Morphing is an increasingly investigated topic in aeronautics due to the performance improvements brought by aerodynamic shapes adaptivity on large aircraft. Being aerodynamics mainly driven by geometry, a structure that can modify its shape may achieve tremendous capability enhancement, especially if its operating scenario is wide. However, the implementation of morphing structures leads to many issues that still need to be properly solved to make the technology fully operative in real application scenarios. For instance, additional DOFs generate systems with increased modal density and then with more complex aeroelastic behaviour, and premature onset of dynamic instabilities. The authors of the present paper have dealt with this problem in other publications, in cooperation with several colleagues, and interesting results are available in literature, to some extent. In this general framework, there are peculiar aspects that only recently have started to catch the attention of the scientific community. Among those, a particular one is the objective of the present work, referring to the numerical simulation strategy of adaptive devices. The kinematic system at the basis of a wide class of morphing structures is driven by an actuation chain, which gives an important contribution to the already cited aeroelastic behaviour. For safety-critical embedded subsystems, it is crucial to detect potential failures and predict their impacts since the early design stages. Now, kinematic components significantly affecting the structural dynamics, as torsion bars and bearings, are assumed rigid in the traditional simulation strategy. If such a concept may be supposed valid for standard layouts (as in the case of flap, ailerons and other moveable systems), it cannot be held for architectures integrating hundreds of those mechanical parts. This work addresses preliminary investigations on systematic analyses carried out on detailed simulations of selected components of aircraft morphing structures, trying to evaluate the effects of elasticity of bearings and hinged connections on the global dynamic response.
After pioneering examples in the ’70 and the ’80, technology advances have brought aircraft morphing systems close to the exploitation on commercial vehicles. However, in spite of many successes, further steps shall be accomplished before series production lines are entered. They introduce new needs and sometimes exasperate aspects till now under control in the design phase. The increased number and kind of parts pushes for implementing additive manufacturing techniques; their modelling gives rise in turn to important simulation challenges. In case of mechanical, alternative to compliant systems, modelling of elements shall take in consideration behavior that is substantially different from the analogous counterparts on classical devices. Hinges and torsion bars are more diffused and smaller in these architectures. This work deals with hinges modelling inside mechanically-driven architectures for adaptive winglets. Impact of these aerodynamic surfaces on aircraft stability is crucial and accurate models are required to guarantee their correct implementation. Morphing capability emphasizes this occurrence even more. Schematization effects are investigated in terms of both static and dynamic response. The variation of the deformed shape is therefore examined, identifying the strain map and internal forces distribution changes, essential for design purposes and stress analysis. Modal characteristics deviations are then explored, which may substantially influence aeroelastic stability margins. It is envisaged that this approach could be exploited to consider lags effect. A parametric investigation is finally carried out to identify structural behavior sensitivity to such kind of modifications.
The adoption of mechanical systems represents a very promising solution to realistically enable wing-camber morphing for large civil aircraft. These systems implement the change of shape through the relative motion of parts usually interconnected by means of hinges, and therefore, without any morphing-induced elastic deformation of the load carrying structure; conversely to what happens in compliant structures, the energy provided by the actuation system is here spent to counteract only the external aerodynamic loads which are in turn dependant on shape, speed and flight altitude. Apart of the more effective use of the available power, the mechanical systems show a higher level of technological maturity and readiness for flight thanks to their higher robustness, reliability and maintainability, as well as in force of their similarity with conventional airworthy architectures already in flight. On the other hand, the use of multiple-hinges connections imposes a careful analysis of the effects induced by any degradation of their mechanical performance leading to overall system malfunction or local failures. 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 a camber-morphing flap specifically tailored for EASA CS-25 category aircraft. The shape transition is obtained through a smart architecture based on segmented (finger-like) ribs with embedded electromechanical actuators. Three large tabs were located at the flap trailing edge to actively control the shape of the wing in cruise and to optimize the aerodynamic load distribution along the span. Aeroelastic phenomena related to these flap components were duly addressed since the very preliminary design stage in order to avoid the maturation of a potentially unstable architecture; rational approaches compliant with applicable airworthiness requirements were implemented to properly model and investigate the aeroelastic behaviour of the flap tabs in nominal working conditions. Finally, free plays and internal failures were accurately simulated and their effects on the aeroelastic stability of the aircraft were duly investigated in order to assess the robustness of the conceived tabs as well as of the embedded mechanical subsystems driving their motion.
