Limiting grip force and maintaining minimum jaw opening force in position control mode, and controlling grip force when transitioning between position control mode and force mode

Abstract

Systems and methods are disclosed for limiting the grip force generated by closing robot wrist jaws while operating in a positional mode where the jaws are commanded to a desired jaw angle before being commanded to generate a grip force, systems and methods are disclosed for maintaining the opening force generated by robot wrist jaws operating in a positional mode where the jaws are commanded to a desired jaw angle before being commanded to generate a grip force, and systems and methods are disclosed for achieving a smooth transition in grip force when the wrist jaws transition between positional mode and force mode.

Description

Technical Field

[0001] The subject technology generally relates to robots and surgical systems, and more particularly to controlling the gripping or releasing force of a surgical tool, such as a wrist joint of a robotic-assisted surgical system.

Background Art

[0002] Minimally invasive surgery (MIS), such as laparoscopic surgery, uses techniques intended to reduce tissue damage during surgery. Laparoscopic procedures typically require making a number of small incisions in a patient, e.g., in the abdomen, and then inserting several surgical tools, such as an endoscope, scalpel, gripper, and needle, through these incisions into the patient. Gas is injected into the abdomen to aerate the abdomen, thereby providing more space around the tip of the tool and making it easier for the surgeon to view and manipulate the tissue at the surgical site (via the endoscope). MIS can also be performed using a robotic system, in which surgical tools are operably attached to the distal end of robotic arms, and a control system actuates the arms and their attached tools so that the latter mimics the movement of a user input device (UID) and tool-specific commands when the latter is being manually operated by a surgeon.

[0003] A surgical tool may include a robotic wrist that supports a pair of opposing jaws. The wrist and jaws may move in multiple degrees of freedom to perform grasping, cutting, suturing, and other surgical tasks, as controlled by commands from a remote operator. For example, actuators within the tool drive unit of a robotic arm may drive the multi-axis movement (e.g., pitch and yaw) of the wrist jaws to pivot, open, or close the jaws, or to control the grip or opening force between the jaws while moving the wrist to any angular position. The jaws may perform tasks such as grasping the patient's tissue or holding a cutting instrument. Precise control of the grip or opening force when opening and closing the jaws is important to prevent damage to the tissue or to ensure accurate cutting by the instrument. Additionally, the jaws may operate in a position mode where the angle between the pair of jaws is commanded to a desired jaw angle, and a force mode where the jaws are commanded to apply a desired grip force. A smooth transition between the position mode and the force mode minimizes an undesired sudden change in the grip force that could cause an accidental drop of any object being grasped.

Summary of the Invention

Means for Solving the Problems

[0004] A system and method are disclosed for limiting the grip force generated by closing a robotic wrist jaw while operating in a position control mode where the jaw is commanded to a desired jaw angle before being commanded to generate a grip force. In the position control mode, or simply the position mode, the desired jaw angle is higher than a threshold corresponding to the angle at which both jaws just contact an object between the jaws simultaneously, or the angle at which the jaws begin to contact each other when there is no object to be grasped. When the desired jaw is lower than the threshold, the wrist jaw is operating in a force control mode, or simply the force mode, and the desired jaw angle is converted to a desired grip force. The disclosed system and method prevent damage to tissue that may be grasped by the jaws while the jaws are closing in the position mode In the middle of operationSometimes, limit the maximum amount of gripping force. The gripping force may be estimated or measured. The feedback loop analyzes the desired jaw angle and the measured gripping force to determine whether the jaw is closed in the position mode In the middle of operation and whether the measured gripping force exceeds a pre-specified maximum gripping force threshold. If so, the feedback loop may calculate a gripping force error to limit the measured gripping force to the pre-specified maximum gripping force threshold.

[0005] In another aspect, a system and method are disclosed for achieving a minimum jaw opening force by the wrist joint when operating in the position mode. Maintaining a minimum jaw opening force while the jaw is open in the position mode In the middle of operation helps the jaw overcome the resistance that could prevent the jaw from opening to the desired jaw angle. The opening force representing the jaw opening force and the jaw angle may be measured or estimated. The feedback loop analyzes the desired jaw angle, the estimated jaw angle, and the measured jaw opening force to determine whether the jaw is open in the position mode In the middle of operation and whether the measured jaw opening force is lower than a pre-specified minimum opening force threshold. If so, the feedback loop may calculate a jaw opening force error to maintain the jaw opening force higher than the pre-specified minimum opening force threshold.

[0006] In another aspect, a system and method are disclosed for achieving a smooth transition of the gripping force when the wrist joint transitions between the position mode and the force mode. A smooth transition from the position mode to the force mode and vice versa minimizes an undesirable sudden change in the gripping force that could accidentally drop the object being gripped by the wrist joint when the jaw crosses a discontinuity between the two modes. In one embodiment, to transition from the position mode to the force mode, a debouncing strategy is used to ensure that the desired jaw angle is smaller than the threshold between the position mode and the force mode for a pre-specified minimum duration before the wrist joint transitions to the force mode.

[0007] In one embodiment, the system and method may determine a desired grip force from a desired jaw angle, or may measure or estimate the grip force. The feedback loop analyzes the desired jaw angle, the desired grip force, and the measured grip force to determine whether the jaw is transitioning from a position mode to a force mode, whether the error between the measured grip force and the desired grip force is greater than a pre-specified maximum force error, and whether the desired grip force is increasing. If so, the feedback loop may set the desired grip force as the measured grip force at present minus a pre-specified margin when the jaw transitions from the position mode to the force mode.

[0008] In one embodiment, the feedback loop analyzes the desired jaw angle, the desired grip force determined from the desired jaw angle, and the measured grip force to determine whether the jaw is transitioning from a force mode to a position mode, whether the desired grip force is less than a 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 a pre-specified maximum force error. If so, the feedback loop may set the desired grip force to the minimum grip force value when the jaw transitions from the force mode to the position mode.

[0009] A method for controlling the jaw grip force generated by the jaws of a gripper tool is disclosed. The method may include determining whether the jaws are closed in a position mode based on a desired jaw angle between the jaws. The position mode is characterized by applying a position command to drive the jaws to a desired position at the desired jaw angle. The method may also determine whether the jaws are closed in the position mode In the middle of operation or not. The position mode is characterized by applying a position command to drive the jaws to a desired position at the desired jaw angle. The method may also determine whether the jaws are closed in the position mode In the middle of operationThis includes determining whether the measured gripping force exceeds a maximum gripping force threshold. The method further includes generating a gripping force error that is combined with a position command to limit the measured gripping force to the maximum gripping force threshold when the measured gripping force exceeds the maximum gripping force threshold.

[0010] Another method for controlling the jaw opening force generated by the jaws of a gripper tool is disclosed. The method may include determining whether the jaws are in a position mode based on a desired jaw angle between the jaws. The position mode is characterized by applying a position command to drive the jaws to a desired position at a desired jaw angle. The method also includes determining whether a jaw angle error between the desired jaw angle and the measured jaw angle is greater than an error threshold when the jaws are in the position mode. The method further includes determining whether the measured opening force is less than a minimum opening force threshold when the jaw angle error is greater than the error threshold. The method further includes generating an opening force error that is combined with the position command to maintain the measured opening force higher than the minimum opening force threshold when the measured opening force is less than the minimum opening force threshold.

[0011] Yet another method for controlling the gripping force generated by the jaws of a gripper 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 a desired jaw angle between the jaws. During the position mode, the jaws are driven at a commanded jaw angle that can be the desired jaw angle. During the force mode, the jaws are driven at a commanded gripping force determined based on a desired jaw angle having a negative value. The method also includes determining whether to adjust the commanded gripping force during a transition between the position mode and the force mode based on the commanded gripping force and the measured gripping force. If so, the method further includes adjusting the commanded gripping force to reduce a change in the measured gripping force determined otherwise based on the desired jaw angle during the transition.

Brief Description of the Drawings

[0012] The accompanying drawings are provided with the following description of various aspects and embodiments of the subject technology for a better understanding of the present invention. The drawings and embodiments are illustrative of the present invention and are not intended to limit the scope of the present invention. It is understood that one of ordinary skill in the art can modify the drawings to generate drawings of other embodiments that are still within the scope of the present invention.

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Best Mode for Carrying Out the Invention

[0013] 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 these embodiments, but rather is intended to enable one of ordinary skill in the art to make and use the invention.

[0014] A feedback control system and method for controlling the gripping force or opening force of an end effector of a robotic arm for surgery, such as a wrist joint, are disclosed. The wrist joint can be coupled to an actuator of a tool drive unit via a cable to effect multi-axis movement of the wrist joint. The feedback control system may command a pitch angle, a yaw angle, and an inter-joint angle of the wrist joint. When the commanded joint angle is higher than a threshold value, also referred to as a threshold value for detent, the wrist joint may operate in a position mode to move the wrist joint to the commanded position and orientation. The commanded joint angle may also be referred to as a desired joint angle. When the commanded joint angle is lower than the threshold value for detent, the wrist joint may operate in a force mode from the position and orientation in the position mode, and a desired gripping force is generated by a grip force controller based on the commanded joint angle. In one embodiment, the feedback control system analyzes the desired joint angle, measures or estimates the actually applied gripping force, and determines whether the measured gripping force exceeds a pre-specified maximum gripping force threshold, thereby limiting the maximum gripping force when the joint is closed in the position mode. If so, the feedback control system may calculate a grip force error so that the measured grip force is limited to the pre-specified maximum grip force threshold and adjust the grip force. In the middle of operation In one embodiment, the feedback control system is when the joint is open in the position mode

[0015] In one embodiment, the feedback control system is when the joint is open in the position mode In the middle of operationSometimes, the minimum jaw opening force may be maintained. The feedback control system may measure or estimate the actual applied jaw angle. The feedback control system may also measure or estimate the actual applied grip force or opening force of the jaw. The feedback control system analyzes the desired jaw angle, the measured jaw angle, and the measured jaw opening force to determine whether the jaw is in the position mode, whether the difference between the desired jaw angle and the estimated jaw angle is greater than a threshold value, and whether the measured jaw opening force is less than a predefined minimum opening force threshold. If so, the feedback control system may calculate an opening force error and adjust the grip force or opening force to maintain the measured jaw opening force higher than the predefined minimum opening force threshold.

[0016] In one embodiment, the feedback control system may use a debouncing algorithm to prevent the wrist joint from oscillating between the position mode and the force mode when the jaw angle is set near the detent. The feedback control system may determine whether the desired jaw angle is less than a threshold for the detent over a predefined duration. If so, the feedback control system may switch the wrist joint from the position mode to the force mode. In one embodiment, the debouncing algorithm may be one-sided such that the wrist joint can transition back to the position mode as soon as the desired jaw angle becomes greater than or equal to the threshold.

[0017] In one embodiment, the feedback control system may minimize an undesirable sudden change in the grip force when transitioning between the position mode and the force mode. The grip force controller may calculate a current command for a desired grip force from a desired joint angle. The feedback control system may measure or estimate the grip force actually applied. The feedback control system analyzes the desired joint angle, the desired grip force, and the measured grip force to determine whether the joystick is transitioning from the position mode to the force mode, whether the error between the measured grip force and the desired grip force is greater than a pre-specified maximum force error, and whether the desired grip force is increasing. If so, the feedback control system may set the grip force as the measured grip force minus a pre-specified margin when transitioning from the position mode to the force mode.

[0018] In one embodiment, the feedback control system analyzes the desired joint angle, the desired grip force, and the measured grip force to determine whether the joystick is transitioning from the force mode to the position mode, whether the desired grip force is less than a pre-specified 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 a pre-specified maximum force error. If so, the feedback control system may set the grip force to a pre-specified minimum grip force value when transitioning from the force mode to the position mode. In one embodiment, the pre-specified minimum grip force value may be set to 3 N.

[0019] FIG. 1 is a depiction of an exemplary surgical robotic system 1 in an operating room according to aspects of the subject technology. The robotic system 1 includes a user console 2, a control tower 3, and a surgical robotic platform 5, such as one or more surgical robotic arms 4 on a stand, bed, etc. The arm 4 may be attached to a stand or bed on which the patient lies, as shown in the example of FIG. 1, or may be attached to a cart separate from the stand or bed. The system 1 can incorporate any number of devices, tools, or accessories used to perform surgery on a patient 6. For example, the system 1 may include one or more surgical tools 7 used to perform surgery. The surgical tool 7 may be an end effector attached to the distal end of the surgical arm 4 to perform surgery.

[0020] Each surgical tool 7 may be operated manually, robotically, or both during surgery. For example, the surgical tool 7 may be a tool used to enter, view, or manipulate the internal anatomical structure of the patient 6. In one aspect, the surgical tool 7 is a gripper such as a wrist joint that can grip the patient's tissue. The surgical tool 7 may be configured to be controlled manually by an operator 8 standing beside the bed, robotically through the actuated movement of the surgical robotic arm 4 to which the surgical tool is attached, or both. The robotic arm 4 is shown attached to a stand, but in other configurations, the arm 4 may be attached to a cart, ceiling, or sidewall, or another suitable structural support.

