Fixed wing ejection type unmanned aerial vehicle launching device

Abstract

The utility model relates to a fixed wing ejection type unmanned aerial vehicle launching device, which belongs to the field of unmanned aerial vehicles, and comprises an ejection frame slide rail, an ejection bracket, a supporting assembly, an ejection support and a launching rib. A supporting assembly is fixedly installed at the top end of the ejection support and used for supporting and limiting the ejection support. 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 surfaces of the strip-shaped emission ribs are 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. The catapulting frame sliding rail is installed on an unmanned aerial vehicle launching vehicle, and the catapulting support provides catapulting power through the vehicle-mounted air pressure catapulting system to move along the catapulting frame sliding rail to achieve The device is reasonable in force transmission path, uniform in load distribution and free of stress concentration, and the problems that an existing launching device supporting form is complex in structure and uneven in launching stress, and a machine body is prone to being damaged are solved.

Description

Technical Field

[0001] The present invention belongs to the field of unmanned aerial vehicles (UAVs), and in particular relates to a fixed-wing catapult-type UAV launching device. Background Art

[0002] Because catapult-type fixed-wing drones can take off without a runway, unlike traditional taxiing fixed-wing drones, they are free from runway dependence. They can be launched from small, uneven surfaces, or even from mobile platforms like vehicles and ships, requiring less space. Furthermore, the drone can take off after simply mounting and securing it on the catapult bracket. Therefore, this method of takeoff is widely used in the small UAV sector.

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

[0004] The key to the design of a catapult-type fixed-wing UAV launcher lies in the fulcrum connection form and fulcrum force transmission method between the ejection bracket and the UAV. Existing common launcher fulcrum forms include 4-point form, 3-point form and 2-point form. The 4-point launcher is designed with 4 hooks under the UAV wing, which are connected to the ejection bracket. The two hooks at the rear are mainly used to support the UAV, lifting the UAV on the ejection bracket and not affected by the ejection thrust; the two hooks at the front are affected by the ejection thrust. The 4-point launcher is designed with a limiting mechanism to limit the forward movement of the UAV caused by engine vibration or large thrust. However, the 4-point form has a complex structure and a complex force form. During ejection, the fulcrums are unevenly stressed, which can easily 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. A three-point launcher consists of two wing support assemblies and a front or rear support. Because the front or rear support can interfere with the propeller launch channel of a fixed-wing drone located at the rear of the fuselage, a separate release control mechanism is required to prevent this interference. The moment the drone leaves the launcher, the front or rear support falls, clearing the launch channel and allowing the drone to be successfully launched. However, the design of the support release control mechanism is difficult, requiring strict calculation of the release timing. Furthermore, multiple ejection flights accelerate wear of the mechanism, making it inconvenient to use and maintain. A two-point launcher has two support points arranged below the wings, providing both support and ejection thrust for the drone. Complex limit mechanisms and self-locking devices are typically designed to prevent the drone from prematurely falling off the launcher due to engine vibration and ejection thrust, potentially causing a launch accident. Furthermore, the two-point structure is complex and has high maintenance costs, failing to meet the low-cost, high-reliability design philosophy of drones.

[0005] In addition to the fulcrum type, the fulcrum force transmission method directly affects the safety and lifespan of drones. Because the catapult takeoff of drones requires a large amount of kinetic energy to be obtained in a very short period of time, the instantaneous catapult overload on the drone body during launch is relatively high, placing higher demands on the drone body strength design. In order to be able to effectively transfer the ejection load from the ejection fulcrum to the drone's main beam, thereby driving the entire drone to take off, and to ensure 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 four-point fulcrum type, three-point fulcrum type, and two-point fulcrum type do not provide a clear design method for the ejection load transmission path. Most of them follow past experience and perform simple engineering calculations to check the body strength after the drone design is completed to meet the ejection strength design requirements of fixed-wing drones. The failure to fully consider the design of a reasonable force transmission path during the design stage often leads to unexpected design defects, such as skin tearing, fulcrum deformation, and screw connection failure. At present, there is little research on the design of catapult thrust transmission path, and there are no specific design methods and guidelines, 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 catapult-type fixed-wing UAVs. Summary of the Invention

