Adaptive observer combined with HF signal injection for sensorless control of PMSM drives

The paper presents a speed and position estimation method for the sensorless control of permanent magnet synchronous motors. The method is based on a speed-adaptive flux observer that is augmented with a high-frequency signal injection technique at low speeds and standstill. In the adaptive observer, a flux model is used as the reference model and a voltage model as the adaptive model. At low speeds, the estimation is further corrected with an error signal from the signal injection method by influencing the direction of the estimated stator flux. The fast dynamic response of the adaptive observer is thus combined with the steady-state accuracy of the high-frequency signal-injection method. According to simulations and experiments, the proposed approach is stable and robust, and can cope with stepwise changes in the speed or position reference. The capability of rejecting load torque transients is also good