Cooperative observers for nonlinear systems

A new methodology to design preserving order observers for a class of nonlinear systems, in absence and in presence of perturbations, is proposed. The preserving order observers are those whose estimates always stay above or below the true trajectory of the state. The design methodology combines two important systemic properties: dissipativity and cooperativity. The first is used to assure the convergence of the estimation error dynamics. Cooperativity is the basic property of the error dynamics in order to assure the order preserving properties of the observer. The design of these observers can be reduced, in most cases, to linear matrix inequalities (LMI).