A robust certainty equivalence controller for discrete-time nonlinear systems

This paper addresses the problem of determining H_∞ optimal output feedback controllers for a large class of partially observed nonlinear systems. With an eye toward digital implementation, the authors´ approach to implementing H_∞ output feedback controllers has emphasized issues like reasonable computational complexity, knowledge of observable quantities only, and implementability in finite time. Examples have been provided to investigate the robustness properties of the controllers we have developed. Through direct simulation, the authors have demonstrated that the controller has been observed to be locally stabilizing and robust to noise for systems with even a large degree of nonlinearity.