Service diagnosis of dynamical systems based on local structural models

The paper presents a new approach to the selection of tests used in service diagnosis of dynamical systems. It proposes a method to select input signals that steer the system into a particular operating region and to find the corresponding local residuals for evaluating the system´s I/O behavior. The tests allow the isolation of faults that are generally not distinguishable, but become isolable under specific operation conditions. The method is based on the analysis of the structure graph, which represents the couplings among external and internal signals of the system and the possible faults. This graph changes if the system variables are restricted to different operating regions. Accordingly, the local structure of the system distinguishes from the global structure that holds for the unrestricted variables. By utilizing this difference, it is possible to determine tests that are sensitive to specific faults. The method is illustrated by its application to a throttle valve.