CIRCUITS SYSTEMS AND SIGNAL PROCESSING, vol.11, no.3, pp.421-430, 1992 (SCI-Expanded)
Concepts of observability and strong observability for singular systems are introduced and characterized geometrically in terms of the system matrices without using the Weierstrass decomposition. Duality relations between observability and controllability and that between reachability and strong observability are established. A canonical form for the action of the output injection group on the set of observable systems is presented.