulable wrist that interposes the end effector and the distal end, the wrist including an articulation joint pivotable about an axis and a linkage mounted to the first and second jaws, a distal wedge positioned distal to the articulation joint and within a central portion of the wrist, and an electrical conductor extending through the wrist and to an electrode located at the end effector, wherein the distal wedge guides the electrical conductor to the electrode. In a further embodiment, the first jaw provides a first jaw extension and the second jaw provides a second jaw extension, and the wrist further includes first and second pulleys rotatably mounted to the articulation joint, the first jaw extension being pinned to the first pulley and the second jaw extension being pinned to the second pulley, and wherein the distal wedge is positioned between the first and second jaw extensions. In another further embodiment, the robotic surgical tool further includes a knife rod extending through the central portion of the wrist and terminating at a knife, wherein the distal wedge defines a knife housing that houses the knife and through which the knife rod extends to guide the knife to the end effector. In another further embodiment, the distal wedge defines a channel that receives and guides the electrical conductor to the electrode. In another further embodiment, the channel provides at least one of a vertical direction change and a horizontal direction change. In another further embodiment, an opening or an exit of the channel is flared outward. In another further embodiment, the electrical conductor is loosely received within the channel. In another further embodiment, the end effector is selected from the group consisting of a surgical stapler, a tissue grasper, surgical scissors, an advanced energy vessel sealer, a clip applier, a needle driver, a babcock including a pair of opposed grasping jaws, bipolar jaws, and any combination thereof. 
     Embodiments disclosed herein also include a method of operating a robotic surgical tool including locating a robotic surgical tool adjacent a patient, the robotic surgical tool having an end effector arranged at a distal end of an elongate shaft and including opposing first and second jaws, and an articulable wrist interposing the end effector and the distal end, the wrist including an articulation joint, and a linkage mounted to the first and second jaws. The method further includes providing electrical current to an electrode located at the end effector with an electrical conductor, wherein the electrical conductor is guided through the wrist and to the electrode with a distal wedge positioned distal to the articulation joint and within a central portion of the wrist. In a further embodiment, the distal wedge defines a knife housing and the method further comprises advancing a knife through the knife housing of the distal wedge and toward the end effector, and guiding the knife to a guide track provided by the end effector with the distal wedge. In another further embodiment, the method further includes loosely receiving the electrical conductor within a channel defined by the distal wedge. In another further embodiment, a portion of the channel provides a gap and the method further comprises managing slack in the electrical conductor by allowing the electrical conductor to reciprocate within the gap as the end effector moves. 
     Embodiments disclosed herein further include an end effector for a robotic surgical tool that includes a first jaw providing a first jaw extension, a second jaw providing a second jaw extension, an articulable wrist operatively coupled to the first and second jaws and including an articulation joint, first and second pulleys rotatably mounted to the articulation joint, the first jaw extension being pinned to the first pulley and the second jaw extension being pinned to the second pulley, and a linkage mounted to the first and second jaws. The end effector further includes a distal wedge positioned distal to the articulation joint and within a central portion of the wrist, and an electrical conductor extending through the wrist and to an electrode, wherein the distal wedge guides the electrical conductor to the electrode. In a further embodiment, the distal wedge is positioned between the first and second jaw extensions. In another further embodiment, the opposing first and second jaws are bifurcating jaws. In another further embodiment, the distal wedge is detached from any portion of the first and second jaws and the wrist. In another further embodiment, the distal wedge defines a knife housing through which a knife extends. In another further embodiment, the distal wedge defines a channel that loosely receives and guides the electrical conductor to the electrode. In another further embodiment, the channel provides a horizontal direction change, where a course of the channel assumes an in-plane angular turn in a horizontal plane, and a vertical direction change, where the course of the channel assumes an in-plane angular turn in a vertical plane. In another further embodiment, an opening or an exit of the channel is flared outward. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosed aspects will hereinafter be described in conjunction with the appended drawings, provided to illustrate and not to limit the disclosed aspects, wherein like designations denote like elements. 
         FIG. 1  illustrates an embodiment of a cart-based robotic system arranged for diagnostic and/or therapeutic bronchoscopy procedure(s). 
         FIG. 2  depicts further aspects of the robotic system of  FIG. 1 . 
         FIG. 3A  illustrates an embodiment of the robotic system of  FIG. 1  arranged for ureteroscopy. 
         FIG. 3B  illustrates an embodiment of the robotic system of  FIG. 1  arranged for a vascular procedure. 
         FIG. 4  illustrates an embodiment of a table-based robotic system arranged for a bronchoscopy procedure. 
         FIG. 5  provides an alternative view of the robotic system of  FIG. 4 . 
         FIG. 6  illustrates an example system configured to stow robotic arm(s). 
         FIG. 7A  illustrates an embodiment of a table-based robotic system configured for a ureteroscopy procedure. 
         FIG. 7B  illustrates an embodiment of a table-based robotic system configured for a laparoscopic procedure. 
         FIG. 7C  illustrates an embodiment of the table-based robotic system of  FIGS. 4-7B  with pitch or tilt adjustment. 
         FIG. 8  provides a detailed illustration of the interface between the table and the column of the table-based robotic system of  FIGS. 4-7 . 
         FIG. 9A  illustrates an alternative embodiment of a table-based robotic system. 
         FIG. 9B  illustrates an end view of the table-based robotic system of  FIG. 9A . 
         FIG. 9C  illustrates an end view of a table-based robotic system with robotic arms attached thereto. 
         FIG. 10  illustrates an exemplary instrument driver. 
         FIG. 11  illustrates an exemplary medical instrument with a paired instrument driver. 
         FIG. 12  illustrates an alternative design for an instrument driver and instrument where the axes of the drive units are parallel to the axis of the elongated shaft of the instrument. 
         FIG. 13  illustrates an instrument having an instrument-based insertion architecture. 
         FIG. 14  illustrates an exemplary controller. 
         FIG. 15  depicts a block diagram illustrating a localization system that estimates a location of one or more elements of the robotic systems of  FIGS. 1-7C , such as the location of the instrument of  FIGS. 11-13 , in accordance to an example embodiment. 
         FIG. 16  is an isometric side view of an example surgical tool that may incorporate some or all of the principles of the present disclosure. 
         FIG. 17  depicts separated isometric end views of the instrument driver and the surgical tool of  FIG. 16 . 
         FIG. 18  is an enlarged isometric view of the distal end of the surgical tool of  FIGS. 16 and 17 , according to one or more embodiments. 
         FIGS. 19A and 19B  are isometric, partially exploded views of the end effector of  FIG. 18  from right and left vantage points, according to one or more embodiments. 
         FIGS. 20A and 20B  are additional isometric, partially exploded views of the end effector of  FIG. 18  from the right and left vantage points. 
         FIGS. 21A and 21B  are additional isometric, partially exploded views of the end effector of  FIG. 18  from the right and left vantage points. 
         FIG. 22  is an enlarged isometric view of the distal end of the surgical tool of  FIGS. 16 and 17 , according to one or more additional embodiments. 
         FIG. 23  is an isometric, partially exploded view of the end effector of  FIG. 22 , as taken from a right vantage point. 
         FIGS. 24A and 24B  are additional isometric, partially exploded views of the end effector of  FIG. 22  from right and left vantage points. 
         FIG. 25  is a perspective end view of the end effector of  FIG. 18 , according to one or more embodiments. 
         FIGS. 26A and 26B  are right and left isometric views, respectively, of the distal wedge of  FIG. 25 , according to one or more embodiments. 
         FIG. 27  is a perspective end view of the end effector of  FIG. 22 , according to one or more embodiments. 
         FIGS. 28A and 28B  are right and left isometric views, respectively, of the distal wedge of  FIG. 27 , according to one or more embodiments. 
         FIG. 29  is an isometric top view of the end effector and the wrist of  FIG. 18 , according to one or more embodiments. 
         FIG. 30  is an isometric top view of the end effector and wrist of  FIG. 29 , with the wrist partially exploded, according to one or more embodiments. 
         FIG. 31  is an enlarged side view of the end effector of  FIG. 18 , according to one or more embodiments. 
         FIG. 32  is an isometric view of the distal clevis and accompanying enlarged views of the distal joint interface, according to one or more embodiments. 
         FIG. 33  is a cross-sectional side view of the end effector and the wrist of  FIG. 18 , according to one or more embodiments of the disclosure. 
         FIG. 34A  is an isometric view of the proximal clevis and the mid-articulation insert, according to one or more embodiments. 
         FIG. 34B  is an isometric view of the proximal clevis and the mid-articulation insert, according to one or more additional embodiments. 
         FIGS. 35A and 35B  are back and front isometric views, respectively of an example knife drive system, according to one or more embodiments. 
         FIG. 36  is an isometric view of an example end effector, according to one or more additional embodiments of the disclosure. 
         FIG. 37  is a cross-sectional end view of the jaws of  FIG. 36  taken along the plane indicated in  FIG. 36 , according to one or more embodiments. 
         FIG. 38  depicts an alternative embodiment of the removable cartridge of  FIG. 37 . 
         FIG. 39  is an isometric view of the end effector of  FIG. 36  with an exposed electrical system, according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     1. Overview. 
     Aspects of the present disclosure may be integrated into a robotically-enabled medical system capable of performing a variety of medical procedures, including both minimally invasive (e.g., laparoscopy) and non-invasive (e.g., endoscopy) procedures. Among endoscopy procedures, the system may be capable of performing bronchoscopy, ureteroscopy, gastroscopy, etc. 
     In addition to performing the breadth of procedures, the system may provide additional benefits, such as enhanced imaging and guidance, to assist the physician. Additionally, the system may provide the physician with the ability to perform the procedure from an ergonomic position without the need for awkward arm motions and positions. Still further, the system may provide the physician with the ability to perform the procedure with improved ease of use such that one or more of the instruments of the system can be controlled by a single user. 
     Various embodiments will be described below in conjunction with the drawings for purposes of illustration. It should be appreciated that many other implementations of the disclosed concepts are possible, and various advantages can be achieved with the disclosed implementations. Headings are included herein for reference and to aid in locating various sections. These headings are not intended to limit the scope of the concepts described with respect thereto, as such concepts may have applicability throughout the entire specification. 
     A. Robotic System—Cart. 
     The robotically-enabled medical system may be configured in a variety of ways depending on the particular procedure.  FIG. 1  illustrates an embodiment of a cart-based robotically-enabled system  100  arranged for a diagnostic and/or therapeutic bronchoscopy procedure. For a bronchoscopy procedure, the robotic system  100  may include a cart  102  having one or more robotic arms  104  (three shown) to deliver a medical instrument (alternately referred to as a “surgical tool”), such as a steerable endoscope  106  (e.g., a procedure-specific bronchoscope for bronchoscopy), to a natural orifice access point (i.e., the mouth of the patient) to deliver diagnostic and/or therapeutic tools. As shown, the cart  102  may be positioned proximate to the patient&#39;s upper torso in order to provide access to the access point. Similarly, the robotic arms  104  may be actuated to position the bronchoscope relative to the access point. The arrangement in  FIG. 1  may also be utilized when performing a gastro-intestinal (GI) procedure with a gastroscope, a specialized endoscope for GI procedures. 
     Once the cart  102  is properly positioned adjacent the patient, the robotic arms  104  are operated to insert the steerable endoscope  106  into the patient robotically, manually, or a combination thereof. The steerable endoscope  106  may comprise at least two telescoping parts, such as an inner leader portion and an outer sheath portion, where each portion is coupled to a separate instrument driver of a set of instrument drivers  108 . As illustrated, each instrument driver  108  is coupled to the distal end of a corresponding one of the robotic arms  104 . This linear arrangement of the instrument drivers  108 , which facilitates coaxially aligning the leader portion with the sheath portion, creates a “virtual rail”  110  that may be repositioned in space by manipulating the robotic arms  104  into different angles and/or positions. Translation of the instrument drivers  108  along the virtual rail  110  telescopes the inner leader portion relative to the outer sheath portion, thus effectively advancing or retracting the endoscope  106  relative to the patient. 
     As illustrated, the virtual rail  110  (and other virtual rails described herein) is depicted in the drawings using dashed lines, thus not constituting any physical structure of the system  100 . The angle of the virtual rail  110  may be adjusted, translated, and pivoted based on clinical application or physician preference. For example, in bronchoscopy, the angle and position of the virtual rail  110  as shown represents a compromise between providing physician access to the endoscope  106  while minimizing friction that results from bending the endoscope  106  into the patient&#39;s mouth. 
     After insertion into the patient&#39;s mouth, the endoscope  106  may be directed down the patient&#39;s trachea and lungs using precise commands from the robotic system  100  until reaching a target destination or operative site. In order to enhance navigation through the patient&#39;s lung network and/or reach the desired target, the endoscope  106  may be manipulated to telescopically extend the inner leader portion from the outer sheath portion to obtain enhanced articulation and greater bend radius. The use of separate instrument drivers  108  also allows the leader portion and sheath portion to be driven independent of each other. 
     For example, the endoscope  106  may be directed to deliver a biopsy needle to a target, such as, for example, a lesion or nodule within the lungs of a patient. The needle may be deployed down a working channel that runs the length of the endoscope  106  to obtain a tissue sample to be analyzed by a pathologist. Depending on the pathology results, additional tools may be deployed down the working channel of the endoscope for additional biopsies. After identifying a tissue sample to be malignant, the endoscope  106  may endoscopically deliver tools to resect the potentially cancerous tissue. In some instances, diagnostic and therapeutic treatments can be delivered in separate procedures. In those circumstances, the endoscope  106  may also be used to deliver a fiducial marker to “mark” the location of a target nodule as well. In other instances, diagnostic and therapeutic treatments may be delivered during the same procedure. 
     The system  100  may also include a movable tower  112 , which may be connected via support cables to the cart  102  to provide support for controls, electronics, fluidics, optics, sensors, and/or power to the cart  102 . Placing such functionality in the tower  112  allows for a smaller form factor cart  102  that may be more easily adjusted and/or re-positioned by an operating physician and his/her staff. Additionally, the division of functionality between the cart/table and the support tower  112  reduces operating room clutter and facilitates improving clinical workflow. While the cart  102  may be positioned close to the patient, the tower  112  may alternatively be stowed in a remote location to stay out of the way during a procedure. 
     In support of the robotic systems described above, the tower  112  may include component(s) of a computer-based control system that stores computer program instructions, for example, within a non-transitory computer-readable storage medium such as a persistent magnetic storage drive, solid state drive, etc. The execution of those instructions, whether the execution occurs in the tower  112  or the cart  102 , may control the entire system or sub-system(s) thereof. For example, when executed by a processor of the computer system, the instructions may cause the components of the robotics system to actuate the relevant carriages and arm mounts, actuate the robotics arms, and control the medical instruments. For example, in response to receiving the control signal, motors in the joints of the robotic arms  104  may position the arms into a certain posture or angular orientation. 
     The tower  112  may also include one or more of a pump, flow meter, valve control, and/or fluid access in order to provide controlled irrigation and aspiration capabilities to the system  100  that may be deployed through the endoscope  106 . These components may also be controlled using the computer system of the tower  112 . In some embodiments, irrigation and aspiration capabilities may be delivered directly to the endoscope  106  through separate cable(s). 
     The tower  112  may include a voltage and surge protector designed to provide filtered and protected electrical power to the cart  102 , thereby avoiding placement of a power transformer and other auxiliary power components in the cart  102 , resulting in a smaller, more movable cart  102 . 
     The tower  112  may also include support equipment for sensors deployed throughout the robotic system  100 . For example, the tower  112  may include opto-electronics equipment for detecting, receiving, and processing data received from optical sensors or cameras throughout the robotic system  100 . In combination with the control system, such opto-electronics equipment may be used to generate real-time images for display in any number of consoles deployed throughout the system, including in the tower  112 . Similarly, the tower  112  may also include an electronic subsystem for receiving and processing signals received from deployed electromagnetic (EM) sensors. The tower  112  may also be used to house and position an EM field generator for detection by EM sensors in or on the medical instrument. 
     The tower  112  may also include a console  114  in addition to other consoles available in the rest of the system, e.g., a console mounted to the cart  102 . The console  114  may include a user interface and a display screen (e.g., a touchscreen) for the physician operator. Consoles in the system  100  are generally designed to provide both robotic controls as well as pre-operative and real-time information of the procedure, such as navigational and localization information of the endoscope  106 . When the console  114  is not the only console available to the physician, it may be used by a second operator, such as a nurse, to monitor the health or vitals of the patient and the operation of system, as well as provide procedure-specific data, such as navigational and localization information. In other embodiments, the console  114  may be housed in a body separate from the tower  112 . 
     The tower  112  may be coupled to the cart  102  and endoscope  106  through one or more cables  116  connections. In some embodiments, support functionality from the tower  112  may be provided through a single cable  116  extending to the cart  102 , thus simplifying and de-cluttering the operating room. In other embodiments, specific functionality may be coupled in separate cabling and connections. For example, while power may be provided through a single power cable to the cart  102 , support for controls, optics, fluidics, and/or navigation may be provided through one or more separate cables. 
       FIG. 2  provides a detailed illustration of an embodiment of the cart  102  from the cart-based robotically-enabled system  100  of  FIG. 1 . The cart  102  generally includes an elongated support structure  202  (also referred to as a “column”), a cart base  204 , and a console  206  at the top of the column  202 . The column  202  may include one or more carriages, such as a carriage  208  (alternatively “arm support”) for supporting the deployment of the robotic arms  104 . The carriage  208  may include individually configurable arm mounts that rotate along a perpendicular axis to adjust the base  214  of the robotic arms  104  for better positioning relative to the patient. The carriage  208  also includes a carriage interface  210  that allows the carriage  208  to vertically translate along the column  202 . 
     The carriage interface  210  is connected to the column  202  through slots, such as slot  212 , that are positioned on opposite sides of the column  202  to guide the vertical translation of the carriage  208 . The slot  212  contains a vertical translation interface to position and hold the carriage  208  at various vertical heights relative to the cart base  204 . Vertical translation of the carriage  208  allows the cart  102  to adjust the reach of the robotic arms  104  to meet a variety of table heights, patient sizes, and physician preferences. Similarly, the individually configurable arm mounts on the carriage  208  allow a base  214  of the robotic arms  104  to be angled in a variety of configurations. 
     In some embodiments, the slot  212  may be supplemented with slot covers (not shown) that are flush and parallel to the slot surface to prevent dirt and fluid ingress into the internal chambers of the column  202  and the vertical translation interface as the carriage  208  vertically translates. The slot covers may be deployed through pairs of spring spools positioned near the vertical top and bottom of the slot  212 . The covers are coiled within the spools until deployed to extend and retract from their coiled state as the carriage  208  vertically translates up and down. The spring-loading of the spools provides force to retract the cover into a spool when carriage  208  translates towards the spool, while also maintaining a tight seal when the carriage  208  translates away from the spool. The covers may be connected to the carriage  208  using, for example, brackets in the carriage interface  210  to ensure proper extension and retraction of the cover as the carriage  208  translates. 
     The column  202  may internally comprise mechanisms, such as gears and motors, which are designed to use a vertically aligned lead screw to translate the carriage  208  in a mechanized fashion in response to control signals generated in response to user inputs, e.g., inputs from the console  206 . 
     The robotic arms  104  may generally comprise robotic arm bases  214  and end effectors  216  (three shown), separated by a series of linkages  218  connected by a corresponding series of joints  220 , each joint  220  including an independent actuator, and each actuator including an independently controllable motor. Each independently controllable joint  220  represents an independent degree of freedom available to the corresponding robotic arm  104 . In the illustrated embodiment, each arm  104  has seven joints  220 , thus providing seven degrees of freedom. A multitude of joints  220  result in a multitude of degrees of freedom, allowing for “redundant” degrees of freedom. Redundant degrees of freedom allow the robotic arms  104  to position their respective end effectors  216  at a specific position, orientation, and trajectory in space using different linkage positions and joint angles. This allows for the system  100  to position and direct a medical instrument from a desired point in space while allowing the physician to move the arm joints  220  into a clinically advantageous position away from the patient to create greater access, while avoiding arm collisions. 
     The cart base  204  balances the weight of the column  202 , the carriage  208 , and the arms  104  over the floor. Accordingly, the cart base  204  houses heavier components, such as electronics, motors, power supply, as well as components that either enable movement and/or immobilize the cart. For example, the cart base  204  includes rolling casters  222  that allow for the cart to easily move around the room prior to a procedure. After reaching an appropriate position, the casters  222  may be immobilized using wheel locks to hold the cart  102  in place during the procedure. 
     Positioned at the vertical end of the column  202 , the console  206  allows for both a user interface for receiving user input and a display screen (or a dual-purpose device such as, for example, a touchscreen  224 ) to provide the physician user with both pre-operative and intra-operative data. Potential pre-operative data on the touchscreen  224  may include pre-operative plans, navigation and mapping data derived from pre-operative computerized tomography (CT) scans, and/or notes from pre-operative patient interviews. Intra-operative data on the touchscreen  224  may include optical information provided from the tool, sensor and coordinate information from sensors, as well as vital patient statistics, such as respiration, heart rate, and/or pulse. The console  206  may be positioned and tilted to allow a physician to access the console from the side of the column  202  opposite carriage  208 . From this position, the physician may view the console  206 , the robotic arms  104 , and the patient while operating the console  206  from behind the cart  102 . As shown, the console  206  also includes a handle  226  to assist with maneuvering and stabilizing cart  102 . 
