# US 11,998,398 B2 · System and method for force or torque limit compensation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,998,398 B2 - Document ID: US11998398B2 - Status: Granted - Kind: B2 - Application number: 17/110,944 - Filed: 2020-12-03 - Published: 2021-03-25 - Granted: 2024-06-04 - Earliest claimed: 2015-05-15 - Assignees: Intuitive Surgical Operations, Inc. - Applicants: Intuitive Surgical Operations, Inc. - Inventors: Melody Wu; David W. Weir - Web page: https://patentgrep.com/patent/US11998398B2 ## CPC - A61B 90/03: {Automatic limiting or abutting means, e.g. for safety} - A61B 17/285: combined with cutting implements - A61B 17/3205: Excision instruments - A61B 18/085: {Forceps, scissors} - A61B 34/00: Computer-aided surgery; Manipulators or robots specially adapted for use in surgery - A61B 34/10: Computer-aided planning, simulation or modelling of surgical operations - A61B 34/20: Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis - A61B 34/30: Surgical robots - A61B 34/32: operating autonomously - A61B 34/35: for telesurgery - B25J 9/163: {learning, adaptive, model based, rule based expert control} - B25J 9/1633: {compliant, force, torque control, e.g. combined with position control} - A61B 18/1445: {at the distal end of a shaft, e.g. forceps or scissors at the end of a rigid rod} - A61B 34/71: {Manipulators operated by drive cable mechanisms} - A61B 2017/003: {Steerable} - A61B 2017/07285: {characterised by its cutter} - A61B 2018/1455: {having a moving blade for cutting tissue grasped by the jaws} - A61B 2034/102: {Modelling of surgical devices, implants or prosthesis} - A61B 2034/306: {Wrists with multiple vertebrae} - A61B 2090/031: {torque limiting} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - B25J: MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES ({manipulators specially adapted for use in surgery A61B34/70; manipulators used in cleaning hollow articles B08B9/04}; manipulators associated with rolling mills B21B39/20; manipulators associated with forging machines B21J13/10; {manipulators associated with picking-up and placing mechanisms B23P19/007}; means for holding wheels or parts thereof B60B30/00; {vehicles with ground-engaging propulsion means, e.g. walking members B62D57/02, B62D57/032; devices for picking-up and depositing articles or materials between conveyors B65G47/90, B65G47/91; manipulators with gripping or holding means for transferring packages B65H67/065}; cranes B66C; {manipulators used in the protection or supervision of pipe-line installations F17D5/00; walking equipment adapted for nuclear steam-generators F22B37/006}; manipulators specially adapted for, or associated with, nuclear reactors G21C; {apparatus used for handling wafers during manufacture or treatment of semiconductor H10P72/50}) ## Abstract A system and method of force or torque limit compensation includes a surgical instrument for use with a computer-assisted medical device. The surgical instrument includes an end effector located at a distal end of the instrument, a drive unit for operating a degree of freedom of the instrument, a shaft coupled to the drive unit, and one or more drive mechanisms in the shaft for coupling force or torque from the drive unit to the end effector and the articulated wrist. To control the degree of freedom, the instrument is configured to determine a current position of the degree of freedom, determine a force or torque limit compensation based on the current position, alter one or more force or torque limits based on the force or torque limit compensation, and adjust the degree of freedom subject to the one or more force or torque limits. ## Claims ### Claim 1 A method of operating an instrument for use with a computer-assisted device comprising: determining, by a control unit, a current position of a degree of freedom of the instrument; determining, by the control unit, a force limit compensation or a torque limit compensation based on the current position; altering, by the control unit, one or more force limits or one or more torque limits based on the force limit compensation or the torque limit compensation; and adjusting, by the control unit using a drive unit, the degree of freedom subject to the one or more force limits or the one or more torque limits. ### Claim 2 (depends on 1) The method of claim 1, wherein the degree of freedom is associated with: an angle of gripping jaws of an end effector of the instrument; an amount of extension of a cutting blade of the end effector; or a flex angle of an articulated wrist coupling the end effector to a shaft of the instrument. ### Claim 3 (depends on 1) The method of claim 1, wherein the