Research On The Control System Of The Three-stage Linear Vernier Permanent Magnet Machine

New energy rail transit(light rail transit,subway,etc.)uses electric engines as the main electric drive system.It takes the fancy of the public because it is without exhaust emissions,environmentally friendly and energy efficient.Compared with traditional rotary electric machines,the Linear Vernier Permanent Magnet Machine(LVPMM)can offer direct linear motion without any rotation to translation conversion equipment,which can provide high power conversion efficiency and better dynamic property.What’s more,it can provide high thrust density and high-speed operation.Because of these characteristics,LVPMM has a great development potential in new energy rail transportation.However,the lack of an intermediate transmission mechanism makes it more sensitive to the internal structural parameter of the motor,load disturbances and thrust fluctuation,which has a bad effect on the system control accuracy and stability.In order to solve these problems,the optimized control algorithms and compensation strategies are proposed to improve the anti-interference ability of the control system.Specific research is carried out from following three aspects.Firstly,to solve the problem of the system oscillation and current error due to the system delay and motor parameter variation,a Predictive Current Control(PCC)considering system delay and parameter variation is introduced to improve the current response speed and control accuracy.At the same time,the Proportional Integral Disturbance Observer(PIDO)is used to estimate the amount of disturbance voltage resulting from motor parameter error.And correspondent voltage for compensation is injected into the system,which can improve the antidisturbance and robustness of the current controller.Secondly,an improved sliding model speed control based on an Extended Disturbance Observe(EDO)is designed.A new sliding model approach law based on the combination of power law and exponential law is proposed,which can suppress the high-frequency chattering of the Sliding Mode Control(SMC)and improve the control accuracy of the no-linear control system.Besides,an extended disturbance observe is provided to calculate the load disturbance(thrust force ripple,non-linear friction,etc.)and converted it into correspondent feedforward compensation current,which can improve the stability of the speed controller.Finally,for the sensorless control based on I/f control and sliding model observer,there are some problems of the high-frequency chattering of the traditional sliding mode observer and speed fluctuation during the switching.In order to solve these issues,an improved sensorless control based on optimized Second-Order Sliding Model Observer(SOSMO)and new switching strategy is researched,which can suppress the chattering of the sliding model and improve the robustness of the system.What’s more,by the estimated back-EMF under the dq coordinate system and the orthogonal Phase-Locked Loop(PLL)to obtain the position of the LVPMM can improve the accuracy of the estimated position and the ability to resist the high frequency noise.A switching method based on linear weight change of the angle and the speed can avoid switching overcurrent.Using the Sliding Model Observer(SMO)to inject the correspondent compensation current into the system can reduce the speed and thrust fluctuations due to the switching.