A novel and easy-realizing initial rotor position detection method and speedup algorithm for sensorless BLDC motor drives

This paper presents a novel startup method of a brushless DC motor (BLDCM) without any reverse rotation and vibration. Using short pulse sensing method, the rotor position can be detected dynamically based on the saturation effect of the stator iron. After accelerating the motor to a certain speed at which the back-electromotive force (EMF) method is applied, all the power devices are turned off and the terminal voltage variation can be used to determine the switch moment and the corresponding commutation phases. The back-EMF zero-crossing point detection is conducted at the end of PWM on-state and the true zero-crossing point is extracted through the proposed algorithm. The experiment results have verified the feasibility and validity of the presented method.