UAV directional antenna self-tracking system and tracking method

Abstract

The present invention belongs to the field of unmanned aerial vehicle ground control technology, and in particular relates to a directional antenna self-tracking system and tracking method for unmanned aerial vehicles. The system includes a ground radio station, a directional antenna, a sensor module, a servo control module, and a core control module. The ground radio station inputs the GPS data of the unmanned aerial vehicle into the core control module; the servo control module feeds back the pitch angle information to the core control module; the sensor module collects the GPS data of the unmanned aerial vehicle directional antenna self-tracking system and the horizontal azimuth information of the directional antenna, and feeds back to the core control module; the core control module calculates the pitch angle deviation and azimuth deviation of the unmanned aerial vehicle relative to the unmanned aerial vehicle directional antenna self-tracking system; the servo control module adjusts the directional antenna according to the control instruction so that the main antenna beam of the directional antenna is aligned with the unmanned aerial vehicle. The present invention proposes a tracking deduction mode, which can greatly improve the tracking capability of the unmanned aerial vehicle when it loses contact compared to the traditional scanning mode.

Description

Technical Field

[0001] The present invention belongs to the technical field of unmanned aerial vehicle ground control, and in particular relates to a self-tracking system and a tracking method for a directional antenna of an unmanned aerial vehicle. Background Art

[0002] With the rapid development of unmanned aerial vehicle (UAV) technology, its applications are becoming increasingly widespread, with broad prospects in areas such as meteorological observation, agricultural farming, public security monitoring, military reconnaissance, and personnel rescue. In many applications, large amounts of observation and control data need to be transmitted in real time between the UAV and the ground control system. To ensure accurate and reliable data transmission and reception, while also improving reception gain and anti-interference capabilities, this long-distance, high-bandwidth communication often utilizes directional antennas. Directional antennas achieve high gain only when the main lobes of the transmitting and receiving antennas are aligned. Failure to ensure real-time alignment of directional antennas will disrupt the signal between the UAV and the ground control system. This not only results in loss of observation data, hindering mission completion, but can also cause the UAV to lose control and potentially lead to serious accidents such as loss or crash. Therefore, ensuring real-time alignment of directional antennas is essential. There are two main methods for achieving directional antenna alignment and tracking. Manual tracking has drawbacks such as large errors and poor real-time performance. Automatic tracking, in which a directional antenna automatically tracks a target based on its motion, is the current predominant tracking method. Directional antenna automatic tracking (hereinafter referred to as directional antenna self-tracking) can be categorized into two main types, depending on the method used to determine the target angle:

[0003] ① The most commonly used method is to judge the target angle through the signal phase relationship, which requires a complex antenna servo feedback system and is very expensive. In addition, this method has poor anti-interference ability.

[0004] 2. Using the GPS position information sent by the drone to the ground station in real time, the tracking target angle is determined based on the relative position of the drone and the directional antenna. Because GPS position signals are more stable and simpler to implement than the former tracking signal, the latter has more advantages.

[0005] However, during development, directional antenna self-tracking methods encountered the following shortcomings: Currently, various methods determine the tracking target angle based on the relative position of the UAV and the directional antenna. However, to reduce computational complexity, these methods often simplify the process or determine the quadrant of the true azimuth angle based on the relative position of the directional antenna and the UAV. This can easily lead to ambiguity at quadrant boundaries, increasing the complexity of control system implementation. Due to the limited transmission capacity of the communication link and the dynamic characteristics of low-cost GPS receivers, the frequency of position updates sent by the UAV to the ground control system is typically low. During close-range tracking, the tracking angle fluctuates significantly, which can easily cause motion fluctuations and large tracking errors in the tracking system, significantly increasing system wear. With the widespread use of UAVs, many applications require directional antenna self-tracking systems with maneuverable tracking capabilities to improve system mobility and concealment. However, during maneuvering, the GPS position information of the directional antenna is easily interfered with by tunnels, trees, and buildings, resulting in inaccurate position information and, consequently, loss of the tracked target.

