Coordinate measuring machine

Patent metadata

Field	Value
Publication number	US-9797706-B2
Application number	US-201615014371-A
Country	US
Kind code	B2
Filing date	Feb 3, 2016
Priority date	Feb 4, 2015
Publication date	Oct 24, 2017
Grant date	Oct 24, 2017

Abstract

Some embodiments of the present invention relate to a coordinate measuring machine CMM, comprising a carrier as a support and positioning structure for an end-effector as a target, the end-effector being movable in at least three degrees of freedom and positionable by the carrier, a stationary metrology table as a support for a possible target object, and a control unit controlling the moving of the end-effector by the carrier. The CMM further comprises at least one, in particular at least two, imaging detectors for measuring and determining in six degrees of freedom a position of the possible target object, and an analysing unit for processing electronic signals and/or data delivered by the imaging detectors. According to the invention, the imaging detectors are firmly mounted to the metrology table, mechanically de-coupled from the carrier.

First claim

What is claimed is:

1. A method of determining a position of an end-effector of a coordinate measuring machine, the coordinate measuring machine comprising:
a carrier as a support and positioning structure for the end-effector, the end-effector being movable in at least three degrees of freedom and positionable by the carrier,
a stationary metrology table as a support for a possible target object and
at least one imaging detector for capturing images;

the method comprising:
moving of the end-effector by the carrier and
capturing an image of at least a part of a measuring volume with the imaging detector, wherein:
receiving image data representing the image covering at least a part of the end-effector,
determining image-positions of reference points related to the end-effector in the image by image processing and
deriving a position of the end-effector based on the image-positions of the reference points,
wherein the at least one imaging detector is firmly mounted to the metrology table and arranged mechanically de-coupled from the carrier.

2. The method as claimed in claim 1 , wherein:
the coordinate measuring machine comprises at least two imaging detectors, wherein the method comprises
capturing images of at least a part of the measuring volume with the at least two imaging detectors,
receiving the image data representing the images each of which being captured with a different of the imaging detectors and covering at least a part of the end-effector,
determining the image-positions of the reference points related to the end-effector in each image by image processing and
deriving the position of the end-effector based on the image-positions of the reference points,
wherein the imaging detectors are firmly mounted to the metrology table and arranged mechanically de-coupled from the carrier.

3. The method as claimed in claim 2 , wherein:
triggering shutter times of the imaging detectors so that a temporally common image acquisition period is provided for the imaging detectors,
illuminating the end-effector for a defined illumination period during the common image acquisition period and
acquiring the images of the image data with the imaging detectors each representing the end-effector in a defined state corresponding to the illumination period,
wherein
the end-effector is illuminated in a pulsed manner having an illumination frequency, the illumination frequency being synchronized with the shutter times for the imaging detectors.

4. The method as claimed in claim 1 , wherein:
movements of the end-effector are synchronized with frame rates of the respective imaging detectors such that images are taken only when the carrier remains static during the acquisition period, wherein high-frequency movements faster than 200 Hz are avoided.

5. The method as claimed in claim 1 , wherein:
covering reference markers provided at the stationary metrology table by at least one image of the image data,
determining respective marker-positions in the respectively at least one image by image processing and
deriving a respective pose of a respective imaging detector based on the marker-positions,
wherein a calibration of the poses of the imaging detectors against the reference markers is provided.

6. A coordinate measuring machine (CMM), comprising:
a carrier as a support and positioning structure for an end-effector, the end-effector being movable in at least three degrees of freedom and positionable by the carrier,
a stationary metrology table as a support for a possible target object,
at least one imaging detector for capturing images,
a control unit controlling the moving of the end-effector by the carrier and controlling image acquisition with the imaging detector, and
an analysing unit for processing electronic signals and/or data delivered by the imaging detector, wherein:
the imaging detector is firmly mounted to the metrology table and mechanically de-coupled from the carrier and
the analysing unit being configured to determine a position of the end-effector in six degrees of freedom by
receiving image data representing an image covering at least a part of the end-effector,
determining image-positions of reference points related to the end-effector in the image and
deriving a position of the end-effector based on the image-positions of the reference points.

7. The coordinate measuring machine as claimed in claim 6 , wherein:
the coordinate measuring machine comprises at least two imaging detectors firmly mounted to the metrology table and mechanically de-coupled from the carrier and
the analysing unit being configured to determine the position of the end-effector in six degrees of freedom by
receiving the image data representing images each of which being captured with a different of the imaging detectors and covering at least a part of the end-effector,
determining the image-positions of the reference points related to the end-effector in each image and
deriving the position of the end-effector based on the image-positions of the reference points.

8. The coordinate measuring machine as claimed in claim 7 , wherein:
the control unit is designed and configured so that the image data is generated by acquiring images with each imaging detectors of the end-effector being in one and the same position.

9. The coordinate measuring machine as claimed in claim 7 , wherein:
the control unit is designed and configured so that the image data is generated by acquiring images with each imaging detectors of the end-effector being in one and the same position, acquiring the images at the same time.

10. The coordinate measuring machine as claimed in claim 7 , wherein:
the position determination is based on images from all imaging detectors.

11. The coordinate measuring machine as claimed in claim 10 , wherein:
the geometrical pattern is provided in a material having a low and/or stable coefficient of thermal expansion (CTE).

12. The coordinate measuring machine as claimed in claim 10 , wherein:
the cooperative target being manufactured from Borofloat glass and/or the geometrical pattern of the cooperative target being printed in high image quality, specifically with low gloss, high contrast and high sharpness.

13. The coordinate measuring machine as claimed in claim 6 , wherein:
the carrier is built as or comprises a Delta robot, wherein the Delta robot comprises three arms, each of them having a first part jointed to a second part, the first parts being connected to a stationary base and the second parts being connected to the end-effector.

14. The coordinate measuring machine as claimed in claim 6 , wherein:
the end-effector is provided with a geometrical pattern providing the reference points, wherein the end-effector comprises a cooperative target having a triangular shape and being provided with a triangular or chessboard-like geometrical pattern and/or with markers for orientating and positioning the cooperative target.

15. The coordinate measuring machine as claimed in claim 6 , wherein:
the coordinate measuring machine comprises an LED array for illuminating the end-effector.

16. The coordinate measuring machine as claimed in claim 6 , wherein:
the coordinate measuring machine comprises reference markers on the metrology table in a region where the possible target object is placed, enabling a calibration of positions of the imaging detectors against the reference markers.

17. The coordinate measuring machine as claimed in claim 6 , wherein:
the coordinate measuring machine comprises a sensor unit compri

Assignees

• Hexagon Technology Ct Gmbh

Inventors

• Jordil Pascal
• Stigwall Johan

Classifications

• G01B21/047

  Accessories, e.g. for positioning, for tool-setting, for measuring probes · CPC title

• G01B11/005 Primary

  coordinate measuring machines · CPC title