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    Item type:Publication, Access status: without files ,
    Aircraft load estimation using linear parameter-varying system-based hybrid observers
    (American Institute of Aeronautics and Astronautics (AIAA), 2025-05-01)
    Luderer, Oliver
    ;
    Thielecke, Frank
    The hybrid loads observer has demonstrated its precision in estimating structural loads and wind disturbances in prior applications. This level of precision is attained by combining a high-fidelity physical, nonlinear flight dynamics model with a data-driven correction model. To mitigate the typically high computational effort, the nonlinear model is substituted in this work with a linear parameter-varying (LPV) system. Therefore, the nonlinear model is approximated by scheduled Linear Time-Invariant models derived from Jacobian linearization. The robustness of this novel approach against parameter uncertainties is evaluated through simulated flight test studies using a subscale test aircraft as an example. It is demonstrated that increased model uncertainties lead to wind estimation accuracy reduction. Additionally, increased parameter uncertainties adversely affect the accuracy of structural load estimation within the model-based (physical) part of the observer. Nonetheless, this loss of accuracy can be compensated by the correction model, leading to the typical high load estimation accuracy of the hybrid loads observer. Finally, experimental data from wind-tunnel tests, utilizing a 1-degree-of-freedom representative test wing, confirms the high estimation accuracy of the LPV-based hybrid loads observer. Despite employing low-fidelity models, achieving high accuracy is feasible while maintaining the characteristic low complexity of the correction model.
    Publicationtype: Journal Article
      43
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    Linear Parameter-Varying (LPV) system based hybrid loads observer using an uncertain aircraft model
    (ARC, 2024-01)
    Luderer, Oliver
    ;
    Thielecke, Frank
    The hybrid loads observer has consistently demonstrated its effectiveness in precisely estimating structural loads and wind disturbances in prior applications. This level of precision is attained through the combination of a high-fidelity physical, nonlinear flight dynamics model with a data-driven correction model. To mitigate the typically high computational effort, the nonlinear model of the loads observer is substituted in this work with a linear parameter-varying (LPV) system while preserving a comparable level of accuracy of the hybrid observer. For this purpose, the model is approximated by scheduled Linear Time-Invariant (LTI) models derived from Jacobian linearization of the nonlinear model. The robustness of this linear parameter-varying hybrid approach against parameter uncertainties is evaluated through virtual flight test studies using the subscale test aircraft Wingfinity-BL as an application example. It is demonstrated that increased model uncertainties lead to a reduction in wind estimation accuracy of the hybrid loads observer. Additionally, increased parameter uncertainties adversely affect the quality of structural loads estimation within the model-based (physical) approach of the observer. Nonetheless, this loss of accuracy can be effectively compensated by the data-driven correction model, leading to a high degree of loads estimation accuracy. Finally, experimental data from a wind tunnel test campaign, utilizing a 1-DOF representative test wing of the aircraft, confirms the high estimation accuracy of the LPV-based hybrid loads observer. Despite employing low-fidelity models, achieving high accuracy is feasible while maintaining the characteristic low complexity of the correction model.
    Publicationtype: Conference Paper
      22
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    Development and testing of a complementary sensor network for robust estimation of maneuver and gust loads
    (Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V. (DGLR), 2023-10-20)
    Luderer, Oliver
    ;
    Thielecke, Frank
    In this publication, a complementary sensor network is presented with the primary objective of increasing the robustness of structural loads estimation. This augmentation is achieved through the combination of measurement methodologies and model-based load observers, thereby creating synergistic effects that mitigate the limitations associated with each approach. This work outlines the development of the complementary sensor network by means of laboratory tests and virtual flight tests. The sensor technologies employed include strain gauges, fiber bragg sensors, inertial measurement units, camera-based optical deformation measurements, and MEMS pressure measurement profiles. For each of these technologies, the laboratory test setup and testing process, alongside the derivation of sensor models for virtual testing of the sensor network is presented. The redundant and partially complementary sensors are fused through the utilization of both local and centralized fusion using Kalman filters and machine learning based approaches. The local fusion strategy exploits the integral correlation between inertial measurement unit (IMU) and camera data at specific observation points, establishing the basis for employing a data-driven local-model network approach wherein local deformations are trained on structural loads data. The centralized loads fusion combines a data association algorithm based on a quadruple-voting scheme and an extended Kalman filter. Finally, the performance and robustness of the whole sensor network is demonstrated based on virtual flight tests considering a load sensor failure.
