A fixed-wing catapult-launched unmanned aerial vehicle launcher and a design method thereof

Abstract

The application discloses a fixed-wing launching type unmanned aerial vehicle launching device and a design method thereof, and belongs to the field of unmanned aerial vehicles.The launching device comprises a launching frame slide rail, launching supports, supporting assemblies, launching supports and launching ribs.Two launching supports are slidably arranged on the launching frame slide rail.The top end of each launching support is fixedly provided with a supporting assembly, which supports and limits the launching support.Two launching supports are symmetrically arranged below the wings, and are respectively and fixedly connected with the launching ribs symmetrically arranged in the wings.The bottom surface of the launching rib is glued and fixed to the inner wall of the lower wing surface skin.The end of the launching support facing the trailing edge of the wing is detachably limited and matched with the supporting assembly, so that the launching support can only displace along the launching direction.The device adopts a long strip supporting mode, and the force transmission path is reasonably designed through the research on the force transmission path, so that the load is evenly distributed, and there is no stress concentration phenomenon.The design and research of the force transmission path provide actual technical guidance for engineering practice.

Description

Technical Field

[0001] This invention belongs to the field of unmanned aerial vehicles (UAVs), specifically relating to a fixed-wing catapult-launched UAV launcher and its design method. Background Technology

[0002] Catapult-launched fixed-wing drones, unlike traditional runway-launched fixed-wing drones, do not require a runway for takeoff. They can be launched from confined spaces, uneven terrain, or even from mobile platforms such as vehicles and ships, thus having lower requirements for launch sites. Furthermore, the drone can take off simply by being mounted and secured on the catapult mount. Therefore, this takeoff method is widely used in the field of small drones.

[0003] When launching a drone by catapult, the catapult-type fixed-wing drone is mounted on the catapult support of the launch device. After receiving the catapult energy, the catapult support propels the drone forward along a fixed track and accelerates continuously. At the same time, the drone on the catapult support also receives continuous acceleration along with the catapult support. After the drone reaches the predetermined speed, the catapult support decelerates rapidly under the action of the designed energy absorption device, and the drone detaches from the catapult support under the action of inertia and continues to move forward at the predetermined speed to complete the takeoff.

[0004] The key design considerations for catapult-launched fixed-wing UAV launchers lie in the connection method and force transmission mechanism between the catapult support and the UAV. Common launcher support configurations include four-point, three-point, and two-point configurations. The four-point configuration features four hooks under the UAV wing, which connect to the catapult support. The two rear hooks primarily support the UAV, holding it aloft on the support and freeing it from catapult thrust; the two front hooks are subjected to catapult thrust. The four-point configuration incorporates a limit mechanism to restrict forward movement of the UAV due to engine vibration or large thrust. However, the four-point structure is complex, with a complex force distribution. Uneven force distribution during launch can introduce significant additional bending moments, potentially damaging the airframe's strength and compromising structural safety and launch lifespan. A three-point launch system includes two wing support components and one front or rear pivot. Because the front or rear pivot can interfere with the propeller launch channel of a fixed-wing UAV located at the tail, a separate release control mechanism is needed to prevent this interference. At the moment the UAV leaves the launch pad, the front or rear pivot collapses to clear the launch channel, allowing for a successful launch. However, designing this pivot release control mechanism is difficult, requiring precise calculation of the release timing. Furthermore, repeated ejection flights accelerate wear and tear on the mechanism, making use and maintenance inconvenient. A two-point system has two pivots located on either side of the wing, providing both support and ejection thrust. It typically involves complex limiting mechanisms and self-locking devices to prevent premature detachment due to engine vibration and ejection thrust, which could lead to launch accidents. The two-point structure is also complex and has high maintenance costs, failing to meet the design principles of low cost and high reliability for UAVs.

[0005] Besides the fulcrum configuration, the force transmission method at the fulcrum directly affects the safety and lifespan of the UAV. Because UAV catapult takeoff requires acquiring a large amount of kinetic energy in a very short time, the instantaneous catapult overload on the UAV body during launch is high, placing higher demands on the UAV's structural strength design. To effectively transfer the catapult load from the catapult fulcrum to the UAV's main beam, thereby propelling the entire UAV into takeoff and ensuring the airframe remains undamaged during catapult launch, a reasonable force transmission path must be designed for the launch fulcrum. Existing 4-fulcrum, 3-fulcrum, and 2-fulcrum configurations do not offer a clear design method for the catapult load force transmission path. Most rely on past experience, performing simple engineering calculations to verify the airframe strength after the UAV design is completed, to meet the catapult strength design requirements for fixed-wing UAVs. Because a reasonable force transmission path design is not fully considered during the design phase, unexpected design flaws often occur, such as skin tearing, fulcrum deformation, and screw connection failure. Currently, there is limited research on the design of catapult thrust transmission paths, and there are no specific design methods or criteria, which cannot provide practical technical guidance for engineering practice. Therefore, it is urgent to summarize a set of design methods for fixed-wing UAV launch devices to guide practical engineering applications and solve the aforementioned problems encountered by catapult-launched fixed-wing UAVs. Summary of the Invention

[0006] The technical problem to be solved:

[0007] To overcome the shortcomings of existing technologies, this invention provides a fixed-wing catapult-launched UAV launcher and its design method. It changes the traditional launcher's fulcrum support method by installing strip-shaped launch ribs inside the wing, fixing catapult supports that mate with the launch ribs under the wing, and installing support components matching the catapult supports on the catapult bracket. This achieves strip-shaped fulcrum support for both wings. Furthermore, by studying the force path of the launcher, it solves the problems of complex structure, uneven catapult force, and potential damage to the airframe inherent in existing launcher support methods. Simultaneously, it provides a systematic launcher design method.

