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This research aims to enhance the performance of unmanned aerial vehicles (UAVs) by investigating the impact of twisting wingtip (TWT) on UAVs' wing aeroelastic and structural behavior using MATLAB and ANSYS simulations. The study focuses on a simplified twisting wingtip design and its aeroelastic effect. This study includes both static and dynamic aeroelastic phenomena. Previous research has primarily focused on only flutter speed while neglecting divergence speed and lift-effectiveness in design results. Numerical and experimental validation underscores the model's fidelity and its practical applicability. The TWT is designed to exhibit a predominant torsional mode using a guide mode preference technique. The design results reveal that the twist morphing wing improves structural and aeroelastic performance due to its unique twisting deformation capabilities. Furthermore, this research contributes fundamental insights into a specific twist morphing wing concept, highlighting its potential to enhance UAV performance through twisting wingtip technologies. The torsional mode can be predetermined using the guide mode preference technique. Notably, the divergence speed analysis confirms that the twisting shaft position should not exceed the aerodynamic center, which is located at 0.2103 of the chord length. This serves as the theoretical foundation for the TWT design in this study. The adjustment of the TWT's twisting angle is confirmed to provide optimal divergence speed improvement within a range of 0% to 27.7%. Additionally, the relative aeroelastic efficiencies indicate that the highest lift effectiveness is 0.68% at a twisting angle of 30°, following an exponential relationship, which can be further extended to aircraft control laws. However, the relative efficiency of flutter speed is not significantly improved by the TWT, showing only a marginal improvement of 0% to 1.84% when twisting up and down, in accordance with previous research findings. [ABSTRACT FROM AUTHOR]

Honeycomb structures of shape memory alloy (SMA) have become one of the most promising materials for flexible skins of morphing aircraft due to their excellent mechanical properties. However, due to the nonlinear material and geometric large deformation, the SMA honeycomb exhibits significant and complex nonlinearity in the skin and there is a lack of relevant previous research. In this paper, the nonlinear properties of the SMA honeycomb structure with arbitrary geometry are investigated for the first time for large deformation flexible skin applications by theoretical and experimental analysis. Firstly, a novel theoretical model of SMA honeycomb structure considering both material and geometric nonlinearity is proposed, and the corresponding calculation method of nonlinear governing equations is given based upon the shooting method and Runge–Kutta method. Then, the tensile behaviors of four kinds of SMA honeycomb structures, i.e., U-type, V-type, cosine-type, and trapezoid-type, are analyzed and predicted by the proposed theoretical model and compared with the finite element analysis (FEA) results. Moreover, the tensile experiments were carried out by stretching U-type and V-type honeycomb structures to a global strain of 60% and 40%, respectively, to perform large deformation analysis and verify the theoretical model. Finally, experimental verification and finite element validation show that the curves of the theoretical model results, experimental results, and simulation results are in good agreement, illustrating the generalizability and accuracy of the proposed theoretical model. The theoretical model and experimental investigations in this paper are considered to provide an effective foundation for analyzing and predicting the mechanical behavior of SMA honeycomb flexible skins with large extensional deformations. [ABSTRACT FROM AUTHOR]

This paper examines sensing mechanisms and stability issues of flexible sensors used in morphing wing applications. A key challenge is the lack of theoretical frameworks that accurately predict sensor behavior during complex deformation. Current models struggle to fully capture the relationships between mechanical strain, electrical response, and material properties. We first analyze the microscopic mechanisms and macroscopic sensing characteristics of 2D material-based sensitive films, developing strain-sensitive models based on crack effects and pressure-sensitive models based on slip effects. Through power spectrum analysis, we establish a quantitative model linking microscopic cracks to macroscopic electrical properties. Using this model, we study the factors affecting flexible sensing stability and propose a quantitative description model using dual-layer multi-channel flexible sensors. After simulation validation, our model successfully guides the structural design of flexible sensing films, offering a clear approach to improve flexible sensor stability. [ABSTRACT FROM AUTHOR]

Camber-morphing wing technology enables adaptive adjustments to wing curvature by optimizing aerodynamic performance and efficiency for varying flight conditions. This study emphasizes the novel Trailing Edge Morphing Airfoil (TEMA) design and analysis, showcasing its noteworthy aerodynamic characteristics. The design uses the parabolic morphing method to obtain TEMA profiles for deflection angles. The different shapes of the TEMA and base airfoil were analyzed using the XFOIL solver with a linear-vorticity stream function formulation. TEMA with a flexible zigzag section was developed using a 3D printing technique with TPU material. The rectangular wing model was developed using TEMA and tested in a low-speed subsonic wind tunnel with Reynolds numbers of 1.19 x105, 2.54 x 105 and 3.18 x 105 for different angles of attack. The test cases had a combination of different Reynolds numbers, deflection angles, and angles of attack. The aerodynamic characteristics were calculated by measuring the pressure coefficient around the TEMA using an advanced pressure scanner. The results show that TEMA with a moderate deflection angle has the potential to improve the lift-to-drag ratios by around 30%. It was concluded that TEMA with +5° and +10° deflection angles demonstrated superior aerodynamic efficiency at the Reynolds numbers mentioned compared to the conventional NACA 2412 airfoil. [ABSTRACT FROM AUTHOR]

