Rotor Position Observer Utilizing a Sinc-filter for Permanent Magnet Synchronous Motor

Sensorless control systems became a standard for industrial drives. The sensorless control systems utilize observers for the estimation of the rotor position which is mandatory for torque control. One of the commonly used methods is a back-EMF observer, which estimates back-EMF and the rotor position of the permanent magnet synchronous motor as well. However, the accuracy of the observer is strictly dependent on the type of the filter used to distinguish back-EMF, which causes the phase delay in the position estimation. This paper proposes to use sinc-filter of the third order to achieve a higher accuracy in the position estimation. As the sequence coming from sliding mode observer has the properties of delta-sigma modulated signal, extra information can be extracted for the specified measurement time and provides higher accuracy than the use of simple moving average filter. The proposed algorithm was verified using MATLAB Simulink and showed better accuracy compared to conventional method.