Robot cyclic locomotion using a dynamic object

• US 9,156,159 B2
• Filed: 03/08/2012
• Issued: 10/13/2015
• Est. Priority Date: 03/08/2012
• Status: Active Grant

• Current Assignee: Disney Enterprises Incorporated (The Walt Disney Company)
• Original Assignee: Disney Enterprises Incorporated (The Walt Disney Company)
• Inventors: Hodgins, Jessica, Yamane, Katsu, Zheng, Yu
• Primary Examiner(s): Hollaway, Jason
• Assistant Examiner(s): Bendidi, Rachid
• Application Number:
  US13/415,605
• Publication Number:
  US 20130238122A1
• Time in Patent Office: 1,314 Days
• Field of Search: 700245-264, 901/1
• US Class Current: 1/1
• CPC Class Codes: B25J 13/085 Force or torque sensors B25J13/082, B25J13/084 take precedence
• CPC Class Codes: B25J 13/088 with position, velocity or acceleration sensors
• CPC Class Codes: B25J 9/00 Programme-controlled manipulators
• CPC Class Codes: B62D 57/02 with ground-engaging propulsion means, e.g. walking members
• 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: G05B 15/00 Systems controlled by a computer G05B13/00, G05B19/00 take precedence; automatic controllers with particular characteristics G05B11/00

Abstract

Techniques are disclosed for optimizing and maintaining cyclic biped locomotion of a robot on an object. The approach includes simulating trajectories of the robot in contact with the object. During each trajectory, the robot maintains balance on the object, while using the object for locomotion. The approach further includes determining, based on the simulated trajectories, an initial state of a cyclic gait of the robot such that the simulated trajectory of the robot starting from the initial state substantially returns to the initial state at an end of one cycle of the cyclic gait. In addition, the approach includes sending joint angles and joint velocities of the initial state to a set of joint controllers of the robot to cause a leg of the robot to achieve the initial state so the robot moves through one or more cycles of the cyclic gait.

Claims

1. A computer-implemented method comprising:

simulating, via one or more processors, one or more trajectories of a robot in contact with a dynamic secondary object, wherein the robot maintains balance on the secondary object throughout each of the one or more simulated trajectories;

determining, based on the one or more simulated trajectories, a first initial state of a cyclic gait of the robot such that the simulated trajectory of the robot starting from the first initial state substantially returns to the first initial state at an end of one cycle of the cyclic gait; and

sending joint angles and joint velocities of the first initial state to a set of joint controllers of the robot to cause a leg of the robot to achieve the first initial state and to cause the robot to move through one or more cycles of the cyclic gait in motion with the secondary object,

wherein determining the first initial state includes;

substantially minimizing a difference between a simulated center-of-mass position of the first initial state and a simulated center-of-mass position of a final state, the final state being the state of the robot at the end of the one cycle of the cyclic gait, and

substantially minimizing a difference between simulated joint velocities of the first initial state and simulated joint velocities of the final state.

2. The computer-implemented method of claim 1, wherein the simulated trajectories account, via a collision model, for changes of state upon a leg of the robot colliding with the secondary object.

3. The computer-implemented method of claim 1, wherein the secondary object is a ball or a cylinder.

4. The computer-implemented method of claim 1, wherein determining the first initial state is subject to a constraint that the secondary object move at a predefined average velocity.

5. The computer-implemented method of claim 1, wherein determining the first initial state is subject to a constraint that a contact point between a supporting foot of the robot and the secondary object be within the sole of the supporting foot during an entirety of each step of the cyclic gait.

6. The computer-implemented method of claim 1, wherein determining the first initial state is subject to a friction constraint.

7. The computer-implemented method of claim 1, wherein simulating one or more trajectories includes modeling the robot as a lump mass, two feet, two ankle joints, and two sets of springs and dampers.

8. The computer-implemented method of claim 1, wherein the robot maintains balance on the secondary object via a balance controller which continuously attempts to return the robot to an equilibrium state.

9. The computer-implemented method of claim 1, further comprising:

determining a difference between the simulated trajectory corresponding to the first initial state and an actual trajectory during a step of the cyclic gait;

determining, based on the difference, a second initial state for a next step of the cyclic gait such that a trajectory of the robot starting from the second initial state is closer to the simulated trajectory corresponding to the first initial state than is a trajectory of the robot without correction; and

sending joint angles and joint velocities of the second initial state to the set of joint controllers of the robot to cause the robot to undertake the next step of the cyclic gait.