[0006] A Chinese invention patent, titled "System and Method for Adjusting Directional Antennas for Unmanned Aerial Vehicles" (publication number CN112909547A, publication date December 4, 2022), describes a system and method for adjusting a directional antenna for a drone. The system controls a first rotary motor and a first pitch motor to adjust the direction of a scanning antenna. Furthermore, a second rotary motor and a second pitch motor are controlled to adjust the direction of a transceiver antenna based on the signal strength of a communication signal from at least one direction collected by the scanning antenna. This method of adjusting the direction of a drone's directional antenna by scanning requires a certain signal strength, and the method loses its tracking effectiveness if the drone completely loses contact.

[0007] A Chinese invention patent, entitled "A Design Method for a UAV Directional Antenna Self-Tracking System" (publication number CN104932548A, published on November 21, 2017), describes a design method for a UAV directional antenna self-tracking system. The method uses the position of the directional antenna and the UAV to determine the directional antenna's tracking target angle. The directional antenna and the UAV's speed are used to smooth the position prediction and to add feedforward to the azimuth motion when the UAV flies over the apex of the directional antenna. An azimuth and pitch angle measuring instrument is installed on the carrier vehicle to measure the vehicle's current azimuth and pitch angles. The current angle of the directional antenna is then determined by combining the measurements from the angle sensor. A main controller calculates a control variable based on the difference between the directional antenna's tracking target angle and its current angle, driving the directional antenna to the target position. This method improves the system's maneuverability and stealth, is easy to implement, effectively smooths the directional antenna's tracking motion, reduces over-the-top tracking errors, and improves system reliability and adaptability. However, it does not consider tracking methods in the event of a UAV loss of contact. Summary of the Invention

[0008] In light of this, the present invention aims to provide a self-tracking system and method for directional antennas used in drones. This system addresses the existing problem of GPS location information from directional antennas being easily affected by interference from tunnels, trees, and buildings during maneuvers, resulting in inaccurate location information and, consequently, loss of tracking targets. This invention proposes a tracking deduction mode, which significantly improves tracking capabilities when a drone loses contact, compared to the traditional scanning mode.

[0009] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0010] A directional antenna self-tracking system for unmanned aerial vehicles (UAVs) comprises a ground radio station, a directional antenna, a sensor module, a servo control module and a core control module, wherein the ground radio station receives radio signals from an onboard radio station of the UAV and inputs GPS data of the UAV into the core control module; the servo control module collects pitch angle information of the directional antenna and feeds the pitch angle information back to the core control module; the sensor module collects GPS data of the UAV directional antenna self-tracking system and horizontal azimuth information of the directional antenna, and feeds the collected information back to the core control module; the core control module calculates the pitch angle deviation and azimuth deviation of the UAV relative to the UAV directional antenna self-tracking system based on the GPS data of the UAV, the GPS data of the UAV directional antenna self-tracking system, the horizontal azimuth information of the directional antenna and the pitch angle information of the directional antenna, and outputs control instructions to the servo control module; the servo control module adjusts the directional antenna according to the control instructions so that the main antenna beam of the directional antenna is aligned with the UAV.

[0011] Furthermore, the sensor module includes a GNSS submodule and an electronic compass. The GNSS submodule collects GPS data of the drone's directional antenna self-tracking system, and the electronic compass collects horizontal azimuth information of the directional antenna. The horizontal azimuth information is the angle between the geographical location of the drone's directional antenna self-tracking system and the true north direction of the earth.

[0012] Furthermore, the GPS data of the UAV directional antenna self-tracking system includes the latitude, longitude and altitude geographic location information of the UAV directional antenna self-tracking system.

[0013] Furthermore, the directional antenna is fixed on a two-degree-of-freedom gimbal, and the servo control module adjusts the azimuth and pitch angles of the two-degree-of-freedom gimbal according to control instructions so that the main beam of the directional antenna is aligned with the drone.

[0014] Furthermore, the UAV directional antenna self-tracking system also includes a communication module, which sends relevant data of the UAV received by the directional antenna to the ground control station, and sends remote control information of the UAV from the ground control station to the UAV.

[0015] A method for self-tracking a directional antenna of a UAV is implemented using a directional antenna self-tracking system of a UAV, and specifically comprises the following steps:

[0016] S1: Turn on the drone's directional antenna self-tracking system to enable the drone's directional antenna self-tracking system to complete self-test calibration;

[0017] S2: Determine whether the core control module has read the drone route. If so, execute step S3. Otherwise, the drone's directional antenna self-tracking system enters a standby state, and a voice prompt is given to the operator to upload the drone route to the ground control station. Repeat step S2 until the core control module has read the drone route.

