Automatic calibration method for robot systems using a vision sensor

Patent metadata

Field	Value
Publication number	US-10112301-B2
Application number	US-201615233440-A
Country	US
Kind code	B2
Filing date	Aug 10, 2016
Priority date	Feb 11, 2014
Publication date	Oct 30, 2018
Grant date	Oct 30, 2018

Abstract

An automatic calibration method for a robot system is disclosed. The automatic calibration method for a robot system includes the steps of calibrating a sensor and a sensor coordinate system of the sensor with respect to a world coordinate system, controlling a robot under the guidance of the sensor to move a point of a tool mounted on the robot to reach a same target point with a plurality of different poses, the point of the tool in a tool coordinate system, and calculating a transformation matrix tcp T t of the tool coordinate system with respect to a tool center point coordinate system based on pose data of the robot at the same target point.

First claim

What is claimed is:

1. An automatic calibration method for a robot system, comprising:
calibrating a sensor and a sensor coordinate system of the sensor with respect to a world coordinate system;
controlling a robot under the guidance of the sensor to move a point of a tool mounted on the robot to reach a same target point with a plurality of different poses, the point of the tool being in a tool coordinate system; and
calculating a transformation matrix tcp T t of the tool coordinate system with respect to a tool center point coordinate system based on pose data of the robot at the same target point.

2. The automatic calibration method for a robot system according to claim 1 , wherein the calibrating step is performed by means of a calibration plate.

3. The automatic calibration method for a robot system according to claim 1 , wherein the controlling step includes performing a closed-loop feedback control on the robot until a position error between an actual position of the point of the tool sensed by the sensor and a target position of the target point becomes zero.

4. The automatic calibration method for a robot system according to claim 3 , further comprising calculating a transformation matrix R T t of the tool coordinate system with respect to a robot coordinate system based on the transformation matrix tcp T t .

5. The automatic calibration method for a robot system according to claim 4 , further comprising controlling the robot under the guidance of the sensor to move the tool to reach a known target pose by closed-loop feedback control, until a pose error between an actual pose of the tool sensed by the sensor and the target pose becomes zero.

6. The automatic calibration method for a robot system according to claim 5 , further comprising calculating a transformation matrix T R of the robot coordinate system with respect to the world coordinate system based on a transformation matrix T of the known target pose with respect to the world coordinate system and the transformation matrix R T t .

7. The automatic calibration method for a robot system according to claim 6 , further comprising determining a transformation matrix T O of an object to be machined by the tool with respect to the world coordinate system using the sensor.

8. The automatic calibration method for a robot system according to claim 7 , further comprising determining a transformation matrix O T P of a target region on the object with respect to an object coordinate system using the sensor.

9. The automatic calibration method for a robot system according to claim 8 , wherein the transformation matrix O T P is constant.

10. The automatic calibration method for a robot system according to claim 9 , wherein a pose of the object with respect to the world coordinate system is constant.

11. The automatic calibration method for a robot system according to claim 9 , wherein a pose of the object with respect to the world coordinate system is continuously variable.

12. The automatic calibration method for a robot system according to claim 1 , wherein the sensor is a vision sensor or a laser tracker.

13. The automatic calibration method for a robot system according to claim 12 , wherein the sensor is a camera having calibrated parameters including at least one of a focal length, a lens distortion, a pixel ratio, and a geometric relationship between a chip pose and a lens pose of the camera.

14. The automatic calibration method for a robot system according to claim 13 , wherein the robot system has a plurality of cameras.

15. The automatic calibration method for a robot system according to claim 14 , wherein the robot system has a plurality of robots.

16. The automatic calibration method for a robot system according to claim 13 , wherein the camera visually guides the robot to machine an object.

17. The automatic calibration method for a robot system according to claim 1 , further comprising re-identifying the transformation matrix tcp T t automatically and immediately after the tool is replaced by a new tool.

18. An automatic calibration method for a robot system, comprising:
calibrating a sensor and a sensor coordinate system of the sensor with respect to a world coordinate system;
controlling a robot under the guidance of the sensor to move a point of a tool mounted on the robot to reach a same first target point with a first plurality of different poses, the point of the tool in a tool coordinate system;
calculating a first transformation matrix tcp T t of the tool coordinate system with respect to a tool center point coordinate system based on pose data of the robot at the first target point;
controlling the robot under the guidance of the sensor to move the point of the tool to reach a same second target point with a second plurality of different poses;
calculating a second transformation matrix tcp T t of the tool coordinate system with respect to a tool center point coordinate system based on pose data of the robot at the second target point; and
determining whether an error between the first transformation matrix tcp T t and the second transformation matrix tcp T t is within an allowable range, returning to the calibrating step if the error is not within the allowable range, and using an average of the first transformation matrix tcp T t and the second transformation matrix tcp T t as an overall transformation matrix tcp T t if the error is within the allowable range.

19. An automatic calibration method for a robot system, comprising:
calibrating a sensor and a sensor coordinate system of the sensor with respect to a world coordinate system;
controlling a robot under the guidance of the sensor to move a point of a tool mounted on the robot to reach a plurality of target points with a plurality of different poses, the point of the tool being in a tool coordinate system;
calculating a plurality of transformation matrices tcp T t of the tool coordinate system with respect to a tool center point coordinate system based on pose data of the robot at the plurality of target points, each transformation matrix tcp T t corresponding to one target point; and
determining an overall transformation matrix tcp T t by using the least squares method on the plurality of transformation matrices tcp T t .

20. The automatic calibration method for a robot system of claim 19 , wherein the plurality of target points is at least three target points.

Assignees

• Tyco Electronics Shanghai Co Ltd
• Tyco Electronics Corp
• Te Connectivity Corp

Inventors

• Deng Yingcong
• Zhang Dandan
• Lu Roberto Francisco-Yi
• Hu lvhai

Classifications

• G05B2219/39011

  Fixed camera detects deviation end effector from reference on workpiece, object · CPC title

• G05B2219/39026

  Calibration of manipulator while tool is mounted · CPC title

• B25J9/1692 Primary

  Calibration of manipulator · CPC title

• G05B2219/40557

  Tracking a tool, compute 3-D position relative to camera · CPC title