CN116322557A - Limits clamping force in position control mode and maintains minimum opening force of the jaws and controls clamping force when transitioning between position control mode and force mode - Google Patents

Abstract

The present invention discloses systems and methods for limiting the gripping force generated by closing the jaws of a robotic wrist while operating in a position mode in which the jaws are commanded before the jaws are commanded to generate the gripping force The mouth reaches the desired jaw angle. Also disclosed are systems and methods for maintaining the opening force generated by a robotic wrist jaw operating in a position mode in which the jaw is commanded to a desired jaw before commanding the jaw to generate a gripping force angle. Systems and methods for achieving smooth transitions in clamping force when the wrist jaw transitions between position and force modes are also disclosed.

Description

limit the clamping force and maintain a minimum opening force of the jaws in position control mode and Controls clamping force when transitioning between position control mode and force mode

technical field

The present technology relates generally to robotics and surgical systems, and more particularly to controlling the clamping or opening force of surgical tools, such as wrist jaws of robotic-assisted surgery systems.

Background technique

Minimally invasive surgery (MIS) such as laparoscopic surgery uses techniques aimed at reducing tissue damage during surgical procedures. Laparoscopic procedures typically require making multiple small incisions in the patient's body (eg, in the abdomen) and then inserting several surgical tools (such as endoscopes, scalpels, graspers, and needles) into the patient through these small incisions. 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 visualize (via the endoscope) and manipulate tissue at the surgical site. MIS can also be performed using a robotic system where a surgical tool is operatively attached to the distal end of a robotic arm and the control system actuates the arm and its attached tool so that when a user input device (UID) is being operated by the surgical The arm and its attached tool mimic the movement and tool specific commands of the UID as the physician manipulates it in his hand.

The surgical tool may include a robotic wrist supporting a pair of opposing jaws. The wrist and jaws can move with multiple degrees of freedom when controlled by commands from a teleoperator to perform grasping, cutting, stapling, and other surgical tasks. For example, actuators in the tool drive of a robotic arm can drive multi-axis motion (e.g., pitch and yaw) of the wrist jaws to pivot, open, close, or control the clamping force between the jaws Or turn on the force while moving the wrist to any angular position. The jaws can grasp patient tissue, hold cutting instruments, and the like. Precise control of the clamping or opening force when closing or opening the jaws is critical to prevent damage to tissue or ensure precise cutting of the instrument. Additionally, the jaws are operable in a position mode, in which the angle between a pair of jaws is commanded to be a desired jaw angle, and a force mode, in which the jaws are commanded to apply a desired clamping force. The smooth transition between position mode and force mode minimizes undesired sudden changes in clamping force that could result in an unintentional drop of any object being grasped.

Contents of the invention

Systems and methods are disclosed for limiting the gripping force generated by closing the jaws of a robotic wrist while operating in a position control mode in which the jaws are commanded before the jaws are commanded to generate the gripping force Achieve desired jaw angle. In position control mode, or simply position mode, the desired jaw angle is above the threshold corresponding to the angle at which both jaws are in contact with an object between the jaws at exactly the same time, or if there is no object to grasp, the The angle at which the jaws begin to touch each other. When the desired jaw angle is below a threshold, the wrist jaw operates in a force control mode, or simply force mode, and the desired jaw angle is translated into a desired gripping force. The disclosed systems and methods limit the maximum amount of clamping force when the jaws are closing in position mode to prevent damage to tissue graspable by the jaws. Clamping force can be estimated or measured. A feedback loop may analyze the desired jaw angle and measured clamping force to determine if the jaws are closing in position mode and if the measured clamping force exceeds a pre-specified maximum clamping force threshold. If so, a feedback loop may calculate a clamping force error to limit the measured clamping force to a pre-specified maximum clamping force threshold.

In another aspect, a system and method are disclosed for achieving minimal jaw opening force by wrist jaws while operating in a position mode. Maintaining a minimum jaw opening force when the jaws are open in position mode helps the jaws overcome resistance that may prevent the jaws from opening to a desired jaw angle. The opening force representing the jaw opening force and the jaw angle can be measured or estimated. Feedback loop analyzes desired jaw angle, estimated jaw angle and measured jaw opening force to determine if the jaw is opening in position mode and if the measured jaw opening force is below a pre-specified minimum opening force force threshold. If so, a feedback loop may 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 of clamping force when a wrist jaw transitions between a position mode and a force mode is disclosed. The smooth transition from position mode to force mode and vice versa minimizes undesired abrupt changes in clamping force that occur when the jaws pass through the discontinuity between the two modes. Variations can cause the wrist jaws to accidentally drop the grasped object. In one embodiment, to transition from position mode to force mode, an anti-shake strategy may be used to ensure that the desired jaw angle is less than a threshold between position mode and force mode for a pre-specified period before the wrist jaw transitions to force mode minimum duration of .

In one embodiment, the system and method can determine a desired clamping force from a desired jaw angle and can measure or estimate the clamping force. Feedback loop analyzes desired jaw angle, desired grip force, and measured grip force to determine if the jaw is transitioning from position mode to force mode, error between measured grip force and expected grip force Is it greater than the pre-specified maximum force error, and the desired clamping force is increasing. If so, when the jaw transitions from position mode to force mode, the feedback loop can set the desired clamping force to be the currently measured clamping force minus a pre-specified margin.

In one embodiment, a 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 if the jaws are transitioning from force mode to position mode, desired clamping force Whether the holding force is less than the minimum holding force value, whether the expected holding force is decreasing, and whether the absolute value of the error between the measured holding force and the minimum holding force is less than the pre-specified maximum force error. If so, the feedback loop may set the desired clamping force to the minimum clamping force value when the jaws transition from force mode to position mode.

A method for controlling the jaw clamping force generated by the jaws 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 the application of position commands to drive the jaws to a desired position with a desired jaw angle. The method also includes determining whether the measured clamping force exceeds a maximum clamping force threshold if the jaws are closing in the position mode. The method also includes generating a clamping force error to be combined with the position command to limit the measured clamping force to the maximum clamping force threshold if the measured clamping force exceeds the maximum clamping force threshold.

Another method for controlling the jaw opening force generated by the jaws 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 the application of position commands to drive the jaws to a desired position with a desired jaw angle. The method also includes determining whether a jaw angle error between the expected jaw angle and the measured jaw angle is greater than an error threshold if the jaw is in the position mode. The method also 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 also 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.

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

Description of drawings

To provide a more complete understanding of the present invention, the accompanying drawings are provided together 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 persons of ordinary skill in the art may modify the drawings to generate drawings of other embodiments that will still fall within the scope of the invention.

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

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

3A and 3B are schematic diagrams illustrating an exemplary tool drive apparatus with and without a loaded tool, respectively, in accordance with aspects of the subject technology.

4A and 4B are end effectors illustrating an exemplary gripper having a robotic wrist, a pair of opposing jaws, and a gripper for holding the robotic wrist in accordance with aspects of the subject technology. and the pair of jaws are coupled to the pulley and cable system of the actuator of the tool drive.

5 is a block diagram of an example 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.

6A is a graph showing the commanded jaw angle of the wrist jaws, the measured jaw angle, the commanded clamping force and the measured The time curve of the clamping force.

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

7 is a flowchart illustrating a method for feedback control of a surgical robotic system by analyzing desired jaw angles and measured gripping forces in a jaw-in-position mode in accordance with aspects of the subject technology. Limits the gripping force of the wrist jaws to a pre-specified maximum threshold during closure.

8A is a graph showing the commanded jaw angle, measured jaw angle, commanded gripping force and Time plot of the measured opening force.

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

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

10 is a block diagram of an example control system for use when the end effector of the robotic surgical tool is in position mode or force mode, or when the end effector is in position mode, in accordance with aspects of the subject technology. Controls the position and clamping force of the end effector when transitioning between modes and force modes.

11A is a graph showing the commanded jaw angle, measured jaw angle, Time plot of commanded gripping force, measured gripping force, and activity of the gripping force controller.