[0008] The technical solution of the present invention is: a fixed-wing catapult-type UAV launch device, including a catapult slide rail and a catapult bracket slidably mounted on the catapult slide rail for supporting the UAV; two catapult brackets are provided and symmetrically mounted on both sides of the catapult slide rail along their sliding direction;

[0009] It also includes a support assembly, a catapult mount, and a launch rib; each catapult mount has a support assembly fixedly installed at its top to support and limit the catapult mount; two catapult mounts are symmetrically installed under the wings on both sides of the UAV, corresponding one-to-one with and fixedly connected to two launch ribs symmetrically installed inside the wings on both sides; the launch ribs are strip-shaped, with their bottom surface fixed to the inner wall of the lower wing skin, and their end facing the leading edge of the wing abutting against the inner main spar of the wing; the end of the catapult mount facing the trailing edge of the wing is separably limited to the support assembly, which restricts the catapult mount to displacement only in the direction of travel when it is launched and slid along the catapult mount within the supported plane.

[0010] A further technical solution of the present invention is as follows: the support assembly includes a support body and a stop block. The support body is provided with a U-shaped groove along the axial direction, and its groove opening faces the top of the catapult bracket and is sleeved and fixed thereto. The stop block is installed on one end of the catapult bracket near the trailing edge of the wing and is sleeved on the support body. The stop block is a U-shaped plate structure, including two side plates and a top plate. The side plates are fixedly connected to the catapult bracket. The top plate is provided with an inner groove at the end facing the leading edge of the wing for limiting and cooperating with the boss at the end of the catapult bracket facing the trailing edge of the wing.

[0011] A further technical solution of the present invention is as follows: the main body of the ejection support is strip-shaped, with its top surface in contact with the lower wing skin surface of the wing; its bottom surface is parallel to the horizontal plane of the UAV body and in contact with the upper surface of the support; the end of the ejection support facing the leading edge of the wing has a partially spherical structure to reduce air resistance; the ejection support has a boss at its spherical end, which is embedded in the inner groove of the stop block and limited by the top plate and the two side plates; the ejection support has two through holes along its length, which penetrate the ejection support and are perpendicular to the bottom surface of the ejection support, for passing through screws and launching ribs for connection.

[0012] A further technical solution of the present invention is: the ejection support is provided with a weight-reducing groove for reducing the weight of the ejection support; the groove opening faces the top surface of the ejection support, the weight-reducing groove is arranged along the strip length direction of the ejection support, and avoids the through hole.

[0013] A further technical solution of the present invention is: a push block is provided at one end of the launch rib for abutting against the inner main beam of the wing; the bottom surface of the launch rib is glued to the inner wall of the lower wing skin of the wing; the launch rib is provided with screw holes corresponding to the two through holes of the ejection support for fixed connection with the ejection support by screws.

[0014] A further technical solution of the present invention is: the launching rib is provided with a weight reduction groove, which is located on the top surface of the launching rib and is used to reduce the weight of the launching rib.

[0015] A design method for the fixed-wing unmanned aerial vehicle (UAV) launcher includes the following:

[0016] S100. Design of the geometry and installation position of the catapult fulcrum:

[0017] The ejection support and launch ribs are designed in a strip-shaped fulcrum configuration, symmetrically supporting the wings on both sides of the fuselage through the ejection support and launch ribs. The length of the strip-shaped ejection support is greater than the theoretical front and rear limits of the UAV's center of gravity. Taking the UAV's nose position as the coordinate zero point (unit: cm), calculate the length of the ejection support and its axial installation position:

[0018] L leading_edge <L Gmin -2cm (1)

[0019] L trailing_edge >L Gmax +2cm (2)

[0020] L all ≥L trailing_edge -L leading_edge (3)

[0021] In the formula: L Gmax L represents the maximum permissible rear limit of the drone's center of gravity. Gmin L represents the maximum permissible front limit of the drone's center of gravity. all L represents the length of the ejection support. leading_edge Indicates the position of the leading edge of the ejection support, L trailing_edge Indicates the position of the rear edge of the ejection support;

[0022] Calculation of the height of the ejection support:

[0023] h≥2t (4)

[0024] In the formula: h represents the height of the catapult support, and t represents the connection thickness of the screw that passes through the catapult support and the threaded connection of the launching rib.

[0025] The width of the ejection support is determined based on the diameter of the screws connecting the ejection support and the launch rib.

[0026] Calculation of the span between the two ejection mounts on both sides of the fuselage:

[0027] L p ≥W L +5cm (5)

[0028] In the formula: L p W represents the span between the ejection mounts on both sides of the fuselage. L Indicates the width of the propeller launch channel;

[0029] S200. Ejection pivot strength design:

[0030] Calculations were performed using the screw closest to the trailing edge of the wing, connecting the ejection mount and the launch rib, as the weakest point under stress, to preliminarily determine the screw type:

[0031] Because there is a distance δ between the bottom surface of the catapult support and the center of gravity of the drone. L An additional torque will be generated during launch.

[0032] m δ =F thrust ·δ L (6)

[0033] In the formula: F thrust This indicates the ejection load, calculated based on a 20-fold overload.

[0034] F thrust =20×Mg (7),

[0035] In the formula: M represents the weight of the drone, and g represents the acceleration due to gravity;

[0036] Force analysis during drone launch: The drone is subjected to a ejection thrust F1 and a support force F2 from the ejection support, and its own weight G, where F1 = F2. thrust The ejection thrust and the center of gravity are separated by a distance d1, where d1 = δ L The ejection thrust will introduce an additional bending moment M1, M1 = m δ The supporting force F2 generates a torque M2. M1 and M2 are in equilibrium, so M2 = M1.

[0037] Force analysis of the screws on both sides of the fuselage near the trailing edge of the wing: They are subjected to the ejection thrust F1, the tension F3 generated by the UAV on the ejection support, the reaction force F1' of F1, and the reaction force F3' of F3.

[0038] The screw is subjected to shear and tension forces simultaneously due to the ejection thrust and the additional bending moment:

[0039]

[0040] Where: N V and N t These represent the design values ​​of the shear force and tensile force that the screw can withstand, respectively. and These represent the design values ​​for the shear and tensile bearing capacities of the screw, respectively.

[0041] The design shear force for a single-sided screw is:

[0042] N V =F thrust / 2 (9)

[0043] The tensile force borne by a single-sided screw is generated by an additional bending moment, the value of which is:

[0044] N t =m δ / (2×L all(10)

[0045] Design value of screw shear capacity:

[0046]

[0047] In the formula: A b Indicates the cross-sectional area of ​​the screw. Indicates the shear design strength of the screw;

[0048] Design value of tensile bearing capacity of screw:

[0049]

[0050] In the formula: f t b To determine the tensile design strength of the screw, you need to consult the design documentation.

