HUMAN MOTION TRACKING CONTROL WITH STRICT CONTACT FORCE CONTSTRAINTS FOR FLOATING-BASE HUMANOID ROBOTS

• US 20150051734A1
• Filed: 10/30/2013
• Published: 02/19/2015
• Est. Priority Date: 08/15/2013
• Status: Active Grant

• Current Assignee: Disney Enterprises Incorporated (The Walt Disney Company)
• Original Assignee: Disney Enterprises Incorporated (The Walt Disney Company)
• Inventors: Zheng, Yu, Yumane, Katsu
• Granted Patent: US 9,120,227 B2
• Time in Patent Office: Days
• US Class Current: 700/261
• CPC Class Codes: B25J 9/1633 compliant, force, torque control, e.g. combined with position control
• CPC Class Codes: B62D 57/032 with alternately or sequentially lifted supporting base and legs; with alternately or sequentially lifted feet or skid B62D57/024 takes precedence
• CPC Class Codes: Y10S 901/01 Mobile robot

Abstract

A controller for floating-base humanoid robots that can track motion capture data while maintaining balance. Briefly, the controller includes a proportional-derivative (PD) controller that is adapted to compute the desired acceleration to track a given reference trajectory at every degree-of-freedom (DOF) of the robot including the six unactuated ones of the floating base. Second, the controller includes a component (joint torque optimization module) that computes the optimal joint torques and contact forces to realize the desired accelerations given by the first component (i.e., the PD controller). The joint torque optimization module performs this computation considering the full-body dynamics of the robot and the constraints on contact forces. The desired accelerations may not be feasible for the robot due to limits in normal contact forces and friction (e.g., the robot sometimes cannot exactly copy or perform the modeled human motion defined by motion capture data).

Claims

1. A method for controlling a floating-base robot to track a reference motion, comprising:

sensing the state of the floating-base robot with reference to an operating environment;

determining desired joint and contact link accelerations based on the reference motion and the state of the floating-base robot;

computing contact wrenches and joint torques to generate the desired joint and contact link accelerations; and

repeating the sensing of the state, the determining of desired joint and contact link accelerations, and the computing contact wrenches and joint torques for each control cycle for the floating-base robot.

2. The method of claim 1, wherein the desired joint and contact link accelerations are calculated by a feedback controller based on the reference motion and the state of the floating-base robot.

3. The method of claim 1, wherein contact wrenches and joint torques are computed separately by solving two sequential optimization problems.

4. The method of claim 3, wherein the joint torques are calculated based on the desired joint and contact link accelerations, the state of floating-base robot, and the computed contact wrenches.

5. The method of claim 1, wherein the contact wrenches and joint torques are computed based on the state and the full-body dynamics model of the floating-base robot.

6. The method of claim 1, wherein the contact wrenches are calculated based on the desired joint accelerations, desired contact states of contact links, and the state of the floating-base robot.

7. The method of claim 6, wherein the contact wrenches are calculated such that the contact force applied by the operating environment at each contact point satisfies the inequality constraints on the direction and magnitude of the contact force.

8. The method of claim 6, wherein the desired contact states change during the reference motion.

9. The method of claim 1, wherein the reference motion is human motion capture data.

10. The method of claim 1, wherein the reference motion is key frame animation.

11. A robot, comprising:

a floating-base body comprising a plurality of links and torque-controlled joints; and

a tracking controller comprising;

sensing a state of the robot with reference to an operating environment;

determining desired joint and contact link accelerations based on a reference motions and the state of the floating-base robot;

computing contact wrenches and joint torques to generate the desired joint and contact link accelerations; and

repeating the sensing of the state, the determining of desired joint and contact link accelerations, and the computing contact wrenches and joint torques for each control cycle for the robot.

12. The robot of claim 11, wherein the desired joint and contact link accelerations are calculated by a feedback controller based on the reference motion and the state of the floating-base body.

13. The robot of claim 11, wherein contact wrenches and joint torques are computed separately by solving two sequential optimization problems.

14. The robot of claim 13, wherein the joint torques are calculated based on the desired joint and contact link accelerations, the state of floating-base body, and the computed contact wrenches.

15. The robot of claim 11, wherein the contact wrenches and joint torques are computed based on the state and the full-body dynamics model of the floating-base body.

16. The robot of claim 11, wherein the contact wrenches are calculated based on the desired joint accelerations, desired contact states of contact links, and the state of the floating-base body.

17. The robot of claim 16, wherein the contact wrenches are calculated such that the contact force applied by the operating environment at each contact point satisfies the inequality constraints on the direction and magnitude of the contact force.

18. The robot of claim 16, wherein the desired contact states change during the reference motion.

19. The robot of claim 11, wherein the reference motion is human motion capture data.

20. The robot of claim 11, wherein the reference motion is key frame animation.

21. A method for controlling a floating-base robot to track a set of reference motions, comprising:

sensing the state of the floating-base robot with reference to an operating environment;

predicting the future state of the floating-base robot;

interpolating the reference motions based on predicted future state;

determining desired joint and contact link accelerations based on the interpolated reference motions and the state of the floating-base robot;

computing contact wrenches and joint torques to generate the desired joint and contact link accelerations; and

repeating the sensing of the state, the interpolating of the reference motions, the determining of desired joint and contact link accelerations, and the computing contact wrenches and joint torques for each control cycle for the floating-base robot.

22. The method of claim 21, wherein the set of reference motions comprises a motion that maintains a static equilibrium pose of the floating-base robot.

23. The method of claim 21, wherein the motions are interpolated based on the predicted center of mass position.