[0018] S3: The core control module monitors the link packet loss rate of the communication module in real time. If the link packet loss rate is less than a%, step S4 is executed; otherwise, step S6 is executed.

[0019] S4: The UAV directional antenna self-tracking system enters the automatic mode. The core control module calculates the pitch angle deviation and azimuth angle deviation of the UAV relative to the UAV directional antenna self-tracking system and outputs control instructions to the servo control module.

[0020] S5: The servo control module adjusts the directional antenna according to the control instruction so that the main beam of the directional antenna is aligned with the drone, and then executes step S7;

[0021] S6: The drone's directional antenna self-tracking system switches to tracking mode. The core control module calculates the drone's track based on the drone's latitude and longitude at the time of loss of contact and the drone's route. Based on the calculated result, the directional antenna is adjusted to align the main beam of the directional antenna with the drone.

[0022] S7: Determine whether the UAV has completed the navigation mission. If so, turn off the UAV directional antenna self-tracking system and end the UAV directional antenna self-tracking mission. Otherwise, execute step S3.

[0023] Furthermore, in step S3, a is any integer between 60 and 80.

[0024] Furthermore, the drone's directional antenna self-tracking system includes a two-degree-of-freedom gimbal. If the drone's directional antenna self-tracking system has an angle calculation error or the two-degree-of-freedom gimbal fails, the operator starts the manual mode to deprive the two-degree-of-freedom gimbal of input signals, and manually adjusts the azimuth of the directional antenna so that the directional antenna receives data from the drone.

[0025] Furthermore, in step S3, the link packet loss rate is monitored by the UAV ground station software.

[0026] Furthermore, in step S6, the specific steps of calculating the trajectory of the UAV include:

[0027] S61: The track line includes straight segments and turning arc segments, according to the wind speed of the drone at the time of loss of contact. and Jingwei Gao calculated the waypoint of the drone from the moment of loss of contact To waypoint distance, and calculate the drone's position at the waypoint longitude and latitude;

[0028] S62: Calculate the desired azimuth angle and desired elevation angle of the directional antenna based on the spherical model;

[0029] S63: After adjusting the directional antenna according to the calculated desired azimuth and pitch angle, record the drone at the waypoint. The moment , and estimate the directional antenna to the waypoint Staring time , if the current moment When the UAV continues to perform the straight line segment deduction of step S61, the reference point of the straight line segment deduction is replaced by the waypoint at the time of loss of contact , until the UAV's trajectory line is calculated, otherwise execute step S4.

[0030] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0031] (1) The self-tracking system and tracking method for the directional antenna of a UAV created by the present invention are provided with an automatic mode, a tracking and deduction mode, and a manual mode, which can fully adapt to all working conditions of the directional antenna of a UAV and have good adaptability.

[0032] (2) The present invention creates the UAV directional antenna self-tracking system and tracking method, and proposes a tracking deduction mode, which can greatly improve the tracking capability of the UAV when it loses contact compared to the traditional scanning mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0034] Figure 1 This is a schematic diagram of the structure of the UAV directional antenna self-tracking system according to an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of a flow chart of a self-tracking method for a directional antenna of a UAV according to an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the structure of the track described in the embodiment of the present invention;

[0037] Figure 4 A schematic diagram of the locations of waypoints 1 and 2 according to an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of a spherical structure according to an embodiment of the present invention;

[0039] Figure 6 This is a schematic structural diagram of the spherical model described in an embodiment of the present invention;

[0040] Figure 7 A schematic diagram showing a data comparison between the actual azimuth and pitch angles of the directional antenna according to an embodiment of the present invention and the actual position information of the drone;

[0041] Figure 8 This is a data comparison diagram of the actual flight azimuth angle of the UAV and the rotation azimuth angle of the directional antenna described in the embodiment of the present invention.

