A Combined On-Line/Off-Line Framework for Black-Box Fault Diagnosis

We propose a framework for fault diagnosis that relies on a formal specification that links system behavior and faults. This specification is not intended to model system behavior, but only to capture relationships between properties of system behavior (defined separately) and the faults. In this paper we use a simple specification language: assertions written in propositional logic (possible extensions are also discussed). These assertions can be used together with a combined on-line/off-line diagnostic system to provide a symbolic diagnosis, as a propositional formula that represents which faults are known to be present or absent. Our framework guarantees monotonicity (more knowledge about properties implies more knowledge about faults) and allows to explicitly talk about diagnosability, implicit assumptions on behaviors or faults, and consistency of specifications. State-of-the-art diagnosis frameworks, in particular from the automotive domain, can be cast and generalized in