Abstract In this study, a numerical investigation into the sustained aerodynamic performance of a morphing wing equipped with a flexible leading edge, employing a 2-dimensional NACA0012 airfoil configuration, is conducted. The compressible governing equations of the flow are employed, simulating 2 distinct states: the airfoil without motion and the airfoil featuring a flexible leading edge with a chord length of 0.856 m, assessing various angles of attack utilizing the k-ω SST turbulence approach within Fluent software. Dynamic mesh, facilitated by a user-defined function, is utilized in Fluent software to simulate the movement of the airfoil wall at the leading edge. The study thoroughly analyzes the flow behavior concerning diverse angles of attack and deviations, evaluating their impact on aerodynamic coefficients, velocity, and pressure fields under steady-state settings. Validation of the chosen numerical approach demonstrates close alignment of the front and back coefficients with experimental settings. Outcomes from the steady-state flow simulation of the morphing wing reveal that positive deflection angles correspond to increased lift coefficients and decreased drag coefficients, with lift coefficient increases of up to 15% and drag coefficient reductions of up to 10% at specific angles. Meanwhile, the negative deflection angles have shown a decline in lift coefficients, with the drag coefficients increasing with the decrease in deflection angle. All these observations show that at the flexible leading edge, there is a considerable improvement in aerodynamic efficiency. Hence, it should find more applications in different regimes of flight.

This study explored the design, performance evaluation, and application of two types of in-plane motion actuators that were scalable to larger sizes—that is, the extension-type electrothermal actuator (ExACT) and retraction-type electrothermal actuator (ReACT). These actuators were based on the displacement amplification mechanism (DAM) principles and regularly arranged structures in mechanical metamaterials. A modular design approach allowed these actuators to be easily configured to the desired size and scaled to create large-scale in-plane motion actuators. Studies were conducted to assess the performance of the ExACT and ReACT, focusing on the actuator displacement and blocking force. The actuation displacements for the 3 × 1 ExACT and ReACT matrices were measured at 2.0 and 0.8 mm, respectively. Similarly, the blocking forces achieved by the actuator matrices were 2.24 and 3.78 N for the ExACT and ReACT, respectively. Subsequently, the ExACT and ReACT were applied to implement large deformable morphing wings, referred to as the ExMOW and ReMOW, respectively. These wings incorporated an additional thickness amplification mechanism resembling an elliptical bridge-type DAM. The wing thickness of the ExMOW increased by approximately one-third of its initial value, whereas that of the ReMOW decreased to approximately one-quarter of its original thickness. [ABSTRACT FROM AUTHOR]

In this study, a numerical investigation into the sustained aerodynamic performance of a morphing wing equipped with a flexible leading edge, employing a 2-dimensional NACA0012 airfoil configuration, is conducted. The compressible governing equations of the flow are employed, simulating 2 distinct states: the airfoil without motion and the airfoil featuring a flexible leading edge with a chord length of 0.856 m, assessing various angles of attack utilizing the k-ω SST turbulence approach within Fluent software. Dynamic mesh, facilitated by a user-defined function, is utilized in Fluent software to simulate the movement of the airfoil wall at the leading edge. The study thoroughly analyzes the flow behavior concerning diverse angles of attack and deviations, evaluating their impact on aerodynamic coefficients, velocity, and pressure fields under steady-state settings. Validation of the chosen numerical approach demonstrates close alignment of the front and back coefficients with experimental settings. Outcomes from the steady-state flow simulation of the morphing wing reveal that positive deflection angles correspond to increased lift coefficients and decreased drag coefficients, with lift coefficient increases of up to 15% and drag coefficient reductions of up to 10% at specific angles. Meanwhile, the negative deflection angles have shown a decline in lift coefficients, with the drag coefficients increasing with the decrease in deflection angle. All these observations show that at the flexible leading edge, there is a considerable improvement in aerodynamic efficiency. Hence, it should find more applications in different regimes of flight. [ABSTRACT FROM AUTHOR]

A novel frequency-domain analytical-numerical model for the aerodynamic solution of camber morphing wings is developed. The model combines an unsteady lifting-line formulation with Küssner-Schwarz aerodynamic theory to provide the pressure distribution and thus the transcendental aerodynamic matrix that relates the generalized aerodynamic forces to the Lagrangian coordinates of a given wing structural dynamics model. The state-space form of the aerodynamic loads is obtained from the rational matrix approximation of the aerodynamic matrix. This, combined with the wing structural dynamics operator, can readily provide the state-space form of the aeroelastic problem. To assess the accuracy of the proposed aerodynamic solution method, numerical investigations are performed. These consist of its application to several conventional wing configurations and wings with camber morphing, followed by the comparisons of the corresponding solutions with the predictions given by a well-validated panel-method solver for potential flows. These results are shown to be in very good agreement, thus demonstrating that the proposed approach can capture the effects due to wing tapering, sweep angle, and camber morphing, while requiring a remarkably lower computational effort. The excellent accuracy of a few-pole finite-state approximation of the aerodynamic matrix is finally proven for a swept wing with camber morphing. [ABSTRACT FROM AUTHOR]

