Bounded Robust Control of Constrained Multivariable Systems

This work focuses on output feedback control of a class of multi-input multi-output nonlinear systems with timevarying uncertain variables and input constraints. A robust dynamic output feedback controller is constructed through combination of a stabilizing bounded robust multivariable state feedback controller with high-gain observers and saturation filters. The state feedback component is designed through Lyapunov-based inverse optimal control techniques and provides an explicit characterization of the state feedback stability region. Using singular perturbation techniques, the output feedback controller is shown to enforce asymptotic stability and robust asymptotic referenceinput tracking, with an arbitrary degree of attenuation of the effect of uncertainty on the outputs of the constrained closed-loop system, for initial conditions in arbitrarily large compact subsets of the state feedback stability region, provided that the observer gains are sufficiently large. The proposed output feedback controller design is demonstrated for the robust stabilization of a chemical reactor example.