A retractable and rotatable ventral fin of a shipborne UAV

Abstract

The invention discloses a retractable and rotatable ventral fin of a shipborne unmanned aerial vehicle, wherein two ventral fins are symmetrically mounted on the left and right sides of the belly at the tail end of a fuselage in an eight-shaped arrangement; the ventral fins are assembled by movably connecting a front ventral fin segment (1), a middle ventral fin segment (2) and a root ventral fin segment (3); the front ventral fin segment (1) can be fitted inside the middle ventral fin segment (2), and the middle ventral fin segment (2) can be fitted inside the root ventral fin segment (3); the ventral fin comprises a skin, ribs, a sliding rod, a retractable device and a rotating device; the retractable device drives the ventral fin to retract along the span direction to adjust the size of the ventral fin; the rotating device drives the ventral fin to rotate up and down in the longitudinal direction to adjust the attitude angle; the ventral fins can be retracted and rotated individually or simultaneously without interfering with each other.

Description

Technical Field

[0001] The invention belongs to the field of overall aerodynamic shape design of fixed-wing aircraft, and particularly relates to a ventral fin of a shipborne unmanned aerial vehicle. Background Art

[0002] The maritime environment faced by shipborne drones is complex and volatile. When subjected to lateral disturbances such as turbulent wake turbulence from ships and sea breezes, they are prone to sideslip, yaw, or even loss of balance and crashes. Therefore, shipborne drones require very high stability in their at-sea flight. An aircraft's ventral fin is an aerodynamically shaped device, typically located on the rear end of the fuselage, aligned with the airflow. Its primary function is to provide lateral damping and stabilizing torque to enhance the aircraft's directional stability. Existing aircraft ventral fins are often riveted to the fuselage. This results in a fixed attitude angle for the ventral fin during missions, preventing mid-flight adjustments as the maritime flight environment and flight state change. Furthermore, the ventral fin's size is difficult to adjust, making it susceptible to ground damage. Furthermore, current movable single-piece ventral fins are limited to the lower area within the fuselage's plane of symmetry. Constrained by the limited internal mounting space at the rear of the fuselage, the ventral fin's design and area are relatively small, potentially ineffective in enhancing the aircraft's directional stability. Therefore, designing a shipborne drone ventral fin that overcomes these limitations is an urgent technical challenge. Summary of the Invention

[0003] The technical problem solved by the present invention is to provide a retractable and rotatable ventral fin of a shipborne UAV, which can ensure the stable flight of the shipborne UAV.

[0004] A retractable and rotatable ventral fin of a shipborne unmanned aerial vehicle (UAV) comprises two ventral fins symmetrically mounted on the left and right sides of the belly at the tail end of a fuselage in a figure-eight arrangement; the ventral fins are assembled by movably connecting a front ventral fin segment 1, a middle ventral fin segment 2, and a root ventral fin segment 3; the front ventral fin segment 1 can be fitted inside the middle ventral fin segment 2, and the middle ventral fin segment 2 can be fitted inside the root ventral fin segment 3; the ventral fin comprises a skin, ribs, a sliding rod, a retractable device, and a rotating device; the retractable device drives the ventral fin to retract along the span direction to adjust the size of the ventral fin; the rotating device drives the ventral fin to rotate up and down longitudinally to adjust the attitude angle; the ventral fins can retract and rotate individually or simultaneously without interfering with each other.

[0005] Furthermore, the skin includes the skin of the ventral fin root segment 1, the skin of the ventral fin middle segment 2 and the skin of the ventral fin front segment 3; the ventral fin root segment 1 and the ventral fin middle segment 2 are movably connected through the screw rod 5, the nut 20, the ventral fin root segment front slide rod 12 and the ventral fin root segment rear slide rod 13; the ventral fin middle segment 2 and the ventral fin front segment 3 are movably connected through the ventral fin middle segment front slide rod 14, the ventral fin middle segment rear slide rod 15 and the connecting rod motion module.

