Robot controller for executing calibration, measurement system and calibration method

• US 10,569,418 B2
• Filed: 08/29/2018
• Issued: 02/25/2020
• Est. Priority Date: 09/22/2017
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Murata, Yuusuke
• Primary Examiner(s): Rink, Ryan
• Application Number:
  US16/115,562
• Publication Number:
  US 20190091866A1
• Time in Patent Office: 545 Days
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: B25J 9/1697 Vision controlled systems
• CPC Class Codes: G05B 2219/39024 Calibration of manipulator
• CPC Class Codes: G05B 2219/39045 Camera on end effector detects reference pattern

Abstract

A robot controller, a measurement system and a calibration method, by which measurement regions for improving positioning accuracy of a robot can be appropriately generated. First and second measurement regions are specified in a movable range of the robot, the calibration of a mechanical parameter of the robot is executed in each measurement region, and calibration results are stored as first and second calibration results. When the difference between the calibration results exceeds a predetermined threshold, a third measurement region is specified between the first and second measurement regions, and the calibration is further executed in the third measurement region. The result of the further calibration is stored as a third calibration result.

Claims

1. A robot controller configured to control a robot, comprising:

a specifying section configured to specify at least two measurement regions within a movable range of a movable part of the robot, the at least two measurement regions including a first measurement region and a second measurement region different from the first measurement region;

a calibration executing section configured to execute a calibration of a mechanical parameter of the robot by moving the movable part of the robot into the first measurement region, and execute a calibration of the mechanical parameter of the robot by moving the movable part of the robot into the second measurement region; and

a storing section configured to store the mechanical parameter obtained by the calibration in the first measurement region as a first calibration result, and store the mechanical parameter obtained by the calibration in the second measurement region as a second calibration result,

wherein the specifying section specifies a third measurement region between the first and second measurement regions, based on the first and second calibration results stored in the storing section;

the calibration executing section executes a calibration of the mechanical parameter of the robot by moving the movable part of the robot into the third measurement region; and

the storing section stores the mechanical parameter obtained by the calibration in the third measurement region as a third calibration result.

2. The robot controller as set forth in claim 1, wherein the specifying section specifies the third measurement region when a difference between the first and second calibration results exceeds a predetermined threshold.

3. The robot controller as set forth in claim 1, wherein the specifying section specifies the third measurement region when, with respect to an intermediate position between the first and second measurement regions, a difference between a position calculated by using the first calibration result and a position calculated by using the second calibration result exceeds a predetermined threshold.

4. The robot controller as set forth in claim 1, further comprising a parameter applying section configured to, when a motion program of the robot is executed, apply the mechanical parameter to each teaching point included in the motion program, wherein the applied mechanical parameter corresponds to the calibration result in one of the measurement regions which is the nearest to the teaching point.

5. A measurement system comprising:

a target;

a light-receiving device configured to capture an image of the target;

a robot having a movable part to which the target or the light-receiving device is attached;

a robot controller configured to control the robot;

a specifying section configured to specify at least two measurement regions within a movable range of the movable part of the robot, the at least two measurement regions including a first measurement region and a second measurement region different from the first measurement region;

a calibration executing section configured to execute a calibration of a mechanical parameter of the robot by moving the movable part of the robot into the first measurement region, and execute a calibration of the mechanical parameter of the robot by moving the movable part of the robot into the second measurement region; and

a storing section configured to store the mechanical parameter obtained by the calibration in the first measurement region as a first calibration result, and store the mechanical parameter obtained by the calibration in the second measurement region as a second calibration result,

wherein the specifying section specifies a third measurement region between the first and second measurement regions, based on the first and second calibration results stored in the storing section;

the calibration executing section executes a calibration of the mechanical parameter of the robot by moving the movable part of the robot into the third measurement region; and

the storing section stores the mechanical parameter obtained by the calibration in the third measurement region as a third calibration result.

6. The measurement system as set forth in claim 5, wherein the specifying section specifies the third measurement region when a difference between the first and second calibration results exceeds a predetermined threshold.

7. The measurement system as set forth in claim 5, wherein the specifying section specifies the third measurement region when, with respect to an intermediate position between the first and second measurement regions, a difference between a position calculated by using the first calibration result and a position calculated by using the second calibration result exceeds a predetermined threshold.

8. The measurement system as set forth in claim 5, further comprising a parameter applying section configured to, when a motion program of the robot is executed, apply the mechanical parameter to each teaching point included in the motion program, wherein the applied mechanical parameter corresponds to the calibration result in one of the measurement regions which is the nearest to the teaching point.

9. A calibration method for a robot included in a measurement system, the measurement system including:

a target;

a light-receiving device configured to capture an image of the target;

the robot having a movable part to which the target or the light-receiving device is attached; and

a robot controller configured to control the robot, the calibration method comprising the steps of;

specifying at least two measurement regions within a movable range of the movable part of the robot, the at least two measurement regions including a first measurement region and a second measurement region different from the first measurement region;

executing a calibration of a mechanical parameter of the robot by moving the movable part of the robot into the first measurement region, and executing a calibration of the mechanical parameter of the robot by moving the movable part of the robot into the second measurement region;

storing the mechanical parameter obtained by the calibration in the first measurement region as a first calibration result, and storing the mechanical parameter obtained by the calibration in the second measurement region as a second calibration result;

specifying a third measurement region between the first and second measurement regions based on the first and second calibration results;

executing a calibration of the mechanical parameter of the robot by moving the movable part of the robot into the third measurement region; and

storing the mechanical parameter obtained by the calibration in the third measurement region as a third calibration result.

10. The calibration method as set forth in claim 9, wherein the third measurement region is specified when a difference between the first and second calibration results exceeds a predetermined threshold.

11. The calibration method as set forth in claim 9, wherein the third measurement region is specified when, with respect to an intermediate position between the first and second measurement regions, a difference between a position calculated by using the first calibration result and a position calculated by using the second calibration result exceeds a predetermined threshold.

12. The calibration method as set forth in claim 9, further comprising the step of, when a motion program of the robot is executed, applying the mechanical parameter to each teaching point included in the motion program, wherein the applied mechanical parameter corresponds to the calibration result in one of the measurement regions which is the nearest to the teaching point.