Tricopter amphibious trans-medium variable structure unmanned vehicle

Abstract

The application discloses a three-rotor amphibious cross-medium variable-structure unmanned vehicle, which comprises a waterproof cabin, three deformable arms which are hinged to the rear end of the waterproof cabin and can be switched between an unfolded state and a folded state relative to the waterproof cabin, wherein in the unfolded state, the three deformable arms are unfolded outward to increase the rotor arm distance, and in the folded state, the three deformable arms are folded to the side of the waterproof cabin to form a streamlined shape together with the waterproof cabin; three coaxial water-air propulsion assemblies are arranged at the ends of the three deformable arms respectively; each coaxial water-air propulsion assembly comprises a rotor power unit for air flight and an underwater propulsion power unit for underwater propulsion, and the rotor power unit and the underwater propulsion power unit are coaxially arranged.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicles, and in particular to a three-rotor amphibious trans-medium variable structure unmanned aerial vehicle. Background Technology

[0002] Current research on cross-medium unmanned aerial vehicles (UAVs) both domestically and internationally can be categorized into three main types based on their airframe structure: fixed-wing, rotor, and biomimetic structures. Fixed-wing UAVs experience large stress areas upon re-entry into water, resulting in significant stress at the wing-to-cabin connection and requiring high material strength, making them prone to damage. Rotor mechanisms demand high stability control and suffer from relatively weak power system load. Biomimetic structures present significant challenges in power system design, with most existing research remaining at the single-medium stage, and also placing high demands on materials. Small cross-medium amphibious vehicles face a series of challenges: efficient flight and low-drag underwater navigation cannot be simultaneously achieved; power control during the water-to-air transition is complex, and efficient power system switching is not feasible.

[0003] Existing unmanned aerial vehicles (UAVs) that can operate across water and air media mostly employ fixed-wing, traditional rotor, or biomimetic structures. Fixed-wing systems experience high stress on the wings when entering and exiting water, require high material strength, and suffer from significant water resistance. Traditional rotors struggle to balance lift in the air with low drag underwater. Biomimetic structures, on the other hand, have complex propulsion systems and are often limited to a single medium. Therefore, existing solutions generally suffer from problems such as the incompatibility between flight efficiency and underwater drag, complex power switching, and insufficient sealing reliability.

[0004] To address the aforementioned challenges, it is necessary to design an unmanned aerial vehicle that is more adaptable to different media. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention adopts the following solution.

[0006] A three-rotor amphibious cross-medium variable structure unmanned aerial vehicle includes: a waterproof compartment;

[0007] Three deformable arms are hinged to the rear end of the waterproof cabin and can switch between an extended state and a retracted state relative to the waterproof cabin. In the extended state, the three deformable arms open outward to increase the rotor wheelbase. In the retracted state, the three deformable arms retract towards the side of the waterproof cabin to form a streamlined shape together with the waterproof cabin.

[0008] Three coaxial hydro-aerial propulsion assemblies are respectively disposed at the ends of the three deformable arms; each coaxial hydro-aerial propulsion assembly includes a rotor power unit for aerial flight and an underwater propulsion power unit for underwater propulsion, wherein the rotor power unit and the underwater propulsion power unit are coaxially disposed.

[0009] Optionally, the deformable arms are deployed and retracted via a drive mechanism. The drive mechanism includes a lead screw driven by a servo motor and a nut assembly that works with the lead screw to convert rotational motion into linear motion. The nut assembly is connected to the three deformable arms via a linkage mechanism.

[0010] Optionally, the nut assembly is a three-pronged ball nut, with its three connecting arms connected to the corresponding deformable arms via connecting rods.

[0011] Optionally, an O-ring is provided between the body of the waterproof compartment and the front and rear flanges to achieve static sealing; a stuffing box and a plug seal are provided on the rear cover of the waterproof compartment.

[0012] Optionally, at least one of the coaxial hydro-air propulsion components is a vector thruster, and the thrust direction of its underwater propulsion power unit is adjustable.

[0013] Optionally, the rotor power unit is a rotor driven by a brushless motor, and the underwater propulsion power unit is an underwater propeller driven by a waterproof motor.

[0014] Optionally, in the deployed state, the angle between the three deformable arms and the axis of the waterproof chamber is 20° to 40°; in the retracted state, the three deformable arms are parallel to the side of the waterproof chamber.

[0015] A cross-medium navigation control method based on a three-rotor amphibious cross-medium variable structure unmanned aerial vehicle includes the following steps:

[0016] Step 1: Control the deformable arm to unfold and start the rotor power unit to perform aerial flight;

[0017] Step 2: During the transition from air to water, control the vehicle to descend and shut down the rotor power unit;

[0018] Step 3: Control the deformable arm to retract, forming a streamlined shape;

[0019] Step 4: Start the underwater propulsion unit to perform underwater navigation;

[0020] Step 5: The underwater propulsion unit operates at full power, pushing the air section propeller above the sea-air interface. After the propeller leaves the water, it starts up quickly, achieving takeoff in the water and flight in the air medium.

[0021] Optionally, in step 1, the vector thruster is controlled to deflect to generate torque, which counteracts the anti-torque generated by the rotor power unit.

[0022] Optionally, in step 2, the vehicle is controlled to hover near the water surface and gradually descend, and the brushless motor is shut down when the water surface approaches the brushless motor of the rotor power unit.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] The deformable arms deploy in the air to increase the rotor wheelbase, thereby improving lift and stability; they retract in the water and become parallel to the fuselage, forming a streamlined "torpedo-like" shape that significantly reduces water resistance.

[0025] A composite sealing method, including O-rings, plug seals, stuffing boxes, and waterproof screws, is adopted to ensure the watertightness of the electronic compartment in cross-media environments.

[0026] By integrating the air rotor motor and the underwater waterproof propulsion motor into the same propulsion unit and introducing a vector thruster to counteract the anti-torque generated by the three rotors and assist in steering, the power system can be efficiently reused in both media. Attached Figure Description

[0027] The accompanying drawings illustrate exemplary embodiments of the invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification.

