Memoryless output feedback nullification and canonical forms, for time varying systems

We study the possibility of nullifying time-varying systems with memoryless output feedback. The systems we examine are discrete-time linear single-input single-output finite-dimensional time-varying systems. For generic completely controllable and completely observable discrete-time systems, we show that any state at any time can be steered to the origin within finite time. An algorithm for nullification and an upper bound for nullification time, depending only on the system's dimension, are provided. The algorithm is described using a representation of the system in time-varying controller canonical form. We verify that every completely controllable system has such a representation.