Suppression of torque ripple due to phase commutation in brushless DC motor drives considering the stator resistance

This paper presents a theoretical analysis on the torque ripple due to phase commutation in BLDCM (brushless DC motor) drives for EPS (electric power steering) applications. Given the characteristics of the system's low supply voltage and high operating current, the influences of phase resistances on commutation torque ripple was investigated. Then a more precise rule than conventional method is derived to determine which commutated phase needs the compensation indeed within the commutation intervals, which makes up for the lake of error compensation of conventional scheme near the critical point. In order to improve the precise of suppression of torque ripples, a piecewise linearization method considering phase resistance was proposed to evaluate the slopes of the incoming and outgoing phase current to obtain the duty of the correct phase. The commutated phase current is balanced by using the PWM control method to reducing the commutation torque ripple. Effectiveness of the proposed scheme is verified through simulations and experiments.