[0028] Figure 1 This is a front view of the arm deployment state of a three-rotor amphibious cross-medium variable structure unmanned aerial vehicle according to an embodiment of the present invention;

[0029] Figure 2 This is a perspective view of a three-rotor amphibious cross-medium variable structure unmanned aerial vehicle according to an embodiment of the present invention;

[0030] Figure 3 This is an internal view of the waterproof compartment of the aircraft described in this embodiment of the invention;

[0031] Figure 4 This is a side view of the rear hatch of the waterproof compartment of the aircraft described in this embodiment of the invention;

[0032] Figure 5 This is a schematic diagram of the ball screw mechanism driven by the 360° bus servo motor of the aircraft described in this embodiment of the invention;

[0033] Figure 6 This is a schematic diagram of the aircraft motor arm and fixed thruster described in an embodiment of the present invention;

[0034] Figure 7 This is a schematic diagram of the vector thruster of the aircraft described in an embodiment of the present invention;

[0035] Figure 8This is a schematic diagram of the underwater vehicle in the embodiment of the present invention with its arms retracted.

[0036] Figure 9 This is a schematic diagram of the electrical framework of the aircraft described in an embodiment of the present invention;

[0037] Figure 10 This is a diagram of the motion attitude of the aircraft described in this embodiment of the invention;

[0038] Among them, the components are: 1. Acrylic hemispherical dome; 2. Front flange; 3. Acrylic compartment; 4. Rear flange; 5. Rear hatch cover; 6. Stuffing box; 7. Rubber-coated bearing; 8. Electronic compartment front bracket; 9. Electronic component board; 10. Battery; 11. Sheet metal fastener; 12. Electronic speed controller; 13. Switch module; 14. Capacitor; 15. Underwater control board; 16. Electronic compartment front fixing plate; 17. Flight controller; 18. Underwater rotary switch; 19. Rear hatch cover guide flange; 20. Sealing ring pressure plate; 21. Plug seal.

[0039] 360° bus servo motor 22, drive gear 23, driven gear 24, servo motor bracket 25, lead screw 26, lead screw tail end support 27, three-pronged ball nut 28, rotary joint seat 29, carbon tube sleeve 30, carbon fiber tube motor arm 31, carbon fiber connecting rod 32, carbon fiber connecting rod connector 33.

[0040] Motor mount 34, rotor brushless motor 35, rotor 36, waterproof motor 37, underwater propeller 38, vector thruster including vector axis servo mount 39, waterproof servo 40, vector axis motor mount 41. Detailed Implementation

[0041] The following is in conjunction with the appendix Figures 1 to 10 The present invention will be further described in detail below with reference to the embodiments. It is to be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The technical solution of this invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] Unless otherwise stated, the exemplary embodiments / exemplifications shown are to be understood as providing exemplary features of various details that provide ways in which the technical concept of the invention can be implemented in practice. Therefore, unless otherwise stated, the features of the various embodiments / exemplifications may be additionally combined, separated, interchanged and / or rearranged without departing from the technical concept of the invention.

[0044] The use of crosshairs and / or shading in the accompanying drawings is generally used to clarify the boundaries between adjacent components. Thus, unless otherwise stated, the presence or absence of crosshairs or shading does not convey or indicate any preference or requirement for the specific material, material properties, dimensions, proportions, commonalities between the illustrated components, or any other characteristics, properties, etc., of the components. Furthermore, in the accompanying drawings, the dimensions and relative dimensions of components may be exaggerated for clarity and / or descriptive purposes. When exemplary embodiments can be implemented differently, a specific process sequence may be performed in a different order than that described. For example, two consecutively described processes may be performed substantially simultaneously or in the reverse order of their description. Furthermore, the same reference numerals denote the same components.

[0045] When a component is referred to as being "on" or "above" another component, "connected to," or "joined to" another component, the component may be directly on, directly connected to, or directly joined to the other component, or there may be intermediate components. However, when a component is referred to as being "directly on" another component, "directly connected to," or "directly joined to" another component, there are no intermediate components. Therefore, the term "connection" can refer to a physical connection, an electrical connection, etc., and may or may not have intermediate components.

[0046] For descriptive purposes, the present invention may use spatial relative terms such as “below,” “under,” “below,” “down,” “above,” “above,” “higher,” and “side (e.g., in a “sidewall”)” to describe the relationship between one component and another component as shown in the accompanying drawings. In addition to the orientations depicted in the drawings, the spatial relative terms are also intended to encompass different orientations of the device during use, operation, and / or manufacture. For example, if the device in the drawings is flipped, a component described as “below” or “under” another component or feature would subsequently be positioned “above” said other component or feature. Thus, the exemplary term “below” can encompass both “above” and “below” orientations. Furthermore, the device may be otherwise positioned (e.g., rotated 90 degrees or in other orientations), thus interpreting the spatial relative descriptive terms used herein accordingly.

[0047] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms “a” and “the” are intended to include the plural forms as well. Furthermore, when the terms “comprising” and / or “including” and variations thereof are used in this specification, it indicates the presence of the stated features, integrals, steps, operations, parts, components, and / or groups thereof, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, parts, components, and / or groups thereof. It should also be noted that, as used herein, the terms “substantially,” “about,” and other similar terms are used as approximate terms rather than as terms of degree, thus explaining the inherent biases in measurements, calculated values, and / or provided values ​​that would be recognized by one of ordinary skill in the art.

[0048] In one embodiment, the present invention provides a three-rotor amphibious trans-medium variable structure unmanned aerial vehicle, comprising: a waterproof compartment;

[0049] Three deformable arms are hinged to the rear end of the waterproof cabin and can switch between an extended state and a retracted state relative to the waterproof cabin. In the extended state, the three deformable arms open outward to increase the rotor wheelbase. In the retracted state, the three deformable arms retract towards the side of the waterproof cabin to form a streamlined shape together with the waterproof cabin.

[0050] Three coaxial hydro-aerial propulsion assemblies are respectively disposed at the ends of the three deformable arms; each coaxial hydro-aerial propulsion assembly includes a rotor power unit for aerial flight and an underwater propulsion power unit for underwater propulsion, wherein the rotor power unit and the underwater propulsion power unit are coaxially disposed.

[0051] This invention utilizes the deployment and retraction deformation of the arms, combined with a coaxial hydro-aerial propulsion system, to achieve morphological and propulsion adaptation of the vehicle in both air and water media, thereby enhancing its cross-media operational capabilities. Three arms are hinged to the rear of the waterproof hull and can switch between deployed and retracted states. When deployed, the rotor wheelbase is increased, improving lift and stability during flight; when retracted, the arms conform to the hull, forming a streamlined shape with the waterproof hull and reducing underwater drag. Each arm is equipped with a coaxial hydro-aerial propulsion assembly at its end, coaxially arranging the airborne rotor and underwater propeller, enabling the reuse of the propulsion system in both media, simplifying the structure and improving integration.

