Output regulation of discrete-time systems with time-varying delays

In this paper the output regulation problem for discrete-time linear systems with time-varying delays is considered. Solvability of the above problem is completely characterized in structural geometric terms and a sufficient condition that can be practically checked, together with a procedure to construct solutions, if any exists, is given. The basic method used to analyze the considered problem consists in representing the discrete-time linear systems with time-varying delays as switching linear systems, whose properties can be studied by a powerful structural approach. In this way, the considered problem can be reduced to the corresponding problem for switched linear systems, whose solvability has been recently characterized.