Search

Variable camber wing technology stands out as the most promising morphing technology currently available in green aviation. Despite the ongoing advancements in smart materials and compliant structures, they still fall short in terms of driving force, power, and speed, rendering mechanical structures based on kinematics the preferred choice for large long-range civilian aircraft. In line with this principle, this paper introduces a linkage-based variable camber trailing edge design approach. Covering coordinated design, internal skeleton design, flexible skin design, and drive structure design, the method leverages a two-dimensional supercritical airfoil to craft a seamless, continuous two-dimensional wing full-size variable camber trailing edge structure, boasting a 2.7 m span and 4.3 m chord. Given the significant changes in aerodynamic load direction, ground tests under cruise load utilize a tracking-loading system based on tape and lever. Results indicate that the designed single-degree-of-freedom Watt I mechanism and Stephenson III drive mechanism adeptly accommodate the slender trailing edge of the supercritical airfoil. Under a maximum cruise vertical aerodynamic load of 17,072 N, the structure meets strength requirements when deflected to 5°. The research in this paper can provide some insights into the engineering design of variable camber wings. [ABSTRACT FROM AUTHOR]

The occurrence of probabilistic common cause errors (PCCEs) in man‐machine systems can lead to multiple human errors being affected by common causes and will contribute greatly to the reliability of the system. In this paper, A reliability modeling method based on event tree (ET)‐fault tree (FT) model for man‐machine systems subjected to PCCEs is proposed. Under the influence of PCCEs, risk factors in the system are not independent, and human errors affected by the same common cause will occur with different probabilities. To describe the dependencies among risk factors, a PCCE gate is proposed to extend FTs in the ET‐FT model. To analyze the impact of common causes on the human error probabilities and quantify the extended FT, an explicit method and an implicit method based on the Cognitive Reliability and Error Analysis Method are proposed. The proposed quantification methods consider the different relationships among multiple common causes in a single model. Finally, the proposed methods are validated in the reliability assessment of the emergency response system under malfunction of the solar wing mechanism. [ABSTRACT FROM AUTHOR]

Purpose: Endurance time is an important factor limiting the progress of flapping-wing aircraft. In this study, this paper developed a prototype of a double-wing flapping-wing micro air vehicle (FMAV) that mimics insect-scale flapping wing for flight. Besides, novel methods for optimal selection of motor, wing length and battery to achieve prolonged endurance are proposed. The purpose of this study is increasing the flight time of double-wing FMAV by optimizing the flapping mechanism, wings, power sources, and energy sources. Design/methodology/approach: The 20.4 g FMAV prototype with wingspan of 21.5 cm used an incomplete gear flapping wing mechanism. The motor parameters related to the lift-to-power ratio of the prototype were first identified and analyzed, then theoretical analysis was conducted to analyze the impact of wing length and flapping frequency on the lift-to-power ratio, followed by practical testing to validate the theoretical findings. After that, analysis and testing examined the impact of battery energy density and efficiency on endurance. Finally, the prototype's endurance duration was calculated and tested. Findings: The incomplete gear facilitated 180° symmetric flapping. The motor torque constant showed a positive correlation with the prototype's lift-to-power ratio. It was also found that the prototype achieved the best lift-to-power ratio when using 100 mm wings. Originality/value: A gear-driven flapping mechanism was designed, capable of smoothly achieving 180° symmetric flapping. Besides, factors affecting long-duration flight – motor, wings and battery – were identified and a theoretical flight duration analysis method was developed. The experimental result proves that the FMAV could achieve the longest hovering time of 705 s, outperforming other existing research on double-wing FMAV for improving endurance. [ABSTRACT FROM AUTHOR]

As the population of the world's major cities increases, urban ground transportation capability reaches its limits. Consequently, electric vertical takeoff and landing aircraft have been developed to address this issue. Modern vertical takeoff and landing designs vary in configurations, each possessing distinct aerodynamic properties. In this work, we focus on the interaction between rotors and fixed wings in a parallel layout, using a prototype with an unconventional configuration as an example. The interaction between the slipstream of rotors and the wake of fixed wings is analyzed using the vortex particle method. Actuator surface model is used to deal with the boundary problem between the wing and the rotors. The applicability of the simulation method adopted in this paper is verified through experimental tests on the thrust and torque of the rotors. The results indicate that under the condition of forward flight at zero angle of attack, the existence of rotor slipstream induces a significant increase by three to four times the local lift on the wing. Correspondingly, under vertical takeoff and hovering conditions, the existence of the rotor slipstream causes the local effective velocity and circulation of the wing to increase. On the other hand, at zero angle of attack and a forward flight, the lift coefficient of the rear rotors increases slightly due to the presence of the wing wake. The lift distribution of the rear rotors along the radial direction also changes greatly. [ABSTRACT FROM AUTHOR]

This paper studies static test methods and test loads of Carbon Fiber Reinforced Polymer (CFRP) wing-box, analyzes the test results, and compares the test results of T800 CFRP wing-box from HENGSHEN Co., LTD and TORAY. It comes out that the stiffness of the T800 CFRP wing-box from HENGSHEN is equivalent with that of TORAY, while the strength meets the structural design requirements, which can be applied on the scheduled aircraft structure for further verification. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to propose a structural sizing approach of an unmanned aerial vehicle (UAV) wing that takes into account the aeroelasticity effects through a fluid–structure interaction analysis. Design/methodology/approach: The sizing approach proposed in this study is an iterative process, each iteration of which consists of two sub-loops, a multidisciplinary analysis (MDA) loop followed by a structural optimization loop. The MDA loop seeks the aeroelastic equilibrium between aerodynamic forces and structural displacements using a fixed-point iteration scheme. Once the equilibrium is reached, the converged pressure loads are used for the structural optimization, which aims to find the structural thicknesses that minimize the wing weight under failure criteria. The two sub-loops are run sequentially in an iterative process until the mass is converged. The analysis models are implemented in open-source software, namely, PANUKL for aerodynamics and MYSTRAN for structures, while the whole process is automated with Python and integrated in the open-source optimization framework OpenMDAO. Findings: The approach was applied to the design of the Predator MQ-1 wing. The results of the MDAs show the convergence of the wing deformations to the flight shape after few iterations. At the end of the aeroelastic sizing loop, the result is a structurally sized wing with minimal weight considering the aeroelasticity effects. Originality/value: The approach proposed takes into account the wing aero-structural coupling effects while sizing its structure instead of a fixed load distribution. In addition, the approach is fully based on open-source codes, which are freely available for public use and can be fully reproducible. [ABSTRACT FROM AUTHOR]

