Calibration method for coordinate system of robot manipulator

Patent metadata

Field	Value
Publication number	US-9782899-B2
Application number	US-201514687045-A
Country	US
Kind code	B2
Filing date	Apr 15, 2015
Priority date	Apr 30, 2014
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

A calibration method for a coordinate system of a workpiece held by a robot manipulator, which includes the following steps: setting a predicted coordinate system on the workpiece; controlling the drive mechanism to drive the workpiece to move a specific distance along a coordinate axis in the predicted coordinate system and measuring the distance change of the workpiece in a direction perpendicular to the move; using the measured distance change to determine an orientation error between the predicted coordinate system and the actual coordinate system; correcting the orientation parameters of the predicted coordinate system; controlling the drive mechanism to drive the workpiece to rotate by a specific angle around a coordinate axis of the predicted coordinate system and measuring the distance change after being rotated; using the measured distance change to determine a position error; correcting the position parameters of the predicted coordinate system.

First claim

What is claimed is:

1. A calibration method for a coordinate system of a robot manipulator, the robot manipulator comprises a drive mechanism, a controller configured to control the drive mechanism, a tool assembled to a distal end of the drive mechanism, the distal end of the drive mechanism having a basic coordinate system; an assistant measurement tool comprises a measurement device; a workpiece comprises an attachment plane coupled with the tool, a processing plane at the opposite side of the attachment plane, a first side plane and a second side plane connected to the attachment plane and the processing plane, the calibration method comprising:
A. making the processing plane of the workpiece face toward the measurement device;
B. setting a predicted coordinate system (X m , Y m , Z m , R x , R y , R z ) on the workpiece with assumed position errors (Δx,Δy,Δz) and assumed orientation errors (ΔR x ,ΔR y ,ΔR z ) between the predicted coordinate system and an actual coordinate system;
C. controlling the drive mechanism to drive the workpiece a distance L in the direction of an X m axis in the predicted coordinate system and measuring a distance change from a movement of the processing plane of the workpiece to obtain ΔR y via the measurement device;
D. modifying the value of (R x ,R y ,R z ) in the predicted coordinate system according to A R y , and redefining the predicted coordinate system as a first new predicted coordinate system (X m 1 , Y m 1 , Z m 1 , R x 1 , R y 1 , R z 1 ) with a position error (Δx 1 , Δy 1 , Δz 1 ) and an orientation error (ΔR x 1 , ΔR y 1 , ΔR z 1 ) between the predicted coordinate system and the actual coordinate system;
E. controlling the drive mechanism to drive the workpiece a distance L′ in the direction of an Y m 1 axis in the first new predicted coordinate system and measuring the distance change from the movement of the processing plane of the workpiece to obtain ΔR x 1 via the measurement device;
F. modifying the value of (R x 1 , R y 1 , R z 1 ) in the predicted coordinate system according to Δ R x 1 , and redefining the predicted coordinate system as a second new predicted coordinate system (X m 2 , Y m 2 , Z m 2 , R x 2 , R y 2 , R z 2 ) with a position error (Δx 2 , Δy 2 , Δz 2 ) and an orientation error (ΔR x 2 , ΔR y 2 , A R z 2 ) between the predicted coordinate system and the actual coordinate system;
G. controlling the drive mechanism to drive the work piece a distance L″ in the direction of an X m 2 axis or an Y m 2 axis in the second new predicted coordinate system and measuring the distance change from the movement of the first side plane of the workpiece or the movement of the second side plane of the workpiece to obtain ΔR z 2 via the measurement device;
H. modifying the value of (R x 2 , R y 2 , R z 2 ) in the predicted coordinate system according to A R z z , and redefining the predicted coordinate system as a third new predicted coordinate system (X m 3 , Y m 3 , Z m 3 , R x 3 , R y 3 , R z 3 ) with a position error (Δx 3 , Δy 3 , Δz 3 ) and an orientation error (ΔR x 3 , ΔR y 3 , ΔR z 3 ) between the predicted coordinate system and the actual coordinate system;
I. controlling the drive mechanism by the controller to drive the workpiece to rotate by 180 degrees around an axis Z m 3 in the third new predicted coordinate system and measuring the distance change between one point of the first side plane before being rotated and another point of the first side plane after being rotated to obtain Δy 3 ;
J. modifying the value of (X m 3 , Y m 3 , Z m 3 ) in the predicted coordinate system according to Δy 3 and redefining the predicted coordinate system as a fourth new predicted coordinate system (X m 4 , Y m 4 , Z m 4 , R x 4 , R y 4 , R z 4 ) with a position error (Δx 4 , Δy 4 , Δz 4 ) and an orientation error (ΔR x 4 , ΔR y 4 , ΔR z 4 ) between the predicted coordinate system and the actual coordinate system;
K. controlling the drive mechanism by the controller to drive the workpiece to rotate by 180 degrees around an axis Z m 4 in the fourth new predicted coordinate system, and measuring the distance change between one point of the second side plane before being rotated and another point of the second side plane after being rotated to obtain Δx 4 ;
L. modifying the parameter of (X m 4 , Y m 4 , Z m 4 ) in the predicted coordinate system according to Δx 4 and redefining the predicted coordinate system as a fifth new predicted coordinate system (X m 5 , Y m 5 , Z m 5 , R x 5 , R y 5 , R z 5 ) with a position error (A x 5 , A y 5 , A z 5 ) and an orientation error (ΔR x 5 , ΔR y 5 , ΔR z 5 ) between the predicted coordinate system and the actual coordinate system;
M. controlling the drive mechanism by the controller to drive the workpiece to rotate by −90 degrees around an axis Y m 5 in the fifth new predicted coordinate system and measuring the distance change between one point of the second side plane before being rotated and another point of the processing plane after being rotated to obtain Δz 5 ;
N. modifying the value of (X m 5 , Y m 5 , Z m 5 ) in the fifth predicted coordinate system according to Δz 5 and redefining the predicted coordinate system as a calibrated coordinate system (X m 6 , Y m 6 , Z m 6 , R x 6 , R y 6 , R z 6 ).

