Perfect decoupling in nonminimum-phase multivariable systems: a complete geometric framework

This paper deals with exact decoupling of external signals known with preview. Necessary and sufficient geometric conditions are provided both in the case where the preview is finite and in the case where preview is infinite. The overall control structure turns out to be a two-degree-of-freedom controller, where a dynamic feedforward unit achieves exact decoupling of the previewed external input, while an output dynamic feedback unit prestabilizes the plant. The design procedure for the dynamic feedforward compensator is thoroughly illustrated: the precompensator is completely devised in the geometric approach context by exploiting steering along zeros techniques