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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.

Unmanned Aerial Vehicles are prime targets for morphing implementation as they must adapt to large changes in flight conditions associated with locally varying wind or large changes in mass associated with payload delivery. The Spanwise Morphing Trailing Edge concept locally varies the trailing edge camber of a wing or control surface, functioning as a modular replacement for conventional ailerons without altering the spar box. Utilizing alternating active sections of Macro Fiber Composites (MFCs) driving internal compliant mechanisms and inactive sections of elastomeric honeycombs, the SMTE concept eliminates geometric discontinuities associated with shape change, increasing aerodynamic performance. Previous work investigated a representative section of the SMTE concept and investigated the effect of various skin designs on actuation authority. The current work experimentally evaluates the aerodynamic gains for the SMTE concept for a representative finite wing as compared with a conventional, articulated wing. The comparative performance for both wings is evaluated by measuring the drag penalty associated with achieving a design lift coefficient from an off-design angle of attack. To reduce experimental complexity, optimal control configurations are predicted with lifting line theory and experimentally measured control derivatives. Evaluated over a range of off-design flight conditions, this metric captures the comparative capability of both concepts to adapt or “morph” to changes in flight conditions. Even with this simplistic model, the SMTE concept is shown to reduce the drag penalty due to adaptation up to 20% at off-design conditions, justifying the increase in mass and complexity and motivating concepts capable of larger displacement ranges, higher fidelity modelling, and condition-sensing control.

Smart materials offer several potential advantages for UAV flight control applications compared to traditional servo actuators. One important benefit is that smart materials are lightweight and can be embedded directly into the structure of a wing or control surface. Therefore, they can reduce the overall weight of the vehicle and eliminate the need for mechanical appendages that may compromise the form factor of the wing, benefits that become more significant as the size of the vehicle decreases. In addition, smart materials can be used to realize continuous camber change of aerodynamic surfaces. Such designs offer improved aerodynamic efficiency compared to the discontinuous deflections of traditional hinged control surfaces driven by servo actuators. In the research discussed in this paper, macro-fiber composite (MFC) aileron actuators are designed for implementation on a medium-scale, fixed-wing UAV in order to achieve roll control. Macro-fiber composites, which consist of piezoceramic fibers and electrodes embedded in an epoxy matrix, are an attractive choice for UAV actuation because they are manufactured as lightweight, thin sheets and, when implemented as bending actuators, can provide both large structural deflections and high bandwidth. In this study, several MFC aileron actuator designs were evaluated through a combination of theoretical and experimental analysis. The current design consists of glass fiber composite ailerons with two unimorph MFC actuators embedded in each aileron to produce upward deflection. Wind tunnel test results are presented to assess the changes in lift and drag coefficients for different levels of MFC aileron actuation. Preparations for open-loop flight testing using a Skywalker UAV with MFC ailerons are also discussed. In addition, the development of a closed-loop, autonomous flight control system for the Skywalker is overviewed in preparation for conducting simulations and flight testing of an autonomous Skywalker with MFC aileron actuators.

A process for the design and optimization of a morphing aileron using flexible matrix composite (FMC) actuators is developed. Design requirements were based on the use of a morphing aileron with an existing medium size commercial transport aircraft limiting the planform to the existing conventional aileron. The design uses two sets of contracting FMC actuators operating independently to actuate the deformable aileron in both trailing edge up and down cases while matching coefficient of lift values of a conventional aileron. The design was optimized by developing a series of response models which were then used to understand the sensitivity to material, geometric and loading design variables while minimizing required force from the FMC actuators. Using a combination of response models and sequential quadratic programming algorithm, a design is chosen that matched the conventional ailerons performance at multiple flight conditions.

A process for the design and optimization of a morphing aileron using flexible matrix composite (FMC) actuators is developed. Design requirements were based on the use of a morphing aileron with an existing medium size commercial transport aircraft limiting the planform to the existing conventional aileron. The design uses two sets of contracting FMC actuators operating independently to actuate the deformable aileron in both trailing edge up and down cases while matching coefficient of lift values of a conventional aileron. The design was optimized by developing a series of response models which were then used to understand the sensitivity to material, geometric and loading design variables while minimizing required force from the FMC actuators. Using a combination of response models and sequential quadratic programming algorithm, a design is chosen that matched the conventional ailerons performance at multiple flight conditions.