[0021] A remote operator 9, such as a surgeon or other human operator, may use the user console 2 to remotely operate the arms 4 and the surgical tools 7 attached thereto, which is herein referred to as teleoperation. The user console 2 may be located in the same operating room as the rest of the system 1, as shown in FIG. 1. However, in other environments, the user console 2 may be located in an adjacent or nearby room, or even at a remote location, such as a different building, city, or country. The user console 2 may include a seat 10, a foot-operated control unit 13, one or more handheld user input devices (UIDs) 14, and at least one user display 15 configured to display, for example, a view of the surgical site within the patient 6. In an exemplary user console 2, the remote operator 9 sits on the seat 10 and operates the foot-operated control unit 13 and the handheld UID 14 while viewing the user display 15 to remotely control the arms 4 and the surgical tools 7 attached to the distal ends of the arms 4.

[0022] In some variations, an operator 8 standing beside the bed may operate the system 1 in a "bed-facing" mode. In this mode, the operator 8 (user) standing beside the bed is beside the patient 6 and simultaneously operates a robot-driven tool (end effector attached to the arm 4) by a handheld UID 14 held in one hand and a manual laparoscopic tool with the other hand. For example, the left hand of the operator standing beside the bed may operate the handheld UID to control the robot-driven tool, while the right hand of the operator standing beside the bed may operate the manual laparoscopic tool. Thus, in a variation of the system 1, the operator 8 standing beside the bed may perform both robot-assisted minimally invasive surgery and manual laparoscopic surgery on the patient 6.

[0023] During an exemplary procedure (surgery), patient 6 is sterilized, prepared, and covered to achieve anesthesia. The initial access to the surgical site can be performed manually, during which the arms of the robotic system 1 are in a stowed or retracted configuration (thereby facilitating access to the surgical site). Once access is complete, an initial positioning or setup of the robotic system 1, including arm 4, can be performed. Next, a remote operator 9, next to the user console 2, operates various end effectors and possibly an imaging system for performing the surgery, using the foot pedal controller 13 and the handheld user input device 14. Manual assistance can also be provided by a person, such as operator 8 next to the bed, wearing a sterile gown, on a treatment bed or table, who can perform tasks such as retracting tissue, performing manual repositioning, and changing tools for one or more of the robotic arms 4. Also, a non-sterile person may be present to assist the remote operator 9 of the user console 2. When the procedure or surgery is complete, the system 1 and the user console 2 can be configured or set to facilitate various post-operative procedures, such as cleaning or sterilization, and input or printing of medical records via the user console 2.

[0024] In one embodiment, the remote operator 9 holds and moves the UID 14 to provide an input command for moving the robot arm actuator 17 of the robot system 1. The UID 14 can be communicatively coupled to the rest of the robot system 1, for example, via the console computer system 16. The UID 14 can generate a spatial state signal corresponding to the movement of the UID 14, for example, the position and orientation of the handheld housing of the UID, and the spatial state signal may be an input signal for controlling the movement of the robot arm actuator 17. The robot system 1 can control the proportional movement of the actuator 17 using a control signal derived from the spatial state signal. In one embodiment, the console processor of the console computer system 16 receives the spatial state signal and generates a corresponding control signal. Based on these control signals, i.e., the signals that control how the actuator 17 is energized to move the segments or links of the arm 4, the operation of the corresponding surgical tool attached to the arm can mimic the operation of the UID 14. Similarly, the interaction between the remote operator 9 and the UID 14 can generate, for example, a grip control signal for closing the jaws of the gripper of the surgical tool 7 to grip the tissue of the patient 6.

[0025] The surgical robot system 1 may include several UIDs 14. In that case, for each handheld user input device, respective control signals are generated to control the actuator of each arm 4 and the surgical tool (end effector). For example, the remote operator 9 can move the first UID 14 to control the movement of the actuator 17 within the left robot arm. In that case, the actuator will respond by operating the connections, gears, etc. within that arm 4. Similarly, when the remote operator 9 moves the second UID 14, it will control the movement of another actuator 17, and this movement will operate other connections, gears, etc. of the robot system 1. The robot system 1 may include a right arm 4 fixed to the bed or table on the right side of the patient and a left arm 4 on the left side of the patient. The actuator 17 may include one or more motors that are controlled to drive the rotation of the joints of the arm 4. By this rotation, for example, with respect to the patient, the orientation of the endoscope or gripper of the surgical tool 7 attached to that arm can be changed. The movement of several actuators 17 within the same arm 4 can be controlled by a spatial state signal generated from a particular UID 14. The UID 14 can also control the movement of each surgical tool gripper. For example, each UID 14 can generate respective gripping signals for controlling the movement of an actuator, such as a linear actuator, that opens and closes the jaws of the gripper at the distal end of the surgical tool 7 for gripping tissue within the patient 6.

[0026] In some embodiments, communication between the platform 5 and the user console 2 may be via the control tower 3, which may convert user commands received from the user console 2 (more specifically, from the console computer system 16) into robot control commands that are sent to the arm 4 on the robot platform 5. The control tower 3 may also send status signals and feedback back from the platform 5 to the user console 2. The communication connections between the robot platform 5, the user console 2, and the control tower 3 may be via wired and / or wireless links using any suitable one of a variety of data communication protocols. Any wired connection may optionally be built into the floor and / or walls or ceiling of the operating room. The robot system 1 may provide video output to one or more displays, including a display within the operating room and a remote display accessible via the Internet or other network. The video output (video feed) may also be encrypted to ensure privacy, and all or part of the video output may be stored on a server or an electronic health record system.

[0027] FIG. 2 is a schematic diagram illustrating one exemplary design of a robotic arm, a tool drive unit, and a cannula loaded with a robotic surgical tool according to an aspect of the subject technology. As shown in FIG. 2, an exemplary surgical robotic arm 112 may include a plurality of links (e.g., link 202) and a plurality of actuated joint modules (e.g., joint 204) for actuating the plurality of links relative to each other. The joint modules can include various types such as pitch joints or roll joints, which may substantially restrict the movement of adjacent links relative to others about a particular axis. The exemplary design of FIG. 2 also shows a tool drive unit 210 attached to the distal end of the robotic arm 112. The tool drive unit 210 may include a cannula 214 coupled to its end for receiving and guiding a surgical instrument 220 (e.g., an endoscope, a stapler, etc.). The surgical instrument (or “tool”) 220 may include an end effector 222 at the distal end of the tool. The plurality of joint modules of the robotic arm 112 can be actuated to position and orient the tool drive unit 210 that actuates the end effector 222 for robotic surgery.

[0028] FIGS. 3A and 3B are schematic diagrams illustrating, respectively, an exemplary tool drive unit loaded with a tool and an exemplary tool drive unit not loaded with a tool according to an aspect of the subject technology. As shown in FIGS. 3A and 3B, in one variation, the tool drive unit 210 may include an elongated base (or “stage”) 310 having a longitudinal track 312 and a tool carriage 320 slidably engaged with the longitudinal track 312. The stage 310 may be configured to couple to the distal end of the robotic arm, such that the articulation of the robotic arm can position and / or orient the tool drive unit 210 in space. Additionally, the tool carriage 320 may be configured to receive a tool base 352 of the tool 220, which may also include a tool shaft 354 extending from the tool base 352 through the cannula 214, with an end effector 222 (not shown) disposed at the distal end.

[0029] In addition, the tool carriage 320 may actuate a set of articulating motions of the end effector through a cable system or wire (the terms "cable" and "wire" are used interchangeably throughout this application) that is manipulated and controlled by an actuation drive unit. The tool carriage 320 may include actuation drive units of different configurations. For example, the rotary shaft drive unit may include a motor having a hollow rotor and a planetary gear transmission disposed at least partially within the hollow rotor. The plurality of rotary shaft drive units may be arranged in any suitable manner. For example, the tool carriage 320 can include six rotary drive units 322A-322F arranged in two rows extending longitudinally along the base, and these rotary drive units are staggered slightly from each other to reduce the width of the carriage and increase the compactness of the tool drive unit. As clearly shown in FIG. 3B, the rotary drive units 322A, 322B, and 322C may generally be arranged in a first row, and the rotary drive units 322D, 322E, and 322F may generally be arranged in a second row that is slightly longitudinally offset from the first row.

[0030] FIGS. 4A and 4B are schematic diagrams illustrating an end effector of an exemplary gripper having a robotic wrist, a pair of opposing jaws, and a pulley and cable system for coupling the robotic wrist and the pair of jaws to an actuator of a tool drive unit. The following tool model and controller design are described with reference to an exemplary surgical robotic gripper, but note that the proposed control system for position and grip force control can be adapted to any tool that includes an end effector coupled to a tool shaft through a robotic wrist that enables multi-axis motion (e.g., pitch and yaw) of the end effector. Exemplary tools include, but are not limited to, grippers, clamps, forceps, needle holders, retractors, and cautery instruments.

[0031] As shown in FIG. 4A, a pair of opposing jaws 401A and 401B are movably coupled to a first yoke 402 of a robot wrist via a mandrel 412 extending along a first axis 410. The first yoke 402 may be movably coupled to a second yoke 403 of the robot wrist via a second mandrel 422 extending along a second axis 420. The pair of jaws 401A and 401B may each be coupled to or integrally formed with pulleys 415A and 415B via the mandrel 412, so that both jaws can rotate about the axis 410. Pulleys 425A, 425B, 425C, and 425D are coupled to the mandrel 422 and rotate about the axis 420. The pulleys 425A, 425B, 425C, and 425D are arranged in a first set of pulleys 425B and 425C on one side of the yoke 402 and a second set of pulleys 425A and 425D on the other side of the yoke 402. Pulleys 425A and 425C are outer pulleys, and pulleys 425B and 425D are inner pulleys. Similarly, a third set of pulleys 435A, 435B, 435C, and 435D are coupled to a third mandrel 432 and rotate about an axis 430 parallel to the axis 420.

[0032] The gripper 220 can be actuated to move one or both of the jaws 401A and 401B in various ways around the axis 410. For example, the jaws 401A and 401B may open and close relative to each other. The jaws 401A and 401B may also be actuated to rotate together as a pair to provide yaw movement of the gripper 220. Additionally, the first yoke 402, the pulleys 415A and 415B, and the jaws 401A and 401B can rotate about the axis 420 to provide pitch movement of the gripper 220. The movement of the robot wrist and / or the jaws of the tool can be actuated by controlling four independent cables 405A - 405D. As shown in FIG. 4A, cable 405A starts (or terminates) from one side of pulley 415A and can proceed along pulleys 425A and 435A, and cable 405B terminates on the other side of pulley 415A and is configured to proceed through pulleys 425B and 435B. Similarly, another pair of cables 405C and 405D can be coupled to jaw 401B. For example, cable 405C extends from one side of pulley 415B to pulleys 425C and 435C, and cable 405D proceeds through pulleys 425D and 435D and terminates on the other side of pulley 415B. A third set of pulleys 435A, 435B, 435C, and 435D are arranged to keep the cables 405A - 405D fixed to the second set of pulleys 425A - 425D and prevent the cables from slipping or sliding relative to the pulleys 425A - 425D.

[0033] As shown in FIGS. 4A and 4B, the gripper 220 can be actuated to move the jaws 401A and 401B in various ways, such as gripping (e.g., jaws that rotate independently about axis 410), yawing (e.g., jaws that rotate together about axis 410), and pitching (e.g., jaws that rotate about axis 420), by applying motion to one or more of the pulleys 415A, 415B, 425A, 425B, 425C, and 425D, thereby applying motion to the first yoke 402 and / or one or both of the jaws 401A and 401B. The cables 405A - 405D can be grouped into two antagonistic pairs, i.e., the jaws rotate in one direction while one cable of an antagonistic pair is actuated or tensioned and the other cable is relaxed. On the other hand, when tension is applied to only the other cable, the jaws rotate in the opposite direction.

[0034] For example, cables 405A and 405B are a first antagonistic pair for moving jaw 401A, and cables 405C and 405D are a second antagonistic pair for controlling jaw 401B. When cable 405B is relaxed and tension is applied to cable 405A (e.g., by at least one of the rotary drive units 322a - 322f), jaw 401A closes (moves towards the opposing jaw 401B). On the other hand, when tension is applied to cable 405B and cable 405A is relaxed, jaw 401A opens (moves away from the opposing jaw 401B). Similarly, cable 405C closes jaw 401B (moves towards the opposing jaw 401A) when tension is applied, and cable 405D opens jaw 401B (moves away from the opposing jaw 401A) while the other cable is relaxed. As another example, the gripping force between jaw 401A and jaw 401B can be achieved by continuously applying tension to both cable 405A and cable 405C after the jaws are closed (in contact with each other) (while cables 405B and 405D are relaxed).

[0035] If tension is applied simultaneously to both cables of a pair while the cables of the other pair are slack, pulley 415A or pulley 415B does not rotate. Instead, the first yoke 402, together with jaws 401A and 401B, is caused to pitch about axis 420 by pulleys 415A and 415B. For example, while a pair of cables 405C and 405D are slack, tension is applied simultaneously to both of a pair of cables 405A and 405B, and the jaw (along with yoke 402) pitches in a direction out of the plane of the paper. On the other hand, when tension is applied simultaneously to both of cables 405C and 405D and the pair 405A and 405B is left slack, the jaw pitches in a direction into the plane of the paper.

