A cross-media variable body tilt-rotor aircraft and a control method thereof

Abstract

This invention discloses a trans-medium variable tiltrotor aircraft and its control method, relating to the field of trans-medium aircraft technology. It includes a fuselage, symmetrically mounted front rotor units on high-mounted platforms on both sides of the fuselage, a tail tiltrotor assembly located at the tail end of the fuselage and rotatable around a lateral tilt axis, symmetrically mounted and foldable main wing units, a wing deployment and retraction mechanism connected to the root of the main wing units, a buoyancy adjustment unit located inside the fuselage, and a control system located inside the fuselage. This invention, through the synergistic design of a biomimetic fuselage integration, compound rotor, variable main wing, active buoyancy adjustment, and closed-loop control, overcomes the bottleneck of traditional single propulsion, achieving cross-medium adaptability, balanced takeoff, landing, and cruise performance, and smooth transition, adapting to multiple scenarios and providing breakthrough support for engineering applications.

Description

Technical Field

[0001] This invention relates to the field of cross-medium aircraft technology, specifically to a cross-medium variable tiltrotor aircraft and its control method. Background Technology

[0002] In recent years, as drone technology has evolved towards multi-scenario and multi-functional applications, its application areas have expanded from traditional aerial operations to multi-domain collaborative operations across land, sea, and air. Cross-medium aircraft with dual capabilities of aerial flight and underwater navigation have demonstrated enormous application potential. They have shown irreplaceable application value in key scenarios such as marine environmental monitoring, underwater resource exploration, emergency rescue reconnaissance, and island and reef security patrols, becoming a research hotspot in the current interdisciplinary field of aerospace and underwater engineering.

[0003] Currently, most cross-medium aircraft use either rotorcraft or a single fixed-wing mode for aerial propulsion. Cross-medium aircraft using fixed-wing flight methods face difficulties in precisely controlling their entry and exit points from the water; those using rotorcraft have relatively short endurance and slow speeds, making them unsuitable for missions requiring rapid coverage of large areas. Both approaches inevitably introduce inconveniences to cross-medium operations due to their single fixed-wing or rotorcraft modes. To balance vertical takeoff and landing flexibility with cruise efficiency, hybrid propulsion technology integrating fixed-wing and rotorcraft has developed rapidly.

[0004] Therefore, how to break through the technical bottleneck of a single propulsion mode, deeply integrate the compound propulsion advantages of tilt rotors with the needs of cross-medium operations, and improve performance through configuration optimization has become a core technical problem that urgently needs to be solved in the field of cross-medium aircraft. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a transmedium variable tiltrotor aircraft and its control method.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A transmedium variable tiltrotor aircraft includes a fuselage, a front rotor unit that is symmetrically mounted on high mounting platforms on both sides of the fuselage, a tail tiltrotor assembly that is mounted at the tail end of the fuselage and can rotate around a lateral tilt axis, a symmetrical and foldable main wing unit, a wing extension and retraction mechanism connected to the root of the main wing unit, a buoyancy adjustment unit disposed inside the fuselage, and a control system disposed inside the fuselage;

[0007] The rotor of the front rotor unit has an annular duct around its rotor and is fixedly connected to the high-mounted installation platform. The wing extension and retraction mechanism is used to switch between the extended and retracted states of the main wing unit and lock it in the extended state. The buoyancy adjustment unit has a variable volume cavity and a fluid channel that communicates with the outside.

[0008] The front rotor unit, tail tilt rotor assembly, main wing unit, buoyancy adjustment unit, and control system are arranged in coordination with the fuselage and form a structural link along the longitudinal direction of the fuselage for air-to-water transition.

[0009] Furthermore, the front rotor unit includes a drive motor, a hub, and blades. The drive motor is fixed to the high-mounted mounting platform via a bracket. The annular duct forms a circumferential envelope relative to the rotating disk surface of the front rotor unit. An annular gap is formed radially between the inner wall of the annular duct and the blade tip, and is fixedly connected to the high-mounted mounting platform via evenly distributed mounting ribs.

[0010] Furthermore, the tail tilt rotor assembly is located on the longitudinal centerline of the tail end of the fuselage. The tail tilt rotor assembly includes a tilt base fixedly connected to the tail section frame of the fuselage, a tilt platform that can rotate relative to the tilt base around a transverse tilt axis, a propulsion motor mounted on the tilt platform and the air propeller it drives, and a tilt servo and servo stick for driving the tilt platform to rotate relative to the tilt base. The output end of the rotor motor is connected to the rotor hub and drives the air propeller to rotate.

[0011] The tilt servo is fixed to the tilt base or fuselage structure. The output end of the tilt servo is hinged to one end of the servo stick, the other end of the servo stick is hinged to one end of the connecting rod, and the other end of the connecting rod is hinged to the drive hinge point of the tilt platform. This allows the output torque of the servo to be transmitted to the tilt platform sequentially through the servo stick and the connecting rod, causing it to rotate around the transverse tilt axis. The transverse tilt axis is supported by bearings and is equipped with mechanical limits to limit the tilt angle range, so that the thrust direction of the air propeller is continuously adjustable between vertical and horizontal.

[0012] Furthermore, the wing retraction mechanism is located inside the fuselage and is arranged coaxially with the root hinge axis of the main wing assembly;

[0013] The wing extension and retraction mechanism includes an annular interface, a worm gear, a worm, and a folding servo. The annular interface is fixed to the root of the main wing and is coaxial with the hinge axis. The worm gear is fixedly connected to the annular interface and is coaxial with it. The worm meshes with the worm gear and its rotation axis intersects and is perpendicular to the rotation axis of the worm gear. The folding servo is fixed to the fuselage structure and its output shaft is connected to the worm via a coupling.

[0014] The folding servo drives the worm gear to rotate, thereby switching the main wing unit between unfolded and retracted modes, and uses the self-locking of the worm wheel-worm gear pair to lock the position between the two modes.

[0015] Furthermore, the buoyancy adjustment unit is arranged longitudinally along the fuselage and includes a buoyancy cylinder, a piston that reciprocates within the buoyancy cylinder, an electric actuator and / or push rod fixedly connected to the piston, and a hose connecting to the outside to form an inlet / outlet and outlet channel. An electrically controlled on / off valve is installed on the channel to achieve fluid control during water entry, depth setting, and water exit processes.

