A large folding ratio flapping wing structure capable of being folded

Abstract

This invention discloses a foldable flapping wing structure with a large fold-out ratio. This flapping wing structure mimics the wings of a katydid, achieving both storage and deployment through a folding mechanism. By employing a bistable composite material wing rod instead of a conventional wing rod, the flapping wing's deployment and retraction motion can be achieved using the inherent "folding" and "stretching" stable equilibrium states of the bistable wing rod material. Through this folding mechanism, the fold-out ratio of this flapping wing structure can reach over 10, significantly reducing the aircraft's storage size and greatly improving portability. This effectively solves the problems of large storage space and easily damaged wing membranes in flapping-wing micro-aircraft. When the flapping-wing micro-aircraft is in use, the flapping wing structure can be unfolded from its folded state. This design helps improve the ease of use, deployment versatility, and adaptability to complex environments of flapping-wing micro-aircraft, expanding its application scenarios.

Description

Technical Field

[0001] This invention relates to the field of flapping-wing micro-aircraft, specifically a flapping-wing structure with a large flapping ratio that can be rolled up and folded. Technical Background

[0002] Flapping-wing micro-aircraft mimic the flight patterns of hummingbirds or insects, generating lift and thrust through wing flapping. They possess high maneuverability, low noise, and excellent hovering and low-speed flight capabilities. Their compact structure and low energy consumption allow them to adapt well to complex or confined environments, making them suitable for urban reconnaissance, indoor search and rescue, and environmental monitoring. Compared to traditional fixed-wing or rotary-wing aircraft, flapping-wing micro-aircraft are more stealthy, possess stronger biomimetic features, and can effectively blend into the natural environment, minimizing interference with targets, demonstrating unique application potential and technological advantages.

[0003] Due to the rigid connection between the flapping wing and the fuselage, most known flapping-wing micro-aircraft can only maintain their flapping wings in an extended state, with only a small number possessing a limited flapping-out ratio, unable to achieve a large flapping-out ratio. This results in a large storage space and makes them prone to damage to the wingstock and wing membrane, hindering large-scale transportation and storage. Therefore, the key to significantly reducing the size of such aircraft is to design flapping wings with a large flapping-out ratio.

[0004] Ladybugs, beetles, and katydids in nature fold their wings to their sides when on the ground, but their folding methods differ. Ladybugs and beetles primarily use in-plane folding, hiding their wings beneath the elytra. Although the elytra protect the wing structure, the in-plane folding method allows for a relatively small unfolding ratio. When katydids crawl on the ground, their wings fold circumferentially like a paper fan, then curl from the wingtip to the wing root—a typical curling folding method with an unfolding ratio exceeding 10. Research has found that the hollow wing vein structure of insect wings automatically curls when not filled with fluid, causing the wing membrane to complete the curling fold; when the thorax pumps body fluid into the hollow wing vein structure, the curled wings gradually unfold and maintain rigidity. Inspired by this, by designing a bistable composite material wing rod and rationally designing the connection method at the wing root, it is possible to achieve the wing-folding behavior around the root. The bistable composite wing rod can freely switch between deployed and coiled states under load excitation, driving the flapping wing to complete the deployment and retraction behavior. This will significantly reduce the spanwise dimension of the aircraft and reduce the design difficulty of the supporting storage container; after removing the container's constraints, the flapping wing can deploy and maintain its flapping configuration under the excitation of inertial loads from reciprocating flapping.

[0005] Bistable composite wing rods are a novel type of multifunctional composite material structure. They are formed by high-temperature curing of carbon fiber prepreg at a specific layup angle, maintaining stability in both coiled and deployed states without external constraints. They offer advantages such as light weight, high storage efficiency, reliable deployment, and excellent mechanical properties. Under external loads, the bistable composite wing rod can achieve a steady-state transition using its own strain energy, thus providing effective support for flapping wing deployment and retraction. Summary of the Invention

[0006] This invention addresses the field of deployable flapping-wing micro-aircraft, proposing to add the function of retracting and deploying the flapping wings on both sides to existing flapping-wing micro-aircraft. This better simulates the natural state of the wings of the cricket *Ceratophyllum demersum*, where the wings are folded and stored at the wing root to the sides of the body in the non-flying state, reducing the space occupied by the wings; and the folded wings are deployed when taking off. This biomimetic design effectively reduces the storage space of the aircraft, enriches its application scenarios, and improves its stealth and portability.

