A rigid-flexible coupled deformable airfoil with variable camber range optimization design method

Abstract

This invention belongs to the field of numerical simulation and analysis technology for unmanned aerial vehicles (UAVs), and relates to an optimization design method for a deformable wing with a variable camber range and rigid-flexible coupling. The method includes the following steps: obtaining the operating conditions of the aircraft to determine the airfoil and basic parameters of the wing; establishing a three-dimensional aerodynamic model of the wing; performing aerodynamic simulations of the aircraft under takeoff and cruise conditions with varying angles of attack; determining the optimal camber value and corresponding aerodynamic loads of the wing under multiple operating conditions; adjusting the position of the rotating joint of the deformable wing rib to obtain a first-optimized deformable wing rib; dividing the optimization range of the first-optimized deformable wing rib into a fixed region and an optimizable region; applying aerodynamic loads at the optimal camber value to the optimizable region and performing aerodynamic simulations to obtain a second-optimized deformable wing rib and structural optimization; making deformable wing rib samples and conducting performance tests; adjusting the optimizable region until the wing performance meets the preset requirements. This invention can improve the aerodynamic efficiency of the entire flight envelope.

Description

Technical Field

[0001] This invention belongs to the field of numerical simulation and analysis technology for unmanned aerial vehicles (UAVs), specifically relating to an optimization design method for a deformable wing with a variable camber range and rigid-flexible coupling. Background Technology

[0002] In recent years, with the rapid development of UAV technology, morphing wings, as a key technology for improving the aerodynamic efficiency of aircraft and expanding the flight envelope, have a core advantage in adapting to the aerodynamic requirements of different flight phases such as takeoff, cruise, dive, and landing by changing the wing camber. For example, a larger camber is needed to obtain high lift during takeoff, a smaller camber is needed to reduce drag during cruise, and a larger camber is needed again during landing to improve low-speed stability. However, existing morphing wing design methods have the following key problems:

[0003] (1) Fixed camber range: Most designs only set a fixed camber adjustment range for a single or a few working conditions, and cannot dynamically adjust the camber range according to real-time flight parameters such as speed, altitude and load, resulting in a significant decrease in aerodynamic performance under non-design working conditions.

[0004] (2) Multi-objective optimization is fragmented: Existing technologies often optimize aerodynamic performance such as lift-to-drag ratio or structural performance such as weight or strength separately, but ignore the coupling relationship between the two. Excessive pursuit of large curvature may lead to excessive structural stress, while excessive restriction of structural weight may sacrifice aerodynamic efficiency. Summary of the Invention

[0005] In view of this, the present invention provides an optimized design method for a deformable wing with a variable camber range and rigid-flexible coupling, which solves the existing technical problems.

[0006] The technical solution of this invention is:

[0007] A rigid-flexible coupled deformable airfoil optimization design method with variable camber range includes the following steps:

[0008] Based on the aircraft's flight altitude range, maximum takeoff weight, and flight speed range, determine the airfoil and basic parameters of the aircraft's wings;

[0009] A three-dimensional aerodynamic model of the wing is established based on the airfoil and basic parameters of the aircraft wing.

[0010] Based on the three-dimensional aerodynamic model of the wing, aerodynamic simulation of variable angle of attack is performed on the aircraft during takeoff and cruise. The pressure distribution file on the surface of the deformable wing rib is obtained, and the optimal camber range of the wing under the corresponding conditions is determined. Combined with the stall angle of attack constraint, the optimal camber value and the aerodynamic load under the optimal camber value are selected by the lift-to-drag ratio.

[0011] Based on the three-dimensional aerodynamic model of the wing and the optimal variable camber range, the structural constraints were verified, and the structural topology including the skin, spars, ribs, and drive mechanism mounting positions was designed. Based on the aerodynamic simulation results of variable angle of attack, the position of the rotating joint of the deformable rib was adjusted to obtain the first-optimized deformable rib.

[0012] The optimization range of the deformable rib after the first optimization is divided into a fixed region and an optimizable region. The pressure file is mapped to the structural surface mesh of the three-dimensional aerodynamic model of the wing, and the mesh is associated through shared topology. Aerodynamic loads under cruise and optimal camber values ​​are applied. Based on the simulation results, the parameters of the optimizable region are adjusted to obtain the deformable rib after the second optimization.

[0013] Structural simulation optimization was performed on the deformed rib after secondary optimization to obtain the deformed rib after structural simulation optimization.

[0014] The deformable ribs after structural simulation optimization were prototyped, and wing performance was tested. The structural parameters of the optimizable area were adjusted until the wing performance met the preset requirements.

