Translated Abstract
Kinematic parameter calibration of robot is the necessary means to guarantee and optimize the accuracy of robot end motion. The calibration technique based on distance error model establish the relationship between the distance error and the error of the kinematic parameters. The calibration process avoids the conversion error of the coordinate system, and can significantly improve the calibration accuracy. The vision measurement technology has the advantages of high precision, non-contact, real-time et al. Compared with the traditional method, it has the advantages of low cost, easy operation et al. This paper will study a robot calibration method which combines the distance error model with the visual measurement technology, for improving the accuracy of industrial robot in specific workspace. In this paper, stereo vision system is adopted, and the camera is outside the robot, and the robot parameters are calibrated based on the distance error model. It is of certain engineering significance to improve the motion accuracy of robot which mainly working in a specific workspace. Specific contents are as follows.
The kinematics of the robot is modeled, and the DH model is used to solve the pose matrix of the robot end in the robot coordinate system. At the same time, the singularity of DH model is improved, and the MDH model is obtained. The differential motion of the robot is analyzed, and the relationship between the robot end positioning error and the error of the kinematic parameters of the robot is established. The theoretical basis is established for the kinematic parameter calibration of the robot. Then by the analysis of the principle of calibration method based on distance error model, the relation between kinematic parameter error and distance error of robot is built up. The corresponding calibration equation and Calibration method for specific parameters is established, which explicit the main direction of the following measurements. Study on the realization of binocular vision system, including the selection of hardware, camera calibration, the calculation of spatial coordinates of target points. And the corresponding observation target board is designed, and a fast recognition algorithm of the dot on the target board is put forward, which has a certain anti-jamming and real-time performance, which lays a theoretical foundation for the realization of the software.Established a combination of visual measurement and robot calibration technology, that is, the form of eye off hand. Based on the scheme, the corresponding motion path of the robot is designed, and the software of visual measurement and data processing is realized, which completes the whole scheme design of robot vision calibration method.
The robot vision calibration method is tested. The algorithm for the identification of the dot on the target board is analyzed. The results show that the algorithm is accurate and robust. The experimental data were collected and the calibration results were obtained by data processing software. The kinematic parameters are compensated using the calibration results. Binocular vision system and laser interferometer were used to measure the distance error before and after calibration respectively. On the calibration trajectory, the average error of the absolute distance is reduced from 0.2799mm to 0.1044mm, and the error of the uncalibrated trajectory is decreased by more than 50% .The results show that the distance error in the specific calibration workspace has been improved, which proves the correctness and feasibility of the method.
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