There are complex coupling relationships between flight motion and energy management for hybrid electric fixed wing UAVs with photovoltaic/fuel cell/battery. Aiming at realizing high-energy-efficiency long endurance autonomous flight, this paper proposes a coordinated optimization method of trajectory optimization and energy management for hybrid electric UAVs. Numerical simulation and experiment are carried out. Separated by surplus demand energy except that produced by PV, this method includes an optimal energy flight trajectory optimization layer and an energy management layer. For the former, fuzzy neural network sequential convex optimization (FNNSCP) is proposed to handle the flight trajectory optimization problem for maximizing utilization solar energy. For the latter, an online energy management strategy based on convex quadratic programming MPC (CQPMPC) is proposed to realize the power allocation. Numerical simulation results show that FNNSCP reduced 2% energy requirement compared with Radau pseudo-spectral method (RPM) from flight trajectory optimization level. From energy management level, CQPMPC saves hydrogen consumption by 3.1% and 16.3% compared with nonlinear model predictive control (NMPC) and fuzzy logic state machine (FLSM), respectively. In the experiment, less hydrogen fuel is consumed by proposed method by 5.2% and 15.6% compared with NMPC and FLSM, respectively. Experimental results show that the proposed method has better energy-saving performance and excellent real time performance. It indicates that optimizing flight trajectory and improving energy management efficiency can realize the high-energy-efficiency flight of hybrid electric UAVs. This method is conducive to promoting the application of hydrogen energy in the field of UAVs. [Display omitted] • A coordinated optimization method is proposed for the high-energy-efficiency flight. • Fuzzy neural network adaptive sequential convex optimization method is proposed. • Online energy management strategy with convex quadratic programming MPC is proposed. • The proposed method is verified by simulation and energy management experiment. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to assess the feasibility of additively manufactured wind tunnel models. The additively manufactured model was used to validate a computational framework allowing the evaluation of the performance of five wing models. Design/methodology/approach: An optimized fighter wing was additively manufactured and tested in a low-speed wind tunnel to obtain the aerodynamic coefficients and deflections at different speeds and angles of attack. The flexible wing model with optimized curvilinear spars and ribs was used to validate a finite element framework that was used to study the aeroelastic performance of five wing models. As a computationally efficient optimization method, homogenization-based topology optimization was used to generate four different lattice internal structures for the wing in this study. The efficiency of the spline-based optimization used for the spar-rib model and the lattice-based optimization used for the other four wings were compared. Findings: The aerodynamic loads and displacements obtained experimentally and computationally were in good agreement, proving that additive manufacture can be used to create complex accurate models. The study also shows the efficiency of the homogenization-based topology optimization framework in generating designs with superior stiffness. Originality/value: To the best of the authors' knowledge, this is the first time a wing model with curvilinear spars and ribs was additively manufactured as a single piece and tested in a wind tunnel. This research also demonstrates the efficiency of homogenization-based topology optimization in generating enhanced models of different complexity. [ABSTRACT FROM AUTHOR]

In this paper, a numerical analysis of a biomimetic unmanned aerial vehicle (UAV) is presented. Its wings feature three grids at the tip similar to the primary feathers of birds in order to modify the lift distribution over the wing and help in reducing the induced drag. Numerical analysis using computational fluid dynamics (CFD) is presented to analyze the aerodynamic effects of the changes in dihedral and angle of attack (with respect of the rest of the wing) of these small grids at the tip. The aerodynamic performances (lift, drag, and efficiency) and rolling capabilities are obtained under different flight conditions. The effects of changing the dihedral are small. However, the change in the grid angle of attack increases aerodynamic efficiency by up to 2.5 times when the UAV is under cruise flight conditions. Changes to the angle of attack of the grids also provide increased capabilities for rolling. Finally, boundary values of the pressure coefficient and non-dimensional velocity contours are presented on the surfaces of the UAV, in order to relate the aerodynamic results to the aerodynamic patterns observed over the wing. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this research paper is to recover the autonomous flight performance of a mini unmanned aerial vehicle (UAV) via stochastically optimizing the wing over certain parameters (i.e. wing taper ratio and wing aspect ratio) while there are lower and upper constraints on these redesign parameters. Design/methodology/approach: A mini UAV is produced in the Iskenderun Technical University (ISTE) Unmanned Aerial Vehicle Laboratory. Its complete wing can vary passively before the flight with respect to the result of the stochastic redesign of the wing while maximizing autonomous flight performance. Flight control system (FCS) parameters (i.e. gains of longitudinal and lateral proportional-integral-derivative controllers) and wing redesign parameters mentioned before are simultaneously designed to maximize autonomous flight performance index using a certain stochastic optimization strategy named as simultaneous perturbation stochastic approximation (SPSA). Found results are used while composing UAV flight simulations. Findings: Using stochastic redesign of mini UAV and simultaneously designing mini ISTE UAV over previously mentioned wing parameters and FCS, it obtained a maximum UAV autonomous flight performance. Research limitations/implications: Permission of the directorate general of civil aviation in the Republic of Türkiye is essential for real-time UAV autonomous flights. Practical implications: Stochastic redesign of mini UAV and simultaneously designing mini ISTE UAV wing parameters and FCS approach is very useful for improving any mini UAV autonomous flight performance cost index. Social implications: Stochastic redesign of mini UAV and simultaneously designing mini ISTE UAV wing parameters and FCS approach succeeds confidence, highly improved autonomous flight performance cost index and easy service demands of mini UAV operators. Originality/value: Creating a new approach to recover autonomous flight performance cost index (e.g. satisfying less settling time and less rise time, less overshoot during flight trajectory tracking) of a mini UAV and composing a novel procedure performing simultaneous mini UAV having passively morphing wing over certain parameters while there are upper and lower constraints and FCS design idea. [ABSTRACT FROM AUTHOR]

