A multi-rotor electromagnetic signal interference troubleshooting system and direction finding positioning method

Abstract

The present application belongs to the technical field of electromagnetic signal interference troubleshooting, and particularly relates to a multi-rotor electromagnetic signal interference troubleshooting system and a direction finding positioning method. The system comprises an aerial part and a ground control part; the aerial part comprises a multi-rotor unmanned aerial vehicle platform and a monitoring direction finding load, a task computer, a load link aerial end and a power management module mounted on the multi-rotor unmanned aerial vehicle platform; the monitoring direction finding load is used for receiving electromagnetic signals, discovering electromagnetic targets and measuring the target direction; the monitoring direction finding load comprises a direction finding device and a monitoring direction finding receiver. The troubleshooting system provided by the present application can realize continuous direction finding of the unmanned aerial vehicle in flight, realize target positioning based on a direction finding algorithm, and realize optimal track optimization based on the positioning result, and has the beneficial effects of accelerating the convergence speed of target positioning, improving the positioning accuracy and improving the efficiency of electromagnetic signal interference troubleshooting.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic signal interference investigation technology, specifically relating to a multi-rotor electromagnetic signal interference investigation system and a direction finding and positioning method. Background Technology

[0002] Emergency monitoring, direction finding, and interference investigation of electromagnetic signals are important aspects of electromagnetic control. Traditional methods of electromagnetic signal monitoring and location mainly rely on manual investigation, fixed monitoring stations, and mobile monitoring vehicles. These methods are not only time-consuming and labor-intensive, but also fail to quickly and accurately identify concealed signal sources. Furthermore, the direction finding accuracy drops significantly when encountering building obstructions or complex geographical environments, and radio signals may not even be received at low monitoring locations.

[0003] Therefore, in recent years, aerial monitoring and positioning systems based on UAV platforms have become a research hotspot. Typical products currently include the German OBSERVERAMU series UAVs, Jiuhua Yuantong UAV monitoring and direction finding equipment, Huari HR-62X aerial monitoring and direction finding system, DJI Sky Cells interference investigation system, and the UAV-based illegal broadcast search and positioning system developed by Nanjing University of Aeronautics and Astronautics. These systems, as a supplement to traditional electromagnetic signal monitoring modes, can significantly improve the mobility of monitoring and direction finding equipment. Using UAVs equipped with relevant equipment for aerial investigation and positioning of abnormal electromagnetic signals offers advantages over traditional methods such as manual investigation, fixed monitoring stations, and mobile monitoring vehicles. These advantages include improved visibility, avoidance of signal obstruction, and high mobility. Combined with image recognition technology, the location and type of interference sources can be determined more accurately and quickly, effectively reducing system usage and maintenance costs and expanding application scope. This greatly compensates for the shortcomings of traditional electromagnetic interference signal investigation and positioning methods. Therefore, in recent years, aerial electromagnetic signal monitoring and positioning systems based on UAV platforms have become a research hotspot.

[0004] However, most monitoring and positioning systems based on UAV platforms, represented by the aforementioned devices, simply use the UAV platform to mount corresponding monitoring and direction-finding equipment, achieving positioning through multi-point hovering cross-directional finding or by flying along a pre-planned trajectory. This simple combination fails to fully leverage the system's performance advantages. Research indicates that for single-station passive positioning systems, station maneuvering is a prerequisite for target positioning, and the UAV station's maneuver trajectory affects the convergence process and final positioning accuracy. Therefore, trajectory planning based on current target estimation results, with the optimal goal of improving observability, is the ideal operating mode.

[0005] There are various implementation schemes for UAV-borne monitoring and direction-finding systems. For example, invention patent application CN114326784A discloses a device and method for autonomous flight path planning of UAVs for spectrum mapping, which has a certain trajectory planning capability. However, the data acquisition module on the UAV platform unit of this invention is mainly used to collect spectrum intensity information at path points and does not have direction-finding function. Its path calculation module first plans the initial flight path of the entire area to be measured based on the user input module, and locates the target in the process. After completion, it calculates the radiation source access order and the path information of flying around the radiation source based on the endpoint position on the initial parallel path and the radiation source position; essentially, it does not have the function of trajectory planning based on the current target positioning result.

