3. Fault Diagnosis

In this chapter we describe first the basic fault monitoring tasks, such as fault detection, fault isolation, fault estimation and fault identification. The concepts of fault detectability and fault isolability are then introduced and characterized. Six “canonical” fault detection problems are formulated for the class of linear time-invariant systems with additive faults. The formulation of the exact and approximate synthesis problems are independent of any possible solution method and allow the derivation of general solvability conditions in terms of ranks of certain transfer function matrices. An important aspect to emphasize is that the formulations of approximate problems include, as particular cases, the formulations of exact problems. This chapter is concluded with a discussion of performance requirements for fault diagnosis systems and the selection of thresholds to be used for decision-making.