A method for designing blended wing-body UAVs based on key parameters

Abstract

The application discloses a wing-body fusion unmanned aerial vehicle shape design method based on key parameters, and comprises the following steps: S1, initially designing the overall shape of the wing-body fusion unmanned aerial vehicle and key parameters; S2, initially constructing a plane sketch on the basis of the determined overall shape of the unmanned aerial vehicle, and performing key parameterization constraint on the plane sketch; S3, selecting a suitable airfoil, and constructing an initial framework on the basis of the plane sketch; S4, adding spline lines as guide lines at the maximum thicknesses of the lower surfaces and upper surfaces of each airfoil section of the initial framework; S5, constructing a multi-section curved surface through the guide lines, and completing wing-body fusion model design; and S6, defining related parameters for the wing-body fusion shape according to the previously constrained key parameters, and completing unmanned aerial vehicle shape design. The application can reduce the number of wing-body fusion aerodynamic shape design parameters, improve the wing-body fusion shape design efficiency, and the wing-body fusion unmanned aerial vehicle model can be locally modified without affecting the overall shape.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) shape design technology, and in particular to a method for designing the shape of a blended wing-body UAV based on key parameters. Background Technology

[0002] There are three shortcomings in the existing methods for parameterizing the shape of blended wing-body UAVs.

[0003] (1) Currently, B-spline curves, NURBS curves or CST (Class Shape Transformation) methods are commonly used to construct airfoil curves. These methods describe airfoil degrees of freedom, but at the same time, they result in a large number of parameters and a more complex design process.

[0004] (2) Using mathematical expressions to parameterize the blended wing-body shape, the influence of each parameter on the model is not intuitive, which reduces the efficiency of shape design and increases the threshold of aerodynamic shape design.

[0005] (3) When modifying a single parameter using B-spline curves, NURBS curves or CST methods, it usually leads to changes in the overall shape. The parameters are not independent of each other, resulting in a large workload in the shape optimization process and reducing the efficiency of shape optimization. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a wing-body blended unmanned aerial vehicle (UAV) shape design method based on key parameters, which can reduce the number of wing-body blended aerodynamic shape design parameters, improve the efficiency of wing-body blended shape design, and allow for local parameter modifications to the wing-body blended UAV model without affecting the overall shape.

[0007] The present invention solves the technical problem by adopting the following technical solution:

[0008] A method for designing the shape of a blended wing-body UAV based on key parameters includes the following steps:

[0009] S1, Preliminary design of the overall shape and key parameters of the blended wing-body UAV;

[0010] S2. Based on the determined overall shape of the UAV, a preliminary planar sketch is constructed and key parameterized constraints are applied to it.

[0011] S3. Select a suitable airfoil and build a preliminary framework based on the planar sketch;

[0012] S4. Add splines as guide lines at the maximum thickness of the upper and lower surfaces of each airfoil section of the preliminary frame.

[0013] S5, using guide lines to construct multi-section curved surfaces, completes the wing-body blending model design;

[0014] S6 defines relevant parameters for the blended wing-body shape based on the previously constrained key parameters, thus completing the UAV shape design.

[0015] Furthermore, in S1, three main categories of parameters are determined based on the overall shape of the UAV: ​​planar parameters, airfoil parameters, and blended section parameters. These include 16 key parameters: fuselage sweep angle, wing sweep angle, fuselage half-span, blended section half-span, wing half-span, dihedral angle, fuselage tip-root ratio, wing tip-root ratio, fuselage airfoil thickness, fuselage airfoil chord length, wing airfoil thickness, wing airfoil chord length, upper surface control curve, lower surface control curve, leading edge control curve, and trailing edge control curve.

[0016] Furthermore, in S2, the method for constructing a planar sketch includes: designing the blended wing-body layout into three segments, namely the fuselage segment, the blended wing-body segment, and the wing segment, and drawing a half-model planar sketch based on the double-sweep layout in the UAV.

[0017] Furthermore, in S3, the method for constructing the preliminary framework includes: setting a suitable offset plane and projecting the airfoil curve along the leading edge of the planar sketch to form a preliminary wing-body blending framework.

