Automatic tuning technique for low speed position sensorless method based on block commutation drive

A block commutation based position sensorless method for the low speed regions has previously been reported [8-10]. This method introduces "Induced Voltage caused by Magnetic Saturation (IVMS)". The IVMS is detected in the open phase of a Permanent Magnet Synchronous Motor (PMSM) driven by the block commutation. The commutating phases in this method are switched in accordance with the detected IVMS in the open phase. The detected IVMS is compared with the threshold voltage that was adjusted in advance. When the IVMS corresponds to the threshold voltage, the commutating phase is switched to the next phase. Therefore, the threshold voltages for the IVMS need to be correctly adjusted. However, several factors are involved in changing the threshold voltages, such as the motor characteristics, carrier frequency, and detection circuit. An automatic tuning technique for the threshold voltages of the IVMS-based position sensorless method is proposed in this paper. The principle for it and the experimental results are also presented.