[0007] The aforementioned large flapping wing structure, which can be rolled up and folded, is installed on a flapping wing micro-aircraft and includes a bistable composite material wing rod, a wing membrane, a rocker arm connector, and a leading edge wing rod rotating component.

[0008] The bistable composite material wing rod is a three-dimensional, slender beam structure with a circular arc cross-section, enabling both curling and folding behavior while ensuring high bending stiffness during deployment. The structure is specifically divided into three parts: the leading-edge wing rod, the root wing rod, and the wing membrane support wing rod. These parts work together to support and fix the wing surface, driving the flapping wing in a reciprocating flapping motion. When the flapping wing curls and folds, the structure, upon reaching a threshold external load, activates its inherent bistable switching characteristics, causing the wing membrane to curl and retract. When the flapping wing deploys, the structure, under the centrifugal force generated by the flapping wing, autonomously ejects outward, straightening the wing membrane.

[0009] The wing membrane material is coarse benzene fiber, which has the characteristics of being lightweight, thin, and tough, and can withstand repeated tensile and bending stresses during flapping motion; the wing membrane has an asymmetrical curved surface shape, and its planar projection outline is approximately fan-shaped, with sleeves at both ends for the wing rod to pass through.

[0010] The rocker arm connector has a three-dimensional structure, consisting of a rocker arm connecting part, a rotating shaft part, and a rectangular slotted column part. The main structure of the rocker arm connecting part is approximately a rectangular plate structure with chamfered edges and through holes for mounting pins to connect to the aircraft fuselage. The main structure of the rotating shaft part is a cylinder with a coaxial cylindrical rotating shaft at one end for mounting the leading edge wing rod rotating component. The rocker arm connecting part is perpendicular to the rectangular slotted column part and connected to the side of the cylinder. One end of the rectangular slotted column part has a rectangular groove for inserting and installing the root wing rod.

[0011] The leading-edge wing rod rotating component is a three-dimensional structure, mounted on the rotation axis of the rocker arm connector, enabling the installation and rotation of the leading-edge wing rod. This component consists of two main parts: a cylindrical sleeve and a rectangular slotted column, which are integrated into a single structure through a coplanar transition. The cylindrical sleeve is coaxial with the rotation axis of the rocker arm connector, and its inner hole can fit snugly against the rotation axis. The outer wall of the sleeve has small bosses for limiting rotation. One end of the rectangular slotted column is connected to the cylindrical sleeve, and the other end has a rectangular slot for inserting and installing the leading-edge wing rod.

[0012] The large flapping wing structure with a large folding-out ratio that can be rolled up and folded is characterized in that the position of the boss of the leading edge wing rod connector should be matched by reasonable calculation and design to meet the limiting function in the unfolded state, so that the wing membrane can open to a suitable degree, so that the flapping wing structure can generate the largest possible lift when flapping.

[0013] The large flapping wing structure with a large flapping ratio that can be rolled up and folded is characterized in that the geometric dimensions of the bistable composite material wing rod (such as length, cross-sectional arc central angle, etc.) should be designed through reasonable calculation, taking into account the strength during flapping and the curling performance during folding, and the rectangular slotted column channel of the rocker arm connector and the leading edge wing rod rotating component should match the designed bistable composite material wing rod.

[0014] The large flapping wing structure with a large flapping ratio that can be rolled up and folded is characterized in that the sleeve of the wing membrane can rotate around the bistable composite material wing rod when the flapping wing structure flaps, which is more conducive to generating an angle of attack with excellent aerodynamic performance than the fixed bonding method.

[0015] The method for implementing a large folding-ratio flapping wing structure is characterized in that, when the flapping wing structure is retracted, the leading edge wing rod rotating component is rotated 90°, and the position and direction of the wing membrane support wing rod adhered to the wing membrane are adjusted so that the wing rod coincides with the leading edge wing rod and the root wing rod. At the same time, the wing membrane is combed to make the fold flat, and the wing rod and the folded wing membrane are rolled up together, utilizing the inherent rolling characteristics of the bistable material to achieve storage. When the flapping wing structure is unfolded, the rolled wing rod and wing membrane are straightened, and the leading edge wing rod rotating component is rotated to the boss limit position to ensure the subsequent flapping movement of the wing.