[0016] Furthermore, it also includes a tail fin unit, which includes a horizontal tail fin and a vertical tail fin, and is disposed adjacent to the mounting area of ​​the tail tilt rotor assembly.

[0017] Furthermore, the control system includes a flight controller, an inertial measurement unit, an attitude / altitude sensor, a depth / pressure sensor, a servo actuator, a valve actuator, and a power management unit;

[0018] The flight controller is electrically connected to the attitude / altitude sensor, depth / pressure sensor, and servo actuator. The servo actuator is also electrically connected to the folding servo of the wing retraction mechanism and the tilt servo of the tail tilt rotor assembly. The valve actuator is electrically connected to the valves of the water inlet and water outlet and the air inlet and outlet channels of the buoyancy adjustment unit. The flight controller is also electrically connected to the drive motor of the front rotor unit and the propulsion motor of the tail tilt rotor assembly.

[0019] Furthermore, the outer contour of the main wing unit in the folded-down configuration does not exceed the maximum outer contour of the fuselage on both sides, and a positioning contact surface is provided between the wingtip and the outer surface of the fuselage to limit the folded-down position.

[0020] Furthermore, the fuselage interior is divided into an upper space and a lower space by a partition. The upper space houses the control system and onboard electrical equipment, while the lower space accommodates the buoyancy adjustment unit.

[0021] The present invention also provides a control method for a transmedium variable tiltrotor aircraft, comprising the following steps:

[0022] S1: Vertical takeoff and landing / hovering: The control system simultaneously drives the front rotor unit and the tail tilt rotor assembly to generate vertical lift, enabling the aircraft to take off or hover.

[0023] S2: Cruise Conversion: Control the tilt servo of the tail tilt rotor assembly to transition it from the vertical thrust direction to the horizontal thrust direction around the lateral tilt axis, and control the folding servo of the wing extension and retraction mechanism to put the main wing unit in the extended state so that the main wing can provide lift to achieve fixed-wing cruise.

[0024] S3: Water Entry Preparation and Entry: Before water entry, the folding servo drives the worm gear transmission to retract the main wing unit to a state where its outer profile does not exceed the maximum outer profile on both sides of the fuselage and locks it in place; during water entry, the flight controller receives real-time data from the depth / pressure sensor and attitude sensor, and drives the electric actuator of the buoyancy adjustment unit to drive the piston to reciprocate based on the current ground clearance, water entry speed and attitude parameters, and links the electronically controlled opening and closing valves of the inlet and outlet channels to adjust the fluid volume of the cavity, so that the aircraft can obtain a horizontal water entry attitude and a preset descent speed to avoid water entry impact;

[0025] S4: Underwater Propulsion and Depth Holding: During the underwater phase, the propulsion motor of the tail tilt rotor assembly is reversed to activate the one-way reducer, adjusting the transmission ratio of the motor speed to the air propeller speed to a preset ratio, increasing the propeller output torque to adapt to the high-drag underwater environment and providing the main propulsion force for the aircraft; at the same time, the flight controller continuously drives the electric actuators and valves to adjust the effective volume of the buoyancy adjustment unit based on the real-time water depth data fed back by the depth / pressure sensors, balancing buoyancy and gravity to maintain the set depth, and can be linked with the front rotor unit to operate at low speed to provide auxiliary thrust for heading adjustment;

[0026] S5: Water Exit and In-Flight Reset: The flight controller drives the air intake and exhaust valves of the buoyancy adjustment unit to open, and the electric actuator drives the piston to compress the chamber and discharge the liquid, increasing buoyancy and causing the aircraft to rise to the water surface; after the attitude sensor detects that the fuselage is level, the tilt servo is controlled to reset the tail tilt rotor assembly to the vertical thrust direction, and the front rotor unit and the tail tilt rotor assembly are activated to generate lift together; after leaving the water surface to a safe altitude, the folding servo is controlled to unfold and lock the main wing unit to restore hovering or enter cruise.

[0027] The present invention has the following beneficial effects: The present invention provides a transmedium variable tiltrotor aircraft and its control method:

[0028] (1) Its integrated biomimetic design of fuselage and rotor platform and annular duct rotor configuration effectively eliminate the stress concentration problem of split structure, effectively improve the aerodynamic / hydraulic efficiency under air-water dual medium, and solve the pain point of excessive multi-medium drag of traditional aircraft.

[0029] (2) The combination of the tail tilting rotor and the foldable main wing, along with the worm gear self-locking deployment and retraction mechanism, achieves the unity of vertical take-off and landing flexibility and horizontal cruise efficiency, making up for the shortcomings of short range of pure rotor and limited take-off and landing of pure fixed wing.

[0030] (3) The buoyancy adjustment unit ensures the stability of cross-medium transition processes such as water entry, underwater depth setting, and water exit through the linkage control of piston-electric actuator-electric control valve and the closed-loop feedback of depth / pressure sensor, thus avoiding the attitude loss risk of traditional passive buoyancy design.

[0031] (4) The hierarchical architecture control system achieves full-condition automated and precise control through multi-sensor data fusion and multi-execution component collaborative scheduling, which greatly improves the reliability of operation. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0033] Figure 2 This is a schematic diagram of the fuselage structure of the present invention;

[0034] Figure 3 This is a schematic diagram of the internal structure of the fuselage of the present invention;

[0035] Figure 4 This is a cross-sectional view of the buoyancy adjustment unit of the present invention;

[0036] Figure 5 This is a schematic diagram of the tail fin unit and tilting structure of the present invention;

[0037] Figure 6 This is a schematic diagram of the tilting structure of the present invention;

[0038] Figure 7 This is a schematic diagram of the wing deployment and retraction mechanism of the present invention;

[0039] Figures 1 to 7 The reference numerals in the attached figures represent: 1-fuselage, 12-high-mounted platform, 13-wing extension and retraction mechanism, 14-bulge, 15-nose, 21-horizontal tail, 22-vertical tail, 23-linkage, 24-tilt base, 25-tilt servo, 26-servo stick, 27-tilt platform, 28-propulsion motor, 29-tail tilt rotor assembly, 210-tail unit, 311-front rotor unit, 312-drive motor, 313-bracket, 321-ring interface, 322-worm gear, 323-worm, 324-folding servo, 331-ring duct, 332-main wing unit, 4-buoyancy adjustment unit, 41-hose, 42-buoyancy cylinder, 43-piston, 44-push rod, 45-electric push rod. Detailed Implementation

[0040] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0041] like Figures 1 to 7 As shown, a transmedium-modulated variable tiltrotor aircraft includes a fuselage 1, a nose 15, a front rotor unit 311 symmetrically mounted on high mounting platforms 12 on both sides of the fuselage 1, a tail tiltrotor assembly 29 mounted at the tail end of the fuselage 1 and rotatable about a lateral tilt axis, a symmetrical and foldable main wing unit 332, a wing deployment and retraction mechanism 13 connected to the root of the main wing unit 332, a buoyancy adjustment unit 4 disposed inside the fuselage 1, and a control system disposed inside the fuselage 1.