[0042] Description of reference numerals:

[0043] 1. Ground control station; 2. Communication module; 3. Core control module; 4. Servo control module; 5. Directional antenna; 6. Sensor module; 7. GNSS submodule; 8. Electronic compass. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0045] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0046] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, features defined as "first", "second" and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0047] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0048] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0049] like Figure 1As shown, the present invention proposes a self-tracking system for a directional antenna of a UAV, which is used to receive GPS data of the UAV and collect position and attitude information of the directional antenna 5, calculate the target angle and current angle of the directional antenna 5, and then align the directional antenna 5 with the UAV through the servo control module 4. The self-tracking system for the directional antenna 5 of the UAV includes a ground radio station, a directional antenna 5, a sensor module 6, a servo control module 4 and a core control module 3, wherein the ground radio station receives the radio signal of the UAV onboard radio station (including the attitude, position, speed, route information and other information of the UAV), and inputs the GPS data of the UAV into the core control module 3, and at the same time sends the GPS data to the ground control station 1 through the communication module 2; the servo control module 4 collects the GPS data of the UAV and ... The directional antenna 5 obtains the pitch angle information of the directional antenna 5 and feeds the pitch angle information back to the core control module 3; the sensor module 6 collects the GPS data of the self-tracking system of the directional antenna 5 of the UAV and the horizontal azimuth information of the directional antenna 5, and feeds the collected information back to the core control module 3; the core control module 3 calculates the pitch angle deviation and azimuth deviation of the UAV relative to the self-tracking system of the directional antenna 5 of the UAV based on the GPS data of the UAV, the GPS data of the self-tracking system of the directional antenna 5 of the UAV, the horizontal azimuth information of the directional antenna 5 and the pitch angle information of the directional antenna 5, and outputs a control instruction to the servo control module 4; the servo control module 4 adjusts the directional antenna 5 according to the control instruction so that the main antenna beam of the directional antenna 5 is aligned with the UAV.

[0050] The sensor module 6 includes a GNSS submodule 7 and an electronic compass 8. The GNSS submodule 7 collects GPS data from the drone's directional antenna self-tracking system, and the electronic compass 8 collects horizontal azimuth information from the directional antenna 5. The horizontal azimuth information is the angle between the geographical location of the drone's directional antenna self-tracking system and the true north direction of the earth.

[0051] The GPS data of the UAV directional antenna self-tracking system includes the latitude, longitude and altitude geographic location information of the UAV directional antenna 5 self-tracking system.

[0052] Directional antenna 5 is paired with the data transmission module carried by the drone. It is fixed to a two-degree-of-freedom gimbal. The servo control module 4 adjusts the azimuth and pitch angles of the gimbal according to control commands, causing the gimbal to rotate the directional antenna 5, aligning its main beam with the drone.

[0053] The UAV directional antenna self-tracking system also includes a communication module 2, which sends the relevant data of the UAV received by the directional antenna 5 to the ground control station 1, and sends the remote control information of the UAV from the ground control station 1 to the UAV.

[0054] The core control module 3 consists of a minimum processor system, including a power module. It receives GPS data from the drone via a ground radio, collects GPS data from the drone's directional antenna self-tracking system via a universal asynchronous receiver / transmitter (UART), and acquires horizontal azimuth information from the directional antenna 5 via an I2C or SPI protocol. Using the pitch angle information of the directional antenna 5 fed back by the servo control module 4, the core control module 3 calculates the pitch and azimuth deviations of the drone relative to the directional antenna self-tracking system. The core control module 3 then outputs control commands (PWM signals) to drive the motors of the two-degree-of-freedom gimbal, aligning the main beam of the directional antenna 5 with the drone.

[0055] like Figure 2 As shown, a method for self-tracking a directional antenna of a UAV is implemented using a directional antenna self-tracking system of a UAV, and specifically includes the following steps:

[0056] S1: Turn on the drone's directional antenna self-tracking system to enable the drone's directional antenna self-tracking system to complete self-test calibration;

[0057] When the drone directional antenna self-tracking system is in the off state, long press the on / off button to turn on the system, power on all modules, and the drone directional antenna self-tracking system enters the self-test and calibration mode to complete the self-test and calibration.

[0058] S2: Determine whether the core control module 3 has read the drone route. If so, execute step S3. Otherwise, the drone directional antenna self-tracking system enters the standby state, and voice prompts the operator to upload the drone route to the ground control station 1. Repeat step S2 until the core control module 3 reads the drone route.

