The Role of Exosystems in Output Regulation

In this technical note we study the role of the exosystem in the theory of output regulation for linear infinite-dimensional systems. The main result of this technical note shows that a stabilizing autonomous controller that achieves output tracking of an almost periodic reference signal is also capable of tracking any signal generated by a full exosystem. Moreover, given an almost periodic reference signal, we present a method for constructing a minimal exosystem generating this signal.