[0052] Optionally, the deformable arms are deployed and retracted via a drive mechanism. The drive mechanism includes a lead screw driven by a servo motor and a nut assembly that works with the lead screw to convert rotational motion into linear motion. The nut assembly is connected to the three deformable arms via a linkage mechanism.

[0053] Optionally, the nut assembly is a three-pronged ball nut, with its three connecting arms connected to the corresponding deformable arms via connecting rods.

[0054] Optionally, an O-ring is provided between the body of the waterproof compartment and the front and rear flanges to achieve static sealing; a stuffing box and a plug seal are provided on the rear cover of the waterproof compartment.

[0055] Optionally, at least one of the coaxial hydro-air propulsion components is a vector thruster, and the thrust direction of its underwater propulsion power unit is adjustable.

[0056] Optionally, the rotor power unit is a rotor driven by a brushless motor, and the underwater propulsion power unit is an underwater propeller driven by a waterproof motor.

[0057] Optionally, in the deployed state, the angle between the three deformable arms and the axis of the waterproof chamber is 20° to 40°; in the retracted state, the three deformable arms are parallel to the side of the waterproof chamber.

[0058] In another embodiment, the present invention provides a three-rotor amphibious cross-medium variable structure unmanned aerial vehicle, comprising: a waterproof compartment, the waterproof compartment having a cylindrical torpedo-shaped structure, and a rear hatch provided at the rear end; the waterproof compartment houses a flight control module, a battery, and communication equipment, and achieves static sealing through double O-rings provided between the front and rear flanges and the acrylic body; the rear hatch is provided with a stuffing box for cable introduction, a plug seal for dynamic sealing screws, and waterproof screw holes with sealing rings;

[0059] The waterproof compartment achieves static sealing through double O-ring seals between the front and rear flanges and the transparent compartment body. The rear cover is equipped with a stuffing box for cable entry, a plug seal for dynamic sealing of the screw, and waterproof screw holes with sealing rings, forming a composite sealing system. The plug seal adopts a semi-open structure, is embedded in the rear cover guide flange, and is fixed with a sealing ring pressure plate. A rubber gasket is sandwiched between the rear cover guide flange and the rear cover to enhance the seal.

[0060] Three deformable arms are hinged at equal angles to the rear hatch of the waterproof compartment. Each arm is connected to a three-pronged ball nut via a linkage mechanism. The three-pronged ball nut is fitted onto an axially fixed lead screw. The lead screw is designed as a stepped shaft and is axially fixed in conjunction with a support at the tail end of the lead screw. A bearing is embedded in the top shaft hole of the support at the tail end of the lead screw to reduce frictional resistance. The lead screw is driven to rotate by a servo motor. The servo motor drives the rotation through a drive gear meshing with a driven gear fixed on the lead screw, thereby switching the three deformable arms between the extended and retracted states.

[0061] Preferably, the lead screw is driven to rotate by a 360° bus servo motor.

[0062] Three coaxial hydro-aerial propulsion assemblies are respectively mounted at the ends of the three deformable arms. Each coaxial hydro-aerial propulsion assembly includes a rotor brushless motor and its rotor for aerial flight, and a waterproof motor and its underwater propeller for underwater propulsion. The rotor brushless motor and the waterproof motor are coaxially arranged. At least one of the coaxial hydro-aerial propulsion assemblies is a vector thruster. The waterproof motor of the vector thruster is mounted on a deflectable vector axis motor mount, which is driven by a waterproof servo to deflect at an angle ranging from 10° to 30°, in order to counteract the anti-torque generated by the three rotors and assist in steering.

[0063] When flying in the air, the three arms extend to form a 30° angle with the axis of the waterproof compartment, and the plane of the rotor is parallel to the rear hatch; when navigating underwater, the three arms retract to be parallel to the side of the waterproof compartment, and the whole is in the shape of a streamlined torpedo.

[0064] During flight, the three deformable arms extend to form an angle of 20° to 40° (preferably 30°) with the axis of the waterproof compartment, with the rotor plane parallel to the rear hatch to achieve maximum lift. During underwater navigation, the three deformable arms retract to be parallel to the sides of the waterproof compartment, with the rotor plane forming an angle of 20° to 40° (preferably 30°) with the rear hatch, resulting in a streamlined torpedo configuration that significantly reduces underwater drag. The distance between the front and rear flange ends of the waterproof compartment is 200mm to 300mm (preferably 236.4mm), and the compartment diameter is 80mm to 100mm (preferably 90mm).

[0065] In another embodiment, the present invention provides a cross-medium navigation control method based on a three-rotor amphibious cross-medium variable structure unmanned aerial vehicle, comprising the following steps:

[0066] Step 1: Control the deformable arm to unfold and start the rotor power unit to perform aerial flight;

[0067] Step 2: During the transition from air to water, control the vehicle to descend and shut down the rotor power unit;

[0068] Step 3: Control the deformable arm to retract, forming a streamlined shape;

[0069] Step 4: Start the underwater propulsion unit to perform underwater navigation;

[0070] Step 5: The underwater propulsion unit operates at full power, pushing the air section propeller above the sea-air interface. After the propeller leaves the water, it starts up quickly, achieving takeoff in the water and flight in the air medium.

[0071] Optionally, in step 1, the vector thruster is controlled to deflect to generate torque, which counteracts the anti-torque generated by the rotor power unit.

[0072] Optionally, in step 2, the vehicle is controlled to hover near the water surface and gradually descend, and the brushless motor is shut down when the water surface approaches the brushless motor of the rotor power unit.

[0073] In another embodiment, the present invention provides a cross-medium navigation control method based on the above-described three-rotor amphibious cross-medium variable structure unmanned aerial vehicle, comprising the following steps:

[0074] Step 1, during the flight phase, control the servo motor to drive the lead screw to rotate, so that the three-pronged ball nut drives the three deformable arms to extend to an angle of 20° to 40° with the axis of the waterproof compartment through the linkage mechanism. Start the rotor brushless motor to drive the rotor to rotate and generate lift, and at the same time control the vector thruster to deflect to counteract the anti-torque generated by the three rotors.

[0075] Step 2, the transition from air to water: control the unmanned vehicle to hover near the water surface and gradually descend. When the water surface approaches the brushless motor, shut down the brushless motor.

