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In nature, gliding birds frequently execute intricate flight maneuvers such as aerial somersaults, perched landings, and swift descents, enabling them to navigate obstacles or hunt prey. It is evident that birds rely on different wing–tail configurations to accomplish a wide range of aerial maneuvers. For traditional fixed‐wing unmanned aerial vehicles (UAVs), pitch control primarily comes from the tail's elevators, while adjusting flight lift and drag involves deploying wing flaps. Although these designs ensure reliable flight, they compromise the drones' maneuverability to maintain longitudinal stability. Therefore, the study introduces a biomimetic morphing wing UAV, and presents a pitch control strategy that simultaneously engages morphing wings, ailerons, and tail elevators. The pull‐up maneuver tests indicate that the proposed control method results in a pitch rate that is approximately 2.5 times greater than when using only the elevator control. A closed‐loop control system for the drone is also established. The closed‐loop flight experiment, which tracks a 45° pitch angle, demonstrates the effectiveness of the proposed coupled control method in adjusting the flight attitude. In addition, during cruising, the UAV employs three configurations, straight wing, forward‐swept wing, and back‐swept wing, to cater to different mission objectives and augment its flight capabilities. [ABSTRACT FROM AUTHOR]

The variable-sweep wing, as an important morphing wing technology, has received widespread attention because it can change the sweep angle according to different flight conditions. It has the advantage of simultaneously utilizing a large sweep angle to reduce shock wave drag at high speeds and improving lift characteristics at small sweep angles. However, it has always been the case that the variable-sweep wing will bring about a rearward shift of the center of gravity when the sweep angle increases, leading to a decrease in aircraft stability. This paper focuses on a structural design of a variable-sweep wing based on a four-bar planar linkage. The novel variable-sweep wing structure containing a four-bar planar linkage and an outer wing section is proposed, and key parameters are extracted to establish a mathematical model of the mechanism. Through parametric analysis, main parameters have been identified, and the structure is optimized: the longitudinal position (direction of the fuselage) of the wing's center of gravity is designed to maintain minimal change during the morphing process, but remain the same at both the beginning and ending states of the transformation. The structural design of the variable-sweep wing is carried out based on this. Then, the finite-element model is established to validate the load-bearing capacity of the variable-sweep wing and derive the driving force. Finally, as one of the main novelties, a full-size prototype is successfully manufactured for load testing. The results of finite-element simulation and load testing show that this variable-sweep wing structure can achieve movement from 30° to 70° under an aerodynamic load that is up to 460 kg/m2. The present study demonstrates the effectiveness and potential of the proposed morphing trailing edge concept for real application on aircraft. [ABSTRACT FROM AUTHOR]

In nature, gliding birds frequently execute intricate flight maneuvers such as aerial somersaults, perched landings, and swift descents, enabling them to navigate obstacles or hunt prey. It is evident that birds rely on different wing–tail configurations to accomplish a wide range of aerial maneuvers. For traditional fixed‐wing unmanned aerial vehicles (UAVs), pitch control primarily comes from the tail's elevators, while adjusting flight lift and drag involves deploying wing flaps. Although these designs ensure reliable flight, they compromise the drones’ maneuverability to maintain longitudinal stability. Therefore, the study introduces a biomimetic morphing wing UAV, and presents a pitch control strategy that simultaneously engages morphing wings, ailerons, and tail elevators. The pull‐up maneuver tests indicate that the proposed control method results in a pitch rate that is approximately 2.5 times greater than when using only the elevator control. A closed‐loop control system for the drone is also established. The closed‐loop flight experiment, which tracks a 45° pitch angle, demonstrates the effectiveness of the proposed coupled control method in adjusting the flight attitude. In addition, during cruising, the UAV employs three configurations, straight wing, forward‐swept wing, and back‐swept wing, to cater to different mission objectives and augment its flight capabilities.

