Morphing Wingtip Research Articles

Effect of Trailing Edge and Span Morphing on the Performance of an Optimised NACA6409 Wing in Ground Effect

Abstract A CFD investigation was carried out on a three-dimensional NACA6409 wing in ground effect at a Reynolds number of 320,000. Using a Multi-Objective-SHERPA algorithm, a root angle of 4 degrees angle of attack, a tip angle of 6 degrees, a forward sweep and a tip chord of 20% of the root chord produced an optimum aerodynamic efficiency across all ground clearances. Optimisation showed a gain in aerodynamic efficiency of 41% at h/c = 0.05 ground clearance and a 31% gain at h/c = 0.2 compared to a rectangular planform wing. Next FishBAC camber morphing was applied to the optimised wing varying the morphing start locations along the chord at both the tip and root. A later start location produced the highest aerodynamic efficiency but increased manufacturing complexity. Extendable span morphing was also tested and was found increasing the span from 1c to 1.5c increased the aerodynamic efficiency of the optimised wing by 27.4% at h/c = 0.1. Varying the span from 0.8c to 1.2c in ground effect had a small effect on the drag for small ground clearances, for large ground clearances the total drag decreased as the span increased. Smaller gains were seen when the span morphing was applied to the rectangular wing. The FishBAC morphing was applied in the spanwise direction to morph the wing tip, sealing the flow beneath the wing. Also, the proportion of the morphing wing tip caused the trailing edge to be closer to the ground further enhancing ground effect.

Autonomous flight performance optimization of fixed-wing unmanned aerial vehicle with morphing wingtip

PurposeThe purpose of this paper is to improve autonomous flight performance of a fixed-wing unmanned aerial vehicle (UAV) via simultaneous morphing wingtip and control system design conducted with optimization, computational fluid dynamics (CFD) and machine learning approaches.Design/methodology/approachThe main wing of the UAV is redesigned with morphing wingtips capable of dihedral angle alteration by means of folding. Aircraft dynamic model is derived as equations depending only on wingtip dihedral angle via Nonlinear Least Squares regression machine learning algorithm. Data for the regression analyses are obtained by numerical (i.e. CFD) and analytical approaches. Simultaneous perturbation stochastic approximation (SPSA) is incorporated into the design process to determine the optimal wingtip dihedral angle and proportional-integral-derivative (PID) coefficients of the control system that maximizes autonomous flight performance. The performance is defined in terms of trajectory tracking quality parameters of rise time, settling time and overshoot. Obtained optimal design parameters are applied in flight simulations to test both longitudinal and lateral reference trajectory tracking.FindingsLongitudinal and lateral autonomous flight performances of the UAV are improved by redesigning the main wing with morphing wingtips and simultaneous estimation of PID coefficients and wingtip dihedral angle with SPSA optimization.Originality/valueThis paper originally discusses the simultaneous design of innovative morphing wingtip and UAV flight control system for autonomous flight performance improvement. The proposed simultaneous design idea is conducted with the SPSA optimization and a machine learning algorithm as a novel approach.

Impacts of Tapered Wingtip on Lateral-Directional Stability Coefficients of a Morphing Fixed-wing UAV

Recent developments in unmanned aerial vehicle (UAV) technologies have shown the possibility of morphing applications to provide improvement in various performance metrics in the desired manner. In rotary-wing UAVs, applications mainly focused on propeller blades and rotor arms, while efforts on fixed-wing UAVs mainly concentrated on the main wing and tail geometries. Although every morphing design has its own advantages and disadvantages, all of the applications have similar common purposes to have improved aerodynamics, flight performance, control responses, or a combination of such objectives. In that context, new morphing design attempts require a precise investigation of their pros and cons. Thus, in this study, a new morphing scenario of tapering morphing wingtip is applied to ZANKA-I fixed-wing UAV and investigated in terms of lateral-directional stability considerations. The lateral dynamic model of the aircraft is constituted and necessary aerodynamic, geometric, and inertial assessments are numerically and analytically performed. The lateral-directional stability coefficients are discussed and an improvement in lateral stability is obtained, while directional stability is found to be affected negatively by the morphing application.

