Stealth multi-rotor unmanned aerial vehicle

Abstract

This invention discloses a stealthy multi-rotor unmanned aerial vehicle (UAV), belonging to the field of UAV technology. The fuselage has a cross-shaped symmetrical structure, including a central upper plate, a central lower plate, and four circumferentially distributed lever arms. The stealth shroud is mounted circumferentially on the fuselage via a bracket, employing a swept-back wraparound design. The shroud's profile in the frontal direction features a wedge design to shield against strong scattering sources carried by the UAV. The power system includes propellers, brushless motors, and batteries. The flight control system includes a flight control terminal, a multi-sensor fusion navigation unit, and an RTK antenna. The flight control terminal adopts a dual-processor architecture, achieving precise positioning through the multi-sensor fusion navigation unit and the RTK antenna. The data link is used for air-to-ground data, image, and video transmission. This invention features extremely low RCS, extremely weak micro-Doppler effect, high structural strength, and strong modular expansion capabilities, making it suitable for covert reconnaissance and penetration missions in complex combat environments.

Description

Technical Field

[0001] This invention belongs to the field of unmanned aerial vehicle (UAV) technology, specifically relating to a stealth multi-rotor UAV with low detectability, high structural strength and high-precision navigation capabilities, suitable for covert reconnaissance, surveillance and penetration missions in complex electromagnetic warfare environments. Background Technology

[0002] Multirotor drones, due to their vertical takeoff and landing capabilities, strong hovering ability, and flexible control, have been widely used in military reconnaissance, target designation, electronic warfare, and special operations. However, traditional multirotor drones have significant shortcomings in stealth performance. Their exposed motors, propellers, batteries, flight control modules, and complex cable layouts all constitute strong radar scattering sources, resulting in a large radar cross-section (RCS). This makes them easy to detect, track, and intercept by enemy air defense radars, especially fire control radars and low-altitude detection radars. This severely limits their survivability and mission effectiveness in modern high-intensity combat environments.

[0003] In existing technologies, attempts to improve the stealth performance of UAVs have mainly focused on fixed-wing UAV platforms, reducing their radar cross-section (RCS) through methods such as shape modification (e.g., sloping design, parallel edges), the use of radar-absorbing materials, and structural stealth (e.g., S-shaped air intakes, internal weapons bays). However, due to their inherent power layout (multiple exposed rotors and motors) and compact airframe structure, it is difficult to directly apply the stealth design concepts of fixed-wing UAVs. How to effectively shield or handle these dispersed strong scattering sources within a limited space, while ensuring flight performance, structural strength, and necessary functional expandability, is the main technical challenge currently facing the stealth design of multi-rotor UAVs.

[0004] Furthermore, while some existing multi-rotor UAVs have improved in aerodynamic efficiency or payload capacity, there is still no mature and reliable solution for systematic stealth design, especially in achieving extremely low RCS across a wide frequency band (such as covering typical fire control and detection radar bands like X and Ku). Therefore, there is an urgent need for a comprehensive stealth design scheme specifically tailored to the characteristics of multi-rotor platforms to significantly enhance their penetration and survivability under dense air defense networks. Summary of the Invention

[0005] The purpose of this invention is to overcome the deficiencies in the prior art and to provide a stealthy multi-rotor unmanned aerial vehicle.

[0006] The specific technical solution adopted in this invention is as follows: This invention provides a stealth multi-rotor unmanned aerial vehicle, including an airframe, a stealth shroud, a power system, a flight control system, and a data link; The fuselage has a cross-shaped symmetrical structure, including a central upper plate, a central lower plate, and four circumferentially distributed lever arms. The central upper plate is a composite PCB power distribution board with integrated electrical connection functions. Its bottom is connected to the central lower plate, and there is a sandwich space between the two. The power system, flight control system, and data link are installed in the sandwich space. The central lower plate and the lever arms are both made of carbon fiber material. The stealth hood is mounted on the circumference of the aircraft via a bracket and adopts a swept-back wrap-around design. The hood contour in the frontal direction adopts a wedge design to shield against strong scattering sources carried on the UAV. The power system includes a propeller, a brushless motor, and a battery; the output end of the brushless motor is connected to the central shaft of the propeller, and four sets are respectively fixed to the outer end of each lever arm. The flight control system includes a flight control terminal, a multi-sensor fusion navigation unit, and an RTK antenna; the flight control terminal adopts a dual-processor architecture and achieves precise positioning through the multi-sensor fusion navigation unit and the RTK antenna. The data link is used for air-to-ground data, image, and video transmission.