Many flying and swimming creatures have morphing pectoral propulsors (wings or fins) for propulsion, typically with flapping, rowing, and pitching motions; flapping and rowing motions are responsible for the stroke plane angle that is important for a broader performance space of the propulsor, while the stroke plane angle has been less characterized and implemented by artificial propulsors of biomimetic vehicles and thus has lack of stroke plane angle control. In this paper, we consider robotic pectoral propulsors with combined flapping and rowing motions for a stroke plane angle that can be generally specified. We consider two possible rotation axes configurations (i.e., the dependence of the rotation axes for flapping and rowing). For each rotation axes configuration, we propose the kinematic relations between the flapping and rowing motions for a generally specified stroke plane angle and provide the general flapping (or rowing) kinematics as a function of the rowing (or flapping) kinematics, which have not been characterized previously. These results serve as the reference trajectories of the propulsor for specified stroke plane angles and have implications for stroke plane angle control and thus have implications to achieve a broader performance space for biomimetic propulsors. [ABSTRACT FROM AUTHOR]

The perch landing maneuver of a wing-deforming unmanned aerial vehicle (UAV) was investigated through a framework that uses the free, open-source OpenFOAM with 6 degrees of freedom (6DOF) simulations. The framework uses a moving grid to follow the trajectory of the UAV, reducing computational resources. Together with the ability to allow internal grid deformation, sliding mesh, and algorithm addition, it can accurately mimic the entire landing process. Different wing deformation speeds, additional elevator rotation and emulated propeller lift were added to the 6DOF simulations to investigate their effects on the landing maneuver. The results showed that the wing deformation retraction speed has a considerable effect on the trajectory and velocity of the UAV. The wing deformation reduced the forward velocity of the UAV by 32%, from 13.89 to 9 m/s. With the elevator control, the velocity was reduced to 5 m/s. Lastly, and an activation time of 1 s for the emulated propeller lift can further decrease the velocity to around 4.2 m/s. A better algorithm for the emulated propeller lift may be able to give a superior performance. This framework allows us to understand the underlying perch landing maneuver aerodynamics. It can also be used on problems like fast-turning agile and flapping wing flight. [ABSTRACT FROM AUTHOR]

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This paper examines sensing mechanisms and stability issues of flexible sensors used in morphing wing applications. A key challenge is the lack of theoretical frameworks that accurately predict sensor behavior during complex deformation. Current models struggle to fully capture the relationships between mechanical strain, electrical response, and material properties. We first analyze the microscopic mechanisms and macroscopic sensing characteristics of 2D material-based sensitive films, developing strain-sensitive models based on crack effects and pressure-sensitive models based on slip effects. Through power spectrum analysis, we establish a quantitative model linking microscopic cracks to macroscopic electrical properties. Using this model, we study the factors affecting flexible sensing stability and propose a quantitative description model using dual-layer multi-channel flexible sensors. After simulation validation, our model successfully guides the structural design of flexible sensing films, offering a clear approach to improve flexible sensor stability.

In this paper, a design optimization approach is developed to design the placement and stroke of actuators at a conceptual design phase. This method is applied to the actuator design problem of the morphing leading edge of a high-performance sailplane to achieve predetermined optimal shapes. The centerpiece of this work is the derived analytical sensitivity analysis via direct differentiation to efficiently and effectively find the optimal design. This methodology is illustrated by breaking the solving routine into five blocks: meshing module, actuation stroke module, actuated deformation module, geometric deviation module and geometric constraint module. Although applied here to a morphing wing profile, the methodology and derived equations are general and can be applied to a number of applications of form-variable structures in which the optimal placement of actuators is desired. [ABSTRACT FROM AUTHOR]

Actuators based on soft elastomers offer significant advantages to the field of robotics, providing greater adaptability, improving collision resilience, and enabling shape‐morphing. Thus, soft fluidic actuators have seen an expansion in their fields of application. Closed‐cycle hydraulic systems are pressure agnostic, enabling their deployment in extremely high‐pressure conditions, such as deep‐sea environments. However, soft actuators have not been widely adopted on unmanned underwater vehicle control surfaces for deep‐sea exploration due to their unpredictable hydrodynamic behavior when camber‐morphing is applied. This study presents the design and characterization of a soft wing and investigates its feasibility for integration into an underwater glider. It is found that the morphing wing enables the glider to adjust the lift‐to‐drag ratio to adapt to different flow conditions. At the operational angle of attack of 12.5°, the lift‐to‐drag ratio ranges from −70% to +10% compared to a rigid version. Furthermore, it reduces the need for internal moving parts and increases maneuverability. The findings lay the groundwork for the real‐world deployment of soft robotic principles capable of outperforming existing rigid systems. With the herein‐described methods, soft morphing capabilities can be enabled on other vehicles. [ABSTRACT FROM AUTHOR]

Morphing structures are a relatively new aircraft technology currently being investigated for a variety of applications, from civil to military. Despite the lack of literature maturity and its complexity, morphing wings offer significant aerodynamic benefits over a wide range of flight conditions, enabling reduced aircraft fuel consumption and airframe noise, longer range and higher efficiency. The aim of this study is to investigate the impact of morphing horizontal tail design on aircraft performance and flight mechanics. This study is conducted on a 1:5 scale model of a Preceptor N-3 Pup at its trim condition, of which the longitudinal dynamics is implemented in MATLAB release 2022. Starting from the original horizontal tail airfoil NACA 0012 with the elevator deflected at the trim value, this is modified by using the X-Foil tool to obtain a smooth morphing airfoil trailing edge shape with the same C L α . By comparing both configurations and their influence on the whole aircraft, the resulting improvements are evaluated in terms of stability in the short-period mode, reduction in the parasitic drag coefficient C D 0 , and increased endurance at various altitudes. [ABSTRACT FROM AUTHOR]