       FIG. 3A  illustrates an embodiment of the system  100  of  FIG. 1  arranged for ureteroscopy. In a ureteroscopic procedure, the cart  102  may be positioned to deliver a ureteroscope  302 , a procedure-specific endoscope designed to traverse a patient&#39;s urethra and ureter, to the lower abdominal area of the patient. In ureteroscopy, it may be desirable for the ureteroscope  302  to be directly aligned with the patient&#39;s urethra to reduce friction and forces on the sensitive anatomy. As shown, the cart  102  may be aligned at the foot of the table to allow the robotic arms  104  to position the ureteroscope  302  for direct linear access to the patient&#39;s urethra. From the foot of the table, the robotic arms  104  may insert the ureteroscope  302  along a virtual rail  304  directly into the patient&#39;s lower abdomen through the urethra. 
     After insertion into the urethra, using similar control techniques as in bronchoscopy, the ureteroscope  302  may be navigated into the bladder, ureters, and/or kidneys for diagnostic and/or therapeutic applications. For example, the ureteroscope  302  may be directed into the ureter and kidneys to break up kidney stone build-up using a laser or ultrasonic lithotripsy device deployed down a working channel of the ureteroscope  302 . After lithotripsy is complete, the resulting stone fragments may be removed using baskets deployed down the working channel of the ureteroscope  302 . 
       FIG. 3B  illustrates another embodiment of the system  100  of  FIG. 1  arranged for a vascular procedure. In a vascular procedure, the system  100  may be configured such that the cart  102  may deliver a medical instrument  306 , such as a steerable catheter, to an access point in the femoral artery in the patient&#39;s leg. The femoral artery presents both a larger diameter for navigation as well as a relatively less circuitous and tortuous path to the patient&#39;s heart, which simplifies navigation. As in a ureteroscopic procedure, the cart  102  may be positioned towards the patient&#39;s legs and lower abdomen to allow the robotic arms  104  to provide a virtual rail  308  with direct linear access to the femoral artery access point in the patient&#39;s thigh/hip region. After insertion into the artery, the medical instrument  306  may be directed and advanced by translating the instrument drivers  108 . Alternatively, the cart  102  may be positioned around the patient&#39;s upper abdomen in order to reach alternative vascular access points, such as, for example, the carotid and brachial arteries near the patient&#39;s shoulder and wrist. 
     B. Robotic System—Table. 
     Embodiments of the robotically-enabled medical system may also incorporate the patient&#39;s table. Incorporation of the table reduces the amount of capital equipment within the operating room by removing the cart, which allows greater access to the patient.  FIG. 4  illustrates an embodiment of such a robotically-enabled system  400  arranged for a bronchoscopy procedure. As illustrated, the system  400  includes a support structure or column  402  for supporting platform  404  (shown as a “table” or “bed”) over the floor. Much like in the cart-based systems, the end effectors of the robotic arms  406  of the system  400  comprise instrument drivers  408  that are designed to manipulate an elongated medical instrument, such as a bronchoscope  410 , through or along a virtual rail  412  formed from the linear alignment of the instrument drivers  408 . In practice, a C-arm for providing fluoroscopic imaging may be positioned over the patient&#39;s upper abdominal area by placing the emitter and detector around the table  404 . 
       FIG. 5  provides an alternative view of the system  400  without the patient and medical instrument for discussion purposes. As shown, the column  402  may include one or more carriages  502  shown as ring-shaped in the system  400 , from which the one or more robotic arms  406  may be based. The carriages  502  may translate along a vertical column interface  504  that runs the length (height) of the column  402  to provide different vantage points from which the robotic arms  406  may be positioned to reach the patient. The carriage(s)  502  may rotate around the column  402  using a mechanical motor positioned within the column  402  to allow the robotic arms  406  to have access to multiples sides of the table  404 , such as, for example, both sides of the patient. In embodiments with multiple carriages  502 , the carriages  502  may be individually positioned on the column  402  and may translate and/or rotate independent of the other carriages  502 . While carriages  502  need not surround the column  402  or even be circular, the ring-shape as shown facilitates rotation of the carriages  502  around the column  402  while maintaining structural balance. Rotation and translation of the carriages  502  allows the system  400  to align medical instruments, such as endoscopes and laparoscopes, into different access points on the patient. 
     In other embodiments (discussed in greater detail below with respect to  FIG. 9A ), the system  400  can include a patient table or bed with adjustable arm supports in the form of bars or rails extending alongside it. One or more robotic arms  406  (e.g., via a shoulder with an elbow joint) can be attached to the adjustable arm supports, which can be vertically adjusted. By providing vertical adjustment, the robotic arms  406  are advantageously capable of being stowed compactly beneath the patient table or bed, and subsequently raised during a procedure. 
     The arms  406  may be mounted on the carriages  502  through a set of arm mounts  506  comprising a series of joints that may individually rotate and/or telescopically extend to provide additional configurability to the robotic arms  406 . Additionally, the arm mounts  506  may be positioned on the carriages  502  such that when the carriages  502  are appropriately rotated, the arm mounts  506  may be positioned on either the same side of the table  404  (as shown in  FIG. 5 ), on opposite sides of table  404  (as shown in  FIG. 7B ), or on adjacent sides of the table  404  (not shown). 
     The column  402  structurally provides support for the table  404 , and a path for vertical translation of the carriages  502 . Internally, the column  402  may be equipped with lead screws for guiding vertical translation of the carriages, and motors to mechanize the translation of said carriages based the lead screws. The column  402  may also convey power and control signals to the carriage  502  and robotic arms  406  mounted thereon. 
     A table base  508  serves a similar function as the cart base  204  of the cart  102  shown in  FIG. 2 , housing heavier components to balance the table/bed  404 , the column  402 , the carriages  502 , and the robotic arms  406 . The table base  508  may also incorporate rigid casters to provide stability during procedures. Deployed from the bottom of the table base  508 , the casters may extend in opposite directions on both sides of the base  508  and retract when the system  400  needs to be moved. 
     In some embodiments, the system  400  may also include a tower (not shown) that divides the functionality of system  400  between table and tower to reduce the form factor and bulk of the table  404 . As in earlier disclosed embodiments, the tower may provide a variety of support functionalities to the table  404 , such as processing, computing, and control capabilities, power, fluidics, and/or optical and sensor processing. The tower may also be movable to be positioned away from the patient to improve physician access and de-clutter the operating room. Additionally, placing components in the tower allows for more storage space in the table base  508  for potential stowage of the robotic arms  406 . The tower may also include a master controller or console that provides both a user interface for user input, such as keyboard and/or pendant, as well as a display screen (or touchscreen) for pre-operative and intra-operative information, such as real-time imaging, navigation, and tracking information. In some embodiments, the tower may also contain holders for gas tanks to be used for insufflation. 
     In some embodiments, a table base may stow and store the robotic arms when not in use.  FIG. 6  illustrates an embodiment of the system  400  that is configured to stow robotic arms in an embodiment of the table-based system. In the system  400 , one or more carriages  602  (one shown) may be vertically translated into a base  604  to stow one or more robotic arms  606 , one or more arm mounts  608 , and the carriages  602  within the base  604 . Base covers  610  may be translated and retracted open to deploy the carriages  602 , the arm mounts  608 , and the arms  606  around the column  612 , and closed to stow and protect them when not in use. The base covers  610  may be sealed with a membrane  614  along the edges of its opening to prevent dirt and fluid ingress when closed. 
       FIG. 7A  illustrates an embodiment of the robotically-enabled table-based system  400  configured for a ureteroscopy procedure. In ureteroscopy, the table  404  may include a swivel portion  702  for positioning a patient off-angle from the column  402  and the table base  508 . The swivel portion  702  may rotate or pivot around a pivot point (e.g., located below the patient&#39;s head) in order to position the bottom portion of the swivel portion  702  away from the column  402 . For example, the pivoting of the swivel portion  702  allows a C-arm (not shown) to be positioned over the patient&#39;s lower abdomen without competing for space with the column (not shown) below table  404 . By rotating the carriage (not shown) around the column  402 , the robotic arms  406  may directly insert a ureteroscope  704  along a virtual rail  706  into the patient&#39;s groin area to reach the urethra. In ureteroscopy, stirrups  708  may also be fixed to the swivel portion  702  of the table  404  to support the position of the patient&#39;s legs during the procedure and allow clear access to the patient&#39;s groin area. 
       FIG. 7B  illustrates an embodiment of the system  400  configured for a laparoscopic procedure. In a laparoscopic procedure, through small incision(s) in the patient&#39;s abdominal wall, minimally invasive instruments may be inserted into the patient&#39;s anatomy. In some embodiments, the minimally invasive instruments comprise an elongated rigid member, such as a shaft, which is used to access anatomy within the patient. After inflation of the patient&#39;s abdominal cavity, the instruments may be directed to perform surgical or medical tasks, such as grasping, cutting, ablating, suturing, etc. In some embodiments, the instruments can comprise a scope, such as a laparoscope. As shown in  FIG. 7B , the carriages  502  of the system  400  may be rotated and vertically adjusted to position pairs of the robotic arms  406  on opposite sides of the table  404 , such that an instrument  710  may be positioned using the arm mounts  506  to be passed through minimal incisions on both sides of the patient to reach his/her abdominal cavity. 
     To accommodate laparoscopic procedures, the system  400  may also tilt the platform to a desired angle.  FIG. 7C  illustrates an embodiment of the system  400  with pitch or tilt adjustment. As shown in  FIG. 7C , the system  400  may accommodate tilt of the table  404  to position one portion of the table  404  at a greater distance from the floor than the other. Additionally, the arm mounts  506  may rotate to match the tilt such that the arms  406  maintain the same planar relationship with table  404 . To accommodate steeper angles, the column  402  may also include telescoping portions  712  that allow vertical extension of the column  402  to keep the table  404  from touching the floor or colliding with the base  508 . 
       FIG. 8  provides a detailed illustration of the interface between the table  404  and the column  402 . Pitch rotation mechanism  802  may be configured to alter the pitch angle of the table  404  relative to the column  402  in multiple degrees of freedom. The pitch rotation mechanism  802  may be enabled by the positioning of orthogonal axes A and B at the column-table interface, each axis actuated by a separate motor  804   a  and  804   b  responsive to an electrical pitch angle command. Rotation along one screw  806   a  would enable tilt adjustments in one axis A, while rotation along another screw  806   b  would enable tilt adjustments along the other axis B. In some embodiments, a ball joint can be used to alter the pitch angle of the table  404  relative to the column  402  in multiple degrees of freedom. 
     For example, pitch adjustments are particularly useful when trying to position the table in a Trendelenburg position, i.e., position the patient&#39;s lower abdomen at a higher position from the floor than the patient&#39;s lower abdomen, for lower abdominal surgery. The Trendelenburg position causes the patient&#39;s internal organs to slide towards his/her upper abdomen through the force of gravity, clearing out the abdominal cavity for minimally invasive tools to enter and perform lower abdominal surgical or medical procedures, such as laparoscopic prostatectomy. 
       FIGS. 9A and 9B  illustrate isometric and end views, respectively, of an alternative embodiment of a table-based surgical robotics system  900 . The surgical robotics system  900  includes one or more adjustable arm supports  902  that can be configured to support one or more robotic arms (see, for example,  FIG. 9C ) relative to a table  904 . In the illustrated embodiment, a single adjustable arm support  902  is shown, though an additional arm support can be provided on an opposite side of the table  904 . The adjustable arm support  902  can be configured so that it can move relative to the table  904  to adjust and/or vary the position of the adjustable arm support  902  and/or any robotic arms mounted thereto relative to the table  904 . For example, the adjustable arm support  902  may be adjusted in one or more degrees of freedom relative to the table  904 . The adjustable arm support  902  provides high versatility to the system  900 , including the ability to easily stow the one or more adjustable arm supports  902  and any robotics arms attached thereto beneath the table  904 . The adjustable arm support  902  can be elevated from the stowed position to a position below an upper surface of the table  904 . In other embodiments, the adjustable arm support  902  can be elevated from the stowed position to a position above an upper surface of the table  904 . 
     The adjustable arm support  902  can provide several degrees of freedom, including lift, lateral translation, tilt, etc. In the illustrated embodiment of  FIGS. 9A and 9B , the arm support  902  is configured with four degrees of freedom, which are illustrated with arrows in  FIG. 9A . A first degree of freedom allows for adjustment of the adjustable arm support  902  in the z-direction (“Z-lift”). For example, the adjustable arm support  902  can include a carriage  906  configured to move up or down along or relative to a column  908  supporting the table  904 . A second degree of freedom can allow the adjustable arm support  902  to tilt. For example, the adjustable arm support  902  can include a rotary joint, which can allow the adjustable arm support  902  to be aligned with the bed in a Trendelenburg position. A third degree of freedom can allow the adjustable arm support  902  to “pivot up,” which can be used to adjust a distance between a side of the table  904  and the adjustable arm support  902 . A fourth degree of freedom can permit translation of the adjustable arm support  902  along a longitudinal length of the table. 
     The surgical robotics system  900  in  FIGS. 9A and 9B  can comprise a table  904  supported by a column  908  that is mounted to a base  910 . The base  910  and the column  908  support the table  904  relative to a support surface. A floor axis  912  and a support axis  914  are shown in  FIG. 9B . 
     The adjustable arm support  902  can be mounted to the column  908 . In other embodiments, the arm support  902  can be mounted to the table  904  or the base  910 . The adjustable arm support  902  can include a carriage  906 , a bar or rail connector  916  and a bar or rail  918 . In some embodiments, one or more robotic arms mounted to the rail  918  can translate and move relative to one another. 
     The carriage  906  can be attached to the column  908  by a first joint  920 , which allows the carriage  906  to move relative to the column  908  (e.g., such as up and down a first or vertical axis  922 ). The first joint  920  can provide the first degree of freedom (“Z-lift”) to the adjustable arm support  902 . The adjustable arm support  902  can include a second joint  924 , which provides the second degree of freedom (tilt) for the adjustable arm support  902 . The adjustable arm support  902  can include a third joint  926 , which can provide the third degree of freedom (“pivot up”) for the adjustable arm support  902 . An additional joint  928  (shown in  FIG. 9B ) can be provided that mechanically constrains the third joint  926  to maintain an orientation of the rail  918  as the rail connector  916  is rotated about a third axis  930 . The adjustable arm support  902  can include a fourth joint  932 , which can provide a fourth degree of freedom (translation) for the adjustable arm support  902  along a fourth axis  934 . 
       FIG. 9C  illustrates an end view of the surgical robotics system  900  with two adjustable arm supports  902   a  and  902   b  mounted on opposite sides of the table  904 . A first robotic arm  936   a  is attached to the first bar or rail  918   a  of the first adjustable arm support  902   a.  The first robotic arm  936   a  includes a base  938   a  attached to the first rail  918   a.  The distal end of the first robotic arm  936   a  includes an instrument drive mechanism or input  940   a  that can attach to one or more robotic medical instruments or tools. Similarly, the second robotic arm  936   b  includes a base  938   a  attached to the second rail  918   b.  The distal end of the second robotic arm  936   b  includes an instrument drive mechanism or input  940   b  configured to attach to one or more robotic medical instruments or tools. 
     In some embodiments, one or more of the robotic arms  936   a,b  comprises an arm with seven or more degrees of freedom. In some embodiments, one or more of the robotic arms  936   a,b  can include eight degrees of freedom, including an insertion axis (1-degree of freedom including insertion), a wrist (3-degrees of freedom including wrist pitch, yaw and roll), an elbow (1-degree of freedom including elbow pitch), a shoulder (2-degrees of freedom including shoulder pitch and yaw), and base  938   a,b  (1-degree of freedom including translation). In some embodiments, the insertion degree of freedom can be provided by the robotic arm  936   a,b,  while in other embodiments, the instrument itself provides insertion via an instrument-based insertion architecture. 
     C. Instrument Driver &amp; Interface. 
     The end effectors of a system&#39;s robotic arms comprise (i) an instrument driver (alternatively referred to as “tool driver,” “instrument drive mechanism,” “instrument device manipulator,” and “drive input”) that incorporate electro-mechanical means for actuating the medical instrument, and (ii) a removable or detachable medical instrument, which may be devoid of any electro-mechanical components, such as motors. This dichotomy may be driven by the need to sterilize medical instruments used in medical procedures, and the inability to adequately sterilize expensive capital equipment due to their intricate mechanical assemblies and sensitive electronics. Accordingly, the medical instruments may be designed to be detached, removed, and interchanged from the instrument driver (and thus the system) for individual sterilization or disposal by the physician or the physician&#39;s staff. In contrast, the instrument drivers need not be changed or sterilized, and may be draped for protection. 
       FIG. 10  illustrates an example instrument driver  1000 , according to one or more embodiments. Positioned at the distal end of a robotic arm, the instrument driver  1000  includes one or more drive outputs  1002  arranged with parallel axes to provide controlled torque to a medical instrument via corresponding drive shafts  1004 . Each drive output  1002  comprises an individual drive shaft  1004  for interacting with the instrument, a gear head  1006  for converting the motor shaft rotation to a desired torque, a motor  1008  for generating the drive torque, and an encoder  1010  to measure the speed of the motor shaft and provide feedback to control circuitry  1012 , which can also be used for receiving control signals and actuating the drive output  1002 . Each drive output  1002  being independently controlled and motorized, the instrument driver  1000  may provide multiple (at least two shown in  FIG. 10 ) independent drive outputs to the medical instrument. In operation, the control circuitry  1012  receives a control signal, transmits a motor signal to the motor  1008 , compares the resulting motor speed as measured by the encoder  1010  with the desired speed, and modulates the motor signal to generate the desired torque. 
     For procedures that require a sterile environment, the robotic system may incorporate a drive interface, such as a sterile adapter connected to a sterile drape that sits between the instrument driver and the medical instrument. The chief purpose of the sterile adapter is to transfer angular motion from the drive shafts of the instrument driver to the drive inputs of the instrument while maintaining physical separation, and thus sterility, between the drive shafts and drive inputs. Accordingly, an example sterile adapter may comprise a series of rotational inputs and outputs intended to be mated with the drive shafts of the instrument driver and drive inputs on the instrument. Connected to the sterile adapter, the sterile drape, comprised of a thin, flexible material such as transparent or translucent plastic, is designed to cover the capital equipment, such as the instrument driver, robotic arm, and cart (in a cart-based system) or table (in a table-based system). Use of the drape would allow the capital equipment to be positioned proximate to the patient while still being located in an area not requiring sterilization (i.e., non-sterile field). On the other side of the sterile drape, the medical instrument may interface with the patient in an area requiring sterilization (i.e., sterile field). 
     D. Medical Instrument. 
       FIG. 11  illustrates an example medical instrument  1100  with a paired instrument driver  1102 . Like other instruments designed for use with a robotic system, the medical instrument  1100  (alternately referred to as a “surgical tool”) comprises an elongated shaft  1104  (or elongate body) and an instrument base  1106 . The instrument base  1106 , also referred to as an “instrument handle” due to its intended design for manual interaction by the physician, may generally comprise rotatable drive inputs  1108 , e.g., receptacles, pulleys or spools, that are designed to be mated with drive outputs  1110  that extend through a drive interface on the instrument driver  1102  at the distal end of a robotic arm  1112 . When physically connected, latched, and/or coupled, the mated drive inputs  1108  of the instrument base  1106  may share axes of rotation with the drive outputs  1110  in the instrument driver  1102  to allow the transfer of torque from the drive outputs  1110  to the drive inputs  1108 . In some embodiments, the drive outputs  1110  may comprise splines that are designed to mate with receptacles on the drive inputs  1108 . 
     The elongated shaft  1104  is designed to be delivered through either an anatomical opening or lumen, e.g., as in endoscopy, or a minimally invasive incision, e.g., as in laparoscopy. The elongated shaft  1104  may be either flexible (e.g., having properties similar to an endoscope) or rigid (e.g., having properties similar to a laparoscope) or contain a customized combination of both flexible and rigid portions. When designed for laparoscopy, the distal end of the shaft  1104  may be connected to an end effector extending from a jointed wrist formed from a clevis with at least one degree of freedom and a surgical tool or medical instrument, such as, for example, a grasper or scissors, that may be actuated based on force from the tendons as the drive inputs  1008  rotate in response to torque received from the drive outputs  1110  of the instrument driver  1102 . When designed for endoscopy, the distal end of the flexible elongated shaft  1104  may include a steerable or controllable bending section that may be articulated and bent based on torque received from the drive outputs  1110  of the instrument driver  1102 . 
     In some embodiments, torque from the instrument driver  1102  is transmitted down the elongated shaft  1104  using tendons along the shaft  1104 . These individual tendons, such as pull wires, may be individually anchored to individual drive inputs  1108  within the instrument handle  1106 . From the handle  1106 , the tendons are directed down one or more pull lumens along the elongated shaft  1104  and anchored at the distal portion of the elongated shaft  1104 , or in the wrist at the distal portion of the elongated shaft. During a surgical procedure, such as a laparoscopic, endoscopic, or a hybrid procedure, these tendons may be coupled to a distally mounted end effector, such as a wrist, a grasper, or scissors. Under such an arrangement, torque exerted on the drive inputs  1108  would transfer tension to the tendon, thereby causing the end effector to actuate in some way. In some embodiments, during a surgical procedure, the tendon may cause a joint to rotate about an axis, thereby causing the end effector to move in one direction or another. Alternatively, the tendon may be connected to one or more jaws of a grasper at distal end of the elongated shaft  1104 , where tension from the tendon cause the grasper to close. 