2. The calibration method of claim 1 , wherein the assistant measurement tool further comprises a data transmitting module, wherein the data transmitting module is electrically coupled to the controller and configured to transmit measured data to the controller.

3. The calibration method of claim 1 , wherein the controller is configured to control the drive mechanism to drive the second side plane of the workpiece to contact the measurement device to obtain the first measurement value d 1 ″, the drive mechanism drives the work piece to rise by a height H″, the drive mechanism then rotates the workpiece by −90 degrees around an axis Y m 5 of the predicted coordinate system T m 5 , the controller is configured to control the drive mechanism to descend by a height (H″+h/2) and drive the processing plane of the workpiece to contact the measurement device to obtain the second measurement value d 2 ″, the distance change after the movement of the work piece is Δ d″=d 2 ″-d 1 ″ , and Δz 5 =d 2 ″-d 1 ″.

4. The calibration method of claim 1 , wherein measuring the distance change as Δc occurs via the measurement device after steps C and D, and determining if Δc is larger than a maximum allowable position deviation or not, if Δc is larger than the maximum allowable position deviation, then repeating steps C and D for the calibration, if Δc is less than or equal to the maximum allowable position deviation, then finishing the calibration of ΔR y and going to step E.

5. The calibration method of claim 1 , wherein measuring the distance change as Δc′ occurs via the measurement device after steps E and F, and determining if Δc′ is larger than a maximum allowable position deviation or not, if Δc′ is larger than the maximum allowable position deviation, then repeating the steps E and F for the calibration, if Δc′ is less than or equal to the maximum allowable position deviation, then finishing the calibration of ΔR x 1 and going to step G.

6. The calibration method of claim 1 , wherein measuring the distance change as Δc″ occurs via the measurement device after the steps G and H, and determining if Δc″ is larger than a maximum allowable position deviation or not, if Δc″ is larger than the maximum allowable position deviation, then repeating steps G and H for the calibration. if Δc″ is less than or equal to the maximum allowable position deviation, then finishing the

Assignees

• Hong Fu Jin Prec Ind (Shenzhen) Co Ltd
• Hon Hai Prec Ind Co Ltd

Inventors

• Chiu Long-En
• Wu Yong

Classifications

• G05B2219/39026

  Calibration of manipulator while tool is mounted · CPC title

• B25J9/1692 Primary

  Calibration of manipulator · CPC title

• Y10S901/02

  Arm motion controller · CPC title

• G05B2219/39021

  With probe, touch reference positions · CPC title