Self-corrective nut running for robotic applications

Patent metadata

Field	Value
Publication number	US-2016279798-A1
Application number	US-201615062297-A
Country	US
Kind code	A1
Filing date	Mar 7, 2016
Priority date	Mar 27, 2015
Publication date	Sep 29, 2016
Grant date	—

Abstract

A method for position correction of a machine relative to a work piece. The machine may be provided with an end effector. The work piece may be engaged with the end effector. A force or a moment resulting from engaging the work piece with the end effector may be measured. A pose error may be determined from the force and/or the moment, wherein the pose error may define a misalignment of the end effector. The end effector may be repositioned an amount equal to the pose error to correct the misalignment. One application may involve torqueing nuts with a nut runner, which may be accomplished through the use of an automated machine such as a robot.

First claim

What is claimed is:

1 . A method for position correction relative to a workpiece of a machine with a nut runner comprising:
engaging the work piece with the nut runner; operating the nut runner; determining whether the nut runner operation was successful; if the nut runner operation was not successful, measuring at least one of a force or a moment resulting from engaging the work piece with the nut runner; determining a pose error from at least one of the force or the moment, wherein the pose error defines a misalignment of the nut runner and a direction thereof; and repositioning the nut runner in the direction of the pose error to correct the misalignment.

2 . The method according to claim 1 wherein the nut runner contacts the work piece and further comprising the step of calculating the misalignment of the nut runner from the force or moment, after the nut runner contacts the workpiece.

3 . The method according to claim 1 further comprising the step of determining whether the nut runner is aligned, after repositioning the nut runner.

4 . The method according to claim 1 further comprising the steps of recording the pose error, and using the recorded pose error to correct a programmed position of the motion for future operations.

5 . The method according to claim 1 wherein the nut runner includes multiple spindles, and wherein the step of engaging the work piece with the nut runner comprises engaging the work piece with a first one of the multiple spindles.

6 . The method according to claim 5 further comprising the step of engaging the work piece with a second one of the multiple spindles and repeating the steps: measuring a force and a moment resulting from engaging the work piece with the nut runner; determining a pose error from the force or moment, wherein the pose error defines a misalignment of the nut runner and a direction thereof; and repositioning the nut runner in a direction of the pose error to correct the misalignment, for the second one of the multiple spindles.

7 . A method for position correction of a nut runner relative to a work piece comprising:
engaging the work piece with the nut runner at a contact interface, wherein an application force arises at the contact interface along a line of action; measuring a resultant force and moment at a sensor point that is spaced apart from the contact interface; calculating an error in at least one of the position or orientation of the work piece, based on the resultant force and moment; and repositioning the nut runner to correct any misalignment of the nut runner with the work piece.

8 . The method according to claim 7 further comprising the step of providing the nut runner with a socket configured to drive a tube nut.

9 . The method according to claim 7 further comprising the step of determining whether the nut runner is aligned, after repositioning the nut runner.

10 . The method according to claim 9 further comprising repeating the steps: engaging the work piece with the nut runner at a contact interface, where a contact force arises;
measuring a resultant force and moment at a sensor point that is spaced apart from the contact interface;
calculating an error in at least one of the position or orientation of the work piece, based on the resultant force and moment; and
repositioning the nut runner to correct any misalignment of the nut runner with the work piece, after determining whether the nut runner is aligned results in a negative determination.

11 . The method according to claim 7 wherein the nut runner includes multiple spindles, and wherein the step of engaging the work piece with the nut runner comprises engaging the work piece with a first one of the multiple spindles.

12 . The method according to claim 11 further comprising the step of engaging the work piece with a second one of the multiple spindles and repeating the steps: measuring a resultant force and moment at a sensor point that is spaced apart from the contact interface;
calculating an error in at least one of the position or orientation of the work piece, based on the resultant force and moment; and
repositioning the nut runner to correct any misalignment of the nut runner with the work piece, after determining whether the nut runner is aligned results in a negative determination, for the second one of the multiple spindles.

13 . The method according to claim 12 wherein repositioning the nut runner corrects a pose error in an iterative process, and further comprising the steps of recording the pose error for each of the multiple spindles, and calculating a new starting position for the nut runner that results in a minimum net position error of the multiple spindles.

14 . A method for position correction of a nut runner relative to a work piece comprising:
providing the work piece with a threaded feature; engaging the nut runner with the work piece; rotating the nut runner to thread the fastener with the threaded feature; measuring a resulting torque on the fastener; when the resulting torque is below a threshold, contacting the workpiece with at least one of the nut runner or the fastener; measuring a resulting force and moment; and repositioning the nut runner an amount based on the resultant force and moment.

15 . The method according to claim 14 further comprising recording the resultant force and moment along with the amount to improve the step of moving the fastener tightening tool to engage the fastener with the threaded feature.

16 . The method according to claim 14 wherein one of the fastener tightening tool and the fastener contacts the threaded feature at a contact interface and further comprising the step of calculating a misalignment of the nut runner using the resultant force and moment, after the fastener tightening tool contacts the threaded fastener.

17 . The method according to claim 14 further comprising the step of determining whether the nut runner is aligned with the threaded feature, after repositioning the nut runner.

18 . The method according to claim 14 wherein the nut runner includes multiple fastener tightening tools loaded with multiple fasteners, and wherein the work piece includes multiple threaded features, and wherein the step of moving the fastener tightening tool to engage the fastener with the threaded feature comprises moving the multiple fastener tightening tools to engage the multiple fasteners with the multiple threaded features.

19 . A robotic system comprising a programmable machine, a nut runner, a force sensor on the programmable machine positioned to measure a reaction force on the nut runner, a controller communicating with the force sensor and the programmable machine.

20 . The system from claim 19 where the controller may command an adjusted position for the machine in response to an error in the fastening operation.

21 . The system from claim 20 where the adjusted position depends on the sensed reaction force.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Abdallah Muhammad E
• Villeneuve Gary L
• Zakula Sreten

Classifications

• B25J9/1687

  Assembly, peg and hole, palletising, straight line, weaving pattern movement · CPC title

• B25J9/1692 Primary

  Calibration of manipulator · CPC title

• G05B2219/39024

  Calibration of manipulator · CPC title

• G05B2219/40033

  Assembly, microassembly · CPC title

• G05B2219/49113

  Align elements like hole and drill, centering tool, probe, workpiece · CPC title