Nonsquare spectral factorization for nonlinear control systems

Abstract

Abstract-This paper considers nonsquare spectral factorization of nonlinear input affine state space systems in continuous time. More specifically, we obtain a parametrization of nonsquare spectral factors in terms of invariant Lagrangian submanifolds and associated solutions of Hamilton-Jacobi inequalities. This inequality is a nonlinear analogue of the bounded real lemma and the control algebraic Riccati inequality. By way of an application, we discuss an alternative characterization of minimum and maximum phase spectral factors and introduce the notion of a rigid nonlinear system. Index Terms-Hamilton-Jacobi inequalities, invariant Lagrangian manifolds, nonlinear nonsquare spectral factors.