The advancements in aircraft materials, manufacturing technology, controller and hardware design allow developing increasingly flexible aircraft concepts. Generally, the flexibility comes as a side effect of lighter aircraft design and needs to be adequately accounted for, however, a more natural approach is to utilise the flexibility for the benefit of better performance, much like it is seen in nature. Active morphing is a technology that holds the potential to improve the performance and to extend the natural flight envelope of rigid aircraft. In this study, the design approach and the methodology behind the development of a fully composite the smart morphing wing are discussed.  This autonomous smart wing concept, called the Smart-X wing, aims to demonstrate in-flight performance optimisation of multiple objectives such as (i) drag optimisation, (ii) load alleviation, (iii) flutter suppression and (iv) shape control through multidisciplinary utilisation of smart sensing, control, actuation and integration.

The autonomous wing is composed of six morphing trailing edge modules, equipped with fast piezoelectric actuators at the morphing trailing for drag minimisation. The morphing is achieved by the TRIC (TRanslation Induced Camber) concept, where the skin is actuated internally, allowing smooth and seamless morphing along the chord. The target morphing shape is commanded using high-performance servos embedded in the wing box, allowing the trailing edge bottom skin to slide chordwise and partly spanwise direction inside a specifically designed slot. Each module is equipped with two pairs of actuators allowing local symmetric

(pure bending) and asymmetric (twist) morphing. Interconnected diagonal segments joined by an elastomer material allow seamless spanwise transition of lift distribution between de morphing modules. To sustain the required loads, meet the actuator constraints and achieve the desired morphing shapes for lift control increments, the composite structure of the wing is tailored and optimised. To achieve this optimised design, an FSI (Fluid-Structure Interaction) structural optimisation tool is developed, that allows (i) fast analysis and (ii) fast optimisation of ply orientation and thickness in terms of given input loads, desired target shapes and actuator limits. 

 

Both symmetric and asymmetric load are considered producing twist and pure bending morphing. The assessment shows that ply dropping produces the best design for given criteria and manufacturing constraints. Comparisons are made with ply orientation optimisation and convergence criteria and repeatability of the closed-loop FSI optimisation are discussed. Furthermore, the impact of the actuator performance in relation to the actuator selection, the actuator constraints and the actuation mechanism are investigated.

 

The developed tool also allows quick assessment of airfoil performance under given aerodynamic load and commanded actuators input position. This assessment is used to produce a Deep Neural Network  (DNN) based input-output mapping of actuator input versus deflected shape output and the control effectiveness in terms of lift increment needed for real-time active morphing control. Control strategies using this DNN based surrogate model are discussed in the study. 

 

The FSI optimisation is run in closed-loop until convergence is reached for a maximum of 30mm up, 20mm down (bending) and 20mm up/down (twist) of tip deflection under 60N actuator input load limit at 30 m/s flow velocity, the performance limit of the Open Jet Facility (OJF) of the Delft University of Technology where the wing is to be tested. During the wind tunnel test, static and dynamic loads, as well as the real-time drag, will be measured to assess the abovementioned multiple objectives that were defined for the Smart-X project.


Design of a Smart Morphing Wing Using Integrated and Distributed Trailing Edge Camber Morphing

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

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