FAULT-DIAGNOSIS AND RECONFIGURATION OF SYSTEMS USING FUZZY-LOGIC - APPLICATION TO A THERMAL PLANT

A fault evaluation and reconfiguration method using fuzzy logic is pro posed. The motivation for this study is the desire to ensure good degr aded performances for systems that cannot afford an immediate stop whe n failures occur as, for example, planes, the cooling circuit of nucle ar plants and so on. In the case of actuator failures occurring in a p lant, it is often possible to use remaining functional control element s 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 propo sed approach is based on the failure detection and isolation scheme co mbined with a control reconfiguration algorithm (FDIR). Once the failu re is isolated, the control energy is redistributed among the remainin g 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 pr esented. A description of the methods proposed for diagnosis and recon figuration are given.