CN116322557A

CN116322557A - Limiting the clamping force and maintaining a minimum opening force of the jaws in the position control mode and controlling the clamping force when transitioning between the position control mode and the force mode

Info

Publication number: CN116322557A
Application number: CN202180066795.4A
Authority: CN
Inventors: E·I·埃尔格塔特赫里纳; A·哈里里
Original assignee: Verb Surgical Inc
Current assignee: Verb Surgical Inc
Priority date: 2020-09-30
Filing date: 2021-08-24
Publication date: 2023-06-23
Also published as: EP4221614A1; KR20230079178A; JP2023544318A

Abstract

Systems and methods are disclosed for limiting a clamping force generated by closing a robot wrist jaw when operating in a positional mode in which the jaw is commanded to a desired jaw angle before the jaw is commanded to generate the clamping force. Systems and methods for maintaining an opening force generated by a robotic wrist jaw operating in a positional mode in which the jaw is commanded to a desired jaw angle prior to commanding the jaw to generate a clamping force are also disclosed. Systems and methods for achieving a smooth transition of gripping force when the wrist-jaw transitions between position and force modes are also disclosed.

Description

Limiting the clamping force and maintaining a minimum opening force of the jaws in the position control mode and controlling the clamping force when transitioning between the position control mode and the force mode

Technical Field

The present technology relates generally to robots and surgical systems, and more particularly to controlling the clamping or opening force of a surgical tool, such as a wrist jaw of a robotic-assisted surgical system.

Background

Minimally Invasive Surgery (MIS) such as laparoscopic surgery uses techniques that aim to reduce tissue damage during surgical procedures. Laparoscopic procedures typically require a plurality of small incisions to be made in the patient (e.g., in the abdomen) through which several surgical tools, such as endoscopes, scalpels, graspers, and needles, are then inserted into the patient. Gas is injected into the abdomen, which inflates the abdomen, providing more space around the tip of the tool, making it easier for the surgeon to see (via the endoscope) and manipulate tissue at the surgical site. MIS may also be performed using a robotic system, wherein a surgical tool is operatively attached to the distal end of the robotic arm, and the control system actuates the arm and its attached tool such that when a User Input Device (UID) is being manipulated by a surgeon in his hand, the arm and its attached tool simulate movement of the UID and tool-specific commands.

The surgical tool may include a robotic wrist supporting a pair of opposing jaws. The wrist and jaw may be moved in multiple degrees of freedom when controlled by commands from a remote operator to perform grasping, cutting, stapling, and other surgical tasks. For example, an actuator in a tool drive arrangement of a robotic arm may drive multi-axis movement (e.g., pitch and yaw) of the wrist jaws to pivot, open, close the jaws, or control the gripping or opening force between the jaws, while moving the wrist to any angular position. The jaws may grasp patient tissue, hold a cutting instrument, and the like. Precise control of the clamping or opening force is critical to prevent damage to tissue or to ensure accurate cutting of the instrument when closing or opening the jaws. Further, the jaws can be operated in a position mode in which the angle between a pair of jaws is commanded to a desired jaw angle and a force mode in which the jaws are commanded to apply a desired clamping force. The smooth transition between the position mode and the force mode minimizes an undesirable abrupt change in clamping force that could result in an unexpected drop of any object being gripped.

Disclosure of Invention

Systems and methods are disclosed for limiting a clamping force generated by closing a robot wrist jaw when operating in a position control mode in which the jaw is commanded to a desired jaw angle before the jaw is commanded to generate the clamping force. In the position control mode, or simply position mode, it is desirable that the jaw angle is higher than a threshold value, which corresponds to the angle at which two jaws are in contact with an object between the jaws at exactly the same time, or if there is no object to grasp, the angle at which the jaws start touching each other. When the desired jaw angle is below the threshold, the wrist jaw is operated in a force control mode or force mode for short, and the desired jaw angle is converted to the desired gripping force. The disclosed systems and methods limit the maximum amount of clamping force when the jaws are closing in the position mode to prevent damage to tissue that may be grasped by the jaws. The clamping force may be estimated or measured. The feedback loop can analyze the desired jaw angle and the measured clamping force to determine if the jaws are closing in the position mode and if the measured clamping force exceeds a pre-specified maximum clamping force threshold. If so, the feedback loop may calculate a clamp force error to limit the measured clamp force to a pre-specified maximum clamp force threshold.

In another aspect, a system and method for achieving a minimum jaw opening force by a wrist jaw when operating in a positional mode is disclosed. Maintaining a minimum jaw opening force when the jaws are opened in the positional mode helps the jaws overcome resistance that may prevent the jaws from opening to a desired jaw angle. The opening force, which represents the jaw opening force and jaw angle, may be measured or estimated. The feedback loop may analyze the desired jaw angle, the estimated jaw angle, and the measured jaw opening force to determine whether the jaw is open in the positional mode, and whether the measured jaw opening force is below a pre-specified minimum opening force threshold. If so, the feedback loop can calculate a jaw opening force error to maintain the jaw opening force above a pre-specified minimum opening force threshold.

In another aspect, a system and method for achieving a smooth transition in gripping force when a wrist-jaw transitions between a positional mode and a force mode is disclosed. The smooth transition from position mode to force mode and vice versa minimizes unwanted abrupt changes in gripping force that could result in the wrist jaws accidentally dropping a gripped object as the jaws pass through a discontinuity between the two modes. In one embodiment, to transition from the positional mode to the force mode, an anti-shake strategy may be used to ensure that the desired jaw angle is less than a threshold between the positional mode and the force mode for a pre-specified minimum duration before the wrist jaw transitions to the force mode.

In one embodiment, the system and method can determine a desired clamping force based on a desired jaw angle and can measure or estimate the clamping force. The feedback loop may analyze the desired jaw angle, the desired clamping force, and the measured clamping force to determine whether the jaw is transitioning from the positional mode to the force mode, whether an error between the measured clamping force and the desired clamping force is greater than a pre-specified maximum force error, and whether the desired clamping force is increasing. If so, the feedback loop can set the desired clamping force to the currently measured clamping force minus a pre-specified margin when the jaws transition from the position mode to the force mode.

In one embodiment, the feedback loop may analyze the desired jaw angle, the desired clamping force determined from the desired jaw angle, and the measured clamping force to determine whether the jaw is transitioning from the force mode to the position mode, whether the desired clamping force is less than a minimum clamping force value, whether the desired clamping force is decreasing, and whether an absolute value of an error between the measured clamping force and the minimum clamping force is less than a pre-specified maximum force error. If so, the feedback loop can set the desired clamping force to a minimum clamping force value when the jaws transition from the force mode to the position mode.

A method for controlling a jaw clamping force generated by a jaw of a clamping tool is disclosed. The method may include determining whether the jaws are closing in the position mode based on a desired jaw angle between the jaws. The position mode is characterized by applying a position command to drive the jaws to a desired position having a desired jaw angle. The method further includes determining if the measured clamping force exceeds a maximum clamping force threshold if the jaws are closing in the position mode. The method further includes generating a clamp force error to be combined with the position command to limit the measured clamp force to the maximum clamp force threshold if the measured clamp force exceeds the maximum clamp force threshold.

Another method for controlling a jaw opening force generated by a jaw of a gripping tool is disclosed. The method may include determining whether the jaws are in a position mode based on a desired jaw angle between the jaws. The position mode is characterized by applying a position command to drive the jaws to a desired position having a desired jaw angle. The method further includes determining if a jaw angle error between the desired jaw angle and the measured jaw angle is greater than an error threshold if the jaw is in the position mode. The method further includes determining whether the measured opening force is less than a minimum opening force threshold if the jaw angle error is greater than an error threshold. The method further includes generating an opening force error to be combined with the position command to maintain the measured opening force above the minimum opening force threshold if the measured opening force is less than the minimum opening force threshold.

A further method for controlling a clamping force generated by a jaw of a clamping tool is disclosed. The method may include determining that the jaws are transitioning between the position mode and the force mode based on a change in a desired jaw angle between the jaws. During the position mode, the jaws are driven at a commanded jaw angle, which may be a desired jaw angle. During the force mode, the jaws are driven with a commanded clamping force determined based on the desired jaw angle having a negative value. The method further includes determining whether to adjust the commanded clamping force during a transition between the position mode and the force mode based on the commanded clamping force and the measured clamping force. If so, the method further includes adjusting the commanded clamping force to reduce a change in the measured clamping force, which is otherwise determined based on the desired jaw angle during the transition.

Drawings

For a more complete understanding of the present invention, the accompanying drawings are provided along with the following description of various aspects and embodiments of the subject technology. The drawings and embodiments are illustrative of the invention and are not intended to limit the scope of the invention. It should be understood that one of ordinary skill in the art could modify the drawings to create drawings of other embodiments that would still fall within the scope of the present invention.

Fig. 1 is a pictorial view of an exemplary surgical robotic system 1 in a surgical field, in accordance with aspects of the subject technology.

FIG. 2 is a schematic diagram illustrating one exemplary design of a robotic arm, tool drive device, and cannula loaded with a robotic surgical tool in accordance with aspects of the subject technology.

Fig. 3A and 3B are schematic diagrams illustrating exemplary tool drives with and without loaded tools, respectively, in accordance with aspects of the subject technology.

Fig. 4A and 4B are end effectors illustrating an example grasper having a robot wrist, a pair of opposing jaws, and a pulley and cable system for coupling the robot wrist and the pair of jaws to an actuator of a tool drive in accordance with aspects of the subject technology.

FIG. 5 is a block diagram of an exemplary control system for controlling the position and clamping force of an end effector of a robotic surgical tool in accordance with aspects of the subject technology.

Fig. 6A is a time graph showing a commanded jaw angle, a measured jaw angle, a commanded clamping force, and a measured clamping force of a wrist jaw when the measured clamping force is unrestricted when the jaws are closed in a position mode.

Fig. 6B is a time graph illustrating a commanded jaw angle, a measured jaw angle, a commanded clamping force, and a measured clamping force of a wrist jaw when a control system limits the measured clamping force to a pre-specified maximum threshold during closing of the jaws in a jaw position mode, in accordance with aspects of the subject technology.

Fig. 7 is a flow chart illustrating a method for feedback control of a surgical robotic system to limit the clamping force of a wrist jaw to a pre-specified maximum threshold during closing of the jaw in a position mode by analyzing a desired jaw angle and a measured clamping force in accordance with aspects of the subject technology.

Fig. 8A is a time graph showing a commanded jaw angle, a measured jaw angle, a commanded gripping force, and a measured opening force of a wrist jaw when the measured opening force is not maintained above a minimum level while the jaws are opening in a position mode.

Fig. 8B is a time graph illustrating a commanded jaw angle, a measured jaw angle, a commanded clamping force, and a measured opening force of a wrist jaw when a control system maintains a measured opening force above a pre-specified minimum opening force threshold during opening of the jaw in a position mode, in accordance with aspects of the subject technology.

Fig. 9 is a flow chart illustrating a method for feedback control of a surgical robotic system to maintain an opening force of a wrist jaw above a pre-specified minimum opening force threshold during opening of the jaw in a jaw position mode by analyzing a desired jaw angle, an estimated jaw angle, and a measured opening force, in accordance with aspects of the subject technology.

FIG. 10 is a block diagram of an exemplary control system for controlling the position and clamping force of an end effector of a robotic surgical tool when the end effector is in a position mode or force mode, or when the end effector transitions between a position mode and force mode, in accordance with aspects of the subject technology.

Fig. 11A is a time graph showing a commanded jaw angle, a measured jaw angle, a commanded clamping force, a measured clamping force, and an activity of a clamping force controller of a wrist jaw when the jaw angle is set near a threshold between a position mode and a force mode without an anti-shake algorithm.

Fig. 11B is a time graph illustrating a commanded jaw angle, a measured jaw angle, a commanded clamping force, a measured clamping force, and an activity of a clamping force controller of a wrist jaw when the control system employs an anti-shake algorithm when setting the jaw angle near a threshold between a position mode and a force mode, in accordance with aspects of the subject technology.

Fig. 12A is a time graph showing a commanded jaw angle, a measured jaw angle, a commanded clamping force, and a measured clamping force of a wrist jaw when the jaw transitions from a position mode to a force mode and back to the position mode without restriction.

Fig. 12B is a time graph illustrating a commanded jaw angle, a measured jaw angle, a commanded clamping force, and a measured clamping force of a wrist jaw as the control system constrains a change in clamping force as the jaw transitions between position and force modes in accordance with aspects of the subject technology.

Fig. 13 is a flow chart illustrating a method for feedback control of a surgical robotic system for employing an anti-shake algorithm when setting a desired jaw angle of a wrist jaw near a threshold between a position mode and a force mode, or for limiting a change in measured clamping force when the jaw transitions between the position mode and the force mode, in accordance with aspects of the subject technology.

FIG. 14 is a block diagram illustrating exemplary hardware components of a surgical robotic system in accordance with aspects of the subject technology.

Detailed Description

Examples of various aspects and variations of the subject technology are described herein and illustrated in the accompanying drawings. The following description is not intended to limit the invention to those embodiments, but is intended to enable any person skilled in the art to make and use the invention.

