Giulio Molinari

Aero-Structural Optimization of Morphing Airfoils for Adaptive Wings

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.

Aero-Structural Optimization of Three-Dimensional Adaptive Wings with Embedded Smart Actuators

The design of morphing wings involves the disciplines of aerodynamics and structural mechanics; the aero-structural coupling is of chief importance in case smart materials are used as distributed actuators. Considering these specific requirements, this paper presents an approach to optimize concurrently the variables describing the wing external shape, the internal compliant structure, and the embedded actuators. An aeroelastic analysis tool is developed to simulate the response of distributed compliance three-dimensional wings, considering the activation of the smart materials. A method to formulate the optimization requirements based on the aircraft mission is presented, using the aerodynamic performance from the aeroelastic study in the optimization goal. To prove the validity and the computational feasibility of this methodology, a morphing wing for a 3-m-wingspan radio-controlled plane is optimized. A structural concept actuated by single crystal Macro Fiber Composites and dielectric elastomers is in...

Design and experimental characterisation of a morphing wing with enhanced corrugated skin

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.

Design, realization and structural testing of a compliant adaptable wing

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.

Design and Realization of a Compliant Adaptable Wing

This paper presents the design, optimization, realization and testing of a novel wing morphing concept based on compliant structures actuated by Macro Fiber Composites. The geometry of the compliant morphing ribs is determined through multidisciplinary optimizations. The static and dynamic behavior of the wing, and the effect of activating the actuators, is assessed using 3‑D aeroelastic simulations. The performance and manufacturability of a wing designed according to this approach are investigated. The achieved active deformations produce sufficient roll control authority to replace conventional ailerons. Abstract The numerical simulation for the conformal shape adaptation of the wing is compared to experimental results, showing good agreement. The aerodynamic and structural behavior of the introduced concept is investigated through a validated finite element model, revealing the potential of the presented morphing wing. Abstract A closed-loop controller driving high-voltage electronics counteracts the nonlinearity and hysteresis of the piezoelectric actuators, allowing for controlling the wings’ morphing level.

Aerostructural Performance of Distributed Compliance Morphing Wings: Wind Tunnel and Flight Testing

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 ...

Planform, aero-structural, and flight control optimization for tailless morphing aircraft

Tailless airplanes with swept wings rely on variations of the spanwise lift distribution to provide controllability in roll, pitch and yaw. Conventionally, this is achieved utilizing multiple control surfaces, such as elevons, on the wing trailing edge. As every flight condition requires different control moments (e.g. to provide pitching moment equilibrium), these surfaces are practically permanently displaced. Due to their nature, causing discontinuities, corners and gaps, they bear aerodynamic penalties, mostly in terms of shape drag. Shape adaptation, by means of chordwise morphing, has the potential of varying the lift of a wing section by deforming its profile in a way that minimizes the resulting drag. Furthermore, as the shape can be varied differently along the wingspan, the lift distribution can be tailored to each specific flight condition. For this reason, tailless aircraft appear as a prime choice to apply morphing techniques, as the attainable benefits are potentially significant. In this work, we present 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 Macro Fiber Composite (MFC) piezoelectric elements. The multidisciplinary optimization is performed considering the static and dynamic aeroelastic behavior of the resulting structure. The goal is the maximization of the aerodynamic efficiency while guaranteeing the controllability of the plane, by means of morphing, in a set of flight conditions.

Aero-StructurAl optimizAtion of 3-D ADAptive WingS With embeDDeD SmArt ActuAtorS

Molinari, G., Quack, M., Dmitriev, V., Morari, M., Jenny, P., and Ermanni, P., “Aero-structural optimization of Morphing Airfoils for Adaptive wings,” Journal of Intelligent Material Systems and Structures, Vol. 22, No. 10, Sept. 2011, pp. 1075-1089. Molinari, G., Quack, M., Dmitriev, V., Morari, M., Jenny, P., and Ermanni, P., “A Multidisciplinary Approach for wing Morphing,” in 21st International Conference on Adaptive Structures and Technologies (ICAST), State College, PA, USA, Oct. 4-6, 2010. optimization results