The Modeling Of Position Loop Plant And Delay-dependent Robust Control For Permanent Matnet Synchronous Motor Servo System

Servo system which is also called as position following system is mainly realized tomake the operation part follow the given position accurately, and its demand of performanceand location accuracy is very high. Now, in high-accuracy servo system, permanent magnetsynchronous motor relying on its superior performance has been becoming the trend in theapplication of operation part. Based on the two loop structure of permanent magnetsynchronous motor (PMSM) servo system including current loop and position loop, the studyof position loop is proposed to improve the position control performance of the PMSM servosystem.Firstly, the method of mechanism modeling is to be used to get the higher-order plantmodel of position loop. The higher-order plant model which can truly reflect the actualphysical characteristics of the servo system is different from the second-order plant modelgetting from the equation of motion. A position loop controller for the higher-order plantmodel is designed, and its control performance is compared with that for second-order plantmodel. These two position loop controllers are designed in the same method. The simulationresults show the higher-order plant model is more effective.Secondly, based on the higher-order plant model, usingH_∞control theory, aH_∞mixedsensitivity position controller is designed, which the input signal of position controller is theerror between the reference position signal and feedback position signal. Compared withtraditional PID controller, the higher-order robust position controller has better trackingperformance, robustness and disturbance rejection capability.Thirdly, by selecting the appropriate state variables such as velocity, position and integralof position error, usingH_∞control theory, a state feedback robust position controller isdesigned. The robust controller can be realized easily by the addition of state variablesmultiplying by control parameters, which has better robustness against variation and loadimpact comparing with mixed sensitivity position controller.Lastly, considering the impact of system time delay, the structure of predictive observeris proposed to compensate the phase lag ofH_∞state feedback control system caused by timedelay, which can enhance the control performance of the system and promote the robustnessof the system.