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

Figure 12A is a graph showing the commanded jaw angle, measured jaw angle of the wrist jaw when the change in measured clamping force is unconstrained when the jaw transitions from position mode to force mode and back to position mode , commanded clamping force and measured clamping force over time.

12B is a graph illustrating the commanded jaw angle, measured to Time plot of jaw angle, commanded gripping force, and measured gripping force.

13 is a flowchart illustrating a method for feedback control of a surgical robotic system for setting wrist jaws near a threshold between a position mode and a force mode in accordance with aspects of the subject technology. An anti-shake algorithm is used when the jaw angle is desired, or to limit the change in the measured clamping force when the jaw transitions between position mode and force mode.

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

Detailed ways

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 the embodiments, but rather to enable a person skilled in the art to make and use the invention.

The present invention discloses a feedback control system and method for controlling the clamping force or opening force of an end effector (such as a wrist jaw) of a surgical robot arm. The wrist jaws may be coupled by cables to the actuators of the tool drive for multi-axis movement of the wrist jaws. Feedback control system can command pitch angle, yaw angle and jaw angle from wrist jaw to jaw. When the commanded jaw angle is above a threshold (also referred to as a threshold for detent), the wrist jaw is operable 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 the desired jaw angle. When the commanded jaw angle is below the braking threshold, the wrist jaw may operate in the force mode according to the position and orientation of the position mode, and the desired clamping force is generated by the clamping force controller based on the commanded jaw angle. In one embodiment, when the jaws are closing in position mode, the feedback control system can determine whether the measured clamping force exceeds a pre-specified maximum clamping force by analyzing the desired jaw angle and measuring or estimating the actual clamping force applied. Gripping Force Threshold to limit the maximum gripping force. If so, the feedback control system may calculate a clamping force error to adjust the clamping force such that the measured clamping force is limited to a pre-specified maximum clamping force threshold.

In one embodiment, the feedback control system can maintain a minimum jaw opening force when the jaws are opening in position mode. A feedback control system can measure or estimate the actual applied jaw angle. The feedback control system can also measure or estimate the actual clamping force or opening force of the jaws applied. By analyzing the desired jaw angle, the measured jaw angle, and the measured jaw opening force, the feedback control system can determine if the jaw is in position mode and if the difference between the desired and estimated jaw angle is greater than threshold, and whether the measured jaw opening force is less than a pre-specified minimum opening force threshold. If so, the feedback control system may calculate an opening force error to adjust the clamping force or opening force to keep 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 position mode and 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, a feedback control system can switch the wrist jaw from position mode to force mode. In one embodiment, the anti-shake algorithm can be one-sided, such that the wrist jaw can transition back to position mode whenever the desired jaw angle is greater than or equal to a threshold.

In one embodiment, a feedback control system can minimize undesired sudden changes in clamping force when transitioning between position mode and force mode. A gripping force controller may calculate a current command for a desired gripping force based on the desired jaw angle. A feedback control system can measure or estimate the actual clamping force applied. The feedback control system can analyze the desired jaw angle, desired gripping force and measured gripping force to determine if the jaw is transitioning from position mode to force mode, and the difference between the measured gripping force and the desired gripping force Is the error greater than the pre-specified maximum force error and the desired grip 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 position mode to force mode.

In one embodiment, the feedback control system can analyze the desired jaw angle, desired clamping force, and measured clamping force to determine if the jaws are transitioning from force mode to position mode, if the desired clamping force is less than a pre-specified The minimum grip force value, whether the desired grip force is decreasing, and whether the absolute value of the error between the measured grip force and the minimum grip force is less than the prespecified 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 force mode to position mode. In one embodiment, the pre-specified minimum clamping force value may be set at 3N.

FIG. 1 is a pictorial view of an exemplary surgical robotic system 1 in a surgical setting, 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 (eg, table, bed, etc.). The arms 4 may be mounted to the table or bed on which the patient lies, as shown in the example of Figure 1, or they may be mounted to a trolley separate from the table or bed. System 1 may incorporate any number of devices, tools or accessories for performing procedures on patient 6 . For example, system 1 may include one or more surgical tools 7 for performing surgical procedures. Surgical tool 7 may be an end effector attached to the distal end of surgical arm 4 for performing a surgical procedure.

Each surgical tool 7 may be manipulated manually, robotically, or both during the surgical procedure. For example, surgical tool 7 may be a tool for accessing, viewing or manipulating the internal anatomy of patient 6 . In one aspect, surgical tool 7 is a grasper such as wrist jaws that can grasp patient tissue. The surgical tool 7 may be configured to be controlled manually by the bedside operator 8, robotically controlled via actuated movement of the surgical robotic arm 4 to which it is attached, or both. The robotic arm 4 is shown as bench mounted, but in other configurations the arm 4 could be mounted to a trolley, ceiling or side wall, or to another suitable structural support.

A teleoperator 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 . In other environments, however, the user console 2 may be located in an adjacent or nearby room, or it may be located in a remote location, eg, in a different building, city or country. User console 2 may include a seat 10, foot-activated controls 13, one or more hand-held user input devices (UID) 14, and at least one user display 15 configured to display, for example, a surgical site within patient 6 view. In the exemplary user console 2, the teleoperator 9 sits in the seat 10 and views the user display 15 while manipulating the foot controls 13 and the handheld UID 14 to remotely control the arm 4 and the remote end mounted on the arm 4. Surgical tools on the head7.

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

During an exemplary procedure (surgery), the patient 6 is surgically prepared and aseptically draped to achieve anesthesia. Initial access to the surgical site (to facilitate access to the surgical site) may be performed manually with the arms of the robotic system 1 in the stowed or retracted configuration. Once access is achieved, an initial positioning or preparation of the robotic system 1 including its arm 4 can be performed. The surgery then continues with the teleoperator 9 at the user console 2 utilizing the foot controls 13 and UID 14 to manipulate the various end effectors and possibly the imaging system to perform the surgery. Human assistance may also be provided at the operating bed or table by a bedside personnel (e.g., a 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 changes. Non-sterile personnel may also be present to assist the teleoperator 9 at the user console 2 . When a procedure or surgical procedure is complete, the system 1 and user console 2 can be configured or set to certain states to facilitate completion of post-operative procedures such as cleaning or disinfection as well as entering or printing healthcare records via the user console 2.

In one embodiment, the teleoperator 9 holds and moves the UID 14 to provide input commands to move the robotic arm actuator 17 in the robotic system 1 . UID 14 may be communicatively coupled to the remainder of robotic system 1 , eg, via console computer system 16 . UID 14 may generate spatial state signals corresponding to movement of UID 14 , such as the position and orientation of the UID's hand-held housing, and the spatial state signals may be input signals controlling motion of robotic arm actuator 17 . The robotic system 1 may control the proportional movement of the actuator 17 using a control signal derived from the space state signal. In one embodiment, a console processor of console computer system 16 receives the space state signals and generates corresponding control signals. Movement of a corresponding surgical tool attached to the arm may simulate movement of the UID 14 based on these control signals controlling how the actuator 17 is energized to move the sections or links of the arm 4 . Similarly, interaction between teleoperator 9 and UID 14 may generate, for example, a gripping control signal that closes the jaws of the gripper of surgical tool 7 and grips tissue of patient 6 .

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

In some aspects, communication between platform 5 and user console 2 may pass through control tower 3, which may convert user commands received from user console 2 (and more specifically, from console computer system 16) into transmitted Robot control commands to arm 4 on robot platform 5. The control tower 3 can also transmit status and feedback from the platform 5 back to the user console 2 . The communication link between robotic platform 5, user console 2 and control tower 3 may be via wired and/or wireless links, using any suitable data communication protocol of various data communication protocols. Any wired connections can optionally be built into the floor and/or walls or ceiling of the operating room. The robotic system 1 may provide video output to one or more displays, including displays in the operating room as well as remote displays accessible via the Internet or other network. The video output (video feed) can also be encrypted to ensure privacy, and all or part of the video output can be saved to a server or electronic healthcare record system.

