Sensitivity and robustness properties in the preview control of linear non-minimum phase plants

Non-minimum phase zeros emit the achievable performance and robustness of a feedback control loop. These limitations can be expressed as an upper limit on the bandwidth that may be achieved without necessarily incurring a large peak in closed loop sensitivity. In the case of preview control, it is known that advance (or anti-causal) knowledge of the reference to be tracked permits accurate, rapid tracking over bandwidths which exceed the normal performance limits. The first aim of this paper is to explain this apparent paradox. In addition, we briefly discuss sensitivity and robustness issues for preview control systems