Feedback control systems and methods for controlling the clamping or opening force of an end effector (such as a wrist jaw) of a surgical robotic arm are disclosed. The wrist jaw may be coupled to an actuator of the tool drive means by a cable for effecting multi-axis movement of the wrist jaw. The feedback control system may command the pitch angle, yaw angle, and jaw angle between the wrist jaws. When the commanded jaw angle is above a threshold, also referred to as a braking threshold (threshold for detent), the wrist jaw can be operated in a position mode to move the wrist jaw to a commanded position and orientation. The commanded jaw angle may also be referred to as a desired jaw angle. When the commanded jaw angle is below the braking threshold, the wrist jaw may be operated in a force mode according to the position and orientation of the position mode, and a desired clamping force is generated by the clamping force controller based on the commanded jaw angle. In one embodiment, the feedback control system can limit the maximum clamping force by analyzing the desired jaw angle and measuring or estimating the actual applied clamping force to determine if the measured clamping force exceeds a pre-specified maximum clamping force threshold when the jaws are closing in the position mode. If so, the feedback control system may calculate a clamp force error to adjust the clamp force such that the measured clamp force is limited to a pre-specified maximum clamp force threshold.

In one embodiment, the feedback control system can maintain a minimum jaw opening force when the jaws are opening in the position mode. The feedback control system can measure or estimate the jaw angle for the actual application. The feedback control system can also measure or estimate the clamping or opening force of the jaws that are actually applied. By analyzing the desired jaw angle, the measured jaw angle, and the measured jaw opening force, the feedback control system can determine whether the jaw is in the position mode, whether the difference between the desired jaw angle and the estimated jaw angle is greater than a threshold, and whether the measured jaw opening force is less than a pre-specified minimum opening force threshold. If so, the feedback control system can calculate an opening force error to adjust the clamping or opening force to maintain the measured jaw opening force above a pre-specified minimum opening force threshold.

In one embodiment, the feedback control system may use an anti-shake algorithm to prevent the wrist-jaw from oscillating between the position mode and the force mode when the jaw angle is set near braking. The feedback control system may determine whether the desired angle is less than the braking threshold for a pre-specified duration. If so, the feedback control system can switch the wrist-jaw from the position mode to the force mode. In one embodiment, the anti-shake algorithm may be unilateral, such that the wrist jaw may transition back to the positional mode whenever the desired jaw angle is greater than or equal to the threshold.

In one embodiment, the feedback control system may minimize undesirable abrupt changes in clamping force when transitioning between position and force modes. The clamping force controller can calculate a current command for the desired clamping force based on the desired jaw angle. The feedback control system may measure or estimate the actual applied clamping force. The feedback control system can analyze the desired jaw angle, the desired clamping force, and the measured clamping force to determine whether the jaw is transitioning from the position mode to the force mode, and whether an error between the measured clamping force and the desired clamping force is greater than a pre-specified maximum force error, and whether the desired clamping force is increasing. If so, the feedback control system may set the clamping force to the measured clamping force minus a pre-specified margin when transitioning from the position mode to the force mode.

In one embodiment, the feedback control system can analyze the desired jaw angle, the desired clamping force, and the measured clamping force to determine whether the jaw is transitioning from the force mode to the position mode, whether the desired clamping force is less than a pre-specified minimum clamping force value, whether the desired clamping force is decreasing, and whether an absolute value of an error between the measured clamping force and the minimum clamping force is less than a pre-specified maximum force error. If so, the feedback control system may set the clamping force to a pre-specified minimum clamping force value when transitioning from the force mode to the position mode. In one embodiment, the pre-specified minimum clamping force value may be set to 3N.

Fig. 1 is a pictorial view of an exemplary surgical robotic system 1 in a surgical field, in accordance with aspects of the subject technology. The robotic system 1 includes a user console 2, a control tower 3, and one or more surgical robotic arms 4 at a surgical robotic platform 5 (e.g., table, bed, etc.). The arms 4 may be mounted to a table or bed on which the patient is lying, as shown in the example of fig. 1, or they may be mounted to a trolley separate from the table or bed. The system 1 may incorporate any number of devices, tools or accessories for performing surgery on the patient 6. For example, the system 1 may include one or more surgical tools 7 for performing a surgical procedure. The surgical tool 7 may be an end effector attached to the distal end of the surgical arm 4 for performing a surgical procedure.

Each surgical tool 7 may be manually manipulated during surgery, robotically manipulated, or both. For example, the surgical tool 7 may be a tool for accessing, viewing or manipulating the internal anatomy of the patient 6. In one aspect, the surgical tool 7 is a grasper, such as a wrist jaw, that grasps patient tissue. The surgical tool 7 may be configured to be controlled manually by a bedside operator 8, controlled robotically via actuation movements of a surgical robotic arm 4 to which it is attached, or both. The robotic arm 4 is shown as being table mounted, but in other configurations the arm 4 may be mounted to a cart, ceiling or side wall, or to another suitable structural support.

A remote operator 9, such as a surgeon or other human operator, may use the user console 2 to remotely manipulate the arm 4 and its attached surgical tool 7, for example referred to herein as teleoperation. The user console 2 may be located in the same operating room as the rest of the system 1, as shown in fig. 1. However, in other environments, the user console 2 may be located in a neighboring or nearby room, or it may be located at a remote location, for example, in a different building, city, or country. User console 2 may include a seat 10, a foot control 13, one or more handheld User Input Devices (UIDs) 14, and at least one user display 15 configured to display, for example, a view of a surgical site within patient 6. In the exemplary user console 2, a remote operator 9 sits in a seat 10 and views a user display 15 while manipulating foot control 13 and handheld UID 14 to remotely control arm 4 and surgical tool 7 mounted on the distal end of arm 4.

In some variations, bedside operator 8 may operate system 1 in a "bedside" mode, where bedside operator 8 (user) is located on one side of patient 6 and simultaneously manipulates a robot-driven tool (end effector attached to arm 4), where handheld UID 14 is held with one hand and a manual laparoscopic tool is held with the other hand. For example, the left hand of the bedside operator may manipulate the handheld UID to control the robotic driven tool, while the right hand of the bedside operator may manipulate the manual laparoscopic tool. In this particular variation of the system 1, the bedside operator 8 may perform both robot-assisted minimally invasive surgery and manual laparoscopic surgery on the patient 6.

During an exemplary procedure (surgery), patient 6 is surgically prepared and covered with a drape in a sterile manner to effect anesthesia. Initial access to the surgical site (to facilitate access to the surgical site) may be performed manually while the arms of the robotic system 1 are in the stowed configuration or the retracted configuration. Once the access is completed, an initial positioning or preparation of the robotic system 1 including its arm 4 may be performed. The surgical procedure then continues with the remote operator 9 at the user console 2 manipulating the various end effectors and possibly imaging systems using the foot control 13 and UID 14 to perform the surgical procedure. Manual assistance may also be provided at the operating bed or table by bedside personnel (e.g., bedside operator 8) wearing a sterile surgical gown, who may perform tasks on one or more of the robotic arms 4, such as retracting tissue, performing manual repositioning, and tool changing. Non-sterile personnel may also be present to assist the remote operator 9 at the user console 2. When the procedure or surgical operation is completed, the system 1 and user console 2 may be configured or set to a state to facilitate completion of the post-operative procedure, such as cleaning or sterilization and entry or printing of healthcare records via the user console 2.

In one embodiment, remote operator 9 holds and moves UID 14 to provide input commands to move robotic arm actuator 17 in robotic system 1. UID 14 may be communicatively coupled to the rest of robotic system 1, e.g., via console computer system 16. UID 14 may generate spatial state signals corresponding to movement of UID 14, such as a position and orientation of the handheld housing of the UID, and the spatial state signals may be input signals to control movement of robotic arm actuator 17. The robot system 1 may use control signals derived from the spatial state signals to control proportional movement of the actuators 17. In one embodiment, a console processor of the console computer system 16 receives the spatial state signal and generates a corresponding control signal. Based on these control signals that control how actuators 17 are energized to move segments or links of arm 4, movement of the corresponding surgical tool attached to the arm may simulate movement of UID 14. Similarly, interaction between remote operator 9 and UID 14 may generate, for example, a clamping control signal that closes the jaws of the grasper of surgical tool 7 and clamps tissue of patient 6.

Surgical robotic system 1 may include several UIDs 14, with respective control signals generated for each UID controlling an actuator of a respective arm 4 and a surgical tool (end effector). For example, remote operator 9 may move first UID 14 to control the movement of actuator 17 located in the left robotic arm, where the actuator responds by moving a linkage, gear, etc. in arm 4. Similarly, movement of second UID 14 by remote operator 9 controls movement of another actuator 17, which in turn moves other links, gears, etc. of robotic system 1. The robotic system 1 may comprise a right arm 4 fixed to a bed or table on the right side of the patient, and a left arm 4 located on the left side of the patient. The actuator 17 may comprise one or more motors controlled such that they drive the rotation of the joint of the arm 4 to change the orientation of the endoscope or grasper of the surgical tool 7 attached to the arm, for example, relative to the patient. The movement of several actuators 17 in the same arm 4 may be controlled by a spatial state signal generated from a particular UID 14. UID 14 may also control movement of the corresponding surgical tool gripper. For example, each UID 14 may generate a respective grasping signal to control movement of an actuator (e.g., a linear actuator) that opens or closes a jaw of the grasper at the distal end of surgical tool 7 to grasp tissue within patient 6.

In some aspects, communication between the platform 5 and the user console 2 may be through a control tower 3 that may convert user commands received from the user console 2 (and more specifically from the console computer system 16) into robotic control commands that are transmitted to the arm 4 on the robotic platform 5. The control tower 3 may also transmit status and feedback from the platform 5 back to the user console 2. The communication connections between the robotic platform 5, the user console 2 and the control tower 3 may use any suitable data communication protocol of a variety of data communication protocols via wired and/or wireless links. Any wired connection may optionally be built into the floor and/or wall or ceiling of the operating room. The robotic system 1 may provide video output to one or more displays, including displays in an operating room and remote displays accessible via the internet or other network. The video output (video feed) may also be encrypted to ensure privacy, and all or part of the video output may be saved to a server or electronic healthcare recording system.

FIG. 2 is a schematic diagram illustrating one exemplary design of a robotic arm, tool drive device, and cannula loaded with a robotic surgical tool in accordance with aspects of the subject technology. As shown in fig. 2, the example robotic arm 112 may include a plurality of links (e.g., links 202) and a plurality of actuated joint modules (e.g., joints 204) for actuating the plurality of links relative to one another. The joint module may include various joint types, such as pitch joints or roll joints, that may substantially constrain movement of adjacent links about certain axes relative to other axes. Also shown in the exemplary design of fig. 2 is a tool drive 210 attached to the distal end of the robotic arm 112. Tool drive arrangement 210 can include a cannula 214 coupled to an end thereof to receive and guide a surgical instrument 220 (e.g., an endoscope, stapler, etc.). The surgical instrument (or "tool") 220 includes an end effector 222 at a distal end of the tool. The plurality of joint modules of the robotic arm 112 may be actuated to position and orient the tool drive 210 that actuates the end effector 222 to perform robotic surgery.

Fig. 3A and 3B are schematic diagrams illustrating exemplary tool drives with and without loaded tools, respectively, in accordance with aspects of the subject technology. As shown in fig. 3A and 3B, in one variation, the tool drive device 210 may include an elongated base (or "tray") 310 having a longitudinal rail 312 and a tool rack 320 in sliding engagement with the longitudinal rail 312. The tray 310 may be configured to be coupled to a distal end of the robotic arm such that articulation of the robotic arm positions and/or orients the tool drive 210 in place. In addition, the tool holder 320 may be configured to receive a tool base 352 of the tool 220, which may further include a tool shaft 354 extending from the tool base 352 and through the cannula 214, with the end effector 222 (not shown) disposed at a distal end.

Additionally, the tool rack 320 may actuate a set of joint movements of the end effector, such as by a cable system or wire that is manipulated and controlled by an actuation drive (the terms "cable" and "wire" are used interchangeably throughout this application). The tool holder 320 may comprise different configurations with an actuation drive. For example, the rotary shaft drive may include a motor having a hollow rotor and a planetary gear set at least partially disposed within the hollow rotor. The plurality of rotary shaft driving means may be arranged in any suitable manner. For example, the tool holder 320 may include six rotary drives 322A-322F arranged in two rows extending longitudinally along the base, slightly staggered to reduce the width of the holder and increase the compact nature of the tool drive. As best shown in fig. 3B, the rotary drives 322A, 322B, and 322C may be generally arranged in a first row, whereas the rotary drives 322D, 322E, and 322F may be generally arranged in a second row slightly longitudinally offset from the first row.

