Patent Publication Number: US-2023135824-A1

Title: Surgical tool end effectors with distal wedge slot constraint

Description:
TECHNICAL FIELD 
     The systems and methods disclosed herein are directed to robotic surgical tools and, more particularly to, surgical tool end effectors that provide distal wedge slot constraint that limits unwanted jaw rotations with respect to a distal articulation joint, and thereby reduces jaw backlash. 
     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. 
     Various robotic systems have recently been developed to assist in MIS procedures. Robotic systems can allow for more instinctive hand movements by maintaining natural eye-hand axis. Robotic systems can also allow for more degrees of freedom in movement by including an articulable “wrist” joint that creates a more natural hand-like articulation. In such systems, an end effector positioned at the distal end of the instrument can be articulated (moved) using a cable driven motion system having one or more drive cables (or other elongate members) that extend through the wrist joint. A user (e.g., a surgeon) is able to remotely operate the end effector by grasping and manipulating in space one or more controllers that communicate with a tool driver coupled to the surgical instrument. User inputs are processed by a computer system incorporated into the robotic surgical system, and the tool driver responds by actuating the cable driven motion system and thereby actively controlling the tension balance in the drive cables. Moving the drive cables articulates the end effector to desired angular 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. 
    
    
     
       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.  3 A  illustrates an embodiment of the robotic system of  FIG.  1    arranged for ureteroscopy. 
         FIG.  3 B  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.  7 A  illustrates an embodiment of a table-based robotic system configured for a ureteroscopy procedure. 
         FIG.  7 B  illustrates an embodiment of a table-based robotic system configured for a laparoscopic procedure. 
         FIG.  7 C  illustrates an embodiment of the table-based robotic system of  FIG.  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.  9 A  illustrates an alternative embodiment of a table-based robotic system. 
         FIG.  9 B  illustrates an end view of the table-based robotic system of  FIG.  9 A . 
         FIG.  9 C  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  FIG.  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.  19 A and  19 B  are isometric, partially exploded views of the end effector of  FIG.  18    from right and left vantage points, respectively, according to one or more embodiments. 
         FIGS.  20 A and  20 B  are additional isometric, partially exploded views of the end effector of  FIG.  18    from the right and left vantage points. 
         FIGS.  21 A and  21 B  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, partial cross-sectional side view of the end effector, according to one or more embodiments. 
         FIG.  23    is another enlarged, partial cross-sectional side view of the end effector, according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     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’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’s mouth. 
     After insertion into the patient’s mouth, the endoscope  106  may be directed down the patient’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’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 repositioned 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 moveable 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.  3 A  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’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’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’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’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.  3 B  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’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’s heart, which simplifies navigation. As in a ureteroscopic procedure, the cart  102  may be positioned towards the patient’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’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’s upper abdomen in order to reach alternative vascular access points, such as, for example, the carotid and brachial arteries near the patient’s shoulder and wrist. 
     B Robotic System Table. 
     Embodiments of the robotically-enabled medical system may also incorporate the patient’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’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.  9 A ), 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 j oint) 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.  7 B ), 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.  7 A  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’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’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’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’s legs during the procedure and allow clear access to the patient’s groin area. 
       FIG.  7 B  illustrates an embodiment of the system  400  configured for a laparoscopic procedure. In a laparoscopic procedure, through small incision(s) in the patient’s abdominal wall, minimally invasive instruments may be inserted into the patient’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’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.  7 B , 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.  7 C  illustrates an embodiment of the system  400  with pitch or tilt adjustment. As shown in  FIG.  7 C , 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’s lower abdomen at a higher position from the floor than the patient’s lower abdomen, for lower abdominal surgery. The Trendelenburg position causes the patient’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.  9 A and  9 B  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.  9 C ) 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.  9 A and  9 B , the arm support  902  is configured with four degrees of freedom, which are illustrated with arrows in  FIG.  9 A . 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.  9 A and  9 B  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.  9 B . 
     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.  9 B ) 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.  9 C  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’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’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  FIG.  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’s internal anatomy. When analyzed in the aggregate, image-based models for anatomical cavities, spaces and structures of the patient’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’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. Pat. App. 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’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’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’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’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. 
