A Sensorless Control Method for Permanent Magnet Synchronous Motor Based on Fractional-Order Sliding Mode Observer

In order to weaken the chattering of the conventional sliding mode observer (SMO) and improve the accuracy of rotor position estimation, a sliding mode observer for permanent magnet synchronous motor (PMSM) sensorless control based on fractional calculus theory is proposed. First, a sliding mode observer with a fractional integral sliding mode surface is designed and its stability is analyzed according to Lyapunov theory. Second, the saturation function is used to weaken the chattering of the system. Then, the fractional-order phase-locked loop (FO-PLL) is used to extract the rotor speed and rotor position from the estimated back electromotive force (back-EMF). The low-pass filter and phase compensation module are eliminated. Finally, through experimental verification, the fractional-order sliding mode observer (FO-SMO) has the advantages of less chattering and higher estimation accuracy than the conventional sliding mode observer.