State of the art and future trends in position sensorless brushless DC motor/generator drives

Recent advances in the development of fast digital signal processors (DSPs) have paved the way for sensorless drive techniques of AC motors. The sophisticated sensorless algorithms in DSPs substitute for the mechanical position sensors and other hardware. This paper covers an entire range of topics related to the position sensorless control of brushless DC (BLDC) motor and generator drives including their fundamentals, limitations, present advances, and future trends. The main purpose of this paper is to provide an understanding of the various sensorless control methods and to promote creative thinking based on existing sensorless drive methods. Conventional techniques are reviewed and recent developments in this area are introduced with their inherent advantages and drawbacks. Anticipated research efforts and trends are also be discussed.