Shape memory polymers (SMPs) are used in various industries due to their excellent variable stiffness behavior and innate response to external stimuli. The morphing wing is one of the technologies that employed the SMPs to reduce fuel consumption. This study proposes a novel morphing wing design using epoxy SMP as a wing skin, and a corrugated shape SMP composite (SMPC) as a wing core. The Dynamic mechanical analysis, bending and tensile tests were performed to determine the variable stiffness behavior of the skin, and the anisotropic behavior of the corrugated core. To evaluate the performance of the developed wing, the skin out-of-plane deformation is assessed, and the wing morphology is evaluated using the shape fixity and shape recovery tests. The results revealed that the skin out-of-plane deformation is within the acceptable limit for flight speed up to 0.16 Mach. Moreover, the wing shape recovery was excellent; the trailing edge of the wing is able to restore up to 99% of its bent position. [ABSTRACT FROM AUTHOR]

In the wild, gliding birds dodge obstacles or predators by folding and twisting their wings swiftly to perform a rapid roll. Accordingly, the authors strive to explore the feasibility of improving the roll rate of drones through this bird‐inspired morphing method, by using the asymmetric sweepback of wings to simulate the contraction of birds' wings and the deflection of the aileron to imitate wing torsion. Moreover, the effects of wing morphing on the centroid, inertia matrix, and aerodynamic characteristics of the drone are explored herein, and a nonlinear dynamic model is established. Furthermore, a novel cooperative strategy that combines wing morphing with aileron deflection for roll control is introduced, and a flight controller based on this cooperative strategy is developed. Finally, the superiority of the cooperative strategy and the accuracy of the dynamic modeling have been validated in the outdoor flights of the morphing wing drone. [ABSTRACT FROM AUTHOR]

In the wild, gliding birds dodge obstacles or predators by folding and twisting their wings swiftly to perform a rapid roll. Accordingly, the authors strive to explore the feasibility of improving the roll rate of drones through this bird‐inspired morphing method, by using the asymmetric sweepback of wings to simulate the contraction of birds’ wings and the deflection of the aileron to imitate wing torsion. Moreover, the effects of wing morphing on the centroid, inertia matrix, and aerodynamic characteristics of the drone are explored herein, and a nonlinear dynamic model is established. Furthermore, a novel cooperative strategy that combines wing morphing with aileron deflection for roll control is introduced, and a flight controller based on this cooperative strategy is developed. Finally, the superiority of the cooperative strategy and the accuracy of the dynamic modeling have been validated in the outdoor flights of the morphing wing drone.

Applying fish bone active camber morphing to the wing-in-ground effect to improve the aerodynamic efficiency was investigated using computational fluid dynamics (CFD) at a Reynolds number of 320,000. Steady-static morphing was first carried out with Reynolds-averaged Navier–Stokes (RANS) equations in two dimensions for morphing start locations off (60%, 80%, and 90% chord), ground clearances (h/c=0.1 , 0.2, 0.4, 1), and angles of attack (AoAs) 0°, 2°, 3°, 4°, and 12°. A morphing displacement (wte) of 0.5% increased the efficiency by 2.8% (compared to non-morphing in the ground effect) for the 3° AoA and 90% start location, and by 62% in comparison to the baseline unmorphed airfoil in freestream. Reducing h/c=1 to 0.1 increased the lift between 10% and 17%; the larger gain was with the highest morphing deflection. A key finding was that morphing the airfoil reduced the distance between the trailing edge and ground, enhancing the ground effect. Also, morphing at an earlier start location in the chord direction resulted in a smaller area beneath the airfoil, reducing the total pressure, which reduced the overall lift compared to a later morphing start location. Dynamic morphing at 1 Hz using URANS K-Omega-SST showed a similar amount of lift as static morphing but a slightly higher amount of drag. Reducing the period caused an initial overshoot in drag before settling. The dynamic ground effect showed higher efficiency at low AoAs compared to dynamic morphing in freestream, which is beneficial for aircraft to fly with less pitch. Finally, periodic morphing for h/c=0.1 using sinusoidal motion with morphing starting at 25% along the chord and 4° AoA was investigated between 0.05% to 0.15% wte and 0.5 to 3.5 Strouhal number. Periodically morphing at 0.125% wte and Strouhal number of 0.9 using DES simulations increased the efficiency by 5.4%; however, it reduced the lift by 0.7%, the drag reduced by 5.8%, and it showed Kelvin–Helmholtz instability at 9.8 Strouhal number. The use of UAVs is increasing in popularity for many missions, which include observation, surveys, and the delivery of supplies, including medical. The use of UAVs typically has lower aircraft and operational costs as well as allowing the craft to carry out dangerous missions without putting the crew in danger. A wing-in-ground effect (WIG) craft typically operates on water due to the large fuel consumption savings as well as allowing the craft to travel at higher speed compared to conventional marine craft. The study focused on applying morphing wings to a UAV WIG effect craft to improve the aerodynamic performance of the craft and allow further fuel efficiency savings compared to a marine craft. The improved performance of the WIG craft and applying morphing translates to improvements in flight time and increased range. Morphing wings also allow the wing to adapt to different flight conditions allowing for optimized aerodynamic performance depending on factors such as cargo weight and weather conditions. [ABSTRACT FROM AUTHOR]

