Controlling a compliant-controlled robot

• US 10,576,629 B2
• Filed: 07/13/2016
• Issued: 03/03/2020
• Est. Priority Date: 07/13/2015
• Status: Active Grant

• Current Assignee: KUKA Roboter GmbH (Midea Group Co., Ltd)
• Original Assignee: KUKA Deutschland GmbH (Midea Group Co., Ltd)
• Inventors: Rohmer, Matthias, Reichl, Tobias, Schreiber, Gunter, Monnich, Holger, Mueller-Sommer, Martin, Bonin, Uwe
• Primary Examiner(s): Mancho, Ronnie M
• Application Number:
  US15/208,668
• Publication Number:
  US 20170014997A1
• Time in Patent Office: 1,329 Days
• Field of Search: 700245
• CPC Class Codes: B25J 9/1633 compliant, force, torque control, e.g. combined with position control
• CPC Class Codes: B25J 9/1676 Avoiding collision or forbidden zones
• CPC Class Codes: G05B 19/423 Teaching successive positions by walk-through, i.e. the tool head or end effector being grasped and guided directly, with or without servo-assistance, to follow a path
• CPC Class Codes: G05B 2219/39342 Adaptive impedance control
• CPC Class Codes: G05B 2219/40359 Constraint, physical limitations

Abstract

In one aspect, a method for controlling a compliant-controlled robot includes performing a boundary monitoring of the robot and controlling movement of the robot with a return force that is predetermined by control technology. If the robot is already in a blocked area upon activation of the boundary monitoring, then a first return force operates to return the robot from a current position in the blocked area toward a boundary of the blocked area. If the robot arrived at the current position in the blocked area after activation of the boundary monitoring, then a second return force operates to return the robot from the current position toward the boundary. The first return force is at least temporarily less than the second return force.

Claims

1. A method for controlling a robot, the method comprising:

determining with a robot controller whether or not a boundary monitoring of the robot has been activated;

controlling by the robot controller movement of at least one axis of the robot with a first return force if the robot, upon activation of the boundary monitoring, is already in a blocked area, wherein the first return force operates to return the robot from a current position in the blocked area toward a boundary of the blocked area and the first return force is predetermined independent of a distance of the current position from the boundary; and

controlling by the robot controller movement of at least one axis of the robot with a second return force if the robot arrived at the current position in the blocked area after activation of the boundary monitoring, wherein the second return force operates to return the robot from the current position toward the boundary and the second return force is predetermined;

wherein the first return force is at least temporarily less than the second return force.

2. The method of claim 1, wherein the first return force is at least temporarily zero.

3. The method according to claim 1, further comprising:

predetermining a stiffness of a virtual spring that ties the robot to an anchor position;

wherein a first stiffness is predetermined if the robot, upon activation of the boundary monitoring, is already in a position in the blocked area;

wherein a second stiffness is predetermined if the robot arrived at the current position in the blocked area after activation of the boundary monitoring; and

wherein the first stiffness is less than the second stiffness, at least upon activation of the boundary monitoring.

4. The method of claim 3, wherein the virtual spring ties the robot to an anchor position on the boundary.

5. The method of claim 1, further comprising:

predetermining a stiffness of a virtual spring that ties the robot to an anchor position;

wherein the stiffness is predetermined based on a time lag from the activation of the boundary monitoring.

6. The method of claim 5, wherein the virtual spring ties the robot to an anchor position on the boundary.

7. The method of claim 5, wherein the stiffness is predetermined based on a time lag if the robot is already in the blocked area upon activation of the boundary monitoring.

8. The method of claim 5, wherein the stiffness is predetermined based on a time lag only if the robot is already in the blocked area upon activation of the boundary monitoring.

9. The method of claim 1, further comprising:

predetermining a stiffness of a virtual spring that ties the robot to an anchor position;

wherein the stiffness is predetermined based on a motion of the robot relative to the boundary.

10. The method of claim 9, wherein the predetermined stiffness is greater when the motion is in a direction away from the boundary than when the motion is in a direction that is not away from the boundary.