    Publicationtype: Conference Paper
      24
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    Validation of a hybrid loads observer for a subscale test aircraft with distributed electric propulsion
    (ICAS, 2022-09)
    Luderer, Oliver
    ;
    Thielecke, Frank
    In this paper, a hybrid loads observer for the estimation of aircraft maneuver and gust loads is extended to account for propeller-wing-interaction induced loads using the subscale test aircraft Wingfinity-BL as an example. For this purpose, the results of the well-established program XROTOR are used as inputs of a simplified physically motivated interaction model. Subsequently, the model is corrected by linear terms to approximate the induced wing lift from preliminary wind tunnel experiments. The physical part of the loads observer is implemented as a Luenberger observer based on a low-fidelity non-linear flight dynamics model with strip aerodynamics and a structural loads model. It's physical basis allows for the simple integration of the derived interaction-model. Thereby, the use of low-fidelity models in the Luenberger observer offers the potential to significantly reduce the development time. However, this naturally increases the estimation error, as the validation with wind tunnel data shows. To account for the remaining error, a data-driven correction model is used based on the results of a 1-DOF wind tunnel test of a true to scale wing. It is shown that despite the use of low-fidelity models, a characteristically low complexity of the correction model can be realized within the hybrid observer. Moreover, the validation shows that a high accuracy of the loads estimation is still achieved. In a direct comparison with a purely data-driven observer, the advantages of the physical part in the hybrid observer become apparent, especially in the area of extrapolation.
    Publicationtype: Conference Paper
      130
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    Validation of an Aerodynamic Model for the Analysis of Subscale Test Aircraft with Distributed Electrical Propulsion
    (2021-09)
    Luderer, Oliver
    ;
    Jünemann, Marc
    ;
    Thielecke, Frank
    In this publication an aerodynamic model for the estimation of aerodynamic effects of propeller-wing-interaction for analysis, design and construction of subscale test aircraft (STA) is presented. The well-established programmes XFOIL, XROTOR and LIFTING_LINE are used as subroutines in an automated analysis process. The model for propeller-induced velocities is based on a combination of blade-element theory and a vortex theory. The effect of propeller slipstream contraction on the simplified velocity field is considered with a semi-empirical model. To estimate the spanwise lift distribution of the wing, a multi-lifting line method was chosen which accounts for the additional axial and transverse slipstream velocities. Comparison of simulation results with measurement data from wind tunnel tests shows satisfying accuracies regarding thrust, wing polars, and spanwise lift distribution. In addition, the toolchain is integrated into a modular software framework for design and construction of SubsCALe test AircRaft (SCALAR). Its application is exemplified with a resizing study of a subscale aicraft model with distributed electrical propulsion. The study shows that the overall impact on the layout of the subscale test aircraft is of minor importance. Nonetheless, it is outlined that the presented aero-dynamic toolchain serves well as a basis for mission-dependent wing load estimation in planned technology demonstration campaigns.
    Publicationtype: Conference Paper
      231
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    Aerodynamische Analyse verteilter Antriebe an einem Flügelsegment eines hochgestreckten Flügels
    (Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V. (DGLR), 2019)
    Lemke, Lars-Hendrik
    ;
    Luderer, Oliver
    ;
    Jünemann, Marc
    ;
    Montel, Mike
    ;
    Zumegen, Clemens
    In dieser Veröffentlichung wird der Einfluss von verteilten Antrieben an einem Flügelsegment auf die Tragflächenaerodynamik experimentell und numerisch untersucht. Für die numerische Modellierung werden die Bereiche Propellerebene, Propellernachlauf und Tragfläche betrachtet. Dabei wird für die Modellierung der Strömung innerhalb der Propellerebene eine Blattelement-Impuls-Theorie (BEMT), für den Propellernachlauf ein auf der Rankine?schen Strahltheorie basierendes Propellerstrahl- Kontraktionsmodell und zur Modellierung der Tragflächenaerodynamik ein Mehrfachtraglinienverfahren verwendet. Zusätzlich werden Experimente durchgeführt, um Versuchsdaten zu gewinnen und die theoretischen Modelle für eine spätere Verwendung in der Flugzeugvorentwurfsumgebung MICADO validieren zu können. Die implementierten Modelle werden mit Ergebnissen aus Windkanalversuchen für ein rechteckiges Flügelsegment mit drei verteilten Antrieben verglichen. Dazu wird ein modulares Flügelkonzept (TETRIS) zur Messung von dynamischen Drücken und aerodynamischen Lasten entwickelt. Die modulare Bauweise erlaubt für die betrachtete Reynoldszahl von ungefähr 5 105 eine flexible Anordnung der Komponenten und damit die Untersuchung unterschiedlicher Propeller-Flügel- Konfigurationen mit nur einem Windkanalmodell. Im Vergleich mit den Messdaten konnte gezeigt werden, dass die numerischen Ergebnisse mit dem entwickelten Propellermodell insbesondere im linearen Auftriebspolarenbereich eine geringe Abweichung zu den experimentellen Ergebnissen aufweisen. Die lokalen Auftriebsverläufe können zudem mit einem hohen Detailgrad abgebildet werden, wenngleich signifikante Abweichungen zu den experimentellen Daten auftreten. Diese können primär auf eine Unterschätzung der tangentialen Komponente der durch den Propeller induzierten Geschwindigkeit zurückgeführt werden.
    Publicationtype: Conference Paper
      29