[0006] Furthermore, the wing ribs include the ventral fin root segment tail end rib 8, the ventral fin middle segment tail end rib 9, the ventral fin front segment tail end rib 10 and the ventral fin front segment connecting rib 11; the ventral fin root segment tail end rib 8 is fixedly installed with the ventral fin root segment front slide bar 12, the ventral fin root segment rear slide bar 13 and the ventral fin root segment tail end rib ear piece 16, the ventral fin middle segment tail end rib 9 moves on the slide bar to drive the ventral fin middle segment 2 to move; the ventral fin middle segment tail end rib 9 is fixedly installed with the ventral fin middle segment tail end rib It is equipped with a front ventral fin middle section 14, a rear ventral fin middle section sliding rod 15, a ventral fin middle section tail end rib ear 17 and a nut 20. The ventral fin front section tail end rib 10 moves on the sliding rod to drive the ventral fin front section 3 to move; the ventral fin front section connecting rib ear 18 is fixedly installed on the ventral fin front section connecting rib 11, and the connecting rod motion module hinged to the ventral fin front section connecting rib ear 18 drives the ventral fin front section connecting rib 11 to move to drive the ventral fin front section 3 to move.

[0007] Furthermore, the telescopic device includes a screw mechanism and a connecting rod motion module; the screw mechanism drives the ventral fin middle segment 2 to move along the ventral fin span direction; the screw mechanism is composed of a screw 5, a nut 20 and a bearing 6 inside the ventral fin hollow main shaft; the screw 5 is movably connected to the ventral fin hollow main shaft 4 through the bearing 6 inside the ventral fin hollow main shaft, and when the screw cap 25 is driven by the servo motor, the screw 5 only rotates but cannot move, driving the nut 20 to pull the ventral fin middle segment tail end rib 9 to move on the ventral fin root segment front slide 12 and the ventral fin root segment rear slide 13, and when the ventral fin middle segment tail end rib 9 moves, it drives the ventral fin middle segment 2 to move; when the ventral fin middle segment tail end rib 9 moves, it triggers the connecting rod motion module to telescope along the ventral fin span direction to drive the ventral fin front segment 3 to move;

[0008] The connecting rod motion module drives the front segment 3 of the ventral fin to move when it is extended and retracted along the span of the ventral fin; the connecting rod motion module is composed of a driving connecting rod 21, multiple transmission connecting rods 22 and multiple tension springs 23; the driving connecting rod 21 has a short handle that is bent and extended, and the end of the short handle is connected to the spiral spring 19; the number of transmission connecting rods 22 is based on the ability to maintain the connecting rod motion module to freely extend and retract without getting stuck, the transmission connecting rods 22 are hinged to each other, and the transmission connecting rods 22 are hinged to the driving connecting rods 21; the tension springs 23 are connected between the transmission connecting rods 22 or the driving connecting rods 21, and the tension springs 23 are spaced between two transmission connecting rods 22 Arrangement is performed; when the tail end rib 9 of the middle section of the ventral fin moves in the direction away from the tail end rib 8 of the root section of the ventral fin, the spiral spring 19 fixedly connected to the tail end rib ear 16 of the root section of the ventral fin pulls the short handle of the driving connecting rod 21 to trigger the connecting rod motion module to extend outward, driving the front section 3 of the ventral fin to move in the direction away from the tail end rib 9 of the middle section of the ventral fin; when the tail end rib 9 of the middle section of the ventral fin moves in the direction close to the tail end rib 8 of the root section of the ventral fin, the tension spring 23 pulls the connecting rod motion module inward to contract, driving the front section 3 of the ventral fin to move in the direction close to the tail end rib 9 of the middle section of the ventral fin.