[0036] FIG. 4B is a schematic diagram illustrating exemplary angle definitions for various movements of gripper 220 according to aspects of the subject technology. The angles are defined with reference to axes 410 and 420, and axis 452 of the first yoke 402 and 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 rotational angle of yoke 402 about axis 420, which may also be defined as the pitch angle (θ ピッチ ) of gripper 220 (whereas in FIG. 4A, since the jaw remains in the reference position, i.e., there is no pitch movement, axis 452 of yoke 402 is superimposed on axis 453 of yoke 403). Additionally, the angles (θ 2 ) and (θ 3 ) may each represent the angle between each of jaws 401A and 401B and axis 452 of yoke 402 (with the origin). To distinguish the sides of axis 452, the angles (θ 2 ) and (θ 3 ) may have different signs. For example, as illustrated in FIG. 4B, the angle (θ 2 ) is negative and the angle θ ( 3 ) is positive.

[0037] For performing control tasks, it is often beneficial to define a consistent coordinate frame for joint angles. For example, the jaw angle (θジョー ) is defined as the angle between two joes 401A and 401B, the yaw angle (θ ヨー ) may be further defined as the angle between the axis 452 and the line bisecting the joe angle. As described above, the pitch angle (θ ピッチ ) may be defined as the angle (θ 1 ) between the axis 452 and the axis 453. Therefore,

[0038]

Number

[0039] A method and system for controlling the angular position and grip force of a distal end effector of a robotic surgical instrument are described below. The end effector may include a robotic wrist and a pair of opposing members (e.g., joes or jaws), each movable between an open position and a closed position actuated by two antagonistic wires. As illustrated in FIGS. 3 and 4, a total of four wires may be driven by respective independent actuators or motors. The control system may include a feedback loop with position and velocity feedback from the actuators and force feedback measured on the four wires to provide a desired position and grip force. In some implementations, the actuator controller may be operating in a position plus feedforward current mode. For example, the position controller in the position mode may drive the distal end effector to a desired angular position in space based on position feedback, and in the force mode, the grip force controller may provide an additional feedforward current based on the grip force measured by load cells on the four wires to achieve a desired grip force between the opposing members.

[0040] FIG. 5 is a block diagram illustrating a high-level control system for controlling a surgical tool according to an aspect of the subject technology. The control system includes an input 560, a controller 562, a plant 564, an output 568, and a sensor and estimator 566 on a feedback path between the output 568 and the controller 562. The plant 564 may include a tool actuator and an end effector (see also, e.g., the rotary drives 322A-322F of FIG. 3B and the cables 405A-405D of the wrist joint of FIG. 4A, the actuator unit 510 of FIG. 10, and the cables and wrist links 512). The controller 562 may include one or more processors configured by software instructions stored in memory to calculate the motion of the plant 564 in response to the input 560, which input may indicate desired motions of the end effector of the surgical tool such as a desired θ ピッチ of the wrist joint of FIG. 4B, a desired θ ヨー , and a desired θ ジョー . Thus, the commands generated by the controller 562 may drive the tool actuator to facilitate the desired motion of the end effector. In one embodiment, the desired θ ピッチ , θ ヨー , and θ ジョー may be generated by the UID 14 under the control of the remote operator 9 of FIG. 1. Outputs 568 such as the position, velocity, cable tension, and grip or release force of the end effector may be directly measured or estimated by the sensor and estimator 566 and fed back to the controller 562 for closed-loop control.

[0041] In one embodiment, when the desired joint angle θ ジョー of the wrist joint is above a threshold value, a desired θ ジョー , also referred to as a commanded θ ジョーmay be treated as a position control command in the position mode. The threshold value is used to determine the stop position and may correspond to the angle at which both jaws just contact the object therebetween. When there is no object to be grasped, the threshold value when the jaws start to contact each other is 0 degrees. In the position mode, the controller 562 may convert the desired θ ジョー , as well as the desired θ ピッチ and the desired θ ヨー into corresponding actuator position commands to drive the wrist jaws to the desired position and orientation. When the desired θ ジョー is lower than the threshold value, the wrist jaws operate in the force control mode, or simply in the force mode, and the desired jaw angle is converted into a desired grip force command. The controller 562 may generate a current command in addition to the position command to achieve the desired grip force.

[0042] In one embodiment, the controller 562 may limit the maximum amount of grip force when the jaws are closed in the position mode to prevent damage to the tissue that can be grasped by the jaws. The grip force of the jaws may be estimated or measured by the sensor and estimator 566. The controller 562 may analyze the desired θ In the middle of operation ジョー and the measured grip force to determine whether the jaws are closed in the position mode In the middle of operation and whether the measured grip force exceeds a pre-specified maximum grip force threshold. If so, the controller 562 may calculate a grip force error to limit the measured grip force to the pre-specified maximum grip force threshold. For example, to determine whether the jaws are closed in the position mode In the middle of operation , the controller 562 may first verify that the desired θ ジョー is greater than or equal to the threshold value for the stop position and thus is in the position mode for a pre-specified duration. The controller 562 may use a debouncing technique to verify that the desired θ ジョー is decreasing over a pre-specified length of time. In one embodiment, the desired θ​ジョー When sampled at a periodic frequency, the controller 562 may verify that the samples of the desired θ ジョー are decreasing over a pre-specified number of samples.

[0043] To determine whether the measured grip force exceeds a pre-specified maximum grip force threshold, the controller 562 may also use a debouncing technique. In one embodiment, the feedback control loop of the control system of FIG. 5 may operate at a loop cycle time. The grip force counter may increment by one count per control loop cycle while the measured grip force is less than the value obtained by subtracting a margin from the maximum grip force threshold. In one embodiment, the grip force counter may stop incrementing after reaching a maximum count. When the measured grip force is greater than the maximum grip force threshold, the grip force counter may be reset. The debouncing technique may declare that the measured grip force exceeds the maximum grip force threshold over an entire window of loop cycle numbers equal to the grip force counter when the measured grip force is greater somewhere within the window than the value obtained by subtracting a margin from the maximum grip force.

[0044] As an example, assume that the measured grip force is initially below the maximum grip force threshold minus the margin, and the grip force counter is incrementing. When the measured grip force increases beyond the maximum grip force threshold, the grip force counter may be reset. The feedback control loop of the controller 562 may attempt to drive the wrist joint to limit the measured grip force to the maximum grip force threshold by changing the actuator position command. However, even if the measured grip force decreases below the maximum grip force threshold but remains above the maximum grip force threshold minus the margin, the feedback control loop may still consider the measured grip force to be greater than the maximum grip force threshold so as to limit the maximum measured grip force. Assume that the measured grip force decreases below the maximum grip force threshold minus the margin for only a few loop cycles and then increases again to be higher than this level. The grip force counter may increment up to the number of loop cycles during which the measured grip force is temporarily lower than the maximum grip force threshold minus the margin. As long as the measured grip force remains above the maximum grip force threshold minus the margin within a window that extends up to the number of loop cycles equal to the grip force counter (for example, the number of loop cycles during which the measured grip force decreased to be temporarily lower than the maximum grip force threshold minus the margin), the feedback control loop may still consider the measured grip force to be greater than the maximum grip force threshold throughout the duration of the window so as to limit the maximum measured grip force.

[0045] The controller 562 closes in the position mode for the joint In the middle of the ongoing operationFurther, when it is determined that the measured grip force exceeds the maximum grip force threshold, the controller may limit the measured grip force to the maximum grip force threshold. In one embodiment, the controller 562 may calculate a grip force error that is the difference between the maximum grip force threshold and the measured grip force. A steady-state type controller such as a proportional-integral (PI) force controller may be arranged to receive the grip force error and maintain or limit the measured grip force to the maximum grip force threshold. The output of the PI force controller may be combined with the output of the inverse kinematics acting on the error in the desired position and orientation of the wrist joint to generate a compensated actuator position command. The compensated actuator position command is added to the existing actuator position command to drive the wrist joint to limit the maximum amount of grip force when the joint is closed in the position mode In the middle of operation at the maximum amount of grip force when the joint is closed in the position mode.

[0046] FIG. 6A is a time plot showing the commanded θ In the middle of operation 603, measured θ ジョー 605, commanded grip force 607, and measured grip force 609 of the wrist joint when the measured grip force 609 is not limited while the joint is closed in the position mode. The threshold θ ジョー between the position mode and the force mode is set to 0 such that the wrist joint operates in the position mode when the commanded θ ジョー 603 is 0 degrees or more. When the commanded θ ジョー 603 is less than 0 degrees, the wrist joint operates in the force mode. ジョー

[0047] FIG. 6A shows that the wrist joint operates in the position mode from 20 to 35 seconds and again from 44 to 47 seconds. The measured θ ジョー 605 follows the commanded θ ジョー ​Even if 603 changes within the position mode or the force mode, it remains within a relatively narrow range, probably because Joe is gripping the object. During the position mode, the commanded grip force 607, which is the desired grip force, may be set to a default value of 0 N because the wrist joe is not operating in the force mode. However, the measured grip force 609 may be much larger. For example, from 26 to 28 seconds and from 31 to 35 seconds, when Joe is closed in the position mode In the middle of operation or, when held in the closed position, the measured grip force 609 exceeds 10 N and, since the measured grip force is not limited, can reach as high as 15 N. In the force mode (e.g., after 35 - 44 seconds and 47 seconds), the grip force controller may set the commanded grip force 607 as a function of the commanded θ ジョー 603, and the feedback control loop may maintain the measured grip force 609 to be the same as the commanded grip force 607.

[0048] Figure 6B is a time plot showing the commanded θ In the middle of operation 613 of the wrist joe, the measured θ ジョー 615, the commanded grip force 617, and the measured grip force 619 when the control system limits the measured grip force to a pre - specified maximum threshold while Joe is closed in the position mode ジョー The maximum grip force threshold is set to 8.5 N.

[0049] In Figure 6B, the time plots of the commanded θ ジョー 613 and the measured θ ジョー 615 are the same as the commanded θ ジョー 603 and the measured θ ジョー 605 in Figure 6A when the measured grip force is not limited. During the position mode, the commanded grip force 617 is reset to a default value of 0 N by the grip force controller. However, the measured grip force 619 is such that Joe is closed In the middle of operationOr, during the position mode held in the closed position (e.g., 27 - 30 seconds, 32 - 36 seconds, and 41 - 45 seconds), it is limited to a maximum grip force threshold of 8.5 N by the grip force controller. Note that the limitation on the maximum grip force in the position mode does not affect the force mode. Therefore, in the force mode, the measured grip force 619 can exceed the maximum grip force threshold of 8.5 N by following the commanded grip force 617.

[0050] Figure 7 shows that, according to an aspect of the subject technology, while the jaw is closed in the position mode by analyzing the desired jaw angle and the measured grip force, In the middle of operation a flowchart illustrating method 700 for feedback control of a surgical robot system to limit the grip force of the wrist - jaw to a pre - specified maximum threshold during the time the wrist - jaw is closed in the position mode. Method 700 may be implemented by controller 562 of the control system of FIG. 5, which receives the desired θ ジョー from user input and the measured grip force from sensor and estimator 566 and generates an actuator position command for driving the wrist - jaw.

[0051] In block 701, method 700 determines whether the wrist - jaw is in the position mode. In one embodiment, block 701 determines whether the desired θ ジョー is above a threshold θ ジョー between the position mode and the force mode for a period exceeding a pre - specified period. In one embodiment, the threshold θ ジョー may be set to 0. If the wrist - jaw is not in the position mode, the wrist - jaw is in the force mode and the grip force is not restricted. In block 709, method 700 generates an actuator position command without imposing a constraint on the grip force. In one embodiment, in addition to generating the actuator position command, block 709 converts the desired θ ジョー to a desired grip force command to achieve the desired grip force.

[0052] When Joe is in the position mode, block 703 determines whether Joe is closed. In the middle of operation In one embodiment, block 703 may use a debouncing technique to determine whether the desired θ ジョー is decreasing over a pre-specified duration or over a pre-specified number of samples. In one embodiment, if the desired θ ジョー is held in a stationary state without increasing, Joe may be considered closed. In the middle of operation If Joe is not closed, In the middle of the ongoing operation the grip force is not limited even in the position mode. Method 700 defaults to block 709 that generates an actuator position command without imposing a constraint on the grip force.

