Direct instantaneous force control: A method to eliminate mode-0-borne noise in switched reluctance machines

Switched reluctance machines (SRM) are widely accepted to be a cost-efficient alternative to rotating field machines for various applications. However, besides potential torque ripple mainly loud acoustic noise often makes industry go the conventional way. Vibration mode 0 can often be the most prominent noise source in larger sized SRM applications as for electric vehicles. This paper presents a control strategy to reduce this particular vibration mode. Because mode 0 is excited by all phases together the direct instantaneous torque control approach has been modified to regulate the phases' radial forces to achieve smooth overall radial force. It was found that it is possible to reduce mode 0 excitation effectively compared to standard control strategies such as, for instance, current hysteresis control. Controlling radial force smoothly can come along with mentionable torque ripple. Although, some operating points showed that further improvements on the employed force sharing algorithm can potentially extend the operating region which is characterized by both: smooth overall force and torque. Simulations prove that mode 0 vibration can be reduced or even be eliminated by means of control, leaving only the other occurring vibration modes to be attenuated (e.g. by machine design or notch-filtering the force reference) to develop a low noise switched reluctance drive.