Control For Trajectory Tracking Of Permanent Magnet Spherical Motor

The Permanent Magnet Spherical Motor(PMSM) is a multivariable, nonlinearand strong coupling system. The external disturbance, the evaluated error of theparameters and the model error all result in the uncertainty of the actual system model,which has a great influence on the control performance of the motor. In order toobtain a better static and dynamic performance, and improve the tracking performance,two trajectory tracking control strategies of PMSM based on acomputed-torque-method and a robust-control-method are proposed. The simulationresults indicate the validity and feasibility of the proposed methods.Firstly, two sets of Cartesian Coordinates are established and the structurecharacteristics of the PMSM are analyzed. The PMSM simplified dynamic model andthe more complete one are both established according to their structure characteristics.The simulation results show that the more complete model significantly improve theaccuracy of the model and can achieve better accuracy than the simplified one.Secondly, to improve the trajectory tracking performance, the trajectory trackingcontrol strategy based on computed-torque-method is proposed according to its morecomplete dynamic model. The trajectory tracking results, and the robustness of theproposed method are both simulated respectively. Furthermore, the trajectory trackingerror results and the decoupling results are both compared to the traditional controlstrategies，including the PD algorithm and the direct feed-forward compensationalgorithm. The simulation results indicate that the proposed method can eliminate theinfluences of inter-axis nonlinear coupling effectively, and has better robustnessagainst the external disturbance and the model error. In addition, the excellenttracking performance can also be realized.In the end, to improve the stability against the uncertainty, a control algorithmbased on a robust-control-method is proposed according to its complete dynamicmodel. Besides, the trajectory tracking results and the trajectory tracking error resultsare also analyzed and compared to the PD algorithm, the direct feed-forwardcompensation algorithm and the computed-torque one. Furthermore, The robustnessof the proposed method is analyzed in details. Simulation results show that theproposed control algorithm is effective and yields superior tracking performance. Most importantly, it has excellent robustness against the uncertainty, which lays thefoundation for the further research of the motion control about the PMSM.