A variable-camber wing structure topology optimization method based on variable-density method
Patent Information
- Application Number
- CN202311169361.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-12
- Publication Date
- 2026-11-03
- Estimated Expiration
- 2043-09-12
AI Technical Summary
Traditional wing structures are difficult to achieve flexible camber, resulting in discontinuous camber, which affects flutter, noise and aerodynamic characteristics during flight, and also leads to low control efficiency.
A topology optimization method for variable camber wing structures based on the variable density method is adopted. Combined with two-way shape memory alloy actuators and 3D printing technology, a flexible wing structure is designed. The continuous deformation capability of the leading and trailing edges is obtained through deformation parameters and topology optimization.
It achieves smooth and continuous deformation of the leading and trailing edges of the wing, meets aerodynamic shape requirements, improves handling efficiency, reduces flutter and noise, and optimizes aerodynamic characteristics.
Smart Images
Figure CN117216870B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fluid topology optimization technology in computational fluid dynamics, and particularly to a topology optimization method for variable camber airfoils based on the variable density method. Background Technology
[0002] Topology optimization is a structural optimization method that, based on known design variables, constraints, and stress states, aims to increase stiffness and reduce weight. It utilizes limited prior information to improve structural optimization efficiency by finding the optimal material distribution within a given region. Depending on the element structure, structural topology optimization is mainly divided into two categories: discrete topology and continuous topology. Discrete topology optimization is generally used for spatial structures such as beams and trusses, introducing the concept of a base structure and iteratively optimizing the retention or removal of each element within the design region. Continuous topology optimization is generally used for planar structures, introducing the concept of material elements and iteratively optimizing the retention or removal of each type of material element within the design region. Airfoil sections are continuous planar structures and therefore fall under the category of continuous topology optimization. Commonly used methods for solving continuous topology optimization problems include homogenization methods, variable thickness methods, variable density methods, independent continuous mapping methods, and asymptotic structural optimization methods. The variable density method transforms the structural optimization problem into a material distribution problem. Its core idea can be described as: assuming a material with variable density, in topology optimization, the density field of the structure is a function defined throughout the entire structural domain to represent the material density at different locations. Typically, each point in the density field corresponds to a cell or a small region in the structure. The numerical value in the density field represents the proportion or density of material occupied at that location. In topology optimization, the density field usually varies between 0 and 1 and has a nonlinear relationship with the macroscopic elasticity model. By selecting a reasonable material interpolation model and optimization algorithm, the relative density values of material cells within the design domain are calculated. 0 indicates that the cell is empty and needs to be removed, while 1 indicates that the cell is solid and needs to be added. Then, a penalty variable is introduced to aggregate intermediate density values towards 0 and 1. Finally, the distribution of material within the design domain is determined based on the magnitude of the relative density values of the cells. Because the variable density topology optimization method introduces the concepts of pseudo-density and penalty factor, its computational efficiency and convergence are better than other methods. It also has better practicality and versatility, making it more suitable for wing structure topology optimization problems.
[0003] Traditional airfoils rely on hinged linkage mechanisms to deflect flaps, which is insufficient to meet the high-performance requirements of future aircraft. The traditional wing camber drive structures are mostly rigid, such as those that extend and deform the leading-edge flaps via linkages. This rigidity results in discontinuous wing camber changes, significantly impacting wing flutter, noise, and aerodynamic characteristics during flight, and is also limited by control surface efficiency and trajectory variations. Summary of the Invention
[0004] The problem this invention aims to solve is to address the shortcomings of the prior art by providing a topology optimization method for variable camber wing structures based on the variable density method. This method is applicable to complex shapes and flexible mechanisms, and avoids the phenomenon of discontinuity in wing camber.
