An advanced twelve step sensor-less control of brushless DC motor for vehicle cooling fan drive system

This paper presents an advanced sensor-less control for a brushless DC motor (BLDCM) based on twelve step drive scheme. In twelve step drive, the large torque ripple is caused by the current commutation between three phase windings of BLDCM. To solve the problem, this paper proposes the advanced twelve-step sensor-less control to reduce torque ripple. The proposed control has two modes. In two phase commutation mode (TWPCM), the rotor position of BLDCM is estimated by zero crossing point of back EMF and the reference value of duty ratio to control speed of BLDCM is calculated. In three phase commutation mode (THPCM), torque ripple is reduced using the reference duty value that calculated by TWPCM and three phase currents that measured by a single shunt resistor. The effectiveness of the proposed control is verified by the simulation and experiment according to the comparison of the output characteristics between the traditional controls and proposed control.