Fig. 4A and 4B are end effectors illustrating an example grasper having a robot wrist, a pair of opposing jaws, and a pulley and cable system for coupling the robot wrist and the pair of jaws to an actuator of a tool drive in accordance with aspects of the subject technology. It should be noted that while the following tool model and controller designs are described with reference to an exemplary surgical robotic gripper, the proposed control system for position and clamping force control may be adapted to include any tool coupled to an end effector of a tool shaft via a robotic wrist that allows multi-axis movement (e.g., pitch and yaw) of the end effector. Similar tools include, but are not limited to, graspers, holders, forceps, needle drivers, retractors, and cautery instruments.

As shown in fig. 4A, a pair of opposing jaws 401A and 401B are movably coupled to a first yoke 402 of the robot wrist along a first axis 410 via an extension shaft 412. The first yoke 402 may be movably coupled to the second yoke 403 of the robot wrist along a second axis 420 via a second extension shaft 422. A pair of jaws 401A and 401B may each be coupled or integrally formed with pulleys 415A and 415B, respectively, via extension shaft 412 such that both jaws may rotate about axis 410.

Pulleys

425A, 425B, 425C, and 425D are coupled to extension shaft 422 and rotate about axis 420.

Pulleys

425A, 425B, 425C and 425D are arranged as a first set of pulleys 425B and 425C on one side of the yoke 402 and a second set of pulleys 425A and 425D on the other side of the yoke 402. Pulleys 425A and 425C are outer pulleys and pulleys 425B and 425D are inner pulleys. Similarly, a third set of

pulleys

435A, 435B, 435C, and 435D are coupled to the third extension shaft 432 and rotate about an axis 430 parallel to the axis 420.

Gripper 220 may be actuated to move one or both of jaws 401A and 401B about axis 410 in various ways. For example, jaws 401A and 401B can open and close relative to each other. Jaws 401A and 401B can also be actuated to rotate together as a pair to provide a deflection motion of gripper 220. Further, first yoke 402, pulleys 415A and 415B, and jaws 401A and 401B can be rotated about axis 420 to provide pitch motion of gripper 220. Movement of the robot wrist and/or jaws of the tool may be actuated by controlling four independent cables 405A-405D. As shown in fig. 4A, cable 405A may start (or terminate) from one side of pulley 415A and run along pulleys 425A and 435A, and cable 405B is configured to terminate at the other side of pulley 415A and run through pulleys 425B and 435B. Similarly, another pair of cables 405C and 405D can be coupled to jaw 401B. For example, cable 405C extends from one side of pulley 415B to pulleys 425C and 435C; and cable 405D is routed through pulleys 425D and 435D and terminates on the other side of pulley 415B. The third set of

pulleys

435A, 435B, 435C and 435D are arranged in a manner such that the retaining cables 405A-405D are attached to the second set of pulleys 425A-425D and prevent the cables from slipping or sliding relative to the pulleys 425A-425D.

As shown in fig. 4A and 4B, gripper 220 may be actuated to move jaws 401A and 401B in various ways, such as grasping (e.g., jaws independently rotate about axis 410), deflecting (e.g., jaws rotate together about axis 410), and pitching (e.g., jaws rotate about axis 420) by imparting motion to one or more of

pulleys

425A, 415B, 415A, 425B, 425C, and 425D to thereby impart motion to first yoke 402 and/or one or both of jaws 401A and 401B. The cables 405A-405D can be grouped into two pairs, i.e., when one cable of the pairs is actuated or tensioned and the other cable is released, the jaws will rotate in one direction. And when only the other cable is tensioned, the jaws will rotate in the opposite direction.

For example, cables 405A and 405B are a first counter pair for moving jaw 401A, and cables 405C and 405D are a second counter pair for controlling jaw 401B. When cable 405A is tensioned (e.g., by rotating at least one of drives 322a-322 f) and cable 405B is released, jaw 401A closes (moves toward opposing jaw 401B). On the other hand, when cable 405B is tensioned and cable 405A is released, jaw 401A opens (moves away from opposing jaw 401B). Similarly, when tensioned, cable 405C closes jaw 401B (moves toward opposing jaw 401A) and cable 405D opens jaw 401B (moves away from opposing jaw 401A) while the other cable is released. As another example, the clamping force between jaws 401A and 401B can be achieved by continuing to

tension cables

405A and 405C (while loosening cables 405B and 405D) after the jaws are closed (in contact with each other).

In the case where the two cables of the opposing pair are simultaneously tensioned and the two cables of the other pair are released, the pulley 415A or the pulley 415B does not rotate. Instead, first yoke 402, along with jaws 401A and 401B, is imparted to pitch about axis 420 by pulleys 415A and 415B. For example, when a pair of cables 405A and 405B are simultaneously tensioned and a pair of cables 405C and 405D are released, the jaws (along with yoke 402) pitch out of the plane of the paper. However, when both cables 405C and 405D are simultaneously tensioned and the pair 405A and 405B remain loose, the jaws pitch into the plane of the paper.

Fig. 4B is a schematic diagram illustrating an exemplary angular definition of various motions for gripper 220 in accordance with aspects of the subject technology. The

angular reference axes

410 and 420 are defined as the axis 452 of the first yoke 402 and the axis 453 of the second yoke 403. For example, as shown in fig. 4B, an angle (θ ₁ ) The angle of rotation of yoke 402 about axis 420 may be represented and may also be defined as the pitch angle (θ _Pitching ) (whereas in fig. 4A, the axis 452 of yoke 402 is superimposed on the axis 453 of yoke 403, because the jaws rest in the reference position, i.e., without pitching motion). In addition, the angle (θ ₂ ) Sum (theta) ₃ ) The angle between each of jaws 401A and 401B, respectively, and axis 452 of yoke 402 (as the origin). To distinguish the side of the axis 452, the angle (θ ₂ ) Sum (theta) ₃ ) Different symbols may be taken. For example, as shown in fig. 4B, the angle (θ ₂ ) Is negative and angle (theta ₃ ) Is positive.

To perform control tasks, it is often beneficial to define a consistent coordinate system for the joint angle. For example, we can further adjust the jaw angle (θ _Jaw ) Defined as being between two jaws 401A and 401BAngle, and deflect the angle (θ _{Deflection of} ) Defined as the angle between the axis 452 and a line bisecting the jaw angle. As described above, the pitch angle (θ _Pitching ) May be defined as the angle (θ) between axis 452 and axis 453 ₁ ). Thus:

described below are methods and systems for controlling the angular position and clamping force of a distal end effector of a robotic surgical instrument. The end effector may include a robotic wrist and a pair of opposing members (e.g., jaws or claws), each movable between an open position and a closed position, actuated by two opposing wires. The total of four wires may each be driven by an independent actuator or motor, as shown in fig. 3 and 4. The control system may include a feedback loop that involves position and velocity feedback from the actuators and force feedback measured on the four wires to achieve the desired position and clamping force. In some implementations, the actuator controller may be operable to position the feed-forward current mode. For example, a position controller in a position mode may drive the distal end effector to a desired angular position in space based on position feedback, while in a force mode, the clamp force controller provides additional feed-forward current based on clamp forces measured by load cells on four wires to achieve a desired clamp force between opposing members.

FIG. 5 is a block diagram illustrating a high-level control system for controlling a surgical tool in accordance with aspects of the subject technology. The control system includes an input 560, a controller 562, a device 564, an output 568, and a sensor and estimator 566 in a feedback path between the output 568 and the controller 562. The apparatus 564 may include tool actuators and end effectors (e.g., the rotary drives 322A-322F of fig. 3B and the cables 405A-405D of the wrist jaws of fig. 4A; see also the actuator unit 510 and cable and wrist links 512 of fig. 10). The controller 562 may include one or more processors configured by software instructions stored on a memory to count in response to input 560Movement of computing device 564, which may indicate a desired movement of an end effector of a surgical tool, such as a desired θ of the wrist jaw of fig. 4B _Pitching Desired theta _{Deflection of} And desired theta _Jaw . The commands generated by controller 562 can drive the tool actuator to facilitate desired movement of the end effector. In one embodiment, it is desired that θ _Pitching 、θ _{Deflection of} And theta _Jaw May be generated by UID 14 under control of remote operator 9 of fig. 1. Output 568 (such as position, speed, cable tension, and end effector clamping or opening force) can be measured or estimated directly by sensor and estimator 566 and fed back to controller 562 for closed loop control.

In one embodiment, when the desired jaw angle θ of the wrist jaw _Jaw Greater than or equal to a threshold, also referred to as command θ _Jaw Desired theta of (2) _Jaw Can be considered as a position control command in position mode. The threshold is used to determine braking and may correspond to the angle at which two jaws are just simultaneously in contact with an object therebetween. In the case where there is no object to grasp, the threshold is zero degrees when the jaws start touching each other. In the positional mode, the controller 562 may expect θ _Jaw Desired θ _Pitching And desired theta _{Deflection of} To a corresponding actuator position command to drive the wrist-jaw to a desired position and orientation. When it is desired to theta _Jaw Below the threshold, the wrist-jaw operates in a force control mode or simply force mode, and the desired jaw angle is converted to the desired gripping force command. In addition to the position command, the controller 562 may also generate a current command to achieve the desired clamping force.

In one embodiment, the controller 562 can limit the maximum amount of clamping force when the jaws are closing in the position mode to prevent damage to tissue that can be grasped by the jaws. The clamping force of the jaws may be estimated or measured by the sensor and estimator 566. Controller 562 can analyze the desired θ _Jaw And measuring the clamping force to determine whether the jaws are closing in the positional mode and whether the measured clamping force exceeds a pre-specified maximumA clamping force threshold. If so, the controller 562 can calculate a clamp force error to limit the measured clamp force to a pre-specified maximum clamp force threshold value. For example, to determine whether the jaws are closing in the position mode, the controller 562 can first verify that the desired θ _Jaw Greater than or equal to the braking threshold and thus last for more than a pre-specified duration in the position mode. Controller 562 may employ anti-shake techniques to verify the desired θ _Jaw Has been reduced for a pre-specified length of time. In one embodiment, if θ is desired _Jaw Sampled at a periodic frequency, controller 562 may verify that θ is desired _Jaw Has been reduced by a pre-specified number of samples.

Controller 562 may also employ anti-shake techniques in order to determine whether the measured clamping force exceeds a pre-specified maximum clamping force threshold. In one embodiment, the feedback control loop of the control system of fig. 5 may operate at a loop cycle time. The clamp force counter may increment a count for each control loop cycle during which the measured clamp force is less than the maximum clamp force threshold minus the margin. In one embodiment, the clamp force counter may stop incrementing after it reaches a maximum count. The clamp force counter may be reset when the measured clamp force is greater than a maximum clamp force threshold. When the measured clamp force is greater than the maximum clamp force minus a margin anywhere within the window, the anti-shake technique may declare that the measured clamp force exceeds the maximum clamp force threshold for an entire window equal to the number of loop cycles of the clamp force counter.

As an example, assume that the measured clamping force is initially below the maximum clamping force threshold minus the margin, and the clamping force counter is incrementing. The clamp force counter may be reset when the measured clamp force increases beyond a maximum clamp force threshold. The feedback control loop of the controller 562 can attempt to change the actuator position command to drive the wrist jaw to limit the measured clamping force to the maximum clamping force threshold. However, even if the measured clamping force drops below the maximum clamping force threshold but remains above the maximum clamping force threshold minus the margin, the feedback control loop may still consider the measured clamping force to be greater than the maximum clamping force threshold in order to limit the maximum measured clamping force. It is assumed that the measured clamping force drops below the maximum clamping force threshold minus the margin for only a few loop cycles, but then increases again above this level. The clamp force counter may be incremented to the number of loop cycles where the measured clamp force is briefly below the maximum clamp force threshold minus the margin. As long as the measured clamping force remains above the maximum clamping force threshold minus a margin (e.g., the number of loop cycles where the measured clamping force briefly drops below the maximum clamping force threshold minus the margin) within a window spanning a number of loop cycles equal to the clamping force counter, the feedback control loop may still consider the measured clamping force to be greater than the maximum clamping force threshold for the entire duration of the window in order to limit the maximum measured clamping force.

When the controller 562 determines that the jaws are closing in the position mode and the measured clamping force exceeds a maximum clamping force threshold, the controller can limit the measured clamping force to the maximum clamping force threshold. In one embodiment, the controller 562 can calculate a clamp force error as the difference between the maximum clamp force threshold value and the measured clamp force. A zero steady state controller, such as a proportional Plus Integral (PI) force controller, may be deployed to receive the clamp force error to maintain or limit the measured clamp force to a maximum clamp force threshold. The output of the PI force controller may be combined with the output of an inverse kinematics matrix that operates on errors in the desired position and orientation of the wrist jaws to generate compensated actuator position commands. The compensated actuator position command is added to the existing actuator position command to drive the wrist jaws to limit the maximum amount of clamping force when the jaws are closing at the desired position and orientation in the position mode.

FIG. 6A is a graph showing the wrist-jaw command θ when the measured gripping force 609 is unrestricted when the jaws are closed in the jaw-in-position mode _Jaw 603. Measured θ _Jaw 605. When the clamping force 607 and the measured clamping force 609 are commandedGraph of the graph. Threshold θ between position mode and force mode _Jaw Is set to zero so that when the command theta _Jaw 603 greater than or equal to zero degrees, the wrist jaw operates in the positional mode. When command theta _Jaw 603 is less than zero degrees, the wrist jaw operates in a force mode.