[0042] The front rotor unit 311 has an annular duct 331 around its rotor and is fixedly connected to the high-mounted platform 12. The wing extension and retraction mechanism 13 is used to switch between the extended and retracted states of the main wing unit 332 and lock it in the extended state. The buoyancy adjustment unit 4 has a variable volume cavity and a fluid channel communicating with the outside. By changing the volume of the fluid (water / air) inside the cavity, the buoyancy is increased when entering water to prevent the fuselage 1 from sinking rapidly; when underwater, the volume is finely adjusted to achieve constant depth hovering; when exiting water, the liquid is discharged and air is drawn in to reduce the discharge volume, which, together with the lift, enables buoyancy. The opening and closing of the inlet / outlet / air inlet / exhaust port is controlled by an electronically controlled valve to adapt to cross-medium conditions. When in the air, all valves are closed to keep the cavity sealed; when entering water, the inlet / outlet port is opened to inject liquid; when exiting water, the air inlet / exhaust port is opened to discharge liquid.

[0043] The front rotor unit 311, the tail tilt rotor assembly 29, the main wing unit 332, the buoyancy adjustment unit 4, and the control system are arranged in coordination with the fuselage 1 and form a structural link for air-to-water transition along the longitudinal direction of the fuselage 1.

[0044] In this embodiment, the fuselage 1 serves as the mounting reference for all components, undertaking the functions of structural support, space allocation, and aerodynamic / hydraulic optimization. The fuselage 1 and the high-mounted mounting platform 12 are integrally formed or connected by threads, riveting, or adhesive bonding, with reinforcing ribs and rounded transition surfaces at the transition points. This helps to evenly transfer the loads generated by the rotor operation (air lift and underwater thrust) to the fuselage 1, avoiding localized stress concentration. The interior of the fuselage 1 is divided into independent areas to accommodate the buoyancy adjustment unit 4 and the control system, achieving physical isolation and integration of functional modules. In addition, the streamlined design of the fuselage 1 reduces air cruising drag and underwater navigation energy consumption, providing basic morphological support for cross-medium movement.

[0045] The high-mounted mounting platform 12 provides a high-mounted mounting reference for the front rotor unit 311, while optimizing the multi-media flow field environment. The front rotor unit 311 is raised to a high position on the side of the fuselage 1 by the high-mounted mounting platform 12, which avoids the rotor from colliding with underwater obstacles during underwater navigation, and at the same time reduces the obstruction and interference of the fuselage 1 on the rotor airflow / water flow.

[0046] The outer contour of the main wing unit 332 in the folded state does not exceed the maximum outer contour of both sides of the fuselage 1, and a positioning contact surface is provided between the wingtip of the main wing and the outer surface of the fuselage 1 to limit the folded position.

[0047] In this embodiment, the front rotor unit 311 provides auxiliary lift and disturbance rejection in the air, and assists in heading adjustment underwater. In the air, it works in conjunction with the tail tilt rotor assembly 29 to generate lift. The annular duct 331 can constrain airflow, improving rotor lift efficiency, and simultaneously assists in correcting the roll attitude of the fuselage 1 by adjusting the speed difference between the two rotors. Underwater, the annular duct 331 can streamline the underwater flow field, reducing water flow turbulence during rotor rotation, generating auxiliary thrust at low speeds, and working with the tail rotor to adjust underwater heading, improving directional cruise accuracy. The annular duct 331 solves both the efficiency loss caused by airflow diffusion in the air and the problem of thrust instability caused by rotor turbulence underwater.

[0048] Specifically, the front rotor unit 311 includes a drive motor 312, a hub, and blades. The drive motor 312 is fixed to the high-mounted mounting platform 12 via a bracket 313. As a power source, the drive motor 312 provides continuous torque for the blade rotation. The hub, as a key component connecting the output shaft of the drive motor 312 and the blade, undertakes the dual functions of torque transmission and blade positioning, converting the rotational motion of the motor into the circular motion of the blade, while ensuring that the blade is evenly distributed circumferentially to ensure stable power output. The blades are the actuators that directly interact with the fluid. By cutting the fluid at high speed, they generate force. In aerial scenarios, the blades push the air downwards, generating upward lift to support the aircraft's hovering, takeoff, and landing. At the same time, the difference in rotational speed between the two blades can correct the roll attitude of the fuselage 1. In underwater scenarios, the blades stir the water flow backwards, generating forward auxiliary thrust, which, together with the tail tilt rotor assembly 29, adjusts the underwater heading and improves the accuracy of directional cruise.

[0049] The annular duct 331 forms a circumferential envelope with respect to the rotating disk of the front rotor unit 311, constraining the diffused airflow into an axially concentrated airflow. At the same time, the airflow velocity at the inlet of the annular duct 331 increases due to the contraction effect, further increasing the pressure difference between the upper and lower surfaces of the blade and improving the lift output efficiency.