10. The computer-implemented method of claim 9, wherein determining the second initial state includes:

determining, via inverse kinematics, joint angles which permit a simulated center of mass of the robot at a collision of a swinging foot with the secondary object to be substantially equivalent, relative to the secondary object, to a simulated center of mass of the robot at a collision of the swinging foot with the secondary object according to the simulated trajectory corresponding to the first initial state; and

substantially minimizing the difference between a simulated center-of-mass position of an initial state and a simulated center-of-mass position of a final state and the difference between simulated joint velocities of the initial state and simulated joint velocities of the final state, the final state being the state of the robot at the end of one cycle of the cyclic gait.

11. A non-transitory computer-readable storage medium storing a program, which, when executed by a processor performs an operation, the operation comprising:

simulating one or more trajectories of a robot in contact with a dynamic secondary object, wherein the robot maintains balance on the secondary object throughout each of the one or more simulated trajectories;

determining, based on the one or more simulated trajectories, a first initial state of a cyclic gait of the robot such that the simulated trajectory of the robot starting from the first initial state substantially returns to the first initial state at an end of one cycle of the cyclic gait; and

sending joint angles and joint velocities of the first initial state to a set of joint controllers of the robot to cause a leg of the robot to achieve the first initial state and to cause the robot to move through one or more cycles of the cyclic gait in motion with the secondary object,

wherein determining the first initial state includes;

substantially minimizing a difference between a simulated center-of-mass position of the first initial state and a simulated center-of-mass position of a final state, the final state being the state of the robot at the end of the one cycle of the cyclic gait, and

substantially minimizing a difference between simulated joint velocities of the first initial state and simulated joint velocities of the final state.

12. The computer-readable storage medium of claim 11, wherein the simulated trajectories account, via a collision model, for changes of state upon a leg of the robot colliding with the secondary object.

13. The computer-readable storage medium of claim 11, wherein the secondary object is a ball or a cylinder.

14. The computer-readable storage medium of claim 11, wherein determining the first initial state is subject to a constraint that the secondary object move at a predefined average velocity.

15. The computer-readable storage medium of claim 11, wherein determining the first initial state is subject to a constraint that a contact point between a supporting foot of the robot and the secondary object be within the sole of the supporting foot during an entirety of each step of the cyclic gait.

16. The computer-readable storage medium of claim 11, wherein the operation further comprises:

determining a difference between the simulated trajectory corresponding to the first initial state and an actual trajectory during a step of the cyclic gait;

determining, based on the difference, a second initial state for a next step of the cyclic gait such that a trajectory of the robot starting from the second initial state is closer to the simulated trajectory corresponding to the first initial state than is a trajectory of the robot without correction; and

sending joint angles and joint velocities of the second initial state to the set of joint controllers of the robot to cause the robot to undertake the next step of the cyclic gait.

17. The computer-readable storage medium of claim 16, wherein determining the second initial state includes:

determining, via inverse kinematics, joint angles which permit a simulated center of mass of the robot at a collision of a swinging foot with the secondary object to be substantially equivalent, relative to the secondary object, to a simulated center of mass of the robot at a collision of the swinging foot with the secondary object according to the simulated trajectory corresponding to the first initial state; and

substantially minimizing the difference between a simulated center-of-mass position of an initial state and a simulated center-of-mass position of a final state and the difference between simulated joint velocities of the initial state and simulated joint velocities of the final state, the final state being the state of the robot at the end of one cycle of the cyclic gait.

18. A system, comprising:

a balance controller which maintains balance of a robot in contact with a dynamic secondary object, the secondary object used by the robot during locomotion;

a dynamics simulator to compute a trajectory of the robot in contact with the secondary object and controlled by the balance controller starting from an initial state;

a computer-implemented process for optimizing an initial state of a cyclic gait of the robot such that the trajectory of the robot starting from the initial state substantially returns to the initial state after one cycle of the gait; and

a set of joint controllers to cause a leg of the robot to achieve the initial state and the robot to move through one or more cycles of the cyclic gait in motion with the secondary object, wherein

optimizing the initial state includes;

substantially minimizing a difference between a simulated center-of-mass position of the initial state and a simulated center-of-mass position of a final state, the final state being the state of the robot at the end of the one cycle of the cyclic gait, and

substantially minimizing a difference between simulated joint velocities of the initial state and simulated joint velocities of the final state.