Actuator fault-tolerant control design: demonstration on a three-tank-system

Fault-tolerant control or reconfigurable control systems are generally based on a nominal control law associated with a fault detection and isolation module. A general review of techniques dealing with this problem is given and a new fault-tolerant control approach is presented. This method is based on the on-line estimation of an eventual fault and the addition of a new control law to the nominal control law in order to reduce the fault effect once this fault is detected and isolated. The performances of this method depend on the time delay between the occurrence of the fault and its detection and isolation. A modified approach is then proposed in order to avoid the problems generated by delays, false alarms or non-detection inherent to diagnosis techniques. These methods are applied to a pilot plant and their performances are compared and discussed.