Perfect tracking control based on multirate feedforward control and applications to motion control and power electronics-a simple solution via transfer function approach

In this paper, a novel perfect tracking control method based on multirate feedforward control is proposed. The advantages of the proposed method are: (1) the proposed multirate feedforward controller eliminates the notorious unstable zero problem in designing the discrete-time inverse system; (2) the plant states track the desired trajectories with zero error at every sampling point of reference input; and (3) the feedback characteristics are completely independent of the proposed controller. Thus, highly robust performance is assured by the robust feedback controller. Moreover, the proposed design method via transfer function approach is much simpler than that of the state space approach which was previously presented by authors. Illustrative examples of position control using servomotor, hard disk drive, and voltage control of an inverter are presented, and simulations and experiments demonstrate the advantages of this approach.