Variable Sweep Wing Research Articles

An unsteady aerodynamic force calculation method for shear variable-sweep wing considering sweep angle and airfoil changes

The backward shift of the aerodynamic center and insufficient morphing capability are critical design bottlenecks of traditional rotary variable-sweep wings. This paper presents a new shear variable-sweep morphing form that reduces the backward shift of the aerodynamic center by allowing the leading edge of the wing to slide forward. The shear variable-sweep wing (SVSW) with this morphing form enables coordinated changes in both planform and airfoil shape, achieving greater aerodynamic benefits. However, during the shear morphing process, the wing experiences unsteady aerodynamic phenomena, and this multi-dimensional morphing form further complicates the calculation of unsteady aerodynamic forces. To address this challenge, this paper investigates the three-dimensional changes of the SVSW surface during the shear morphing process and proposes an unsteady aerodynamic force calculation method, which considers variations in sweep angle and airfoil. The results showed that as the sweep angle increases, both the lift and drag coefficients decrease, and the unsteady aerodynamic characteristics exhibit significant flow hysteresis, with the unsteady lift and drag coefficients deviating from the steady-state results and forming a clockwise dynamic hysteresis loop. Finally, the study analyzed the effects of shear morphing rates and flow conditions on the wing's unsteady aerodynamic characteristics and validated the feasibility and effectiveness of the proposed method through continuous morphing wind tunnel tests. The proposed method also fully considers the effects of shear motion, curved aerodynamic configurations, and unsteady vortices on aerodynamic characteristics, offering a low-cost and effective solution for the optimization design and aeroelastic analysis of the SVSW.

Experimental Structural Design of a Novel Variable-Sweep Wing Based on a Four-Bar Planar Linkage

Experimental Structural Design of a Novel Variable-Sweep Wing Based on a Four-Bar Planar Linkage

Prediction of pressure distribution and aerodynamic coefficients for a variable-sweep wing

To satisfy the performance requirements across multiple speed ranges, a variable-sweep wing (sweep angle range from 25° to 40°) is derived from the BQM-34 “Firebee” drone model. However, predicting aerodynamic characteristics across various flight conditions and sweep angles is a challenging task. Traditional methods like CFD and wind tunnel testing are both time consuming and expensive. In order to efficiently predict the pressure distributions and aerodynamic coefficients, a novel network that combines a Radial Basis Function Network (RBFN) and a Convolutional Auto-Encoder (CAE) is proposed. Two distinct loss function methods, the standard Pressure-Targeted Method (PTM) and the newly developed Comprehensive Evaluation Method (CEM), are employed to optimize the network's predictive performance. These methods are evaluated on datasets with both trained and untrained sweep angles. The results show that while both PTM and CEM accurately predict pressure distributions, the enhanced CEM provides more uniform and reliable predictions. Moreover, the CEM method significantly outperforms PTM in predicting aerodynamic coefficients, reducing errors by over 50%. The proposed RBFN-CAE network with the CEM loss function offers an effective way to predict the aerodynamic characteristics of a variable-sweep wing, improving predictive models in aerodynamic applications.

Advanced Cooperative Formation Control in Variable-Sweep Wing UAVs via the MADDPG–VSC Algorithm

UAV technology is advancing rapidly, and variable-sweep wing UAVs are increasingly valuable because they can adapt to different flight conditions. However, conventional control methods often struggle with managing continuous action spaces and responding to dynamic environments, making them inadequate for complex multi-UAV cooperative formation control tasks. To address these challenges, this study presents an innovative framework that integrates dynamic modeling with morphing control, optimized by the multi-agent deep deterministic policy gradient for two-sweep control (MADDPG–VSC) algorithm. This approach enables real-time sweep angle adjustments based on current flight states, significantly enhancing aerodynamic efficiency and overall UAV performance. The precise motion state model for wing morphing developed in this study underpins the MADDPG–VSC algorithm’s implementation. The algorithm not only optimizes multi-UAV formation control efficiency but also improves obstacle avoidance, attitude stability, and decision-making speed. Extensive simulations and real-world experiments consistently demonstrate that the proposed algorithm outperforms contemporary methods in multiple aspects, underscoring its practical applicability in complex aerial systems. This study advances control technologies for morphing-wing UAV formation and offers new insights into multi-agent cooperative control, with substantial potential for real-world applications.