[0006] Technical issues to be solved:

[0007] In order to avoid the shortcomings of the existing technology, the present invention provides a fixed-wing catapult-type UAV launch device, which changes the traditional launch device fulcrum support method. By installing strip-shaped launch ribs inside the wings, fixing an ejection support that cooperates with the launch ribs under the wings, and installing a support assembly that matches the ejection support on the ejection bracket, strip-shaped fulcrum support is achieved for the wings on both sides. By studying the force path of the launch device, the problems of complex structure, uneven ejection force, and easy damage to the body of the existing launch device support are solved.

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

[0009] The cam is fixedly mounted on the top of the unmanned aerial vehicle (UAV) so as to support and limit the position of the ejection bracket. The two ejection brackets are symmetrically mounted under the wings on both sides of the UAV, and correspond to and are fixedly connected to the two ejection ribs symmetrically mounted in the wings on both sides. The ejection rib is strip-shaped, and the bottom surface of the ejection rib is fixed to the inner wall of the lower wing skin. The end facing the leading edge of the wing is against the main beam inside the wing, and the top surface facing the trailing edge of the wing is in contact with the inner wall of the upper wing skin. The ejection bracket is separably limited in position with the support assembly at one end facing the trailing edge of the wing, so as to limit the ejection bracket to a displacement within the supported plane only along the direction of travel of the ejection bracket during ejection and sliding. The ejection bracket slide rail is mounted on the UAV launch vehicle, and the ejection bracket is connected to the vehicle-mounted pneumatic ejection system, which provides ejection power for the ejection bracket.

[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 therewith; 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, and 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, which is used to reduce 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 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, and 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.

[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 that correspond one to one 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 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 to reduce the weight of the emission rib.

[0015] A further technical solution of the present invention is that the bottom surface of the emitting rib is fixed to the inner wall of the lower wing skin by using epoxy glue.

[0016] A further technical solution of the present invention is that the launching rib, ejection support and stop block are all made of aluminum alloy plates.

[0017] Beneficial effects

[0018] The beneficial effects of the present invention are: the invention provides a fixed-wing catapult-type UAV launch device and a design method thereof, 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 the 4-point form, 3-point form and two-point form, it has the advantages of simple structure, high reliability, no complex transmission mechanism, and simple manufacturing process.

[0019] The present invention installs two strip-shaped launching ribs symmetrically along the wing chord length inside the wing. Their bottom surfaces are 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 via a push block. The upper and lower surfaces of the main beam are bonded to the wing skin using epoxy glue. A strip-shaped ejection support is installed below each launching rib, and the two are connected by screws. The ejection support transmits thrust to the launching rib via the ejection support. The two ejection supports are supported by two ejection brackets and limited in position by a stopper mounted on the top of the ejection bracket. The ejection thrust is transmitted from the ejection bracket to the ejection support, then from the ejection support to the launching rib. Finally, the ejection thrust is transmitted to the main beam via the shear flow between the bottom surface of the launching rib and the wing skin. This results in a rational force transmission path, evenly distributed load, and no stress concentration, which increases the service life of the device. The stopper limits the left and right and rearward displacement of the ejection support, allowing it to eject only in the direction of its forward thrust, ensuring stability during the drone support and ejection process.

[0020] The ejection support of the present invention is detachable, so that the adapted UAV can support dual-mode take-off and landing of ejection and taxiing. When used for taxiing take-off, it is only necessary to remove the ejection support.

