Control of non-minimum-phase nonlinear systems through constrained input-output linearization

This paper presents a novel control method that provides optimal output-regulation with guaranteed closed-loop asymptotic stability within an assessable domain of attraction. The closed-loop stability is ensured by requiring state variables to satisfy a hard, second-order Lyapunov constraint. Whenever input-output linearization alone cannot ensure asymptotic closed-loop stability, the closed-loop system evolves while being at the hard constraint. Once the closed-loop system enters a state-space region in which input-output linearization can ensure asymptotic stability, the hard constraint becomes inactive. Consequently, the nonlinear control method is applicable to stable and unstable processes, whether non-minimum- or minimum-phase. The control method is implemented on a chemical reactor with multiple steady states, to show its application and performance