Control of PMBLDC motor using back EMF sensing with adaptive filtering

This paper presents a significant improvement in sensorless control technique for a PMBLDC motor drive to enable the drive to work satisfactorily over a wide range of speed. The filters used in conventional techniques for filtering the back EMF obtained from the motor are designed for a particular speed having a particular value of time constant. Adaptive filtering technique is proposed in this paper; the filter characteristics are changed in real-time according to speed hence making the firing signal generation error-free for the devices in the converter feeding the PMBLDC drive. Further, the back EMF obtained is obtained from line voltage differences and hence it eliminates the requirement for a virtual neutral.