This paper shows a series of tools that help in the research of morphing micro air vehicles (MAVs). These tools are aimed at generating parametric CAD models of wings in a few seconds that can be used in aerodynamic studies, either via CFD directly using the model obtained or via wind tunnel through rapid prototyping with 3D printers. It also facilitates the analysis of morphing wings by allowing for the continuous parametric deformation of the airfoils and the wing geometry. In addition, one of the tools greatly simplifies the purely experimental design of this type of vehicle, allowing the transfer of experimental measurements to the computer, generating virtual models with the same deformation as the physical model. This software has two fundamental parts. The first one is the parameterization of the airfoils, for which the CST (Class-Shape Transformation) method will be used. CST coefficients can be modified according to the actuator variable that changes the wing geometry. The second part is the generation of a three-dimensional parametric model of the wing. We used OpenCASCADE technology in its Python version called PythonOCC, which enables the generation of geometries with good surface quality for typical and non-standard wing shapes. Finally, the use of this software for the study of a morphing aircraft will be shown, as well as improvements that could be incorporated in the future to increase its capabilities for the design and analysis of MAVs. [ABSTRACT FROM AUTHOR]

Aeronautics research has continually sought to achieve the adaptability and morphing performance of avian wings, but in practice, wings of all scales continue to use the same hinged control-surface embodiment. Recent research into compliant and bio-inspired mechanisms for morphing wings and control surfaces has indicated promising results, though often these are mechanically complex, or limited in the number of degrees-of-freedom (DOF) they can control. Seeking to improve on these limitations, we apply a new paradigm denoted Autonomous Material Composites to the design of avian-scale morphing wings. With this methodology, we reduce the need for complex actuation and mechanisms, and allow for three-dimensional placement of stretchable fiber optic strain gauges (Optical Lace) throughout the metamaterial structure. This structure centers around elastomeric conformal lattices, and by applying functionally-graded warping and thickening to this lattice, we allow for local tailoring of the compliance properties to fit the desired morphing. As a result, the wing achieves high-deformation morphing in three DOF: twist, camber, and extension/compression, with these morphed shapes effectively modifying the aerodynamic performance of the wing, as demonstrated in low-Reynolds wind tunnel testing. Our sensors also successfully demonstrate differentiable trends across all degrees of morphing, enabling the future state estimation and control of this wing. [ABSTRACT FROM AUTHOR]

In recent research works, morphing wings were studied as an interesting field for a small unmanned aerial vehicle (UAV). The previous studies either focused on selecting suitable material for the morphing wings or performing experimental tests on UAVs with morphing wings. Though, the dynamic modeling of active flexible morphing wings and their involved interactions with the aerodynamics of the UAV body are challenging subjects. Using such a model to control a small UAV to perform specific maneuvering is not investigated yet. The dynamic model of UAV with active morphing wings generates a multi-input multi-output (MIMO) system which rises the difficulty of the control system design. In this paper, the aeroelastic dynamic model of morphing wing activated by piezocomposite actuators is established using the finite element method and modal decomposition technique. Then, the dynamic model of the UAV is developed taking into consideration the coupling between the wing and piezocomposite actuators, as well as the dynamic properties of the morphing actuators with the aerodynamic wind disturbances. A model predictive control (MPC) is designed for the MIMO control system to perform specific flight maneuvering by tracking desired trajectories of UAV altitude and yaw angle. Additionally, the MPC achieves constrained behavior of pitch and roll angles to get satisfactory UAV motion. Also, the behaviors of the UAV control system using MPC are evaluated after adding Dryden wind turbulence to the UAV outputs. Finally, a UAV flight simulation is conducted which shows that the control system successfully rejects the applied disturbances and tracks the reference trajectories with acceptable behavior of pitch and roll angles. [ABSTRACT FROM AUTHOR]

