Sensorless control of interior permanent magnet synchronous motors based on an improved sliding mode observer

To address the issues of inherent chattering and low estimation accuracy in the position sensorless control of an interior permanent magnet synchronous motor (IPMSM) using a traditional sliding mode observer (SMO), this paper proposes an improved sliding mode observer method. First, the sign function is replaced with a sigmoid function to substantially reduce the sliding mode chattering of SMO. Secondly, moreover, a position sensor-less control method based on a higher-order sliding mode observer is proposed to replace the traditional sliding mode observer combined with a low-pass filter. Specifically, by constructing a sliding mode surface incorporating higher-order derivatives of the error and combining it with a continuous control law, the proposed method enables accurate estimation of back EMF and real-time tracking of rotor position. Finally, by replacing the arctangent function with a phase-locked loop (PLL) to extract rotor position information, the proposed approach achieves higher accuracy and better stability in the sensorless control system. As a result, the improved SMO can effectively mitigate the chattering phenomenon and enhance the position estimation accuracy as well as system robustness. The effectiveness of the improved method is validated through Simulink simulation results.