Robust Flux Estimation Method for Linear Induction Motors Based on Improved Extended State Observers

Flux estimation is of great importance for high-performance linear induction motor (LIM) drives. However, due to the end effects of LIMs, range of variation in mutual inductance and secondary resistance is quite high with the change in operating condition, and the flux estimation suffers from these LIM parameter variations. To alleviate the influence of these parameter variations, this paper proposes a new flux estimation algorithm based on two improved extended state observers (ESOs) with expanded bandwidth for observing disturbances. One of them is especially designed to observe the ac disturbance at certain frequency. Taking advantage of the improved ESOs, the robustness of the flux observer to parameter deviations can be significantly strengthened, and the vector control strategy based on this new flux observer can achieve better dynamic performance. Finally, the effectiveness of the proposed method is validated by both simulation and experimental results on an LIM prototype.