Fixed wing ejection type unmanned aerial vehicle launching device and design method thereof

Abstract

The invention discloses a fixed wing ejection type unmanned aerial vehicle launching device and a design method thereof, and belongs to the field of unmanned aerial vehicles. The launching device comprises an ejection frame sliding rail, an ejection support, a supporting assembly, an ejection support and a launching rib. The two ejection supports are installed on the ejection frame sliding rails in a sliding mode. Supporting assemblies are fixedly installed at the top ends of the ejection supports and used for supporting and limiting the ejection supports. The two ejection supports are symmetrically installed below the wings on the two sides, correspond to the two launching ribs symmetrically installed in the wings on the two sides in a one-to-one mode and are fixedly connected with the launching ribs. And the bottom surface of the launching rib is glued and fixed with the inner wall of the lower airfoil skin. The end, facing the rear edge of the wing, of the ejection support is in separable limiting fit with the supporting assembly, so that the ejection support can only move in the ejection direction. According to the device, a long-strip-shaped supporting mode is adopted, the stress path is researched, so that the force transmission path is reasonable, loads are evenly distributed, the stress concentration phenomenon is avoided, and the design research of the force transmission path provides actual technical guidance for engineering practice.

Description

Technical Field

[0001] The present invention belongs to the field of unmanned aerial vehicles, and in particular relates to a fixed-wing catapult-type unmanned aerial vehicle launching device and a design method thereof. Background Art

[0002] Since catapult-type fixed-wing UAVs can take off without a runway, they are free from the dependence on runways compared to traditional taxiing fixed-wing UAVs. They can be launched on narrow, uneven surfaces or even on mobile platforms such as vehicles and ships, and have lower requirements for launch sites. At the same time, the UAV can take off after being simply installed and fixed on the catapult bracket. Therefore, this take-off method of UAVs is widely used in the field of small UAVs.

[0003] When the UAV is launched by catapult, the catapult-type fixed-wing UAV is installed on the catapult bracket of the launch device. After obtaining the ejection energy, the ejection bracket drives the UAV to continuously accelerate forward along the fixed slide rail. At the same time, the UAV located on the ejection bracket also obtains continuous acceleration with the ejection bracket. After the UAV reaches a predetermined speed, the ejection bracket quickly decelerates under the action of a designed energy absorption device, and the UAV separates from the ejection bracket under the action of inertia, continues to move forward at a predetermined speed, and completes takeoff.

[0004] The key to the design of the ejection-type fixed-wing UAV launcher lies in the fulcrum connection form and fulcrum force transmission method between the ejection bracket and the UAV. The existing common launcher fulcrum forms include 4-fulcrum form, 3-fulcrum form and 2-fulcrum form. The 4-fulcrum form launcher is designed with 4 hooks under the UAV wing, and the hooks are connected to the ejection bracket. The two hooks at the rear are mainly used to support the UAV and lift the UAV on the ejection bracket without being affected by the ejection thrust; the two hooks at the front are affected by the ejection thrust. The 4-fulcrum form launcher is designed with a limited position mechanism, which can limit the forward movement of the UAV caused by engine vibration or large thrust. However, the 4-fulcrum form has a complex structure and a complex force form. The fulcrum is unevenly stressed during ejection, which is easy to introduce a large additional bending moment, which may damage the strength of the fuselage and make it difficult to ensure structural safety and ejection life. The three-point launch device includes two wing support components and a front or rear fulcrum. Since the front or rear fulcrum of the three-point launch device will interfere with the propeller launch channel of the fixed-wing UAV set at the tail of the fuselage, in order to prevent interference, a separate release control mechanism needs to be designed. At the moment the UAV leaves the frame, the front or rear fulcrum falls down to make way for the launch channel, allowing the UAV to be successfully launched. However, the design of the fulcrum release control mechanism is difficult, and the timing of the fulcrum release needs to be strictly calculated. In addition, multiple ejection flights will accelerate the wear of the mechanism, making it inconvenient to use and maintain. The two-point form is that the two fulcrums are arranged under the two sides of the wing, providing support and ejection thrust for the UAV at the same time. Usually, a more complex limit mechanism and self-locking device are designed to prevent the UAV from falling off the frame prematurely due to engine vibration and ejection thrust, causing a launch accident. In addition, the two-point structure is more complex and the maintenance cost is high, which cannot meet the design concept of low cost and high reliability of UAVs.

[0005] In addition to the fulcrum form, the fulcrum force transmission method directly affects the safety and life of the drone. Because the UAV catapult takeoff requires a large amount of kinetic energy in a very short time, the instantaneous ejection overload on the UAV body during launch is relatively high, which puts higher requirements on the strength design of the UAV body. In order to effectively transfer the ejection load from the ejection fulcrum to the main beam of the UAV, thereby driving the entire UAV to take off and ensuring that the body is not damaged during the ejection process, it is required to design a reasonable force transmission path for the launch fulcrum. The existing 4-point form, 3-point form and two-point form do not propose a clear design method for the ejection load transmission path. Most of them follow previous experience. After the UAV design is completed, a simple engineering calculation and verification of the body strength is performed to meet the ejection strength design requirements of fixed-wing UAVs. Due to the failure to fully consider the reasonable force transmission path design during the design stage, unexpected design defects often occur, such as skin tearing, fulcrum deformation, and screw connection failure. At present, there is little research on the design of ejection thrust transmission path, and there are no specific design methods and criteria, which cannot provide practical technical guidance for engineering practice. Therefore, it is urgent to summarize a set of fixed-wing UAV launch device design methods to guide practical engineering applications and solve the above-mentioned problems encountered by ejection-type fixed-wing UAVs. Summary of the invention

[0006] Technical issues to be solved:

[0007] In order to avoid the shortcomings of the prior art, the present invention provides a fixed-wing catapult-type UAV launch device and a design method thereof, which changes the traditional fulcrum support method of the launch device, installs strip-shaped launch ribs inside the wing, fixes an ejection support that cooperates with the launch ribs under the wing, and installs a support component that matches the ejection support on the ejection bracket, thereby realizing strip-shaped fulcrum support for the wings on both sides, and through the study of the force path of the launch device, solves the problems of complex structure, uneven ejection force, and easy damage to the body of the existing launch device support form, and at the same time provides a set of systematic launch device design methods.

