Water-air cross-medium vehicle with tail seat folding wing and mode switching method thereof

Abstract

The application discloses a water-air cross-medium aircraft with a tail seat type folding wing and a mode switching method thereof, and belongs to the technical field of cross-medium aircrafts and variable wing design. The aircraft comprises a middle fuselage, a middle wing, a folding mechanism, an aerial power unit, an outer wing assembly, an underwater propulsion device and a control system. The folding mechanism can drive the outer wing to switch between an unfolded "I" shaped fixed wing mode and a folded "∩" shaped quadrotor mode, and the aircraft has high efficient cruising and vertical take-off and landing capabilities. Folded propellers are used to reduce underwater resistance, and airbag attitude adjustment structures and wing drainage holes are used to realize controllable water entry and exit. The underwater propulsion device is matched with a reusable aileron to realize underwater maneuvering. The application can complete a whole process cross-medium task including land take-off, air cruising, water entry, water exit and take-off, and is suitable for scenes such as marine inspection, underwater detection and emergency rescue.

Description

Technical Field

[0001] This invention relates to the field of transmedium aircraft and morphing wing design technology, and in particular to a tail-seat folding wing transmedium aircraft and its mode switching method. Background Technology

[0002] Trans-medium aircraft can move in both air and water, enabling rapid deployment in scenarios such as maritime inspection, ocean observation, emergency rescue, and military reconnaissance. For tasks such as offshore wind power operation and maintenance, near-shore facility monitoring, and close-range detection of marine targets, the operating platform needs to have both rapid air cruising and arrival capabilities, as well as underwater maneuverability and close-range detection capabilities after entering the water. Single-medium aircraft or underwater vehicles cannot simultaneously meet the requirements of air range, water entry safety, underwater propulsion efficiency, and repeated entry and exit from the water.

[0003] Tail-seat vertical takeoff and landing (VTOL) aircraft offer advantages such as simple structure, no runway required, and high cruise efficiency compared to fixed-wing aircraft. However, conventional tail-seat configurations suffer from issues such as large changes in wing frontal area, difficulty in matching the thrust center with the center of gravity, and insufficient low-speed attitude control margin when switching between hovering and cruise modes. Existing tail-seat aircraft with deployable wings are mostly designed for pure air-medium flight scenarios and have not addressed core issues such as water entry impact protection, efficient underwater propulsion, and stable attitude control upon exiting the water for cross-medium water-air scenarios.

[0004] Existing transmedium-water aircraft mostly employ vector rotors, flexible wing surfaces, or dedicated underwater propulsion structures to achieve transmedium motion, but they generally struggle to simultaneously achieve vertical takeoff and landing on land, long-range fixed-wing cruise, low-speed controllable water entry, and underwater maneuverability. In particular, within the complete mission chain of "land departure - long-distance flight to target water area - low-speed water entry - underwater operation - surfacing and returning," there is a lack of an integrated configuration that can reliably switch between quadcopter mode, fixed-wing mode, and underwater navigation mode.

[0005] Therefore, there is an urgent need to develop a trans-medium watercraft that combines land vertical takeoff and landing, efficient air cruise, controllable low-speed water entry, underwater propulsion, and attitude maneuverability to improve the response speed, range efficiency, and environmental adaptability of trans-medium missions. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a tail-seat folding wing water-air transmedia aircraft and its mode switching method. The folding wing mechanism, waterproof drive structure, airbag attitude adjustment system, and underwater propulsion layout are integrated into a single design, enabling multi-mode switching between fixed-wing efficient cruise, quadcopter vertical take-off and landing, and underwater navigation and maneuvering. This solves the problems of large water entry impact, high underwater drag, and difficult attitude control upon exiting the water during the water-air transmedia process.

