External Force Control Method, External Force Control System and External Force Control Program

• US 20080139968A1
• Filed: 11/29/2005
• Published: 06/12/2008
• Est. Priority Date: 12/16/2004
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Hara, Ritsuo, Endo, Yosuke
• Granted Patent: US 7,860,562 B2
• Time in Patent Office: Days
• US Class Current: 600/595
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61F 2/72 Bioelectric control, e.g. myoelectric
• CPC Class Codes: A61H 1/0237 for the lower limbs
• CPC Class Codes: A61H 3/00 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

Abstract

A method of controlling an external force applied to an animal to achieve as a target relation the relation between the external force and a motion variable varying with the motion of the animal.

A value of an external force f applied to a human leg according to an external force function f(x) on the basis of a measured value of a myoelectric potential x that occurs in the human leg, current I of a motor 220 is controlled according to the set value, and the external force f is applied to the leg through an orthosis 222. A resultant force (the sum of an internal torque and an external torque around a knee joint) F is measured as “a motion variable.” Moreover, a value of a factor γ is set according to a factor function γ(f, F) on the basis of the set value of the external force f and the measured value of the resultant force F. If a deviation δ between the set value of the factor γ and target value γ_t thereof is equal to or greater than a reference value ε, a new external force function f(x) is set in such a way that the set value of the factor γ approaches the target value γ_t.

Claims

1. An external force control method for controlling an external force applied to an animal through an orthosis attached to the animal that makes a movement along with the activities of muscle fibers, the method comprising:

a myoelectric potential measurement step of measuring a myoelectric potential x that occurs in the body of the animal;

an external force setting step of setting a value of an external force f applied to the animal through the orthosis according to an external force function f(x) with the myoelectric potential x as a variable on the basis of the measured value of the myoelectric potential x;

a motion variable measurement step of measuring a motion variable y varying with the motion of the animal under the condition of the external force applied through the orthosis;

a factor setting step of setting a value of a factor y according to a factor function γ

(f, y) with the external force f and the motion variable y as variables on the basis of the set value of the external force f and the measured value of the motion variable y;

a determination step of determining whether a deviation δ

between the set value of the factor y and target value γ

_t thereof is less than a reference value ε

; and

an external force function setting step of setting a new external force function f(x) in such a way that the set value of the factor y approaches the target value γ

_t if the deviation δ

is determined to be equal to or greater than the reference value ε

in the determination step.

2. The external force control method according to claim 1, wherein the external force function setting step comprises setting a value of a coefficient α

that represents the relation between the myoelectric potential x and the external force f and setting the external force function f(x) according to a basic function F(x, α

) with the myoelectric potential x and the coefficient α

as variables on the basis of the set value of the coefficient α

.

3. The external force control method according to claim 1, wherein the external force function setting step comprises finding the external force target value f_t according to the factor function γ

(f, y) on the basis of the measured value of the motion variable y and the target value γ

_t of the factor γ and

setting the external force function f(x) in such a way that the external force f approaches the external force target value f_t.

4. The external force control method according to claim 3, wherein the external force function setting step comprises setting the external force function f(x) in such a way that the maximum measured value of the external force f approaches the maximum value of the external force target value f_t.

5. The external force control method according to claim 1, wherein the determination step is omitted and the external force function setting step is performed after the first external force setting step.

6. The external force control method according to claim 1, wherein:

the motion variable measurement step comprises measuring the resultant force of an internal force and an external force of the animal as the motion variable y; and

the factor setting step comprises setting the ratio of the external force f to the resultant force of the internal force and the external force of the animal as the factor γ

(0≦

γ

<

1).

7. The external force control method according to claim 1, wherein the motion variable measurement step comprises measuring a primitive motion variable varying with the motion of the animal and measuring the motion variable according to an inverse dynamics model that represents the behaviors of the animal on the basis of the measured value of the primitive motion variable.

