Robust stabilization of nonminimum phase nonlinear systems

The problem of robust stabilization for nonlinear systems with mismatched uncertainties is further studied by extending the results of Liao (1992) to the case where nonlinear systems either fail to have well-defined relative degree or have unstable zero dynamics. The approach is based on the approximate input/output linearization introduced by Hauser (1992) and an appropriate transformation introduced by Allgower (1997) which transforms the given nonlinear system into a special normal form. The proposed feedback controller guarantees that all the states will remain bounded