[0009] Furthermore, the rotating device includes a ventral fin hollow main shaft 4, gear teeth 7 and a fuselage connecting bearing 24; the ventral fin hollow main shaft 4 is movably connected to the fuselage through the fuselage connecting bearing 24, and the end face of the ventral fin hollow main shaft 4 on the outside of the fuselage is fixedly connected to the ventral fin root segment tail end rib 8. When the gear teeth 7 on the ventral fin hollow main shaft 4 are driven by the servo motor to rotate, the ventral fin hollow main shaft 4 drives the ventral fin to rotate up and down longitudinally, so that the ventral fin attitude angle changes.

[0010] Furthermore, the maximum variation rate of the ventral fin wingspan is 64%; the maximum variation range of the ventral fin attitude angle is ±35°.

[0011] Beneficial effects of the present invention:

[0012] 1. The shape, size, area and attitude angle of the aircraft's ventral fin can be adjusted according to changes in the maritime flight environment and flight status to meet the requirements of static heading stability and aerodynamic drag reduction of ship-borne UAVs.

[0013] 2. The space activity area that can be obtained by extending and rotating the aircraft's ventral fins individually or simultaneously is expanded, which greatly reduces the restrictions of the internal installation space of the tail fuselage on the design shape and area of ​​the ventral fins.

[0014] 3. The aircraft ventral fin is assembled by movably connecting multiple segmented structures, and the aircraft ventral fin is movably connected to the fuselage. The aircraft ventral fin can be quickly disassembled, and the segmented structure can be partially repaired or replaced, with low economic cost of use and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the appearance of the ventral fin of the present invention when it is fully extended;

[0016] Figure 2 This is a schematic diagram of the appearance of the ventral fins of the present invention when they are fully retracted;

[0017] Figure 3 This is a schematic diagram of the internal structure of the present invention when the ventral fin is fully extended;

[0018] Figure 4 This is a schematic diagram of the internal structure of the present invention when the ventral fins are fully retracted;

[0019] Figure 5 Schematic diagram of the segmented tail end rib of the ventral fin root of the present invention;

[0020] Figure 6 Schematic diagram of the segmented tail rib of the ventral fin of the present invention;

[0021] Figure 7 Schematic diagram of the tail end rib of the front segment of the ventral fin of the present invention;

[0022] Figure 8 This is a schematic diagram of the front segment of the ventral fin connected to the ribs of the present invention;

[0023] Figure 9 A schematic diagram of a driving connecting rod of the present invention;

[0024] Figure 10 Schematic diagram of the transmission connecting rod of the present invention;

[0025] Figure 11 This is a side view schematic diagram of the double ventral fins of the present invention installed on the fuselage;

[0026] Figure 12 This is a schematic diagram of the reference attitude angle position of the double ventral fins installed on the fuselage of the present invention;

[0027] Figure 13 This is a schematic diagram of the double ventral fins of the present invention rotating vertically upward;

[0028] Figure 14 It is a schematic diagram of the double ventral fins of the present invention lowering their heads and rotating downward in the longitudinal direction.

[0029] In the above figure, 1 is the ventral fin root segment, 2 is the ventral fin middle segment, 3 is the ventral fin front segment, 4 is the ventral fin hollow main shaft, 5 is the screw rod, 6 is the inner bearing of the ventral fin hollow main shaft, 7 is the gear tooth, 8 is the ventral fin root segment tail end rib, 9 is the ventral fin middle segment tail end rib, 10 is the ventral fin front segment tail end rib, 11 is the ventral fin front segment connecting rib, 12 is the ventral fin root segment front slider, 13 is the ventral fin root segment rear slider, 14 is the ventral fin middle segment front slider, 15 is the ventral fin middle segment rear slider, 16 is the ventral fin root segment tail end rib ear , 17 is the rib ear piece at the tail end of the middle section of the ventral fin, 18 is the rib ear piece connecting the front section of the ventral fin, 19 is the scroll spring, 20 is the nut, 21 is the driving connecting rod, 22 is the transmission connecting rod, 23 is the tension spring, 24 is the fuselage connecting bearing, 25 is the screw rod top cap, 26 is the screw rod tail end face, 27 is the driving connecting rod straight ear piece, 28 is the driving connecting rod folded ear piece, 29 is the driving connecting rod slot, 30 is the driving connecting rod connecting piece, 31 is the transmission connecting rod straight ear piece, 32 is the transmission connecting rod folded ear piece, 33 is the transmission connecting rod connecting piece. DETAILED DESCRIPTION