This paper shows a series of tools that help in the research of morphing micro air vehicles (MAVs). These tools are aimed at generating parametric CAD models of wings in a few seconds that can be used in aerodynamic studies, either via CFD directly using the model obtained or via wind tunnel through rapid prototyping with 3D printers. It also facilitates the analysis of morphing wings by allowing for the continuous parametric deformation of the airfoils and the wing geometry. In addition, one of the tools greatly simplifies the purely experimental design of this type of vehicle, allowing the transfer of experimental measurements to the computer, generating virtual models with the same deformation as the physical model. This software has two fundamental parts. The first one is the parameterization of the airfoils, for which the CST (Class-Shape Transformation) method will be used. CST coefficients can be modified according to the actuator variable that changes the wing geometry. The second part is the generation of a three-dimensional parametric model of the wing. We used OpenCASCADE technology in its Python version called PythonOCC, which enables the generation of geometries with good surface quality for typical and non-standard wing shapes. Finally, the use of this software for the study of a morphing aircraft will be shown, as well as improvements that could be incorporated in the future to increase its capabilities for the design and analysis of MAVs.

In the last decades, wing morphing structures have aroused great interest due to their capability to improve the aerodynamic efficiency of modern aircraft. DE actuators, also known as “artificial muscles” due to their ability to exhibit large actuation strains at high voltages, are suitable candidates for morphing applications. This paper focuses on the research and development of miniature dielectric elastomeric actuators for variable-thickness morphing wings. A conical elastomeric actuation configuration has been proposed, consisting of a VHB4910 dielectric membrane preloaded with a spring mechanism and constrained to a rigid circular ring. The mini-actuators are developed to be fixed in an actuation array, mounted to the wing skin. This new electromechanical actuation system is designed to be integrated on thin airfoil wings, where conventional morphing structures cannot be used, because of restricted mass and space requirements. By controlling the thickness distribution using the proposed actuators, we may be able to maintain and delay the location of the laminar-turbulent transit towards the trailing edge, promoting laminar flow over the wing surface. Experimental models and prototypes will be developed in the next phase of the research project for further investigations.

The ability of morphing aircraft to adapt their shape in flight hinges on the incredible flexibility of their skins, which have multiple degrees of freedom. This paper presents a compact overview of the latest advancements in polymorphing skins for morphing aircraft, focusing on polymeric skins, electroactive polymers, and shape memory polymers. It examines the critical mechanical properties such as flexibility, durability, and resilience that influence their application in morphing wings. By detailing the synthesis processes, including the use of natural rubber, silicone, acrylic, and fiber-reinforced composites, and exploring various modeling and simulation approaches, the paper highlights the importance of flexible material selection and design principles tailored to morphing aircraft needs. It emphasizes a multidisciplinary strategy integrating polymer material science, mechanical engineering, and aerodynamics to innovate in the morphing aircraft domain. This review aims to serve as an essential resource for researchers and practitioners, paving the way for future developments in aerospace morphing technologies. • Innovative Material Synthesis : Explores synthesis of cutting-edge materials like SMPs, EAPs, and advanced composites for aerospace applications. • Material Property Evaluation : Evaluates key mechanical properties like tensile strength, elasticity, and fatigue resistance for polymorphic skins in morphing wings. • Advanced Modeling Techniques : Reviews modeling and simulation methods to predict the behavior of morphing skins under operational conditions. • Design and Implementation Strategies : Discusses design principles for polymer-based skins, focusing on morphing mechanisms and integration with structural components. • Challenges and Solutions in Morphing Skins : Addresses challenges like wrinkling and buckling in polymeric skins and optimizes actuation parameters for SMP and EAP skins, proposing future research directions. [ABSTRACT FROM AUTHOR]

Unmanned Combat Aerial Vehicles (UCAVs) are believed by many to be the future of aerial strike/reconnaissance capability. This belief led to the design of the UCAV 1303 by Boeing Phantom Works and the US Airforce Lab in the late 1990s. Because UCAV 1303 is expected to take on a wide range of mission roles that are risky for human pilots, it needs to be highly adaptable. Geometric morphing can provide such adaptability and allow the UCAV 1303 to optimise its physical feature mid-flight to increase the lift-to-drag ratio, manoeuvrability, cruise distance, flight control, etc. This capability is extremely beneficial since it will enable the UCAV to reconcile conflicting mission requirements (e.g. loiter and dash within the same mission). In this study, we conduct several modifications to the wing geometry of UCAV 1303 via Computational Fluid Dynamics (CFD) to analyse its aerodynamic characteristics produced by a range of different wing geometric morphs. Here we look into two specific geometric morphing wings: linear twists on one of the wings and linear twists at both wings (wash-in and washout). A baseline CFD of the UCAV 1303 without any wing morphing is validated against published wind tunnel data, before proceeding to simulate morphing wing configurations. The results show that geometric morphing wing influences the UCAV-1303 aerodynamic characteristics significantly, improving the coefficient of lift and drag, pitching moment and rolling moment. [ABSTRACT FROM AUTHOR]

In the last decades, wing morphing structures have aroused great interest due to their capability to improve the aerodynamic efficiency of modern aircraft. DE actuators, also known as "artificial muscles" due to their ability to exhibit large actuation strains at high voltages, are suitable candidates for morphing applications. This paper focuses on the research and development of miniature dielectric elastomeric actuators for variable-thickness morphing wings. A conical elastomeric actuation configuration has been proposed, consisting of a VHB4910 dielectric membrane preloaded with a spring mechanism and constrained to a rigid circular ring. The mini-actuators are developed to be fixed in an actuation array, mounted to the wing skin. This new electromechanical actuation system is designed to be integrated on thin airfoil wings, where conventional morphing structures cannot be used, because of restricted mass and space requirements. By controlling the thickness distribution using the proposed actuators, we may be able to maintain and delay the location of the laminar-turbulent transit towards the trailing edge, promoting laminar flow over the wing surface. Experimental models and prototypes will be developed in the next phase of the research project for further investigations. [ABSTRACT FROM AUTHOR]

In a previous paper, the authors dealt with the current showstoppers that inhibit commercial applicability of morphing systems. In this work, the authors express a critical vision of the current status of the proposed architectures and the needs that should be accomplished to make them viable for installation onboard of commercial aircraft. The distinction is essential because military and civil issues and necessities are very different, and both the solutions and difficulties to be overcome are widely diverse. Yet, still remaining in the civil segment, there can be other differences, depending on the size of the aircraft, from large jets to commuters or general aviation, which are classifiable in tourism, acrobatic, ultralight, and so on, each with their own peculiarities. Therefore, the paper aims to trace a common technology denominator, if possible, and envisage a future perspective of actual applications.

A methodology to simulate the unsteady, nonlinear aeroelastic behavior of a folding-wing concept in multiple flight configurations is presented. It is based on a partitioned or co-simulation scheme, which divides the dynamical system into interacting aerodynamic and structural models. The aerodynamic model that predicts the loads is based on the unsteady vortex-lattice method. The structural model that predicts the motion of the folding wing is based on the finite-element method. The grids in the two models are non-matching. The method for simultaneously integrating the combined set of equations is based on the fourth-order predictor-corrector method developed by Hamming. The technique for transferring information between the non-matching grids is the radial basis interpolation method. This system is partially validated by showing that the predicted loads here agree very closely with numerical results based on the Euler equations for a wing with prescribed unsteady twisting and pitching motion and with analytical solutions available in the literature. Finally, a series of numerical simulations related to the aeroelastic behavior of a folding-wing concept inspired by gull wings provide new insights into flutter boundaries as a function of the dihedral angles of the inner and outer wings. The findings in this paper strongly suggest that the present numerical aeroelastic model will be a valuable computational tool for further studies of aircraft with morphing wings. [ABSTRACT FROM AUTHOR]

One of the persistent challenges facing the development of morphing aerostructures is the need to have material and structural solutions which provide a compromise between the competing design drivers of low actuation energy and high stiffness under external loads. This work proposes a solution to this challenge in the form of a novel switchable stiffness structural concept based on the principle of granular jamming. In this article, the concept of using granular jamming for controlling stiffness is first introduced. Four-point bending tests are used to obtain the flexural rigidity and bending stiffness of three different granular materials under different levels of applied vacuum loading. Nonlinear finite element analysis simulations using experimentally derived nonlinear material properties show good agreement with experiment. A specific application of this concept is then proposed based on the Fish Bone Active Camber morphing airfoil. A unit cell of this concept is built, tested and analysed, followed by the first prototype of a complete switchable stiffness Fish Bone Active Camber morphing airfoil, which is experimentally shown to be able to achieve an increase in stiffness of up to 300% due to granular jamming. [ABSTRACT FROM AUTHOR]

