Determining Positions

• US 20100103431A1
• Filed: 03/03/2008
• Published: 04/29/2010
• Est. Priority Date: 03/05/2007
• Status: Active Grant

• Current Assignee: inos Automationssoftware GmbH
• Original Assignee: inos Automationssoftware GmbH
• Inventors: Demopoulos, Andreas Haralambos
• Granted Patent: US 8,290,618 B2
• Time in Patent Office: Days
• US Class Current: 356/622
• CPC Class Codes: B25J 9/1692 Calibration of manipulator

Abstract

The position of a movable element such as the end of a robot arm (10) which has several degrees of freedom, being mounted on a base (11) and including a wrist mechanism, is determined by installing a multiplicity of base targets (32, 74) around the base of the robot, and a multiplicity of arm targets (42, 74) around the base (14) of the wrist mechanism (15), and an optical means (90) that moves with the movable element to determine the positions of at least some of the base targets and of at least some of the arm targets. The optical means may be a laser tracker or a camera system (90), and it may be mounted on the part (13) of the robot arm to which the base (14) of the wrist mechanism (15) is connected. This enables existing robots (10) to achieve absolute positional accuracy relative to a fixed external frame of reference.

Claims

1. An apparatus for determining the position of an element that is movable within a frame of reference, wherein a multiplicity of first targets are fixed relative to the movable element, and a multiplicity of base elements are provided at fixed positions relative to the frame of reference, the apparatus comprising a measurement system including means movable with the movable element, the measurement system comprising means for determining the position of the movable means relative to at least some of the base elements, and for determining the position of at least some of the first targets relative to the position of the movable means.

2. An apparatus as claimed in claim 1 wherein the measurement system comprises an optical means.

3. An apparatus as claimed in claim 2 for determining the position of the end of a robot arm, the robot arm having several degrees of freedom, the robot arm being mounted on a base and including a wrist mechanism, the wrist mechanism including a rotational support element, wherein the base elements are around the base of the robot, and the first targets are arranged as arm targets around the rotational support element, and the optical means is mounted on or adjacent to the robot arm to enable the positions of at least some of the base elements relative to the optical means and the positions of at least some of the arm targets relative to the optical means to be determined.

4. An apparatus as claimed in claim 2 wherein the optical means comprises a laser tracker.

5. An apparatus as claimed in claim 1 wherein the base elements are base targets.

6. An apparatus as claimed in claim 3 wherein the base elements comprise base cameras, and the optical means comprises at least one target and at least one camera to view the arm targets.

7. An apparatus as claimed in claim 5 wherein the base elements comprise retro-reflectors.

8. An apparatus as claimed in claim 1 wherein the base elements are mounted on a base element support structure of a material of low thermal expansivity.

9. An apparatus as claimed in claim 8 wherein the base element support structure is arranged to rest on three spaced-apart support elements.

10. An apparatus as claimed in claim 8 wherein the base elements are readily removable from and replaceable on the base element support structure.

11. An apparatus as claimed in claim 1 wherein the first targets comprise retro-reflectors.

12. An apparatus as claimed in claim 1 wherein the first targets are mounted on an arm target support structure of a material of low thermal expansivity surrounding and mounted to the movable element.

13. An apparatus as claimed in claim 3 wherein the optical means is mounted on an arm element to which the rotational support element of the wrist mechanism is attached.

15. A method for determining the position of the end of a robot arm, comprising using an apparatus as claimed in claim 1.

16. A method for repeatedly determining the positions of the ends of a plurality of robot arms as claimed in claim 15 in which the targets or base targets or the optical means are exchanged between different robot arms cyclically.

14. (canceled)

17. A method for determining the position of an element that is movable within a frame of reference, wherein a multiplicity of first targets are fixed relative to the movable element, and a multiplicity of base elements are provided at fixed positions relative to the frame of reference, the method utilising a measurement system including means movable with the movable element, the method comprising determining the position of the movable means relative to at least some of the base elements, and determining the position of at least some of the first targets relative to the position of the movable means, and hence determining the position of the movable element.