Abstract
In this paper, adaptive observers for a single-input, single-output linear unknown plant are considered. It is shown that the observers can be classified into six types according to the stability condition and the structure of the observer. A unified design method of the six types of adaptive observers is described after the preliminary lemmas, which are necessary in the design, are presented. The adaptive observers which have been reported in the articles fall into the four types in the above classification. The remaining two types are newly given in this paper as a result of the unified approach. The characteristics of these observes are summarized and the numerical simulation is given.