[0076] Step 3, during the arm retraction phase, the servo motor is activated to drive the lead screw to rotate in the opposite direction, so that the three-pronged ball nut pulls the three deformable arms to retract parallel to the side of the waterproof hull through the linkage mechanism, forming a streamlined torpedo configuration;

[0077] Step 4, underwater navigation phase: Start the waterproof motor to drive the underwater propeller to generate thrust and adjust the body attitude to a horizontal state for underwater navigation;

[0078] Step 5, the transboundary phase, the aircraft transitions from horizontal to vertical suspension, and the three-rotor arms are fully extended. Then the underwater thrusters will operate at full power, pushing the air section propellers above the sea-air interface. After the propellers leave the water, they start up quickly, achieving takeoff in the water and flight in the air medium.

[0079] In another embodiment, refer to Figures 1 to 4 The present invention provides a three-rotor amphibious cross-medium variable structure unmanned aerial vehicle, comprising: a waterproof cabin and deformable arms;

[0080] The waterproof compartment includes: an acrylic hemispherical cover 1, a front flange 2, an acrylic compartment 3, a rear flange 4, a rear compartment cover 5, a stuffing box 6, a rubber-coated bearing 7, a front bracket for the electronic compartment 8, an electronic component board 9, a battery 10, sheet metal fasteners 11, an electronic speed controller 12, a switch module 13, a capacitor 14, an underwater control board 15, a front mounting plate for the electronic compartment 16, a flight controller 17, an underwater rotary switch 18, a guide flange for the rear compartment cover 19, a sealing ring pressure plate 20, and a plug seal 21.

[0081] The electronic component board 9 is fixed to the front and rear flanges using sheet metal fasteners and the front mounting plate 16 of the electronic compartment, clamped together with square nuts. Control modules, batteries, and communication modules are installed on it. Double O-rings are installed on both the front and rear flanges to form a static seal with the acrylic compartment. All screw holes on the aluminum alloy rear hatch cover that penetrate into the waterproof compartment are sealed with screws and sealing rings. The contact point between the lead screw and the rear hatch cover is sealed with a plug seal, using a semi-open structure. During installation, the plug seal must be embedded into the rear hatch cover guide flange before the sealing ring pressure plate is fixed with screws. A rubber gasket is sandwiched between the rear hatch cover guide flange and the rear hatch cover to enhance the seal. External motor cables are inserted into the stuffing box installed on the rear hatch cover and connected to the interior of the waterproof compartment. The waterproof compartment is cylindrical, similar to a torpedo, with an acrylic hemispherical dome installed at the front.

[0082] The hardware system is functionally divided into five main parts: power management system, flight control system, underwater control system, central processing system, and ground control system. Each subsystem consists of a core management unit and corresponding external sensors or actuators. Internally, the system utilizes various communication methods (such as serial port, CAN bus, I²C, SPI, etc.) to achieve data exchange and collaborative operation between the various systems.

[0083] The environmental adaptability of electronic equipment must be fully considered in the structural design of the aircraft. Except for the GNSS module, other core electronic equipment such as the inertial measurement unit, flight control system, and power management system must be housed within a watertight pressure chamber. To achieve high-quality satellite signal reception, the GNSS module's antenna must be exposed to an unobstructed open area, avoiding signal obstruction from any overhead electronic structures or metal materials. Therefore, the GNSS module is independently placed on the top of the aircraft, outside the cabin.

[0084] Reference Figure 9 This is a schematic diagram of the aircraft's electrical framework. The system is powered by a 6S lithium battery, with an effective operating range of 25.2V (fully charged) - 19.8V (safety cutoff). The power system has a maximum output power of 7069W, using two parallel high-power MOSFETs to control the main circuit's on / off state. Low-voltage logic controls this switching, allowing for system power-on / off without opening the battery compartment for insertion / removal, while also preventing electrical sparks from frequent battery insertion / removal from impacting the control system. The main power supply uses a step-down module to achieve multi-stage output: 24V drives the flight and underwater thrusters, 8.4V powers the servo motors, and 5V provides operating power for the onboard computing platform, flight controller, underwater controller, and various sensor modules.

[0085] During installation, all electronic components are first fixed onto the electronic device board. Then, sheet metal fasteners are used to install the electronic device board onto the rear flange. Next, square nuts are installed on the front of the electronic device board near the waterproof compartment, and the acrylic compartment is fitted over it. Finally, the other side of the square nuts is screwed onto the front mounting plate of the electronic compartment, which is mounted on the front flange. A front bracket for the electronic compartment is pre-installed on the front mounting plate to support the batteries inside. Rubber-coated bearings are also installed at the two front corners of the electronic device board to absorb shock and prevent damage during impacts. Two O-rings are installed on each of the front and rear flanges to form a static seal with the acrylic compartment. All screw holes on the aluminum alloy rear cover that penetrate into the waterproof compartment are sealed with screws and O-rings. The contact point between the lead screw and the rear cover uses a plug seal with a semi-open structure. During installation, the plug seal must be embedded into the rear cover guide flange before the sealing ring pressure plate is fixed with screws. The shaft hole of the rear cover guide flange is chamfered to facilitate plug seal installation. The mounting hole of the sealing ring pressure plate is a blind hole to reduce the risk of leakage. A rubber gasket is inserted between the rear hatch guide flange and the rear hatch to enhance the seal. The external motor cable is inserted into the stuffing box installed on the rear hatch and connected to the interior of the waterproof tank. The underwater power switch for the entire unit is installed on the rear hatch along with the stuffing box, using a waterproof switch, and has a built-in sealing ring on the contact surface with the rear hatch.

[0086] Combination Figure 5 The deformable arm includes: a 360° bus servo motor 22, a drive gear 23, a driven gear 24, a servo motor bracket 25, a lead screw 26, a lead screw tail end support 27, a three-pronged ball nut 28, a rotary joint seat 29, a carbon tube sleeve 30, a carbon fiber tube motor arm 31, a carbon fiber connecting rod 32, a carbon fiber connecting rod connector 33, and a coaxial hydro-aerial propulsion assembly. The UAV is powered by a tri-rotor, with the three motor arms evenly distributed and hinged to an aluminum alloy rear hatch. Graphite gaskets are installed between the carbon tube sleeve and the rotary joint seat for lubrication. The lead screw 26 is designed as a stepped shaft, which, in conjunction with the tail end support, allows for axial fixation. Support at both ends also reduces the bending moment on the lead screw, preventing deformation and thus extending its service life. A bearing is embedded in the top shaft hole of the lead screw tail end support 27 to reduce lead screw resistance.

