On Existence of Non-stationary Realization of a Linear Multivariable Control System

We define the main conception for the methodology, which forms the basis of the procedures for constructing abstract Kalman-Mesarovic realization of a dynamic system with state equations that belong to the class of linear non-stationary differential equations. From this viewpoint, the authors interpreted the key approaches to solving classical problems of realization theory in terms of the Rayleigh-Ritz operator.