[0015] Furthermore, the basic parameters of an aircraft wing include: wingspan, chord length, aspect ratio, root-to-tip ratio, camber adjustment rate, and target camber range.

[0016] Furthermore, the structural constraints include:

[0017] A main wing sparb is installed along the wingspan direction at a position of 15% to 20% of the wing chord. Multiple wing ribs are installed perpendicular to the wing sparb direction, with the spacing of the multiple wing ribs evenly distributed according to the span.

[0018] The mounting holes for the drive mechanism on the wing rib are located at 30% to 50% of the wing chord.

[0019] The skin is fully covered across the wingspan, with the skin thickness reduced in the curvature adjustment area.

[0020] Furthermore, during the aerodynamic simulation of the wing, 20 to 25 boundary layer meshes are divided along the airfoil normal. The height of the first mesh layer is 0.03 mm to 0.05 mm, and the mesh is refined in the leading and trailing edge regions. The far-field region mesh constructs a cylindrical computational domain. The distance from the far-field boundary to the leading edge, trailing edge, and spanwise end of the wing is between 10 and 50 times the chord length. The far-field mesh size gradually transitions from the airfoil surface outwards, with the maximum mesh size being 30 mm to 50 mm.

[0021] Furthermore, 23 boundary layer grids are divided along the airfoil normal. The height of the first grid layer is 0.04 mm. The far-field boundary is located at 30 times the chord length from the leading edge, trailing edge, and spanwise end of the wing. The maximum grid size in the far field is 40 mm.

[0022] Furthermore, variable angle-of-attack aerodynamic simulations are performed on the aircraft's takeoff and cruise conditions, including the following steps:

[0023] For a single working condition, four to eight different curvature ranges are set, and the lift coefficient, drag coefficient, and lift-to-drag ratio are simulated and calculated for each curvature range.

[0024] Furthermore, the camber range is based on the wing chord length, with the chord length deformation area gradually increasing from the leading edge to the trailing edge.

[0025] Furthermore, the leading edge ranges from 10% to 25% of the wing chord length, and the trailing edge ranges from 60% to 90% of the wing chord length.

[0026] Furthermore, the fixed area includes anterior and posterior edge deformable joints, flexible deformable bones, transmission channel holes / tendon fixation holes, and flexible skin connection edges, and the optimizable area includes fixed wing ribs.

[0027] Furthermore, structural simulation optimization is performed on the deformed rib after secondary optimization to obtain the deformed rib after structural simulation optimization, including the following steps:

[0028] The 3D aerodynamic model of the wing is imported into the structural simulation environment for strength and deformation verification.

[0029] When there is concentrated stress, optimization can be achieved by adding fillets or reinforcing ribs to the areas where the concentrated stress occurs, until the concentrated stress is eliminated.

[0030] Compared with existing technologies, this invention provides a rigid-flexible coupled deformable wing optimization design method with variable camber range, which takes into account multiple operating conditions. By performing aerodynamic simulations of the aircraft's takeoff and cruise conditions with varying angles of attack, the optimal camber range of the wing under the corresponding conditions is determined, enhancing flight maneuverability and mission adaptability. It also considers the synergistic effect of aerodynamic and structural performance. The surface pressure distribution file of the deformable wing rib is obtained through aerodynamic simulation and mapped to the structural surface mesh of the wing's three-dimensional aerodynamic model. Mesh association is achieved through shared topology. Aerodynamic loads are applied under cruise and optimal camber values. Based on the simulation results, the parameters of the optimizable region are adjusted to obtain the deformable wing rib after secondary optimization. Structural simulation optimization is then performed on the deformable wing rib after secondary optimization to obtain the deformable wing rib after structural simulation optimization. Finally, through structural prototyping and performance testing, the structural parameters are further adjusted so that the wing performance meets the preset requirements. The wing obtained using the solution provided by this invention improves low-speed takeoff and landing performance, significantly enhances aerodynamic efficiency across the entire flight envelope, reduces energy consumption, reduces maintenance costs by reducing structural complexity, and improves structural reliability. It is highly practical and worthy of promotion. Attached Figure Description

[0031] Figure 1 This is a flowchart of the present invention.

[0032] Figure 2 This is a schematic diagram of the arrangement of the wing main spars and ribs of the present invention.

[0033] Figure 3 This is a schematic diagram of the multi-jointed variable camber rib of the deformable wing of the present invention.

[0034] Figure 4 This is the initial configuration of the multi-jointed variable camber rib of the rigid-flexible coupled deformable wing of the present invention.

[0035] Figure 5 This is a cross-sectional view of the initial configuration of the multi-jointed variable camber rib of the deformable wing according to the present invention.

[0036] Figure 6 This is a schematic diagram showing the distribution of the rigid and flexible structures of the present invention.

[0037] Figure 7 This is the final optimized deformed structure of the present invention.

[0038] Figure 8 This is a cross-sectional view of the final optimized deformed structure of the present invention.

[0039] Figure 9 This is a structural diagram of the variable camber wing of the present invention.

[0040] Figure 10 This is a physical image of the test platform for the variable camber wing of this invention. Detailed Implementation

[0041] This invention provides an optimized design method for a deformable airfoil with a variable camber range and rigid-flexible coupling to solve the above-mentioned problems. In order to enable those skilled in the art to better understand and implement the technical solution of this invention, the technical solution of this invention will be clearly and thoroughly described below with reference to the accompanying drawings.

[0042] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] Furthermore, it should be further explained that in the description of the embodiments of the present invention, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present invention, "multiple" means two or more.

[0044] The terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0047] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this invention are for illustrative purposes only and do not represent the only possible implementation.

[0048] Example 1

[0049] An optimization design method for a deformable airfoil with a variable camber range and rigid-flexible coupling, such as... Figure 1 As shown, it includes the following steps:

[0050] Based on the aircraft's flight altitude range, maximum takeoff weight, and flight speed range, the airfoil and basic parameters of the aircraft's wing are determined, and a three-dimensional aerodynamic model of the wing is established. Based on the 3D aerodynamic model of the wing, variable angle-of-attack aerodynamic simulations are performed on the aircraft's takeoff and cruise conditions to obtain the surface pressure distribution file of the deformable ribs. The optimal camber range of the wing under corresponding conditions is determined, and combined with stall angle-of-attack constraints, the optimal camber value and the aerodynamic load under the optimal camber value are selected based on the lift-to-drag ratio. Based on the 3D aerodynamic model of the wing and the optimal camber range, structural constraints are verified, and a structural topology including skin, spars, ribs, and drive mechanism mounting positions is designed. Based on the variable angle-of-attack aerodynamic simulation results, the position of the deformable rib rotation joint is adjusted to obtain the optimized deformable rib. The optimization range of the deformable rib after the first optimization is divided into a fixed region and an optimizable region. The pressure file is mapped to the structural surface mesh of the 3D aerodynamic model of the wing, and mesh association is achieved through shared topology. Aerodynamic loads under cruise and optimal camber values ​​are applied. Based on the simulation results, the parameters of the optimizable region are adjusted to obtain the deformable rib after the second optimization. Structural simulation optimization is then performed on the deformable rib after the second optimization to obtain the deformable rib after structural simulation optimization. The deformable rib after structural simulation optimization is prototyped, and wing performance is tested. The structural parameters of the optimizable region are adjusted until the wing performance meets the preset requirements.

[0051] Specifically, the following is a detailed description of each of the above steps in conjunction with the specific operation process:

[0052] S1. Aircraft airfoil verification

[0053] Its purpose is to clarify the core fundamental parameters of an aircraft wing, providing input for subsequent aerodynamic analysis and structural design.

[0054] Obtain the flight altitude range, maximum takeoff weight, and flight speed range of the aircraft. Based on the flight altitude range, maximum takeoff weight, and flight speed range of the aircraft, determine the airfoil and basic parameters of the aircraft's wings.

[0055] In this embodiment, the maximum takeoff weight of the UAV is 50kg, the design speed is 18m / s~40m / s, and the flight altitude is 0m~1000m.

[0056] The basic parameters of an aircraft wing include: wingspan, chord length, aspect ratio, root-to-tip ratio, camber adjustment rate, and target camber range.

[0057] The basic parameters of the aircraft's wing are: wingspan 3m, chord length 0.5m, aspect ratio 6, and root-to-tip ratio 0.8. The camber adjustment rate (v_b) and target camber range are variable camber control parameters.

[0058] Specifically, the camber adjustment rate is ≥0.5° / s, and the initial takeoff / landing camber range is set to 8%~18% and cruise camber range to 2%~6% (in chord percentage).

[0059] From the perspectives of aerodynamic performance and structural safety, the constraints that the design must meet should be clearly defined:

[0060] (a) Aerodynamic constraints: The wing stall angle of attack must meet the standard under different operating conditions. The stall angle of attack in cruise condition is greater than 16°, and the stall angle of attack in takeoff and landing condition is ≥20°. There is no risk of flutter.

[0061] Specifically, "no flutter risk" means that for high-speed aircraft, the flutter critical speed must be ≥ 1.2 times the maximum design speed.

[0062] (b) Structural constraints: The maximum stress of the structure σ_max ≤ the allowable stress of the material [σ], for example, carbon fiber composite material [σ] = 1200~1500MPa, the maximum deformation of the wing δ_max ≤ 1 / 500 of the wingspan, i.e. δ_max ≤ L / 500, and the structural weight ≤ 15% of the total design weight of the aircraft, for example, the wing weight of a 50kg UAV ≤ 7.5kg.

[0063] Example: The takeoff and cruise process of a typical small-to-medium-sized aircraft, such as the Cessna 172, is selected as the research background, with a reference free-flow velocity of 34 m / s and a Reynolds number of approximately 280,000. During takeoff, traditional simple flaps are typically lowered by 10°~20° to increase lift. The takeoff angle of attack is set to 6°, and the cruise angle of attack is set to 4°. An appropriate airfoil is selected based on the wing application scenario; for example, the NACA2412 airfoil, which offers excellent low-speed lift performance, can be chosen for civil airliners, while the NACA4412 airfoil, which balances high and low-speed performance, can be chosen for UAVs. The two-dimensional profile of the airfoil is created using SolidWorks 2023 or CATIA V6 software, and the chord length is set according to the operational requirements.

[0064] S2. Aerodynamic parameter analysis during takeoff and cruise

[0065] Fluent 2023R2 or STAR-CCM+ 2023.1 are preferred. Fluent has strong convergence in low-speed to subsonic aerodynamic simulations and is suitable for complex flow field calculations under takeoff conditions. STAR-CCM+ has better multiphysics coupling capabilities and can quickly handle boundary layer separation problems under cruise conditions. Aerodynamic simulations can be performed for each typical takeoff and cruise condition to determine the optimal camber range under that condition.

[0066] Simulation model construction:

[0067] like Figures 2 to 8 As shown, a three-dimensional aerodynamic model of the wing is established using the Pointwise or STAR-CCM+ built-in mesh generator. Structured meshing is employed to improve computational accuracy and convergence speed on the airfoil surface. Specifically, 20-25 boundary layer meshes are created along the airfoil normal. The height of the first mesh layer is ≤0.05mm, selectable between 0.03mm and 0.05mm, ensuring the y-value is between 30 and 100 to accommodate the k-ωSST turbulence model. The surface mesh size is ≤1mm, and mesh refinement is performed in regions with large curvature changes, such as the leading and trailing edges, reducing the mesh size to 0.5mm to avoid distortion in the flow field calculation. A cylindrical computational domain is constructed for the far-field region. The far-field boundary is ≥10 times the chord length from the leading, trailing, and spanwise ends of the wing. For example, with a chord length of 3m, the far-field radius is ≥30m. The far-field mesh size gradually transitions outward from the airfoil surface, with a maximum mesh size ≤50mm, preferably within the range of 30mm-50mm, to ensure a stable far-field flow field.

[0068] Boundary conditions are set on the three-dimensional aerodynamic model of the wing: the inlet is a velocity boundary, which is set according to the operating conditions; the outlet is a pressure boundary, which corresponds to the atmospheric pressure at the altitude; and the wing surface is a non-slip wall.

[0069] Multi-range simulation: For a single working condition, set 4 to 8 different camber ranges, for example, the cruise working condition is set as follows:

[0070] 40% chord length deformation, 30% chord length deformation, 20% chord length deformation and 10% chord length deformation.

[0071] The core design logic is as follows:

[0072] Based on the wing chord length, the chord length deformation area gradually increases from 10% to 25% at the leading edge and from 60% to 90% at the trailing edge. The range of both the leading and trailing edges is expanded simultaneously, and the lift coefficient (C_L), drag coefficient (C_D), and lift-to-drag ratio (L / D) are simulated and calculated for each range.

[0073] Specifically, assuming the wing chord length is 1m, the chord deformation area gradually increases from 0.1m to 0.25m of the chord length, and gradually increases from 0.6m to 0.9m of the chord length, completing the simultaneous expansion of the leading and trailing edges. The lift coefficient (C_L), drag coefficient (C_D), and lift-to-drag ratio (L / D) are simulated and calculated for each range.

[0074] Simulation of multi-curvature scheme: With "maximum lift-to-drag ratio" as the core objective, the total deformation angle at the leading edge increases uniformly from 4° to 20° with a step size of 4°, and the total deformation angle at the trailing edge increases uniformly from 6° to 30° with a step size of 6°. The simulation ensures coverage of the "low curvature - medium curvature - high curvature" range to avoid missing optimal values. Combined with stall angle of attack constraints, the optimal curvature value under this condition is selected based on the lift-to-drag ratio.

[0075] For example, if the simulation results of cruise conditions show that the lift-to-drag ratio L / D is the largest at a 4% camber, then the optimal camber for cruise is determined to be 4%.

[0076] S3. Deformable Wing Shape Optimization Design

[0077] Determine structural constraints: Based on the wing geometry and camber requirements, design the structural topology including skin, spars, ribs, and drive mechanism mounting positions, and determine the key structural dimensions and their locations, and accurately divide the design space: The skin covers the entire wingspan and adopts an "upper skin + lower skin" structure. In the camber adjustment area, such as the middle and rear sections of the wing, the skin thickness is thinner to facilitate deformation, while the thickness is thicker at the wing root and leading edge to improve rigidity.

[0078] The wing spars installation constraints are as follows: one main wing spars are set along the wingspan direction, with the main wing spars located at the 15%~20% position of the wing chord. Five to eight wing ribs are set perpendicular to the wing spars, and the spacing between the multiple wing ribs is evenly distributed according to the span. For example, six ribs are set with a spacing of 500mm for a 3m wingspan, forming a "beam-rib" frame to support the skin.

[0079] The drive mechanism is constrained by the following conditions: mounting holes for servos or hydraulic actuators on the wing ribs are located at 30% to 50% of the wing chord to ensure sufficient driving torque and achieve camber adjustment.

[0080] Based on the constraint results and the optimal deformation range of S2, the position of the rotating joint of the deformable rib is adjusted, and the variable curvature structure is as follows: Figure 3 As shown, its chord length is set to 30cm, and the reference airfoil is NACA4412. Taking the variable camber part at the rear edge as an example, this part consists of three deformable joints and a fixed wing rib. The three joints are equidistantly distributed along the chord length direction with a spacing of 5cm~6cm. Deformable joint J1 is close to the fixed wing rib, deformable joint J2 is in the middle, and deformable joint J3 is far away from the fixed wing rib. Deformable joints J1, J2 and J3 are all connected to the adjacent fixed wing ribs / joints through flexible skeletons.

[0081] Based on the position of the deformable joint, a rigid-flexible coupling integrated deformable rib design is adopted. The deformable joint and rib have an extension transmission channel and a retraction transmission channel. The end of the deformable joint is connected to the end of the tendon. At the initial moment, the drive mechanism is in a neutral state. When the retraction transmission channel is used and the extension transmission is stretched, the contraction amount is transmitted to the corresponding joint through the tendon and converted into joint deflection.

[0082] (a) Initial state (neutral state)

[0083] The drive mechanism is in a de-energized state, the pull ropes of the extension and retraction transmission channels are both in a slack state, the tendon maintains a preload of 5N, the flexible hinge of the deformable joint has no rotation angle, the trailing edge curvature section maintains the original NACA4412 airfoil, and the total curvature is 2%, which is the lower limit of the optimal deformation range of S2.

[0084] Here, the drive mechanism refers to the servo motor, and the slack state refers to the case where the tension is ≤1N.

[0085] (ii) The process of increasing curvature (e.g., from 6% to 2%)

[0086] Drive command trigger: When the flight speed decreases, lift needs to be increased. At this time, the trailing edge camber needs to be increased. The control system sends a command to activate the servo in the retractable transmission channel, retract the flexor tendon. The contraction of the flexor tendon is 0mm~5mm. At the same time, the transmission channel is extended to stretch the tendon. The extension of the tendon is 0mm~5mm.

[0087] Force and motion transmission: The retractable pull rope pulls the retractable channel hole of the deformable joint through the transmission channel, causing the joint to rotate clockwise around the flexible hinge. That is, the rotation angle increases sequentially from deformable joint J1 to deformable joint J3, with the rotation angle of deformable joint J1 being 3°, the rotation angle of deformable joint J2 being 6°, and the rotation angle of deformable joint J3 being 9°. At the same time, the pull rope is extended to help pull the joint and prevent the joint from shifting.

[0088] Tendon synergy: The tendons are gradually tightened as the deformed joints rotate, and the contraction is transmitted to the three joints through the tendons to ensure that the deformed joints rotate synchronously with an angle error of ≤0.5°, ultimately achieving an overall downward deviation of 12° at the posterior edge and increasing the total curvature to 6%.

[0089] (iii) The process of reducing curvature (e.g., from 6% to 2%)

[0090] Drive the reverse action: The servo motor extends the transmission channel and retracts the flexor tendon, and the pulling force is transmitted to the deformable joint through the transmission channel, causing the flexible joint to rotate counterclockwise.

[0091] Tendon reduction: The tendon gradually relaxes with joint rotation, the preload is restored to 5N, the joint angle gradually decreases to 0°, the posterior curved portion returns to the original airfoil shape, and the total curvature is restored to 2%.

[0092] Topology optimization of wing rib structure: Based on the characteristics of deformable wing rib structure, the optimization range is divided into "fixed region" and "optimizable region" to avoid affecting deformation function and key load-bearing components. The specific division is as follows:

[0093] The fixed areas are: 1. anterior and posterior deformable joints, 2. flexible deformable skeleton, 3. transmission channel holes / tendon fixation holes, and 4. flexible skin connection edges. Here, "tendon fixation holes" refers to tendon fixation holes with reinforcing bosses, and "flexible skin connection edges" refers to the 5mm range at each end of the spanwise direction of the fixed wing ribs.

[0094] Optimizable region: Fixed ribs. Redundant material is removed through topology optimization while retaining the force path, aiming for a 15%~20% weight reduction. ANSYS Workbench is used to preserve original load parameters such as aerodynamic, transmission, and inertial loads. Precise loading is achieved in ANSYS through the following steps: First, the pressure distribution on the deformable rib surface is obtained through Fluent simulation in S2. In ANSYS Mechanical, the "Import Pressure" function is selected to map the pressure file to the wing surface mesh. Simultaneously, mesh association is achieved through "Shared Topology," ensuring a one-to-one correspondence between Fluent and Mechanical mesh nodes. Aerodynamic loads under cruise and optimal camber values ​​are automatically applied. Based on the simulation results, the structural parameters of the optimizable region are adjusted to obtain the optimized rib structure, as shown below. Figure 9 As shown.

[0095] S4. Structural Iterative Optimization

[0096] Using finite element analysis software such as ANSYS or ABAQUS, strength and deformation simulations are performed on the designed wing structure to verify whether it meets the design conditions. The specific steps include:

[0097] (1) Finite element model construction:

[0098] Import the 3D aerodynamic model of the wing and mesh it. The spars and ribs are made of solid elements with an element size of 5mm to 10mm, the skin is made of shell elements with an element size of 2mm to 5mm, and the drive mechanism mounting position is made of refined mesh with an element size of 1mm to 2mm.

[0099] (2) Load and constraint application: Obtain aerodynamic loads from fluid simulation and apply them to the three-dimensional aerodynamic model of the wing. For example, the maximum aerodynamic pressure on the wing surface during cruise is 500 Pa. The structural self-weight load is calculated based on the material density. Set the constraint condition to be fully fixed at the wing root to simulate the connection between the wing and the fuselage.

[0100] (3) Simulation analysis and verification:

[0101] When checking the strength, calculate the maximum stress value (σmax) of the structure. If σmax ≤ [σ], the strength meets the standard. For example, carbon fiber skin σ_max = 950MPa ≤ 1200MPa, and aluminum alloy wing beam σ_max = 480MPa ≤ 572MPa.

[0102] When checking the deformation, the maximum deformation of the wing (δ_max) needs to be calculated. If δ_max≤L / 500 (for example, for a 3m wingspan wing, δ_max=5mm≤6mm), then the deformation meets the standard.

[0103] If concentrated stress (σ>1.2[σ]) occurs in the mounting holes of the drive mechanism or at the connection between the wing beam and the wing rib, it is necessary to optimize the process by increasing the fillet radius (≥5mm) or adding reinforcing ribs until the concentrated stress is eliminated.

[0104] S5. Additive Manufacturing

[0105] Variable camber wings require sufficient structural strength and stiffness to withstand various loads and dynamic deformations during flight. The structural design should consider the stress distribution of the wing under different flight conditions to ensure the overall stability of the wing structure. Secondly, a lightweight variable camber wing structure is required to reduce overall weight and improve flight performance and fuel efficiency. Using lightweight materials, such as composite materials and aluminum alloys, can effectively reduce the wing's weight. Thirdly, the leading and trailing edge camber mechanisms should be designed as reliable and stable systems capable of synchronous and asynchronous deformation control. The design should consider the reliability, accuracy, and response speed of both the deformation mechanism and the control system.

[0106] Material selection is based on the camber requirements and structural constraints determined by aerodynamic analysis. Suitable wing materials are selected, prioritizing those with "high strength, lightweight, and easy deformation" characteristics. For small and medium-sized UAVs, PLA or carbon fiber are selected as rigid load-bearing materials, while TPU is selected as a flexible transition material.

[0107] Combining the wing camber requirements with the advantages of MM3D printing's "one-step molding of complex structures," the structural topology and printing path are optimized to achieve integration of function and structure.

[0108] Model splitting: In computer-aided design, the ribs and transmission components are split into two independent STL files.

[0109] Extruder assignment: Import the model into Cura, right-click and select "Assign Extruder", assign the PLA ribs to extruder 0 and the TPU parts to extruder 1.

[0110] Enable "Multi-material mode" and set the switching delay time to 3 to 5 seconds. There is an interval between the two materials to prevent them from mixing.

[0111] Combined with strength optimization: design an interlocking structure at the junction, or print a 0.3mm thick PLA transition layer at a temperature of 210℃ and a speed of 30mm / s.

[0112] The flaps and aileron control surfaces are designed, and fixed and deformable ribs are connected in series. The variable camber wing structure design uses carbon fiber I-beams connected to the ribs, with carbon tubing assisting in load-bearing. Drive structures are installed at the wingtips and flaps, with gears driving the servoless motor components, achieving multi-modal hybrid control with fewer actuators. Taking a wing segment with a span of 1000mm and a chord length of 300mm as an example, where the flaps and ailerons each account for 40% of the span (as shown in the figure), the corresponding wing structure deformation results are derived based on the aerodynamic requirements of multiple flight conditions as follows:

[0113] 1. Takeoff state: The variable camber flaps bend synchronously through the leading and trailing edges, with the leading edge deflecting 20° at 25% chord length and the trailing edge deflecting 30° at 60% chord length, thereby increasing lift and enabling short takeoff and landing.

[0114] 2. Cruise mode: The variable camber flaps bend synchronously through the leading and trailing edges, with the leading edge deflecting by 8° at 15% chord length and the trailing edge deflecting by 12° at 80% chord length, achieving high lift-to-drag ratio cruise.

[0115] Based on the original full wing with a span of 100cm, a chord length of 30cm, and 12 sets of "rib + joint" units, 5 sets of units on one side of the span were selected as the processing range for the half wing. The half wing test did not pursue full-size load-bearing performance, but focused on verifying the core function of the deformation mechanism. The wing prototype is shown below. Figure 9 As shown.

[0116] Building an experimental platform, such as Figure 10 As shown, the test conditions are as follows: five trailing edge camber target values ​​(6°, 12°, 18°, 24°, 30°) are set, and five corresponding leading edge camber target values ​​(4°, 8°, 12°, 16°, 20°) are matched to perform coordinated camber changes and test the deformation range.

[0117] Test steps:

[0118] 1. Power on the controller and send a curvature adjustment command. Maintain each operating condition for 5 minutes and obtain the response time.

[0119] 2. Measure the actual deflection angle using a protractor (measure 3 times and take the average value).

[0120] 3. Calculate the cornering error value, where the cornering error value = (actual value - target value) * 100%, and record the maximum cornering error value.

[0121] The data measured in the experiment are detailed in Tables 1 and 2 below:

[0122] Table 1. Trailing edge deflection test values

[0123]

[0124] Table 2 Leading edge deflection test values

[0125]

[0126] When all test items in the three dimensions of the test meet the standards, namely, the angle error value ≤5%, the response time ≤0.5s, and the structure is undamaged, it means that the half-wing test is passed. If the half-wing test fails, the structural parameters of the optimizable area of ​​the wing can be further adjusted, and the wing can be re-produced and tested again until the wing performance meets the preset requirements.

[0127] In actual performance testing, the core functions of the morphing mechanism can be verified at low cost and in a short cycle through half-wing processing and testing, providing a reliable process basis for the large-scale processing of the full wing and reducing the risk of full-size development.

[0128] This invention provides an optimized design method for a deformable wing with a rigid-flexible coupling and variable camber range. It breaks through the limitations of traditional airfoils, improves low-speed takeoff and landing performance, significantly enhances the aerodynamic efficiency of the entire flight envelope, reduces energy consumption, strengthens flight maneuverability and mission adaptability, reduces maintenance costs by reducing structural complexity, and improves structural reliability. It is highly practical and worthy of promotion.

