Hardstop detection and handling for surgical tool

Patent metadata

Field	Value
Publication number	US-12478451-B2
Application number	US-202418774132-A
Country	US
Kind code	B2
Filing date	Jul 16, 2024
Priority date	Oct 12, 2021
Publication date	Nov 25, 2025
Grant date	Nov 25, 2025

Abstract

The disclosed embodiments relate to systems and methods for a surgical tool or a surgical robotic system. One example system for detecting a hardstop for a surgical tool includes a wrist connected to and driven by a plurality of cables of a tool driver, a plurality of sensors configured to detect forces associated with the plurality of cables one or more processors configured to perform a comparison of the forces associated with the plurality of cables, selected a highest tension cable from the plurality of cables based on the comparison of the forces associated with the plurality of cables, set a force assigned to the highest tension cable to a predetermined value, calculate a variable torque threshold for the wrist based on a sum of the predetermined value for the highest tension cable and detected forces for remaining cables in the plurality of cables, receive a joint torque value for the wrist, perform a comparison of the received joint torque value for the wrist to a variable wrist torque threshold and identify a hardstop based on the comparison of the received joint torque value for the wrist to the variable wrist torque threshold.

First claim

What is claimed is:

1 . An apparatus for detecting a hardstop for a surgical tool including a plurality of sensors and a plurality of cables, the apparatus comprising:
a memory configured to store a hardstop detection program; and a controller configured to execute the hardstop detection program to select a highest tension cable from the plurality of cables based on a comparison of the forces associated with the plurality of cables, calculate a torque threshold based at least on the highest tension cable, and detect a hardstop based on a comparison of a received joint torque value to the torque threshold.

2 . The apparatus of claim 1 , wherein the controller is configured to, when the comparison indicates that the received joint torque value exceeds the torque threshold, generate a user message with an instruction to move the surgical tool.

3 . The apparatus of claim 2 , wherein the instruction to move includes an instruction to move in a yaw direction closer to a home position, an instruction to move in a pitch direction closer to the homing position, or operate an end effector.

4 . The apparatus of claim 1 , wherein the forces associated with the plurality of cables are determined from respective motor torque sensors and associated with pulley dimensions for respective pulleys for the cables.

5 . The apparatus of claim 4 , wherein the torque threshold for a pitch angle is a minimum pitch angle when one cable is the highest selected cable or a maximum pitch angle when another cable is the highest selected cable.

6 . The apparatus of claim 5 , wherein when the comparison indicates that the torque threshold is less than the minimum pitch angle, the hardstop is on a negative side of a pitch joint of the surgical tool; or
wherein when the comparison indicates that the torque threshold is greater than the maximum pitch angle, then the hardstop is on a positive side of the pitch joint of the surgical tool.

7 . The apparatus of claim 4 , wherein the torque threshold for a yaw angle is a minimum yaw angle when one cable is the highest selected cable or a maximum yaw angle when another cable is the highest selected cable.

8 . The apparatus of claim 7 , wherein when the comparison indicates that the torque threshold is less than the minimum yaw angle, then the hardstop is on a negative side of a yaw joint of the surgical tool; or
wherein when the comparison indicates that the torque threshold is greater than the maximum yaw angle, then the hardstop is on a positive side of the yaw joint of the surgical tool.

9 . The apparatus of claim 1 , wherein the controller is configured to activate a hardstop handling phase in response to the comparison of the received joint torque value for the torque threshold.

10 . The apparatus of claim 9 , the wherein the controller is configured to identify a user input angle and provide a motor command independent of the user input angle when the received joint torque value exceeds the torque threshold.

11 . The apparatus of claim 10 , wherein the controller is configured to provide a second motor command based on the user input angle when the received joint torque value does not exceed the torque threshold.

12 . The apparatus of claim 1 , wherein the controller is configured to identify a user input jaw angle for a jaw of the surgical tool, calculate a force error as a difference between the force assigned to the highest tension cable to the predetermined value; and compensate for the force error to modify the user input jaw angle with a proportional control algorithm.

13 . The apparatus of claim 12 , wherein the controller is configured to activate a catching up algorithm for the jaw, latch a last joint command from a proportional control algorithm as an initial jaw catching up amount, identify a subsequent user input jaw angle to open the jaw or close the jaw, and generate a jaw command adjusted based on the subsequent user input jaw angle.

14 . The apparatus of claim 13 , wherein the controller is configured to subtract the initial jaw catching up amount from the subsequent user input jaw angle for a jaw command when the user input jaw angle is to open the jaw.

15 . The apparatus of claim 13 , wherein the controller is configured to subtract a predefined step size from the subsequent user input jaw angle for a jaw command when the user input jaw angle is to close the jaw.

16 . A method for detecting a hardstop for a surgical tool including a plurality of cables, the method comprising:
select a highest tension cable from the plurality of cables based on a comparison of the forces associated with the plurality of cables; calculate a torque threshold based at least on the highest tension cable; and detect a hardstop based on a comparison of a received joint torque value to the torque threshold.

17 . The method of claim 16 , wherein the forces associated with the plurality of cables are determined from respective motor torque sensors and associated with pulley dimensions for respective pulleys for the cables.

18 . The method of claim 17 , wherein:
the torque threshold is a minimum pitch angle when a first cable or second cable is the highest selected cable; or the torque threshold is a maximum pitch angle when a third cable or a fourth cable is the highest selected cable; or the torque threshold is a minimum yaw angle when the first cable or the fourth cable is the highest selected cable; or the torque threshold is a maximum yaw angle when another cable the second cable or the third cable is the highest selected cable.

19 . The method of claim 18 , wherein when the comparison indicates that the torque threshold is less than the minimum pitch angle, then the hardstop is on a negative side of a pitch joint of the surgical tool; or
wherein when the comparison indicates that the torque threshold is greater than the maximum pitch angle, then the hardstop is on a positive side of the pitch joint of the surgical tool; or wherein when the comparison indicates that the torque threshold is less than the minimum yaw angle, then the hardstop is on the negative side of a yaw joint of the surgical tool; or wherein when the comparison indicates that the torque threshold is greater than the maximum yaw angle, then the hardstop is on the positive side of the yaw joint of the surgical tool.

20 . A non-transitory computer readable medium including instructions that when executed are operable to perform a method for detecting a hardstop for a surgical tool, the method comprising:
select a highest tension cable from the plurality of cables based on a comparison of the forces associated with the plurality of cables; calculate a torque threshold based at least on the highest tension cable; and detect a hardstop based on a comparison of a received joint torque value to the torque threshold.

Assignees

• Verb Surgical Inc

Inventors

• Zhang Xiaobin
• Zhou Renbin
• Hariri Alireza

Classifications

• A61B34/71 Primary

  Manipulators operated by drive cable mechanisms · CPC title

• A61B2034/715

  Cable tensioning mechanisms for removing slack · CPC title

• A61B2090/066

  for measuring torque · CPC title

• A61B34/35 Primary

  for telesurgery · CPC title

• A61B2034/305

  Details of wrist mechanisms at distal ends of robotic arms · CPC title