Two-riccati H∞ controllers for descriptor systems

H^∞ formulae based on the 2-Riccati procedure are presented for plants in descriptor form. It is expected that this would lead to a method which is more numerically reliable method than those which currently exist for state-space realizations. The theory is developed first for the case where the E-matrix is nonsingular and the possibility of applying these formulae to cases where E is singular is discussed.