     In endoscopy, the tendons may be coupled to a bending or articulating section positioned along the elongated shaft  1104  (e.g., at the distal end) via adhesive, control ring, or other mechanical fixation. When fixedly attached to the distal end of a bending section, torque exerted on drive inputs  1108  would be transmitted down the tendons, causing the softer, bending section (sometimes referred to as the articulable section or region) to bend or articulate. Along the non-bending sections, it may be advantageous to spiral or helix the individual pull lumens that direct the individual tendons along (or inside) the walls of the endoscope shaft to balance the radial forces that result from tension in the pull wires. The angle of the spiraling and/or spacing there between may be altered or engineered for specific purposes, wherein tighter spiraling exhibits lesser shaft compression under load forces, while lower amounts of spiraling results in greater shaft compression under load forces, but also exhibits limits bending. On the other end of the spectrum, the pull lumens may be directed parallel to the longitudinal axis of the elongated shaft  1104  to allow for controlled articulation in the desired bending or articulable sections. 
     In endoscopy, the elongated shaft  1104  houses a number of components to assist with the robotic procedure. The shaft may comprise a working channel for deploying surgical tools (or medical instruments), irrigation, and/or aspiration to the operative region at the distal end of the shaft  1104 . The shaft  1104  may also accommodate wires and/or optical fibers to transfer signals to/from an optical assembly at the distal tip, which may include of an optical camera. The shaft  1104  may also accommodate optical fibers to carry light from proximally-located light sources, such as light emitting diodes, to the distal end of the shaft. 
     At the distal end of the instrument  1100 , the distal tip may also comprise the opening of a working channel for delivering tools for diagnostic and/or therapy, irrigation, and aspiration to an operative site. The distal tip may also include a port for a camera, such as a fiberscope or a digital camera, to capture images of an internal anatomical space. Relatedly, the distal tip may also include ports for light sources for illuminating the anatomical space when using the camera. 
     In the example of  FIG. 11 , the drive shaft axes, and thus the drive input axes, are orthogonal to the axis of the elongated shaft. This arrangement, however, complicates roll capabilities for the elongated shaft  1104 . Rolling the elongated shaft  1104  along its axis while keeping the drive inputs  1108  static results in undesirable tangling of the tendons as they extend off the drive inputs  1108  and enter pull lumens within the elongated shaft  1104 . The resulting entanglement of such tendons may disrupt any control algorithms intended to predict movement of the flexible elongated shaft during an endoscopic procedure. 
       FIG. 12  illustrates an alternative design for a circular instrument driver  1200  and corresponding instrument  1202  (alternately referred to as a “surgical tool”) where the axes of the drive units are parallel to the axis of the elongated shaft  1206  of the instrument  1202 . As shown, the instrument driver  1200  comprises four drive units with corresponding drive outputs  1208  aligned in parallel at the end of a robotic arm  1210 . The drive units and their respective drive outputs  1208  are housed in a rotational assembly  1212  of the instrument driver  1200  that is driven by one of the drive units within the assembly  1212 . In response to torque provided by the rotational drive unit, the rotational assembly  1212  rotates along a circular bearing that connects the rotational assembly  1212  to a non-rotational portion  1214  of the instrument driver  1200 . Power and control signals may be communicated from the non-rotational portion  1214  of the instrument driver  1200  to the rotational assembly  1212  through electrical contacts maintained through rotation by a brushed slip ring connection (not shown). In other embodiments, the rotational assembly  1212  may be responsive to a separate drive unit that is integrated into the non-rotatable portion  1214 , and thus not in parallel with the other drive units. The rotational assembly  1212  allows the instrument driver  1200  to rotate the drive units and their respective drive outputs  1208  as a single unit around an instrument driver axis  1216 . 
     Like earlier disclosed embodiments, the instrument  1202  may include an elongated shaft  1206  and an instrument base  1218  (shown in phantom) including a plurality of drive inputs  1220  (such as receptacles, pulleys, and spools) that are configured to mate with the drive outputs  1208  of the instrument driver  1200 . Unlike prior disclosed embodiments, the instrument shaft  1206  extends from the center of the instrument base  1218  with an axis substantially parallel to the axes of the drive inputs  1220 , rather than orthogonal as in the design of  FIG. 11 . 
     When coupled to the rotational assembly  1212  of the instrument driver  1200 , the medical instrument  1202 , comprising instrument base  1218  and instrument shaft  1206 , rotates in combination with the rotational assembly  1212  about the instrument driver axis  1216 . Since the instrument shaft  1206  is positioned at the center of the instrument base  1218 , the instrument shaft  1206  is coaxial with the instrument driver axis  1216  when attached. Thus, rotation of the rotational assembly  1212  causes the instrument shaft  1206  to rotate about its own longitudinal axis. Moreover, as the instrument base  1218  rotates with the instrument shaft  1206 , any tendons connected to the drive inputs  1220  in the instrument base  1218  are not tangled during rotation. Accordingly, the parallelism of the axes of the drive outputs  1208 , the drive inputs  1220 , and the instrument shaft  1206  allows for the shaft rotation without tangling any control tendons. 
       FIG. 13  illustrates a medical instrument  1300  having an instrument based insertion architecture in accordance with some embodiments. The instrument  1300  (alternately referred to as a “surgical tool”) can be coupled to any of the instrument drivers discussed herein above and, as illustrated, can include an elongated shaft  1302 , an end effector  1304  connected to the shaft  1302 , and a handle  1306  coupled to the shaft  1302 . The elongated shaft  1302  comprises a tubular member having a proximal portion  1308   a  and a distal portion  1308   b.  The elongated shaft  1302  comprises one or more channels or grooves  1310  along its outer surface and configured to receive one or more wires or cables  1312  therethrough. One or more cables  1312  thus run along an outer surface of the elongated shaft  1302 . In other embodiments, the cables  1312  can also run through the elongated shaft  1302 . Manipulation of the cables  1312  (e.g., via an instrument driver) results in actuation of the end effector  1304 . 
     The instrument handle  1306 , which may also be referred to as an instrument base, may generally comprise an attachment interface  1314  having one or more mechanical inputs  1316 , e.g., receptacles, pulleys or spools, that are designed to be reciprocally mated with one or more drive outputs on an attachment surface of an instrument driver. 
     In some embodiments, the instrument  1300  comprises a series of pulleys or cables that enable the elongated shaft  1302  to translate relative to the handle  1306 . In other words, the instrument  1300  itself comprises an instrument-based insertion architecture that accommodates insertion of the instrument  1300 , thereby minimizing the reliance on a robot arm to provide insertion of the instrument  1300 . In other embodiments, a robotic arm can be largely responsible for instrument insertion. 
     E. Controller. 
     Any of the robotic systems described herein can include an input device or controller for manipulating an instrument attached to a robotic arm. In some embodiments, the controller can be coupled (e.g., communicatively, electronically, electrically, wirelessly and/or mechanically) with an instrument such that manipulation of the controller causes a corresponding manipulation of the instrument e.g., via master slave control. 
       FIG. 14  is a perspective view of an embodiment of a controller  1400 . In the present embodiment, the controller  1400  comprises a hybrid controller that can have both impedance and admittance control. In other embodiments, the controller  1400  can utilize just impedance or passive control. In other embodiments, the controller  1400  can utilize just admittance control. By being a hybrid controller, the controller  1400  advantageously can have a lower perceived inertia while in use. 
     In the illustrated embodiment, the controller  1400  is configured to allow manipulation of two medical instruments, and includes two handles  1402 . Each of the handles  1402  is connected to a gimbal  1404 , and each gimbal  1404  is connected to a positioning platform  1406 . 
     As shown in  FIG. 14 , each positioning platform  1406  includes a selective compliance assembly robot arm (SCARA)  1408  coupled to a column  1410  by a prismatic joint  1412 . The prismatic joints  1412  are configured to translate along the column  1410  (e.g., along rails  1414 ) to allow each of the handles  1402  to be translated in the z-direction, providing a first degree of freedom. The SCARA arm  1408  is configured to allow motion of the handle  1402  in an x-y plane, providing two additional degrees of freedom. 
     In some embodiments, one or more load cells are positioned in the controller  1400 . For example, in some embodiments, a load cell (not shown) is positioned in the body of each of the gimbals  1404 . By providing a load cell, portions of the controller  1400  are capable of operating under admittance control, thereby advantageously reducing the perceived inertia of the controller  1400  while in use. In some embodiments, the positioning platform  1406  is configured for admittance control, while the gimbal  1404  is configured for impedance control. In other embodiments, the gimbal  1404  is configured for admittance control, while the positioning platform  1406  is configured for impedance control. Accordingly, for some embodiments, the translational or positional degrees of freedom of the positioning platform  1406  can rely on admittance control, while the rotational degrees of freedom of the gimbal  1404  rely on impedance control. 
     F. Navigation and Control. 
     Traditional endoscopy may involve the use of fluoroscopy (e.g., as may be delivered through a C-arm) and other forms of radiation-based imaging modalities to provide endoluminal guidance to an operator physician. In contrast, the robotic systems contemplated by this disclosure can provide for non-radiation-based navigational and localization means to reduce physician exposure to radiation and reduce the amount of equipment within the operating room. As used herein, the term “localization” may refer to determining and/or monitoring the position of objects in a reference coordinate system. Technologies such as pre-operative mapping, computer vision, real-time EM tracking, and robot command data may be used individually or in combination to achieve a radiation-free operating environment. In other cases, where radiation-based imaging modalities are still used, the pre-operative mapping, computer vision, real-time EM tracking, and robot command data may be used individually or in combination to improve upon the information obtained solely through radiation-based imaging modalities. 
       FIG. 15  is a block diagram illustrating a localization system  1500  that estimates a location of one or more elements of the robotic system, such as the location of the instrument, in accordance to an example embodiment. The localization system  1500  may be a set of one or more computer devices configured to execute one or more instructions. The computer devices may be embodied by a processor (or processors) and computer-readable memory in one or more components discussed above. By way of example and not limitation, the computer devices may be in the tower  112  shown in  FIG. 1 , the cart  102  shown in  FIGS. 1-3B , the beds shown in  FIGS. 4-9 , etc. 
     As shown in  FIG. 15 , the localization system  1500  may include a localization module  1502  that processes input data  1504   a,    1504   b,    1504   c,  and  1504   d  to generate location data  1506  for the distal tip of a medical instrument. The location data  1506  may be data or logic that represents a location and/or orientation of the distal end of the instrument relative to a frame of reference. The frame of reference can be a frame of reference relative to the anatomy of the patient or to a known object, such as an EM field generator (see discussion below for the EM field generator). 
     The various input data  1504   a - d  are now described in greater detail. Pre-operative mapping may be accomplished through the use of the collection of low dose CT scans. Pre-operative CT scans are reconstructed into three-dimensional images, which are visualized, e.g. as “slices” of a cutaway view of the patient&#39;s internal anatomy. When analyzed in the aggregate, image-based models for anatomical cavities, spaces and structures of the patient&#39;s anatomy, such as a patient lung network, may be generated. Techniques such as center-line geometry may be determined and approximated from the CT images to develop a three-dimensional volume of the patient&#39;s anatomy, referred to as model data  1504   a  (also referred to as “preoperative model data” when generated using only preoperative CT scans). The use of center-line geometry is discussed in U.S. patent application Ser. No. 14/523,760, the contents of which are herein incorporated in its entirety. Network topological models may also be derived from the CT-images, and are particularly appropriate for bronchoscopy. 
     In some embodiments, the instrument may be equipped with a camera to provide vision data  1504   b.  The localization module  1502  may process the vision data  1504   b  to enable one or more vision-based location tracking. For example, the preoperative model data may be used in conjunction with the vision data  1504   b  to enable computer vision-based tracking of the medical instrument (e.g., an endoscope or an instrument advance through a working channel of the endoscope). For example, using the preoperative model data  1504   a,  the robotic system may generate a library of expected endoscopic images from the model based on the expected path of travel of the endoscope, each image linked to a location within the model. Intra-operatively, this library may be referenced by the robotic system in order to compare real-time images captured at the camera (e.g., a camera at a distal end of the endoscope) to those in the image library to assist localization. 
     Other computer vision-based tracking techniques use feature tracking to determine motion of the camera, and thus the endoscope. Some features of the localization module  1502  may identify circular geometries in the preoperative model data  1504   a  that correspond to anatomical lumens and track the change of those geometries to determine which anatomical lumen was selected, as well as the relative rotational and/or translational motion of the camera. Use of a topological map may further enhance vision-based algorithms or techniques. 
     Optical flow, another computer vision-based technique, may analyze the displacement and translation of image pixels in a video sequence in the vision data  1504   b  to infer camera movement. Examples of optical flow techniques may include motion detection, object segmentation calculations, luminance, motion compensated encoding, stereo disparity measurement, etc. Through the comparison of multiple frames over multiple iterations, movement and location of the camera (and thus the endoscope) may be determined. 
     The localization module  1502  may use real-time EM tracking to generate a real-time location of the endoscope in a global coordinate system that may be registered to the patient&#39;s anatomy, represented by the preoperative model. In EM tracking, an EM sensor (or tracker) comprising of one or more sensor coils embedded in one or more locations and orientations in a medical instrument (e.g., an endoscopic tool) measures the variation in the EM field created by one or more static EM field generators positioned at a known location. The location information detected by the EM sensors is stored as EM data  1504   c.  The EM field generator (or transmitter), may be placed close to the patient to create a low intensity magnetic field that the embedded sensor may detect. The magnetic field induces small currents in the sensor coils of the EM sensor, which may be analyzed to determine the distance and angle between the EM sensor and the EM field generator. These distances and orientations may be intra-operatively “registered” to the patient anatomy (e.g., the preoperative model) in order to determine the geometric transformation that aligns a single location in the coordinate system with a position in the pre-operative model of the patient&#39;s anatomy. Once registered, an embedded EM tracker in one or more positions of the medical instrument (e.g., the distal tip of an endoscope) may provide real-time indications of the progression of the medical instrument through the patient&#39;s anatomy. 
     Robotic command and kinematics data  1504   d  may also be used by the localization module  1502  to provide localization data  1506  for the robotic system. Device pitch and yaw resulting from articulation commands may be determined during pre-operative calibration. Intra-operatively, these calibration measurements may be used in combination with known insertion depth information to estimate the position of the instrument. Alternatively, these calculations may be analyzed in combination with EM, vision, and/or topological modeling to estimate the position of the medical instrument within the network. 
     As  FIG. 15  shows, a number of other input data can be used by the localization module  1502 . For example, although not shown in  FIG. 15 , an instrument utilizing shape-sensing fiber can provide shape data that the localization module  1502  can use to determine the location and shape of the instrument. 
     The localization module  1502  may use the input data  1504   a - d  in combination(s). In some cases, such a combination may use a probabilistic approach where the localization module  1502  assigns a confidence weight to the location determined from each of the input data  1504   a - d.  Thus, where the EM data  1504   c  may not be reliable (as may be the case where there is EM interference) the confidence of the location determined by the EM data  1504   c  can be decrease and the localization module  1502  may rely more heavily on the vision data  1504   b  and/or the robotic command and kinematics data  1504   d.    
     As discussed above, the robotic systems discussed herein may be designed to incorporate a combination of one or more of the technologies above. The robotic system&#39;s computer-based control system, based in the tower, bed and/or cart, may store computer program instructions, for example, within a non-transitory computer-readable storage medium such as a persistent magnetic storage drive, solid state drive, or the like, that, upon execution, cause the system to receive and analyze sensor data and user commands, generate control signals throughout the system, and display the navigational and localization data, such as the position of the instrument within the global coordinate system, anatomical map, etc. 
     2. Description. 
       FIG. 16  is an isometric side view of an example surgical tool  1600  that may incorporate some or all of the principles of the present disclosure. The surgical tool  1600  may be similar in some respects to any of the surgical tools and medical instruments described above with reference to  FIGS. 11-13  and, therefore, may be used in conjunction with a robotic surgical system, such as the robotically-enabled systems  100 ,  400 , and  900  of  FIGS. 1-9C . As illustrated, the surgical tool  1600  includes an elongated shaft  1602 , an end effector  1604  arranged at the distal end of the shaft  1602 , and an articulable wrist  1606  (alternately referred to as a “wrist joint”) that interposes and couples the end effector  1604  to the distal end of the shaft  1602 . In some embodiments, the wrist  1606  may be omitted, without departing from the scope of the disclosure. 
     The terms “proximal” and “distal” are defined herein relative to a robotic surgical system having an interface configured to mechanically and electrically couple the surgical tool  1600  to a robotic manipulator. The term “proximal” refers to the position of an element closer to the robotic manipulator and the term “distal” refers to the position of an element closer to the end effector  1604  and thus closer to the patient during operation. Moreover, the use of directional terms such as above, below, upper, lower, upward, downward, left, right, and the like are used in relation to the illustrative embodiments as they are depicted in the figures, the upward or upper direction being toward the top of the corresponding figure and the downward or lower direction being toward the bottom of the corresponding figure. 
     The surgical tool  1600  can have any of a variety of configurations capable of performing one or more surgical functions. In the illustrated embodiment, the end effector  1604  comprises a surgical stapler, alternately referred to as an “endocutter,” configured to cut and staple (fasten) tissue. As illustrated, the end effector  1604  includes opposing jaws  1610 ,  1612  configured to move (articulate) between open and closed positions. Alternatively, the end effector  1604  may comprise other types of instruments with opposing jaws such as, but not limited to, other types of surgical staplers (e.g., circular and linear staplers), tissue graspers, surgical scissors, advanced energy vessel sealers, clip appliers, needle drivers, a babcock including a pair of opposed grasping jaws, bipolar jaws (e.g., bipolar Maryland grasper, forceps, a fenestrated grasper, etc.), etc. In other embodiments, the end effector  1604  may instead comprise any end effector or instrument capable of being operated in conjunction with the presently disclosed robotic surgical systems and methods, such as a suction irrigator, an endoscope (e.g., a camera), or any combination thereof. 
     One or both of the jaws  1610 ,  1612  may be configured to pivot to actuate the end effector  1604  between open and closed positions. In the illustrated example, the second jaw  1612  may be rotatable (pivotable) relative to the first jaw  1610  to actuate the end effector  1604  between an open, unclamped position and a closed, clamped position. In other embodiments, however, the first jaw  1610  may move (rotate) relative to the second jaw  1612  to move the jaws  1610 ,  1612  between open and closed positions. In yet other embodiments, as discussed in more detail below, both jaws  1610 ,  1612  may simultaneously move (e.g., bifurcating jaws) to move the jaws  1610 ,  1612  between open and closed positions. 
     In the illustrated example, the first jaw  1610  is referred to as a “cartridge” or “channel” jaw, and the second jaw  1612  is referred to as an “anvil” jaw. The first jaw  1610  includes a frame that houses or supports a staple cartridge, and the second jaw  1612  is pivotally supported relative to the first jaw  1610  and defines a surface that operates as an anvil to deform staples ejected from the staple cartridge during operation. 
     The wrist  1606  enables the end effector  1604  to articulate (pivot) relative to the shaft  1602  and thereby position the end effector  1604  at various desired orientations and locations relative to a surgical site. In the illustrated embodiment, the wrist  1606  is designed to allow the end effector  1604  to pivot (swivel) left and right relative to a longitudinal axis A 1  of the shaft  1602 . In other embodiments, however, the wrist  1606  may be designed to provide multiple degrees of freedom, including one or more translational variables (i.e., surge, heave, and sway) and/or one or more rotational variables (i.e., Euler angles or roll, pitch, and yaw). The translational and rotational variables describe the position and orientation of a component of a surgical system (e.g., the end effector  1604 ) with respect to a given reference Cartesian frame. “Surge” refers to forward and backward translational movement, “heave” refers to translational movement up and down, and “sway” refers to translational movement left and right. With regard to the rotational terms, “roll” refers to tilting side to side, “pitch” refers to tilting forward and backward, and “yaw” refers to turning left and right. 
     The end effector  1604  is depicted in  FIG. 16  in the unarticulated position where the longitudinal axis of the end effector  1604  is substantially aligned with the longitudinal axis A 1  of the shaft  1602 , such that the end effector  1604  is at a substantially zero angle relative to the shaft  1602 . In the articulated position, the longitudinal axis of the end effector  1604  would be angularly offset from the longitudinal axis A 1  such that the end effector  1604  would be oriented at a non-zero angle relative to the shaft  1602 . 
     Still referring to  FIG. 16 , the surgical tool  1600  may include a drive housing or “handle”  1614 , and the shaft  1602  extends longitudinally through the handle  1614 . The handle  1614  houses an actuation system designed to move the shaft  1602  relative to the handle  1614 , and further designed to facilitate articulation of the wrist  1606  and actuation (operation) of the end effector  1604  (e.g., clamping, firing, rotation, articulation, energy delivery, etc.). More specifically, the systems and mechanisms housed within the handle  1614  are actuatable to move (translate) a plurality of drive members (mostly obscured in  FIG. 16 ) that extend along at least a portion of the shaft  1602 , either on the exterior or within the interior of the shaft  1602 . Example drive members include, but are not limited to, cables, bands, lines, cords, wires, woven wires, ropes, strings, twisted strings, elongate members, belts, shafts, flexible shafts, drive rods, or any combination thereof. The drive members can be made from a variety of materials including, but not limited to, a metal (e.g., tungsten, stainless steel, nitinol, etc.) a polymer (e.g., ultra-high molecular weight polyethylene), a synthetic fiber (e.g., KEVLAR®, VECTRAN®, etc.), an elastomer, or any combination thereof. 
