Torque control methods for an exoskeleton device

Patent metadata

Field	Value
Publication number	US-10555865-B2
Application number	US-201715605520-A
Country	US
Kind code	B2
Filing date	May 25, 2017
Priority date	May 25, 2016
Publication date	Feb 11, 2020
Grant date	Feb 11, 2020

Abstract

This document describes systems and methods for controlling an exoskeleton. The system receives a measurement of a first torque applied to a rotational joint coupling a first component to a second component, the first torque being applied by a motor via a cable. The system determines, based on the measurement of the first torque, a first portion of a second torque to apply to the rotational joint. The system determines, based on the measurement of the first torque, a second portion of the second torque to apply to the rotational joint. The system determines a value of the second torque to apply to the rotational joint based on the first portion and the second portion. The system controls the motor for applying the second torque to the rotational joint via the cable.

First claim

What is claimed is:

1. A method of controlling an exoskeleton, comprising:
receiving a measurement of a first torque applied to a rotational joint coupling a first component to a second component, the first torque being applied by a motor via a cable;
determining, based on the measurement of the first torque, a first portion of a second torque to apply to the rotational joint;
determining, based on the measurement of the first torque, a second portion of the second torque to apply to the rotational joint by:
determining, for an interval of a cycle, a target value as a function of an error value measured at the same interval of one or more previous cycles; and
determining, from the target value, a feed-forward response portion of the second torque;

determining a value of the second torque to apply to the rotational joint based on the first portion and the second portion including the feed-forward response portion; and
controlling the motor for applying the second torque to the rotational joint by the cable.

2. The method of claim 1 , wherein the first portion of the second torque to apply to the rotational joint includes a feedback response portion, the feedback response portion being a first function of the error value, wherein the error value comprises a torque error value.

3. The method of claim 2 , wherein the first function comprises a proportional response component.

4. The method of claim 2 , wherein the first function further comprises an integral component and a damping component.

5. The method of claim 2 , wherein the feed-forward response portion comprises a second function of the value of the torque error value, the second function being different from the first function.

6. The method of claim 5 , wherein the method further comprises adjusting the iterative learning component based on the torque error value and an additional torque error value.

7. The method of claim 5 , further comprising determining a value of a torque to apply to the rotational joint comprises based on a neuromuscular model.

8. The method of claim 5 , further comprising determining a value of a torque to apply to the rotational joint based on one or more measured electromyography signals.

9. The method of claim 5 , wherein a gain of the feed-forward response portion is greater than a gain of the feedback response portion.

10. The method of claim 1 , further comprising:
measuring a plurality of torques;
measuring a plurality of angles of rotation of the rotational joint;
determining a plurality of torque error values for the plurality of torques;
generating an array of torque-angle pairs by associating each measured angle of rotation with a determined torque error of the plurality;
calculating a gain parameter for each torque-angle pair in the array of torque-angle pairs; and
determining the second portion of the second torque using the gain parameter for each torque-angle pair.

11. The method of claim 1 , further comprising:
measuring a plurality of torques;
determining a plurality of torque error values for the plurality of torques;
generating an array of torque-time pairs by associating each determined torque error value with a cycle time;
calculating a gain parameter for each torque-time pair in the array of torque-time pairs; and
determining the second portion of the second torque using the gain parameter for each torque-time pair.

12. The method of claim 1 , wherein the measurement of a first torque comprises a measurement of a strain on one or both of the first component and the second component.

13. The method of claim 1 , wherein controlling the motor to apply the second torque to the rotational joint by the cable comprises controlling one or both of a position of the motor or a velocity of the motor.

14. The method of claim 1 , wherein the cable is in series with a spring, and wherein a spring stiffness of the spring is tuned to reduce a torque error value relative to the torque error value that occurs independent of the spring stiffness being tuned.

15. The method of claim 1 , wherein the first component and the second component are portions of a multi joint exoskeleton, and further comprising:
receiving a measurement of a third torque applied to a second rotational joint coupling a third component to a fourth component, the third torque being applied by a second motor via by a second cable;
determining, based on the measurement of the third torque, a first portion of a fourth torque to apply to the second rotational joint;
determining, based on the measurement of the third torque, a second portion of the fourth torque to apply to the second rotational joint;
determining a value of the fourth torque to apply to the second rotational joint based on the first portion and the second portion; and
controlling the second motor for applying the fourth torque to the second rotational joint by the second cable.

16. An exoskeleton system comprising:
a rotational joint that couples a first component and a second component;
a cable connected to one or more of the first component and the second component;
a motor coupled to the cable, the motor configured to apply a torque to the rotational joint by the cable; and
a motor controller configured for communication with the motor, the motor controller further configured to control the torque applied to the rotational joint by the cable by performing operations comprising:
measuring a first torque applied by the cable to the rotational joint;
determining, based on the first torque, a first portion of a second torque to apply to the rotational joint;
determining, based on the first torque, a second portion of the second torque to apply to the rotational joint by:
determining, for an interval of a cycle, a target value as a function of an error value measured at the same interval of one or more previous cycles; and
determining, from the target value, a feed-forward response portion of the second torque;

determining a value of the second torque to apply to the rotational joint by combining the first portion and the second portion including the feed-forward response portion; and
controlling the motor to apply the second torque to the rotational joint by the cable.

17. The exoskeleton system of claim 16 , wherein the first portion of the second torque to apply to the rotational joint includes a feedback response portion, the feedback response portion being a first function the error value, wherein the error value includes a torque error value.

18. The exoskeleton system of claim 17 , wherein the first function comprises a proportional response component.

19. The exoskeleton system of claim 17 , wherein the first function further comprises an integral component and a damping component.

20. The exoskeleton system of claim 17 , wherein the feed-forward response portion comprises a second function of the value of the torque error value, the second function being different from the first function.

21. The exoskeleton system of claim 20 , wherein the motor controller is configured to adjust the iterative learning component based on the torque error value and an additional torque error value.

22. The exoskeleton system of claim 20 , further comprising determining a value of a torque to apply to the rotational joint based on a neuromuscular model.

23. The exoskeleton system of claim 20 , further comprising determining a value of a torque to apply to the rotational joint based on one or more measur

Assignees

• Univ Carnegie Mellon

Inventors

• Zhang Juanjuan
• Collins Steven H

Classifications

• F16C1/108

  Reducing or controlling of vibrations, e.g. by resilient damping of noise · CPC title

• G05D17/02

  characterised by the use of electric means · CPC title

• A61H2201/5061

  Force sensors · CPC title

• A61H2201/5069

  Angle sensors · CPC title

• A61H3/00 Primary

  Appliances for aiding patients or disabled persons to walk about (apparatus for helping babies to walk A47D13/04 {; applying electrical currents by contact electrodes for stimulating motor muscles, e.g. walking assistance A61N1/36003}) · CPC title