The efficient design of the aerodynamic surfaces in the aircraft allows the optimal performance of the vehicle and the reduction of the fuel consumption. Among these surfaces, the wing is the main contributor to the force which lifts the aircraft enabling the flight. However, the application of this force out of the center of gravity generates a moment that must be balanced through a force applied in the Horizontal-Tail-Plane (HTP) reaching the longitudinal trim of the aircraft. Traditionally, the design of the wing and HTP have been performed iteratively attaining suboptimal or time ineffective results. In this paper, we solve this problem through the application of a Genetic Algorithm for the combined optimization of the wing and the HTP by adjusting the aspect ratio, the taper ratio, the twist angle and the incidence angle of both surfaces to produce the optimal balance of lift adjusting its distribution to an elliptical configuration and enabling the longitudinal trim. Results show the automatic adjustment of the parameters of the aerodynamic surfaces thus fulfilling the objectives of this paper. [ABSTRACT FROM AUTHOR]

Purpose: Determining the variation law of the oxygen concentration in the ullage space of the fuel tank is the key to the design of the inert system. Among various factors affecting the oxygen concentration in the ullage space of the fuel tank, the temperature difference between day and night shows particular importance while relevant analysis and calculation are scarce. Design/methodology/approach: This study establishes a theoretical simulation model of the central wing fuel tank of an aircraft according to the relevant provisions of day-night temperature variation in FAR25 airworthiness regulations, verifies the model with the existing experimental data and discusses the corresponding relationship between the oxygen concentration in the ullage space of the fuel tank and the day-night temperature difference. The influence of day and night temperature difference, fuel type, fuel load rate, initial oxygen concentration, dissolved oxygen evolution and other factors on the oxygen concentration in the ullage space of the fuel tank were analyzed, and the limit of initial oxygen concentration of the fuel tank before the shutdown at night meeting the requirements of the airworthiness provisions was proposed. Findings: The results show that the temperature difference between day and night, fuel load rate, initial oxygen concentration and other factors have different effects on the oxygen concentration in the ullage space of fuel tank. The initial oxygen concentration limit before shutdown shall be 2% below the 12% oxygen concentration stipulated by FAA. Research limitations/implications: The research results in this paper will be of good reference value to the design of the inert system and the calculation of the flammability exposure evaluation time. This paper aims to be good reference of the design of the inert system and the calculation of the flammability exposure evaluation time. Originality/value: The research results of this paper can provide practical guidance for the current civil airworthiness certification work. [ABSTRACT FROM AUTHOR]

Aircraft employing the boost-glide-cruise combination flight mode can achieve longer range, but traditional single configurations struggle to achieve good aerodynamic performance. This paper introduces a novel design method for a combined two-stage waverider, aiming to enhance aerodynamic performance while considering the integration of different engines. After completing the boosting and gliding phases, the lower surface and engines of the first-stage waverider are discarded to promptly reduce aircraft weight, allowing for improved aerodynamic performance and more efficient propulsion during the cruising phase. The airbreathing cruising waverider is designed based on the principle of osculating cone at a fixed Mach number, combining the waverider forebody, afterbody, and stretched body to obtain a complete waverider configuration, equipped with a scramjet engine. The flow field corresponding to the wide-speed-range gliding waverider is reverse-designed using the upper surface of the airbreathing waverider, allocating different Mach numbers and shock angles for the conical flow field, obtaining the wide-speed-range waverider configuration through streamline tracing, and equipping it with a rocket engine. The two waveriders are combined by sharing the upper surface, while constraints on the inlet cross-section are provided to ensure no intersection or overlap of the lower surfaces. Subsequently, numerical simulations were conducted to analyze the aerodynamic performance of the two-stage waverider, verifying the validity of the design method. Finally, the configuration was applied to a boost-glide-cruise flight trajectory, revealing that the two-stage waverider designed in this paper is highly suitable for long-distance flight. Compared with a single-stage wide-speed-range gliding waverider with the same configuration, the range is increased by 147.8 %, further validating the rationality of the design method presented in this paper. • A separable two-stage waverider design based on boost-glide-cruise combined trajectories is proposed. • A wide-speed-range waverider and a fixed Mach number airbreathing waverider are employed to optimize performance. • It achieves a significant range increase in the cruising phase than the single-stage waverider. [ABSTRACT FROM AUTHOR]

New instruments and telescopes covering the optical and ultraviolet spectral regions have revealed a range of small-scale dynamic features, many which may be related. For example, the range of spicule-like features hints towards a spectrum of features and not just two types; however, direct observational evidence in terms of tracking spicules across multiple wavelengths is needed in order to provide further insight into the dynamics of the Sun's outer atmosphere. This paper uses H α data obtained with the CRisp Imaging SpectroPolarimeter instrument on the Swedish 1-m Solar Telescope, and in the transition region using the Interface Region Imaging Spectrograph with the SJI 1400 Å channel plus spectral data via the Si iv 1394 Å line to track spicules termed rapid blueshifted excursions (RBEs). The RBEs as seen in the H α blue wing images presented here can be subdivided into two categories: a single or multithreaded feature. Based on the H α spectra, the features can be divided into events showing broadening and line core absorption, events showing broadening and line core emission, events with a pure blueshifted H α profile without any absorption in the red wing, and broadened line profile with the absorption in the blue stronger compared to the red wing. From the RBE-like events that have a Si iv 1394 Å line profile, 78  per cent of them show a Si iv line flux increase. Most of these features show a second broadened Si iv component that is slightly blueshifted. [ABSTRACT FROM AUTHOR]

