Robot teaching program correction method

• US 5,572,103 A
• Filed: 05/02/1995
• Issued: 11/05/1996
• Est. Priority Date: 09/14/1993
• Status: Expired due to Term

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Terada, Tomoyuki
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US08/428,221
• Time in Patent Office: 553 Days
• Field of Search: 318/560-646, 219/121.64, 219/124.34, 901/3.42, 395/80-95
• US Class Current: 318/568.13
• CPC Class Codes: B25J 9/1656 characterised by programming, planning systems for manipulators
• CPC Class Codes: G05B 2219/36407 Follow path with probe, store deviations for correction during normal operation
• CPC Class Codes: G05B 2219/37567 3-D vision, stereo vision, with two cameras

Abstract

An industrial-robot teaching program is prepared off-line without using a robot. Then, cameras serving as vision sensors are mounted on a wrist flange of the robot to obtain measured position data for a teaching point P1. The teaching point P1 is on a workpiece in a sensor coordinate system and is detected by the vision sensor. The position data for the teaching point in the teaching program is converted into position data in the sensor coordinate system. Next, an error of the robot wrist flange coordinate system is estimated in accordance with a difference between measured position data for the teaching point and converted position data in the teaching program. Then, the teaching point data included in the teaching program is corrected based on the estimated error of the robot wrist flange coordinate system. The vision sensor may also be attached to an end effector of the robot.

Claims

1. A robot teaching program correction method for controlling a robot having a vision sensor comprising the steps of:

forming a mark which can be identified by the vision sensor on a portion of a workpiece corresponding to at least one teaching point selected from teaching points in a teaching program, wherein each of the teaching points has corresponding position data;

measuring a position of the formed mark by the vision sensor while maintaining the robot at the selected teaching point;

obtaining correction amounts corresponding to the position data for some teaching points in the teaching program in accordance with the measured mark position; and

correcting the position data in accordance with the correction amounts.

2. A robot teaching program correction method for controlling a robot comprising the steps of:

(1) preparing an industrial-robot teaching program including a plurality of teaching points and corresponding program position data off-line without using the robot;

(2) obtaining measured position data of one teaching point on a workpiece in a sensor coordinate system by mounting a vision sensor to a wrist flange of the robot and detecting the one teaching point by the vision sensor;

(3) converting program position data for the detected one teaching point in the teaching program into program position data in a sensor coordinate system in accordance with a calibrated positional relation between the sensor coordinate system and a robot wrist flange coordinate system;

(4) estimating an error of the robot wrist flange coordinate system based on a difference between the measured position data for the one teaching point obtained in the above Item (2) and the program position data obtained in the above Item (3); and

(5) correcting program teaching point data corresponding to the teaching points included in the teaching program based on the estimated error of the robot wrist flange coordinate system estimated in the above Item (4).

3. A robot teaching program correction method comprising the steps of:

(1) preparing an industrial-robot teaching program including a plurality of teaching points and corresponding program position data off-line without using the robot;

(2) obtaining measured position data for one teaching point on a workpiece in a sensor coordinate system by mounting a vision sensor to an end effector of the robot and detecting the one teaching point by the vision sensor;

(3) converting program position data for the detected one teaching point in the teaching program into program position data in a sensor coordinate system in accordance with a calibrated positional relation between the sensor coordinate system and a tool coordinate system;

(4) estimating an error of the tool coordinate system based on a difference between the measured position data of the one teaching point obtained in the above item (2) and the program position data obtained in the above Item (3); and

(5) correcting program teaching point data corresponding to the teaching points included in the teaching program based on the estimated error of the tool coordinate system estimated in the above Item (4).

4. The robot teaching program correction method according to claim 2, wherein the detection of the one teaching point on the workpiece using the vision sensor is performed by forming a mark which can be recognized by the vision sensor on a portion of the workpiece corresponding to one of the teaching points and detecting the mark by the vision sensor.

5. The robot teaching program correction method according to claim 2, wherein the detection of the one teaching point on the workpiece by the vision sensor is performed by detecting a characteristic point inherent to the shape of the workpiece which corresponds to the teaching point by the vision sensor.

6. A method for correcting a robot teaching program which includes a plurality of teaching points comprising the steps of:

forming a mark on a portion of a workpiece;

identifying the formed mark by a robot vision sensor;

selecting a teaching point from the plurality of teaching points in the teaching program corresponding to the identified mark;

measuring a position of the identified mark by the vision sensor; and

correcting a portion of said plurality of teaching points by calculating a difference between the selected teaching point and the measured position of the identified mark.