[0008] The technical solution of the present invention is: a fixed-wing ejection type UAV launch device, comprising an ejection frame slide rail, an ejection bracket slidably mounted on the ejection frame slide rail and used to support the UAV; the ejection bracket is provided with two, and is symmetrically mounted on both sides of the ejection frame slide rail along the sliding direction thereof;

[0009] It also includes a support assembly, an ejection support and a launching rib; a support assembly is fixedly installed on the top of each ejection support for supporting and limiting the ejection support; two ejection supports are symmetrically installed under the wings on both sides of the UAV, and correspond to and are fixedly connected with two launching ribs symmetrically installed in the wings on both sides; the launching rib is strip-shaped, and the bottom surface of the launching rib is fixed to the inner wall of the lower wing skin, and the end facing the leading edge of the wing is against the main beam inside the wing; the end of the ejection support facing the trailing edge of the wing is detachably limited and cooperated with the support assembly, which is used to limit the ejection support within the supported plane, and can only be displaced along the direction of travel when the ejection support is ejected and slid.

[0010] A further technical solution of the present invention is: the support assembly includes a support body and a stopper, the support body is provided with a U-shaped groove along the axial direction, and the groove faces the top of the ejection bracket and is sleeved and fixed thereon; the stopper is installed at one end of the ejection bracket close to the trailing edge of the wing, and is sleeved on the support body, the stopper is a U-shaped plate structure, including side plates on both sides and a top plate, the side plates are fixedly connected to the ejection bracket, and the top plate is provided with an inner groove at one end facing the leading edge of the wing, which is used to limit the engagement with the boss at one end of the ejection bracket facing the trailing edge of the wing.

[0011] A further technical solution of the present invention is: the ejection support body is strip-shaped, and its top surface is 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 body; the end of the ejection support facing the leading edge of the wing is a partial spherical structure for reducing air resistance; the ejection support is provided with a boss away from its spherical end, and the boss is embedded in the inner groove of the block and limited by the top plate and the side plates on both sides; the ejection support is provided with two through holes along its length direction, and the through holes penetrate the ejection support and are perpendicular to the bottom surface of the ejection support, and are used to pass screws and connect with the launch ribs.

[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 notch of the weight-reducing groove 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 launching rib, which is used to abut against the main beam inside the wing; the bottom surface of the launching rib is glued and fixed to the inner wall of the lower wing skin of the wing; the launching rib is provided with screw holes corresponding to the two through holes of the ejection support, which are used to fix the connection with the ejection support through screws.

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

[0015] A design method for the fixed-wing UAV launch device includes the following contents:

[0016] S100. Ejection fulcrum geometry and installation position design:

[0017] The strip-shaped fulcrum is adopted, and the ejection support and the launch rib are designed to be strip-shaped. The ejection support cooperates with the launch rib to symmetrically support the wings on both sides of the fuselage. The length of the strip ejection support is greater than the front and rear limits of the theoretical center of gravity of the drone. The coordinate zero point is represented by the position of the drone head, and the unit is cm. The length of the ejection support and the axial installation position are calculated:

[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] Where: L Gmax Indicates the maximum allowable rear limit of the drone's center of gravity, L Gmin Indicates the maximum allowable UAV center of gravity front limit, L all Indicates the length of the ejection support, L leading_edge Indicates the front edge position of the ejection support, L trailing_edge Indicates the position of the trailing edge of the ejection support;

[0022] Calculation of ejection support height:

[0023] h≥2t (4)

[0024] Where: h represents the height of the ejection support, t represents the connection thickness of the screw penetrating the ejection support and the threaded connection of the launch rib;

[0025] The width of the ejection support is determined by the diameter of the screws connecting the ejection support and the firing rib;

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

[0027] L p ≥W L +5cm (5)

[0028] Where: L p Indicates the span of the ejection supports on both sides of the fuselage, W L Indicates the propeller launch channel width;

[0029] S200. Ejection fulcrum strength design:

[0030] The screws connecting the ejection support and the launch rib close to the trailing edge of the wing are used as the weakest point of the fulcrum for calculation, and the screw selection is preliminarily determined:

[0031] Since there is a distance δ between the bottom surface of the ejection support and the center of gravity of the UAV L , additional torque will be generated during launch

[0032] m δ =F thrust ·δ L (6)

[0033] Where: F thrust Indicates ejection load, calculated as 20 times overload;

[0034] F thrust =20×Mg (7),

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

[0036] Force analysis of the drone during launch: the ejection thrust F1 and support force F2 of the ejection bracket on the drone, and the drone’s own gravity G, F1 = F thrust , there is a distance d1 between the ejection thrust and the center of gravity, d1 = δ L , the ejection thrust will introduce additional bending moment M1, M1 = m δ , the support force F2 generates the moment M2, M1 and M2 are balanced, M2 = M1;

