Research On Robot Pose Calibration Method Based On Binocular Vision

With the maturity of industrial robot technology,its application field will be larger and larger.However,industrial robots generally have the problems of high repetition positioning accuracy and low absolute positioning accuracy.Robot calibration technology can improve the absolute positioning accuracy of robot in a low-cost way without modifying the robot body.At present,the mature industrial robot calibration system has some problems,such as heavy equipment,high price,limited application scenarios and so on.In this paper,a robot calibration method based on binocular vision using stereo target is proposed,and a robot calibration system based on binocular vision is developed.Firstly,aiming at the problems of high complexity,large amount of computation and low accuracy of feature point extraction algorithm in binocular vision,a stereo target which can be installed on the end flange of robot is designed.The target has the characteristics of easy identification of feature points and free calibration angle.In this method,feature points extraction and matching algorithm are designed for the target.Through the stereo target calibration algorithm,the coordinate system of the stereo target and the position of the feature points on the target in the coordinate system of the target are obtained.By using the stereo target calibration algorithm,the size error of target in processing and assembly can be reduced.Secondly,in the pose measurement of the robot,a set of transformation relationship between the robot base coordinate system and the camera coordinate system is designed by controlling the robot to carry out a series of typical motions,taking the pose of the three-dimensional target in the camera coordinate system as the intermediary.Using the seven points calibration method,the position and attitude relationship between the target coordinate system and the robot end flange coordinate system are obtained,and then the pose of the robot end flange coordinate system in the camera coordinate system is obtained.When the relationship between the base coordinate system,the end flange coordinate system and the camera coordinate system is known,the pose of the end of the robot is calculated.In the measurement experiment,the error processing algorithm is designed to improve the reliability of the calculation results.Finally,in order to verify the effectiveness of the robot calibration system proposed in this paper,through the comparison experiment between the commercial laser tracker at960 and the calibration system designed in this paper,the accuracy of the target is between-0.31mm-0.34 mm.The experimental results verify the reliability and effectiveness of the robot calibration system designed in this paper.