     Selective actuation of one or more of the drive members, for example, may cause the shaft  1602  to translate relative to the handle  1614 , as indicated by the arrows B, and thereby advance or retract the end effector  1602 . Selective actuation of one or more other drive members may cause the end effector  1604  to articulate (pivot) relative to the shaft  1602  at the wrist  1606 . Selective actuation of one or more additional drive members may cause the end effector  1604  to actuate (operate). Actuating the end effector  1604  depicted in  FIG. 16  may entail closing and/or opening the jaws,  1610 ,  1612  and thereby enabling the end effector  1604  to grasp (clamp) onto tissue. Once tissue is grasped or clamped between the opposing jaws  1610 ,  1612 , actuating the end effector  1604  may further include “firing” the end effector  1604 , which may refer to causing a cutting element or knife (not visible) to advance distally within a slot or “guide track”  1616  defined in the first jaw  1610 . As it moves distally, the knife transects any tissue grasped between the opposing jaws  1610 ,  1612 . Moreover, as the knife advances distally, a plurality of staples contained within the staple cartridge (e.g., housed within the first jaw  1610 ) are urged (cammed) into deforming contact with corresponding anvil surfaces (e.g., pockets) provided on the second jaw  1612 . The deployed staples may form multiple rows of staples that seal opposing sides of the transected tissue. 
     As will be appreciated, however, the end effector  1604  may be replaced with any of the other types of end effectors mentioned herein, and in those cases actuating the end effector  1604  may entail a variety of other actions or movements, without departing from the scope of the disclosure. For example, in some embodiments, the end effector  1604  may be replaced with a vessel sealer and actuating such an end effector  1604  may further entail triggering energy delivery (e.g., RF energy) to cauterize and/or seal tissue or vessels. 
     The handle  1614  provides or otherwise includes various coupling features that releasably couple the surgical tool  1600  to an instrument driver  1618  (shown in dashed lines) of a robotic surgical system. The instrument driver  1618  may be similar in some respects to the instrument drivers  1102 ,  1200  of  FIGS. 11 and 12 , respectively, and therefore may be best understood with reference thereto. Similar to the instrument drivers  1102 ,  1200 , for example, the instrument driver  1618  may be mounted to or otherwise positioned at the end of a robotic arm (not shown) and is designed to provide the motive forces required to operate the surgical tool  1600 . Unlike the instrument drivers  1102 ,  1200 , however, the shaft  1602  of the surgical tool  1600  extends through and penetrates the instrument driver  1618 . 
     The handle  1614  includes one or more rotatable drive inputs matable with one or more corresponding drive outputs (not shown) of the instrument driver  1618 . Each drive input is actuatable to independently drive (actuate) the systems and mechanisms housed within the handle  1614  and thereby operate the surgical tool  1600 . In the illustrated embodiment, the handle  1614  includes a first drive input  1620   a,  a second drive input  1620   b,  a third drive input  1620   c,  a fourth drive input  1620   d,  a fifth drive input  1620   e,  and a sixth drive input  1620   f.  While six drive inputs  1620   a - f  are depicted, more or less than six may be included in the handle  1614  depending on the application, and without departing from the scope of the disclosure. Each drive input  1620   a - f  may be matable with a corresponding drive output (not shown) of the instrument driver  1618  such that movement (rotation) of a given drive output correspondingly moves (rotates) the associated drive input  1620   a - f  and thereby causes various operations of the surgical tool  1600 . 
     In some embodiments, actuation of the first drive input  1620   a  may cause the knife to fire at the end effector  1604 , thus advancing or retracting the knife, depending on the rotational direction of the first drive input  1620   a.  Actuation of the third drive input  1620   c  may cause the shaft  1602  to move (translate) relative to the handle  1614  along the longitudinal axis A 1 , depending on the rotational direction of the third drive input  1620   c.  In some embodiments, actuation of the second drive input  1620   b  may shift operation or activation within the handle  1614  between the first and third drive inputs  1620   a,c.  Consequently, actuation of the second drive input  1620   b  will dictate whether the knife is fired or whether the shaft  1602  is moved (translated). Actuation of the fourth drive input  1620   d  may lock and unlock z-axis translation of the shaft  1602 , and actuation of the fifth drive input  1620   e  may cause articulation of the end effector  1604  at the wrist  1606 . Lastly, actuation of the sixth drive input  1620   f  may cause the jaws  1610 ,  1612  to open or close, depending on the rotational direction of the sixth drive input  1620   f.  In some embodiments, actuation of the sixth drive input  1620   f  may operate a toggle mechanism  1622  arranged at the proximal end of the shaft  1602 , and actuation of the toggle mechanism  1622  may cause the jaws  1610 ,  1612  to open and close. 
       FIG. 17  depicts separated isometric end views of the instrument driver  1618  and the surgical tool  1600  of  FIG. 16 . With the jaws  1610 ,  1612  closed, the shaft  1602  and the end effector  1604  can penetrate the instrument driver  1618  by extending through a central aperture  1702  defined longitudinally through the instrument driver  1618  between first and second ends  1704   a,b.  In some embodiments, to align the surgical tool  1600  with the instrument driver  1618  in a proper angular orientation, one or more alignment guides  1706  may be provided or otherwise defined within the central aperture  1702  and configured to engage one or more corresponding alignment features (not shown) provided on the surgical tool  1600 . The alignment feature(s) may comprise, for example, a protrusion or projection (not shown) defined on or otherwise provided by an alignment nozzle  1708  extending distally from the handle  1614 . In one or more embodiments, the alignment guide(s)  1706  may comprise a curved or arcuate shoulder or lip configured to receive and guide the alignment feature as the alignment nozzle  1708  enters the central aperture  1702 . As a result, the surgical tool  1600  is oriented to a proper angular alignment with the instrument driver  1618  as the alignment nozzle  1708  is advanced distally through the central aperture  1702 . In other embodiments, the alignment nozzle  1708  may be omitted and the alignment feature  1712  may alternatively be provided on the shaft  1602 , without departing from the scope of the disclosure. 
     A drive interface  1710  is provided at the first end  1704   a  of the instrument driver  1618  and is matable with a driven interface  1712  provided on the distal end of the handle  1614 . The drive and driven interfaces  1710 ,  1712  may be configured to mechanically, magnetically, and/or electrically couple the handle  1614  to the instrument driver  1618 . To accomplish this, in some embodiments, the drive and driven interfaces  1710 ,  1712  may provide one or more matable locating features configured to secure the handle  1614  to the instrument driver  1618 . In the illustrated embodiment, for example, the drive interface  1710  provides one or more interlocking features  1714  (three shown) configured to locate and mate with one or more complementary-shaped pockets  1716  (two shown, one occluded) provided on the driven interface  1712 . In some embodiments, the features  1714  may be configured to align and mate with the pockets  1716  via an interference or snap fit engagement, for example. 
     The instrument driver  1618  also includes one or more drive outputs that extend through the drive interface  1710  to mate with corresponding drive inputs  1620   a - f  provided at the distal end of the handle  1614 . More specifically, the instrument driver  1618  includes a first drive output  1718   a  matable with the first drive input  1620   a,  a second drive output  1718   b  matable with the second drive input  1620   b,  a third drive output  1718   b  matable with the third drive input  1620   c,  a fourth drive output  1718   d  matable with the fourth drive input  1620   d,  a fifth drive output  1718   e  matable with the fifth drive input  1620   e,  and a sixth drive output  1718   f  matable with the sixth drive input  1620   f.  In some embodiments, as illustrated, the drive outputs  1718   a - f  may define splines or features designed to mate with corresponding splined receptacles of the drive inputs  1620   a - f.  Once properly mated, the drive inputs  1620   a - f  will share axes of rotation with the corresponding drive outputs  1718   a - f  to allow the transfer of rotational torque from the drive outputs  1718   a - f  to the corresponding drive inputs  1620   a - f.  In some embodiments, each drive output  1718   a - f  may be spring loaded and otherwise biased to spring outwards away from the drive interface  1710 . Each drive output  1718   a - f  may be capable of partially or fully retracting into the drive interface  1710 . 
     In some embodiments, the instrument driver  1618  may include additional drive outputs, depicted in  FIG. 17B  as a seventh drive output  1718   g.  The seventh drive output  1718   g  may be configured to mate with additional drive inputs (not shown) of the handle  1614  to help undertake one or more additional functions of the surgical tool  1600 . In the illustrated embodiment, however, the handle  1614  does not include additional drive inputs matable with the seventh drive output  1718   g.  Instead, the driven interface  1712  defines a corresponding recess  1720  (partially occluded) configured to receive the seventh drive output  1718   g.  In other applications, however, a seventh drive input (not shown) could be included in the handle  1614  to mate with the seventh drive output  1718   g,  or the surgical tool  1600  might be replaced with another surgical tool having a seventh drive input, which would be driven by the seventh drive output  1718   g.    
     While not shown, in some embodiments, an instrument sterile adapter (ISA) may be placed at the interface between the instrument driver  1618  and the handle  1614 . In such applications, the interlocking features  1714  may operate as alignment features and possible latches for the ISA to be placed, stabilized, and secured. Stability of the ISA may be accomplished by a nose cone feature provided by the ISA and extending into the central aperture  1702  of the instrument driver  1618 . Latching can occur either with the interlocking features  1714  or at other locations at the interface. In some cases, the ISA will provide the means to help align and facilitate the latching of the surgical tool  1600  to the ISA and simultaneously to the instrument driver  1618 . 
     Multi-Function Closing/Opening and Dissection/Sealing Enabled by Clevis Jaw Constraint of Jaws 
       FIG. 18  is an enlarged isometric view of the distal end of the surgical tool  1600  of  FIGS. 16 and 17 .  FIG. 18 , however, depicts an enlarged view of an alternative embodiment of the end effector  1604  and the wrist  1606 . In contrast to the end effector  1604  of  FIGS. 16 and 17 , which depicts a surgical stapler with the second jaw  1612  pivotable relative to the first jaw  1610  to open and close the jaws  1610 ,  1612 , the end effector  1604  depicted in  FIG. 18  is a vessel sealer where both jaws  1610 ,  1612  simultaneously move to actuate the jaws  1610 ,  1612  between open and closed positions, e.g., bifurcating jaws. 
     The wrist  1606  interposes the shaft  1602  and the end effector  1604  and thereby operatively couples the end effector  1604  to the shaft  1602 . In some embodiments, however, a shaft adapter may be directly coupled to the wrist  1606  and otherwise interpose the shaft  1602  and the wrist  1606 . Accordingly, the wrist  1606  may be operatively coupled to the shaft  1602  either through a direct coupling engagement where the wrist  1606  is directly coupled to the distal end of the shaft  1602 , or an indirect coupling engagement where a shaft adapter interposes the wrist  1606  and the distal end of the shaft  1602 . As used herein, the term “operatively couple” refers to a direct or indirect coupling engagement between two components. 
     To operatively couple the end effector  1604  to the shaft  1602 , the wrist  1606  includes a first or “distal” clevis  1802   a  and a second or “proximal” clevis  1802   b.  The devises  1802   a,b  may alternatively be referred to herein as “articulation joints” of the wrist  1606  and extend from the shaft  1602 , or alternatively a shaft adapter. As described herein, the devises  1802   a,b  are operatively coupled to facilitate articulation of the wrist  1606  relative to the shaft  1602 . The wrist  1606  may also include a linkage  1804  arranged distal to the distal clevis  1802   a  and operatively mounted to the jaws  1610 ,  1612 . 
     As illustrated, the proximal end of the distal clevis  1802   a  may be rotatably mounted to the proximal clevis  1802   b.  In some embodiments, for example, the proximal end of the distal clevis  1802   a  may be pivotably coupled to the proximal clevis  1802   b  at a first pivot axis P 1  of the wrist  1602 . In other embodiments, however, the proximal end of the distal clevis  1802   a  may alternatively be rotatably coupled to the proximal clevis  1802   b,  such as in the “snake wrist” rotatable coupling between adjacent articulation joints (links) disclosed in U.S. Patent Pub. 2020/0093554, the contents of which are hereby incorporated by reference in their entirety. As will be appreciated, any of the wrists described or disclosed herein may alternatively, comprise a type of “snake wrist,” without departing from the scope of the disclosure. 
     First and second pulleys  1806   a  and  1806   b  may be rotatably mounted to the distal end of the distal clevis  1802   a  at a second pivot axis P 2  of the wrist  1602 . The linkage  1804  may be arranged distal to the second pivot axis P 2  and operatively mounted to the jaws  1610 ,  1612 . The first pivot axis P 1  is substantially perpendicular (orthogonal) to the longitudinal axis A 1  of the shaft  1602 , and the second pivot axis P 2  is substantially perpendicular (orthogonal) to both the longitudinal axis A 1  and the first pivot axis P 1 . Movement of the end effector  1604  about the first pivot axis P 1  provides “yaw” articulation of the wrist  1606 , and movement about the second pivot axis P 2  provides “pitch” articulation of the wrist  1606 . 
     A plurality of drive members, shown as drive members  1808   a,    1808   b,    1808   c,  and  1808   d,  extend longitudinally within a lumen  1810  defined by the shaft  1602  (or a shaft adaptor) and extend at least partially through the wrist  1606 . The drive members  1808   a - d  may form part of the actuation systems housed within the handle  1614  ( FIGS. 16 and 17 ), and may comprise cables, bands, lines, cords, wires, woven wires, ropes, strings, twisted strings, elongate members, belts, shafts, flexible shafts, drive rods, or any combination thereof. The drive members  1808   a - d  can be made from a variety of materials including, but not limited to, a metal (e.g., tungsten, stainless steel, nitinol, etc.) a polymer (e.g., ultra-high molecular weight polyethylene), a synthetic fiber (e.g., KEVLAR®, VECTRAN®, etc.), an elastomer, or any combination thereof. While four drive members  1808   a - d  are depicted in  FIG. 18 , more or less than four may be employed, without departing from the scope of the disclosure. 
     The drive members  1808   a - d  extend proximally from the end effector  1604  and the wrist  1606  toward the handle  1614  ( FIGS. 16 and 17 ) where they are operatively coupled to various actuation mechanisms or devices that facilitate longitudinal movement (translation) of the drive members  1808   a - d  within the lumen  1810 . Selective actuation of the drive members  1808   a - d  applies tension (i.e., pull force) to the given drive member  1808   a - d  in the proximal direction, which urges the given drive member  1808   a - d  to translate longitudinally within the lumen  1810 . 
     In the illustrated embodiment, the drive members  1808   a - d  each extend longitudinally through the proximal clevis  1802   b.  The distal end of each drive member  1808   a - d  terminates at the first or second pulleys  1806   a,b,  thus operatively coupling each drive member  1808   a - d  to the end effector  1604 . In some embodiments, the distal ends of the first and second drive members  1808   a,b  may be coupled to each other and terminate at the first pulley  1806   a,  and the distal ends of the third and fourth drive members  1808   c,d  may be coupled to each other and terminate at the second pulley  1806   b.  In at least one embodiment, the distal ends of the first and second drive members  1808   a,b  and the distal ends of the third and fourth drive members  1808   c,d  may each be coupled together at a corresponding ball crimp (not shown) mounted to the first or second pulley  1806   a,b,  respectively. 
     In the illustrated embodiment, the drive members  1808   a - d  operate “antagonistically”. More specifically, when the first drive member  1808   a  is actuated (moved), the second drive member  1808   b  naturally follows as coupled to the first drive member  1808   a,  and when the third drive member  1808   c  is actuated, the fourth drive member  1808   d  naturally follows as coupled to the third drive member  1808   c,  and vice versa. Antagonistic operation of the drive members  1808   a - d  can open or close the jaws  1610 ,  1612  and can further cause the end effector  1604  to articulate at the wrist  1606 . More specifically, selective actuation of the drive members  1808   a - d  in known configurations or coordination can cause the end effector  1604  to articulate about one or both of the pivot axes P 1 , P 2 , thus facilitating articulation of the end effector  1604  in both pitch and yaw directions. Moreover, selective actuation of the drive members  1808   a - d  in other known configurations or coordination will cause the jaws  1610 ,  1612  to open or close. Antagonistic operation of the drive members  1808   a - d  advantageously reduces the number of cables required to provide full wrist  1606  motion, and also helps eliminate slack in the drive members  1808   a - d,  which results in more precise motion of the end effector  1604 . 
     In the illustrated embodiment, the end effector  1604  is able to articulate (move) in pitch about the second or “pitch” pivot axis P 2 , which is located near the distal end of the wrist  1606 . Thus, the jaws  1610 ,  1612  open and close in the direction of pitch. Moving both articulation axes P 1 , P 2  closer to the therapeutic jaw surface enables minimization of the distance between the remote center of motion, therapeutic surface and articulation axis. Having the pitch pivot axis P 2  as far distal as possible may be advantageous in providing a geometric advantage that helps an operator more easily get under vessels and facilitate touch and spread dissection. This may also reduce the overall length of the end effector  1604  and thereby improve surgeon access to patient anatomy during surgery by allowing articulate motion in smaller surgical spaces. This may improve the robotic control of the instrument making user applied motions seem more natural. This may also result in providing better reach to anatomy during dissection, such as for lymph node removal or other tissue mobilization. In other embodiments, however, the wrist  1606  may alternatively be configured such that the second pivot axis P 2  facilitates yaw articulation of the jaws  1610 ,  1612 , without departing from the scope of the disclosure. 
     In some embodiments, an electrical conductor  1812  may also extend longitudinally within the lumen  1810 , through the wrist  1606 , and terminate at an electrode  1814  to supply electrical energy to the end effector  1604 . In some embodiments, the electrical conductor  1812  may comprise a wire, but may alternatively comprise a rigid or semi-rigid shaft, rod, or strip (ribbon) made of a conductive material. The electrical conductor  1812  may be partially covered with an insulative covering (overmold) made of a non-conductive material. Using the electrical conductor  1812  and the electrode  1814 , the end effector  1604  may be configured for monopolar or bipolar RF operation. 
     In the illustrated embodiment, the end effector  1604  comprises a combination tissue grasper and vessel sealer that includes a knife  1816  (mostly occluded), alternately referred to as a “cutting element” or “blade.” The knife  1816  is aligned with and configured to traverse the guide track  1616  defined longitudinally in one or both of the upper and lower jaws  1610 ,  1612 . The knife  1816  may be operatively coupled to the distal end of a drive rod  1818  that extends longitudinally within the lumen  1810  and passes through the wrist  1606 . Longitudinal movement (translation) of the drive rod  1818  correspondingly moves the knife  1816  within the guide track(s)  1616 . Similar to the drive members  1808   a - d,  the drive rod  1818  may form part of the actuation systems housed within the handle  1614  ( FIGS. 16 and 17 ). Selective actuation of a corresponding drive input will cause the drive rod  1818  to move distally or proximally within the lumen  1810 , and correspondingly move the knife  1816  in the same longitudinal direction. 
       FIGS. 19A and 19B  are isometric, partially exploded views of the end effector  1604  of  FIG. 18 , as taken from right and left vantage points.  FIGS. 19A-19B  depict the distal clevis  1802   a  and the linkage  1804  exploded laterally from the remaining portions of the end effector  1604  and the wrist  1606 , thus exposing the distal ends of drive members  1808   a - d  terminating at the pulleys  1806   a,b.    
     In some embodiments, one or both of the distal clevis  1802   a  and the linkage  1804  may comprise two or more component parts that are joined to help form the wrist  1606  and rotatably secure the jaws  1610 ,  1612  to the wrist  1606 . In the illustrated embodiment, for example, the linkage  1804  comprises opposing first and second linkage portions  1902   a,b,  and the distal clevis  1802   a  comprises opposing first and second distal clevis portions  1904   a,b.  In building the wrist  1606 , joining the linkage portions  1902   a,b  and joining the distal clevis portions  1904   a,b  may help rotatably secure the jaws  1610 ,  1612  to the wrist  1606  and may further secure the pulleys  1806   a,b  and other component parts within the wrist  1606 . The linkage portions  1902   a,b  and the distal clevis portions  1904   a,b  may be joined, respectively, by welding, soldering, brazing, an adhesive, an interference fit, or by using one or more mechanical fasteners, such as pins, rivets, bolts, or any combination of the foregoing. In other embodiments, however, it is contemplated herein that one or both of the devises  1802   a,b  may alternatively comprise a monolithic, one-piece structure, without departing from the scope of the disclosure. 
     As indicated above, the proximal end of the distal clevis  1802   a  may be rotatably mounted to the proximal clevis  1802   b  at the first pivot axis P 1  of the wrist  1602 . As illustrated, the proximal clevis  1802   b  may provide or otherwise define one or more pins  1906  (one shown) and the distal clevis  1802   a  may provide or define one or more corresponding apertures  1908  matable with the pins  1906 . Mating the aperture(s)  1908  with the pin(s)  1906  may allow the wrist  1606  to articulate in “yaw” about the first pivot axis P 1 . In alternative embodiments, however, the pin(s)  1906  may be provided by the distal clevis  1802   a,  and the aperture(s)  1908  may be provided by the proximal clevis  1802   b,  without departing from the scope of the disclosure. Moreover, in some embodiments, the aperture(s)  1908  need not be through-holes, as depicted, but could alternatively comprise recesses defined in the distal clevis  1802   a  (or the proximal clevis  1802   b ) and sized and otherwise configured to receive the pin(s)  1906 . 
     As also indicated above, the first and second pulleys  1806   a  and  1806   b  may be rotatably mounted to the distal end of the distal clevis  1802   a  at the second pivot axis P 2  of the wrist  1602 . As illustrated, the distal clevis  1802   a  may provide or otherwise define opposing pins  1910  and the pulleys  1806   a,b  may each define an aperture  1912  sized to receive or mate with the corresponding pin  1910 . In alternative embodiments, however, the pins  1910  may be provided by the pulleys  1806   a,b,  and the apertures  1912  may be provided by the distal clevis  1802   a,  without departing from the scope of the disclosure. Moreover, in some embodiments, the apertures  1912  need not be through-holes, as depicted, but could alternatively comprise recesses defined in the pulleys  1806   a,b  (or the distal clevis  1802   a ) and sized and otherwise configured to receive the pins  1910 . 
