Improved Sliding Mode Observer for Position Sensorless Control of Permanent Magnet Synchronous Motor

This paper proposes an improved sliding-mode observer (SMO) for the sensorless control of permanent-magnet synchronous motor (PMSM). In the conventional SMO, a low-pass filter (LPF) is used to reduce the chattering caused by the signum function. That will bring the phase lag and affect the precision of the observer. The improved SMO adopts the self-adapting complex-coefficient filter (SACCF) to replace the LPF. The SACCF has no phase lag and amplitude attenuation at the mid-frequency. Thus, it can extract the back electromotive force (EMF) without distortions while suppressing the chattering. Then the improved SMO use the normalized phase-locked loop (PLL) to track the rotor position and speed accurately. Finally, the simulations and experiments are carried out with a 3kW PMSM, and the results verify the effectiveness of the proposed method.