11. The method of claim 10, wherein the predetermined stiffness is greater in a direction away from the boundary when the robot is already in the blocked area upon activation of the boundary monitoring.

12. The method of claim 10, wherein the predetermined stiffness is greater in a direction away from the boundary only when the robot is already in the blocked area upon activation of the boundary monitoring.

22. The method of claim 1, further comprising:

controlling the robot with a damping force counteracting a motion of the robot, the damping force based on a current speed of the robot;

wherein the damping force increases more strongly in a second speed range above a predetermined minimum speed than in a first speed range below the minimum speed.

13. A method for controlling a robot, the method comprising:

performing by a robot controller a boundary monitoring of the robot;

controlling by the robot controller movement of at least one axis of the robot with a first return force, wherein the first return force operates to return the robot from a current position in a blocked area to a boundary of the blocked area and the first return force is predetermined independent of a distance of the current position from the boundary, if the robot is moved a specified distance toward the boundary or parallel to the boundary; and

controlling by the robot controller movement of at least one axis of the robot with a second return force, which is greater than the first return force, the second return force being predetermined, if the robot is moved by the specified distance away from the boundary.

14. The method of claim 13, wherein the first return force is equivalent to zero.

15. The method of claim 13, wherein the robot is moved with the second return force if the current position of the robot is already in the blocked area when the boundary monitoring begins.

16. The method of claim 13, wherein the robot is moved with the second return force only if the current position of the robot is already in the blocked area upon activation of the boundary monitoring.

17. The method of claim 13, further comprising:

controlling movement of at least one axis of the robot with a third return force if the robot, upon activation of the boundary monitoring, is already in a blocked area, wherein the third return force operates to return the robot from a current position in the blocked area toward a boundary of the blocked area and is predetermined; and

controlling movement of at least one axis of the robot with a fourth return force if the robot arrived at the current position in the blocked area after activation of the boundary monitoring, wherein the fourth return force operates to return the robot from the current position toward the boundary and is predetermined;

wherein the third return force is at least temporarily less than the fourth return force.

18. The method of claim 13, wherein an anchor position of a virtual spring to which the robot is tied cannot be displaced away from the boundary by an external impingement of force.

19. The method of claim 18, wherein the external impingement force is an external manual guidance force applied to the robot.

20. The method of claim 13, further comprising:

setting an anchor position of a virtual spring to which the robot is tied as a current position of the robot or as a position within a connection between the current position and the boundary that is spaced apart from the current position toward the boundary by a distance.

21. The method of claim 20, wherein the connection is the shortest connection between the current position and the boundary.

23. A controller for controlling a robot, the controller having program code stored on a non-transitory computer-readable storage medium and that, when executed by the controller, causes the controller to:

determine whether or not a boundary monitoring of the robot has been activated;

control movement of at least one axis of the robot with a first return force if the robot, upon activation of the boundary monitoring, is already in a blocked area, wherein the first return force operates to return the robot from a current position in the blocked area to a boundary of the blocked area and is predetermined independent of a distance of the current position from the boundary; and

control movement of at least one axis of the robot with a second return force if the robot arrived at the current position in the blocked area after activation of the boundary monitoring, wherein the second return force operates to return the robot from the current position toward the boundary and is predetermined;

wherein the first return force is at least temporarily less than the second return force.

24. A robot arrangement comprising:

a multi-axis robot; and

the controller of claim 23 communicating with the robot and controlling operation the robot.

25. A computer programming product having program code stored on a non-transitory computer-readable storage medium, the program code, when executed by a controller associated with a multi-axis robot, causing the controller to:

determine whether or not a boundary monitoring of the robot has been activated;

control movement of at least one axis of the robot with a first return force if the robot, upon activation of the boundary monitoring, is already in a blocked area, wherein the first return force operates to return the robot from a current position in the blocked area to a boundary of the blocked area and is predetermined independent of a distance of the current position from the boundary; and

control movement of at least one axis of the robot with a second return force if the robot arrived at the current position in the blocked area after activation of the boundary monitoring, wherein the second return force operates to return the robot from the current position toward the boundary and is predetermined;

wherein the first return force is at least temporarily less than the second return force.