Figure 6A shows the wrist jaw operating in the position mode from 20 seconds to 35 seconds and again from 44 seconds to 47 seconds. Measured θ _Jaw 605 remains within a relatively narrow range even when command θ _Jaw 603, or when changed in position mode or in force mode, presumably because the jaws are gripping an object. During the positional mode, the commanded gripping force 607, which is the desired gripping force, may be set to a default value of zero N because the wrist jaws are not operating in the force mode. However, the measured clamping force 609 may be much greater. For example, from 26 seconds to 28 seconds and from 31 seconds to 35 seconds, the measured clamping force 609 exceeds 10N and may be as high as 15N when the jaws are closed or held in the closed position in the position mode, as the measured clamping force is not limited. In force mode (e.g., 35 seconds-44 seconds and after 47 seconds), the clamp force controller may set the commanded clamp force 607 to the commanded θ _Jaw 603, and the feedback control loop may maintain the measured clamping force 609 the same as the commanded clamping force 607.

FIG. 6B is a graph illustrating a wrist-jaw command θ when the control system limits the measured clamping force to a pre-specified maximum threshold during jaw-in-position mode closure 617 in accordance with aspects of the subject technology _Jaw 613. Measured θ _Jaw 615. A time profile of commanded clamp force 617 and measured clamp force 619. The maximum clamping force threshold is set to 8.5N.

In FIG. 6B, command θ when the measured clamping force is unrestricted _Jaw 613 and measured theta _Jaw 615 and command θ of fig. 6A _Jaw 603 and measured θ _Jaw 605 are identical. During position mode, the commanded clamping force 617 is again set by the clamping force controller to a default value of zero N. However, when the jaws are closingWhen closed or held in the closed position (e.g., 27 seconds-30 seconds, 32 seconds-36 seconds, and 41 seconds-45 seconds), the measured clamp force 619 is limited by the clamp force controller to a maximum clamp force threshold of 8.5N during the position mode. In addition, the limitation of the maximum clamping force in the position mode has no influence on the force mode. Thus, in the force mode, the measured clamp force 619 may be allowed to exceed the maximum clamp force threshold of 8.5N by following the commanded clamp force 617.

Fig. 7 is a flow chart illustrating a method 700 for feedback control of a surgical robotic system that limits the clamping force of a wrist jaw to a pre-specified maximum threshold during closing of the jaw in a jaw position mode by analyzing a desired jaw angle and a measured clamping force in accordance with aspects of the subject technology. Method 700 may be implemented by controller 562 of the control system of FIG. 5, receiving a desired θ from user input _Jaw And receives the measured clamping force from the sensor and estimator 566 to generate actuator position commands for driving the wrist jaws.

In block 701, the method 700 determines whether the wrist-jaw is in position mode. In one embodiment, block 701 may determine the desired θ _Jaw Whether or not it is greater than or equal to a threshold value theta between the position mode and the force mode _Jaw For more than a pre-specified period of time to confirm that the wrist-jaw is in position mode. In one embodiment, the threshold θ _Jaw May be set to zero. If the wrist jaw is not in the positional mode, the wrist jaw is in the force mode and the clamping force is unrestricted. In block 709, the method 700 generates an actuator position command without imposing a constraint on the clamping force. In one embodiment, block 709 will expect θ in addition to generating the actuator position command _Jaw To a desired clamping force command to achieve the desired clamping force.

If the jaws are in the position mode, block 703 determines if the jaws are closing. In one embodiment, block 703 may employ anti-shake techniques to determine the desired θ _Jaw Whether the duration of the pre-specified time has been reduced or the number of pre-specified samples has been reduced. In one embodimentIf θ is desired _Jaw Maintaining a stationary state without increasing, the jaws may be considered to be closing. If the jaws are not closing, the clamping force is not limited even in the position mode. The method 700 defaults to block 709 to generate an actuator position command without imposing a constraint on the clamping force.

If the jaws are closing in position mode, block 705 determines whether the measured clamping force exceeds a pre-specified maximum clamping force threshold. In one embodiment, block 705 may employ an anti-shake technique to determine whether the measured clamping force is greater than a maximum clamping force threshold minus a margin anywhere within a window spanning a number of samples equal to the clamping force counter. In one embodiment, the measured clamp force may be sampled at the loop cycle time of the feedback control system of fig. 5. The clamp force counter may be incremented by one for each control loop cycle during which the measured clamp force is less than the maximum clamp force threshold minus the margin. The clamp force counter may be reset when the measured clamp force is greater than a maximum clamp force threshold. The measured clamping force is considered to be above the maximum clamping force threshold for the entire window as long as the measured clamping force exceeds the maximum clamping force threshold minus a margin anywhere within the window spanning a number of samples equal to the clamping force counter. Otherwise, the measured clamping force does not exceed the maximum clamping force threshold, and the method 700 defaults to block 709 to generate an actuator position command without imposing a constraint on the clamping force.

If the measured clamping force exceeds the maximum clamping force threshold while the jaws are closing in the position mode, block 707 generates a compensating actuator position command to limit the measured clamping force to the maximum clamping force threshold. In one embodiment, block 707 may calculate a clamp force error that is the difference between the maximum clamp force threshold and the measured clamp force. A zero steady state controller, such as a proportional Plus Integral (PI) force controller, may receive the clamp force error to generate a compensated clamp force command. The output of the PI force controller may be combined with the output of an inverse kinematics matrix that operates on errors in the desired position and orientation of the wrist jaws to generate compensated actuator position commands. The compensated actuator position command can be added to an existing actuator position command to drive the jaws so as to limit the measured clamping force to a maximum clamping force threshold.

In another aspect, the controller 562 can maintain a minimum jaw opening force through the wrist jaw when operating in the positional mode. The minimum jaw opening force may also be referred to as a minimum clamping force. Maintaining a minimum jaw opening force when the jaws are opened in the positional mode helps the jaws overcome resistance that may prevent the jaws from opening to a desired jaw angle. The jaw angle and opening force of the jaws may be estimated or measured by a sensor and estimator 566. Controller 562 can analyze the desired θ _Jaw Estimated θ _Jaw And a measured opening force to determine whether the jaws are opening in the position mode, desired θ _Jaw And estimated θ _Jaw Whether the jaw angle error therebetween is greater than a threshold value, and whether the measured opening force is below a pre-specified minimum jaw opening force threshold value. If so, the controller 562 can calculate an opening force error between the pre-specified minimum jaw opening force threshold value and the measured opening force to maintain the measured opening force above the pre-specified minimum jaw opening force threshold value.

In one embodiment, to determine whether the jaws are opening in the position mode, the controller 562 can first verify that the desired θ _Jaw Greater than or equal to the braking threshold and thus last for more than a pre-specified duration in the position mode. The controller 562 can then determine whether the jaws opened in the position mode meet the requirement of preventing the jaws from opening to the desired θ _Jaw Is a resistance of (a). In one embodiment, controller 562 may employ anti-shake techniques to verify the desired θ _Jaw Greater than estimated theta _Jaw And as the desired theta _Jaw And estimated θ _Jaw θ of the difference between _Jaw Error is greater than theta _Jaw The error threshold continues for a pre-specified length of time. In one embodiment, if θ is desired _Jaw And estimated θ _Jaw Sampled at a periodic frequency, the controller 562 may be directed toA pre-specified number of sample validations θ _Jaw Error is greater than theta _Jaw Error threshold.

To determine whether the measured opening force is below a pre-specified minimum jaw opening force threshold, the controller 562 can also employ anti-shake techniques. The jaw opening force counter may increment one count for each control loop cycle during which the measured opening force is greater than the minimum opening force threshold plus a margin. In one embodiment, the jaw opening force counter may stop incrementing after it reaches a maximum count. The jaw opening force counter may be reset when the measured opening force is less than a minimum jaw opening force threshold. When the measured opening force is less than the minimum jaw opening force threshold plus a margin anywhere within the window, the anti-shake technique may declare that the measured opening force is less than the minimum jaw opening force threshold for a duration across the entire window equal to the number of loop cycles of the jaw opening force counter.

As an example, assume that the measured opening force is initially above the minimum jaw opening force threshold plus a margin, and that the jaw opening force counter is being incremented. The jaw opening force counter may be reset when the measured opening force falls below a minimum jaw opening force threshold. The feedback control loop of the controller 562 can attempt to change the actuator position command to drive the wrist jaw to maintain the measured opening force above the minimum jaw opening force threshold. However, even if the measured opening force increases above the minimum jaw opening force threshold but remains below the minimum jaw opening force threshold plus a margin, the feedback control loop may still consider the measured opening force to be less than the minimum jaw opening force threshold in order to maintain the minimum jaw opening force. It is assumed that the measured opening force rises above the minimum jaw opening force threshold plus a margin for only a few loop cycles, but then falls below this level again. The jaw opening force counter may be incremented to a number of loop cycles where the measured opening force is momentarily above the minimum jaw opening force threshold plus a margin. As long as the measured opening force remains below the minimum jaw opening force threshold plus a margin within a window spanning a number of loop cycles equal to the jaw opening force counter (e.g., the measured opening force is briefly above the minimum jaw opening force threshold plus the number of loop cycles of the margin), the feedback control loop may still consider the measured opening force to be less than the minimum jaw opening force threshold for the entire duration of the window in order to maintain the minimum jaw opening force.

When the controller 562 determines that the jaws are open in the position mode, θ _Jaw Error is greater than theta _Jaw The error threshold, and the measured opening force is below a pre-specified minimum jaw opening force threshold, the controller may maintain the measured opening force above the minimum jaw opening force threshold. In one embodiment, the controller 562 can calculate a jaw opening force error as the difference between a minimum jaw opening force threshold and a measured opening force. A zero steady state controller, such as a proportional Plus Integral (PI) force controller, may be deployed to receive the jaw opening force error to maintain the measured opening force at or above a minimum jaw opening force threshold. The output of the PI force controller may be combined with the output of an inverse kinematics matrix that operates on errors in the desired position and orientation of the wrist jaws to generate compensated actuator position commands. The compensated actuator position command is added to the existing actuator position command to drive the wrist jaw to maintain a minimum amount of opening force when the jaw is opening at the desired position and orientation in the position mode.

FIG. 8A is a graph showing the wrist-jaw command θ when the measured opening force is not maintained above a minimum level when the jaws are open in the position mode _Jaw 803. Measured θ _Jaw 805. A time graph of commanded clamping force 807 and measured opening force 809. The threshold θjaw between the position mode and the force mode is set to zero such that when the command θjaw 603 is greater than or equal to zero degrees, the wrist jaw operates in the position mode. When command theta _Jaw 603 is less than zero degrees, the wrist jaw operates in a force mode. θ _Jaw The error threshold is set to 5 degrees and the minimum opening force threshold is set to 4.4N.

FIG. 8A showsFrom 49 seconds to 60 seconds and from 62 seconds to 67 seconds, the wrist-jaw operates in the positional mode. Measured θ _Jaw 805 remains within a relatively narrow range, even when command θ _Jaw 803 to close or open in the position mode, presumably because the jaw that was open in the position mode is encountering resistance or is constrained to fully command θ _Jaw 803. From 49 seconds to 52 seconds, 56 seconds to 59 seconds, and 62 seconds to 66 seconds, open or remain at the same θ when the jaws are in the position mode _Jaw At the time of theta _Jaw Error (larger command θ _Jaw 803 with smaller measured θ _Jaw 805) may be greater than 5 degrees θ _Jaw Error threshold.

During position mode, the commanded clamping force 807 may be set to a default value of zero N by the clamping force controller. Even during force mode, command clamping force 807 is set to zero N. The positive value of the measured opening force 809 corresponds to the opening force of the jaws in the position mode, while the negative value corresponds to the clamping force in the force mode when the jaws are closed. The measured opening force 809 in position mode generally follows the command θ _Jaw 803 because the jaws are opened to the command θ _Jaw 803 is constrained. As a result, when the command θ _Jaw 803 increases to allow the jaws to open more widely, the measured opening force 809 is stronger, conversely, when θ is commanded _Jaw 803 are reduced to allow the jaws to open more narrowly, the measured opening force 809 is weaker. Because the feedback control loop is not enabled to maintain the measured opening force 809 above the minimum opening force threshold of 4.4N between 53 seconds and 60 seconds, the measured opening force 809 may drop below the minimum opening force threshold.

FIG. 8B is a diagram illustrating a command θ for a wrist jaw when a control system maintains a measured opening force 819 above a pre-specified minimum opening force threshold during jaw opening in a position mode 817 in accordance with aspects of the subject technology _Jaw 813. Measured θ _Jaw 815. A time profile of commanded clamp force 817 and measured opening force 819.θ _Jaw The error threshold is again set to 5 degrees and the minimum opening forceThe threshold is set to 4.4N.

