Current Integral Method for Fine Commutation Tuning of Sensorless Brushless DC Motor

Abstract

This paper presents a method for fine commutation tuning of brushless direct current (BLDC) motor. First, we analyze the phase current waveform under commutation error and nonideal back-EMF. From the relationship derived, we propose a feedback compensation method in combination with a sensored BLDC motor or any sensorless drive technique to adjust commutation instant by forcing the current integrals of the two half periods in one 60 degrees conducting period to be equal. The method is robust to variations in resistance and inductance, as well as to nonideal back-EMF, pushing the peak values of the current waveform at the front and back of each conducting period to be more identical. Simulations are presented and a digital signal processor (DSP)-based sensorless scheme contingent on a disturbance observer for back electromotive force (back-EMF) estimation in combination with the proposed control method is implemented to verify its effectiveness experimentally. The results show that proposed method is capable of running the motor at different speeds, load torque, and under the speed-varying operating condition with low levels of motor vibration and power consumption.