Model-based, multiple fault diagnosis of time-varying, continuous physical devices

A model-based approach to diagnosing time-varying continuous physical devices is presented. It is capable of detecting multiple faults. The diagnosis algorithm represents an extension of R. Reiter´s (Artificial Intelligence, vol.32, p.57-95, 1987) algorithm to handle physical devices whose behavior varies continuously over time. The continuously changing states of a physical device are modeled by a discrete set of qualitative simulation (QSIM) states over time and its behavior is governed by a set of QSIM constraints. A prototype system that correctly diagnosed a double fault present in a proportional-control heater/cooler has been developed. The feasibility of extending Reiter´s algorithm to diagnose these physical devices is demonstrated