[0007] Preferably, the stealth shroud is coated with a radar-absorbing coating, capable of shielding radar scattering sources including brushless motors, batteries, and flight control systems, and blocking most of the propellers. Through the design of the stealth shroud, the average radar cross-section of the aircraft in the head-on direction, including X-band and Ku-band fire control radar and detection radar bands, is less than 0.001 m². 2 .

[0008] Preferably, the stealth shroud is made of lightweight composite material.

[0009] Preferably, the RTK antenna enables real-time dynamic differential positioning, satisfying a horizontal positioning accuracy of ≤5cm and a vertical positioning accuracy of ≤10cm.

[0010] Preferably, the brushless motor is an external rotor brushless motor, and is equipped with an electronic speed controller.

[0011] Preferably, the flight control terminal adopts a dual-processor heterogeneous architecture, including an FMU processor and an IO processor; the FMU processor is responsible for running complex navigation, guidance and control algorithms, while the IO processor is responsible for real-time tasks including sensor data acquisition, actuator control and communication interface management.

[0012] Preferably, the multi-sensor fusion navigation unit integrates an inertial measurement unit for providing triaxial acceleration and angular velocity, a magnetometer for providing a heading reference, and a high-sensitivity GNSS antenna.

[0013] Preferably, the data link uses a short antenna module.

[0014] Compared with the prior art, the present invention has the following advantages: 1) Extremely low radar detectability: Through the combined application of physical shielding with a swept-back stealth radome, shape modification, and optional radar-absorbing coatings, the most critical head-on RCS of the multi-rotor UAV is reduced to 0.001 m. 2 The following design reduces the detection range of enemy radar by 1-2 orders of magnitude compared to conventional designs, significantly shortening the detection range and improving penetration and battlefield survivability.

[0015] 2) Extremely low micro-Doppler detectability: The propeller is physically shielded by the stealth shroud, thus avoiding detection by micro-Doppler radar due to the periodic echo characteristics generated by the rotation of traditional multi-rotors.

[0016] 3) Excellent structural and functional integration: The use of a high-strength carbon fiber lever arm and a composite PCB center board ensures both lightweight design and structural strength and impact resistance. The PCB power distribution board design simplifies internal wiring, improves reliability, and reduces potential sources of electromagnetic scattering.

[0017] 4) High-precision flight and positioning capabilities: Based on a dual-processor flight control architecture and multi-sensor fusion navigation, combined with RTK centimeter-level positioning technology, the UAV has high-precision attitude control, stable hovering and precise flight path tracking capabilities, meeting the needs of precision operations in complex environments.

[0018] 5) Excellent mission adaptability: The modular airframe design provides flexible installation space and electrical interfaces for a variety of mission payloads. Combined with data link and stealth characteristics, it is capable of performing covert reconnaissance, surveillance, target designation and even some electromagnetic countermeasures missions.

[0019] 6) Comprehensive low signature signal: While optimizing radar stealth, the design of aerodynamic shape and propulsion system also takes into account the suppression of infrared signature, achieving multi-dimensional low detectability. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural diagram of the stealth multi-rotor UAV of the present invention (in the figure, the upper part is the front of the UAV and the lower part is the rear of the UAV).

[0021] Explanation of the labels in the diagram: 1-Lever arm, 2-Center plate upper plate, 3-Center plate lower plate, 4-Stealth cover, 5-Propeller, 6-Brushless motor, 7-Battery, 8-Flight control terminal, 9-Multi-sensor fusion navigation unit, 10-RTK antenna, 11-Data link. Detailed Implementation

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Technical features in various embodiments of the present invention can be combined accordingly without mutual conflict.

[0023] like Figure 1 As shown, this invention provides a stealthy multi-rotor unmanned aerial vehicle (UAV). The UAV mainly includes an airframe, a stealth radome 4, a power system, a flight control system, and a data link 11. Through innovative shape design, material application, and system integration, the UAV of this invention achieves an extremely low RCS across a wide radar band, while maintaining excellent flight performance, structural strength, and mission module expandability.

