Robust Position Sensorless Technique for a PMBLDC Motor

The main objective of this paper is to present a new mechanical sensorless control technique of a permanent magnet brushless dc (PMBLDC) motor, which relies on the speed independent H functions. Two major challenges in the sensorless operation of PMBLDC motor drive are the starting the motor and driving it from a low speed to the rated speed. A speed independent H function is used to decide the commutation instant. Due to speed independence, the commutation instant is predicted even at low speed. The H function depends only on line voltages, which makes the overall system simple and cost effective. The proposed technique does not require any analog filter circuit or any phase compensation circuit. To eliminate the commutation ripple from the line voltages, digital low-pass filters and digital phase compensators are used. This makes the system compact, simple, and cost effective. This cost-effective solution proves perfect for low-cost appliances such as fan, air-conditioner, refrigerator, vacuum cleaner, and other home appliances. The proposed algorithm is implemented on a low-cost DSP (TMS320F28377S) to justify the effectiveness of the proposed sensorless technique for wide speed variation.