[0053] If Joe is closed in the position mode, In the middle of operation block 705 determines whether the measured grip force exceeds a pre-specified maximum grip force threshold. In one embodiment, block 705 may use a debouncing technique to determine whether the measured grip force is greater than a value obtained by subtracting a margin from the maximum grip force threshold anywhere within a window spanning a number of samples equal to the grip force counter. In one embodiment, the measured grip force may be sampled at the loop cycle time of the feedback control system of FIG. 5. The grip force counter may be incremented by 1 for each control loop cycle in which the measured grip force is less than a value obtained by subtracting a margin from the maximum grip force threshold. The grip force counter may be reset when the measured grip force is greater than the maximum grip force threshold. As long as the measured grip force exceeds a value obtained by subtracting a margin from the maximum grip force threshold anywhere within a window spanning a number of samples equal to the grip force counter, the measured grip force is considered to exceed the maximum grip force threshold for the entire window. Otherwise, the measured grip force does not exceed the maximum grip force threshold, and method 700 defaults to block 709 that generates an actuator position command without imposing a constraint on the grip force.

[0054] Joe is closed in the position mode In the middle of operation During, if the measured grip force exceeds the maximum grip force threshold, block 707 generates a compensated actuator position command to limit the measured grip force to the maximum grip force threshold. In one embodiment, block 707 may calculate a grip force error that is the difference between the maximum grip force threshold and the measured grip force. A zero steady-state type controller such as a proportional-integral (PI) force controller may receive the grip force error and generate a compensated grip force command. The output of the PI force controller may be combined with the output of the inverse kinematics acting on the error in the desired position and orientation of the wrist joe to generate a compensated actuator position command. The compensated actuator position command may be added to the existing actuator position command to drive the wrist joe so as to limit the measured grip force to the maximum grip force threshold.

[0055] In another aspect, the controller 562 may maintain a minimum joe opening force by the wrist joe when operating in the position mode. The minimum joe opening force may also be referred to as the minimum grip force. Joe is open in the position mode In the middle of operation Maintaining the minimum joe opening force during helps the joe overcome the resistance that may prevent the joe from opening to the desired joe angle. The joe angle and opening force of the joe may be estimated or measured by the sensor and estimator 566. The controller 562 analyzes the desired θ ジョー , the estimated θ ジョー , and the measured opening force to determine whether the joe is open in the position mode In the middle of operation , whether the joe angle error between the desired θ ジョー and the estimated θ ジョー is greater than a threshold, and whether the measured opening force is lower than a pre-specified minimum joe opening force threshold. If so, the controller 562 may calculate an opening force error between the pre-specified minimum joe opening force threshold and the measured opening force and maintain the measured opening force to be higher than the pre-specified minimum joe opening force threshold.

[0056] In one embodiment, Joe is open in the position mode Is it in the middle of operation? To determine whether, the controller 562 may first verify that the desired θ ジョー is above a threshold for detent, and thus that it has been in the position mode for a time longer than a pre-specified duration. Next, the controller 562 may determine whether the Joe that is open in the position mode In the middle of operation is receiving a resistance that prevents the Joe from opening to the desired θ ジョー In one embodiment, the controller 562 uses a debouncing technique to verify that the desired θ ジョー is greater than the estimated θ ジョー and that the θ ジョー error, which is the difference between the desired θ ジョー and the estimated θ ジョー is greater than a θ ジョー error threshold over a pre-specified length of time. In one embodiment, when the desired θ ジョー and the estimated θ ジョー are sampled at a periodic frequency, the controller 562 may verify that the θ ジョー error is greater than a θ ジョー error threshold over a pre-specified number of samples.

[0057] To determine whether the measured opening force is lower than a pre-specified minimum Joe opening force threshold, the controller 562 may also use a debouncing technique. The Joe opening force counter may increment by one count for each control loop cycle in which the measured opening force is greater than the minimum Joe opening force threshold plus a margin. In one embodiment, the Joe opening force counter may stop incrementing after reaching a maximum count. The Joe opening force counter may be reset when the measured opening force is less than the minimum Joe opening force threshold. The debouncing technique may declare that the measured opening force is less than the minimum Joe opening force threshold over an entire window of loop cycles equal to the Joe opening force counter when the measured opening force is anywhere within the window below the minimum Joe opening force threshold plus a margin.

[0058] As an example, assume that the measured opening force is higher than the minimum jaw opening force threshold plus a margin, and the jaw opening force counter is incrementing. The jaw opening force counter may be reset when the measured opening force is lower than the minimum jaw opening force threshold. The feedback control loop of the controller 562 may attempt to change the actuator position command to drive the wrist joint so as to maintain the measured opening force higher than the minimum jaw opening force threshold. However, even if the measured opening force increases higher than the minimum jaw opening force threshold but remains lower than 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 so as to maintain the minimum jaw opening force. Assume that the measured opening force rises higher than the minimum jaw opening force threshold plus a margin for only a few loop cycles and then drops again below this level. The jaw opening force counter may be incremented up to the number of loop cycles during which the measured opening force was temporarily higher than the minimum jaw opening force threshold plus a margin. As long as the measured opening force remains lower than the minimum jaw opening force threshold plus a margin within a window spanning the number of loop cycles equal to the jaw opening force counter (e.g., the number of loop cycles during which the measured opening force was temporarily higher than 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 throughout the duration of the window so as to maintain the minimum jaw opening force.

[0059] When the controller 562 opens the jaw in the position mode In the middle of the ongoing operation , θ ジョー The error is θ ジョーWhen it is determined that the measured opening force is greater than the error threshold and lower than a pre-specified minimum jaw opening force threshold, the controller may maintain the measured opening force to be higher than the minimum jaw opening force threshold. In one embodiment, the controller 562 may calculate a jaw opening force error, which is the difference between the minimum jaw opening force threshold and the measured opening force. A zero steady-state type controller, such as a proportional-integral (PI) force controller, may be deployed to receive the jaw opening force error and maintain the measured opening force above the minimum jaw opening force threshold. The output of the PI force controller may be combined with the output of the inverse kinematics acting on the error of the desired position and orientation of the wrist joint to generate a compensated actuator position command. The compensated actuator position command is added to the existing actuator position command to drive the wrist joint so as to maintain the minimum amount of the opening force when the jaw is open in the position mode at the desired position and orientation. In the middle of operation when the measured opening force 809 is not maintained higher than the minimum level during the opening between the jaws in the position mode.

[0060] FIG. 8A shows the commanded θ In the middle of operation 803 of the wrist joint, the measured θ ジョー 805, the commanded grip force 807, and the measured opening force 809 when the measured opening force 809 is not maintained higher than the minimum level during the opening between the jaws in the position mode. The threshold θ ジョー between the position mode and the force mode is set to 0 so that the wrist joint operates in the position mode when the commanded θ ジョー 603 is 0 degrees or more. When the commanded θ ジョー 603 is less than 0 degrees, the wrist joint operates in the force mode. The error threshold is set to 5 degrees and the minimum opening force threshold is set to 4.4 N. ジョー ジョー ジョー ジョー

[0061] FIG. 8A shows that the wrist joint operates in the position mode from 49 to 60 seconds and from 62 to 67 seconds. The measured θ ジョー 805 follows the commanded θ ジョーEven if 803 is set to close or open Joe within the position mode, it remains within a relatively narrow range, probably because it is open in the position mode. In the middle of operation Whether Joe is experiencing resistance or the commanded θ ジョー is restricted from fully opening to 803. Joe is open in the position mode. In the middle of operation or is maintained at the same θ ジョー at 49 - 52 seconds, 56 - 59 seconds, and 62 - 66 seconds, the θ ジョー error, that is, the difference between the larger commanded θ ジョー 803 and the smaller measured θ ジョー 805 can be greater than the 5 - degree θ ジョー error threshold.

[0062] During the position mode, the commanded grip force 807 may be set to a default value of 0N by the grip force controller. Even during the force mode, the commanded grip force 807 remains set to 0N. The positive value of the measured release force 809 corresponds to the release force of Joe in the position mode, and the negative value corresponds to the grip force in the force mode when Joe is closed. The measured release force 809 in the position mode generally follows the profile of the commanded θ ジョー 803, because Joe is restricted from opening to the commanded θ ジョー 803. The result is a stronger measured release force 809 when the commanded θ ジョー 803 is increased for a wider opening of Joe, and conversely, a weaker measured release force 809 when the commanded θ ジョー 803 is decreased for a narrower opening of Joe. The feedback control loop may not be able to maintain the measured release force 809 above the 4.4N minimum release force threshold between 53 - 60 seconds, so the measured release force 809 may drop below the minimum release force threshold.

[0063] Figure 8B shows the commanded θ ジョー 813 of the wrist joint when the control system maintains the measured release force 819 above a pre - specified minimum release force threshold during Joe opening in the position mode, the measured θジョー A time plot showing command grip force 815, command grip force 817, and measured release force 819. θ ジョー The error threshold is set to 5 degrees again, and the minimum release force threshold is set to 4.4 N.

[0064] In FIG. 8B, command θ ジョー 813 and measured θ ジョー The time plot of 815 is substantially the same as command θ ジョー 803 and measured θ ジョー 805 in FIG. 8A when the minimum jaw release force is not maintained. During the position mode, the command grip force 817 is reset to the default value of 0 N by the grip force controller. However, θ ジョー the error, that is, a larger command θ ジョー 813 and a smaller measured θ ジョー 815, when the difference between them is greater than the 5-degree θ ジョー error threshold, the measured release force 819 is maintained above the minimum release force threshold of 4.4 N during the 30 - 43 second position mode by the feedback control loop and the grip force controller. Specifically, when the jaw is open In the middle of operation and the same θ ジョー is being maintained, or even when it is closed in the position mode In the middle of operation

[0065] In the middle of operation FIG. 9 is a flowchart illustrating a method 900 for feedback control of a surgical robot system to maintain the release force of a wrist joint above a pre-specified minimum jaw release force threshold while the jaw is open in the position mode by analyzing the desired jaw angle, the estimated jaw angle, and the measured release force according to aspects of the subject technology. Method 900 includes a desired θ In the middle of operation from user input, an estimated or measured θ ジョー , estimated or measured θ ジョーand implemented by a controller 562 of the control system of FIG. 5 that receives a measured release force from a sensor and an estimator 566 and generates an actuator position command for driving the wrist joint.

[0066] In block 901, method 900 determines whether the wrist joint is in the position mode. In one embodiment, block 901 checks whether the wrist joint is in the position mode by determining whether a desired θ ジョー exceeds a threshold θ ジョー between the position mode and the force mode for a pre-specified period. In one embodiment, the threshold θ ジョー may be set to 0. If the wrist joint is not in the position mode, the wrist joint is in the force mode and the minimum release force is not enabled. In block 909, method 900 generates an actuator position command without maintaining the minimum release force. In one embodiment, in addition to generating an actuator position command, block 909 converts a desired θ ジョー to a desired grip force command to achieve a desired grip force or release force.

[0067] If the joint is in the position mode, block 903 determines whether the joint is prevented from opening to the desired θ ジョー by determining whether a θ ジョー error, which is the difference between the desired θ ジョー and the estimated or measured θ ジョー , is greater than or equal to a θ ジョー error threshold. In one embodiment, block 903 uses a debouncing technique to determine whether the desired θ ジョー is greater than the estimated θ ジョー , and whether the θ ジョー error is greater than or equal to the θ ジョー error threshold for a pre-specified length of time. In one embodiment, block 903 determines whether the desired θ ジョー is increasing, remaining the same, or decreasing, thereby determining whether the joint is opening In the middle of operation , static θ ジョーremain as is, or detect that it is closed In the middle of operation This may be detected. θ ジョー The error is θ ジョー If the error is less than the error threshold, method 900 defaults to block 909 that generates an actuator position command without maintaining a minimum opening force.

[0068] When Joe is in position mode, θ ジョー The error is θ ジョー If the error is greater than or equal to the error threshold, block 905 determines that the measured opening force is lower than a pre-specified minimum Joe opening force threshold. In one embodiment, block 905 may use a debouncing technique to determine that the measured opening force is less than the minimum Joe opening force threshold plus a margin somewhere within a window spanning a number of samples equal to the Joe 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 Joe opening force counter may be incremented by one for each control loop where the measured opening force is greater than the minimum Joe opening force threshold plus a margin. The Joe opening force counter may be reset when the measured opening force is less than the minimum Joe opening force threshold. As long as the measured opening force is less than the minimum Joe opening force threshold plus a margin somewhere within a window spanning a number of samples equal to the Joe opening force counter, the measured opening force is considered lower than the minimum Joe opening force threshold for the entire window. Otherwise, the measured opening force is greater than or equal to the minimum Joe opening force threshold, and method 900 defaults to block 909 that generates an actuator position command without maintaining a minimum opening force.

[0069] When Joe is in position mode, the measured opening force is less than the minimum Joe opening force threshold, and θ ジョー The error is θ ジョーIf it is above the error threshold, block 907 generates a compensated actuator position command to maintain the measured opening force above the minimum jaw opening force threshold. In one embodiment, block 907 may calculate a jaw opening force error that is the difference between the minimum jaw opening force threshold and the measured opening force. A zero steady state type controller such as a proportional integral (PI) force controller may receive the jaw opening force error and be arranged to maintain the measured opening force above the minimum jaw opening force threshold. The output of the PI force controller may be combined with the output of the inverse kinematics acting on the error in the desired position and orientation of the wrist joint to generate a compensated actuator position command. The compensated actuator position command is added to the existing actuator position command to drive the wrist joint to maintain the minimum amount of opening force when the jaw is open in the position mode. In the middle of operation when the opening force is maintained.