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

3A and 3B are schematic diagrams illustrating an exemplary tool drive apparatus with and without a loaded tool, respectively, in accordance with aspects of the subject technology. As shown in FIGS. 3A and 3B , in one variation, the tool drive 210 may include an elongated base (or "tray") 310 having a longitudinal track 312 and a tool rack 320 slidably engaged with the longitudinal track 312 . The tray 310 may be configured to be coupled to the distal end of the robotic arm such that articulation of the robotic arm positions and/or orients the tool drive 210 in place. Additionally, 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 passing through the cannula 214, wherein the end effector 222 (not shown ) is disposed at the distal end.

Additionally, the tool holder 320 may actuate a set of articulations of the end effector, such as through a system of cables or wires that are manipulated and controlled by an actuation drive (the terms "cables" and "wires" may be used throughout this application. used interchangeably). Tool holder 320 may include different configurations with actuation drives. For example, the rotary shaft drive may comprise a motor with a hollow rotor and a planetary gear arranged at least partially within the hollow rotor. The plurality of rotary shaft drives may be arranged in any suitable manner. For example, tool rack 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 rack and increase the compact nature of the tool drives. As clearly shown in FIG. 3B , the rotary drive devices 322A, 322B, and 322C may be generally arranged in a first row, whereas the rotary drive devices 322D, 322E, and 322F may be generally arranged in a second row slightly longitudinally offset from the first row. .

4A and 4B are end effectors illustrating an exemplary gripper having a robotic wrist, a pair of opposing jaws, and a gripper for holding the robotic wrist in accordance with aspects of the subject technology. and the pair of jaws are coupled to the pulley and cable system of the actuator of the tool drive. It should be noted that although the following tool model and controller design are described with reference to an exemplary surgical robotic gripper, the proposed control system for position and gripping force control can be adapted to include Any tool with an end effector that allows multi-axis movement of the end effector (eg, pitch and yaw). Similar tools include, but are not limited to, graspers, grippers, 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 is 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 to or integrally formed with a pulley 415A and 415B, respectively, via an extension shaft 412 such that both jaws are rotatable about axis 410 . Pulleys 425A, 425B, 425C, and 425D are coupled to extension shaft 422 and rotate about axis 420 . The 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 is coupled to a third extension shaft 432 and rotates about an axis 430 that is parallel to axis 420 .

Gripper 220 can 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 be opened and closed relative to each other. Jaws 401A and 401B may also be actuated to rotate together as a pair to provide deflection motion of gripper 220 . Additionally, first yoke 402 , pulleys 415A and 415B, and jaws 401A and 401B are rotatable about axis 420 to provide pitching motion of gripper 220 . Movement of the robot wrist and/or the tool's jaws can be actuated by controlling four separate cables 405A-405D. As shown in FIG. 4A , cable 405A may start (or terminate) on one side of pulley 415A and be routed along pulleys 425A and 435A, and cable 405B may be configured to terminate on the other side of pulley 415A and pass through pulleys 425B and 435A. 435B wiring. Similarly, another pair of cables 405C and 405D may 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 such a way that the cables 405A-405D are kept attached to the second set of pulleys 425A-425D and the cables are prevented from slipping or sliding relative to the pulleys 425A-425D.

As shown in FIGS. 4A and 4B , gripper 220 can be actuated to move jaws 401A and 401B in various ways, such as by imparting motion to one of pulleys 425A, 415B, 415A, 425B, 425C, and 425D. or more so as to thereby impart motion to the first yoke 402 and/or one or both of the jaws 401A and 401B for gripping (e.g., the jaws independently rotate about axis 410), deflection (e.g., the jaws about axis 410) and pitch (eg, the jaws rotate about axis 420). The cables 405A-405D may be grouped into two opposing pairs, ie when one cable of the opposing pair 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 opposing pair for moving jaw 401A, and cables 405C and 405D are a second opposing pair for controlling jaw 401B. Jaw 401A closes (moves toward opposing jaw 401B) when cable 405A is tensioned (eg, by at least one of rotational drive devices 322a-322f) and cable 405B is loosened. On the other hand, when the cable 405B is tensioned and the cable 405A is released, the jaw 401A opens (moves away from the 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 loosens. As another example, the clamping force between jaw 401A and jaw 401B can be achieved by continuing to tension cable 405A and cable 405C (while loosening cable 405B and cable 405D) after the jaws are closed (in contact with each other). )to fulfill.

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

4B is a schematic diagram illustrating exemplary angle definitions for various movements of gripper 220 in accordance with aspects of the subject technology. The angles are defined with reference to the axes 410 and 420 and the axis 452 of the first yoke 402 and the axis 453 of the second yoke 403 . For example, as shown in FIG. 4B , the angle (θ ₁ ) between axis 452 and axis 453 may represent the angle of rotation of yoke 402 about axis 420 , which may also be defined as the pitch angle of gripper 220 (θ _pitch ) (whereas in FIG. 4A the axis 452 of the yoke 402 is superimposed on the axis 453 of the yoke 403 because the jaws stay in the reference position, ie there is no pitching motion). Furthermore, angles (θ ₂ ) and (θ ₃ ) may represent the angles between each of jaws 401A and 401B, respectively, and axis 452 of yoke 402 (as the origin). In order to differentiate the sides of the axis 452, the angles (θ ₂ ) and (θ ₃ ) may take different signs. For example, as shown in Figure 4B, the angle (θ ₂ ) is negative and the angle (θ ₃ ) is positive.

To perform control tasks, it is often beneficial to define a consistent coordinate system for joint angles. For example, we can further define the jaw angle ( _θjaw ) as the angle between the two jaws 401A and 401B, and the deflection angle ( _θdeflection ) as the distance between the axis 452 and the line bisecting the jaw angle. angle. As described above, the pitch angle ( _θpitch ) may be defined as the angle (θ ₁ ) between the axis 452 and the axis 453 . therefore:

Described below are methods and systems for controlling the angular position and gripping force of a distal end effector of a robotic surgical instrument. An end effector may include a robotic wrist and a pair of opposing members (eg, jaws or jaws), each movable between an open position and a closed position, actuated by two opposing wires. A total of four wires can each be driven by an independent actuator or motor, as shown in FIGS. 3 and 4 . The control system may include a feedback loop involving position and velocity feedback from the actuator and force feedback measured on four wires to achieve the desired position and clamping force. In some implementations, the actuator controller can operate in a position plus feed-forward current mode. For example, a position controller in position mode can drive the distal end effector to a desired angular position in space based on position feedback, while in force mode, the grip force controller is based on four-wire load cell The measured clamping force provides additional feed-forward current to achieve the desired clamping force between opposing members.

5 is a block diagram illustrating a high-level control system for controlling surgical tools 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 on a feedback path between the output 568 and the controller 562 . Apparatus 564 may include tool actuators and end effectors (e.g., cables 405A-405D of rotary drives 322A-322F of FIG. 3B and wrist jaws of FIG. 4A; see also actuator unit in FIG. 10 510 and cables and wrist linkage 512). Controller 562 may include one or more processors configured by software instructions stored on memory to calculate movement of device 564 in response to input 560, which may indicate desired movement of the end effector of the surgical tool, such as shown in FIG. Desired _theta pitch, desired theta _yaw , and desired theta _jaw of the wrist jaw of 4B. Commands generated by the controller 562 can thus drive the tool actuators to facilitate the desired movement of the end effector. In one embodiment, the desired theta _pitch , theta _yaw , and theta _jaw may be generated by the UID 14 under the control of the teleoperator 9 of FIG. 1 . Outputs 568 such as position, velocity, cable tension, and clamping or opening force of the end effector can be directly measured or estimated by sensors and estimators 566 and fed back to controller 562 for closed loop control.

