Experimental Analysis of the Dynamics of Flared Folding Wingtips via a Novel Tethered Flight Test

Healy, Fintan; Pontillo, Alessandro; Rezgui, Djamel; Cooper, Jonathan E.; Kirk, James R.; Wilson, Thomas; Castrichini, Andrea

doi:10.2514/6.2022-1757

Cited by 6 publications

(10 citation statements)

References 30 publications

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“…14,15 In parallel with the development of fully operational and large machines, the AWE community has also prepared small-scale infrastructures fully dedicated to the flight testing and the experimental study of a large variety of relevant topics like the dynamics, control, estimation, and aerodynamics of AWE systems. These infrastructures include for instance laboratory test platforms for single-tethered aircraft for the static and dynamic characterization by means of a pendulum-like facility 16 and a carousel system for the study of the launch and recovery of unpropelled tethered airplanes. 17 Takeoff and landing of a rigid AWE airplane were tested with a small-scale outdoor system consisting of a winch and a linear motion system [18][19][20] demonstrating the feasibility of short-run takeoff and landing of AWE systems.…”

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confidence: 99%

Automatic testbed with a visual motion tracking system for airborne wind energy applications

et al. 2023

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The architecture and a flight test campaign of a small‐scale testbed aimed at aerodynamic and dynamic characterization of airborne wind energy systems are presented. The testbed involves a two‐line rigid‐framed delta kite and an automatic ground station for the lateral control of the kite and reel‐in/reel‐out of the two tethers. The environment, and the states of the kite, the tethers and the actuators are measured by a set of on‐ground and onboard sensors that include, among others, an inertial measurement unit, GNSS receivers, load cells, actuator encoders, a wind station, and a visual motion tracking (VMT) system based on three cameras and an artificial neural network (YOLOv2). The results of a 5‐min flight, including the take‐off, cross‐wind flight, and landing, were used to analyze the capabilities of the testbed. It was shown that the time derivative of the kite course angle exhibits a linear correlation with both the delayed steering input and the delayed differential tether tension, being the dispersion lower for the latter. The intrinsic and extrinsic calibrations proposed for the VMT system led to a good agreement between the estimation of the kite position and course angle provided by the VMT system and the onboard computer. Moreover, although the YOLOv2 algorithm failed in the detection of the kite within around 5% of the images, the simultaneous non‐detection from the three cameras was below 0.1% during the full flight. Such a reliability suggests that a VMT system can be used as a redundant or backup sensor for the GNSS.

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confidence: 99%

Automatic testbed with a visual motion tracking system for airborne wind energy applications

et al. 2023

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“…The model of the aircraft with the folding wingtip can be obtained from the equations of model one considering the additional contributions from the wingtip and taking into account that the elastic wing is composed of two contributions from wingspan s 1 and wingspan s 2 , as shown in Figure 2. 8. It is worth noting that in the region of s 2 the chord is not constant, but is a function of the flare angle γ, of the elastic wingspan s and of the span position y.…”

Section: Structural and Aerodynamic Model Of An Aircraft With A Strai...mentioning

confidence: 99%

“…. 9 1.7 Wing in the wind tunnel in a free-hinge configuration (directly adapted from [7] 1.9 Tethered flight test of the AlbatrossOne model (directly adapted from [8]). 14 1.10 Discrete-gust approach to design (directly adapted from [9]).…”

Section: Titlementioning

confidence: 99%

“…The wing load alleviation effect from the free wingtips was confirmed through different flights [60]. Healy et al [8] described a novel flight test method for a UAV constrained by a tether, resulting in steady, controlled, elliptical flight paths. Figure 1.9 shows AlbatrossOne in a tethered flight test.…”

Section: Semi Aeroelastic Hinge Conceptmentioning

confidence: 99%

“…The wingtip is considered as a rigid body of mass m wt with the centre of mass at Γ = (Γ x , Γ y ) defined in a reference coordinate system with the origin at the leading edge of the elastic wing tip and with the x-axis parallel to the hinge axis, as shown in Figure 2. 8. θ is the degree of freedom related to the wingtip rotation and it is defined such that a positive angle variation produces a downwards displacement.…”