[0007] The technical solution adopted in this invention, a tail-seat folding wing water-air transmedia aircraft and its mode switching method, is as follows: A tail-seat folding wing trans-medium water-to-air aircraft includes a mid-fuselage, a mid-wing section, a folding mechanism, an airborne power unit, an outer wing assembly, an underwater propulsion device, and a control system. The mid-wing section is symmetrically connected to both sides of the mid-fuselage. The outer wing assembly is connected to the outer end of the mid-wing section via the folding mechanism. The airborne power unit is mounted on the outer wing assembly. The underwater propulsion device is located at the tail of the mid-fuselage. The control system is electrically connected to the folding mechanism, the airborne power unit, and the underwater propulsion device. The folding mechanism is used to drive the outer wing assembly to switch between the deployed state and the folded state; in the deployed state, the middle wing and the outer wing assembly form a “I”-shaped four-engine fixed wing mode along the span; in the folded state, the outer wing assembly bends towards the fuselage, and when viewed from above, it forms a “∩”-shaped quadcopter mode. The control system is used to regulate the working status of each component, enabling the aircraft to switch modes between fixed-wing cruise, quadcopter vertical take-off and landing, underwater navigation, and water-air cross-medium entry and exit.

[0008] A further improvement to the technical solution of the present invention is that: the folding mechanism includes a motor bearing housing, an outer wing connector, a waterproof servo, a carbon fiber support assembly, and a circular servo arm; the motor bearing housing is fixed to the outer end of the middle wing, the waterproof servo is fixedly mounted on the motor bearing housing, and its output end is fixedly connected to the circular servo arm; the circular servo arm is fixedly connected to the outer wing connector, and the outer wing connector is connected to the outer wing assembly; the carbon fiber support assembly, together with a bearing with a flange, constitutes a rotational support structure.

[0009] A further improvement of the technical solution of the present invention is that: the folding mechanism is also provided with a limit block, and both the unfolded state and the folded state are mechanically limited by the limit block; and when the aircraft is in unfolded cruising, the force direction of the limit block is matched with the lift direction of the wing to form a stable self-locking mechanism.

[0010] A further improvement of the technical solution of the present invention is that: the air power unit includes a brushless motor and a folding propeller; when the air power unit is working, the folding propeller unfolds under centrifugal force to provide thrust or lift; after stopping or entering the water, the folding propeller automatically retracts to reduce the impact of entering the water and the resistance of underwater navigation.

[0011] A further improvement of the technical solution of the present invention is that it also includes a fuselage airbag and an outer end airbag, wherein the fuselage airbag is disposed at the rear of the middle fuselage and the outer end airbag is disposed at the outer end of the outer wing assembly; the trailing edge of the outer wing assembly is provided with a drainage hole for draining internal water.

[0012] A further improvement of the technical solution of the present invention is that: the outer wing assembly includes an outer main wing and an aileron control assembly; the aileron control assembly is located at the trailing edge of the outer main wing, and is used for air roll attitude control in fixed wing mode, and serves as an underwater control surface in underwater navigation mode, and works with the underwater propulsion device to achieve underwater maneuvering.

[0013] A further improvement of the technical solution of the present invention is that: the intermediate fuselage includes a sealed cabin, a front cover of the sealed cabin and a rear cover of the sealed cabin, forming a sealed accommodating cavity; the underwater propulsion device includes an underwater thruster and an underwater propeller, which are fixed to the tail of the intermediate fuselage by a streamlined support structure, and the thrust direction is arranged along the longitudinal direction of the fuselage.

[0014] A further improvement of the technical solution of the present invention is that: the control system includes an airborne processing unit, a flight controller, a water depth detection unit, and an airbag aerodynamic control loop; the airborne processing unit is communicatively connected to the flight controller, the flight controller is used to collect attitude information and control the airborne power unit, the folding mechanism, and the aileron control components, the water depth detection unit is used to detect the water entry depth and the water surface contact state, and the airbag aerodynamic control loop is used to regulate the inflation and deflation process of the airbag.

[0015] A mode switching method for a tail-seat folding-wing water-to-air trans-medium aircraft, used to control the mode switching of the aforementioned aircraft, includes the following steps: S1. Vertical takeoff from land: The folding mechanism remains folded, and the aircraft takes off vertically in quadcopter mode. S2, Aerial Wing-Spreading Cruise: After the aircraft accelerates, the folding mechanism drives the outer wing components to unfold, switching to fixed-wing mode to perform cruise missions; S3, Deceleration and Folding into Water: After reaching the target water area, the aircraft decelerates, the folding mechanism folds the wings to restore the quadcopter mode, and enters the water at a low speed and controllable attitude, while the air power unit stops rotating. S4. Underwater navigation and maneuvering: The underwater propulsion system is activated to provide navigation power, and the underwater motion attitude is adjusted through the aileron control components; S5. Attitude Adjustment and Water Exit Takeoff: After receiving the cross-medium takeoff command, the fuselage airbag and the outer end airbag are inflated, the aircraft attitude is adjusted so that the air power unit is exposed above the water surface, the air power unit is activated and the aircraft takes off in quadcopter mode, and the water accumulated inside the wings is discharged through the drain holes.

