Compatibility of Observer to Variation of Plant Parameters

The compatibility of an observer to a plant is comprehensively discussed assuming that the plant changes its characteristics. The class of plants compatible to the given observer is characterized both in the case that the observer is used in the open-loop systems and in the case that it is used in the feedback systems as a regulator. It is shown that the observerr installed in the feedback systems is more robust than the one in the open-loop systems.