Variation of trailing edge camber proved to be one of the easiest and most effective ways to modify aerofoil shape to match different aircraft operational weights, with benefits approaching 3% of fuel savings or, equivalently, range extension. This is particularly the case of commercial planes, where both initial take-off conditions (because of the unpredictable payload or the specific required mission – transfer flight, for instance) and in-flight states (for the kerosene consumption) can undergo significant differences. Several studies (like the European Research Programs SARISTU or JTI-GRA) demonstrated that the most sensible region for installing an adaptive trailing edge system for those aims is towards the wing tip. This is unfortunately a very delicate area where usually ailerons are deployed and where significant mass insertions could affect the aeroelastic response with some risks of instabilities. Furthermore, the volume available are really limited so that the installation of a fully embedded system is challenging.
Moving from the experience taken in many former projects as the cited ones, the authors faced the problem of installing a fully integrated adaptive trailing edge system within the existing structural skeleton of a reference aileron and defined a design strategy to take into account the aeroelastic modifications due to the installation of such a device. Besides, the architecture preserved the original function of that control surface so that it could work as a standard aileron (classical rigid tab movement) with the augmented function of a deformable, quasi-static shape. In this sense, the proposed system exhibited a double functionality: a conventional rigid aileron with augmented shape modification capability plus a continuous, slow change of the trailing edge, occurring during flight for compensating aircraft weight variation.
The research was carried out within the Italian-Canadian program MDO-505 and led to the realisation of a multifunctional aileron with two operational motor systems (one for the classical aileron working and the other for the morphing enforcement), completely integrated so that no external element was visible or affected the aerodynamics of the wing. The manufacture of this device was possible thanks to the development of a suitable design process that allowed taking into account both the structural and the aeroelastic response of the integrated architecture. This system was part of an adaptive wing section that was completed with the realisations made by the ETS of Montreal, the Quebecoise Consortium for Aerospace Research and Innovation (CRIAQ) and the IAR-NRC, supported by Bombardier and Thales Canada. The joint demonstrator was tested in the wind tunnel at the NRC facilities in Ottawa and gave confirmation of the aerodynamic, aeroelastic and structural predictions.
The paper that is herein presented deals therefore with the design process and the manufacture of an adaptive trailing edge, installed within the existing aileron system of a wing segment, to undergo wind tunnel tests. The resulting device considers the definition of the kinematic structural system, the development of the integrated actuator system, their integration and the assessment of their static and dynamic structural response, and the verification of a safe aeroelastic behavior. Numerical and experimental results are presented, achieved in lab and wind tunnel environments.
Aeronautic and aerospace engineering is recently moving in the direction of developing morphing wing devices, with the aim of making adaptable the aerodynamic shapes to different operational conditions. Those devices may be classified according to two different conceptual architectures: kinematic or compliant systems. Both of them embed within their body all the active components (actuators and sensors), necessary to their operations. In the first case, the geometry variation is achieved through an augmented classical mechanism, while in the second case the form modification is due to a special arrangement of the inner structure creating a distributed elastic hinges arrangement. Whatever is the choice, novel design schemes are introduced. Then, it is almost trivial to conclude that standard methods and techniques cannot be applied easily to these innovative layouts. In other words, because new architectures are produced, the former construction paradigms cannot be maintained as they are but shall be somehow transformed and assimilated by the design engineers’ community. In the meantime, the realization process should go on and morphing elements shall be realized, irrespectively of the full maturity of the associated concepts. Therefore, if optimization methods are important for the better exploitation of usual constructions, they become absolutely necessary for the technological demonstration of the capability of such breakthrough systems. In fact, standing their aim of improving the effectiveness of the aircraft flight and reducing then its overall weight, mass impact plays a fundamental role. Promised benefits could completely vanish if the added should overcome the saved weight!