[0129] The above-disclosed embodiments are merely preferred embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for optimizing the design of a deformable airfoil with a variable camber range and rigid-flexible coupling, characterized in that, Includes the following steps: Based on the aircraft's flight altitude range, maximum takeoff weight, and flight speed range, determine the airfoil and basic parameters of the aircraft's wings; A three-dimensional aerodynamic model of the wing is established based on the airfoil and basic parameters of the aircraft wing. Based on the three-dimensional aerodynamic model of the wing, aerodynamic simulation of variable angle of attack is performed on the aircraft during takeoff and cruise. The pressure distribution file on the surface of the deformable wing rib is obtained, and the optimal camber range of the wing under the corresponding conditions is determined. Combined with the stall angle of attack constraint, the optimal camber value and the aerodynamic load under the optimal camber value are selected by the lift-to-drag ratio. Based on the three-dimensional aerodynamic model of the wing and the optimal variable camber range, the structural constraints were verified, and the structural topology including the skin, spars, ribs, and drive mechanism mounting positions was designed. Based on the aerodynamic simulation results of variable angle of attack, the position of the rotating joint of the deformable rib was adjusted to obtain the first-optimized deformable rib. The optimization range of the deformable rib after the first optimization is divided into a fixed region and an optimizable region. The pressure file is mapped to the structural surface mesh of the three-dimensional aerodynamic model of the wing, and the mesh is associated through shared topology. Aerodynamic loads under cruise and optimal camber values ​​are applied. Based on the simulation results, the parameters of the optimizable region are adjusted to obtain the deformable rib after the second optimization. Structural simulation optimization was performed on the deformed rib after secondary optimization to obtain the deformed rib after structural simulation optimization. The deformable ribs after structural simulation optimization were prototyped, and wing performance was tested. The structural parameters of the optimizable area were adjusted until the wing performance met the preset requirements.

2. The method for optimizing the design of a deformable wing with a variable camber range and rigid-flexible coupling according to claim 1, characterized in that, The basic parameters of an aircraft wing include: wingspan, chord length, aspect ratio, root-to-tip ratio, camber adjustment rate, and target camber range.

3. The method for optimizing the design of a deformable wing with a variable camber range and rigid-flexible coupling according to claim 2, characterized in that, Structural constraints include: A main wing sparb is installed along the wingspan direction at a position of 15% to 20% of the wing chord. Multiple wing ribs are installed perpendicular to the wing sparb direction, with the spacing of the multiple wing ribs evenly distributed according to the span. The mounting holes for the drive mechanism on the wing rib are located at 30% to 50% of the wing chord. The skin is fully covered across the wingspan, with the skin thickness reduced in the curvature adjustment area.

4. The method for optimizing the design of a deformable wing with a variable camber range and rigid-flexible coupling according to claim 1, characterized in that, During wing aerodynamic simulation, 20 to 25 boundary layer meshes are divided along the airfoil normal. The height of the first mesh layer is 0.03 mm to 0.05 mm, and the mesh is refined in the leading and trailing edge regions. The far-field region mesh constructs a cylindrical computational domain. The far-field boundary is 10 to 50 times the chord length from the leading edge, trailing edge, and spanwise end of the wing. The far-field mesh size gradually transitions from the airfoil surface outwards, with the maximum mesh size ranging from 30 mm to 50 mm.

5. The method for optimizing the design of a deformable airfoil with a variable camber range and rigid-flexible coupling according to claim 4, characterized in that, The boundary layer grid is divided into 23 layers along the airfoil normal. The height of the first layer is 0.04 mm. The far-field boundary is located at 30 times the chord length from the leading edge, trailing edge and spanwise end of the wing. The maximum far-field grid size is 40 mm.

6. The method for optimizing the design of a deformable airfoil with a variable camber range and rigid-flexible coupling according to claim 4, characterized in that, Performing variable angle-of-attack aerodynamic simulations for the aircraft's takeoff and cruise conditions includes the following steps: For a single working condition, four to eight different curvature ranges are set, and the lift coefficient, drag coefficient, and lift-to-drag ratio are simulated and calculated for each curvature range.

7. The method for optimizing the design of a deformable airfoil with a variable camber range and rigid-flexible coupling according to claim 6, characterized in that, The camber range is based on the wing chord length, and the chord length deformation area gradually increases from the leading edge to the trailing edge.

8. The method for optimizing the design of a deformable airfoil with a variable camber range and rigid-flexible coupling according to claim 7, characterized in that, The leading edge ranges from 10% to 25% of the wing chord length, and the trailing edge ranges from 60% to 90% of the wing chord length.

9. The method for optimizing the design of a deformable wing with a variable camber range and rigid-flexible coupling according to claim 1, characterized in that, The fixed area includes anterior and posterior edge deformable joints, flexible deformable bones, transmission channel holes / tendon fixation holes, and flexible skin connection edges; the optimizable area includes fixed wing ribs.

10. The method for optimizing the design of a deformable wing with a variable camber range and rigid-flexible coupling according to claim 1, characterized in that, The deformed rib after secondary optimization is subjected to structural simulation optimization to obtain the deformed rib after structural simulation optimization, including the following steps: The 3D aerodynamic model of the wing is imported into the structural simulation environment for strength and deformation verification. When there is concentrated stress, optimization can be achieved by adding fillets or reinforcing ribs to the areas where the concentrated stress occurs, until the concentrated stress is eliminated.

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