An unappealing characteristic of all real-world systems is the fact that
they are vulnerable to faults, malfunctions and, more generally,
unexpected modes of - haviour. This explains why there is a continuous
need for reliable and universal monitoring systems based on suitable and
e?ective fault diagnosis strategies. This is especially true for
engineering systems, whose complexity is permanently growing due to the
inevitable development of modern industry as well as the information and
communication technology revolution. Indeed, the design and operation of
engineering systems require an increased attention with respect to
availability, reliability, safety and fault tolerance. Thus, it is
natural that fault diagnosis plays a fundamental role in modern control
theory and practice. This is re?ected in plenty of papers on fault
diagnosis in many control-oriented c- ferencesand journals.Indeed, a
largeamount of knowledgeon model basedfault diagnosis has been
accumulated through scienti?c literature since the beginning of the
1970s. As a result, a wide spectrum of fault diagnosis techniques have
been developed. A major category of fault diagnosis techniques is the
model based one, where an analytical model of the plant to be monitored
is assumed to be available