In FIG. 8B, command θ when the minimum jaw opening force is not maintained _Jaw 813 and measured θ _Jaw 815 with command θ of fig. 8A _Jaw 803 and measured θ _Jaw 805 are substantially identical. During position mode, the commanded clamping force 817 is again set to the default value zero N by the clamping force controller. However, when θ _Jaw Error (larger command θ _Jaw 813 with a smaller measured θ _Jaw 815) is greater than 5 degrees _Jaw At the error threshold, the measured opening force 819 is maintained at or above a minimum opening force threshold of 4.4N by the feedback control loop and clamp force controller during a position mode between 30 seconds and 43 seconds. In particular, when the jaws are opening, the same θ is maintained _Jaw Or even when closed in the position mode, a minimum measured opening force 819 is maintained. Note that the minimum opening force threshold in position mode has no effect on the force mode when the measured opening force 819 may be negative.

Fig. 9 is a flow chart illustrating a method 900 for feedback control of a surgical robotic system that maintains a wrist jaw opening force above a pre-specified minimum jaw opening force threshold during jaw opening in a jaw position mode by analyzing a desired jaw angle, an estimated jaw angle, and a measured opening force, in accordance with aspects of the subject technology. Method 900 may be implemented by controller 562 of the control system of FIG. 5, receiving a desired θ from user input _Jaw Estimated or measured theta _Jaw And receives the measured opening force from the sensor and estimator 566 to generate an actuator position command for driving the wrist jaw portion.

In block 901, the method 900 determines whether the wrist jaw is in position mode. In one embodiment, block 901 may determine the desired θ _Jaw Whether or not it is greater than or equal to a threshold value theta between the position mode and the force mode _Jaw For more than a pre-specified period of time to confirm that the wrist-jaw is in position mode. In one embodiment, the threshold θ _Jaw May be set to zero. If the wrist jaw is not in the position mode, the wrist jaw is in the force mode and the minimum opening force is not enabled. In block 909, the method 900 generates the actuator position command without maintaining the minimum opening force. In one embodiment, in addition to generating the actuator position command, block 909 will expect θ _Jaw To a desired clamping force command to achieve a desired clamping force or opening force.

If the jaws are in position mode, block 903 is performed by determining θ _Jaw Error (the error is the expected θ) _Jaw And estimated or measured theta _Jaw Difference between them) is greater than or equal to theta _Jaw Error threshold to determine if the jaws are prevented from opening to a desired θ _Jaw . In one embodiment, block 903 may employ anti-shake techniques to determine the desired θ _Jaw Whether or not it is greater than the estimated theta _Jaw And θ _Jaw Whether the error is greater than or equal to theta _Jaw The error threshold continues for a pre-specified length of time. In one embodiment, block 903 may be performed by separately determining the desired θ _Jaw Is increasing, remains the same, or decreases to detect that the jaws are opening and remain static θ _Jaw Or closed. If theta is _Jaw Error is less than theta _Jaw Error threshold value, then the method 900 defaults to block 909 to generate the actuator position command without maintaining the minimum opening force.

If theta when the jaw is in position mode _Jaw Error greater than or equal to theta _Jaw An error threshold value, block 905 determines whether the measured opening force is below a pre-specified minimum jaw opening force threshold. In one embodiment, block 905 may employ an anti-shake technique to determine that the measured opening force is less than the minimum jaw opening force threshold plus a margin anywhere within the window spanning a number of samples equal to the jaw opening force counter. In one embodiment, the measured opening force may be sampled at the loop cycle time of the feedback control system of fig. 5. The jaw opening force counter may be incremented by one for each control loop cycle during which a measured stroke is measured The opening force is greater than the minimum jaw opening force threshold plus a margin. The jaw opening force counter may be reset when the measured opening force is less than a minimum jaw opening force threshold. The measured opening force is considered to be below the minimum jaw opening force threshold for the entire window as long as the measured opening force is less than the minimum jaw opening force threshold plus a margin anywhere within the window spanning a number of samples equal to the jaw opening force counter. Otherwise, the measured opening force is greater than or equal to the minimum jaw opening force threshold, and the method 900 defaults to block 909 to generate the actuator position command without maintaining the minimum opening force.

If the measured opening force is less than the minimum jaw opening force threshold and θ when the jaws are in position mode _Jaw Error greater than or equal to theta _Jaw An error threshold value, block 907 generates a compensation actuator position command to maintain the measured opening force above the minimum jaw opening force threshold value. In one embodiment, block 907 may calculate a jaw opening force error, which is the difference between the minimum jaw opening force threshold and the measured opening force. A zero steady state controller, such as a proportional Plus Integral (PI) force controller, may be deployed to receive the jaw opening force error to maintain the measured opening force at or above a minimum jaw opening force threshold. The output of the PI force controller may be combined with the output of an inverse kinematics matrix that operates on errors in the desired position and orientation of the wrist jaws to generate compensated actuator position commands. The compensated actuator position command is added to the existing actuator position command to drive the wrist jaw to maintain a minimum amount of opening force when the jaw is opening in position mode.

In another aspect, the controller 562 can adjust the commanded gripping force to smooth the gripping force applied when the wrist jaw transitions between the positional mode and the force mode. Smoothing the clamping force applied during a mode transition minimizes unwanted abrupt changes in the clamping force caused by changes in position and commanded clamping force of the jaws, which may result in the jaws accidentally falling out when they pass through a discontinuity between the two modesFalling the gripped object. During position mode, it is desirable for θ _Jaw Greater than or equal to the braking threshold. The position controller may expect θ _Jaw Desired θ _Pitching And desired theta _{Deflection of} To a corresponding actuator position command to drive the wrist-jaw to a desired position and orientation. During the force mode, when θ is desired _Jaw Below the braking threshold, e.g. when θ is desired _Jaw For a braking set to zero degrees to be negative, the clamp force controller may be enabled to expect θ _Jaw Interpreted as a clamping force command and can interpret the desired θ _Jaw Converted into a compensation current that can be added to the current for the existing position command to drive the wrist jaw to achieve the commanded clamping force.

In one embodiment, to smooth out the clamping force applied during mode transitions, the feedback control system may employ anti-shake techniques when the braking is set to zero degrees. When it is desired to theta _Jaw The anti-shake technique may prevent the clamp force controller from being repeatedly enabled and disabled when oscillating around positive and negative values to generate oscillations in the commanded clamp force.

In one embodiment, the feedback control system may determine the desired θ by analyzing _Jaw The gripping force and the measured gripping force are commanded to minimize abrupt changes in gripping force as the wrist jaw transitions from the positional mode to the force mode. The feedback control system can determine whether the commanded clamping force is due to, for example, a desired θ _Jaw Decreasing below the braking threshold indicates an activated clamping force controller and increasing, and whether the error between the measured clamping force and the commanded clamping force is greater than a pre-specified maximum force error. If so, the feedback control system can set the commanded gripping force to the measured gripping force minus a pre-specified margin when the wrist jaw transitions from position mode to force mode.

In one embodiment, the feedback control system may determine the desired θ by analyzing _Jaw The gripping force and the measured gripping force are commanded to minimize abrupt changes in gripping force as the wrist jaw transitions from the force mode to the position mode. Reverse-rotationThe feed control system may determine whether the commanded clamping force is less than a pre-specified minimum clamping force value, whether the commanded clamping force is due to, for example, a desired θ _Jaw Increasing above the braking threshold and decreasing by the clamping force controller being disabled as indicated by the braking threshold, and whether the absolute value of the error between the measured clamping force and the minimum clamping force is less than a pre-specified maximum clamping force error value. If so, the feedback control system can set the commanded gripping force to a pre-specified minimum gripping force value when the wrist jaw transitions from force mode to position mode.

FIG. 10 is a block diagram of an exemplary control system 1000 for controlling the position and clamping force of an end effector of a robotic surgical tool when the end effector is in a position mode or force mode, or when the end effector transitions between a position mode and force mode, in accordance with aspects of the subject technology. In one embodiment, the end effector comprises a wrist jaw. The robotic control system 1000 includes an input processing unit 502, an actuator command generator 504, a position controller 506, a gripping force controller 508, a device including one or more actuator units 510 and/or cables and wrist links 512, a slack controller 514, a position estimator 522, and a gripping force estimator 524.

The input processing unit 502 and the actuator command generator 504 receive a desired angular position of the wrist jaw and convert the desired angular position into a corresponding actuator position command (via inverse kinematics algorithms) that is output to the position controller 506 and/or the clamping force controller 508. For example, the input of the desired angular position may include a desired θ _Jaw Desired theta _Pitching And desired theta _{Deflection of} . When it is desired to theta _Jaw When greater than or equal to the braking threshold, it is desirable that θ _Jaw Can be considered as a location command. When it is desired to theta _Jaw When less than the braking threshold, it is desirable for θ _Jaw The desired clamping force command (e.g., commanded clamping force) may be converted by the clamping force controller 508, which may generate a current command to achieve the desired clamping force.

The position controller 506 may receive position feedback from position and/or speed sensors on the actuator unit 510. Achieving the desired actuator position may in turn result in a desired position of the wrist jaw due to the kinematic relationship between the actuator and the wrist jaw. Since the actuator unit 510 is coupled to the robot wrist by a flexible cable (or wire) that may change length under force, an estimate based solely on the pure kinematic relationship between actuator position and wrist movement may be inaccurate. By taking cable elasticity into account in the estimation algorithm (e.g., using a kalman filter), the position estimator 522 may provide a more accurate estimate of wrist joint position and velocity to the actuator command generator 504 and the clamp force estimator 524. The estimated position and velocity information can then be used for accurate positioning of the wrist and estimation of friction.

In one embodiment, the clamp force controller 508 takes feedback of the cable tension measured by a load cell or torque sensor on the cable wire. The clamping force estimator 524 may then use an algorithm to estimate the clamping force between the jaws based on the tension value measured on the cable. The clamp force controller 508 may compare the estimated value to the desired clamp force and generate additional current commands to achieve the desired clamp force. The wrist jaws may be coupled to the tool drive means by four independent cables, each of which is actuated by an independent motor. In one embodiment, the motor may be driven by an electric current. The current command may include two parts: a first portion of the drive current may come from the position controller 506 and a second portion from the clamp force controller 508. These two current commands may be summed and sent to the actuator unit 510.

The slack controller 514 can perform the task of ensuring that the tension on the cable never drops below zero (or a predetermined positive value to compensate for the slack). The cable is the only tensile member of the end effector to which negative forces cannot be applied. Therefore, it is desirable to prevent the tension on the cable from dropping to zero. To achieve this, the slack controller 514 can monitor the force values from the load cells on the cable and compare the minimum of these force values to a predetermined threshold. If the minimum force value across all cables falls below the threshold value, the slack controller 514 can generate additional position commands to all actuators to ensure that the desired minimum tension is maintained.

In order to smooth the clamping force applied during the mode transition, the input processing unit 502 may employ an anti-shake technique when the brake is set to zero degrees. The anti-shake technique may determine the desired θ before enabling the grip force controller 508 to transition the wrist jaw from the positional mode to the force mode _Jaw Whether less than the braking threshold for a pre-specified minimum duration. When transitioning from force mode to position mode, as long as θ is desired _Jaw Greater than or equal to the braking threshold, the input processing unit 502 may disable the clamp controller 508. Thus, the anti-shake technique may be unilateral. Anti-shake techniques prevent clamp force controller 508 from being repeatedly enabled and disabled when θ is desired _Jaw Oscillation near braking may result in conditions that command the clamping force to oscillate.

Fig. 11A is a graph showing when command θ is to be commanded without the anti-shake algorithm _Jaw 1103 are set to be in the vicinity of the threshold value, and the wrist jaw command θ _Jaw 1103. Measured θ _Jaw 1105. A time plot of command clamping force 1107, measured clamping force 1109, and current command 1106 from a clamping force controller (e.g., clamping force controller 508 of fig. 10). The braking threshold is set to zero such that when θ is commanded _Jaw 1103 are greater than or equal to zero degrees, the wrist jaws operate in a positional mode. When command theta _Jaw 1103 are less than zero degrees, the wrist jaw operates in a force mode. The positive clamping force indicates the clamping force in the force mode and the negative clamping force indicates the clamping force in the position mode.

Figure 11A shows the wrist jaw operating in the positional mode between time 11.6 seconds and 12 seconds. After 12 seconds, since the User Input Device (UID) is set at the brake, command θ _Jaw 1103 are set near the braking threshold. Measured θ _Jaw 1105 remain above about 20 degrees, presumably because the jaws are gripping an object. The grip force controller 508 is repeatedly turned over when the wrist jaw is shifted between the position mode and the force modeEnabled and disabled, thereby causing oscillations of commanded clamping force 1107 and current command 1106 from clamping force controller 508 when clamping force controller 508 is enabled during force mode. The result is an undesirably large swing in the measured clamping force 1109 observed between 12 seconds and 12.4 seconds. Measured θ _Jaw 1105 also illustrates some undesired oscillations due to the measured oscillation of the clamping force 1109.