The flexure-box morphing aileron concept utilizes Macro-Fiber Composites (MFCs) and a compliant box to create a conformal morphing aileron. This work evaluates the impact of the number of MFCs on the performance, power and mass of the aileron by experimentally investigating two different actuator configurations: unimorph and bimorph. Implemented in a NACA 0012 airfoil with 304.8 mm chord, the unimorph and bimorph configurations are experimentally tested over a range of flow speeds from 5 to 20 m/s and angles of attack from -20 to 20 degrees under aerodynamic loads in a wind tunnel. An embedded flexible sensor is installed in the aileron to evaluate the effect of aerodynamic loading on tip position. For both design choices, the effect of actuation on lift, drag and pitching moment coefficients are measured. Finally, the impact on aileron mass and average power consumption due to the added MFCs is considered. The results showed the unimorph exhibiting superior ability to influence flow up to 15 m/s, with equivalent power consumption and lower overall mass. At 20 m/s, the bimorph exhibited superior control over aerodynamic forces and the unimorph experienced significant deformation due to aerodynamic loading.

Aircraft wings with smooth, hinge-less morphing ailerons exhibit increased chordwise aerodynamic efficiency over conventional hinged ailerons. Ideally, the wing would also use these morphing ailerons to smoothly vary its airfoil shape between spanwise stations to optimize the lift distribution and further increase aerodynamic efficiency. However, the mechanical complexity or added weight of achieving such a design has traditionally exceeded the potential aerodynamic gains. By expanding upon the previously developed cascading bimorph concept, this work uses embedded Macro-Fiber Composites and a flexure box mechanism, created using multi-material 3D printing, to achieve the Spanwise Morphing Trailing Edge (SMTE) concept. The morphing actuators are spaced spanwise along the wing with an elastomer spanning the gaps between them, which allows for optimization of the spanwise lift distribution while maintaining the continuity and efficiency of the morphing trailing edge. The concept is implemented in a representative section of a UAV wing with a 305 mm chord. A novel honeycomb skin is created from an elastomeric material using a 3D printer. The actuation capabilities of the concept are evaluated with and without spanning material on a test stand, free of aerodynamic loads. In addition, the actuation restrictions of the spanning elastomer, necessary in adapting the morphing concept from 2D to 3D, are characterized. Initial aerodynamic results from the 1’×1’ wind-tunnel also show the effects of aerodynamic loading on the actuation range of the SMTE concept for uniform morphing.

In this paper, a small seamless morphing wing aircraft of MTOW=51 kg is investigated. The leading edge (LE) and trailing edge (TE) control surfaces are positioned in the wing section in span wise. Based on the studying results of aeroelastic wing characteristics, the controller should be designed depending on the flight speed. Compared with a wing of rigid hinged aileron, the morphing wing produces the rolling moment by deflecting the flexible TE and LE surfaces. An iteration method of pseudo-inverse allocation and quadratic programming allocation within the constraints of actuators have be investigated to solve the nonlinear control allocation caused by the aerodynamics of the effectors. The simulation results will show that the control method based on control allocation can achieve the control target.

Conducting polymer actuators are employed to create actively shaped hydrodynamic foils. The active foils are designed to allow control over camber, much like the ailerons of an airplane wing. Control of camber promises to enable variable thrust in propellers and screws, increased maneuverability, and improved stealth. The design and fabrication of the active foils are presented, the forces are measured and operation is demonstrated both in still air and water. The foils have a "wing" span of 240 mm, and an average chord length (width) of 70 mm. The trailing 30 mm of the foil is composed of a thin polypyrrole actuator that curls chordwise to achieve variable camber. The actuator consists of two 30 μm thick sheets of hexafluorophosphate doped polypyrrole separated from each other by a gel electrolyte. A polymer layer encapsulates the entire structure. Potentials are applied between the polymer layers to induce reversible bending by approximately 35 degrees, and generating forces of 0.15 N. These forces and displacements are expected to enable operation in water at flow rates of > 1 m/s and ~ 30 m/s in air.

Building on the research performed during the DARPA / AFRL Smart Wing Phase 1 program to improve vehicle aerodynamic efficiency using control surfaces actuated by smart materials, the goal of the Phase 2, Test 1 effort was to increase the size of the model and the control surfaces and conduct wind tunnel tests at higher dynamic pressure and Mach number. This paper describes 1) model design for required safety and increased aileron effectiveness at high dynamic pressure; 2) model instrumentation; 3) SMA actuator control system design and implementation and 4) wind tunnel test results. Pictured below (Figure 1) is the model installed in the NASA Langley's Transonic Dynamic Tunnel (TDT).