[0070] In another aspect, the controller 562 may adjust the commanded grip force to smooth the grip force applied when the wrist joint transitions between the position mode and the force mode. Smoothing the grip force applied during mode transition minimizes unwanted sudden changes in the grip force caused by changes in the position of the jaw and the commanded grip force, which can accidentally drop an object being gripped by the jaw as it passes through a discontinuity between the two modes. During the position mode, the desired θ ジョー is above the threshold for detent. The position controller may convert the desired θ as well as the desired θ ピッチ and the desired θ ヨー into corresponding actuator position commands to drive the wrist joint to the desired position and orientation. During the force mode, when the desired θ ジョー is lower than the threshold for detent, for example, when the desired θ ジョー is negative with respect to a detent set at 0 degrees, the grip force controller may be enabled to interpret the desired θ ジョー as a grip force command, and the desired θ ジョーIt may be converted into a compensation current, and this compensation current may be added to the current for the existing position command to drive the wrist joint to achieve the commanded gripper force.

[0071] In one embodiment, to smooth the gripper force applied during mode transition, the feedback control system may use a debouncing technique when the detent is set to 0 degrees. The debouncing technique may prevent the gripper force controller from being repeatedly enabled and disabled to generate oscillations in the commanded gripper force when the desired θ ジョー oscillates around positive and negative values.

[0072] In one embodiment, the feedback control system may minimize a sudden change in gripper force when the wrist joint transitions from the position mode to the force mode by analyzing the desired θ ジョー , the commanded gripper force, and the measured gripper force. The feedback control system may determine whether the commanded gripper force is increasing due to the gripper force controller being enabled as indicated by the desired θ ジョー decreasing below a threshold value for the detent, and whether the error between the measured gripper force and the commanded gripper force is greater than a predefined maximum force error. If so, the feedback control system may set the commanded gripper force as the measured gripper force minus a predefined margin when the wrist joint transitions from the position mode to the force mode.

[0073] In one embodiment, the feedback control system may minimize a sudden change in gripper force when the wrist joint transitions from the force mode to the position mode by analyzing the desired θ ジョー , the commanded gripper force, and the measured gripper force. The feedback control system may determine whether the commanded gripper force is less than a predefined minimum gripper force value, and the desired θ ジョーWhether the commanded grip force is decreasing because the grip force controller is deactivated as indicated by increasing above a threshold for backstop, and whether the absolute value of the error between the measured grip force and the minimum grip force is less than a predefined maximum grip force error value may be determined. If so, the feedback control system may set the commanded grip force to a predefined minimum grip force value when the wrist joint transitions from the force mode to the position mode.

[0074] FIG. 10 is a block diagram of an exemplary control system 1000 for controlling the position and grip force of an end effector of a robotic surgical tool when the end effector is in a position mode or a force mode, or when the end effector is transitioning between the position mode and the force mode, according to an aspect of the subject technology. In one embodiment, the end effector includes a wrist joint. The robotic control system 1000 includes an input processing unit 502, an actuator command generator 504, a position controller 506, a grip force controller 508, a plant including one or more actuator units 510 and / or cables and wrist links 512, a slack controller 514, a position estimator 522, and a grip force estimator 524.

[0075] The input processing unit 502 and the actuator command generator 504 receive a desired angular position of the wrist joint and convert the desired angular position (via an inverse kinematic algorithm) into a corresponding actuator position command, which is output to the position controller 506 and / or the grip force controller 508. For example, the input desired angular position may include a desired θ ジョー a desired θ ピッチ and a desired θ ヨー . The desired θ ジョー may be treated as a position command when the desired θ ジョー is above a threshold for backstop. When the desired θ ジョー is below the threshold for backstop, the desired θ ジョーIt may be converted into a desired grip force command (e.g., a commanded grip force) by a grip force controller 508 that can generate a current command to achieve the desired grip force.

[0076] The position controller 506 may receive position feedback from position and / or velocity sensors on the actuator unit 510. Achieving the desired actuator position can then result in the desired position of the wrist joint, due to the kinematic relationship between the actuator and the wrist joint. Since the actuator unit 510 is coupled to the robotic wrist through an elastic cable (or wire) whose length can change with force, an estimation based solely on the pure kinematic relationship between the actuator position and the wrist movement may not be accurate. The position estimator 522 may provide more accurate estimates of the wrist joint position and velocity to the actuator command generator 504 and the grip force estimator 524 by taking into account cable elasticity in the estimation algorithm (e.g., using a Kalman filter). The estimated position and velocity information can then be used for accurate positioning of the wrist and estimation of friction.

[0077] In one embodiment, the grip force controller 508 takes feedback of the cable tension measured by a load cell or torque sensor on the cable wire. The grip force estimator 524 can then use an algorithm to estimate the grip force between the jaws based on the tension value measured on the cable. The grip force controller 508 may compare the estimated value with the desired grip force and generate an additional current command to achieve the desired grip force. The wrist joints may be coupled to the tool drive through four independent cables, each actuated by an independent motor. In one embodiment, the motor may be driven by current. The current command may include two parts. The first part of the drive current may be from the position controller 506, and the second part may be from the grip force controller 508. The two current commands may be summed and sent to the actuator unit 510.

[0078] The slack controller 514 may perform the task of ensuring that the cable tension never drops below 0 (or a predetermined positive value to compensate for slack). The cable is a member of only the tension of the end effector and cannot apply a negative force. Therefore, it is desirable to prevent the cable tension from dropping to 0. To achieve this goal, the slack controller 514 may monitor the force value from the cable load cell and compare the minimum value of the force value with a predetermined threshold. If the minimum force value across all cables drops below the threshold, the slack controller 514 may generate additional position commands for all actuators to ensure that the desired minimum tension is maintained.

[0079] To smooth the grip force applied during mode transition, the input processing unit 502 may use a debouncing technique when the detent is set to 0 degrees. The debouncing technique may determine whether the desired θ ジョー is less than the threshold for detent for a predetermined minimum duration before the grip force controller 508 is allowed to transition the wrist joint from position mode to force mode. When transitioning from force mode to position mode, the input processing unit 502 may disable the grip controller 508 as soon as the desired θ ジョー becomes greater than or equal to the threshold for detent. Therefore, the debouncing technique may be one-sided. The debouncing technique prevents the grip force controller 508 from being repeatedly enabled and disabled in a state where it can cause oscillation of the commanded grip force when the desired θ ジョー oscillates around the detent.

[0080] FIG. 11A shows the commanded θ ジョー 1103 of the wrist joint, the measured θ ジョー 1103, and the measured θ ジョー1105, Command grip force 1107, measured grip force 1109, and a time plot showing the current command 1106 from the grip force controller (e.g., grip force controller 508 in FIG. 10). The threshold for backlash is the command θ ジョー 1103 is set to 0 so that the wrist joint operates in the position mode when 1103 is 0 degrees or more. Command θ ジョー When 1103 is less than 0 degrees, the wrist joint operates in the force mode. The positive grip force indicates the grip force in the force mode, and the negative grip force indicates the grip force in the position mode.

[0081] FIG. 11A shows that the wrist joint is operating in the position mode between times 11.6 and 12 seconds. After time 12 seconds, the command θ ジョー 1103 is set near the threshold for backlash due to a user input device (UID) set to backlash. Measured θ ジョー 1105 remains above about 20 degrees, probably because the joint is gripping an object. The grip force controller 508 is repeatedly enabled and disabled when the wrist joint oscillates between the position mode and the force mode, and when the grip force controller 508 is enabled during the force mode, it causes vibrations in the commanded grip force 1107 and the current command 1106 from the grip force controller 508. The result is an undesirable large oscillation in the measured grip force 1109 observed between times 12 and 12.4 seconds. Measured θ ジョー 1105 also shows some undesirable vibrations due to the oscillation of the measured grip force 1109.

[0082] FIG. 11B shows the command θ ジョー 1113 when it is set near backlash, when the control system (e.g., input processing unit 502 and actuator command generator 504 in FIG. 10) uses a debouncing algorithm, for the command θ of the wrist joint ジョー 1113, measured θ ジョー1115, the commanded grip force 1117, the measured grip force 1119, and a time plot showing the current command 1116 from the grip force controller 508. The threshold for backlash is reset to 0 again. Between times 30.2 and 30.9 seconds, the wrist joint is operating in position mode. After time 30.9 seconds, the command θ ジョー 1113 is set near the threshold for backlash.

[0083] The debouncing algorithm may allow the grip force controller 508 to transition the wrist joint from position mode to force mode only if the desired θ ジョー is less than 0 degrees for a pre-specified minimum duration. Since the control system does not detect this condition, the wrist joint remains in position mode and the grip force controller 508 is not activated. As a result, the commanded grip force 1117 remains at the default value of 0 N and the current command 1116 from the grip force controller 508 also remains at 0. The measured grip force 1119 does not exhibit large fluctuations, and the measured θ ジョー 1115 does not exhibit the vibrations observed in FIG. 11A, ensuring a smooth application of the grip force (the measured grip force 1119 is shown as positive even if the wrist joint remains in position mode).

[0084] A smooth application of the grip force may also be important when the wrist joint is gripping an object when transitioning between position and force modes. For example, during position mode, even if the grip force controller 508 is not activated, if the wrist joint is gripping an object, a non-zero measured grip force may exist. The desired θ ジョーWhen it drops below the threshold for backstop and indicates a transition from the position mode to the force mode, the gripper force controller 508 may first drive the commanded gripper force from 0 N. Similarly, when transitioning from the force mode to the position mode, when the gripper force controller 508 is deactivated, the commanded gripper force may be reset to the default value of 0 N output from the position controller 506. As a result, there may be a sudden change in the measured gripper force during the transition, and the wrist joint may drop the object.

[0085] FIG. 12A is a time plot showing the commanded θ of the wrist joint when the wrist joint transitions from the position mode to the force mode and returns to the position mode, and the control system does not attempt to limit the change in the measured gripper force 1209. ジョー 1203, measured θ ジョー 1205, commanded gripper force 1207, and measured gripper force 1209. The threshold for backstop is reset to 0 again so that the wrist joint operates in the position mode when the commanded θ ジョー 1203 is 0 degrees or more. When the commanded θ ジョー 1203 is less than 0 degrees, the wrist joint is operating in the force mode.

[0086] The wrist joint is initially operating in the position mode. The commanded θ ジョー 1203 is initially 0 degrees, and the commanded gripper force 1207 is initially 0 N. The measured θ ジョー 1205 is 25 degrees, and the measured gripper force 1209 is 8 N due to the object being held between the joints. At time 27.5 seconds, the commanded θ ジョー 1203 becomes negative, transitioning the wrist joint from the position mode to the force mode. When the gripper force controller 508 is activated, the commanded gripper force 1207 ramps up from 0 N until the commanded θ ジョー 1203 reaches its most negative value. However, the measured gripper force 1209 experiences a sudden drop of 5 N during the transition before ramping up as commanded. At time 30 seconds, the commanded θ ジョー1203 begins to decrease in negative value. The commanded grip force 1207 begins the ramp-down, and the measured grip force 1209 follows as commanded. At 31 seconds, the command θ ジョー 1203 becomes positive and transitions the wrist joint to return from force mode to position mode. When the grip force controller 508 is deactivated, the measured grip force 1209 experiences a sudden jump from 0 N to the static 8 N in position mode with some overshoot. It is desirable to minimize the sudden change in the measured grip force 1209 during the transition.

[0087] In one embodiment, to minimize the sudden change in the grip force of the wrist joint when holding an object during the transition from position mode to force mode, the grip force controller 508 may adjust the commanded grip force. For example, the grip force controller 508 may command θ ジョー When the grip force controller 508 is activated when the command θ becomes less than a threshold value for backlash and certain conditions are met, the commanded grip force may be set to the current measured grip force minus a predefined margin. By doing so, it is possible to prevent the measured grip force from decreasing to a value close to 0 N during the transition, thereby reducing the possibility that the joint drops the object held between the joints. In one embodiment, the measured grip force may be generated by a grip force estimator 524 based on the tension value measured by the cable and the cable from the wrist link 512.

[0088] To evaluate a first condition for adjusting the commanded grip force, the grip force controller 508 commands θ ジョーAs indicated by decreasing below a threshold for backlash prevention, due to the activation of the grip force controller 508, it may be determined whether the commanded grip force is increasing or will increase. For a second condition, the grip force controller 508 may determine whether the error between the measured grip force and the commanded grip force is greater than a predefined maximum force error. In one embodiment, the grip force controller 528 may use a debouncing technique for one or both of the conditions. If these two conditions are met, the grip force controller 508 may set the commanded grip force to the current measured grip force minus a predefined margin.

[0089] In one embodiment, to minimize a sudden change in the grip force of the wrist joint when holding an object during a transition from a force mode to a position mode, the grip force controller 508 may adjust the commanded grip force. For example, the grip force controller 508 may command θ ジョー When the grip force controller 508 is deactivated when θ becomes greater than a threshold for backlash prevention and when certain conditions are met, the commanded grip force may be set to a predefined minimum grip force value. Doing so instead of starting from the default 0 N in the position mode may reduce the change in the measured grip force as it rises to the static grip force in the position mode.