[0050] A radial annular gap is formed between the inner wall of the annular duct 331 and the blade tip, and is fixedly connected to the high-level mounting platform 12 by evenly distributed mounting ribs. The radial annular gap design avoids mechanical friction between the blade and the inner wall of the annular duct 331 during high-speed rotation, and enhances the airflow / water flow constraint effect through the narrow annular gap effect. The bracket 313 connects the drive motor 312 to the high-level mounting platform 12, transmitting the motor's weight and counter-torque to the fuselage 1. It typically uses lightweight, high-strength materials such as aluminum alloy and carbon fiber, ensuring support rigidity while reducing weight. Furthermore, the evenly distributed mounting ribs disperse the fluid load (such as airflow pressure and underwater water flow impact) borne by the annular duct 331 to the fuselage 1, preventing structural deformation caused by localized stress concentration. It also reduces the obstruction effect of the mounting ribs on the fluid inside and outside the annular duct 331 (non-evenly distributed mounting ribs easily generate localized eddies), ensuring smooth fluid flow along the annular duct 331.

[0051] In this embodiment, the tail tilt rotor assembly 29 achieves continuous switching of thrust direction by rotating around a lateral tilt axis, and is a key power component for realizing "vertical takeoff and landing - horizontal cruise - underwater propulsion". During the hovering / takeoff and landing phase when switching between air states, it tilts to the vertical direction and works with the front rotor unit 311 to generate vertical lift to achieve vertical takeoff and landing; during the cruise phase, it slowly tilts to the horizontal direction to generate horizontal thrust to drive the fuselage 1 forward. At this time, the lift generated by the main wing unit 332 supports the weight of the fuselage 1, improving cruise efficiency. In the underwater state, it tilts to the direction parallel to the fuselage 1, close to the surface of the fuselage 1 to reduce underwater navigation drag. At the same time, the speed and torque can be adjusted by a one-way reducer to adapt to the high drag underwater environment.

[0052] Specifically, the tail tilt rotor assembly 29 is located on the longitudinal centerline of the tail end of the fuselage 1. The tail tilt rotor assembly 29 includes a tilt base 24 fixedly connected to the tail section frame of the fuselage 1, a tilt platform 27 rotatable relative to the tilt base 24 around a transverse tilt axis, a propulsion motor 28 mounted on the tilt platform 27 and its driven air propeller, and a tilt servo 25 and servo stick 26 for driving the tilt platform 27 to rotate relative to the tilt base. The output end of the propulsion motor 28 is connected to the propeller hub and drives the air propeller to rotate. The tilt base 24 provides an installation reference for the tilt platform 27 and the tilt servo 25, and is rigidly connected to the tail section frame of the fuselage 1 by bolts or other fasteners. The propulsion motor 28, the air propeller, and the propeller hub are integrated and mounted on the tilt platform 27, forming a power module. Rotation around the transverse tilt axis drives the entire power module to change orientation. The propulsion motor 28 serves as the power source, outputting different speeds and torques according to the working conditions. High speeds are required in the air to generate lift / thrust, while high torque is required underwater to adapt to high-resistance environments. The propeller hub connects the motor output shaft to the air propeller, converting the motor's rotational motion into the propeller's circular motion, while ensuring that the propeller blades are evenly distributed circumferentially to ensure stable power output.

[0053] The tilt servo 25 is fixed to the tilt base 24 or the fuselage 1 structural component. The output end of the tilt servo 25 is hinged to one end of the servo rod 26, the other end of the servo rod 26 is hinged to one end of the connecting rod 23, and the other end of the connecting rod 23 is hinged to the drive hinge point of the tilt platform 27. This allows the output torque of the servo to be transmitted sequentially to the tilt platform 27 via the servo rod 26 and the connecting rod 23, causing it to rotate around the transverse tilt axis. The transverse tilt axis is supported by bearings and has mechanical limits to define the tilt angle range, allowing the thrust direction of the air propeller to be continuously adjustable between vertical and horizontal, achieving continuous deflection of the thrust direction from vertical to horizontal. The tilt servo 25, servo rod 26, and connecting rod 23 realize the power transmission from servo torque to the rotation of the tilt platform 27, forming the execution link for precise control of the thrust direction. As a power source, the tilt servo 25 has high-precision angle control capabilities and can output set torque and rotation angle according to the control system commands to provide deflection power for the tilt platform 27. The servo lever 26 and connecting rod 23 act as force transmission intermediaries, forming a flexible transmission link through a hinged connection. One end of the servo lever 26 is hinged to the output end of the servo motor, receiving the rotational motion of the servo motor and converting it into linear / oscillating motion. The other end is hinged to the drive hinge point of the tilting platform 27 through the connecting rod 23, transmitting the motion to the tilting platform 27 and driving it to rotate around the transverse tilt axis. The hinged structure can compensate for installation errors between components, avoid transmission jamming, and absorb impact loads during cross-medium movement. In specific operation, the servo lever 26 drives the connecting rod 23 to oscillate through the hinge, and the connecting rod 23 transmits the motion to the drive hinge point of the tilting platform 27, driving the tilting platform 27 to rotate around the transverse tilt axis bearing support until the target angle is mechanically limited, completing the thrust direction adjustment.

[0054] When hovering in the air / vertical take-off and landing state, the tilt servo 25 drives the tilt platform 27 to rotate around the lateral tilt axis to the vertical direction (thrust direction upward). The air propeller and the front rotor unit 311 rotate synchronously at high speed, generating vertical upward lift, which works in conjunction with the lift of the front rotor to balance the weight of the fuselage 1, so as to realize the aircraft's vertical take-off and landing or hovering in the air without a runway.

[0055] During horizontal cruising in the air, the tilt servo 25 drives the tilt platform 27 to slowly tilt from the vertical direction to the horizontal direction (thrust direction forward). During this process, the speed of the air propeller gradually increases, generating horizontal forward thrust to drive the fuselage 1 to accelerate. At this time, the main wing unit 332 unfolds to generate lift to support the weight of the fuselage 1, and the front rotor can reduce power to standby state, greatly reducing energy consumption and increasing cruising speed and range.

[0056] In underwater propulsion / depth-holding mode, the tilt servo 25 drives the tilt platform 27 to rotate parallel to the longitudinal direction of the fuselage 1 (thrust direction forward, propeller close to the surface of the fuselage 1), and the propulsion motor 28 switches to low-speed high-torque mode (can be used with a one-way reducer). The air propeller rotates at low speed to generate forward main thrust, driving the aircraft to cruise underwater; at the same time, the propeller's close-to-the-fuselage 1 attitude can reduce underwater flow resistance, and together with the buoyancy adjustment unit 4, it can achieve depth-holding navigation.