FIG. 11B is a diagram illustrating an example of a control system (e.g., input processing unit 502 and actuator command generator 504 of FIG. 10) at a command θ in accordance with aspects of the subject technology _Jaw 1113 is set to the command θ of the wrist jaw when the anti-shake algorithm is used in the vicinity of the threshold value _Jaw 1113. Measured θ _Jaw 1115. A time plot of commanded clamping force 1117, measured clamping force 1119, and current command 1116 from clamping force controller 508. The braking threshold is again set to zero. Between 30.2 seconds and 30.9 seconds, the wrist jaw operates in the positional mode. After 30.9 seconds, command θ _Jaw 1113 is set near the braking threshold.

Only when theta is desired _Jaw The anti-shake algorithm enables the grip force controller 508 to transition the wrist-jaw from the position mode to the force mode for less than zero degrees for a pre-specified minimum duration. Because the control system does not detect this, the wrist-jaw remains in position mode and the clamp force controller 508 is not enabled. As a result, command clamping force 1117 remains at the default value of 0N, and current command 1116 from clamping force controller 508 also remains at 0. The measured clamping force 1119 does not exhibit large oscillations, and the measured θ _Jaw 1115 does not exhibit the oscillations observed in fig. 11A, thereby ensuring a smooth application of the clamping force (the measured clamping force 1119 is shown as positive even though the wrist jaw remains in position mode).

A smooth application of the gripping force may also become important when the wrist jaw is gripping an object when transitioning between the positional mode and the force mode. During the position mode, for example, even if the clamp force controller 508 is not enabled,if the wrist jaw is gripping an object, there may also be a non-zero measured gripping force. When it is desired to theta _Jaw Upon dropping below the braking threshold, thereby indicating a transition from position mode to force mode, the clamp force controller 508 may initially drive the commanded clamp force from 0N. Similarly, when transitioning from force mode to position mode, the commanded clamping force may be reset to a default value of 0N output from position controller 506 when clamping force controller 508 is disabled. As a result, there may be abrupt changes in the clamping force measured during the transition, which may result in the wrist-jaw dropping of the object.

FIG. 12A is a graph showing the wrist-jaw command θ when the control system does not attempt to limit the change in measured clamping force 1209 as the jaw transitions from position mode to force mode and back to position mode _Jaw 1203. Measured θ _Jaw 1205. A time profile of commanded clamping force 1207 and measured clamping force 1209. The braking threshold is again set to 0 so that when θ is commanded _Jaw 1203 are greater than or equal to 0 degrees, the wrist jaw operates in a positional mode. When command theta _Jaw 1203 are less than 0 degrees, the wrist jaw is operated in force mode.

The wrist jaw initially operates in a positional mode. Command θ _Jaw 1203 are initially 0 degrees and command clamping force 1207 is initially 0N. Measured θ _Jaw 1205 is 25 degrees and the measured clamping force 1209 is 8N due to the object being grasped between the jaws. At time 27.5 seconds, command θ _Jaw 1203 become negative to transition the wrist jaw from position mode to force mode. When the clamp force controller 508 is enabled, the commanded clamp force 1207 ramps up from 0N until the commanded θ _Jaw 1203 reach their most negative values. However, the measured clamping force 1209 experienced a sudden drop of 5N during the transition prior to ramping up as commanded. At time 30 seconds, command θ _Jaw 1203 begin to become less negative. The clamping force 1207 is commanded to begin ramping down and the measured clamping force 1209 follows as commanded. At time 31 seconds, command θ _Jaw 1203 are turned positive to transition the wrist jaw from the force mode back to the position mode. When the clamping force controller 508 is actuatedWhen disabled, the measured clamping force 1209 experiences a sudden jump from 0N to stationary 8N in position mode with some overshoot. It is desirable to minimize abrupt changes in the clamping force 1209 measured during the transition.

In one embodiment, to minimize abrupt changes in the gripping force of the wrist jaws when gripping an object during the transition from position mode to force mode, the gripping force controller 508 may adjust the commanded gripping force. For example, when at command θ _Jaw When becoming less than the braking threshold and if the clamp force controller 508 is enabled when certain conditions are met, the clamp force controller 508 may set the commanded clamp force to the currently measured clamp force minus a pre-specified margin. This prevents the measured clamping force from dropping to a value near 0N during the transition, thereby reducing the likelihood that the jaws will drop an object gripped between the jaws. In one embodiment, the measured clamping force may be generated by the clamping force estimator 524 based on the measured tension value on the cable from the cable and wrist link 512.

To evaluate the first condition for adjusting the commanded clamping force, the clamping force controller 508 may determine whether the commanded clamping force is or will be due to the clamping force controller 508, such as from a commanded θ that decreases below the braking threshold _Jaw As indicated, is enabled to increase. For the second condition, the clamp force controller 508 may determine whether the error between the measured clamp force and the commanded clamp force is greater than a pre-specified maximum force error. In one implementation, the clamp force controller 528 may use anti-shake techniques for one or both of the conditions. If both conditions are met, the clamp force controller 508 may set the commanded clamp force to the currently measured clamp force minus a pre-specified margin.

In one embodiment, to minimize abrupt changes in the gripping force of the wrist jaws when gripping an object during the transition from force mode to position mode, the gripping force controller 508 may adjust the commanded gripping force. For example, when at command θ _Jaw Becomes greater than the braking threshold and if the clamp force controller 508 is disabled when certain conditions are met, clamp force controlThe controller 508 may set the commanded clamping force to a pre-specified minimum clamping force value. Doing so, rather than starting from the default 0N for position mode, may reduce the measured change in clamping force up to the static clamping force for position mode.

To evaluate the conditions for adjusting the clamping force, the clamping force controller 508 may determine whether the commanded clamping force is less than a pre-specified minimum clamping force value. The clamp force controller 508 may also determine whether the commanded clamp force is being commanded, as by command θ _Jaw Increasing toward or beyond the braking threshold indicates decreasing. The clamp force controller 508 may additionally determine whether the absolute value of the error between the measured clamp force and the minimum clamp force value is less than a pre-specified maximum clamp force error value. In one implementation, the clamp force controller 528 may use anti-shake techniques for one or more of the conditions. If all conditions are met, the clamp force controller 508 may set the commanded clamp force to a pre-specified minimum clamp force value. In one embodiment, the pre-specified minimum clamping force value may be set to 3N.

FIG. 12B is a graph illustrating a wrist-jaw command θ when the control system limits the measured change in clamping force 1219 as the jaw transitions between position and force modes in accordance with aspects of the subject technology _Jaw 1213. Measured θ _Jaw 1215. Time graphs of commanded clamping force 1217 and measured clamping force 1219. The braking threshold is again set to 0 so that when θ is commanded _Jaw 1213 is greater than or equal to 0 degrees, the wrist jaw operates in the positional mode. When command theta _Jaw 1213 is less than 0 degrees, the wrist jaw operates in a force mode. The pre-specified maximum clamping force error value, which is not exceeded by the absolute value of the error between the measured clamping force and the commanded clamping force, is set to be greater than 8N. The pre-specified minimum clamping force value is set to 3N.

The wrist jaw initially operates in position mode, command θ _Jaw 1213. Measured θ _Jaw 1215. The initial state of the commanded clamping force 1217 and the measured clamping force 1219 is the same as in fig. 12A. At time 37.4 seconds, command θ _Jaw 1203 become negative to transition the wrist jaw from position mode to force mode. However, the commanded clamping force 1217 begins at about 6.2N instead of 0N in force mode, which 6.2N is obtained by subtracting a pre-specified margin from the measured clamping force 1219 at this time. Because the absolute value of the error between the measured clamping force 1219 and the commanded clamping force 1217 is less than the pre-specified maximum force error, the conditions for adjusting the commanded clamping force 1217 are satisfied. As a result, during the transition from position mode to force mode, the measured clamping force 1219 experiences significantly less drop than without adjustment of the commanded clamping force 1217. Command clamping force 1217 remains at 6.2N until commanded by the gradual negative command θ _Jaw The commanded clamping force 1217, as determined by 1213, becomes greater than 6.2N.

At time 39.8 seconds, command θ _Jaw 1213 begins to become less negative. The commanded clamping force 1217 begins to ramp down and the measured clamping force 1219 follows as commanded. At time 40.5 seconds, the commanded clamping force 1217 is maintained at a pre-specified minimum clamping force value of 3N, rather than continuing to ramp down to 0N, otherwise at command θ _Jaw 1213 to transition the wrist jaw from force mode to position mode will occur without adjustment. Because the measured clamping force 1219 is less than the pre-specified minimum clamping force value 3N and the absolute value of the error between the measured clamping force 1219 and the commanded clamping force 1217 is less than the pre-specified maximum force error, the conditions for adjusting the commanded clamping force 1217 are satisfied. As a result, when the measured clamping force 1219 jumps to rest 8N of the positional mode during the transition, the measured clamping force 1219 experiences significantly less variation than without adjustment of the commanded clamping force 1217. Command clamping force 1217 remains at 3N until commanded by command θ _Jaw The command clamping force 1217 determined by 1213 becomes 0N.

Fig. 13 is a flow chart illustrating a method 1300 for feedback control of a surgical robotic system for setting a desired θ of a wrist jaw when near a braking threshold in accordance with aspects of the subject technology _Jaw When employing anti-shake algorithms, or for use when the wristThe jaws limit the change in measured clamping force when transitioning between the position mode and the force mode. The method 1300 may be implemented by the controller 562 of the control system of fig. 5 or the clamp force controller 508 of the control system of fig. 10, which respectively receives the desired θ from user input _Jaw And the measured clamping force from the sensor and estimator 566 of fig. 5 or the clamping force estimator 524 of fig. 10 to generate a commanded clamping force for driving the wrist jaws.

Beginning with the position mode in block 1301, method 1300 determines the desired θ in block 1303 _Jaw Whether less than the braking threshold for a minimum duration. In one embodiment, the minimum duration may be pre-specified or may be configurable. Block 1303 implements an anti-shake algorithm to prevent repeated enabling and disabling of the force mode when θ is desired _Jaw Conditions that may cause oscillations in the commanded clamping force when set near the braking threshold. In one embodiment, block 1303 may determine whether the commanded clamping force is or will be as expected θ _Jaw Decreasing below the braking threshold and increasing as indicated. If theta is desired _Jaw Not less than the brake threshold for a pre-specified minimum duration, the wrist-jaw remains in the position mode of block 1301.

Otherwise, if θ is desired _Jaw Less than the brake threshold for a pre-specified minimum duration, the wrist-jaw is transitioning from the position mode to the force mode. Block 1304 determines whether the commanded clamping force is increasing. If this condition is false, block 1307 sets the commanded clamping force to be from the desired θ _Jaw The switching is performed and the commanded clamping force is not adjusted to limit the change in measured clamping force during the mode transition. Otherwise, if the condition in block 1304 is true, block 1305 determines whether the error between the measured clamp force and the commanded clamp force is greater than the maximum force error during the mode transition. In the position mode prior to the mode transition, the commanded clamping force may be a default of 0N. The measured gripping force may be different from the commanded gripping force prior to the mode transition because the wrist jaw may be gripping an object. In one embodiment, the maximum ofThe force error may be pre-specified or may be configurable.

If the condition in block 1305 is true, block 1309 sets the commanded grip force to the measured grip force minus the margin when the wrist jaw transitions from position mode to force mode. In one embodiment, the margin may be pre-specified or may be configurable. Otherwise, if the condition in block 1305 is false, block 1307 sets the commanded clamping force to be from the desired θ _Jaw The switching is performed and the commanded clamping force is not adjusted to limit the change in measured clamping force during the mode transition.

When the wrist jaw is in force mode in block 1311, method 1300 determines the desired θ in block 1313 _Jaw Whether greater than or equal to a braking threshold. In one embodiment, block 1311 may determine whether the commanded clamping force is as desired θ _Jaw Decreasing as indicated by increasing toward the braking threshold, and expecting θ _Jaw Just below the braking threshold. If theta is desired _Jaw Not greater than or equal to the brake threshold, the wrist jaw remains in the force mode of block 1311.

Otherwise, if θ is desired _Jaw Greater than or equal to the braking threshold, the wrist jaw is transitioning from the force mode to the position mode. Block 1315 determines whether the commanded clamping force is decreasing and whether the commanded clamping force is less than the minimum clamping force during the mode transition. In one embodiment, the minimum clamping force may be pre-specified or may be configurable. If the commanded clamping force is not decreasing or if the commanded clamping force is not less than the minimum clamping force during the mode transition, block 1307 sets the commanded clamping force to be from the desired θ _Jaw The switching is performed and the commanded clamping force is not adjusted to limit the change in measured clamping force during the mode transition.

Otherwise, if the commanded clamping force is decreasing and if the commanded clamping force is less than the minimum clamping force during the mode transition, block 1317 determines whether the absolute value of the error between the measured clamping force and the minimum clamping force value is less than the maximum force error during the mode transition. In one embodiment, the maximum force error may be pre-specified or may be configurable. The maximum force error in block 1317 for the force to position mode transition may be the same as or different from the maximum force error in block 1305 for the position to force mode transition.

