Manipulator and Method for Controlling the Manipulator Based on Joint Limits

Patent metadata

Field	Value
Publication number	US-2017000577-A1
Application number	US-201615266691-A
Country	US
Kind code	A1
Filing date	Sep 15, 2016
Priority date	Aug 3, 2012
Publication date	Jan 5, 2017
Grant date	—

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.

First claim

What is claimed is:

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;
model the surgical tool as a virtual rigid body;
compute 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; and
determine a commanded joint angle for each joint based on the computed forces and torques 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 one or more joint boundary angles comprise minimum and maximum joint boundary angles and the at least one controller is configured to compare, for each joint, the actual joint angle to the minimum and maximum joint boundary angles to determine a boundary exceeded angle.

3 . The manipulator of claim 2 , 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.

4 . The manipulator of claim 2 , 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.

5 . The manipulator of claim 2 , 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.

6 . The manipulator of claim 5 , 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.

7 . The manipulator of claim 2 , wherein the at least one controller is configured to output a joint limit torque based on the boundary exceeded angle.

8 . The manipulator of claim 7 , wherein the at least one controller is configured to convert the joint limit torque into equivalent forces and torques to apply to the virtual rigid body.

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

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; modeling the surgical tool as a virtual rigid body; 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; and determining a commanded joint angle for each joint based on the computed forces and torques 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 , including comparing the actual joint angle to minimum and maximum joint boundary angles for each joint to determine a boundary exceeded angle for each joint.

12 . The method of claim 11 , 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.

13 . The method of claim 11 , 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.

14 . The method of claim 11 , 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.

15 . The method of claim 14 , 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.

16 . The method of claim 11 , including outputting a joint limit torque based on the boundary exceeded angles.

17 . The method of claim 16 , including converting the joint limit torque into the computed forces and torques to apply to the virtual rigid body.

Assignees

• Stryker Corp

Inventors

• Bowling David Gene
• Stuart John Michael
• Culp Jerry A
• Malackowski Donald W
• Moctezuma De La Barrera Jose Luis
• Roessler Patrick
• Beer Joel N

Classifications

• A61B34/37

  Leader-follower robots (A61B34/35 takes precedence) · CPC title

• A61B34/20

  Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis · CPC title

• A61B2034/107

  Visualisation of planned trajectories or target regions · CPC title

• A61B34/70 Primary

  Manipulators specially adapted for use in surgery · CPC title

• A61B34/10

  Computer-aided planning, simulation or modelling of surgical operations · CPC title