Yaw slip handling in a robotic device

• US 9,352,470 B1
• Filed: 11/26/2014
• Issued: 05/31/2016
• Est. Priority Date: 11/11/2014
• Status: Active Grant

• Current Assignee: Boston Dynamics, Inc. (SoftBank Group Corp.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: da Silva, Marco, Rose, Michael, Blankespoor, Kevin
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): Dunn, Alex C
• Application Number:
  US14/554,951
• Time in Patent Office: 552 Days
• Field of Search: 701/23
• 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 9/0003 Home robots, i.e. small robots for domestic use
• 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: G01C 19/5705 using masses driven in reciprocating rotary motion about an axis
• CPC Class Codes: G05D 1/0891 specially adapted for land vehicles
• CPC Class Codes: Y10S 901/01 Mobile robot

Abstract

An example method may include determining a requested yaw for a body of a robot, where the biped robot comprises a foot coupled to the body via a leg. The robot may then detect, via one or more sensors, a yaw rotation of the body with respect to a ground surface, where the foot is in contact with the ground surface. Based on the detected yaw rotation of the body, the robot may determine a measured yaw for the body. The robot may also determine a target yaw for the body, where the target yaw for the body is between the measured yaw for the body and the requested yaw for the body. The robot may then cause the foot to rotate the body to the target yaw for the body.

Claims

1. A method comprising:

determining a force allocation for a foot of a biped robot, wherein the biped robot further comprises a body coupled to the foot via a leg;

determining a yaw rotation of the body with respect to a ground surface, wherein the foot is in contact with the ground surface;

based on the determined yaw rotation of the body, updating the determined force allocation for the foot, wherein updating the determined force allocation for the foot comprises increasing at least one of (i) a forward shear force component for the foot or (ii) a lateral shear force component for the foot; and

causing, by the biped robot, the foot to act on the ground surface based on the updated force allocation for the foot.

2. The method of claim 1, wherein the biped robot further comprises six degrees of freedom, the method further comprising:

determining a relative control priority for each of the six degrees of freedom, wherein determining the force allocation for the foot is based on the relative control priorities.

3. The method of claim 2, the method further comprising:

based on the determined yaw rotation of the body, updating the relative control priorities for each of the six degrees of freedom, wherein updating the determined force allocation for the foot is further based on the updated relative control priorities.

4. The method of claim 2, wherein the determined force allocation for the foot comprises a forward shear force component, a lateral shear force component, and a vertical normal force component, the method further comprising:

determining a representation of a coefficient of friction between the foot and the ground surface;

based on the determined representation of the coefficient of friction, determining maximum relative values for (i) the forward shear force component, (ii) the lateral shear force component, and (iii) the vertical normal force component, wherein determining the force allocation for the foot is further based on the determined maximum relative values.

5. The method of claim 1, wherein the yaw rotation of the body is a net yaw rotation of the body, and wherein determining the net yaw rotation of the body comprises:

detecting, by a first set of sensors, a first yaw rotation of the body with respect to the foot;

detecting, by a second set of sensors, a second yaw rotation of the body with respect to the ground surface; and

determining a difference between the first detected yaw rotation and the second detected yaw rotation to be the net yaw rotation of the body.

6. The method of claim 5, wherein updating the determined force allocation for the foot is further based on a determination that the net yaw rotation of the body is greater than a non-zero threshold rotation.

7. The method of claim 1, wherein the determined force allocation for the foot comprises a yaw moment component, and wherein updating the determined force allocation for the foot comprises reducing the yaw moment component.

8. The method of claim 1, further comprising:

determining a requested yaw for the body;

based on the determined yaw rotation of the body, determining a measured yaw for the body;

determining a target yaw for the body, wherein the target yaw for the body is between the measured yaw for the body and the requested yaw for the body; and

causing the foot to rotate the body to the target yaw for the body.

9. A method comprising:

determining a requested yaw for a body of a biped robot, wherein the biped robot comprises a foot coupled to the body via a leg;

determining a force allocation for the foot;

detecting, via one or more sensors of the robot, a yaw rotation of the body with respect to a ground surface, wherein the foot is in contact with the ground surface;

based on the detected yaw rotation of the body, determining a measured yaw for the body;

determining a target yaw for the body, wherein the target yaw for the body is between the measured yaw for the body and the requested yaw for the body; and

causing, by the biped robot, the foot to rotate the body to the target yaw for the body, wherein causing the foot to rotate the body to the target yaw for the body comprises (i) updating the force allocation for the foot and (ii) causing the foot to act on the ground surface based on the updated force allocation for the foot.

10. The method of claim 9, wherein determining the target yaw for the body comprises determining that a difference between the measured yaw for the body and the requested yaw for the body is greater than a non-zero threshold difference.

