Commutation torque ripple reduction in PM brushless DC motor with nonideal trapezoidal back EMF

To improve the precision and reduce the speed ripple of magnetically suspended control moment gyro (MSCMG) gimbal servo system, It was analyzed that the unbalance back electromotive force (EMF) during commutation is the reason that produces the torque ripple considering the nonideal trapezoidal back EMF of permanent magnet brushless DC motor (PMBLDCM), witch is the main factor effecting the torque ripple of low speed torque motor. And the paper presents an auto-balance control method of commutation torque based on single DC current sensor. The controller is consisted of commutation torque balance point observer and fast optimization estimation algorithm. The method reduces the commutation torque ripple effectively and improves the precision of speed servo.