[0005] To achieve the above objectives, this invention provides a topology optimization method for variable camber airfoils based on the variable density method, comprising the following steps:
[0006] Step 1: Determine the initial airfoil of the wing;
[0007] Step 2, based on the initial airfoil, defines the wing's partitions and establishes the wing's geometric model by introducing six deformation parameters: leading edge deflection position, leading edge deflection angle, leading edge transition section, trailing edge deflection angle, trailing edge deflection position, and trailing edge transition section. The wing's partitions include the leading edge deflection region, leading edge transition region, fixed region, trailing edge transition region, and trailing edge deflection region.
[0008] Step 3: Based on the variable density topology optimization method, perform variable density topology optimization on the wing to obtain the leading and trailing edge topology optimization structure;
[0009] Step 3.1 Based on the wing geometric model and deformation parameters, the leading edge deflection region, leading edge transition region, trailing edge transition region, and trailing edge deflection region are determined as the design domain for topology optimization of the variable camber wing. A function for the design domain is established, defining fixed constraints applied to both ends of the leading edge, fixed constraints applied to the upper surface of the trailing edge, and the lower surface that can be compressed inwards. The design domain includes an optimized region, a non-optimized region, and a reserved region. The optimized region is the area inside the wing profile; the non-optimized region is the area outside the wing profile; and the reserved region is the area of the wing profile thickness.
[0010] The function of the design domain is:
[0011]
[0012]
[0013] Where a(x,y) and b(x,y) are the relative densities of the leading edge structure and the trailing edge structure, respectively, and y u The y-coordinate represents the vertical coordinate of the upper surface of the airfoil. d The vertical coordinate represents the lower surface of the airfoil; x is the horizontal coordinate value; y is the vertical coordinate value.
[0014] Step 3.2 Obtain the coordinates of the front and rear edge observation points and the target displacement of the front and rear edge observation points through aerodynamic shape calculation, and allocate weight factors according to the curvature value. Select several monitoring points on the front edge contour line and the rear edge contour line respectively to analyze the deformation capability of the topology under driving force.
[0015] Step 3.3 Select the RAMP interpolation model as the interpolation model for the variable density topology optimization method, and set the topology optimization parameters; the topology optimization parameters include volume constraint factor, filter radius, driving force, penalty factor, and damping factor;
[0016] Step 3.4 Select the material for processing the topology;
[0017] Step 3.5 Establish the objective function to control airfoil deformation. Define the total variance between the displacement of each monitoring point on the leading and trailing edge profile and the target displacement as the objective function to control airfoil deformation.
[0018] Step 3.5.1 Use the least squares difference method to determine the objective function for controlling airfoil deformation;
[0019] The objective function for controlling airfoil deformation is:
[0020]
[0021] Among them, u x,i u is the abscissa of the relative position coordinates of the monitoring point after the curvature change. y,i The ordinate of u' represents the relative position coordinate of the monitoring point after the curvature change. x,i The x-coordinate u′ of the target's relative position coordinates at the monitoring point y,i The vertical coordinate represents the relative position coordinates of the target at the monitoring point; n is the number of monitoring points, and i is the serial number of the monitoring point.
[0022] Step 3.5.2 Introduce weights and curvature errors at negative curvature points into the objective function for controlling airfoil deformation obtained in step 3.5.1 to obtain the final objective function for controlling airfoil deformation.
[0023] The final objective function for controlling airfoil deformation is:
[0024]
[0025] Among them, w i κ' represents the weight value of the monitoring point, m represents the number of negative curvature points among the monitoring points, and κ' represents the weight value of the monitoring point. j κ represents the target curvature at the negative curvature point in the curve. j The actual curvature of the negative curvature point is represented by j; j is the index of the negative curvature point.
[0026] Step 3.6 Based on the final objective function for controlling airfoil deformation, the leading and trailing edge topology is obtained using the RAMP interpolation model with pre-set parameters and the variable density method topology optimization program.
[0027] Step 4 involves extracting and reconstructing the topology of the leading and trailing edges, modifying structural details, fixed ends, and force-applying ends to obtain a three-dimensional model of the leading and trailing edge topology. Strength and deformation analysis is then performed on the obtained three-dimensional model of the leading and trailing edge topology. The structural details include strength distribution and structural orientation.
[0028] Step 5: Based on the leading and trailing edge topology and the dimensional constraints of the fixed region of the airfoil, the intermediate ribs for driving deformation are designed using software.
[0029] The middle rib has a longitudinally energized conduit in the middle position, and a cylindrical metal wire guide hole extending laterally to both sides of the energized conduit. The energized conduit is connected to the metal wire guide hole. There is a horizontal rectangular through hole on each side of the middle rib, and threaded holes are provided at the four corners.
[0030] Step 6: Based on the leading and trailing edge topology, a two-way shape memory alloy wire is used as the core component for the leading and trailing edge variable curvature drive control, and it is installed on the middle wing rib to obtain the drive structure.
[0031] The drive structure consists of a dual-path memory alloy wire, a middle wing rib, an energized conduit, and a DC power supply. The energized conduit is placed in the energized conduit channel of the middle wing rib. The dual-path memory alloy wire is placed in the metal wire guide hole. One end of the dual-path memory alloy wire is fixed in the leading edge force-applying circular through hole. It winds and connects along the metal wire guide hole through the energized conduit, and then passes through the metal wire guide hole again before finally being fixed in the trailing edge force-applying circular through hole at the other end. The energized conduit is connected to the DC power supply and is powered by the DC power supply.
[0032] Step 7: Use 3D printing to create the leading and trailing edge topologies, assemble the drive structure and the leading and trailing edge topologies to obtain the complete wing ribs;
[0033] Step 8 involves assembling multiple wing ribs using modular splicing wing spars to achieve the spanwise structure assembly of the variable camber wing.
[0034] Compared with the prior art, the technical solution adopted in this invention has the following technical effects:
[0035] A topology optimization method for variable camber wings based on the variable density method is proposed. The topology optimization design of the leading and trailing edges of the variable camber wing is carried out based on the variable density topology optimization, and the strength is checked by finite element analysis. At the same time, the leading and trailing edge structural prototypes are fabricated using 3D printing technology. A spanwise structural model of the variable camber wing is established using a two-way shape memory alloy actuator and a segmented wing spars. Under the control of the internal drive components, the deflection angle and position of the leading and trailing edges of the wing can be smoothly and continuously adjusted, thereby maximizing the achievement of the given aerodynamic shape requirements. Attached Figure Description
[0036] Figure 1 This is a flowchart of a topology optimization method for a variable camber wing structure based on the variable density method in an embodiment of the present invention;
[0037] Figure 2 This is a diagram of the airfoil geometry model in an embodiment of the present invention;
[0038] Figure 3 This is a schematic diagram of the topology optimization design domain of the leading and trailing edges of a variable camber wing in an embodiment of the present invention;
[0039] Figure 4 This is a schematic diagram showing the selection of monitoring points on the wing in an embodiment of the present invention;
[0040] Figure 5 This is a diagram of the leading and trailing edge topology optimization structure in an embodiment of the present invention;
[0041] (a) is the leading edge topology diagram; (b) is the trailing edge topology diagram;
[0042] Figure 6 This is a three-dimensional model diagram of the leading and trailing edge topology of the wing in an embodiment of the present invention;
[0043] Figure 7 This is a static analysis diagram of the leading edge deformation in an embodiment of the present invention;
[0044] (a) is the stress contour plot of the leading edge structure; (b) is the displacement contour plot of the leading edge structure.
[0045] Figure 8 Static analysis of trailing edge deformation in an embodiment of the present invention;
[0046] (a) is the stress contour plot of the trailing edge structure; (b) is the displacement contour plot of the trailing edge structure.
[0047] Figure 9 This is a schematic diagram illustrating the deformation principle of a two-way shape memory alloy in an embodiment of the present invention.
[0048] Figure 10 This is a schematic diagram of a single wing rib structure in an embodiment of the present invention;
[0049] Figure 11This is a schematic diagram of the overall assembly of the variable camber wing in an embodiment of the present invention. Detailed Implementation
[0050] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.
[0051] This embodiment presents a topology optimization method for a variable camber wing structure based on the variable density method, such as... Figure 1 As shown, the method includes the following steps:
[0052] Step 1: Determine the initial airfoil of the wing;
[0053] In this embodiment, the NACA3412 airfoil is selected as the initial airfoil, and the wing chord length of this airfoil is 1000mm.
[0054] Step 2: Based on the initial airfoil, the wing's partitions are defined and a geometric model is established by introducing six deformation parameters: leading edge deflection position, leading edge deflection angle, leading edge transition section, trailing edge deflection angle, trailing edge deflection position, and trailing edge transition section. The wing partitions include the leading edge deflection region, leading edge transition region, fixed region, trailing edge transition region, and trailing edge deflection region.
[0055] In this embodiment, the airfoil deflection region (0–0.15 times the chord length), leading edge transition region (0.15–0.19 times the chord length), fixed region (0.19–0.75 times the chord length), trailing edge transition region (0.75–0.80 times the chord length), and trailing edge deflection region (0.80–1 times the chord length) are defined. This parametric design method ensures continuous variation of the airfoil curve while making the airfoil camber variation segmentally controllable, making it more suitable for aerodynamic design optimization needs. Then, an airfoil geometric model is established using a Matlab self-programming module, such as… Figure 2 As shown.
[0056] Step 3: Based on the variable density topology optimization method, perform variable density topology optimization on the wing to obtain the leading and trailing edge topology optimization structure;
[0057] Step 3.1 Based on the wing geometric model and deformation parameters, the leading edge deflection region, leading edge transition region, trailing edge transition region, and trailing edge deflection region are determined as the design domain for topology optimization of the variable camber wing. A function for the design domain is established, defining fixed constraints applied to both ends of the leading edge, fixed constraints applied to the upper surface of the trailing edge, and the lower surface that can be compressed inwards. The design domain includes an optimized region, a non-optimized region, and a reserved region. The optimized region is the area inside the wing profile; the non-optimized region is the area outside the wing profile; and the reserved region is the area of the wing profile thickness.
[0058] Design domain for topology optimization of variable camber wings, such as Figure 3As shown, fixed constraints are applied to both ends of the leading edge, and a fixed constraint is applied to the upper surface of the trailing edge, while the lower surface can be compressed inward. The leading edge is simplified to a rectangular area of 190mm × 125mm, and the trailing edge is simplified to a rectangular area of 250mm × 71mm. The dotted area is the optimized area for variable density topology optimization of the wing's leading and trailing edges, and the white area within the rectangle is the non-optimized area. During program initialization, the relative density of the non-optimized area is set to 0. The black edge between the dotted area and the white area is the outer contour of the wing, with a contour thickness of 5mm, and is set as a reserved area. During program initialization, its relative density is set to 1. The above settings are implemented by functions.
[0059] The function of the design domain described in this embodiment is:
[0060]
[0061]
[0062] Where a(x,y) and b(x,y) are the relative densities of the leading edge structure and the trailing edge structure, respectively, and y u The y-coordinate represents the vertical coordinate of the upper surface of the airfoil. d The vertical coordinate represents the lower surface of the airfoil; x is the horizontal coordinate value; y is the vertical coordinate value.
[0063] Step 3.2 Obtain the coordinates of the front and rear edge observation points and the target displacement of the front and rear edge observation points through aerodynamic shape calculation, and allocate weight factors according to the curvature value. Select several monitoring points on the front edge contour line and the rear edge contour line respectively to analyze the deformation capability of the topology under driving force.
[0064] In this embodiment, as follows Figure 4 As shown, 14 points were selected as monitoring points on the leading and trailing edge surfaces to analyze the deformation capacity of the topology under the action of driving force.
