The paper presents the research carried out to handle the air resonance mode that occurs on the DLR EC135 ACT/FHS (Active Control Technology/Flying Helicopter Simulator) research helicopter. To damp the air resonance mode when rate feedback is used, two appropriate controller concepts are flight-tested: the adaptive notch filter and the DCC. The air resonance controllers are implemented independent of the main flight controller (SAS, MBC, etc.). An 11-DoF model identified from flight-test data is effectively tuned to show good correlation with the behavior of the air resonance phenomenon observed in flight tests. The model is an appropriate tool to design and evaluate air resonance controllers. Flight-test evaluations showed that the DCC provides the best damping and performance in suppressing the air resonance mode. Therefore, it is chosen as integral part of the ACT/FHS controller environment. Improvements of handling qualities for the ACT/FHS in level forward flight and hover can be demonstrated, in terms of bandwidth and cross-coupling. Regarding the ADS-33E-PRF bandwidth criterion, an enhancement from level 2 to level 1 becomes possible due to the designed controller. Improvements of MBC performance for an ACAH response type can be demonstrated. The tight following of the helicopter response compared to the required response can only be achieved with the DCC engaged that effectively damps the coupled air resonance mode. The research reported in this paper confirms that in advanced flight control designs, rate feedback can be used to its full extent, on the EC 135 ACT/FHS when air resonance is effectively damped by a virtually independent DCC controller.
Flight Control and Handling Qualities Evaluations Considering Air Resonance
Flugregelung und Dämpfung von Rollschwingungen eines Helikopters
Journal of the American Helicopter Society ; 59 , 2 ; 022001/1-022001/11
2014
11 Seiten, Bilder, Tabellen, 18 Quellen
Article (Journal)
English
Evaluations of helicopter instrument-flight handling qualities
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