Unmanned aerial vehicle directional antenna self-tracking system and tracking method

Abstract

The invention belongs to the technical field of unmanned aerial vehicle ground control, and particularly relates to an unmanned aerial vehicle directional antenna self-tracking system and tracking method. The system 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 inputs GPS data of the unmanned aerial vehicle to the core control module; the servo control module feeds back pitch angle information to the core control module; the sensor module collects GPS data of an unmanned aerial vehicle directional antenna self-tracking system and horizontal orientation information of a directional antenna and feeds back the GPS data and the horizontal orientation information to the core control module. The core control module calculates pitch angle deviation and azimuth angle deviation of the unmanned aerial vehicle relative to the unmanned aerial vehicle directional antenna self-tracking system; and the servo control module adjusts the directional antenna according to the control instruction, so that the antenna main beam of the directional antenna is aligned with the unmanned aerial vehicle. According to the invention, a tracing deduction mode is provided, and compared with a traditional scanning mode, the tracking capability of the unmanned aerial vehicle when the unmanned aerial vehicle is out of communication can be greatly improved.

Description

Technical Field

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

[0002] With the rapid development of unmanned aerial vehicle (UAV) technology, its applications are becoming more and more extensive, and it has broad application prospects in fields such as meteorological observation, agricultural cultivation, public security monitoring, military reconnaissance, and personnel rescue. In many applications, a large amount of observation data and control data need to be transmitted in real time between the UAV and the ground control system. To ensure the accurate and reliable data transmission and reception, and at the same time improve the receiving gain and anti-interference ability, this long-distance and high-bandwidth communication usually uses directional antennas. When a directional antenna works, only when the main lobes of the transmitting antenna and the receiving antenna are aligned, can there be a higher gain. If the real-time alignment of the directional antenna cannot be ensured, the signal between the UAV and the ground control system will be interrupted, which will not only cause the loss of observation data and affect the completion of the task, but also cause the UAV to lose control, possibly leading to serious accidents such as the loss and crash of the UAV. Therefore, it is necessary to ensure the real-time alignment of the directional antenna. The realization of the alignment and tracking of the directional antenna mainly includes manual tracking and automatic tracking. Manual tracking has disadvantages such as large errors and poor real-time performance. Automatic tracking is that the directional antenna automatically realizes the tracking of the target according to the movement of the target, and it is the main tracking method at present. According to the different methods for determining the target angle, the automatic tracking of the directional antenna (hereinafter referred to as the self-tracking of the directional antenna) can be divided into two main methods: ① The most commonly used method is to judge the target angle through the signal phase relationship, which requires a set of complex antenna servo feedback systems and has a high cost. In addition, the anti-interference ability of this method is poor.

[0003] ② Using the GPS position information sent by the UAV to the ground station in real time, and determining the tracking target angle according to the relative positions of the UAV and the directional antenna. Since the GPS position signal has characteristics such as being more stable and simpler to implement than the former tracking signal, therefore, compared with the two, the latter has more advantages.

[0004] However, during the research and development process, the following deficiencies exist in the self-tracking method of the directional antenna: Currently, there are various methods to determine the tracking target angle based on the relative position between the UAV and the directional antenna. However, in order to reduce the computational complexity, simplification is carried out or the true azimuth angle quadrant is judged according to the relative position between the directional antenna and the UAV during the calculation, which is prone to ambiguity at the quadrant boundary and increases the complexity of the control system implementation. Due to the limitations of the communication link transmission capacity and the dynamic characteristics of low-cost GPS receivers, the position update frequency sent by the UAV to the ground control system is usually low. During close-range tracking, the tracking angle changes fluctuate greatly, which is likely to cause movement fluctuations and large tracking errors in the tracking system, significantly increasing system wear. With the wide application of UAVs, in many application fields, the directional antenna self-tracking system is required to have maneuverable tracking capabilities to improve the mobility and concealment of the system. However, during the maneuvering process, the GPS position information of the directional antenna is easily interfered by tunnels, trees, buildings, etc., resulting in inaccurate position information and thus leading to the loss of the tracking target.

