A low-noise bionic flapping wing and its preparation method

Abstract

The present invention discloses a low-noise bionic flapping wing and a preparation method thereof. The flapping wing includes a wing membrane and wing veins. The wing membrane of the flapping wing is formed by laminating a low-permeability material membrane and a porous fiber material membrane. The two material membranes are placed one above the other, and the wing veins are placed in the middle to form a composite sandwich structure of the low-permeability material membrane - wing veins - porous fiber material membrane. The wing veins are divided into main wing veins, bifurcated wing veins, contour wing veins and arc wing veins; in order to improve the bending resistance of the wing, contour wing veins and arc wing veins are respectively arranged at the boundary and in the middle of the wing membrane. There are five main wing veins, which are radially and evenly distributed from the wing root to the wing tip. The bifurcated wing veins are in a three-bifurcation form and bifurcate from the corresponding main wing veins. The design of this flapping wing maintains the deformation mode for efficient generation of high lift and further restricts the wrinkling deformation during wing flapping, achieving low-noise generation.

Description

Technical Field

[0001] The present invention relates to the field of aircraft design and manufacturing, and more specifically, to a low-noise bionic flapping wing and a preparation method thereof. Background Art

[0002] Micro air vehicles exhibit unique characteristics and infinite potential in the military. Their small and flexible bodies enable them to perform diverse tasks in complex environments: in the field of reconnaissance and intelligence gathering, micro air vehicles quietly enter enemy airspace to obtain real-time intelligence and images, providing the military with accurate enemy information and battlefield situations to assist commanders in making wise decisions; in the field of target recognition and strike, micro air vehicles can use their concealment to become an ideal choice for marking and identifying enemy targets. Bionic micro air vehicles are also an important topic in recent years. Their shapes and movement patterns are similar to those of natural organisms, with better concealment, which reduces the possibility of being detected. However, at present, the noise generated by bionic micro air vehicles is much greater than that of natural birds, and the acoustic stealth of the vehicles is poor. Reducing the noise of bionic micro air vehicles helps reduce the risk of being detected by the enemy. Therefore, the low-noise design of bionic flapping wing micro air vehicles has become an important topic at present.

[0003] The noise measurement of bionic flapping wing micro air vehicles finds that the flapping wing noise is an important noise source of the vehicle, and its noise mainly comes from the mid-high frequency noise of the wing, which is mainly caused by the high-frequency flapping of the wing and local wing surface wrinkles. In the past, the primary concern of scientific researchers in designing bionic flapping wing micro air vehicles was the aerodynamic performance (such as lift and efficiency) of the bionic flapping wing aircraft, and they mainly selected wing membrane materials for these objectives, such as the commonly used polyimide film today. However, it was also found during the low-noise design that this material wing would generate significant noise during the flapping process. Subsequently, in the wing noise measurement experiments of different wing membrane materials, we also found that materials such as spun cloth can significantly reduce the noise level of the vehicle during the flapping process of the bionic flapping wing micro air vehicle, but its disadvantage is that the lift of this membrane wing is relatively low. Generally speaking, how to balance the requirements of lift and low noise in the low-noise flapping wing design and improve the stealth and maneuverability of the vehicle still needs to be studied. Summary of the Invention

[0004] A low-noise bionic flapping wing and a preparation method thereof according to the present invention are mainly proposed to reduce the flapping wing noise of a bionic flapping wing micro air vehicle under the condition of maintaining high lift of the vehicle.

[0005] The low-noise bionic flapping wing is in the shape of an insect wing and adopts a large root-to-tip ratio design scheme to reduce the aerodynamic load and noise generated by the wing tip part during high-speed flapping.