Section: Structural and Aerodynamic Model Of An Aircraft With A Strai...mentioning

confidence: 99%

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Numerical and experimental studies of aeroelastic hinged wingtips

Balatti¹

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Aeroelasticity is the science that investigates the mutual interaction between aerody-namic, elastic, and inertia forces and how this affects the static and dynamic structural response. Aeroelastic models can be defined considering different levels of fidelity de-pending on the models’ aim. Gust loads are among the most critical cases an aircraft can encounter, and so mitigating the loads enables the design of a lighter structure, consequently reducing production and fuel consumption costs. Hinged wingtips have shown potential to improve the wing aerodynamic performance while alleviating struc-tural loads. The aim of this work is the numerical and experimental study of aeroelastic wings with hinged wingtips subjected to gusts. Measurements from wind tunnel tests are used to validate the numerical model. Two numerical models, representative of the same aircraft with hinged wingtips subjected to gusts, were considered, a detailed and a simplified one. The latter model, due to its low number of degrees of freedom, was used for wingtip design optimisation. Gust and turbulence events cannot be measured di-rectly, but they can be identified from in-flight measurements. Cubic B-spline functions were used for gust identification considering simulated flight data from the simplified and detailed models. Results have shown the ability of the simplified model to identify the gust and turbulence considering simulated data from the detailed model. To validate the numerical models, a gust generator was designed, installed and commissioned for the Swansea University wind tunnel. Experimental results have shown the difficulty of creating a perfect ‘1-cos’ gust at the desired location. Two techniques to improve the ‘1-cos’ gust were considered. In the first case, the transfer function between the vane rotation and the gust produced at the aircraft model location was identified, and its in-verse was used to calculate the vane rotation. The improvements using this approach are limited by the strong nonlinearity of the aerodynamics. A parametric study of the vane rotation has shown that a more complicated vane rotation function allows ‘1-cos’ gusts at the aircraft model location to be obtained with a mean square error two orders of magnitude smaller than the initial case. An elastic wing able to accommodate different wingtips was manufactured. Three wingtips, namely a fixed wingtip, a hinged wingtip, and a hinged wingtip with a torsional spring at the hinge were considered. Static and dynamic wind tunnel tests have shown the potential of hinged wingtips in reducing wing gust loads. Measured gust loads were used to validate the aeroelastic models.

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Aeroelastic Scaling of a High-Aspect-Ratio Wing Incorporating a Semi-Aeroelastic Hinge

Gu,

Healy,

Constantin

et al. 2024

AIAA Journal

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There has been a growing interest in utilizing flared folding wingtips as an in-flight load alleviation device to enable increased wing spans that meet airport gate limits but with little increase in wing weight. The semi-aeroelastic hinge (SAH) concept is implemented in high-aspect-ratio wings to enable wingtips to be released during severe load cases such as maneuvers and gusts to alleviate the bending moments while maintaining optimum aerodynamic shape for the rest of the flight. In this paper, scaling methods for wings incorporating the SAH are explored, allowing for the development of equivalent scaled unmanned aerial vehicles or wind tunnel models with similar aeroelastic behavior as full-size aircraft. Three scaling approaches are considered in this study, namely, Iso-Froude, Iso-Frequency, and Iso-Strain, where a set of governing nondimensional quantities and scaling factors are determined. Despite the significant nonlinearities resulting from large wingtip fold angles, it is shown that a linear scaling approach can be appropriate for such a wing configuration. Furthermore, the aeroelastic properties of each scaled model are compared to those of the full-scale model, where the best match was obtained from the Iso-Strain model, although it is challenging to meet the required operational conditions.

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Experimental Analysis of the Dynamics of Flared Folding Wingtips via a Novel Tethered Flight Test

Cited by 6 publications

References 30 publications

Automatic testbed with a visual motion tracking system for airborne wind energy applications

Automatic testbed with a visual motion tracking system for airborne wind energy applications

Numerical and experimental studies of aeroelastic hinged wingtips

Aeroelastic Scaling of a High-Aspect-Ratio Wing Incorporating a Semi-Aeroelastic Hinge

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