[0065] Step 3.3 Select the RAMP interpolation model as the interpolation model for the variable density topology optimization method, and set the topology optimization parameters; the topology optimization parameters include volume constraint factor, filter radius, driving force, penalty factor, and damping factor;
[0066] In this embodiment, the volume constraint factor is set to r = 0.3, the driving force is F = 100N, the penalty factor is q = 3, the filter radius is rH = 3, and the damping factor is η = 0.3.
[0067] Step 3.4 Select the material for processing the topology;
[0068] By comparing the elastic modulus, Poisson's ratio, and allowable stiffness of commonly used 3D printing materials, materials for processing the leading and trailing edge topological structures are selected. In this embodiment, nylon material is selected for processing the leading and trailing edge topological structures.
[0069] Step 3.5 Establish the objective function to control airfoil deformation. Define the total variance between the displacement of each monitoring point on the leading and trailing edge profile and the target displacement as the objective function to control airfoil deformation.
[0070] The purpose of defining the objective function is to define an accurate mathematical expression in the deformation control problem to guide the airfoil deformation to achieve the desired shape, while ensuring that the airfoil deformation meets certain specific requirements and constraints. The objective function achieves shape matching and accurate deformation by calculating the difference between the position of the monitoring point after deformation and its target position, and by minimizing the root mean square error of the control point coordinates on the curves before and after deformation.
[0071] Step 3.5.1 Use the least squares difference method to determine the objective function for controlling airfoil deformation;
[0072] For deformation control problems, a common approach is to define the objective function using the least squares difference (LES) of the coordinates of control points on the curve before and after deformation. Therefore, the objective function for controlling airfoil deformation is:
[0073]
[0074] Among them, u x,i u is the abscissa of the relative position coordinates of the monitoring point after the curvature change. y,i The ordinate of u' represents the relative position coordinate of the monitoring point after the curvature change. x,i The x-coordinate u′ of the target's relative position coordinates at the monitoring point y,i The vertical coordinate represents the relative position coordinates of the target at the monitoring point; n is the number of monitoring points, and i is the serial number of the monitoring point.
[0075] Step 3.5.2 Introduce weights and curvature errors at negative curvature points into the objective function for controlling airfoil deformation obtained in step 3.5.1 to obtain the final objective function for controlling airfoil deformation;
[0076] The closer the points on the airfoil curve are to the leading and trailing edges, the greater their impact on aerodynamic efficiency. Furthermore, based on the definition of deformation parameters in step 2 and the model of the design domain in step 3, the curvature change of the lower leading edge surface is more complex, and the compressed portion of the curve is prone to curvature "concavity" phenomena. Therefore, when establishing the objective function, a curvature error at negative curvature points is added to the original LES function to ensure that the curvature values at all points on the deformation curve are positive. The objective function is to minimize the total displacement variance before and after the change at each point. The specific mathematical expression is as follows:
[0077]
[0078] Among them, w iκ' represents the weight value of the monitoring point, m represents the number of negative curvature points among the monitoring points, and κ' represents the weight value of the monitoring point. j κ represents the target curvature at the negative curvature point in the curve. j The actual curvature of the point with negative curvature is represented by j, where j is the index of the point with negative curvature.
[0079] Step 3.6 Based on the final objective function for controlling airfoil deformation, the leading and trailing edge topology is obtained using the RAMP interpolation model with pre-set parameters and the variable density method topology optimization program;
[0080] In this embodiment, the leading and trailing edge topology is as follows: Figure 5 As shown.
[0081] Step 4 involves extracting and reconstructing the topology of the leading and trailing edges, modifying structural details, fixed ends, and force-applying ends to obtain a three-dimensional model of the leading and trailing edge topology. Strength and deformation analysis is then performed on the obtained three-dimensional model of the leading and trailing edge topology. The structural details include strength distribution and structural orientation.
[0082] In this embodiment, Solidworks software is used to extract and reconstruct the topology of the leading and trailing edges, and to modify structural details, fixed ends, and force-applying ends. The final three-dimensional model of the leading and trailing edge topology is as follows: Figure 6 As shown.
[0083] The 3D models of the leading and trailing edge topologies were imported into Ansys Workbench, and corresponding constraints and driving loads were applied for static analysis. The right ends of the leading edge structure were fixed, while the upper left end of the trailing edge structure was fixed, and the lower end was compressible. The spring design stiffness was Ks = 2 N / mm. The deformation results of the leading edge structure are shown below. Figure 7 and Figure 8 As shown in the figure. According to the simulation results, the allowable stress of each part of the structure is less than the allowable stress of the material, and the front and rear edges meet the design requirements.
[0084] Step 5: Based on the leading and trailing edge topology and the dimensional constraints of the fixed region of the airfoil, the intermediate ribs for driving deformation are designed using software.
[0085] The middle rib has a longitudinally energized conduit in the middle position, and a cylindrical metal wire guide hole extending laterally to both sides of the energized conduit. The energized conduit is connected to the metal wire guide hole. There is a horizontal rectangular through hole on each side of the middle rib, and threaded holes are provided at the four corners.
[0086] In this embodiment, based on the aforementioned leading and trailing edge topology and the size constraints of the fixed area of the airfoil, cylindrical shape memory alloy wire guide holes are designed inside the fixed area of the airfoil using SolidWorks software. The diameter of the holes needs to be slightly larger than that of the metal wire to prevent the structure from jamming. At the same time, a conduit to accommodate the energized conduit is designed, and rectangular through holes are designed to accommodate the deformation of the force-applied parts at the leading and trailing edges. Threaded holes for fixing are designed at both ends of the fixed area, ultimately resulting in an intermediate rib suitable for driving deformation.
[0087] Step 6: Based on the leading and trailing edge topology, a two-way shape memory alloy wire is used as the core component for the leading and trailing edge variable curvature drive control, and it is installed on the middle wing rib to obtain the drive structure.
[0088] The drive structure consists of a dual-path memory alloy wire, a middle wing rib, an energized conduit, and a DC power supply. The energized conduit is placed in the energized conduit channel of the middle wing rib. The dual-path memory alloy wire is placed in the metal wire guide hole. One end of the dual-path memory alloy wire is fixed in the leading edge force-applying circular through hole. It winds and connects along the metal wire guide hole through the energized conduit, and then passes through the metal wire guide hole again before finally being fixed in the trailing edge force-applying circular through hole at the other end. The energized conduit is connected to the DC power supply and is powered by the DC power supply.
[0089] In this embodiment, the DC power supply is model S-120-24; the two-way shape memory alloy SMA changes phase state according to temperature changes, has high energy density and power-to-weight ratio, and is suitable for internal wing drive structures. Figure 7 The diagram illustrates the two-way shape memory effect of SMA.
[0090] Utilizing the temperature sensing and driving characteristics of a two-way SMA, such as Figure 9 As shown, it is used as the core component of the leading and trailing edge variable camber drive control, and based on the above-mentioned leading and trailing edge topology optimization structure, a single rib drive structure is established, as follows. Figure 10 As shown, a two-way shape memory alloy (SMA) is placed inside a cylindrical guide hole within the middle wing rib and connected to the left and right force application points. Its expansion and contraction are controlled by adjusting the temperature of the shape memory alloy. The two ends of the connector are connected to two circular force application holes on the leading and trailing edges, respectively. The metal wires are clamped and fixed using aluminum alloy clamps. Since the leading and trailing edges need to deform simultaneously, each metal wire is powered by the same power source. The leading and trailing edge skeletons of the wing are fixed to the middle wing rib, and the driving force of the leading and trailing edges of each wing rib is the chordal tension generated by the alloy wire. The two-way shape memory alloy wires at the force application ends of the leading and trailing edges are wound around the energized conduit of the fixed part. When the energized conduit is energized, the alloy wire contracts, driving the leading and trailing edges to deflect downwards simultaneously. A NiTiO2 two-way shape memory alloy with a shrinkage rate of 4% and an energizing current of 4A is selected. Continuous energizing for 10 seconds reaches the phase transition temperature (70℃), and after the power is cut off and the wires cool naturally for 20 seconds, they return to their original length.