[0006] The invention patent application CN114035150A discloses a radio frequency source direction finding device and method based on a UAV launch platform. Its direction finding principle involves a stepper motor driving a direction finding antenna to rotate 360 ​​degrees to determine the direction of the maximum signal from the radio radiation source. However, due to the use of a single antenna, the direction finding accuracy is poor. This method, with only one degree of rotational freedom, is susceptible to errors when the UAV is in flight or in windy conditions, or when the aircraft tilts. Furthermore, the direction finding and positioning method described in this invention requires hovering direction finding at multiple launch points followed by cross-positioning, making the process cumbersome, inefficient, and ultimately affecting the positioning accuracy.

[0007] The invention patent application CN114281101A discloses a joint search method for interference sources using a UAV and a gimbal based on reinforcement learning. The core idea of ​​this invention is to control the rotation and scanning of the gimbal on the UAV so that the directional antenna receives radio signals. Then, a reinforcement learning algorithm is used to process the radio signals received by the directional antenna to calculate the UAV's flight direction and locate the interference source. However, in this invention, the UAV needs to control the gimbal to scan signals and perform trajectory planning at each step, resulting in low direction-finding efficiency. Furthermore, the trajectory planning objective is signal strength, rather than being guided by localization convergence or the observability of direction-finding localization.

[0008] In summary, the existing technical solutions have the following shortcomings:

[0009] (1) Direction finding methods generally employ multi-antenna arrays or rely on a single directional antenna. Multi-antenna array direction finding can directly output the direction finding angle, but it has disadvantages such as large size and weight, complex calibration, and being fixed to the airframe and greatly affected by flight attitude. For single directional antenna direction finding, the amplitude comparison method is used, which can usually only monitor signals of constant power and has poor accuracy. It requires antenna rotation for searching, resulting in low efficiency.

[0010] (2) Existing UAV direction-finding and positioning systems usually use fixed-point hovering for direction finding and then cross-positioning, or fly according to a pre-planned flight path. The entire process is inefficient and cannot improve the positioning convergence process and final positioning accuracy by optimizing the flight path.

[0011] (3) Lack of auxiliary positioning devices. Due to the limitation of the UAV's own navigation accuracy, it will affect the final positioning accuracy of the target. Summary of the Invention

[0012] In view of the above technical problems, the present invention provides a multi-rotor electromagnetic signal interference detection system and a direction-finding and positioning method. The detection system can realize continuous direction finding of the UAV during flight, achieve target positioning based on the direction-finding algorithm, and optimize the optimal flight path based on the positioning result, having the beneficial effects of accelerating the target positioning convergence speed, improving the positioning accuracy, and improving the electromagnetic signal interference detection efficiency.

[0013] The present invention is realized through the following technical solutions:

[0014] A multi-rotor electromagnetic signal interference detection system, the system includes an air part and a ground control part;

[0015] The air part includes a multi-rotor UAV platform and a monitoring and direction-finding payload, a mission computer, an air end of the payload link, and a power management module mounted on the multi-rotor UAV platform;

[0016] The monitoring and direction-finding payload is used to receive electromagnetic signals, detect electromagnetic targets, and measure the target azimuth; the monitoring and direction-finding payload includes a direction-finding device and a monitoring and direction-finding receiver; the direction-finding device combines amplitude comparison direction finding with a gimbal tracking control to realize continuous tracking and direction finding of the electromagnetic signal interference source by the UAV in the flight state; the monitoring and direction-finding receiver is a dual-channel monitoring and direction-finding receiver, and the monitoring and direction-finding receiver is electrically connected to two directional antennas;

[0017] The mission computer is connected to the monitoring and direction-finding receiver, the multi-rotor UAV platform, and the air end of the payload link.

