Sensorless control of brushless DC motor for low speed aerospace applications

The rotor position in a brushless DC motor can be acquired by means of sensors, like hall sensor or by using sensorless control algorithms. The conventional method in aerospace applications is sensor based where hall sensors are used to obtain the rotor position. Sensorless control methods have the advantage of better reliability, reduced space requirements and weight. In this paper, a sensorless control method utilizing a speed independent function is presented. Using this method, speed control can be done in wide speed range, including the low speed range. The control circuitry is simple and robust as motor parameters are not used in developing the control algorithm. Simulation results are obtained for a permanent magnet BLDC motor which validate the performance of the sensorless control algorithm at a low speed of 100rpm.