Fault detection and diagnosis in aerospace systems using analytical redundancy

Performance requirements in aeronautics and the rapid growth of electronics, especially of digital computers, have gradually led to the combination of advanced control theories and fly-by-wire technology. This has resulted in designs for which the control systems are flight critical. The required reliability is usually achieved by a multiplication of sensors, computers and actuators accompanied by a voting system. The on-board computer provides the possibility of replacing the sensor hardware replication, which is very expensive, with a management of the functional or analytical redundancy constituted by the knowledge of the system. Different techniques have been proposed; the aim of this article is to outline an review the state of the art and describe some of the studies of analytical methods of fault diagnosis procedures, based on fault monitoring in aircraft and spacecraft sensor systems