[0005] The Chinese invention patent named "Adjustment System and Method for UAV Directional Antenna" (publication number: CN112909547A, publication date: December 4, 2022) provides an adjustment system and method for a UAV directional antenna. The direction of the scanning antenna is adjusted by controlling the first rotation motor and the first pitching motor, and the direction of the transceiver antenna is adjusted by controlling the second rotation motor and the second pitching motor according to the signal strength of the communication signals in at least one direction collected by the scanning antenna. The prerequisite for the method of adjusting the UAV directional antenna direction by scanning is the existence of a certain signal strength, and when the UAV is completely out of contact, this method loses the tracking effect.

[0006] The Chinese invention patent named "Design Method for a UAV Directional Antenna Self-Tracking System" (publication number: CN104932548A, publication date: November 21, 2017) provides a design method for a UAV directional antenna self-tracking system. The tracking target angle of the directional antenna is obtained by using the position of the directional antenna and the UAV, and the position prediction smoothing is realized by using the speed of the directional antenna and the UAV, and the feedforward of the azimuth movement is increased when the UAV flies over the vertex of the directional antenna. An azimuth angle and a pitching angle measuring instrument are installed on the vehicle to measure the current azimuth angle and pitching angle of the vehicle, and the current angle of the directional antenna is obtained by combining the measured values of the angle sensors. The main controller calculates the control quantity according to the difference between the tracking target angle and the current angle of the directional antenna, and drives the directional antenna to reach the target position. The present invention improves the mobility and concealment of the system, is easy to implement in engineering, effectively smooths the tracking action of the directional antenna, reduces the over-the-top tracking error, and improves the system reliability and adaptability. However, the tracking method in the case of UAV disconnection is not considered. Summary of the Invention

[0007] In view of this, the present invention aims to provide an unmanned aerial vehicle (UAV) directional antenna self-tracking system and a tracking method to solve the problem that in the prior art, during the maneuvering process, the GPS position information of the directional antenna is easily interfered by tunnels, trees, buildings, etc., resulting in inaccurate position information and thus the loss of the tracked target. The present invention proposes a tracing and deduction mode, which can greatly improve the tracking ability of the UAV when it loses contact compared with the traditional scanning mode.

[0008] To achieve the above object, the technical solution of the present invention is realized as follows: An unmanned aerial vehicle (UAV) directional antenna self-tracking system includes a ground station, a directional antenna, a sensor module, a servo control module, and a core control module. Among them, the ground station receives the radio signal of the UAV's on-board 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 back the pitch angle information 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 back the collected information to the core control module; 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 according to 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.

[0009] Further, the sensor module includes a GNSS sub-module and an electronic compass. The GNSS sub-module collects the GPS data of the UAV directional antenna self-tracking system, and the electronic compass collects the horizontal azimuth information of the directional antenna. The horizontal azimuth information is the angle between the geographical location where the UAV directional antenna self-tracking system is located and the true north direction of the earth.

[0010] Further, the GPS data of the UAV directional antenna self-tracking system includes the longitude, latitude, and altitude geographical location information of the UAV directional antenna self-tracking system.

[0011] Further, the directional antenna is fixed on a two-degree-of-freedom pan-tilt. The servo control module adjusts the azimuth angle and pitch angle of the two-degree-of-freedom pan-tilt according to the control instruction so that the main beam of the directional antenna is aligned with the UAV.

[0012] Further, the UAV directional antenna self-tracking system further includes a communication module. The communication module sends the relevant data of the UAV received by the directional antenna to the ground control station and sends the remote control information of the ground control station for the UAV to the UAV.

[0013] A method for self-tracking of a UAV directional antenna, which is realized by using a UAV directional antenna self-tracking system, specifically includes the following steps: S1: Turn on the UAV directional antenna self-tracking system to enable the UAV directional antenna self-tracking system to complete self-check calibration; S2: Determine whether the core control module has read the UAV flight path. If so, execute step S3. Otherwise, put the UAV directional antenna self-tracking system into the standby state and voice prompt the operator to upload the UAV flight path at the ground control station, and repeat step S2 until the core control module reads the UAV flight path; 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%, execute step S4. Otherwise, execute step S6; 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 a control command to the servo control module; S5: The servo control module adjusts the directional antenna according to the control command to align the main beam of the antenna with the UAV, and execute step S7; S6: The UAV directional antenna self-tracking system switches to the trace tracking mode. The core control module calculates the flight path of the UAV based on the longitude, latitude and altitude of the UAV at the moment of disconnection and the read UAV flight path, and adjusts the directional antenna according to the calculation result to align the main beam of the antenna with the UAV; S7: Determine whether the UAV has completed the flight mission. If so, turn off the UAV directional antenna self-tracking system and end the UAV directional antenna self-tracking task. Otherwise, execute step S3.