[0030] The technical solution adopted in the present invention is as follows:

[0031] The invention discloses a retractable and rotatable ventral fin of a shipborne UAV, which is mainly composed of a skin, wing ribs, a slide rod, a retractable device and a rotating device.

[0032] The skin consists of the skin of the ventral fin root segment 1, the skin of the ventral fin middle segment 2, and the skin of the ventral fin front segment 3. The ventral fin front segment 3 is mounted inside the ventral fin middle segment 2, and the ventral fin middle segment 2 is mounted inside the ventral fin root segment 1. The ventral fin root segment 1 and the ventral fin middle segment 2 are movably connected via a screw 5, a nut 20, a ventral fin root segment front slide 12, and a ventral fin root segment rear slide 13. The ventral fin middle segment 2 and the ventral fin front segment 3 are movably connected via a ventral fin middle segment front slide 14, a ventral fin middle segment rear slide 15, and a connecting rod motion module.

[0033] The wing ribs include the tail end rib 8 of the ventral fin root segment, the tail end rib 9 of the ventral fin middle segment, the tail end rib 10 of the ventral fin front segment and the connecting rib 11 of the ventral fin front segment. The ventral fin root segment tail end rib 8 is fixedly mounted with a ventral fin root segment front slide bar 12, a ventral fin root segment rear slide bar 13 and a ventral fin root segment tail end rib ear 16, and the ventral fin middle segment tail end rib 9 moves on the slide bar to drive the ventral fin middle segment 2 to move; the ventral fin middle segment front 14, the ventral fin middle segment rear slide bar 15, the ventral fin middle segment tail end rib ear 17 and a nut 20 are fixedly mounted on the ventral fin middle segment tail end rib 9, and the ventral fin front segment tail end rib 10 moves on the slide bar to drive the ventral fin front segment 3 to move; the ventral fin front segment connecting rib ear 18 is fixedly mounted on the ventral fin front segment connecting rib 11, and the connecting rod motion module hinged to the ventral fin front segment connecting rib ear 18 drives the ventral fin front segment connecting rib 11 to move to drive the ventral fin front segment 3 to move.

[0034] The telescopic device drives the ventral fin to telescope along the span direction to adjust the size of the ventral fin. The device includes a screw mechanism and a connecting rod motion module. The screw mechanism drives the ventral fin middle segment 2 to move along the span direction of the ventral fin. The screw mechanism consists of a screw 5, a nut 20 and an inner bearing 6 of the ventral fin hollow main shaft. The screw 5 is movably connected to the ventral fin hollow main shaft 4 through the inner bearing 6 of the ventral fin hollow main shaft. When the screw top cap 25 is driven by the servo motor, the screw 5 only rotates but cannot move, driving the nut 20 to pull the tail end rib 9 of the ventral fin middle segment to move on the front slide bar 12 of the ventral fin root segment and the rear slide bar 13 of the ventral fin root segment. When the tail end rib 9 of the ventral fin middle segment moves, it drives the ventral fin middle segment 2 to move; when the tail end rib 9 of the ventral fin middle segment moves, it triggers the connecting rod motion module to telescope along the span direction of the ventral fin to drive the front segment 3 of the ventral fin to move.