[0087] Reference Figure 7 The coaxial hydro-aerial propulsion assembly includes a vector thruster and a fixed thruster. The fixed thruster includes a motor mount 34, a waterproof motor 37, an underwater propeller 38, a rotor brushless motor 35, and a rotor 36. The vector thruster includes a vector axis servo mount 39, a waterproof servo 40, a vector axis motor mount 41, a rotor brushless motor 35, and a waterproof motor 37. The vector thruster is used to counteract the torque caused by the odd number of rotors and to assist in steering.

[0088] The deformable arm is driven by a 360° bus servo motor. The servo motor's direct drive gear meshes with the driven gear fixed on the lead screw, and is then driven by a ball screw. The three-pronged lead screw nut reciprocates, driving the arm to open and close via a connecting rod. The maximum movable angle is 30°. In actual operation, it only switches between two states: fully extended in the air, with the rotor plane parallel to the rear hatch; and retracted in the water, parallel to the side of the waterproof compartment, with the propeller plane at a 30° angle to the rear hatch, coupling translational and rotational motions to form an underactuated system.

[0089] In flight: The servo drive screw rotates forward, the ball bearing nut moves to its outermost position, and the three arms extend to form a 30° angle with the waterproof compartment axis, with the arms symmetrically distributed at 120°. The rotor wheelbase (distance between the centers of adjacent rotors) reaches its maximum value of 320mm, and the plane of the rotor is parallel to the rear hatch. The unmanned aerial vehicle hovers or flies vertically, with the waterproof compartment axis perpendicular to the ground. The rotor brushless motor operates at 8500rpm, generating a total lift of 1800g from the three rotors. The vector thruster deflects by 15°, and the waterproof motor rotates at 2000rpm, generating a horizontal thrust component F_h = 2.5 × sin(15°) ≈ 0.65N, and an anti-torque compensation torque M_vector = 0.65 × 0.18 ≈ 0.12N·m, balancing the rotor anti-torque.

[0090] Underwater navigation status: The servo drive screw rotates in the opposite direction, the ball bearing nut moves to its innermost position, and the three arms retract to be parallel to the side of the waterproof compartment (0° angle). The carbon fiber tube motor arm is in close contact with the outer surface of the acrylic compartment. The plane containing the rotor and underwater propeller forms a 30° angle with the rear hatch (determined by the mechanism's geometry). The overall shape is a streamlined torpedo configuration, with a maximum outer diameter of approximately 100mm (compared to 90mm for the compartment diameter + 16mm for the arm thickness / 2 × 2 ≈ 98mm) and a length of approximately 500mm (compared to 236.4mm for the waterproof compartment + 220mm for the arm length + 60mm for the propeller diameter ≈ 516mm). The unmanned vehicle adjusts its attitude to a horizontal position, with the waterproof compartment axis parallel to the water surface. The rotor brushless motor shuts down, the waterproof motor operates at 3000rpm, and the three propellers generate a total thrust of 7.5N, propelling the entire vehicle underwater at a speed of 0.8m / s. In the retracted state, the arms are parallel to the fuselage, and the frontal area is reduced to the cylindrical cross-sectional area S=πd² / 4=π×0.09² / 4≈0.0064m². Compared with the deployed state, the frontal area is reduced by about 75% (about 0.025m², including the deployed arms and rotors). The underwater navigation resistance is reduced from about 25N to 6N, a resistance reduction of 76%, which greatly improves energy efficiency and endurance.

[0091] In another embodiment, the waterproof compartment adopts a cylindrical torpedo-shaped structure with a distance of 236.4 mm between the front and rear flange ends and a compartment diameter of 90 mm. An acrylic hemispherical dome 1, a transparent observation window with a thickness of 5 mm, is installed at the front end and can withstand pressure at a depth of 3 meters underwater. The main body of the waterproof compartment is composed of an acrylic compartment 3 with a wall thickness of 4 mm, connected at both ends by a front flange 2 and a rear flange 4, respectively. The front and rear flanges are made of 6061-T6 aluminum alloy with an anodized surface, a flange thickness of 8 mm, an outer diameter of 94 mm, and an inner diameter that fits tightly with the acrylic compartment. Two O-rings (specification NBR70-90×2.65 mm) are installed between the front and rear flanges and the acrylic compartment, forming a double static seal structure. The O-rings are installed in trapezoidal sealing grooves on the inner side of the flanges, with a groove depth of 2.8 mm and a width of 3.2 mm. During assembly, insert the two ends of the acrylic chamber into the sealing grooves of the front and rear flanges respectively, and tighten the eight M4 stainless steel bolts evenly to achieve a tight connection between the flange and the chamber. The bolt tightening torque is 2.5 N·m to ensure that the sealing ring is uniformly compressed and the deformation rate reaches 20%~25%, forming a reliable static seal.

[0092] The rear hatch 5 is made of 7075-T6 aluminum alloy, with a thickness of 12mm and an outer diameter of 94mm. It is connected to the rear flange by 12 M5 stainless steel bolts with a tightening torque of 4.5N·m.

[0093] The rear hatch is equipped with a variety of sealing structures: (1) Stuffing gland 6 is used to introduce external motor cables. It adopts PG9 waterproof stuffing gland with a sealing level of IP68. It can introduce 6 cables (diameter 1.5~2.5mm) at the same time. After the cable is inserted into the stuffing gland, the internal rubber sealing ring is pressed by the compression nut to form a circumferential seal for the cable; (2) Plug seal 21 is used for dynamic sealing of the screw. It adopts fluororubber plug seal with an inner diameter of 16mm and an outer diameter of 28mm. The temperature range is -20℃~150℃. The plug seal is installed in a semi-open structure: first, the plug seal is embedded in the inner groove of the rear hatch guide flange 19 (groove depth 3mm). The guide flange shaft hole is designed with a 30° chamfer for easy installation. Then, the sealing ring pressure plate 20 is fixed with 4 M3 bolts (tightening torque 1.2N·m). The installation hole of the sealing ring pressure plate is a blind hole design to avoid the risk of water leakage due to through holes. A 1mm thick rubber gasket is sandwiched between the rear hatch guide flange and the rear hatch to further enhance the sealing performance; (3) All screw holes (16 in total) on the rear hatch that penetrate into the waterproof compartment are made of waterproof screws with sealing rings. The screws are matched with NBR O-rings (specifications M4×0.7mm or M5×0.8mm). When the screws are screwed in, the sealing rings are compressed to form a sealing surface. The layout of the electronic system inside the waterproof compartment adopts a layered design. The electronic component board 9 is a double-layer PCB board (size 220mm×80mm×1.6mm), which is fixed between the front and rear flanges by the sheet metal fasteners 11 and the front fixing plate 16 of the electronic compartment.

