Accuracy of a Novel Parallel Robot with Orthogonal Chains

A novel parallel robot with orthogonal chains and redundant actuators was designed for simulator. In order to improve the accuracy of the simulator, a comprehensive error model and a new method of kinematic calibration were studied. Based on the orthogonal feature of the mechanism and the principle of the influence coefficients, the error model was established, which accommodated all possible geometrical errors: the joint manufacturing errors, the installation errors, the actuation errors etc. A sensitivity index was designed to characterize the influence of the error sources on the end precision. Based on the index, error analysis was carried out to decide the major errors that need to be identified in kinematic calibration. Furthermore, a new calibration method based on relative displacement measurement was presented for avoiding the high-cost end pose measurement. Finally, the simulation of the calibration gave the validation of the new method.