A comparison of IFD schemes: a decision aid for designers

This contribution deals with output-estimator based structures to solve the robust-fault-detection-and-isolation problem (RFDIP). These estimator schemes use analytical redundancy to generate and evaluate residuals. The residuals have to be robust against internal inaccuracies and decoupled from external disturbances (unknown inputs) to allow a unique detection of a malfunction and isolation of a faulty actuator, component or sensor. For the case of instrument fault detection and isolation (IFD), seven groups of estimator schemes will be described and analysed regarding their structure, function and application limits. The analysis is a basis for the proposed method that allows to compare the schemes and to select the most convenient scheme for solving the RFDIP. The proposed method serves as a decision aid to the designer. The results will be presented in a list and a table where the application of this table will be exemplified