[0059] For a UAV executing a predetermined route, during the route injection phase before the UAV takes off, the ground control station 1 injects the route into the UAV's onboard flight controller and the core control module 3 respectively.

[0060] S3: The core control module 3 monitors the link packet loss rate of the communication module 2 in real time. If the link packet loss rate is less than a%, step S4 is executed; otherwise, step S6 is executed.

[0061] In step S3, a is any integer between 60 and 80. In step S3, the link packet loss rate is monitored by the UAV ground station software (specifically, iPerf software or Wireshark software).

[0062] S4: The UAV directional antenna self-tracking system enters the automatic mode. The core control module 3 calculates the pitch angle deviation and azimuth angle deviation of the UAV relative to the UAV directional antenna self-tracking system and outputs control instructions to the servo control module 4.

[0063] The core control module 3 analyzes and solves the GPS data from both devices, determining their relative deflection angle. This is then compared with the attitude information (azimuth and pitch) of the local receiving directional antenna. The core control module 3 then calculates the required azimuth and pitch angles for the directional antenna 5. The servo control module 4 then controls the rotation of the two-degree-of-freedom gimbal, aligning the main beam of the directional antenna 5 with the drone. This process repeats indefinitely throughout the drone's flight. While controlling the rotation of the directional antenna 5, the drone's directional antenna self-tracking system transmits the received data via the communication module 2 to the nearby ground control station 1. The data is then displayed by the ground control station's image display software, allowing the ground operator to monitor and adjust the drone's flight status in real time, ensuring proper communication between the drone and the ground control station 1.

[0064] S5: The servo control module 4 adjusts the directional antenna 5 according to the control instruction so that the main antenna beam of the directional antenna 5 is aligned with the drone, and then executes step S7.

[0065] S6: The self-tracking system of the drone's directional antenna 5 switches to the tracking mode. The core control module 3 calculates the drone's track line based on the drone's latitude and longitude at the time of loss of contact and the read drone route, and adjusts the directional antenna 5 based on the calculation result so that the main antenna beam of the directional antenna 5 is aligned with the drone.

[0066] When a drone flies into an urban area, mountain canyons, hidden areas, or other areas with weak GPS signals, the system may not be able to track the drone correctly. At this time, the system enters the dead reckoning process.

[0067] S7: Determine whether the UAV has completed the navigation mission. If so, turn off the UAV directional antenna 5 self-tracking system and end the UAV directional antenna 5 self-tracking mission. Otherwise, execute step S3.

[0068] The drone directional antenna self-tracking system includes a two-degree-of-freedom gimbal. If the drone directional antenna self-tracking system has an angle calculation error or the two-degree-of-freedom gimbal fails, the operator starts the manual mode to make the two-degree-of-freedom gimbal have no input signal, and manually adjusts the azimuth of the directional antenna 5 so that the directional antenna 5 receives the data from the drone.

[0069] In some embodiments, in step S6, the specific steps of calculating the trajectory of the drone include:

[0070] S61: The track line includes straight segments and turning arc segments, according to the wind speed of the drone at the time of loss of contact. and Jingwei Gao calculated the waypoint of the drone from the moment of loss of contact To waypoint distance, and calculate the drone's position at the waypoint longitude and latitude;

[0071] S62: Calculating the desired azimuth angle and desired elevation angle of the directional antenna 5 based on the spherical model;

[0072] S63: After adjusting the directional antenna according to the calculated desired azimuth and pitch angle, record the drone at the waypoint. The moment , and estimate 5 pairs of waypoints for directional antennas Staring time , if the current moment When the UAV continues to perform the straight line segment deduction of step S61, the reference point of the straight line segment deduction is replaced by the waypoint at the time of loss of contact , until the UAV's trajectory line is calculated, otherwise execute step S4.

[0073] like Figure 3 As shown, a track line is composed of straight segments and turning arcs. The beginning or end of a track line can be a straight segment or a turning arc. A track segment represents the path flown from the start of the current maneuver to the next maneuver. Therefore, if a track line has N maneuver points, then the track line can be divided into N segments.