[0035] The connecting rod motion module in the telescopic device drives the front ventral fin segment 3 to move as it expands and contracts along the ventral fin span. The connecting rod motion module consists of a driving connecting rod 21, multiple transmission connecting rods 22, and multiple tension springs 23. The driving connecting rod 21 has a short, bent, extended handle, the end of which is connected to the spiral spring 19. The number of transmission connecting rods 22 is based on the principle that the connecting rod motion module can freely expand and contract without getting stuck. The transmission connecting rods 22 are hinged to each other and to the driving connecting rod 21. The tension springs 23 are connected between the transmission connecting rods 22 or the driving connecting rods 21, and are arranged so that the two transmission connecting rods 22 are spaced apart. When the tail end rib 9 of the middle section of the ventral fin moves away from the tail end rib 8 of the root section of the ventral fin, the spiral spring 19 fixedly connected to the tail end rib ear 16 of the root section of the ventral fin pulls the short handle of the driving connecting rod 21 to trigger the connecting rod motion module to extend outward, driving the front section 3 of the ventral fin to move away from the tail end rib 9 of the middle section of the ventral fin; when the tail end rib 9 of the middle section of the ventral fin moves toward the tail end rib 8 of the root section of the ventral fin, the tension spring 23 pulls the connecting rod motion module inward, driving the front section 3 of the ventral fin to move toward the tail end rib 9 of the middle section of the ventral fin.

[0036] The rotation mechanism drives the ventral fin to rotate vertically to adjust the attitude angle. This mechanism includes the ventral fin's hollow main shaft 4, gear teeth 7, and fuselage connection bearing 24. The ventral fin's hollow main shaft 4 is movably connected to the fuselage via the fuselage connection bearing 24. The end surface of the ventral fin's hollow main shaft 4 on the fuselage's exterior is fixedly connected to the rib 8 at the tail end of the ventral fin's root segment. When the gear teeth 7 on the ventral fin's hollow main shaft 4 rotate, driven by a servo motor, the hollow main shaft 4 drives the ventral fin to rotate vertically, causing the ventral fin's attitude angle to change.

[0037] The pelvic fins can be extended and rotated independently or simultaneously without interfering with each other. The maximum span variation rate of the pelvic fins reaches 64%, and the pelvic fins can continuously change within the maximum variation rate. The maximum range of the pelvic fin attitude angle is ±35°, and the pelvic fin attitude angle can continuously change within the maximum variation range.

[0038] The two ventral fins are symmetrically installed on the left and right sides of the belly at the tail end of the fuselage in an eight-shaped layout. According to the changes in the sea flight environment and flight status of the ship-borne UAV, the ventral fins on both sides are synchronously extended and rotated in equal amounts to maintain symmetry at all times.

[0039] The present invention will be described in further detail below with reference to the accompanying drawings.

[0040] like Figure 1 、 Figure 2 、 Figure 3 and Figure 4 As shown, a retractable and rotatable shipborne UAV ventral fin of the present invention includes a skin, wing ribs, a slide rod, a retractable device and a rotating device.

[0041] like Figure 1As shown, when the ventral fin is in a fully extended state, the skin of the ventral fin root segment 1, the skin of the ventral fin middle segment 2 and the skin of the ventral fin front segment 3 are all exposed along the span direction of the ventral fin; Figure 2 In the figure, when the ventral fin is in a fully retracted state, the skin of the ventral fin front segment 3 is completely hidden inside the ventral fin middle segment 2, and the skin of the ventral fin middle segment 2 is completely hidden inside the ventral fin root segment 1.

[0042] like Figure 3 and Figure 4 As shown, the tail end rib 8 of the ventral fin root segment is fixedly connected to the hollow main shaft 4 of the ventral fin, and when the hollow main shaft 4 of the ventral fin rotates, the ventral fin is driven to rotate up and down in the longitudinal direction to change the attitude angle of the ventral fin; the nut 20 is fixedly installed on the tail end rib 9 of the middle segment of the ventral fin, and when the nut 20 is driven by the screw rod 5, it drives the tail end rib 9 of the middle segment of the ventral fin to move on the front slide bar 12 of the ventral fin root segment and the rear slide bar 13 of the ventral fin root segment; when the ventral fin front segment connecting rib 11 is driven by the connecting rod motion module, it moves along the span direction of the ventral fin, driving the ventral fin front segment 3 and the tail end rib 10 of the ventral fin front segment to move on the front slide bar 14 of the middle segment of the ventral fin and the rear slide bar 15 of the middle segment of the ventral fin.