[0018] Furthermore, the ground control part includes ground measurement and control equipment, an RTK base station, a ground end of the payload link, and a remote controller supporting the multi-rotor UAV platform.

[0019] Furthermore, the air part and the ground control part are connected by two wireless communication links;

[0020] The first wireless communication link is the own data link of the multi-rotor UAV platform. The first wireless communication link is connected to the remote controller and is used to transmit video information, status information, and remote control instructions taken by the multi-rotor UAV platform;

[0021] The second wireless communication link includes the air end of the payload link and the ground end of the payload link; the second wireless communication link is connected to the mission computer and is used to perform data interaction with the mission computer.

[0022] Furthermore, the multi-rotor UAV platform and the mission computer interact with each other, and the multi-rotor UAV platform supplies power to the power management module; the multi-rotor UAV platform is wirelessly connected to the remote controller through the first wireless communication link, and the multi-rotor UAV platform receives remote control commands sent by the remote controller through the first wireless communication link, and sends image information down.

[0023] Furthermore, the direction-finding device includes a first directional antenna, a second directional antenna, and a three-axis gimbal; the first directional antenna and the second directional antenna are mounted on the three-axis gimbal to achieve three-axis rotation, and the first directional antenna and the second directional antenna form a specific angle θ, which satisfies the following relationship:

[0024]

[0025] In the formula, Δα is the angle measurement error of the direction finding device, in rad; e is the signal amplitude measurement error of the monitoring direction finding receiver, in dBm, which is determined by the receiver performance; φ(·) is the antenna horizontal plane radiation pattern function; the antenna radiation pattern function is a conventional technique, and all parameters except for the specific included angle θ are known.

[0026] The monitoring and direction-finding receiver simultaneously measures the signal amplitude information received by the two antennas, and obtains the angle between the electromagnetic target and the central symmetry plane of the two antennas by comparison, which is called the angle deviation angle.

[0027] Furthermore, the three-axis gimbal includes: an azimuth servo motor, a roll servo motor, and a pitch servo motor; the centers of mass of the three servo motors are located in the same plane; the azimuth servo motor and the roll servo motor are connected by a first bracket, the roll servo motor and the pitch servo motor are connected by a second bracket, and a third bracket is installed on the rotor of the pitch servo motor (specifically, the third bracket is installed on the rotor of the pitch motor by screws, and the pitch servo motor is used to control the pitch movement of the third bracket); the three-axis gimbal is connected to the multi-rotor UAV platform through the azimuth servo motor;

[0028] The third bracket is a U-shaped structure, including a first side and a second side that are parallel to each other. A first directional antenna bracket and a second directional antenna bracket are fixedly connected to the first side and the second side, respectively. A first directional antenna is installed on the first directional antenna bracket, and a second directional antenna is installed on the second directional antenna bracket.

[0029] Furthermore, when the UAV is stationary or moving, the three-axis gimbal is rotated according to the angle measurement deviation angle and the UAV attitude to decouple the antenna from the UAV attitude and ensure that the center of the dual antenna beam always points to the target. By measuring the angles of the pitch servo motor, the roll servo motor and the pitch motor, and combining the UAV attitude, the azimuth information of the target relative to the UAV is calculated, so as to realize continuous direction finding of electromagnetic targets in the flight state of the UAV.

[0030] The formula for calculating the target's position relative to the UAV is shown below:

[0031]

[0032] Where, q β The target azimuth angle, in rad, is defined as the angle between the line connecting the UAV and the target and true north. A positive angle is defined when the target is east of the UAV. 31 and a 33 For the corresponding element (a) in matrix A 31 and a 33 The selection is based on the derivation; the formula for calculating matrix A is as follows:

[0033]

[0034] In the formula, Let θ be the drone's pitch angle, ψ be the drone's yaw angle, and γ be the drone's roll angle. For the pitch servo motor (1-5) rotation angle, q γ q represents the rotation angle of the roll servo motors (1-3). ψ The rotation angle of the azimuth servo motor (1-1) is Δq. β The angle measurement deviation angle is given above, and all angles are in rad.

