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

Automatic controlled systems are susceptible to faults. Faults can be amplified by closed loop control systems, and they can cause a malfunction of the loop. The closed loop may alternatively hide a fault from being observed until the plant eventually reaches a state in which loop failure is inevitable. A control loop failure can easily cause production stoppage or malfunction at the plant level. One way of obtaining increased reliability in automated systems is to introduce fault-tolerant control. This is an emerging area in automatic control in which several disciplines and theoretical areas are combined to achieve this function. Fault tolerance can be obtained by employing fault detection and on-line diagnosis, and sending a discrete event signal when a fault is detected to a supervisor-agent, who in turn activates accommodation actions. (C) 2001 Elsevier Science Ltd. All rights reserved.