Diese Arbeit untersucht die Ursachen von Fehlerfällen des primären Flugsteuerungssystems und deren robuste Erkennung mittels analytischer Redundanz. Im Besonderen werden Oszillationen der Aktuatorstellsysteme, sogenannte Oscillatory Failure Cases (OFCs) und deren Auswikungen auf die Flugzeugstruktur betrachtet. Im Vergleich zu signalbasierten Monitorverfahren ermöglicht ein modellbasierter Ansatz unter Verwendung eines Störgrößenbeobachters die Erkennung von Stellflächenoszillationen sowie Runwaways bei signifikant reduzierten Detektionsamplituden. Die infolge aeroservoelastischer Kopplung auftretenden fehlerinduzierten Strukturlasten können auf diese Weise reduziert werden, was ein Potenzial für Gewichtseinsparungen im Flugzeugbentwurfsprozess aufzeigt.

    This dissertation presents a comprehensive approach to the investigation of oscillatory failure cases with three main fields of interest. First, the causes for the emergence of control surface oscillations are analyzed. In compliance with the experience of aircraft manufacturers and flight control system suppliers, the great variety of conceivable fault scenarios suggests that the OFC problem cannot be tackled by merely tightening the level of design requirements. Still, the investigations offer valuable clues to minimize design-inherent OFCs during the development of an actuation system. Moreover, they allowthe determination of the necessary and sufficient number of sensors for an OFC detection device. The second part of this work presents a model-based, minimum sensor-dependent OFC monitoring system (OFC-MS), which copes with the given on-board sensor equipment of an exemplary actuator control system. It is demonstrated through hardware-in-the-Ioop testing that the proposed method complies with all compulsory system requirements. These include robustness to disturbances, a zero false alarm rate, highest possible detection speeds at minimum achievable detection amplitudes, and an automated system reconfiguration after the failure detection. Compared to the reference monitoring system of an exemplary aircraft, the monitoring performance of the new OFC-MS concept enables a considerable reduction in the OFC detection amplitudes. Transient actuator failures like powered runaways are detected much earlier and at lower limit values, too. Thus, the main benefits of the proposed failure detection method, which is based on analytical redundancy, are imprüved detection amplitudes. It is finally shown in the last part of this thesis that through the availability of the OFC-MS the level of failure case loads, which are decisive for the dimensioning of the structure, can be reduced. This leads to a weight saving potential for the structural airframe design.


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    Title :

    Fault investigation and robust failure detection of oscillating aircraft actuation systems using analytical redundancy


    Contributors:

    Published in:

    Publication date :

    2010


    Size :

    184 Seiten, Bilder, Tabellen, 117 Quellen




    Type of media :

    Theses


    Type of material :

    Print


    Language :

    German




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