Radar stealth was a remarkable technical feature of the fourth-generation fighter aircraft, the damage of the stealth coating would seriously affect the stealth performance of the aircraft. This paper focuses on the membrane treatment of coating in the process of stealth coating damage repair, the effect of laser cleaning process on the cleaning effect of stealth coating on the surface of aircraft metal construction was studied. The results show that laser pulse width has the greatest influence on the laser cleaning of stealth coating, so pulse width should be prioritized when selecting the process parameters. And during the process experiment, the relationship between the effect of laser cleaning and process parameters were respectively negative correlation with scanning speed, positive correlated first and then weakly correlation with laser power, weakly correlated first and then positive correlation with pulse width, positive correlation with scan number. Finally, the optimal laser cleaning process parameters for the stealth coating of 500 μm on the surface of the metal structures were obtained by comparing the experiments between the preferred and the solution groups. [ABSTRACT FROM AUTHOR]

The layout of the wing's internal structure not only dramatically influences the wing's strength stiffness but also directly affects the aerodynamic characteristics of the aircraft. Based on the original wing structure, a more flexible spatial design layout to achieve improved overall structural load-bearing performance, and a reasonable structural lightweight design are the research priorities to be considered for the development of future aircraft. Therefore, this paper attempted to design and analyze a lightweight airfoil that meets the performance requirements. Combining the strategy of hierarchical optimization design with the advantages of engineering bionics, the diatom Arachnoidiscus bionic structure, topological optimization, partial least squares regression (PLSR), and multi-objective particle swarm algorithm (PSO) are applied to optimize the placement and size of wing's internal components. The simulation results show that the weight of the optimized wing structure is reduced by 6% while satisfying the requirements of maximum stress and maximum deformation. [ABSTRACT FROM AUTHOR]

As unmanned vehicles become smaller and more autonomous, it is becoming feasible to use them in large groups with comparatively few human operators. Design and analysis of such distributed systems are complicated by the many interactions among agents and phenomena of human behavior. In particular, human susceptibility to fatigue and cognitive overload can introduce errors and uncertainty into the system. In this paper, we demonstrate how advanced computational tools can help to overcome these engineering difficulties by optimizing multirobot, multioperator surveillance systems for cost, speed, accuracy, and stealth according to diverse user preferences in multiple case studies. The tool developed is a graphical user interface that returns the optimal number and mix of diverse agent types as a function of the user's trade‐off preferences. System performance prediction relies on a multiagent simulation with submodels for human operators, fixed‐wing unmanned aerial vehicles (UAVs), quadrotor UAVs, and flapping wing UAVs combined in different numbers. [ABSTRACT FROM AUTHOR]

An aircraft wing is the carrier of imaging payload (interferometric synthetic aperture radar (SAR) or array SAR) of a high-resolution aerial remote sensing system, and high-precision estimation of wing deformation is the key. There are two main traditional modelling methods for wing deformation, namely stochastic theory modelling and material mechanics modelling only dealing with single disturbance, of which the model parameters are derived from empirical values. Aiming at the complex multi-source disturbance of an aircraft wing, this paper separately probes the influence of external disturbance (air disturbance) and internal disturbance (engine vibration) based on the real-time observation of sensors and classifies the wing deformation on the basis of auto-regressive (AR) modelling for parameter identification. With the authentic flight data of a certain types of aircraft, the experimental analysis shows that the wing deformation under the influence of engine vibration is the 14th-order AR model, and the wing deformation under the influence of turbulence is the fifth-order AR model. Meanwhile, this paper also provides an experimental verification idea for the wing deflection modelling built on the second- or third-order Markov model. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to find the droplets impact on the airplane wing structure. Two kinds of characteristics of the droplet at different velocity and viscosity are assumed. The droplet is assumed to be spherical cubic form and it is injected from the convergent divergent nozzle with a passive control. Design/methodology/approach: This paper presents the results of a numerical simulation of droplet impact on the horizontal surface. The effects of impact parameters are studied. The splash effect of the droplet also visualized. The results are presented in form of stress, strain, displacement magnitude of the droplet. Findings: Crosswire is used as passive control. The behavior of the droplet impact is observed based on the kinetic energy and the gravitational forces. Originality/value: The results predict that smooth particle hydrodynamic designed droplet not only depend on the equation of state of the droplet but also the injection velocity from the nozzle. It also determined that droplet velocity is depending on the viscosity of the fluid. [ABSTRACT FROM AUTHOR]

High-lift systems are designed to expand the flight envelope and have a most important effect on the size of the wing, economy, and safety of many airliner configurations. Even a small increment of lift using a high-lift system can significantly impact an aircraft's profitability. The effective design of the airfoil shape with the required aerodynamic performance is still difficult. In the early days, the designs of airfoils were randomly set up and tested in the flow section, and then, the Wright brothers emerged with a cambered section. NACA has provided an appropriate airfoil definition that supports us in making airfoil designs using formulas, not randomly. This paper describes the influence of aerodynamic analysis of wing with flaps at various deflection angles. Aerodynamic variables for the aircraft wing, which is made up of the NACA airfoil 6412 model with and without flaps, have been studied at various angle of attack (AOA) (i.e., -4, -2, 0, 2, 4, 6, 8, 10, 12, and 16) and different Mach number at 0.2, 0.3, and 0.4. Also, the analysis was done for the 15000 ft altitude to check the density effects for the real-time applications. The coefficients of lift and drag are gained by examining the pressure distribution over the surface of the wing. Lift increases as the approach ascends from a low to a high angle of attack, and the most extreme lift is produced at a specific point. After that, when the angle of attack increases further, the drag component increases, so the stall occurs at that point in time. The results showed that the NACA 6412 airfoil obtained the maximum lift at 14°, and the lift value started to decrease. The CFD computations are performed in Ansys Fluent by performing hybrid mesh using ICEM-CFD. The analysis is performed for various configurations of the wing section, and the effects of flow parameters like angle of attack, altitude, and the gap distance between the main wing and slotted flap were compared to identify the better configurations. [ABSTRACT FROM AUTHOR]

