Pathcorrection for an industrial robot

• US 7,130,718 B2
• Filed: 04/09/2001
• Issued: 10/31/2006
• Est. Priority Date: 04/10/2000
• Status: Expired due to Term

• Current Assignee: ABB Schweiz AG (ABB Limited)
• Original Assignee: ABB AB (ABB Limited)
• Inventors: Carlsson, Ulf, Brogardh, Torgny, Hovland, Geir, Svensson, Tommy, Gunnarsson, Svante, Norrlof, Mikael, Moberg, Stig
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Marc, McDieunel
• Application Number:
  US10/257,254
• Publication Number:
  US 20040093119A1
• Time in Patent Office: 2,031 Days
• Field of Search: 700/245, 700/193, 700/250, 700/253, 318/568.13, 318570-573, 318/568.18, 318/568.23, 318/568.24, 701/23, 701/25, 901/3, 219/124.1, 414/730
• US Class Current: 700/254
• 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 for an industrial robot to increase accuracy in movements of the robot. A first path is formed by bringing a tool supported by the robot to adopt a plurality of generated positions. A plurality of observed positions of the tool moving along the first path are determined. A second path is formed of the determined tool positions. A correction is determined by a path deviation between geometrically determined positions in the first path and the second path.

Claims

1. A method for an industrial robot to increase accuracy in movements of the robot, the method comprising:

forming a first path comprising a plurality of generated positions;

directing a tool supported by the robot to assume the plurality of generated positions;

determining a plurality of observed positions of the tool as the tool is directed to assume the plurality of generated positions;

forming a second path of the observed tool positions; and

determining a correction by a path deviation between the observed positions and the generated positions.

2. The method according to claim 1, wherein the path deviation is calculated based on a vector from a first position in the first path to a second position in the second path, wherein the first position and the second position lie substantially opposite to each other.

3. The method according to claim 2, wherein the first position and the second position are extracted from the same path index.

4. The method according to claim 2, wherein the second position lies in a plane normal to a tangent through the first position.

5. The method according to claim 1, wherein calculation of the path deviation comprises:

adapting the second path to adopt the same orientation as the first path;

adapting the oriented second path to adopt the same position as the first path; and

adapting the oriented and translated second path to adopt the same shape as the first path.

6. The method according to claim 1, wherein the path deviation forms the basis for a parameter adjustment for the drive device.

7. The method according to claim 6, wherein the path deviation is calculated from a mean value of the magnitude of the vectors in an interval, arranged along the first path, around a third position.

8. The method according to claim 7, wherein the third position comprises a position where the movement of a drive device changes direction.

9. The method according to claim 1, wherein the first path comprises a circle.

10. The method according to claim 1, wherein corrections are stated as values.

11. The method according to claim 1, wherein the path deviation forms the basis of a reference adjustment.

12. The method according to claim 11, wherein the first path is arranged on the surface of the work object.

13. The method according to claim 1, wherein the first path is adapted to form a reference path and the second path is adapted to form an outcome path.

14. The method according to claim 1, wherein the adjusted values form the basis of a new outcome path, whereupon the method is repeated for the new outcome path.

15. Use of a method according to claim 1 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;

an interpreter module;

a trajectory generator;

a module for inverse kinematics;

a servo;

an axis-angle measurer;

a measuring module;

a module for calculation of path deviation, which receives data from the trajectory generator and from the measuring module.

17. The control system according to claim 16, wherein the measuring module comprises a module for direct kinematics and wherein the control system further comprises a module for parameter adjustment, which receives and machines results from the module for calculating the path deviation.

18. The control system according to claim 16, wherein the module for calculating the path deviation comprises a binary search method, the control system further comprising:

a friction compensator, via a friction model, receives the result from the calculation of the path deviation.

19. The control system according to claim 16, wherein the measuring module comprises an external measuring system, the control system further comprising:

a module for adjusting the reference path in the trajectory generator.

20. Use of a control system according to claim 16 for increasing the accuracy of movement in an industrial robot during laser machining.

21. A computer program, comprising:

a computer readable medium; and

instructions recorded on the computer readable medium for influencing a processor to control a robot, for increasing the accuracy in the movements of the robot, the instructions for carrying out the steps of

forming a first path comprising a plurality of generated positions, directing a tool supported by the robot to assume the plurality of generated positions,

determining a plurality of observed positions of the tool as the tool is directed to assume the plurality of generated positions,

forming a second path of the observed tool positions, and

determining a correction by a path deviation between the observed positions and the generated positions.

22. The computer program according to claim 21, wherein the instructions further 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. The computer program according to claim 21, wherein the instructions further 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. The computer program according to claim 21, provided at least partly over a network such as the Internet.

25. A method to increased accuracy in movements of an industrial robot, the method comprising:

forming a predefined path comprising a plurality of generated positions;

directing a tool supported by the robot to assume the plurality of generated positions;

determining a plurality of observed positions of the tool as the tool is directed to assume the plurality of generated positions;

forming an actual tool path of the observed tool positions;

determining a path deviation between the actual tool path and the predefined path; and

determining at least one correction that will result in bringing the actual tool path closer to the predefined path.

26. The method according to claim 25, wherein the correction adjusts at least one of an orientation, position and shape of the actual tool path.