On the integration of actuator fault detection and isolation in model based fault diagnosis

The main goal of the Fault Detection and Isolation (FDI) is to effectively detect faults and accurately isolate them to a failed component in the shortest time possible. This capability leads to reduction in diagnostic time, therefore, increased the system availability. Also, a good inherent diagnostic of a system enhances the operating system confidence. This paper proposes a new formulation of the linear system to obtain the conditions of the actuator fault detection and isolation. We consider the actuator as a dynamic subsystem connected with the process subystem in a cascade manner and we look for the fault detectability and isolability problems. An example illustrates the performances of such interval observer approach for simple actuator fault diagnosis. In fact two mathematical models are given: a simple model for the actuator subsystem and a continuous time state-space description for the process subsystem of a speed governor for large diesel engines.