[0094] The assembly method is as follows: First, all electronic components (underwater control board 15, flight control module 17, electronic speed controller 12, switch module 13, capacitor 14, etc.) are welded and fixed onto the electronic component board, with optimized component layout to lower the center of gravity. Then, the electronic component board is mounted on the rear flange 4 using sheet metal fasteners. The sheet metal fasteners are L-shaped brackets made of 304 stainless steel with a thickness of 1.5mm. Four M3 square nuts are pre-installed on the front end of the electronic component board near the waterproof compartment. After fitting the acrylic compartment 3, the other side of the square nuts is fixed to the front mounting plate 16 of the electronic compartment, which is pre-installed on the front flange 2, using M3 bolts. The bolt tightening torque is 1.0 N·m. The front mounting plate 16 of the electronic compartment has a pre-installed front bracket 8 to support the 4S 5000mAh lithium battery 10 (weighing approximately 450g). The bracket is an aluminum alloy bracket with a soft sponge pad to prevent the battery from sliding during movement. Rubber-coated bearings (size 608ZZ bearings with silicone sleeves) are installed at the two front corners of the electronic component board to absorb shock and prevent damage to the electronic component board during water impact or underwater collision. The shock absorption system can absorb impact acceleration up to 30g. The power supply of the whole machine is controlled by an underwater rotary switch. The switch and stuffing box are installed together on the rear hatch cover. The switch body has an IP68 waterproof rating and the contact surface with the rear hatch cover has an NBR sealing ring (2mm thick).

[0095] The deformable arm system consists of a drive mechanism and the arm body. The core of the drive mechanism is a 360° bus servo motor 22 (model BusServo LX-15D, output torque 17 kg·cm, operating voltage 12V). The servo motor is fixed to the rear cover 5 via a servo motor bracket 25, which is made of aluminum alloy and is 3mm thick. A drive gear 23 (module 0.8, number of teeth 20) is mounted on the servo motor's output shaft. This drive gear meshes with a driven gear 24 (module 0.8, number of teeth 60) fixed to a lead screw 26, forming a 1:3 reduction ratio. This amplifies the servo motor's output torque to 51 kg·cm, ensuring it can overcome the resistance (resistance torque approximately 35 kg·cm) during the arm's extension / retraction process. The gears are made of 45# steel, heat-treated, surface carburized and quenched, with a hardness of HRC58-62 and a tooth surface precision of grade 6, ensuring smooth and noiseless transmission.

[0096] The lead screw 26 is designed as a stepped shaft structure with a total length of 180mm, divided into three sections: the middle section (100mm in length) is a threaded section with a trapezoidal thread specification of Tr16×4 (4mm lead), and the surface is hard chrome plated to improve wear resistance; the front section (12mm in diameter, 40mm in length) is inserted into the rear hatch guide flange 19, and a dynamic seal is achieved through the plug seal 21; the rear section (14mm in diameter, 40mm in length) is inserted into the top shaft hole of the lead screw tail end support 27, and a stainless steel deep groove ball bearing 6201ZZ (inner diameter 12mm, outer diameter 32mm, thickness 10mm) is embedded in the shaft hole of the support, with a bearing preload of 50N, reducing the lead screw rotation resistance to below 0.3N·m. The lead screw tail end support 27 is fixed to the outside of the rear hatch and connected by four M5 bolts, made of aluminum alloy 7075-T6 with a thickness of 10mm. The stepped shaft design provides axial support to the lead screw from both ends, which, together with the lead screw tail end support, achieves axial fixation (axial movement <0.2mm). The support at both ends reduces the bending moment on the lead screw to 1 / 4 of that under single-end support, preventing bending deformation when the lead screw is subjected to radial forces (approximately 200N) during arm extension / retraction, thus extending its service life to over 10,000 cycles. The three-pronged ball nut 28 is a custom-made part made of 6061-T6 aluminum alloy. It features a center-mounted ball nut (specification Tr16×4, containing 16 3mm diameter steel balls circulating), with three connecting arms evenly distributed on the outer side of the nut (120° included angle, 25mm length, 12mm width, 8mm thickness). Each connecting arm has a pin hole (6mm diameter) at its end for connecting the carbon fiber connecting rod 32. A three-pronged ball screw nut is fitted onto the threaded section of the lead screw 26. When the servo drives the lead screw to rotate, the ball screw nut converts the rotational motion into axial linear motion, with a moving speed of v = nL / 60 (n is the lead screw speed in rpm, and L is the lead of 4mm). The maximum servo speed is 60 rpm, so the maximum moving speed of the ball screw nut is 4mm / s. The stroke from fully retracted to fully extended is 80mm, taking approximately 20 seconds. The ball screw transmission efficiency can reach over 90%, significantly reducing drive power consumption compared to ordinary trapezoidal threaded lead screws (efficiency 30%~40%). The arm body consists of a rotary joint seat 29, a carbon tube sleeve 30, a carbon fiber tube motor arm 31, and a carbon fiber connecting rod 32. The rotary joint seat 29 is fixed to the rear cover 5, made of aluminum alloy 6061-T6, and connected by four M5 bolts (tightening torque 4.5 N·m). The joint seat has a cylindrical shaft hole (diameter 18mm, depth 25mm). The carbon tube sleeve 30 is a round tube made of carbon fiber composite material (outer diameter 18mm, inner diameter 16mm, length 30mm), which is bonded to the carbon fiber tube motor arm 31 with epoxy resin adhesive. The bonding area is >500mm² and the tensile strength is >15MPa.The clearance between the outer surface of the carbon tube sleeve and the inner surface of the rotary joint seat shaft hole is 0.05mm (H7 / g6 fit). A graphite gasket (0.5mm thick, 18×20×0.5mm) is installed as a self-lubricating layer to reduce the coefficient of friction to below 0.08, eliminating the need for additional lubrication. The carbon fiber tube motor arm 31 is a carbon fiber composite round tube (outer diameter 16mm, inner diameter 14mm, length 220mm). The carbon fiber layers are symmetrically laid up at [0° / ±45° / 90°], with a fiber volume fraction of 60%, tensile strength >1500MPa, elastic modulus >150GPa, and density of only 1.6g / cm³. The weight of a single arm is only about 55g. The carbon fiber connecting rod 32 (14mm×8mm×150mm flat rod) connects the ball nut connecting arm and the carbon fiber tube motor arm respectively through the carbon fiber connecting rod connector 33. The connector uses a pin connection (pin diameter 6mm, stainless steel 304 material), forming a planar four-bar linkage.

