Robust current control for brushless DC motors

The winding current exciting responses of brushless DC motors significantly affect their torque generating characteristics and hence the whole drive c ontrol performance. To obtain a quick and accurate current command tracking response, the application of control strategies for compensating the effec ts of key parameter variations is necessary. Robust control for achieving i mproved current response is studied. First, the model parameters for perfor ming the current control loop design are estimated. Then a novel current co ntrol scheme is proposed, which consists of a feedback controller, a comman d feedforward controller and a robust disturbance cancellation feedforward controller. The former two controllers are designed to fulfil the desired c urrent control characteristics at nominal case, and the robust controller i s employed to reduce the effects of back electromotive force and parameter variations. The theoretic basis and design of the proposed control scheme a re presented in detail. Through applying the designed current controller, t he winding current response is speeded up and thus the motor drawn line cur rent is decreased owing to the improved torque generating characteristics. The effectiveness of the proposed robust current control approach is demons trated by simulation and measured results.