A hybrid approach of sensorless rotor position self-sensing for brushless Dc motor

Based on the detailed discussion of the basic principles and merits for stator core saturation method and sliding mode observer (SMO) method, a hybrid rotor position self-sensing approach is investigated by combining the two methods. To detect the initial rotor position, a method based on the magnetic saturation characteristic of the stator core is presented. To detect the rotor position at low speed and high speed, a new SMO is designed. To increase the precision of the rotor position estimation at low speed and the stability of the system at high speed, the estimated back electromotive force (back-EMF) is feedback to current observer. To solve the chattering problem in traditional SMO, the sign function is replaced by a saturation function. The application of this scheme to an surface brushless dc motor (BLDC) with sinusoidal-wave back-EMF is carried out successfully. The experimental results show that the proposed sensorless control algorithm is valid and suitable for the sensorless control in full-speed range (zero speed to base speed).