[0021] The launch device of the present 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 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the overall structure of the fixed-wing catapult-type UAV launch device;

[0023] Figure 2 This is a front view of the overall structure of the fixed-wing catapult-type UAV launcher;

[0024] Figure 3 It is a schematic diagram of the support status of the top of the ejection bracket and the ejection support;

[0025] Figure 4 This is a schematic diagram of the installation of the support body and the stopper at the top of the ejection bracket;

[0026] Figure 5 This is a schematic diagram of the installation of the ejection support under the wing;

[0027] Figure 6 It is a structural diagram of the ejection support;

[0028] Figure 7 Schematic diagram of the structure of the stopper;

[0029] Figure 8 Schematic diagram of the structure of the launch rib;

[0030] Figure 9 This is a schematic diagram of the installation and force of the launch rib in the wing;

[0031] Figure 10 The bonding area between the launch rib and the skin;

[0032] Figure 11 This is a schematic cross-sectional view of the connection support between the launch device and the wing of the present invention;

[0033] Figure 12 for Figure 11 Enlarged view of point A in the middle;

[0034] Figure 13 Design a flow chart for the launch device of the present invention;

[0035] Figure 14 This is the force analysis diagram of the drone during ejection;

[0036] Figure 15 This is the force analysis diagram of the ejection support when the UAV is ejected;

[0037] Figure 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.

[0038] Explanation of the accompanying reference numerals: 1. Ejection frame slide rail, 2. Ejection bracket, 3. Support assembly, 31. Support body, 32. Stop block, 321. Side panel, 322. Top panel, 323. Inner groove, 4. Ejection support, 41. Boss, 42. Through hole, 43. Weight-reducing groove, 5. Launch rib, 51. Push block, 52. Screw hole, 53. Weight-reducing groove, 54. Bottom adhesive area of ​​launch 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

[0039] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0040] 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 to 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 device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0041] This embodiment provides a fixed-wing catapult-type UAV launch device, which uses a long strip support method to support the wings on both sides of the UAV. It has a simple structure, uniform force, high reliability, and no complex transmission mechanism and limiting mechanism.

[0042] See Figure 1 、 2 The present embodiment provides a fixed-wing catapult-type UAV launch device, comprising an ejection frame rail 1 and an ejection bracket 2 that is slidably mounted on the ejection frame rail 1 and can slide along the ejection frame rail 1 to support a UAV 6. In the present embodiment, two ejection brackets 2 are provided, which are symmetrically mounted on both sides of the ejection frame rail 1 along the sliding direction thereof. The ejection bracket 2 is a vertically arranged plate-shaped bracket that is slidably connected to the ejection frame 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 rail 1 is mounted on the UAV launch vehicle. Driven by the on-board pneumatic ejection system, the ejection bracket 2 can instantly obtain a large amount of kinetic energy and slide along the ejection frame rail 1.

[0043] See 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 an elongated shell with a U-shaped through groove along its length. The 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 the side plates 321 and the support body 31 are fixedly connected to the ejection support 2 by sharing three connecting bolts. 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 .

[0044] See Figure 5-6 8-11, two ejection supports 4 are symmetrically installed under the wings 7 on both sides of the drone 6, and correspond to and are fixedly connected to two launch ribs 5 symmetrically installed in the wings 7 on both sides of the drone. Specifically:

[0045] The launch rib 5 is strip-shaped and arranged along the chord length of the wing. Its bottom surface is glued to the inner wall of the lower wing skin 71 of the wing 7 using epoxy glue. A push block 51 is provided on the end facing the wing leading edge 73, which is used to abut against the wing inner main beam 75. The inner wall of the skin and the main beam 75 are glued together using epoxy glue. The top surface of the launch rib 5, facing the wing trailing edge 74, contacts the inner wall of the upper wing skin 72. Two glue holes 55 are provided along its length, perpendicular to the bottom surface of the launch rib 5 and extending through the launch rib 5. When gluing the bottom surface of the launch rib 5, excess glue can flow out of the glue holes.

[0046] The ejection support 4 is strip-shaped. Its top surface conforms to the lower surface of the wing 7, making surface contact with the lower wing skin 71. Its bottom surface is parallel to the horizontal plane of the aircraft and contacts the upper surface of the support body 31, thus supporting the drone 6. The end of the ejection support 4 facing the wing leading edge 73 is a partially spherical structure, which reduces air resistance during ejection. A wedge-shaped boss 41 is located on the end of the ejection support 4 facing away from the spherical end, toward the wing trailing edge 74. This boss 41 engages within the inner groove 323 of the stopper 31. The rear end of the ejection support 4, located above the boss 41, abuts against the top plate 322 of the stopper 32, transmitting the ejection load and limiting rearward movement of the drone. Side plates 321 of the stopper 32 form left and right stoppers for the boss 41. This restraint by the stopper 32 ensures that the ejection support 4 can only move within the supported plane in the direction of travel of the ejection cradle 2 during ejection. The tail boss 41 of the ejection support 4 cooperates with the groove 323 in 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.