[0090] To evaluate the conditions for adjusting the grip force, the grip force controller 508 may determine whether the commanded grip force is less than a predefined minimum grip force value. The grip force controller 508 may also command θ ジョーIt may be determined whether the commanded grip force is decreasing, as indicated by increasing towards a threshold for backstop or exceeding the backstop threshold. Additionally, the grip force controller 508 may determine whether the absolute value of the error between the measured grip force and the minimum grip force value is less than a pre-specified maximum grip force error value. In one embodiment, the grip force controller 528 may use a debouncing technique for one or more conditions. If all conditions are met, the grip force controller 508 may set the commanded grip force to a pre-specified minimum grip force value. In one embodiment, the pre-specified minimum grip force value may be set to 3N.

[0091] FIG. 12B is a time plot showing the commanded θ ジョー 1213, measured θ ジョー 1215, commanded grip force 1217, and measured grip force 1219 of the wrist joint as the control system limits the change in the measured grip force 1219 when the wrist joint transitions between the position mode and the force mode according to aspects of the subject technology. The threshold for backstop is reset to 0 again when the commanded θ ジョー 1213 is 0 degrees or more so that the wrist joint is operating in the position mode. When the commanded θ ジョー 1213 is less than 0 degrees, the wrist joint is operating in the force mode. The pre-specified maximum grip force error value should not be exceeded by the absolute value of the error between the measured grip force and the commanded grip force and is set to be greater than 8N. The pre-specified minimum grip force value is set to 3N.

[0092] The wrist joint is initially operating in the position mode, and the initial states of the commanded θ ジョー 1213, measured θ ジョー 1215, commanded grip force 1217, and measured grip force 1219 are the same as in FIG. 12A. At time 37.4 seconds, the commanded θ ジョー1203 becomes negative, transitioning the wrist joint from position mode to force mode. However, instead of starting at 0N in force mode, the commanded grip force 1217 starts at approximately 6.2N, which is obtained by subtracting a predefined margin from the measured grip force 1219 at this point. Since the absolute value of the error between the measured grip force 1219 and the commanded grip force 1217 is less than the predefined maximum force error, the condition for adjustment to the commanded grip force 1217 is satisfied. As a result, the measured grip force 1219 experiences a significantly smaller drop during the transition from position mode to force mode than it would without adjustment to the commanded grip force 1217. The commanded grip force 1217 gradually becomes negative as the commanded θ ジョー 1213 remains at 6.2N until the commanded grip force 1217 determined from 1213 becomes greater than 6.2N.

[0093] At time 39.8 seconds, the commanded θ ジョー 1213 begins to decrease in negative value. The commanded grip force 1217 starts to ramp down, and the measured grip force 1219 follows as commanded. At time 40.5 seconds, instead of ramping down to 0N as it would without adjustment when the commanded θ ジョー 1213 becomes positive to transition the wrist joint from force mode to position mode, the commanded grip force 1217 remains at a predefined minimum grip force value of 3N. Since the measured grip force 1219 is less than the predefined minimum grip force value of 3N and the absolute value of the error between the measured grip force 1219 and the commanded grip force 1217 is less than the predefined maximum force error, the condition for adjustment to the commanded grip force 1217 is satisfied. As a result, the measured grip force 1219 experiences a significantly smaller change during the transition as it jumps to the stationary 8N in position mode. The commanded grip force 1217 is the commanded θ ジョー 1213 remains at 3N until the commanded grip force 1217 determined from 1213 becomes 0N.

[0094] FIG. 13 illustrates a method 1300 for feedback control of a surgical robot system for using a debouncing algorithm when setting a desired θ of the wrist joint near a threshold for return, or for adjusting a commanded grip force to limit changes in measured grip force when the wrist joint transitions between a position mode and a force mode. Method 1300 may be implemented by a controller 562 of the control system of FIG. 5 or a grip force controller 508 of the control system of FIG. 10, which receives a desired θ from user input, ジョー as well as a measured grip force from the sensor and estimator 566 of FIG. 5 or the grip force estimator 524 of FIG. 10, respectively, and generates a commanded grip force for driving the wrist joint. ジョー Starting from the position mode at block 1301, method 1300 determines, at block 1303, whether the desired θ

[0095] is less than a threshold for return for a minimum duration. In one embodiment, the minimum duration may be pre-specified or may be configurable. Block 1303 implements a debouncing algorithm to prevent a situation where the force mode is repeatedly enabled and disabled, i.e., to prevent oscillations in the commanded grip force when the desired θ ジョー is set near the threshold for return. In one embodiment, block 1303 may determine whether the commanded grip force is increasing or is about to increase as indicated by the desired θ ジョー decreasing below the threshold for return. If the desired θ ジョー is not less than the threshold for return for a pre-specified minimum duration, the wrist joint remains in the position mode of block 1301. ジョー Otherwise, if the desired θ

[0096] is less than the threshold for return for the minimum duration, method 1300 proceeds to block 1305, where the wrist joint is transitioned to the force mode. At block 1307, a commanded grip force is generated based on the measured grip force. At block 1309, the commanded grip force is adjusted to limit changes in the measured grip force as the wrist joint transitions between the position mode and the force mode. At block 1311, it is determined whether the wrist joint has reached the desired θ ジョーIf it is less than the threshold for detent for a pre-specified minimum duration, the wrist joint is transitioning from a position mode to a force mode. Block 1304 determines whether the commanded grip force is increasing. If this condition is false, block 1307 sets the commanded grip force as being converted from a desired θ ジョー and the commanded grip force is not adjusted to limit the change in the measured grip force during the mode transition. Instead, if the condition of block 1304 is true, block 1305 determines whether the error between the measured grip force and the commanded grip force is greater than the maximum force error during the mode transition. The commanded grip force may be 0N default in the position mode before the mode transition. Since the wrist joint may be holding an object, the measured grip force may be different from the commanded grip force before the mode transition. In one embodiment, the maximum force error may be pre-specified or may be configurable.

[0097] If the condition of block 1305 is true, block 1309 sets the commanded grip force to the measured grip force minus a margin when the wrist joint transitions from the position mode to the force mode. In one embodiment, the margin may be pre-specified or may be configurable. Instead, if the condition of block 1305 is false, block 1307 sets the commanded grip force as being converted from a desired θ ジョー and the commanded grip force is not adjusted to limit the change in the measured grip force during the mode transition.

[0098] In block 1311, when the wrist joint is in the force mode, method 1300, in block 1313, determines whether the desired θ ジョー is greater than or equal to the threshold for detent. In one embodiment, block 1311 determines whether the commanded grip force is decreasing as indicated by the desired θ ジョー increasing towards the threshold for detent, and whether the desired θ ジョー is just below the threshold for detent. The desired θ ジョーIf it is not greater than or equal to the threshold for the backstop, the wrist joint remains in the force mode of block 1311.

[0099] Otherwise, the desired θ ジョー If it is greater than or equal to the threshold for the backstop, the wrist joint is transitioning from the force mode to the position mode. Block 1315 determines whether the commanded grip force is decreasing and whether the commanded grip force is less than the minimum grip force during the mode transition. In one embodiment, the minimum grip force may be specified in advance or may be configurable. If the commanded grip force is not decreasing, or if the commanded grip force is not less than the minimum grip force during the mode transition, block 1307 sets the commanded grip force as being converted from the desired θ ジョー and the commanded grip force is not adjusted to limit the change in the measured grip force during the mode transition.

[0100] Otherwise, if the commanded grip force is decreasing and the commanded grip force is less than the minimum grip force during the mode transition, block 1317 determines whether the absolute value of the error between the measured grip force and the minimum grip force value is less than the maximum force error during the mode transition. In one embodiment, the maximum force error may be specified in advance or may be configurable. The maximum force error in block 1317 for the mode transition from force to position may be the same as or different from the maximum force error in block 1305 for the mode transition from position to force.

[0101] If the condition of block 1317 is true, block 1319 sets the commanded grip force to the minimum grip force when the wrist joint transitions from the force mode to the position mode. Otherwise, if the condition of block 1317 is false, block 1307 sets the commanded grip force as being converted from the desired θ ジョー and the commanded grip force is not adjusted to limit the change in the measured grip force during the mode transition.

[0102] FIG. 14 is a block diagram illustrating exemplary hardware components of a surgical robot system according to aspects of the subject technology. The surgical robot system may include an interface device 50, a surgical robot 80, and a control tower 70. The surgical robot system may include other or additional hardware components, and the figure is provided as an example and is not a limitation to this system architecture.

[0103] The interface device 50 includes a camera 51, a sensor 52, a display 53, a user command interface 54, a processor 55, a memory 56, and a network interface 57. The camera 51 and the sensor 52 may be configured to capture color and depth image information of the surgical robot system. The images captured by the camera 51 and the sensor 52 may be projected onto the display 53. The processor 55 may be configured to operate an operating system to control the operation of the interface device 50. The memory 56 may store image processing algorithms, an operating system, program code, and other data memory used by the processor 55. The interface device 50 may be used to generate desired θ ピッチ 、θ ヨー 、and θ ジョー under the control of a remote operator.

[0104] The user command interface 54 may include an interface for other functions such as a web portal. The hardware components can communicate via a bus. The interface device may communicate with the surgical robot system through an external interface using the network interface 57. The external interface may be a wireless or wired interface.

[0105] The control tower 70 may be a treatment-site mobile cart that houses a touch screen display, a computer that controls the operation of the surgeon's robot-assisted instruments, a safety system, a graphical user interface (GUI), a light source, and a video and graphics computer. The control tower 70 may include a central computer 71 that may include at least a visualization computer, a control computer, and an auxiliary computer, various displays 73 that may include a team display and a nurse display, and a network interface 78 that couples the control tower 70 to both the interface device 50 and the surgical robot 80. The control tower 70 may also house third-party devices such as an advanced light engine 72, an electrosurgical unit (ESU) 74 for electrosurgery, and an insufflator and CO2 tank 75. The control tower 70 may provide additional features for user convenience, such as a nurse display touch screen, soft power and E-hold buttons, a user-facing USB for video and still images, and an electronic caster control interface. The auxiliary computer may also run real-time Linux and provide logging / monitoring and interaction with cloud-based web services. The central computer 71 of the control tower 70 may receive the desired θ ピッチ , θ ヨー , and θ ジョー received by the interface device 50 and implement the methods described herein for controlling the grip or release force of the joe.

[0106] The surgical robot 80 includes an articulating operating table 84 having a plurality of integral arms 82 that can be positioned over the anatomical structure of a target patient. A set of interchangeable tools 83 may be attached to or removed from the distal ends of the arms 82 to enable a surgeon to perform various surgical procedures. The surgical robot 80 may also include a control interface 85 for manual control of the arms 82, the operating table 84, and the tools 83. The control interface 85 may include items such as, but not limited to, remote control, buttons, panels, and touchscreens. Other accessories such as trocars (sleeves, seal cartridges, and plugs) and drapes may also be manipulated to perform a procedure by the system. In one embodiment, the plurality of arms 82 may include four arms mounted on both sides of the operating table 84 having two arms on each side. For a particular surgical procedure, the arms mounted on one side of the operating table 84 can be positioned on the opposite side of the operating table 84 by extending and crossing under the operating table 84 and the arms mounted on the other side, thereby resulting in a total of three arms positioned on the same side of the operating table 84. The surgical tool may also include a table computer 81 and a network interface 88, which may communicate with the control tower 70 to position the surgical robot 80.

[0107] The foregoing description has used a specific terminology system for the purpose of explanation to provide a complete understanding of the present invention. However, it will be apparent to those skilled in the art that many specific details are not required to practice the present invention. Therefore, the foregoing description of specific embodiments of the present invention has been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Clearly, many modifications and variations 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, thereby enabling others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The following claims and their equivalents are intended to define the scope of the present invention.

[0108] The methods, devices, processes, and logics described above may be implemented in many different ways and in many different combinations of hardware and software. The controller and estimator may include electronic circuits. For example, all or part of the implementation may include a circuit including 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 including discrete logic or other circuit components including analog circuit components, digital circuit components, or both; or any combination thereof. The circuit may, by way of example, include discrete interconnected hardware components and / or may be combined on a single integrated circuit die, may be distributed among multiple integrated circuit dies, or may be implemented within a multi-chip module (MCM) of multiple integrated circuit dies within a common package.

[0109] The circuit may further include instructions for execution by the circuit or access the instructions. The instructions can be stored in a tangible storage medium other than a temporary signal, such as flash memory, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), etc., or on a magnetic or optical disk such as a compact disc 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 can include a storage medium and instructions stored in or on the medium, and when the instructions are executed by a circuit in a device, the device can be caused to perform any of the processes described above or shown in the drawings.