Investigation of a Tube-Launched Unmanned Aerial Vehicle with a Variable-Sweep Wing

Foldable wings are designed for tube-launched unmanned aerial vehicles (UAVs), aiming to improve portability and meet launch platform requirements. However, conventional tube-launched UAVs cannot operate across the wide speed ranges required for the performance of multiple missions, due to the fixed configuration of their wings after launch. This study therefore proposes a tube-launched UAV which can change wing-sweep angle to expand the flight speed range and enhance the UAV’s agility. A computational aerodynamics method is employed to assess the transient aerodynamic performance of the UAV during the sweep morphing process. The simulation results indicate that the transient aerodynamic forces generate a dynamic hysteresis loop around the quasi-steady data. The lift and drag coefficients exhibit maximum relative deviations of 18.5% and 12.7% from the quasi-steady data for the sweep morphing period of 0.5 s. The hysteresis effect of the flow structure, rather than the additional velocity resulting from wing-sweep morphing, is the major contributor to the aerodynamic hysteresis loop. Compared to the conventional tube-launched UAVs, the proposed tube-launched UAV with a variable-sweep wing shows a wider flight speed range, from 22.59 to 90.12 m/s, and achieves an 82.84% increase in loitering speed. To verify the effectiveness of the wing-sweeping concept, a prototype was developed, and a flight test was carried out. The test data obtained from flight control system agree well with the simulation data, which demonstrates the feasibility and effectiveness of the variable-sweep wing in widening the speed range for tube-launched UAVs. This work can provide a reference for the design of tube-launched UAVs for wide speed range flight.

A novel videogrammetry-based full-field dynamic deformation monitoring method for variable-sweep wings

A novel videogrammetry-based full-field dynamic deformation monitoring method for variable-sweep wings

Design and thermal protection performance analysis of insulated wing storage box for hypersonic variable-sweep aircraft

Utilizing variable-sweep wing technology can further enhance the flight performance of hypersonic aircraft in a wide range of high-altitude, high-speed environments. Existing research on hypersonic variable-sweep flying wings has mainly focused on aerodynamic shape design, with limited research on the internal thermal protection of the aircraft. This study firstly investigates the performance improvement of a hypersonic flying wing using variable-sweep technology through CFD simulations. Secondly, to address the high-temperature issues induced by variable-sweep wings, an insulated wing storage box with a corrugated structure is designed, incorporating a thermal insulation layer made of corrugated webs and insulating materials. Heat transfer simulations are conducted by applying thermal loads to the wing storage box to study the temperature distribution during the variable-sweep process. Finally, a comparison between the corrugated structure design and the non-corrugated structure design of the wing storage box is performed to analyze the thermal insulation performance of the insulation layer. The results show that the heated area of the wing storage box is primarily influenced by the wing’s sweep angle, and the corrugated thermal insulation layer can effectively reduce heat transfer efficiency, resulting in a 30% reduction in the external temperature of the wing storage box.

A Shear-Sliding Rigid-Flexible Coupled Skin Variable-Sweep Wing Design and Heat-Fluid-Structure Multifield Coupling Analysis

