Analysis of PMLSM direct thrust control system based on sliding mode variable structure

The permanent magnet linear synchronous motor (PMLSM) direct thrust control (DTC) systems using space vector modulation (SVM) and sliding mode variable-structure are presented and analyzed. Firstly, simulation results of the classical DTC system and the system based on SVM and predictive PI controller are compared. Both systems based on SVM can keep the fast response characteristics of the conventional DTC and apparently reduce the mover flux and thrust force ripples, and furthermore, it can improve the inverter's switching frequency at low speeds. Under the same conditions, simulation results show that the systems using SVM produce almost the same mover flux and thrust ripples. But the system using sliding mode variable structure controller is more robust to the mover flux estimated angle error caused by the change of the mover resistance. The conventional DTC and the proposed system have been realized on the experiment platform based on TMS320LF2407. Experiment results show that the system has good performances.