Fault detection: Different strategies for modelling applied to the three tank benchmark — A case study

In this contribution different modelling strategies for fault detection and isolation (FDI) in view of the model complexity are studied at the benchmark problem Three Tank System. The particularities of models needed for model-based FDI in contrast to models used in control are pointed out. Of special interest is the question of complexity. This depends basically on the given situation such as the kind of plant, the kind and number of faults to be detected, the demands for fault isolation and robustness and the measurements available. The paper shows for a certain process that diagnostic models for controllable and observable plants comprise only a partial description of the input/output model and are therefore less complex than those for control. This issue is discussed in terms of different model-based FDI approaches - analytical and data-based. The results are demonstrated in a case study, where several model-based FDI approaches are applied to the Three Tank System, which has been declared as a benchmark within the COSY project of the European Science Foundation (ESF).