The influence of trailing edge deformation on the aerodynamic characteristics of camber morphing wings is an important topic in the aviation field. In this paper, a new memory alloy actuator is proposed to realize trailing edge deformation, and computational fluid dynamics (CFD) and wind tunnel experiments are used to study the influence of trailing edge deformation on the aerodynamic characteristics of the camber morphing wings. The experiments was carried out in a transonic wind tunnel with Mach numbers ranging from 0.4 to 0.8 and angles of attack ranging from 0° to 6°. The external flow fields and aerodynamic force coefficients with and without deformation were calculated using the CFD method. A loose coupled method based on data exchange was used to achieve a fluid–structure interaction (FSI) analysis. The research results indicate that when the trailing edge is deflected downwards, the phenomenon of shock wave forward movement reduces the negative pressure area on the upper wing surface, increases the pressure on the lower wing surface, and ultimately increases the total lift. This work provides a new approach for the implementation of trailing edge deformation and a powerful data reference for the design of camber morphing wings.

Actuators based on soft elastomers offer significant advantages to the field of robotics, providing greater adaptability, improving collision resilience, and enabling shape‐morphing. Thus, soft fluidic actuators have seen an expansion in their fields of application. Closed‐cycle hydraulic systems are pressure agnostic, enabling their deployment in extremely high‐pressure conditions, such as deep‐sea environments. However, soft actuators have not been widely adopted on unmanned underwater vehicle control surfaces for deep‐sea exploration due to their unpredictable hydrodynamic behavior when camber‐morphing is applied. This study presents the design and characterization of a soft wing and investigates its feasibility for integration into an underwater glider. It is found that the morphing wing enables the glider to adjust the lift‐to‐drag ratio to adapt to different flow conditions. At the operational angle of attack of 12.5°, the lift‐to‐drag ratio ranges from −70% to +10% compared to a rigid version. Furthermore, it reduces the need for internal moving parts and increases maneuverability. The findings lay the groundwork for the real‐world deployment of soft robotic principles capable of outperforming existing rigid systems. With the herein‐described methods, soft morphing capabilities can be enabled on other vehicles.

The perch landing maneuver of a wing-deforming unmanned aerial vehicle (UAV) was investigated through a framework that uses the free, open-source OpenFOAM with 6 degrees of freedom (6DOF) simulations. The framework uses a moving grid to follow the trajectory of the UAV, reducing computational resources. Together with the ability to allow internal grid deformation, sliding mesh, and algorithm addition, it can accurately mimic the entire landing process. Different wing deformation speeds, additional elevator rotation and emulated propeller lift were added to the 6DOF simulations to investigate their effects on the landing maneuver. The results showed that the wing deformation retraction speed has a considerable effect on the trajectory and velocity of the UAV. The wing deformation reduced the forward velocity of the UAV by 32%, from 13.89 to 9 m/s. With the elevator control, the velocity was reduced to 5 m/s. Lastly, and an activation time of 1 s for the emulated propeller lift can further decrease the velocity to around 4.2 m/s. A better algorithm for the emulated propeller lift may be able to give a superior performance. This framework allows us to understand the underlying perch landing maneuver aerodynamics. It can also be used on problems like fast-turning agile and flapping wing flight.

The morphing wing has recently received a lot of interest due to the development of smart materials and sophisticated control structures. During different phases of flight, such as take-off, cruising, and landing, the aerodynamic shape of a morphing wing can be improved. Various morphing wing structure concepts have been explored in recent years to improve flight performance. The morphing wing with a flexible leading edge, which is smooth and continuous without step or slot, is easier to construct and it promises more reliability than traditional high-lift configurations such as leading-edge slats. Significant geometric changes in an aircraft's wing during flight may enable efficient performance in disparate mission roles or enable new multi-role missions that would not be possible with a fixed-geometry aircraft. Traditional actuators and mechanisms are used in current aircraft to vary wing sweep for flight in different speed regimes, as well as to change the wing area and camber, and extend the flaps during landing and takeoff. An integrated actuator with problem detection, feedback and position control, onboard controls, and communication capabilities is called a smart actuator. This eliminates the need for external controllers and makes it simpler to install, operate, configure, and monitor the actuator. There are three different types of morphing mechanisms: airfoil morphing, in-plane morphing, and out-ofplane morphing. Each one of these categories has a different effect on aerodynamic qualities, and this project will focus on camber change and controlling it by using Intelligent Artificial then using it in model tests and ANSYS simulations. Copyright © 2023 Praise Worthy Prize S.r.l. - All rights reserved. [ABSTRACT FROM AUTHOR]

Aerial vehicle design process usually aims to maximize performance in a specific flight phase regarding a particular topic such as aerodynamics, flight qualities, or control. This paper proposes a multidisciplinary enhancement both in aerodynamics and longitudinal autonomous flight performance (LAFP) via modern simultaneous design methodology conducted with a novel morphing idea. In this regard, the main wing of a fixed-wing unmanned aerial vehicle (UAV) is redesigned with wingtips capable of altering its taper ratio which results in a semi-tapered planform. The dynamic model of morphing aircraft is constituted from data obtained by numerical and analytical approaches for a number of morphing scenarios. The LAFP is identified as the sum of trajectory tracking parameters which are rise time, settling time, and maximum overshoot, while aerodynamic performance is defined as lift-to-drag ratio. A hierarchically structured control system is designed and the proportional-integral-differential (PID) controller coefficients and the taper ratio of the morphing wingtip are optimized via the Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm. The k-Nearest Neighbor (k-NN) machine learning algorithm is also conducted to expand the data limited within the investigated range of morphing scenarios so as to have higher accuracy in optimization. Finally, flight simulations of the morphing UAV with optimal wing and control system design are carried out, closed-loop responses are examined in the presence of the von-Karman turbulence model, and the obtained satisfactory results are presented for both disciplines. [ABSTRACT FROM AUTHOR]