Integrating the operation of airborne wind energy systems safely into the airspace requires a systematic qualification process. It seems likely that the European Union Aviation Safety Agency will approve commercial systems as unmanned aircraft systems within the "specific" category, requiring risk-based operational authorization. In this paper, we interpret the risk assessment methodology for airborne wind energy systems, going through the ten required steps of the recommended procedure and discussing the particularities of tethered energy-harvesting systems. Although the described process applies to the entire field of airborne wind energy, we detail it for a commercial flexible-wing airborne wind energy system. We find that the air risk mitigations improve the consolidated specific assurance and integrity level by a factor of two. It is expected that the framework will increase the safety level of commercial airborne wind energy systems and ultimately lead to operation approval. [ABSTRACT FROM AUTHOR]

This paper examines a Distributed Propulsion (DP) concept and involves CFD verification, optimisation and evaluation. The first part of the study validates the employed simulation methods using experimental data from the NASA Workshop for Integrated Propeller Prediction (WIPP) and the Folding Conformal High Lift Propeller (HLP) project, for isolated and installed cases under various conditions. Additionally, validation for rotor-rotor interactions was also conducted using the GARTEUR Action Group 26 measurements. The second part of the paper examines installed propeller configurations to identify performance differences based on their position relative to a lifting wing. The results indicate that distributed propellers with small radii interfere more with the wing, than tip-mounted, large propellers. Additionally, propeller and wing performance vary with respect to the propeller installation location. The propeller in tractor configuration showed higher efficiency than the over-the-wing (OTW) configuration by about 7%. However, results from this work showed a 2% improvement in the propeller efficiency when the OTW configuration had a pylon installed. This study also found that optimising the propeller from a tractor to OTW configuration, significantly improved the wing performance. At take-off and landing, the Lift-to-Drag (L/D) ratio of the OTW configuration almost quadrupled, and the overall propulsive efficiency increased by about 5%. The simulations showed that the OTW configuration with different numbers of propellers, outperformed the tractor configurations with the same number of propellers. Furthermore, up to 26% improvement in lift and overall propulsive efficiency was found by introducing the DP system in the OTW configuration. [ABSTRACT FROM AUTHOR]

In this paper, the design problem of Gain‐Scheduled Output‐Feedback (GSOF) controllers using inexact scheduling parameters for morphing aircraft during the wing transition process is addressed. Both the stability of the closed‐loop system and the L2 gain performance can be guaranteed under the controller based on measured (not actual) scheduling parameters. Firstly, the linear parameter‐varying (LPV) model of morphing aircraft is established by Jacobian linearization and the additive uncertainty is introduced into the scheduling parameters. By employing non‐linear transformations, the problem is formulated as the solution to a set of parameter‐dependent linear matrix inequalities (LMI) with a single‐line search parameter. Finally, the robustness of the flight control system to the wing transition process is verified under the condition of both the uncertainty of aerodynamic parameters and of scheduling parameters. [ABSTRACT FROM AUTHOR]

Due to the efficient and flexible flight ability of bats, bat-like robots have become the focus of research in the field of bionic robots. Aerodynamic calculation is an important part of the research field of bat-like robot, which is the basis of the structure design and flight controller design of bat-like robot. However, due to the complex flight mechanism of bats, there is no mature theoretical method to calculate the flight aerodynamic force of bat-like robots. To solve this problem, this paper takes the membrane of a bat-like robot as the research object and analyzes in detail the effects of wing folding and unfolding and flexible deformation of the membrane on the chord length, passive torsion angle and relative velocity. Based on quasi-steady state model and blade element method, a set of aerodynamic calculation method for flexible deformed wing is established. In order to verify the effectiveness of the proposed method, the theoretical calculation results and the results of the fluid-structure interaction simulation are compared and analyzed under various working conditions. The two results are in good agreement under each working condition, and the errors are all within reasonable range, which proves the effectiveness of the method. This study can provide a theoretical basis for rational structure design and precise flight control of bat-like robot. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the possibility of lowering the time taken during the aircraft design for unmanned aerial vehicles by using machine learning (ML) for the configuration selection phase. In this work, a database of unmanned aircraft is compiled and is proposed that decision tree classifiers (DTC) can understand the relations between mission and operational requirements and the resulting aircraft configuration. Design/methodology/approach: This paper presents a ML-based approach to configuration selection of unmanned aircraft. Multiple DTC are built to predict the overall configuration. The classifiers are trained with a database of 118 unmanned aircraft with 57 characteristics, 47 of which are inputs for the classification problem, and 10 are the desired outputs, such as wing configuration or engine type. Findings: This paper shows that DTC can be used for the configuration selection of unmanned aircraft with reasonable accuracy, understanding the connections between the different mission requirements and the culminating configuration. The framework is also capable of dealing with incomplete databases, maximizing the available knowledge. Originality/value: This paper increases the computational usage for the aircraft design while retaining requirements' traceability and increasing decision awareness. [ABSTRACT FROM AUTHOR]