[0037] Force analysis of the screws on both sides of the fuselage near the trailing edge of the wing: subjected to ejection thrust F1, the pulling force 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-tension action simultaneously due to the ejection thrust and additional bending moment:

[0039]

[0040] Where: N V and N t They represent the design values ​​of shear force and tension force borne by the screw respectively. and They represent the design values ​​of shear and tensile bearing capacity of the screw respectively;

[0041] The design value of shear force borne by a single-sided screw is:

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

[0043] The tensile force on the single-sided screw is generated by the additional bending moment, and its value is:

[0044] N t =m δ / (2×L all) (10)

[0045] Design value of screw shear bearing capacity:

[0046]

[0047] Where: A b represents the cross-sectional area of ​​the screw, Indicates the shear design strength of the screw;

[0048] Design value of screw tensile bearing capacity:

[0049]

[0050] Where: f t b Indicates the tensile design strength of the screw, and the design data needs to be consulted;

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

[0052]

[0053] in,

[0054] The minimum value of the major diameter d of the screw thread is obtained by equations (13) and (14); the screw specification is selected according to the calculation results;

[0055] S300. Ejection fulcrum force transmission design:

[0056] According to the d value calculated by S200, the bearing capacity of the screw hole wall is verified:

[0057]

[0058] Where: N V Indicates the design value of the shear force borne by the screw. Indicates the design value of the screw hole wall pressure;

[0059]

[0060] Where: d represents the major diameter of the screw thread, t represents the minimum total pressure-bearing thickness of the connection, and the connection thickness of the screw and the launch rib thread connection is taken as Indicates the bearing design strength of the screw;

[0061] According to formulas (15) and (16), determine whether the screw diameter meets the requirements of the hole wall pressure strength. If not, 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 pressure strength until the requirements of the hole wall pressure strength are met.

[0062] The width of the ejection support and the width of the launch rib are calculated based on the final major diameter d of the thread, and the width of the ejection support and the width of the launch rib ensure the installation of the screw;

[0063] S400. Weight and rent reduction optimization design:

[0064] The launching ribs, ejection supports and blocks are made of aluminum alloy plates, and strip-shaped weight-reducing grooves are designed on the launching ribs and ejection supports 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: the calculation method of the width of the ejection support and the width of the launching rib is as follows:

[0066] W1≥2×1.5×d (17)

[0067] Where: W1 is the width of the ejection support;

[0068] W2≥2×1.5×d (18)

[0069] Where: W2 is the width of the emitting rib.

[0070] A further technical solution of the present invention is that the length L2 of the transmitting rib is determined according to the span W3 of its two connecting screws and the chord length c of the wing,

[0071] W3 <L2<c (19)

[0072] The bonding area of ​​the launch rib is:

[0073] S g =W2·L2 (20)

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

[0075]

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

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

[0078] Skin thickness meets shear strength requirements:

[0079]

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

[0081] S c =2×L2×δ c (twenty three)

[0082] Where δ c Indicates the skin thickness, that is, the minimum thickness of the skin; if the current skin shear strength is insufficient, increase the skin thickness δ c Or the launch rib length 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 a design method thereof, wherein the launch device supports the wings of the fixed-wing UAV in a long strip-shaped support manner, and compared with the four-point, three-point and two-point forms of traditional catapult supports, the launch device has the advantages of simple structure, high reliability, no complex transmission mechanism and simple manufacturing process.

[0085] The present invention installs two strip-shaped launching ribs symmetrically inside the wing along the chord length direction of the wing, and the bottom surface thereof is glued to the wing skin. The front end of the launching rib, i.e., the end facing the leading edge of the wing, contacts the main beam inside the wing through a push block, and the upper and lower surfaces of the main beam and the wing skin are glued by epoxy glue. A strip-shaped ejection support is correspondingly installed under each launching rib, and the two are connected by screws, and the thrust is transmitted to the launching rib through the ejection support. The two ejection supports are respectively supported by two ejection brackets, and are limited by a stopper installed on the top of the ejection bracket. The ejection thrust is transmitted to the ejection support by the ejection bracket, and then to the launching rib by the ejection support, and then to the main beam through the shear flow of the bottom surface of the launching rib and the wing skin. The force transmission path is reasonable, the load is evenly distributed, there is no stress concentration phenomenon, and the service life of the device is increased. The ejection support is limited by the stopper to the left and right and backward displacements, so that it can only be ejected along its forward thrust direction, thereby ensuring the stability of the unmanned aerial vehicle during support and ejection.

[0086] The ejection support of the present invention is detachable, so that the adapted UAV can support ejection and taxiing dual-mode take-off and landing. When used for taxiing take-off, it is only necessary to remove the ejection support.

[0087] The launch device of the present invention is small in size and light in weight, which plays an active role in reducing the weight of the UAV system and reducing air resistance. At the same time, the load-bearing parts such as the ejection support, ejection support, and stopper are all made of aluminum alloy, which is light in weight, low in cost, and easy to use and maintain.

