Sensorless control of the BLDC motors from near-zero to full speed

This dissertation proposes a novel sensorless operation technique for the brushless DC (BLDC) motor. The proposed new sensorless drive method breaks through the chronic problems of the sensorless BLDC motor drives: lack of low speed operation and position error in transient state, so that it ensures highly accurate, robust sensorless operation from near-zero to full speed. For this purpose, a physically insightful, speed-independent function, based on a new flux linkage function, is used. A theoretical basis is first developed considering the electrical and magnetic aspects of the machine and control. Based on the theory, a simulation of the proposed sensorless method is performed, and the results discussed. Also, to verify the proposed method, an experimental test-bed is built and performance of the sensorless drive is tested. As a final step, the characteristics of the sensorless method such as accuracy and speed range are studied in detail, which is required in order to use the method in high performance applications.