Manipulator and method for controlling the manipulator based on joint limits

• US 10,350,017 B2
• Filed: 09/15/2016
• Issued: 07/16/2019
• Est. Priority Date: 08/03/2012
• Status: Active Grant

• Current Assignee: Stryker Corporation
• Original Assignee: Stryker Corporation
• Inventors: Bowling, David Gene, Beer, Joel N.
• Primary Examiner(s): Weber, Tamara L
• Application Number:
  US15/266,691
• Publication Number:
  US 20170000577A1
• Time in Patent Office: 1,034 Days
• Field of Search: None
• 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 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 2034/104 Modelling the effect of the tool, e.g. the effect of an implanted prosthesis or for predicting the effect of ablation or burring
• 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 2034/2055 Optical tracking systems
• CPC Class Codes: A61B 2034/2059 Mechanical position encoders
• CPC Class Codes: A61B 34/10 Computer-aided planning, simulation or modelling of surgical operations
• 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 34/74 Manipulators with manual electric input means
• 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 9/161 Hardware, e.g. neural networks, fuzzy logic, interfaces, processor
• CPC Class Codes: B25J 9/1633 compliant, force, torque control, e.g. combined with position control
• CPC Class Codes: Y10S 901/09 : Closed loop, sensor feedback controls arm movement

Abstract

A manipulator is provided that supports a surgical tool used in a surgical procedure. The manipulator includes a plurality of links and joints and a controller that evaluates an actual joint angle of each joint relative to one or more joint boundary angles for each joint. The controller computes forces and torques to apply to a virtual rigid body based on the evaluation. The controller then determines a commanded joint angle for each joint based on the computed forces and torques so that actuators move the surgical tool to a commanded pose associated with the commanded joint angles.

Claims

1. A manipulator for supporting a surgical tool, the manipulator comprising:

a plurality of links and joints;

a plurality of actuators with each actuator arranged to move one or more of the links;

a plurality of sensors with each sensor arranged to measure an actual joint angle for one of the joints; and

at least one controller configured to;

evaluate the actual joint angle relative to one or more joint boundary angles for each joint, wherein the one or more joint boundary angles comprise minimum and maximum joint boundary angles;

compare, for each joint, the actual joint angle to the minimum and maximum joint boundary angles to determine a boundary exceeded angle;

output a joint limit torque based on the boundary exceeded angle;

model the surgical tool as a virtual rigid body;

convert the joint limit torque into forces and torques to apply to the virtual rigid body; and

determine a commanded joint angle for each joint based on the forces and torques applied to the virtual rigid body so that the plurality of actuators move the surgical tool to a commanded pose associated with the commanded joint angles.

2. The manipulator of claim 1, wherein the minimum and maximum joint boundary angles fall within a predetermined range of motion for each joint, the predetermined range of motion defined by minimum and maximum joint limit angles.

3. The manipulator of claim 1, wherein the at least one controller is configured to output a value for the boundary exceeded angle of zero when the actual joint angle is greater than the minimum joint boundary angle and less than the maximum joint boundary angle.

4. The manipulator of claim 1, wherein the at least one controller is configured to output a value for the boundary exceeded angle that is non-zero when the actual joint angle is less than the minimum joint boundary angle or greater than the maximum joint boundary angle.

5. The manipulator of claim 4, wherein the at least one controller is configured to generate forces and torques to apply to the virtual rigid body based on evaluating the actual joint angles if the value for the boundary exceeded angle is non-zero.

6. The manipulator of claim 1, wherein the sensors are rotary encoders.

7. The manipulator of claim 1, wherein the joint limit torque has greater than first order relationship to the magnitude of the boundary exceeded angle.

8. The manipulator of claim 1, wherein the joint limit torque is set using a look-up table.

9. The manipulator of claim 1, wherein the controller is further configured to determine the commanded joint angle for each joint based on the forces and torques so that the plurality of actuators move the surgical tool to the commanded pose associated with the commanded joint angles when the actual joint angle is less than the minimum joint boundary angle or greater than the maximum joint boundary angle.

10. A method for controlling a manipulator supporting a surgical tool, wherein the manipulator includes a plurality of links and joints, a plurality of actuators with each actuator arranged to move one or more of the links, and a plurality of sensors with each sensor arranged to measure an actual joint angle for one of the joints, said method comprising the steps of:

evaluating the actual joint angle relative to one or more joint boundary angles for each joint;

comparing the actual joint angle to minimum and maximum joint boundary angles for each joint to determine a boundary exceeded angle for each joint;

outputting a joint limit torque based on the boundary exceeded angles;

modeling the surgical tool as a virtual rigid body;

converting the joint limit torque into forces and torques to apply to the virtual rigid body; and

determining a commanded joint angle for each joint based on the computed forces and torques applied to the virtual rigid body so that the plurality of actuators move the surgical tool to a commanded pose associated with the commanded joint angles.

11. The method of claim 10, wherein the minimum and maximum joint boundary angles fall within a predetermined range of motion for each joint, the predetermined range of motion defined by minimum and maximum joint limit angles.

12. The method of claim 10, including outputting a value for the boundary exceeded angle of zero when the actual joint angle is greater than the minimum joint boundary angle and less than the maximum joint boundary angle.

13. The method of claim 10, including outputting a value for the boundary exceeded angle that is non-zero when the actual joint angle is less than the minimum joint boundary angle or greater than the maximum joint boundary angle.

14. The method of claim 13, wherein computing forces and torques to apply to the virtual rigid body based on evaluating the actual joint angles relative to the one or more joint boundary angles includes computing the forces and torques if the value for the boundary exceeded angle is non-zero.

15. The method of claim 10 wherein the joint limit torque has greater than first order relationship to the magnitude of the boundary exceeded angle.

16. The method of claim 10, wherein the joint limit torque is set using a look-up table.

17. The method of claim 10, wherein the plurality of actuators move the surgical tool to the commanded pose associated with the commanded joint angles when the actual joint angle is less than the minimum joint boundary angle or greater than the maximum joint boundary angle.