[0088] The launch device design method provided by the present invention provides a set of design criteria for the fixed-wing UAV launch device. The method conducts detailed research and calculation on the ejection thrust transmission path, has the significance of guiding practical engineering applications, and can effectively solve the problems of skin tearing, fulcrum deformation and connection screw failure that may occur in the existing launch device support method. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Figure 1 It is a schematic diagram of the overall structure of the fixed-wing catapult-type UAV launch device;

[0090] Figure 2 This is a front view of the overall structure of the fixed-wing catapult-type UAV launcher;

[0091] Figure 3 It is a schematic diagram of the support state of the top of the ejection bracket and the ejection support;

[0092] Figure 4 It is a schematic diagram of the installation of the support body and the stopper at the top of the ejection bracket;

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

[0094] Figure 6 It is a structural schematic diagram of the ejection support;

[0095] Figure 7 is a schematic diagram of the structure of the stopper;

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

[0097] Fig. 9 This is a schematic diagram of the installation and force of the launch rib in the wing;

[0098] Fig.10 The bonding area between the launch rib and the skin;

[0099] Fig.11 It is a schematic diagram of the cross-sectional structure of the connection support between the launch device and the wing of the present invention;

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

[0101] Fig.13 Design a flow chart for the launch device of the present invention;

[0102] Fig.14 This is the force analysis diagram of the drone during ejection;

[0103] Fig.15 This is the force analysis diagram of the ejection support when the UAV is ejected;

[0104] Fig.16 This is a force analysis diagram of the screws connecting the ejection support and the launch rib near the trailing edge of the wing.

[0105] Explanation of the reference numerals: 1. ejection frame slide rail, 2. ejection bracket, 3. support assembly, 31. support body, 32. block, 321. side plate, 322. top plate, 323. inner groove, 4. ejection support, 41. boss, 42. through hole, 43. weight-reducing groove, 5. launching rib, 51. push block, 52. screw hole, 53. weight-reducing groove, 54. bottom adhesive area of ​​launching rib, 55. glue 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 DESCRIPTION

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

[0107] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0108] Embodiment 1:

[0109] The present embodiment provides a fixed-wing catapult-type UAV launch device, which supports the wings on both sides of the UAV in a long strip-shaped support manner, has a simple structure, uniform force, high reliability, and no complex transmission mechanism and limit mechanism.

[0110] See also Figure 1 , 2 A fixed-wing ejection type UAV launch device provided in this embodiment includes an ejection frame slide rail 1 and an ejection bracket 2 slidably mounted on the ejection frame slide rail 1, capable of sliding along the ejection frame slide rail 1, and used to support the UAV 6. Two ejection brackets 2 in this embodiment are provided, which are symmetrically mounted on both sides of the ejection frame slide rail 1 along the sliding direction thereof. The ejection bracket 2 is a vertically arranged plate-shaped bracket, which is slidably connected to the ejection frame slide rail 1. In order to reduce weight, irregular weight-reducing holes are provided on the wall panel of the ejection bracket 2. The ejection frame slide rail 1 is installed on the UAV launch vehicle. Driven by the vehicle-mounted pneumatic ejection system, the ejection bracket 2 can instantly obtain a large amount of kinetic energy and slide along the ejection frame slide rail 1.

[0111] See also Figure 3 , 4, 7, 11, the launch device of this embodiment also includes a support assembly 3, an ejection support 4 and a launch rib 5. A support assembly 3 is fixedly installed on the top of each ejection support 2, which is used to support and limit the ejection support 4. Specifically, the support assembly 3 includes a support body 31 and a stopper 32. The support body 31 is a long strip-shaped shell, and a U-shaped through groove is provided along its length direction. Its groove is downwardly sleeved with the top of the ejection support 2, and the two are fixedly connected by three connecting bolts. The stopper 32 is installed at one end of the ejection support 2 close to the trailing edge 74 of the wing. The stopper 32 is a U-shaped plate structure, including side plates 321 and a top plate 322 on both sides. The U-shaped opening of the stopper 32 is downwardly sleeved on the support body 31, and its side plates 321 and the support body 31 share three connecting bolts to be fixedly connected to the ejection support 2. A gap is left between the top plate 322 and the support body 31 , and an inner groove 323 is provided at one end of the top plate 322 facing the wing leading edge 73 for detachable and limited cooperation with the ejection support 4 .

[0112] See also Figure 5-6 8-11, two ejection supports 4 are symmetrically installed under the wings 7 on both sides of the UAV 6, and correspond to and are fixedly connected with two ejection ribs 5 symmetrically installed in the wings 7 on both sides of the UAV. Specifically:

[0113] The launch rib 5 is strip-shaped and arranged along the chord length of the wing. Its bottom surface is fixed to the inner wall of the lower wing skin 71 of the wing 7 by epoxy glue. Its end facing the wing leading edge 73 is provided with a push block 51 for abutting against the main beam 75 inside the wing. The skin 71 and the main beam 75 are glued with epoxy glue. The top surface of the end of the launch rib 5 facing the wing trailing edge 74 is in contact with the inner wall of the upper wing skin 72. The launch rib 5 is provided with two glue leakage holes 55 perpendicular to the bottom surface of the launch rib 5 and penetrating the launch rib 5 along its length direction. When gluing the bottom surface of the launch rib 5, excess glue can flow out from the glue leakage holes.

[0114] The main body of the ejection support 4 is strip-shaped, and its top surface is designed in accordance with the lower wing surface of the wing 7, and is in contact with the lower wing surface skin 71. Its bottom surface is parallel to the horizontal plane of the fuselage, and is in contact with the upper surface of the support body 31, playing the role of supporting the UAV 6. The ejection support 4 has a partial spherical structure at one end facing the wing leading edge 73, which is used to reduce air resistance during ejection. The ejection support 4 is provided with a wedge-shaped boss 41 at one end away from its spherical end, that is, toward the wing trailing edge 74, and the boss 41 is embedded in the inner groove 323 of the stopper 31. The rear end surface of the ejection support 4 located above the boss 41 is against the top plate 322 of the stopper 32, which is used to transmit the ejection load and limit the backward movement of the UAV. The side plates 321 on both sides of the stopper 32 form left and right limits on the boss 41. Through the limit of the stopper 32, the ejection support 4 can only be displaced in the supported plane along the direction of travel when the ejection bracket 2 is ejected and slid. The tail boss 41 of the ejection support 4 cooperates with the inner groove 323 of the stopper 32 on the ejection bracket 2 to prevent the UAV 6 from falling off the frame prematurely due to engine vibration or thrust.