[0016] The installation method of the large flapping wing structure that can be rolled up and folded:

[0017] (1) The cylindrical sleeve of the leading edge wing rod rotating part is fitted with the rotating shaft of the rocker arm connecting part;

[0018] (2) Insert the leading edge wing rod and the root wing rod into the rectangular slotted column groove of the rocker arm connector and the leading edge wing rod rotating part respectively. At this time, after the leading edge wing rod rotating part is retracted, the directions of the leading edge wing rod and the root wing rod should be consistent.

[0019] (3) The sleeves at both ends of the wing membrane are fitted onto the leading edge wing rod and the root wing rod respectively, and rubber rings are installed on both sides to restrict the sliding of the sleeves on the wing rod;

[0020] (4) Fix the wing support rod to the wing membrane by adhesive bonding. At this time, the extension line of the wing rod should pass through the rotation axis of the rocker arm connector, and ensure that the three wing rods are in the same direction when retracted.

[0021] The advantages of this invention are:

[0022] (1) It can retract the flapping wings close to the side of the fuselage, reducing the spanwise dimension of the aircraft;

[0023] (2) By reducing the size, storage space can be further optimized, making it easier for long-term large-scale storage and carrying;

[0024] (3) Inspired by insects in nature, enhance the biomimicry of flapping-wing aircraft. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the unfolded state of a large flapping wing structure that can be rolled up and folded according to the present invention;

[0027] Figure 2 This is a schematic diagram of a bistable composite material wing rod of a large flapping wing structure that can be rolled up and folded according to the present invention;

[0028] Figure 3 This is a schematic diagram of a flapping wing structure with a large flapping ratio that can be rolled up and folded according to the present invention;

[0029] Figure 4 This is a schematic diagram of a rocker arm connector for a large flapping wing structure that can be rolled up and folded according to the present invention;

[0030] Figure 5 This is a schematic diagram of the leading edge wing rod rotating component of a large flapping wing structure that can be rolled up and folded according to the present invention;

[0031] Figure 6 This is a schematic diagram of the retracted state of a large flapping wing structure with a rollable and foldable structure according to the present invention;

[0032] In the picture:

[0033] 101-Leading edge wing rod; 102-Root wing rod; 103-Wing membrane support wing rod; 2-Wing membrane; 3-Rocker arm connector; 301-Rocker arm connection part; 302-Rotation shaft part; 303-Rectangular slotted column part; 4-Leading edge wing rod rotating part; 401-Boss. Detailed Implementation

[0034] The specific implementation method of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] The aforementioned large flapping wing structure, which can be rolled up and folded, is installed on a flapping wing micro-aircraft and includes a bistable composite material wing rod, a wing membrane 2, a rocker arm connector 3, and a leading edge wing rod rotating component 4.

[0036] like Figure 2 As shown, the bistable composite material wing rod is a three-dimensional, slender beam structure with a circular arc cross-section. This structure is specifically divided into three parts: the leading edge wing rod 101, the root wing rod 102, and the wing membrane support wing rod 103. These parts work together to support and fix the wing surface during deployment, driving the flapping wing to perform a reciprocating flapping motion. When the flapping wing is curled up and folded, this structure utilizes its inherent bistable curling characteristics to curl up and retract along with the wing membrane 2.

[0037] like Figure 3 As shown, the wing membrane 2 is made of coarse benzene fiber, which has the characteristics of being lightweight, thin, and tough, and can withstand repeated tensile and bending stresses during flapping motion; the wing membrane 2 has an asymmetrical curved surface shape, and its planar projection outline is approximately fan-shaped, with sleeves at both ends for the wing rod to pass through.

[0038] like Figure 4As shown, the rocker arm connector 3 has a three-dimensional structure, and its main structure consists of a rocker arm connecting part 301, a rotating shaft part 302, and a rectangular slotted column part 303. The main structure of the rocker arm connecting part 301 is approximately a rectangular plate structure with chamfered edges, and it has through holes for mounting pins to connect with the aircraft fuselage. The main structure of the rotating shaft part 302 is a cylinder, and one end of the cylinder has a coaxial cylindrical rotating shaft for mounting the leading edge wing rod rotating part 4. The rocker arm connecting part 301 is perpendicular to the rectangular slotted column part 303 and connected to the side of the cylinder. One end of the rectangular slotted column part 303 has a rectangular groove for inserting and installing the root wing rod 102.