Performance improvement of a wing with a controlled spanwise bending wingtip

This paper aims to investigate the unsteady force characteristics and performance improvement of a wing with a controlled morphing wingtip. Taking the geometry nonlinearity of morphing into consideration, a new predictor-corrector method is developed to get the updated coordinates of nodes on the morphing wing surface. The effects of morphing frequency and amplitude are investigated. The results indicate that the unsteady force amplitude increases with the morphing frequency and amplitude. Meanwhile, the morphing amplitude affects the phase and harmonic characteristics of the force. The wingtip morphing influence on the unsteady force is divided into the shape effect and the additional angle of attack effect. The force can be described by a simple scaling law using a generalized Duffing-van-der-Pol nonlinear model. This scaling law depicts the nonlinear effect of large amplitude bending in essence. Afterward, the in-depth wake structures analysis of the flow field finds that the morphing frequency does not affect the essential feature of wake topology, while the morphing amplitude does. As the morphing amplitude increases, the vortical structures shift from vortical tubes to ring-like vortices, which induces the change of the phase and harmonic characteristic of force response.

Morphing wingtip structure based on active inflatable honeycomb and shape memory polymer composite skin: A conceptual work

Morphing wingtip technology could improve the reduction of the induced drag, fuel consumption, and take-off and landing distances in fixed wing configurations. We describe in this work a morphing winglet concept based on active inflatable honeycombs and Shape Memory Polymer Composite (SMPC) skins. The combination of the two materials and structural subsystems allow the winglet deployment, with a morphing skin able to withstand the aerodynamic loading, also through the use of distributed pneumatic muscle fibers. An actuation geometric and mechanical model that represents the morphing wingtip concept is developed and analyzed. A morphing wingtip prototype is also fabricated to demonstrate the kinematics and actuation of the concept. Experiments and simulations show agreement about the output angle/input pressure relationship necessary for the wingtip deployment.

Artificial Neural Networks-Extended Great Deluge Model to predict Actuators Displacements for a Morphing Wing Tip System

Resin-based fiber composite materials have received attention in aerospace composite engineering, particularly in aircraft morphing structures, due to their high mechanical characteristics, such as stiffness, and because of their potential to highly reduce the structural mass of modern aircraft. Aircraft morphing is referred to as the ability of an aircraft’s surface to change its geometry in flight. The modelling of a dynamic morphing wing system is here studied. The morphing wing was controlled using four electric actuators situated inside of the wing model. The main role of these actuators was to modify the wing upper surface shape designed and manufactured with a flexible material, so that the laminar-to-turbulent flow transition point can move closer to the wing trailing edge, thus causing a minimum viscous drag, for various flow conditions. To determine the skin deflections in the four actuators points, both LVDT and dial indicator gages were positioned on the wing. Four Linear Variable Differential Transducers (LVDTs) were used to indicate the positions of the four actuators, and four Dial Indicators gages were positioned on the wing to measure the real deflections of the flexible composite skin in the four actuation points. The relationship between the Dial Indicators’ values and the LVDTs’ values for a same set-point command signal had a nondeterministic and unpredictable behavior (not a linear one). The values of the displacements given by the LVDTs were different than the values given by the Dial Indicators. In this paper, an Artificial Neural Network (ANN) model was investigated created with the aim to predict the displacements of the wing upper surface skin in real time using four actuators. The proposed model was trained using the Extended Great Deluge (EGD) algorithm.

Passive energy balancing design for a linear actuated morphing wingtip structure

A passive energy balancing concept for linear actuation is investigated in the current work by adopting a negative stiffness mechanism. The proposed negative stiffness mechanism uses a pre-tensioned spring to produce a passive torque and therefore to transfer the passive torque through a crankshaft for linear motion.The proposed passive energy balancing design is supposed to be applied in a morphing wingtip, of which the shape change comes from the elastic deformation of the morphing structure. A significant amount of linear actuation force can be required to deform the structure, and therefore it is important to reduce the required force and the consumed energy by adopting the passive energy balancing design.The kinematics of the negative stiffness mechanism is developed to satisfy the required linear motion and its geometry is then optimised to reduce the energy requirements. The performance of the optimised negative stiffness mechanism is evaluated through the net force and the total required energy, which shows the potential of the design in the morphing wingtip application.

