Abstract:Geometric parameters modeling is the basis of robot calibration, which directly affects the robot positioning accuracy. The common geometric parameters model has the singularity when the two adjacent axes of the robot are vertical and close to vertical. To solve this problem, a zero reference model (ZRM) based on the direction vector and the connection vector is formulated. It not only meets the requirements of completeness and continuity, but also it is simple and intuitive to calculate the robot endeffector position and orientation. The error model of geometric parameters is established. The endeffector positions and orientations of Staubli Tx60 and ER10LC10 industrial robots are measured by Leica AT960 laser tracker. The reduntant parameters are removed by the orthogonal triangle decomposition method and the geometric parameters errors are identified by the LM algorithm. The results are compared with the output of the MDH model. Experimental results show that the average absolute positioning accuracy of robot endeffector cabibrated by ZRM model is improved by 75%~90%, which is obviously higher than that cabibrated by MDH model. This method is suitable for industrial robots with high positioning accuracy requirements. .txt