MRAS velocity observation method for a linear induction motor considering edge effects and parameter variations
This study focused on the speed observer of a linear induction motor(LIM)traction drive system in the context of addressing real-time and robust limitations caused by edge effects and variations in motor parameters.An improved model reference adaptive system(MRAS)speed observation method was proposed based on the second-order super-twisting sliding mode.Initially,a standard MRAS speed observer for LIM was designed by incorporating dynamic edge effects into the primary voltage-current magnetic link equation,mitigating the impact of edge effects on speed identification performance.Subsequently,the influence of the primary skin effect and primary lateral misalignment on the identification performance of the standard MRAS speed observer was analyzed.Building upon this,an enhanced MRAS reference model using a second-order super-twisting algorithm was developed to compensate for disturbances in secondary magnetic link observation using the primary sliding mode surface and an auxiliary sliding mode surface.This enhancement not only suppressed system oscillations introduced by sliding mode algorithms but also enhanced the robustness and dynamic performance of the speed observer.Simulation and hardware-in-the-loop experiments were conducted to validate the proposed algorithm.The experimental results demonstrate that the standard MRAS observer exhibits significant speed identification errors due to changes in the excitation mutual inductance and other motor parameters resulting from edge effect correction factors,particularly under sudden load changes,measurement errors,and motor parameter variations.In contrast,the enhanced MRAS observer achieves rapid and accurate speed identification for linear induction motors,meeting design requirements for control performance in scenarios involving abrupt load changes,measurement errors,and motor parameter variations.The outcomes of this research can provide valuable insights for the study of speed sensorless traction drive systems in linear induction motors for rail transportation applications.