Contents I. Introduction
Over the past decades, the development on fault-detection (FD) and fault-tolerant control approaches for complex nonlinear dynamic processes has attracted considerable attention from the application and research areas [1]–[4]. Among various FD studies, significant research effort has been made to the application of the well-established observer theory to deal with nonlinear FD issues [5]–[7]. For instance, sliding-mode observer-based FD [8], adaptive observer-based FD [9], [10], diagnostic observer-based FD [11], [12], and fuzzy technique based FD [13] have been reported in the literature. In general, an integrated nonlinear observer-based FD system is composed by a nonlinear observer-based residual generator, a residual evaluator and a decision making unit including a threshold. Fault in complex systems could lead to hazardous consequences in both economic damage and physical security issues. This motivates the investigations on real-time process monitoring and FD schemes so as to detect and remove potential fault in the early stage [14], [15].