[0057] In this embodiment, the wing extension and retraction mechanism 13 enables controllable switching between "extension" and "retraction" of the main wing, and ensures structural stability in both modes.

[0058] Specifically, the wing extension and retraction mechanism 13 is located inside the fuselage 1 and is coaxially arranged with the root hinge axis of the main wing unit 332. The wing extension and retraction mechanism 13 includes an annular interface 321, a worm gear 322, a worm 323, and a folding servo 324. The annular interface 321 is fixed to the root of the main wing and is coaxial with the hinge axis. The worm gear 322 is fixedly connected to the annular interface 321 and is coaxial with it. The worm 323 meshes with the worm gear 322 and its rotation axis intersects with and is perpendicular to the rotation axis of the worm gear 322. The folding servo 324 is fixed to the structural component of the fuselage 1 and its output shaft is connected to the worm 323 via a coupling. The folding servo 324 drives the worm 323 to rotate to drive the main wing unit 332 to switch between the extended and retracted states, and uses the self-locking of the worm gear pair to lock the position of the two states.

[0059] The folding servo motor 324, as the core power unit of the mechanism, possesses high-precision angle control capabilities. It can output set torque and rotation angle according to control system commands, providing driving force for the entire extension and retraction process. It is fixed to the fuselage 1 structural component to ensure no displacement during power output. The coupling, as a flexible connector between the output shaft of the folding servo motor 324 and the worm gear 323, compensates for installation coaxiality errors between the servo motor output shaft and the worm gear 323, avoiding transmission jamming or component wear caused by rigid connections, while ensuring efficient torque transmission. The worm gear 323, as the driving component of the transmission chain, has its rotation axis perpendicularly intersecting the rotation axis of the worm wheel 322, converting the rotational motion of the folding servo motor 324 into the rotational motion of the worm wheel 322. The worm gear 323 employs a helical tooth structure, transmitting torque through meshing with the worm wheel 322, and its tooth profile design meets the self-locking condition (lead angle less than the friction angle of the meshing surface). The worm gear 322, as the driven component of the transmission chain, is fixedly connected to and coaxial with the annular interface 321. It receives the torque transmitted by the worm 323 and drives the annular interface 321 and the main wing unit 332 to rotate.

[0060] Specifically, the control system sends angle control signals to the folding servo motor 324 according to the operating conditions. The folding servo motor 324 outputs rotational power, which is transmitted to the worm gear 323 via a coupling, driving the worm gear 323 to rotate around its own axis. The worm gear 323 meshes with the worm wheel 322 through helical teeth. Since the axes of the two intersect perpendicularly, the rotational motion of the worm gear 323 is converted into the rotational motion of the worm wheel 322. The worm wheel 322 is rigidly connected to the annular interface 321. Therefore, the rotation of the worm wheel 322 directly drives the annular interface 321 and the root of the main wing unit 332 fixed thereto around the hinge. The axis rotation enables the main wing unit 332 to unfold and rotate forward or fold and rotate backward. When the main wing unit 332 reaches the target position, the folding servo 324 stops working. Due to the self-locking characteristics of the worm gear-worm pair, the worm gear 322 cannot drive the worm 323 to rotate in the reverse direction (that is, when the main wing is subjected to external force, the reaction force of the worm gear 322 cannot drive the worm 323 to rotate). Therefore, the main wing is stably locked in the current position, and it can resist the impact load of airflow / water flow without the need for an additional locking mechanism. This achieves efficient form switching and stable operation of the main wing unit 332 in both air and water media.

[0061] In this embodiment, the buoyancy adjustment unit 4 dynamically balances the gravity and buoyancy of the fuselage 1 by adjusting the "displaced fluid volume". The buoyancy adjustment unit 4 is arranged longitudinally along the fuselage 1. The buoyancy adjustment unit 4 includes a buoyancy cylinder 42, a piston 43 that reciprocates in the buoyancy cylinder 42, an electric push rod 45 and / or a push rod 44 that are fixedly connected to the piston 43, and a hose 41 that communicates with the outside to form an inlet / outlet and outlet channel. An electrically controlled opening and closing valve is provided on the inlet / outlet and outlet channel to realize fluid control during the water entry, depth setting and water exit processes.

[0062] Piston 43, as the actuator that changes the effective fluid volume inside buoyancy cylinder 42, is the direct carrier for buoyancy adjustment. Driven by electric actuator 45, piston 43 reciprocates inside buoyancy cylinder 42, changing the volume of fluid inside the cavity. When entering water, it increases the discharge volume to enhance buoyancy and prevent the fuselage 1 from sinking rapidly; when underwater, it finely adjusts the volume to achieve constant depth hovering; when exiting water, it discharges liquid and draws in air to reduce the discharge volume, which, together with lift, enables buoyancy.

[0063] The opening and closing of the inlet / outlet / air / exhaust ports are controlled by an electronically controlled valve to adapt to cross-media conditions. When in the air, all valves are closed to keep the cavity sealed. When entering water, the inlet / outlet ports are opened to inject liquid, and when exiting water, the air / exhaust ports are opened to discharge liquid. The buoyancy cylinders 42 are glued side by side to the lower part of the partition plate 14. The bottom of the buoyancy cylinder 42 facing the head 15 has a small hole, which is connected to the hose 41. The hose 41 then contacts the outside through a small hole in the belly of the fuselage.

[0064] In this embodiment, the aircraft also includes a tail unit 210, which includes a horizontal tail 21 and a vertical tail 22, and is arranged adjacent to the mounting area of ​​the tail tilt rotor assembly 29. By being arranged adjacent to the tail tilt rotor, the additional pitching moment generated when the rotor tilts can be counteracted. For example, during the process of the tail rotor tilting from vertical lift to horizontal thrust, the thrust application point shifts backward, generating a nose-down moment. The horizontal tail 21 can quickly balance this moment through aerodynamic damping to avoid attitude fluctuations.

[0065] In addition, the tail fin position avoids the core rotating flow field of the tail rotor. For example, the horizontal tail fin 21 is slightly lower than the rotor rotation plane, and the vertical tail fin 22 is located on the rear center line of the rotor. This not only avoids the vibration caused by the direct impact of the rotor airflow / water flow on the tail fin, but also uses the secondary flow out of the rotor to enhance the aerodynamic / hydrodynamic damping effect of the tail fin.

