“…Up to date, considerable research attention has been devoted to the theoretical research on the fault estimation problem, and a great number of fault estimation approaches have been proposed in existing literature, see e.g. [6,[11][12][13]15,17,19,27,30] and the references therein. For example, in [11,12,19,29], the problems of fault estimation have been investigated by applying adaptive fault diagnosis observers that can improve the rapidity of fault estimation.…”