A sensorless direct speed control for brushless DC motor drives

This paper presents the groundwork for a novel concept of sensorless direct speed control (SDSC) in brushless DC (BLDC) motor drives. Unlike the conventional sensorless speed controls, the proposed strategy does not need proportional plus integral (PI) regulators. Thus feedback mechanism is minimized. Speed regulation is achieved by controlling rotational speed of stator flux linkage. The PI regulator is replaced with a simple comparator. The BLDC motor is excited based on a look-up table. This proposal is applicable to both two-phase and three-phase conduction modes of the BLDC motors. In this paper, principles of the proposed sensorless strategy and speed ripple calculation are described in details. The validity of this claim is verified through the simulation results.