Flexible antenna folding and unfolding mechanism suitable for small unmanned aerial vehicle platform and control method of flexible antenna folding and unfolding mechanism

Abstract

The invention discloses a flexible antenna folding and unfolding mechanism suitable for a small unmanned aerial vehicle platform and a control method of the flexible antenna folding and unfolding mechanism, and belongs to the technical field of unmanned aerial vehicle communication equipment. The mechanism comprises a retracting and releasing mechanism configured to adjustably release the flexible conductor; the guide assembly is arranged below the fuselage and used for guiding the flexible conductor to be away from the rotor plane; a flexible antenna assembly having a proximal end connected to the retractable mechanism and a free distal end suspended in the air; and the linkage control unit is in communication connection with the flight controller, controls retraction and release based on the flight state data and realizes anti-winding protection. The core of the invention lies in that the flexible conductor is released to a predetermined length by the retracting and releasing mechanism, so that the effective signal receiving part of the flexible conductor extends out of an electromagnetic interference near-field area generated by the power system. The EMI problem of the airborne antenna of the small unmanned aerial vehicle is solved in a physical isolation mode, the receiving quality of medium-wave digital broadcast signals is remarkably improved, and the unmanned aerial vehicle is supported to obtain wide-area differential positioning data in an area with insufficient public network coverage.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) communication equipment technology, and specifically to a flexible antenna deployment and take-off mechanism and its deployment and take-off control method suitable for small UAV platforms. Background Technology

[0002] With the booming development of the low-altitude economy, small drones are increasingly being used in logistics delivery, agricultural plant protection, surveying and inspection, emergency rescue and other fields. These application scenarios are placing increasingly higher demands on the positioning accuracy of drones, and centimeter-level or even millimeter-level real-time dynamic (RTK) positioning has become a basic requirement for many tasks.

[0003] Traditional RTK positioning schemes rely on terrestrial base stations or mobile communication networks (4G / 5G) to transmit differential correction data (RTCM format). However, this approach faces significant challenges in the following scenarios:

[0004] • Remote mountainous areas, forests, deserts, and other areas with weak or no public network coverage;

[0005] • Offshore operating environments such as oceans and islands;

[0006] • Emergency rescue scenarios where ground communication infrastructure is damaged after a natural disaster;

[0007] • Special mission scenarios requiring electromagnetic silence.

[0008] Medium-wave (MW, 530-1700 kHz) digital broadcasting technology, especially the Digital Radio Mondiale (DRM) standard, offers a promising alternative to address the aforementioned issues. Medium-wave signals offer advantages such as wide coverage (a single transmitter can cover hundreds of kilometers), strong diffraction capability, and the elimination of the need for complex network infrastructure. Through the DRM data channel (SDC / MSC), BeiDou / GNSS differential correction data can be broadcast, providing UAVs with wide-area, blind-spot-free, high-precision positioning services.

[0009] Technical Challenges: However, receiving medium-wave digital broadcast signals on small drone platforms faces a fundamental technical obstacle—electromagnetic interference (EMI).

[0010] The power systems of small drones (brushless motors, electronic speed controllers (ESC), switching power supplies, etc.) generate strong electromagnetic noise during operation. Due to the limited size of drones, the physical distance between the onboard antenna and the interference source is extremely short, often placing it in the near-field region of electromagnetic interference. In this region, the relationship between the interference field strength and distance is not a simple inverse square decay, but rather exhibits a more drastic change, leading to a sharp deterioration in the signal-to-noise ratio (SNR) at the antenna.

[0011] For DRM digital broadcasting, the OFDM modulation and high-order QAM mapping (such as 64-QAM) used have high requirements for signal-to-noise ratio. When the airborne antenna is flooded by strong EMI, the receiver cannot demodulate the signal correctly, the differential correction data transmission link is interrupted, and the high-precision positioning function fails.

[0012] In existing technologies, common methods for solving EMI problems in drones include:

[0013] • Electromagnetic shielding: Adding a metal shielding cover to sensitive components;

[0014] • Filtering circuit: Install EMI filters on power lines and signal lines;

[0015] • Layout optimization: Place the antenna as far away from interference sources as possible.

