Commutation torque ripple restraint in BLDC motor over whole speed range

The un-commutated phase current of the brushless de motor (BLDCM) is distorted during phase current commutation intervals, the distortion results in commutation torque ripples. This paper proposes a novel control method to restrain the commutation torque ripple according to different speed ranges. In the proposed method, the un-commutated phase current is directly controlled through a chopping action with correct current feedback mode in the low speed range, indirectly controlled by decreasing the slope of the outgoing phase current in the middle speed range, and indirectly controlled not only by decreasing the slope of the outgoing phase current but also by modifying the reference current value in the high speed range. The un-commutated phase current is validly controlled over the entire speed range, so the commutation torque ripple is reduced. The effectiveness of the control method presented here is verified by the simulation and experimental results.