US-12622762-B2 - Detecting collisions in a robotic surgical system

US12622762B2US 12622762 B2US12622762 B2US 12622762B2US-12622762-B2

Abstract

Surgical systems and methods involve a surgical manipulator with a plurality of links and joints that is configured to support and move a surgical instrument for manipulation of an anatomy. A controller is coupled to the surgical manipulator and is configured to measure an actual torque for at least one active joint and calculate an expected torque for the at least one active joint. The controller compares the actual torque and the expected torque to estimate an external force. The controller determines, based on the external force, that the surgical manipulator and/or the surgical instrument has collided with an object.

Inventors

David G Bowling
John M. Stuart
Jerry A. Culp
Donald W. Malackowski
José Luis Moctezuma de La Barrera
Patrick Roessler
Joel N. Beer

Assignees

STRYKER CORPORATION

Dates

Publication Date: 20260512
Application Date: 20240716

Claims (20)

1 . A surgical system comprising: a surgical manipulator comprising a plurality of links and joints and being configured to support and move a surgical instrument for manipulation of an anatomy; a controller coupled to the surgical manipulator and being configured to: operate the surgical manipulator to control movement of the surgical instrument in a semi-autonomous mode; measure an actual torque for at least one active joint; calculate an expected torque for the at least one active joint; compare the actual torque and the expected torque to estimate an external force; determine, based on the external force, that the surgical manipulator and/or the surgical instrument has collided with an object; and in response to the determination that the surgical manipulator and/or the surgical instrument has collided with the object, switch operation of the surgical manipulator to enable movement of the surgical instrument in a manual mode.
2 . The surgical system of claim 1 , wherein the controller is configured to: compare the external force to a threshold; and determine that the surgical manipulator and/or the surgical instrument has collided with the object in response to the external force exceeding the threshold.
3 . The surgical system of claim 1 , wherein the controller is configured to measure the actual torque by being configured to: measure currents applied to a joint motor of the at least one active joint; and/or utilize a torque sensor associated with the at least one active joint.
4 . The surgical system of claim 1 , wherein the controller is configured to calculate the expected torque based on an angular position of the at least one active joint and a commanded joint angle for the at least one active joint.
5 . The surgical system of claim 4 , wherein: the surgical manipulator supports and moves the surgical instrument along a tool path for manipulation of the anatomy; and the commanded joint angle for the at least one active joint is based on a commanded pose for the surgical instrument relative to the tool path.
6 . The surgical system of claim 5 , wherein: the controller is configured to determine, based on the external force, that the surgical manipulator and/or the surgical instrument has collided with the object along the tool path.
7 . The surgical system of claim 1 , wherein the surgical manipulator comprises a sensor configured to sense a force/torque applied to the surgical instrument.
8 . The surgical system of claim 7 , wherein the controller is configured to determine that the surgical manipulator and/or the surgical instrument has collided with the object based on a combination of the external force and the force/torque sensed by the sensor.
9 . The surgical system of claim 1 , wherein the controller is configured to estimate the external force based on components of the external force that have an absolute value magnitude greater than a threshold.
10 . The surgical system of claim 1 , wherein the controller is configured to filter the external force by being configured to zero components of the external force that have an absolute value magnitude less than a threshold.
11 . A method of operating a surgical system, the surgical system including a surgical manipulator having a plurality of links and joints and being configured to support and move a surgical instrument for manipulation of an anatomy, and a controller coupled to the surgical manipulator, the method comprising the controller performing the following: operating the surgical manipulator for controlling movement of the surgical instrument in a semi-autonomous mode; measuring an actual torque for at least one active joint; calculating an expected torque for the at least one active joint; comparing the actual torque and the expected torque for estimating an external force; determining, based on the external force, that the surgical manipulator and/or the surgical instrument has collided with an object; and in response to determining that the surgical manipulator and/or the surgical instrument has collided with the object, switching operation of the surgical manipulator for enabling movement of the surgical instrument in a manual mode.
12 . The method of claim 11 , comprising the controller: comparing the external force to a threshold; and determining that the surgical manipulator and/or the surgical instrument has collided with the object in response to the external force exceeding the threshold.
13 . The method of claim 11 , comprising the controller measuring the actual torque by: measuring currents applied to a joint motor of the at least one active joint; and/or utilizing a torque sensor associated with the at least one active joint.
14 . The method of claim 11 , comprising the controller calculating the expected torque based on an angular position of the at least one active joint and a commanded joint angle for the at least one active joint.
15 . The method of claim 14 , comprising the surgical manipulator supporting and moving the surgical instrument along a tool path for manipulating the anatomy; and comprising the controller: determining the commanded joint angle for the at least one active joint based on a commanded pose for the surgical instrument relative to the tool path.
