Phase back EMF space vector oriented control of brushless DC motor for torque ripple minimization

Abstract

As the back-EMF of the BLDCM is not sinusoidal, the change of back EMF in time axis dose not synchronize with the rotor position, and it's more difficulty to convert the back-EMF from time axis to space axis. This paper starts from the non-sinusoidal change law of the back-EMF of the BLDCM, and introduces the back-EMF space vector, then obtains the armature current space vector based on the equivalent principle of torque, then gains the conclusion that electromagnetic torque is direct proportion to the q axis component of the resultant current vector by normalization processing for the back-EMF space vector. So the electromagnetic torque can be controlled by the q axis component of the resultant current vector. In addition, considering that the BLDCM usually adopts half-bridge modulation method, so this paper also chooses the half-bridge modulation method which has the upcoming and outgoing phase to PWM chopper control in each sector, and realizes the decoupling control of the duty cycles of the upcoming and outgoing phase. Finally, simulations by Matlab and experiments with DSP are presented to verify the feasibility and effectiveness of the proposed strategy.