The design and application of adaptive devices are currently ambitious targets in the field of aviation research addressed at new generation aircraft. The development of intelligent structures involves aspects of multidisciplinary nature: the combination of compact architectures, embedded electrical systems and smart materials, allows for developing a highly innovative device. The paper aims to present the control system design of an innovative morphing flap tailored for the next generation regional aircraft, within Clean Sky 2 – Airgreen 2 European Research Scenario. A distributed system of electromechanical actuators (EMAs) has been sized to enable up to three operating modes of a structure arranged in four blocks along the chord-wise direction:
•upwards/downwards deflection and twisting of the final tip segment.
A state-of-art feedback logic based on a decentralized control strategy for shape control is outlined, including the results of dynamic stability analysis based on the blocks rational schematization within Matlab/Simulink® environment. Such study has been performed implementing a state-space model, considering also design parameters as the torsional stiffness and damping of the actuation chain. The design process is flowing towards an increasingly “robotized” system, which can be externally controlled to perform certain operations. Future developments will be the control laws implementation as well as the functionality test on a real flap prototype.
The in-flight control of the wing shape is widely considered as one of the most promising solutions to enhance the aerodynamic efficiency of the aircraft thus minimizing the fuel burnt per mission (-). In force of the fallout that the implementation of such a technology might have on the greening of the next generation air transport, ever increasing efforts are spent worldwide to investigate on robust solutions actually compliant with industrial standards and applicable airworthiness requirements. In the framework of the CleanSky2, a research program in aeronautics among the largest ever founded by the European Union, the authors focused on the design and validation of two devices enabling the camber-morphing of winglets and flaps specifically tailored for EASA CS-25 category aircraft (). The shape transition was obtained through smart architectures based on segmented (finger-like) ribs with embedded electromechanical actuators. The combined actions of the two smart systems was conceived to modulate the load distribution along the wing while keeping it optimal at all flight conditions with unequalled benefits in terms of lift-over-drag ratio increase and root bending moment alleviation. Although characterized by a quasi-static actuation, and not used as primary control surfaces, the devices were deeply analysed with reference to their impact on aircraft aeroelastic stability. Rational approaches were adopted to duly capture their dynamics through a relevant number of elastic modes; aeroelastic coupling mechanisms were identified in nominal operative conditions as well as in case of systems’ malfunctioning or failure. Trade off flutter and divergence analyses were finally carried out to assess the robustness of the adopted solutions in terms of movable parts layout, massbalancing and actuators damping.
Within the framework of the JTI-Clean Sky (CS) project, and during the first phase of the Low Noise
Configuration Domain of the Green Regional Aircraft – Integrated Technological Demonstration (GRA-ITD, the
preliminary design and technological demonstration of a novel wing flap architecture were addressed. Research
activities were carried out to substantiate the feasibility of morphing concepts enabling flap camber variation in
compliance with the demanding safety requirements applicable to the next generation green regional aircraft, 130-
seats with open rotor configuration.
The driving motivation for the investigation on such a technology was found in the opportunity to replace a
conventional double slotted flap with a single slotted camber-morphing flap assuring similar high lift
performances -in terms of maximum attainable lift coefficient and stall angle- while lowering emitted noise and
system complexity. Studies and tests were limited to a portion of the flap element obtained by slicing the actual
flap geometry with two cutting planes distant 0.8 meters along the wing span.
Further activities were then addressed in order to increase the TRL of the validated architecture within the second
phase of the CS-GRA. Relying upon the already assessed concept, an innovative and more advanced flap device
was designed in order to enable two different morphing modes on the basis of the A/C flight condition / flap
Mode1, Overall camber morphing to enhance high-lift performances during take-off and landing (flap deployed);
Mode2, Tab-like morphing mode. Upwards and downwards deflection of the flap tip during cruise (flap stowed)
for load control at high speed.
A true-scale segment of the outer wing flap (4 meters span with a mean chord of 0.9 meters) was selected as
investigation domain for the new architecture in order to duly face the challenges posed by real wing installation.
Advanced and innovative solutions for the adaptive structure, actuation and control systems were duly analyzed
and experimentally validated thus proving the overall device compliance with industrial standards and applicable