Walking robot and method for controlling posture thereof

Patent metadata

Field	Value
Publication number	US-9043029-B2
Application number	US-201113293455-A
Country	US
Kind code	B2
Filing date	Nov 10, 2011
Priority date	Dec 2, 2010
Publication date	May 26, 2015
Grant date	May 26, 2015

Abstract

A walking robot having joints which move using a torque servo, a posture of the robot being stably controlled, and a method of controlling a posture of the robot. It is possible to maintain a stable angle of the upper body while keeping an erect posture and balance using the COG of the robot and the inclination and the direction of the upper body and the pelvis of the robot, even in an external variation including external force or an inclination angle of the ground. Even in a state in which terrain information is not known in advance, the robot may keep an erect posture in a direction of gravity. Even when a plane where the robot stands is gradually inclined, the postures of the upper body and the legs of the robot may be kept while actively changing the angle of the ankle joint.

First claim

What is claimed is:

1. A method for controlling a posture of a robot including an upper body, a pelvis link connected to a lower side of the upper body, a plurality of hip joint portions connected to a lower side of the pelvis link, a plurality of legs respectively connected to the plurality of hip joint portions, and a plurality of feet respectively provided for the plurality of legs, the method comprising:
computing, by a computer, a position of a current Center of Gravity (COG) of the robot;
setting a position of a desired COG of the robot;
computing, by a computer, an error between the set position of the desired COG and the computed position of the current COG;
computing, by a computer, a force to be compensated for keeping balance of the robot using the computed error;
distributing the computed force to the plurality of legs;
computing, by a computer, joint torque of each of the legs in accordance with the distributed, computed force; and
performing torque servo control using the computed joint torque,
wherein the distributing of the computed force includes:
computing distances between a point of the current COG of the robot projected on the ground and the plurality of feet; and
enabling a leg closer to the point of the current COG of the robot projected on the ground to have a larger value, based on the computed distances.

2. The method according to claim 1 , wherein the position of the desired COG is set to a position separated from a middle portion between the plurality of feet which touch the ground in a vertical direction.

3. The method according to claim 1 , wherein the position of the desired COG is set to a position separated from a certain point of the plurality of feet which touch the ground in a vertical direction.

4. The method according to claim 1 , wherein the force represents a virtual spring between the computed position of the current COG and the set position of the desired COG.

5. The method according to claim 1 , further comprising:
measuring an actual rotation angle of the pelvis link;
computing an error between the measured actual rotation angle and a desired rotation angle; and
computing moment to be compensated to keep the robot balanced using the computed error between the measured actual rotation angle and the desired rotation angle,
wherein the computing of the joint torque includes computing the joint torque to generate the computed moment and the computed force.

6. The method according to claim 5 , wherein the measuring of the actual rotation angle of the pelvis link includes measuring the rotation angle in a yaw direction (Z-axis rotation), a pitch direction (Y-axis rotation) and a roll direction (X-axis direction) with respect to inclination of a torso using an inertial measurement unit (IMU).

7. The method according to claim 5 , further comprising computing gravity compensation torque of each of the legs,
wherein the computing of the joint torque includes compensating for the joint torque of each of the legs using the computed gravity compensation torque.

8. The method according to claim 7 , further comprising computing damping torque of each of the legs,
wherein the computing of the joint torque compensates for the computed joint torque of each of the legs using the computed damping torque.

9. The method according to claim 7 , wherein the gravity compensation torque is computed using angles q of all joints of the feet, masses and COG positions of all links belonging to the legs and the total mass and the current COG position of the upper body.

10. The method according to claim 7 , wherein the computing of the gravity compensation torque of each of the legs includes performing gravity compensation in consideration of the weight of the upper body according to the distributed force.

11. The method according to claim 7 , wherein the computing of the gravity compensation torque of each of the legs includes performing gravity compensation in consideration of the weight of another leg according to the states of the plurality of legs.

12. The method according to claim 11 , wherein the states of the plurality of legs are divided into an upper body supporting state or a swing state depending on whether or not the feet respectively provided to the plurality of legs touch the ground.

13. A walking robot including an upper body, a pelvis link connected to a lower side of the upper body, a plurality of hip joint portions connected to a lower side of the pelvis link, a plurality of legs respectively connected to the plurality of hip joint portions, and a plurality of feet respectively provided for the plurality of legs, the walking robot comprising:
a computation unit to calculate a position of a current Center of Gravity (COG) of the robot;
a setting unit to set a position of a desired COG of the robot;
a posture control unit to compute an error between the set position of the desired COG and the computed position of the current COG, to compute a force to be compensated to keep the robot balanced using the computed error, to distribute the computed force to the plurality of legs, and to compute joint torque of each of the legs in accordance with the distributed, computed force; and
a servo control unit to perform torque servo control using the computed joint torque,
wherein the posture control unit computes distances between a point of the current COG of the robot projected on the ground and the plurality of feet, and distributes the computed force to the plurality of legs so as to enable a leg closer to the point of the current COG of the robot projected on the ground to have a larger value based on the computed distances.

14. The walking robot according to claim 13 , further comprising an inertial measurement unit (IMU) to measure an actual rotation angle of the pelvis link,
wherein the posture control unit computes an error between the measured actual rotation angle and a desired rotation angle and computes moment to be compensated to keep the robot balanced using the computed error between the measured actual rotation angle and the desired rotation angle.

15. The walking robot according to claim 14 , wherein the posture control unit computes gravity compensation torque of each of the legs and compensates for the joint torque of each of the legs using the computed gravity compensation torque.

16. The walking robot according to claim 15 , wherein the posture control unit computes damping torque of each of the legs and compensates for the joint torque of each of the legs using the computed damping torque.

17. The walking robot according to claim 14 , wherein the posture control unit computes the joint torque to generate the computed moment and the computed force, and controls the posture of each of the plurality of legs in accordance with the computed joint torque.

18. The walking robot according to claim 14 , wherein the posture control unit measures the rotation angle in a yaw direction (Z-axis rotation), a pitch direction (Y-axis rotation) and a roll direction (X-axis direction) with respect to inclination of a torso using an inertial measurement unit (IMU).

19. The walking robot according to claim 13 , wherein the force represents a virtual spring between the computed position, of the current COG and the set position of the desired COG.

20. A method comprising:
computing, by a computer, a position of a current Center of Gravity (COG) of a robot having;
setting a position of a desired COG of the robot;
computing, by a computer, an error between the set position of

Assignees

• Seo Kee Hong
• Samsung Electronics Co Ltd

Inventors

• Seo Kee Hong

Classifications

• B25J9/104 Primary

  with cables, chains or ribbons · CPC title

• B62D57/032

  with alternately or sequentially lifted supporting base and legs; with alternately or sequentially lifted feet or skid (B62D57/024 takes precedence) · CPC title