Study On Torque Ripple Suppression Technique Of Brushless DC Motor

Brushless DC motor is widely used in many areas due to its electroniccommutation. It possesses characters like uncomplicated structure, high powerdensity, good performance in starting and speed adjustment, which overcome thedisadvantage of sparking generated by traditional DC motor. Because of motorstructure and control methods, brushless DC motor is likely to produce torqueripples, which yields vibration and noise, degenerates robustness and lifetime, andconstrains its application and promotion in many aspects.In this paper, we first introduced development and application of brushless DCmotor, then described about jeopardy of torque ripple of brushless DC motor andsome current research in restraining torque ripple. And we analyzed inevitability oftorque ripple of brushless DC motor by modeling and simulation of motor.We then analyzed causes of torque ripple from aspects, together withrespective solutions. Torque ripple introduced by cogging torque ripple andnon-ideal back-EMF is caused by motor’s self structure, so solutions for that arebased on optimization of motor design. On the other hand, commutation is causedby sudden change of inductance impeding current， this is a inherent problem of theway that brushless DC motor applies120°conduction mode, which can only besolved by optimizing control strategy.Finally, after comprehensive consideration of all possible schemes, weproposed Direct Torque Control applied on brushless DC motor. Direct TorqueControl is an advanced control strategy which examines torque ripple problem byregarding motor as a whole. It can improve torque ripple and system function atmean time. In this paper, we simulate the system and demonstrate that DirectTorque Control is able to be applied on brushless DC motor，and optimization onmotor function and torque ripple condition is well achieved.