[0047] The ejection support 4 has two through-holes 42 along its length, extending perpendicularly to its bottom surface. These holes are used to pass screws 8 through the ejection support 4 and securely connect the ejection rib 5. Correspondingly, the ejection rib 5 has screw holes 52 that correspond one-to-one with the two through-holes in the ejection support 4. During connection, the screws 8 penetrate the ejection support 4 and the lower wing skin 71 from bottom to top, with the threaded portion of the screws 8 threadedly engaging the screw holes 52 in the ejection rib 5.

[0048] According to the specific structure of the UAV 6, the ejection support 4 can also be installed below the wing-body fusion body.

[0049] See Figure 6 、 8 To reduce weight, the ejection support 4 is provided with strip-shaped weight-reducing grooves 43 along its length. The notches of the weight-reducing grooves 43 face the top surface of the ejection support 4 and avoid the through-holes 42 to avoid affecting the connection strength between the screws 8 and the firing rib 5. At the same time, the firing rib 5 is also provided with weight-reducing grooves 53. The weight-reducing grooves 53 of the firing rib 5 are located on the top surface of the firing rib 5 and are arranged along its length.

[0050] During use, the launch ribs 5 are symmetrically installed within the wings 7 on both sides of the drone, and two ejection supports 4 are fixedly installed below the launch ribs 5 on both sides. The drone 6 is then 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. At the same time, the bosses 41 of the ejection supports 4 are embedded in the inner grooves 323 of the stoppers 31 to form a limit position, and the drone 6 can 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 pneumatic pressure, and accelerates forward along the ejection bracket slide 1, driving the drone 6 to accelerate. When the drone 6 reaches a predetermined speed, the ejection bracket 2 is rapidly decelerated by the energy absorption device, and the drone 6 is separated from the ejection bracket 2 by inertia, completing takeoff.

[0051] 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.

[0052] This embodiment also provides a design method for the above-mentioned fixed-wing UAV launch device, Figure 13 The following is a design flow chart. The design method includes the following:

[0053] S100. Ejection fulcrum geometry and installation position design:

[0054] 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 fulcrum fusion design of the ejection bracket 2, transmits the ejection thrust to the rear end face of the strip fulcrum. 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, thereby improving the UAV's flight safety.

[0055] During the ejection process, the elongated pivot prevents unbalanced force between the front and rear pivots, allowing the combined force of the ejection bracket 2 on the drone 7 to pass through the drone's center of gravity, balancing the additional torque that may be generated by the ejection thrust. Before ejection, the groove of the block 32 on the ejection bracket 2 fits tightly with the ejection support 4, limiting the rearward and left-right movement of the drone 6. This eliminates the risk of the drone 6 falling off the bracket, both when it is resting on the ejection bracket 2 and when it is being ejected.

[0056] 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. 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 nose, and the unit is cm. The length and axial installation position of the ejection support 4 are calculated as follows:

[0057]

[0058]

[0059]

[0060] Where: Indicates the maximum allowed rear limit of the drone's center of gravity, 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.

[0061] 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 calculated as 2 times the thickness of the threaded connection.

[0062] h≥2t (4)

[0063] Wherein: 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 firing rib 5 threaded connection.

[0064] The width of the ejection support 4 is determined by the diameter of the screw 8 connecting the ejection support 4 and the firing rib 5;

[0065] 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 limitations of the propeller launch channel at the rear of the drone and the strength of the wings 7, the ejection support span must not be less than the width of the propeller launch channel, and the wing strength must 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 .