[0043] like Figure 5 As shown, the ventral fin root segment tail end rib 8 is fixedly mounted with the ventral fin root segment front slide bar 12 and the ventral fin root segment rear slide bar 13 for the ventral fin middle segment 2 to slide within the ventral fin root segment 1; the ventral fin root segment tail end rib ear piece 16 is fixedly mounted on the ventral fin root segment tail end rib 8 to fix the spiral spring 19; the ventral fin root segment tail end rib 8 is provided with a large circular hole to accommodate the screw rod 5 to pass through. Figure 6 As shown, the front slide bar 14 and the rear slide bar 15 of the middle segment of the ventral fin are fixedly installed on the rib 9 at the tail end of the middle segment of the ventral fin, so as to enable the front segment 3 of the ventral fin to slide in the middle segment 2 of the ventral fin; the nut 20 and the ear piece 17 of the middle segment of the ventral fin are fixedly installed on the rib 9 at the tail end of the middle segment of the ventral fin, and a circular hole is opened on the ear piece 17 of the middle segment of the ventral fin so as to be hinged with the driving connecting rod 21 in the connecting rod motion module; two small circular holes are opened on the rib 9 at the tail end of the middle segment of the ventral fin to accommodate the front slide bar 12 and the rear slide bar 13 of the root segment of the ventral fin; a rectangular hole is opened on the rib 9 at the tail end of the middle segment of the ventral fin to accommodate the ear piece 16 of the root segment of the ventral fin and the spiral spring 19 to pass through.

[0044] like Figure 7 As shown, the rib 10 at the tail end of the front ventral fin segment is provided with two pairs of small circular holes, one large circular hole, and one rectangular hole. Each pair of small circular holes can accommodate the front sliding rod 12 of the ventral fin root segment, the rear sliding rod 13 of the ventral fin root segment, the front sliding rod 14 of the ventral fin middle segment, and the rear sliding rod 15 of the ventral fin middle segment. The large circular hole can accommodate the screw rod 5 and the nut 20. The rectangular hole can accommodate the driving connecting rod 21 and the transmission connecting rod 22. Figure 8As shown, two pairs of small circular holes and one large circular hole are opened on the ventral fin front segment connecting rib 11; each pair of small circular holes can respectively accommodate the ventral fin root segment front slide rod 12, the ventral fin root segment rear slide rod 13, the ventral fin middle segment front slide rod 14 and the ventral fin middle segment rear slide rod 15 to pass through; the large circular hole can accommodate the screw rod 5 and the nut 20 to pass through; the ventral fin front segment connecting rib ear 18 is fixedly installed on the ventral fin front segment connecting rib 11, and a circular hole is opened on the ventral fin front segment connecting rib ear 18 so as to be hinged with the transmission connecting rod 22 in the connecting rod motion module.

[0045] like Figure 9 and Figure 10 As shown, the link motion module in the telescopic device includes a driving link 21 , a transmission link 22 and a tension spring 23 . The driving link 21 has a short handle that is bent and extended, and a driving link folding ear piece 28 is provided at the end of the short handle; the driving link 21 is hinged to the wing rib ear piece 17 of the tail end of the ventral fin segment at the position of the driving link slot 29; the cross-sections of the driving link 21 and the transmission link 22 are both U-shaped groove sheets to reduce weight, and the driving link connecting piece 30 and the transmission link connecting piece 33 are respectively fixed in the grooves of the driving link 21 and the transmission link 22; the driving link straight ear piece 27 is hinged to the transmission link folding ear piece 32 to realize the movable connection between the driving link 21 and the transmission link 22, and the transmission link straight ear piece 31 and the transmission link folding ear piece 32 are hinged to realize the movable connection between different transmission links 22, and the two ends of the tension spring 23 are respectively hooked in the small holes of the driving link connecting piece 30 or the transmission link connecting piece 33 to drive the link motion module to retract inward. The spiral spring 19 is connected to the small hole of the driving link folding ear piece 28 to pull the short handle of the driving link 21 and thereby drive the link motion module to extend outward.