In the study herein presented, the design process of a morphing winglet is reported. The research is collocated within the Clean Sky 2 Regional Aircraft IADP, a large European programme targeting the development of novel technologies for the next generation regional aircraft. The ultimate scope concerns the definition of an adaptive system for alleviating the gust loads and possibly modifying the wing load distribution in the sense of minimizing the attachment momentum (the parameter that governs the wing sizing). The proposed kinematic system is characterized by movable surfaces, each with its own domain authority, sustained by a winglet skeleton and completely integrated with a devoted actuation system. Preliminary aeroelastic investigations did already establish the robustness of the referred structural layout. This paper summarizes the activities relating to the optimization of the envisaged morphing system architecture. Moving from a standard configuration, a process is carried out to identify the lighter adaptive layout that can bear the external and internal loads without experiencing excessive stress levels for its safe operation. The most severe loads are taken into account for this process, as provided by the industrial partner, showing the reliability of the proposed solution on-board of a standard commercial aircraft. The optimization process produces interesting, sometime surprising, results that promise to reduce the weight impact of the structural skeleton for more than 40% with exclusive reference to the regions undergoing the optimization process. Such figure reduces to 15% if the complete structure is taken into account, and 12% if the skin contribution is included. The innovative outcomes are discussed in detail. Results are verified with a dedicated study that proves the consistency of the procedure and the trustworthiness of the computations.
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.
The development of adaptive morphing wings has been individuated as one of the crucial topics in the
greening of the next generation air transport. Research programs have been lunched and are still running
worldwide to exploit the potentials of morphing concepts in the optimization of aircraft efficiency and in the
consequent reduction of fuel burn. In the framework of CRIAQ MDO 505, a joint Canadian and Italian
research project, an innovative camber morphing architecture was proposed for the aileron of a reference
civil transportation aircraft; aileron shape adaptation was conceived to increase roll control effectiveness as
well as to maximize overall wing efficiency along a typical flight mission. Implemented structural solutions
and embedded systems were duly validated by means of ground tests carried out on a true scale prototype.
Relying upon the experimental modes of the device in free-free conditions, a rational analysis was carried out
in order to investigate the impacts of the morphing aileron on the aeroelastic stability of the reference
aircraft. Flutter analyses were performed in compliance with EASA CS-25 airworthiness requirements and
referring -at first- to nominal aileron functioning. In this way, safety values for aileron control harmonic and
degree of mass-balance were defined to avoid instabilities within the flight envelope. Trade-off analyses were
finally addressed to justify the robustness of the adopted massbalancing as well as the persistence of the
flutter clearance in case of relevant failures/malfunctions of the morphing system components.
The study herein described is aimed at investigating the feasibility of an innovative full-scale camber morphing
aileron device. In the framework of the “Adaptive Aileron” project, an international cooperation between Italy and
Canada, this goal was carried out with the integration of different morphing concepts in a wing-tip prototype. As
widely demonstrated in recent European projects such as Clean Sky JTI and SARISTU, wing trailing edge morphing
may lead to significant drag reduction (up to 6%) in off-design flight points by adapting chord-wise camber
variations in cruise to compensate A/C weight reduction following fuel consumption. Those researches focused on
the flap region as the most immediate solution to implement structural adaptations. However, there is also a growing
interest in extending morphing functionalities to the aileron region preserving its main functionality in controlling
aircraft directional stability. In fact, the external region of the wing seems to be the most effective in producing “lift
over drag” improvements by morphing. Thus, the objective of the presented research is to achieve a certain drag
reduction in off-design flight points by adapting wing shape and lift distribution following static deflections. In
perspective, the developed device could also be used as a load alleviation system to reduce gust effects, augmenting
its frequency bandwidth. In this paper, the preliminary design of the adaptive aileron is first presented, assessed on
the base of the external aerodynamic loads. The primary structure is made of 5 segmented ribs, distributed along 4
bays, each splitted into three consecutive parts, connected with spanwise stringers. The aileron shape modification is
then implemented by means of an actuation system, based on a classical quick-return mechanism, opportunely
suited for the presented application. Finite element analyses were assessed for properly sizing the load-bearing
structure and actuation systems and for characterizing their dynamic behavior. Obtained results are reported and
Like any other technology, morphing has to demonstrate system level performance benefits prior to implementation onto a real aircraft. The current status of morphing structures research efforts (as the ones, sponsored by the European Union) involves the design of several subsystems which have to be individually tested in order to consolidate their general performance in view of the final integration into a flyable device. This requires a fundamental understanding of the interaction between aerodynamic, structure and control systems. Important worldwide research collaborations were born in order to exchange acquired experience and better investigate innovative technologies devoted to morphing structures. The “Adaptive Aileron” project represents a joint cooperation between Canadian and Italian research centers and leading industries. In this framework, an overview of the design, manufacturing and testing of a variable camber aileron for a regional aircraft is presented. The key enabling technology for the presented morphing aileron is the actuation structural system, integrating a suitable motor and a load-bearing architecture. The paper describes the lab test campaign of the developed device. The implementation of a distributed actuation system fulfills the actual tendency of the aeronautical research to move toward the use of electrical power to supply non-propulsive systems. The aileron design features are validated by targeted experimental tests, demonstrating both its adaptive capability and robustness under operative loads and its dynamic behavior for further aeroelastic analyses. The experimental results show a satisfactory correlation with the numerical expectations thus validating the followed design approach.
