Automatic Calibration Method For Robot Systems Using a Vision Sensor

Patent metadata

Field	Value
Publication number	US-2016346932-A1
Application number	US-201615233440-A
Country	US
Kind code	A1
Filing date	Aug 10, 2016
Priority date	Feb 11, 2014
Publication date	Dec 1, 2016
Grant date	—

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

Inventors

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

Classifications

• G05B2219/40557

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

• G05B2219/39026

  Calibration of manipulator while tool is mounted · CPC title

• G05B2219/39011

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

• B25J9/1692 Primary

  Calibration of manipulator · CPC title