[0066] Calculation of the span of the two ejection supports 4 on both sides of the fuselage:

[0067] L p ≥W L +5cm (5)

[0068] Where: L p Indicates the span of the ejection supports 4 on both sides of the fuselage, W LIndicates the propeller launch channel width.

[0069] S200. Ejection fulcrum strength design:

[0070] Under normal circumstances, the ejection support point 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. The additional bending moment generated during ejection is small, which reduces the requirements for the strength of the UAV body. The ejection support point is the distance δ between the support surface position of the ejection bracket 4 and the center of gravity. L The smaller the better, you can take δ L = 0 as the fulcrum position, but due to other reasons such as the UAV shape limitation (upper wing or lower wing), catapult width limitation or wing strength limitation, 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 surface of the left and right fulcrums of the UAV, that is, the bottom surface of the ejection support 4 on both sides and the center of gravity of the UAV is δ L , additional torque will be generated during launch:

[0071] m δ =F thrust ·δ L (6)

[0072] Where: F thrust Indicates the ejection load, calculated based on 20 times overload, and its value is:

[0073] F thrust =20×Mg (7),

[0074] Where: M represents the weight of the drone, and g represents the acceleration due to gravity.

[0075] The additional torque will act on the UAV body and balance the support force of the ejection support 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 bracket 2 on the UAV 6, and the UAV 6's 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 UAV, 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.

[0076] However, the UAV body is required to be able 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 long, the front end of the ejection support 4 is under pressure and the rear end is under tension. The force conditions are as follows: Figure 15 As shown, Figure 15In the diagram, F3 represents the tensile force exerted by drone 6 on ejection support 4, which is caused by the additional bending moment. F4 represents the compressive force exerted by drone 6 on ejection support 4, which is caused by gravity G and the additional bending moment. Since ejection support 4 is connected to the launch rib 5 fixed inside drone 6's wing 7 via two front and rear screws 8 of the same specifications, screws 8 must be able to withstand the combined effects of thrust, shear force, and tensile force caused by the additional bending moment.

[0077] like Figure 16 As shown, screw 8 is subjected to both shear and tension due to the ejection thrust and additional bending moment, resulting in a complex stress situation. Calculations were performed using screw 8, located near the wing trailing edge 74 and connecting the ejection support 4 and the launch rib 5, as the weakest point of the fulcrum. The selection of screw 8 was initially determined as follows:

[0078] Force analysis of screws 8 on both sides of the fuselage near the wing trailing edge 74: The ejection thrust F1 is applied to the screws, which bear the tensile force. The UAV exerts a tensile force F3 on the ejection support 4, which is also applied to the screws. The reaction force to F1 is F1', and the reaction force to F3 is F3'.

[0079] Calculate the shear-tension effect of screw 8 according to the reference bolt connection strength calculation method:

[0080]

[0081] Where: N V and N t They represent the design values ​​of shear force and tension borne by screw 8, and They represent the design values ​​of shear and tensile bearing capacity of screw 8 respectively.

[0082] 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. The design value of the shear force that the unilateral screw 8 bears is:

[0083] N V =F thrust / 2 (9)

[0084] The tensile force on the unilateral screw 8 is generated by the additional bending moment, and its value is:

[0085] N t =m δ / (2×L all ) (10)

[0086] Design value of shear bearing capacity of screw 8:

[0087]

[0088] Where: A b represents the cross-sectional area of ​​the screw, Indicates the shear design strength of the screw, which requires reference to design data;

[0089] Design value of tensile bearing capacity of screw 8:

[0090]

[0091] Where: Indicates the tensile design strength of the screw, and the design data needs to be consulted;

[0092] 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 formulas (8) to (12), the design principle of the screw major diameter can be obtained, namely:

[0093]

[0094] Since the cross-sectional area of ​​the screw is:

[0095]

[0096] 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 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.

[0097] S300. Ejection fulcrum force transmission design:

[0098] 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 only transmitted through the 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 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, driving the entire UAV to move.

[0099] The ejection thrust is transmitted to the launch rib 5 via screw 8. Considering the additional bending moment, screw 8 is subjected to shear-tension loads. Under this load condition, in addition to shear and tensile failure of screw 8, it may also cause compressive failure of the launch rib hole wall.

