Transmission with integrated overload protection for a legged robot

Patent metadata

Field	Value
Publication number	US-11920649-B2
Application number	US-202217898371-A
Country	US
Kind code	B2
Filing date	Aug 29, 2022
Priority date	Dec 15, 2016
Publication date	Mar 5, 2024
Grant date	Mar 5, 2024

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 transmission system, comprising:
a transmission comprising:
an input member coupled to and configured to rotate with a motor,
an output member, and
an intermediate member that engages the output member, the input member configured to engage the intermediate member and rotate within an open annular space defined by the intermediate member, wherein, when the input member rotates, the output member rotates at a different speed;

a clutch comprising a clutch surface frictionally coupled to a first side surface of the output member of the transmission; and
a compliant member configured to apply an axial preload on the clutch, the axial preload defining a torque limit indicating a torque load that causes the output member of the transmission to slip relative to the clutch surface when a torque received at the output member exceeds the torque limit.

2. The system of claim 1 , wherein the clutch surface comprises a friction material.

3. The system of claim 1 , further comprising a flexure member disposed between, and interfacing with, the clutch and the compliant member, wherein the flexure member is torsionally stiff and axially flexible.

4. The system of claim 1 , wherein the clutch comprises the first clutch surface and a second clutch surface frictionally coupled to a second side surface of the output member.

5. The system of claim 1 , further comprising a constraint ring defining the open annular space where the output member of the transmission is mounted.

6. The system of claim 5 , further comprising a constraint bushing mounted between the constraint ring and the output member of the transmission, the constraint bushing comprising 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 output member of the transmission.

7. The system of claim 1 , wherein:
the input member is elliptically shaped and configured to cause the intermediate member to deform as the input member rotates;
the intermediate member comprises external teeth disposed on an external peripheral surface of the intermediate member; and
the output member comprises internal teeth disposed on an interior peripheral surface of the output member, the internal teeth configured to engage the external teeth of the intermediate member.

8. A transmission assembly, comprising:
a transmission comprising:
an input member coupled to and configured to rotate with a motor,
an output member, and
an intermediate member that engages the output member, the input member configured to engage the intermediate member and rotate within an open annular space defined by the intermediate member, and when the input member rotates, the output member rotates at a different speed;

a first friction surface frictionally coupled to both a distal side surface of the output member;
a second friction surface frictionally coupled to a proximal side surface of the output member;
a compliant member configured to apply an axial preload on the first and second friction surfaces, the axial preload defining a torque limit, and when a torque load satisfies the torque limit, the output member slips relative to at least one of the first or second friction surfaces; and
an output member disposed between and interfacing with the first friction surface and the compliant member.

9. The assembly of claim 8 , wherein the transmission comprises a harmonic drive, and wherein:
the input member comprises a wave generator;
the intermediate member comprises a flexspline, and
the output member comprises a circular spline.

10. The assembly of claim 8 , wherein the second friction surface is coupled to a presser plate.

11. The assembly of claim 9 , further comprising a constraint ring, the constraint ring defining an open annular space, wherein the output member and the first and second friction surfaces frictionally coupled to the output member are mounted within the open annular space.

12. The assembly of claim 11 , further comprising a cross-roller bearing mounted between an exterior peripheral surface of the constraint ring and an interior surface of a housing of a motor.

13. The assembly of claim 12 , further comprising a constraint bushing mounted between the constraint ring and the circular spline, the constraint bushing comprising 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.

14. The assembly of claim 12 , wherein the first friction surface defines a first open annular space and the second friction surface defines a second open annular space, the assembly further comprising:
a first O-ring mounted within the first open annular space defined by the first friction surface; and
a second O-ring mounted within the second open annular space defined by the second friction surface.

15. The assembly of claim 12 , wherein the intermediate member 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 a motor and coupled to a portion of the thin-walled cylinder.

16. The assembly of claim 12 , wherein the compliant member comprises a Belleville compliant member.

17. A system comprising:
a transmission comprising:
an input member coupled to and configured to rotate with a motor,
an output member, and
an intermediate member that engages the output member, the input member configured to engage the intermediate member and rotate within an open annular space defined by the intermediate member, and when the input member rotates, the output member rotates at a different speed;

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

18. The system of claim 17 , wherein the transmission comprises a harmonic drive, and wherein the input comprises a wave generator, the intermediate member comprises a flexspline, and the output member comprises a circular spline.

19. The system of claim 17 , further comprising a torque sensor mounted to a housing of the motor and coupled to the output member, the torque sensor configured to measure the torque load on output member.

20. The system of claim 17 , wherein the one or more clutch surfaces comprise:
a first surface frictionally coupled to both a distal side surface of the output member; and
a second surface frictionally coupled to a proximal side surface of the output member.

21. The system of claim 1 , wherein the output surface comprises a flexspline and the first side surface of the output member comprises a sidewall of the flexspline.

Assignees

• Boston Dynamics Inc

Inventors

• Jackowski Zachary John
• Young Adam

Classifications

• F16D7/025 Primary

  with flat clutching surfaces, e.g. discs · CPC title

• B25J9/1025

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

• B25J19/06

  Safety devices · CPC title

• F16H35/10

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

• F16H49/001

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