Linear dynamic hidden by input-output linearization for square systems

Input-output linearization is one of the useful methods in the analysis and design of nonlinear systems. However, this method often hides part of the nonlinear system which is linearizable. The problem of uncovering linear subsystems from square multivariable systems is considered. The usual input-output linearization procedure yields a linear system of a certain dimension. A sufficient condition is proved for the existence of a larger linear subsystem, which can be found by feedback and coordinate changes