[0100] According to the minimum d value calculated by S200, the bearing capacity of the hole wall of screw 8 is verified:

[0101]

[0102] Where: N V Indicates the design value of the shear force borne by screw 8, Indicates the design value of the hole wall pressure of screw 8;

[0103]

[0104] 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 as follows: Indicates the design pressure strength of the screw, which requires reference to the data.

[0105] According to formula (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 thread connection, or change the material of screw 8 to use a material with greater bearing strength. Higher, until the hole wall pressure strength requirements are met.

[0106] The width of the ejection 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 ejection support 4 and the width of the launching rib 5 ensure the installation of the screw 8.

[0107] 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:

[0108] W1≥2×1.5×d (17)

[0109] Similarly, the width W2 of the emission rib 5 is:

[0110] W2≥2×1.5×d (18)

[0111] 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.

[0112] W3 <L2<c (19)

[0113] The launch rib 5 is connected to the fuselage skin by gluing. The launch rib has a length of L2 and a width of W2. The gluing area of ​​the launch rib 5 is:

[0114] S g =W2·L2 (20)

[0115] Since the bonding area of ​​the launching rib 5 transmits the ejection thrust, the bonding strength σ b_g satisfy:

[0116]

[0117] 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.

[0118] After the ejection thrust is transmitted through the bonding area, shear flow is formed on the fuselage skin, such as Figure 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:

[0119]

[0120] Where, σ b_c Indicates the skin shear strength, which is related to the skin material and requires reference to the data; S c Represents the shear cross-sectional area.

[0121] The skin shear cross-sectional area is the skin shear cross-sectional area on both sides of the launch rib, and its value is:

[0122] S c =2×L2×δ c (twenty three)

[0123] Where δ c Indicates the skin thickness, i.e. 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.

[0124] S400. Weight and rent reduction optimization design:

[0125] The launch rib 5, ejection support 4, and stopper 32 are constructed from aluminum alloy sheet material. Strip-shaped weight-reducing grooves are designed into the launch rib 5 and 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 catapult-type UAV uses a rolling takeoff and landing method, the ejection support 4 can be removed, reducing the weight of the UAV and reducing air resistance.

[0126] 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, Figure 12 The 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 launch device design 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.

[0127] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative 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 purpose of the present invention.

Claims

1. A fixed-wing catapult-type UAV launch device, comprising a catapult frame slide rail and a catapult bracket slidably mounted on the catapult frame slide rail for supporting 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; The UAV also includes a support assembly, an ejection support, and a launch rib; each ejection support is fixedly mounted on the top of a support assembly for supporting and limiting the ejection support; two ejection supports are symmetrically mounted below the wings on both sides of the UAV, corresponding one-to-one with and fixedly connected to two launch ribs symmetrically mounted inside the wings on both sides; the launch rib is strip-shaped, with its bottom surface fixed to the inner wall of the lower wing skin, its end facing the leading edge of the wing abuts against the main beam inside the wing, and its top surface facing the trailing edge of the wing contacts the inner wall of the upper wing skin; The ejection support is configured to engage with the support assembly at one end facing the trailing edge of the wing in a detachable and limiting manner, so as to restrict the ejection support to be displaced within the supported plane and only in the direction of travel of the ejection bracket during ejection and sliding. The ejection frame slide rail is installed on the UAV launch vehicle, and the ejection bracket is connected to the vehicle-mounted pneumatic ejection system, which provides ejection power for the ejection bracket.

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 therewith; 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, 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.

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, 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, 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 that correspond one to one with the two through holes of the ejection support, which are used to fix the connection with the ejection support through 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, which is located on the top surface of the emission rib and is used to reduce the weight of the emission rib.

7. The fixed-wing catapult-type UAV launch device according to claim 5, characterized in that: The bottom surface of the launching rib is fixed to the inner wall of the lower wing skin by using epoxy glue.

8. The fixed-wing catapult-type UAV launch device according to claim 5, characterized in that: The launching ribs, ejection supports and stop blocks are all made of aluminum alloy plates.

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