| Direct torque control has been applied to linear motor, namely direct thrust control (DTC). DTC technique is a further expansion area of the direct torque control. With the development of power electronic technology, the appearance of novel power electronic devices and various high performance and lower price permanent magnet materials, permanent magnet linear synchronous motor (PMLSM) direct driving system has many advantages over rotating motors and other linear motor.Firstly, according to the mathematical thrust model of PMLSM, the basic principle and implemental method of DTC are discussed. Thrust and flux are researched theoretically. The simulation model for PMLSM drive based on DTC is set up. Simulation results show that it has fast response characteristics, but the disadvantages are serious thrust and flux ripples.Secondly, in order to minimize thrust and flux ripples of conventional DTC drive, this thesis presents two control methods based on space vector modulation (SVM). One is predicting the next PWM period's flux amplitude to control the thrust and flux to resist motor nonlinear, uncertainties such as variable parameters and load disturbances. The other uses the sliding mode variable structure controller (SMVSC) to control them. Two simulation systems are set up, the simulation results show that both systems using SVM can keep fast response characteristics of the conventional DTC which apparently reduces the flux and thrust ripples. Furthermore, under the same conditions, SMVSC can produce small thrust ripple than the other two DTC systems and it has high robustness.Finally, different control strategies are compared by simulation. The simulation results show that using predicting PI controller, the thrust ripple is 8.9%, and using SMVSC, the thrust ripples is 4.1%. The proposed control system not only keeps fast response, but also has more robust. At last, experiments of PMLSM control system are conducted.
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