     As further indicated above, the linkage  1804  may be mounted or otherwise operatively coupled to the jaws  1610 ,  1612 . As illustrated, the linkage  1804  may provide or define one or more lateral arms  1914  and the jaws  1610 ,  1612  may define a corresponding one or more grooves  1916  configured to receive the lateral arms  1914  and provide corresponding jaw pivot surfaces for the jaws  1610 ,  1612 . In the illustrated embodiment, one lateral arm  1914  is received within a groove  1916  defined by the first jaw  1610 , and the other lateral arm  1914  is received within a groove  1916  defined by the second jaw  1612 . Receiving the lateral arms  1914  in the grooves  1916  creates a jaw pivot point where the jaws  1610 ,  1612  are able to pivot between the open and closed positions. The lateral arms  1914  interact with the corresponding grooves  1916  and help prevent the jaws  1610 ,  1612  from separating from each other. In some embodiments, the lateral arms  1914  slidably engage the grooves  1916  as the jaws  1610 ,  1612  open and close about the jaw pivot point, thus the grooves  1916  may operate as corresponding cam surfaces. The jaw pivot points created by interaction between the lateral arms  1914  and the grooves  1916  may be substantially parallel to the second pivot axis P 2 . 
     The wrist  1606  may further provide a jaw constraint that prevents the jaws  1610 ,  1612  from rotating out of alignment with each other as the jaws  1610 ,  1612  open and close. In the illustrated embodiment, the jaw constraint includes one or more alignment arms, shown as a first alignment arm  1918   a  ( FIG. 19A ) and a second alignment arm  1918   b  ( FIG. 19B ). As described in more detail below, the proximal end of the first alignment arm  1918   a  may be coupled (e.g., pinned) to the first pulley  1806   a,  and the proximal end of the second alignment arm  1918   b  may be coupled (e.g., pinned) to the second pulley  1806   b,  such that movement (rotation) of the pulleys  1806   a,b  correspondingly moves the alignment arms  1918   a,b,  respectively. In contrast, the distal end of the first alignment arm  1918   a  may be received within a first slot  1920   a  ( FIG. 19B ) defined in the first linkage portion  1902   a  of the linkage  1804 , and the distal end of the second alignment arm  1918   b  may be received within a second slot  1920   b  ( FIG. 19A ) defined in the second linkage portion  1902   b  of the linkage  1804 . As the pulleys  1806   a,b  rotate to move the jaws  1610 ,  1612  between the open and closed positions, as described below, the distal ends of the alignment arms  1918   a,b  will correspondingly be urged to rotatably slide within the corresponding slots  1920   a,b,  respectively. Without the jaw constraint provided by the alignment arms  1918   a,b  and the corresponding slots  1920   a,b,  the jaws  1610 ,  1612  would tend to rotate out of alignment during opening and closing, thus preventing accurate positioning during opening and closing. This jaw condition is sometimes referred to as extreme backlash or slop. 
       FIGS. 20A and 20B  are additional isometric, partially exploded views of the end effector  1604  of  FIG. 18  from the right and left vantage points. In  FIGS. 20A-20B , the distal and proximal devises  1802   a,b  ( FIGS. 19A-19B ) are removed (omitted) for simplicity, and the first and second pulleys  1806   a,b  and the drive members  1808   a - d  are shown exploded laterally from the remaining portions of the end effector  1604  and the wrist  1606 . 
     As illustrated, the first jaw  1610  provides a first jaw extension  2002   a  ( FIG. 20A ) and the second jaw  1612  provides a second jaw extension  2002   b  ( FIG. 20B ), and each jaw extension  2002   a,b  extends proximally from the corresponding jaws  1610 ,  1612 . The first jaw extension  2002   a  may be rotatably coupled (e.g., pinned) to the first pulley  1806   a  such that movement (rotation) of the first pulley  1806   a  correspondingly moves the first jaw  1610  to pivot about the jaw pivot point, and the second jaw extension  2002   b  may be rotatably coupled (e.g. pinned) to the second pulley  1806   b  such that movement (rotation) of the second pulley  1806   b  correspondingly moves the second jaw  1612  to pivot about the jaw pivot point. 
     In the illustrated embodiment, the first pulley  1806   a  may provide or define a first jaw pin  2004   a  ( FIG. 20B ) configured to mate with a first jaw aperture  2006   a  ( FIG. 20A ) defined on the first jaw extension  2002   a,  and the second pulley  1806   b  may provide or define a second jaw pin  2004   b  ( FIG. 20A ) configured to mate with a second jaw aperture  2006   b  ( FIG. 20B ) defined on the second jaw extension  2002   b.  The first and second jaw pins  2004   a,b  are eccentric to the second pivot axis P 2 . Consequently, mating the first and second jaw pins  2004   a,b  with the first and second jaw apertures  2006   a,b,  respectively, allows the pulleys  1806   a,b  to rotate about the second pivot axis P 2  to pivot the jaws  1610 ,  1612  about the jaw pivot points and between the open and closed positions, as constrained by the lateral arms  1914  ( FIGS. 19A-19B ). 
     In an alternative embodiment, the first and second jaw pins  2004   a,b  may be provided on the first and second jaw extensions  2002   a,b,  respectively, and the first and second jaw apertures  2006   a,b  may be provided on the pulleys  1806   a,b,  respectively, or any combination thereof. Moreover, the jaw apertures  2006   a,b  need not be through-holes, as depicted, but could alternatively comprise recesses defined in the jaw extensions  2002   a,b  (or the pulleys  1806   a,b ) and sized and otherwise configured to receive the jaw pins  2004   a,b.    
     As mentioned above, the first and second alignment arms  1918   a,b  may also be rotatably coupled (e.g., pinned) to the first and second pulleys  1806   a,b,  respectively, such that movement (rotation) of the pulleys  1806   a,b  correspondingly moves the alignment arms  1918   a,b.  In the illustrated embodiment, for example, the first pulley  1806   a  may provide or define a first arm pin  2008   a  configured to mate with a first arm aperture  2010   a  defined by the first alignment arm  1918   a,  and the second pulley  1806   b  may provide or define a second arm pin  2008   b  ( FIG. 20A ) configured to mate with a second arm aperture  2010   b  ( FIG. 20B ) defined by the second alignment arm  1918   b  ( FIG. 20B ). Similar to the first and second jaw pins  2004   a,b,  the first and second arm pins  2008   a,b  are eccentric to the second pivot axis P 2 , and the arm pins  2008   a,b  are also angularly offset from the first and second jaw pins  2004   a,b.  Consequently, as the pulleys  1806   a,b  rotate about the second pivot axis P 2 , the alignment arms  1918   a,b  are moved and the distal ends of the alignment arms  1918   a,b  are urged to slide within (traverse) the corresponding slots  1920   a,b  ( FIGS. 19A-19B ), respectively. This helps maintain the jaws  1610 ,  1612  moving distally and/or proximally in a straight line during closing and opening (i.e., axial constraint), instead of rotating about the jaw pins  2004   a,b.    
     In an alternative embodiment, the first and second arm pins  2008   a,b  may be provided on the alignment arms  1918   a,b,  respectively, and the first and second arm apertures  2010   a,b  may be provided on the pulleys  1806   a,b,  respectively, or any combination thereof, without departing from the scope of the disclosure. Moreover, the arm apertures  2010   a,b  need not be through-holes, as depicted, but could alternatively comprise recesses defined in the alignment arms  1918   a,b  (or the pulleys  1806   a,b ) and sized and otherwise configured to receive the arm pins  2008   a,b.    
     As indicated above, selective actuation and antagonistic operation of the drive members  1808   a - d  can open or close the jaws  1610 ,  1612 . Because the jaws  1610 ,  1612  are pinned to the pulleys  1806   a,b  and pivotally constrained at the jaw pivot point by the lateral arms  1914  ( FIGS. 19A-19B ) at the grooves  1916 , as generally described above, selectively actuating the drive members  1808   a - d  such that the pulleys  1806   a,b  rotate in opposite angular directions may result in the jaws  1610 ,  1612  opening or closing. Simultaneously pulling proximally on the first and fourth drive members  1808   a,d,  for example, while allowing the second and third drive members  1808   b,c  to pay out slack, will cause the pulleys  1806   a,b  to rotate in first opposing directions and thereby cause the jaws  1610 ,  1612  to move (pivot) toward the closed position. In contrast, simultaneously pulling proximally on the second and third drive members  1808   b,c  while allowing the first and fourth drive members  1808   a,d  to pay out slack, will cause the pulleys  1806   a,b  to rotate in second opposing directions opposite the first opposing directions and thereby cause the jaws  1610 ,  1612  to move (pivot) toward the open position. 
     As also indicated above, selective actuation and antagonistic operation of the drive members  1808   a - d  may also cause the end effector  1604  to articulate at the wrist  1606  in both pitch and yaw directions. Again, because the jaws  1610 ,  1612  are pinned to the pulleys  1806   a,b  and pivotally constrained at the jaw pivot point by the lateral arms  1914  ( FIGS. 19A-19B ) at the grooves  1916 , selectively actuating the drive members  1808   a - d  such that the pulleys  1806   a,b  rotate in the same angular direction may result in the jaws  1610 ,  1612  pivoting about the second pivot axis P 2  and thereby moving the end effector  1604  up or down in pitch. More specifically, simultaneously pulling on the first and third drive members  1808   a,c  while allowing the second and fourth drive members  1808   b,d  to pay out slack may cause the pulleys  1808   a,b  to rotate in a first angular direction and thereby pivot the end effector  1604  about the second pivot axis P 2  in upward pitch. In contrast, simultaneously pulling on the second and fourth drive members  1808   b,d  while allowing the first and third drive members  1808   a,c  to pay out will cause the pulleys  1808   a,b  to rotate in a second angular direction opposite the first angular direction and thereby pivot the end effector  1604  about the second pivot axis P 2  in downward pitch. 
     Furthermore, selective actuation of a first connected pair of drive members  1808   a - d  while relaxing a second pair of connected drive members  1808   a - d  may cause the end effector  1604  to pivot about the first pivot axis P 1  and thereby move in yaw. More specifically, pulling on the first and second drive members  1808   a,b  while simultaneously slackening the third and fourth drive members  1808   c,d  (e.g., allowing the third and fourth drive members  1808   c,d  to pay out) will pivot the end effector  1604  in yaw in a first direction. In contrast, pulling on the third and fourth drive members  1808   c,d  while simultaneously slackening the first and second drive members  1808   a,b  (e.g., allowing the first and second drive members  1808   a,b  to pay out) will pivot the end effector  1604  in yaw in a second direction opposite the first direction. 
       FIGS. 21A and 21B  are additional isometric, partially exploded views of the end effector  1604  of  FIG. 18  from the right and left vantage points. In  FIGS. 21A-21B , the distal clevis  1802   a,  the linkage  1804  ( FIGS. 19A-19B ), the drive members  1808   a - d  ( FIGS. 20A-20B ), the pulleys  1806   a,b  ( FIGS. 20A-20B ), and the first or “upper” jaw  1612  are all removed (omitted) for simplicity. The first and second alignment arms  1918   a,b  are shown in  FIGS. 21A-21B  exploded laterally from the remaining portions of the end effector  1604  and the wrist  1606 . 
     In some embodiments, as illustrated, each alignment arm  1918   a,b  may provide or otherwise define a head  2102  configured or otherwise sized to be received within the corresponding slot  1920   a,b  ( FIGS. 19A-19B ) defined in the linkage  1804  ( FIGS. 19A-19B ). The head  2102  may be provided at or near the distal end of each alignment arm  1918   a,b,  but may alternatively be arranged at any location along the alignment arm  1918   a,b  and distal to the arm apertures  2010   a,b.    
     The wrist  1606  may further include an alignment link  2104  that forms part of the jaw constraint mentioned above. The alignment link  2104  may comprise a generally U-shaped (e.g., horseshoe shaped) member having opposing first and second link extensions  2106   a,b  configured to rotatably couple to the first and second alignment arms  1918   a,b,  respectively, and thereby help maintain the axial position of each alignment arm  1918   a,b  with respect to the opposing alignment arm  1918   a,b.  More specifically, the first alignment arm  1918   a  may provide or define a first link pin  2108   a  configured to be received within a corresponding first link aperture  2110   a  defined in the first link extension  2106   a,  and the second alignment arm  1918   b  may provide or define a second link pin  2108   b  configured to be received within a corresponding second link aperture  2110   b  defined in the second link extension  2106   b.  Mating the first and second link pins  2108   a,b  with the first and second link apertures  2110   a,b  effectively couples the first alignment arm  1918   a  to the second alignment arm  1918   b  for mutual movement as the alignment arms  1918   a,b  translate within the corresponding slots  1920   a,b  ( FIGS. 19A-19B ), respectively, as the pulleys  1806   a,b  ( FIGS. 20A-20B ) rotate. 
     In an alternative embodiment, the first and second link pins  2108   a,b  may be provided on the alignment links  2104  and the first and second link apertures  2110   a,b  may be provided on the alignment arms  1918   a,b,  or any combination thereof. Moreover, the link apertures  2110   a,b  need not be through-holes, as depicted, but could alternatively comprise recesses defined in the link extensions  2106   a,b  (or the alignment arms  1918   a,b ) and sized and otherwise configured to receive the link pins  2108   a,b.    
     Accordingly, the jaw constraint may help prevent the jaws  1610 ,  1612  from rotating out of alignment with each other as the jaws  1610 ,  1612  open and close. More specifically, because the jaws  1610 ,  1612  are eccentrically pinned to the pulleys  1806   a,b,  as generally described above, rotating the pulleys  1806   a,b  about the second pivot axis P 2  will cause the jaws  1610 ,  1612  to move (translate) distally or proximally, depending on the rotational direction of the pulleys  1806   a,b.  The jaw constraint helps prevent the jaws  1610 ,  1612  from rotating about the jaw pins  2004   a,b  as the jaws axially translate. During example operation, as the pulleys  1806   a,b  rotate to open or close the jaws  1610 ,  1612 , the heads  2102  of the alignment arms  1918   a,b  translate within the slots  1920   a,b  ( FIGS. 19A-19B ), and during this motion, any rotational torque that may be imparted to the jaws  1610 ,  1612  by rotation about the jaw pins  2004   a,b  will be assumed by the linkage  1804  ( FIGS. 19A-19B ) at the slots  1920   a,b,  and thus helping to prevent the jaws  1610 ,  1612  from rotating about the jaw pins  2004   a,b  as the jaws axially translate and open or close. 
     The alignment link  2104  may be fixed or free as arranged within the wrist  1606 . The general U-shape of the alignment link  2104  may prove advantageous in allowing the wrist  1606  to be generally open through its central portions (e.g., middle). As a result, the wrist  1606  may be capable of accommodating the knife  1816  (occluded in  FIG. 21B ) and the drive rod  1818  ( FIG. 18 ) through the middle of the wrist  1606  such that the knife  1816  can be received within the guide track  1616  upon firing the end effector  1604 . In some embodiments, the open central portions of the wrist  1606  may also accommodate the electrical conductor  1812 , which terminates at the electrode  1814 . 
     In the illustrated embodiment, the wrist  1606  may further include a distal wedge  2112  and a mid-articulation insert  2114  arranged in series and positioned in the central portion or middle of the wrist  1606 . The distal wedge  2112  may be arranged between the electrode  1814  and the distal clevis  1802   a  ( FIGS. 19A-19B ) and generally arranged within the linkage  1804  ( FIGS. 18 and 19A-19B ), and the mid-articulation insert  2114  may be generally arranged within the distal clevis  1802   a  ( FIGS. 18 and 19A-19B ). The distal wedge  2112  and the mid-articulation insert  2114  may be positioned between (interpose) the first and second jaw extensions  2102   a,b  of the jaws  1610 ,  1612 . The distal wedge  2112  and mid-articulation insert  2114  may act to guide the jaw extensions  2102   a,b  in planar rotation as the jaws  1610 ,  1612  open, close, and articulate in pitch. The distal wedge  2112  further acts between the jaws  1610 ,  1612  during spread dissection, where the jaws  1610 ,  1612  are placed between tissue planes or through an aperture in tissue, and then opened to separate tissue. In some embodiments, the distal wedge  2112  and the mid-articulation insert  2114  may receive and help guide one or both of the knife  1816  and the electrical conductor  1812  to the jaws  1610 ,  1612 . In at least one embodiment, as illustrated, the distal wedge  2112  may also extend partially through the alignment link  2104  and between the first and second link extensions  2106   a,b.    
       FIG. 22  is another enlarged isometric view of the distal end of the surgical tool  1600  of  FIGS. 16 and 17 . More specifically,  FIG. 22  depicts an enlarged view of an alternative embodiment of the end effector  1604  and the wrist  1606 . The end effector  1604  may be similar in some respects to the end effector  1604  depicted in  FIGS. 18, 19A-19B, 20A-20B , and  21 A- 21 B and, therefore, may be best understood with reference thereto, where like numerals indicated similar components not described again in detail. Similar to the end effector of  FIG. 18 , for example, the end effector  1604  depicted in  FIG. 22  is a vessel sealer where both jaws  1610 ,  1612  simultaneously move to actuate the jaws  1610 ,  1612  between open and closed positions, e.g., bifurcating jaws. 
     Moreover, the wrist  1606  includes a first or “distal” clevis  2202   a,  a second or “proximal” clevis  2202   b,  and the linkage  1804 . The devises  2202   a,b  may be alternatively referred to herein as “articulation joints” of the wrist  1606  and extend in series. The devises  1802   a,b  are operatively coupled to facilitate articulation of the wrist  1606  relative to the shaft  1602 . As illustrated, the proximal end of the distal clevis  2202   a  may be rotatably mounted to the proximal clevis  2202   b  at the first pivot axis P 1 , and first and second pulleys  2204   a  and  2204   b  may be rotatably mounted to the distal end of the distal clevis  2202   a  at the second pivot axis P 2 . The linkage  1804  may be arranged near the distal end of distal clevis  2202   a  and operatively coupled or mounted to the jaws  1610 ,  1612 . 
     The drive members  1808   a - d  extend longitudinally within the lumen  1810  and extend at least partially through the wrist  1606 . In the illustrated embodiment, the drive members  1808   a - d  each extend longitudinally through the proximal clevis  2202   b.  The distal end of each drive member  1808   a - d  terminates at the first or second pulleys  2204   a,b,  thus operatively coupling each drive member  1808   a - d  to the end effector  1604 . In some embodiments, distal ends of the first and second drive members  1808   a,b  may be coupled to each other and terminate at the first pulley  2204   a,  and distal ends of the third and fourth drive members  1808   c,d  may be coupled to each other and terminate at the second pulley  2204   b.  In at least one embodiment, the distal ends of the first and second drive members  1808   a,b  and the distal ends of the third and fourth drive members  1808   c,d  may each be coupled together at a corresponding ball crimp  2206  (only one shown) mounted to the first or second pulley  2204   a,b,  respectively. As discussed above, the drive members  1808   a - d  may be configured to operate “antagonistically” to open or close the jaws  1610 ,  1612  and/or cause the end effector  1604  to articulate at the wrist  1606  in pitch or yaw directions. 
     The electrical conductor  1812  may also extend longitudinally within the lumen  1810 , through the wrist  1606 , and terminate at the electrode  1814  to supply electrical energy to the end effector  1604 . The electrical conductor  1812  is depicted as exposed at the jaws  1610 ,  1612 , but would otherwise be coupled to the electrode  1814  for proper operation. Moreover, the end effector  1604  further includes the knife  1816  (partially occluded), which is aligned with and configured to traverse the guide track  1616  as moved by the drive rod  1818 . 
       FIG. 23  is an isometric, partially exploded view of the end effector  1604  of  FIG. 22 , as taken from a right vantage point. In  FIG. 23 , the distal clevis  2202   a  and the linkage  1804  are shown exploded vertically from the remaining portions of the end effector  1604  and the wrist  1606 , thus exposing the internal parts of the wrist  1606 . In some embodiments, one or both of the distal clevis  2202   a  and the linkage  1804  may comprise two or more component parts that are joined to secure the wrist  1606  and rotatably secure the jaws  1610 ,  1612  to the wrist  1606 . In the illustrated embodiment, for example, the linkage  1804  comprises opposing first and second linkage portions  2302   a,b,  that may be joined by welding, soldering, brazing, an adhesive, an interference fit, or by using one or more mechanical fasteners, such as pins, rivets, bolts, or any combination of the foregoing. The distal clevis  2202   a,  however, is depicted as a monolithic, one-piece structure, but could alternatively be made of two or more component parts, without departing from the scope of the disclosure. 
     In the illustrated embodiment, the proximal end of the distal clevis  2202   a  may be rotatably mounted to the proximal clevis  2202   b  by mating apertures  2304  defined on the distal clevis  2202   a  with the pins  1906  (one shown) defined on the proximal clevis  2202   b.  Mating the aperture(s)  2304  with the pin(s)  1906  may allow the wrist  1606  to articulate in “yaw” about the first pivot axis P 1 . In alternative embodiments, however, the pin(s)  1906  may be provided by the distal clevis  2202   a,  and the aperture(s)  2304  may be provided by the proximal clevis  2202   b.  Moreover, in some embodiments, the aperture(s)  2304  need not be through-holes, as depicted, but could alternatively comprise recesses defined in the distal clevis  2202   a  (or the proximal clevis  2202   b ) and sized and otherwise configured to receive the pin(s)  1906 . 
     In the illustrated embodiment, the pulleys  2204   a,b  may be rotatably mounted to the distal end of the distal clevis  2202   a  at the second pivot axis P 2  of the wrist  1602 . In some embodiments, for example, each pulley  2204   a,b  may provide or otherwise define a pin  2306  (only one shown) and the distal clevis  2202   a  may define opposing apertures  2308  sized to receive or mate with the corresponding pin  2306 . In alternative embodiments, however, the pins  2306  may be provided by the distal clevis  2202   a,  and the apertures  2308  may be provided by the pulleys  2204   a,b.  Moreover, in some embodiments, the apertures  2308  need not be through-holes, as depicted, but could alternatively comprise recesses defined in the distal clevis  2202   a  (or the pulleys  2204   a,b ) and sized and otherwise configured to receive the pins  2306 . 
