The servomechanism problem for unknown MIMO LTI positive systems: Feedforward and robust tuning regulators

In this paper we study the servomechanism problem for unknown MIMO positive LTI systems under constant reference signals and constant measurable disturbances. In particular, we show that in general the servomechanism problem for standard positive systems is not solvable. Thereafter, we show what subclass of reference and disturbance signals can be considered, and more importantly, we provide the controller structure that solves the problem for the feasible subclass of reference and disturbance signals.