Two Degree-of-Freedom Control For Permanent Magnet Synchronous Motors

The permanent magnet synchronous motors (PMSM) have the advantages of high speed, high efficient, high dependability performances etc., meanwhile has many characters such as low noise, low cost and long life. With the development of the new material, the PMSM has been rapidly developed and widely applied in recent year. The control performance of the servo system is influenced by factors as plant parameter variations, external load disturbances, unmodeled and nonlinear dynamics. At the same time, it needs to notice that the controller parameter perturbation is also one of the important factors which influence the robustness of the servo system.In order to reduce the influence caused by the controller parameter variations and the plant parameter perturbation, and assurance the tracking performance and the restraint disturbance performance, the improved robust two degree-of-freedom (DOF) control structure and the linear matrix inequation design method are adopted to design the robust two DOF controller of the servo system in this thesis.The improved robust two DOF control structure has the merit of the traditional two DOF control structure. The tracking to the preset signal and the restrain to the disturbance are achieved with two DOF. The asymptotic tracking or the attainment of zero tracking error in the steady-state which is robust with respect to the plant parameters can be accomplished with the robust two DOF. The tolerances of controller parameter variation in two different control structures are compared. The results show that the servo system with the former control structure has lower sensitivity to the controller parameter variations and has better robustness.In order to simplify the design process of the controller and optimizes the controller performance, the linear matrix inequality method is employed to design the two degrees of freedom controllers in the thesis. It eliminates the influence of the human factors such as theweight function choice, overcome the disadvantage of dealing with Riccati equation and gets the controller by convex optimization.Simulation results show that the servo system with the designed controllers provides a good performance. At the same time, it reduces the sensitivity of the system performance to the controller parameter perturbation. Then, the robustness of the system are improved.