A low cost position sensorless brushless DC motor drive

A low cost position sensorless brushless DC motor drive is presented in this paper. The motor starts with simple align and go methodology, to a speed where a traditional sensorless algorithm based on winding back EMF, detects accurate commutation instants and then filtered line to line back EMF crossings are utilized to find the rotor position. The speed and current are controlled with variable structure sliding mode control. The drive uses a low cost microcontroller and only one current sensor, which makes it a cost effective drive. The performance of the presented drive is proved by simulation and experimentally on low cost high performance DSP microcontroller. The presented control drive is useful for developing low cost commercial and domestic applications.