[0074] Deduction method of straight line segment:

[0075] When the UAV is performing a flight mission, it is generally in a constant speed flight, that is, the UAV airspeed unchanged, but ground speed It will change with the wind direction. Assume that the wind speed is The wind direction is stable and the connection is lost. Take the time of loss of contact , that is, to obtain the wind speed of the drone at the time of loss of contact , according to the latitude and longitude of the drone at the time of loss of contact, determine which route the drone is on. Assuming the drone is at the waypoint To waypoint During the flight, the waypoint is calculated based on the latitude and longitude of the drone at the time of loss of contact. To waypoint distance ;

[0076] Use the UAV ground speed to make a smooth prediction of the UAV's position (obtain the current straight line segment to be calculated) Length):

[0077] ;

[0078] ;

[0079] in, To predict the frequency period, is the drone ground speed, is the airspeed of the drone, is the wind speed, Waypoint To waypoint Straight-line distance;

[0080] Assuming the azimuth angle is α, from the waypoint ( , ) to waypoint( , ) are as follows: The horizontal distance is sinα, the vertical distance is: cosα, where d = , it is stipulated that due north is 0 degrees. Figure 4 As shown, the latitude and longitude of waypoint 1 (long1, lat1) and distance d = is known, find the current longitude and latitude (long2, lat2) of the drone at waypoint 2.

[0081] Through waypoints ( , ) can know the radius of the section at the current latitude, such as Figure 5 The red line, denoted by arc, assumes that the Earth is approximately spherical. The equatorial radius is ARC, and the polar radius, the distance from the center of the Earth to the North Pole or South Pole, is approximately 3,950 miles (6,356.9088 kilometers) (the difference between the poles is negligible). The equatorial radius, the distance from the center of the Earth to the equator, is approximately 3,963 miles (6,377.830 kilometers). For approximate calculations, we'll take the average distance, resulting in an average radius of approximately 3,959 miles (6,371.393 kilometers). This number is the average distance from the center of the Earth to all points on the Earth's surface. In other words, the average radius here is ARC = 6,371.393 × 1,000 meters.

[0082] Calculate the current latitude and longitude of the drone using the following formula:

[0083] ;

[0084] ;

[0085] in,( , ) is the latitude and longitude of the UAV at the current waypoint, ( , ) is a waypoint The latitude and longitude of , ARC is ( , )and( , ) is the radius of the equatorial circle formed by .

[0086] Calculate the desired azimuth and elevation angles of directional antenna 5 based on the spherical model:

[0087] like Figure 6 As shown in the figure, A is the location of the directional antenna 5, that is, the observation point; G is the target point, and the projection of G on the ground is B; A and G are both in the northern hemisphere (0-90° north latitude) and the eastern hemisphere (0-180° east longitude). Let point A be the observation point, and its geodetic coordinates are ( , , ), G is the target point, and its geodetic coordinates are ( , , ),in and Indicates the latitude of points A and G, and Indicates the longitude of points A and G. and Represents the altitude of points A and G. Let N be the true north direction, the radius of the earth be R, and the calculation of the azimuth angle starts from true north as 0°, and rotates 360° clockwise from east to south and then to west. Approximate the earth as a sphere, let the dihedral angle B-ON-A be ∠ON, arc AB is the spherical distance between points A and B, AN' direction is the true north direction of point A, and plane PAN' is the reference horizontal plane of point A. Then ∠PAG is the elevation angle of the antenna, set as γ, ∠N'AP (that is, ∠A in the spherical triangle ABN) is the azimuth angle, set as θ, then according to the trihedral angle cosine formula:

[0088] ;

[0089] Substitute the known data into:

[0090] ;

[0091] That is, the azimuth angle θ is:

[0092] ;

[0093] Here, we need to discuss the situation where the target point G is in the four quadrants relative to the location A of the directional antenna 5, and process the calculation results differently according to different situations. Assuming that point A is fixed at the origin, then:

[0094] Point G is in the first quadrant, azimuth = ;

[0095] Point G is in the second quadrant, azimuth = 360 + ;

[0096] Point G is in the third or fourth quadrant, azimuth = 180 - ;

[0097] Obtain the cross-section triangle AGO, and according to the sine theorem of the cross-section triangle, get the pitch angle γ:

[0098] ;

[0099] The deduction method of the turning arc segment:

[0100] When the distance <Waypoint Radius When the waypoint is reached At this time, the drone will turn and go to the next waypoint During the turn, the drone’s reference latitude and longitude are considered as waypoints. The desired elevation angle and azimuth angle of the directional antenna can be calculated according to the spherical model.