[0046] like Figure 11 and Figure 12 As shown, two ventral fins are symmetrically mounted on the left and right sides of the fuselage's rear end, forming a figure-eight pattern. Based on the carrier-based drone's flight environment and flight state, the two ventral fins simultaneously expand and contract and rotate in equal amounts to maintain symmetry at all times, without interfering with each other. The ventral fins are adjustable in spanwise direction using a telescoping mechanism, with a maximum span variation of 64%, allowing for continuous movement within this maximum variation range.

[0047] like Figure 13 and Figure 14 As shown, the ventral fin is rotated up and down longitudinally by a rotating device to adjust the attitude angle. The maximum variation range of the ventral fin attitude angle is ±35°, and the ventral fin attitude angle can be continuously changed within the maximum variation range.

[0048] The above specific embodiments are limited to explaining and illustrating the technical solutions of the present invention, and do not constitute a limitation on the scope of protection of the claims. It should be clear to those skilled in the art that any new technical solutions obtained by making any simple modification or substitution based on the technical solutions of the present invention fall within the scope of protection of the present invention.

Claims

1. A retractable and rotatable ventral fin of a shipborne UAV, characterized in that: Two ventral fins are symmetrically mounted on the left and right sides of the belly at the tail end of the fuselage in an eight-shaped arrangement; the ventral fins are assembled by movably connecting a ventral fin front segment (3), a ventral fin middle segment (2) and a ventral fin root segment (1); the ventral fin front segment (3) is mounted inside the ventral fin middle segment (2), and the ventral fin middle segment (2) is mounted inside the ventral fin root segment (1); the ventral fins include skin, ribs, a slide rod, a telescopic device and a rotating device; The telescopic device drives the ventral fin to extend and retract along the span direction to adjust the size of the ventral fin; the rotation device drives the ventral fin to rotate up and down in the longitudinal direction to adjust the attitude angle; the ventral fin can be extended and retracted and rotated individually or simultaneously without interfering with each other; The wing ribs include a ventral fin root segment tail end rib (8), a ventral fin middle segment tail end rib (9), a ventral fin front segment tail end rib (10) and a ventral fin front segment connecting rib (11); a ventral fin root segment front sliding rod (12), a ventral fin root segment rear sliding rod (13) and a ventral fin root segment tail end rib ear (16) are fixedly mounted on the ventral fin root segment tail end rib (8), and the ventral fin middle segment tail end rib (9) moves on the sliding rod to drive the ventral fin middle segment (2) to move; The telescopic device includes a screw mechanism and a connecting rod motion module; the screw mechanism drives the ventral fin middle segment (2) to move along the ventral fin span direction; the screw mechanism consists of a screw (5), a nut (20) and a ventral fin hollow main shaft inner bearing (6); the screw (5) and the ventral fin hollow main shaft (4) are movably connected through the ventral fin hollow main shaft inner bearing (6), and when the screw cap (25) is driven by the servo motor, the screw (5) only rotates but cannot move, and the driving nut (20) pulls the ventral fin middle segment tail end rib (9) to move on the ventral fin root segment front slide bar (12) and the ventral fin root segment rear slide bar (13), and when the ventral fin middle segment tail end rib (9) moves, the ventral fin middle segment (2) is driven to move; when the ventral fin middle segment tail end rib (9) moves, the connecting rod motion module is triggered to telescope along the ventral fin span direction to drive the ventral fin front segment (3) to move; The connecting rod motion module drives the front segment (3) of the ventral fin to move when the connecting rod motion module is extended and retracted along the ventral fin span; the connecting rod motion module is composed of a driving connecting rod (21), a plurality of transmission connecting rods (22) and a plurality of tension springs (23); the driving connecting rod (21) has a short handle that is bent and extended, and the end of the short handle is connected to the spiral spring (19); the number of the transmission connecting rods (22) is based on the ability to maintain the connecting rod motion module to freely extend and retract without being stuck, the transmission connecting rods (22) are hinged to each other, and the transmission connecting rods (22) and the driving connecting rod (21) are hinged to each other; the tension spring (23) is connected between the transmission connecting rod (22) or the driving connecting rod (21), and the tension spring (23) is spaced between two transmission connecting rods ( 22) is arranged; when the ventral fin middle section tail end rib (9) moves in a direction away from the ventral fin root section tail end rib (8), the vortex spring (19) fixedly connected to the ventral fin root section tail end rib ear (16) pulls the short handle of the driving connecting rod (21) to trigger the connecting rod motion module to extend outward, driving the ventral fin front section (3) to move in a direction away from the ventral fin middle section tail end rib (9); when the ventral fin middle section tail end rib (9) moves in a direction close to the ventral fin root section tail end rib (8), the tension spring (23) pulls the connecting rod motion module inward to retract, driving the ventral fin front section (3) to move in a direction close to the ventral fin middle section tail end rib (9).