[0016] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows: This invention achieves reliable switching between the "∩"-shaped quadcopter mode and the "I"-shaped four-engine fixed-wing mode through a folding mechanism. It retains the land vertical take-off and landing, low-speed hovering and water take-off capabilities of the quadcopter mode, while also gaining the long-range and efficient cruise capability of the fixed-wing mode. When the cruise is deployed, the limiting block and the wing lift form a stable self-locking mechanism, which can reduce the energy consumption of the waterproof servo motor to maintain torque for a long time and improve the reliability of the mechanism.

[0017] This invention integrates a single underwater propulsion unit in the middle rear section of the fuselage, while reusing the ailerons of the outer wing section as underwater control surfaces. After entering the water, it can complete underwater navigation and turning maneuvers without relying on the air propeller, avoiding the need for additional redundant control surfaces or multiple propulsion units. Combined with the attitude adjustment functions of the fuselage airbag and the outer end airbag, it can stably realize the process of the air power unit emerging from the water and taking off, improving the reliability of cross-medium switching.

[0018] This invention employs a synergistic design of a folding propeller, a sealed fuselage, an airbag attitude adjustment structure, and drainage holes on the trailing edge of the wing. This effectively reduces the impact load upon entering the water and underwater drag, and solves the problems of water accumulation on the wing and attitude stability during takeoff. The mode switching process covers the entire process from land takeoff, aerial cruise, deceleration into the water, underwater navigation, to takeoff from the water. It is suitable for various mission scenarios such as maritime inspection, cross-media reconnaissance, target delivery, and close-range underwater detection. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the tail-seat type folding wing water-air transmedia aircraft of the present invention in its deployed state. Figure 2 This is a schematic diagram of the overall structure of the tail-seat type folding wing water-air transmedia aircraft of the present invention in its folded state. Figure 3 This is a cross-sectional structural schematic diagram of the unfolding mechanism of the tail-seat type folding wing water-air trans-medium aircraft of the present invention in its unfolded state; Figure 4 This is a cross-sectional structural schematic diagram of the folding mechanism of the tail-seat type folding wing trans-medium water-air aircraft of the present invention in the folded state; Figure 5 This is an isometric structural diagram of the deployment mechanism of the tail-seat type folding wing of the present invention, showing the deployed state of the trans-medium water-air aircraft. Figure 6 This is an isometric structural diagram of the folding mechanism of the tail-seat folding wing of the present invention, showing the folded state of the folding mechanism of the trans-medium water-air aircraft. Figure 7 This is a schematic diagram of the intermediate fuselage of the tail-mounted folding wing water-air transmedia aircraft of the present invention. In the attached diagram

[0020] 1. Middle fuselage; 101. Front cover of the sealed compartment; 102. Sealed compartment body; 103. Stainless steel pipe clamp; 104. Bolt-clamped open shaft sleeve seat; 105. Rear cover of the sealed compartment; 106. Streamlined underwater motor support; 107. Underwater thruster; 108. Underwater propeller; 2. Fuselage airbags; 3. Mid-section wing; 4. Folding and unfolding mechanism; 401. Motor bearing housing; 402. Outer wing connector; 403. Waterproof servo; 404. First carbon fiber tube; 406. Second carbon fiber tube; 407. Bearing with side guard; 408. Circular servo arm; 5. Airborne power unit; 501. Brushless motor; 502. Folding propeller; 503. Propeller mount; 504. Folding propeller mount; 505. Bullet-shaped propeller clip; 6. Outer wing assembly; 601. Outer main wing; 602. Outer aileron; 603. Aileron strut; 604. Waterproof servo; 7. External motor mount; 8. External airbag. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. In the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concept of this invention. Example 1

[0022] like Figure 1 , Figure 2 and Figure 7 As shown, this embodiment provides a tail-mounted folding wing trans-medium water-air aircraft, which mainly includes a middle fuselage 1, fuselage airbag 2, middle wing 3, folding mechanism 4, airborne power unit 5, outer wing assembly 6, outer motor mount 7, outer end airbag 8, underwater thruster 107, underwater propeller 108, and control system.

