Torque ripple reduction in BLDC torque motor with nonideal back EMF

In order to improve the speed precision and stabilization of the gimbal servo system of double gimbal magnetically suspended control moment gyro, a comprehensive analysis of the reason of electromagnetic torque ripples of brushless direct current motor with nonideal back electromotive force (EMF) drives in the conduction and commutation regions is presented. A novel automatic control method of torque is proposed. With this method, the current control rule is designed, and the duty cycle of pulse width modulation (PWM) is regulated in real time by measuring the wave function of back EMF. In order to eliminate the diode freewheeling of the inactive phase, the PWM-ON-PWM scheme is used. Simulation and experiment results are given to show that, compared with the conventional current control method, the proposed method can reduce the torque ripple effectively and improve the speed precision and stabilization as well.