[0051] The screw diameter design is obtained from equations (8) to (12):

[0052]

[0053] in,

[0054] The minimum value of the screw thread major diameter d is obtained from equations (13) and (14); the screw specification is selected based on the calculation results.

[0055] S300. Ejection fulcrum force transmission design:

[0056] Based on the d value calculated using S200, verify the bearing capacity of the screw hole wall:

[0057]

[0058] Where: N V This indicates the design value of the shear force that the screw must withstand. This indicates the design value for the bearing pressure of the screw hole wall;

[0059]

[0060] In the formula: d represents the major diameter of the screw thread, and t represents the minimum total thickness of the connector under pressure, which is the connection thickness of the screw and the threaded connection of the launching rib. Indicates the screw's bearing capacity design strength;

[0061] According to formulas (15) and (16), it is determined whether the screw diameter meets the hole wall bearing strength requirements. If it does not meet the requirements, it is necessary to increase the major diameter d of the thread, increase the thread connection thickness t, or change the screw material to a material with greater bearing strength until the hole wall bearing strength requirements are met.

[0062] The width of the ejector support and the width of the launch rib are calculated based on the final determined major diameter d of the thread. The width of the ejector support and the width of the launch rib ensure the installation of the screw.

[0063] S400 Weight Reduction and Rent Reduction Optimization Design:

[0064] The launch ribs, ejection supports, and stops are made of aluminum alloy sheets, and the launch ribs and ejection supports are designed with strip-shaped weight reduction grooves to reduce weight; the end of the ejection support facing the leading edge of the wing is spherical to reduce air resistance.

[0065] A further technical solution of the present invention is as follows: the calculation method for the width of the catapult support and the width of the launching rib is as follows:

[0066] W1≥2×1.5×d (17)

[0067] In the formula: W1 is the width of the catapult support;

[0068] W2≥2×1.5×d (18)

[0069] In the formula: W2 is the width of the launching rib.

[0070] A further technical solution of the present invention is that the length L2 of the launch rib is determined based on the span W3 of its two connecting screws and the wing chord length c.

[0071] W3 <L2<c (19)

[0072] The area of ​​the adhesive bonding region of the launching rib is:

[0073] S g =W2·L2 (20)

[0074] The adhesive bonding area of ​​the launch rib transmits the ejection thrust, and the adhesive bonding strength of the adhesive bonding area meets the following requirements:

[0075]

[0076] Determine whether the bonding strength meets the requirements according to formula (21). If it does not meet the requirements, increase the bonding area S. g .

[0077] A method for designing the skin thickness of a UAV using the design method of the fixed-wing UAV launcher:

[0078] The skin thickness meets the shear strength requirements:

[0079]

[0080] In the formula, σ b_c S represents the skin shear strength. c Represents the shear cross-sectional area;

[0081] S c =2×L2×δ c (twenty three)

[0082] In the formula δ c This represents the skin thickness, i.e., the minimum skin thickness; if the current skin shear strength is insufficient, the skin thickness δ is increased. c Or the length of the launching rib, L2.

[0083] Beneficial effects

[0084] The beneficial effects of the present invention are as follows: The invention provides a fixed-wing catapult-type UAV launch device and its design method. The launch device uses a long strip support method to support the wings of the fixed-wing UAV. Compared with the traditional catapult support of 4-point, 3-point and 2-point forms, it has the advantages of simple structure, high reliability, no complex transmission mechanism and simple manufacturing process.

[0085] This invention symmetrically installs two strip-shaped launch ribs along the wing chord direction inside the wing. Their bottom surfaces are glued to the wing skin, and the front end of the launch rib, facing the wing leading edge, contacts the inner wing main spar via a push block. The upper and lower surfaces of the main spar and the wing skin are bonded together with epoxy adhesive. A strip-shaped ejection support is installed below each launch rib, and the two are connected by screws, transmitting thrust to the launch rib through the ejection support. The two ejection supports are supported by two corresponding ejection brackets, and limited by stops installed on top of the ejection brackets. The ejection thrust is transmitted from the ejection brackets to the ejection supports, then from the ejection supports to the launch ribs, and finally through the shear flow between the bottom surface of the launch rib and the wing skin to the main spar. This optimized force transmission path ensures even load distribution, eliminates stress concentration, and extends the device's service life. The stops limit the lateral and rearward displacement of the ejection supports, ensuring that they can only be ejected along their forward thrust direction, guaranteeing stability during UAV support and ejection.

[0086] The catapult support of this invention is detachable, enabling the compatible UAV to support both catapult and runway dual-mode take-off and landing. When used for runway take-off, only the catapult support needs to be removed.

[0087] The launching device of this invention is small in size and light in weight, which plays a positive role in reducing the weight of the UAV system and reducing air resistance. At the same time, the load-bearing components such as the ejection support, ejection bracket, and stop are all made of aluminum alloy, which is lightweight, low in cost, and easy to use and maintain.

[0088] The launch device design method provided by this invention offers a set of design guidelines for fixed-wing UAV launch devices. This method conducts detailed research and calculation on the catapult thrust transmission path, which is of significance for guiding practical engineering applications and can effectively solve the problems of skin tearing, fulcrum deformation and connecting screw failure that may occur in existing launch device support methods. Attached Figure Description

[0089] Figure 1 A schematic diagram of the overall structure of a fixed-wing catapult-launched UAV launcher.

[0090] Figure 2 Front view of the overall structure of a fixed-wing catapult-launched UAV launcher;

[0091] Figure 3 A schematic diagram showing the support state between the top of the ejection support and the ejection base;

[0092] Figure 4 This is a schematic diagram showing the installation of the support and stop at the top of the catapult bracket;

[0093] Figure 5 This is a schematic diagram showing the installation of the ejection support under the wing;

[0094] Figure 6 This is a schematic diagram of the ejection support structure;

[0095] Figure 7 This is a schematic diagram of the block's structure;

[0096] Figure 8 This is a schematic diagram of the launching rib structure;

[0097] Figure 9 This is a schematic diagram showing the installation and stress of the launch ribs inside the wing.