The variable-sweep wing is very attractive for cross-speed domain aircraft. The shear-sliding rigid-flexible coupled skin variable-sweep wing and its associated mechanism are designed and optimized. The variable-sweep wing has smooth continuous deformation and rigid-flexible coupling features. The calculation model of the sliding skin patch segmentation strategy is established, and the aerodynamic characteristics of the two-dimensional airfoil before and after the deformation of the wing skin are analyzed. According to the deformation characteristics of sliding skin, the configuration of the associated mechanism is determined, and the kinematic characteristics of the reference points of each skin are calculated. The kinematic simulation verifies the force of the mechanism model at the joint of skin surfaces during the deformation process. Considering the aerodynamic heat at supersonic speed, the heat transfer, heat distribution, and structural thermal modes between the flow field and the skin are calculated based on the finite element method. The dynamic characteristics of the swept wing with different flight speeds and different morphologies are analyzed. The natural frequencies are found to be reduced by about 30% to 50% compared to cold models at supersonic speeds. Based on the results of the thermal fluid-solid coupling calculation, the skeleton structure of the swept wing is optimized, and the skeleton structure with 25% mass reduction and better performance is obtained.

Dynamic Analysis and Experiment of Multiple Variable Sweep Wings on a Tandem-Wing MAV

The current morphing technologies are mostly regarded as auxiliary tools, providing additional control torques to enhance the flight maneuverability of unmanned aerial vehicles (UAVs), and they cannot exist independently of the traditional control surfaces. In this paper, we propose a tandem-wing micro aerial vehicle (MAV) with multiple variable-sweep wings, which can reduce the additional inertia forces and moments and weaken the dynamic coupling between longitudinal and lateral motion while the MAV morphs symmetrically for pitch control or asymmetrically for roll control, thereby flying without the traditional aileron and elevator. First, load experiments were conducted on the MAV to verify the structural strength of the multiple variable sweep wings, and the control moments caused by the morphing of the MAV were presented through numerical simulations. Then, the effects caused by symmetric and asymmetric morphing were investigated via dynamic response simulations based on the Kane dynamic model of the MAV, and the generated additional inertia forces and moments were also analyzed during morphing. Finally, dynamic response experiments and open-loop flight experiments were conducted. The experimental results demonstrated that the morphing mode in this study could weaken the coupling between the longitudinal and lateral dynamics and that it was feasible for attitude control without the traditional aileron and elevator while flying.

Data-Driven Based Model-Free Adaptive Optimal Control Method for Hypersonic Morphing Vehicle

Aiming at the attitude control of a class of hypersonic morphing vehicles (HMVs) with variable sweep wings, a model-free adaptive dynamic planning (MFADP) optimal control method based on data-driven and finite-time fuzzy disturbance observer is proposed in this paper. An integrated oriented-control attitude-morphing model is established, and morphing is considered as the state to carry out the integrated coupling attitude control. The control scheme is organized by a steady-feedback-compensation framework. To overcome the dependence on the unknown dynamic knowledge of HMVs, the dynamic model is reconstructed using neural networks for steady-state control. Subsequently, based on the MFADP algorithm, an Off-On serial policy learning strategy is designed for the error model to obtain a real-time approximate optimal feedback control. Additionally, a fuzzy disturbance observer with finite-time convergence ability is proposed to estimate and compensate the multiple uncertainties. Finally, the stability of the closed-loop system is proved theoretically and the simulation results demonstrate the improved performance of the proposed method.

Surrogate-based aerodynamic shape optimization of a sliding shear variable sweep wing over a wide Mach-number range with plasma constraint relaxation

Surrogate-based aerodynamic shape optimization of a sliding shear variable sweep wing over a wide Mach-number range with plasma constraint relaxation

Mechanism analysis of hysteretic aerodynamic characteristics on variable-sweep wings