[0018] Furthermore, in S4, the method of adding splines as guide lines at the maximum thickness of the upper and lower surfaces of each airfoil section in the preliminary frame includes: first, creating points at the maximum thickness of the airfoil curves of the three sections; second, using the spline function to connect the three points, and adding tangent directions at the two endpoints, with the tangent directions being horizontal; using this method, draw the upper and lower surface curves connecting the maximum thickness of the airfoil, and the two curves connecting each leading edge and each trailing edge.

[0019] Furthermore, in S5, the method for completing the wing-body blending model design by constructing multi-section surfaces using guide lines includes: selecting the constructed section curves, adding the upper and lower surfaces and leading and trailing edge curves as guide lines, using the multi-section surface function to construct the wing-body blending surface, and finally using the symmetry function to complete the model design.

[0020] Furthermore, in S6, the relevant parameters for the blended wing-body shape are defined based on the key parameters of the previous constraints, including: the sweep angle is defined by the parameter constraints of the planar sketch, the half-span is defined by the offset value of the offset plane where each section is located, the dihedral angle is defined by the vertical translation distance of the wingtip section, the airfoil thickness is defined by the vertical scaling of each section curve, the chord length is defined by the longitudinal scaling of each section curve, and each guide line is defined by the tangent direction and tangent rate of the spline.

[0021] The present invention discloses a method for designing the shape of a blended wing-body unmanned aerial vehicle based on key parameters, which has the following beneficial effects:

[0022] This invention provides a method for designing the shape of a blended wing-body UAV based on key parameters. For the shape of a blended wing-body UAV, the shape design based on key parameters is more suitable for the initial design of the aircraft. The shape design based on key parameters effectively reduces the number of design parameters. Compared with B-spline curves, NURBS curves, or CST methods, the shape design method based on key parameters has lower complexity, a simple and clear design process, and clear geometric meaning. Attached Figure Description

[0023] Figure 1 This is a flowchart of the method of the present invention;

[0024] Figure 2 This is a general outline drawing of the UAV of the present invention;

[0025] Figure 3 This is a schematic diagram of the key parameters of the wing-body integration of the present invention;

[0026] Figure 4 This is a half-model planar sketch of the present invention;

[0027] Figure 5 This is a preliminary wing-body fusion framework diagram of the present invention;

[0028] Figure 6 This is a schematic diagram of the guide lines on the upper and lower surfaces of the present invention;

[0029] Figure 7 This is a schematic diagram of the wing-body blending model of the present invention;

[0030] Figure 8 Design drawing of a blended wing-body drone. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention upgrades the original wing-body blending shape design mode, which described curved surfaces based on B-spline curves, NURBS curves, or CST methods, to a shape design mode based on key parameters. It improves the original method of describing curved surfaces using expressions to a comprehensive design process based on the blended wing-body geometry and key parameters of the basic airfoil.

[0033] refer to Figure 1 The present invention discloses a method for designing the shape of a blended wing-body unmanned aerial vehicle based on key parameters, comprising the following steps:

[0034] S1, Preliminary design of the overall shape and key parameters of the blended wing-body UAV;

[0035] S2. Based on the determined overall shape of the UAV, a preliminary planar sketch is constructed and key parameterized constraints are applied to it.

[0036] S3. Select a suitable airfoil and build a preliminary framework based on the planar sketch;

[0037] S4. Add splines as guide lines at the maximum thickness of the upper and lower surfaces of each airfoil section of the preliminary frame.

[0038] S5, using guide lines to construct multi-section curved surfaces, completes the wing-body blending model design;

[0039] S6 defines relevant parameters for the blended wing-body shape based on the previously constrained key parameters, completing the UAV shape design, such as... Figure 8 As shown.

