Intelligent Stepping For Humanoid Fall Direction Change

• US 20100161120A1
• Filed: 11/02/2009
• Published: 06/24/2010
• Est. Priority Date: 12/19/2008
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Yun, Seung-kook, Sakagami, Yoshiaki, Goswami, Ambarish
• Granted Patent: US 8,332,068 B2
• Time in Patent Office: Days
• US Class Current: 700/245
• CPC Class Codes: B62D 57/032 with alternately or sequentially lifted supporting base and legs; with alternately or sequentially lifted feet or skid B62D57/024 takes precedence

Abstract

A system and method is disclosed for controlling a robot having at least two legs that is falling down from an upright posture. An allowable stepping zone where the robot is able to step while falling is determined. The allowable stepping zone may be determined based on leg Jacobians of the robot and maximum joint velocities of the robot. A stepping location within the allowable stepping zone for avoiding an object is determined. The determined stepping location maximizes an avoidance angle comprising an angle formed by the object to be avoided, a center of pressure of the robot upon stepping to the stepping location, and a reference point of the robot upon stepping to the stepping location. The reference point, which may be a capture point of the robot, indicates the direction of fall of the robot. The robot is controlled to take a step toward the stepping location.

Claims

1. A method for controlling a robot having at least two legs, the robot falling down from an upright posture, the method comprising:

determining a stepping location on a ground surface for avoiding an object, comprising;

determining an allowable stepping zone where the robot is able to step while falling; and

determining a stepping location within the allowable stepping zone, the stepping location maximizing an avoidance angle comprising an angle formed by the object to be avoided, a center of pressure of the robot upon stepping to the stepping location, and a reference point of the robot upon stepping to the stepping location, wherein the direction of fall of the robot is toward the reference point; and

controlling the robot to take a step toward the stepping location.

2. The method of claim 1, wherein the reference point upon stepping to the stepping location comprises a capture point, and wherein a distance of the capture point from a center of mass (CoM) of the robot is proportional to a linear velocity of the CoM of the robot.

3. The method of claim 1, further comprising:

determining a control duration, the control duration comprising an estimate of remaining time until the robot has fallen past a threshold angle.

4. The method of claim 3, wherein the allowable stepping zone is determined based on leg Jacobians of the robot and based on maximum joint velocities of the robot.

5. The method of claim 1, further comprising:

dividing the allowable stepping zone into cells, each cell being associated with a location within the allowable stepping zone and with a stepping foot orientation;

for each cell, determining the reference point associated with the cell; and

determining, based on reference points associated with each cell, which cell maximizes the avoidance angle, and wherein the determined stepping location comprises a location within the cell maximizing the avoidance angle.

6. The method of claim 1, further comprising:

determining a foot rotation angle based on a comparison between a trunk orientation angle of the robot and joint angles in a leg of the robot; and

controlling leg joints of the robot to cause a swing foot of the robot to be substantially flat upon touching the ground surface, the controlling based on a transformation matrix from a support foot of the robot to the swing foot of the robot.

7. A system for controlling a robot having at least two legs, the robot falling down from an upright posture, the system comprising:

a computer-readable storage medium storing executable computer program modules configured for;

determining a stepping location on a ground surface for avoiding an object, comprising;

determining an allowable stepping zone where the robot is able to step while falling; and

determining a stepping location within the allowable stepping zone, the stepping location maximizing an avoidance angle comprising an angle formed by the object to be avoided, a center of pressure of the robot upon stepping to the stepping location, and a reference point of the robot upon stepping to the stepping location, wherein the direction of fall of the robot is toward the reference point; and

controlling the robot to take a step toward the stepping location.

8. The system of claim 7, wherein the reference point upon stepping to the stepping location comprises a capture point, and wherein a distance of the capture point from a center of mass (CoM) of the robot is proportional to a linear velocity of the CoM of the robot.

9. The system of claim 7, wherein the modules are further configured for:

determining a control duration, the control duration comprising an estimate of remaining time until the robot has fallen past a threshold angle.

10. The system of claim 9, wherein the allowable stepping zone is determined based on leg Jacobians of the robot and based on maximum joint velocities of the robot.

11. The system of claim 7, wherein the modules are further configured for:

dividing the allowable stepping zone into cells, each cell being associated with a location within the allowable stepping zone and with a stepping foot orientation;

for each cell, determining the reference point associated with the cell; and

determining, based on reference points associated with each cell, which cell maximizes the avoidance angle, and wherein the determined stepping location comprises a location within the cell maximizing the avoidance angle.

12. The system of claim 7, wherein the modules are further configured for:

determining a foot rotation angle based on a comparison between a trunk orientation angle of the robot and joint angles in a leg of the robot; and

controlling leg joints of the robot to cause a swing foot of the robot to be substantially flat upon touching the ground surface, the controlling based on a transformation matrix from a support foot of the robot to the swing foot of the robot.