[0066] Regarding the horizontal stabilizer 21: In the air, the horizontal stabilizer 21 is a symmetrical airfoil or an airfoil with a slightly negative angle of attack, forming a front and rear wing layout with the main wing element 332. When the aircraft pitches up or down due to airflow disturbances, the angle of attack of the horizontal stabilizer 21 will change accordingly. When pitching up, the angle of attack of the stabilizer increases, generating additional downward lift; when pitching down, the angle of attack of the stabilizer decreases, generating additional upward lift. This damping effect quickly corrects pitch deviation.

[0067] When navigating underwater, the density of the water flow is much greater than that of the air. The horizontal tail fin 21 adopts a streamlined thin wing design, which can reduce the drag of the water flow during underwater navigation. At the same time, when the aircraft adjusts its diving / surfacing depth, it works with the buoyancy adjustment unit 4 to provide a small amount of pitch force to help control the pitch angle of the fuselage 1.

[0068] Regarding the vertical tail 22: In the air, the vertical tail 22 is arranged longitudinally perpendicular to the fuselage 1, acting as a longitudinal stabilizer. When the aircraft deviates from the preset direction due to factors such as crosswinds or differences in the speed of the front rotor, the windward surface of the vertical tail 22 will generate lateral drag. The windward area of ​​the tail on the yaw side increases, and the drag is greater than that on the other side, forming a torque opposite to the yaw direction, which pulls the course back onto the correct track.

[0069] When navigating underwater, the vertical tail fin 22 acts like a rudder, reducing course drift caused by water flow disturbances. At the same time, in conjunction with the lateral thrust generated by the low-speed rotation of the front rotor, it enables precise underwater course control. If underwater exploration requires straight-line navigation, the vertical tail fin 22 can counteract the interference of lateral water flow forces.

[0070] In this embodiment, the interior of the fuselage 1 is divided into an upper space and a lower space by a partition. The upper space is equipped with a control system and onboard electrical equipment, while the lower space accommodates the buoyancy adjustment unit 4.

[0071] In this embodiment, the control system adopts a hierarchical architecture design, with each component working collaboratively according to the perception layer, decision-making layer, execution drive layer, and energy layer to form a complete control link. Specifically, the control system includes a flight controller, an inertial measurement unit, an attitude / altitude sensor, a depth / pressure sensor, a servo actuator, a valve actuator, and a power management unit. Specifically, the flight controller is electrically connected to the attitude / altitude sensor, the depth / pressure sensor, and the servo actuator. The servo actuator is also electrically connected to the folding servo 324 of the wing retraction mechanism 13 and the tilt servo 25 of the tail tilt rotor assembly 29. The valve actuator is electrically connected to the valves of the water inlet / outlet and air inlet / exhaust channels of the buoyancy adjustment unit 4. The flight controller is also electrically connected to the drive motor 312 of the front rotor unit 311 and the propulsion motor 28 of the tail tilt rotor assembly 29.

[0072] The perception layer, which serves as the terminal for collecting environmental and state data, consists of an inertial measurement unit (IMU), attitude / altitude sensors, and depth / pressure sensors. It acts as the "eyes and ears" of the control system, responsible for collecting real-time data on the aircraft's attitude and the surrounding environment, providing a basis for decision-making.

[0073] As the core attitude sensing component, the inertial measurement unit integrates a gyroscope, accelerometer, and geomagnetic sensor. It can output the aircraft's three-axis attitude angles (roll angle, pitch angle, and yaw angle) and three-axis acceleration in real time with an accuracy of ±0.1° and ±0.01g. It is the core data source for determining whether the aircraft is tilting or swaying (such as detecting roll angle deviation during air cruise and triggering attitude correction commands).

[0074] Attitude / altitude sensors, as segmented scene perception components, include attitude sensors and altitude sensors such as a combination of barometric pressure sensors and ultrasonic sensors. In the air, they calculate flight altitude by changing air pressure, and switch to ultrasonic sensors when near the ground to ensure controllable altitude during hovering, takeoff, and landing. They work with IMUs to determine the attitude at the moment of water entry (such as whether it is horizontal) to avoid impact overload.

[0075] Depth / pressure sensors, as dedicated underwater sensing components, calculate underwater depth by detecting water pressure and simultaneously provide feedback on the rate of change of water pressure (to determine the descent / ascent speed). They are the core data source for underwater hovering at a constant depth and constant speed navigation.

[0076] The decision-making layer uses the flight controller as its sole core, typically employing the mature open-source PIXHawk hardware platform (compatible with PX4 / APM firmware), and undertakes three core functions: data fusion, logical judgment, and command generation.

[0077] ① Data fusion processing: Receive multi-source data from the sensing layer (IMU attitude angle, height of the altitude sensor, water depth of the depth sensor), eliminate single sensor errors (such as fluctuations in the barometric pressure sensor due to airflow interference) through the Kalman filter algorithm, and output fused accurate state data.

[0078] ② Operating condition logic judgment: Built-in preset operating condition logic such as aerial cruise, water entry preparation, underwater depth setting, and water exit reset, which automatically identifies the current operating condition based on fused data;

[0079] ③ Control command generation: Generate precise control commands according to operating conditions, such as during the cruise phase: send a tilt command to the horizontal direction to the tilt servo motor 25 driver; during the underwater phase: send a command to the valve driver to close the intake and exhaust valves and open the intake and exhaust valves.

[0080] The actuator layer, consisting of servo actuators, valve actuators, and directly connected motors, serves as a bridge between decision commands and mechanical actions, resolving the issue that flight controller output signals cannot directly drive actuators.

[0081] Among them, the servo drive is adapted to the high-precision angle control requirements. It receives the angle command from the flight controller, converts the weak electrical signal into a strong electrical drive signal, and accurately controls the folding servo 324 of the wing extension and retraction mechanism 13 and the tilt servo 25 of the tail tilt rotor assembly 29, with an angle control error of ≤0.5°.

[0082] The valve actuator adapts to the fluid channel switching requirements, receives the opening and closing commands from the flight controller, and drives the inlet and outlet valves and the air inlet and outlet valves of the buoyancy adjustment unit 4. The response time is ≤0.1s, ensuring timely fluid exchange.

