HYFA

The aim of this project is:

Modern society depends strongly upon the availability and correct operation of complex technological systems (cars, planes, trains, etc.) and processes (water and energy distribution networks, chemical factories, ...). Due to the simultaneously increasing economic demands and the numerous ecological and safety restrictions to be met, high dependability of those systems and processes has become a dominant goal in the recent years. However, malfunctions can appear causing economic losses, damage to operators and machines, disturbance to the users, etc. Moreover, although automation using feedback controllers has avoided manual operation of systems and process, it has not immunized them against malfunctions. In a general sense, a fault2 is any change in the behaviour of a process/system component. Moreover, control loops can either amplify or hide faults avoiding to be observed until they cause the system/process failure.

One way to increase the reliability of a system/process is based on including fault tolerance mechanisms that will allow system/process operation, even after the appearance of the fault may be with a degraded performance. For this reason there is in the industry (especially in critical applications) an increasing need and interest in developing control system that can operate systems/process in faulty conditions in an acceptable way. This type of control systems are known as fault-tolerant controllers (FTC).

A fault can be viewed as a discrete event affecting the system by changing some of its particular properties (either the structure, the parameters, or both of them). Then, in turn, an active FTC should detect and isolate the fault and, if possible, estimate its magnitude (fault diagnosis) through the FDI module, and adapt the controller to the faulty situation such that the control objectives could be satisfied even in the fault presence (control re-design). A FTC system can be considered as an hybrid system if the discrete event nature of the fault occurrence and the controller re-design actions are taken into account, what makes not trivial its analysis and design. So far, the hybrid nature has been traditionally neglected in order to facilitate a simple design, reliable implementation, and systematic testing. Therefore, the analysis and design of fault-tolerant controllers require the use of techniques that are being developed for hybrid systems.

Another way to increase the system reliability is through the use of predictive maintenance. The purpose of predictive maintenance is to predict required schedules of maintenance by using sensitive measures of changes and faults in the system. The idea is to provide greater plant availability and economy, estimate the residual plant lifetime, calculate the accumulated wear (e.g. for mechanical/mechatronic systems) and detect incipient (hard to detect) faults. To achieve these goals, model-based fault diagnosis capable of dealing with incipient faults and reliability analysis methods will be used.

There are several reasons for using hybrid systems and methods on researching new methods for diagnosis, fault-tolerant control and predictive maintenance: