This paper presents the design, optimization, realization and testing of a novel wing morphing concept, based on distributed compliance structures, and actuated by piezoelectric elements. The adaptive wing features ribs with a selectively compliant inner structure, numerically optimized to achieve aerodynamically efficient shape changes while simultaneously withstanding aeroelastic loads. The static and dynamic aeroelastic behavior of the wing, and the effect of activating the actuators, is assessed by means of coupled 3D aerodynamic and structural simulations. To demonstrate the capabilities of the proposed morphing concept and optimization procedure, the wings of a model airplane are designed and manufactured according to the presented approach. The goal is to replace conventional ailerons, thus to achieve controllability in roll purely by morphing. The mechanical properties of the manufactured components are characterized experimentally, and used to create a refined and correlated finite element model. The overall stiffness, strength, and actuation capabilities are experimentally tested and successfully compared with the numerical prediction. To counteract the nonlinear hysteretic behavior of the piezoelectric actuators, a closed-loop controller is implemented, and its capability of accurately achieving the desired shape adaptation is evaluated experimentally. Using the correlated finite element model, the aeroelastic behavior of the manufactured wing is simulated, showing that the morphing concept can provide sufficient roll authority to allow controllability of the flight. The additional degrees of freedom offered by morphing can be also used to vary the plane lift coefficient, similarly to conventional flaps. The efficiency improvements offered by this technique are evaluated numerically, and compared to the performance of a rigid wing.
The design of an airfoil structure involves the disciplines of aerodynamics and structural mechanics, both of which are considered in the design methodology presented in this article. The approach described in this article starts from a requirement formulation based on a time-series of spanwise lift distributions on a morphing wing, representing the mission profile of the aircraft as a whole. This allows to specify goals based directly on aerodynamic performances instead of prescribing fixed geometrical shapes. Using the aero-structural analysis tool presented here, together with a parametrization representing the airfoil outer shape as well as its mechanical properties, allows the formulation of a combined aero-structural optimization problem. Promising aerodynamic and structural morphing performances have been obtained by applying the method to a morphing concept using Dielectric Elastomers (DEs) as actuators. Although the coupled physics are considered and a detailed material model has been used, results can be obtained within reasonable computational time by parallel evaluation of the candidate solutions. Improved aerodynamic performances have been obtained using this concurrent coupled method, in comparison to a sequential aerodynamic and structural optimization.
In this article, a compliant morphing wing featuring an innovative load-carrying, highly anisotropic, doubly corrugated morphing skin is introduced. A multi-disciplinary design methodology is used to optimally generate the compliant structure with the aim of maximising the produced rolling moment, while minimising mass and drag. The design tool considers the three-dimensional, aeroelastic behaviour and structural constraints. In particular, a parametric metamodel is used to identify the best morphing skin design. The results show that the wing can achieve high levels of control authority and has a lower or equivalent weight compared to conventional wings. A wing demonstrator is manufactured and its aeroelastic performance is tested. The measurements of the displacement field show an appreciable deformation without shape discontinuities. Low-speed wind tunnel tests indicate that the designed wing can produce roll moments that are sufficient for replacing conventional ailerons. Moreover, the obtained changes in shape have a negligible effect on the zero-lift drag, thus demonstrating the aerodynamic efficiency of profile changes achieved through morphing. An effective solution for covering the used corrugation while allowing for shape changes is also introduced and tested.
The aerodynamic and structural performance of a morphing wing concept, based on fully compliant structures and actuated by closed-loop controlled solid state piezoelectric actuators, is investigated numerically and experimentally. The morphing wings are designed for a 1.75-m-span unmanned aerial vehicle operating at up to 30 m∕s, following lightweight aeronautical construction principles. The goal of providing roll controllability exclusively through morphing is achieved with a concurrent aerostructural optimization, considering static and dynamic aeroelastic effects. The aeroelastic response of the wings is experimentally assessed through wind tunnel tests, performed at different speeds, angles of attack, and actuation levels. The test campaign confirms the ability to achieve lift and rolling moment variations while maintaining a high aerodynamic efficiency, and the results closely match the numerical predictions. An 8-min flight test is performed by replacing the unmanned aerial vehicle wings with the morphing system, demonstrating the capabilities of the concept in its operational environment. This experimental assessment confirms the performance of the design, its robustness, and the possibility of implementing the morphing concept and the required high-voltage control system in small unmanned aerial vehicles. Ultimately, the results show the possibility of replacing the conventional ailerons of similarly sized airplanes with the proposed solution, achieving significant efficiency improvements while guaranteeing controllability.
This article presents the design, optimization and performance assessment of a novel structure-actuation morphing concept for a flying wing, enabling the flight control for straight flight and around the pitch and roll axes. The applied camber-morphing concept utilizes an optimized selectively compliant internal structure, combined with electromechanical actuators to achieve a trailing edge deflection. These deflections lead to variations of the local and global lift, permitting to control the flight of the aircraft. The aero-structural behaviour of the wing is analysed using a coupled three-dimensional aerodynamic and structural simulation tool. An optimization of the planform, aerodynamic shape, internal structure and actuation parameters is performed to attain a longitudinally stable and aerodynamically efficient flying wing. The drag increment caused by morphing is minimized through the numerical optimization, resulting in high aerodynamic efficiency across a range of flight speeds. The stiffness and morphing capabilities of the manufactured wing are characterized experimentally and are compared with the numerical predictions, and the aerodynamic and aeroelastic behaviour of the wing is investigated through wind tunnel tests. The test results indicate the ability of the flying wing to achieve sufficient variations in lift, roll and pitch to control the flight completely through camber morphing.
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