Morphing wing is one of the important development directions of future aircraft design, and the study of in-plane deformation of the morphing wing surface has received widespread attention. In this paper, four aspects in-cluding variable span length, variable sweep angle, variable chord length and combined deformation are analyzed to describe the current status of domestic and international research on in-plane morphing wings, summarize the defor-mation mechanism and its advantages and disadvantages, and analyze the future development trend of morphing wing. In view of the current research situation and the application requirements of the morphing wing, the key tech-nologies of the morphing wing are proposed, including the morphing skin technology, morphing mechanism, intelli-gent actuator, sensor and control network. The application requirements of each key technology and the existing problems are analyzed furthermore. The future development direction is summarized, which can provide some references for the design and application realization of in-plane morphing wings.

The present study numerically investigates the aerodynamic performance of the morphing airfoil and wing with leading edge (LE) and trailing edge (TE) parabolic flaps. Reynolds-averaged Navier-Stokes (RANS) equations coupled with the Spalart-Allmaras (S-A) turbulence model are employed to simulate the flow fields. Firstly, the parameterization method for the morphing airfoil with LE and TE parabolic flaps is proposed. Secondly, the influence of several design parameters, namely, LE droop angle, LE droop position, TE deflection angle, and TE deflection position, on the airfoil aerodynamics are further explored. Moreover, the aspect ratio (AR) effect for the wing based on the morphing airfoil is also investigated. Simulation results demonstrate that the parabolic flaps outperform the articulated flaps in lift generation, drag reduction, and aerodynamic efficiency enhancement, with an improvement in CL and L/D by 39.2% and 108.4% at α=4° , respectively. A larger LE droop angle can increase the stall margin, whereas the LE droop position barely influences airfoil aerodynamics at small angles of attack. The increment of the TE deflection angle significantly augments the lift. As the TE deflection position moves downstream, the suction peaks at the LE and TE are decreased and flow separation is also delayed. Furthermore, a larger AR can achieve higher efficiency, whereas a smaller AR is more beneficial for flow separation suppression. [ABSTRACT FROM AUTHOR]

The paper exposes some of the results obtained in a major research project related to the design, development, and experimental testing of a morphing wing demonstrator, with the main focus on the development of the automatic control of the actuation system, on its integration into the experimental developed morphing wing system, and on the gain related to the extension of the laminar flow over the wing upper surface when it was morphed based on this control system. The project was a multidisciplinary one, being realized in collaboration between several Canadian research teams coming from universities, research institutes, and industrial entities. The project's general aim was to reduce the operating costs for the new generation of aircraft via fuel economy in flight and also to improve aircraft performance, expand its flight envelope, replace conventional control surfaces, reduce drag to improve range, and reduce vibrations and flutter. In this regard, the research team realized theoretical studies, accompanied by the development and wind tunnel experimental testing of a rectangular wing model equipped with a morphing skin, electrical smart actuators, and pressure sensors. The wing model was designed to be actively controlled so as to change its shape and produce the expansion of laminar flow on its upper surface. The actuation mechanism used to change the wing shape by morphing its flexible upper surface (manufactured from composite materials) is based on Shape Memory Alloys (SMA) actuators. Shown here are the smart mechanism used to actuate the wing's upper surface, the design of the intelligent actuation control concept, which uses a self–tuning fuzzy logic Proportional–Integral–Derivative plus conventional On–Off controller, and some of the results provided by the wind tunnel experimental testing of the model equipped with the intelligent controlled actuation system. The control mechanism uses two fuzzy logic controllers, one used as the main controller and the other one as the tuning controller, having the role of adjusting (to tune) the coefficients involved in the operation of the main controller. The control system also took into account the physical limitations of the SMA actuators, including a software protection section for the SMA wires, implemented by using a temperature limiter and by saturating the electrical current powering the actuators. The On–Off component of the integrated controller deactivates or activates the heating phase of the SMA wires, a situation when the actuator passes into the cooling phase or is controlled by the Self–Tuning Fuzzy Logic Controller. [ABSTRACT FROM AUTHOR]

A multi-dimensional morphing wing skeleton mechanism is proposed with double-sided triangular pyramid units, which can realize continuous variable span-wise bend, span-wise twist, and sweep. A lockable morphing unit is designed, and its mechanism/structure characteristics, degree of freedom, and the deformable function of its deformable wing skeleton mechanism are analyzed. One kind of flexible skin is proposed to meet the performance requirements, consisting of an internal metastructure and a flexible surface bonded on both sides. The morphing wing skeleton mechanism and the equivalent treated metastructure flexible skin are then combined. Subsequently, a two-way fluid–structure interaction analysis is conducted to investigate the influence of aerodynamic loads on the flexible skin and skeleton mechanism in different deformation states, including the influence of structural passive deformation on the aerodynamic characteristics of the morphing wing. The computational fluid dynamics method is employed to analyze the aerodynamic characteristics of the morphing wing in its initial state, as well as in three deformation states, and to study its aerodynamic performance in different flight environments. [ABSTRACT FROM AUTHOR]