[0083] The flight controller directly controls the drive motor 312 of the front rotor and the propulsion motor 28 of the tail rotor through PWM signals, adjusting the motor speed to achieve stepless adjustment of lift / thrust.

[0084] The energy layer, centered on the Power Management Unit (PMU), is responsible for power distribution, status monitoring, and safety protection, ensuring stable power for all components. Power distribution converts the battery's 14.8V voltage into the required voltage for each component, providing precise power through multiple output interfaces. Status monitoring collects real-time data on battery voltage, current, and remaining charge, transmitting this information to the flight controller. When the remaining charge is less than 20%, a return-to-home command is automatically triggered. In case of a sudden current surge (such as motor jamming), power supply protection components are quickly cut off. The system features overvoltage, overcurrent, and short-circuit protection to prevent circuit damage during cross-medium processes, improving system reliability.

[0085] The present invention also provides a control method for a transmedium variable tiltrotor aircraft, comprising the following steps:

[0086] S1: Vertical takeoff and landing / hovering: The control system simultaneously drives the front rotor unit 311 and the tail tilt rotor assembly 29 to generate vertical lift, enabling the aircraft to take off or hover.

[0087] S2: Cruise transition: Control the tilt servo 25 of the tail tilt rotor assembly 29 to transition it from the vertical thrust direction to the horizontal thrust direction around the lateral tilt axis, and control the folding servo 324 of the wing extension and retraction mechanism to put the main wing unit 332 in the extended state so that the main wing provides lift to achieve fixed-wing cruise.

[0088] S3: Water Entry Preparation and Entry: Before water entry, the folding servo 324 drives the worm gear 322 and worm 323 to retract the main wing unit 332 to a state where its outer profile does not exceed the maximum outer profile on both sides of the fuselage 1 and locks it in place; during water entry, the flight controller receives real-time data from the depth / pressure sensor and attitude sensor, and drives the electric push rod 45 of the buoyancy adjustment unit 4 to drive the piston 43 to reciprocate based on the current ground clearance, water entry speed and attitude parameters, and links the electronically controlled opening and closing valve of the inlet and outlet channels to adjust the fluid volume of the cavity, so that the aircraft can obtain a horizontal water entry attitude and a preset descent speed, avoiding water entry impact;

[0089] S4: Underwater Propulsion and Depth Holding: During the underwater phase, the propulsion motor 28 of the tail tilt rotor assembly 29 is reversed to activate the one-way reducer, adjusting the transmission ratio of the motor speed to the air propeller speed to a preset ratio, increasing the propeller output torque to adapt to the high-drag underwater environment, and providing the main propulsion force for the aircraft; at the same time, the flight controller continuously drives the electric actuator 45 and valves to adjust the effective volume of the buoyancy adjustment unit 4 based on the real-time water depth data fed back by the depth / pressure sensor, balancing buoyancy and gravity to maintain the set depth, and can be linked to the front rotor unit 311 to operate at low speed to provide auxiliary thrust for heading adjustment;

[0090] S5: Water Exit and In-flight Reset: The flight controller drives the air intake and exhaust port electronic valves of the buoyancy adjustment unit 4 to open, and the electric push rod 45 drives the piston 43 to compress the chamber and discharge the liquid, increasing buoyancy and causing the aircraft to float to the water surface; after the attitude sensor detects that the fuselage 1 is horizontal, the tilt servo 25 is controlled to reset the tail tilt rotor assembly 29 to the vertical thrust direction, and the front rotor unit 311 and the tail tilt rotor assembly 29 are started to work together to generate lift; after leaving the water surface to a safe altitude, the folding servo 324 is controlled to unfold and lock the main wing unit 332 to restore hovering or enter cruise.

[0091] Additionally, it should be noted that components not described in detail in this article are existing technologies.

[0092] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A transmedium-variable tiltrotor aircraft, characterized in that, It includes a fuselage (1), a front rotor unit (311) symmetrically mounted on high mounting platforms (12) on both sides of the fuselage (1), a tail tilt rotor assembly (29) mounted at the tail end of the fuselage (1) and rotatable around a lateral tilt axis, a symmetrical and foldable main wing unit (332), a wing extension and retraction mechanism (13) connected to the root of the main wing unit (332), a buoyancy adjustment unit (4) located inside the fuselage (1), and a control system located inside the fuselage (1); The front rotor unit (311) has an annular duct (331) on the outer periphery of the rotor and is fixedly connected to the high-mounted installation platform (12). The wing extension and retraction mechanism (13) is used to switch between the extended and retracted states of the main wing unit (332) and lock it in both states. The buoyancy adjustment unit (4) has a variable volume cavity and a fluid channel communicating with the outside. Among them, the front rotor unit (311), the tail tilt rotor assembly (29), the main wing unit (332), the buoyancy adjustment unit (4) and the control system are arranged in coordination with the fuselage (1) and form a structural link for air-water transition along the longitudinal direction of the fuselage (1); The tail tilt rotor assembly (29) is located on the longitudinal centerline of the tail end of the fuselage (1). The tail tilt rotor assembly (29) includes a tilt base (24) fixedly connected to the tail section frame of the fuselage (1), a tilt platform (27) rotatable relative to the tilt base (24) around a transverse tilt axis, a propulsion motor (28) mounted on the tilt platform (27) and the air propeller it drives, and a tilt servo (25) and servo stick (26) for driving the tilt platform (27) to rotate relative to the tilt base. The output end of the propulsion motor (28) is connected to the propeller hub and drives the air propeller to rotate. The tilt servo (25) is fixed to the tilt base (24) or the fuselage (1) structural component. The output end of the tilt servo (25) is hinged to one end of the servo rod (26), the other end of the servo rod (26) is hinged to one end of the connecting rod (23), and the other end of the connecting rod (23) is hinged to the drive hinge point of the tilt platform (27). The output torque of the servo is transmitted to the tilt platform (27) in sequence through the servo rod (26) and the connecting rod (23), which drives it to rotate around the transverse tilt axis. The transverse tilt axis is supported by bearings and is mechanically limited to limit the tilt angle range, so that the thrust direction of the air propeller is continuously adjustable between vertical and horizontal. The wing extension and retraction mechanism (13) is located inside the fuselage (1) and is arranged coaxially with the root hinge axis of the main wing unit (332); The wing extension and retraction mechanism (13) includes an annular interface (321), a worm gear (322), a worm (323), and a folding servo (324). The annular interface (321) is fixed to the root of the main wing and coaxial with the hinge axis. The worm gear (322) is fixedly connected to the annular interface (321) and coaxial with it. The worm (323) meshes with the worm gear (322) and its rotation axis intersects and is perpendicular to the rotation axis of the worm gear (322). The folding servo (324) is fixed to the fuselage (1) structural component and its output shaft is connected to the worm (323) via a coupling. The folding servo (324) drives the worm (323) to rotate so as to switch the main wing unit (332) between unfolded and retracted modes, and uses the self-locking of the worm wheel (322) and worm (323) to lock the position of the two modes. The buoyancy adjustment unit (4) is arranged longitudinally along the fuselage (1). The buoyancy adjustment unit (4) includes a buoyancy cylinder (42), a piston (43) that reciprocates in the buoyancy cylinder (42), an electric push rod (45) and / or a push rod (44) that are fixedly connected to the piston (43), and a water inlet and outlet channel formed by a hose (41) that communicates with the outside. An electrically controlled opening and closing valve is provided on the water inlet and outlet channel to realize fluid control during the water inlet, depth setting and water outlet processes. The control system includes a flight controller, an inertial measurement unit, an attitude / altitude sensor, a depth / pressure sensor, a servo actuator, a valve actuator, and a power management unit. The flight controller is electrically connected to the attitude / altitude sensor, the depth / pressure sensor, and the servo drive. The servo drive is also electrically connected to the folding servo (324) of the wing retraction mechanism (13) and the tilt servo (25) of the tail tilt rotor assembly (29). The valve drive is electrically connected to the valves of the water inlet and outlet and the air inlet and outlet channels of the buoyancy adjustment unit (4). The flight controller is also electrically connected to the drive motor (312) of the front rotor unit (311) and the propulsion motor (28) of the tail tilt rotor assembly (29).