     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 - 9 C . 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 vessel sealer capable of cutting and cauterizing/sealing tissue or vessels. 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, a surgical stapler, tissue graspers, surgical scissors, 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. 
     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, both jaws  1610 ,  1612  simultaneously move to pivot the jaws  1610 ,  1612  between an open, unclamped position and a closed, clamped position and are thus referred to as “bifurcating” jaws. In other embodiments, however, only one of the jaws  1610 ,  1612  may be rotatable (pivotable) relative to the opposing jaw to actuate the end effector  1604  between the open and closed positions. 
     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 (through) 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 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 within the guide track  1616 , the knife transects any tissue grasped between the opposing jaws  1610 ,  1612 . In at least one embodiment, actuating the end effector  1604  may further entail triggering energy delivery (e.g., RF energy) to cauterize and/or seal tissue or vessels grasped between the jaws  1610 ,  1612 . 
     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  may 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. Those skilled in the art, however, will readily appreciate that the handle  1614  may be alternatively designed such that the drive inputs  1620   a - f  carry out other functions, without departing from the scope of the disclosure. Indeed, the operations described above for the drive inputs  1620   a - f  are merely provided as examples, and alternative configurations or operations may instead be provided. 
       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 other mechanical 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.  17    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 . 
       FIG.  18    is an enlarged isometric view of the distal end of the surgical tool  1600  of  FIGS.  16  and  17   . As illustrated, 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 clevises  1802   a ,b are alternatively referred to as “articulation joints” of the wrist  1606  and extend from the shaft  1602 , or alternatively a shaft adapter. The clevises  1802   a ,b are operatively coupled to facilitate articulation of the wrist  1606  relative to the shaft  1602 . As illustrated, the wrist  1606  also includes 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 or pivotably coupled to the proximal clevis  1802   b  at a first pivot axis P 1  of the wrist  1602 . In some embodiments, an axle may extend through the first pivot axis P 1  and the distal and proximal clevises  1802   a ,b may be rotatably coupled via the axle. In other embodiments, however, such as is depicted in  FIG.  18   , the distal and proximal clevises  1802   a ,b may be engaged in rolling contact, such as via an intermeshed gear relationship (not shown) that allows the clevises  1802   a ,b to rotate relative to each other similar to a rolling joint. Accordingly, the first pivot axis P 1  will be referred to herein as the rolling joint P 1 . 
     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 rolling joint 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 rolling joint P 1 . Movement of the end effector  1604  about the rolling joint 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 corresponding ball crimps (not shown) mounted to the first and second pulley  1806   a ,b, respectively. 
     In at least one embodiment, the drive members  1808   a - d  may 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. 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 entirely or 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 (not shown), alternately referred to as a “cutting element” or “blade.” The knife is aligned with and configured to traverse the guide track  1616  ( FIG.  16   ) defined longitudinally in one or both of the upper and lower jaws  1610 ,  1612 . The knife may be operatively coupled to the distal end of a drive rod  1816  that extends longitudinally within the lumen  1810  and passes through the wrist  1606 . Longitudinal movement (translation) of the drive rod  1816  correspondingly moves the knife within the guide track(s)  1616 . Similar to the drive members  1808   a - d , the drive rod  1816  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  1816  to move distally or proximally within the lumen  1810 , and correspondingly move the knife  1816  in the same longitudinal direction. 
       FIGS.  19 A and  19 B  are isometric, partially exploded views of the end effector  1604  of  FIG.  18   , as taken from right and left vantage points, respectively.  FIGS.  19 A- 19 B  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 the drive members  1808   a - d  terminating at the pulleys  1806   a ,b. 
     In some embodiments, as illustrated, 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, screws, bolts, or any combination of the foregoing. In other embodiments, however, it is contemplated herein that one or both of the distal clevis  1802   a  and the linkage  1804  may alternatively comprise a monolithic, one-piece structure, without departing from the scope of the disclosure. 