The focus of this study is to evaluate the aeroelastic performance and control of adaptive wings. Ailerons and flaps have been designed and implemented into 3D wings for comparison with adaptive structures and active aerodynamic surface control methods. The adaptive structures concept, the experimental setup and the control design are presented. The wind-tunnel tests of the wing models are presented for the open- and closed-loop systems. The wind tunnel testing has allowed for quantifying the effectiveness of the piezoelectric vibration control of the wings, and also provided performance data for comparison with conventional aerodynamic control surfaces. The results indicate that a wing utilizing skins as active structural elements with embedded piezoelectric actuators can be effectively used to improve the aeroelastic response of aeronautical components. It was also observed that the control authority of adaptive wings is much greater than wings using conventional aerodynamic control surfaces.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A technique for deforming a flexible wing to achieve a specified roll rate within a specified time at different Mach Numbers is examined. Rather than using an aileron system for roll, antisymmetric elastic twist and camber is determined to achieve the required rolling moment for a specified roll rate. The elastic twist and camber is achieved by providing a system of actuating elements distributed within the internal substructure of the wing to provide control forces. The modal approach is used to develop the dynamic equilibrium equations which culminates in the steady roll maneuver of a wing subjected to aerodynamic loads and the actuating forces. The distribution of actuating forces to achieve the specified steady flexible roll rate within a specified time was determined by using Independent Modal-Space Control (IMSC) design approach. Here, a full-scale realistic wing is considered for the assessment of the strain energy required to produce the antisymmetric twist and camber deformation to achieve the specified roll performance.

The DARPA/AFRL/NASA Smart Wing program, conducted by a team led by Northrop Grumman Corporation (NGC) under the DARPA Smart Materials and Structures initiative, addresses the development of smart technologies and demonstration of relevant concepts to improve the aerodynamic performance of military aircraft. This paper presents an overview of the smart wing program. The program is divided into two distinct phases. Under Phase 1, (Jan 1995 - Feb 1999) the NGC team developed adaptive wing structures with integrated actuation mechanisms to replace standard hinged control surfaces and provide variable, optimal aerodynamic shapes for a variety of flight regimes. A smart wing 16% scale wind tunnel model, representative of an advanced military aircraft wing, was fabricated and tested in the NASA Langley Research Center (LaRC) Transonic Dynamics Tunnel (TDT) wind tunnel during two series of tests, conducted in May 1996 and June 1998, respectively. The smart wing model incorporated contoured, hingeless flap and aileron designs actuated using built-in SMA tendons. Control surface deflections of up to 10 degrees were obtained. Variable spanwise twist of the model was achieved using SMA torque tubes that employed novel connection mechanisms to effect a high degree of torque transfer to the structure. Up to 5 degrees of twist at the tip was demonstrated. Under steady-state conditions, performance improvements of 8-12% in comparison to a conventional design incorporating hinged control surfaces, over a broad range of wind tunnel and model test conditions, were established. The paper summarizes the Phase 1 effort. Detailed discussions of the wind tunnel testing, model design and fabrication, and torque tube development, are presented in References 6-8. An important limitation of the Phase 1 effort, i.e., the limited band-width provided by the SMA based actuation mechanisms, is being addressed in Phase 2 by developing and validating hybrid concepts. Phase 2 research and development is focused on application of smart technologies to uninhabited air vehicles (UAVs) that (from a scaling standpoint), offer a higher near-term technology transition potential than their tactical aircraft counterparts. Phase 2 efforts are also discussed, albeit briefly, in the paper.

The development of an aircraft-qualified 18-fiber optical ribbon cable was accomplished under the fly-by-light advanced system hardware program, sponsored by the Defense Advanced Research Projects Agency. This cable was developed because there was no suitable ribbon cable available which could survive the requirements of commercial transport and military tactical aircraft. In addition to developing this cable, aircraft-qualified of commercial transport and military tactical aircraft. In addition to developing this cable, aircraft-qualified connectors and conversion units to convert from the ribbon configuration to single-fiber configuration, referred to as 'fan-out boxes,' were also designed and constructed. All of this developed hardware flew aboard Boeing Company Aircraft Group-Long Beach Division's MD-90 test vehicle as part of the Fly-By-Light Optical Aileron Trim program.

In January of 1998 Boeing conducted successful flight testing of a prototype fly-by-light/power-by-wire concept demonstration system performing a flight control function. This paper discusses the demonstration system and the concepts it was designed to illustrate. Additionally, the aircraft installation and flight test effort will be overviewed.