2. The retractable and rotatable ventral fin of a shipborne UAV according to claim 1, characterized in that: The skin comprises the skin of the ventral fin root segment (1), the skin of the ventral fin middle segment (2) and the skin of the ventral fin front segment (3); the ventral fin root segment (1) and the ventral fin middle segment (2) are movably connected via a screw rod (5), a nut (20), a ventral fin root segment front slide rod (12) and a ventral fin root segment rear slide rod (13); the ventral fin middle segment (2) and the ventral fin front segment (3) are movably connected via a ventral fin middle segment front slide rod (14), a ventral fin middle segment rear slide rod (15) and a connecting rod motion module.

3. The retractable and rotatable ventral fin of a shipborne UAV according to claim 1, characterized in that: The ventral fin middle segment tail end rib (9) is fixedly mounted with a ventral fin middle segment front slide rod (14), a ventral fin middle segment rear slide rod (15), a ventral fin middle segment tail end rib ear (17) and a nut (20), and the ventral fin front segment tail end rib (10) moves on the slide rod to drive the ventral fin front segment (3) to move; the ventral fin front segment connecting rib ear (18) is fixedly mounted on the ventral fin front segment connecting rib (11), and a connecting rod motion module hinged to the ventral fin front segment connecting rib ear (18) drives the ventral fin front segment connecting rib (11) to move to drive the ventral fin front segment (3) to move.

4. The retractable and rotatable ventral fin of a shipborne UAV according to claim 1, characterized in that: The rotating device comprises a ventral fin hollow main shaft (4), gears (7) and a fuselage connecting bearing (24); the ventral fin hollow main shaft (4) is movably connected to the fuselage through the fuselage connecting bearing (24); the end surface of the ventral fin hollow main shaft (4) on the outside of the fuselage is fixedly connected to the ventral fin root segment tail end rib (8); when the gears (7) on the ventral fin hollow main shaft (4) are driven by the servo motor to rotate, the ventral fin hollow main shaft (4) drives the ventral fin to rotate up and down in the longitudinal direction, so that the ventral fin attitude angle changes.

5. The retractable and rotatable ventral fin of a shipborne UAV according to claim 1, characterized in that: The maximum variation rate of ventral fin wingspan is 64%; the maximum variation range of ventral fin attitude angle is ±35 o .

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