Morphing wings, which control the flight by changing their own shapes, have attracted much attention by their potential for improving aerodynamic performance. Corrugated structures, which have flexibility in the corrugation direction and high rigidity in the transverse direction to the corrugation, were proposed as good candidates for morphing wings. This research suggests a new fluid-structure interaction (FSI) analysis model which shows better accuracy at low computational cost for the design of flexible morphing wings. A RANS based computational fluid dynamics (CFD) solver, UTCart, and a panel method, XFOIL, are both implemented in the FSI analysis combined with nonlinear flexible beam model in the present scheme. Aerodynamic pressure distributions obtained using UTCart are different from those obtained by the traditional XFOIL analysis, especially when angle of attack is high. This leads to the differences in the driving forces to deform the wing. In contrast, the differences in the deformed shapes of the airfoils are relatively small between the two. With the knowledge obtained above, a new FSI analysis model is proposed; in the FSI analysis model, firstly the deformation of the airfoil in the airflow is analyzed using XFOIL, and after the deformation shape is obtained, UTCart evaluates the aerodynamic performances and the pressure distribution of the converged airfoil, and finally the driving force is recalculated using the pressure distribution newly obtained by UTCart.

In this paper, a flexible morphing wing with piezoelectric materials for morphing actuation is studied. The objectives of this paper are 1) to develop an integrated geometrically nonlinear electro-aeroelastic framework, which allows evaluating performances of flexible morphing wings with piezoelectric actuators, 2) to validate the developed analysis framework, and 3) to demonstrate the capability of the framework and explore the performance. This paper provides a description of the electro-aeroelastic equations of morphing wings taking into account piezoelectric effects, which can be used to actuate morphing wings. The electro-mechanical model is validated by comparing with experimental results. The validation with a single macro fiber composite showed a very good agreement between the experimental result and the simulation. The result of an actuation test with an integrated corrugated structure and macro fiber composite also reasonably agreed with the solution from the present code. Aeroelastic behaviors of a corrugated wing with the piezoelectric actuator are then explored. The camber morphing wing with the corrugated structure actuated by the piezoelectric actuator could provide a larger lift in the vicinity of the trailing edge. Such a camber morphing has a good potential to control aeroelastic response by wing morphing with piezoelectric actuation.

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Tailless swept wing airplanes rely on variations of the spanwise lift distribution to achieve controllability in all axes. As every flight condition requires different control moments, the conventional discrete control surfaces will be practically continuously deflected, leading to drag penalties. Shape adaptation base on chordwise morphing can achieve continuous deformations of the wing profile, leading to local lift variations with minimum drag penalties. As the shape is varied continuously along the wingspan, the lift distribution can be tailored to each flight condition. Tailless aircraft appear therefore as prime candidates for morphing, as the attainable benefits are potentially significant. This work presents a methodology to determine the optimal planform, profile shape, and morphing structure for a tailless aircraft. The employed morphing concept is based on a distributed compliance structure, actuated by piezoelectric elements. The multidisciplinary optimization considers the static and dynamic aeroelastic behavior of the structure and aims to maximize the aerodynamic efficiency of the plane while guaranteeing its controllability by means of morphing. The potential of the resulting wing design is fully exploited by means of a second optimization process, which identifies the actuation configuration resulting in the highest aerodynamic efficiency for a wide variety of control moments. [ABSTRACT FROM AUTHOR]

Morphing wings have a large potential to improve the overall aircraft performances, in a way like natural flyers do. By adapting or optimising dynamically the shape to various flight conditions, there are yet many unexplored opportunities beyond current proof-of-concept demonstrations. This review discusses the most prominent examples of morphing concepts with applications to two and three-dimensional wing models. Methods and tools commonly deployed for the design and analysis of these concepts are discussed, ranging from structural to aerodynamic analyses, and from control to optimisation aspects. Throughout the review process, it became apparent that the adoption of morphing concepts for routine use on aerial vehicles is still scarce, and some reasons holding back their integration for industrial use are given. Finally, promising concepts for future use are identified. [ABSTRACT FROM AUTHOR]

