H∞ observers design for a class of discrete time nonlinear singular systems

In this paper the H_∞ observers design problem for a class of discrete time Lipschitz nonlinear singular systems is considered. The approach is based on the parameterization of the obtained algebraic constraints from the estimation errors. Sufficient conditions for the existence of the observers which guarantee stability and the worst case observers error energy over all bounded energy disturbances is minimized are given. The method also unifies the design for the full-order, reduced-order, minimal-order observers for discrete time systems. Application to standard systems with unknown input is presented via a numerical example.