Pathcorrection for an industrial robot

• US 20040093119A1
• Filed: 06/09/2003
• Published: 05/13/2004
• Est. Priority Date: 04/10/2000
• Status: Active Grant

• Current Assignee: ABB Schweiz AG (ABB Limited)
• Original Assignee: ABB AB (ABB Limited)
• Inventors: Moberg, Stig, Carlsson, Ulf, Brogardh, Torgny, Gunnarsson, Svante, Hovaland, Geir, Norrlof, Miakel, Svenson, Tommy
• Granted Patent: US 7,130,718 B2
• Time in Patent Office: Days
• US Class Current: 700/245
• CPC Class Codes: B25J 9/1638 compensation for arm bending/inertia, pay load weight/inertia
• CPC Class Codes: B25J 9/1641 compensation for backlash, friction, compliance, elasticity in the joints
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: G05B 2219/36415 Adjust path and attitude tool by detecting path, line with a photosensor, laser
• CPC Class Codes: G05B 2219/39024 Calibration of manipulator
• CPC Class Codes: G05B 2219/39033 Laser tracking of end effector, measure orientation of rotatable mirror
• CPC Class Codes: G05B 2219/39056 On line relative position error and orientation error calibration
• CPC Class Codes: G05B 2219/39176 Compensation deflection arm
• CPC Class Codes: G05B 2219/39181 Compensation of coulomb friction in joint
• CPC Class Codes: G05B 2219/39191 Compensation for errors in mechanical components
• CPC Class Codes: G05B 2219/41084 Compensation speed axis with changing, reversing direction, quadrant circle
• CPC Class Codes: Y02P 90/80 Management or planning

Abstract

A method in an industrial robot for increasing the accuracy in the movements of the robot, where a tool supported by the robot is brought to adopt a plurality of positions generated by the control system, which are each determined by a measuring system, whereby a deviation between the generated position and the position determined by the measuring system is introduced as a correction in the control system for adjusting the movement. The generated positions and the positions determined by the measuring system, respectively, are adapted to form a first path an a second path, respectively, whereby the correction is determined by a path deviation between geometrically calculated positions in the respective path.

Claims

1. A method for an industrial robot to increase the accuracy in the movements of the robot, where a tool (2:

9) supported by the robot is brought to adopt a plurality of positions generated by the control system, which are each determined by a measuring system, wherein a deviation between the generated position and the position determined by the measuring system is introduced as correction in the control system for adjusting the movement, characterized in that the generated positions are arranged to form a first path (4;

1) and the positions determined by the measuring system are arranged to form a second path (4;

2), whereby the correction is determined by a path deviation between geometrically determined positions in the respective path.

2. A method according to claim 1, characterized in that the path deviation is calculated based on a vector from a first position (4:

7) in the first path to a second position (4;

6) in the second path, which positions are adapted to lie substantially opposite to each other.

3. A method according to claim 2, characterized in that the first position and the second position are extracted from the same path index in the control system.

4. A method according to claim 2, characterized in that the second position is adapted to lie in a plane (4:

4) normal to a tangent (4;

5) through the first position.

5. A method according to any of the preceding claims, characterized in that the calculation of the path deviation comprises a first step, in which the second path (9:

1) is adapted to adopt the same orientation as the first path (9;

4), a second step, in which the thus oriented second path (9;

2) is adapted to adopt the same position as the first path, and a third step, in which the thus oriented and translated second path (9;

3) is adapted to adopt the same shape as the first path.

6. A method according to any of the preceding claims, characterized in that the measuring system comprises a measuring system associated with the robot, and that the path deviation forms the basis for a parameter adjustment (3:

3) for the drive device.

7. A method according to claim 6, characterized in that the path deviation is calculated from a mean value of the magnitude of the vectors in an interval (5:

5-5;

10), arranged along the first path, around a third position (5;

9).

8. A method according to claim 7, characterized in that the third position comprises a position where the movement of a drive device changes direction.

9. A method according to any of the preceding claims, characterized in that the first path comprises a circle (5:

3).

10. A method according to any of the preceding claims, characterized in that corrections are stated as values in a coordinate system.

11. A method according to claims 1-5, characterized in that the measuring system comprises an external measuring system and that the path deviation forms the basis of a reference adjustment of the control system.

12. A method according to claim 11, characterized in that the external measuring system is adapted to measure also the work object (14:

13, 14;

14, 14;

15) and the tool position (14;

11, 14;

12).

13. A method according to claim 11 or 12, characterized in that the first path is arranged on the surface of the work object.

14. A method according to any of the preceding claims, characterized in that the first path is adapted to form a reference path and the second path is adapted to form an outcome path.

15. A method according to any of the preceding claims, characterized in that the adjusted values form the basis of a new outcome path, whereupon the method is repeated for the new outcome path.

20. Use of a method according to claims 1-15, or a control system according to claims 16-19 for increasing the accuracy of movement in an industrial robot during laser machining.

16. A control system for an industrial robot comprising a program module (2:

1), an interpreter module (2;

2), a trajectory generator (2;

3), a module for inverse kinematics (2;

4), a servo (2;

6) and an axis-angle measurement, respectively, arranged for each drive device, characterized in that the control system further comprises a module for calculation of path deviation (3;

2), which receives data from the trajectory generator (2;

3) and from a measuring module (3;

1, 7;

1).

17. A control system according to claim 16, characterized in that the measuring module (2:

6, 7;

1) comprises a module for direct kinematics (3;

1) and that the control system further comprises a module for parameter adjustment (3;

3), which receives and machines results from the module for calculating the path deviation (3;

2).

18. A control system according to claim 16 or 17, characterized in that module for calculating the path deviation (3:

2) comprises a binary search method and that a friction compensator (6;

11), via a friction model (6;

10), receives the result from the calculation of the path deviation.

19. A control system according to claim 16, characterized in that the measuring module (2:

6, 7;

1) comprises an external measuring system (7;

1) and that the control system further comprises a module for adjusting the reference path in the trajectory generator (2;

3).

21. A computer program comprising instructions for influencing a processor to control a robot, for increasing the accuracy in the movements of the robot, whereby a tool supported by the robot is brought to adopt a plurality of positions, generated by the control system, which are each determined by a measuring system, wherein a deviation between the generated position and the position determined by the measuring system is inserted as a correction in the control system for adjustment of the movement, characterized in that the generated positions and the positions determined by the measuring system, respectively, are adapted to form a first path and a second path, respectively, whereby the correction is determined by a path deviation between geometrically calculated positions in the respective path.

22. A computer program according to claim 21, characterized in that the instructions comprise calculating the path deviation based on a vector from a first position in the first path to a second position in the second path, whereby the second position is adapted to lie in a normal plane to a tangent through the first position.

23. A computer program according to claim 21 or 22, characterized in that the instructions comprise carrying out the calculation of the path deviation in a first step, in which the second path is adapted to adopt the same orientation as the first path, a second step, in which the thus oriented second path is adapted to adopt the same position as the first path, and a third step, in which the thus oriented and translated second path is adapted to adopt the same shape as the first path.

24. A computer program according to claims 21-23, provided at least partly over a network such as the Internet.

25. A computer-readable medium, characterized in that a computer program comprising instructions for influencing a processor to control a robot, in order to increase the accuracy of the movements of the robot, whereby a tool supported by the robot is brought to adopt a plurality of positions generated by the control system, which are each determined by a measuring system, that the generated positions and the positions determined by the measuring system, respectively, are adapted to form a first path and a second path, respectively, whereby the correction is determined by a path deviation between geometrically calculated positions in the respective path.