[0115] The ejection support 4 is provided with two through holes 42 along its length direction, which penetrate the ejection support 4 and are perpendicular to the bottom surface of the ejection support 4, and are used to pass the screws 8 and the launch rib 5 for fixed connection. Correspondingly, the launch rib 5 is provided with screw holes 52 corresponding to the two through holes of the ejection support 4. When connected, the screw 8 passes through the ejection support 4 and the lower wing skin 71 from bottom to top, and the threaded portion of the screw 8 is threadedly connected with the screw hole 52 of the launch rib 5.

[0116] According to the specific structure of the UAV 6, the ejection support 4 can also be installed under the wing-body fusion body.

[0117] See also Figure 6 , 8 In order to reduce weight, the ejection support 4 is provided with a strip-shaped weight-reducing groove 43 along its length direction, and the notch of the weight-reducing groove 43 faces the top surface of the ejection support 4 and avoids the through hole 42, so as not to affect the connection strength between the screw 8 and the firing rib 5. At the same time, the firing rib 5 is also provided with a weight-reducing groove 53 for weight reduction, and the weight-reducing groove 53 of the firing rib 5 is located on the top surface of the firing rib 5 and arranged along its length direction.

[0118] When in use, the launch ribs 5 are symmetrically installed in the wings 7 on both sides of the drone, and then the two ejection supports 4 are fixedly installed under the launch ribs 5 on both sides, and then the drone 6 is placed on the ejection bracket 2, so that the ejection supports 4 at the bottom of the wings 7 on both sides are placed on the corresponding support bodies 31 on both sides, and at the same time, the bosses 41 of the ejection supports 4 are embedded in the inner grooves 323 of the stopper 31 to form a limit, and then the drone 6 can be launched. During the launch, the ejection bracket 2 is driven by the vehicle-mounted air pressure ejection system, and due to the release of air pressure, a large amount of kinetic energy is instantly obtained to accelerate forward along the ejection frame slide rail 1, driving the drone 6 to accelerate. When the drone 6 reaches a predetermined speed, the ejection bracket 2 quickly decelerates under the action of the energy absorption device, and the drone 6 is separated from the ejection bracket 2 under the action of inertia to complete the take-off.

[0119] The ejection support 4 of the present invention supports dual-mode take-off and landing. If the UAV 6 supports taxiing flight, after installing the landing gear, the ejection support 4 can be removed in consideration of weight reduction and drag reduction.

[0120] Embodiment 2:

[0121] This embodiment provides a design method for the fixed-wing UAV launch device in Embodiment 1. Fig.13 The design flow chart is shown below. The design method includes the following:

[0122] S100. Ejection fulcrum geometry and installation position design:

[0123] Design concept: The geometric design of the ejection fulcrum takes into account the static holding state and ejection state of the UAV 6 on the ejection bracket 2. It integrates the advantages of the three types of ejection fulcrums in the background technology, connects the front and rear fulcrums in the form of 4 fulcrums, and integrates them into a long strip fulcrum. The bottom surface of the strip fulcrum supports the UAV and does not bear the ejection thrust. The rear part of the strip fulcrum, that is, the end facing the trailing edge 74 of the wing and the ejection bracket 2, is designed to integrate the ejection thrust. The rear end face of the strip fulcrum transmits the ejection thrust. The lower plane of the strip fulcrum is required to be parallel to the horizontal plane of the UAV 6 body. At the moment the UAV 6 is ejected, the UAV's angle of attack is close to the favorable angle of attack, that is, the angle of attack corresponding to the maximum lift-to-drag ratio, which improves the flight safety of the UAV.

[0124] During the ejection process, the long strip-shaped fulcrum will not produce the phenomenon of unbalanced force on the front and rear fulcrums, so that the ejection bracket 2 can make the combined force on the drone 7 pass through the center of gravity of the drone, balancing the additional torque that may be generated by the ejection thrust. Before the ejection, the groove of the block 32 on the ejection bracket 2 and the ejection bracket 4 fit tightly, limiting the displacement of the drone 6 in the backward and left and right directions. There is no risk of the drone falling off the frame in both the state of the drone 6 being stationary on the ejection bracket 2 and the drone 6 being ejected and taken off on the ejection bracket 2.

[0125] Therefore, the present invention adopts a strip-shaped fulcrum form, and designs the ejection support 4 and the launch rib 5 into a strip shape, and the ejection support 4 cooperates with the launch rib 5 to symmetrically support the wings 7 on both sides of the fuselage. The strip-shaped ejection support 4 is a fulcrum, and its length is greater than the front and rear limits of the theoretical center of gravity of the drone 6. The coordinate zero point is represented by the position of the drone 6 head, and 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] Where: L Gmax Indicates the maximum allowable rear limit of the drone's center of gravity, L Gmin Indicates the maximum allowable UAV center of gravity front limit, L all Indicates the length of the ejection support 4, L leading_edge Indicates the front edge position of the ejection support 4, L trailing_edge Indicates the rear edge position of the ejection support 4.

[0130] Calculation of the height of the ejection support 4: The height of the ejection support 4 generally does not affect the strength of the ejection fulcrum. The weak point is generally at the connecting screw, so it 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 penetrating the ejection support 4 and the threaded connection of the launching rib 5.