[0091] The actual deflection angles of the leading and trailing edge structures were measured using a non-contact blue light photogrammetric scanner. Based on the experimental results, the deformation trend of the leading edge flexible structure was similar to that of the finite element analysis, but the concave curve of the upper wing surface was more pronounced than in the finite element analysis. The actual displacement and deflection angle at the leading edge point were slightly smaller than the target deformation and the finite element analysis results. The deformation trend characteristics of the trailing edge flexible structure were consistent with the finite element analysis results.
[0092] Comparative analysis of the experimental data and simulation results shows that the flexible structural components at the front and rear edges can undergo bending deformation under the action of driving force. The deformation trend of the front and rear edges is consistent with the simulation results and can achieve the target deformation angle.
[0093] Step 7: Use 3D printing to create the leading and trailing edge topologies, assemble the drive structure and the leading and trailing edge topologies to obtain the complete wing ribs;
[0094] The topology-optimized structure of the leading and trailing edges is fabricated using 3D printing. The fixed part in the middle of the rib does not participate in deformation and is fixedly connected to the leading and trailing edge structure (binding all degrees of freedom).
[0095] Step 8 uses modular splicing wing spars to assemble multiple wing ribs, realizing the assembly of the spanwise structure of the variable camber wing;
[0096] Modular spliced wing spars are employed: maintaining the integrity of the center wingplate and leading and trailing edges, and using flexible hinges to fix the wing ribs, helps maintain the aerodynamic shape. Simultaneously, using flexible hinges to splice and fix the wing ribs allows for the possibility of spanwise deformation while maintaining chordal deformation of the wing, which is beneficial for subsequent improvements in wing spanwise camber design, such as... Figure 11 The image shows the overall assembly of the variable camber wing.
Claims
1. A topology optimization method for a variable camber airfoil based on the variable density method, characterized in that, Includes the following steps: Step 1: Determine the initial airfoil of the wing; Step 2, based on the initial airfoil, defines the wing's partitions and establishes the wing's geometric model by introducing six deformation parameters: leading edge deflection position, leading edge deflection angle, leading edge transition section, trailing edge deflection angle, trailing edge deflection position, and trailing edge transition section. The wing's partitions include the leading edge deflection region, leading edge transition region, fixed region, trailing edge transition region, and trailing edge deflection region. Step 3: Based on the variable density topology optimization method, perform variable density topology optimization on the wing to obtain the leading and trailing edge topology optimization structure; Step 3 specifically includes: Step 3.1 Based on the wing geometric model and deformation parameters, the leading edge deflection region, leading edge transition region, trailing edge transition region, and trailing edge deflection region are determined as the design domain for topology optimization of the variable camber wing. A function for the design domain is established, defining fixed constraints applied to both ends of the leading edge, fixed constraints applied to the upper surface of the trailing edge, and the lower surface that can be compressed inwards. The design domain includes an optimized region, a non-optimized region, and a reserved region. The optimized region is the area inside the wing profile; the non-optimized region is the area outside the wing profile; and the reserved region is the area of the wing profile thickness. The structural details include strength distribution and structural orientation. The function of the design domain in step 3.1 is: （1） （2） in, and These are the relative densities of the leading edge structure and the trailing edge structure, respectively. This represents the ordinate of the upper surface of the airfoil. The vertical coordinate represents the lower surface of the airfoil; The x-axis value; The vertical axis value; Step 3.2 Obtain the coordinates of the observation points at the front and rear edges and the target displacement of the observation points at the front and rear edges through aerodynamic shape calculation, and allocate weight factors according to the curvature value. Select several monitoring points on the front edge contour line and the rear edge contour line respectively, and analyze the deformation capability of the topology under driving force. Step 3.3 Select the RAMP interpolation model as the interpolation model for the variable density topology optimization method, and set the topology optimization parameters; the topology optimization parameters include volume