Birds can perform different flight phases such as climb, cruise and descent efficiently thanks to their adaptive wings. In conventional aircrafts, auxiliary control surfaces are used for different flight phases. In this study, it is aimed to increase the flight efficiency of small unmanned aerial vehicles with the morphing wing approach. The flexible wing is designed to be produced using a 3D printer. Airfoils can be classified as symmetrical, semi-symmetrical and cambered. Symmetrical wings allow higher speeds to be achieved, while cambered wing profiles provide more lift. It is intended that the aircraft wing can be transformed to specified airfoils. The wing is designed to have a morphing leading and trailing edge. In this way, it is aimed that the wing can have variable camber during flight. In order to shape the wing during flight, deformable flexible 3D printed structures were designed on the upper surface of the wing, and a structure with a slotted guide on the lower surface. Static and aerodynamic analyzes of the designed wing were carried out using simulation tools. After the optimization studies, prototype wing was manufactured using a FDM 3D printer, and then the morphing wing was tested in the wind tunnel. The aerodynamic behavior of the designed deformable wing in different conditions was analyzed using XFRL5 software. As a result of the aerodynamic analysis, it was seen that the camber wing had the highest lift coefficient (CL). It has been observed that the symmetrical wing has a lower drag coefficient (CD), resulting in higher aerodynamic efficiency. In wind tunnel tests, wing lift measurements were made for different wind speeds and angles of attacks. It has been observed that a wide range of different wing behaviors can be obtained with the developed morphing wing. [ABSTRACT FROM AUTHOR]

Birds are capable of morphing their wings across different flight modes and speeds to improve their aerodynamic performance. In light of this, the study aims to investigate a more optimized solution compared to conventional structural wing designs. The design challenges faced by the aviation industry today require innovative techniques to improve flight efficiency and minimize environmental impact. This study focuses on the aeroelastic impact validation of wing trailing edge morphing, which undergoes significant structural changes to enhance performance as per mission requirements. The approach to design-concept, modeling, and construction described in this study is generalizable and requires lightweight and actively deformable structures. The objective of this work is to demonstrate the aerodynamic efficiency of an innovative structural design and trailing edge morphing concept compared to conventional wing-flap configurations. The analysis revealed that the maximum displacement at a 30-degree deflection is 47.45 mm, while the maximum stress is 21 MPa. Considering that the yield strength of ABS material is 41.14 MPa, this kerf morphing structure, with a safety factor of 2.5, can withstand both structural and aerodynamic loads. The analysis results of the flap and morph configurations showed a 27% efficiency improvement, which was confirmed through the convergence criteria in ANSYS CFX. [ABSTRACT FROM AUTHOR]

In this paper, two preliminary designs of morphing wings based on multistage displacement amplification mechanisms (DAMs) are proposed, and their characteristics are evaluated by analytical modeling and experiments. The first design of a morphing wing (Re-MOW) is based on two-stage rhombus-type DAMs. In the first stage, a retraction-type electrothermal actuator (ReACT) consisting of a diamond-shaped displacement amplification structure (DAS) and an actuating bar that is thermally expanded by thin-film heaters is applied. In the second stage, the retraction displacement of the ReACT is again amplified by wings with rhombic DAS. The second morphing wing design (Ex-MOW) is based on a chevron and rhombus-shaped DAS. In the first stage, an extension-type electrothermal actuator (ExACT) operated by a diamond-shaped DAS consisting of a pair of V-shaped chevron beams and supporting bars is applied. Similar to the Re-MOW, the deformation of the ExACT is again amplified by the four flat wings assembled in a rhombus in the second stage. In the analysis results, it was deduced that the wing thicknesses of Re-MOW and Ex-MOW were amplified by 22.6 times and 21.2 times, respectively, compared to the thermal expansion length of the actuating bar and chevron beam. Afterward, the morphing wings were fabricated using a 3D printer with polyamide as the material, and their amplification ratio and total deformation as temperature and time are measured at various input voltages. In the experimental results, the thickness changes of the Re-MOW and Ex-MOW reached approximately 14 and 32 % of the initial total thickness of the wing, respectively. [ABSTRACT FROM AUTHOR]

This study presents a novel approach to parameterize the geometry of a morphing trailing-edge flap that allows its aerodynamics to be optimized while capturing the expected structural behavior of the flap. This approach is based on the finite frame element method, whereby the initial flap surface is defined as a structure with constraints that are similar to those of a morphing flap with passive skin. The initial shape is modified by placing a series of distributed loads on the surface. The finite frame element method is modified with rigid rotation corrections to maintain the initial element length without requiring nonlinear calculations and to achieve accurate surface-length results by only solving the linear FEM equations twice. The proposed method enables the shape of the morphing flaps to be rapidly formulated while maintaining the initial upper surface-length and trailing-edge angle. The constraints are inherently integrated into the algorithm, eliminating the need for unnecessary feasibility checks during the aerodynamic optimization. By using the proposed airfoil parameterization method, a case study was conducted by using a genetic algorithm to optimize the lift-to-drag ratio of the NACA 23012 airfoil flap starting at 0.7c with 10 degrees of deflection. The optimizer resulted in a structurally feasible morphing flap that achieved a 10% increase in the lift-to-drag ratio in the optimized angle of attack range. [ABSTRACT FROM AUTHOR]

