Novel Kinematic Calibration Method of Parallel Mechanisms Using the Equivalent Kinematic Chains

doi:10.3901/JME.2022.14.071

Abstract

Abstract: The error modeling of parallel robot is difficult to solve accurately because of the complex structure. In order to solve this problem, a kinematic calibration method based on equivalent kinematic chains is proposed. Firstly, the analytic expression of the twist space on the moving platform is obtained through the join and meet operators. The virtual serial kinematic chain equivalent to the twist space of the moving platform is established, and the error model can be constructed for the equivalent virtual serial kinematic chain. The end error is compensated to the end of the equivalent kinematics chain. Finally, the corresponding driving values of the end pose of the moving platform after the error compensation is calculated by the inverse kinematics of the parallel mechanisms, and compensated to the driving joints of the parallel mechanisms. Taking the 2-UPR-RPU parallel robot and 2-UPR-2-RPU redundant actuated parallel robot as examples. The twist space of the both is equivalent to an RPR serial kinematic chain. The error modeling of the virtual serial RPR kinematic chain is established, and it is verified by simulation and calibration experiments. The experimental results show that both the average position error and the average orientation error of 2-UPR-RPU and2-UPR-2-RPU parallel robots are dropped sharply, which verifies the correctness of the proposed method. This method transforms the error modeling of parallel robots into the error modeling of the equivalent serial kinematic chain. The compensation value of the driving joint can be obtained by solving inverse kinematic equations of parallel robot without any forward kinematics, which has the advantage of simple calculation.

Key words: parallel robots, grassmann-cayley algebra, equivalent kinematic chains, error modeling, kinematic calibration

CLC Number:

TD156

XIA Chun, ZHANG Haifeng, LI Qinchuan, CHAI Xinxue. Novel Kinematic Calibration Method of Parallel Mechanisms Using the Equivalent Kinematic Chains[J]. Journal of Mechanical Engineering, 2022, 58(14): 71-84.

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