[0098] Figure 10 This is the bonding area between the ribs and the skin;

[0099] Figure 11 This is a cross-sectional structural diagram of the connection support between the launching device and the wing of the present invention;

[0100] Figure 12 for Figure 11 Enlarged view of point A in the middle;

[0101] Figure 13 This is a flowchart illustrating the design of the launching device of the present invention;

[0102] Figure 14 This is a force analysis diagram of the drone during ejection;

[0103] Figure 15 This is a force analysis diagram of the ejection support during drone ejection;

[0104] Figure 16 This diagram shows the stress analysis of the screws connecting the catapult support and the launch rib near the trailing edge of the wing.

[0105] Explanation of reference numerals in the attached drawings: 1. Catapult rail, 2. Catapult support, 3. Support assembly, 31. Support body, 32. Stop block, 321. Side plate, 322. Top plate, 323. Inner groove, 4. Catapult support, 41. Boss, 42. Through hole, 43. Weight reduction groove, 5. Launch rib, 51. Push block, 52. Screw hole, 53. Weight reduction groove, 54. Adhesive area on the bottom surface of the launch rib, 55. Adhesive leakage hole, 6. UAV, 7. Wing, 71. Lower wing skin, 72. Upper wing skin, 73. Wing leading edge, 74. Wing trailing edge, 75. Main beam, 8. Screw. Detailed Implementation

[0106] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0107] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0108] Example 1:

[0109] This embodiment provides a fixed-wing catapult-type UAV launcher, which uses a long strip support to support the two wings of the UAV. It has a simple structure, uniform force distribution, high reliability, and no complex transmission mechanism or limiting mechanism.

[0110] See Figure 1 , 2 This embodiment provides a fixed-wing catapult-launched UAV launcher, including a catapult rail 1 and a catapult support 2 slidably mounted on the catapult rail 1, capable of sliding along the catapult rail 1 to support the UAV 6. In this embodiment, two catapult supports 2 are provided, symmetrically mounted on both sides of the catapult rail 1 along their sliding direction. The catapult supports 2 are vertically arranged plate-shaped supports, slidably connected to the catapult rail 1. To reduce weight, irregular weight-reduction holes are provided on the wall panels of the catapult supports 2. The catapult rail 1 is mounted on the UAV launch vehicle, and the catapult supports 2, driven by the vehicle-mounted pneumatic catapult system, can instantly acquire a large amount of kinetic energy to slide along the catapult rail 1.

[0111] See Figure 3 , 47, 11, the launching device in this embodiment also includes a support assembly 3, an ejection support 4, and a launching rib 5. Each ejection bracket 2 has a support assembly 3 fixedly installed at its top to support and limit the ejection support 4. Specifically, the support assembly 3 includes a support body 31 and a stop block 32. The support body 31 is a long strip-shaped shell with a U-shaped through groove along its length. The groove opening faces downwards and fits onto the top of the ejection bracket 2, and the two are fixedly connected by three connecting bolts. The stop block 32 is installed at one end of the ejection bracket 2 near the trailing edge 74 of the wing. The stop block 32 has a U-shaped plate structure, including side plates 321 on both sides and a top plate 322. The U-shaped opening of the stop block 32 fits downwards onto the support body 31, and its side plates 321 and the support body 31 are fixedly connected to the ejection bracket 2 by three connecting bolts. A gap is left between the top plate 322 and the support body 31. The top plate 322 has an inner groove 323 on the end facing the leading edge 73 of the wing, which is used to separate and limit the engagement with the ejection support 4.

[0112] See Figure 5-6 8-11, Two catapult supports 4 are symmetrically installed below the wings 7 on both sides of the UAV 6, corresponding one-to-one with and fixedly connected to the two launch ribs 5 symmetrically installed inside the wings 7 on both sides of the UAV. Specifically:

[0113] The launch rib 5 is strip-shaped and arranged along the wing chord. Its bottom surface is bonded to the inner wall of the lower wing skin 71 of the wing 7 with epoxy adhesive. A pusher block 51 is provided at the end facing the leading edge 73 of the wing to abut against the inner main sparsity 75 of the wing. The skin 71 and the main sparsity 75 are bonded together with epoxy adhesive. The top surface of the launch rib 5 facing the trailing edge 74 of the wing contacts the inner wall of the upper wing skin 72. The launch rib 5 has two glue leakage holes 55 perpendicular to its bottom surface and penetrating the rib 5 along its length, allowing excess adhesive to flow out when the bottom surface of the launch rib 5 is glued.

[0114] The ejection support 4 is strip-shaped, with its top surface conforming to the lower wing surface of the wing 7 and contacting the lower wing skin 71. Its bottom surface is parallel to the horizontal plane of the fuselage and contacts the upper surface of the support 31, thus supporting the UAV 6. The end of the ejection support 4 facing the leading edge 73 of the wing has a partially spherical structure to reduce air resistance during ejection. A wedge-shaped protrusion 41 is provided at the end of the ejection support 4 away from its spherical end, i.e., towards the trailing edge 74 of the wing. The protrusion 41 is embedded in the inner groove 323 of the stop block 31. The rear end face of the ejection support 4, located above the protrusion 41, abuts against the top plate 322 of the stop block 32 to transfer the ejection load and limit the backward movement of the UAV. The side plates 321 of the stop block 32 provide lateral restraint to the protrusion 41. Through the restraint of the stop block 32, the ejection support 4 can only move in the direction of travel during the ejection sliding of the ejection support 2 within the supported plane. The tail boss 41 of the ejection support 4 and the inner groove 323 of the upper stop block 32 of the ejection bracket 2 cooperate to prevent the UAV 6 from disengaging prematurely due to engine vibration or thrust before it leaves the frame.

[0115] The ejection support 4 has two through holes 42 along its length, which penetrate the ejection support 4 and are perpendicular to its bottom surface. These through holes 42 are used to pass through the screw 8 and the launching rib 5 for fixed connection. Correspondingly, the launching rib 5 has screw holes 52 that correspond one-to-one with the two through holes of the ejection support 4. During connection, the screw 8 passes through the ejection support 4 and the lower wing skin 71 from bottom to top, and the threaded part of the screw 8 is threadedly connected to the screw hole 52 of the launching rib 5.