In one embodiment, the desired θ jaw, also referred to as the commanded θ _jaw , may be considered a position control _command in position mode when the desired jaw angle θ _jaw of the wrist jaw is greater than or equal to a threshold . This threshold is used to determine braking and may correspond to the angle at which both jaws come into contact with an object between them at exactly the same time. With no object to grasp, the threshold is zero degrees when the jaws start touching each other. In the position mode, the controller 562 may translate the desired theta _jaw and the desired theta _pitch and desired theta _yaw into corresponding actuator position commands to drive the wrist jaw to the desired position and orientation. When the desired theta _jaw is below a threshold, the wrist jaw operates in a force control mode, or simply force mode, and the desired jaw angle is translated into a desired grip force command. In addition to position commands, controller 562 may also generate current commands to achieve a 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 graspable by the jaws. The clamping force of the jaws may be estimated or measured by sensor and estimator 566 . The controller 562 can analyze the expected theta _jaw and the measured clamping force to determine if the jaws are closing in position mode and the measured clamping force exceeds a pre-specified maximum clamping force threshold. If so, the controller 562 may calculate a clamping force error to limit the measured clamping force to a pre-specified maximum clamping force threshold. For example, to determine whether the jaws are closing in the position mode, the controller 562 may first verify that the desired θ _jaw is greater than or equal to the braking threshold, and thus persists in the position mode for more than a pre-specified duration. Controller 562 may employ anti-shake techniques to verify that the desired theta _jaw has decreased for a pre-specified length of time. In one embodiment, if the desired _theta-jaw is sampled at a periodic frequency, the controller 562 may verify that the samples of the desired theta _-jaw have been reduced by a pre-specified number of samples.

In order to determine whether the measured clamping force exceeds a pre-specified maximum clamping force threshold, the controller 562 may also employ anti-vibration techniques. In one embodiment, the feedback control loop of the control system of FIG. 5 may operate with a loop cycle time. The clamping force counter may increment by one count for each control loop cycle during which the measured clamping force is less than the maximum clamping force threshold minus the margin. In one embodiment, the clamping force counter may stop incrementing after it reaches a maximum count. The clamping force counter may be reset when the measured clamping force is greater than the maximum clamping force threshold. When the measured gripping force is greater than the maximum gripping force minus the margin anywhere within the window, the debounce technology can declare that the measured gripping force exceeds the max gripping force threshold for a continuous span of loop cycles equal to the gripping force counter The number of whole windows.

As an example, assume that the measured clamping force is initially below the maximum clamping force threshold minus a margin, and that the clamping force counter is incrementing. The clamping force counter may be reset when the measured clamping force increases beyond a maximum clamping force threshold. The feedback control loop of controller 562 may attempt to vary the actuator position command to drive the wrist jaws so as to limit the measured clamping force to a 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. Assume that the measured clamping force drops below the maximum clamping force threshold minus the margin for only a few loop cycles, but then increases above this level again. The clamping force counter may be incremented to the number of loop cycles in which the measured clamping force is briefly below the maximum clamping force threshold minus the margin. As long as the measured clamping force remains above the maximum clamping force threshold minus a margin within a window spanning a number of loop cycles equal to the clamping force counter (e.g., the measured clamping force briefly drops below the maximum clamping force clamping force threshold minus the number of loop cycles of the margin), the feedback control loop can 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 force.

When the controller 562 determines that the jaws are closing in the position mode and the measured clamping force exceeds the maximum clamping force threshold, the controller may limit the measured clamping force to the maximum clamping force threshold. In one embodiment, the controller 562 may calculate a clamping force error that is the difference between the maximum clamping force threshold and the measured clamping force. A zero steady-state type controller, such as a proportional-plus-integral (PI) force controller, may be deployed to receive clamping force errors to maintain or limit the measured clamping force at a maximum clamping force threshold. The output of the PI force controller can 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 in the position mode at the desired position and orientation.

6A is a graph showing the commanded θ jaw 603, measured θ _jaw 605, commanded _clamping force of the wrist jaws when the measured clamping force 609 is unrestricted when the jaws are closing in position mode. 607 and the time plot of the measured clamping force 609. The threshold θ _jaw between position mode and force mode is set to zero such that when the command θ _jaw 603 is greater than or equal to zero degrees, the wrist jaw operates in position mode. When theta _jaw 603 is commanded to be less than zero degrees, the wrist jaw operates in force mode.

Figure 6A shows the wrist jaws operating in position mode from 20 seconds to 35 seconds and again from 44 seconds to 47 seconds. The measured theta _jaw 605 remains within a relatively narrow range even when the commanded theta _jaw 603 changes within position mode or within force mode, presumably because the jaws are gripping an object. During position mode, the commanded clamping force 607 as the desired clamping force may be set to a default value of zero N, since the wrist jaws do not operate in force mode. However, the measured clamping force 609 can be much greater. For example, from 26 seconds to 28 seconds and from 31 seconds to 35 seconds, when the jaws are closed in position mode or held in the closed position, the measured clamping force 609 exceeds 10N and can be as high as 15N because the measured The clamping force is not limited. In force mode (e.g., 35 seconds - 44 seconds and after 47 seconds), the clamping force controller can set the commanded clamping force 607 as a function of the commanded theta _jaw 603, and the feedback control loop can keep measuring up to The clamping force 609 is the same as the commanded clamping force 607.

6B is a graph illustrating the command θ _clamp of the wrist jaws when the control system limits 617 the measured clamping force to a pre-specified maximum threshold during jaw closure in position mode, in accordance with aspects of the subject technology. Time plot of _jaw 613, measured θ _jaw 615, commanded clamping force 617, and measured clamping force 619. The maximum clamping force threshold was set at 8.5N.

In FIG. 6B, the time plot of the commanded theta _jaw 613 and the measured _{theta jaw} 615 is compared to the commanded _{theta jaw} 603 and the measured theta _jaw of FIG. 6A when the measured clamping force is not limited. 605 is the same. During position mode, the commanded clamping force 617 is again set to a default value of zero N by the clamping force controller. However, when the jaws are closing or remaining in the closed position (for example, 27 seconds-30 seconds, 32 seconds-36 seconds, and 41 seconds-45 seconds), during the position mode, the clamping force 619 measured is determined by the clamp The holding force controller is limited to a maximum holding force threshold of 8.5N. Also, the limitation on the maximum clamping force in position mode has no effect on force mode. Thus, in force mode, the measured clamping force 619 may be allowed to exceed the maximum clamping force threshold of 8.5N by following the commanded clamping force 617 .

FIG. 7 is a flowchart illustrating a method 700 for feedback control of a surgical robotic system by analyzing desired jaw angles and measured gripping forces in a jaw-in-position mode in accordance with aspects of the subject technology. Limit the gripping force of the wrist jaws to a pre-specified maximum threshold during lower closure. Method 700 may be implemented by controller 562 of the control system of FIG. 5, which receives the desired θ _jaw from user input and the measured gripping force from sensor and estimator 566 to generate The actuator position command of .

In block 701, the method 700 determines whether the wrist jaw is in position mode. In one embodiment, block 701 may determine whether the desired theta _jaw is greater than or equal to a threshold between position mode and force mode theta _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 can be set to zero. If the wrist jaw is not in position mode, the wrist jaw is in force mode and the clamping force is not limited. In block 709 , method 700 generates actuator position commands without imposing constraints on the clamping force. In one embodiment, in addition to generating actuator position commands, block 709 converts the desired theta _jaw into desired clamping force commands to achieve the desired clamping force.

If the jaws are in position mode, block 703 determines whether the jaws are closing. In one embodiment, block 703 may employ anti-shake techniques to determine whether the expected theta _jaw has decreased for a pre-specified duration or for a pre-specified number of samples. In one embodiment, the jaws may be considered closing if it is desired that the theta _jaws remain at rest without increasing. If the jaws are not closing, the clamping force is not limited even in position mode. Method 700 defaults to block 709 to generate actuator position commands without imposing constraints 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 the maximum clamping force threshold minus a margin spanning anywhere within a window equal to the number of samples of the clamping force counter. In one embodiment, the measured clamping force may be sampled at the loop cycle time of the feedback control system of FIG. 5 . The clamping force counter may be incremented by one for each control loop cycle during which the measured clamping force is less than the maximum clamping force threshold minus the margin. The clamping force counter may be reset when the measured clamping force is greater than the maximum clamping force threshold. The measured grip force is considered to exceed the max grip force threshold for the entire window as long as the measured grip force exceeds the max grip force threshold minus a margin spanning anywhere within a window equal to the number of samples of the grip force counter . Otherwise, the measured clamping force does not exceed the maximum clamping force threshold, and method 700 defaults to block 709 to generate actuator position commands without imposing constraints on the clamping force.