     As indicated above, the first and second pulleys  1806   a ,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 a corresponding one of the pins  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 or pockets defined in the pulleys  1806   a ,b (or the distal clevis  1802   a ) and sized and otherwise configured to receive the pins  1910 . 
     As also 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 inner jaw pivot surfaces for the jaws  1610 ,  1612 . In the illustrated embodiment, one lateral arm  1914  is received within the groove  1916  defined by the first jaw  1610 , and the other lateral arm  1914  is received within the 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 corresponding 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, and may also help prevent the jaws  1610 ,  1612  from inadvertently moving in pitch while opening or closing. In the illustrated embodiment, the jaw constraint includes one or more alignment arms, shown as a first alignment arm  1918   a  ( FIG.  19 A ) and a second alignment arm  1918   b  ( FIG.  19 B ). The proximal end of the first alignment arm  1918   a  may be rotatably coupled (e.g., pinned) to the first pulley  1806   a  at the second pivot axis P 2 , and the proximal end of the second alignment arm  1918   b  may be rotatably coupled (e.g., pinned) to the second pulley  1806   b  at the second pivot axis P 2 . In contrast, the distal end of the first alignment arm  1918   a  may be received within a first slot  1920   a  ( FIG.  19 B ) 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.  19 A ) defined in the second linkage portion  1902   b  of the linkage  1804 . The slots  1920   a ,b extend distally and proximally such that the direction or axis of the slots  1920   a ,b is generally parallel to a longitudinal axis A 2  of the end effector  1604 . When the end effector  1604  is in an unarticulated position, the longitudinal axis A 2  and the longitudinal axis A 1  ( FIG.  16   ) of the shaft  1602  ( FIG.  16   ) are the same and otherwise concentric. 
     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 and potentially move in pitch during opening and closing, thus preventing accurate positioning during opening and closing. This jaw condition is sometimes referred to as extreme backlash or slop. While two alignment arms  1918   a ,b are included in the illustrated embodiments, only one alignment arm  1918   a ,b may be required for the purposes of the present disclosure. 
       FIGS.  20 A and  20 B  are additional isometric, partially exploded views of the end effector  1604  of  FIG.  18    from the right and left vantage points, respectively. In  FIGS.  20 A- 20 B , the distal and proximal clevises  1802   a ,b ( FIGS.  19 A- 19 B ) are 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.  20 A ) and the second jaw  1612  provides a second jaw extension  2002   b  ( FIG.  20 B ), and each jaw extension  2002   a ,b extends proximally from the corresponding jaw  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.  20 B ) configured to mate with a first jaw aperture  2006   a  ( FIG.  20 A ) 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.  20 A ) configured to mate with a second jaw aperture  2006   b  ( FIG.  20 B ) 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.  19 A- 19 B ). 
     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 be rotatably coupled (e.g., pinned) to the first and second pulleys  1806   a ,b, respectively, at the second pivot axis P 2 . In the illustrated embodiment, for example, the first pulley  1806   a  may provide or define a first arm pin  2008   a  ( FIG.  20 B ) 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.  20 A ) configured to mate with a second arm aperture  2010   b  ( FIG.  20 B ) defined by the second alignment arm  1918   b  ( FIG.  20 B ). The first and second arm pins  2008   a ,b are concentric to (with) the second pivot axis P 2 , thus allowing the pulleys  1806   a ,b to rotate without directly affecting the position of the alignment arms  1918   a ,b. However, actuation of the pulleys  1806   a ,b to open and close the jaws  1610 ,  1612  may result in the distal ends of the alignment arms  1918   a ,b sliding (traversing) within the corresponding slots  1920   a ,b ( FIGS.  19 A- 19 B ), 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 points by the lateral arms  1914  ( FIGS.  19 A- 19 B ) 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.  19 A- 19 B ) 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 will 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 rolling joint P 1  ( FIG.  18   ) 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.  21 A and  21 B  are additional isometric, partially exploded views of the end effector  1604  of  FIG.  18    from the right and left vantage points, respectively. In  FIGS.  21 A- 21 B , the distal clevis  1802   a , the linkage  1804  ( FIGS.  19 A- 19 B ), the drive members  1808   a - d  ( FIGS.  20 A- 20 B ), the pulleys  1806   a ,b ( FIGS.  20 A- 20 B ), and the first or “upper” jaw  1612  are all omitted for simplicity. The first and second alignment arms  1918   a ,b are shown in  FIGS.  21 A- 21 B  exploded laterally from the remaining portions of the end effector  1604  and the wrist  1606 . As mentioned above, however, only one of the alignment arms  1918   a ,b need be included, without departing from the scope of the disclosure. 