[0039] like Figure 5 As shown, the leading edge wing rod rotating component 4 has a three-dimensional structure and is mounted on the rotation axis of the rocker arm connector 3, enabling the installation and rotation of the leading edge wing rod 101. This component consists of two main parts: a cylindrical sleeve and a rectangular slotted column, which are integrated into a single structure through a coplanar transition. The cylindrical sleeve is coaxial with the rotation axis of the rocker arm connector 3, and its inner hole can fit snugly against the rotation axis. The outer wall of the sleeve has a small protrusion 401 for limiting rotation. One end of the rectangular slotted column is connected to the cylindrical sleeve, and the other end has a rectangular slot for inserting and installing the leading edge wing rod 101.

[0040] The large flapping wing structure with a large flapping ratio that can be rolled up and folded is characterized in that the position of the boss 401 of the leading edge wing rod connector 4 should be matched by reasonable calculation and design to meet the limiting function in the unfolded state. At this time, the wing membrane 2 can open to a suitable degree, so that the flapping wing structure generates the largest possible lift when flapping.

[0041] The large flapping wing structure with a large flapping ratio that can be rolled up and folded is characterized in that the geometric dimensions of the bistable composite material wing rod (such as length, cross-sectional arc central angle, etc.) should be designed through reasonable calculation, taking into account the strength during flapping and the curling performance during folding, and the rectangular slotted column channel of the rocker arm connector 3 and the leading edge wing rod rotating component 4 should match the designed bistable composite material wing rod.

[0042] The large flapping wing structure with a large flapping ratio that can be rolled up and folded is characterized in that the sleeve of the wing membrane 2 can rotate around the bistable composite material wing rod when the flapping wing structure flaps, which is more conducive to generating an angle of attack with excellent aerodynamic performance than the fixed bonding method.

[0043] The method for implementing a large folding-ratio flapping wing structure is characterized in that, when the flapping wing structure is retracted, the leading edge wing rod rotating member 4 is rotated 90°, and the position and direction of the wing membrane support wing rod 103 adhered to the wing membrane 2 are adjusted so that the wing rod coincides with the leading edge wing rod 101 and the root wing rod 102. At the same time, the wing membrane 2 is combed to make the fold flat, and the wing rod and the folded wing membrane 2 are rolled up together, utilizing the inherent rolling characteristics of the bistable material to achieve storage; when the flapping wing structure is unfolded, the rolled wing rod and wing membrane 2 are straightened, and the leading edge wing rod rotating member 4 is rotated to the boss 401 limit position to ensure the subsequent flapping wing movement.

[0044] The installation method of the large flapping wing structure that can be rolled up and folded:

[0045] (1) The cylindrical sleeve of the leading edge wing rod rotating part 4 is fitted with the rotating shaft of the rocker arm connecting part 3;

[0046] (2) Insert the leading edge wing rod 101 and the root wing rod 102 into the rectangular slotted column groove of the rocker arm connector 3 and the leading edge wing rod rotating part 4 respectively. At this time, after the leading edge wing rod rotating part 4 is retracted, the directions of the leading edge wing rod 101 and the root wing rod 102 should be consistent.

[0047] (3) The sleeves at both ends of the wing membrane 2 are fitted onto the leading edge wing rod 101 and the root wing rod 102 respectively, and rubber rings are installed on both sides to restrict the sliding of the sleeves on the wing rods;

[0048] (4) Fix the wing support rod 103 to the wing membrane 2 by adhesive bonding. At this time, the extension line of the wing rod should pass through the rotation axis of the rocker arm connector 3, and ensure that the three wing rods are in the same direction when retracted.

