Position servo control of brushless DC motor based on the second discrete filter

A novel position servo controller for brushless DC motor is designed based on the improved second discrete smooth trajectory filter. The output of the filter is suitable for the feed-forward control for the servo system, especially for the second order system, which guarantees minimum time response and smooth trajectory tracking. Based on the second order model of Brushless DC motor, the cascade servo control of the brushless DC motor is implemented upon the second discrete filter algorithm. The outer-loop of the whole control system is realized by the second discrete filter, and the inner-loop is the traditional PI current controller. It has the integrative merits of the linear and nonlinear control methods. Moreover, a load torque observer is advanced to enhance the anti-disturb ability of the servo system when the brushless DC motor running with motor parameters change and/or external load variation. The proposed control method can obtain the excellent position tracking performance as well as the good speed response ability. Simulation and experiment results have verified the validity and effectiveness of this control scheme.