     In the illustrated embodiment, the linkage  1804  may provide or define one or more lateral arms  2310 , and the jaws  1610 ,  1612  may define a corresponding one or more grooves  2312  configured to receive the lateral arms  2310  and provide corresponding jaw pivot surfaces for the jaws  1610 ,  1612 . In the illustrated embodiment, one lateral arm  2310  is received within a groove  2312  defined by the first jaw  1610 , and the other lateral arm  2310  is received within a groove  2312  defined by the second jaw  1612 . As the jaws  1610 ,  1612  move between the open and closed positions, the lateral arms  2310  interact with the corresponding grooves  2312  and thereby provide a jaw pivot point that helps prevent the jaws  1610 ,  1612  from separating from each other. In some embodiments, the lateral arms  2310  slidably engage the grooves  2312  as the jaws  1610 ,  1612  open and close, thus the grooves  2312  may operate as corresponding cam surfaces. 
       FIGS. 24A and 24B  are additional isometric, partially exploded views of the end effector  1604  of  FIG. 22  from right and left vantage points. In  FIGS. 24A-24B , the distal clevis  2202   a  ( FIG. 23 ) is removed (omitted) for simplicity, and the first and second pulleys  2204   a,b  and the drive members  1808   a - d  are shown exploded laterally from the remaining portions of the end effector  1604  and the wrist  1606 . 
     The first jaw  1610  provides the first jaw extension  2002   a  ( FIG. 24A ) defining the first jaw aperture  2006   a,  and the second jaw  1612  provides the second jaw extension  2002   b  ( FIG. 24B ) defining the second jaw aperture  2006   b  ( FIG. 24B ). The first jaw extension  2002   a  may be rotatably coupled (e.g., pinned) to the first pulley  2204   a  at the first jaw pin  2004   a  (FG.  24 B) such that movement (rotation) of the first pulley  2204   a  correspondingly moves the first jaw  1610 , and the second jaw extension  2002   b  may be rotatably coupled (e.g. pinned) to the second pulley  2204   b  at the second jaw pin  2004   b  ( FIG. 24A ) such that movement (rotation) of the second pulley  2204   b  correspondingly moves the second jaw  1612 . The first and second jaw pins  2004   a,b  are eccentric to the second pivot axis P 2 , and thus mating the first and second jaw pins  2004   a,b  with the first and second jaw apertures  2006   a,b,  respectively, allows rotation of the pulleys  2204   a,b  about the second pivot axis P 2  to move the jaws  1610 ,  1612  and thereby pivot the jaws  1610 ,  1612  about the jaw pivot between the open and closed positions as constrained by the lateral arms  2310 . 
     Selective actuation and antagonistic operation of the drive members  1808   a - d  can open or close the jaws  1610 ,  1612 . Because the jaws  1610 ,  1612  are pinned to the pulleys  2204   a,b  and pivotally constrained by the lateral arms  2310  at the grooves  2312 , as generally described above, selectively actuating the drive members  1808   a - d  such that the pulleys  2204   a,b  rotate in opposite angular directions may result in the jaws  1610 ,  1612  opening or closing. Selective actuation and antagonistic operation of the drive members  1808   a - d  may also cause the end effector  1604  to articulate at the wrist  1606  in both pitch and yaw directions. More particularly, selectively actuating the drive members  1808   a - d  such that the pulleys  2204   a,b  rotate in the same angular direction may result in the jaws  1610 ,  1612  pivoting about the second pivot axis P 2  and thereby moving the end effector  1604  up or down in pitch. Moreover, selective actuation of a first connected pair of drive members  1808   a - d  while relaxing a second pair of connected drive members  1808   a - d  may cause the end effector  1604  to pivot about the first pivot axis P 1  and thereby move in yaw. 
     The wrist  1606  may further provide a jaw constraint that helps prevent the jaws  1610 ,  1612  from rotating out of alignment with each other as the jaws  1610 ,  1612  open and close. More specifically, because the jaws  1610 ,  1612  are pinned to the pulleys  2204   a,b,  as generally described above, rotating the pulleys  2204   a,b  about the second pivot axis P 2  will cause the jaws  1610 ,  1612  to move (translate) distally or proximally, depending on the rotational direction of the pulleys  2204   a,b.  The jaw constraint helps prevent the jaws  1610 ,  1612  from rotating about the jaw pins  2004   a,b  as the jaws axially translate. 
     In the illustrated embodiment, the jaw constraint includes first and second alignment arms  2402   a,b  provided by or defined on the linkage  1804 . The alignment arms  2402   a,b  extend proximally from the linkage  1804  and are engageable with first and second cams  2404   a,b,  respectively, provided on the pulleys  2204   a,b.  More specifically, an inner arcuate surface  2406   a  of the first alignment arm  2402   a  may be arranged in the wrist  1606  to slidably engage an outer arcuate surface  2408   a  of the first cam  2404   a,  and an inner arcuate surface  2406   b  of the second alignment arm  2402   b  may be arranged in the wrist  1606  to slidably engage an outer arcuate surface  2408   b  of the second cam  2404   b.  During example operation, as the pulleys  2204   a,b  rotate to open or close the jaws  1610 ,  1612 , the outer arcuate surfaces  2408   a,b  of the cams  2404   a,b  will slide against the opposing inner arcuate surfaces  2406   a,b  of the alignment arms  2402   a,b,  respectively. During this motion, any rotational torque that may be imparted to the jaws  1610 ,  1612  by rotation about the jaw pins  2004   a,b  will be assumed by the linkage  1804  at the alignment arms  2402 , and thus helping to prevent the jaws  1610 ,  1612  from rotating about the jaw pins  2004   a,b  as the jaws axially translate and open or close. 
     The jaw constraint may also prove advantageous in allowing the wrist  1606  to be generally open through its central portions (e.g., middle). As a result, the wrist  1606  may be capable of accommodating the knife  1816  (mostly occluded) and the drive rod  1818  through the middle of the wrist  1606  such that the knife  1816  can be received within the guide track  1616  upon firing the end effector  1604 . The open central portions of the wrist  1606  may also be able to accommodate the electrical conductor  1812 , which terminates at the electrode  1814 . In at least one embodiment, the distal wedge  2112  ( FIG. 24A ) may be positioned in the central portion or middle of the wrist  1606  and may receive and help guide one or both of the knife  1816  and the electrical conductor  1812  to the jaws  1610 ,  1612 . 
     Tool with Bifurcation Wire Routing 
       FIG. 25  is a perspective end view of the end effector  1604  of  FIG. 18 . More specifically,  FIG. 25  shows the opposing jaws  1610 ,  1612  and portions of the wrist  1606 , including the second linkage portion  1902   b  of the linkage  1804 , the second alignment arm  1918   b,  and the alignment link  2104  rotatably coupled to the second alignment arm  1918   b,  as generally described above. Various remaining portions of the wrist  1606  are omitted for simplicity and for discussion purposes. 
       FIG. 25  also depicts the distal wedge  2112  arranged within a central portion or middle of the wrist  1606  and distal to the distal articulation joint  1802   a  ( FIGS. 19A-19B ), according to one or more embodiments. As illustrated, the distal wedge  2112  is generally arranged within the linkage  1804  and positioned between the first and second jaw extensions  2102   a,b  of the jaws  1610 ,  1612 . The distal wedge  2112  may also extend at least partially through the alignment link  2104  between the first and second link extensions  2106   a,b,  as discussed above. In some embodiments, the lateral sides of the distal wedge  2112  may slidingly engage opposing inner surfaces of some or all of the alignment arms  1918   a,b,  the jaw extensions  2102   a,b,  and the link extensions  2106   a,b.    
     In some embodiments, the distal wedge  2112  is not coupled (fixed) to any portion of the end effector  1604  or the wrist  1606  and, therefore, may be detached from any portion thereof. Instead, in such embodiments, the distal wedge  2112  is secured between portions of the linkage  1804 , the alignment arms  1918   a,b,  the jaw extensions  2102   a,b,  and the link extensions  2106   a,b  as the wrist  1606  is assembled. 
     In some embodiments, the distal wedge  2112  may receive and help guide the knife  1816  to the jaws  1610 ,  1612 . In the illustrated embodiment, the distal wedge  2112  defines a knife cavity or housing  2502  through which the knife  1816  and the drive rod  1818  are able to extend to move the knife  1816  into and along the guide track  1616 . More specifically, upon firing the end effector  1604 , the drive rod  1818  is moved (urged) distally, which correspondingly moves the knife  1816  out of the knife housing  2502  and into the guide track  1616 . After firing is complete, the drive rod  1818  is retracted proximally, which pulls the knife  1816  proximally and back into the knife housing  2502  until it is desired to fire the end effector  1604  again. In at least one embodiment, the knife housing  2502  may be provided or otherwise defined by one or both of the jaws  1610 ,  1612 , or alternatively an electrode component (not shown), made of a non-conductive plastic, may provide the knife housing  2502 , without departing from the scope of the disclosure. 
     In some embodiments, as illustrated, the distal wedge  2112  may also receive and help guide the electrical conductor  1812  to the jaws  1610 ,  1612  and, more particularly, to the electrode  1814  to provide an electrical current generated by at least one electrosurgical generator in electrical communication with the handle  1614  ( FIGS. 16 and 17 ). The electrical conductor  1812  may pass through, around, above, below, or on one or both sides of the distal wedge  2112 , or any combination thereof. 
     The distal wedge  2112  may also be configured to protect the electrical conductor  1812  from damage and manage slack in the electrical conductor  1812  while the end effector  1604  and the wrist  1606  to operate. More specifically, the distal wedge  2112  may be designed to guide the electrical conductor  1812  to ensure that it is isolated from moving parts and/or mechanisms of the end effector  1604  or the wrist  1606 , which may inadvertently abrade or damage the electrical conductor  1812  and thereby potentially result in arcing or shorting. Example moving parts and/or mechanisms of the end effector  1604  or the wrist  1606  include the knife rod  1818 , the devises  1802   a,b,  the articulation arms  1918   a,b,  and the articulation link  2104 , all of which could inadvertently contact and damage the electrical conductor  1812  during operation if not properly protected by the distal wedge  2112 . 
       FIGS. 26A and 26B  are right and left isometric views, respectively, of the distal wedge  2112  of  FIG. 25 , according to one or more embodiments. The distal wedge  2112  may be made of a variety of rigid materials including, but not limited to, a metal, a cast metal alloy, a wrought metal, a polymer composite, a ceramic, a negative-index metamaterial (NIM), a metal injection molding (MIM), a reinforced plastic or thermoplastic, (e.g., nylon, polyetherimide or Ultem®, polyether ether ketone or PEEK, etc.), or any combination thereof. In some embodiments, the reinforced plastics or thermoplastics may be carbon or glass filled. 
     As described above, the distal wedge  2112  defines the knife housing  2502  that receives and guides the knife  1816  as driven by the drive rod  1818 . Moreover, the distal wedge  2112  may further provide or otherwise define one or more channels  2602  (one visible in  FIG. 26B ) configured to receive and guide the electrical conductor  1812  toward the electrode  1814  ( FIG. 25 ). As best seen in  FIG. 26B , the channel  2602  may extend from a first or “proximal” end  2604   a  of the distal wedge  2112  to a second or “distal” end  2604   b  of the distal wedge  2112 , but could alternatively begin or terminate at any point between the ends  2602   a,b,  without departing from the scope of the disclosure. 
     In some embodiments, the channel  2602  may define or otherwise provide one or more vertical and/or horizontal curves, undulations, or direction changes that alter the course or pathway of the channel  2602  and thereby change the course of the electrical conductor  1812  received within the channel  2602 . In the illustrated embodiment, for example, the channel  2602  includes at least one vertical direction change  2606  where the route of the channel  2602  moves vertically, and at least one horizontal direction change  2608  where the route of the channel  2602  moves laterally or horizontally. In other embodiments, however, more than one vertical and lateral direction change  2606 ,  2608  may be included in the channel  2602 , without departing from the scope of the disclosure. 
     In at least one embodiment, the opening to the channel  2602  at the first end  2604   a  may be enlarged and otherwise flared outward. This may prove advantageous in providing strain relief for the electrical conductor  1812  while the end effector  1604  ( FIG. 25 ) articulates in pitch, and as the bifurcating jaws  1610 ,  1612  ( FIG. 25 ) open and close. Accordingly, the distal wedge  2112  can help relieve potential strain in the electrical conductor  1812 , which may help avoid premature fatigue. The enlarged opening at the first end  1604   a  may also prove advantageous in helping to manage slack in the electrical conductor  1812  as the end effector  1604  articulates. For example, the electrical conductor  1812  may be loosely received within the channel  2602 , which allows the electrical conductor  1812  to move back and forth within the channel  2602  during operation to manage slack. The channel  2602  further acts to establish the minimum bend radius of the electrical conductor  1812  by preventing too sharp a bend, often referred to as a kink, as the electrical conductor  1812  traverses the channel  2602  to reach the electrode  1814  ( FIG. 25 ). Limiting the minimum bend radius is critical in preventing fatigue failure of conductor strands housed inside the insulative jacket of the electrical conductor  1812 . 
     In some embodiments, as illustrated, the distal wedge  2112  may provide or otherwise define one or more arcuate surfaces, shown as a first or “upper” arcuate (concave) surface  2610   a  and a second or “lower” arcuate (concave) surface  2610   b.  The arcuate surfaces  2610   a,b  may receive and engage corresponding curved (convex) portions of the jaws  1610 ,  1612  ( FIG. 25 ). In operation, the arcuate surfaces  2610   a,b  may operate as cam surfaces as the jaws  1610 ,  1612  open and close. In particular, the arcuate surfaces  2610   a,b  may prove advantageous in touch and spread dissection operations, where a user opens the jaws  1610 ,  1612  to move tissue. In such operations, a load is applied on the top or bottom of the jaw jaws  1610 ,  1612  and this load is transferred to the distal wedge  2112  at the arcuate surfaces  2610   a,b.  Accordingly, the arcuate surfaces  2610   a,b  may support the jaws  1610 ,  1612  and bear loading required to move the tissue. 
       FIG. 27  is a perspective end view of the end effector  1604  of  FIG. 22 . More specifically,  FIG. 27  shows the opposing jaws  1610 ,  1612  in the open position and an alternative example of the distal wedge  2112 , according to one or more additional embodiments. Remaining portions of the wrist  1606  ( FIG. 22 ) and the end effector  1604  are omitted for simplicity and for discussion purposes. 
     The distal wedge  2112  of  FIG. 27  is similar in some respects to the distal wedge  2112  of  FIG. 25 . For instance, the distal wedge  2112  is able to be arranged within the central portions or middle of the wrist  1606  ( FIG. 22 ) and distal to the distal articulation joint  1802   a  ( FIGS. 19A-19B ). Moreover, the distal wedge  2112  may be generally situated within the linkage  1804  ( FIG. 22 ), which is mounted to the jaws  1610 ,  1612  at the grooves  2312 , as generally described above. As illustrated, the distal wedge  2112  is positioned between the first and second jaw extensions  2102   a,b  of the jaws  1610 ,  1612  and, in some embodiments, the lateral sides of the distal wedge  2112  may slidingly engage opposing inner surfaces of the jaw extensions  2102   a,b.  The distal wedge  2112  may not be coupled (fixed) to any portion of the end effector  1604  or the wrist  1606  and, therefore, may be detached from any portion thereof. Instead, in such embodiments, the distal wedge  2112  is secured between portions of the linkage  1804  and the jaw extensions  2102   a,b  as the wrist  1606  is assembled. 
     In some embodiments, the distal wedge  2112  may receive and help guide the knife  1816  to the jaws  1610 ,  1612 . In the illustrated embodiment, the distal wedge  2112  defines a knife housing  2702  through which the knife  1816  and the drive rod  1818  are able to extend to move the knife  1816  into and along the guide track  1616  upon firing the end effector  1604 . After firing is complete, the drive rod  1818  is retracted proximally, which pulls the knife  1816  proximally and back into the knife housing  2702  until it is desired to fire the end effector  1604  again. 
     The distal wedge  2112  may also receive and help guide the electrical conductor  1812  to the jaws  1610 ,  1612  and, more particularly, to the electrode  1814  to provide an electrical current to the end effector  1604 . Similar to the distal wedge  2112  of  FIG. 25 , the distal wedge of  FIG. 27  may guide the electrical conductor  1812  through, around, above, below, or on one or both sides of the distal wedge  2112 , or any combination thereof. Moreover, the distal wedge  2112  may also protect the electrical conductor  1812  from damage by guiding the electrical conductor  1812  such that it is isolated from moving parts and/or mechanisms of the end effector  1604  or the wrist  1606 , which may inadvertently abrade or damage the electrical conductor  1812  and thereby potentially result in arcing or shorting. The distal wedge  2112  may also help manage slack in the electrical conductor  1812  while the end effector  1604  and the wrist  1606  to operate, as discussed below. 
       FIGS. 28A and 28B  are right and left isometric views, respectively, of the distal wedge  2112  of  FIG. 27 , according to one or more embodiments. As described above, the distal wedge  2112  defines the knife housing  2702  that receives and guides the knife  1816  ( FIG. 27 ) as driven by the drive rod  1818  ( FIG. 27 ). Moreover, similar to the distal wedge  2112  of  FIGS. 26A-26B , the distal wedge  2112  of  FIGS. 28A-28B  may provide the arcuate surfaces  2610   a,b  configured to receive and engage corresponding curved portions of the jaws  1610 ,  1612  ( FIG. 27 ). 
     The distal wedge  2112  may further provide or otherwise define one or more channels  2802  configured to receive and guide the electrical conductor  1812  toward the electrode  1814  ( FIG. 27 ). In some embodiments, the channel  2802  may extend from a first or “proximal” end  2804   a  of the distal wedge  2112  to a second or “distal” end  2804   b  of the distal wedge  2112 , but could alternatively begin or terminate at any point between the ends  2802   a,b,  without departing from the scope of the disclosure. In the illustrated embodiment, the electrical conductor  1812  is received within the channel  2802  at the proximal end  2804   a,  routed through the channel  2802  until exiting at the distal end  2804   b.    
     In some embodiments, the channel  2802  may define or otherwise provide one or more vertical and/or horizontal curves, undulations, or direction changes that alter the course or pathway of the channel  2802  and thereby changes the course and direction of the electrical conductor  1812  as it follows the channel  2802 . In the illustrated embodiment, for example, the channel  2802  includes a horizontal direction change  2806 , where the course of the channel  2802  assumes an in-plane angular turn (e.g., 180°) in a generally horizontal plane and back toward the proximal end  2804   a,  and a vertical direction change  2808  ( FIG. 28A ), where the course of the channel assumes another in-plane angular turn (e.g., 180°) in a generally vertical plane and back toward the distal end  2804   b.  As best seen in  FIG. 28B , the channel  2802  may also include a second vertical direction change  2810  leading into the horizontal direction change  2806 . Accordingly, the channel  2802  may be defined in the distal wedge  2112  to allow the electrical conductor  1812  to partially wrap around a portion of the distal wedge  2112 . 
     The electrical conductor  1812  is depicted in  FIGS. 28A-28B  as exiting the channel  2802  straight (solid lines) and at a downward angle (dashed lines). This is representative of pitch movement and opening and closing of the bifurcating jaws  1610 ,  1612  ( FIG. 27 ) that might occur during operation of the end effector  1604  ( FIG. 27 ) and which the electrical conductor  1812  will simultaneously have to assume. To help relieve potential strain in the electrical conductor  1812  and avoid premature fatigue during operation, the opening to the channel  2802  at the distal end  2804   b  may be enlarged and otherwise flared outward to allow the electrical conductor  1812  to move within the channel  2802  along with movement of the jaws  1610 ,  1612  and without binding the electrical conductor  1812  against adjacent structures. 
     The distal wedge  2112  may also help with slack management of the electrical conductor  1812  during operation. The enlarged opening at the distal end  1804   b  may help somewhat in this regard, but the channel  2802  may also provide a gap  2812  ( FIG. 28A ) for the electrical conductor  1812  to move back and forth (reciprocate) within during operation. In the illustrated embodiment, the gap  2812  is provided in the vertical direction change  2808 , but could alternatively be provided in other locations of the channel  2802 , without departing from the scope of the disclosure. Since the electrical conductor  1812  is loosely received within the channel  2802 , the gap  2812  allows the electrical conductor  1812  to move back and forth during operation to manage slack. The channel  2802  further acts to establish the minimum bend radius of the electrical conductor  1812  by preventing too sharp a bend, often referred to as a kink, as the electrical conductor  1812  traverses the channel  2802  to reach the electrode  1814  ( FIG. 27 ). Limiting the minimum bend radius is critical in preventing fatigue failure of conductor strands housed inside the insulative jacket of the electrical conductor  1812 . 
     Hybrid Concept to Drive End Effector Closure and Pitch 
       FIG. 29  is an isometric top view of the end effector  1604  and the wrist  1606  of  FIG. 18 , according to one or more embodiments. As discussed above, the wrist  1606  interposes the shaft  1602  and the end effector  1604  and helps facilitate articulation of the end effector  1604  relative to the shaft  1602 . The wrist  1606  can include the linkage  1804 , the distal articulation joint  1802   a,  and the proximal articulation joint  1802   b,  where the proximal articulation joint  1802   b  may form an integral part or extension of the shaft  1602  (or a shaft adapter), or may alternatively comprise a separate or discrete portion of the wrist  1602  coupled to the shaft  1602  (or a shaft adapter). 