2. The transmedium-variable tiltrotor aircraft according to claim 1, characterized in that, The front rotor unit (311) includes a drive motor (312), a hub and blades. The drive motor (312) is fixed to the high-mounted mounting platform (12) via a bracket (313). The annular duct (331) forms a circumferential envelope relative to the rotating disk surface of the front rotor unit (311). An annular gap is formed radially between the inner wall of the annular duct (331) and the blade tip, and is fixedly connected to the high-mounted mounting platform (12) by evenly distributed mounting ribs.

3. The transmedium-variable tiltrotor aircraft according to claim 2, characterized in that, It also includes a tail fin unit (210), which includes a horizontal tail fin (21) and a vertical tail fin (22) and is disposed adjacent to the mounting area of ​​the tail tilt rotor assembly (29).

4. The transmedium-variable tiltrotor aircraft according to claim 1, characterized in that, The outer contour of the main wing unit (332) in the retracted state does not exceed the maximum outer contour of the fuselage (1) on both sides, and a positioning contact surface is provided between the wingtip of the main wing and the outer surface of the fuselage (1) to limit the retracted position.

5. The transmedium-variable tiltrotor aircraft according to claim 1, characterized in that, The fuselage (1) is divided into an upper space and a lower space by a partition. The upper space is equipped with the control system and airborne electrical equipment, and the lower space accommodates the buoyancy adjustment unit (4).

6. A control method for a transmedium variable tiltrotor aircraft according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Vertical takeoff and landing / hovering: The control system simultaneously drives the front rotor unit (311) and the tail tilt rotor assembly (29) to generate vertical lift, enabling the aircraft to take off or hover; S2: Cruise transition: Control the tilt servo (25) of the tail tilt rotor assembly (29) to transition it from the vertical thrust direction to the horizontal thrust direction around the lateral tilt axis, and control the folding servo (324) of the wing extension and retraction mechanism to put the main wing unit (332) in the extended state so that the lift provided by the main wing can achieve fixed-wing cruise. S3: Water entry preparation and water entry: Before entering the water, control the folding servo (324) to drive the worm gear (322) and worm (323) to make the main wing unit (332) fold up to the state where the outer contour does not exceed the maximum outer contour on both sides of the fuselage (1) and lock it; during the water entry process, the flight controller receives real-time data from the depth / pressure sensor and attitude sensor, and drives the electric push rod (45) of the buoyancy adjustment unit (4) to drive the piston (43) to reciprocate according to the current ground altitude, water entry speed and attitude parameters, and links the electric control opening and closing valves of the water inlet and drainage and water inlet and exhaust channels to adjust the fluid volume of the cavity, so that the aircraft can obtain a horizontal water entry attitude and a preset descent speed, and avoid water entry impact; S4: Underwater Propulsion and Depth Holding: During the underwater phase, the propulsion motor (28) of the tail tilt rotor assembly (29) is reversed to activate the one-way reducer, adjusting the transmission ratio of the motor speed and the air propeller speed to a preset ratio, increasing the propeller output torque to adapt to the high-drag underwater environment, and providing the main propulsion force for the aircraft; at the same time, the flight controller continuously drives the electric push rod (45) and valve to adjust the effective volume of the buoyancy adjustment unit (4) based on the real-time water depth data fed back by the depth / pressure sensor, balancing buoyancy and gravity to maintain the set depth, and can be linked to the front rotor unit (311) to operate at low speed to provide auxiliary thrust for heading adjustment; S5: Water Exit and In-flight Reset: The flight controller drives the air intake and exhaust port electronic control valve of the buoyancy adjustment unit (4) to open, and the electric push rod (45) drives the piston (43) to compress the chamber to discharge liquid, thereby increasing buoyancy and causing the aircraft to float to the water surface; after the attitude sensor detects that the fuselage (1) is horizontal, the tilt servo (25) is controlled to reset the tail tilt rotor assembly (29) to the vertical thrust direction, and the front rotor unit (311) and the tail tilt rotor assembly (29) are started to work together to generate lift; after leaving the water surface to a safe altitude, the folding servo (324) is controlled to unfold and lock the main wing unit (332) to restore hovering or enter cruise.

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