Variable Structure Control Of Electromechanical Actuator

Electromechanical actuator （EMA） is a high-precision servo system, and it isan important sub-system in the control system of missile. This paper is to design areal-time control system which can quickly and accurately track the command signal.In order to improve the robustness of EMA, this subject mainly to complete thesetasks:This paper designed a variable structure control (VSC) for EMA system basedon exponential reaching law. It not only improved the quality of theelectromechanical actuator system, and achieved the tracking accuracy. Since theVSC has severe chattering problem, this paper uses fuzzy control method which canreal-time adjust the switching intensity to weaken the chattering.This paper do some simulation analysis on the simulation platform to test thefuzzy VSC method’s result. Simulation results show that the overshoot of VSC isless than1%, while the traditional PID controller’s overshoot is4.6%; VSC’s settlingtime is0.052s, while the traditional PID controller’s setting time is0.091s. In otherwords VSC has a smaller overshoot and response time; and fuzzy VSC has a lowerswitching frequency chattering weak.This paper designed a hardware platform and software modules of EMA systemfor precision position tracking. And use the traditional VSC and fuzzy VSC tocontrol the EMA system, respectively. The results show that the traditional PID controller’s overshoot is2.1%,while the VSC’s overshoot and the fuzzy VSC’sovershoot is less than1%; The VSC and fuzzy VSC’s settling time is about60ms, itis as same as the traditional PID controller’s setting time; the traditional PIDcontroller’s steady-state error is less than0.002°which is as same as the fuzzyVSC’s, while the VSC’s steady-state error is about0.02°which is terrible. Otherwords VSC method has a better robustness and the lower overshoot; the chatteringintensity significantly weakened after the introduction of fuzzy control method.This paper designed a VSC system for EMA which has a better trackingaccuracy and robustness capacity than PID. As VSC system has severe chatteringphenomenon, this paper brings in fuzzy control method to cut down the chattering.In a word, the research has some engineering significance and has a certainreference value to the further study of EMA in the future work.