Gianluca Amendola

Real-time monitoring of a variable-camber aileron rib by original strain-angle transducer:

The object of this work is the conceptual design and modelling of a transducer based on fibre optic sensor and conceived to measure rotations of rigid components around a pivot. The device, namely, post-buckling-fibre Bragg grating, is constituted of a flexible metal plate hosting a fibre Bragg grating strain sensor; the edges of the plates are hinged onto the rotating rigid bodies, eccentrically with respect to the pivot. In this way, any increase in rotation produces a further bending of the plate corresponding to a fibre Bragg grating wavelength shift. Among the different applications, an aileron morphing architecture is considered. This architecture is composed of a rib made of three rigid parts, hinged each other and moved through a dedicated kinematic chain. Two post-buckling-fibre Bragg grating devices are installed between the adjacent rib blocks giving a measure of their current angular rotation. A peculiarity of the proposed device is its ability in working in post-buckling configuration, with two main advantages: (1) easy, plug-and-play, installation (the device supporting plate can be manually bent and plugged within the connection hinges) and (2) tuning of the sensitivity or range of measure, on the basis of the fibre Bragg grating location onto the plate and of the initial post-buckling level. At first, the conceptual design was dealt with a theoretical model describing the post-buckling behaviour of beams, highlighting the effect of the main design parameters; then, the plate displacement field was related to rotation angle of the rib; a dedicated numerical (finite element) model was thus realized to prove the concept feasibility and simulate in detail its functionality. Finally, experimental set-up was provided in order to validate the design.

Actuation System Design for a Morphing Aileron

In the field of European and International morphing structures projects, the CRIAQ MD0-505 enables collaboration among Italian and Canadian research centers and industries paying particular attention to the development of innovative design in the area of adaptive technologies. The main project goals involve the design of a wing trailing edge device capable to improve aerodynamic efficiency in all the flight envelope leading to fuel consumption reduction with positive impact on aircraft weight. This paper deals with the design and modeling of a novel actuation system of a full scale morphing aileron for a regional aircraft wing. The proposed aileron architecture is characterized by segmented adaptive ribs. Each rib is composed of two movable blocks connected by means of rotational hinges in which are housed bearings and bushing in a finger-like mechanism. Rib actuation is guaranteed by an actuation system composed of a dedicated kinematic chain derived from a quick-return mechanism. In order to achieve the aileron target shapes, the system is driven by a set of servo-rotary electro mechanical actuators that permit a highly integrated design which lay the groundwork for the technological transition from the torque shaft to the distributed actuation architecture.

Modal stability assessment for a morphing aileron subjected to actuation system failures: Numerical analysis supported by test evidence

The meaningful growth process and the exponential development related to aircraft industry has currently introduced new requirements concerning the fuel burn reduction and the noise emitted. The awareness on meeting the comfort targets implied a significant evolution of the assessments in aircraft design, aimed at reducing the problems that have emerged in empirical investigations. The aircraft renewal process involves targeted technical choices both to careful observance of safety as to the market requirements. In the current “low-noise” research scenario on a global scale, the morphing technology is playing a dominant role for the many benefits available in the greening of the next generation air transport. The research project CRIAQ-MDO505, born by an intense synergy among industries, research centers and universities has allowed for investigating morphing structures potentials through the design and manufacturing of a variable camber aileron tailored for CS-25 category aircraft applications. In this framework, the authors focused on the setup of an advanced finite element model (FEM) and on its validation through ground resonance tests performed on a true-scale prototype. A very good correlation between numerical and experimental modal parameters was proven thus showing the adequacy of the adopted modelling strategies as well as the reliability of the FEM. Relying upon the validated FEM, sensitivity modal analyses were carried out to evaluate the stability of results with respect to single and combined failures of the actuation line enabling morphing. Modal parameters pertinent to each failure scenario were arranged into a rational database for further studies on the aero-servo-elastic behavior of the morphing system.

Preliminary aeroelastic assessment of a large aeroplane equipped with a camber-morphing aileron

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.

Experimental characterization of an adaptive aileron: lab tests and FE correlation

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.

