Dynamic output feedback control of nimimum-phase nonlinear processes

This paper concerns the synthesis of dynamic output feedback controllers for minimum-phase nonlinear processes. The problem is addressed first for open-loop stable and then for general minimum-phase nonlinear processes, leading to one- and two-degree-of-freedom controllers, respectively. The synthesis of the controllers essentially involves combination of state feedback and state observers. An input/output interpretation of the resulting control structures illustrates the importance of alternative state-space realizations of the process inverse for the controller implementation. Internal stability conditions are derived for the closed-loop system. Simulation studies in a chemical reactor example illustrate the application of the control methodology developed.