Modified Flux Linkage Observer For Sensorless Direct Thrust Force Control Of Linear Vernier Permanent Magnet Motor

Rail transit traction system is an important method to solve the problem of serious traffic jam.Conventional rail transit traction system usually uses rotary motor,which costs huge.The Linear vernier permanent-magnet(LVPM)motor incorporates the merits of low cost,high efficiency and high force density.So,it is suitable for the application in rail transit traction system,especially when adopting direct thrust force control(DTFC).However,the installation of the position sensor for linear motor costs huge.Therefore,sensorless operation is necessary.Nevertheless,sensorless operation will degrad the accuracy of estimated flux linkages.Hence,a novel method with the advantage of high accuracy,strong robustness and zero lag is demanded.A modified flux linkage observer,which is accurate and robust,will be investigated in this thesis.Combine the proposed observer with sensorless control,a novel control system called modified flux linkage observer for sensorless DTFC of LVPM motor is implemented.The novel control system uses modified flux linkage observer to replace the conventional flux linkage calculation method and uses sensorless algorithm to substitude the position sensor.The accuracy of the flux linkage estimaton is guaranteed by the advantage of the proposed observer.The main research contents of this paper are as follows:1.The structural characteristic and the static characteristics of the LVPM motor id researched.The magnetic field distribution,back EMF and cogging force are analyzed by Ansoft.The mathematical model of the LPMV motor is established and the formulas of voltage,flux linkage and thrust force are derived.2.The basic theory of the DTFC strategy for LVPM motor is researched,including the calculation of the thrust force and the control of the flux.A modified flux linkage observer is established to solve the problem of conventional flux linkage calculation methods,such as inaccuracy and unsteady.The correctness of the proposed observer is verified by formula derivation and stability analysis.The proposed observer for DTFC system is analyzed by building simulation mode and the feasibility of the proposed observer is validated.3.The position estimation module,which consists of back EMF observer and phase locked loop(PLL),is introduced.The accuracy of the flux linkage estimaton under sensorless operation is guaranteed by combining the modified flux linkage observer with sensorless algorithm.The proposed observer for sensorless DTFC system is verfied by simulation.4.The LVPM motor experiment platform based on DSP2812 is introduced,including the design of hardware and software.Experiments are carried out to verify the feasibility of the modified flux linkage observer for sensorless DTFC system.The accuracy and robustness of the proposed observer is validated by comparing with conventional methods.