Full-Order Terminal Sliding Mode Observer With Adaptive Gain Based Sensorless Control for Linear Induction Machine in Urban Rail Transit

Speed sensorless control is essential for linear induction machines (LIMs) in urban rail transit. However, it is difficult to obtain the accurate speed when the mutual inductance of LIM is changed nonlinearly due to the end effect, especially in high-speed flux-weakening (FW) region. To enhance the robustness of the sensorless control system against such parameter changes, an improved speed sensorless control based on full-order terminal sliding mode (FOTSM) observer with adaptive gain is proposed in this paper. Firstly, to implement the minimum use of parameters affected by end effect, an active flux observer with improved FOTSM is constructed in the back electromotive force (EMF)-primary current model. Then, an adaptive gain is designed to guarantee the stability and effectively attenuate the chattering. After acquiring the accurate estimated active flux, a novel speed observer based FOTSM is established, where the mutual inductance and estimated active flux are decoupled. Finally, comprehensive simulation and experimental results have demonstrated the effectiveness and feasibility of the proposed method.