| For AC servo system of quick changing and non-linear complex system, many kinds of methods are presented. Among them, the robustness is one of the important indexes. Sliding mode control method has been paid attention by many scholars, because of its no overshoot, quick response and the robustness to system parameters and outer interrupts.An AC servo system with grading fuzzy sliding mode controller is presented in this paper and the deeper analysis and research have been done. Firstly, in order to increase the robustness of AC servo system, the position controller of sliding mode is designed. With the error position and rotor speed as inputs, the controller can decide the current of stator through the uninterrupted control that satisfies the sliding mode condition. So, the servo system has the good robustness to the change of parameters and outer interrupts.Because the chattering problem is the main reason of baffling the abroad application of sliding mode control method, the fuzzy arithmetic is added to solve the inhere chattering problem. The rules of the fuzzy arithmetic is that for the position of running point of phase track, the speed and the direction of the point, the adjustive control is added to the former control. So. the system can keep the robustness and can decrease the chattering. At the same time, the result of deceasing chattering is analyzed.In addition, at the moment of startup, the exponent approaching sliding mode control is adopted. Then when the running point is reaching the threshold the fuzzy sliding mode control is changed. Because the point is running with the exponent deceasing speed, the response of system is speed up. Moreover, the smooth of control is realized and the time of response is optimized.Finally, this paper analyses the results of the simulation. Simulated results obtained verify the validity of the proposed method in terms of robust performance, quick response and reduced chattering, good dynamic-static performance in AC servo system. |
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