[0116] Depending on the specific structure of the UAV 6, the ejection support 4 can also be installed under the blended wing-body.

[0117] See Figure 6 , 8 To reduce weight, the ejection support 4 has a strip-shaped weight-reducing groove 43 along its length. The groove opening of the weight-reducing groove 43 faces the top surface of the ejection support 4 and avoids the through hole 42 to avoid affecting the connection strength between the screw 8 and the launching rib 5. At the same time, the launching rib 5 also has a weight-reducing groove 53 for weight reduction. The weight-reducing groove 53 of the launching rib 5 is located on the top surface of the launching rib 5 and is arranged along its length.

[0118] In use, launch ribs 5 are symmetrically installed inside the wings 7 on both sides of the UAV. Two ejection supports 4 are then fixedly installed below the launch ribs 5 on both sides. The UAV 6 is then placed on the ejection bracket 2, with the ejection supports 4 at the bottom of the wings 7 placed on the corresponding supports 31 on both sides. Simultaneously, the protrusions 41 of the ejection supports 4 are embedded in the grooves 323 of the stop blocks 31 to form a limit, allowing the UAV 6 to be launched. During launch, the ejection bracket 2, driven by the vehicle-mounted pneumatic ejection system, instantly gains a large amount of kinetic energy due to the release of air pressure, accelerating forward along the ejection rack rail 1, thus accelerating the UAV 6. When the UAV 6 reaches the predetermined speed, the ejection bracket 2 rapidly decelerates under the action of the energy absorption device, and the UAV 6 detaches from the ejection bracket 2 under inertia, completing takeoff.

[0119] The ejection support 4 of this invention supports dual-mode take-off and landing. If the UAV 6 supports taxiing flight, the ejection support 4 can be removed after the landing gear is installed to reduce weight and drag.

[0120] Example 2:

[0121] This embodiment provides a design method for the fixed-wing UAV launcher as described in Embodiment 1. Figure 13 The diagram shown is a design flowchart. This design methodology includes the following:

[0122] S100. Design of catapult fulcrum geometry and installation location:

[0123] Design Concept: The catapult pivot geometry design considers both the static lifting and catapult states of the UAV 6 on the catapult support 2. Integrating the advantages of three types of catapult pivots in the background technology, the four pivot points are connected front and rear, merging into a long strip-shaped pivot. The bottom surface of this strip-shaped pivot supports the UAV but does not bear the catapult thrust. The rear end of the strip-shaped pivot, facing the trailing edge 74 of the wing and the fusion design with the catapult support 2, transmits the catapult thrust. The lower plane of the strip-shaped pivot is required to be parallel to the horizontal plane of the UAV 6 fuselage. At the moment of catapult launch, the UAV's angle of attack should be close to the advantageous angle of attack, i.e., the angle of attack corresponding to the maximum lift-to-drag ratio, thus improving the safety of the UAV's launch flight.

[0124] The elongated fulcrum prevents force imbalance between the front and rear fulcrums during launch, ensuring that the combined force of the launch support 2 and the drone 7 passes through the drone's center of gravity, balancing any additional torque that may be generated by the launch thrust. Before launch, the groove of the stop block 32 on the launch support 2 and the launch bracket 4 fit tightly, restricting the drone 6's backward and left-right displacement. This ensures that the drone 6 will not detach from the launch support in either the stationary state on the launch support 2 or when it is launched from the launch support 2.

[0125] Therefore, this invention adopts a strip-shaped support form, designing the ejection support 4 and launch rib 5 as strips, so that the ejection support 4 and launch rib 5 symmetrically support the wings 7 on both sides of the fuselage. The strip-shaped ejection support 4 is the seat support point, and its length is greater than the theoretical front and rear limits of the center of gravity of the UAV 6. Taking the position of the nose of the UAV 6 as the coordinate zero point, the unit is cm. The length and axial installation position of the ejection support 4 are calculated as follows:

[0126] L leading_edge <L Gmin -2cm (4)

[0127] L trailing_edge >L Gmax +2cm (5)

[0128] L all ≥L trailing_edge -L leading_edge (6)

[0129] In the formula: L Gmax L represents the maximum permissible rear limit of the drone's center of gravity. Gmin L represents the maximum permissible front limit of the drone's center of gravity. all L represents the length of the ejection support 4. leading_edge Indicates the position of the leading edge of ejection support 4, L trailing_edge This indicates the position of the rear edge of the ejection support 4.

[0130] Calculation of the height of ejection support 4: The height of ejection support 4 generally does not affect the strength of the ejection fulcrum. The weak point is usually at the connecting screw, so the value is taken as twice the thickness of the threaded connection.

[0131] h≥2t (4)

[0132] In the formula: h represents the height of the ejection support 4, and t represents the threaded connection thickness, that is, the connection thickness of the screw 8 that passes through the ejection support 4 and the threaded connection of the launching rib 5.

[0133] The width of the ejection support 4 is determined based on the diameter of the screw 8 that connects the ejection support 4 and the launching rib 5.

[0134] Since the two catapult supports 4 are located on both sides of the fuselage, supporting the left and right wings 7 respectively, considering factors such as the propeller launch channel at the rear of the UAV and the strength limitations of the wings 7, the span of the catapult support points must not be less than the width of the propeller launch channel, and the wing strength must be sufficient to withstand the bending moment generated by the catapult thrust on the wing. Therefore, the initial span of the catapult support points can be taken as L. p .

[0135] Calculation of the span of the two ejection supports 4 on both sides of the fuselage:

[0136] L p ≥W L+5cm (5)

[0137] In the formula: L p W represents the span between the ejection mounts 4 on both sides of the fuselage. L This indicates the width of the propeller launch channel.