Claims

1. A large flapping wing structure that can be rolled up and folded, mounted on a flapping wing micro-aircraft, comprising a bistable composite material wing rod, a wing membrane, a rocker arm connector, and a leading-edge wing rod rotating component, characterized in that: The bistable composite material wing rod is a three-dimensional, slender beam structure with a circular arc cross-section, enabling both curling and folding behavior while ensuring high bending stiffness during deployment. The structure is specifically divided into three parts: the leading-edge wing rod, the root wing rod, and the wing membrane support wing rod. These parts work together to support and fix the wing surface, driving the flapping wing in a reciprocating flapping motion. When the flapping wing curls and folds, the structure, upon reaching a threshold external load, activates its inherent bistable switching characteristics, causing the wing membrane to curl and retract. When the flapping wing deploys, the structure, under the centrifugal force generated by the flapping wing, autonomously ejects outward, straightening the wing membrane. The wing membrane material is coarse benzene fiber, which has the characteristics of being lightweight, thin, and highly tough, and can withstand repeated tensile and bending stresses during flapping motion; the wing membrane has an overall asymmetrical curved surface shape, and its planar projection outline is approximately fan-shaped, with sleeves at both ends for the wing rod to pass through. The rocker arm connector has a three-dimensional structure, consisting of a rocker arm connecting part, a rotating shaft part, and a rectangular slotted column part. The main structure of the rocker arm connecting part is approximately a rectangular plate with chamfered edges and through holes for mounting pins to connect to the aircraft fuselage. The main structure of the rotating shaft part is cylindrical, with a coaxial cylindrical rotating shaft at one end for mounting the leading edge wing rod rotating component. The rocker arm connecting part is perpendicular to the rectangular slotted column part and connected to the side of the cylinder. One end of the rectangular slotted column part has a rectangular groove for inserting and installing the root wing rod. The leading-edge wing rod rotating component is a three-dimensional structure, mounted on the rotation axis of the rocker arm connector, enabling the installation and rotation of the leading-edge wing rod. This component consists of two main parts: a cylindrical sleeve and a rectangular slotted column, which are integrated into a single structure through a coplanar transition. The cylindrical sleeve is coaxial with the rotation axis of the rocker arm connector, and its inner hole can fit snugly against the rotation axis. The outer wall of the sleeve has small bosses for limiting rotation. One end of the rectangular slotted column is connected to the cylindrical sleeve, and the other end has a rectangular slot for inserting and installing the leading-edge wing rod.

2. The large flapping wing structure with a rollable and foldable aspect ratio as described in claim 1, characterized in that, The position of the boss of the leading edge wing rod connector should be matched by reasonable calculation and design to meet the function of limiting when in the deployed state. At this time, the wing membrane can open to a suitable degree so that the flapping wing structure can generate the maximum lift when flapping.

3. The large flapping wing structure with a rollable and foldable aspect ratio as described in claim 1, characterized in that, The geometric dimensions (such as length, central angle of cross-section arc, etc.) of the bistable composite material wing rod should be designed through reasonable calculations, taking into account both the strength during flapping and the curling performance during retraction. Furthermore, the rectangular slotted column channels of the rocker arm connector and the leading edge wing rod rotating component should match the designed bistable composite material wing rod.

4. The large flapping wing structure with a rollable and foldable aspect ratio as described in claim 1, characterized in that, The sleeve of the wing membrane can rotate around the bistable composite material wing rod when the flapping wing structure flaps, which is more conducive to generating an angle of attack with excellent aerodynamic performance compared to the fixed bonding method.

5. The method for realizing a large flapping wing structure with a rollable and foldable aspect ratio as described in claims 1-4, characterized in that, When the flapping wing structure is retracted, the leading edge wing rod rotating component is rotated 90°, and the position and direction of the wing membrane support wing rod adhered to the wing membrane are adjusted so that the wing rod coincides with the leading edge wing rod and the root wing rod. At the same time, the wing membrane is combed to make the fold flat, and the wing rod and the folded wing membrane are rolled up together, utilizing the inherent rolling characteristics of the bistable material to achieve storage. When the flapping wing structure is deployed, the rolled-up wing rod and wing membrane are straightened, and the leading edge wing rod rotating component is rotated to the boss limit position to ensure the subsequent flapping wing movement.

6. An installation method for a large flapping wing structure with a rollable and foldable flapping ratio as described in any one of claims 1-4: (1) The cylindrical sleeve of the leading edge wing rod rotating part is fitted with the rotating shaft of the rocker arm connector; (2) The leading edge wing rod and the root wing rod are respectively inserted into the rectangular slotted column groove of the rocker arm connector and the leading edge wing rod rotating part. At this time, the directions of the leading edge wing rod and the root wing rod should be consistent after the leading edge wing rod rotating part is retracted; (3) The sleeves at both ends of the wing membrane are respectively fitted onto the leading edge wing rod and the root wing rod, and rubber rings are installed on both sides to restrict the sliding of the sleeves on the wing rods; (4) The wing membrane support wing rod is fixed on the wing membrane by adhesive. At this time, the extension line of the wing rod should pass through the rotating shaft of the rocker arm connector, and the directions of the three wing rods should be consistent when retracted.

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