The T-S fuzzy model is considered to be able to approximate nonlinear systems due to its precise approximation ability [1–4], which prompts the study of T-S fuzzy systems in this book. The filtering problems of T-S fuzzy systems have been studied in Chaps.  3 – 5 . In Chap.  6 and this chapter, the design of event-triggered fault detection observers for T-S fuzzy systems has also been discussed, and the corresponding fault detection methods in Refs. [5–11] were introduced. For example, a switching mechanism in Ref. [8] was introduced for designing fault detection filters for T-S fuzzy systems with unknown membership functions. In Refs. [9, 10], the fault detection filters were constructed to detect faults for discrete-time affine T-S fuzzy systems and T-S fuzzy systems, respectively. In Ref. [11], the problem of fault detection for interval type-2 fuzzy systems with event-triggered mechanism was investigated, in which the asynchronous problem of the premise variables caused by the introduction of event-triggered mechanism is addressed.