Transmission with integrated overload protection for a legged robot

Patent metadata

Field	Value
Publication number	US-11460076-B2
Application number	US-202016858800-A
Country	US
Kind code	B2
Filing date	Apr 27, 2020
Priority date	Dec 15, 2016
Publication date	Oct 4, 2022
Grant date	Oct 4, 2022

Abstract

An example robot includes: a motor disposed at a joint configured to control motion of a member of the robot; a transmission including an input member coupled to and configured to rotate with the motor, an intermediate member, and an output member, where the intermediate member is fixed such that as the input member rotates, the output member rotates therewith at a different speed; a pad frictionally coupled to a side surface of the output member of the transmission and coupled to the member of the robot; and a spring configured to apply an axial preload on the pad, wherein the axial preload defines a torque limit that, when exceeded by a torque load on the member of the robot, the output member of the transmission slips relative to the pad.

First claim

What is claimed is:

1. A robot comprising:
a motor disposed at a joint configured to control motion of a member of the robot;
a harmonic drive comprising:
a wave generator coupled to and configured to rotate with the motor;
a flexspline; and
a circular spline,
wherein when the wave generator rotates, the flexspline is rotationally fixed while the circular spline rotates at a different speed than the wave generator;

one or more pads frictionally coupled to the circular spline and the member of the robot;
a compliant member configured to apply an axial preload on the one or more pads, the axial preload defining a torque limit;
a constraint ring coupled to the member of the robot, the constraint ring defining an open annular space where the circular spline is mounted; and
a constraint bushing mounted between the constraint ring and the circular spline,
wherein when a torque load on the member of the robot satisfies the torque limit, the circular spline slips relative to at least one of the one or more pads.

2. The robot of claim 1 , further comprising a torque sensor mounted to a housing of the motor and coupled to the circular spline, the torque sensor configured to measure the torque load on the member of the robot.

3. The robot of claim 1 , wherein the member of the robot corresponds to a leg of the robot.

4. The robot of claim 3 , wherein the joint corresponds to a hip joint of the leg of the robot.

5. The robot of claim 1 , wherein the one or more pads comprise:
a first pad frictionally coupled to both a distal side surface of the circular spline and the member of the robot; and
a second pad frictionally coupled to a proximal side surface of the circular spline.

6. The robot of claim 5 , wherein the second pad is coupled to a presser plate, the presser plate coupled to the member of the robot.

7. The robot of claim 5 , further comprising an O-ring mounted within a second annular space defined by the first pad or the second pad.

8. The robot of claim 1 , wherein the constraint bushing comprises an exterior peripheral surface interfacing with an interior peripheral surface of the constraint ring and an interior peripheral surface interfacing with an exterior peripheral surface of the circular spline.

9. The robot of claim 1 , wherein the robot comprises a biped robot.

10. The robot of claim 1 , wherein the robot comprises a quadruped robot.

11. An assembly comprising:
a motor disposed at a hip joint of a leg of a robot, the motor configured to control motion of the leg of the robot;
a harmonic drive comprising:
a wave generator coupled to and configured to rotate with the motor;
a flexspline; and
a circular spline,
wherein when the wave generator rotates, the flexspline is rotationally fixed while the circular spline rotates at a different speed than the wave generator;

a first pad frictionally coupled to both a distal side surface of the circular spline and the leg of the robot;
a second pad frictionally coupled to a proximal side surface of the circular spline; and
a compliant member configured to apply an axial preload on the first and second pads, the axial preload defining a torque limit;
a constraint ring coupled to the leg of the robot, the constraint ring defining a first open annular space, the circular spline and the first and second pads frictionally coupled to the circular spline mounted within the first open annular space; and
a constraint bushing mounted between the constraint ring and the circular spline,
wherein when a torque load on the leg of the robot satisfies the torque limit, the circular spline slips relative to at least one of the first or second pads.

12. The assembly of claim 11 , wherein the robot comprises a quadruped robot having four legs, and wherein the leg comprises one leg of the four legs of the quadruped robot.

13. The assembly of claim 11 , wherein the second pad is coupled to a presser plate, the presser plate coupled to the leg of the robot.

14. The assembly of claim 13 , wherein the presser plate is coupled to the leg of the robot by a radial array of bolts that couple the presser plate to the constraint ring.

15. The assembly of claim 14 , further comprising a cross-roller bearing mounted between an exterior peripheral surface of the constraint ring and an interior surface of a housing of the motor.

16. The assembly claim 11 , wherein the constraint bushing comprises an exterior peripheral surface interfacing with an interior peripheral surface of the constraint ring and an interior peripheral surface interfacing with an exterior peripheral surface of the circular spline.

17. The assembly of claim 11 , wherein the first pad defines a second open annular space and the second pad defines a third open annular space, the assembly further comprising:
a first O-ring mounted within the second open annular space defined by the first pad; and
a second O-ring mounted within the third open annular space defined by the second pad.

18. The assembly of claim 11 , wherein the flexspline comprises a thin-walled cylinder with external teeth formed circumferentially on a portion of an outer surface of the thin-walled cylinder, and the assembly further comprises a torque sensor mounted on a housing of the motor and coupled to a portion of the thin-walled cylinder.

19. The assembly of claim 11 , wherein the compliant member comprises a Belleville spring.

Assignees

• Boston Dynamics Inc

Inventors

• Jackowski Zachary John
• Young Adam

Classifications

• B25J19/06

  Safety devices · CPC title

• F16H49/001

  Wave gearings, e.g. harmonic drive transmissions · CPC title

• F16H35/10

  Arrangements or devices for absorbing overload or preventing damage by overload · CPC title

• B25J9/1025

  Harmonic drives (in general: F16H49/001) · CPC title

• F16H25/20

  Screw mechanisms (with automatic reversal F16H25/12) · CPC title