8. The external force control method according to claim 1, further comprising a motion state determination step of determining the motion state of the animal according to a given correspondence between the primitive motion variable and the motion state of the animal on the basis of the measured value of the primitive motion variable after measuring the primitive motion variable varying with the motion of the animal, wherein the motion variable measurement step comprises measuring the motion variable y according to a given correspondence between the motion state of the animal and the motion variable on the basis of the motion state determined in the motion state determination step.

9. The external force control method according to claim 1, further comprising a step of measuring the external force f, wherein the factor setting step comprises setting a value of the factor γ

according to the factor function γ

(f, y) with the external force f and the motion variable y as variables on the basis of the measured value of the external force f, instead of the set value of the external force f, and the measured value of the motion variable y.

10. The external force control method according to claim 1, further comprising a motion state determination step of determining the motion state of the animal according to a given correspondence between the primitive motion variable and the motion state of the animal on the basis of the measured value of the primitive motion variable after measuring the primitive motion variable varying with the motion of the animal, wherein the external force function setting step comprises setting a new external force function f(x) responsive to each motion state determined in the motion state determination step.

11. The external force control method according to claim 10, wherein:

the determination step comprises determining whether the deviation δ

is less than the reference value ε

on the basis of the factor target value γ

_t set for each motion state according to the motion state determined in the motion state determination step; and

the external force function setting step comprises setting a new external force function f(x) on the basis of the factor target value γ

_t set for each motion state according to the motion state determined in the motion state determination step.

12. The external force control method according to claim 1, wherein the determination step comprises determining whether the deviation δ

is less than a threshold ε

according to the threshold ε

depending on whether the deviation δ

is positive or negative.

13. An external force control system for controlling an external force applied to an animal through an orthosis attached to the animal that makes a movement along with the activities of muscle fibers, the system comprising:

myoelectric potential measurement means for measuring a myoelectric potential x that occurs in the body of the animal;

external force setting means for setting a value of an external force f applied to the animal through the orthosis according to an external force function f(x) with the myoelectric potential x as a variable on the basis of the measured value of the myoelectric potential x measured by the myoelectric potential measurement means;

motion variable measurement means for measuring a motion variable y varying with the motion of the animal under the condition of the external force applied through the orthosis;

factor setting means for setting a value of a factor γ

according to a factor function γ

(f, y) with the external force f and the motion variable y as variables on the basis of the set value of the external force f set by the external force setting means and the measured value of the motion variable y measured by the motion variable measurement means;

determination means for determining whether a deviation δ

between the set value of the factor γ

set by the factor setting means and target value γ

_t thereof is less than a reference value ε

; and

external force function setting means for setting a new external force function f(x) in such a way that the set value of the factor γ

approaches the target value γ

_t if the deviation δ

is determined to be equal to or greater than the reference value ε

by the determination means.

14. An external force control program for providing a computer with functions for controlling an external force applied to an animal through an orthosis attached to the animal that makes a movement along with the activities of muscle fibers, the program providing the computer with:

a myoelectric potential measurement function of measuring a myoelectric potential x that occurs in the body of the animal;

an external force setting function of setting a value of an external force f applied to the animal through the orthosis according to an external force function f(x) with the myoelectric potential x as a variable on the basis of the measured value of the myoelectric potential x;

a motion variable measurement function of measuring a motion variable y varying with the motion of the animal under the condition of the external force applied through the orthosis;

a factor setting function of setting a value of a factor γ

according to a factor function γ

(f, y) with the external force f and the motion variable y as variables on the basis of the set value of the external force f and the measured value of the motion variable y;

a determination function of determining whether a deviation δ

between the set value of the factor y and target value γ

_t thereof is less than a reference value ε

; and

an external force function setting function of setting a new external force function f(x) in such a way that the set value of the factor γ

approaches the target value γ

_t if the deviation δ

is determined to be equal to or greater than the reference value ε

by the determination function.