Research on a Novel Close-loop Speed Control Technique of Brushless DC Motor

To reduce the low precision of speed feedback of brushless DC motor (BLDCM) used three-phase position signal, a new speed control strategy of BLDCM is proposed. A cascade DC-DC with full-bridge circuit is introduced, and motor close-loop speed control is achieved by control output voltage of buck circuit and with motor phase current positive feedback compensation. In addition, the reasons for output voltage ripple are analyzed. The control strategy introduces the idea of phase current prediction to reduce the voltage ripples during commutation interval. The current during commutation interval is predicted and the given current is adjusted, accordingly. Experiment results prove that using output voltage feedback and phase current positive feedback can realize close-loop speed control of BLDCM, and the ripple of output voltage can be eliminated by phase current predictive control technique during commutation interval.