Camber morphing aerofoils have the potential to significantly improve the efficiency of fixed and rotary wing aircraft by providing significant lift control authority to a wing, at a lower drag penalty than traditional plain flaps. A rapid, mesh-independent and two-dimensional analytical model of the fish bone active camber concept is presented. Existing structural models of this concept are one-dimensional and isotropic and therefore unable to capture either material anisotropy or spanwise variations in loading/deformation. The proposed model addresses these shortcomings by being able to analyse composite laminates and solve for static two-dimensional displacement fields. Kirchhoff-Love plate theory, along with the Rayleigh-Ritz method, are used to capture the complex and variable stiffness nature of the fish bone active camber concept in a single system of linear equations. Results show errors between 0.5% and 8% for static deflections under representative uniform pressure loadings and applied actuation moments (except when transverse shear exists), compared to finite element method. The robustness, mesh-independence and analytical nature of this model, combined with a modular, parameter-driven geometry definition, facilitate a fast and automated analysis of a wide range of fish bone active camber concept configurations. This analytical model is therefore a powerful tool for use in trade studies, fluid-structure interaction and design optimisation. [ABSTRACT FROM AUTHOR]

Aerodynamic properties and aeroelastic responses of morphing wings can be improved via active shape control using piezoelectric actuators. In this article, a type of piezocomposite material called macro-fiber composite is used for actuation to achieve shape control of the morphing wing. This study focuses on the vibration suppression of the wing during dynamic morphing motion in open-loop architecture. The aeroelastic model is established using finite element method and Theodorsen unsteady aerodynamic loads. Because the arbitrary selection of any admissible control voltage profiles will cause vibrations of the wing structure and fluctuations in aerodynamic lift, a dynamic shape control approach is presented to optimize the voltage profiles for the actuators. A proof-of-concept simulation is presented for a scaled high-aspect-ratio wing. The results show that continuous, smooth morphing motion with gentle aeroelastic responses can be realized by applying the optimum voltage profiles. The dynamic shape control performance of the morphing wing can be improved compared with step and ramp voltage profiles. [ABSTRACT FROM AUTHOR]

In the design and analysis of morphing wings, several sciences need to be integrated. This article tries to answer the question, “What is the most appropriate actuation mechanism to morph the wing profile?„ by introducing the synthesis, analysis, and design of a novel scissor-structural mechanism (SSM) for the trailing edge of a morphing wing. The SSM, which is deployable, is created via a combination of various scissor-like elements (SLEs). In order to provide mobility requirements, a four-bar linkage (FBL) is assembled with the proposed SSM. The SSM is designed with a novel kinematic synthesis concept, so it follows the airfoil camber with minimum design error. In this concept, assuming a fully-compliant wing skin, various types of SLEs are assembled together, and emergent SSM provide the desired airfoil geometries. In order to provide the required aerodynamic efficiency of newly-created airfoil geometries and obtain pressure distribution over the airfoil, two-dimensional (2D) aerodynamic analyses have been conducted. The analyses show similar aerodynamic behavior with the desired NACA airfoils. By assigning the approximate link masses and mass centers, the dynamic force analysis of the mechanism has also been performed, and the required torque to drive the newly-developed SSM is estimated as feasible.

Presented in this paper is a method for the development of variable geometry truss manipulators (VGTMs) with enhanced static characteristics. The concept of statically redundant parallel robots is introduced and used to design the VGTM module through under-actuation. Under this design, each module is over-constrained, composed of both active and passive limbs. To enhance the stiffness, the passive limbs are designed using lockable prismatic joints. It is shown that through proper sequencing of the locking and unlocking of these passive limbs in correspondence to actuated motion, system rigidity can be maintained in the course of reconfiguration. In this paper, the proposed method is first explained using a planar system, then it is shown how to apply this method to the design of the variable geometry wing-box for an aircraft morphing wing. [ABSTRACT FROM AUTHOR]

