Global Robust Control Design of Nonlinearly-Bounded Interconnected Systems

This paper presents a novel approach to a new problem of global stabilization with L2 disturbance attenuation and local matching for a class of uncertain nonlinear systems. An innovative concept of state-dependent scaling is developed to deal with interconnection of nonlinear-gain bounded dynamic systems which unnecessarily have finite linear-gain. The state-dependent scaling approach is not only a natural extension of robust linear H∞ control, but also the approach offers flexibility to render the nonlinear controller identical with the linear control at the equilibrium. The effect of the disturbance on the controlled output can be attenuated to an arbitrarily small level with global asymptotic stability by partial-state feedback control if the nonlinear system belongs to a generalized class of interconnected strict-feedback systems. A procedure of designing such partial-state feedback controllers is described in the form of recursive selection of state-dependent scaling factors