Calibration and programming of robots

Patent metadata

Field	Value
Publication number	US-9248573-B2
Application number	US-201213630380-A
Country	US
Kind code	B2
Filing date	Sep 28, 2012
Priority date	Sep 28, 2011
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

The invention pertains to a method of calibrating robots without the use of external measurement equipment. The invention furthermore pertains to a method of copying working programs between un-calibrated robots. Both methods utilize the properties of a closed chain and the relative position of the links in the chain in order to update the kinematic models of the robots.

First claim

The invention claimed is:

1. A method of calibrating robots, the method comprising:
(a) providing at least two robots, each robot having a respective tool flange and joints and/or links connecting two flanges: a base flange and the respective tool flange of the robot,
(b) forming a closed chain from the at least two robots,
(c) manipulating at least one of the links or joints in the closed chain, thereby inducing manipulations of some of the other links or joints in the closed chain, and then
(d) estimating kinematic models for each robot based on sensor information associated with the joints and/or links of each of the at least two robots.

2. The method according to claim 1 , where the sensor information is obtained from the same sensors, which are used to drive the robot joints and/or links.

3. The method according to claim 2 , where the sensor information is only obtained from the same sensors, which are used to drive the robot joints and/or links.

4. The method according to claim 1 , wherein step (c) comprises:
changing the joint positions, and thereby the position of the joints of each of the at least two robots, and
collecting corresponding position pairs.

5. The method according to claim 4 , wherein the sensor information is information about the position of the joints, and wherein step (d) comprises estimating the kinematic models based on the collected corresponding position pairs.

6. The method according to claim 4 , further comprising evaluating whether sufficient position pair data are obtained after step (d), and then
repeat step (d) if not sufficient position pair data are obtained in order to update the kinematic models.

7. The method according to claim 1 , wherein the sensor information comprises any of the following and/or changes in any of the following: angles, position coordinates, or derivatives of the angles or the position coordinates.

8. The method according to claim 1 , wherein the sensor information comprises any of the following and/or changes in any of the following: force, torque, or derivatives of the force or the torque.

9. The method according to claim 1 , wherein step (b) of forming a closed chain from the at least two robots is performed by physically connecting said at least two robots at least at their base flanges, and/or at their respective tool flanges.

10. The method according to claim 1 , wherein step (b) of forming the closed chain from the at least two robots further comprises a step of fixing at least one distance between the at least two robots.

11. The method according to claim 1 , wherein step (b) of forming a closed chain from the at least two robots further comprises a step of fixing at least one direction of a connection between the at least two robots in the closed chain.

12. The method according to claim 1 , wherein step (b) of forming a closed chain from the at least two robots comprises a step of using measurement equipment to measure relative positions between the at least two robots.

13. The method according to claim 12 , wherein the measurement equipment is configured for measuring a distance between parts of the at least two robots.

14. The method according to claim 12 , wherein the measurement equipment is configured for determining a direction between parts of the at least two robots.

15. The method according to claim 14 , wherein the measurement equipment is at least one ball bar connecting the at least two robots.

16. The method according to claim 1 , wherein a connecting flanges of the at least two robots do not share a same rotational axis.

17. The method according to claim 1 , wherein the step (d) of estimating the kinematic models is furthermore based on an estimation or measurement of the offset between the at least two robots at their base flanges, and at their respective tool flanges.

18. The method according to claim 1 , wherein the step (d) of estimating the kinematic models is furthermore based on statistical information about at least one part of the closed chain.

19. The method according to claim 18 , wherein the statistical information is used to estimate the models based on sensor information which exceeds the number of equations, without statistical information, to be solved.

20. The method according to claim 1 , further comprising evaluating whether sufficient sensor information associated with the joints of each of the at least two robots is obtained after step (c), but before step (d).

21. The method according to claim 20 , wherein sufficient sensor information corresponds to a number of unknowns, which does not exceed number of equations to be solved in order to estimate the kinematic models.

22. The method according to claim 21 , comprising collecting an overhead percentage (OPI) of sensor information, in addition to what is necessary for solving the equations in order to estimate the kinematic models.

23. The method according to claim 22 , further comprising:
retaining at least a fraction of said overhead percentage (OPI) of sensor information from being used to update the kinematic models,
saving said fraction of said overhead percentage (OPI) of sensor information on a data storage device, and
verifying a calibration using said fraction of overhead percentage of sensor information.

24. The method according to claim 23 , wherein verifying the calibration comprises the steps of comparing said fraction of the overhead percentage of sensor information with corresponding values predicted by the kinematic models for the robots.

25. The method according to claim 24 , wherein said comparison is performed by calculating a difference between every one of said fraction of the overhead percentage of sensor information and corresponding values predicted by the kinematic models for the robots, and comparing said difference or its numerical value with a threshold value.

26. The method according to claim 22 , wherein said overhead percentage of sensor information is in the range between 10% and 200%, preferably between 20% and 80%, even more preferably between 20% and 60% or alternatively in the range between 10% and 20%, or in the range between 20% and 40%, or in the range between 40% and 60%, or in the range between 60% and 80%, or in the range between 80% and 100%, or in the range between 100% and 120%, or in the range between 120% and 140%, or in the range between 140% and 160%, or in the range between 160% and 200%.

27. The method according to claim 1 , further comprising the step of saving the kinematic models on a data storage device.

28. The method according to claim 1 , wherein the step (c) of manipulating at least one of the joints or links in the closed chain is performed by turning off at least one position regulator of the joints of one of said at least two robots, and letting it be led around by the other robot.

29. The method according to claim 1 , wherein the step (c) of manipulating at least one of the joints or links in the closed chain is performed by turning off at least one position regulator of the joints of each of said at least two robots, and changing a joint position externally.

30. The method according claim 29 , wherein the step (c) of manipulating at least one of the joints or links in the closed chain is performed by turning off at least one position regulator of the joints of each of said at least two robots, and ch

Assignees

• Universal Robots As

Inventors

• Søe-Knudsen Rune
• Østergaard Esben Hallundbæk
• Petersen Henrik Gordon

Classifications

• B25J9/1692 Primary

  Calibration of manipulator · CPC title

• G05B19/4083

  Adapting program, configuration · CPC title

• B25J9/1656 Primary

  characterised by programming, planning systems for manipulators · CPC title

• B25J9/1682 Primary

  Dual arm manipulator; Coordination of several manipulators · CPC title

• G05B2219/39049

  Calibration cooperating manipulators, closed kinematic chain by bolting · CPC title