Fuzzy-Sliding Mode Variable Structure Control For AC Linear Servo System

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 variable structure control which sliding mode can be designed is insensitive to system parameters change and load disturbance, and has the advantages of good robustness, quick response, easy realization and so on. Accordingly, it's hopeful to design a control strategy of high quality by applying sliding mode control (SMC) to the control of PMLSM servo system.For a direct-drive ac linear servo system, this paper presents a fuzzy sliding mode variable structure mode switch control (SMC) method. Deeply 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 system as input, 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 other interrupts.Secondly, because the chattering problem is the main reason of batting the abroad application of sliding mode control method. Therefore, the fuzzy arithmetic is adopted in this paper to solve the inhered chattering problem of the sliding mode control method. The idea of the control with fuzzy arithmetic is that for the position of running point of phase track. The speed and the direction of the point, original sliding mode variable structure control of the switch is instead of the output of fuzzy controller. The equivalent control is used in AC linear servo system without external interference and indentified, once the disturbance by adding, switching to a fuzzy control. So the system can keep the robustness and can decrease the chatting at the same time, Sliding-mode system makes variable structure in ensuring the robustness of the original control at the same time, the weakening of sliding can be effectively generated by the switching control of chatting. The thrust ripple arise from the end effect of permanent-magnet linear synchronous motor (PMLSM) is eliminated, and the position precision is improved greatly.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 chatting, good dynamic-static performance in AC servo system.