Semi-global robust stabilization of MIMO nonlinear systems by partial state and dynamic output feedback

We study the problem of semi-global robust stabilization for a class of multi-input multi-output (MIMO) uncertain nonlinear systems which cannot be transformed, via a change of coordinates and a state feedback, into a lower dimensional zero dynamics driven by a set of chains of integrators, but more complicated interconnected structures. The systems considered here, which distinguish from those studied early in the literature, possess a new feature that they are non-affine in the control inputs. Sufficient conditions are presented for the existence of a linear high-gain partial state controller and/or a nonlinear dynamic output compensator, achieving robust semi-global asymptotic stability. Both the partial state and output dynamic controllers are also explicitly constructed. (C) 2001 Elsevier Science Ltd. All rights reserved.