In the present paper, semi-analytical design sensitivity analysis of a morphing forward wing section modeled as a flexible multibody system is developed. The flexible multibody dynamics model consists of a flexible external wing skin and an actuation mechanism with rigid bodies. The floating frame of reference formulation is used for the formulation of the equations of motion, while time integration is carried out with the generalized- α method and Newton–Raphson iterations for the nonlinear analysis. These steps are considered in both the primal analysis and the developed efficient design sensitivity analysis. The calculation of the design sensitivities is based on direct differentiation and carried out with a semi-analytical approach. The responses of interest include the deviations of the wing profile from the targeted morphed geometry and the resulting stresses in the wing skin. The design variables considered in this work are geometric parameters, material parameters and loading parameters. The calculations with the shown method provide reliable and accurate results combined with high computational efficiency. The visualization of the computed sensitivity values gives an easy interpretation of the sensitivities and facilitates the understanding of the design engineer on how to change the design variables to improve the design of the system. The introduced sensitivity analysis enables future investigations, including the application of the method to gradient-based design optimization and uncertainty analysis. [ABSTRACT FROM AUTHOR]

The main two mechanisms of morphing wall flow control are direct injection of momentum in the streamwise direction and indirect momentum transfer via triggering instabilities. Traveling waves have been shown to perform better than standing waves, probably because they can use both mechanisms. However, the relative importance of the two mechanisms is not known. To differentiate between the mechanisms, a range of parameters (frequency, amplitude, and starting location) at stall (15 deg angle of attack) and poststall (20 deg angle of attack) is tested using wall-resolved large-eddy simulations with a sharp-interface curvilinear immersed boundary method at a low Reynolds number of Re=50,000 over a NACA0018 airfoil. The results of the simulations demonstrate that the flow is reattached within a range of nondimensional frequencies, actuation amplitudes, and starting locations of oscillation at the stall and poststall angles of attack. Significant lift enhancement and drag reduction are also observed within these ranges. The nondimensional frequency range at which the flow is reattached is found to be similar to the dominant nondimensional frequencies of leading-edge vortex shedding of the unactuated airfoil. These indicate that the indirect transfer of momentum is the dominant mechanism because direct injection of momentum increases with the increase of amplitude and frequency; that is, separation should reduce as they increase. Nevertheless, direct injection of momentum improves the performance relative to pure excitations of standing waves when instabilities are triggered. [ABSTRACT FROM AUTHOR]

Detrimental environmental impacts due to the increasing demands of the aviation industry have gained tremendous global attention. With a potential fuel saving, along with high aerodynamic performance and maneuverability during different phases of a flight, adaptable wing design has become a viable alternative to its fixed-shape counterpart. A morphing wing design embraces, and can respond accordingly to, most of the flight condition variations effectively and efficiently. Despite these prospects, morphing wing design comes with some challenges due to its inherent complexity caused by an increased number of degrees of freedom. With the availability of various morphing parameters, the vibration signature of a morphing wing design plays a vital role in terms of its structural as well as aeroelastic characteristics. In the present paper, the dynamic characteristics of a re-configurable modular morphing wing developed in-house by a research team at Toronto Metropolitan University are investigated. This modular morphing wing, developed based on the idea of a parallel robot, consists of a number of structural elements connected to each other and to the wing ribs through eyebolt joints. Timoshenko bending beam theories, in conjunction with finite element methodology, are exploited. The free vibration of un-morphed (original) and morphed configurations undergoing multiple levels of sweep and spanwise morphing is presented through a design of experiment methodology. [ABSTRACT FROM AUTHOR]

Since the taper ratio of most wings is not equal to 1, the beam-disk trailing edge deflection mechanism originally designed for the rectangular wing is not fully applicable to the non-equal chord wing. Moreover, it is not only expected that the wing shape can achieve excellent aerodynamic performance under different flight conditions, but one also needs to consider whether the flexible skin can achieve this deformation. This paper used the honeycomb composite structure with zero Poisson's ratio as the flexible skin of the trailing edge for the variable camber wing, and designed the beam-disk trailing edge deflection mechanism for the non-equal chord wing. The aerodynamic configuration was optimized considering the deformation capability of the skin, and the multidisciplinary design and optimization method of the variable camber wing with non-equal chord was studied. The results show that the aerodynamic performances of the optimized non-equal chord wings were better than before under all given flight conditions. The flexible skin could withstand the strain caused by the maximum deflection of the trailing edge of the wing, and the weight of the wing structure was reduced by 47.1% compared with the initial design when the structural stiffness and strength were satisfied. [ABSTRACT FROM AUTHOR]

The spanwise morphing wing can change its aerodynamic shape to suit its flight environment, thereby having the potential to improve the flight performance of the aircraft, especially in gusty conditions. To investigate the potential of morphing wings, the aerodynamic performance of a spanwise morphing wing with a flapping wingtip in a gust environment was analyzed in this paper. The aerodynamic characteristics of the morphing wing are hard to measure accurately, and thus a wind tunnel test was carried out to study the influences of morphing parameters, such as the morphing length, amplitude and frequency on the gust alleviation effect. The flow mechanism of the designed spanwise morphing wing was analyzed in detail by the instantaneous lift results of the wind tunnel test and the flow field results of the CFD method. The results have shown that with appropriate morphing parameters, the spanwise morphing wing designed in this paper can effectively achieve gust alleviation during flight. The conclusions obtained in this paper can be useful guidance for the design of morphing aircraft. [ABSTRACT FROM AUTHOR]