     In some embodiments, as illustrated, each alignment arm  1918   a ,b may provide or otherwise define an alignment head  2102  configured or otherwise sized to be received within the corresponding and adjacent slot  1920   a ,b ( FIGS.  19 A- 19 B ) defined in the linkage  1804  ( FIGS.  19 A- 19 B ). The alignment head  2102  may be provided at or near the distal end of each alignment arm  1918   a ,b, or may otherwise be arranged at any location along the alignment arm  1918   a ,b and distal to the arm apertures  2010   a ,b. 
     In the illustrated embodiment, the wrist  1606  may further include a distal wedge  2104  and a mid-articulation insert  2106  arranged in series and positioned in the central portion or middle of the wrist  1606 . The distal wedge  2104  may be arranged between the electrode  1814  and the distal clevis  1802   a  ( FIGS.  19 A- 19 B ) and generally arranged within the linkage  1804  ( FIGS.  18  and  19 A- 19 B ), and the mid-articulation insert  2106  may be generally arranged within the distal clevis  1802   a  ( FIGS.  18  and  19 A- 19 B ). The distal wedge  2104  and the mid-articulation insert  2106  may be positioned between (interpose) the first and second jaw extensions  2002   a ,b of the jaws  1610 ,  1612  (only the first jaw extension  2002   a  of the lower jaw  1610  depicted in  FIGS.  21 A- 21 B ). The distal wedge  2104  and mid-articulation insert  2106  may act to guide the jaw extensions  2002   a ,b in planar rotation as the jaws  1610 ,  1612  open, close, and articulate in pitch. 
     The distal wedge  2104  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. 
     In some embodiments, the distal wedge  2104  may receive and help guide the knife (not shown) to the jaws  1610 ,  1612 . More specifically, the distal wedge  2104  may define a knife cavity (not shown) through which the knife and the drive rod  1818  are able to extend to move the knife into and along the guide track  1616 . Upon firing the end effector  1604 , the drive rod  1818  is moved (urged) distally, which correspondingly moves the knife out of the distal wedge  2104  and into the guide track  1616 . After firing is complete, the drive rod  1818  is retracted proximally, which pulls the knife proximally and back into distal wedge  2104  until it is desired to again fire the end effector  1604 . 
     In some embodiments, the distal wedge  2104  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 distal wedge  2104  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  2104  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 clevises  1802   a ,b, and the articulation arms  1918   a ,b, all of which could inadvertently contact and damage the electrical conductor  1812  during operation if not properly protected by the distal wedge  2104 . 
     To guide and protect the electrical conductor  1812  from damage, the distal wedge  2104  may provide or otherwise define one or more conductor conduits  2108  (one visible in  FIG.  21 A ) configured to receive and guide the electrical conductor  1812  to the electrode  1814 . The conductor conduit(s)  2108  may pass through, around, above, below, or on one or both sides of the distal wedge  2104 , or any combination thereof. In some embodiments, the conductor conduit  2108  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 conductor conduit  2108  and thereby change the course of the electrical conductor  1812  received within the conductor conduit  2108 . 
     The distal wedge  2104  may further provide or otherwise define one or more arcuate surfaces, shown as a first or “upper” arcuate surface  2110   a  and a second or “lower” arcuate surface  2110   b  (not visible in  FIGS.  21 A- 21 B ). As illustrated, the arcuate surfaces  2110   a ,b may comprise concave surfaces, and may be configured to receive and engage corresponding curved (convex) portions of the jaws  1610 ,  1612 . As described in more detail below, the arcuate surfaces  2110   a ,b may operate as camming surfaces for the jaws  1610 ,  1612  as they open and close. 
