Design of a Sensorless Control System for LFSPM Based on Non-singular Fast Terminal Sliding Mode

In order to achieve speed sensorless control and enhance observation accuracy for a Linear Flux-Switching Permanent Magnet (LFSPM) motor in rail transit applications, a sensorless control system is proposed in this paper, utilizing a non-singular fast terminal sliding mode observer (NFTSMO) with a developed control law, and an improved phase-locked loop (PLL). First of all, the mathematical model of the LFSPM is established, and a conventional sliding mode observer (SMO) control strategy is designed. Subsequently, a non-singular fast terminal sliding mode surface is selected to replace the traditional linear sliding mode surface, and a control law tailored for the NFTSMO is developed. The improved observer effectively mitigates chattering and enhances observation precision. Furthermore, the super-twisting sliding mode control (STSMC) algorithm is integrated into the traditional PLL to refine observation accuracy further. Finally, the results of the simulation and hardware-in-the-loop (HIL) experiments show that the proposed control strategy significantly improves the system’s robustness, suppresses chattering, and validates effectiveness and feasibility.