Robust H^∞ control of an uncertain system via a stable output feedback controller

This technical note presents a new approach to the robust control of an uncertain system via a stable output feedback controller. The uncertain systems under consideration contain structured uncertainty described by integral quadratic constraints. The controller is designed to achieve absolute stabilization with a specified level of disturbance attenuation. The main result involves solving a state feedback version of the problem by solving an algebraic Riccati equation dependent on a set of scaling parameters. Then two further algebraic Riccati equations are solved, which depend on a further set of scaling parameters.