[0138] S200. Ejection pivot strength design:

[0139] Under normal circumstances, the support force of the ejection fulcrum on the ejection support 2 in the static lifting state should pass through the center of gravity of the UAV to ensure the static stability of the UAV. At the same time, the ejection thrust line should pass through or be as close as possible to the center of gravity of the UAV to minimize the additional bending moment generated during ejection and reduce the strength requirements of the UAV body. The ejection fulcrum is the distance δ between the support surface of the ejection support 4 and the center of gravity. L The smaller the better, we can take δ. L The position = 0 is used as the fulcrum position, but due to limitations in the shape of the UAV (high-wing or low-wing), catapult width limitations, or wing strength limitations, it is impossible to achieve this at δ. L =0, the ejection support 4 is set. At this point, the preliminary design value is given. The distance from the bottom surface of the ejection support 4 on both sides of the UAV to the center of gravity of the UAV is δ. L An additional torque will be generated during launch:

[0140] m δ =F thrust ·δ L (6)

[0141] In the formula: F thrust This represents the ejection load, calculated based on a 20x overload, and its value is:

[0142] F thrust =20×Mg (7),

[0143] In the formula: M represents the weight of the drone, and g represents the acceleration due to gravity.

[0144] The additional torque will act on the drone's body, balancing the supporting force of the ejection mount 4, such as... Figure 14 As shown, when the UAV 6 is launched, it is subjected to the ejection thrust F1 and the support force F2 of the ejection support 2, and the weight of the UAV 6 itself is G, F1 = F thrust There is a distance d1 between the catapult thrust and the center of gravity of the drone, where d1 = δ L The additional bending moment M1 introduced by the catapult thrust is an internal force of the UAV, M1 = m δ The supporting force F2 generates a torque M2, which is an internal force of the drone. M2 and M1 are in balance, so M2 = M1.

[0145] However, during balancing, the UAV body must be able to withstand this additional torque and meet its strength requirements. This additional torque is the nose-down torque, which is applied to the ejection support 4. Since the ejection support 4 is elongated, its front end bears pressure, and its rear end bears tension, as shown in the following stress distribution. Figure 15 As shown, Figure 15 In the diagram, F3 represents the tensile force exerted by the UAV 6 on the catapult support 4, generated by the additional bending moment, and F4 represents the compressive force exerted by the UAV 6 on the catapult support 4, generated by gravity G and the additional bending moment. Since the catapult support 4 is connected to the launch rib 5 fixed inside the wing 7 of the UAV 6 by two identical screws 8 at the front and rear, the screws 8 are required to withstand the combined shear and tensile forces caused by the thrust and the additional bending moment.

[0146] like Figure 16 As shown, screw 8 experiences complex stress conditions due to both ejection thrust and additional bending moment, as well as shear-tension forces. Calculations are performed using screw 8, located near the wing trailing edge 74 and connecting the ejection support 4 and launch rib 5, as the weakest point of stress, to preliminarily determine the appropriate screw type:

[0147] Force analysis of screws 8 located at position 74 near the trailing edge of the wing on both sides of the fuselage: The screws bear the tensile force of the ejection thrust F1; the screws also bear the tensile force of the tension F3 generated by the UAV on the ejection support 4. The reaction force of F1 is F1', and the reaction force of F3 is F3'.

[0148] The shear-tensile force of screw 8 was verified according to the reference bolt connection strength calculation method:

[0149]

[0150] Where: N V and N t These represent the design values ​​of the shear force and tensile force that screw 8 will withstand. and These represent the design values ​​of the shear and tensile bearing capacity of screw 8, respectively.

[0151] The design values ​​for shear and tensile forces borne by the screws take into account a 20-fold ejection overload and gravitational acceleration g. Therefore, the design value for the shear force borne by a single-sided screw 8 is:

[0152] N V =F thrust / 2 (9)

[0153] The tensile force borne by the single-sided screw 8 is generated by an additional bending moment, the value of which is:

[0154] N t =m δ / (2×L all (10)

[0155] Design value of shear bearing capacity of screw 8:

[0156]

[0157] In the formula: A b Indicates the cross-sectional area of ​​the screw. To determine the shear strength of a screw, you need to consult the design documentation.

[0158] Design value of tensile bearing capacity of screw 8:

[0159]

[0160] In the formula: f t b To determine the tensile design strength of the screw, you need to consult the design documentation.

[0161] According to the design principle of formula (12), the only unknown quantity is the cross-sectional area A of screw 8. b That is, the screw specification is unknown. According to equations (8) to (12), the design principle for the screw's major diameter can be obtained, namely:

[0162]

[0163] Since the cross-sectional area of ​​the screw is:

[0164]

[0165] The minimum value of the major diameter d of the screw 8 thread is obtained from equations (13) and (14), and the screw specification is selected based on the calculation results. The subsequent design work of the ejection fulcrum is continued with the screw 8 specification. If the size of the screw 8 can meet the subsequent force transmission strength requirements, the design of the ejection fulcrum position is completed. If it cannot meet the requirements, the process is iterated again to select a suitable screw 8 diameter.

[0166] S300. Ejection fulcrum force transmission design:

[0167] The ejection support 4 is fixedly connected to the launch rib 5 by screws 8. The ejection support 4 is not glued to the UAV body, so the ejection thrust is transmitted only through screws 8. After the launch rib 5 is subjected to the ejection thrust, since its lower surface is glued to the body skin, the ejection thrust will be transmitted to the lower wing skin 71 of the body through the glued area, and then transmitted to the main beam 75 of the UAV through the skin, driving the entire UAV to move.

[0168] The ejection thrust is transmitted to the launching rib 5 through screw 8. Considering the additional bending moment, screw 8 is subjected to shear-tensile loads. Under this stress condition, in addition to causing shear and tensile failure of screw 8, it may also cause pressure failure of the launching rib hole wall.

[0169] Based on the minimum d value calculated using S200, verify the bearing capacity of the screw hole wall (8 holes):

[0170]

[0171] Where: N V This indicates the design value of the shear force that screw 8 will withstand. This indicates the design value for the bearing pressure of the hole wall of screw 8;

[0172]

[0173] In the formula: d represents the major diameter of the screw 8 thread, t represents the minimum total thickness of the connector under pressure, which is the connection thickness of the screw 8 and the launching rib 5 threaded connection, and f c b This indicates the screw's bearing capacity design strength, which needs to be consulted.

[0174] According to equations (15) and (16), determine whether the diameter of screw 8 meets the bearing strength requirements of the hole wall. If it does not meet the requirements, it is necessary to increase the major diameter d of the thread, increase the thread connection thickness t, or change the material of screw 8 to a material with greater bearing strength, i.e., take f. c b Higher, until the borehole wall bearing strength requirement is met.