The aerodynamic characteristics of turboprop aircraft are greatly affected by the running propellers. In this paper, propeller slipstream effects on the static lateral-directional stability characteristics of a typical twin-engine turboprop aircraft with clockwise rotating propellers were investigated through unsteady computational fluid dynamics (CFD) simulations and wind tunnel experiments. The propeller slipstream led to a significant decrease in the lateral static stability contribution of the wing-body-nacelle (WBN), and the most affected wing sections were located near the left boundary of the port propeller slipstream region. Moreover, the influence of the propeller slipstream on the lateral static stability contribution of the vertical tail plane (VTP) significantly altered the rolling moment curve slope of the entire airframe. Due to the effects of the propeller slipstream on the local dynamic pressure and therefore the effectiveness of the VTP, the aircraft showed significantly different directional static stability behaviors between the positive and negative sideslip conditions. Furthermore, it was found that the configurations with clockwise rotating propellers readily experience dramatic losses in directional static stability at large negative sideslip angles. [ABSTRACT FROM AUTHOR]

The performance parameters of automobiles are mainly determined by aerodynamic characteristics such as lift and drag. To maximize vehicle performance, besides optimizing the vehicle itself, various aerodynamic devices can be used. To determine the efficiency of these devices, it is important to study how they affect the vehicle's aerodynamic characteristics. This paper analyzes the effect of a rear wing on the aerodynamic characteristics of a fastback type vehicle using computational fluid dynamics (CFD). The DrivAer model is used to simulate the vehicle and an S1223 high-lift airfoil is selected as the rear wing. Several CFD cases are considered, in which the rear wing is positioned at different angles of attack and heights and the effects of these parameters on the lift and drag coefficients are studied. The results for low vehicle velocity show that CD and CL are increased by 14 and decreased by 72 counts, respectively. For higher vehicle velocity, CD variation shows not much difference, however, CL variation shows further decrease of 35 counts. Furthermore, the effect of these parameters on the flow characteristics is analyzed, enabling guidelines for the design of efficient rear wings for fastback type vehicles to be suggested. [ABSTRACT FROM AUTHOR]

Wind tunnel test is an important means to obtain aerodynamic loads. However, due to the limited space location and experimental cost, it is usually difficult to arrange enough pressure taps on the complex model surface to obtain complete surface pressure distribution information. Hence, the accuracy of the lift and the pitching moment calculated by the direct integration may fail to meet expectations. This paper presents a sparse fusion method to reconstruct the complete surface pressure distribution based on the limited wind tunnel test data. By integrating the reconstruction resulting surface data over a complete aerodynamic surface, the corresponding aerodynamic coefficients are obtained and are in good agreement with the experimental results. The accuracy of the proposed method is verified by two-dimensional airfoil flow and three-dimensional steady ONER-M6 wing flow examples. The reconstruction results can accurately match the experimental results. The developed reconstruction method largely solves the problem of fine reconstruction of distributed load under the condition of limited space and sparse observation. [ABSTRACT FROM AUTHOR]

The multi-objective reliability-based design optimization (MORBDO) of an aircraft structure employing a non-probabilistic model, at present, still has a high level of analysis complexity while solving the possibility safety index (PSI) as they are a triple-loop nested problem. Many techniques have been proposed to expedite the process of solving their inner loop with a single objective function; however, research on applying multi-objective optimization to complete this task is required. This research paper aims to reduce the solution complexity in the MORBDO of an aircraft wing structure, which is a symmetrical part of the aircraft structure. The present framework is comprised of a two-step technique that begins with the multi-objective optimization (MODO) of the wing structure, followed by its reliability analysis. A non-probabilistic model is adopted for uncertainty consideration, contrary to frequently used probabilistic models. The reliability design problem has aircraft wing mass, flutter speed, and the possibility safety index as objective functions. According to the results, the proposed MORBDO technique is highly effective in reducing the complexity of aircraft wing structural design and can generate more conservative and feasible design solutions with various PSI values. Such a design can be achieved within a single run, which has not been done in previous studies. The results show that the highest reliability aircraft wing structure mass is 104.8504 kg at a flutter speed of 584.5670 m/s. Additionally, the developed framework explicitly states the relationship between MODO and MORBDO. [ABSTRACT FROM AUTHOR]

• Chaotic snap-through phenomena are studies for bistable cantilever shell. • Transverse foundation excitation subjects to fixed end of bistable cantilever shell. • Analytical results of frequency-amplitude and force-amplitude responses are obtained. • Chaotic, quasi-periodic and snap-through vibrations are presented for bistable shell.5. Vibration experiment is carried out to investigate dynamic snap-though behaviors. The realization of the dynamic snap-through behaviors provides the new design ideas in the fields of the morphing aircraft and piezoelectric energy harvesting. This paper studies 1:2 internal resonance, nonlinear vibrations and chaotic snap-through phenomena of the bistable asymmetric composite laminated (BSCL) cantilever shell with the lower-frequency and higher-frequency primary resonances for the first time. The transverse foundation excitation subjects to the fixed end of the bistable cantilever shell. The perturbation analysis of two-degrees-of-freedom nonlinear ordinary differential equations is carried out by using the first-order approximate multiple scale method. The analytical results of the frequency-amplitude and force-amplitude response curves are obtained under the small foundation excitation. The obtained results reveal that the BSCL cantilever shell exhibits the double-jumping characteristics when 1:2 internal and primary resonances occur. There is a continuous energy exchange back and forth between two modes of the bistable laminated cantilever shell. As the foundation excitation increases, the BSCL cantilever shell exhibits saturation phenomenon. Numerical simulations are finished to further investigate the effects of the large excitation on the chaotic, quasi-periodic and snap-through vibrations for the BSCL cantilever shell. The vibration experiment is carried out to investigate the internal resonance and dynamic snap-though motions of the BSCL cantilever shell. Using the snap-though behaviors of the BSCL cantilever shell, we obtain the morphing structure of the aircraft wing. [ABSTRACT FROM AUTHOR]

