Adaptive Second-Order Disturbance Observer-Based Position Sensorless Drive Strategy for PMSM

In this article, an adaptive second-order disturbance observer (SODO)-based position sensorless drive strategy for permanent magnet synchronous motor (PMSM) considering disturbance compensation is proposed. To achieve finite time observation of disturbance in the case of the boundaries of the system disturbance and its derivative are unknown, an adaptive SODO is put forward first. Under the premise that the upper and lower bounds of the adaptive coefficient are not required, the adaptive mechanism of the SODO cannot only guarantee the occurrence of sliding mode, but also make the adaptive coefficient small enough to suppress chattering. Next, to estimate the extended back electromotive force (EMF), a stator current observer is designed by adopting the proposed adaptive SODO. Afterward, to estimate rotor position information through the extended back EMF without adopting phase-locked loop, a speed observer that can omit the low-pass filter used for the estimated extended back EMF filtering and diminish the position estimation error is designed by employing the adaptive SODO. In addition, the disturbance of the speed loop is also observed and compensated. The stability of the adaptive SODO is analyzed by the Lyapunov function. The effectiveness of the proposed position sensorless drive strategy has been verified through comparative experiments on a surface-mounted PMSM.