[0110] Embodiments can be distributed as a circuit among multiple system components, such as among multiple processors and memories, optionally including multiple distributed processing systems. Parameters, databases, and other data structures may be stored and managed separately, incorporated into a single memory or database, logically and physically organized in many different ways, and implemented in many different ways including data structures such as linked lists, hash tables, arrays, records, objects, or implicit storage mechanisms. Programs may be part of a single program (e.g., a subroutine), separate programs distributed across several memories and processors, or implemented in many different ways in libraries such as shared libraries (e.g., dynamic link libraries (DLLs)). A DLL may store, for example, instructions that perform any of the processes described above or shown in the drawings when executed by a circuit.

[0111] In addition, the various controllers described in this specification can take the form of a processing circuit, a microprocessor or a processor, and a computer-readable medium storing computer-readable program code (e.g., firmware) executable by a (micro)processor, a logic gate, a switch, an application-specific integrated circuit (ASIC), a programmable logic controller, and an embedded microcontroller. The controller can be composed of hardware and / or firmware to execute various functions described below and shown in the flowcharts. Also, some of the components shown as being inside the controller may be stored outside the controller, and other components may be used.

[0112] 〔Embodiment〕 (1) A method for controlling the grip force generated by a jaw of a gripper tool of a surgical robot system, comprising: determining, by a processor, that the jaws are closed in a position mode based on an input jaw angle between the jaws, wherein the position mode is characterized by using a position command to position the jaws at the input jaw angle; In the middle of operation measuring the grip force between the jaws in the position mode; determining, by the processor, whether the measured grip force exceeds a threshold in the position mode; and generating a grip force error to limit the measured grip force to the threshold in response to the processor determining that the measured grip force exceeds the threshold. (2) The determining that the jaws are closed in the position mode In the middle of operation is The method according to Embodiment 1, comprising determining by the processor that the input jaw angle is equal to or greater than a threshold jaw angle for a period exceeding a minimum period, 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 contact each other without an object being held. (3) the jaws are closed in the position mode In the middle of operation Determining that includes determining by the processor that the input jaw angle is decreasing over a minimum period in the position mode, the method according to Embodiment 1. (4) Determining whether the measured grip force exceeds the threshold includes determining by the processor that the measured grip force exceeds the threshold as long as the measured grip force exceeds a value obtained by subtracting a margin from the threshold anywhere within a time window, the method according to Embodiment 1. (5) The length of the time window is measured by a grip force counter, and the operation of the grip force counter includes incrementing the grip force counter by one each time the measured grip force is sampled when the measured grip force is less than a value obtained by subtracting the margin from the threshold, and resetting the grip force counter when the measured grip force is greater than the threshold, the method according to Embodiment 4.

[0113] (6) Determining whether the measured grip force exceeds the threshold further includes determining by the processor that the measured grip force exceeds the threshold over the entire length of the time window equal to the grip force counter when the measured grip force exceeds a value obtained by subtracting the margin from the threshold anywhere within the time window, the method according to Embodiment 5. (7) The grip force error includes the difference between the measured grip force and the threshold, the method according to Embodiment 1. (8) Generating the grip force error so as to limit the measured grip force to the threshold value includes generating, by the processor, a compensation position command from the grip force error; and generating, by the processor, an updated position command by combining the compensation position command and the position command, according to the method of Embodiment 1. (9) Further including applying the updated position command to drive the jaw so as to limit the measured grip force to the threshold value, according to the method of Embodiment 8. (10) An apparatus for controlling a jaw of a gripper tool of a surgical robot system, a sensor configured to estimate a grip force generated by the jaw and generate a measured grip force; a processor, determining that the jaw is closed in a position mode based on a desired jaw angle between the jaws, the position mode being characterized by application of a position command to position the jaw at the desired jaw angle; In the middle of operation determining whether the measured grip force exceeds a threshold value in the position mode; and in response to a determination that the measured grip force exceeds the threshold value, generating a grip force error to limit the measured grip force to the threshold value and updating the position command, wherein the processor is configured to perform the above operations; and an actuator drive unit configured to apply the updated position command to drive the jaw so as to limit the measured grip force to the threshold value.

[0114] (11) The processor is configured to determine that the jaw is closed in the position mode, In the middle of operation which means Determining that the desired jaw angle is equal to or greater than a threshold jaw angle for a period exceeding a minimum period, the threshold jaw angle including the jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to contact each other without an object being held, the apparatus according to embodiment 10. (12) the jaws are closed in the position mode In the middle of operation the processor is configured to determine that Determining that the desired jaw angle is decreasing over a minimum period in the position mode, the apparatus according to embodiment 10. (13) the processor is configured to determine whether the measured grip force exceeds the threshold Determining that the measured grip force exceeds the threshold as long as the measured grip force exceeds what is obtained by subtracting a margin from the threshold anywhere within a time window, the apparatus according to embodiment 10. (14) the length of the time window is measured by a grip force counter, the grip force counter Incrementing by one each time the measured grip force is estimated by the sensor and the measured grip force is less than what is obtained by subtracting the margin from the threshold, and Resetting the grip force counter when the measured grip force is greater than the threshold, the apparatus according to embodiment 13. (15) the processor is configured to determine whether the measured grip force exceeds the threshold Further including determining that the measured grip force exceeds the threshold over the entire length of the time window equal to the grip force counter when the measured grip force exceeds what is obtained by subtracting the margin from the threshold anywhere within the time window, the apparatus according to embodiment 14.

[0115] (16) The apparatus according to embodiment 10, wherein the grip force error includes a difference between the measured grip force and the threshold value. (17) The processor being configured to generate the grip force error and update the position command includes: generating a compensation position command from the grip force error; and generating the updated position command to limit the measured grip force to the threshold value by combining the compensation position command and the position command. The apparatus according to embodiment 10. (18) A surgical robot system, comprising: an end effector including 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 being configured to: determine that the jaws are closed in a position mode, the position mode being characterized by application of a position command to position the jaws at the input jaw angle; In the middle of operation measure a grip force between the jaws in the position mode; determine whether the measured grip force exceeds a threshold value in the position mode; generate a grip force error to limit the measured grip force to the threshold value in response to a determination that the measured grip force exceeds the threshold value, and update the position command; and apply the updated position command to position the jaws to limit the measured grip force to the threshold value. A surgical robot system. (19) The processor being configured to determine that the jaws are closed in the position mode includes: (19) Determining that the jaws are closed in the position mode. In the middle of operation The processor being configured to determine that the jaws are closed in the position mode includes: Determining that the input jaw angle is equal to or greater than a threshold jaw angle for a first minimum period, the threshold jaw angle including the jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to contact each other without an object being held, Determining that the input jaw angle is decreasing over a second minimum period in the position mode, the surgical robot system according to embodiment 18, including: (20) The processor is configured to determine whether the measured grip force exceeds the threshold, The surgical robot system according to embodiment 18, including determining, using a debouncing algorithm, that the measured grip force exceeds a value obtained by subtracting a margin from the threshold.

[0116] (21) A method for controlling an opening force generated by a jaw of a gripper tool of a surgical robot system, Determining by a processor that the jaws are in a position mode based on an input jaw angle between the jaws, the position mode being characterized by using a position command to position the jaws at the input jaw angle, 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, Generating an opening force error to maintain the measured opening force higher than the minimum opening force threshold in response to the processor determining that the measured opening force is less than the minimum opening force threshold, the method including. (22) Determining that the jaw is in the position mode includes, determining by the processor that the input jaw angle is greater than or equal to a threshold jaw angle for a minimum period, the threshold jaw angle including the jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to contact each other without an object being held, according to the method of embodiment 21. (23) Determining whether the jaw angle error is greater than a jaw angle error threshold includes, 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, according to the method of embodiment 21. (24) Determining whether the measured opening force is less than a minimum opening force threshold includes, determining by the processor that the measured opening force is 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 a time window, according to the method of embodiment 21. (25) The length of the time window is measured by an opening force counter, and the operation of the opening force counter includes, incrementing the opening force counter by 1 each time the measured opening force is sampled and the measured opening force is greater than the minimum opening force threshold plus the margin, and resetting the opening force counter when the measured opening force is less than the minimum opening force threshold, according to the method of embodiment 24.

[0117] (26) Determining whether the measured opening force is less than a minimum opening force threshold includes, The method according to embodiment 25, further comprising, by the processor, determining that the measured opening force is less than the minimum opening force threshold over the entire length of the time window equal to the opening force counter when the measured opening force is less than the minimum opening force threshold plus the margin anywhere within the time window. (27) The method according to embodiment 21, wherein the opening force error includes a difference between the measured opening force and the minimum opening force threshold. (28) Generating the opening force error to maintain the measured opening force higher than the minimum opening force threshold includes generating, by the processor, a compensation position command from the opening force error; and generating, by the processor, an updated position command by combining the compensation position command and the position command, the method according to embodiment 21. (29) The method according to embodiment 28, further comprising positioning the jaw to maintain the measured opening force higher than the minimum opening force threshold by applying the updated position command. (30) An apparatus for controlling a jaw of a gripper tool of a surgical robotic system, comprising a sensor configured to estimate an angle between the jaws and generate a measured jaw angle; and estimate an opening force generated by the jaws and generate a measured opening force; and a processor configured to determine that the jaw is in a position mode based on a desired jaw angle between the jaws, the position mode being characterized by application of a position command to position the jaw at the desired jaw angle; and determine 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; and In response to determining that the jaw angle error is greater than the jaw angle error threshold, determining whether the measured release force is less than a minimum release force threshold; In response to determining that the measured release force is less than the minimum release force threshold, generating a release force error for updating the position command to maintain the measured release force higher than the minimum release force threshold; and a processor configured to perform; An actuator drive unit configured to apply the updated position command to position the jaw so as to maintain the measured release force higher than the minimum release force threshold. An apparatus comprising:

[0118] (31) The processor being configured to determine that the jaw is in the position mode includes Determining that the desired jaw angle is greater than or equal to a threshold jaw angle for a period exceeding a minimum period, the threshold jaw angle including the jaw angle when the jaws simultaneously contact an object held therebetween or when the jaws begin to contact each other without an object being held. The apparatus according to embodiment 30. (32) The processor being configured to determine whether the jaw angle error is greater than the jaw angle error threshold includes 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. The apparatus according to embodiment 30. (33) The processor being configured to determine whether the measured release force is less than the minimum release force threshold includes Determining that the measured release force is less than the minimum release force threshold as long as the measured release force is less than the minimum release force threshold plus a margin anywhere within the time window. The apparatus according to embodiment 30. (34) The length of the time window is measured by a release force counter, the release force counter Each time the measured opening force is estimated by the sensor, incrementing by one when the measured opening force is greater than the minimum opening force threshold plus the margin, resetting the opening force counter when the measured opening force is less than the minimum opening force threshold, the apparatus according to Embodiment 33, which is configured to perform the above. (35) The fact that the processor is configured to determine whether the measured opening force is less than the minimum opening force threshold further includes determining that the measured opening force is less than the minimum opening force threshold over the entire length of the time window equal to the opening force counter when the measured opening force is less than the minimum opening force threshold plus the margin anywhere within the time window, the apparatus according to Embodiment 34.

[0119] (36) The apparatus according to Embodiment 30, wherein the opening force error includes the difference between the measured opening force and the minimum opening force threshold. (37) The fact that the processor is configured to generate the opening force error and update the position command generating a compensation position command from the opening force error, combining the compensation position command and the position command to generate the updated position command and positioning the jaw to maintain the measured opening force higher than the minimum opening force threshold, the apparatus according to Embodiment 30. (38) A surgical robot system, an end effector including a pair of jaws, a user interface device configured to generate an input jaw angle between the jaws, a processor communicably coupled to the end effector, the processor including Based on the input jaw angle between the jaws, determining that the jaws are in a position mode, the position mode being characterized by the application of a position command for positioning the jaws at the input jaw angle; Measuring the jaw angle and the 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 in the position mode is greater than a jaw angle error threshold; In response 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 for updating the position command so as to maintain the measured opening force higher than the minimum opening force threshold; Applying the updated position command to position the jaws so as to maintain the measured opening force higher than the minimum opening force threshold, a surgical robot system configured to perform. (39) The processor being configured to determine whether the jaw angle error is greater than the jaw angle error threshold is Determining that the input jaw angle is greater than the measured jaw angle; Determining that the jaw angle error is greater than the jaw angle error threshold for at least a minimum period, the surgical robot system according to embodiment 38, comprising. (40) The processor being configured to determine whether the measured opening force is less than the minimum opening force threshold is Using a debouncing algorithm to determine that the measured opening force is less than the minimum opening force threshold plus a margin, the surgical robot system according to embodiment 38, comprising.

