Realization problem of SISO nonlinear systems: A transfer function approach

This paper studies the nonlinear realization problem, i.e. the problem of finding an observable state space representation of a SISO nonlinear system described by an input-output differential equation, within an alternative polynomial approach. To find the solution the so-called adjoint polynomials and adjoint transfer functions are introduced for nonlinear systems. Thereby the clear connection to the solution known from linear systems is established.