[0023] The intermediate fuselage 1 is the core load-bearing and sealing structure of the entire aircraft, including a hemispherical sealed cabin front cover 101, a sealed cabin body 102, a stainless steel pipe clamp 103, a bolt-clamped open shaft sleeve seat 104, a sealed cabin rear cover 105, and a streamlined underwater motor support 106. The hemispherical sealed cabin front cover 101 is fastened to the front end of the sealed cabin body 102, and the sealed cabin rear cover 105 is installed at the rear end of the sealed cabin body 102. The three together form a sealed cavity, which houses the control system, battery, and mission payload. The stainless steel pipe clamp 103 and the bolt-clamped open shaft sleeve seat 104 are used to fix the root of the mid-section wing 3, realizing a rigid connection between the mid-section wing 3 and the intermediate fuselage 1. A streamlined underwater motor support 106 is fixedly mounted at the center of the tail of the sealed cabin rear cover 105. An underwater thruster 107 is installed at the rear end of the streamlined underwater motor support 106. An underwater propeller 108 is mounted on the output shaft of the underwater thruster 107. The thrust direction is arranged along the longitudinal axis of the fuselage, which can reduce the flow field interference with the wing structures on both sides during underwater navigation.

[0024] The mid-wing section 3 consists of two sections, symmetrically fixed to the middle sides of the fuselage 1. Each mid-wing section 3 has a folding mechanism 4 installed at its outer end. Figures 3 to 6 As shown, the folding mechanism 4 adopts a waterproof servo direct drive scheme, including a motor bearing housing 401, an outer wing connector 402, a waterproof servo 403, a first carbon fiber tube 404, a second carbon fiber tube 406, a bearing with a flange 407, and a circular servo arm 408. The motor bearing housing 401 is fixedly installed inside the outer end of the middle wing 3, and the waterproof servo 403 is fastened to the mounting end face of the motor bearing housing 401 by bolts; the output axis of the waterproof servo 403 extends outward, and the end is fixedly fitted with a circular servo arm 408. The circular servo arm 408 is fixedly connected to the end face of the outer wing connector 402 by bolts, thereby directly transmitting the torque of the waterproof servo 403 to the outer wing connector 402. The first carbon tube 404 and the second carbon tube 406 are respectively embedded in the motor bearing housing 401 and the outer wing connector 402. The bearing with a flange 407 is fitted between the carbon tubes, together forming a rotating support pair to bear the radial and axial loads of the outer wing assembly 6.

[0025] Limit blocks are provided at both the unfolded and folded positions of the folding mechanism 4. When the outer wing assembly 6 rotates to the target position, the limit blocks form a mechanical hard limit to prevent over-rotation. When the aircraft is in fixed-wing cruise mode, the lift of the wing causes the outer wing assembly 6 to bend upward. This trend is opposite to the support direction of the unfolding limit blocks, thus forming a stable mechanical self-locking mechanism. This eliminates the need for the waterproof servo motor 403 to output high torque for a long time, reducing system energy consumption and improving the reliability of long-term cruise.

[0026] There are two sets of outer wing assemblies 6, which are respectively installed on the outer wing connectors 402 of the left and right folding mechanisms 4. Each set of outer wing assemblies 6 includes an outer main wing 601, an outer aileron 602, an aileron strut 603, and a waterproof servo 604. The root of the outer main wing 601 is fixedly connected to the outer wing connector 402, and an outer motor mount 7 is installed at the outer end. The outer aileron 602 is hinged to the trailing edge of the outer main wing 601. The waterproof servo 604 is installed inside the outer main wing 601 and is connected to the outer aileron 602 through the aileron strut 603 to drive its deflection. Several drainage holes are opened at the lower part of the trailing edge of the outer main wing 601, penetrating the wing skin and the internal cavity, to drain water that has seeped into the wing during takeoff.

