Stable adaptive controller design for uncertain phase shift

In order to construct stable adaptive control systems, several assumptions are needed, and those require some prior information of unknown plants, such as degrees and relative degrees. However, those assumptions sometimes become too restrictive, since it is difficult to obtain reasonable estimations of those indices a priori for unknown practical processes. This paper reviews the authors' research works where some of those assumptions can be relaxed partially. The basic concepts behind those and the restrictions of the present version are summarized, and the future possibilities of the proposed methodologies are also discussed.