Monica Ciminello

Distributed Actuation and Control of a Morphing Wing Trailing Edge

In a morphing wing trailing edge device, the actuated system stiffness, load capacity, and integral volumetric requirements drive flutter, actuation strength, and aerodynamic performance. Design studies concerning aerodynamic loads, structural properties, and actuator response provide sensitivities to aeroelastic performance, actuation authority, and overall weight. Based on these considerations, actuation mechanism constitutes a very crucial aspect for morphing structure design because the main requirement is to accomplish variable shapes for a given trailing edge structural mechanism within the limits of the maximum actuation torque, consumed power, and allowable size and weight. In this work, a lightweight and compact lever driven by electromechanical actuators is investigated to actuate the morphing trailing edge device. An unshafted distributed servoelectromechanical actuation arrangement driven by a dedicated control system is deployed to realize the transition from the baseline configuration to a set of design target ones and, at the same time, to withstand the external loads. Numerical and experimental investigations are detailed to demonstrate system effectiveness and reliability using a feedback sensing data from integrated FBG sensors.

Structural Design of an Adaptive Wing Trailing Edge for Large Aeroplanes

The structural design process of an adaptive wing trailing edge (ATED) was addressed in compliance with the demanding requirements posed by the implementation of the architecture on large aeroplanes. Fast and reliable elementary methods combined with rational design criteria were adopted in order to preliminarily define ATED box geometry, structural properties, and the general configuration of the embedded mechanisms enabling box morphing under the action of aerodynamic loads. Aeroelastic stability issues were duly taken in account in order to safely assess inertial and stiffness distributions of the primary structure as well as to provide requirements for the actuation system harmonics. Results and general guidelines coming from the preliminary design were then converted into detailed drawings of each box component. Implemented solutions were based on designer’s industrial experience and were mainly oriented to increase the structural robustness of the device, to minimize its manufacturing costs, and to simplify assembly and maintenance procedures. The static robustness of the executive layout was verified by means of linear and nonlinear stress analyses based on advanced FE models; dynamic aeroelastic behaviour of the stress-checked structure was finally investigated by means of rational analyses based on theoretical mode association.

Manufacturing and Testing of Smart Morphing SARISTU Trailing Edge

Increasing environmental awareness and increasing fuel prices push aircraft industry to enhance aircraft efficiency. Morphing is considered a promising technology for future and next-generation aircrafts. Morphing aircraft changes its external geometry significantly during flight which moderates the design requirements. Adaptive Trailing Edge Device (ATED) is designed and manufactured under SARISTU (Smart Intelligent Aircraft Structures) project. The main challenge is to design and manufacture the smart ATED structure able to support the necessary loads, but it is also capable of changing its geometry. The structure design and actuation system are interrelated. Integration methodology drives multi-disciplinary thinking group from the preliminary design phase. In essence, this considerably amplifies the overall complexity of this work. After manufacturing the ATED, functionality tests have been performed successfully.

Piezoresistive strain sensing of carbon nanotubes-based composite skin for aeronautical morphing structures

Nowadays, smart composites based on different nano-scale carbon fillers, such as carbon nanotubes (CNTs), are increasingly being thought of as a more possible alternative solution to conventional smart materials, mainly for their improved electrical properties. Great attention is being given by the research community in designing highly sensitive strain sensors for more and more ambitious challenges: in such context, interest fields related to carbon nanotubes have seen extraordinary development in recent years. The authors aim to provide the most contemporary overview possible of carbon nanotube-based strain sensors for aeronautical application. A smart structure as a morphing wing needs an embedded sensing system in order to measure the actual deformation state as well as to “monitor” the structural conditions. Looking at more innovative health monitoring tools for the next generation of composite structures, a resin strain sensor has been realized. The epoxy resin was first analysed by means of a micro-tension test, estimating the electrical resistance variations as function of the load, in order to demonstrate the feasibility of the sensor. The epoxy dogbone specimen has been equipped with a standard strain gauge to quantify its strain sensitivity. The voltamperometric tests highlight a good linearity of the electrical resistance value as the load increases at least in the region of elastic deformation of the material. Such intrinsic piezoresistive performance is essentially attributable to the re-arrangement of conductive percolating network formed by MWCNT, induced by the deformation of the material due to the applied loads. The specimen has been prepared within this investigation, to demonstrate its performance for a future composite laminate typical of aerospace structures. The future carbon-fiber sensor can replace conventional metal foil strain gauges in aerospace applications. Furthermore, dynamic tests will be carried out to detect any non-reversible changes to the sensing response.