A Review on Applications and Effects of Morphing Wing Technology on UAVs

Unmanned aerial vehicles (UAVs) have excelled with their ability to perform the intended task on or without personnel. In recent years, UAVs have been designed for civilian purposes as well as military applications. Morphing wings are changeable wing applications developed as a result of the need for a different lift and drag forces in various phases of the flight of aircraft. It is an application that enables altering the wing aspect ratio, wing airfoil, wing airfoil camber ratio, wing reference area and even different angles of attack are obtained in different parts of the wing. Although morphing wing application has just begun on today’s UAVs, modern airliners already have morphing wingtip devices such as Boeing 777-X’s. The benefits of the use of morphing wings for UAVs make this technology important. UAVs with morphing wing technology; may increase its payload ratio, may achieve a shorter take-off distance, may land and stop in shorter distance, may take-off where runway clearance is limited, has more efficient altitude change at lower engine RPMs, can obtain higher cruise speeds, may decrease its stall speed, may lower its drag if necessary, thus; saving energy and time. This study concludes a review of literature over morphing wing technology.

Fuzzy Logic-Based Control for a Morphing Wing Tip Actuation System: Design, Numerical Simulation, and Wind Tunnel Experimental Testing.

The paper presents the design, numerical simulation, and wind tunnel experimental testing of a fuzzy logic-based control system for a new morphing wing actuation system equipped with Brushless DC (BLDC) motors, under the framework of an international project between Canada and Italy. Morphing wing is a prime concern of the aviation industry and, due to the promising results, it can improve fuel optimization. In this idea, a major international morphing wing project has been carried out by our university team from Canada, in collaboration with industrial, research, and university entities from our country, but also from Italy, by using a full-scaled portion of a real aircraft wing equipped with an aileron. The target was to conceive, manufacture, and test an experimental wing model able to be morphed in a controlled manner and to provide in this way an extension of the laminar airflow region over its upper surface, producing a drag reduction with direct impact on the fuel consumption economy. The work presented in the paper aims to describe how the experimental model has been developed, controlled, and tested, to prove the feasibility of the morphing wing technology for the next generation of aircraft.

Development of a morphing wingtip based on compliant structures

Compliant structures, such as flexible corrugated panels and honeycomb structures, are promising structural solutions for morphing aircraft. The compliant structure can be tailored to carry aerodynamic loads and achieve the geometry change simultaneously, while the reliability of the morphing aircraft can be guaranteed if conventional components and materials are used in the fabrication of the morphing structure. In this article, a compliant structure is proposed to change the dihedral angle of a morphing wingtip. Unsymmetrical stiffness is introduced in the compliant structure to induce the rotation of the structure. Trapezoidal corrugated panels are used, whose geometry parameters can be tailored to provide the stiffness asymmetry. An equivalent model of the corrugated panel is employed to calculate the deformation of the compliant structure. To provide the airfoil shape, a flexible honeycomb structure is used in the leading and trailing edges. An optimisation is performed to determine the geometry variables, while also considering the actuator requirements and the available space to instal the compliant structure. An experimental prototype has been manufactured to demonstrate the deformation of the morphing wingtip and conduct basic wind tunnel tests.

Performance based multidisciplinary design optimization of morphing aircraft

The aeronautical industry is currently facing contradictory aircraft design requirements. There is a need to increase speed and capacity while minimizing the environmental impact. Novel configurations and morphing solutions are being proposed to address these requirements. In order to achieve the optimal aircraft configuration or the best morphing solution for a given mission, it is necessary to explore Multidisciplinary Design Optimization (MDO) solutions during the conceptual design phase. To this end, a MDO framework is proposed for conceptual design and analysis of new aircraft configurations, including the capability to analyze and quantify the effect of morphing wing solutions on aircraft performance. To illustrate the versatility and capabilities of the MDO tool, the design of a morphing wingtip on a conventional aircraft for two different flight conditions is assessed based on a reference model transport aircraft. Also, the performance of a morphing bending and twist control applied to a reference joined-wing configuration to improve lateral-directional stability is quantified. The results obtained show a significant reduction in fuel consumption when introducing a wingtip, although an incremental and negligible reduction was verified when enabling the wingtip with morphing capabilities. A considerable increase in yaw authority was achieved for the joined-wing model with the bending-twist morphing wingtip, however this morphing concept was not able to reach the same roll authority as conventional ailerons.

