In this paper, the effect of nonlinear actuator dynamics on the performance of an active load alleviation system for an experimental flexible wing is studied. Common nonlinearities such as backlash or rate limits are considered for the control surface actuator. An aeroelastic simulation model of a flexible wing with control surface is being used. With this, a parameter study is carried out to quantify the impact of the individual nonlinearities on the overall closed-loop performance by means of describing functions. Finally, the nonlinear actuator model with parameters identified from dedicated tests is experimentally validated allowing for an accurate prediction of the expected gust load alleviation performance.

/pdf/identification-and-assessment-of-a-nonlinear-dynamic-1vtssxycs9.pdf

Identification and assessment of a nonlinear dynamic actuator model for controlling an experimental flexible wing

Das Paper gibt eine Ubersicht uber die Arbeiten und Ergebnisse im Projekt KonTeKst. Im Projekt wurden im ersten Hauptarbeitspaket zwei Flugzeugkonfigurationen mit einer konfigurativen Larmreduktion im Vergleich zu einem Referenzflugzeug entworfen sowie hinsichtlich Leistung, Larmabstrahlung und Emissionen bewertet. Das zweite Hauptarbeitspaket befasste sich mit ausgewahlten Technologien, die im Bereich des Kurzstreckenflugzeugs die Larmreduktion am Flugzeug zum Ziel haben. Dazu gehorten Untersuchungen an Hochauftriebshilfen sowie Masnahmen zur ihrer konstruktiven Gestaltung sowie Analysen des Larmverhalten unterschiedlicher Treibwerkskonfigurationen. Im dritten Hauptarbeitspaket wurde der DLR-ubergreifende Lastenprozess um spezifische Funktionalitaten erweitert. Die Verfahren wurden durch experimentelle Untersuchungen, so z. B. Auswertungen von Flugversuchen sowie Durchfuhrung eines Windkanalversuches fur aktive und passive Lastabminderung von Boenlasten, validiert. Im Hauptarbeitspaket vier wurden die Auswirkungen des Einsatzprofils von Kurzstreckenflugzeugen, d. h. eine hoheren Anzahl von Starts- und Landungen pro Tag, auf den Flughafen, die Prozesse fur die Abfertigung von Passagieren und Fracht sowie fur die Fuhrung des Flugzeugs am Boden und in der Luft untersucht.
Zunachst wird die Motivation des Projekts herausgearbeitet, vor allem vor dem Hintergrund der Leitkonzepte des DLR. Anschliesend werden die Arbeiten im Projekt kurz vorgestellt und projektubergreifende Ergebnisse prasentiert. Schlieslich wird ein Ausblick auf die weitere Arbeit im neuen Leitkonzept 'Transportflugzeug' gegeben.

Das DLR-Projekt KonTeKst: Konzepte und Technologien für emissionsarme Kurzstreckenflugzeuge

Creep forming of very thin AlMgSc sheets for aeronautical applications

The research aircraft DLR HALO (High Altitude and Long Range Research Aircraft) is able to carry external stores. These stores are mounted at the wing hardpoints and can house several measurement instruments for atmospheric research. However, to ensure the safety and structural integrity of the aircraft and the stores, modifications on the aircraft have to be investigated with numerical analyses and experimental data. The DLR project iLOADS aims at the development of an internal DLR loads process, among others also to be able to support certification capabilities for the DLR aircraft fleet. To assist the DLR HALO operations, a simulation model of the aircraft was set up and loads analyses have been carried out in the Institute of Aeroelasticity at DLR Gottingen. For the experimental part, a flight test campaign with DLR HALO has been performed in April 2016, totaling 14 flying hours. In the test flights strain data of wing external stores, acceleration data of installed sensors and turbulence data were collected. First analyses have been carried out and the findings can be utilized in the further development of the DLR loads process.

Flight Loads Analysis and Turbulence Measurements on an Atmospheric Research Aircraft

The estimation of the loads is a key aspect of the extensive aircraft design process and also an important task during the life-time of an aircraft. DLRs joint efforts regarding the loads estimation and application, the latter also in view of structural aspects, both simulation based and experimentally were part of the DLR project KonTeKst (2016-2019). The loads activities cover the loads process, with one focus on the component loads process. Therein, the various possibilities to introduce loads to the structure were investigated as well as the consideration of flight control methods. On the structural side experiments were executed to estimate damage tolerance parameters for composite structures. Furthermore, fatigue and damage tolerance properties of metallic fuselage structures were estimated. Therefore, a novel AlCuLi sheet material was investigated regarding anisotropic fatigue crack growth. Finally, the consideration of aerodynamic loads for high lift configurations was investigated. The experimental investigations comprise flight tests to measure loads as well as a special wind tunnel test to investigate loads control. For the DLR research glider Discus-2c, the wing loads measured with calibrated electrical strain gauge were compared to the loads determined from the pressure sensors (MEMS), distributed around a wing section. For the DLR HALO, a Gulfstream G550, the loads at special measurement devices attached to the wing used for atmospheric investigation, were measured. Eventually, the structural design of a wind tunnel model with movable control surfaces was done as well as the execution of wind tunnel tests in the DLRs Crosswind Test Facility (SWG), the latter by applying active loads control even in failure cases.

/pdf/aircraft-loads-a-wide-range-of-disciplinary-and-process-1tvj9f4yeh.pdf

Aircraft Loads - A Wide Range of Disciplinary and Process-Related Issues in Simulation and Experiment

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Aircraft Loads - A Wide Range of Disciplinary and Process-Related Issues in Simulation and Experiment