Properties of algebraic Riccati inequalities and H/sub infinity / robust sub-optimal controller design

Properties of the solutions of ARI (algebraic Riccati inequality), which appear in H/sup infinity / control theory, are studied. Positive matrix solutions of a set of ARI with perturbations in coefficient matrices are examined, and necessary and sufficient conditions for the existence are given in terms of nominal coefficient matrices. Using these properties, an H/sup infinity / robust sub-optimal controller design is given for a plant with uncertainties in the system, control input, and disturbance input matrices.<<ETX>>