[0016] However, the above methods have limited effectiveness on small drone platforms. Shielding and filtering increase weight and cost, while the size limitations of the fuselage severely restrict the scope for layout optimization. More importantly, these methods cannot fundamentally solve the problem of strong near-field interference—at distances on the order of centimeters, any shielding measure struggles to provide sufficient isolation.

[0017] Therefore, there is an urgent need for an innovative technical solution that can effectively isolate EMI from the drone's power system and ensure high-quality reception of medium-wave digital broadcast signals. Summary of the Invention

[0018] To address the aforementioned problems in existing technologies, this invention provides a flexible antenna deployment and take-off mechanism and its control method suitable for small unmanned aerial vehicle (UAV) platforms. By physically releasing the antenna to a position away from the UAV fuselage, the effective receiving part of the antenna is located outside the near-field region of electromagnetic interference from the power system, thereby fundamentally solving the EMI problem of airborne medium-wave antennas.

[0019] To achieve the above objectives, the present invention adopts the following technical solution:

[0020] In a first aspect, the present invention provides a flexible antenna deployment and retraction mechanism suitable for small unmanned aerial vehicle (UAV) platforms, comprising:

[0021] • A take-up mechanism configured as a rotary take-up unit that can adjustably release or retrieve the flexible conductor;

[0022] • A guide component, located below the fuselage of the UAV platform, is configured to guide the flexible conductor away from the rotor plane;

[0023] • Flexible antenna assembly, having a near end connected to the deployment and take-off mechanism and a free far end suspended in the air;

[0024] • The linkage control unit communicates with the flight controller and controls the retraction and extension actions based on flight status data, while also providing anti-entanglement protection.

[0025] Secondly, the present invention provides a method for controlling the deployment and retraction of a flexible towed antenna, including steps such as flight status monitoring, deployment and retraction permission determination, deployment and retraction action execution, and tension feedback adjustment.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. Significantly Improved Signal-to-Noise Ratio: By extending the antenna beyond the near-field region of the power system's EMI, the electromagnetic environment at the antenna is fundamentally improved. Based on near-field attenuation characteristics, when the antenna's distal end is several meters away from the UAV fuselage, the interference field strength can decrease by more than 40dB, enabling the correct demodulation of high-order modulated DRM signals.

[0028] 2. Wide-area positioning without ground base stations: Combining the differential data transmission capability of medium-wave DRM broadcast, this invention enables UAVs to acquire RTK correction data in areas with insufficient public network coverage, achieving centimeter-level positioning and supporting the business expansion of the low-altitude economy in remote areas.

[0029] 3. Automated Deployment and Retraction with Safety Redundancy: The linkage control unit automatically controls the release and retrieval of the antenna based on flight status, requiring no manual intervention. Anti-entanglement protection logic can take timely protective measures upon detecting abnormal attitude, preventing accidents caused by the antenna entanglement with the propeller.

[0030] 4. Power failure self-locking protection: The optional worm gear transmission mechanism has a self-locking characteristic, which can maintain the current length of the antenna in the event of an accidental power failure, preventing the antenna from sliding out freely and causing safety hazards.

[0031] 5. Wide platform adaptability: The structure and method of this invention can be adapted to various UAV platforms such as multi-rotor and fixed-wing, and deployment can be achieved by adjusting the installation position and control parameters. Attached Figure Description

[0032] Figure 1 This is a system architecture block diagram of the flexible antenna take-up and take-up mechanism of the present invention;

[0033] Figure 2 This is a flowchart of the release and take-up control method of the present invention;

[0034] Figure 3 This is an exploded view of the structure of the launching and receiving mechanism of the present invention;

[0035] Figure 4 This is a schematic diagram of the installation of the present invention on a multi-rotor drone;

[0036] Figure 5 This is a schematic diagram of the flexible antenna of the present invention in its working state.

[0037] In the diagram: 100, take-up and take-down mechanism; 101, winding drum; 102, drive unit; 103, transmission assembly; 104, tension sensor; 200, flexible conductor; 201, proximal end; 202, free distal end; 203, end counterweight; 300, guide assembly; 301, guide tube; 400, linkage control unit; 500, flight controller; 600, UAV platform; 601, fuselage; 602, rotor / propeller; 700, SDR receiver module; 701, DRM demodulator; 702, RTCM resolver. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention.

