METHOD OF OPERATING A WEARABLE ROBOT

• US 20130173060A1
• Filed: 06/21/2012
• Published: 07/04/2013
• Est. Priority Date: 01/04/2012
• Status: Active Grant

• Current Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Original Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Inventors: Yang, Woo Sung, Yoo, Su Jung
• Granted Patent: US 9,114,524 B2
• Time in Patent Office: Days
• US Class Current: 700/261
• CPC Class Codes: B25J 9/0006 Exoskeletons, i.e. resembling a human figure
• CPC Class Codes: B25J 9/16 Programme controls programme controls in general G05B19/00, e.g. numerical pogramme controls G05B19/18; recording or playback systems G05B19/42
• CPC Class Codes: B25J 9/1633 compliant, force, torque control, e.g. combined with position control
• CPC Class Codes: G05B 2219/40305 Exoskeleton, human robot interaction, extenders

Abstract

Disclosed herein is a method of obtaining the intended manipulation torque of a user for a wearable robot. The method allows the wearable robot, the motion of each joint of which is operated by a motor and which is capable of measuring a variation in current in the motor of each joint and calculating a torque at each joint, to simply and rapidly extract the intended manipulation torque of the user using both an acceleration value (e.g., measured by an acceleration sensor installed on a gripper), and the current variation of the motor, in a state in which the wearable robot does not know the weight of a weight object to be lifted with the gripper. Accordingly, the wearable robot may be suitably controlled at a comparatively lower cost.

Claims

1. A method of obtaining a manipulation torque for a wearable robot, comprising:

a) obtaining, at a control unit, an actuator torque value of the robot, wherein the robot comprises at least one arm with one or more joints and a gripper, and a control handle;

b) moving, by the gripper of the robot, an object to a predetermined position set by the control unit;

c) calculating, at the control unit, an additional torque value created by the addition of the weight object at the job position when step b) is completed, wherein the additional torque value is calculated using a variation in a current required by each of the one or more joints of the at least one arm of the robot when step b) is performed, relative to the current required by each of the one or more joints of the at least one arm of the robot in step a);

d) calculating, at the control unit, a mass of the weight object using the actuator torque value obtained in step a), the additional torque calculated in step c), and a position of the weight object;

e) computing, by the control unit, an external force value caused by the weight object using an acceleration value and the mass calculated in step d);

f) computing, by the control unit, an external force torque value caused by a change in the position of the weight object using the external force value computed in step e);

g) calculating, by a control unit, a total torque value required to make a motion of the arm of the robot in which the weight object is held, wherein the total torque value is based on the variation in the current required by each joint of the robot to implement the motion of the weight object; and

h) calculating, by the control unit, an intended torque value by subtracting the actuator torque value of the robot and the external force torque value from the total torque value calculated in step g).

2. The method according to claim 1, wherein the control unit calculates the actuator torque value as

M_a{umlaut over (q)}+C_a(q,{dot over (q)})+G_a(q)=τ

_a,

where τ

_a denotes the actuator torque value, M_a denotes inertia based on the robot'"'"'s design, C_a denotes friction caused by a centrifugal force at each joint based on the robot'"'"'s design, G_a denotes gravity based on the robot'"'"'s design, and q denotes the angle of the joint.

3. The method according to claim 1, wherein the job position in step b) is spatially distinct from an initial position at which the arm of the robot holds the weight object.

4. The method according to claim 3, wherein the spatial distinction between the initial position and the job position allows the variation in the torque required by the robot due to the weight object to be suitably sensed.

5. The method according to claim 1, wherein calculating in step d) further comprises:

calculating the position of the weight object using a geometrical calculation based on a posture of the robot that is stationary at the job position; and

calculating the mass of the weight object as

M_a,e{umlaut over (q)}+C_a,e(q,{dot over (q)})+G_a,e(q)−

τ

_a=τ

_e(job)

where M_a,e denotes inertia based on the robot'"'"'s own design and the weight object, C_a,e denotes friction based on the robot'"'"'s own design and a centrifugal force at each joint occurring due to the weight object, G_a,e denotes gravity based on the robot'"'"'s own design and the weight object, τ

_a denotes the actuator torque value, τ

_e(job) denotes the additional torque value, and q denotes the angle of the joint.

6. The method according to claim 1, wherein computing in step f) further comprises:

computing the external force torque value that varies each time the position of the weight object changes by multiplying a Jacobian transpose specifying a relationship among positions of each of the one or more joints of the robot by the external force value in step e).

7. The method according to claim 1, wherein calculating in step h) further comprises:

calculating the intended torque value applied by the user as

τ

_h=τ

−

τ

_a−

τ

_e

where τ

_h denotes the intended user torque value, τ

denotes the total torque value, τ

_a denotes the actuator torque value, and τ

_e denotes the external force torque value.

8. The method according to claim 1, wherein the acceleration value in step e) is measured with an accelerometer.

9. The method according to claim 8, wherein the accelerometer is located between any of the one or more joints and the gripper.

10. A method of obtaining an intended manipulation torque of a user for a wearable robot, comprising:

obtaining, by a controller, an actuator torque value of the robot in a state in which a weight object is not held, wherein the robot comprises at least one arm with one or more joints and a gripper, and a control handle;

calculating, by a controller, a torque value created by addition of the weight object at a predetermined job position, wherein the torque value is calculated using a variation in a current required by each of the one or more joints of the robot while moving the weight object to the job position;

calculating, by a controller, a mass of the weight object using the actuator torque value, the torque value caused by the addition of the weight object, and a position of the weight object;

calculating, by a controller, an external force value caused by the weight object and a torque value caused by the external force, using both an acceleration value measured by an acceleration sensor when the weight object is moved in a state in which a user applies an operating force to the control handle of the robot and the gripper holds the weight object, and the mass of the weight object;

calculating, by a controller, a total torque value using a variation in the current required by each of the one or more joints of the robot when the robot is moved according to an intended manipulation of the user; and

calculating, by a controller, the intended user torque by subtracting the actuator torque value of the robot and the torque value caused by the external force from the calculated total torque value.

11. The method according to claim 10, wherein the acceleration sensor is an accelerometer.

12. A non-transitory computer readable medium containing program instructions executed by a processor or controller, the computer readable medium comprising:

program instructions that obtain an actuator torque value from a control unit of a robot;

program instructions that calculate an additional torque value relative to the actuator torque value based an amount of current required by one or more joints of one or more arms of the robot to move the weight object to a job position;

program instructions that calculate a mass of the weight object using the actuator torque value, the additional torque value and a position of the weight object;

program instructions that compute an external force value using an acceleration value and the calculated mass;

program instructions that compute an external force torque caused by a change in the position of the weight object;

program instructions that calculate a total torque value required to translate an input torque value by a user on a control handle of the robot into a motion of the arm of the robot carrying a weight object; and

program instructions that calculate an intended torque value by subtracting the actuator torque value and the external force torque value from the total torque value.