     In some embodiments, as illustrated, a channel  2112  ( FIG.  21 B ) may be provided or otherwise defined on one or both lateral sides of the distal wedge  2104  and may be configured to receive and slidably mate with a corresponding projection  2114  provided by an adjacent alignment arm  1918   a ,b. In the illustrated embodiment, the channel  2112  is provided on only one lateral side of the distal wedge  2104  and is configured to receive and slidably mate with a projection  2114  provided by the second alignment arm  1918   b . In other embodiments, however, channels  2112  could alternatively be provided on both lateral sides of the distal wedge  2104  and configured to mate with adjacent projections  2114  provided by each alignment arm  1918   a ,b, without departing from the scope of the disclosure. 
     As illustrated, the projection  2114  may be provided on one lateral side of the alignment arm  1918   b  to slidably mate with the channel  2112 , while the alignment head  2102  may be provided on the opposing lateral side of the alignment arm  1918   b  to slidably mate with the second slot  1920   b  ( FIG.  19 A ). In some embodiments, the channel  2112  may extend distally and proximally such that the direction or axis of the channel  2112  is generally parallel to the longitudinal axis A 2  ( FIGS.  19 A- 19 B ) of the end effector  1604 . In other embodiments, however, the channel  2112  may be arcuate or otherwise non-straight, without departing from the scope of the disclosure. In such embodiments, for example, both alignment arms  1918   a ,b may be used with pin-in-slot arrangements on each side. Depending on the specifics of the arrangement, a coupled motion between jaw closure and pitch cold be achieved, and this type of coupling could result in a predefined end effector rotation during jaw closure, coupled with robotic arm motion can create the user perceived effect of the bottom jaw remaining stationary against tissue while the top jaw completes the clamping motion. As discussed in more detail below, slidably mating the projection  2114  within the channel  2112  may help rotationally constrain the distal wedge  2104  to the alignment arm  1918   b , which may help reduce backlash in the jaws  1610 ,  1612 . 
     While  FIGS.  21 A- 21 B  depict the channel  2112  as being provided on the distal wedge  2104  and the projection  2114  as being provided on the alignment arm  1918   b , the component features may be switched, without departing from the scope of the disclosure. More specifically, it is contemplated herein that the channel  2112  may alternatively be provided on the alignment arm  1918   b  and the projection  2114  may alternatively be provided on the distal wedge  2104 . 
       FIG.  22    is an enlarged, partial cross-sectional side view of the end effector  1604 , according to one or more embodiments. As mentioned above, the distal wedge  2104  may provide upper and lower arcuate (concave) surfaces  2110   a ,b configured to receive and engage corresponding curved (convex) portions of the jaws  1610 ,  1612 . More specifically, the upper jaw  1612  may provide or define a first or “upper” journal  2202   a  configured to engage the upper arcuate surface  2110   a , and the lower jaw  1610  may provide or define a second or “lower” journal  2202   b  configured to engage the lower arcuate surface  2110   b . Engagement between the opposing arcuate surfaces  2110   a ,b and journals  2202   a ,b, respectively, provides or facilitates the jaw pivot point discussed herein, where the jaws  1610 ,  1612  pivot between open and closed positions. As the jaws  1610 ,  1612  move between the open and closed positions, the opposing arcuate surfaces  2110   a ,b and journals  2202   a ,b act in sliding engagement as opposing camming surfaces. 
     The arcuate surfaces  2110   a ,b of the distal wedge  2104  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 jaws  1610 ,  1612  and this load is transferred to the distal wedge  2104  at the corresponding arcuate surface  2110   a ,b. Furthermore, the distal wedge  2104  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 and such loads are transferred to the arcuate surfaces  2110   a ,b and borne by the distal wedge  2104 . Accordingly, the arcuate surfaces  2110   a ,b help support the jaws  1610 ,  1612  and bear loading forces that are required to move or spread tissue. 