[0024] The structure of each component will be described in detail below.

[0025] In a preferred embodiment of the present invention, the fuselage adopts a classic cross-shaped symmetrical structural layout, serving as the main load-bearing and mounting platform for the UAV. The fuselage mainly includes a central upper plate 2, a central lower plate 3, and four circumferentially distributed lever arms 1. The four lever arms 1 are precision-machined from high-strength carbon fiber sheets, extending uniformly outwards from the center. This material is lightweight, has high specific strength, is impact-resistant, and fatigue-resistant, effectively withstanding aerodynamic loads and potential collision impacts during flight, thus improving the overall structural durability of the aircraft. The lever arms 1 are firmly connected to the central plate assembly, together forming the main load-bearing frame. The central plate assembly includes a central upper plate 2 and a central lower plate 3.

[0026] In a preferred embodiment of the present invention, the center plate 2 is a composite PCB power distribution board with integrated electrical connection functions, manufactured using a multi-layer composite PCB process. It incorporates power traces and connector pads, achieving a triple function of power distribution and structural support. The center plate 2 not only provides structural support but also integrates power distribution functionality. This integrated design reduces the complex independent cable routing within traditional UAVs, lowers the risk of electromagnetic scattering and malfunctions caused by messy cables, and improves the reliability and neatness of electrical connections.

[0027] In a preferred embodiment of the present invention, the lower plate 3 of the center plate is a carbon fiber plate, which can be fixedly connected to the upper plate 2 of the center plate via connecting columns. There is a certain gap between the upper plate 2 and the lower plate 3 of the center plate, forming a sandwich space. This sandwich space is used to safely house the power system, flight control system, and data link 11, such as the battery 7, the core components of the flight control terminal 8, and the data link module 11. The lower plate 3 provides mounting interfaces and physical protection for the main functional modules, and its structural strength and lightweight characteristics match those of the upper plate.

[0028] In a preferred embodiment of the present invention, the stealth radome 4 is mounted circumferentially on the fuselage via a bracket and is one of the core components for achieving low detectability. The stealth radome 4 adopts a swept-back, enveloping design with a smooth overall shape and no obvious right angles or concave structures. The design of the radome in the head-on direction is particularly important; its contour adopts a wedge design, which can guide incident radar waves in other directions, effectively avoiding the formation of corner reflector effects, thereby significantly reducing radar echo reflection in the head-on direction. The stealth radome 4 physically encloses the motors, propellers, and major radar scattering sources installed in the fuselage, such as batteries and flight control modules, forming an effective shield. This reduces the probability of interception by enemy detection systems or greatly shortens their detection range, thereby improving the target's survivability.

[0029] The stealth hood 4, through a combination of shape shielding and material absorption, ensures that the average radar cross-section of the UAV in the head-on direction of typical fire control and detection radar bands such as X and Ku is less than 0.001 m². 2 .

[0030] Specifically, the stealth shroud 4 has a streamlined, continuous curved surface that sweeps backward from the middle of the fuselage. It effectively conceals the four lever arms 1, the brushless motors 6 and propellers 5 mounted at the ends of the lever arms, and also shields the electronic equipment in the central plate area from above and below. The stealth shroud 4 effectively conceals the propellers 5, preventing detection by micro-Doppler radar.

[0031] In practical use, the stealth shroud 4 can be made of lightweight composite materials, effectively controlling the overall weight while ensuring overall strength. The outer surface of the stealth shroud 4 can also be coated with lightweight radar-absorbing materials. These lightweight composite materials can be made of glass fiber or foam sandwich materials, while the lightweight radar-absorbing materials can be made of graphene, silicon carbide, or magnetic iron nanomaterials. The radar-absorbing coating can effectively absorb electromagnetic wave energy, converting some of the incident electromagnetic wave energy into heat energy, further weakening radar echo signals and significantly reducing oncoming radar echo reflection.

[0032] In a preferred embodiment of the present invention, the power system provides flight power for the UAV and mainly includes a propeller 5, a brushless motor 6, and a battery 7. The output end of the brushless motor 6 is connected to the central shaft of the propeller 5, and four sets are respectively fixed to the outer end of each lever arm 1.