Variable-sweep wings have large shape-changing capabilities and wide flight envelops, which are considered as one of the most promising directions for intelligent morphing UAVs. Aerodynamic investigations always focus on several static states in the varying sweep process, which ignore the unsteady aerodynamic characteristics. However, deviations to static aerodynamic forces are inevitably caused by dynamic sweep motion. In this work, first, unsteady aerodynamic characteristics on a typical variable-sweep UAV with large aspect ratio were analyzed. Then, deep mechanism of unsteady aerodynamic characteristics in the varying sweep process was studied. Finally, numerical simulation method integrated with structured moving overset grids was applied to solve the unsteady fluid of varying sweep process. The simulation results of a sweep forward-backward circle show a distinct dynamic hysteresis loop surrounding the static data for the aerodynamic forces. Compared with the static lift coefficients , at the same sweep angles, dynamic lift coefficient in sweep forward process are all smaller, while dynamic sweep backward lift coefficient are all larger. In addition, dynamic deviations to static lift coefficient are positively related with the varying sweep speeds. Mechanism study on the unsteady aerodynamic characteristics indicates that three key factors lead to the dynamic hysteresis loop in varying sweep process. They are the effects of additional velocity caused by varying sweep motion, the effects of flow hysteresis and viscosity. The additional velocity induced by sweep motion affects the transversal flow direction along the wing and the effective angle of attack at the airfoil profile. The physical properties of flow, the hysteresis and viscosity affect the unsteady aerodynamic characteristics by flow separation and induced vortexes.

Actuation performance of machined helical springs from NiTi shape memory alloy

Machined helical springs were designed and fabricated from NiTi shape memory alloy tube stock by cutting helical slots to make the coils, which provided them with high design flexibility and actuation potential. The springs were then subjected to isothermal tensile testing at temperatures of 20°C and 80°C, the experimental data showed that they could generate more than 50% actuation stroke at the applied force of 300 N. A material model was introduced to describe the thermally-induced actuation behavior of the machined NiTi spring. Finite element simulation of the springs was carried out to investigate the effects of geometries and applied loads on the actuation performance. With increasing applied load, the actuation stroke and transformation temperature increased as well, indicating more actuation potential at high loads. The actuation stroke was positively correlated to the outer diameter and the cross-sectional aspect ratio, negatively correlated to the cross-sectional area, and independent of the coil pitch. A variable-sweep wing actuated by two antagonistic machined springs was designed and numerically analyzed, the actuator could generate a steady cyclic motion up to 40 mm and allowed the swept-back angle of the wings to be continuously varied from zero to 90 degrees.

Integrated Aerodynamic and Trajectory Studies of a Long-Range Morphing Missile

A morphing missile aims to get optimal flight performances at different flight conditions by a variable aerodynamic shape according to the requirements of multiple missions. For a long-range missile with morphing wings, an integrated method with a morphing geometry, an aerodynamic analysis, and a trajectory simulation program was studied for a wider range. The morphing configuration was designed to improve aerodynamic properties by variable-sweep wings. Those aerodynamic features were then divided into three parts, including both flight Mach numbers and lift-to-drag ratios through detailed aerodynamic analyses. Based on such classifications, we first proposed the combination rules to morph by combining the maximal lift-to-drag ratio with the minimal drag or the maximum pitching moment gradient coefficient. The trajectory simulation program used within the gliding and morphing strategies was then launched. Our results demonstrated both strategies were beneficial for extending the attack ranges of long-range missiles subject to the constraints of stabilities and variable flight conditions. The gliding strategy provided 119.5–45.6% increases in range over the baseline geometry; the morphing scheme also succeeded in increasing the range over the deployment of the gliding strategy by an additional 20.7–46.8%.

Shear-driving Force and Critical Shear Angle Analysis of Kevlar/Carbon Fiber Hybrid Composite Skins for a Shear Variable-sweep Wing Based on the Classical Plate Theory

Shear-driving Force and Critical Shear Angle Analysis of Kevlar/Carbon Fiber Hybrid Composite Skins for a Shear Variable-sweep Wing Based on the Classical Plate Theory

A Micro Aircraft With Passive Variable-Sweep Wings

Traditional fixed-wing vehicles are equipped with multiple active aerodynamic surfaces for flight control. This inevitably necessitates several actuators, complicates the mechanical structure, and adversely impacts the flight efficiency, particularly for small aerial vehicles. As a lightweight and efficient solution, this work proposes to employ passive variable-sweep wings on a micro airplane to eliminate the need for active control surfaces while retaining effective pitch maneuverability. Depending on the thrust produced by the propellers, the wings passively sweep back and forth, relocating the center of pressure and affecting the pitch moment. The thrust-induced deformation substitutes the elevators for pitch control. Through aerodynamic modeling, the flight dynamics of the proposed vehicle is analyzed. The results show that the proposed design brings about amplified and accelerated pitch response. Lastly, a prototype was constructed to demonstrate and verify the enhanced aircraft’s pitch control ability.