[0014] Further, in step S3, a is any integer in the range of 60-80.

[0015] Further, the UAV directional antenna self-tracking system includes a two-degree-of-freedom pan-tilt. When an angle calculation error occurs in the UAV directional antenna self-tracking system or a fault occurs in the two-degree-of-freedom pan-tilt, the operator starts the manual mode to make the two-degree-of-freedom pan-tilt have no input signal, and manually adjusts the azimuth of the directional antenna to enable the directional antenna to receive the data of the UAV.

[0016] Further, in step S3, the link packet loss rate is monitored through the UAV ground station software.

[0017] Further, in step S6, the specific steps for calculating the flight path of the UAV include: S61: The flight path includes straight line segments and turning arc segments. According to the wind speed of the UAV at the moment of disconnection and the longitude, latitude and altitude, calculate the flight points of the UAV from the moment of disconnection To the waypoint distance, and calculate the longitude and latitude of the UAV at the waypoint ; S62: Calculate the expected azimuth angle and expected pitch angle of the directional antenna based on the spherical model; S63: After adjusting the directional antenna according to the calculated expected azimuth angle and expected pitch angle, record the time of the UAV at the waypoint , and estimate the staring time of the directional antenna at the waypoint . If the current time , the UAV continues to perform the deduction of the straight line segment in step S61, and replaces the waypoint at the moment of loss of connection with the waypoint as the reference point for the straight line segment deduction until the track line calculation of the UAV is completed, otherwise execute step S4.

[0018] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) The UAV directional antenna self-tracking system and tracking method of the present invention are provided with an automatic mode, a trace deduction mode, and a manual mode, which can fully adapt to all working conditions of the UAV directional antenna and have good adaptability.

[0019] (2) The UAV directional antenna self-tracking system and tracking method of the present invention propose a trace deduction mode, which can greatly improve the tracking ability when the UAV loses connection compared with the traditional scanning mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is a schematic structural diagram of the UAV directional antenna self-tracking system according to an embodiment of the present invention; Figure 2 is a schematic flowchart of the UAV directional antenna self-tracking method according to an embodiment of the present invention; Figure 3 is a schematic structural diagram of the track according to an embodiment of the present invention; Figure 4 is a schematic diagram of the positions of waypoint one and waypoint two according to an embodiment of the present invention; Figure 5 is a schematic diagram of an approximate spherical structure according to an embodiment of the present invention; Figure 6 is a schematic structural diagram of the spherical model according to an embodiment of the present invention; Figure 7 ​​Schematic diagram of data comparison between the actual azimuth and elevation angles of the directional antenna described in the embodiments of the present invention and the actual position information of the drone Figure 8 Schematic diagram of data comparison between the actual flight azimuth angle of the drone and the rotation azimuth angle of the directional antenna described in the embodiments of the present invention.

[0021] Explanation of reference numerals: 1. Ground control station; 2. Communication module; 3. Core control module; 4. Servo control module; 5. Directional antenna; 6. Sensor module; 7. GNSS sub-module; 8. Electronic compass. Detailed implementation manners

[0022] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be 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 to the present invention.

[0023] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0024] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the 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 thus should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0025] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0026] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0027] As Figure 1 shown, the present invention proposes a self-tracking system for a drone directional antenna, which is used to receive the GPS data of the drone and collect the position and attitude information of the directional antenna 5, calculate the target angle and the current angle of the directional antenna 5, and then make the directional antenna 5 align with the drone through the servo control module 4. The self-tracking system for the drone directional antenna 5 includes a ground station, a directional antenna 5, a sensor module 6, a servo control module 4, and a core control module 3. Among them, the ground station receives the radio signals of the drone on-board station (including information such as the attitude, position, speed, and flight path information of the drone), inputs the GPS data of the drone 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 pitch angle information of the directional antenna 5 and feeds back the pitch angle information to the core control module 3; the sensor module 6 collects the GPS data of the self-tracking system for the drone directional antenna 5 and the horizontal azimuth information of the directional antenna 5, and feeds back the collected information to the core control module 3; the core control module 3 calculates the pitch angle deviation and azimuth angle deviation of the drone relative to the self-tracking system for the drone directional antenna 5 according to the GPS data of the drone, the GPS data of the self-tracking system for the drone directional antenna 5, the horizontal azimuth information of the directional antenna 5, and the pitch angle information of the directional antenna 5, and outputs a control command to the servo control module 4; the servo control module 4 adjusts the directional antenna 5 according to the control command, so that the main beam of the antenna of the directional antenna 5 aligns with the drone.