If the condition in block 1317 is true, block 1319 sets the commanded gripping force to the minimum gripping force as the wrist jaw transitions from force mode to position mode. Otherwise, if the condition in block 1317 is false, block 1307 sets the commanded clamping force to be from the desired θ _Jaw The switching is performed and the commanded clamping force is not adjusted to limit the change in measured clamping force during the mode transition.

FIG. 14 is a block diagram illustrating exemplary hardware components of a surgical robotic system in accordance with aspects of the subject technology. The surgical robotic system may include an interface device 50, a surgical robot 80, and a control tower 70. The surgical robotic system may include other hardware components or additional hardware components; accordingly, the diagram is provided by way of example, and not limitation of the system architecture.

Interface device 50 includes a camera 51, a sensor 52, a display 53, a user command interface 54, a processor 55, a memory 56, and a network interface 57. The camera 51 and sensor 52 may be configured to capture color image and depth image information of the surgical robotic system. The images captured by the camera 51 and the sensor 52 may be projected on a display 53. Processor 55 may be configured to run an operating system to control the operation of interface device 50. Memory 56 may store image processing algorithms, operating systems, program codes, and other data storage used by processor 55. Interface device 50 may be used to generate a desired θ for the wrist jaw under control of a remote operator _Pitching 、θ _{Deflection of} And theta _Jaw 。

User command interface 54 may include interfaces for other features such as a Web portal. The hardware components may communicate via a bus. The interface device may communicate with the surgical robotic system through an external interface using the network interface 57. The external interface may be a wireless or wired interface.

The control tower 70 may be a mobile point-of-care cart housing a touch screen displayA computer controlling the surgeon to manipulate the instrument through the robotic assist, a safety system, a Graphical User Interface (GUI), a light source, and a video computer and a graphics computer. The control tower 70 may include a central computer 71 (which may include at least a visualization computer, a control computer, and an auxiliary computer), various displays 73 (which may include a team display and a nurse display), and a network interface 78 that couples the control tower 70 to both the interface device 50 and the surgical robot 80. The control tower 70 may also house third party equipment such as advanced light engines 72, electrosurgical generator units (ESUs) 74, and insufflators and CO2 tanks 75. The control tower 70 may provide additional functionality to enable user convenience such as a nurse display touch screen, soft power and E-hold buttons, user-oriented USB for video and still images, and electronic caster control interfaces. The secondary computer may also run real-time Linux, providing logging/monitoring and interaction with cloud-based web services. The central computer 71 of the control tower 70 may receive the desired θ of the wrist jaw generated by the interface device 50 _Pitching 、θ _{Deflection of} And theta _Jaw To implement the methods described herein for controlling the gripping or opening force of the jaws.

Surgical robot 80 includes an articulating operating table 84 having a plurality of integrated arms 82 positionable over a target patient anatomy. A set of compatible tools 83 may be attached/detached from the distal end of the arm 82 so that the surgeon can perform a variety of surgical procedures. Surgical robot 80 may also include a control interface 85 for manual control arm 82, operating table 84, and tool 83. The control interface 85 may include items such as, but not limited to, remote controls, buttons, a panel, and a touch screen. Other accessories such as trocars (cannulas, sealed cartridges, and tampons) and drapes may also be manipulated to perform surgery using the system. In one embodiment, the plurality of arms 82 may include four arms mounted on two sides of the operating table 84, with two arms on each side. For a particular surgical procedure, the arms mounted on one side of the operating table 84 may be positioned on the other side of the operating table 84 by stretching and crossing under the operating table 84 and the arms mounted on the other side, such that a total of three arms are positioned on the same side of the operating table 84. The surgical tool may also include a station computer 81 and a network interface 88 that may place the surgical robot 80 in communication with the control tower 70.

The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the invention. The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed; many modifications and variations of the present disclosure are possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application. These embodiments, therefore, will enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The following claims and their equivalents are intended to define the scope of the invention.

The above-described methods, apparatus, processes, and logic components may be implemented in a number of different ways and in a number of different combinations of hardware and software. The controller and the estimator may comprise electronic circuitry. For example, all or part of an embodiment may be a circuit comprising an instruction processor, such as a Central Processing Unit (CPU), microcontroller, or microprocessor; an Application Specific Integrated Circuit (ASIC), a Programmable Logic Device (PLD), or a Field Programmable Gate Array (FPGA); or a circuit comprising discrete logic components or other circuit components (including analog circuit components, digital circuit components, or both); or any combination thereof. By way of example, the circuit may include discrete interconnected hardware components and/or may be combined on a single integrated circuit die, distributed among multiple integrated circuit dies, or implemented in a multi-chip module (MCM) of multiple integrated circuit dies in a common package.

The circuitry may also include or access instructions for execution by the circuitry. The instructions may be stored in a tangible storage medium other than a transitory signal, such as flash memory, random Access Memory (RAM), read Only Memory (ROM), erasable Programmable Read Only Memory (EPROM); or on a magnetic or optical disk, such as a Compact Disk Read Only Memory (CDROM), hard Disk Drive (HDD) or other magnetic or optical disk; or in or on another machine-readable medium. An article of manufacture, such as a computer program product, may comprise a storage medium and instructions stored in or on the medium and which, when executed by circuitry in a device, may cause the device to implement any of the processes described above or shown in the accompanying drawings.

These embodiments may be distributed as circuitry between multiple system components, such as between multiple processors and memory, optionally including multiple distributed processing systems. Parameters, databases, and other data structures may be separately stored and managed, may be combined into a single memory or database, may be logically and physically organized in many different ways, and may be implemented in many different ways including as a data structure such as a linked list, hash table, array, record, object, or implicit storage mechanism. The programs may be portions of a single program (e.g., subroutines), separate programs, distributed across multiple memories and processors, or implemented in a variety of different manners, such as in a library, such as a shared library (e.g., a Dynamically Linked Library (DLL)). For example, the DLL, when executed by a circuit, may store instructions that perform any of the processes described above or shown in the figures.

In addition, the various controllers discussed herein may take the form of, for example, processing circuits, microprocessors or processors, and computer-readable media storing computer-readable program code (e.g., firmware) executable by the (micro) processor, logic gates, switches, application Specific Integrated Circuits (ASICs), programmable logic controllers, and embedded microcontrollers. The controller may be configured with hardware and/or firmware to perform the various functions described below and shown in the flowcharts. In addition, some components shown as being internal to the controller may also be stored external to the controller, and other components may be used.

Claims

1. A method for controlling a clamping force generated by a jaw of a clamping tool of a surgical robotic system, comprising:

determining, by a processor, that the jaws are closing in a position mode based on an input jaw angle between the jaws, the position mode characterized by positioning the jaws at the input jaw angle using a position command;

measuring a clamping force between the jaws in the position mode;

determining, by the processor, whether the measured clamping force exceeds a threshold in the position mode; and

in response to determining that the measured clamping force exceeds the threshold, a clamping force error is generated to limit the measured clamping force to the threshold.

2. The method of claim 1, wherein determining that the jaws are closing in the position mode comprises:

determining, by the processor, that the input jaw angle is greater than or equal to a threshold jaw angle for more than a minimum period of time, wherein the threshold jaw angle comprises a jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin touching each other without holding an object.

3. The method of claim 1, wherein determining that the jaws are closing in the position mode comprises:

determining, by the processor, that the input jaw angle is decreasing in the position mode for a minimum period of time.

4. The method of claim 1, wherein determining whether the measured clamping force exceeds the threshold comprises:

whenever the measured clamping force exceeds the threshold value minus a margin anywhere within a time window, it is determined by the processor that the measured clamping force exceeds the threshold value.

5. The method of claim 4, wherein a length of the time window is measured by a clamp force counter, wherein operation of the clamp force counter comprises:

Incrementing the clamp force counter by one whenever the measured clamp force is sampled, when the measured clamp force is less than the threshold value minus the margin; and

and resetting the clamping force counter when the measured clamping force is greater than the threshold value.

6. The method of claim 5, wherein determining whether the measured clamping force exceeds the threshold value further comprises:

when the measured clamping force exceeds the threshold value minus the margin anywhere within the time window, determining, by the processor, that the measured clamping force exceeds the threshold value for the entire length of the time window of the clamping force counter.

7. The method of claim 1, wherein the clamp force error comprises a difference between the measured clamp force and the threshold value.

8. The method of claim 1, wherein generating the clamp force error to limit the measured clamp force to the threshold value comprises:

generating, by the processor, a compensation position command from the clamp force error; and

the compensation position command and the position command are combined by the processor to generate an updated position command.

9. The method of claim 8, further comprising:

the updated position command is applied to drive the jaws to limit the measured clamping force to the threshold.

10. An apparatus for controlling the jaws of a clamping tool of a surgical robotic system, comprising:

a sensor configured to estimate a clamping force generated by the jaws to generate a measured clamping force;

a processor configured to:

determining that the jaws are closing in a position mode based on a desired jaw angle between the jaws, the position mode characterized by applying a position command to position the jaws at the desired jaw angle;

determining whether the measured clamping force exceeds a threshold in the position mode; and is also provided with

In response to determining that the measured clamping force exceeds the threshold, generating a clamping force error to update the position command to limit the measured clamping force to the threshold; and

an actuator drive unit configured to apply an updated position command to drive the jaws to limit the measured clamping force to the threshold.

11. The apparatus of claim 10, wherein the processor being configured to determine that the jaws are closing in the position mode comprises:

determining that the desired jaw angle is greater than or equal to a threshold jaw angle for more than a minimum period of time, wherein the threshold jaw angle comprises a jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to touch each other without holding an object.

12. The apparatus of claim 10, wherein the processor being configured to determine that the jaws are closing in the position mode comprises:

determining that the desired jaw angle is decreasing in the position mode for a minimum period of time.

13. The apparatus of claim 10, wherein the processor being configured to determine whether the measured clamping force exceeds the threshold comprises:

whenever the measured clamping force exceeds the threshold value minus a margin anywhere within the time window, it is determined that the measured clamping force exceeds the threshold value.

14. The apparatus of claim 13, wherein a length of the time window is measured by a clamp force counter, wherein the clamp force counter is configured to:

Incrementing by one whenever the measured clamping force is estimated by the sensor, when the measured clamping force is less than the threshold value minus the margin; and is also provided with

15. The apparatus of claim 14, wherein the processor being configured to determine whether the measured clamping force exceeds the threshold value further comprises:

when the measured clamping force exceeds the threshold value minus the margin anywhere within the window, it is determined that the measured clamping force exceeds the threshold value for the entire length of the time window of the clamping force counter.

16. The apparatus of claim 10, wherein the clamp force error comprises a difference between the measured clamp force and the threshold value.

17. The apparatus of claim 10, wherein the processor configured to generate the clamp force error to update the position command comprises:

generating a compensation position command according to the clamping force error; and

the compensation position command and the position command are combined to generate the updated position command to limit the measured clamping force to the threshold value.

18. A surgical robotic system, comprising:

an end effector comprising a pair of jaws;

a user interface device configured to generate an input jaw angle between the jaws;

a processor communicatively coupled to the end effector, the processor configured to:

determining that the jaws are closing in a position mode based on the input jaw angle between the jaws, the position mode characterized by applying a position command to position the jaws at the input jaw angle;

measuring a clamping force between the jaws in the position mode;

determining whether the measured clamping force exceeds a threshold in the position mode;

an updated position command is applied to position the jaws to limit the measured clamping force to the threshold.

19. The surgical robotic system of claim 18, wherein the processor being configured to determine that the jaws are closing in the position mode comprises:

Determining that the input jaw angle is greater than or equal to a threshold jaw angle for more than a first minimum period of time, wherein the threshold jaw angle comprises a jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin touching each other without holding an object; and

determining that the input jaw angle is decreasing in the position mode for a second minimum period of time.

20. The surgical robotic system of claim 18, wherein the processor configured to determine whether the measured clamping force exceeds the threshold comprises:

an anti-shake algorithm is used to determine that the measured clamping force exceeds the threshold minus a margin.

21. A method for controlling an opening force generated by jaws of a clamping tool of a surgical robotic system, comprising:

determining, by a processor, that the jaws are in a position mode based on an input jaw angle between the jaws, the position mode characterized by positioning the jaws at the input jaw angle using a position command;

measuring a jaw angle and an opening force between the jaws in the position mode;

Determining, by the processor, whether a jaw angle error between the input jaw angle and the measured jaw angle is greater than a jaw angle error threshold in the position mode;

determining, by the processor, whether the measured opening force is less than a minimum opening force threshold in response to determining that the jaw angle error is greater than the jaw angle error threshold; and

in response to determining that the measured opening force is less than the minimum opening force threshold, an opening force error is generated to maintain the measured opening force above the minimum opening force threshold.

22. The method of claim 21, wherein determining that the jaw is in the position mode comprises:

23. The method of claim 21, wherein determining whether the jaw angle error is greater than the jaw angle error threshold comprises:

Determining, by the processor, that the input jaw angle is greater than the measured jaw angle; and

determining, by the processor, that the jaw angle error is greater than the jaw angle error threshold for at least a minimum period of time.