[0035] A multi-rotor electromagnetic signal direction finding and positioning method, employing the aforementioned multi-rotor electromagnetic signal interference investigation system, includes the following steps:

[0036] Step 1: After the multi-rotor UAV platform is powered on, it performs a self-test. If the self-test passes, it will proceed with the operation process. If the self-test fails, it will not be able to take off and troubleshooting will be required.

[0037] Step 2: After entering the operation process, control the multi-rotor UAV platform to fly to the target airspace using the remote controller;

[0038] Step 3: The remote controller transfers control to the ground control equipment; the ground control equipment controls the airborne part to enter the target search mode. In the target search mode, the direction finding device is in the search mode. The direction finding device is in single-antenna operation mode, that is, the monitoring direction finding receiver only outputs the monitoring results of one directional antenna. The monitoring direction finding receiver parameters are set on the ground control equipment, and the three-axis gimbal is controlled to perform scanning search.

[0039] Step 4: After the target signal is detected by the scan, select the signal frequency on the ground control equipment and enter the target positioning mode;

[0040] Step 5: In target positioning mode, the ground control and measurement equipment generates a flight track;

[0041] Step 6: Upload the flight path generated in Step 5 to the mission computer via the second wireless communication link, and the mission computer controls the flight of the multi-rotor UAV platform.

[0042] Step 7: The multi-rotor UAV platform flies along the flight path, and the direction-finding payload continuously tracks and determines the direction of electromagnetic interference sources during flight, continuously outputting direction-finding data and sending it to the ground control equipment; the positioning algorithm module of the ground control equipment performs target positioning based on the direction-finding data; the target positioning here specifically adopts a positioning algorithm based on extended Kalman filter (EKF), which is a conventional technology;

[0043] The mission is considered complete when the positioning reaches a certain accuracy or when the distance between the drone and the target reaches a preset distance.

[0044] Step 8: After the mission is completed, the remote controller takes over the drone and controls it to return and land.

[0045] Furthermore, in step 5, the ground-based telemetry and control equipment includes two track generation modes: manual track generation and automatic track generation. Manual track generation is a conventional technique, which involves manually selecting and generating a track. Automatic track generation is the automatic generation of a track based on the current target location.

[0046] In the automatic trajectory generation mode, when the direction finding only has the target's azimuth information relative to the UAV, the trajectory planning module of the ground control equipment takes the target's azimuth information relative to the UAV as input and automatically generates a trajectory based on the maximum angular velocity criterion. After the preliminary positioning results are available, the trajectory planning module of the ground control equipment takes the current estimated target position as input and automatically generates a trajectory based on the maximum Fisher information matrix determinant det (FIM) criterion.

[0047] Furthermore, the trajectory planning module of the ground-based telemetry and control equipment takes the current estimated target position as input and automatically generates a trajectory based on the maximum det(FIM) criterion, specifically:

[0048] (1) Input the current estimated target location information Current status of drone And the predicted number of waypoints K;

[0049] Using the current state X0 of the UAV as the starting point of the predicted trajectory, the UAV state at the k-th predicted trajectory point is... k represents the k-th predicted waypoint, k = 1:1:K;

[0050] in, y0 and y0 are the estimated x and y coordinates of the target, respectively; V0 is the current velocity of the UAV; x0 and y0 are the x and y coordinates of the current position of the UAV, respectively; ψ0 is the current heading angle of the UAV. V is the current heading angular velocity of the drone; k Let the speed of the UAV at the k-th predicted waypoint be denoted as . Let ψ be the angular velocity of the heading at the position of the k-th predicted waypoint. k Let x be the heading angle of the k-th predicted waypoint position. k ,y k Let x and y be the x and y coordinates of the UAV at the kth predicted waypoint;