If the measured clamping force exceeds the maximum clamping force threshold while the jaws are closing in 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 clamping force error, which is the difference between the maximum clamping force threshold and the measured clamping force. A zero steady state type controller, such as a proportional-plus-integral (PI) force controller, can receive the clamping force error to generate a compensated clamping force command. The output of the PI force controller can 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 may be added to the 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, when operating in the position mode, the controller 562 can maintain a minimum jaw opening force through the wrist jaws. The minimum jaw opening force may also be referred to as the minimum clamping force. Maintaining a minimum jaw opening force when the jaws are open in position 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 sensor and estimator 566 . The controller 562 can analyze the desired theta _jaw , the estimated theta _jaw , and the measured opening force to determine whether the jaws are opening in position mode, the jaw angle error between the desired theta _jaw and the estimated theta _jaw is greater than a threshold and the measured opening force is below a pre-specified minimum jaw opening force threshold. If so, the controller 562 may calculate an opening force error between a prespecified minimum jaw opening force threshold and the measured opening force to maintain the measured opening force above the prespecified minimum jaw opening force threshold .

In one embodiment, to determine whether the jaws are opening in the position mode, the controller 562 may first verify that the desired theta _jaw is greater than or equal to the braking threshold, and thus continues in the position mode for more than a pre-specified duration. The controller 562 may then determine whether the jaws opened in the position mode meet the resistance preventing the jaws from opening to the desired θ _jaw . In one embodiment, the controller 562 may employ an anti-shake technique to verify that the expected theta _jaw is greater than the estimated theta _jaw , and that the theta _jaw error, which is the difference between the expected and estimated _{theta jaws ,} is greater than theta _{The jaw} error threshold persists for a pre-specified length of time. In one embodiment, if the theta _jaw and estimated theta _jaw are expected to be sampled at a periodic frequency, the controller 562 may verify that theta _jaw error is greater than theta _jaw error threshold for a pre-specified number of samples.

In order to determine whether the measured opening force is below a pre-specified minimum jaw opening force threshold, the controller 562 may also employ anti-shake techniques. The jaw opening force counter may increment by 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 the minimum jaw opening force threshold. When the measured opening force is less than the minimum clamp opening force threshold plus a margin anywhere within the window, anti-bounce technology may declare that the measured opening force is less than the minimum clamp opening force threshold for a period of time across a loop cycle equal to the clamp opening force counter Quantity of the entire window.

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 incrementing. The jaw opening force counter may be reset when the measured opening force drops below a minimum jaw opening force threshold. The feedback control loop of controller 562 may attempt to vary the actuator position command to drive the wrist jaws so as 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 Force threshold so that a minimum jaw opening force is maintained. Suppose the measured opening force rises above the minimum jaw opening force threshold plus margin for only a few loop cycles, but then drops below this level again. The jaw opening force counter may increment to the number of loop cycles for which the measured opening force is briefly 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 spanning a window equal to the number of loop cycles of the jaw opening force counter (e.g., the measured opening force is briefly above the minimum jaw opening force opening force threshold plus a margin for the number of loop cycles), 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 opening in position mode, the theta _jaw error is greater than the theta _jaw error threshold, and the measured opening force is below a pre-specified minimum jaw opening force threshold, the controller may hold the measured The opening force is above the minimum jaw opening force threshold. In one embodiment, the controller 562 may calculate the jaw opening force error as the difference between the minimum jaw opening force threshold and the measured opening force. A zero steady-state type controller, such as a proportional-plus-integral (PI) force controller, can be deployed to accept the jaw opening force error, thereby maintaining the measured opening force at or above the minimum jaw opening force threshold Turn on the force threshold. The output of the PI force controller can 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 maintain a minimum amount of opening force when the jaws are opening at the desired position and orientation in position mode.

8A is a graph showing commanded theta jaw 803, measured theta _jaw 805, commanded grip of wrist jaws when the measured opening force does not remain above a minimum level while the _jaws are opening in position mode. Time graph of force 807 and measured opening force 809. The threshold θ jaw between position mode and force mode is set to zero such that when the command θ jaw 603 is greater than or equal to zero degrees, the wrist jaw operates in position mode. When theta _jaw 603 is commanded to be less than zero degrees, the wrist jaw operates in force mode. The theta _jaw error threshold was set at 5 degrees, and the minimum opening force threshold was set at 4.4N.

Figure 8A shows the wrist jaws operating in position mode from 49 seconds to 60 seconds and from 62 seconds to 67 seconds. The measured theta _jaw 805 remains within a relatively narrow range even when theta _jaw 803 is commanded to configure the jaws to close or open within the position mode, presumably because the jaws open in the position mode are _{Theta jaws} 803 encounter resistance or are restricted fully open to command theta. From 49s-52s, 56s-59s, and 62s-66s, when the jaws are opening in position mode or held at the same theta _jaw , theta _jaw error (larger commanded theta _jaw 803 with Smaller measured differences between theta _jaws 805) may be greater than the 5 degree theta _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, the commanded clamping force 807 is still set to zero N. Positive values of the measured opening force 809 correspond to the opening force of the jaws in position mode, while negative values correspond to the clamping force in force mode when the jaws are closed. The measured opening force 809 in position mode generally follows the profile of the commanded theta _jaw 803 as the jaw is constrained from open to the commanded theta _jaw 803 . As a result, the measured opening force 809 is stronger when theta _jaw 803 is commanded to increase to open the jaw wider, and conversely, when theta _jaw 803 is commanded to decrease to open the jaw more narrowly, The measured opening force 809 is weaker. Because the feedback control loop is not enabled to keep 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.

8B is a diagram illustrating wrist jaw commands when the control system maintains a measured opening force 819 above a pre-specified minimum opening force threshold during opening of the jaws in position mode 817 in accordance with aspects of the subject technology. Time plot of theta _jaw 813 , measured theta _jaw 815 , commanded clamping force 817 and measured opening force 819 . The theta _jaw error threshold was again set to 5 degrees, and the minimum opening force threshold was set to 4.4N.

In FIG. 8B, when the minimum jaw opening force is not maintained, the time plots of the commanded theta _jaw 813 and the measured theta _jaw 815 are approximately the same as the commanded _theta jaw 803 and measured theta _jaw 805 of FIG. 8A. same. During position mode, the commanded clamping force 817 is again set to a default value of zero N by the clamping force controller. However, when the theta _jaw error (the difference between the larger commanded _{theta jaw} 813 and the smaller measured theta _jaw 815) is greater than the 5 degree theta _jaw error threshold, between 30 seconds - 43 seconds During the interposition mode, the measured opening force 819 is maintained at or above the minimum opening force threshold of 4.4N by the feedback control loop and clamping force controller. In particular, a minimum measured opening force 819 is maintained when the jaws are opening, maintaining the same theta _jaw , or even closing in position mode. Note that the minimum opening force threshold in position mode has no effect on force mode while the measured opening force 819 may be negative.

9 is a flowchart illustrating a method 900 for feedback control of a surgical robotic system by analyzing desired jaw angles, estimated jaw angles, and measured opening forces in accordance with aspects of the subject technology. Maintains wrist jaw opening force above a pre-specified minimum jaw opening force threshold during jaw opening in position mode. _Method 900 _can be implemented by controller 562 of the control system of FIG. to generate actuator position commands for driving the wrist jaw.

In block 901, the method 900 determines whether the wrist jaw is in position mode. In one embodiment, block 901 may determine whether the desired theta _jaw is greater than or equal to a threshold between position mode and force mode theta _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 can be set to zero. If the wrist jaw is not in position mode, the wrist jaw is in force mode and the minimum opening force is not enabled. In block 909 , method 900 generates actuator position commands without maintaining a minimum opening force. In one embodiment, in addition to generating actuator position commands, block 909 converts desired theta _jaws into desired clamping force commands to achieve the desired clamping force or opening force.