Next-generation flight control actuation technology will be based on “more electric” concepts to ensure benefits in terms of efficiency, weight and maintenance. This paper is concerned with the design of an un-shafted distributed servo-electromechanical actuation system, suited for morphing trailing edge wings of large commercial aircraft. It aims at producing small wing camber variations in the range between -5° and +5° in cruise, to enable aerodynamic efficiency improvements. The deployment kinematics is based on multiple “direct-drive” actuation, each made of light-weight compact lever mechanisms, rigidly connected to compliant ribs and sustained by load-bearing motors. Navier-Stokes computations are performed to estimate the pressure distribution over the interested wing region and the resulting hinge moments. These transfer to the primary structure via the driving mechanism. An electro-mechanical Matlab/Simulink model of the distributed actuation architecture is developed and used as a design tool, to preliminary evaluate the complete system performance. Implementing a multi-shaft strategy, each actuator is sized for the torque acting on the respective adaptive rib, following the effect of both the aerodynamic pressure and the morphing skin stiffness. Elastic trailing edge rotations and power needs are evaluated in operative conditions. Focus is finally given to the key challenges of the proposed concept: targeting quantifiable performance improvements while being compliant to the demanding requirements in terms of reliability and safety.
Nature teaches that the flight of the birds succeeds perfectly since they are able to change the shape of their wings in a
continuous manner. The careful observation of this phenomenon has re-introduced in the recent research topics the study
of “metamorphic” wing structures; these innovative architectures allow for the controlled wing shape adaptation to
different flight conditions with the ultimate goal of getting desirable improvements such as the increase of aerodynamic
efficiency or load control effectiveness.
In this framework, the European research project SARISTU aimed at combining morphing and smart ideas to the leading
edge, the trailing edge and the winglet of a large commercial airplane (EASA CS25 category) while assessing integrated
technologies validation through high-speed wind tunnel test on a true scale outer wing segment. The design process of
the adaptive trailing edge (ATED) addressed by SARISTU is here outlined, from the conceptual definition of the
camber-morphing architecture up to the assessment of the device executive layout. Rational design criteria were
implemented in order to preliminarily define ATED structural layout and the general configuration of the embedded
mechanisms enabling morphing under the action of aerodynamic loads. Advanced FE analyses were then carried out and
the robustness of adopted structural arrangements was proven in compliance with applicable airworthiness requirements.
A key technology to enable morphing aircraft for enhanced aerodynamic performance is the design of an adaptive control system able to emulate target structural shapes. This paper presents an approach to control the shape of a morphing wing by employing internal, integrated actuators acting on the trailing edge. The adaptive-wing concept employs active ribs, driven by servo actuators, controlled in turn by a dedicated algorithm aimed at shaping the wing cross section, according to a pre-defined geometry. The morphing control platform is presented and a suitable control algorithm is implemented in a dedicated routine for real-time simulations.
The work is organized as follows. A finite element model of the uncontrolled, non-actuated structure is used to obtain the plant model for actuator torque and displacement control. After having characterized and simulated pure rotary actuator behavior over the structure, selected target wing shapes corresponding to rigid trailing edge rotations are achieved through both open-loop and closed-loop control logics.
In this paper, a methodology to perform thermal and acoustic characterization of a forest fire event is reported. The
analysis of fire emission properties has been carried out through laboratory and field testing, consisted in the burning of
different fuels placed on tables or on field plots. The objectives of the trials have been the evaluation of fire radiated heat
to fiber optic sensors with cables in open air, buried or inside the flames, and the evaluation of fire acoustic spectra, with
respect to the different fuel types and fire conditions. Post processing algorithms on acquired acoustic signals have been
developed to evaluate the fire frequency content, which defines the signature of the fire noise; the results obtained have
confirmed the main spectrum features reported in literature. The measurement of temperature variations by fiber optic
sensors has been useful to characterize sensors behavior with respect to fire, wind and smoke. The results of the tests
have been used in the design phase of a new fire monitoring system made up of acoustic sensors, able to detect and track
fires from the beginning, and fiber optic sensors, for a capillary monitoring of temperature in forest areas.