Robots with Occlusion Avoidance Functionality

• US 20080312771A1
• Filed: 03/21/2008
• Published: 12/18/2008
• Est. Priority Date: 03/23/2007
• Status: Active Grant

• Current Assignee: Honda Research Institute Europe GmbH (Honda Motor Company)
• Original Assignee: Honda Research Institute Europe GmbH (Honda Motor Company)
• Inventors: Sugiura, Hisashi
• Granted Patent: US 8,160,745 B2
• Time in Patent Office: Days
• US Class Current: 700/259
• CPC Class Codes: B25J 9/1666 Avoiding collision or forbidden zones

Abstract

A method for controlling a robot having at least one visual sensor. A target for a motion of the robot is defined. A motion control signal adapted for the robot reaching the target is calculated. A collision avoidance control signal based on the closest points of segments of the robot and a virtual object between the visual sensing means and the target is calculated. The motion control signal and the collision avoidance control signal are weighted and combined. The weight of the motion control signal is higher when a calculated collision risk is lower. The motion of the robot is controlled according to the combined signal so that no segment of the robot enters the space defined by the virtual object.

Claims

1. A method for controlling a robot having at least one visual sensor, comprising:

defining a target for a motion of the robot;

calculating a motion control signal adapted to command the robot to reach the target;

calculating a collision avoidance control signal based on closest points of segments of the robot and a virtual object, the virtual object between the at least one visual sensor and the target and representing an area where the segments of the robot are not to enter;

assigning weights to the motion control signal and the collision avoidance control signal to generate a weighted motion control signal and a weighted collision avoidance control signal, a weight of the motion control signal higher responsive to risk of the segments of the robot colliding with the virtual object being higher;

combining the weighted motion control signal and the weighted collision avoidance control signal to generate a combined signal; and

controlling motion of the robot according to the combined signal.

2. The method of claim 1, wherein the virtual object has a shape that is symmetrical around an axis connecting between a center of the at least one visual sensor and a center of the target.

3. The method of claim 1, wherein the virtual object has a shape of a three dimensional ellipsoid.

4. The method of claim 1, wherein the weights are changed gradually over time to perform a soft task switching between motion for reaching the target and collision avoidance.

5. The method of claim 1, wherein calculating the motion control signal comprises mapping a collision avoidance motion in null space and a target reaching motion in task space.

6. The method of claim 5, wherein the null space of the collision avoidance control is assigned to the target reaching motion.

7. The method of claim 1, wherein the weight of the collision avoidance control signal is zero when a distance between the closest points being larger than a predetermined value.

8. The method of claim 1, further comprising performing collision avoidance control by controlling the robot to move a segment of the robot in a direction parallel to a line connecting between the closest points.

9. The method of claim 1, wherein the collision avoidance control signal maps the collision avoidance motion to the task space and the motion control signal maps the target reaching motion to the null space.

10. A computer program product comprising a computer readable storage medium structured to store instructions executable by a processor in a computing device, the instructions, when executed cause the processor to:

define a target for a motion of a robot;

calculate a motion control signal adapted to command the robot to reach the target;

calculate a collision avoidance control signal based on closest points of segments of the robot and a virtual object between one visual sensor of the robot and the target, the virtual object representing an area where the segments of the robot are not to enter;

assign weights to the motion control signal and the collision avoidance control signal to generate a weighted motion control signal and a weighted collision avoidance control signal, a weight of the motion control signal higher responsive to risk of the segments of the robot colliding with the virtual object being higher;

combine the weighted motion control signal and the weighted collision avoidance control signal to generate a combined signal; and

control motion of the robot according to the combined signal.

11. A motion control unit in a robot having a visual sensor, comprising:

a distance computing module adapted to calculate a collision avoidance control signal based on two closest points between a segment of the robot and a virtual object, the virtual object between the visual sensor and the target and representing an area where the segment of the robot is not to enter;

a motion control module adapted to calculate a motion control signal commanding a robot to reach a target;

a collision avoidance module adapted to calculate a collision avoidance control signal based on the closest points of the segment of the robot and the virtual object; and

a blending control unit adapted to assign weights to the motion control signal and the collision avoidance control signal to generate weighted motion control signal and weighted collision avoidance signal, a weight of the motion control signal assigned a higher value responsive to risk of collision being lower, a weight of the collision avoidance control signal assigned a higher value responsive to the risk of collision being higher, the blending control unit further adapted to combine the weighted motion control signal and the weighted collision avoidance control signal to generate a combined weighted signal according to which a motion of the robot is controlled.

12. The motion control unit of claim 11, wherein the robot comprises a humanoid biped robot.

13. The motion control unit of claim 11, wherein the robot comprises a head portion that is moveable relative to a main body of the robot, the head portion comprising two cameras at its front portion.