[0028] The sensor module 6 includes a GNSS sub-module 7 and an electronic compass 8. The GNSS sub-module 7 collects the GPS data of the self-tracking system for the drone directional antenna, and the electronic compass 8 collects the horizontal azimuth information of the directional antenna 5. The horizontal azimuth information is the included angle between the geographical location where the self-tracking system for the drone directional antenna is located and the true north direction of the earth.

[0029] The GPS data of the self-tracking system for the drone directional antenna includes the longitude, latitude, and altitude geographical location information of the self-tracking system for the drone directional antenna 5.

[0030] The directional antenna 5 should be matched with the data transmission module carried by the drone. The directional antenna 5 is fixed on a two-degree-of-freedom pan-tilt. The servo control module 4 adjusts the azimuth angle and pitch angle of the two-degree-of-freedom pan-tilt according to the control command, so that the two-degree-of-freedom pan-tilt drives the directional antenna 5 to rotate, and makes the main beam of the antenna of the directional antenna 5 align with the drone.

[0031] The drone directional antenna self-tracking system further includes a communication module 2. The communication module 2 sends the relevant data of the drone received by the directional antenna 5 to the ground control station 1, and sends the remote control information of the ground control station 1 for the drone to the drone.

[0032] The core control module 3 consists of a processor minimum system including a power module. The core control module 3 receives the GPS data of the drone through the ground radio, collects the GPS data of the drone directional antenna self-tracking system through the universal asynchronous receiver / transmitter, collects the horizontal azimuth information of the directional antenna 5 through the I2C or SPI protocol, and then uses the pitch angle information of the directional antenna 5 fed back by the servo control module 4 to calculate the pitch angle deviation and azimuth angle deviation of the drone relative to the drone directional antenna self-tracking system, and outputs a control command (PWM signal) to drive the motor of the two-degree-of-freedom gimbal to rotate, so that the main beam of the antenna of the directional antenna 5 is aligned with the drone.

[0033] As Figure 2 shown, a drone directional antenna self-tracking method is implemented using the drone directional antenna self-tracking system, and specifically includes the following steps: S1: Turn on the drone directional antenna self-tracking system to enable the drone directional antenna self-tracking system to complete self-check and calibration; When the drone directional antenna self-tracking system is in the shutdown state, long press the power on / off key, the system powers on, each module is powered on, and the drone directional antenna self-tracking system enters the self-check and calibration mode to complete self-check and calibration.

[0034] S2: Determine whether the core control module 3 has read the drone route. If so, execute step S3. Otherwise, make the drone directional antenna self-tracking system enter the standby state, and voice prompt the operator to upload the drone route at the ground control station 1, and repeat step S2 until the core control module 3 reads the drone route; For the drone executing the predetermined route, in the route injection link before the drone takes off, the ground control station 1 injects the route into the flight controller of the drone airborne end and the core control module 3 respectively.

[0035] 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%, execute step S4. Otherwise, execute step S6; In step S3, a is any integer in 60-80. In step S3, the link packet loss rate is monitored through the drone ground station software (specifically the iPerf software or Wireshark software).

[0036] S4: The drone 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 drone relative to the drone directional antenna self-tracking system, and outputs control instructions to the servo control module 4; The core control module 3 analyzes and calculates the GPS data of both, obtains their relative deflection angles, and compares them with the attitude information (azimuth angle and pitch angle) of the local receiving directional antenna. Subsequently, it calculates the azimuth angle and pitch angle that the directional antenna 5 needs to rotate, and controls the two-degree-of-freedom gimbal to rotate through the servo control module 4, so that the main beam of the directional antenna 5 is aligned with the drone. This process is infinitely looped during the flight of the drone. While controlling the rotation of the directional antenna 5, the drone directional antenna self-tracking system sends the received data to the surrounding ground control station 1 through the communication module 2, and is displayed by the image display software of the ground control station 1, facilitating the ground operator to grasp and adjust the flight state of the drone in real time, and ensuring the normal communication between the drone and the ground control station 1.