This paper considers a wing system under unknown output disturbances, references, distributed disturbances and boundary disturbances. These signals have unknown frequencies, amplitudes and phases, and are then supposed to be from an exosystem with an unknown matrix. In this sense, we firstly find the wing system merely under the references and output disturbances, for which the PDE observer can be easily designed based on the measurable outputs. Then, an adaptive observer is designed for a detectable exosystem so that the references have known coefficients and approximately known states. Adaptive observer based controls are then proposed for the closed-loop system so that the convergence of tracking error and the boundedness of the states are guaranteed. Two simulation examples are compared to show the robustness of the designed controls. [ABSTRACT FROM AUTHOR]

In response to escalating environmental concerns and stringent economic constraints, there is an urgent need to develop aircraft technologies and configurations that substantially enhance efficiency. A prominent trend in aircraft design aimed at minimizing lift-induced drag, improving fuel efficiency, and mitigating emissions is the adoption of increased wing Aspect Ratio (AR). This paper examines the evolution and current advancements in High Aspect Ratio Wing (HARW) and Ultra-High Aspect Ratio Wing (UHARW) configurations for next-generation transport aircraft. Beginning with a historical overview of wing AR in transport, the paper examines the progress in designing both conventional and novel HARW/UHARW configurations. It reviews a range of promising concepts, such as strut-braced wing, truss-braced wing, twin-fuselage, and folding wingtips, for their potential in HARW applications. The paper emphasizes tailored conceptual design methods and tools specifically developed for HARW/UHARW configurations. It provides an in-depth analysis of preliminary design approaches for HARW aircraft, systematically covering aspects including aerodynamic, aeroelastic, aerostructural, and experimental designs. Key insights from leading-edge research are distilled, highlighting the significant advancements and pinpointing the current challenges in the field. The comprehensive review underscores the critical role of HARW/UHARW in enhancing aircraft performance, particularly in fuel efficiency and environmental impact, setting the stage for future transformative developments in aircraft efficiency. [ABSTRACT FROM AUTHOR]

In preparation for the battlefields of the future, using unmanned aerial vehicles (UAV) loaded with multisensors to track dynamic targets has become the research focus in recent years. According to the air combat tracking scenarios and traditional multisensor weighted fusion algorithms, this paper contains designs of a new data fusion method using a global Kalman filter and LSTM prediction measurement variance, which uses an adaptive truncation mechanism to determine the optimal weights. The method considers the temporal correlation of the measured data and introduces a detection mechanism for maneuvering of targets. Numerical simulation results show the accuracy of the algorithm can be improved about 66% by training 871 flight data. Based on a mature refitted civil wing UAV platform, the field experiments verified the data fusion method for tracking dynamic target is effective, stable, and has generalization ability. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to use numerical methods early in the airframe design process and access the structural performance of wing leading edge devices made of different materials and design details, under bird strike events. Design/methodology/approach: Explicit finite element analysis was used to numerically model bird strike events. Findings: Structural performance charts related to materials and general design details were drawn to explore the design space dictated by the current applicable airworthiness requirements. Practical implications: This paper makes use of the current capability in the numerical tools available for structural simulations and exposes the existing limitations in the terms of material modelling, material properties and fracture simulation using continuum damage mechanics. Such results will always be in the need of fine-tuning with experimental testing, yet the tools can shed some light very early in the design process in a relative inexpensive manner, especially for design details down selection like materials to use, structural thicknesses and even design arrangements. Originality/value: Bird strike simulations have been successfully used on aircraft design, mainly at the manufactured articles design validation, testing and certification. This paper presents a hypothetical early design case study of leading edge devices for appropriate material and skin thickness down selection. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to design a biomimetic surface structure for use in a glass transport device to enhance the suspension lift of a glass transport unit. Design/methodology/approach: This paper presents a surface structure of a suspended glass transport device based on the principle of bionics. First, a mapping model is constructed based on the wing structure. Second, the optimal structural parameters are given according to genetic algorithm optimization. Finally, the experimental comparison of the test bench verified the feasibility of the theory. Findings: Through experimental comparison, the biomimetic suspension glass transport device saves 20% of air pressure compared with the ordinary suspended glass transport device, which verifies the effectiveness of the theoretical method. Originality/value: This paper proposes a suspended glass transport device based on the principle of bionics, which saves the air pressure required for work. It is expected to be used in suspension glass transport devices. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2019-0389/ [ABSTRACT FROM AUTHOR]

The present paper concerns the introduction of a mixed analytical-numerical method for the estimation of the maximum lift coefficient of box-wing aircraft in unflapped configuration. The analytical aspect is related to the adaptation of the method included in the United States Air Force (USAF) Stability and Control Data Compendium (DATCOM) by means of an approach built on the characteristics of the optimal lift distribution of the box-wing and implemented through simplifying assumptions. Since the formulation depends on parameters of the considered aircraft, numerical simulations are performed through a vortex-lattice method to complete the input data set. The method is first presented and then validated for the case of the 2-seater amphibious PrandtlPlane (PrP) and is then applied to two test cases: a 300 passenger midrange PrandtlPlane and a regional hybrid-electric PrandtlPlane. Results are presented and discussed, and the links between the proposed method and relevant parameters of the box-wing design, such as taper ratios and wing loading repartition among the two wings is analyzed. [ABSTRACT FROM AUTHOR]

• New conceptions of balance are introduced based on real backgrounds. • Balance differences of any two groups are considered for the first time. • The forced-down units are considered as warm-standby units for the first time. • New models for balanced systems with multiple functional sectors are built. • Two case studies are presented to validate the applicability of the new models. In this paper, new concepts of balanced systems are proposed based on real engineering problems. The system under study consists of l groups and each group has n functional sectors. The conception of balance difference is proposed for the first time. It is assumed that unbalanced systems are rebalanced by either forcing down some working units into standby or resuming some standby units into operation. In addition, a case that the forced-down units are subject to failure during standby is studied in this paper. Based on different balanced cases and system failure criteria, two reliability models for balanced systems are developed. The proposed systems have widespread applications in aerospace and military industries, such as wing systems of airplane and unmanned aerial vehicles with balanced engine systems. Markov process imbedding method is used to analyze the number of working units in each sector for each model. Finite Markov chain imbedding approach and universal generating function technique are used to obtain the system reliability for different models. Several case studies are finally presented to demonstrate the new models. [ABSTRACT FROM AUTHOR]

