Global Exponential Observers for Two Classes of Nonlinear Systems
  This paper develops sufficient conditions for the existence of global exponential observers for two classes of nonlinear systems: (i) the class of systems with a globally asymptotically stable compact set, and (ii) the class of systems that evolve on an open set. In the first class, the derived continuous-time observer also leads to the construction of a robust global sampled-data exponential observer, under additional conditions. Two illustrative examples of applications of the general results are presented, one is a system with monotone nonlinearities and the other is the chemostat system. 
Iasson Karafyllis and Costas Kravaris
math.OC cs.SY