     The jaws  1610 ,  1612  are depicted in  FIG.  22    in an open position. When in this orientation and brought into contact with an adjacent structure during operation (e.g., a vessel, an organ, tissue, etc.), the jaws  1610 ,  1612  will oftentimes move (shift) until clearance between structural components of the end effector  1604  is taken up and the end effector  1604   eventually stiffens. The effect of such clearance between adjacent structural components of the end effector  1604  manifests as a lack of jaw stiffness, which is often referred to as jaw backlash. Those skilled in the art will readily appreciate that jaw backlash can reduce the effectiveness of surgical tasks, such as blunt dissection and otomy creation in tissue. 
     One prevalent cause of jaw backlash results as the distal wedge  2104  moves, shifts, or rotates when acted upon by movement of the jaws  1610 ,  1612  at the upper and lower journals  2202   a ,b. To the extent permitted by component clearances, the jaws  1610 ,  1612  can shear distal to proximal as the distal wedge  2104  rotates or shifts beneath forces transferred from the journals  2202   a ,b. This jaw motion allows play or backlash to occur in the pitch axis until clearances are taken up. As described here “shearing” is the term given to the top jaw translating distally in the direction of the shaft axis, while the lower jaw simultaneously translates proximally, and vise versa. This jaw motion allows play or backlash to occur in the pitch axis until clearances are taken up. According to embodiments of the present disclosure, the sliding and mated engagement between the projection  2114  ( FIGS.  21 A- 21 B ) and the channel  2112  ( FIGS.  21 A- 21 B ) provided on the distal wedge  2104  may help stabilize and rotationally constrain the distal wedge  2104 , which may help reduce resulting backlash in the jaws  1610 ,  1612 . 
       FIG.  23    is another enlarged, partial cross-sectional side view of the end effector  1604 , according to one or more embodiments. As illustrated, the projection  2114  provided by the second alignment arm  1918   b  is received within the channel  2112  defined or otherwise provided on the lateral side of the distal wedge  2104 . Slidably receiving the projection  2114  within the channel  2112  helps to rotationally constrain the distal wedge  2104  to the alignment arm  1918   b , and, as discussed above, the alignment arm  1918   a  is configured to translate within the slot  1920   b  defined in the linkage  1804 . Consequently, receiving the projection  2114  within the channel  2112  effectively constrains the distal wedge  2104  to the linkage  1804 , and thereby limits unwanted jaw rotation with respect to the distal articulation joint; i.e., reduction in jaw backlash. 
     In some embodiments, the structure that helps define the channel  2112  may further provide or otherwise define an upper surface  2302  engageable with a portion of the upper jaw  1612 . As illustrated, the upper surface  2302  may be ramped, angled, or otherwise arcuate to help support the upper jaw  1612  and further provide clearance for the upper jaw  1612  to move between the open and closed positions. 
     Embodiments disclosed herein include: 
     A. A robotic surgical tool includes an elongate shaft, an end effector arranged at a distal end of the shaft and including opposing first and second jaws, and an articulable wrist interposing the end effector and the distal end of the shaft, the wrist including a linkage mounted to the first and second jaws and defining a slot, a distal wedge arranged at least partially within the linkage, an alignment arm interposing the linkage and the distal wedge and providing an alignment head receivable within the slot, a channel provided on one of the distal wedge or the alignment arm, and a projection provided on the other of the distal wedge or the alignment arm and receivable within the channel, wherein the alignment head is translatable within the slot and the projection is translatable within the channel during operation of the end effector.   B. An end effector for a robotic surgical tool includes opposing first and second jaws, and an articulable wrist operatively coupled to the first and second jaws and including a linkage mounted to the first and second jaws and defining a slot, a distal wedge arranged at least partially within the linkage, an alignment arm interposing the linkage and the distal wedge and providing an alignment head receivable within the slot, a channel provided on one of the distal wedge or the alignment arm, and a projection provided on the other of the distal wedge or the alignment arm and receivable within the channel, wherein the alignment head is translatable within the slot and the projection is translatable within the channel during operation of the end effector.   C. A method of operating a robotic surgical tool includes locating a robotic surgical tool adjacent a patient, the robotic surgical tool having an elongate shaft, an end effector arranged at a distal end of the shaft and including opposing first and second jaws, and an articulable wrist that interposes the end effector and the distal end, the wrist including, a linkage mounted to the first and second jaws and defining a slot, a distal wedge arranged at least partially within the linkage, an alignment arm interposing the linkage and the distal wedge and providing an alignment head receivable within the slot, a channel provided on one of the distal wedge or the alignment arm, and a projection provided on the other of the distal wedge or the alignment arm and receivable within the channel. The method further including operating the end effector or the wrist, stabilizing the distal wedge with the projection received within the channel as the end effector or the wrist operate, and reducing backlash in the end effector with the alignment head received within the slot as the end effector or the wrist operate.   

