Method and apparatus for compliant robotic end-effector

Patent metadata

Field	Value
Publication number	US-10286556-B2
Application number	US-201615294757-A
Country	US
Kind code	B2
Filing date	Oct 16, 2016
Priority date	Oct 16, 2016
Publication date	May 14, 2019
Grant date	May 14, 2019

Abstract

A method and apparatus for performing an operation on a workpiece using a multi-axis compliant end-effector for attachment to a robotic device. The end-effector is positioned at a nominal location of a workpiece feature on which the operation is to be performed. The end-effector is passively aligned with the workpiece feature by contacting the end-effector with the workpiece feature. The operation is performed on the workpiece feature in response to aligning the end effector with the workpiece feature.

First claim

What is claimed is:

1. A multi-axis compliant end-effector for attachment to a robotic device, the end-effector comprising:
a compliant contact probe configured to determine by contact an actual location of a workpiece feature; and
at least one translational joint and at least one rotational joint associated with the compliant probe, the at least one translational joint and the at least one rotational joint configured to passively align the compliant contact probe with the workpiece feature.

2. The multi-axis compliant end-effector of claim 1 , wherein the at least one translational joint further comprises:
a bearing housing slidably secured a within foot collet of the end-effector.

3. The multi-axis compliant end-effector of claim 2 , wherein the at least one rotational joint further comprises:
a spherical bearing rotatably mounted in the bearing housing of the end-effector.

4. The multi-axis compliant end-effector of claim 3 , wherein the compliant contact probe further comprises:
a contactor configured to compliantly contact the workpiece, wherein the compliant contact probe is configured to provide feedback in response to contact between the contactor and the workpiece.

5. The multi-axis compliant end-effector of claim 4 , further comprising:
a linear gauge associated with the compliant contact probe, wherein a thickness of the workpiece at the workpiece feature is determined from the linear gauge when the contactor contacts the workpiece.

6. The multi-axis compliant end-effector of claim 5 , wherein:
the linear gauge is mounted within spherical bearing; and
wherein the thickness of the workpiece at the workpiece feature is determined from the linear gauge when the contactor contacts an underside of the workpiece.

7. The multi-axis compliant end-effector of claim 1 , further comprising:
a number of magnetic detents configured to retain the compliant contact probe in a substantially neutral orientation when the compliant contact probe is not passively aligned with the workpiece feature.

8. The multi-axis compliant end-effector of claim 7 , wherein:
the number of magnetic detents are further configured to retain the compliant contact probe in a passively aligned orientation during data acquisition.

9. The multi-axis compliant end-effector of claim 1 , further comprising:
a kinematically aligned magnetic coupling for attaching the end-effector to the robotic device.

10. A method for automatically performing an operation on a workpiece using a multi-axis compliant end-effector for attachment to a robotic device, the method comprising:
positioning the end-effector at a nominal location of a workpiece feature of the workpiece on which the operation is to be performed;
contacting the end-effector with the workpiece feature to passively align the end-effector with the workpiece feature; and
responsive to aligning the end effector with the workpiece feature, performing the operation on the workpiece feature.

11. The method of claim 10 , further comprising:
responsive to positioning the end-effector at the nominal location of the workpiece feature, determining whether the end-effector can be passively aligned with an actual location for the workpiece feature.

12. The method of claim 11 , wherein determining whether the end-effector can be passively aligned with an actual location for the workpiece feature further comprises:
extending a compliant contact probe from the end effector to determine whether the end-effector can be passively aligned with the actual location for the workpiece feature, wherein the contact probe is vertically compliant to prevent damage to the workpiece.

13. The method of claim 12 , wherein the workpiece feature is a hole in the workpiece, and wherein passively aligning the end-effector with the workpiece feature further comprises:
extending the contact probe through the hole; and
translationally and angularly offsetting the contact probe from a magnetically defined neutral position as the contact probe is extended through the hole until the end-effector is aligned with the hole.

14. The method of claim 13 , wherein the operation comprises determining a thickness of the workpiece at the hole, the method further comprising:
retracting the contact probe until the compliant contact probe contacts an underside of the workpiece; and
determining the thickness of the workpiece at the hole based on an extension of the contact probe.

15. The method of claim 14 , further comprising:
offsetting the end-effector until contact feedback from the compliant contact probe indicates contact with a sidewall of the hole,
wherein the step of retracting the contact probe is performed in response to offsetting the end-effector.

16. The method of claim 14 , further comprising:
responsive to performing the operation, determining whether the compliant contact probe can be removed from the workpiece feature;
responsive to determining that the contact probe cannot be removed from the workpiece feature, performing a retraction search process to locate a position of the end effector at which the contact probe can be retracted from the workpiece feature; and
in response to locating the position of the end effector at which the contact probe can be retracted from the workpiece feature, retracting the end effector from the workpiece to feature from the workpiece feature to remove the compliant contact probe from the workpiece feature.

17. The method of claim 12 , further comprising:
responsive to determining that the nominal location for the workpiece feature is not the actual location for the workpiece feature, performing a search process for the workpiece feature; and
responsive to locating the workpiece feature, storing an offset from the nominal location to the actual location for the workpiece feature.

18. The method of claim 17 , wherein performing the search process for the workpiece feature further comprises:
making small moves of the end-effector and extension checks of the contact probe in an outward spiral path from the nominal location until the actual location for the workpiece feature is determined based on contact feedback from the compliant contact probe.

19. A computer program product for automatically performing an operation on a workpiece using a multi-axis compliant end-effector for attachment to a robotic device, the computer program product comprising:
A non-transitory computer readable storage media;
first program code, stored on the non-transitory computer readable storage media, for positioning the end-effector at a nominal location of a workpiece feature on which the operation is to be performed;
second program code, stored on the non-transitory computer readable storage media, for contacting the end-effector with the workpiece feature to passively align the end-effector with the workpiece feature; and
third program code, stored on the non-transitory computer readable storage media, for performing the operation on the workpiece feature in response to aligning the end effector with the workpiece feature.

20. The computer program product of claim 19 , further comprising:
fourth program code, stored on the non-transitory computer readable storage media, for determining whether the end-effector can be passively aligned with an actual location for the workpiece feature in response to positioning the end-effector at the nominal location of the workpiece feature.

21. The computer program product of claim 20 , wherein the fourth program

Assignees

• Boeing Co

Inventors

• Troy James J
• Wright Daniel J
• Lea Scott W

Classifications

• B25J17/0233

  with radial compliance, i.e. perpendicular to the longitudinal wrist axis · CPC title

• G01B3/20

  Slide gauges · CPC title

• B25J17/0275

  Universal joints, e.g. Hooke, Cardan, ball joints · CPC title

• B25J17/0208 Primary

  Compliance devices · CPC title

• G01B5/06

  for measuring thickness · CPC title