Current Profile Function Strategy for a Brushless DC Motor With Torque Closed-loop Control

Introduction: Brushless DC motor (BLDCM) has the advantages of high-power density and is easy to control. However, large torque ripples are generated during the current commutation process, which affects the stable and reliable operation of the motor. The existing control strategies do not fully utilize the torque output of each phase and require a large current change rate during commutation, decreasing the torque-ampere ratio and increasing the torque ripple. Methods: To address this issue, a torque ripple reduction strategy based on the current profile function is proposed for BLDCM in this paper. Firstly, the factors of torque ripple by utilizing the traditional control strategy of BLDCM are analyzed. Then, according to the torque characteristics of BLDCM, the current profile function is proposed to suppress the torque ripple combined with the torque closed-loop control. Finally, the effect of the non-commutation overlap angle on the control strategy is analyzed to optimize the overlap angle. Results: The torque ripple of BLDCM can be reduced by the torque closed-loop control strategy based on the current profile function. Discussion: The proposed strategy can change the shape of the phase current to reduce the required rate of current change for suppressing torque ripple, and fully utilize the torque output of each phase to improve the torque-ampere ratio. The proposed control strategy provides an effective strategy for high torque-ampere ratio and low torque ripple operation of BLDCM. Conclusion: The simulation results verify that the proposed method can effectively suppress the torque ripple and improve the torque-ampere ratio.