Observers design for nonlinear descriptor systems

In this paper the concept of asymptotic observers for autonomous nonlinear descriptor systems is introduced. The authors propose a method for obtaining general observers structure which satisfies the two basic requirements of state observers. Sufficient conditions for local asymptotic convergence of the error dynamics are established. In the second part of the paper study of reduced-order observers for a class of nonlinear descriptor systems is presented. The problem is formulated in terms of the generalised Sylvester equation which is resolved by means of an attractive technique. Conditions for existence and global stability of the obtained observer are given.