[0037] S5: The servo control module 4 adjusts the directional antenna 5 according to the control instructions, so that the main beam of the antenna of the directional antenna 5 is aligned with the drone, and step S7 is executed.

[0038] S6: The drone directional antenna 5 self-tracking system switches to the trace tracking mode. The core control module 3 calculates the flight path of the drone based on the longitude, latitude and altitude of the drone at the moment of disconnection and the read drone flight path, and adjusts the directional antenna 5 according to the calculation result, so that the main beam of the antenna of the directional antenna 5 is aligned with the drone.

[0039] When the drone flies into areas with weak GPS signals such as urban building complexes, mountain valleys, or concealed places, the system may not be able to correctly track the drone. At this time, the system enters the trace calculation process.

[0040] S7: Determine whether the drone has completed its navigation mission. If so, turn off the drone directional antenna 5 self-tracking system and end the self-tracking task of the drone directional antenna 5; otherwise, execute step S3.

[0041] 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, makes 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 of the drone.

[0042] In some embodiments, in step S6, the specific steps for calculating the flight path of the drone include: S61: The flight path includes straight line segments and turning arc segments. According to the wind speed of the drone at the moment of disconnection and longitude, latitude and altitude, calculate the flight points of the drone from the moment of disconnection Distance to the waypoint, and calculate the longitude and latitude of the UAV at the waypoint ; ; S62: Calculate the expected azimuth angle and expected elevation angle of the directional antenna 5 based on the spherical model; S63: After adjusting the directional antenna according to the calculated expected azimuth angle and expected elevation angle, record the time of the UAV at the waypoint , and estimate the staring time of the directional antenna 5 at the waypoint . If at the current time , the UAV continues to perform the deduction of the straight-line segment in step S61, and replaces the waypoint at the moment of disconnection with the waypoint as the reference point for the straight-line segment deduction until the UAV's flight path calculation is completed, otherwise execute step S4. ; ;

[0043] As Figure 3 shown, the flight path is composed of straight-line segments and turning arcs. The start or end of the flight path can be a straight-line segment or a turning arc. A flight path represents the path flown from the start of the current maneuver to the next maneuver. Therefore, if there are N maneuver points on a flight path, then this flight path can be divided into N flight segments.

[0044] Deduction method for straight-line segments: When the UAV is performing a flight route mission, it is generally flying at a constant speed, that is, the airspeed of the UAV remains unchanged, but the ground speed will change with the wind direction. Assume that during the UAV disconnection process, the wind speed and wind direction are stable, and during the disconnection process is taken as that at the moment of disconnection , that is, obtain the wind speed of the UAV at the moment of disconnection . According to the longitude, latitude and altitude of the UAV at the moment of disconnection, judge which flight route the UAV is on. Assume that the UAV is in the process of flying from waypoint to waypoint . Calculate the distance from waypoint to waypoint based on the longitude, latitude and altitude of the UAV at the moment of disconnection ; Use the ground speed of the UAV to make a smooth prediction of the position of the UAV (obtain the length of the current straight-line segment to be calculated): ; ; where is the prediction frequency period, is the ground speed of the UAV, is the airspeed of the drone, is the wind speed, is the waypoint to waypoint the straight-line distance; Assume the azimuth angle is α. From the waypoint ( , ) to the waypoint ( , ) the translation distances are as follows: the horizontal distance is sinα, and the vertical distance is: cosα, where d = , and it is stipulated that due north is 0 degrees. As Figure 4 shown, the longitude and latitude (long1, lat1) of waypoint one and the distance d = are known. Find the longitude and latitude (long2, lat2) of the drone at waypoint two currently.

[0045] By the latitude where the waypoint ( , ) is located, the radius length of the current latitude section can be known. As Figure 5 shown by the red line, it is represented by arc. Here, it is assumed that the earth is an approximate sphere. The radius of the equatorial circle is ARC, and the polar radius is the distance from the center of the earth to the North Pole or the South Pole, about 3950 miles (6356.9088 km) (the difference at the two poles is extremely small and can be ignored). The equatorial radius is the distance from the center of the earth to the equator, about 3963 miles (6377.830 km). If only approximate calculations are made, the average distance is taken here, and the average radius is about 3959 miles (6371.393 km). This number is the average of the distances from the center of the earth to all points on the earth's surface. That is, the average radius ARC = 6371.393×1000 (m) is taken here.

