A minimal k-step delay controller for robust tracking of non-minimum phase systems

This paper considers the problem of robust tracking for a non-minimum phase system under a sensitivity constraint. Because of non-minimum phase zeros, the exact tracking of arbitrary reference input is impossible. However, with an introduction of some delay, tracking is possible within any given tolerance ε1>0. It is shown in the paper that the minimum delay required to satisfy the tracking performance is decoupled from the sensitivity constraint. Moreover, it is shown that calculation of the minimum delay is simply a binary search problem