A Convenient Kinematic Calibration and Inverse Solution Method for 4-DOF Robot

Abstract

Calibration can improve the absolute positioning accuracy of the robot end-effector. However, the traditional robot calibration method is complicated, time-consuming and its cost is quite high. Moreover, at such a case, robot cannot convert the full inverse kinematics into known sub-problems. To solve above problems, a convenient method of kinematics calibration and inverse kinematics for 4-DOF robot is proposed. Firstly, the screw axis identification (SAI) method is used to identify the robot twist parameters. Then, the product of exponentials (POE) formula of the robot forward kinematics is established based on the twist parameters. Finally, the closed-form solutions of the 4-DOF robot is implemented using a real algebraic geometric (RAG) method, which is suitable for any RRR type robot. The proposed parameter identification method only needs to separately rotate robot n joints of the robot once. Plus, the corners coordinates is measured by a binocular camera, so that the initial transformation between tool and reference frames and the twist parameters can be easily identified. A non-standard structure 4-DOF robot is used as validation, and the experimental results have proved the convenience, high efficiency, and inexpensiveness of above mentioned method.