| Development of advanced electric motor drives has yielded increases in efficiency and reliability. Residential and commercial appliances such as refrigerators and air conditioning systems use conventional motor drive technology. The machines found in these appliances are single phase induction or brushed DC machines which are characterized by low efficiency and high maintenance, respectively. A brush-less DC (BLDC) motor drive (an advanced motor drive system) is characterized by higher efficiency, lower maintenance, and higher cost.; In a market driven by profit margins, the appliance industry is reluctant to replace the conventional motor drives with the advanced motor drives due to their higher cost. In this Ph.D. proposal, a new digital control concept will be introduced for BLDC motor drives. The new digital controller treats the motor like a digital system that may only operate at a few predefined states. Those states establish machine operating conditions which produce distinct constant motor speeds. Speed regulation is achieved by alternating states during operation, which makes the concept of the controller extremely simple for integrated-circuit (IC) development.; A design methodology for this controller, applicable to any BLDC machine, is presented. The design procedure is derived from Newton's 2nd Law and the characteristic equations of a BLDC machine. The design procedure takes into account the acceptable output speed ripple. Also, is demonstrated that through the use of an observer, disturbance rejection is achieved. Computer simulation results are presented along with experimental proof-of-concept. |