[0040] Most existing blended wing-body UAVs are tailless flying wing designs, which can be broadly divided into two types: single-sweep and double-sweep designs, such as... Figure 2 (a) and Figure 2 As shown in (b). The double-swept configuration exhibits better low-speed aerodynamic performance; therefore, this embodiment uses the double-swept configuration as an example. In S1, three main categories of parameters are determined based on the overall shape of the UAV: ​​planar parameters, airfoil parameters, and blended section parameters, such as... Figure 3 As shown, it includes 16 key parameters: fuselage sweep angle, wing sweep angle, fuselage half-span, blended section half-span, wing half-span, dihedral angle, fuselage tip-root ratio, wing tip-root ratio, fuselage airfoil thickness, fuselage airfoil chord length, wing airfoil thickness, wing airfoil chord length, upper surface control curve, lower surface control curve, leading edge control curve, and trailing edge control curve.

[0041] In this embodiment, S2, the method for constructing the planar sketch includes: designing the blended wing-body layout into three segments: fuselage segment, blended wing-body segment, and wing segment; and drawing a semi-model planar sketch in CATIA based on the double-sweep layout of the UAV, such as... Figure 4 As shown.

[0042] In this embodiment, S3, the method for constructing the preliminary frame includes: setting a suitable offset plane and projecting the airfoil curve along the leading edge of the planar sketch to form a preliminary wing-body blending frame, such as... Figure 5As shown. Airfoils form the basis of the blended wing-body shape; different airfoils are required for the fuselage and wing sections. The fuselage section uses a thicker airfoil to achieve greater load capacity; the wing section uses an airfoil with higher lift-to-drag ratio to achieve better aerodynamic characteristics. In CATIA, the offset plane function is used to determine the spanwise position of each section relative to the central section. Then, the projection function is used to project the central symmetrical section along the leading edge of the fuselage to form a second section; the other two sections are treated similarly.

[0043] In this embodiment, S4, the method of adding splines as guide lines at the maximum thickness of the upper and lower surfaces of each airfoil section of the preliminary frame includes: firstly, creating points at the maximum thickness of the airfoil curves of the three sections; secondly, connecting the three points using the spline function, and adding tangent directions at both endpoints, with the tangent directions being horizontal; using this method, drawing the upper and lower surface curves connecting the maximum thickness of the airfoil, and two curves connecting each leading edge and each trailing edge, as shown below. Figure 6 As shown.

[0044] In this embodiment, S5, the method for constructing a multi-section surface using guide lines to complete the wing-body blending model design includes: selecting the constructed section curves, adding upper and lower surface and leading and trailing edge curves as guide lines, using the multi-section surface function to construct the wing-body blending surface, and finally using the symmetry function to complete the model design, such as... Figure 7 As shown.

[0045] In this embodiment, in S6, the parameters defined for the blended wing-body shape based on the previously constrained key parameters include: the sweep angle is defined by the parameter constraints of the planar sketch, the half-span is defined by the offset value of the offset plane where each section is located, the dihedral angle is defined by the vertical translation distance of the wingtip section, the airfoil thickness is defined by the vertical scaling of each section curve, the chord length is defined by the longitudinal scaling of each section curve, and each guide line is defined by the tangent direction and tangent rate of the spline.

[0046] This invention provides a method for designing the shape of a blended wing-body UAV based on key parameters. For the shape of a blended wing-body UAV, the shape design based on key parameters is more suitable for the initial design of the aircraft. The shape design based on key parameters effectively reduces the number of design parameters. Compared with B-spline curves, NURBS curves, or CST methods, the shape design method based on key parameters has lower complexity, a simple and clear design process, and clear geometric meaning.

[0047] Example

[0048] The method for UAV shape design based on parametric modeling is as follows:

[0049] (1) Plan sketch

[0050] Use the sketch function to draw the blended wing-body plan view in the base plane, and the relevant parameters are determined based on the selected key parameters;

[0051] (2) Airfoil introduction and basic frame construction

[0052] Select a suitable airfoil from the airfoil library and import it into the modeling software. The selection of the airfoil needs to take into account the actual usage requirements. In this embodiment, two airfoils with large lift-drag ratios are selected as the basic airfoils for the blended wing-body UAV: ​​the NACA63-412, which has a relatively large thickness for the fuselage, and the S3010, which has good moment characteristics for the wing.

[0053] Then, the basic framework is constructed using the projection function. The projection method is "along a certain direction". The direction is selected as the fuselage and wing leading edge line of the planar sketch. The imported airfoil is then projected onto the four control sections shown in the figure.

