Calibration system and calibration method calibrating mechanical parameters of wrist part of robot

• US 10,189,161 B2
• Filed: 10/20/2016
• Issued: 01/29/2019
• Est. Priority Date: 10/21/2015
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Yoshino, Kiyoshi
• Primary Examiner(s): Jen, Ian
• Application Number:
  US15/298,808
• Publication Number:
  US 20170113351A1
• Time in Patent Office: 831 Days
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: B25J 9/1697 Vision controlled systems
• CPC Class Codes: G05B 2219/39008 Fixed camera detects reference pattern held by end effector
• CPC Class Codes: G05B 2219/39046 Compare image of plate on robot with reference, move till coincidence, camera

Abstract

A calibration system able to calibrate mechanical parameters of a wrist part by a simpler manner is provided. The calibration system utilizes a target fastened at a predetermined position with respect to the joint closest to a hand of a robot and an imaging device set around the robot so as to calibrate the parameters of a mechanical model representing the wrist part of the robot. The posture of the target is changed from a predetermined initial position to generate a plurality of preliminary positions. Using these preliminary positions as starting points, the end point position of the robot whereby the target becomes a predetermined positional relationship with respect to the imaging device on the image obtained by capturing an image of the target is calculated. The calibration system uses the calculated end point position as the basis to calibrate the mechanical parameters of the wrist part.

Claims

1. A calibration system calibrating parameters of a mechanical model representing a wrist part of a robot utilizing a target fastened at a hand of the robot at a predetermined position with respect to a joint closest to the hand, the target being able to be changed in position and posture by the robot, and an imaging device set around the robot, the calibration system comprising:

a preliminary position generating part using a position of the robot when the target is arranged at a position where the target is included in a field of vision of the imaging device as an initial position and changing the posture of the target without changing the position of the target to generate a plurality of positions of the robot as a plurality of preliminary positions,

a target detecting part using an image of the target at the image acquired by the imaging device as the basis to acquire information on the position of the target on the image and the distance between the target and the imaging device,

an end point position storing part using the plurality of preliminary positions as starting points, making the robot move translationally so that the positions of the target detected by the target detecting part become predetermined positions and the distances become predetermined distance, and storing the positions of the robot after the translational movement as end points, and

a parameter calculating part using the positions of the end points stored by the end point position storing part as the basis to calculate the parameters of the mechanical model.

4. The calibration system according to claim 1, wherein the target detecting part is configured to use light generated from the target as the basis to detect the position of the target and the distance.

5. The calibration system according to claim 1, wherein the target detecting part is configured to use a 2D image acquired by the imaging device as the basis to detect the position of the target and the distance.

2. The calibration system according to claim wherein the parameter calculating part is configured to calculate parameters in accordance with the method of optimization of nonlinear functions.

3. The calibration system according to claim wherein the target detecting part is configured to use geometric features including length information of the target as the basis to calculate the distance.

6. A calibration method calibrating parameters of a mechanical model representing a wrist part of a robot utilizing a target fastened at a hand of the robot at a predetermined position with respect to a joint closest to the hand, the target being able to be changed in position and posture by the robot and an imaging device set around the robot, the calibration method comprising:

using a position of the robot when arranged at a position where the target is included in a field of vision of the imaging device as an initial position and changing the posture of the target without changing the position of the target to generate a plurality of positions of the robot as a plurality of preliminary positions,

acquiring information on the position of the target on the image and the distance between the target and the imaging device based on an image of the target at the image acquired by the imaging device,

using the plurality of preliminary positions as starting points, making the robot move translationally so that the positions of the detected target become predetermined positions and the distances become predetermined distance, and storing the positions of the robot after the translational movement as end points, and

calculating the parameters of the mechanical model based on the positions of the stored end points.