Identification of nonlinear plants using left coprime fractional based representations

It has been shown that the set of all nonlinear plants that can be stabilized by a known linear controller which also stabilizes a linear nominal model of the plant can be parametrized by a stable operator known as the Youla-Kucera parameter. This paper extends previous work by allowing the model of the nominal plant in the above scenario to be nonlinear, and hence explores the possibilities of converting the closed loop plant identification problem to one of open loop identification. The ideas rely on a concept of differential coprimeness for nonlinear fractional system descriptions.