Torque Ripple Minimization of BLDC Motor with un-ideal Back EMF

This paper proposes a method of minimization of torque ripple of brushless dc (BLDC) motors, with un-ideal back EMF under MATLAB 7.1/Simulink environment. An idealized BLDC motor has trapezoidal back EMF waveform. However, for practical reasons like non-uniformity of magnetic material and design trade-off it is hard to produce desired trapezoidal wave shape. Therefore torque ripple appears in conventional control. In this paper, the duty cycle of the pulses is calculated in the torque controller in both normal conduction period and commutation period and in combination with a given commutation sequence fed to the inverter gates so as to minimize ripple. Moreover, the influence of finite dc supply voltage is considered in commutation period. Simulation results show that compared with conventional control, this method results apparent reduction of torque ripple.