     Each of embodiments A, B, and C may have one or more of the following additional elements in any combination: Element 1: wherein the first jaw provides a first jaw extension and the second jaw provides a second jaw extension, the articulable wrist further including a distal clevis, and first and second pulleys rotatably mounted to the distal clevis at a pivot axis, the first jaw extension being pinned to the first pulley and the second jaw extension being pinned to the second pulley, wherein the alignment arm is rotatably mounted to the first pulley at the pivot axis. Element 2: wherein the distal wedge is positioned between the first and second jaw extensions. Element 3: wherein the distal wedge defines upper and lower arcuate surfaces engageable with upper and lower journals, respectively, provided by the first and second jaws. Element 4: wherein the first and second jaw extensions are pinned to the first and second pulleys, respectively, eccentric to the pivot axis. Element 5: further comprising 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. Element 6: further comprising a knife rod extendable through the central portion of the wrist and terminating at a knife, the knife rod and the knife being translatable through the distal wedge. Element 7: wherein the slot is a first slot, the alignment arm is a first alignment arm, and the alignment head is a first alignment head, the articulable wrist further including a second alignment arm rotatably mounted to the second pulley at the pivot axis and providing a second alignment head translatable within a second slot defined in the linkage, wherein the second slot extends parallel to a longitudinal axis of the end effector. Element 8: further comprising a handle through which the shaft is extendable, the handle being matable with an instrument driver arranged at an end of a robotic arm, and a plurality of drive members extending along the shaft and terminating at the first and second pulleys, wherein the plurality of drive members are antagonistically operable via the handle to open and close the first and second jaws and articulate the end effector in pitch and yaw. Element 9: wherein 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. 
     Element 10: wherein the first jaw provides a first jaw extension and the second jaw provides a second jaw extension, the articulable wrist further including a distal clevis, and first and second pulleys rotatably mounted to the distal clevis at a pivot axis, the first jaw extension being pinned to the first pulley and the second jaw extension being pinned to the second pulley, wherein the alignment arm is rotatably mounted to the first pulley at the pivot axis. Element 11: wherein the distal wedge is positioned between the first and second jaw extensions. Element 12: wherein the distal wedge defines upper and lower arcuate surfaces engageable with upper and lower journals, respectively, provided by the first and second jaws. Element 13: wherein the projection is provided on a first lateral side of the alignment arm and the alignment head is provided on a second lateral side of the alignment arm. Element 14: wherein the channel extends distally and proximally and parallel to a longitudinal axis of the end effector. Element 15: wherein the channel defines a ramped upper surface engageable with a portion of the first jaw. 
     Element 16: wherein the channel extends parallel to a longitudinal axis of the end effector, and wherein stabilizing the distal wedge with the projection received within the channel comprises translating the projection within the channel as the first and second jaws open and close. Element 17: wherein the first jaw provides a first jaw extension, the second jaw provides a second jaw extension, and the articulable wrist further includes a distal clevis and first and second pulleys rotatably mounted to the distal clevis at a pivot axis, the first jaw extension being pinned to the first pulley, the second jaw extension being pinned to the second pulley, and the alignment arm being rotatably mounted to the first pulley at the pivot axis, the method further comprising, actuating the first and second pulleys to open or close the first and second jaws, and preventing the first and second jaws from rotating in pitch or out of alignment with each other with the alignment head received within the slot. 
     By way of non-limiting example, exemplary combinations applicable to A, B, and C include: Element 1 with Element 2; and Element 10 with Element 11. 
     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.