[0006] A low-noise bionic flapping wing consists of a wing membrane and wing veins. The flapping wing membrane is formed by laminating a low-permeability material membrane and a porous fiber material membrane. The low-permeability material membrane has low air permeability to maintain high aerodynamic performance; the porous fiber material membrane is soft, which can suppress the generation of wrinkles during flapping to achieve low noise. During the processing of the wing membrane, the low-permeability material membrane is placed at the bottom layer, the porous fiber material membrane is placed at the top layer, and wing veins are placed in the middle to form a sandwich structure composed of the low-permeability material membrane - carbon fiber thin sheet wing veins - porous fiber material membrane, and then thermosetting adhesive molding is carried out. The scheme of the wing veins in the middle of the two membranes ensures that the deformation laws of the upstroke and downstroke processes are symmetric during the reciprocating flapping process of the flapping wing, and as much as possible ensures the symmetry of the up and down flapping aerodynamic forces, reducing the initial yaw moment caused by asymmetric wing deformation.

[0007] The wing veins of a low-noise bionic flapping wing are the supporting structures that carry the wing membrane, and are cut and polished from carbon fiber composites. Under the condition of ensuring the wing structure strength, the wing can generate flexible deformation under the combined action of inertial load and aerodynamic load to maintain the generation of high lift and high efficiency.

[0008] The images taken by a high-speed camera during the movement of the previous bionic flapping wing show that for the conventional radially distributed wing veins flapping wing (all wing veins diverge outward from the wing root), the degree and frequency of wrinkles are larger at the positions near the wing tip and the trailing edge of the flapping wing, and the wing membrane deformation is complex during the wing membrane flipping process at the wing root, which are the main sources of high noise.

[0009] Based on the above findings, the wing veins of a low-noise bionic flapping wing are designed by combining the outer contour wrapping type wing veins and the bifurcated type wing veins. The wing veins are cut from carbon fiber sheets and are divided into main wing veins, bifurcated wing veins, outer contour wing veins and arc wing veins. The outer contour wing veins wrap the leading edge, the side edge of the wing tip and the trailing edge of the wing membrane, and limit the wing membrane wrinkles by means of structural strength. When the bifurcated type wing veins develop from the wing root to the wing tip, branch veins are gradually bifurcated. The design principle is to form local restriction and support for the membrane by means of wing veins, strengthen the prestress, tighten the wing membrane, and reduce the wing membrane wrinkles, so as to achieve the goal of reducing noise. To enhance the bending resistance of the flapping wing, arc wing veins are arranged in the middle of the flapping wing.

[0010] The structural position of the wing veins of the low-noise bionic flapping wing of the present invention is related to the lift and physical characteristics of the flapping wing. There are five main wing veins evenly distributed radially from the wing root to the wing tip. The first main wing vein is located at the leading edge of the flapping wing and does not contain bifurcated wing veins thereon. The second, third, fourth and fifth main wing veins have subdivided bifurcated wing veins. The bifurcated wing veins are in the form of three bifurcations, that is, secondary branch veins are bifurcated from the main wing veins, and lower-level branch veins are bifurcated from the secondary branch veins. Considering that the wrinkling deformation of the wing membrane is more obvious at the trailing edge of the flapping wing, the bifurcation points of the bifurcated branch veins are concentrated in the posterior 1 / 3 region of each main wing vein.

[0011] The low-noise bionic flapping wing of the present invention also needs to take into account the efficient lift generation. In order to make the flapping wing produce an aerodynamically efficient deformation form and reduce the weight of the flapping wing, the flapping wing vein adopts a variable stiffness design scheme. The bending stiffness of the wing vein section gradually decreases from the wing root to the wing tip and from the leading edge to the trailing edge. The stiffness change is achieved by adjusting the wing vein width.

[0012] The low-noise bionic flapping wing of this invention requires connection to an aircraft's flapping wing drive mechanism. Specifically, the wing membrane at the wing root connects to the drive mechanism's connecting rod. During wing flapping, the membrane is pulled by the membrane to deform. To ensure smooth membrane deformation, the area near the wing root is free of main and bifurcated wing veins.

[0013] The preparation method of a low-noise bionic flapping wing of the present invention is as follows:

[0014] Step 1: Prepare carbon fiber sheets of uniform thickness. Based on the cross-sectional bending stiffness distribution and wing profile, design the wing vein distribution and width distribution. Draw a wing vein structure distribution diagram with gradually decreasing carbon fiber width from the leading edge to the trailing edge. Use laser cutting or other means to process and tailor the carbon fiber sheets.

