Modelling for fault detection and isolation versus modelling for control

The goal of this paper is to emphasize both the particularities of models n eeded for model-based fault detection and isolation (FDI) and the differenc es with respect to the models used in control. Of special interest is the q uestion of complexity. This depends basically on the given situation such a s the kind of plant, the kind and number of faults to be detected, the dema nds for fault isolation, robustness and the measurements available. However , in contrast to the wide-spread opinion that models for FDI have always to be more complex than those for control, the paper shows that diagnostic mo dels for controllable and observable plants comprise only a partial descrip tion of the input/output model and are therefore less complex than those fo r control. This issue is discussed in terms of different model-based FDI ap proaches - analytical, data- and knowledge-based. As for the analytical app roaches the necessary order of the diagnostic model is that of the transfer operator from the fault vector to the system output. (C) 2000 IMACS. Publi shed by Elsevier Science B.V. All rights reserved.