Fault diagnosis and reconfiguration of systems using fuzzy logic: Application to a thermal plant

A fault evaluation and reconfiguration method using fuzzy logic is proposed. The motivation for this study is the desire to ensure good degraded performances for systems that cannot afford an immediate stop when failures occur as, for example, planes, the cooling circuit of nuclear plants and so on. In the case of actuator failures occurring in a plant, it is often possible to use remaining functional control elements to substitute the impaired actuators automatically (Morse and Ossman 1990). But, the degraded modes that are acceptable with regard to the required performances are supposed to be defined precisely. The proposed approach is based on the failure detection and isolation scheme combined with a control reconfiguration algorithm (FDIR). Once the failure is isolated, the control energy is redistributed among the remaining effective actuators. For illustration, the FDIR method is applied to a thermal plant. Some justifications of the importance of fuzzy logic in FDIR systems are given and the plant used for the simulation is presented. A description of the methods proposed for diagnosis and reconfiguration are given.