Inner-outer factorization for nonlinear noninvertible systems

This paper considers inner-outer factorization of asymptotically stable nonlinear state space systems in continuous time that are noninvertible. Our approach will be via a nonlinear analogue of spectral factorization which concentrates on first finding the outer factor instead of the inner factor. An application of the main result to control of nonminimum phase nonlinear systems is indicated.