[0051] (2) Generate the sampling space of control quantities based on the current UAV speed and angular velocity:

[0052]

[0053] Based on the control quantity sampling space and velocity resolution, the control quantity used for predicting the trajectory is generated and calculated. V k =V min,k :V Step :V max,k ,

[0054] V max,k V is the upper limit of the predicted flight speed of the UAV at the k-th predicted waypoint. min,k The lower limit of the predicted flight speed of the UAV is given for the k-th predicted waypoint; For the k-th predicted waypoint, predict the upper limit of the maximum heading angular velocity of the UAV. V is the lower bound for predicting the minimum heading angular velocity of the UAV at the k-th predicted waypoint; max V is the maximum flight speed of the drone. min The minimum flight speed for the drone, This is the maximum flight acceleration of the drone; This represents the maximum angular velocity of the drone's heading. This is the maximum heading angular acceleration of the drone. For angular velocity resolution; V step V represents velocity resolution, Δt represents the prediction time interval, and V k-1 Let k be the predicted flight speed of the UAV at the (k-1)th waypoint. Let ω be the angular velocity of the (k-1)th predicted track point of the UAV.

[0055] (3) Let in The predicted state of the drone is used to calculate the predicted trajectory. and control quantity Substitute into the UAV's state equation: Calculate the predicted state of the drone at the next moment. The predicted flight path of the UAV is obtained by iterating n times and combining the predicted states into a set.

[0056] Based on the UAV predicted flight path Tr and the current estimated target location information Calculate the objective function for evaluating multi-step positioning tracks. Evaluate the predicted trajectory:

[0057]

[0058] Maximizing the FIM determinant is used as the criterion for optimizing the orientation and positioning trajectory to improve the positioning accuracy of the target.

[0059] Among them, FIM k+n The Fisher information matrix is ​​calculated as follows, obtained by looping n times:

[0060]

[0061] In the formula, Φ k+1|k The target state transition matrix is ​​expressed as follows:

[0062]

[0063] R k To observe the covariance matrix of the noise sequence (which is a fixed value that can be set manually, a common technique), H k The Jacobian matrix of the observation equation is expressed as:

[0064]

[0065] In the formula, The x and y coordinates of the UAV at track point k in the predicted trajectory Tr; These are the estimated x and y coordinates of the target, respectively;

[0066] (4) Find the optimal control quantity U corresponding to the maximum of the multi-step positioning trajectory evaluation objective function. k =argmax(J FIM );

[0067] Update and record the drone's motion status: X k+1 =f(X) k U k );

[0068] (5) Output the generated waypoint W = {X i |i=1,3,...,K}.

[0069] Beneficial technical effects of the present invention:

[0070] The multi-rotor electromagnetic signal interference investigation system proposed in this invention adopts a dual-antenna amplitude comparison direction finding method combined with gimbal tracking control, which can effectively improve the direction finding accuracy of electromagnetic targets, realize continuous direction finding of UAVs in flight, and improve the continuous tracking capability of targets. Simultaneous measurement by dual antennas can realize direction finding and tracking of power fluctuation signals.

[0071] The proposed multi-rotor electromagnetic signal interference investigation system includes an RTK base station, which can improve the navigation and positioning accuracy of the UAV platform itself, thereby further improving the direction finding and positioning accuracy of the entire system for the target.