The drag coefficient and the laminar-to-turbulent transition for the aerofoil component of a wing model are optimised using an adaptive upper surface with two actuation points. The effects of the new shaped aerofoils on the global drag coefficient of the wing model are also studied. The aerofoil was optimised with an ‘in-house’ genetic algorithm program coupled with a cubic spline aerofoil shape reconstruction and XFoil 6.96 open-source aerodynamic solver. The wing model analysis was performed with the open-source solver XFLR5 and the 3D Panel Method was used for the aerodynamic calculation. The results of the aerofoil optimisation indicate improvements of both the drag coefficient and transition delay of 2% to 4%. These improvements in the aerofoil characteristics affect the global drag of the wing model, reducing it by up to 2%. The analyses were conducted for a single Reynolds number and speed over a range of angles of attack. The same cases will also be used in the experimental testing of the manufactured morphing wing model. [ABSTRACT FROM AUTHOR]

The developments of innovative adaptive structures on Unmanned Aerial Vehicles (UAVs), such as morphing wings, can potentially reduce system complexities by eliminating control surfaces and their auxiliary equipment. This technology has the potential of allowing a UAV to adapt to different mission requirements or to execute a particular mission more effectively by maintaining an optimum airfoil section over a range of speeds for different segments of a mission profile. Studies on a number of smart materials candidates are currently available in the open literature to achieve wing morphing. The material selection depends on several factors including fast dynamic response, low weight, capability to operate over a wide range of flight conditions and low power consumption. This paper presents a review on smart materials technologies for UAV morphing wings. A numerical study in terms of power requirements is also presented for two morphing wing concepts: flapped and twisted wing planforms. The energy calculations for both morphing configurations were based on a two-step procedure. The first step consists of computing the aerodynamic energy using an in-house Vortex-Lattice (VL) based program. Subsequently the pressure field obtained from the first step is then mapped into a finite element mesh and the structural strain energy is calculated. The numerical results indicated that flapped morphing wings have a better aerodynamic performance when compared to twisted wings and different morphing levels can be achieved using lighter smart materials with lower specific energy for this configuration.

The developments of innovative adaptive structures on Unmanned Aerial Vehicles (UAVs), such as morphing wings, can potentially reduce system complexities by eliminating control surfaces and their auxiliary equipment. This technology has the potential of allowing a UAV to adapt to different mission requirements or to execute a particular mission more effectively by maintaining an optimum airfoil section over a range of speeds for different segments of a mission profile. Studies on a number of smart materials candidates are currently available in the open literature to achieve wing morphing. The material selection depends on several factors including fast dynamic response, low weight, capability to operate over a wide range of flight conditions and low power consumption. This paper presents a review on smart materials technologies for UAV morphing wings. A numerical study in terms of power requirements is also presented for two morphing wing concepts: flapped and twisted wing planforms. The energy calculations for both morphing configurations were based on a two-step procedure. The first step consists of computing the aerodynamic energy using an in-house Vortex-Lattice (VL) based program. Subsequently the pressure field obtained from the first step is then mapped into a finite element mesh and the structural strain energy is calculated. The numerical results indicated that flapped morphing wings have a better aerodynamic performance when compared to twisted wings and different morphing levels can be achieved using lighter smart materials with lower specific energy for this configuration. [ABSTRACT FROM AUTHOR]

Over the past few years, better knowledge of aerodynamics and structures and the permanent need to improve the performance and efficiency of aircraft have led to the generalized adoption of wingtip devices. The requirements faced by wingtip devices throughout the various flight conditions are, however, different. A static wingtip device (as is the case with existing designs) must be a compromise of these various conflicting requirements, resulting in less than optimal effectiveness in each flight condition. A morphing device, on the other hand, can adapt to the optimum configuration for each flight condition, leading to improved effectiveness. This article presents a morphing wingtip mechanism based on a servo-actuated articulated winglet, able to rotate about two different axes: vertical axis (toe angle) and aircraft’s longitudinal axis (cant angle). These can be controlled independently by servo-actuators. The wingtip behavior is a function of aerodynamic and structural loads which, in turn, are interdependent, requiring a multidisciplinary design optimization procedure in order to determine the ideal wingtip configuration for each case. The proposed concept is applied to a multi-mission unmanned aerial vehicle and the results show that a morphing wingtip can outperform an optimum fixed design. The optimum geometries for the different flight missions are presented and the feasibility of such a morphing wingtip is confirmed by a prototype. The performance metrics of the morphing wingtip are compared to those of a fixed wingtip to quantify the gain associated with the use of the morphing concept and it is seen that the improvement can reach 25%. [ABSTRACT FROM PUBLISHER]