[0027] The airborne power unit 5 comprises four sets, with two sets mounted on each outer motor mount 7, arranged longitudinally along the wingspan. Each airborne power unit 5 includes a brushless motor 501, a folding propeller 502, a propeller mount 503, a folding propeller mount 504, and a bullet-shaped propeller clamp 505. The brushless motor 501 is fixed to the outer motor mount 7 with its output shaft facing upwards. The propeller mount 503 is mounted on the motor shaft end, and the folding propeller mount 504 is hinged to both sides of the propeller mount 503. The folding propeller 502 is secured to the folding propeller mount 504 via the bullet-shaped propeller clamp 505. When the brushless motor 501 rotates, the folding propeller 502 automatically unfolds under centrifugal force, generating lift or thrust. When the brushless motor 501 stops rotating, the folding propeller 502 can retract inward around the hinge axis, close to the outer wall of the outer motor mount 7, thereby reducing the impact area upon entering the water and reducing additional drag during underwater navigation.

[0028] The fuselage airbags 2 are located on the left and right sides of the rear of the middle fuselage 1, and the outer airbags 8 are located on the lower part of the left and right outer motor mounts 7. Both the fuselage airbags 2 and the outer airbags 8 are connected to the airbag pneumatic control circuit, which can adjust their buoyancy by inflating and deflating, thereby changing the position of the center of buoyancy of the whole aircraft, realizing attitude adjustment in the water, and ensuring that all four sets of aerial power units 5 can be exposed above the water surface before takeoff.

[0029] The control system includes an airborne microprocessor, a flight controller, a depth sensor, and an airbag aerodynamic control loop. The airborne microprocessor, which can be a small embedded computing platform, is responsible for mission planning and high-level decision-making. The flight controller communicates with the airborne microprocessor and has a built-in inertial measurement unit, which can acquire the aircraft's attitude, speed, and position information in real time, and output control signals to adjust the rotational speed of the airborne power unit 5, the angle of the folding mechanism 4, and the deflection angle of the outer aileron 602. The depth sensor is installed on the bottom of the fuselage to detect the water surface contact signal and the water depth, providing a trigger basis for water entry mode switching. The airbag aerodynamic control loop receives commands from the control system and controls the inflation and deflation process of each airbag through air pumps and solenoid valves. Example 2

[0030] This embodiment provides a mode switching method for a tail-seat folding-wing water-to-air trans-medium aircraft, including the following steps: S1. Vertical Takeoff from Land: The aircraft is initially in a folded and locked state. The outer wing assembly 6 is bent inward, and the entire aircraft appears as a "∩" shape when viewed from above. The four aerial power units 5 form a quadcopter configuration. The control system activates the four brushless motors 501, and the folding propellers 502 unfold to generate lift. The aircraft then takes off vertically in quadcopter mode.

[0031] S2, Wing-out Cruise Phase: After the aircraft climbs to a safe altitude, the flight controller controls the aircraft to tilt forward and accelerate, while simultaneously sending a deployment command to the waterproof servo 403 of the folding mechanism 4. The waterproof servo 403 drives the outer wing connector 402 to rotate through the circular servo arm 408, causing the outer wing assembly 6 to unfold outward until it touches the deployment limit block and locks. At this time, the mid-wing 3 and the outer wing assembly 6 form a "I"-shaped four-engine fixed wing mode along the span. The wings generate aerodynamic lift, the air power unit 5 provides forward thrust, and the outer aileron 602 cooperates with the power differential to complete attitude control. The aircraft enters a long-range, high-efficiency cruise state and flies to the target water area.

[0032] S3. Deceleration and Water Entry Phase: After reaching the designated water area, the aircraft pulls up and decelerates. The flight controller controls the folding mechanism 4 to rotate in the opposite direction, driving the outer wing assembly 6 to fold inward, restoring the "∩"-shaped quadcopter mode. Subsequently, the airborne power unit 5 maintains a low speed, controlling the aircraft to descend at a low speed and maintain a stable attitude, smoothly contacting the water surface. When the water depth sensor detects a water surface contact signal or a sudden change in water entry acceleration, the control system controls the brushless motor 501 to stop rotating, and the folding propeller 502 automatically retracts, completing the water entry process.

[0033] S4. Underwater navigation and maneuvering phase: After entering the water, the entire aircraft adjusts to an underwater navigation attitude under the action of gravity and buoyancy. The underwater thruster 107 is activated, driving the underwater propeller 108 to rotate and provide forward thrust. The flight controller drives the outer section aileron 602 to deflect through the waterproof servo 604, using the force of water flow to generate pitch, roll and steering torque, realizing three-dimensional underwater maneuvering and performing tasks such as underwater exploration.