11. The method of claim 10, wherein the target yaw for the body is determined to be the non-zero threshold difference from the measured yaw for the body.

12. The method of claim 9, wherein the detected yaw rotation of the body is a first yaw rotation of the body, the method further comprising:

detecting, via the one or more sensors, a second yaw rotation of the body with respect to the ground surface, wherein the foot is in contact with the ground surface;

based on the second detected yaw rotation of the body, updating the measured yaw for the body;

determining that a difference between the updated measured yaw for the body and the requested yaw for the body is less than a non-zero threshold difference; and

based on the determination that the difference between the updated measured yaw for the body and the requested yaw for the body is less than the non-zero threshold difference, causing the foot to rotate the body to the requested yaw for the body.

13. The method of claim 9, wherein the yaw rotation of the body is a net yaw rotation of the body, wherein detecting the net yaw rotation of the body comprises:

detecting, by a first set of sensors in the one or more sensors, a first yaw rotation of the body with respect to the ground surface;

detecting, by a second set of sensors in the one or more sensors, a second yaw rotation of the body with respect to the foot; and

determining a difference between the first yaw rotation of the body and the second yaw rotation of the body to be the net yaw rotation of the body.

18. The method of claim 9, wherein the detected yaw rotation of the body is a first yaw rotation of the body, the method further comprising:

detecting, via the one or more sensors, a second yaw rotation of the body with respect to the ground surface, wherein the foot is in contact with the ground surface;

based on the second detected yaw rotation of the body, updating the measured yaw for the body;

determining that a difference between the updated measured yaw for the body and the requested yaw for the body is less than a non-zero threshold difference; and

based on the determination that the difference between the updated measured yaw for the body and the requested yaw for the body is less than the non-zero threshold difference, causing the foot to move the body such that the updated measured yaw for the body is maintained.

14. A biped robot comprising:

a body;

a foot coupled to the body via a leg;

one or more sensors;

a processor;

a non-transitory computer readable medium; and

program instructions stored on the non-transitory computer readable medium that, when executed by the processor, cause the biped robot to perform functions comprising;

determining a requested yaw for the body;

determining a force allocation for the foot;

detecting, via the one or more sensors, a yaw rotation of the body with respect to a ground surface, wherein the foot is in contact with the ground surface;

based on the detected yaw rotation of the body, determining a measured yaw for the body;

determining a target yaw for the body, wherein the target yaw for the body is between the measured yaw for the body and the requested yaw for the body; and

causing, by the biped robot, the foot to rotate the body to the target yaw for the body, wherein causing the foot to rotate the body to the target yaw for the body comprises (i) updating the force allocation for the foot and (ii) causing the foot to act on the ground surface based on the updated force allocation for the foot.

15. The biped robot of claim 14, wherein determining the target yaw for the body comprises determining that the difference between the measured yaw for the body and the requested yaw for the body is greater than a non-zero threshold difference.

16. The biped robot of claim 14, wherein the target yaw for the body is determined to be the non-zero threshold difference from the measured yaw for the body.

17. The biped robot of claim 14, wherein the detected yaw rotation of the body is a first yaw rotation of the body, and wherein the program instructions, when executed by the processor, further cause the biped robot to perform functions comprising:

detecting, via the one or more sensors, a second yaw rotation of the body with respect to the ground surface, wherein the foot is in contact with the ground surface;

based on the second detected yaw rotation of the body, updating the measured yaw for the body;

determining that a difference between the updated measured yaw for the body and the requested yaw for the body is less than a non-zero threshold difference; and

based on the determination that the difference between the updated measured yaw for the body and the requested yaw for the body is less than the non-zero threshold difference, causing the foot to rotate the body to the requested yaw for the body.

19. The biped robot of claim 14, wherein the yaw rotation of the body is a net yaw rotation of the body, wherein detecting the net yaw rotation of the body comprises:

detecting, by a first set of sensors in the one or more sensors, a first yaw rotation of the body with respect to the ground surface;

detecting, by a second set of sensors in the one or more sensors, a second yaw rotation of the body with respect to the foot; and

determining a difference between the first yaw rotation of the body and the second yaw rotation of the body to be the net yaw rotation of the body.

20. The biped robot of claim 14, wherein the detected yaw rotation of the body is a first yaw rotation of the body, and wherein the program instructions, when executed by the processor, further cause the biped robot to perform functions comprising:

detecting, via the one or more sensors, a second yaw rotation of the body with respect to the ground surface, wherein the foot is in contact with the ground surface;

based on the second detected yaw rotation of the body, updating the measured yaw for the body;

determining that a difference between the updated measured yaw for the body and the requested yaw for the body is less than a non-zero threshold difference; and

based on the determination that the difference between the updated measured yaw for the body and the requested yaw for the body is less than the non-zero threshold difference, causing the foot to move the body such that the updated measured yaw for the body is maintained.