[0039] Example 1

[0040] like Figure 4 As shown, this embodiment uses a quadcopter drone as the carrier. The deployment and take-up mechanism 100 is installed at the center directly below the fuselage 601, which is located on or near the vertical line of the drone's center of gravity, in order to minimize the impact on the flight attitude during antenna release.

[0041] The take-up and unwinding mechanism 100 includes a winding drum 101, a drive unit 102, and a transmission assembly 103. In this embodiment, the transmission assembly 103 adopts a worm gear mechanism with a power-off self-locking function. The drive unit 102 adopts a low-power DC motor, which drives the worm gear through the worm, and the worm gear is coaxially fixed with the winding drum 101.

[0042] The guide assembly 300 includes a guide tube 301, the axis of which is vertically downward or tilted at a small angle to the vertical direction, ensuring that the release path of the flexible conductor 200 is located below the sweeping plane of all rotors 602 and maintains a safe distance from the rotors.

[0043] The flexible conductor 200 uses multi-strand stranded copper wire covered with a lightweight insulating sheath. The core diameter is selected according to the release length: portable type (5-20 meters) uses AWG30 specification, and industrial type (20-100 meters) uses AWG26 specification. The free end 202 is equipped with a streamlined end counterweight 203, which is made of brass or stainless steel and is teardrop-shaped. It serves to straighten the conductor, stabilize its posture, and reduce air resistance.

[0044] Example 2: Fixed-wing UAV platform

[0045] For fixed-wing UAVs, the deployment and recovery mechanism 100 can be installed in the middle of the fuselage or below the tail. When installed in the fuselage, the guide tube 301 is tilted downwards and rearwards, so that the antenna release path is away from the propeller at the nose. When installed in the tail, it can be released directly downwards or slightly backwards.

[0046] Due to the high flight speed of fixed-wing platforms, the mass of the end counterweight 203 needs to be appropriately increased to overcome the drag force of airflow on the antenna and keep the antenna suspended approximately vertically.

[0047] Signal processing flow

[0048] like Figure 1 As shown in the system architecture, the medium-wave signal received by the flexible conductor 200 is transmitted to the SDR receiver module 700 via a coaxial feeder. After the SDR module completes the RF front-end processing, the digital signal enters the DRM demodulator 701 to demodulate the SDC and MSC channel data. The RTCM resolver 702 extracts differential correction information from the data stream and injects it into the GNSS module of the flight controller 500 via a serial port or network interface to achieve RTK positioning.

[0049] Retraction and expansion control logic

[0050] like Figure 2 As shown in the flowchart, the linkage control unit 400 executes the following control logic:

[0051] Takeoff phase: Keep the antenna fully retracted to avoid ground obstacles or airflow disturbances affecting the antenna during takeoff.

[0052] Climbing Phase: Once the GPS altitude exceeds the release altitude threshold (e.g., 50 meters) and the attitude is stable, the antenna is slowly released. The release speed is dynamically adjusted based on tension feedback to ensure smooth antenna deployment.

[0053] Cruise phase: The antenna remains fully deployed and continuously receives medium-wave signals. The linkage control unit continuously monitors the flight status. If abnormal attitude is detected (such as tilt angle exceeding 30 degrees or excessive roll rate), all deployment and retraction actions are immediately stopped, and emergency recovery is triggered if necessary.

[0054] Landing Phase: When a landing command is received or the altitude falls below the recovery altitude threshold (e.g., 30 meters), antenna recovery begins. After recovery is complete, the winding drum is locked to ensure the antenna does not accidentally slip out upon landing.

[0055] Emergency status: When a power failure, loss of remote control signal, or low battery is detected, emergency recovery will be performed with the highest priority to ensure flight safety.

[0056] Definition of EMI near-field region

[0057] The near-field and far-field of electromagnetic interference are typically defined by a fraction of the wavelength. For broadband noise generated by UAV propulsion systems, its energy is mainly concentrated in the tens of kHz to several MHz frequency band. Taking 1 MHz as a reference, the wavelength is approximately 300 meters, and the near-field boundary is approximately λ / 2π ≈ 48 meters. However, for the compact size of small UAVs, the actual strong interference area is mainly concentrated within 1 meter of the interference source.