constraint factor, filter radius, driving force, penalty factor, and damping factor; Step 3.4 Select the material for processing the topology; Step 3.5 Establish the objective function to control airfoil deformation. Define the total variance of the displacement of each monitoring point on the leading and trailing edge profiles and the target displacement as the objective function to control airfoil deformation. Step 3.6 Based on the final objective function for controlling airfoil deformation, the leading and trailing edge topology is obtained using the RAMP interpolation model with pre-set parameters and the variable density method topology optimization program; Step 4: Extract and reconstruct the topology of the leading and trailing edges, and modify the structural details, fixed end, and force-applying end to obtain a three-dimensional model of the leading and trailing edge topology. Perform strength and deformation analysis on the obtained three-dimensional model of the leading and trailing edge topology; the structural details include strength distribution and structural orientation. Step 5: Based on the leading and trailing edge topology and the dimensional constraints of the fixed region of the airfoil, the intermediate rib for driving deformation is designed using software. Step 6: Based on the leading and trailing edge topology, a two-way shape memory alloy wire is used as the core component for the leading and trailing edge variable curvature drive control, and it is installed on the middle wing rib to obtain the drive structure. Step 7: Use 3D printing to create the leading and trailing edge topologies, assemble the drive structure and the leading and trailing edge topologies to obtain the complete wing ribs; Step 8: Assemble multiple wing ribs using modular splicing wing spars to achieve the spanwise structure assembly of the variable camber wing.
2. The topology optimization method for a variable camber wing structure based on the variable density method according to claim 1, characterized in that, Step 3.5 specifically includes: Step 3.5.1 Use the least squares difference method to determine the objective function for controlling airfoil deformation; Step 3.5.2 Introduce weights and curvature errors at negative curvature points into the objective function for controlling airfoil deformation obtained in Step 3.5.1 to obtain the final objective function for controlling airfoil deformation.
3. The topology optimization method for a variable camber wing structure based on the variable density method according to claim 1, characterized in that, The middle rib has a longitudinally energized conduit in the middle position, and a cylindrical metal wire guide hole extending laterally to both sides of the energized conduit. The energized conduit is connected to the metal wire guide hole. There is a horizontal rectangular through hole on each side of the middle rib, and threaded holes are provided at the four corners.
4. The topology optimization method for a variable camber wing structure based on the variable density method according to claim 1, characterized in that, The drive structure consists of a dual-path memory alloy wire, a middle wing rib, an energized conduit, and a DC power supply. The energized conduit is placed in the energized conduit channel of the middle wing rib. The dual-path memory alloy wire is placed in the metal wire guide hole. One end of the dual-path memory alloy wire is fixed in the leading edge force-applying circular through hole. It winds and connects along the metal wire guide hole through the energized conduit, and then passes through the metal wire guide hole again before finally being fixed in the trailing edge force-applying circular through hole at the other end. The energized conduit is connected to the DC power supply and is powered by the DC power supply.
5. The topology optimization method for a variable camber wing structure based on the variable density method according to claim 2, characterized in that, The objective function for controlling airfoil deformation in step 3.5.1 is: （3） in, The x-coordinate of the relative position coordinates of the monitoring point after the curvature change. The ordinate represents the relative position coordinate of the monitoring point after the curvature change. The x-coordinate of the relative position coordinates of the target at the monitoring point The ordinate represents the relative position coordinates of the target at the monitoring point; The number of monitoring points This refers to the monitoring point number.
6. The topology optimization method for a variable camber wing structure based on the variable density method according to claim 2, characterized in that, The final objective function for controlling airfoil deformation in step 3.5.2 is: （4） in, represents the weight value of the monitoring point, and m represents the number of negative curvature points among the monitoring points. The target curvature representing the negative curvature point in the curve. The actual curvature of the negative curvature point is represented by j; j is the index of the negative curvature point.