[0015] Step 2: Upload the designed wing profile to a laser printer and cut the low permeability material membrane and the porous fiber material membrane into shape;

[0016] Step 3: Lay the cut low-permeability material membrane on the bottom layer, apply glue on its upper surface with a brush, stick the wing veins on the designated position of the low-permeability material membrane according to the corresponding shape, then cover the wing veins with a porous fiber material membrane, and use high-pressure thermosetting molding to make flapping wings.

[0017] The advantages of the present invention are:

[0018] 1. Improvements to flapping wing membrane materials have reduced noise and minimized lift loss during flight.

[0019] 2. The flapping wing vein design reduces wing membrane wrinkles and maintains high aerodynamic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of a low-noise bionic flapping wing of the present invention;

[0021] Figure 2 The figure is a schematic cross-sectional view of a low-noise bionic flapping wing according to the present invention along the chord direction of the wing surface.

[0022] In the picture:

[0023] 1-wing membrane 2-wing vein 11-low permeability material membrane

[0024] 12-porous fiber material membrane 21-main wing vein 22-forked wing vein

[0025] 23 - Outer contour vein, 24 - Arc vein, 211 - First main vein

[0026] 212 - Second main vein, 213 - Third main vein, 214 - Fourth main vein

[0027] 215 - Fifth main vein Detailed implementation manners

[0028] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following will describe in detail the specific implementation methods of the present invention with reference to the accompanying drawings.

[0029] A low - noise bionic flapping wing prepared in an embodiment of the present invention. As Figure 1 shown, a low - noise bionic flapping wing is composed of a wing membrane 1 and wing veins 2. The flapping wing membrane is formed by laminating a low - permeability material membrane 11 at the bottom and a porous fiber material membrane 12 at the top.

[0030] The bionic flapping wing veins 2 are the support structures for carrying the wing membrane 1, which are cut and polished from carbon fiber composite materials. The structure of the wing veins 2 consists of main wing veins 21, bifurcated wing veins 22, outer contour wing veins 23 and arc wing veins 24. Among them, the main wing veins 21 are composed of the first main wing vein 211, the second main wing vein 212, the third main wing vein 213, the fourth main wing vein 214, and the fifth main wing vein 215.

[0031] Five main wing veins 21 are radially and evenly distributed from the wing root to the wing tip. The first main wing vein 211 is located at the leading edge of the flapping wing, and it does not contain bifurcated wing veins 22 thereon. The second main wing vein 212, the third main wing vein 213, the fourth main wing vein 214, and the fifth main wing vein 215 contain bifurcated wing veins. The bifurcated wing veins 22 are of a three - bifurcation form, that is, secondary branches branch out from the main wing veins 21, and lower - level branches branch out from the secondary branches. Considering that the wrinkling and deformation of the wing membrane are more obvious at the trailing edge of the flapping wing, the bifurcation points of the bifurcated branches are concentrated in the posterior 1 / 3 region of the corresponding main wing veins 21. The outer contour wing veins 23 wrap the leading edge, the wing - tip side edge and the trailing edge of the wing membrane 1. To enhance the bending resistance of the flapping wing, arc wing veins 24 are arranged in the middle of the flapping wing. At the wing root part, since membrane pulling is required to achieve flipping deformation, the main wing veins 21 and bifurcated wing veins 22 are not arranged.

[0032] When processing the low - noise bionic flapping wing membrane 1 in an embodiment of the present invention, the low - permeability material membrane 11 is placed at the bottom layer, the porous fiber material membrane 12 is placed at the top layer, and the wing veins 2 are placed in the middle. As Figure 2 shown, a composite sandwich structure of low - permeability material membrane 11 - wing veins 2 - porous fiber material membrane 12 is formed and thermoset adhesively formed.

[0033] A preparation method of a low - noise bionic flapping wing provided by an embodiment of the present invention includes the following steps:

[0034] Step 1: Prepare carbon fiber thin plates with equal thickness. According to the sectional flexural stiffness distribution and the wing profile, design the distribution of the wing veins 2 and their width distribution, draw the structural distribution diagram of the wing veins 2 with the carbon fiber width gradually decreasing from the leading edge to the trailing edge, and use means such as laser cutting for processing and cutting the carbon fiber thin plates.