[0133] The width of the ejection support 4 is determined according to the diameter of the screw 8 connecting the ejection support 4 and the firing rib 5;

[0134] Since the two ejection supports 4 are located on both sides of the fuselage, supporting the left and right wings 7 respectively, and considering the propeller launch channel at the rear of the UAV, the strength of the wings 7 and other factors, it is required that the ejection support span shall not be less than the width of the propeller launch channel, and the wing strength shall be able to meet the bending moment effect of the ejection thrust on the wing. Based on this, the ejection support span can be preliminarily 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] Where: L p Indicates the span of the ejection supports 4 on both sides of the fuselage, W L Indicates the propeller launch channel width.

[0138] S200. Ejection fulcrum strength design:

[0139] Normally, the ejection fulcrum of the ejection bracket 2 in the static lifting state should support the UAV through the center of gravity to ensure the static stability of the UAV. At the same time, the ejection thrust line should pass through or be close to the center of gravity of the UAV as much as possible, so that the additional bending moment generated during ejection is small, reducing the requirements for the strength of the UAV body. The ejection fulcrum is the distance δ between the position of the ejection bracket 4 support surface and the center of gravity. L The smaller the better, we can take δ L = 0 as the fulcrum position, but due to the UAV shape restrictions (upper wing or lower wing), ejection width restrictions or wing strength restrictions and other reasons, it is not possible to L =0, the ejection support 4 is set, and the preliminary design value is given at this time. The distance between the bottom surface of the ejection support 4 on both sides and the center of gravity of the drone is δ L , additional torque will be generated during launch:

[0140] m δ =F thrust ·δ L (6)

[0141] Where: F thrust Indicates the ejection load, calculated according to 20 times overload, and its value is:

[0142] F thrust =20×Mg (7),

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

[0144] The additional torque will act on the drone body and balance the support force of the ejection support 4, such as Fig.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 bracket 2 on the UAV 6, and the UAV 6 has its own gravity G, F1=F thrust There is a distance d1 between the ejection thrust and the center of gravity of the drone, d1 = δ L The additional bending moment M1 introduced by the ejection thrust is an internal force of the drone, M1 = m δ The supporting force F2 generates torque M2, which is the internal force of the UAV. M2 and M1 are balanced, M2=M1.

[0145] However, the drone body is required to withstand this additional torque when balancing to meet its strength requirements. The additional torque is the head-down torque, which will be applied to the ejection support 4. Since the ejection support 4 is in a long strip shape, the front end of the ejection support 4 is under pressure and the rear end is under tension. The force conditions are as follows: Fig.15 As shown, Fig.15 In the figure, F3 represents the pulling force generated by the drone 6 on the ejection support 4, which is generated by the additional bending moment, and F4 represents the pressure generated by the drone 6 on the ejection support 4, which is generated by the gravity G and the additional bending moment. At this time, since the ejection support 4 is connected to the launch rib 5 fixed in the wing 7 of the drone 6 by two front and rear screws 8 of the same specifications, the screws 8 are required to be able to withstand the combined effects of the thrust and the shear and pulling forces caused by the additional bending moment.

[0146] like Fig.16 As shown, the screw 8 is subjected to shear-tension action at the same time due to the ejection thrust and additional bending moment, and the stress condition is relatively complex. The screw 8 near the wing trailing edge 74, connecting the ejection support 4 and the launch rib 5, is used as the weakest point of the fulcrum for calculation, and the selection of the screw 8 is preliminarily determined:

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

[0148] According to the reference bolt connection strength calculation method, the shear-tension effect of screw 8 is verified:

[0149]

[0150] Where: N V and N t They represent the design values ​​of shear force and tension force borne by screw 8, respectively. and They respectively represent the design values ​​of the shear and tensile bearing capacities of the screw 8.

[0151] The design value of the shear force and tension that the screw bears takes into account 20 times the ejection overload and gravity acceleration g. Then the design value of the shear force that the single-sided screw 8 bears is:

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

[0153] The tensile force on the single-sided screw 8 is generated by the additional bending moment, and its value is:

[0154] N t =m δ / (2×L all ) (10)

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

[0156]

[0157] Where: A b represents the cross-sectional area of ​​the screw, Indicates the shear design strength of the screw, and the design data needs to be consulted;

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

[0159]

[0160] Where: f t b Indicates the tensile design strength of the screw, and the design data needs to be consulted;

[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 specifications are unknown. According to equations (8) to (12), the design principle of the screw 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 is obtained by equations (13) and (14), and the screw specification is selected according to the calculation result. The subsequent ejection fulcrum design work is continued with this screw 8 specification. If the size of the screw 8 can meet the subsequent force transmission strength requirements, the ejection fulcrum position design is completed. If it cannot meet the requirements, iterate again and select the appropriate screw 8 diameter.

[0166] S300. Ejection fulcrum force transmission design:

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

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

[0169] According to the minimum d value calculated by S200, the bearing capacity of the screw hole 8 is verified:

[0170]

[0171] Where: N V It represents the design value of the shear force borne by screw 8, Indicates the design value of the hole wall pressure of the screw 8;

[0172]

[0173] Where: d represents the major diameter of the screw 8 thread, t represents the minimum pressure-bearing total thickness of the connection, and the thickness of the connection between the screw 8 and the launch rib 5 threaded connection is taken, f c b Indicates the design pressure strength of the screw, which requires reference to the data.

