Robust Reduced-order Output-feedback H∞ Control

The problem of robust H∞ reduced-order control design for linear systems in presence of polytopic type uncertainties is addressed. The controller is obtained by transforming the problem into a robust static output-feedback control design problem. Applying a recent method for solving the latter by means of linear matrix inequalities, a sufficient condition is obtained for the existence of a solution to the problem. A simple method for deriving the reduced-order controller is given in the case where the latter condition is satisfied.