24. The method of claim 21, wherein determining whether the measured opening force is less than the minimum opening force threshold comprises:

the measured opening force is determined by the processor to be less than the minimum opening force threshold as long as the measured opening force is less than the minimum opening force threshold plus a margin anywhere within the time window.

25. The method of claim 24, wherein a length of the time window is measured by an opening force counter, wherein operation of the opening force counter comprises:

incrementing the opening force counter by one whenever the measured opening force is sampled, when the measured opening force is greater than the minimum opening force threshold plus the margin; and

the opening force counter is reset when the measured opening force is less than the minimum opening force threshold.

26. The method of claim 25, wherein determining whether the measured opening force is less than the minimum opening force threshold further comprises:

When the measured opening force is less than the minimum opening force threshold plus the margin anywhere within the window, determining, by the processor, that the measured opening force is less than the minimum opening force threshold for the entire length of the time window of the opening force counter.

27. The method of claim 21, wherein the opening force error comprises a difference between the measured opening force and the minimum opening force threshold.

28. The method of claim 21, wherein generating the opening force error to maintain the measured opening force above the minimum opening force threshold comprises:

generating, by the processor, a compensation position command based on the opening force error; and

29. The method of claim 28, further comprising:

the updated position command is applied to position the jaws to maintain the measured opening force above the minimum opening force threshold.

30. An apparatus for controlling jaws of a clamping tool of a surgical robotic system, comprising:

A sensor configured to:

estimating an angle between the jaws to generate a measured jaw angle; and is also provided with

Estimating an opening force generated by the jaws to generate a measured opening force;

a processor configured to:

determining that the jaws are in a position mode based on a desired jaw angle between the jaws, the position mode characterized by applying a position command to position the jaws at the desired jaw angle;

determining whether a jaw angle error between the desired jaw angle and the measured jaw angle is greater than a jaw angle error threshold in the position mode;

responsive to determining that the jaw angle error is greater than the jaw angle error threshold, determining whether the measured opening force is less than a minimum opening force threshold; and is also provided with

In response to determining that the measured opening force is less than the minimum opening force threshold, generating an opening force error to update the position command to maintain the measured opening force above the minimum opening force threshold; and

an actuator drive unit configured to apply an updated position command to position the jaws to maintain the measured opening force above the minimum opening force threshold.

31. The apparatus of claim 30, wherein the processor being configured to determine that the jaw is in the position mode comprises:

32. The apparatus of claim 30, wherein the processor being configured to determine whether the jaw angle error is greater than the jaw angle error threshold comprises:

determining that the desired jaw angle is greater than the measured jaw angle; and

determining that the jaw angle error is greater than the jaw angle error threshold for at least a minimum period of time.

33. The apparatus of claim 30, wherein the processor being configured to determine whether the measured opening force is less than the minimum opening force threshold comprises:

as long as the measured opening force is less than the minimum opening force threshold plus a margin anywhere within the time window, it is determined that the measured opening force is less than the minimum opening force threshold.

34. The apparatus of claim 33, wherein a length of the time window is measured by an opening force counter, wherein the opening force counter is configured to:

incrementing by one whenever the measured opening force is estimated by the sensor, when the measured opening force is greater than the minimum opening force threshold plus the margin; and

35. The apparatus of claim 34, wherein the processor configured to determine whether the measured opening force is less than the minimum opening force threshold further comprises:

when the measured opening force is less than the minimum opening force threshold plus the margin anywhere within the window, determining that the measured opening force is less than the minimum opening force threshold for the entire length of the time window of the opening force counter.

36. The device of claim 30, wherein the opening force error comprises a difference between the measured opening force and the minimum opening force threshold.

37. The apparatus of claim 30, wherein the processor configured to generate the opening force error to update the position command comprises:

Generating a compensation position command according to the opening force error; and

combining the compensation position command and the position command to generate the updated position command to position the jaws to maintain the measured opening force above the minimum opening force threshold.

38. A surgical robotic system, comprising:

an end effector comprising a pair of jaws;

determining that the jaws are in a position mode based on the input jaw angle between the jaws, the position mode characterized by applying a position command to position the jaws at the input jaw angle;

measuring a jaw angle and an opening force between the pair of jaws in the position mode;

determining whether a jaw angle error between the input jaw angle and the measured jaw angle is greater than a jaw angle error threshold in the position mode;

responsive to determining that the jaw angle error is greater than the jaw angle error threshold, determining whether the measured opening force is less than a minimum opening force threshold;

39. The surgical robotic system of claim 38, wherein the processor configured to determine whether the jaw angle error is greater than the jaw angle error threshold comprises:

determining that the input jaw angle is greater than the measured jaw angle; and

40. The surgical robotic system of claim 38, wherein the processor configured to determine whether the measured opening force is less than the minimum opening force threshold comprises:

an anti-shake algorithm is used to determine that the measured opening force is less than the minimum opening force threshold plus a margin.

41. A method for controlling a clamping force generated by a jaw of a clamping tool of a surgical robotic system, comprising:

Determining, by a processor, that the jaws are transitioning between a position mode and a force mode based on a change in an input jaw angle between the jaws, the position mode characterized by positioning the jaws at the input jaw angle and the force mode characterized by driving the jaws to a commanded clamping force determined based on the input jaw angle having a negative value;

measuring a clamping force between the jaws;

determining, by the processor, whether to adjust the commanded clamping force during the transition between the position mode and the force mode based on the commanded clamping force and the measured clamping force; and

the commanded clamping force is adjusted during the transition between the position mode and the force mode to smooth a change in the measured clamping force in response to determining to adjust the commanded clamping force.

42. The method of claim 41, wherein determining that the jaw transitions between the position mode and the force mode comprises:

determining that the jaw is transitioning from the position mode to the force mode when the input jaw angle is initially greater than or equal to zero and becomes less than zero for a minimum duration; or alternatively

When the input jaw angle is initially less than zero and becomes greater than or equal to zero, it is determined that the jaw is transitioning from the force mode to the position mode.

43. The method of claim 41, wherein determining that the jaw transitions between the position mode and the force mode comprises:

determining, by the processor, that the jaws are initially in the position mode when the input jaw angle is greater than or equal to a threshold jaw angle, wherein the threshold jaw angle includes a jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to touch each other without holding an object; and

when the input jaw angle becomes less than the threshold jaw angle for more than a minimum duration, determining, by the processor, that the jaw transitions from the position mode to the force mode.

44. The method of claim 43, wherein determining whether to adjust the commanded clamping force during the transition comprises:

during the transition from the position mode to the force mode, when the commanded clamping force is increasing and a difference between the measured clamping force and the commanded clamping force is greater than a maximum clamping force error, determining, by the processor, to adjust the commanded clamping force.

45. The method of claim 44, wherein adjusting the commanded clamping force comprises:

responsive to determining to adjust the commanded clamping force, setting, by the processor, the commanded clamping force to the measured clamping force minus a margin; or alternatively

Otherwise, the commanded clamping force is set by the processor based on the input jaw angle in the force mode.

46. The method of claim 41, wherein determining that the jaw transitions between the position mode and the force mode comprises:

determining, by the processor, that the jaws are initially in the force mode when the input jaw angle is less than a threshold jaw angle, wherein the threshold jaw angle includes a jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to touch each other without holding an object; and

when the input jaw angle becomes greater than or equal to the threshold jaw angle, determining, by the processor, a jaw transition from the force mode to the position mode.

47. The method of claim 46, wherein determining whether to adjust the commanded clamping force during the transition comprises:

During the transition from the force mode to the position mode, determining, by the processor, to adjust the commanded clamping force when the commanded clamping force is decreasing, the commanded clamping force is less than a minimum clamping force, and an absolute value of a difference between the measured clamping force and the minimum clamping force is less than a maximum clamping force error.

48. The method of claim 47, wherein adjusting the commanded clamping force comprises:

setting, by the processor, the commanded clamping force to the minimum clamping force in response to determining to adjust the commanded clamping force; or alternatively

Otherwise, the commanded clamping force is set by the processor based on the input jaw angle.

49. The method of claim 41, further comprising:

changing, by the processor, the commanded clamping force to be based on the input jaw angle in the force mode after the transition from the position mode to the force mode when the commanded clamping force is adjusted; or alternatively

When the commanded clamping force is adjusted, the commanded clamping force is changed by the processor to be based on the input jaw angle in the position mode after the transition from the force mode to the position mode.

50. An apparatus for controlling the jaws of a clamping tool of a surgical robotic system, comprising:

a sensor configured to estimate a clamping force between the jaws to generate a measured clamping force;

a processor configured to:

determining a transition of the jaws between a position mode and a force mode based on a change in a desired jaw angle between the jaws, the position mode characterized by positioning the jaws at the desired jaw angle and the force mode characterized by driving the jaws to a commanded clamping force determined based on the desired jaw angle having a negative value;

determining, based on the commanded clamping force and the measured clamping force, whether to adjust the commanded clamping force during the transition between the position mode and the force mode; and

in response to determining to adjust the commanded clamping force, the commanded clamping force is adjusted during the transition between the position mode and the force mode to smooth a change in the measured clamping force.

51. The apparatus of claim 50, wherein the processor being configured to determine that the jaw transitions between the position mode and the force mode comprises:

Determining that the jaw transitions from the position mode to the force mode when the desired jaw angle is initially greater than or equal to zero and becomes less than zero for a minimum duration; and

when the desired jaw angle is initially less than zero and becomes greater than or equal to zero, a transition of the jaw from the force mode to the position mode is determined.

52. The apparatus of claim 50, wherein the processor being configured to determine that the jaw transitions between the position mode and the force mode comprises:

determining that the jaws are initially in the position mode when the desired jaw angle is greater than or equal to a threshold jaw angle, wherein the threshold jaw angle comprises a jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to touch each other without holding an object; and

when the desired jaw angle becomes less than the threshold jaw angle for more than a minimum duration, determining that the jaw transitions from the position mode to the force mode.

53. The apparatus of claim 52, wherein the processor being configured to determine whether to adjust the commanded clamping force during the transition comprises:

During the transition from the position mode to the force mode, determining to adjust the commanded clamping force when the commanded clamping force is increasing and a difference between the measured clamping force and the commanded clamping force is greater than a maximum clamping force error.

54. The apparatus of claim 53, wherein the processor being configured to adjust the commanded clamping force comprises:

adjusting the commanded clamping force in response to the determination, setting the commanded clamping force to the measured clamping force minus a margin; or alternatively

Otherwise, the commanded clamping force is set based on the desired jaw angle in the force mode.

55. The apparatus of claim 50, wherein the processor being configured to determine that the jaw transitions between the position mode and the force mode comprises:

determining that the jaws are initially in the force mode when the desired jaw angle is less than a threshold jaw angle, wherein the threshold jaw angle comprises a jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to touch each other without holding an object; and

Determining that the jaw transitions from the force mode to the position mode when the desired jaw angle becomes greater than or equal to the threshold jaw angle.

56. The apparatus of claim 55, wherein the processor configured to determine whether to adjust the commanded clamping force during the transition comprises:

during the transition from the force mode to the position mode, determining to adjust the commanded clamping force when the commanded clamping force is decreasing, the commanded clamping force is less than a minimum clamping force, and an absolute value of a difference between the measured clamping force and the minimum clamping force is less than a maximum clamping force error.

57. The apparatus of claim 56, wherein the processor being configured to adjust the commanded clamping force comprises:

adjusting the commanded clamping force in response to the determination, setting the commanded clamping force to the minimum clamping force; or alternatively

58. The apparatus of claim 50, wherein the processor is further configured to:

when the processor is configured to adjust the commanded clamping force, after the transition from the position mode to the force mode, changing the commanded clamping force to be based on the desired jaw angle in the force mode; or alternatively

When the processor is configured to adjust the commanded clamping force, the commanded clamping force is changed to be based on the desired jaw angle in the position mode after the transition from the force mode to the position mode.

59. A surgical robotic system, comprising:

an end effector comprising a pair of jaws;

determining a transition of the jaw between a position mode and a force mode based on a change in the input jaw angle, the position mode characterized by positioning the jaw at the input jaw angle and the force mode characterized by driving the jaw to a commanded gripping force determined based on the input jaw angle having a negative value;

measuring a clamping force between the pair of jaws;

60. The surgical robotic system of claim 59, wherein the processor configured to determine that the jaw transitions between the position mode and the force mode comprises:

determining that the jaws are initially in the position mode when the input jaw angle is greater than or equal to a threshold jaw angle, wherein the threshold jaw angle comprises a jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to touch each other without holding an object; and

when the input jaw angle becomes less than the threshold jaw angle for more than a minimum duration, determining that the jaw transitions from the position mode to the force mode, and wherein the processor is configured to determine whether to adjust the commanded clamping force during the transition comprises:

determining to adjust the commanded clamping force during the transition from the position mode to the force mode when the commanded clamping force is increasing and a difference between the measured clamping force and the commanded clamping force is greater than a maximum clamping force error, and wherein the processor being configured to adjust the commanded clamping force comprises:

Otherwise, the commanded clamping force is set based on the input jaw angle in the force mode.