This paper outlines the design, fabrication and testing techniques used for a new class of active wings. In support of recent efforts to shrink high authority, high speed aircraft flight controls for Micro Aerial Vehicles (MAVs), a new wing design was conceived. Quasi-vortex lattice methods were used to determine roll control power of unswept wings with (1) conventional ailerons, (2) active twist, and (3) a new method which employs root twist only. It was shown that linear wing twist provides 3.9 times more roll control than conventional ailerons. Root twist manipulations are shown to provide 1.6 times more control than twist. A comparison of control authority per unit actuator weight also shows that root actuators are more than 20% lighter than the other two systems. To drive the new root pitch actuator, a directionally attached piezoelectric (DAP) torque-late actuator was built. A laminated plate theory analysis of the 4' span, 3' chord DAP torque-plate showed good correlation between theory and experiment. The DAP torque plate was integrated into a 30' span, 4' chord graphite-epoxy wing. Structural testing showed wing pitch deflections up to +/- 1.5 degree(s) at rates in excess of 70 Hz. Wind tunnel tests were conducted between 1 and 20 ft/s (typical MAV flight speeds) and showed rolling moment coefficients up to +/- 0.026 (equivalent to +/- 8.4 degree(s) of aileron deflection), indicating that the new wing is well suited to flight control of micro-sized aircraft.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper is concerned with designing a composite wing structure with enhanced roll maneuver capability at high dynamic pressures using a control system to retwist and recamber the wing. The approach selected in this paper is a two step process. In the first step, minimum weight design satisfying requirements on strength, aileron efficiency and flutter for a specified set of fiber oritations was obtained. The control system was then designed to retwist and recamber the wing to counteract the detrimental twisting moment produced by the aileron. The distribution of control forces was obtained from a technique referred to as `Fictious Control Surfaces'. The technique of retwisting and recambering of a flexible wing demonstrated a full recovery of roll rate at all dynamic pressures.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An active decoupler pylon approach for wing/store flutter suppression is proposed which involves the use of a piezoceramic wafer strut as an actuator for isolating wing torsion modes from store pitch inertia effects. A two degree-of-freedom typical section of an airfoil is used to represent the structural model of the wing, while the circulatory incompressible aerodynamic loads are modeled using Jones' approximation to the Theodorsen function. The analytical model developed neglects store aerodynamics, aileron degree-of-freedom and other flutter critical flexible and rigid body moves. This paper presents some typical perturbation models used to represent such uncertainties and compares their robust stability margins obtained using controllers designed with Loop Transfer Recovery and H(infinity ) control techniques. Singular value Bode plots are used to analyze the robust stability and nominal performance characteristics.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The use of smart materials technologies can provide unique capabilities in improving aircraft aerodynamic performance. Northrop Grumman built and tested a 16% scale semi-span wind tunnel model of the F/A -18 E/F for the on-going DARPA/WL Smart Materials and Structures - Smart Wing Program. Aerodynamic performance gains to be validated included increase in the lift to drag ratio, increased pitching moment (C m ), increased rolling moment (C l ) and improved pressure distribution These performance gains were obtained using hingeless, contoured trailing edge control surfaces with embedded shape memory alloy (SMA) wires and spanwise wing twist via a SMA torque tube and are compared to a conventional wind tunnel model with hinged control surfaces. This paper presents an overview of the results from the first wind tunnel test performed at the NASA Langley's 16ft Transonic Dynamic Tunnel (TDT). Among the benefits demonstrated are 8-12% increase in rolling moment due to wing twist, a 10-15% increase in rolling moment due to contoured aileron, and approximately 8% increase in lift due to contoured flap, and improved pressure distribution due to trailing edge control surface contouring.

Control of the static aeroelastic characteristics of a swept uniform wing in roll using an adaptive structure is examined. The wing structure is modeled as a uniform beam with bending and torsional deformation freedom. Aerodynamic loads are obtained from strip theory. The structure model includes coefficients representing torsional and bending actuation provided by embedded piezoelectric material layers. The wing is made adaptive by requiring the electric field applied to the piezoelectric material layers to be proportional to the wing root loads. The proportionality factor, or feedback gain, is used to control static aeroelastic rolling properties. Example wing configurations are used to illustrate the capabilities of the adaptive structure. The results show that rolling power, damping-in-roll and aileron effectiveness can be controlled by adjusting the feedback gain. And that dynamic pressure affects the gain required. Gain scheduling can be used to set and maintain rolling properties over a range of dynamic pressures. An adaptive wing provides a method for active aeroelastic tailoring of structural response to meet changing structural performance requirements during a roll maneuver.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.