Fault detection and isolation

Fault detection and isolation, often grouped with recovery as FDIR, is a subfield of control engineering concerned with monitoring a system, noticing when a fault has occurred and pinpointing both the type of fault and where it is. Two broad approaches are described. One looks directly for patterns in sensor readings that indicate a fault. The other studies the discrepancy between the sensor readings and the values expected from a model of the system, and in that case a fault is usually declared detected when the discrepancy, called the residual, rises above a chosen threshold. Fault isolation is then the task of classifying the kind of fault and locating it in the machinery. The techniques are commonly sorted into two categories, model-based methods and methods based on signal processing, and the subject is applied wherever equipment must keep running or fail safely under automatic supervision.