The Research Of Torque Ripple Restraining Of BLDCM

BLDCM has many advantages such as high efficiency and good speed regulating performance. It is widely used in motion control. The control technology of BLDCM is now relatively mature. However, it is a hot trend to restrain torque ripple of BLDCM and improve stability and dynamic response to achieve high performance control of the system.In this paper, plenty of domestic and international literatures are checked. The characteristics, working principles and mathematic models of BLDCM are analyzed. The main causes and suppression of torque ripple are discussed. Torque ripple caused by current commutation is mathematically deducted. Through the exported equation between torque ripple and related parameters, four typical PWM modulation methods that effect on torque ripple during commutation period are analyzed. Torque ripple during commutation period is analyzed starting from hardware circuit, which shows PWM commutating will cause torque ripple during commutation period due to freewheel current of silent phase. This situation will also emerge during non-commutation period.BUCK converter is set as an example to explain how to restrain torque ripple by power transformation technology. Through analysis compared to PWM modulation methods, we can draw a conclusion that torque ripple during commutation period due to freewheel current of silent phase is inevitable. However, torque ripple caused by voltage or current fluctuation can be controlled by BUCK converter.Four typical PWM methods are validated by experiment with the help of program. The result indicates that PWM_ON modulation method achieves good effect in restraining commutation torque ripple, which is in accordance with the theoretical prediction.Based on BUCK converter, hardware and software design of the control system combing with Fuzzy-PID algorithm are finished and experimentally tested. Experimental results show that this control method which combines BUCK converter with Fuzzy-PID algorithm can effectively reduce the torque ripple during commutation and non-commutation period.