     The proximal end of the distal articulation joint  1802   a  may be rotatably coupled to the shaft  106  (e.g., at the proximal articulation joint  1802   b ) at the first pivot axis P 1 , and the first and second pulleys  1806   a  and  1806   b  may be rotatably mounted to the distal end of the distal articulation joint  1802   a  at the second pivot axis P 2 . Moreover, the linkage  1804  may be arranged distal to the second pivot axis P 2  and operatively mounted to the jaws  1610 ,  1612 , as generally described above. Movement of the end effector  1604  about the first pivot axis P 1  provides “yaw” articulation of the end effector  1604 , and movement about the second pivot axis P 2  provides “pitch” articulation of the end effector  1604 . 
     Furthermore, the first and second jaw extensions  2002   a,b  extend from the first and second jaws  1610 ,  1612  and may be rotatably coupled (e.g., pinned) to the first and second pulleys  1806   a,b,  respectively, as also discussed above. Consequently, movement (rotation) of the pulleys  1806   a,b  may cause the jaws  1610 ,  1612  to pivot about the jaw pivot point where the lateral arms  1914  (one visible) of the linkage  1804  are received within corresponding grooves  1916  (one visible) defined by the jaws  1610 ,  1612 . 
     As discussed above, in some embodiments, one or both of the distal articulation joint  1802   a  or the linkage  1804  may comprise two or more component parts that are joined to help form and secure the wrist  1606 . The linkage  1804  can include, for example, the opposing first and second linkage portions  1902   a,b,  and the distal articulation joint  1802   a  can include the opposing first and second distal articulation joint portions  1904   a,b.  The linkage portions  1902   a,b  may be joined at one or more linkage interfaces  2902   a  (one visible), and the distal articulation joint portions  1904   a,b  may be joined at one or more distal joint interfaces  2902   b  (one visible). Joining the linkage and articulation joint portions  1902   a,b,    1904   a,b  at their respective joint interfaces  2902   a,b  may be accomplished by welding, soldering, brazing, an adhesive, an interference fit, or by using one or more mechanical fasteners, such as pins, rivets, bolts, or any combination of the foregoing. 
     Joining the linkage and articulation joint portions  1902   a,b,    1904   a,b  helps build and secure the wrist  1606  for operation. Joining the linkage portions  1902   a,b,  for example, may rotatably secure the jaws  1610 ,  1612  to the wrist  1606 , and joining the distal articulation joint portions  1904   a,b  may help secure the pulleys  1806   a,b  and other component parts within the wrist  1606 . In the illustrated embodiment, the pulleys  1806   a,b  interpose portions of the jaws  1610 ,  1612  and the distal articulation joint  1802   a.  More specifically, the first pulley  1806   a  may interpose the first jaw extension  2002   a  and the first distal articulation portion  1904   a,  and the second pulley  1806   b  may interpose the second jaw extension  2002   b  and the second distal articulation portion  1904   b.  Consequently, the first pulley  1806   a  may engage an outer side (lateral) surface of the first jaw extension  2002   a  and/or an inner side surface of the first distal articulation portion  1904   a,  and the second pulley  1806   b  may engage an outer side (lateral) surface of the second jaw extension  2002   b  and/or an inner side surface of the second distal articulation portion  1904   b.  Joining the distal articulation joint portions  1904   a,b  at the distal joint interfaces  2902   b  may help secure the pulleys  1806   a,b  between the jaw extensions  2002   a,b  and opposing distal articulation portions  1904   a,b,  respectively, and thereby orient the pulleys  1806   a,b  in a parallel, planar orientation for consistent operation of the end effector  1604  and the wrist  1606 . 
     The drive members  1808   a - d  (the fourth drive member  1808   d  occluded in  FIG. 29 ) extend longitudinally through the proximal articulation joint  1802   b  and the distal articulation joint  1802   a  and terminate at the pulleys  1806   a,b.  As discussed herein, the distal ends of the first and second drive members  1808   a,b  may be coupled to each other and terminate at the first pulley  1806   a,  and the distal ends of the third and fourth drive members  1808   c,d  may be coupled to each other and terminate at the second pulley  1806   b.  As generally described above, antagonistic operation of the drive members  1808   a - d  may cause the jaws  1610 ,  1612  to open or close, or may alternatively cause the end effector  1604  to articulate at the wrist  1606  about one or both of the pivot axes P 1 , P 2 . More specifically, selectively actuating the drive members  1808   a - d  such that the pulleys  1806   a,b  rotate in opposite angular directions may result in the jaws  1610 ,  1612  opening or closing. Moreover, selectively actuating the drive members  1808   a - d  such that the pulleys  1806   a,b  rotate in the same angular direction may result in the jaws  1610 ,  1612  pivoting about the second pivot axis P 2  and thereby moving the end effector  1604  up or down in pitch. Furthermore, selective actuation of a first connected pair of drive members  1808   a - d  while relaxing a second pair of connected drive members  1808   a - d  may cause the end effector  1604  to pivot about the first pivot axis P 1  and thereby move in yaw. 
       FIG. 30  is an isometric top view of the end effector  1604  and the wrist  1606  of  FIG. 29 , with the wrist  1606  partially exploded, according to one or more embodiments. More specifically, the distal articulation joint  1802   a  and the pulleys  1806   a,b  are shown in  FIG. 30  exploded laterally outward, and the drive members  1801   a - d  ( FIG. 29 ) are omitted for simplicity. 
     The pulleys  1806   a,b  may be rotatably mounted to the distal articulation joint  1802   a  such that a rotational axis is established that extends through the second pivot axis P 2 . More specifically, the distal articulation joint  1802   a  may define the opposing pins  1910  receivable within or otherwise matable with the apertures  1912  defined in the pulleys  1806   a,b.  The pins  1910  and the apertures  1912  may be coaxially aligned with the second pivot axis P 2 , thereby fixing the rotational axis of the pulleys  1806   a,b  along the second pivot axis P 2 . The pins  1910  support the pulleys  1806   a,b  in the wrist  1606  such that the pulleys  1806   a,b  need not be fixed or supported by any other portion of the wrist  1606 . Rather, as mentioned above, the pulleys  1806   a,b  interpose the jaw extensions  2002   a,b  and the distal articulation joint  1802   a  and may be engageable with adjacent surfaces of one or both. Once the distal articulation joint portions  1904   a,b  are joined, as described above, the pulleys  1806   a,b  will be secured within the wrist  1606  and unable to be removed without disassembling (breaching) the wrist  1606 . 
     The pins  1910  may alternatively comprise bosses or cam features, without departing from the scope of the disclosure. Moreover, in alternative embodiments, the pins  1910  (or bosses or cam features) may be provided by the pulleys  1806   a,b,  and the apertures  1912  may instead be provided by the distal articulation joint  1802   a,  without departing from the scope of the disclosure. Moreover, in some embodiments, the apertures  1912  need not be through-holes, as depicted, but could alternatively comprise recesses defined in the pulleys  1806   a,b  (or the distal articulation joint  1802   a ) and sized and otherwise configured to receive (mate with) the pins  1910 . 
     As described herein, the pulleys  1806   a,b  may provide or otherwise define one or more pins that are eccentric to the second pivot axis P 2 . The first and second jaw pins  2004   a,b,  for example, may be defined on or otherwise provided by the pulleys  1806   a,b  and configured to mate with the first and second jaw apertures  2006   a,b  (only the first jaw aperture  1006   a  visible) defined on the first and second jaw extensions  2002   a,b,  respectively. Coupling the jaw pins  2004   a,b  to the jaw apertures  2006   a,b  allows rotation of the pulleys  1806   a,b  to pivot the jaws  1610 ,  1612  between the open and closed positions and move the end effector  1604  in pitch about the second pivot axis P 2 . In other embodiments, the jaw pins  2004   a,b  may instead be provided on the jaw extensions  2002   a,b,  and the jaw apertures  2006   a,b  may be provided on the pulleys  1806   a,b,  or any combination thereof. Moreover, the jaw apertures  2006   a,b  need not be through-holes, but could alternatively comprise recesses defined in the jaw extensions  2002   a,b  (or the pulleys  1806   a,b ) and sized and otherwise configured to receive the jaw pins  2004   a,b.    
     The pulleys  1806   a,b  may also be rotatably coupled (e.g., pinned) to the alignment arms  1918   a,b  (only the first alignment arm  1918   a  visible) such that movement (rotation) of the pulleys  1806   a,b  correspondingly moves the alignment arms  1918   a,b.  As illustrated, the arm pins  2008   a,b  defined on the pulleys  1806   a,b  may be matable with the arm apertures  2010   a,b  (only the first arm aperture  2010   a  visible) defined by the alignment arms  1918   a,b.  Similar to the jaw pins  2004   a,b,  the arm pins  2008   a,b  are eccentric to the second pivot axis P 2 , and the arm pins  2008   a,b  are also angularly offset from the first and second jaw pins  2004   a,b.  Consequently, as the pulleys  1806   a,b  rotate about the second pivot axis P 2 , the alignment arms  1918   a,b  are correspondingly moved and the distal ends of the alignment arms  1918   a,b  are urged to slide within (traverse) the slots  1920   a,b  ( FIGS. 19A-19B ) of the linkage  1804 . In other embodiments, the arm pins  2008   a,b  may be provided on the alignment arms  1918   a,b,  and the arm apertures  2010   a,b  may be provided on the pulleys  1806   a,b,  or any combination thereof. Moreover, the arm apertures  2010   a,b  need not be through-holes, as depicted, but could alternatively comprise recesses defined in the alignment arms  1918   a,b  (or the pulleys  1806   a,b ) and sized and otherwise configured to receive the arm pins  2008   a,b.    
     As discussed above, the mid-articulation insert  2114  may be arranged within the central portion or middle of the wrist  1606  to help guide the electrical conductor  1812  and the knife  1816  ( FIG. 18 ) through the center of the wrist  1606 . The mid-articulation insert  2114  may be generally arranged within the distal clevis  1802   a  and positioned between (interposing) the opposing jaw extensions  2102   a,b  and the opposing alignment arms  1918   a,b.  Accordingly, the mid-articulation insert  2114  may help maintain proper lateral spacing of the jaw extensions  2102   a,b  and the alignment arms  1918   a,b  as pinned to the pulleys  1806   a,b.  Upon joining the distal articulation joint portions  1904   a,b,  as described above, the pulleys  1806   a,b,  the jaws  1610 ,  1612  (e.g., jaw extensions  2002   a,b ), the alignment arms  1918   a,b,  and the mid-articulation insert  2114  will all be secured within the wrist  1606  and unable to be removed without disassembling (breaching) the wrist  1606 . 
     RF Tool with Split Clevis 
     Referring again to  FIGS. 19A-19B , as described above, the linkage  1804  may be mounted to or otherwise encircle the jaws  1610 ,  1612  to help the jaws  1610 ,  1612  pivot between the open and closed positions. More specifically, the linkage  1804  may provide one or more lateral arms  1914 , which are receivable within a corresponding one or more grooves  1916  defined on the jaws  1610 ,  1612 . One lateral arm  1914 , for example, may be received within a groove  1916  defined by the first jaw  1610 , and the other lateral arm  1914  may be received within a groove  1916  defined by the second jaw  1612 . As the jaws  1610 ,  1612  pivot between the open and closed positions, the lateral arms  1914  interact with the corresponding grooves  1916  and help prevent the jaws  1610 ,  1612  from separating from each other. Accordingly, receiving the lateral arms  1914  in the grooves  1916  creates a jaw pivot point or location where the jaws  1610 ,  1612  are able to pivot. In some embodiments, the lateral arms  1914  slidably engage the grooves  1916  as the jaws  1610 ,  1612  open and close at the jaw pivot, thus the grooves  1916  may operate or be characterized as cam surfaces. In other embodiments, however, the, the lateral arms  1914  may move back and forth (i.e., distally and proximally) within the grooves  1916  as the jaws  1610 ,  1612  open and close at the jaw pivot, or a combination of both sliding and non-sliding movement, without departing from the scope of the disclosure. 
     The linkage  1804  can also include the opposing first and second linkage portions  1902   a,b,  which are essentially mirror images of each other. The linkage portions  1902   a,b  may be joined when assembling the wrist  1606  to secure the jaws  1610 ,  1612  in a pivoting relationship. As mentioned above, the linkage portions  1902   a,b  may be joined by welding (e.g., laser welding), soldering, brazing, an adhesive, an interference fit, or by using one or more mechanical fasteners, such as pins, rivets, bolts, or any combination of the foregoing. 
     According to embodiments of the present disclosure, the process of joining the linkage portions  1902   a,b  may also help set a proper jaw gap between the jaws  1610 ,  1612  when the jaws  1610 ,  1612  are fully closed. Jaw gap is critical to effective operation of the end effector  1604  and, in particular, to tissue graspers and vessel sealers in creating proper tissue seals. For example, the jaws  1610 ,  1612  operate to bring tissue together so that it can be properly sealed (cauterized), and the jaw gap should be set such that vessels are flattened upon closing the jaws  1610 ,  1612 , or pinched together tightly, but not too tightly that the tissue fractures. If the jaw gap exceeds predetermined manufacturing tolerances by just a few thousands of an inch, the jaws  1610 ,  1612  may be incapable of proper tissue apposition and sealing. In such cases, the end effector  1604  may be scrapped as unfit for its intended purpose. 
       FIG. 31  is an enlarged side view of the end effector  1604  of  FIGS. 18 and 19A-19B , according to one or more embodiments. Only a portion of the wrist  1606  is depicted in  FIG. 31 , and the first linkage portion  1902   a  ( FIGS. 19A-19B ) of the linkage  1804  is omitted to enable viewing of certain parts for description purposes. As illustrated, the lateral arm  1914  of the second linkage portion  1902   b  is received within the groove  1916  defined by the second jaw  1612 . The groove  1916  defined by the first jaw  1610  is also visible and located on the underside and would receive the lateral arm  1914  of the first linkage portion  1902   a  if present. The grooves  1916  provide arcuate cam surfaces that allow interaction between the lateral arms  1914  and the jaws  1610 ,  1612  during operation. 
     The jaws  1610 ,  1612  are depicted in  FIG. 31  in the closed position and slightly offset from each other such that a jaw gap  3102  is defined between the inner (opposing) surfaces of each jaw  1610 ,  1612 . As mentioned above, the jaw gap  3102  is critical to effective operation of the end effector  1604  in creating proper tissue seals. For instance, the magnitude of the jaw gap  3102  can be tied to a predetermined manufacturing specification, such as 0.005 inches, and if the jaw gap  3102  exceeds the predetermined value by just a few thousands of an inch (in either direction), the jaws  1610 ,  1612  may be incapable of properly sealing cut tissue and, thus, unfit for its intended purpose. 
     In some embodiments, the jaw gap  3102  may be generally uniform along the proximal-to-distal (longitudinal) length of the jaws  1610 ,  1612  such that the inner surfaces of each jaw  1610 ,  1612  are parallel to one another when closed. In other embodiments, however, the jaw gap  3102  may be non-uniform (non-parallel) to enhance sealing performance by creating different gap zones across the opposing surfaces that can accommodate different tissue types or thicknesses. Such gap zones, however, may remain within the overall specified range of the jaw gap  3102 . 
     The jaw gap  3102  may be set during assembly of the end effector  1604  and the wrist  1606 . More specifically, the jaw gap  3102  may be set by first moving the jaws  1610 ,  1612  to the closed position until a distal end  3104   a  of the jaws  1610 ,  1612  engages or comes into close contact with one another. In some embodiments, one or more distal spacers  3106   a  may be provided at or near the distal end  3104   a  to ensure the inner surfaces of the jaws  1610 ,  1612  at the distal end  3104   a  do not touch during operation. In the illustrated embodiment, the distal spacer(s)  3106   a  may extend through the electrode  1814  provided on the first jaw  1610  to engage the inner surface of the second jaw  1612 . The jaws  1610 ,  1612  may then be progressively closed toward a proximal end  3104   b,  which may include one or proximal more spacers  3106   b  that ensure the inner surfaces of the jaws  1610 ,  1612  do not touch at the proximal end  3104   b  during operation. The spacers  3106   a,b  may be made of ceramic or another non-conductive material. 
     Sliding interaction between the lateral arms  1914  of the linkage  1804  and the grooves  1916  allows the jaw gap  3102  to be adjusted at the proximal end  3104   b  of the jaws  1610 ,  1612 . More specifically, the lateral arms  1914  may be able to slide (rotate) within the corresponding grooves  1916  as the proper jaw gap  3102  magnitude is achieved between the distal and proximal ends  3104   a,b.  Sliding interaction between the linkage  1804  and the jaws  1610 ,  1612  may be advantageous in allowing necessary adjustments to the jaw gap  3102  at or near the proximal end  3104   b  so that the proper clamp force applied is matched with the stiffness of the jaws  1610 ,  1612  to deliver distal clamp force and good clamping pressure uniformly between the distal and proximal ends  3104   a,b.  Once the desired the jaw gap  3102  is achieved, the linkage portions  1902   a,b  may be joined (e.g., laser welded) at the linkage interfaces  2902   a  ( FIGS. 29 and 32 ), and thereby permanently set the jaw gap  3102  for operation. 
     Once the linkage portions  1902   a,b  are joined and the jaw gap  3102  is set, if a hard contact between the jaw grooves  1916  and the lateral arms  1914  is located closer to a distal side of the grooves  1916  (i.e., surface of the groove  1916  closer to the distal end  3104   a  of the jaws  1610 ,  1612 ), that may provide a mechanical advantage for the jaws  1610 ,  1612  while closing because of the larger distance from the pulleys  1806   a,b  ( FIGS. 18A-18B ) and, more particularly, from the jaw pins  2004   a.b  ( FIGS. 20A-20B ) mated with the jaw apertures  2006   a,b  ( FIGS. 20A-20B ). In contrast, if there is hard contact between the jaw grooves  1916  and the lateral arms  1914  closer to a proximal side of the grooves  1916  (i.e., surface of the groove  1916  further from the distal end  3104   a  of the jaws  1610 ,  1612 ), that may provide a mechanical advantage for opening the jaws  1610 ,  1612 , which may be advantageous in blunt dissection and touch and spread applications. Accordingly, the mechanical advantage of the jaws  1610 ,  1612  may be adjusted during assembly by dictating where the lateral arms  1914  will engage the corresponding grooves  1916 . 
       FIG. 32  is an isometric view of the linkage  1804  and accompanying enlarged views of the linkage interface  2902   a,  according to one or more embodiments. As discussed above, in some embodiments, the linkage portions  1902   a,b  may be joined at one or more linkage interfaces  2902   a  (two visible) where the lateral arm  1914  of one linkage portion  1902   a,b  is coupled to the opposing linkage portion  1902   a,b,  and thereby joining the two halves to form the linkage  1804 . 
     As the jaw gap  3102  ( FIG. 31 ) is adjusted to the desired magnitude, the linkage portions  1902   a,b  may be able to be pushed together and adjusted up and down relative to each other to help achieve the proper jaw gap  3102 . The enlarged image on the left of  FIG. 32  shows the lateral arm  1914  of the second linkage portion  1902   b  being moved up relative to the first linkage portion  1902   a,  and the enlarged image on the right of  FIG. 32  shows the lateral arm  1914  of the second linkage portion  1902   b  being moved down relative to the first linkage portion  1902   a.  Once the proper magnitude for the jaw gap  3102  is achieved, the linkage portions  1902   a,b  may be joined at the linkage interfaces  2902   a.  This adjustability of the linkage portions  1902   a,b  may be advantageous in achieving precise jaw gap during manufacturing due to component tolerances. Components comprising the jaws  1610 ,  1612  and the distal end of the end effector  1604  ( FIG. 31 ) will vary over time from part to part and batch to batch within the limits established on the component drawings through geometric dimensioning and tolerancing. Adjustability may prove useful in removing this source of jaw gap variation. 
     Referring again to  FIG. 31 , the design of the distal wedge  2112  may also help in the process of setting the jaw gap  2103 . More particularly, receiving a curved portion  3108  (one shown) of each jaw  1610 ,  1612  within a corresponding one of the arcuate surfaces  2610   a,b  (only the first arcuate surface  2610   a  visible) may help set the minimal spacing between the jaws  1610 ,  1612 . The distal wedge may be sized and have tolerances such that it will not interfere with the jaws  1610 ,  1612  coming together and establishing the correct jaw gap  2103 . Sizing and tolerances must again account for the variation of distal components of the end effector  1604 . 
     RF Tool with Split Articulation Joint and Knife Guide 
       FIG. 33  is a cross-sectional side view of the end effector  1604  and the wrist  1606  of  FIG. 18 , according to one or more embodiments of the disclosure. As illustrated, one or more guiding components may be included in the wrist  1606  and arranged in the central portion or middle of the wrist  1606  to help guide one or both of the electrical conductor  1812  and the knife  1816  to the jaws  1610 ,  1612 . More specifically, the distal wedge  2112  and the mid-articulation insert  2114  may comprise guiding components that are arranged axially in series in the middle of the wrist  1606 . As described herein, the distal wedge  2112  may be generally arranged within the linkage  1804  and otherwise positioned between the electrode  1814  and the distal articulation joint  1802   a,  and the mid-articulation insert  2114  may be generally arranged within the distal articulation joint  1802   a.    