If the jaws are in position mode, block 903 is determined by determining whether theta _jaw error (which is the difference between the desired theta _jaw and the estimated or measured theta _jaw ) is greater than or equal to theta _jaw error threshold Whether the jaws are prevented from opening to the desired theta _jaw . In one embodiment, block 903 may employ anti-shake techniques to determine whether the expected theta _jaw is greater than the estimated theta _jaw , and whether the _{theta jaw} error is greater than or equal to theta _jaw error threshold for a pre-specified length of time. In one embodiment, block 903 may detect that the jaws are opening, maintaining a static _{theta jaw} , or closing by determining that the desired theta jaw is increasing, remaining the same, or _decreasing , respectively. If the theta _jaw error is less than the theta _jaw error threshold, method 900 defaults to block 909 to generate an actuator position command without maintaining a minimum opening force.

If the theta _jaw error is greater than or equal to the theta _jaw error threshold when the jaws are in position mode, 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 debounce techniques to determine that the measured opening force is less than the minimum jaw opening force threshold plus a margin anywhere within a window equal to the number of samples of 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 the measured 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 the minimum jaw opening force threshold. A measured opening force is considered to be below the minimum jaw opening force threshold for as long as it is less than the minimum jaw opening force threshold plus a margin spanning anywhere within a window equal to the number of samples of the jaw opening force counter. entire window. Otherwise, the measured opening force is greater than or equal to the minimum jaw opening force threshold, and method 900 defaults to block 909 to generate an actuator position command without maintaining the minimum opening force.

If the measured opening force while the jaw is in position mode is less than the minimum jaw opening force threshold and the theta _jaw error is greater than or equal to the theta _jaw error threshold, block 907 generates a compensating actuator position command to maintain the measured opening The force is above the minimum jaw opening force threshold. In one embodiment, block 907 may calculate a jaw opening force error as the difference between the minimum jaw opening force threshold and the measured opening force. A zero steady-state type controller, such as a proportional-plus-integral (PI) force controller, can be deployed to accept the jaw opening force error, thereby maintaining the measured opening force at or above the minimum jaw opening force threshold Turn on the force threshold. The output of the PI force controller can 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 maintain a minimum amount of opening force when the jaws are opening in position mode.

In another aspect, the controller 562 can adjust the commanded clamping force to smooth the clamping force applied when the wrist jaw transitions between the position mode and the force mode. Smoothing the clamping force applied during mode transitions minimizes undesired abrupt changes in clamping force caused by changes in position and commanded clamping force of the jaws as the jaws traverse the gap between the two modes. In succession, this variation may cause the jaws to accidentally drop the grasped object. During position mode, theta _jaw is expected to be greater than or equal to the braking threshold. The position controller may translate the desired theta _jaw and desired theta _pitch and desired theta _yaw into corresponding actuator position commands to drive the wrist jaw to the desired position and orientation. During force mode, when the desired theta _jaw is below the braking threshold, for example when the desired theta _jaw is negative for braking set at zero degrees, the clamping force controller can be enabled to interpret the desired theta _jaw as is the clamping force command and can convert the desired _{theta jaw} into a compensation current that can be added to the current for the existing position command to drive the wrist jaws to achieve the commanded clamping force.

In one embodiment, in order to smooth the clamping force applied during mode transitions, the feedback control system may employ anti-shock techniques when the brakes are set to zero degrees. When the theta _jaw is expected to oscillate around positive and negative values, the anti-shake technique prevents the clamping force controller from being repeatedly enabled and disabled to generate oscillations in the commanded clamping force.

In one embodiment, a feedback control system can minimize sudden changes in grip force when the wrist jaw transitions from position mode to force mode by analyzing desired theta _jaw , commanded grip force, and measured grip force change. The feedback control system can determine whether the commanded clamping force is increasing due to the clamping force controller being activated as indicated by the desired θ _jaw decrease below the braking threshold, and the measured clamping force is related to the commanded clamping force Whether the error between the holding forces is greater than the pre-specified maximum force error. If so, the feedback control system may set the commanded clamping force to the measured clamping force minus a pre-specified margin when the wrist jaw transitions from position mode to force mode.

In one embodiment, a feedback control system can minimize sudden changes in grip force when the wrist jaw transitions from force mode to position mode by analyzing desired theta _jaw , commanded grip force, and measured grip force change. The feedback 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 disabled due to clamping force control as indicated by the desired θ _jaw increase above the braking threshold and whether the absolute value of the error between the measured clamping force and the minimum clamping force is less than the pre-specified maximum clamping force error value. If so, the feedback control system may set the commanded clamping force to a pre-specified minimum clamping force value when the wrist jaw transitions from force mode to position mode.

10 is a block diagram of an example control system 1000 for use when an end effector of a robotic surgical tool is in a position mode or a force mode, or when the end effector is in a position mode, in accordance with aspects of the subject technology. Controls the position and clamping force of the end effector when transitioning between position mode and force mode. In one embodiment, the end effector includes wrist jaws. 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, one or more actuator units 510 and/or cables and wrist linkages. 512 , slack controller 514 , position estimator 522 and clamping force estimator 524 .

The input processing unit 502 and actuator command generator 504 receive the desired angular position of the wrist jaw and convert the desired angular position into a corresponding actuator position command (via an inverse kinematics algorithm), which is determined by Output to position controller 506 and/or grip force controller 508 . For example, inputting desired angular positions may include desired theta _jaw , desired theta _pitch , and desired theta _yaw . When the desired theta _jaw is greater than or equal to the braking threshold, the desired theta _jaw may be considered a position command. When the desired θ _jaw is less than the braking threshold, the desired θ _jaw can be converted into a desired clamping force command (e.g., commanded clamping force) by clamping force controller 508, which can generate a current command to achieve Expected gripping force.

Position controller 506 may receive position feedback from position and/or velocity sensors on actuator unit 510 . Due to the kinematic relationship between the actuator and the wrist jaw, achieving a desired actuator position may in turn result in a desired position of the wrist jaw. Since the actuator unit 510 is coupled to the robot wrist by an elastic cable (or wire) that can change length under force, it is only based on the difference between the actuator position and the wrist movement. The estimation of the purely kinematic relationship may not be accurate. By accounting for cable elasticity in the estimation algorithm (e.g., using a Kalman filter), position estimator 522 can provide actuator command generator 504 and grip force estimator 524 with a more accurate estimate of wrist joint position and velocity. estimate. The estimated position and velocity information can then be used for precise positioning of the wrist and estimation of friction forces.

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

Slack controller 514 may perform the task of ensuring that the tension on the cable never drops below zero (or a predetermined positive value to compensate for slack). The cable is the tension-only 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 accomplish this goal, slack controller 514 may monitor force values from 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 drops below a threshold, the slack controller 514 may 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 mode transitions, the input processing unit 502 may employ anti-shake techniques when the brakes are set to zero degrees. The anti-shake technique may determine whether the desired _{theta jaw} is less than the braking threshold for a pre-specified minimum duration before enabling the grip force controller 508 to transition the wrist jaw from position mode to force mode. When transitioning from force mode to position mode, the input processing unit 502 may disable the clamp controller 508 whenever the desired θ _jaw is greater than or equal to the braking threshold. Therefore, anti-shake technology can be one-sided. The anti-shake technique prevents the clamping force controller 508 from being repeatedly enabled and disabled, a condition that may cause the commanded clamping force to oscillate when the theta _jaw is expected to oscillate near the brake.

11A is a graph showing the commanded theta _jaw 1103, measured theta _jaw 1105, commanded grip of the wrist jaw when the commanded theta _jaw 1103 is set near a threshold without the anti-shake algorithm. Time plot of force 1107 , measured clamping force 1109 , and current command 1106 from a clamping force controller (eg, clamping force controller 508 of FIG. 10 ). The braking threshold is set to zero such that when the commanded _{theta jaw} 1103 is greater than or equal to zero degrees, the wrist jaw operates in position mode. When theta _jaw 1103 is commanded to be less than zero degrees, the wrist jaw operates in force mode. Positive clamping force indicates clamping force in force mode, and negative clamping force indicates clamping force in position mode.

