Complex-Coefficient Adaptive Disturbance Observer for Position Estimation of IPMSMs With Robustness to DC Errors

Model-based position-sensorless control of interior permanent magnet synchronous motors (IPMSMs) is promising for high-speed operation, besides the fact that the estimation accuracy degrades by dc errors from integration, measurements, and parameter uncertainties. In this article, a new complex-coefficient adaptive disturbance (CCAD) observer based on the back electromotive force estimation is proposed. The proposed CCAD observer has a bandpass characteristic and possesses resonating peak response at the corner frequency which is adapted to the synchronous rotor frequency. This adaptive resonant frequency effectively improves the robustness to dc errors, without magnitude loss and phase delay. The proposed observer is also compact and has lower order as compared to the other bandpass observers, and that substantially benefits in the embedded implementation. To configure the proposed CCAD observer, a reverse observer design scheme is analyzed. The stability of the observer is guaranteed based on a speed adaptation law, and small-signal approximation is then applied to linearize the proposed observer for parameter design and dynamic analyses, which have not been well discussed in literature. The proposed method is verified by experiments for a 15 kW IPMSM drive.