Control System Design for a Morphing Wing Trailing Edge

Shape control of adaptive wings has the potential to improve wing aerodynamic performance in off-design conditions. A possible way to attain this objective is to implement specific technologies for trailing edge morphing, aimed at changing the airfoil camber. In the framework of SARISTU project (EU-FP7), an innovative structural system incorporating a gapless deformable trailing edge was developed. A related key technology is the capability to emulate and maintain pre-selected target wing shapes within an established margin, enabling optimal aerodynamic performance under current operational pressure loads. In this paper, the actuation and control logics aimed at preserving prescribed geometries of an adaptive trailing edge under variable conditions are numerically and experimentally detailed. The actuation concept relies on a quick-return mechanism, driven by load-bearing actuators acting on morphing ribs, directly and individually. The adopted unshafted distributed electromechanical system arrangement uses servo-rotary actuators, each rated for the torque of a single adaptive rib of the morphing structure. The adopted layout ensures compactness and weight limitations, essential to produce a clean aerodynamic system. A Fiber Bragg Grating (FBG)-based distributed sensor system generates the information for appropriate open- and closed-loop control actions and, at the same time, monitors possible failures in the actuation mechanism.

Piezoelectric and electromagnetic solutions aimed at realizing an active Gurney flap

Gurney flaps are small devices whose dimensions are usually percentage units of the airfoil chord. A Gurney flap can change the flow field in the region of the trailing edge by introducing two contra-rotating vortices behind the flap, therein altering Kutta’s condition and circulation. This helps avoiding flow separation and moves stall occurrence to higher angles of attack. Active rotor technologies would, for instance, enable a helicopter to operate at reduced rotor tip speed while preserving flight performance capabilities. This article shows some results carried out on different, original, and feasible solutions, aimed at realizing “smart” Gurney flaps for rotorcraft blades. In particular, piezo patches, piezo stacks, and electromagnet-based solutions were exploited finding that only the last two solutions are able to satisfy specs. The last one (electromagnets) performs better from the viewpoints of implementation, cost (one order of magnitude), weight (less than 100 g with respect to 150 g of piezo stack), and power consumption (5 W with respect to 50 W).

Experimental technologies comparison for strain measurement of a composite main landing gear bay specimen

The development of advanced monitoring system for strain measurements on aeronautical components remain an important target both when related to the optimization of the lead-time and cost for part validation, allowing earlier entry into service, and when related to the implementation of advanced health monitoring systems dedicated to the in-service parameters verification and early stage detection of structural problems. The paper deals with the experimental testing of a composite samples set of the main landing gear bay for a CS-25 category aircraft, realized through an innovative design and production process. The test have represented a good opportunity for direct comparison of different strain measurement techniques: Strain Gauges (SG) and Fibers Bragg Grating (FBG) have been used as well as non-contact techniques, specifically the Digital Image Correlation (DIC) and Infrared (IR) thermography applied where possible in order to highlight possible hot-spot during the tests. The crucial points identification on the specimens has been supported by means of advanced finite element simulations, aimed to assessment of the structural strength and deformation as well as to ensure the best performance and the global safety of the whole experimental campaign.

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 17 – An Adaptive Trailing Edge

Abstract Aircraft wings are usually optimized for a specific design point. However, since they operate in a wide variety of flight regimes, some of these have conflicting impacts on aircraft design, as an aerodynamically efficient configuration in one instance may perform poorly in others. Conventional wing structures preclude any significant adaptation to changing conditions; movable surfaces, such as flaps or slats, lead to limited changes of the overall shape with narrow benefits compared with those that could be obtained from a wing structure that is inherently deformable and adaptable. An adaptive trailing edge concept conceived to enhance wing aerodynamic performance in cruise condition is outlined. The camber of the trailing edge is controlled during flight to compensate the weight reduction following the fuel burning. In this way, the trimmed configuration remains optimal in terms of efficiency (lift to drag ratio) or minimal drag with positive fallouts on aircraft fuel consumption per flight. The main steps concerning the design of the device are reported, with a special focus on each of its relevant architectural elements. In detail, the skin, the structural skeleton, the actuator, sensor, and control systems are dealt with. Some attention is devoted to aspects that are necessary to come to a finalized product of industrial relevance: namely, the aeroelastic and the safety analyses. The former assumes a main relevance because the system has augmented degrees of freedom with respect to a standard layout and then, a more complex dynamic response and a higher risk of instability. The latter is necessary to envisage a future certification process of this kind of device that requires the development of a dedicated path.

A modified Shunted Switch Architecture (SSSA) for active vibration control

During the last years, the research interest in assessing noise and vibration optimization has been addressed on different control typologies, based both on active and passive architectures. Within the paper, some preliminary activities aimed at the realization of a structurally simple, cheap and easily replaceable active control systems is discussed. Under these premises, the paper deals with the assessment of an Enhanced Synchronized Shunted Switch Architecture (SSSA) control architecture, based upon the use of piezoelectric devices, specifically optimized for a cantilver beam structure. Main activities regarded the control system set up and optimization, both under the electronic than the piezo location points of view, and control results under deterministic and stochastic forcing actions. Experimental results have been compared with the numerical one as well as a comparison between the SSSA approach and other active control architectures has been also presented and discussed. Results have shown a good performances of the proposed approach that present also a relative easy implementation if compared with already assessed control technologies.