[0033] In practical use, each brushless motor 6 is an external rotor brushless motor, and each is also equipped with an electronic speed controller. Each motor is connected to the power bus of the upper plate 2 of the center plate via the electronic speed controller. The use of four external rotor brushless motors with electronic speed controllers provides stable, efficient, and responsive torque output. The output shaft of the brushless motor 6 is equipped with a dynamically balanced and calibrated high-efficiency propeller 5. The propeller is preferably of a specific size, providing sufficient lift while taking into account efficiency and noise control. The battery 7, as the energy module, uses a high-energy-density lithium polymer battery, is installed on the lower plate 3 of the center plate, and is covered by a stealth shield 4.

[0034] In a preferred embodiment of the present invention, the flight control system is centrally installed in the central board area and is the core of UAV flight control and mission management. The flight control system mainly includes a flight control terminal 8, a multi-sensor fusion navigation unit 9, and an RTK antenna 10. Among them, the flight control terminal 8 adopts a dual-processor architecture and achieves precise positioning through the multi-sensor fusion navigation unit 9 and the RTK antenna 10.

[0035] In practical use, the Flight Controller Terminal 8 adopts a dual-processor heterogeneous architecture: one is a high-performance FMU (Flight Management Unit, such as an STM32 series chip with a high-performance ARM Cortex-M7 core) processor, responsible for running complex navigation, guidance, and control algorithms; the other is an I / O (Input / Output, such as an STM32 chip with an ARM Cortex-M3 core) processor, specifically responsible for tasks with high real-time requirements such as sensor data acquisition, actuator control, and communication interface management. This architecture balances the computational demands of complex algorithms with the deterministic and reliable nature of system response.

[0036] In practical applications, the multi-sensor fusion navigation unit 9 integrates an inertial measurement unit (IMU consisting of a three-axis MEMS gyroscope and accelerometer, providing three-axis acceleration and angular velocity), a magnetometer (providing a heading reference), and a high-sensitivity GNSS antenna. The collected data is transmitted to the flight control terminal via a high-speed bus. Through advanced data fusion algorithms such as Kalman filtering, this unit can comprehensively process information from multiple sensor sources, outputting attitude, position, and velocity estimates, laying the foundation for stable flight and accurate route tracking.

[0037] In practical use, the RTK antenna 10 (high precision) is mounted in a low-interference location on the top of the fuselage and connected to the RTK navigation calculation module in the flight control system via a coaxial cable. The RTK antenna 10 is used to achieve real-time dynamic differential positioning, which can improve the positioning accuracy of the UAV to the centimeter level, such as horizontal positioning accuracy ≤5 cm and altitude positioning accuracy ≤10 cm. This is crucial for missions that require precise hovering, autonomous landing, or close coupling with geographic information.

[0038] In a preferred embodiment of the present invention, data link 11 is used to enable bidirectional communication between the UAV and the ground control station, transmitting flight control commands, telemetry data, and information acquired by mission payloads (such as image and video sensors). This embodiment preferably employs a short antenna module design, which, while ensuring necessary communication bandwidth and distance, minimizes the electromagnetic radiation characteristics of the antenna itself, helping to reduce the probability of detection by electronic reconnaissance equipment.

[0039] Specifically, Data Link 11 uses a miniaturized, low-power wireless data transmission system with a short helical or patch antenna mounted in a concealed location at the rear or lower side of the fuselage to reduce omnidirectional radiation signature. This data link supports encrypted data transmission for exchanging control commands, telemetry information, and mission payload data with ground stations.

[0040] Through the aforementioned integrated design, the UAV of this invention not only achieves radar stealth, but its smooth shape and low-speed optimized propulsion system also help reduce its acoustic signature. The compact airframe layout and modular design allow the UAV to maintain a small size envelope while leaving ample internal space for carrying different mission payloads, thus expanding its mission adaptability.

[0041] In the actual manufacturing process, the lever arm 1 and the stealth shield 4 of the fuselage are integrally molded using a mold, which effectively controls weight and strength. During assembly, the lever arm 1 is first fixed to the corresponding interface on the lower plate 3 of the center plate. Then, the flight control terminal 8, the multi-sensor fusion navigation unit 9, the battery 7, and the data link 11 are installed at the designated positions on the lower plate 3 of the center plate and electrical connections are completed. Next, the upper plate 2 of the center plate is connected and tightened, and connected to the equipment on the lower layer through the studs on the plate. Finally, the assembled power kit (brushless motor 6 and propeller 5) is installed at the end of the lever arm 1.