[0054] Determine the locations of the maximum thickness of the four sections, and use the intersection command to determine the maximum thickness point. Connect these points using the spline command, and set the tangent direction and tangent rate of the spline at the key locations.

[0055] (3) Construction of three-dimensional surfaces

[0056] Connect the various sections using the multi-section surface function, and use the upper and lower surfaces and front and rear edge splines as guide lines.

[0057] (4) Effect Comparison

[0058] The blended wing-body shape designed using the CST method has a total of 136 parameters, divided into three categories: length parameters, angle parameters, and ratio parameters. Although it describes the shape richly, it is highly complex and has excessive design costs. The shape design scheme based on key parameters has a total of 16 parameters, which meets the basic requirements in terms of design freedom and can be used as an initial design scheme for small civilian UAVs.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing a blended wing body UAV configuration based on key parameters, characterized in that, The method comprises the following steps: S1, preliminary design of the overall shape and key parameters of the blended wing body unmanned aerial vehicle; S2, preliminary construction of a planar sketch based on the determined overall shape of the unmanned aerial vehicle and key parameterization constraint thereon; S3, selection of a suitable airfoil and construction of a preliminary framework based on the planar sketch; S4, addition of a spline line as a guide line at the maximum thickness of the upper and lower surfaces of each airfoil section of the preliminary framework; S5, construction of a multi-section curved surface through the guide line to complete the blended wing body model design; S6, definition of relevant parameters for the blended wing body shape according to the previously constrained key parameters to complete the unmanned aerial vehicle shape design; In S1, the three categories of parameters, including planar parameters, airfoil parameters and blended section parameters, are determined according to the overall shape of the unmanned aerial vehicle, including 16 key parameters: the sweep angle of the fuselage, the sweep angle of the wing, the half-span length of the fuselage, the half-span length of the blended section, the half-span length of the wing, the upper dihedral angle, the tip-to-root ratio of the fuselage section, the tip-to-root ratio of the wing section, the thickness of the fuselage airfoil, the chord length of the fuselage airfoil, the thickness of the wing airfoil, the chord length of the wing airfoil, the upper surface control curve, the lower surface control curve, the leading edge control curve and the trailing edge control curve. In S2, the method for constructing the planar sketch comprises: three-section design of the blended wing body layout, i.e., the fuselage section, the blended wing body section and the wing section, and drawing of a half-module planar sketch according to the double-sweep layout in the unmanned aerial vehicle.

2. The method according to claim 1, wherein, In S3, the method for constructing the preliminary framework comprises: setting a suitable offset plane and projecting the airfoil curve along the leading edge line of the planar sketch to form a preliminary blended wing body framework.

3. The method of claim 2, wherein, In S4, the method for adding a spline line as a guide line at the maximum thickness of the upper and lower surfaces of each airfoil section of the preliminary framework comprises: firstly creating points at the maximum thickness of the airfoil curve of three sections, and secondly connecting the three points using the spline line function and adding tangent directions at the two end points, which are both horizontal directions; the upper and lower surface curves connecting the maximum thickness of the airfoil, the two curves connecting each leading edge and each trailing edge are drawn using this method.

4. The method of claim 3, wherein, In S5, the method for constructing a multi-section curved surface through the guide line to complete the blended wing body model design comprises: selecting each section curve constructed and adding the upper and lower surface curves and the leading and trailing edge curves as guide lines, constructing the blended wing body curved surface using the multi-section curved surface function, and finally completing the model design using the symmetry function.

5. The method of claim 4, wherein, In S6, the definition of relevant parameters for the blended wing body shape according to the previously constrained key parameters comprises: the sweep angle is defined by the parameter constraint of the planar sketch, the half-span length is defined by the offset value of the offset plane where each section is located, the upper dihedral angle is defined by the vertical translation distance of the wing tip section, the airfoil thickness is defined by the vertical scaling of each section curve, the chord length is defined by the longitudinal scaling of each section curve, and each guide line is defined by the tangent direction and the tangent rate of the spline line.

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