BLDC motor full-speed operation using hybrid sliding mode observer

This paper presents a full speed range control scheme for surface mount BLDC motor. The developed topology looks like field-oriented controls for sinusoidal PM motors but the fifth and seventh harmonics variables have been taken into consideration as well as the fundamental variables. The proposed method results in an increase in developed torque. Also, it shows the same controllability as in the sinusoidal PM motor over the flux weakening operation compared to the conventional six-step BLDC drive system. In this paper, the line-to-line average model of the BLDC motor in rotor multiple reference frame (MRF) first is developed. A sliding mode observer then is introduced to estimate the rotor position and speed used in the MRF. After that, a full speed range control algorithm is developed based on the line-to-line average model. Finally, simulation and experiments have been done to verify the validity of the proposed method.