16 . The method of claim 15 , comprising the controller determining, based on the external force, that the surgical manipulator and/or the surgical instrument has collided with the object along the tool path.
17 . The method of claim 11 , comprising the controller utilizing a sensor coupled to the surgical instrument for sensing a force/torque applied to the surgical instrument.
18 . The method of claim 17 , comprising the controller determining that the surgical manipulator and/or the surgical instrument has collided with the object based on a combination of the external force and the force/torque sensed by the sensor.
19 . The method of claim 11 , comprising the controller estimating the external force based on components of the external force that have an absolute value magnitude greater than a threshold.
20 . The method of claim 11 , comprising the controller filtering the external force by zeroing components of the external force that have an absolute value magnitude less than a threshold.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. patent application Ser. No. 18/138,315, filed Apr. 24, 2023, which is a continuation of U.S. patent application Ser. No. 17/511,627, filed Oct. 27, 2021, now U.S. Pat. No. 11,672,620, which is a continuation of U.S. patent application Ser. No. 16/555,838, filed Aug. 29, 2019, now U.S. Pat. No. 11,179,210, which is a continuation of U.S. patent application Ser. No. 15/595,343, filed May 15, 2017, now U.S. Pat. No. 10,426,560, which is a continuation of U.S. patent application Ser. No. 14/739,146, filed on Jun. 15, 2015, now U.S. Pat. No. 9,681,920, which is a continuation of U.S. patent application Ser. No. 14/208,293, filed on Mar. 13, 2014, now U.S. Pat. No. 9,226,796, which is a continuation-in-part of U.S. patent application Ser. No. 13/958,070, filed on Aug. 2, 2013, now U.S. Pat. No. 9,119,655, which claims the benefit of U.S. Provisional Pat. Appln. No. 61/792,251, filed on Mar. 15, 2013 and U.S. Provisional Pat. Appln. No. 61/679,258, filed on Aug. 3, 2012. U.S. patent application Ser. No. 14/208,293, filed on Mar. 13, 2014, now U.S. Pat. No. 9,226,796, also claims the benefit of U.S. Provisional Pat. Appln. No. 61/792,251, filed on Mar. 15, 2013. U.S. patent application Ser. No. 14/739,146, filed on Jun. 15, 2015, now U.S. Pat. No. 9,681,920, is also a continuation-in-part of U.S. patent application Ser. No. 13/958,070, filed on Aug. 2, 2013, now U.S. Pat. No. 9,119,655. The advantages and disclosures of each of the applications set forth above are hereby incorporated by reference in their entirety. FIELD This disclosure relates generally to techniques for detecting collisions related to a robotic surgical system. BACKGROUND Recently, medical practitioners have found it useful to use robotic devices to assist in the performance of surgical procedures. A robotic device typically includes a moveable arm that comprises one or more linkages. The arm has a free, distal end that can be placed with a very high degree of accuracy. A surgical instrument designed to be applied to the surgical site is attached to the free end of the arm. The practitioner is able to precisely position the arm so as to by extrapolation, precisely position the surgical instrument at the site on the patient at which the instrument is to perform a medical or surgical procedure. One advantage of using a robotic system to hold the instrument is that the system arm, unlike the arms and hands of a surgeon, are not subjected to muscle strain or neurological actions like twitching. Thus, in comparison to when an instrument is hand held and therefore hand positioned, using a medical robotic system it is possible to hold an instrument steady, or move the instrument along a defined path with a higher degree of accuracy. Further some robotic surgical systems are designed to be used with surgical navigation systems. A surgical navigation system is a system that is able to generate data that provides a relatively precise indication of the surgical instrument relative to the location of the patient against which the instrument is applied. When a surgical robotic system is provided with the data indicating the position of the instrument relative to the patient, the robotic system may be able to position the instrument to ensure that it is applied to the tissue of the patient against which the instrument is supposed to be applied. This substantially eliminates the likelihood that the instrument will be applied to tissue against which the instrument should not be applied. Some medical robotic systems are designed to work in what is referred to as a “semi-autonomous” mode. In this mode of operation, the robotic system actuates the arm so as to cause the instrument to move against the patient's tissue in a preprogrammed path. This is useful if, for example, the instrument is some sort of cutting device and the goal of the particular procedure is to remove a pre-defined section of the patient's tissue. By way of reference, if a robotic system operates in an “autonomous” mode of operation, the robot, once actuated, performs the procedure with essentially no input from the surgeon. In a “semi-autonomous” mode of operation, the practitioner is able to assert commands to control the operation of the robot. For example, some semi-autonomous robots are constructed so that, in order for the robot to displace the instrument, the practitioner must actuate a command by continually depressing a control button or switch associated with the robot. Upon the negation of the actuate command by the practitioner, the advancement of the instrument by the robot at least temporarily stops. Some robotic systems are not traditional robots in that once activated, they do not automatically move the attached instrument along a pre-programmed path of travel. These systems include control systems through which the practitioner enters commands indicating where the attached instrument is to be posi