[0175] The width of the ejector support 4 and the width of the launching rib 5 are calculated based on the final determined major diameter d of the thread. The width of the ejector support 4 and the width of the launching rib 5 ensure the installation of the screw 8.

[0176] Specifically, since screw 8 fixes the ejection support 4 to the launching rib 5, the distance between screw 8 and the edge of the ejection support 4 is 1.5 times the screw diameter. The width W1 of the ejection support 4 is:

[0177] W1≥2×1.5×d (17)

[0178] Similarly, the width W2 of the launching rib 5 is:

[0179] W2≥2×1.5×d (18)

[0180] The length L2 of the launch rib 5 is calculated based on the span W3 of its two connecting screws 8 and the wing chord c. First, a value is selected for calculation, and then the length of the launch rib is corrected based on the calculation result.

[0181] W3 <L2<c (19)

[0182] The launch rib 5 is connected to the fuselage skin by adhesive bonding. The launch rib has a length of L2 and a width of W2. The area of ​​the adhesive bonding region of the launch rib 5 is:

[0183] S g =W2·L2 (20)

[0184] Since the adhesive area of ​​the launching rib 5 transmits the ejection thrust, the adhesive strength σ of the adhesive area... b_g satisfy:

[0185]

[0186] Determine whether the bonding strength meets the requirements according to formula (21). If it does not meet the requirements, increase the bonding area S. g That is, increase the width W2 of the launch rib or increase the length L2 of the launch rib.

[0187] After the ejection thrust is transmitted through the bonded area, a shear flow is formed on the fuselage skin, such as... Figure 9 As shown, this is transferred to the main beam 75 of the fuselage, so the skin thickness design also needs to meet the shear strength requirements:

[0188]

[0189] In the formula, σ b_c This indicates the shear strength of the skin, which is related to the skin material and requires consulting relevant literature; S c This represents the shear cross-sectional area.

[0190] The shear cross-sectional area of ​​the skin is taken as the shear cross-sectional area of ​​the skin on both sides of the radiating rib, and its value is:

[0191] S c =2×L2×δ c (twenty three)

[0192] In the formula δ c This represents the skin thickness, i.e., the minimum skin thickness. If the current skin shear strength is insufficient, the skin thickness δ is increased. c Or the length L2 of the launching rib 5.

[0193] S400 Weight Reduction and Rent Reduction Optimization Design:

[0194] The launch rib 5, ejection mount 4, and stop block 32 are made of aluminum alloy sheet, and strip-shaped weight-reducing grooves are designed for the launch rib 5 and ejection mount 4 to reduce weight. The end of ejection mount 4 facing the wing leading edge 73 is spherical to reduce air resistance. If the ejection-type UAV uses a runway takeoff and landing method, ejection mount 4 can be removed to reduce the weight of the UAV and reduce air resistance.

[0195] Based on the above-described launch device design method, the length L of the ejection support 4 can be confirmed. all Based on the UAV's shape limitations (high-wing or low-wing), catapult range limitations, or wing strength limitations, a suitable catapult fulcrum position can be selected. At this point, the distance between the catapult fulcrum and the UAV's center of gravity δ is... L From this, we can continue to calculate the screw diameter d and the threaded connection thickness t, i.e. Figure 12The connection thickness of the screw 8 that penetrates the ejection support 4 and the threaded connection of the launch rib 5, the width W1 of the ejection support 4 and the width W2 of the launch rib 5, the length L2 of the launch rib 5 and the skin thickness δ c Following the above design process, the main geometric dimensions of the launching device can be obtained. The design of the launching device and the overall structural design of the UAV complement each other. Trade-offs need to be made during the design process, and continuous optimization is necessary to obtain the best design result.

[0196] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A fixed-wing catapult-launched unmanned aerial vehicle (UAV) launcher, comprising a catapult rail and a catapult support slidably mounted on the catapult rail for supporting the UAV; characterized in that, Two ejection brackets are provided and are symmetrically installed on both sides of the ejection bracket slide rail along the sliding direction. It also includes a support assembly, a catapult mount, and a launch rib; each catapult mount has a support assembly fixedly installed at its top to support and limit the catapult mount; two catapult mounts are symmetrically installed under the wings on both sides of the UAV, corresponding one-to-one with and fixedly connected to two launch ribs symmetrically installed inside the wings on both sides; the launch ribs are strip-shaped, with their bottom surface fixed to the inner wall of the lower wing skin, and their end facing the leading edge of the wing abutting against the inner main spar of the wing; the end of the catapult mount facing the trailing edge of the wing is separably limited to the support assembly, which restricts the catapult mount to displacement only in the direction of travel when it is launched and slid along the catapult mount within the supported plane.

2. The fixed-wing catapult-launched UAV launcher according to claim 1, characterized in that, The support assembly includes a support body and a stop block. The support body has a U-shaped groove along the axial direction, with its groove opening facing the top of the catapult support and being sleeved and fixed thereto. The stop block is installed on the end of the catapult support near the trailing edge of the wing and is sleeved on the support body. The stop block has a U-shaped plate structure, including two side plates and a top plate. The side plates are fixedly connected to the catapult support. The top plate has an inner groove at the end facing the leading edge of the wing, which is used to limit and cooperate with the boss at the end of the catapult support facing the trailing edge of the wing.

3. The fixed-wing catapult-launched UAV launcher according to claim 2, characterized in that, The ejection support is strip-shaped, with its top surface contacting the lower wing skin surface of the wing, and its bottom surface parallel to the horizontal plane of the UAV fuselage and in contact with the upper surface of the support. The end of the ejection support facing the leading edge of the wing has a partially spherical structure to reduce air resistance. The ejection support has a boss at its spherical end, which is embedded in the inner groove of the stop block and limited by the top plate and the two side plates. The ejection support has two through holes along its length, which penetrate the ejection support and are perpendicular to the bottom surface of the ejection support, for screws and launch ribs to pass through.

4. The fixed-wing catapult-launched UAV launcher according to claim 3, characterized in that, The ejection support is provided with a weight-reducing groove for reducing the weight of the ejection support; the groove opening faces the top surface of the ejection support, the weight-reducing groove is arranged along the strip length direction of the ejection support, and avoids the through hole.