[0174] According to formulas (15) and (16), it is determined whether the diameter of screw 8 meets the requirements of the bearing strength of the hole wall. If not, it is necessary to increase the major diameter d of the thread, increase the thickness t of the threaded connection, or change the material of screw 8 to a material with greater bearing strength, that is, take f c b Higher, until the hole wall pressure strength requirements are met.

[0175] The width of the ejection support 4 and the width of the launching rib 5 are calculated according to the finally determined major diameter d of the thread, and the width of the ejection support 4 and the width of the launching rib 5 ensure the installation of the screw 8.

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

[0177] W1≥2×1.5×d (17)

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

[0179] W2≥2×1.5×d (18)

[0180] The length L2 of the launching rib 5 is calculated based on the span W3 of the two front and rear connecting screws 8 and the wing chord length c. Then, the launching rib length is corrected based on the calculation result.

[0181] W3 <L2<c (19)

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

[0183] S g =W2·L2 (20)

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

[0185]

[0186] According to formula (21), determine whether the bonding strength meets the requirements. If it does not meet the requirements, increase the bonding area S g , that is, increasing the emission rib width W2 or increasing the emission rib length L2.

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

[0188]

[0189] In the formula, σ b_c Indicates the skin shear strength, which is related to the skin material and requires reference; S c Represents the shear cross-sectional area.

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

[0191] S c =2×L2×δ c (twenty three)

[0192] Where δ c Indicates the skin thickness, that is, the minimum thickness of the skin. If the current skin shear strength is insufficient, increase the skin thickness δ c Or the length L2 of the emitting rib 5.

[0193] S400. Weight and rent reduction optimization design:

[0194] The launch rib 5, the ejection support 4, and the stopper 32 are made of aluminum alloy plates, and strip-shaped weight-reducing grooves are designed on the launch rib 5 and the ejection support 4 to reduce weight. The end of the ejection support 4 facing the wing leading edge 73 is spherical to reduce air resistance. If the ejection type UAV adopts a taxiing take-off and landing method, the ejection support 4 can also be removed, which can reduce the weight of the UAV and reduce air resistance.

[0195] According to the above launch device design method, the length L of the ejection support 4 can be determined. all According to the UAV 6 shape restriction (upper wing or lower wing), ejection width restriction or wing strength restriction, a suitable ejection fulcrum position can be selected. At this time, the ejection fulcrum is δ away from the center of gravity of the UAV L . From this, we can continue to calculate the diameter d of the screw 8 and the thickness t of the threaded connection, that is, Fig.12The 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 According to the above design process, the main geometric dimensions of the launch device can be obtained. The design of the launch device and the overall structural design of the UAV complement each other. It is necessary to make trade-offs in the design and continuously optimize to obtain the best design results.

[0196] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A fixed-wing ejection type UAV launch device, comprising an ejection frame slide rail, an ejection bracket slidably mounted on the ejection frame slide rail and used to support the UAV; characterized in that: There are two ejection brackets, which are symmetrically installed on both sides of the ejection bracket slide rail along the sliding direction; It also includes a support assembly, an ejection support and a launching rib; a support assembly is fixedly installed on the top of each ejection support for supporting and limiting the ejection support; two ejection supports are symmetrically installed under the wings on both sides of the UAV, and correspond to and are fixedly connected with two launching ribs symmetrically installed in the wings on both sides; the launching rib is strip-shaped, and its bottom surface is fixed to the inner wall of the lower wing skin, and its end facing the leading edge of the wing is against the main beam inside the wing; the end of the ejection support facing the trailing edge of the wing is detachably limited and cooperated with the support assembly, which is used to limit the ejection support within the supported plane, and can only be displaced along the direction of travel when the ejection support is ejected and slid.

2. The fixed-wing catapult-type UAV launch device according to claim 1, characterized in that: The support assembly includes a support body and a stopper. The support body is provided with a U-shaped groove along the axial direction, and the groove faces the top of the ejection bracket and is sleeved and fixed thereon. The stopper is installed at one end of the ejection bracket close to the trailing edge of the wing and sleeved on the support body. The stopper is a U-shaped plate structure, including side plates on both sides and a top plate. The side plates are fixedly connected to the ejection bracket. An inner groove is provided at one end of the top plate facing the leading edge of the wing, which is used to limit the engagement with the boss at one end of the ejection bracket facing the trailing edge of the wing.

3. The fixed-wing catapult-type UAV launch device according to claim 2, characterized in that: 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, and its bottom surface is parallel to the horizontal plane of the UAV body and in contact with the upper surface of the support body; the end of the ejection support facing the leading edge of the wing is a partial spherical structure for reducing air resistance; the ejection support is provided with a boss away from its spherical end, the boss is embedded in the inner groove of the block, and is limited by the top plate and the side plates on both sides; the ejection support is provided with two through holes along its length direction, the through holes pass through the ejection support and are perpendicular to the bottom surface of the ejection support, and are used to pass screws and launch ribs for connection.

4. The fixed-wing catapult-type UAV launch device 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 notch of the weight-reducing groove faces the top surface of the ejection support, and 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-type UAV launch device according to claim 3, characterized in that: A push block is provided at one end of the launching rib for abutting against the main beam inside the wing; the bottom surface of the launching rib is glued and fixed to the inner wall of the lower wing skin of the wing; the launching 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.

6. The fixed-wing catapult-type UAV launch device according to claim 5, characterized in that: The emission rib is provided with a weight-reducing groove, and the weight-reducing groove is located on the top surface of the emission rib, and is used to reduce the weight of the emission rib.