     The electrical conductor  1812  may extend longitudinally through the wrist  1606  and terminate at the electrode  1814  to supply electrical energy to the end effector  1604 . The mid-articulation insert  2114  may provide or otherwise define a first or “upper” passageway  3302   a  sized to receive and support the electrical conductor  1812  as it extends through the distal articulation joint  1802   a.  In at least one embodiment, as illustrated, an exit opening  3304   a  of the first passageway  3302   a  may be enlarged and otherwise flared outward. This may prove advantageous in providing strain relief for the electrical conductor  1812  while the end effector  1604  articulates, thus helping to avoid premature fatigue of the electrical conductor  1812 . After exiting the first passageway  3302   a,  the electrical conductor  1812  may then extend to and be received by the distal wedge  2112 . More specifically, the channel  2602  defined by the distal wedge  2112  may receive the electrical conductor  1812  and may guide the electrical conductor  1812  to the electrode  1814 , as generally described above. 
     The knife  1816  is coupled to the distal end of the drive rod  1818  and configured to be stowed in the knife housing  2502  of the distal wedge  2112  when not in use. As discussed above, longitudinal movement (translation) of the drive rod  1818  correspondingly moves the knife  1816  out of the knife housing  2502  and back and forth within the guide track(s)  1616  defined in the jaws  1610 ,  1612 . Once the knife  1816  is no longer needed, the drive rod  1818  is retracted and the knife  1816  is correspondingly moved back into the knife housing  2502  for safe storage. 
     The drive rod  1818  extends longitudinally through the wrist  1606  to connect to the knife  1816 . The mid-articulation insert  2114  may provide or otherwise define a second or “lower” passageway  3302   b  sized to receive and support the drive rod  1818  through the distal articulation joint  1802   a.  The first and second passageways  3302   a,b  may be separated by a central member  3306 . Similar to the first passageway  3302   a,  in at least one embodiment, an exit opening  3304   b  to the second passageway  3302   b  may be enlarged and otherwise flared outward. This may prove advantageous in providing strain relief for the drive rod  1818  while the end effector  1604  articulates, thus helping to avoid premature fatigue of the drive rod  1818 . 
     After exiting the second passageway  3302   b,  the drive rod  1818  may extend to and be received by the distal wedge  2112 . More specifically, the drive rod  1818  may be received within a drive rod channel  3308  defined by the distal wedge  2112 . The drive rod channel  3308  may extend to and be contiguous with the knife housing  2502 . In at least one embodiment, an opening  3310  to the drive rod channel  3308  may be enlarged and otherwise flared outward. This may prove advantageous in providing strain relief for the drive rod  1818  while the end effector  1604  articulates, thus helping to avoid premature fatigue of the drive rod  1818 . 
     In some embodiments, the drive rod  1818  may comprise a solid shaft, but may alternatively comprise a tube or tubular structure. Moreover, the drive rod  1818  may be made of a variety of flexible materials including, but not limited to, a metal or metal alloy (e.g., a nickel-titanium alloy or “nitinol”), a plastic or thermoplastic material, a composite material, or any combination thereof. The drive rod  1818  may also comprise a braided cable construction of any of the aforementioned materials, and such braided cable may be designed and radially constrained to support axial loads. In some embodiments, as illustrated, a flexible tube  3312  (e.g., a hypotube) may cover all or a portion of the drive rod  1818 . The flexible tube  3312  may support and help prevent buckling of the drive rod  1818  upon assuming compressive loads during articulation of the wrist  1606  and opening and closure of the jaws  1610 ,  1612 . Similar to the drive rod  1818 , the flexible tube  3312  may be made of a variety of flexible materials including, but not limited to, a metal or metal alloy (e.g., a nickel-titanium alloy or “nitinol”), a metallic coil, a plastic or thermoplastic material, a composite material, or any combination thereof. 
     The distal wedge  2112  and the mid-articulation insert  2114  (i.e., the “guiding components”) may prove advantageous in increasing the bend radius of the drive rod  1818  during articulation and actuation of the end effector  1604 . More specifically, the second passageway  3302   b  and the drive rod channel  3308  may help control the proportion of supported length to unsupported length of the drive rod  1818  (and the flexible tube  3312 ), and thus increase the bend radius of the drive rod  1818  as it extends through the wrist  1606 . Consequently, frictional forces assumed by the drive rod  1818  and the flexible tube  3312  when the jaws  1610 ,  1612  are in an articulated pose may be reduced, which can reduce fatigue of the drive rod  1818  and the flexible tube  3312 . Increasing the bend radius also decreases the loading on articulation cables required to achieve given poses of the end effector  1604 . Decreased cable loads can lead to reduced stress, less cable stretch, and better controllability of the robotic instrument. 
     In some embodiments, one or both of the distal wedge  2112  and the mid-articulation insert  2114  may be separate component parts included in the assembly of the wrist  1606 . In such embodiments, the distal wedge  2112  and the mid-articulation insert  2114  may not be coupled or fixed to any portion of the end effector  1604  or the wrist  1606 , but may instead be arranged between adjacent portions of the linkage  1804  and the distal articulation joint  1802   a,  respectively, and secured within the wrist  1606  as the wrist  1606  is assembled. In other embodiments, however, the distal wedge  2112  may form an integral part of the linkage  1804 , and/or the mid-articulation insert  2114  may form an integral part of the distal articulation joint  1802   a,  without departing from the scope of the disclosure. 
       FIG. 34A  is an isometric view of the distal articulation joint  1802   a  and the mid-articulation insert  2114 , according to one or more embodiments. As illustrated, the exit openings  3304   a,b  to the first and second passageways  3302   a,b  ( FIG. 33 ), respectively, are depicted for accommodating the electrical conductor  1812  ( FIG. 33 ) and the drive rod  1818  ( FIG. 33 ), as described above. 
     In the illustrated embodiment, the mid-articulation insert  2114  comprises a separate component part from the distal articulation joint  1802   a.  Moreover, the distal articulation joint  1802   a  includes the opposing first and second distal articulation joint portions  1904   a,b,  and joining the distal articulation joint portions  1904   a,b  at the distal joint interface(s)  2902   b  (one shown) secures the mid-articulation insert  2114  within the wrist  1606 . Accordingly, the mid-articulation insert  2114  may be detached from any portion of the distal articulation joint  1802   a,  and is instead secured within the wrist  1606  as the distal articulation joint portions  1904   a,b  are joined and the wrist  1606  ( FIG. 33 ) is assembled. 
       FIG. 34B  is an isometric view of the distal articulation joint  1802   a  and the mid-articulation insert  2114 , according to one or more additional embodiments. The exit openings  3304   a,b  to the first and second passageways  3302   a,b  ( FIG. 33 ), respectively, are again depicted for accommodating the electrical conductor  1812  ( FIG. 33 ) and the drive rod  1818  ( FIG. 33 ), as described above. In the illustrated embodiment, the mid-articulation insert  2114  forms an integral part of the distal articulation joint  1802   a.  Accordingly, the distal articulation joint  1802   a  may comprise a monolithic structure that does not require jointing by any means during manufacturing; e.g., no welding, soldering, braising, adhesives, or mechanical fasteners are required. 
       FIGS. 35A and 35B  are back and front isometric views, respectively of an example knife drive system  3500 , according to one or more embodiments. The knife drive system  3500  may be incorporated into the surgical tool  1600  of  FIG. 16  to advance and retract the knife  1816  during operation. As illustrated, the knife drive system  3500  may be mounted to a shaft adapter  3502  at or near the wrist  1606  ( FIG. 16 ). In some embodiments, the shaft adapter  3502  may comprise the proximal articulation joint  1802   b  ( FIG. 18 ) or may form an integral part or extension of the shaft  1602  ( FIG. 16 ). In other embodiments, the shaft adapter  3502  may comprise the distal articulation joint  1802   a  of the wrist  1602 , and in yet other embodiments the shaft adapter  3502  may be pivotably coupled to the distal articulation joint  1802   a,  without departing from the scope of the disclosure. 
     The knife drive system  3500  may comprise a cable-based architecture that uses a drive member  3504  to advance or retract the knife  1816 . Similar to the drive members  1808   a - d  ( FIG. 18 ), the drive member  3504  may form part of the actuation systems housed within the handle  1614  ( FIGS. 16 and 17 ), and may comprise a cable, a band, a line, a cord, a wire, a woven wire, a rope, a string, a twisted string, an elongate member, a belt, a flexible shaft, or any combination thereof. Moreover the drive member  3504  can be made from a variety of materials including, but not limited to, a metal (e.g., tungsten, stainless steel, nitinol, etc.), a metallic braided cable, a polymer (e.g., ultra-high molecular weight polyethylene or Dyneema®), a polymer braided cable, a synthetic fiber (e.g., KEVLAR®, VECTRAN®, etc.), an elastomer, or any combination thereof. 
     As illustrated, the drive member  3504  loops around a pulley  3506  ( FIG. 35A ) rotatably mounted to the shaft adapter  3502  at a pin  3507 , thus forming a first drive member portion  3508   a  and a second drive member portion  3508   b.  The drive member portions  3508   a,b  each extend proximally from the pulley  3506  toward the handle  1614  ( FIGS. 16 and 17 ) where they are operatively coupled to one or more actuation mechanisms or device that facilitate antagonistic longitudinal movement (translation) of the drive member  3504 . Selective actuation of one of the drive member portions  3508   a,b  applies tension (i.e., pull force) to the given drive member portion  3508   a,b  in the proximal direction, which urges the given drive member portion  3508   a,b  to move and the drive member portion  3508   a,b  naturally follows as connected thereto. Antagonistic operation of the drive member portions  3508   a,b  of the drive members  1808   a - d  advances or retracts the knife  1816 , depending on the pull direction. 
     More specifically, the knife drive system  3500  may further include a collar  3510  that may be fixed to the drive member  3504  and the drive rod  1818  such that movement of the drive member  3504  correspondingly moves the drive rod  1818  in the same longitudinal direction and thereby advances or retracts the knife  1816 . As illustrated, the drive member  3504  (e.g., the second drive member portion  3508   b ) extends through a first aperture  3512   a  defined through the collar  3510 , and the drive member  3504  may be secured to the collar  3510  at the first aperture  3512   a.  In some embodiments, the drive member  3504  may be crimped or knotted and the crimp or knot may be trapped between the collar  3510  and a stop member  3514  arranged within the first aperture  3512   a.  In one or more embodiments, the stop member  3514  may comprise hypodermic tubing. 
     A proximal end of the drive rod  1818  may extend at least partially through a second aperture  3512   b  defined through the collar  3510 , and the drive rod  1818  may be secured to the collar  3510  at the second aperture  3512   b.  In some embodiments, as illustrated, the drive rod  1818  may be received within the flexible tube  3312 , as generally described above. In such embodiments, the flexible tube  3312  may be slotted at the second aperture  3512   b  to allow effective compression force around the proximal end of the drive rod  1818 . The collar  3510  may also be slotted in various locations to ensure a tight compression fit about the drive rod  1818 . In some embodiments, the collar  3510  may be compressible around the drive rod  1818  and the flexible tube  3312  with a screw and may then be welded in the compressed state to maintain clamp pressure against the drive rod  1818  and the flexible tube  3312 . 
     The drive rod  1818  may extend through a central aperture  3314  defined longitudinally through the shaft adapter  3502 . In some embodiments, a hypotube  3316  may surround the drive rod  1818  and the flexible member  3312  (or only the drive rod  1818 ) as extending through the central aperture  3314 . During operation, the drive rod  1818  and the flexible member  3312  (or only the drive rod  1818 ) slide longitudinally through the hypotube  3316 , and the hypotube  3316  may help to prevent buckling of the drive rod  1818 . 
     In example operation, once the collar  3510  is properly secured to the drive member  3504  and the drive rod  1818 , actuating the first drive member portion  3502   a  in the proximal direction will correspondingly cause the drive rod  1818  and the knife  1816  to move distally. In contrast, actuating the second drive member portion  3502   b  in the proximal direction will correspondingly cause the drive rod  1818  and the knife  1816  to move proximally. 
       FIG. 36  is an isometric view of another example end effector  3600 , according to one or more embodiments. The end effector  3600  may be similar in some respects to the end effector  1604  of  FIG. 18  and, therefore, may be best understood with reference thereto, where like reference numerals refer to like components not described again. Similar to the end effector  1604  of  FIG. 18 , for example, the end effector  3600  may be used with the surgical tool  1600  of  FIG. 16 . Moreover, the end effector  3600  may comprise a vessel sealer that has the first and second jaws  1610 ,  1612  that move simultaneously to actuate the end effector  3600  between open and closed positions; i.e., bifurcating jaws. Accordingly, the end effector  3600  may be configured to compress and cut tissue grasped between the jaws  1610 ,  1612 . 
     Unlike the end effector  1604  of  FIG. 18 , however, the end effector  3600  does not use a knife (or cutting element) to cut tissue. Instead, the end effector  3600  may include a cutting electrode  3602  that extends longitudinally along at least a portion of the first or second jaw  1610 ,  1612  and is configured for electrical cutting (or heating) versus mechanical cutting. In the illustrated embodiment, the cutting electrode  3602  is depicted as forming part of the first jaw  1610 , but could alternatively form part of the second jaw  1612 , or both jaws  1610 ,  1612 , without departing from the scope of the disclosure. Moreover, the cutting electrode  3602  is depicted extending longitudinally through (along) the middle of the electrode  1814 , alternately referred to herein as the “sealing electrode  1814 ”. Accordingly, the cutting electrode  3602  may bifurcate the sealing electrode  1814  and interpose first and second sealing electrode sections  3604   a  and  3604   b.    
     Similar to the sealing electrode  1814 , the cutting electrode  3602  may be configured for high current density monopolar or bipolar radio frequency (RF) operation. In at least one embodiment, the cutting electrode  3602  may comprise a simple wire configured for electrical heating and/or cutting. Moreover, in addition to the electrical conductor  1812  ( FIG. 18 ), the end effector  3600  may include a second electrical conductor (not shown) provides electrical power to the cutting electrode  3602 . In some embodiments, the second electrical conductor may communicate with the same electrical circuit as the sealing electrode  1814 , thus making the end effector  3600  a bipolar operating device. In such embodiments, the sealing and cutting electrodes  1814 ,  3602  may share the same electrical return circuit (e.g., a common ground). In some embodiments, selective operation of the sealing and cutting electrodes  1814 ,  3502  may be based on a control algorithm that commands vessel sealing, cutting, or both vessel sealing and cutting simultaneously as directed by the operator. 
     The cutting electrode  3602  may prove advantageous for a variety of reasons. For example, the cutting electrode  3602  may be capable of replacing the entire mechanical knife system described herein, which eliminates the complexity of driving a knife in and through the system. This also results in reduced parts and frees up at least one drive input  1620   a - f  ( FIGS. 16-17 ) at the handle  1614  ( FIGS. 16-17 ). Moreover, the cutting electrode  3602  may simplify assembly of the end effector  3600  and allow drive members that open and close the jaws  1610 ,  1612  to be routed through the central axis of the wrist  1606  ( FIG. 16 ) and the articulation joints (devises)  1802   a,b  ( FIG. 18 ). This may prove advantageous in reducing or eliminating tip dive of the jaws  1610 ,  1612  and allowing a general rearrangement of lumen ports and configurations of the wrist  1606 . 
       FIG. 37  is a cross-sectional end view of the jaws  1610 ,  1612  as taken along the plane indicated in  FIG. 36 , according to one or more embodiments. In some embodiments, the sealing and cutting electrodes  1814 ,  3602  may be mounted to or otherwise form part of a removable cartridge  3702 , thus providing discrete cutting and sealing electrical paths. In the illustrated embodiment, the removable cartridge  3702  is able to be mounted or secured to the first jaw  1610 , but could alternatively be mounted or secured to the second jaw  1612 , without departing from the scope of the disclosure. The removable cartridge  3702  may be replaced, for example, after each use or otherwise prior to use on the next patient. 
     In some embodiments, the second jaw  1612  may include or otherwise have mounted thereto one or more non-conductive spacers  3704  (two shown) configured to oppose the sealing electrode sections  3604   a,b.  Moreover, another non-conductive spacer  3706  may be included in the second jaw  1612  to oppose the cutting electrode  3602 . The spacers  3704 ,  3706  may be dispersed on corresponding electrically active or passive electrodes. In at least one embodiment, the second jaw  1612  may also have a replaceable cartridge that carries and secures the non-conductive spacers  3704 ,  3706 . 
     The removable cartridge  3702  may be received within a pocket  3708  (alternately referred to as a “shelf”) defined in the first jaw  1610 . The removable cartridge  3702  may be secured within the pocket  3708  via a variety of attachment means including, but not limited to, a snap fit engagement, an interference fit, one or more mechanical fasteners, or any combination thereof. 
     In some embodiments, the cutting electrode  3602  may exhibit a current-density focusing shape. In the illustrated embodiment, for example, the cutting electrode  3602  exhibits a generally triangular cross-sectional shape, thus resulting in current density focused at the exposed tip of the triangular shape. As will be appreciated, other polygonal cross-sectional shapes may be employed and provide current-density focusing properties, without departing from the scope of the disclosure. In one or more embodiments, the cutting electrode  3602  may exhibit flat cross-sectional shape, such as square or rectangle, which may be advantageous for ease of manufacturing. 
       FIG. 38  depicts an alternative embodiment of the removable cartridge  3702  where the cutting electrode  3602  exhibits a generally circular shape. In other embodiments, the cutting electrode  3602  may exhibit other curved shapes, such as oval or ovoid, without departing from the scope of the disclosure. 
       FIG. 39  is an isometric view of the end effector  3600  of  FIG. 36  depicting an exposed electrical system  3900 , according to one or more embodiments.  FIG. 39  also depicts one embodiment of the pocket  3708  provided in the first jaw  1610  and sized to receive the removable cartridge  3702  ( FIGS. 37-38 ). As illustrated, the pocket  3708  may comprise a shelf or recess defined by the first jaw  1610 , but could alternatively be provided in the second jaw  1612 . 
     In the illustrated embodiment, the electrical system  3900  includes the electrical conductor  1812  that extends to and terminates at the end effector  3600  to supply electrical energy to the sealing electrode  1814  ( FIGS. 36-37 ) and, more particularly, to the sealing electrode sections  3604   a,b  ( FIGS. 36-37 ). In some embodiments, as illustrated, the electrical conductor  1812  may split into first and second conductor portions  3902   a  and  3902   b  to simultaneously provide electrical energy to the sealing electrode sections  3604   a,b,  respectively. 
     The electrical system  3900  may also include a second electrical conductor  3904  configured to supply electrical energy to the cutting electrode  3602  ( FIGS. 36-37 ). Similar to the first electrical conductor  1812 , the second electrical conductor  3904  may comprise a wire, but may alternatively comprise a rigid or semi-rigid shaft, rod, or strip (ribbon) made of a conductive material. Moreover, the electrical conductor  1812  may be partially covered with an insulative covering (overmold) made of a non-conductive material. 
     The electrical conductors  1812  (i.e., the conductor portions  3902   a,b ),  3904  may terminate at the jaws  1610 ,  1612  such that receiving the removable cartridge  3702  ( FIGS. 37-38 ) into the pocket  3708  may facilitate electrical connection between the conductor portions  3902   a,b  and the sealing electrode sections  3604   a,b  ( FIGS. 36-37 ), and between the second electrical conductor  3904  and the cutting electrode  3602  ( FIGS. 36-37 ), thus providing electrical power to the sealing and cutting electrodes  1814 ,  3602 . In at least one embodiment, the terminal ends of the electrical conductors  1812 ,  3904  may comprise spring contact electrodes that help facilitate proper electrical coupling and connection upon mounting the cartridge  3702  in the pocket  3708 . 
     Accordingly, in one or more embodiments, the electrical system  3900  may provide two electrically isolated signals from the two electrically isolated electrical conductors  1812 ,  3904 . The first conductor  1812  (i.e., the conductor portions  3902   a,b  of  FIGS. 36-37 ) may provide a first signal to the sealing electrode sections  3604   a,b  ( FIGS. 36-37 ) for sealing, and the second conductor  3904  provides a second signal to the cutting electrode  3602  ( FIGS. 36-37 ) for cutting. In some embodiments, the electrical system  3900  may be configured for bipolar operation and the return path for the current may be through the second jaw  1612 . In other embodiments, however, the electrical system  3900  may be configured for monopolar operation and the return path may be through a patient grounding pad, with electrical isolation zones mating with the cutting electrode  3602 . 
     3. Implementing Systems and Terminology. 
     Implementations disclosed herein provide systems, methods and apparatus for instruments for use with robotic systems. It should be noted that the terms “couple,” “coupling,” “coupled” or other variations of the word couple as used herein may indicate either an indirect connection or a direct connection. For example, if a first component is “coupled” to a second component, the first component may be either indirectly connected to the second component via another component or directly connected to the second component. 
     The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is required for proper operation of the method that is being described, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. 
     As used herein, the term “plurality” denotes two or more. For example, a plurality of components indicates two or more components. The term “determining” encompasses a wide variety of actions and, therefore, “determining” can include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” can include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” can include resolving, selecting, choosing, establishing and the like. 
     The phrase “based on” does not mean “based only on,” unless expressly specified otherwise. In other words, the phrase “based on” describes both “based only on” and “based at least on.” 
     As used herein, the terms “generally” and “substantially” are intended to encompass structural or numeral modification which do not significantly affect the purpose of the element or number modified by such term. 
     To aid the Patent Office and any readers of this application and any resulting patent in interpreting the claims appended herein, applicants do not intend any of the appended claims or claim elements to invoke 35 U.S.C. 112(f) unless the words “means for” or “step for” are explicitly used in the particular claim. 
     The foregoing previous description of the disclosed implementations is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these implementations will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the scope of the invention. For example, it will be appreciated that one of ordinary skill in the art will be able to employ a number corresponding alternative and equivalent structural details, such as equivalent ways of fastening, mounting, coupling, or engaging tool components, equivalent mechanisms for producing particular actuation motions, and equivalent mechanisms for delivering electrical energy. Thus, the present invention is not intended to be limited to the implementations shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.