Design of Causal Observers for Nonlinear Descriptor Systems

Abstract

This contribution not only provides a new necessary and sufficient condition for causal observability of nonlinear descriptor systems but also a method to design the causal observer. The approach is based on the transformation of the descriptor system into a state-space form, the so called coupled state-space system. This description exists for all regular descriptor systems no matter if they are proper or not. If the new condition is satisfied, the coupled state-space system can be modified and can be used to design a state-space observer. It is shown, that this observer is also a causal observer for the original descriptor system. Two examples illustrate the capability of the new approach.