[0120] (41) A method for controlling the gripping force generated by a gripper tool of a surgical robot system, comprising: determining, by a processor, based on a change in an input jaw angle between the jaws, that the jaws are transitioning between a position mode and a force mode, wherein the position mode is characterized by positioning the jaws at the input jaw angle, and the force mode is characterized by driving the jaws to a commanded grip force determined based on the input jaw angle having a negative value; measuring the gripping force between the jaws; determining, by the processor, based on the commanded grip force and the measured grip force, whether to adjust the commanded grip force during the transition between the position mode and the force mode; adjusting, by the processor, the commanded grip force to smooth a change in the measured grip force during the transition between the position mode and the force mode in response to determining to adjust the commanded grip force. (42) The determining that the jaws are transitioning between the position mode and the force mode comprises: determining that the jaws are transitioning from the position mode to the force mode when the input jaw angle is initially 0 or greater and becomes less than 0 over a minimum duration, or determining that the jaws are transitioning from the force mode to the position mode when the input jaw angle is initially less than 0 and becomes 0 or greater, according to the method of embodiment 41. (43) The determining that the jaws are transitioning 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 the jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to contact each other without an object being held; The method according to embodiment 41, comprising: determining, by the processor, that the jaw transitions from the position mode to the force mode when the input jaw angle is less than the threshold jaw angle and exceeds a minimum duration. (44) Determining whether to adjust the commanded gripper force during the transition The method according to embodiment 43, comprising: determining, by the processor, to adjust the commanded gripper force during the transition from the position mode to the force mode when the commanded gripper force is increasing and the difference between the measured gripper force and the commanded gripper force is greater than a maximum gripper force error. (45) Adjusting the commanded gripper force In response to determining, by the processor, to adjust the commanded gripper force, setting the commanded gripper force to be the measured gripper force minus a margin, or Otherwise, setting, by the processor, the commanded gripper force based on the input jaw angle in the force mode. The method according to embodiment 44.

[0121] (46) Determining that the jaw is transitioning between the position mode and the force mode Determining, by the processor, that the jaw is initially in the force mode when the input jaw angle is less than a threshold jaw angle, the threshold jaw angle including the jaw angle when the jaws simultaneously contact an object held therebetween or when the jaws begin to contact each other without an object being held, and Determining, by the processor, that the jaw transitions from the force mode to the position mode when the input jaw angle is greater than or equal to the threshold jaw angle. The method according to embodiment 41. (47) Determining whether to adjust the commanded gripper force during the transition The method according to embodiment 46, comprising determining by the processor to adjust the commanded grip force when, during the transition from the force mode to the position mode, the commanded grip force is decreasing, the commanded grip force is less than the minimum grip force, and the absolute value of the difference between the measured grip force and the minimum grip force is less than the maximum grip force error. (48) Adjusting the commanded grip force comprises setting the commanded grip force to the minimum grip force by the processor in response to determining to adjust the commanded grip force by the processor, or otherwise, the method according to embodiment 47, comprising setting the commanded grip force by the processor based on the input jaw angle. (49) When the commanded grip force is adjusted, the processor changes the commanded grip force based on the input jaw angle in the force mode following the transition from the position mode to the force mode, or the method according to embodiment 41, further comprising, when the commanded grip force is adjusted, the processor changing the commanded grip force based on the input jaw angle in the position mode following the transition from the force mode to the position mode. (50) An apparatus for controlling a jaw of a gripper tool of a surgical robot system a sensor configured to estimate a grip force between the jaws and generate a measured grip force; a processor, wherein the processor determines that the jaw transitions between a position mode and a force mode based on a desired change in jaw angle between the jaws, the position mode being characterized by positioning the jaw at the desired jaw angle, and the force mode being characterized by driving the jaw with a commanded grip force determined based on the desired jaw angle having a negative value; Based on the commanded gripper force and the measured gripper force, determining whether to adjust the commanded gripper force during the transition between the position mode and the force mode; In response to a determination to adjust the commanded gripper force, adjusting the commanded gripper force to smooth a change in the measured gripper force during the transition between the position mode and the force mode, an apparatus configured to perform.

[0122] (51) The processor being configured to determine that the jaw transitions between the position mode and the force mode includes: 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 0 and becomes less than 0 over a minimum duration; Determining that the jaw transitions from the force mode to the position mode when the desired jaw angle is initially less than 0 and becomes greater than or equal to 0, the apparatus of embodiment 50. (52) The processor being configured to determine that the jaw transitions between the position mode and the force mode includes: Determining that the jaw is initially in the position mode when the desired jaw angle is greater than or equal to a threshold jaw angle, the threshold jaw angle including a jaw angle when the jaws simultaneously contact an object held therebetween or when the jaws begin to contact each other without an object being held; Determining that the jaw transitions from the position mode to the force mode when the desired jaw angle is less than the threshold jaw angle for more than a minimum duration, the apparatus of embodiment 50. (53) The processor being configured to determine whether to adjust the commanded gripper force during the transition includes: The apparatus according to embodiment 52, comprising determining to adjust the commanded gripper force when, during the transition from the position mode to the force mode, the commanded gripper force is increasing and the difference between the measured gripper force and the commanded gripper force is greater than the maximum gripper force error. (54) The processor being configured to adjust the commanded gripper force means that in response to the determination to adjust the commanded gripper force, setting the commanded gripper force to the measured gripper force minus a margin, or otherwise, setting the commanded gripper force based on the desired jaw angle in the force mode, as described in embodiment 53 of the apparatus. (55) The processor being configured to determine that the jaw is transitioning between the position mode and the force mode means that when the desired jaw angle is less than a threshold jaw angle, determining that the jaw is initially in the force mode, the threshold jaw angle including the jaw angle when the jaws simultaneously contact an object held therebetween or when the jaws begin to contact each other without an object being held, and when the desired jaw angle is greater than or equal to the threshold jaw angle, determining that the jaw is transitioning from the force mode to the position mode, as described in embodiment 50 of the apparatus.

[0123] (56) The processor being configured to determine whether to adjust the commanded gripper force during the transition means that during the transition from the force mode to the position mode, when the commanded gripper force is decreasing, the commanded gripper force is less than the minimum gripper force, and the absolute value of the difference between the measured gripper force and the minimum gripper force is less than the maximum gripper force error, determining to adjust the commanded gripper force, as described in embodiment 55 of the apparatus. (57) The processor being configured to adjust the commanded gripper force means that In response to said determination to adjust said commanded gripper force, setting said commanded gripper force to said minimum gripper force, or Otherwise, the apparatus of embodiment 56, comprising setting said commanded gripper force based on said desired jaw angle in said force mode. (58) When said processor is configured to adjust said commanded gripper force, subsequent to said transition from said position mode to said force mode, changing said commanded gripper force based on said desired jaw angle in said force mode, or subsequent to said transition from said force mode to said position mode, when said processor is configured to adjust said commanded gripper force, further configured to change said commanded gripper force based on said desired jaw angle in said position mode, the apparatus of embodiment 50. (59) A surgical robotic system, comprising an end effector including a pair of jaws, a user interface device configured to generate an input jaw angle between said jaws, a processor communicatively coupled to said end effector, said processor being configured to determine that said jaws transition between a position mode and a force mode based on a change in said input jaw angle, said position mode being characterized by positioning said jaws at said input jaw angle, said force mode being characterized by driving said jaws with a commanded gripper force determined based on said input jaw angle having a negative value; measuring a gripper force between said pair of jaws; determining whether to adjust said commanded gripper force during said transition between said position mode and said force mode based on said commanded gripper force and said measured gripper force; configured to adjust the commanded gripper force in response to a determination to adjust the commanded gripper force to smooth a change in the measured gripper force during the transition between the position mode and the force mode, a surgical robot system. (60) The processor is configured to determine that the jaw transitions between the position mode and the force mode, when the input jaw angle is greater than or equal to a threshold jaw angle, determining that the jaw is initially in the position mode, the threshold jaw angle including the jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to contact each other without an object being held, when the input jaw angle is less than the threshold jaw angle for a minimum duration, determining that the jaw transitions from the position mode to the force mode, The processor is configured to determine whether to adjust the commanded gripper force during the transition, including determining to adjust the commanded gripper force when the commanded gripper force is increasing and the difference between the measured gripper force and the commanded gripper force is greater than a maximum gripper force error during the transition from the position mode to the force mode, The processor is configured to adjust the commanded gripper force, in response to the determination to adjust the commanded gripper force, setting the commanded gripper force to the measured gripper force minus a margin, or otherwise, setting the commanded gripper force based on the input jaw angle in the force mode, a surgical robot system according to embodiment 59.

Claims

1. 1. An apparatus for controlling jaws of a gripper tool of a surgical robotic system, comprising: a sensor configured to estimate a gripping force generated by the jaws to generate a measured gripping force; 1. A processor comprising: determining that the jaws are in the process of closing in a position mode based on a desired jaw angle between the jaws, the position mode being characterized by application of position commands to position the jaws at the desired jaw angle; determining whether the measured grip force exceeds a threshold in the position mode; a processor configured to: in response to determining that the measured grip force exceeds the threshold, generate a grip force error to limit the measured grip force to the threshold and update the position command; and an actuator drive unit configured to apply the updated position command to drive the jaws to limit the measured gripping force to the threshold value.

2. The processor is configured to determine that the jaws are in the process of closing in the position mode, 2. The apparatus of claim 1, comprising determining that the desired jaw angle is equal to or greater than a threshold jaw angle for more than a minimum period of time, the threshold jaw angle comprising a jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to contact each other without an object being held.

3. The processor is configured to determine that the jaws are in the process of being closed in the position mode, The apparatus of claim 1 including determining that the desired jaw angle is decreasing for a minimum period of time in the position mode.

4. The processor is configured to determine whether the measured grip force exceeds the threshold value, 2. The apparatus of claim 1, further comprising determining that the measured grip force exceeds the threshold as long as the measured grip force exceeds the threshold minus a margin anywhere within a time window.

5. The length of the time window is measured by a grip force counter, the grip force counter incrementing by one each time the measured grip force is estimated by the sensor when the measured grip force is less than the threshold minus the margin; and resetting the grip force counter when the measured grip force is greater than the threshold value.

6. The processor is configured to determine whether the measured grip force exceeds the threshold value, 6. The apparatus of claim 5, further comprising determining that the measured grip force exceeds the threshold value for the entire length of the time window equal to the grip force counter when the measured grip force exceeds the threshold value minus the margin anywhere within the time window.

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

8. The processor is configured to generate the grip force error and update the position command, generating a compensated position command from the grip force error; and combining the compensated position command with the position command to generate an updated position command to limit the measured grip force to the threshold value.

9. 1. A surgical robotic system, comprising: an end effector including 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 comprising: determining that the jaws are in the process of closing in a position mode based on the input jaw angle between the jaws, the position mode being characterized by application of position commands to position the jaws at the input jaw angle; measuring a gripping force between the jaws in the position mode; determining whether the grip force measured in the position mode exceeds a threshold; in response to determining that the measured grip force exceeds the threshold, generating a grip force error to limit the measured grip force to the threshold and updating the position command; and applying the updated position commands to position the jaws to limit the measured gripping force to the threshold.

10. The processor is configured to determine that the jaws are in the process of closing in the position mode, 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, the threshold jaw angle comprising a jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to contact each other without an object being held; and determining that the input jaw angle is decreasing for a second minimum period of time in the positional mode.

11. The processor is configured to determine whether the measured grip force exceeds the threshold. The surgical robot system of claim 9, further comprising using a debouncing algorithm to determine when the measured grip force exceeds the threshold minus a margin.

12. 1. A method for controlling a gripping force generated by jaws of a gripper tool of a surgical robotic system, comprising: determining, by a processor, that the jaws are in the process of closing in a position mode based on an input jaw angle between the jaws, the position mode being characterized by using position commands to position the jaws at the input jaw angle; measuring a gripping force between the jaws while the jaws are in the process of closing in the position mode; determining, by the processor, whether the grip force measured in the position mode exceeds a grip force threshold; generating, by the processor, a grip force error in response to determining that the measured grip force exceeds the grip force threshold, the grip force error comprising a difference between the measured grip force and the grip force threshold; generating an updated position command based on the grip force error; and applying the updated position commands to position the jaws, thereby limiting the grip force to the grip force threshold.

13. Determining that the jaws are in the process of closing in the position mode includes:

13. The method of claim 12, comprising 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, the threshold jaw angle comprising a jaw angle when the jaws simultaneously contact an object held between the jaws or when the jaws begin to contact each other without an object being held.

14. Determining that the jaws are in the process of closing in the position mode includes: The method of claim 12 including determining, by the processor, that the input jaw angle is decreasing for a minimum period of time in the position mode.

15. Determining whether the measured grip force exceeds the grip force threshold includes:

13. The method of claim 12, comprising determining, by the processor, that the measured grip force exceeds the grip force threshold so long as the measured grip force exceeds the grip force threshold minus a margin anywhere within a time window.

16. The length of the time window is measured by a grip force counter, the operation of which is determined by: incrementing the grip force counter by one each time the measured grip force is sampled when the measured grip force is less than the grip force threshold minus the margin; and resetting the grip force counter when the measured grip force is greater than the grip force threshold.

17. Determining whether the measured grip force exceeds the grip force threshold includes:

17. The method of claim 16, further comprising determining, by the processor, that the measured grip force exceeds the grip force threshold for the entire length of the time window equal to the grip force counter when the measured grip force exceeds the grip force threshold minus the margin anywhere within the time window.

18. Generating the updated position command generating, by the processor, a compensated position command from the grip force error; and combining, by the processor, the compensated position command and the position command to generate the updated position command.

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