5. The fixed-wing catapult-launched UAV launcher according to claim 3, characterized in that, One end of the launch rib is provided with a push block for abutting against the inner main beam of the wing; the bottom surface of the launch rib is glued to the inner wall of the lower wing skin; the launch rib is provided with screw holes that correspond one-to-one with the two through holes of the ejection support for fixed connection with the ejection support by screws.

6. The fixed-wing catapult-launched UAV launcher according to claim 5, characterized in that, The launching rib is provided with a weight-reducing groove, which is located on the top surface of the launching rib and is used to reduce the weight of the launching rib.

7. A design method for a fixed-wing catapult-launched UAV launcher as described in claim 5, characterized in that, Includes the following: S100. Design of catapult fulcrum geometry and installation location: A strip-shaped support structure is adopted, with the ejection support and launch ribs designed as strips. The ejection support, in conjunction with the launch ribs, symmetrically supports the wings on both sides of the fuselage. The length of the strip-shaped ejection support is greater than the theoretical front and rear limits of the UAV's center of gravity. Taking the position of the UAV's nose as the coordinate zero point, in cm, calculate the length and axial installation position of the ejection support: (1) (2) (3) In the formula: This indicates the maximum permissible rear limit of the drone's center of gravity. This indicates the maximum permissible front limit of the drone's center of gravity. Indicates the length of the ejection support. Indicates the position of the leading edge of the ejection support. Indicates the position of the rear edge of the ejection support; Calculation of the height of the ejection support: (4) In the formula: Indicates the height of the ejection support. This indicates the connection thickness between the screw that penetrates the ejection support and the threaded connection of the launch rib; The width of the ejection support is determined based on the diameter of the screws connecting the ejection support and the launch rib. Calculation of the span between the two ejection mounts on both sides of the fuselage: (5) In the formula: This indicates the span between the ejection mounts on both sides of the fuselage. Indicates the width of the propeller launch channel; S200. Ejection pivot strength design: Calculations were performed using the screw closest to the trailing edge of the wing, connecting the ejection mount and the launch rib, as the weakest point under stress, to preliminarily determine the screw type: Because there is a distance between the bottom surface of the catapult support and the center of gravity of the drone. An additional torque will be generated during launch. (6) In the formula: This indicates the ejection load, calculated based on a 20-fold overload. （7） In the formula: Indicates the weight of the drone. Represents gravitational acceleration; Force analysis during drone launch: The drone is subjected to the ejection thrust of the ejection support. and support force The drone's own gravity , There is a distance between the ejection thrust and the center of gravity. , Additional bending moment introduced by the catapult thrust. , Support Generate torque , and balance, ; Force analysis of the screws on both sides of the fuselage near the trailing edge of the wing: subjected to catapult thrust The tension generated by the drone on the catapult support , reaction force , reaction force ; The screw is subjected to shear and tension forces simultaneously due to the ejection thrust and the additional bending moment: (8) In the formula: These represent the design values ​​of the shear force and tensile force that the screw can withstand, respectively. These represent the design values ​​for the shear and tensile bearing capacities of the screw, respectively. The design shear force for a single-sided screw is: (9) The tensile force borne by a single-sided screw is generated by an additional bending moment, the value of which is: (10) Design value of screw shear capacity: (11) In the formula: Indicates the cross-sectional area of ​​the screw. Indicates the shear design strength of the screw; Design value of tensile bearing capacity of screw: （12） In the formula: To determine the tensile design strength of the screw, you need to consult the design documentation. The screw diameter design is obtained from equations (8) to (12): (13) in, (14) The minimum value of the screw thread major diameter d is obtained from equations (13) and (14); the screw specification is selected based on the calculation results. S300. Ejection fulcrum force transmission design: Based on the d value calculated using S200, verify the bearing capacity of the screw hole wall: (15) In the formula: This indicates the design value of the shear force that the screw must withstand. This indicates the design value for the bearing pressure of the screw hole wall; (16) In the formula: Indicates the major diameter of the screw thread. This indicates the minimum total thickness of the connector under pressure, taken as the connection thickness of the threaded connection between the screw and the launching rib. Indicates the screw's bearing capacity design strength; Determine whether the screw diameter meets the borehole wall bearing strength requirements according to equations (15) and (16). If it does not meet the requirements, the major diameter of the thread needs to be increased. Increase the thickness of the threaded connection Alternatively, the screw material can be changed to a material with greater compressive strength until the bore wall compressive strength requirement is met. Based on the final determined major diameter of the thread Calculate the width of the ejection support and the width of the launch ribs to ensure the installation of the screws; S400 Weight Reduction and Rent Reduction Optimization Design: The launch ribs, ejection supports, and stops are made of aluminum alloy sheets, and the launch ribs and ejection supports are designed with strip-shaped weight reduction grooves to reduce weight; the end of the ejection support facing the leading edge of the wing is spherical to reduce air resistance.

8. A design method for a fixed-wing catapult-launched UAV launcher as described in claim 7, characterized in that, The calculation methods for the width of the catapult support and the width of the launch rib are as follows: (17) In the formula: The width of the ejection support; (18) In the formula: The width of the launching rib.

9. A design method for a fixed-wing catapult-launched unmanned aerial vehicle (UAV) launcher as described in claim 8, characterized in that, The length of the launching rib Based on the span of its two connecting screws and wing chord Sure, (19) The area of ​​the adhesive bonding region of the launching rib is: (20) The adhesive bonding area of ​​the launch rib transmits the ejection thrust, and the adhesive bonding strength of the adhesive bonding area meets the following requirements: (21) Determine whether the bonding strength meets the requirements according to formula (21). If it does not meet the requirements, increase the bonding area. .

10. A method for designing the skin thickness of a UAV using the design method of the fixed-wing catapult-type UAV launch device as described in claim 9, characterized in that, The skin thickness meets the shear strength requirements: (22) In the formula, Indicates the skin shear strength. Represents the shear cross-sectional area; (23) In the formula This indicates the skin thickness, i.e., the minimum skin thickness; if the current skin shear strength is insufficient, the skin thickness is increased. Or the length of the launching rib .

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