Approximate input-output linearization of nonminimum phase nonlinear systems

In this paper a novel method for the design of input-output linearizing feedback laws for nonlinear systems with unstable zero-dynamics is presented. The approach is based on a suitable stable/antistable factorization of the zero-dynamics and guarantees internal stability of the compensated system. In general an exact I/O-linearization of nonminimum phase systems will not be possible. If a nonlinear system does not permit an exact I/O-linearization with internal stability, then the method presented will allow to approximately linearize the I/O-behavior up to the maximally possible approximation order.