[0097] When the servo drive screw rotates forward, the ball nut moves away from the rear hatch, pulling the arm outward around the rotary joint seat via the connecting rod to extend it. When the servo drive screw rotates in the reverse direction, the ball nut moves towards the rear hatch, pushing the arm inward to retract via the connecting rod. The maximum swing angle of the arm is 30° (angle with the waterproof hull axis), corresponding to a ball nut travel of 80mm. This mechanism is an underactuated system. A single degree of freedom input (servo rotation) is converted into linear motion through the screw and nut mechanism, and then coupled through the connecting rod mechanism to generate synchronous rotational motion of the three arms. The angle error of the three arms is <±1°, ensuring the synchronicity and symmetry of deployment / retraction.

[0098] Three coaxial hydro-aerial propulsion components are mounted at the ends of three deformable arms, two of which are fixed thrusters and one is a vector thruster. The fixed thruster consists of a motor mount 34, a rotor brushless motor 35, a rotor 36, a waterproof motor 37, and an underwater propeller 38. The motor mount 34 is made of 6061-T6 aluminum alloy, 5mm thick, and is fixed to the end of the carbon fiber tube motor arm with four M4 bolts, tightening torque 3.0 N·m. The rotor brushless motor 35 (model 2212 920KV, maximum power 200W, operating voltage 11.1V) is mounted on the upper side of the motor mount, with the motor axis pointing upwards, driving the rotor 36 (9-inch diameter, 5-inch pitch, two-bladed propeller, made of carbon fiber reinforced nylon) to rotate and generate lift. The rotor motor has a rated speed of 8500 rpm, a maximum thrust of approximately 600g per rotor, and a total thrust of 1800g for all three rotors. It can support a total weight of 1200g and a payload of 200g, with the remaining thrust used for attitude control and maneuvering. The waterproof motor 37 (model 2838 3500KV brushless waterproof motor, IP68 waterproof rating, maximum power 150W, operating voltage 11.1V) is mounted on the underside of the motor mount, coaxial and concentric with the rotor motor. The motor shaft points downwards, driving the underwater propeller 38 (60mm diameter, three-bladed, 45mm pitch, made of nylon PA66) to rotate and generate thrust. The waterproof motor employs magnetohydrodynamic sealing technology, filling the shaft seal with magnetic nanofluid, forming a liquid O-ring under the action of a permanent magnet, achieving a sealing pressure of up to 0.5MPa (corresponding to a water depth of 50 meters).

[0099] The underwater propeller generates approximately 2.5N of thrust at a speed of 3000rpm, and the three waterproof motors generate a total thrust of 7.5N, which can propel the entire machine underwater at a speed of 0.8m / s. The drag is approximately 6N (calculated based on a torpedo-like configuration with a drag coefficient Cd=0.08: F=0.5×ρ×v²×S×Cd=0.5×1000×0.8²×0.0254×0.08≈6.5N).

[0100] The vector thruster adds a vectoring mechanism to the fixed thruster. The vector axis servo mount 39 is made of aluminum alloy and is connected to the end of the carbon fiber tube motor arm via a pin (6mm in diameter), allowing it to swing around the pin axis. The waterproof servo 40 (model BusServo LFD-01M, output torque 8kg·cm, waterproof rating IP67, operating voltage 7.4V) is mounted inside the vector axis servo mount, and the servo output shaft drives the vector axis motor mount 41 to swing via a connecting rod. The vector axis motor mount 41 is equipped with a rotor brushless motor 35 and a waterproof motor 37. When the servo is working, the entire propulsion unit (including the motor and propeller) can deflect in a plane perpendicular to the arm, with a deflection angle range of ±15° (i.e., adjustable from 10° to 30°). The deflection mechanism adopts a push rod type linkage structure. The servo output shaft swing arm is 15mm long, the connecting rod is 50mm long, and the vector axis motor mount swing arm is 20mm long, forming a crank rocker mechanism. The servo output angle of 60° corresponds to the vector axis motor mount deflection angle of 30°. The transmission ratio is 1:0.5, and the transmission is smooth without dead spots.

[0101] The working principle of a vector thruster: During flight, the three rotors generate lift while simultaneously producing a counter-torque M = -Q = F × r (where F is the thrust of a single rotor and r is the rotor radius). The counter-torques of the three rotors are in the same direction (either clockwise or counterclockwise), and the total counter-torque M_total = 3 × Q will cause the aircraft to spin. The waterproof motor of the vector thruster deflects at an angle θ (10°~30°), and its thrust F_thrust produces a horizontal component F_h = F_thrust × sin(θ). The torque M_vector = F_h × L (L is the distance from the vector thruster to the center of gravity of the aircraft, approximately 180mm) can counteract the rotor counter-torque. By adjusting the vector deflection angle θ and the waterproof motor speed in real time through flight control, M_vector = M_total is maintained, achieving counter-torque compensation and preventing the aircraft from spinning. Simultaneously, during level flight or turns, the deflection of the vector thruster provides lateral thrust, assisting in steering, reducing the turning radius, and improving maneuverability.

[0102] In another embodiment, such as Figure 10 When the tri-rotor amphibious cross-medium variable structure unmanned aerial vehicle (UAV) is flying in the air, it is in a vertical position. At this time, the angle between the three motor arms and the cabin axis, i.e., the line where the lead screw is located, is 30°, which is the maximum angle of arm extension. The waterproof motor is not working, and the brushless motor of the rotor drives the three rotors to rotate. The plane of the rotor is perpendicular to the cabin axis and parallel to the rear hatch, which generates the maximum lift. The vector motor deflects to counteract the torque of the three rotors.

[0103] During the transition from air to water, the tri-rotor unmanned aerial vehicle (UAV) first hovers near the water surface, then gradually descends. Just as the water surface is about to touch the brushless rotor motors, the rotor motors shut down, and the 360° bus servo motors activate, driving the lead screw to rotate. The three-pronged ball bearing nut moves along the lead screw towards the rear hatch, connecting the three arms via linkages to rotate and retract around the rotary joint seats until they are parallel to the lead screw and the side of the hull, switching to torpedo-style underwater vehicle mode. The waterproof motors then activate, adjusting the aircraft's attitude to level, allowing it to operate normally in the water.