FIG. 11A shows that between times 11.6 seconds and 12 seconds, the wrist jaw was operating in position mode. After time 12 seconds, the command θ _jaw 1103 is set near the brake threshold since the user input device (UID) is set at brake. The measured theta _jaw 1105 remains above about 20 degrees, presumably because the jaw is gripping the object. Gripping force controller 508 is repeatedly enabled and disabled as the wrist jaws transition between position mode and force mode, thereby causing The clamping force 1107 commanded by the device 508 and the current command 1106 oscillate. The result is an undesirably large swing in the measured clamping force 1109 observed between times 12 seconds and 12.4 seconds. The measured theta _jaw 1105 also exhibits some undesired oscillations due to the measured oscillation of the clamping force 1109 .

FIG. 11B is a diagram illustrating the control system (e.g., input processing unit 502 and actuator command generator 504 of FIG. 10 ) employed when setting command θ _jaw 1113 near a threshold in accordance with aspects of the subject technology. During the anti-shake algorithm, the command θ _jaw 1113 of the wrist jaw, the measured θ _jaw 1115, the command clamping force 1117, the measured clamping force 1119 and the current command 1116 from the clamping force controller 508 time graph. The braking threshold is set to zero again. Between times 30.2 seconds and 30.9 seconds, the wrist jaw operates in position mode. After time 30.9 seconds, the commanded theta _jaw 1113 is set near the braking threshold.

The anti-shake algorithm enables the grip force controller 508 to transition the wrist jaw from position mode to force mode only when theta _jaw is expected to be less than zero degrees for a pre-specified minimum duration. Because the control system does not detect this condition, the wrist jaw remains in position mode and the grip force controller 508 is not enabled. As a result, the commanded clamping force 1117 remains at a default value of ON, and the current command 1116 from the clamping force controller 508 also remains at zero. The measured clamping force 1119 did not exhibit large oscillations, and the measured theta _jaw 1115 did not exhibit the oscillations observed in FIG. is shown as positive even though the wrist jaw remains in position mode).

Smooth application of clamping force may also become important when the wrist jaws are grasping objects as they transition between position and force modes. For example, during position mode, even if the grip force controller 508 is not enabled, there may be a non-zero measured grip force if the wrist jaws are gripping an object. The clamping force controller 508 may initially command the clamping force from ON drive when it is desired that theta _jaw drops below the detent threshold, indicating a transition from position mode to force mode. Similarly, when transitioning from force mode to position mode, when clamping force controller 508 is disabled, the commanded clamping force may be reset to the default value ON output from position controller 506 . As a result, there may be sudden changes in the gripping force measured during the transition, which may cause the wrist jaws to drop objects.

12A is a graph showing the command θ _jaw 1203, measured to the wrist jaw, when the control system does not attempt to limit the variation in the measured clamping force 1209 as the jaw transitions from position mode to force mode and back to position mode. Time graph of theta _jaw 1205, commanded clamping force 1207, and measured clamping force 1209. The braking threshold is again set to 0 such that when the commanded theta _jaw 1203 is greater than or equal to 0 degrees, the wrist jaw operates in position mode. When theta _jaw 1203 is commanded to be less than 0 degrees, the wrist jaw operates in force mode.

The wrist jaw initially operates in position mode. Command theta _jaw 1203 initially to 0 degrees and command clamping force 1207 to initially ON. The measured theta _jaws 1205 were 25 degrees and the measured clamping force 1209 was 8N due to grasping the object between the jaws. At time 27.5 seconds, command theta _jaw 1203 to go negative to transition the wrist jaw from position mode to force mode. When the clamping force controller 508 is enabled, the commanded clamping force 1207 is ramped from ON until the commanded theta _jaw 1203 reaches its most negative value. However, the measured clamping force 1209 experiences a sudden drop of 5N during the transition before ramping up as commanded. At time 30 seconds, command theta _jaw 1203 begins to go to a less negative value. The commanded clamping force 1207 starts ramping down, and the measured clamping force 1209 follows as commanded. At time 31 seconds, theta _jaw 1203 is commanded to go positive to transition the wrist jaw from force mode back to position mode. When the clamping force controller 508 is disabled, the measured clamping force 1209 experiences a sudden jump with some overshoot from ON to rest 8N of the position mode. It is desirable to minimize sudden changes in the clamping force 1209 measured during the transition.

In one embodiment, the grip force controller 508 may adjust the commanded grip force in order to minimize sudden changes in the grip force of the wrist jaws when gripping an object during the transition from position mode to force mode. For example, when the clamping force controller 508 is enabled when the commanded θ _jaw becomes less than the braking threshold and if certain conditions are met, the clamping force controller 508 may set the commanded clamping force to the currently measured clamping force holding force minus a pre-specified margin. Doing so prevents the measured clamping force from dropping to a value close to 0 N during the transition, thereby reducing the likelihood that the jaws will drop an object grasped between them. In one embodiment, the measured clamping force may be generated by the clamping force estimator 524 based on measured tension values 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 decreased by the clamping force controller 508 below the command θ of the braking threshold. _Jaws are enabled to increase as indicated. For the second condition, the clamping force controller 508 may determine whether the error between the measured clamping force and the commanded clamping force is greater than a pre-specified maximum force error. In one embodiment, clamp force controller 528 may use anti-shake techniques for one or both of these conditions. If these two conditions are met, the clamping force controller 508 may set the commanded clamping force as the currently measured clamping force minus a pre-specified margin.

In one embodiment, the grip force controller 508 may adjust the commanded grip force in order to minimize sudden changes in the grip force of the wrist jaws when gripping an object during the transition from force mode to position mode. For example, when the clamping force controller 508 is disabled when the commanded θ _jaw becomes greater than the braking threshold and if certain conditions are met, the clamping force controller 508 may set the commanded clamping force to a pre-specified minimum clamping force holding force value. Doing this instead of starting from the position mode's default ON reduces the change in measured clamping force going up to the position mode's static clamping force.

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

12B is a graph illustrating the command θ _clamp of the wrist jaws as the control system limits the variation of the measured clamping force 1219 as the jaws transition between position mode and force mode, in accordance with aspects of the subject technology. Time plot of _mouth 1213, measured _{theta jaw} 1215, commanded clamping force 1217, and measured clamping force 1219. The braking threshold is again set to 0 so that when the commanded theta _jaw 1213 is greater than or equal to 0 degrees, the wrist jaw operates in position mode. When theta _jaw 1213 is commanded to be less than 0 degrees, the wrist jaw operates in force mode. A pre-specified maximum clamping force error value within which the absolute value of the error between the measured clamping force and the commanded clamping force does not exceed is set to be larger than 8N. The pre-specified minimum clamping force value was set at 3N.

The wrist jaws are initially operated in position mode, and the initial state of the commanded _{theta jaw} 1213, measured theta _jaw 1215, commanded clamping force 1217, and measured clamping force 1219 is the same as in Figure 12A. At time 37.4 seconds, command theta _jaw 1203 to go negative to transition the wrist jaw from position mode to force mode. However, the commanded clamping force 1217 is obtained by subtracting a pre-specified margin from the measured clamping force 1219 at that time rather than ON in the force mode from approximately 6.2N. The condition for adjusting the commanded clamping force 1217 is met because the absolute value of the error between the measured clamping force 1219 and the commanded clamping force 1217 is less than the prespecified maximum force error. As a result, during the transition from the position mode to the force mode, the measured clamping force 1219 experiences a significantly smaller drop than without the adjustment to the commanded clamping force 1217 . The commanded clamping force 1217 remains at 6.2N until the commanded clamping force 1217 determined by the negative command θ _jaw 1213 becomes greater than 6.2N.

At time 39.8 seconds, command theta _jaw 1213 begins to go to a less negative value. The commanded clamping force 1217 starts ramping down, and the measured clamping force 1219 follows as commanded. At time 40.5 seconds, the commanded grip force 1217 is maintained at the pre-specified minimum grip force value of 3N, rather than continuing to ramp down to ON, where the commanded theta _jaw 1213 would otherwise go positive to move the wrist jaw from This happens without adjustment when changing from force mode to position mode. Because the measured clamping force 1219 is less than the prespecified minimum clamping force value of 3N, and the absolute value of the error between the measured clamping force 1219 and the commanded clamping force 1217 is less than the prespecified maximum force error, the Conditions for adjusting the commanded clamping force 1217. The result is that when the measured clamping force 1219 jumps to the rest 8N of the position mode during the transition, the measured clamping force 1219 experiences significantly less variation than it would without the adjustment to the commanded clamping force 1217 . The commanded clamping force 1217 remains at 3N until the commanded clamping force 1217 determined by the commanded θ _jaw 1213 becomes ON.