Morphing structures are a relatively new aircraft technology currently being investigated for a variety of applications, from civil to military. Despite the lack of literature maturity and its complexity, morphing wings offer significant aerodynamic benefits over a wide range of flight conditions, enabling reduced aircraft fuel consumption and airframe noise, longer range and higher efficiency. The aim of this study is to investigate the impact of morphing horizontal tail design on aircraft performance and flight mechanics. This study is conducted on a 1:5 scale model of a Preceptor N-3 Pup at its trim condition, of which the longitudinal dynamics is implemented in MATLAB release 2022. Starting from the original horizontal tail airfoil NACA 0012 with the elevator deflected at the trim value, this is modified by using the X-Foil tool to obtain a smooth morphing airfoil trailing edge shape with the same CLα. By comparing both configurations and their influence on the whole aircraft, the resulting improvements are evaluated in terms of stability in the short-period mode, reduction in the parasitic drag coefficient CD0, and increased endurance at various altitudes.

The use of elastomer-based skins in morphing wings has become increasingly popular due to their remarkable stretchability and mechanical properties. However, the possibility of the skin fracturing during multiaxial stretching remains a significant design challenge. The propagation of cracks originating from flaws or notches in the skin can lead to the specimen breaking into two parts. This paper presents an experimental study aimed at comprehensively evaluating crack propagation direction, stretchability, and fracture toughness of silicone-based elastomeric skin (Ecoflex) for morphing wing applications, using varying Shore hardness values (10, 30, and 50). The findings show that the lower Shore hardness value of 10 exhibits a unique Sideways crack propagation characteristic, which is ideal for morphing skins due to its high stretchability, low actuation load, and high fracture toughness. The study also reveals that the Ecoflex 10 is suitable for use in span morphing, with a fracture toughness of approximately 1.1 kJ/m 2 for all thicknesses at a slower strain rate of 0.4 mm/min. Overall, this work highlights the superior properties of Ecoflex 10 and its potential use as a morphing skin material, offering a groundbreaking solution to the challenges faced in this field. [ABSTRACT FROM AUTHOR]

Considering both supersonic and subsonic aerodynamic performances in aircraft design is challenging. This challenge can be alleviated through morphing design or plasma flow control. Therefore, if they are both considered in the aerodynamic optimization, the results can be undoubtedly improved. In this study, first, a new sliding shear variable sweep design scheme which can change both the plane shape (such as the span and sweep angle) and the wing profile (such as the chord length and the relative thickness) is proposed and some information about the elastomeric skin scheme is given. Second, an efficient global optimization framework based on surrogate-based optimization algorithm is established for the aerodynamic shape optimization of this morphing wing. Third, two optimizations are conducted, wherein one considers the effect of plasma actuation while the other does not. Due to the complexity and large calculations required, the effect of plasma actuation is not directly considered in computational fluid dynamics simulation but is indirectly considered by relaxing the subsonic lift constraint, which assumes that plasma actuation can offset the lift loss. Therefore, it is called "plasma constraint relaxation". In the two optimizations, three different configurations of the morphing wing which are 20°-, 30°- and 70°- sweep angle state, and three different flow conditions, which are subsonic (0.25 Ma), transonic (0.85 Ma) and supersonic (3 Ma) are considered. The results show that the comprehensive performance (objective function) improves by 12.6% with the effect of plasma actuation while it improves by 7.6% without the effect of plasma actuation after a two-round optimization. This suggests that the subsonic lift constraint, as an active constraint, significantly impacts the final optimization results. Finally, to verify whether plasma actuation can offset the lift loss, an experiment of nanosecond pulse dielectric barrier discharge plasma controlling flow separation is conducted to increase the subsonic lift of the optimization shape. The results show that the maximum lift increases by 18.1% when the actuation voltage is 8 kV and actuation frequency is 160 Hz and the lift loss caused by the constraint relaxation is 14.5%. [ABSTRACT FROM AUTHOR]

Growing concerns over the CO2 footprint due the exponential demand of the aviation industry, along with the requirements for high aerodynamic performance, cost saving, and manoeuvrability during different phases of a flight, pave the path towards adaptable wing design. Morphing wing design encompasses most, if not all, of the flight condition variations, and can respond interactively. However, functional failure of the morphing wing might bring devastating impacts on the passengers, crew, and/or aircraft. In the present work, the dynamic characteristics of a re-configurable modular morphing wing developed in-house by a research group at the Toronto Metropolitan University, are investigated from the perspective of a functional hazard assessment (FHA). This modular morphing wing, developed based on the idea of a parallel robot, consists of a number of structural elements connected to each other and to the wing ribs through eye-bolt joints. Timoshenko's bending beam theory, in conjunction with the finite element method (FEM), is exploited to model the structural members. Possible hazards, assumed here to be the structural failure of the beam components, have been identified and their failure conditions are assessed. Numerical simulations have been presented to show the impact of various combinations of the identified hazards on the vibration signature of the morphing wing in unmorphed and morphed configurations. Identification of changes in the wing's vibration signature is a vital component in the fail-safe structural and aeroelastic design of an aircraft. The present study is geared towards the structural response of the system in the absence of any aerodynamic loads. [ABSTRACT FROM AUTHOR]