Michael Ungermann

Test signal generation for service diagnosis based on local structural properties

Test signal generation for service diagnosis based on local structural properties The paper presents a new approach to the generation of test signals used in service diagnosis. The tests make it possible to isolate faults, which are isolable only if the system is brought into specific operating points. The basis for the test signal selection is a structure graph that represents the couplings among the external and internal signals of the system and the fault signals. Graph-theoretic methods are used to identify edges that disappear under certain operating conditions and prevent a fault from changing the system behavior at this operating point. These operating conditions are identified by validuals, which are indicators obtained during the graph-theoretic analysis. The test generation method is illustrated by a process engineering example.

Model-Based Test Signal Generation for Service Diagnosis of Automotive Systems

Abstract A main step in service diagnosis is the selection of dedicated tests for a faulty automotive system in order to decide in which component a fault has occurred. This paper develops a test selection approach that is based on structural models of the system. A structure graph represents the physical couplings of the input, state, and output signals. The test selection method aims at finding operating points in which faults distinguish with respect to their physical input-state-output paths through the components and, thus, can be isolated by steering the system into these operating points. The main ideas are illustrated by a spark ignition engine with the faults of a leakage in the intake manifold and damaged intake valves to be distinguished.

Service diagnosis utilizing the dependencies between the system structure and the operating points

The paper presents a new approach to the generation of test signals used in service diagnosis. The tests make it possible to isolate faults, which are generally not isolable, but can be distinguished if the system is brought into specific operating points. The basis for the test signal selection is a graph that represents the couplings among the external and internal signals of the system and the faults. This graph is used to identify edges that disappear under certain operating conditions and prevent a fault from changing the system behavior in this operating point. The test generation method is illustrated by a process engineering example.

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 systems 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.

Testgenerierung für die Werkstattdiagnose auf der Basis struktureller Modelle

Zusammenfassung Es wird ein Verfahren zur Bestimmung von automatischen Tests für die Werkstattdiagnose vorgestellt, das ein strukturelles Modell des zu diagnostizierenden Systems nutzt, in dem die Ursache-Wirkungsbeziehungen im fehlerfreien und im fehlerbehafteten Zustand dargestellt sind. Durch die ausgewählten Tests wird das System in Betriebszustände gesteuert, in denen bestimmte Fehler eine signifikante Wirkung entfalten während die Wirkung anderer Fehler verschwindet. Die Vorgehensweise wird am Beispiel der Drosselklappe eines Pkw-Motors illustriert. Abstract A novel approach for the determination of automatic tests for service diagnosis is presented. It uses a structural model of the system that is to be diagnosed in order to represent the cause-effect interrelations in the faultless and in the faulty situation. The selected tests steer the system into operating points in which specific faults have a significant impact on the system behavior whereas the effect of other faults vanishes. The procedure is exemplified by a throttle valve of an automobile engine.