Method for detecting a disturbance as an energy applicator of a surgical instrument traverses a cutting path

• US 9,226,796 B2
• Filed: 03/13/2014
• Issued: 01/05/2016
• Est. Priority Date: 08/03/2012
• Status: Active Grant

• Current Assignee: Stryker Corporation
• Original Assignee: Stryker Corporation
• Inventors: Bowling, David Gene, Stuart, John Michael, Culp, Jerry A., Malackowski, Donald W., Roessler, Patrick, Beer, Joel N., Ketchel, John, Moctezuma de la Barrera, Jos Luis
• Primary Examiner(s): Edwards, Jerrah
• Assistant Examiner(s): Weber, Tamara
• Application Number:
  US14/208,293
• Publication Number:
  US 20140222207A1
• Time in Patent Office: 663 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 17/16 Bone cutting, breaking or removal means other than saws, e.g. Osteoclasts; Drills or chisels for bones; Trepans arthroscopic bone cutters A61B17/320016; dental implant drills potentially for other surgical use A61C8/0089; bone grinders A61F2/4644, A22C17/06; A61B17/1662 takes precedence over all other subgroups except A61B17/17
• CPC Class Codes: A61B 17/1626 Control means; Display units
• CPC Class Codes: A61B 18/148 having a short, rigid shaft for accessing the inner body transcutaneously, e.g. for neurosurgery or arthroscopy
• CPC Class Codes: A61B 2018/00565 Bone
• CPC Class Codes: A61B 2018/00601 Cutting
• CPC Class Codes: A61B 2034/107 Visualisation of planned trajectories or target regions
• CPC Class Codes: A61B 2034/2046 Tracking techniques
• CPC Class Codes: A61B 2090/066 for measuring torque
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 34/30 Surgical robots
• CPC Class Codes: A61B 34/32 operating autonomously
• CPC Class Codes: A61B 34/37 Master-slave robots A61B34/35 takes precedence
• CPC Class Codes: A61B 34/70 Manipulators specially adapted for use in surgery
• CPC Class Codes: A61B 34/76 Manipulators having means for providing feel, e.g. force or tactile feedback
• CPC Class Codes: B25J 13/00 Controls for manipulators programme controls B25J9/16; control in general G05
• CPC Class Codes: B25J 13/085 Force or torque sensors B25J13/082, B25J13/084 take precedence
• CPC Class Codes: B25J 9/009 being mechanically linked with one another at their distal ends
• CPC Class Codes: B25J 9/1633 compliant, force, torque control, e.g. combined with position control
• CPC Class Codes: G05B 2219/40191 Autonomous manipulation, computer assists operator during manipulation
• CPC Class Codes: G05B 2219/45117 Medical, radio surgery manipulator
• CPC Class Codes: G16H 40/63 : for local operation

Abstract

A method is provided for detecting a disturbance as an energy applicator of a surgical instrument traverses a cutting path. The method includes determining actual torques for each active joint of an actuated arm mechanism and calculating expected torques for each active joint of the actuated arm mechanism, wherein the expected torques are calculated based on an angular position of each active joint and a commanded joint angle for each active joint. The method further determines estimated backdrive torques based on the expected torques and the actual torques, wherein the estimated backdrive torques indicate a disturbance along the cutting path.

Claims

1. A method for detecting a disturbance as an energy applicator of a surgical instrument traverses a cutting path, the method being implemented on at least one computing device having a non-transitory computer-readable storage medium with an executable program stored thereon, said method comprising the steps of:

executing the program stored on the computer-readable storage medium, wherein the program instructs the at least one computing device to;

determine actual torques for each active joint of an actuated arm mechanism supporting the surgical instrument;

calculate expected torques for each active joint of the actuated arm mechanism, wherein the expected torques are calculated based on an angular position of each active joint and a commanded joint angle for each active joint;

determine estimated backdrive torques based on the expected torques and the actual torques, wherein the estimated backdrive torques indicate a disturbance along the cutting path;

convert the estimated backdrive torques to a backdrive force having a force component and a torque component;

filter the backdrive force by;

comparing an absolute value of the magnitude for each component of the backdrive force with a threshold;

setting to zero each component of the backdrive force that has an absolute value less than the threshold; and

calculating a filtered backdrive force based on the differences between the threshold and the components of the backdrive force having an absolute value greater than the threshold; and

generate an external force based on the filtered backdrive force and a sensor force derived from a force/torque sensor mounted to an end effector coupled to the surgical instrument.

2. The method of claim 1, wherein the disturbance is a collision with an object along the cutting path.

3. The method of claim 1, wherein the disturbance is a collision with an object in a workspace of the surgical instrument.

4. The method of claim 1, wherein the program instructs the at least one computing device to determine the actual torques by measuring currents applied to joint motors associated with each active joint.

5. The method of claim 1, wherein the program instructs the at least one computing device to determine the actual torques by measuring the torque for each active joint using a torque sensor.

6. The method of claim 1, wherein the program instructs the at least one computing device to determine the actual torques by blending currents applied to joint motors associated with each active joint with torques measured by a torque sensor for each active joint.

7. The method of claim 1, wherein the estimated backdrive torques are the difference between the expected torques and the actual torques.

8. The method of claim 1, wherein the commanded joint angles position the energy applicator of the surgical instrument to a target position along the cutting path.

9. The method of claim 1, wherein the program instructs the at least one computing device to calculate the commanded joint angles based on a commanded pose to which the energy applicator is advanced along the cutting path.

10. The method of claim 9, wherein the program instructs the at least one computing device to determine the commanded pose based on a summation of a plurality of input forces and torques.

11. The method of claim 1, wherein the disturbance generates a force that opposes movement of the energy applicator along the cutting path.

12. The method of claim 11, wherein the backdrive force is in the same direction as the force generated by the disturbance.

13. The method of claim 1, wherein the threshold for the force components is different than the threshold for the torque components.

14. The method of claim 1, wherein the external force is a weighted sum of the filtered backdrive force and the sensor force.

15. The method of claim 1, wherein the external force has a force vector component and a torque vector component.

16. The method of claim 15, wherein the force vector component is calculated according to the equation:

{right arrow over (F)}_EXT=A_BDR{right arrow over (F)}_BDR+A_FTS{right arrow over (F)}_FTS

where, {right arrow over (F)}_BDR is the force vector component of the filtered backdrive force F_BDR, vector {right arrow over (F)}_FTS is the force vector component of the sensor force F_FTS, and A_BDR and A_FTS are weighting factor coefficients.

17. The method of claim 16, wherein the torque vector component is calculated according to the equation:

{right arrow over (T)}_EXT=B_BDR{right arrow over (T)}_BDR+B_FTS{right arrow over (T)}_FTS

where, {right arrow over (T)}_BDR is the torque vector component of the filtered backdrive force, F_EDR, vector {right arrow over (T)}_FTS is the torque vector component of the sensor force, F_FTS, and B_BDR and B_FTS are weighting factor coefficients.

18. The method of claim 10, wherein the program instructs the at least one computing device to move the energy applicator to the commanded pose in a semi-autonomous mode.

19. The method of claim 18, wherein the program instructs the at least one computing device to reorient the surgical instrument as the energy applicator advances along the cutting path in response to reorientation forces and torques applied to the surgical instrument by a user while in the semi-autonomous mode.

20. The method of claim 18, wherein the program instructs the at least one computing device to transition movement of the energy applicator from the semi-autonomous mode to a manual mode in response to the sensor force being greater than a limit.