[0058] This invention extends the antenna to a length of several meters to tens of meters, keeping the main receiving part of the antenna away from the fuselage. The field strength decreases rapidly with distance, resulting in a significant improvement in the signal-to-noise ratio.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flexible antenna deployment and retraction mechanism suitable for small unmanned aerial vehicle (UAV) platforms, characterized in that, include: The take-up and take-up mechanism (100) is configured to adjustably release or retract a rotating take-up unit of the flexible conductor (200), the take-up and take-up mechanism including a winding drum (101) and a drive unit (102) drivenly connected to the winding drum. A guide component (300) is disposed below the fuselage of the UAV platform and configured to guide the flexible conductor to be released along a predetermined path and to make the release direction of the flexible conductor away from the rotor plane or propeller sweep area of ​​the UAV platform. A flexible antenna assembly includes the flexible conductor (200), the flexible conductor having a proximal end (201) connected to the retraction mechanism and a free distal end (202) suspended in the air, the free distal end being provided with an end counterweight (203). The linkage control unit (400) is communicatively connected to the flight controller (500) of the UAV platform and is configured to monitor flight status data in real time. When the attitude parameters in the flight status data exceed a preset safety threshold, the linkage control unit triggers anti-entanglement protection logic. The retraction mechanism is configured to release the flexible conductor to a predetermined length, such that the effective signal receiving part of the flexible conductor extends beyond the near-field region of electromagnetic interference generated by the power system of the UAV platform.

2. A method for controlling the deployment and retraction of a flexible towed antenna, applied to a small unmanned aerial vehicle (UAV) platform equipped with the deployment and retraction mechanism as described in claim 1, characterized in that... Includes the following steps: S1. Real-time acquisition of flight status data of the UAV platform, including flight altitude, flight stage, fuselage attitude parameters and power system status; S2. Determine the antenna deployment / retraction permission conditions based on the flight status data: When the flight phase is the cruise phase and the flight altitude exceeds the preset release altitude threshold, the antenna release action is allowed. When a landing command is received or the flight altitude is lower than the preset recovery altitude threshold, the antenna is forcibly recovered. When the fuselage attitude parameters meet the preset abnormal attitude conditions, the anti-entanglement protection logic is triggered; S3. Based on the judgment result, control the retraction mechanism to perform the corresponding retraction action, and release the flexible conductor to a predetermined length so that its effective signal receiving part is outside the electromagnetic interference near field region; S4. During the winding and unwinding process, monitor the tension data of the flexible conductor and adjust the winding and unwinding speed according to the tension data to maintain tension stability.

3. The flexible antenna take-up and take-down mechanism according to claim 1, characterized in that, The predetermined length is adapted based on the takeoff weight of the drone platform: For portable unmanned aerial vehicle platforms with a takeoff weight of less than 5 kg, the predetermined length is 5 to 20 meters; For industrial-grade unmanned aerial vehicle platforms with a takeoff weight of 5 to 25 kg, the predetermined length is 20 to 100 meters.

4. The flexible antenna take-up and take-down mechanism according to claim 1, characterized in that, The drive unit employs a worm gear mechanism, which has a power-off self-locking function and is configured to maintain the current release length of the flexible conductor when the drive source is powered off.

5. The flexible antenna take-up and take-down mechanism according to claim 1, characterized in that, The installation layout of the retraction mechanism and guide assembly satisfies the following conditions: The retraction mechanism is installed on or near the center of gravity of the UAV platform; The guide assembly includes a guide tube (301), and the angle between the axis of the guide tube and the rotor plane or propeller sweep plane of the UAV platform is greater than a predetermined angle; The end counterweight (203) has a streamlined shape.

6. The retraction and extension control method according to claim 2, characterized in that, The specific logic for determining the antenna release / retraction permission conditions in step S2 includes: the abnormal attitude conditions include at least one of the following: the fuselage tilt angle exceeding 30 degrees, the fuselage roll rate exceeding a predetermined threshold, and the vertical descent speed exceeding a safety limit; step S2 can also obtain the real-time flight altitude based on the Global Navigation Satellite System, and automatically trigger the antenna release process when the flight altitude first exceeds the release altitude threshold.

7. The retraction and extension control method according to claim 2, characterized in that, When a power system fault signal is detected, the remote control signal is lost for more than a predetermined time, or the battery power is lower than a preset safety threshold, the antenna emergency retrieval action is executed with the highest priority.

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