Error Analysis and Kinematic Calibration of 3-RPS Symmetrical Parallel Bionic Leg

According to the kinematic model of the parallel bionic leg expressed by the Rodrigues Parameters, the model of the position-stance errors was established based on the complete differential-coefficient theory. The error model with Rodrigues parameters has the advantages including least computational parameters, no trigonometric function calculation and convenient real-time estimation. The kinematic calibration model and the corresponding algorithm with the successive approximation algorithm were achieved. The simulation can show that the algorithm is effective to study the calibration question and has concrete directivity reducing the kinematic errors when optimizing iteratively. By comparing with the normal walking gait of a human subject, the end-point trajectory of the parallel bionic leg was better programmed. It was validated that the parallel bionic leg was feasible to realize the human-like motion based on the calibration model and the corresponding algorithm. The experiment results showed the structure characteristics of the parallel bionic leg and the trajectory of the parallel bionic leg is smoother and has more stability.