7. A method for designing a launch device for a fixed-wing UAV as claimed in claim 5, characterized in that: Includes the following: S100. Ejection fulcrum geometry and installation position design: The strip fulcrum form is adopted, and the ejection support and the launch rib are designed to be strip-shaped. The ejection support cooperates with the launch rib to symmetrically support the wings on both sides of the fuselage; the length of the strip ejection support is greater than the front and rear limits of the theoretical center of gravity of the drone. The coordinate zero point is represented by the position of the drone head, and the unit is cm. The length and axial installation position of the ejection support are calculated: THE leading_edge <L Gmin -2cm (1) THE trailing_edge >L Gmax +2cm (2) L all ≥L trailing_edge -L leading_edge (3) Where: L Gmax Indicates the maximum allowable rear limit of the drone's center of gravity, L Gmin Indicates the maximum allowable UAV center of gravity front limit, L all Indicates the length of the ejection support, L leading_edge Indicates the front edge position of the ejection support, L trailing_edge Indicates the position of the trailing edge of the ejection support; Calculation of ejection support height: h≥2t (4) Where: h represents the height of the ejection support, t represents the connection thickness of the screw penetrating the ejection support and the threaded connection of the launch rib; The width of the ejection support is determined by the diameter of the screws connecting the ejection support and the firing rib; Calculation of the span of the two ejection supports on both sides of the fuselage: L p ≥W L +5cm (5) Where: L p Indicates the span of the ejection supports on both sides of the fuselage, W L Indicates the propeller launch channel width; S200. Ejection fulcrum strength design: The screws connecting the ejection support and the launch rib close to the trailing edge of the wing are used as the weakest point of the fulcrum for calculation, and the screw selection is preliminarily determined: Since there is a distance δ between the bottom surface of the ejection support and the center of gravity of the UAV L , additional torque will be generated during launch m δ =F thrust ·d L (6) Where: F thrust Indicates ejection load, calculated as 20 times overload; F thrust =20×Mg (7) Where: M represents the weight of the drone, g represents the acceleration due to gravity; Force analysis of the drone during launch: The ejection thrust F1 and support force F2 of the ejection bracket on the drone, and the drone’s own gravity G, F1 = F thrust , there is a distance d1 between the ejection thrust and the center of gravity, d1 = δ L , the ejection thrust introduces an additional bending moment M1, M1 = m δ , the support force F2 generates the moment M2, M1 and M2 are balanced, M2 = M1; Force analysis of the screws on both sides of the fuselage near the trailing edge of the wing: subjected to ejection thrust F1, the pulling force F3 generated by the UAV on the ejection support, the reaction force F1' of F1, and the reaction force F3' of F3; The screw is subjected to shear-tension action simultaneously due to the ejection thrust and additional bending moment: Where: N V and N t They represent the design values ​​of shear force and tension force borne by the screw respectively. and They represent the design values ​​of shear and tensile bearing capacity of the screw respectively; The design value of shear force borne by a single-sided screw is: N V =F thrust / 2 (9) The tensile force on the single-sided screw is generated by the additional bending moment, and its value is: N t =m δ / (2×L all ) (10) Design value of screw shear bearing capacity: Where: A b represents the cross-sectional area of ​​the screw, Indicates the shear design strength of the screw; Design value of screw tensile bearing capacity: Where: f t b Indicates the tensile design strength of the screw, and the design data needs to be consulted; The screw diameter design is obtained from equations (8) to (12): in, The minimum value of the major diameter d of the screw thread is obtained by equations (13) and (14); the screw specification is selected according to the calculation results; S300. Ejection fulcrum force transmission design: According to the d value calculated by S200, the bearing capacity of the screw hole wall is verified: Where: N V Indicates the design value of the shear force borne by the screw. Indicates the design value of the screw hole wall pressure; Where: d represents the major diameter of the screw thread, t represents the minimum total pressure-bearing thickness of the connection, and the connection thickness of the screw and the launch rib thread connection is taken as Indicates the bearing design strength of the screw; According to formulas (15) and (16), determine whether the screw diameter meets the requirements of the hole wall pressure strength. If not, 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 pressure strength until the requirements of the hole wall pressure strength are met. The width of the ejection support and the width of the launch rib are calculated based on the final major diameter d of the thread, and the width of the ejection support and the width of the launch rib ensure the installation of the screw; S400. Weight and rent reduction optimization design: The launching ribs, ejection supports and blocks are made of aluminum alloy plates, and strip-shaped weight-reducing grooves are designed on the launching ribs and ejection supports 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 according to claim 7, characterized in that: The calculation method of the ejection support width and the launch rib width is as follows: W1≥2×1.5×d (17) Where: W1 is the width of the ejection support; W2≥2×1.5×d (18) Where: W2 is the width of the emitting rib.

9. A design method according to claim 8, characterized in that: The length L2 of the transmitting rib is determined according to the span W3 of its two connecting screws and the chord length c of the wing. W3 <L2<c (19) The bonding area of ​​the launch rib is: S g =W2·L2 (20) The bonding area of ​​the launch rib transmits the ejection thrust, and the bonding strength of the bonding area meets the following requirements: According to formula (21), determine whether the bonding strength meets the requirements. If it does not meet the requirements, increase the bonding area S g .

10. A method for designing the thickness of a UAV skin using the design method of a fixed-wing UAV launch device according to claim 9, characterized in that: Skin thickness meets shear strength requirements: In the formula, σ b_c represents the skin shear strength, S c represents the shear cross-sectional area; S c =2×L2×δ c (23) Where δ c Indicates the skin thickness, that is, the minimum thickness of the skin; if the current skin shear strength is insufficient, increase the skin thickness δ c Or the launch rib length L2.

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