[0034] S5, Posture-adjusting water exiting and take-off stage: When a cross-medium instruction from water to air is received, the airbag pneumatic control loop is activated to inflate the fuselage airbag 2 and the outer end airbags 8, adjust the position of the overall center of buoyancy of the aircraft, gradually adjust the attitude of the aircraft to the attitude of the quadrotor mode, and ensure that all four groups of aerial power units 5 are completely exposed above the water surface; then the control system activates the brushless motor 501, the folding propellers 502 are unfolded to generate lift, and the aircraft exits water vertically and takes off in the quadrotor mode. During the ascent, the accumulated water seeped into the inner portion of the outer main wing 601 is automatically discharged through the drainage holes at the trailing edge under the action of gravity and airflow, so as to prevent the accumulated water from affecting flight performance. After exiting water, the aircraft can unfold its wings again and switch to the fixed-wing mode to perform return or subsequent missions.

[0035] In the above embodiment, a water-air cross-medium aircraft with tail-sitter foldable / unfoldable wings and a mode switching method thereof are provided. The present invention realizes reliable switching between the ∩-shaped quadrotor mode and the I-shaped four-engine fixed-wing mode through a folding / unfolding mechanism, which not only retains the capabilities of vertical take-off and landing on land, low-speed hovering and water exiting take-off in water of the quadrotor mode, but also obtains the long-endurance efficient cruise capability of the fixed-wing mode; during unfolded cruising, the limiting block and the wing lift form a stable self-locking, which can reduce the energy consumption of the waterproof steering gear for maintaining torque through long-time power-on, and improve the reliability of the mechanism. In the present invention, a single underwater propeller is integrated at the rear of the middle fuselage, and the ailerons on the outer wings are reused as underwater control surfaces, so that underwater navigation and steering maneuver can be completed without relying on aerial propellers after entering water, avoiding the need for additionally adding redundant control surfaces or multiple sets of propellers; in cooperation with the attitude adjustment function of the fuselage airbag and the outer end airbags, the process of the aerial power units exiting water and taking off can be stably realized, and the reliability of cross-medium switching is improved; the present invention adopts the cooperative design of folding propellers, sealed cabin type fuselage, airbag attitude adjustment structure and drainage holes at the trailing edge of wings, which effectively reduces water entry impact load and underwater navigation resistance, and solves the problems of wing water accumulation and attitude stability during water exiting take-off; the mode switching process covers the whole process of land take-off, aerial cruise, deceleration water entry, underwater navigation and water exiting take-off from water, and is suitable for various task scenarios such as maritime inspection, cross-medium reconnaissance, target delivery and close-range underwater detection.

[0036] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various variations and improvements made by ordinary persons skilled in the art to the technical solution of the present invention shall all fall within the protection scope of the present invention. The technical content claimed by the present invention has been fully recorded in the claims.

Claims

1. A tail-seat type folding wing water-air transmedia aircraft, characterized in that: The system includes a mid-fuselage (1), a mid-wing section (3), a folding mechanism (4), an airborne power unit (5), an outer wing assembly (6), an underwater propulsion device, and a control system. The mid-wing section (3) is symmetrically connected to both sides of the mid-fuselage (1). The outer wing assembly (6) is connected to the outer end of the mid-wing section (3) through the folding mechanism (4). The airborne power unit (5) is located on the outer wing assembly (6). The underwater propulsion device is located at the tail of the mid-fuselage (1). The control system is electrically connected to the folding mechanism (4), the airborne power unit (5), and the underwater propulsion device. The folding mechanism (4) is used to drive the outer wing assembly (6) to switch between the unfolded state and the folded state; in the unfolded state, the middle wing (3) and the outer wing assembly (6) form a "I"-shaped four-engine fixed wing mode along the span; in the folded state, the outer wing assembly (6) bends towards the fuselage, and when viewed from above, it forms a "∩"-shaped quadcopter mode; The control system is used to regulate the working status of each component, enabling the aircraft to switch modes between fixed-wing cruise, quadcopter vertical take-off and landing, underwater navigation, and water-air cross-medium entry and exit.