English

In this project, a wing tip of a real aircraft was designed and manufactured. This wing tip was composed of a wing and an aileron. The wing was equipped with a composite skin on its upper surface. This skin changed its shape (morphed) by use of 4 electrical in-house developed actuators and 32 pressure sensors. These pressure sensors measure the pressures, and further the loads on the wing upper surface. Thus, the upper surface of the wing was morphed using these actuators with the aim to improve the aerodynamic performances of the wing-tip. Two types of ailerons were designed and manufactured: one aileron is rigid (non-morphed) and one morphing aileron. This morphing aileron can change its shape also for the aerodynamic performances improvement. The morphing wing-tip internal structure is designed and manufactured, and is presented firstly in the paper. Then, the modern communication and control hardware are presented for the entire morphing wing tip equipped with actuators and sensors having the aim to morph the wing. The calibration procedure of the wing tip is further presented, followed by the open loop controller results obtained during wind tunnel tests. Various methodologies of open loop control are presented in this paper, and results obtained were obtained and validated experimentally through wind tunnel tests.

Evaluation of a Compliant Droop-Nose Morphing Wing Tip via Experimental Tests

A morphing droop-nose wing tip with span of 1.3 m and target 2 deg droop was designed, manufactured, and tested as part of the European project Novel Air Vehicle Configurations: From Fluttering Wings to Morphing Flight. The morphing droop-nose device featured a fiberglass composite skin with optimized three-dimensional thickness distribution, which was supported by topology-optimized superelastic nickel titanium and aluminum internal compliant mechanisms. The tests included ground and low-speed wind-tunnel tests () with the aim of assessing the structural performance and the design chain through measurements of shape, strains, surface pressures, and total forces/moments on the model. Comparisons with the experimental results were used for validation of the computational models and optimization tools. The morphing device was able to change shape while resisting the external loads, and it was identified that the distribution of strain and shape accuracy may be improved through the use of a concurrent as opposed to sequential design chain and other developments to the optimization tools. The use of a superelastic material facilitated the high-strain displacement, exceeding 2% strain in the design case and measured up to 4.54%, making it highly suitable for compliant mechanism applications. This paper explains the insights made from the experimental tests and recommendations for the future design of morphing structures.

Design of a Morphing Wingtip

An initial design of a morphing wingtip for a regional jet aircraft is developed and evaluated. The adaptive wingtip concept is based upon a chiral-type internal structure, enabling controlled cant angle orientation, camber, and twist throughout the flight envelope. A baseline turbofan aircraft configuration model is used as the benchmark to assess the device. Computational fluid dynamics based aerodynamics are used to evaluate the required design configurations for the device at different points across the flight envelope in terms of lift/drag and bending moment distribution along the span, complemented by panel-method-based gust load computations. Detailed studies are performed to show how the chiral structure can facilitate the required shape changes in twist, camber, and cant. Actuator requirements and limitations are assessed, along with an evaluation of the aerodynamic gains from the inclusion of the device versus power and weight penalties. For a typical mission, it was found that savings of around 2% in fuel weight are possible using the morphing wingtip device. A similar reduction in weight due to passive gust load alleviation is also possible with a slight change of configuration.

Aero-structural Design Optimization of a Morphing Wingtip

Over the past few years, better knowledge of aerodynamics and structures and the permanent need to improve the performance and efficiency of aircraft have led to the generalized adoption of wingtip devices. The requirements faced by wingtip devices throughout the various flight conditions are, however, different. A static wingtip device (as is the case with existing designs) must be a compromise of these various conflicting requirements, resulting in less than optimal effectiveness in each flight condition. A morphing device, on the other hand, can adapt to the optimum configuration for each flight condition, leading to improved effectiveness. This article presents a morphing wingtip mechanism based on a servo-actuated articulated winglet, able to rotate about two different axes: vertical axis (toe angle) and aircraft’s longitudinal axis (cant angle). These can be controlled independently by servo-actuators. The wingtip behavior is a function of aerodynamic and structural loads which, in turn, are interdependent, requiring a multidisciplinary design optimization procedure in order to determine the ideal wingtip configuration for each case. The proposed concept is applied to a multi-mission unmanned aerial vehicle and the results show that a morphing wingtip can outperform an optimum fixed design. The optimum geometries for the different flight missions are presented and the feasibility of such a morphing wingtip is confirmed by a prototype. The performance metrics of the morphing wingtip are compared to those of a fixed wingtip to quantify the gain associated with the use of the morphing concept and it is seen that the improvement can reach 25%.