Diagnosis

The basic motivation for this thesis is the fact that things go wrong. With the grow-ing complexity of todays engineering systems, the need has arisen for systematic approaches to failure diagnosis, i.e., fault detection and isolation. In the rst part of this thesis an approach for modeling and diagnosis of systems that fall in the area of discrete event dynamic systems is proposed. The approach is applicable to systems that at some level of abstraction have an interesting discrete event dynamics that can display faulty behavior. The systems suitable for this approach typically consist of several interacting components where abrupt, but non-catastrophic, faults can occur in the components. We use a relational framework for discrete event dynamic systems focusing on a conceptually simple representation of the relationship between inputs, outputs and states of a discrete event system. Faults and faulty behavior are modeled locally using the state variables, and the diagnosis problem basically is to infer the possible states of the system using the system model and observations of the real system