Improved Sliding Mode Observer Based Position Sensorless Techniques Of Surface Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor(PMSM)has been widely used in various power level applications such as common servo systems,electric vehicles,CNC machine tools,Aeronautics and Astronautics due to its high power density,high reliability and low loss.The position sensorless control techniques can avoid the problem of the mechanical position sensor easily disturbed by the surrounding environment and realize the low cost and high control accuracy of the PMSM drive system.Therefore,this paper focuses on the position sensorless techniques of Surface PMSM(SPMSM)based on an improved sliding mode observer(SMO).In order to solve the problems of the conventional SMO and improve the accuracy of the estimated rotor position and speed,an improved SMO based on the complex-coefficient filter is presented.The complex-coefficient filter has no phase lag and amplitude attenuation at the center frequency.The improved SMO can avoid the phase lag and amplitude attenuation while the chattering is suppressed by using the complex-coefficient filter replace the low-pass filter.The sliding mode gain coefficient is effectively reduced and the chattering of the system is further weakened by introducing the observed back electromotive force(EMF)extracted from the complex-coefficient filter to the observer state equation.In order to reduce the observed angle error in the process of dynamic speed change,the Compound method of the normalized phase locked loop(PLL)and the arc tangent is used to get the rotor position and speed,and the observation precision is improved.A quasi-proportional-resonant controller based adaptive position observer for PMSM is proposed to realize the position sensorless control,Since the poor observation precision of the improved sliding mode observer under low frequency ratio.The quasi-proportional-resonant controller based adaptive position observer use the quasi proportional resonance controller replace the sign function according to the principle of the internal model.The steady state error of the observer can be reduced to zero by the high gain characteristic of the quasi proportio nal resonance controller at the resonant frequency.At the same time,the other harmonics in the observed back EMF are filtered out,the chattering is reduced,and the position sensorless control performance under low frequency ratio is improved.Furthermo re,the stability analysis and parameter design method of adaptive observer are also given.Finally,a 3kW PMSM experimental platform with a dynamometer as the load is built.Based on the above theoretical analysis and simulation verification,the experiments are carried out and the correctness of the improved SMO and adaptive observer method is verified.