[0042] When the UAV is in operation, the ground control station sends mission commands via data link 11. The FMU processor in the flight control terminal 8, based on mission requirements, combines real-time attitude and position information from the multi-sensor fusion navigation unit 9 with centimeter-level precise positioning information from the RTK antenna 10 to calculate the necessary control quantities. The IO processor then translates these control quantities into specific motor speed control commands, driving the propulsion system to perform precise hovering, autonomous flight, obstacle avoidance, and other maneuvers. Throughout the process, the stealth hood 4 continuously provides effective radar wave shielding and scattering control for key internal scattering sources, making them difficult to effectively identify and track on enemy radar screens. This invention features extremely low RCS, extremely weak micro-Doppler effect, high structural strength, and strong modular expansion capabilities, making it suitable for covert reconnaissance and penetration missions in complex combat environments.

[0043] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A stealthy multi-rotor unmanned aerial vehicle, characterized in that, Includes airframe, stealth shield (4), power system, flight control system and data link (11); The body has a cross-shaped symmetrical structure, including a central upper plate (2), a central lower plate (3), and four circumferentially distributed lever arms (1); the central upper plate (2) is a composite PCB power distribution board with integrated electrical connection function, and its bottom is connected to the central lower plate (3) with a sandwich space between them. The power system, flight control system and data link (11) are installed in the sandwich space; the central lower plate (3) and the lever arms (1) are both made of carbon fiber material; The stealth cover (4) is mounted on the circumference of the body by a bracket and adopts a swept-back wrap design. The outline of the cover in the front direction adopts a wedge design to shield the strong scattering source carried on the UAV. The power system includes a propeller (5), a brushless motor (6) and a battery (7); the output end of the brushless motor (6) is connected to the central shaft of the propeller (5), and four sets are fixed to the outer ends of each lever arm (1); The flight control system includes a flight control terminal (8), a multi-sensor fusion navigation unit (9), and an RTK antenna (10); the flight control terminal (8) adopts a dual-processor architecture and achieves precise positioning through the multi-sensor fusion navigation unit (9) and the RTK antenna (10); The data link (11) is used for air-to-ground data, image and video transmission.

2. The stealth multi-rotor unmanned aerial vehicle according to claim 1, characterized in that, The stealth shroud (4) is coated with radar-absorbing paint, which can shield radar scattering sources including the brushless motor (6), battery (7) and flight control system, and can block most of the propellers (5); through the design of the stealth shroud (4), the average radar cross-section of the aircraft in the head-on direction of fire control radar and detection radar bands, including X and Ku, is less than 0.001 m. 2 .

3. A stealth multi-rotor unmanned aerial vehicle according to claim 1, characterized in that, The stealth shroud is made of lightweight composite materials.

4. A stealth multi-rotor unmanned aerial vehicle according to claim 1, characterized in that, The RTK antenna (10) enables real-time dynamic differential positioning, satisfying horizontal positioning accuracy ≤5cm and vertical positioning accuracy ≤10cm.

5. A stealth multi-rotor unmanned aerial vehicle according to claim 1, characterized in that, The brushless motor (6) is an external rotor brushless motor and is equipped with an electronic speed controller.

6. A stealth multi-rotor unmanned aerial vehicle according to claim 1, characterized in that, The flight control terminal (8) adopts a dual-processor heterogeneous architecture, including an FMU processor and an IO processor. The FMU processor is responsible for running complex navigation, guidance and control algorithms, while the IO processor is responsible for real-time tasks including sensor data acquisition, actuator control and communication interface management.

7. A stealth multi-rotor unmanned aerial vehicle according to claim 1, characterized in that, The multi-sensor fusion navigation unit (9) integrates an inertial measurement unit for providing triaxial acceleration and angular velocity, a magnetometer for providing heading reference, and a high-sensitivity GNSS antenna.

8. A stealth multi-rotor unmanned aerial vehicle according to claim 1, characterized in that, The data link (11) uses a short antenna module.

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