[0046] Calculate the current longitude and latitude of the drone through the following formula: ; ; where, ([[]] , ) is the longitude and latitude of the drone at the current waypoint position, ([[]] , ) is the longitude and latitude of waypoint , and ARC is the radius of the equatorial circle formed by ([[]] , ) and ([[]] , ).

[0047] Calculating the expected azimuth and elevation angle of the directional antenna 5 based on the spherical model: As shown in Figure 6 , A is the location of the directional antenna 5, i.e., the observation point; G is the target point, and the projection of G on the ground is B; both A and G are in the Northern Hemisphere (latitude 0 - 90°N) and the Eastern Hemisphere (longitude 0 - 180°E). Let point A be the observation point with its geodetic coordinates being ( , , ), and G be the target point with its geodetic coordinates being ( , , ), where and represent the latitudes of points A and G, and represent the longitudes of points A and G, and represent the altitudes of points A and G. Let N be the true north direction, the radius of the earth be R, and the azimuth is calculated with the true north as the 0° starting point, rotating 360° clockwise from east to south and then to west. Approximating the earth as a circular sphere, let the dihedral angle B - ON - A be ∠ON, the arc AB be the spherical distance between points A and B, the direction of AN' be the due north direction at point A, and the plane PAN' be the reference horizontal plane at point A. Then ∠PAG is the elevation angle of the antenna, denoted as γ, and ∠N'AP (i.e., ∠A in the spherical triangle ABN) is the azimuth, denoted as θ. According to the cosine formula for trihedral angles: ; Substituting the known data gives: ; That is, the azimuth θ is: ; Here, it is necessary to discuss according to the situation of the target point G relative to the location A of the directional antenna 5 in the four quadrants, and different treatments are carried out on the calculation results according to different situations. Assuming that point A is fixed at the origin, then: When point G is in the first quadrant, azimuth = ; When point G is in the second quadrant, azimuth = 360 + ; When point G is in the third and fourth quadrants, azimuth = 180 - ; Obtaining the cross - section triangle AGO, according to the sine theorem of the triangle in the cross - section, the elevation angle γ is obtained: ; Deduction method for the turning arc segment: When the distance < waypoint radius When it is considered that the waypoint has been reached At this time, the UAV will turn and go to the next waypoint During the turning process, the reference longitude and latitude of the UAV are considered to be the longitude and latitude of the waypoint , and the expected pitch angle and expected azimuth angle of the directional antenna can be calculated according to the spherical model

[0048] Record the current time of the UAV at the waypoint When , during the turning process of the UAV, the staring time of the directional antenna 5 staring at the waypoint is estimated as follows : ; wherein is the ground speed at the current time

[0049] At the current time , the UAV continues to perform the deduction of the straight line segment, and sets the longitude and latitude of the reference point of the straight line segment deduction as .

[0050] The present invention uses a program tracking method to realize the automatic tracking of the UAV. The automatic tracking function means that no matter at what speed, acceleration, and motion trajectory the target moves, the tracking system can adjust the main beam direction of the directional receiving antenna to accurately and automatically align with the target to realize the automatic tracking function. The direction of the main beam is a two-degree-of-freedom parameter, which is described by two parameters: azimuth angle and pitch angle. The azimuth angle refers to the angle between the direction of the main beam of the antenna and the due north direction of the system location, and the pitch angle refers to the angle between the direction of the main beam of the antenna and the horizontal plane of the system location. Therefore, we need to calculate the azimuth angle and pitch angle of the target UAV relative to the location of the tracking system

[0051] At present, the tracking algorithms for solving the azimuth angle and pitch angle include the ellipsoid model, the spherical model, and the plane model. Among them, the ellipsoid model is widely used, the spherical model is applied to the tracking of the directional antenna 5 in rocket detection, and the plane model is suitable for the tracking when the distance between the receiving platform and the target point is relatively close

[0052] Using the UAV directional antenna 5 self-tracking system to conduct actual tracking tests on the UAV. When testing, the takeoff speed of the UAV used is 5m / s, and the full speed after takeoff is 30m / s. Within a flight distance of 10km and a flight height within 200m. Conduct repeated flight tracking tests on the UAV directional antenna 5 self-tracking system, and select a section of test data, including the actual azimuth angle and pitch angle of the directional antenna 5 rotation and the actual position information of the UAV. The comparison results of the two groups of data are as Figure 7 shown

[0053] The pitch angle data selected is the data when the UAV takes off. It is from Figure 8 It can be seen that when the UAV takes off, there is a certain delay in the UAV directional antenna self-tracking system. However, this delay error disappears quickly, and then it enters the stable tracking stage. The UAV loses the link signal at 250 s and recovers the link signal at 310 s. The ground turntable enters the trace deduction mode. Although there is a lag in the tracking process, it is within the range allowed by the system.