one or more force limits or the one or more torque limits include an upper limit associated with a maximum force or a maximum torque that may be applied to adjust the degree of freedom. ### Claim 4 (depends on 1) The method of claim 1, wherein the one or more force limits or the one or more torque limits include an upper limit and a lower limit specifying a range of forces or a range torques that may be applied to adjust the degree of freedom. ### Claim 5 (depends on 1) The method of claim 1, wherein determining the current position comprises measuring the current position at the drive unit. ### Claim 6 (depends on 1) The method of claim 1, wherein a relationship between the current position and the force limit compensation or the torque limit compensation is modeled using a compensation curve. ### Claim 7 (depends on 6) The method of claim 6, wherein the compensation curve includes: a transition region wherein the compensation curve has a first slope; an operational region wherein the compensation curve has a second slope smaller than the first slope; and a saturation region wherein the force limit compensation or the torque limit compensation is at a maximum value. ### Claim 8 (depends on 7) The method of claim 7, wherein the compensation curve further includes a start-up region wherein the force limit compensation or the torque limit compensation is zero. ### Claim 9 (depends on 6) The method of claim 6, wherein the compensation curve includes hysteresis. ### Claim 10 (depends on 6) The method of claim 6, wherein the compensation curve is symmetric about a home position of the degree of freedom. ### Claim 11 (depends on 1) The method of claim 1, wherein a relationship between the current position and the force limit compensation or the torque limit compensation is modeled using a lookup table of control points. ### Claim 12 (depends on 11) The method of claim 11, wherein determining the force limit compensation or the torque limit compensation comprises using the lookup table and interpolation. ### Claim 13 (depends on 1) The method of claim 1, wherein the force limit compensation or the torque limit compensation compensates for a restraining or return to home force or torque applied to the degree of freedom. ### Claim 14 (depends on 1) The method of claim 1, wherein altering the one or more force limits or the one or more torque limits comprises adding the force limit compensation or the torque limit compensation to each of the one or more force limits or the one or more torque limits. ### Claim 15 One or more non-transitory machine-readable media comprising machine-readable instructions, which when executed by one or more processors are adapted to cause the one or more processors to perform a method comprising: determining a current position of a degree of freedom of an instrument of a computer-assisted device; determining a force limit compensation or a torque limit compensation based on the current position; altering one or more force limits or one or more torque limits based on the force limit compensation or the torque limit compensation; and adjusting, using a drive unit, the degree of freedom subject to the one or more force limits or the one or more or torque limits. ### Claim 16 (depends on 15) The one or more non-transitory machine-readable media of claim 15, wherein the degree of freedom is associated with: an angle of gripping jaws of an end effector of the instrument; an amount of extension of a cutting blade of the end effector; or a flex angle of an articulated wrist coupling the end effector to a shaft of the instrument. ### Claim 17 (depends on 15) The one or more non-transitory machine-readable media of claim 15, wherein determining the current position comprises measuring the current position at the drive unit. ### Claim 18 (depends on 15) The one or more non-transitory machine-readable media of claim 15, wherein a relationship between the current position and the force limit compensation or the torque limit compensation is modeled using a compensation curve or a lookup table of control points. ### Claim 19 (depends on 15) The one or more non-transitory machine-readable media of claim 15, wherein the force limit compensation or the torque limit compensation compensates for a restraining or return to home force or torque applied to the degree of freedom. ### Claim 20 (depends on 15) The one or more non-transitory machine-readable media of claim 15, wherein altering the one or more force limits or the one or more torque limits comprises adding the force limit compensation or the torque limit compensation to each of the one or more force limits or the one or more torque limits.