[0101] Recording drone at waypoints The current moment , during the UAV turning process, the directional antenna 5 pairs of waypoints Gaze duration The estimation method is as follows:

[0102] ;

[0103] in, is the ground speed at the current moment.

[0104] Current moment When the UAV continues to perform the straight line segment deduction, and sets the longitude and latitude of the reference point of the straight line segment deduction as .

[0105] The present invention uses a program tracking method to achieve automatic tracking of unmanned aerial vehicles. The automatic tracking function means that no matter what speed, acceleration, or motion trajectory the target moves at, the tracking system can adjust the main beam pointing of the directional receiving antenna to accurately and automatically align with the target, thereby achieving the automatic tracking function. The pointing direction of the main beam is a two-degree-of-freedom parameter, described by two parameters: azimuth and pitch angle. The azimuth angle refers to the angle between the main beam pointing of the antenna and the due north direction of the system location, and the pitch angle refers to the angle between the main beam pointing of the antenna and the horizontal plane of the system location. Therefore, we need to calculate the azimuth and pitch angle of the target unmanned aerial vehicle relative to the location of the tracking system.

[0106] Currently, tracking algorithms for calculating azimuth and elevation angles include ellipsoidal models, spherical models, and plane models. The ellipsoidal model is widely used, the spherical model is applied to directional antenna tracking in rocket detection, and the plane model is suitable for tracking when the receiving platform is relatively close to the target point.

[0107] The drone directional antenna 5 self-tracking system is used to conduct actual drone tracking tests. The takeoff speed of the drone used in the test is 5m / s, and the full speed after takeoff is 30m / s. The flight distance is within 10km and the flight altitude is within 200m. The drone directional antenna 5 self-tracking system is repeatedly tested for flight tracking. A section of test data is selected, including the actual rotation azimuth and pitch angle of the directional antenna 5 and the actual position information of the drone. The results of the two sets of data are compared as shown below. Figure 7 shown.

[0108] The pitch angle data is the data when the drone takes off. Figure 8 It can be seen that when the UAV takes off, there is a certain delay in the UAV's directional antenna self-tracking system, but this delay error disappears quickly, and then enters the stable tracking stage. The UAV loses the link signal at 250s, and the UAV recovers the link signal at 310s. The ground turntable enters the tracking deduction mode. Although there is a lag in the tracking process, it is all within the range allowed by the system.

[0109] The azimuth test selected a period of stable flight data. At 250s, the UAV lost the link signal. At 310s, the UAV restored the link signal and the ground turntable entered the tracking deduction mode. Figure 8 It can be seen that there is a jump around 500s, when the antenna angle changes from 360° to 0°. This transition correctly applies the quadrant rule defined in the sphere model algorithm, ensuring that the antenna angle remains continuous. Analysis of the results from static and dynamic simulation tests and actual flight tracking tests shows that the UAV's directional antenna 5 self-tracking system has excellent tracking performance. While there is some lag within a 10km range, the error does not exceed 5°, ensuring the quality of image and data transmission.

[0110] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved. This is not limited herein.