[0054] For the azimuth angle test, a section of stable flight data is selected. The UAV loses the link signal at 250 s and recovers the link signal at 310 s. The ground turntable enters the trace deduction mode. It is from Figure 8 seen that there is a jump near 500 s. At this time, it is the transition of the antenna rotation angle from 360° to 0°. This transition correctly applies the quadrant rule defined in the spherical model algorithm, making the rotation angle of the antenna always continuous. Through the result analysis of static simulation tests, dynamic simulation tests and actual flight tracking tests, the UAV directional antenna 5 self-tracking system has a good tracking effect. For the tracking within 10 km, although there is a lag angle, the error does not exceed 5°, which can ensure the transmission quality of images and data.

[0055] It should be understood that various forms of the processes shown above can be used, steps can be reordered, added or deleted. For example, the steps recorded in the disclosure of the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved. There is no limitation herein.

[0056] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A UAV directional antenna self-tracking system, characterized by: It includes 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 the radio signal of the radio station onboard the unmanned aerial vehicle, and inputs the GPS data of the unmanned aerial vehicle 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 unmanned aerial vehicle 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 unmanned aerial vehicle relative to the unmanned aerial vehicle directional antenna self-tracking system according to the GPS data of the unmanned aerial vehicle, the GPS data of the unmanned aerial vehicle 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 antenna main beam of the directional antenna is aligned with the unmanned aerial vehicle.

2. The unmanned aerial vehicle directional antenna self-tracking system according to claim 1, characterized in that: The sensor module includes a GNSS submodule and an electronic compass. The GNSS submodule collects GPS data of the UAV 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 UAV directional antenna self-tracking system and the true north direction of the earth.

3. The unmanned aerial vehicle directional antenna self-tracking system according to claim 2, characterized in that: 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 unmanned aerial vehicle directional antenna self-tracking system according to claim 1, characterized in that: 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 a control instruction so that the main antenna beam of the directional antenna is aimed at the UAV.

5. The unmanned aerial vehicle directional antenna self-tracking system 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. A method for self-tracking a directional antenna of an unmanned aerial vehicle, implemented by using the self-tracking system for the directional antenna of an unmanned aerial vehicle according to any one of claims 1 to 5, characterized in that: The specific steps include: S1: Turn on the drone directional antenna self-tracking system to enable the drone directional antenna self-tracking system to complete self-check calibration; S2: Determine whether the core control module has read the UAV route. If so, execute step S3. Otherwise, make the UAV directional antenna self-tracking system enter the standby state, and voice prompt the operator to upload the UAV route at the ground control station. Repeat step S2 until the core control module has read the UAV 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; S4: The UAV directional antenna self-tracking system enters the automatic mode, and 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 aimed at the drone, and then executes step S7; S6: The drone's directional antenna self-tracking system switches to the tracking mode. The core control module calculates the drone's track line based on the drone's latitude and longitude at the time of loss of contact and the drone's route read, and adjusts the directional antenna based on the calculation result so that the directional antenna's main beam is aimed at the drone; 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.

7. The method for self-tracking of a directional antenna of an unmanned aerial vehicle according to claim 6, characterized in that: In step S3, a is any integer between 60-80.

8. The method for self-tracking of a directional antenna of an unmanned aerial vehicle according to claim 6, characterized in that: The UAV directional antenna self-tracking system includes a two-degree-of-freedom gimbal. If the UAV 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 directional antenna's orientation so that the directional antenna receives the UAV data.

9. The method for self-tracking of a directional antenna of an unmanned aerial vehicle according to claim 6, characterized in that: In step S3, the link packet loss rate is monitored by the UAV ground station software.

10. The method for self-tracking of a directional antenna of an unmanned aerial vehicle according to claim 6, characterized in that: In step S6, the specific steps of calculating the trajectory of the drone 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 time of loss of contact To waypoint distance, and calculate the drone at the waypoint The longitude and latitude of S62: Calculate the expected azimuth angle and expected 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 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 is calculated, otherwise execute step S4.

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