[0035] Step 2: Upload the designed wing profile to a laser printer, and cut and form the low-permeability material film 11 and the porous fiber material film 12 respectively.

[0036] Step 3: Lay the cut low-permeability material film 11 on the bottom layer, apply glue on the upper surface of the low-permeability material film 11 with a brush, stick the carbon fiber wing veins 2 to the designated position on the low-permeability material film 11, cover the porous fiber material film 12 above the wing veins 2, and use high-pressure thermosetting molding to fabricate the flapping wing.

Claims

1. A low-noise bionic flapping wing, characterized in that the flapping wing is composed of a wing membrane and wing veins. The wing membrane is formed by laminating a low-permeability material membrane and a porous fiber material membrane; the low-permeability material membrane is placed at the bottom layer, the porous fiber material membrane is placed at the top layer, and wing veins are placed in the middle, forming a composite sandwich structure of low-permeability material membrane-wing veins-porous fiber material membrane; the wing veins are divided into main wing veins, bifurcated wing veins, outer contour wing veins and arc wing veins; the outer contour wing veins wrap the leading edge, the wing tip side edge and the trailing edge of the wing membrane, and limit the wing membrane wrinkles by means of structural strength; to enhance the bending resistance of the flapping wing, arc wing veins are arranged in the middle of the flapping wing; there are five main wing veins, including the first to fifth wing veins, which are evenly distributed radially from the wing root to the wing tip. The first main wing vein is located at the leading edge of the flapping wing and does not contain bifurcated wing veins thereon. The second, third, fourth and fifth main wing veins have subdivided bifurcated wing veins; the bifurcated wing veins are in a three-bifurcation form, that is, secondary branches branch out from the main wing veins, and even lower-level branches branch out from the secondary branches.

2. The low-noise bionic flapping wing according to claim 1, wherein, the composite sandwich structure of low-permeability material membrane-wing veins-porous fiber material membrane of the flapping wing is formed by thermosetting adhesive molding.

3. The low-noise bionic flapping wing according to claim 1, wherein the wing veins adopt a variable stiffness design scheme, and the bending stiffness of the wing vein cross-section gradually decreases from the wing root to the wing tip and from the leading edge to the trailing edge. The stiffness change is achieved by adjusting the width of the wing veins.

4. The low-noise bionic flapping wing according to claim 1, wherein, considering that the wrinkle deformation of the wing membrane is more obvious at the trailing edge of the flapping wing, the bifurcation points of the bifurcated wing veins are concentrated in the posterior 1 / 3 area of the main wing veins.

5. The low-noise bionic flapping wing according to claim 1, characterized in that, in order to make the wing membrane deform smoothly, there are no main wing veins and bifurcated wing veins arranged in the area near the wing root of the flapping wing.

6. The preparation method of a low-noise bionic flapping wing according to claim 1, characterized in that, the preparation method of the flapping wing is as follows: Step 1, prepare carbon fiber thin plates with equal thickness. According to the cross-section bending stiffness distribution and wing contour, design the wing vein distribution and its width distribution, draw a wing vein structure distribution diagram with the carbon fiber width gradually decreasing from the leading edge to the trailing edge, and use means such as laser cutting for processing and cutting of the carbon fiber thin plates; Step 2, upload the designed wing contour to a laser printer, and cut and form the low-permeability material membrane and the porous fiber material membrane respectively; Step 3, lay the cut low-permeability material membrane on the bottom layer, apply glue on its upper surface with a brush, stick the wing veins at the designated positions on the low-permeability material membrane according to the shape correspondence, and then cover the porous fiber material membrane above the wing veins, and use high-pressure thermosetting molding to make the flapping wing.

7. The preparation method of a low-noise bionic flapping wing according to claim 1, characterized in that, the wing membrane can be prepared from a polyimide membrane and a non-woven fabric membrane.

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