[0111] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for self-tracking a directional antenna of a UAV is implemented by using a self-tracking system for a directional antenna of a UAV. The self-tracking system for a directional antenna of a UAV includes a ground station, a directional antenna, a sensor module, a servo control module, and a core control module, wherein: The ground radio station receives the radio signal of the UAV airborne radio station and inputs the GPS data of the UAV into the core control module; the servo control module collects the pitch angle information of the directional antenna and feeds the pitch angle information back to the core control module; the sensor module collects the GPS data of the UAV directional antenna self-tracking system and the horizontal azimuth information of the directional antenna, and feeds the collected information back to the core control module; the core control module calculates the pitch angle deviation and azimuth deviation of the UAV relative to the UAV directional antenna self-tracking system based on the GPS data of the UAV, the GPS data of the UAV directional antenna self-tracking system, the horizontal azimuth information of the directional antenna and the pitch angle information of the directional antenna, and outputs a control instruction to the servo control module; the servo control module adjusts the directional antenna according to the control instruction so that the main beam of the directional antenna is aligned with the UAV; the invention is characterized in that it specifically comprises the following steps: S1: Turn on the drone's directional antenna self-tracking system to enable the drone's directional antenna self-tracking system to complete self-test calibration; S2: Determine whether the core control module has read the drone route. If so, execute step S3. Otherwise, the drone's directional antenna self-tracking system enters a standby state, and a voice prompt is given to the operator to upload the drone route to the ground control station. Repeat step S2 until the core control module has read the drone route. S3: The core control module monitors the link packet loss rate of the communication module in real time. If the link packet loss rate is less than a%, step S4 is executed; otherwise, step S6 is executed. In step S3, a is any integer between 60 and 80; the link packet loss rate is monitored by the UAV ground station software; S4: The UAV directional antenna self-tracking system enters the automatic mode. The core control module calculates the pitch angle deviation and azimuth angle deviation of the UAV relative to the UAV directional antenna self-tracking system and outputs control instructions to the servo control module. S5: The servo control module adjusts the directional antenna according to the control instruction so that the main beam of the directional antenna is aligned with the drone, and then executes step S7; S6: The drone's directional antenna self-tracking system switches to tracking mode. The core control module calculates the drone's track based on the drone's latitude and longitude at the time of loss of contact and the drone's route. Based on the calculated result, the directional antenna is adjusted to align the main beam of the directional antenna with the drone. In step S6, the specific steps of calculating the trajectory of the UAV include: S61: The track line includes straight segments and turning arc segments, according to the wind speed of the drone at the time of loss of contact. and Jingwei Gao calculated the waypoint of the drone from the moment of loss of contact To waypoint distance, and calculate the drone's position at the waypoint longitude and latitude; S62: Calculate the desired azimuth angle and desired elevation angle of the directional antenna based on the spherical model; S63: After adjusting the directional antenna according to the calculated desired azimuth and pitch angle, record the drone at the waypoint. The moment , and estimate the directional antenna to the waypoint Gaze time , if the current moment When the UAV continues to perform the straight line segment deduction of step S61, the reference point of the straight line segment deduction is replaced by the waypoint at the time of loss of contact , until the UAV's trajectory line is calculated, otherwise go to step S4; S7: Determine whether the UAV has completed the navigation mission. If so, turn off the UAV directional antenna self-tracking system and end the UAV directional antenna self-tracking mission. Otherwise, execute step S3.

2. The method for self-tracking a directional antenna of an unmanned aerial vehicle according to claim 1, wherein: The sensor module includes a GNSS submodule and an electronic compass. The GNSS submodule collects GPS data from the drone's directional antenna self-tracking system, and the electronic compass collects horizontal azimuth information of the directional antenna. The horizontal azimuth information is the angle between the geographical location of the drone's directional antenna self-tracking system and the true north direction of the earth.

3. The method for self-tracking a directional antenna of an unmanned aerial vehicle according to claim 2, wherein: The GPS data of the UAV directional antenna self-tracking system includes the latitude, longitude and altitude geographic location information of the UAV directional antenna self-tracking system.

4. The method for self-tracking a directional antenna of an unmanned aerial vehicle according to claim 1, wherein: The directional antenna is fixed on a two-degree-of-freedom platform, and the servo control module adjusts the azimuth and pitch angles of the two-degree-of-freedom platform according to control instructions so that the main beam of the directional antenna is aimed at the UAV.

5. The UAV directional antenna self-tracking method according to claim 1, characterized in that: The UAV directional antenna self-tracking system also includes a communication module, which sends relevant data of the UAV received by the directional antenna to the ground control station, and sends remote control information of the UAV from the ground control station to the UAV.

6. The method for self-tracking a directional antenna of an unmanned aerial vehicle according to claim 1, wherein: The drone's directional antenna self-tracking system includes a two-degree-of-freedom gimbal. If the drone's directional antenna self-tracking system has an angle calculation error or the two-degree-of-freedom gimbal fails, the operator activates manual mode to deprive the two-degree-of-freedom gimbal of input signals, and manually adjusts the directional antenna's orientation so that the directional antenna receives data from the drone.

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