Research of Control Strategy at Lower Speed on the Direct Self-Control of Brushless DC Motor

The control strategy which the direct self-control was proposed to brushless DC motor system achieved the high performance with its simple structure and the torque control was the center. However, at lower speed, the distortion of stator flux-linkage waveform made the operating performance of brushless DC motor lower as the impact of stator resistance voltage drop. Thus, a new approach was brought forward that three motion voltage vectors and two zero voltage vectors were used in every 60 degree sector to the coordination control of flux-linkage and torque in order to improve low-speed performance of brushless DC motor. Finally, the experiment was carried out to validate the theory and improve the performance at lower speed.