Observer design for descriptor systems

Two detectability notions are introduced for the mast general class of Line ar descriptor systems. Necessary and sufficient conditions are derived for the detectabilities and for the existence of observers. Depending on existe nce conditions satisfied, the observers can be either in the familiar Luenb erger form or in a generalized form, i.e,, in descriptor form as the origin al system itself is. A unified procedure is provided for the design of obse rvers in both forms.