13 is a flowchart illustrating a method 1300 for feedback control of a surgical robotic system when setting a desired theta _jaw of the wrist jaw near a braking threshold in accordance with aspects of the subject technology An anti-shake algorithm is employed, or used to limit the change in the measured gripping force when the wrist jaw transitions between position mode and force mode. Method 1300 may be implemented by controller 562 of the control system of FIG. 5 or clamping force controller 508 of the control _system of FIG. 5 or the measured gripping force of the sensor and estimator 566 of FIG. 10 or the gripping force estimator 524 of FIG. 10 to generate a commanded gripping force for driving the wrist jaws.

Beginning with the position pattern in block 1301 , the method 1300 determines in block 1303 whether the desired theta _jaw is 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 repeatedly enabling and disabling the force mode, a condition that may cause oscillations in the commanded clamping force when the desired theta _jaw is set near the braking threshold. In one embodiment, block 1303 may determine whether the commanded clamping force is or is about to increase as indicated by a decrease in the desired θ _jaw below the brake threshold. If the desired theta _jaw is not less than the braking threshold for a pre-specified minimum duration, the wrist jaw remains in the position mode of block 1301 .

Otherwise, if the desired theta _jaw is less than the braking threshold for a prespecified minimum duration, the wrist jaw is transitioning from position mode to 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 transition from the desired theta _jaw and does not adjust the commanded clamping force 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 clamping force and the commanded clamping 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 0N by default. The measured gripping force may differ from the commanded gripping force prior to the mode transition because the wrist jaws may be gripping the object. In one embodiment, the maximum force error may be pre-specified or may be configurable.

If the condition in block 1305 is true, then block 1309 sets the commanded clamping force to the measured clamping 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 transition from the desired θ _jaw and does not adjust the commanded clamping force to limit the change in measured clamping force during the mode transition .

When the wrist jaw is in force mode at block 1311 , method 1300 determines whether the desired theta _jaw is greater than or equal to a brake threshold at block 1313 . In one embodiment, block 1311 may determine whether the commanded clamping force is decreasing as indicated by an increase in the desired theta _jaw toward the braking threshold, and the desired theta _jaw is just below the braking threshold. If the desired θ _jaw is not greater than or equal to the braking threshold, the wrist jaw remains in the force mode of block 1311 .

Otherwise, if the desired θ _jaw is greater than or equal to the braking threshold, the wrist jaw is transitioning from force mode to position mode. Block 1315 determines whether the commanded clamping force is decreasing and 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 transition from the desired θ _jaw and does not adjust the commanded clamping force The force thereby limits the variation of the 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 or different than the maximum force error in block 1305 for the position-to-force mode transition.

If the condition in block 1317 is true, then block 1319 sets the commanded clamping force to the minimum clamping force when 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 transition from the desired θ _jaw and does not adjust the commanded clamping force to limit the change in measured clamping force during the mode transition .

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; thus, this figure is provided by way of example and not as a limitation of system architecture.

Interface device 50 includes camera 51 , sensor 52 , display 53 , user command interface 54 , processor 55 , memory 56 and network interface 57 . Camera 51 and sensor 52 may be configured to capture color image and depth image information of the surgical robotic system. Images captured by camera 51 and sensor 52 may be projected on 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 used by processor 55, an operating system, program code and other data storage. The interface device 50 can be used to generate the desired theta _pitch , theta _yaw , and theta _jaw of the wrist jaw under the control of the teleoperator.

User command interface 54 may include interfaces for other features such as web portals. Hardware components can 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 can be a wireless or a wired interface.

The control tower 70 may be a mobile point-of-care cart housing a touch screen display, a computer to control the surgeon's robotically assisted manipulation of instruments, a security system, a graphical user interface (GUI), light sources, and video and graphics computers. 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 system that couples the control tower 70 to both the interface device 50 and the surgical robot 80. The network interface 78 of the user. The control tower 70 may also house third party equipment such as an advanced light engine 72 , an electrosurgical generator unit (ESU) 74 , and an insufflator and CO2 tank 75 . The control tower 70 may provide additional functionality for user convenience, such as a nurse display touch screen, soft power and E-hold buttons, user-facing USB for video and still images, and electronic caster control interfaces. The secondary computer can also run real-time Linux, providing logging/monitoring and interaction with cloud-based web services. The central computer 71 of the control tower 70 can receive the desired theta pitch, theta _yaw , and theta _jaw of the wrist jaw generated by the interface device 50 to implement the methods described herein for controlling the clamping or opening _force of the jaws .

Surgical robot 80 includes an articulating operating table 84 having a plurality of integrated arms 82 that are positionable over a target patient anatomy. A set of compatible tools 83 can be attached to/detached from the distal end of the arm 82, enabling the surgeon to perform various surgical procedures. Surgical robot 80 may also include a control interface 85 for manually controlling arm 82 , operating table 84 and tools 83 . Control interface 85 may include items such as, but not limited to, remote controls, buttons, panels, and touch screens. Other accessories such as trocars (cannula, sealing cartridge, and obturator) and drapes can also be manipulated to perform procedures using the system. In one embodiment, the plurality of arms 82 may include four arms mounted on both sides of the operating table 84, with two arms on each side. For a particular surgical procedure, an arm mounted on one side of the table 84 can be positioned on the other side of the table 84 by stretching and crossing under the table 84 and the arms mounted on the other side, thereby A total of three arms are positioned on the same side of the operating table 84 . The surgical tool may also include a 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. It will be apparent, however, to one skilled in the art that the specific details are not required 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 form 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 thus enable others skilled in the art to best utilize the invention with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.

The methods, devices, processes, and logic described above can be implemented in many different ways and in many different combinations of hardware and software. Controllers and estimators may include electronic circuits. For example, all or part of an embodiment may be a circuit comprising an instruction processor, such as a central processing unit (CPU), a microcontroller or a 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. As an example, the circuitry may comprise discrete interconnected hardware components and/or may be combined on a single integrated circuit die, distributed among multiple integrated circuit dies, or multiple integrated circuit dies in a common package implemented in a multi-chip module (MCM).

The circuitry may also include or access instructions for execution by the circuitry. The instructions may be stored in tangible storage media other than transient signals, such as flash memory, random access memory (RAM), read only memory (ROM), erasable programmable read only memory (EPROM); or in 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. A product, such as a computer program product, may include a storage medium and instructions stored in or on the medium and which, when executed by circuitry in a device, cause the device to implement any of the functions described above or shown in the accompanying drawings. deal with.

These embodiments may be distributed as circuitry among multiple system components, such as among multiple processors and memories, optionally including multiple distributed processing systems. Parameters, databases, and other data structures can be stored and managed separately, combined into a single memory or database, organized logically and physically in many different ways, and implemented in many different ways , including as data structures such as linked lists, hash tables, arrays, records, objects, or implicit storage mechanisms. A program may be part of a single program (e.g., a subroutine), a stand-alone program, distributed across multiple memories and processors, or implemented in a variety of different ways, such as in a library, such as a shared library (e.g., a dynamic link library (DLL)). For example, the DLL may store instructions to perform any of the processes described above or shown in the Figures when executed by a circuit.

Additionally, the various controllers discussed herein may employ, for example, processing circuitry, microprocessors or processors, and computer-readable media storing computer-readable program code (e.g., firmware) executable by the (micro)processor, logic gates, In the form of circuits, 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. Additionally, some components shown as internal to the controller may also be stored external to the controller, and other components may be used.

Claims (60)

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

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

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;

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 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:

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.

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

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

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:

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.

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

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

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;

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 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;

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

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

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

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

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

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;

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 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;

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.

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:

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 input jaw angle in the force mode.

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