2. The tail-seat type folding wing water-air transmedium aircraft according to claim 1, characterized in that: The folding mechanism (4) includes a motor bearing housing (401), an outer wing connector (402), a waterproof servo (604) (403), a carbon tube support assembly, and a circular servo arm (408). The motor bearing housing (401) is fixed to the outer end of the middle wing (3), the waterproof servo (604) (403) is fixedly mounted on the motor bearing housing (401), and its output end is fixedly connected to the circular servo arm (408). The circular servo arm (408) is fixedly connected to the outer wing connector (402), and the outer wing connector (402) is connected to the outer wing assembly (6). The carbon tube support assembly, together with the bearing with a flange (407), forms a rotating support structure.

3. The tail-seat type folding wing water-air transmedium aircraft according to claim 2, characterized in that: The folding mechanism (4) is also equipped with a limit block. Both the unfolded and folded states are mechanically limited by the limit block. When the aircraft is in unfolded cruise mode, the force direction of the limit block is matched with the lift direction of the wing to form a stable self-locking mechanism.

4. The tail-seat type folding wing water-air transmedium aircraft according to claim 1, characterized in that: The air power unit (5) includes a brushless motor (501) and a folding propeller (502). When the air power unit (5) is working, the folding propeller (502) unfolds under centrifugal force to provide thrust or lift. After stopping or entering the water, the folding propeller (502) automatically retracts to reduce the impact of entering the water and the resistance of underwater navigation.

5. The tail-seat type folding wing water-air transmedium aircraft according to claim 1, characterized in that: It also includes a fuselage airbag (2) and an outer end airbag (8). The fuselage airbag (2) is located at the rear of the middle fuselage (1), and the outer end airbag (8) is located at the outer end of the outer wing assembly (6). The trailing edge of the outer wing assembly (6) is provided with a drainage hole for draining internal water.

6. The tail-seat type folding wing water-air transmedium aircraft according to claim 1, characterized in that: The outer wing assembly (6) includes an outer main wing (601) and an aileron control assembly; The aileron control assembly is located on the trailing edge of the outer main wing (601). In fixed wing mode, it is used for air roll attitude control, and in underwater navigation mode, it serves as an underwater control surface, working in conjunction with the underwater propulsion device to achieve underwater maneuvering.

7. The tail-seat type folding wing water-air transmedium aircraft according to claim 1, characterized in that: The intermediate fuselage (1) includes a sealed cabin (102), a sealed cabin front cover (101) and a sealed cabin rear cover (105), forming a sealed accommodating cavity; the underwater propulsion device includes an underwater thruster (107) and an underwater propeller (108), which are fixed to the tail of the intermediate fuselage (1) by a streamlined support structure, and the thrust direction is arranged along the longitudinal direction of the fuselage.

8. The tail-seat type folding wing water-air transmedium aircraft according to claim 1, characterized in that: The control system includes an airborne processing unit, a flight controller, a water depth detection unit, and an airbag aerodynamic control loop. The airborne processing unit is connected to the flight controller. The flight controller is used to collect attitude information and control the air power unit (5), the folding mechanism (4), and the aileron control components. The water depth detection unit is used to detect the water depth and the contact state with the water surface. The airbag aerodynamic control loop is used to regulate the inflation and deflation process of the airbag.

9. A mode switching method for a tail-seat folding-wing water-air transmedia aircraft, characterized in that, For controlling mode switching of the aircraft according to any one of claims 1-8, the following steps are included: S1, Vertical takeoff from land: The folding mechanism (4) remains folded, and the aircraft takes off vertically in quadcopter mode; S2, Aerial Wing-Spreading Cruise: After the aircraft accelerates, the folding mechanism (4) drives the outer wing assembly (6) to unfold, switching to fixed-wing mode to perform cruise mission; S3, deceleration and folding into water: after reaching the target water area, decelerate, the folding mechanism (4) folds the wings to restore the quadcopter mode, enter the water at a low speed and controllable attitude, and the air power unit (5) stops rotating; S4. Underwater navigation and maneuvering: The underwater propulsion system is activated to provide navigation power, and the underwater motion attitude is adjusted through the aileron control components; S5, Attitude Adjustment and Water Exit Takeoff: After receiving the cross-medium takeoff command, the fuselage airbag (2) and the outer end airbag (8) are inflated, the attitude of the aircraft is adjusted so that the air power unit (5) is exposed above the water surface, the air power unit (5) is activated to take off in quadcopter mode, and the water inside the wing is discharged through the drain hole.

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