Method and system for appraising the wear of axles of a robot arm

• US 7,643,946 B2
• Filed: 06/15/2005
• Issued: 01/05/2010
• Est. Priority Date: 06/15/2004
• Status: Expired due to Fees

• Current Assignee: ABB Patent GmbH (ABB Limited)
• Original Assignee: ABB Patent GmbH (ABB Limited)
• Inventors: Hansen, Sven, Schmidt, Steffen, Henrich, Kim, Bader, Axel
• Primary Examiner(s): Nghiem; Michael P
• Application Number:
  US11/153,069
• Publication Number:
  US 20050278148A1
• Time in Patent Office: 1,665 Days
• Field of Search: 702/34, 702/35, 702/41, 702/36, 702/43, 702183-185, 700/174, 700/175, 738/659
• US Class Current: 702/41
• CPC Class Codes: B25J 9/1641 compensation for backlash, friction, compliance, elasticity in the joints
• CPC Class Codes: G05B 2219/50197 Signature analysis, store working conditions, compare with actual

Abstract

A method determines the wear of axles of a robot arm of an industrial robot. A torque profile of at least one axle taken during at least one working cycle of the industrial robot is used as a basis for an analysis. The torque profile is analyzed for portions of the torque profile that exceed a previously fixed torque band, and current axial wear is determined by assessing the frequency and/or the curve profile of the portions of the torque profile. A system is provided for determining the wear.

Claims

1. A method for appraising axle wear of a robot arm of an industrial robot, which comprises the steps of:

taking a bi-directional torque profile of at least one axle of the robot arm during at least one working cycle of the industrial robot and providing the torque profile to an evaluation device for an analysis;

with the evaluation device, analyzing the torque profile for portions of the torque profile that exceed a previously fixed torque band;

with the evaluation device, determining current axle wear by assessing a frequency and/or a curve profile of the portions of the torque profile;

with the evaluation device, appraising axle wear of the robot arm based on the current axle wear for determining maintenance requirements; and

storing the torque profile within the evaluation device for later use by a user.

2. The method according to claim 1, which further comprises performing one of:

with the evaluation device, measuring the torque profile; and

reading out the torque profile from a data memory of the evaluation device.

3. The method according to claim 1, which further comprises, with the evaluation device, analyzing a ratio of a maximum torque value in a specific portion of the torque profile to an averaged torque value in a previously defined time period within the working cycle considered for assessing the axle wear.

4. The method according to claim 1, which further comprises, with the evaluation device, analyzing at least one curve profile of a portion of the torque profile for assessing the axle wear.

5. The method according to claim 4, which further comprises, with the evaluation device, analyzing a slope of the curve profile at a time directly before and possibly after an extreme, taken from the latter up to at least a next-following point of inflection of the curve profile.

6. The method according to claim 1, wherein the evaluation device uses axle-specific parameters for assessing the axle wear.

7. The method according to claim 6, which further comprises determining the axle-specific parameters empirically or by a neural method.

8. The method according to claim 1, which further comprises representing at least one of the torque profiles and a torque band on a display device.

9. The method according to claim 1, which further comprises, with the evaluation device, appraising an absolute axle wear or axle state by taking into account the current axial wear together with a number of working cycles completed so far.

10. The method according to claim 1, which further comprises, with the evaluation device, estimating a time period until a wear limit for the axle is reached by taking into account the current axial wear and/or a number of working cycles completed so far.

11. A system for determining axle wear of a robot arm of an industrial robot, comprising:

a data module containing data of a bi-directional torque profile of at least one axle during at least one working cycle of the industrial robot;

an analysis module for analyzing portions of the torque profile that exceed a previously fixed torque band; and

an assessment module for interpreting a frequency and/or a curve profile of the portions of the torque profile as axle wear of the robot arm, said assessment module, said data module, and said analysis module coupled to each other for exchanging the data with each other, said assessment module storing the axle wear of the robot arm and the torque profile for later use by a user.

12. The system according to claim 11, wherein at least one of said data module, said analysis module and said assessment module, is disposed in a robot controller.

13. The system according to claim 11, further comprising an evaluation device to be connected to a robot controller, at least one of said data module, said analysis module and said assessment module is disposed in said evaluation device.

14. The system according to claim 11, wherein the torque profile can be read out from a robot controller as direct or indirect values.

15. The system according to claim 11, wherein said data module, said analysis module and said assessment module are in each case computer program products each contained in a computer-readable medium.