Modified Flux Linkage Observer for Sensorless Direct Thrust Force Control of Linear Vernier Permanent Magnet Motor

The linear vernier permanent magnet (LVPM) motor incorporates the merits of high efficiency, simple mechanism, and low cost, which have a bright future in urban rail transportation. This paper proposes a new sensorless direct thrust force control (DTFC) for the LVPM motor. The novelty is the introduction of a modified flux linkage observer, which has strong robustness against the interferences, no phase lag, and no attenuation. Compared with conventional flux linkage calculation methods, the proposed observer can provide desirable flux linkages, which increases the robustness of the sensorless DTFC system. Simulation and experimental results based on an LVPM motor drive demonstrate the accuracy and robustness. The validations in the aspect of the robustness to parameter errors, measurement errors, and noise show the superiorities of the modified flux linkage observer.