This paper presents beam modeling techniques for maximizing mechanical sensitivity of a butterfly resonator for gyroscopic applications. We investigate the geometric aspects of synchronizing beam that connects the wings of a butterfly resonator. Our results show that geometric variation in the synchronizing beam can have a large effect on the frequency split and sensitivity of the device. The model simulation shows a sensitivity of 10 - 12 (m / ∘ / s) for a frequency split of 10 Hz resulting from the optimized synchronized beam. Out of plane actuation was developed to drive and sense the resonators displacement. Fabricated butterfly resonators were tested, and the experimental results show a frequency split of 305 Hz and 400 Hz while the model illustrated a split of 195 Hz and 330 Hz respectively. The design and analysis presented in this paper can further aid the development of MEMS butterfly resonators for inertial sensing applications. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper presents the effects of actively morphing root chord and taper on the energy of the flight control system (i.e. FCS). Design/methodology/approach: Via regarding previously mentioned purposes, sophisticated and realistic helicopter models are benefitted to examine the energy of the FCS. Findings: Helicopters having actively morphing blade root chord length and blade taper consume less control energy than the ones having one of or any of passively morphing blade root chord length and blade taper. Practical implications: Actively morphing blade root chord length and blade taper can be used for cheaper helicopter operations. Originality/value: The main originality of this paper is applying active morphing strategy on helicopter blade root chord and blade taper. In this paper, it is also found that using active morphing strategy on helicopter blade root chord and blade taper reasons less energy consumption than using either passively morphing blade root chord length plus blade taper or not any. This causes also less fuel consumption and green environment. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is finding the optimal geometric parameters and developing of a method for optimizing a light unmanned aerial vehicle (UAV) wing, maximizing, at the same time, its endurance with the assumed parameters of aircraft mission. Design/methodology/approach: The research is based on the experience gained by the author's contribution to the project of building medium-altitude, long-endurance class, light UAV called "Samonit". The author was responsible for the structure design, wind tunnel tests and flight tests of the "Samonit" aircraft. Based on the experience, the author was able to develop an optimization process considering various disciplines involved in the whole aircraft design topics such as aerodynamics, flight mechanics, structural stiffness and weight, aircraft stability and maneuverability. The presented methodology has a multidisciplinary nature, as in the process of optimization both aerodynamic aspects and the influence of wing geometric parameters on the wing structure and weight and the aircraft payload were taken into account. The optimal wing configuration was obtained using the genetic algorithms. Findings: As a result, a set of wing geometrical parameters has been obtained that allowed for achieving twice as long endurance as compared with the initial one. Practical implications: Using the methodology presented in the paper, an aircraft designer can easily find the optimum wing configuration of a designed aircraft, satisfying the mission requirements in a best way. Originality/value: An original procedure has been developed, based on the actual design, wind tunnel tests and numerical calculations of "Samonit" aircraft, enabling the determination of optimum wing configuration for a small unmanned aircraft. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to investigate the possibility of manufacturing fused deposition modelling (FDM) 3D printed structures such as wings or fuselages for small remote control (RC) air craft and mini unmaned aerial vehicles (UAVs). Design/methodology/approach: Material tests, design assumptions and calculations were verified by designing and manufacturing a small radio-controlled motor-glider using as many printed parts as possible and performing test flights. Findings: It is possible to create an aircraft with good flight characteristics using FDM 3D printed parts. Current level of technology allows for reasonably fast manufacturing of 3D printed aircraft with good reliability and high success ratio of prints; however, only some of the materials are suitable for printing thin wall structures such as wings. Practical implications: The paper proves that apart from currently popular small RC aircraft structural materials such as composites, wood and foam, there is also printed plastic. Moreover, 3D printing is highly competitive in some aspects such as first unit production time or production cost. Originality/value: The presented manufacturing technique can be useful for quick and cost-effective creating scale prototypes of the aircraft for performing test flights. [ABSTRACT FROM AUTHOR]

The wing-diesel hybrid ship, utilizes a wind propulsion system, which is significantly influenced by weather conditions. Therefore, a cooperative optimization method for course and speed is proposed based on an improved A* algorithm, considering weather changes and the ship characteristics, to achieve further improvement in the ship operational energy efficiency. Firstly, a meteorological and hydrological dataset is utilized to establish a dynamic maritime area model with complex weather conditions. Based on this model, the paper considers the actual navigation circumstances to define prohibited and navigable areas. Secondly, the improved A* algorithm incorporates the impact of weather on wing-sails. The improved A* algorithm considers the ship operating position and enhances the evaluation function by variables normalization of fuel consumption and voyage time. This cooperative optimization ensures the maximization of wind energy utilization, thereby achieving the goal of reducing fuel consumption while meeting the overall voyage time requirement. Experimental validation is conducted with the ship "New Aden" in the Indian Ocean region, and the results show that, compared to the original route, the optimized route reduces total fuel consumption by 5.48%, increases the navigation distance by up to 2.18% and increases the navigation time by 5.74%. • A cooperative optimization method of wing-diesel hybrid ship is proposed. • Improved A* algorithm is designed considering wing-sail and meteorological data. • Interpolation method is adopted to align meteorological data with ship data. • The algorithm evaluation function is calculated by variables normalization. • Optimized route reduces total fuel consumption by 5.48%. [ABSTRACT FROM AUTHOR]