The Commutation of BLDC Motors in Sensorless Control Via EMF of Rotation

The article presents the sensorless method of commutation control of BLDC motors based on measurements of rotor's rotation angle determined via analysis of EMF of rotation. A BLDC with magnets on the rotor and two sections on the stator was chosen as the object of the experiment. The rotation angles of the rotor in which commutation occurs are selected from the condition of equality of moment's generated sections in the corners on and off the windings. The moments equality, that occurs during the rotor spinning, was determined according to the condition of equality of rotation EMF emerging in stator windings. The function that does not depend on the rotor's angular velocity was developed. This function produces impulses in case the EMF of sections rotation are equal. The function is used in order to determine moments of sections commutation. The simulation of a specific plug-disc type BLDC was carried out and the results confirmed the effectiveness of the proposed method for sensorless control of low-power BL motors. The speed ripple registered for this method reached ~0,01 %

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