Design of a variable-sweep wing structure with flexible shear skin

Design of a variable-sweep wing structure with flexible shear skin

Stability Analysis and Augmentation Design of a Bionic Multi-Section Variable-Sweep-Wing UAV Based on the Centroid Self-Trim Compensation Morphing

In this study, a design scheme for a high-aspect-ratio bionic multi-section variable-sweep wing unmanned aerial vehicle (UAV) that utilizes the reverse coordinated change in the sweep angle of the inner and outer wing sections is proposed, which improves the aerodynamic performance and realizes the self-trim compensation of the wing’s centroid. According to the layout characteristics of this type of UAV, a reasonable distribution design of the wingspan ratio of the inner and outer sections is explored, to reduce the impact of aerodynamic center movement and moment of inertia change. The calculation and analysis results show that the coordinated variable-sweep scheme can significantly improve the influence of sweep angle change on the longitudinal static stability margin of UAVs with a high aspect ratio. The coordinated sweep angle change in the inner and outer wing sections can not only reduce the drag during high-speed flight, but also play a significant role in improving the performance of the aircraft at different stages in the mission profile. Appropriately increasing the wingspan proportion of the inner section can reduce the trim resistance of the V-tail, reduce the thrust of the engine, and increase the range and duration of the UAV. From the perspective of stability change, the multi-section variable-sweep wing UAV with a wingspan ratio of the inner and outer sections that is between 1.41 and 1.78 has better dynamic stability performance. Among them, the UAV with a wingspan ratio of the inner and outer sections that is equal to 1.41 has better longitudinal stability performance, while the UAV with a wingspan ratio of the inner and outer sections that is equal to 1.78 has better lateral/directional stability performance.

Out-of-Plane Stiffness Analysis of Kevlar/Carbon Fiber Hybrid Composite Skins for a Shear Variable-Sweep Wing

Out-of-Plane Stiffness Analysis of Kevlar/Carbon Fiber Hybrid Composite Skins for a Shear Variable-Sweep Wing

Theoretical model proposal on direct calculation of wetted area and maximum lift-to-drag ratio

PurposeAs measuring flight performance by experimental methods requires a lot of effort and cost, theoretical models can bring new perspectives to aircraft design. This paper aims to propose a model on the direct calculation of wetted area and L/Dmax.Design/methodology/approachModel is based on idea that the wetted area is proportional to aircraft gross weight to the power of 2/3 (Wg2/3). Aerodynamic underpinning of this method is based on the square–cube law and the claim that parasitic drag is related to the Swet/Swing. The equation proposed by Raymer was used to find the L/Dmax estimate based on the calculated wetted area. The accuracy of the theoretical approach was measured by comparing the L/Dmax values found in the reference literature and the L/Dmax values predicted by the theoretical approach.FindingsProposed theoretical L/Dmax estimate matches with the actual L/Dmax data in different types of aircraft. Among the conventional tube-wing design, only the sailplanes have a very low Swet/Swing. The Swet/Swing of flying wings, blended wing bodies (BWBs) and large delta wings are lower than conventional tube-wing design. Lower relative wetted area (Swet/Swing) is the key design criterion in high L/Dmax targeted designs.Originality/valueThe proposed model could be used in wing sizing according to the targeted L/Dmax value in aircraft design. The approach can be used to estimate the effect of varying gross weight on L/Dmax. In addition, the model contributes to the L/Dmax estimation of unusual designs, such as variable-sweep wing, large delta wings, flying wings and BWBs. This study is valuable in that it reveals that L/Dmax value can be predicted only with aspect ratio, gross weight (Wg) and wing area (Swing) data.