[0104] During the transition from underwater to air, the vehicle's attitude is first adjusted through the coordinated action of the vector motors and the underwater propulsion unit, gradually transitioning from horizontal navigation to vertical hovering. Simultaneously, the arm deployment mechanism is activated, fully extending the arms. At this point, the angles between the three motor arms and the cabin axis (the line containing the lead screw) are all 30°. After attitude adjustment, the underwater propulsion unit is activated to generate downward thrust, propelling the vehicle from deep water towards the surface and continuing to rise. When the vehicle rises until the air propeller is completely out of the water, the air propeller is activated. Subsequently, the control system distributes control of the vector axis, allowing the air propulsion system to gradually take over attitude control and thrust output, thus achieving a stable transition across the water-air interface. Once the vehicle has fully entered the air medium, the underwater propulsion unit is shut down, and the air propulsion system sustains flight.

[0105] The technical effects of this invention are as follows:

[0106] 1. Excellent adaptability to cross-media environments

[0107] The core technical advantage of this invention lies in its outstanding adaptability to different media. Through an innovative deformable arm mechanism, the vehicle can autonomously change its overall configuration to optimize performance in media with significantly different physical properties, such as air and water. In flight, the arms are fully extended, increasing the rotor wheelbase and allowing for the use of larger rotors. This significantly improves the vehicle's payload capacity and enhances its flight stability and efficiency. Underwater, the arms can be tightly retracted to be parallel to the sides of the waterproof hull, resulting in a streamlined "torpedo-like AUV" shape. This design greatly reduces the vehicle's surface area and shape drag underwater, significantly reducing underwater drag, improving maneuverability and energy efficiency, and solving the problem of excessive underwater drag inherent in traditional UAVs.

[0108] 2. Multiple reliable seals

[0109] Addressing the critical issue of watertightness in cross-medium vehicles, this invention exhibits a multi-layered and highly reliable sealing design for the waterproof compartment. The design employs a composite sealing strategy combining various sealing methods, including O-ring static seals (between the front and rear flanges and the acrylic compartment), waterproof bolts (for the rear cover bolt holes), plug seals (for the screw rod dynamic seal), and stuffing boxes (for cable entry sealing). This design ensures the structural integrity and sealing safety of the electronics compartment under certain water depth and pressure, providing a dry and stable operating environment for critical electronic equipment such as the flight control module, battery, and communication module, thus providing a fundamental guarantee for repeated cross-medium operations.

[0110] 3. Highly integrated power and propulsion system

[0111] This invention employs a coaxial hydro-aerial propulsion assembly design, integrating a brushless rotor motor for aerial flight and a waterproof motor for underwater propulsion into a single unit. This design optimizes spatial layout, reduces external protrusions, and helps lower fluid resistance. The introduction of vector thrusters not only assists in steering but, more importantly, effectively counteracts the anti-torque generated by the odd number of rotors, preventing the aircraft from spinning in mid-air and ensuring stable flight attitude. The entire power system operates efficiently in various media, achieving precise control of power output and efficient energy utilization.

[0112] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0113] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0114] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A three-rotor amphibious trans-medium variable structure unmanned aerial vehicle, characterized in that, include: Waterproof compartment; Three deformable arms are hinged to the rear end of the waterproof cabin and can switch between an extended state and a retracted state relative to the waterproof cabin. In the extended state, the three deformable arms open outward to increase the rotor wheelbase. In the retracted state, the three deformable arms retract towards the side of the waterproof cabin to form a streamlined shape together with the waterproof cabin. Three coaxial hydro-aerial propulsion assemblies are respectively disposed at the ends of the three deformable arms; each coaxial hydro-aerial propulsion assembly includes a rotor power unit for aerial flight and an underwater propulsion power unit for underwater propulsion, wherein the rotor power unit and the underwater propulsion power unit are coaxially disposed.

2. The unmanned aerial vehicle according to claim 1, characterized in that, Preferably, the deformable arms are deployed and retracted via a drive mechanism. The drive mechanism includes a lead screw driven by a servo motor and a nut assembly that works with the lead screw to convert rotational motion into linear motion. The nut assembly is connected to the three deformable arms via a linkage mechanism.

3. The unmanned aerial vehicle according to claim 2, characterized in that, The nut assembly is a three-pronged ball nut, and its three connecting arms are respectively connected to the corresponding deformable arms via connecting rods.

4. The unmanned aerial vehicle according to claim 1, characterized in that, The waterproof compartment is equipped with O-rings between the compartment body and the front and rear flanges to achieve static sealing; the rear cover of the waterproof compartment is equipped with a stuffing box and a plug seal.

5. The unmanned aerial vehicle according to claim 1, characterized in that, At least one of the coaxial hydro-air propulsion components is a vector thruster, and the thrust direction of its underwater propulsion power unit is adjustable.

6. The unmanned aerial vehicle according to claim 1, characterized in that, The rotor power unit is a rotor driven by a brushless motor, and the underwater propulsion power unit is an underwater propeller driven by a waterproof motor.

7. The unmanned aerial vehicle according to claim 1, characterized in that, In the deployed state, the angle between the three deformable arms and the axis of the waterproof chamber is 20° to 40°; in the retracted state, the three deformable arms are parallel to the side of the waterproof chamber.

8. A cross-medium navigation control method for a three-rotor amphibious cross-medium variable structure unmanned aerial vehicle based on any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Control the deformable arm to unfold and start the rotor power unit to perform aerial flight; Step 2: During the transition from air to water, control the vehicle to descend and shut down the rotor power unit; Step 3: Control the deformable arm to retract, forming a streamlined shape; Step 4: Start the underwater propulsion unit to perform underwater navigation; Step S5: The underwater propulsion unit operates at full power, pushing the air section propeller above the sea-air interface. After the propeller leaves the water, it starts up quickly, achieving takeoff in the water and flight in the air medium.

9. The method according to claim 8, characterized in that, In step 1, the vector thruster is controlled to deflect to generate torque, which counteracts the counter-torque generated by the rotor power unit.

10. The method according to claim 8, characterized in that, In step 2, the vehicle is controlled to hover near the water surface and gradually descend. When the water surface approaches the brushless motor of the rotor power unit, the brushless motor is shut down.

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