An improved variable structure design for velocity control of a permanent magnet linear synchronous motor

In this paper, in order to suppress the force ripple of a permanent magnet linear synchronous motor (PMLSM) and ideally to access a constant velocity, a model reference adaptive sliding mode control (SMC) is proposed. The main goal is to reduce velocity variations in the presence of an oscillatory load, uncertainties and parameter variations. Therefore, the emphasis is put on robustness and vibration suppression. Moreover, to eliminate the chattering phenomenon and to improve SMC, some modified techniques are implemented. These enhancing approaches are utilization of saturation function, exponential function, sigmoid function and fuzzy-genetic controller. Finally, in order to evaluate the performance of the proposed method, the simulation results are provided in which the robustness of the controller against the uncertainties and parameter variations is examined by intentional changing of the transfer function.