Fault-tolerant PID controllers using a passive robust fault diagnosis approach

Automatic controlled systems are vulnerable to faults. Faults can be amplified by the closed loop control systems, and they can develop into malfunction of the loop. The closed loop may alternatively hide a fault from being observed until eventually developed to a state where loop failure is inevitable. A control loop failure will easily cause production stop or malfunction at a plant level. A way to obtain increased dependability in automated systems is to introduce fault-tolerant control. This is an emerging area in automatic control where several disciplines and theory areas are combined to obtain this functionality. Fault tolerance can be obtained employing fault detection and diagnosis on-line, getting a discrete event signal to a supervisor-agent when a fault is detected, and in turn activate accommodation actions. Copyright (C) 2000 IFAC.