Morphing Technologies: Adaptive Ailerons

European Union is involving increasing amount of resources on research projects that will dramatically change the costs of building and operating aircraft in the near future. Morphing structures are a key to turn current airplanes to more efficient and versatile means of transport, operating into a wider range of flight conditions. The concept of morphing may aim at a large number of targets, and its assessment strongly depends on the final objectives and the components where it has to be deployed. Maneuver, takeoff, landing, cruise conditions, just to cite few and very general examples, have all their own peculiarities that drive the specifications the wing shape change has to suit on. In general, an adaptive structure ensures a controlled and fully reversible transition from a baseline shape to a set of different configurations, each capable of withstanding the relative external loads. The level of complexity of morphing structures naturally increases as a consequence of the augmented functionality of the reference system. Actuation mechanisms constitute a very crucial aspect for adaptive structures design because has to comply variable wing shapes with associated loads and ensure the prescribed geometrical envelope. This chapter provides a presentation of the state of the art, technical requirements, and future perspectives of morphing ailerons. It addresses morphing aircraft component architecture and design with a specific focus on the structural actuator system integra‐ tion. The approach, including underlying concepts and analytical formulations, combines methodologies and tools required to develop innovative air vehicles. Aileron is a very delicate region, where aeroelastic phenomena may be very important because of the very reduced local stiffness and the complex aerodynamics, typical of the wingtip zone. On the other side, this wing segment showed to be the one where higher cruise benefits could be achieved by local camber variations. This target was achieved while keeping the typical maneuver functions.

Optimization design process of a morphing winglet

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.

Chapter 18 – Morphing Aileron

More severe regulations are growing worldwide due to increasing air traffic in order to reduce fuel consumption and noise. The achievement of challenging targets in terms of pollutant emissions abatement demands for the development of innovative aircraft technologies. Morphing is one of them and plays an extraordinary role for the improvement of aircraft performance. Many research projects are currently focused on morphing both in US and Europe. Among these, the CRIAQ-MDO505 constitute the first trans-European cooperation project on smart technologies. Its aim is to investigate morphing structures potential through the design and manufacturing of a full-scale variable camber aileron designed according to the requirements of a regional aircraft. This project was carried out by Italian and Canadian academies, research centers, and leading industries. In this framework, the authors worked on the development of this technology addressing both numerical and experimental activities up to a thorough validation of a physical prototype. The effective capabilities of the adaptive prototype were proven by means of wind tunnel and ground test campaigns which successfully demonstrated the feasibility and the reliability of a morphing aileron.

Chapter 11 – Sensor Systems for Smart Architectures

Abstract Structurally integrated sensors form the key element of any smart structure. The resident sensing system within such a structure would provide the necessary information on its shape, orientation, load distribution and health monitoring as well. Strain data is an example of information retrieved from the most common and widest used sensors for structural applications. Strain gauge foils and piezoelectric are still referenced for structural monitoring and control. On the other hand, graphene-based and in particular, fiber optic based sensors can be considered the core technologies of 21st century smart structures. Large scale monitoring is the challenging issue to deal with. The distributed capability of fiber optic sensors, the spray deposition of some graphene-based polymers, and the possibility of drastically reducing the cabling by means of wireless technology, can be the way to make smart integration of large scale sensors possible. The purpose of this chapter is to briefly show that certain aspects of this technology could have an important role to play in industrial sectors like the aeronautical one. This is accomplished by some examples on how and where the optical sensing technology has been applied.

Chapter 22 – On the Experimental Characterization of Morphing Structures

Abstract A major difficulty in the design of morphing devices for aircraft wings is to reach an adequate compromise between high load-carrying capacity to withstand aerodynamic loads and sufficient flexibility to achieve better aerodynamic performance. Such counteracting and demanding targets lead to an increased structural complexity whose experimental characterization is a matter of high priority prior to the ultimate physical integration into the aircraft structure. Compared to the passive counterpart, morphing devices enable augmented capabilities by locally adapting wing shape and lift distribution through either a quasistatic or dynamic deflection, with excursions ranging into a few units of degrees, positive and negative. This chapter provides an overview of the verification approaches suitable for morphing devices ranging from the basic concepts applicable to individual subsystems up to the global experimental analysis of the integrated system. A number of test objectives are illustrated at both component and system level, providing practical tips for the experimental analysis of morphing structures combining both compliant structural systems and multibox self-contained actuation mechanisms.