[0072] This invention provides a multi-rotor electromagnetic signal direction finding and positioning method that employs an automatic trajectory planning method based on current observation information, which can significantly improve the system's automation level. The automatic trajectory planning method aims to improve the observability of the direction finding and positioning system, enabling deep integration of the direction finding equipment and the UAV platform. This improves the convergence process and final positioning accuracy of the multi-rotor electromagnetic signal interference investigation system, thereby enhancing the overall system performance. Attached Figure Description

[0073] Figure 1 This is a schematic diagram of a multi-rotor electromagnetic signal interference detection system according to an embodiment of the present invention;

[0074] Figure 2 This is a schematic diagram of the direction-finding device structure in an embodiment of the present invention;

[0075] Figure 3 This is the optimal direction finding and positioning flight track diagram based on the current estimated target position in this embodiment of the invention;

[0076] Figure 4 This is a diagram illustrating the positioning effect of different flight paths on a fixed target in an embodiment of the present invention.

[0077] Figure 5 This is a schematic diagram of a multi-rotor electromagnetic signal interference direction finding and positioning method in an embodiment of the present invention.

[0078] The attached figures are labeled as follows: 1-1. Azimuth servo motor; 1-2. First bracket; 1-3. Roll servo motor; 1-4. Second bracket; 1-5. Pitch servo motor; 1-6. Third bracket; 1-7. First directional antenna bracket; 1-8. First directional antenna; 1-9. Second directional antenna bracket; 1-10. Second directional antenna. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0080] Conversely, this invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the invention as defined in the claims. Furthermore, to provide a better understanding of the invention, certain specific details are described in detail below. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0081] Example 1: This invention provides an example of a multi-rotor electromagnetic signal interference troubleshooting system, such as... Figure 1 As shown, the system includes an airborne component and a ground control component;

[0082] The aerial component includes a multi-rotor unmanned aerial vehicle (UAV) platform and a monitoring and orientation-finding payload, a mission computer, an aerial payload link, and a power management module mounted on the multi-rotor UAV platform.

[0083] The monitoring and direction-finding payload is used to receive electromagnetic signals, detect electromagnetic targets, and measure the target's azimuth. The monitoring and direction-finding payload includes a direction-finding device and a monitoring and direction-finding receiver. The direction-finding device uses dual-antenna amplitude comparison direction finding combined with gimbal tracking control to achieve continuous tracking and direction finding of electromagnetic signal interference sources by the UAV in flight. The monitoring and direction-finding receiver is a dual-channel monitoring and direction-finding receiver, and the monitoring and direction-finding receiver is electrically connected to two directional antennas.

[0084] The mission computer is connected to the monitoring and direction-finding receiver, the multi-rotor UAV platform, and the payload link air terminal.

[0085] In this embodiment, the mission computer is used to receive, parse, and forward the spectrum data of the monitoring and direction-finding receiver; control and read the angle information of the three-axis pan-tilt; receive the heading information of the electronic compass sensor; implement direction finding by amplitude comparison based on the three-axis pan-tilt angle and signal amplitude information; read the navigation and status information of the multi-rotor UAV platform; control the multi-rotor UAV platform; perform time synchronization processing on the signal angle measurement information, UAV navigation, and status information and send them to the airborne end of the payload link; receive ground control commands, including the control of the UAV flight mode, pan-tilt, and receiver parameters.

[0086] The power management module is used to supply power to the airborne end of the payload link, the mission computer, and the monitoring and direction-finding payload.

[0087] In this embodiment, the ground control part includes ground measurement and control equipment, an RTK base station, the ground end of the payload link, and a remote controller supporting the multi-rotor UAV platform.

[0088] Specifically, the RTK base station can greatly improve the navigation and positioning accuracy of the UAV itself, thereby further improving the system positioning result.

[0089] The remote controller is a supporting device for the UAV, and its main functions are to remotely control the UAV, image monitoring, and pan-tilt camera control, and it has the highest control authority;

[0090] The main form of the ground measurement and control equipment is a ruggedized computer, and its main functions include: communicating with the data link; displaying spectrum data and having a control interface for the receiver; having the basic functions of a UAV ground station, being able to display information such as maps, UAV status, and flight tracks; embedding a direction-finding and positioning module and a flight track planning module; being able to automatically upload flight tracks; and being able to call map terrain data.

[0091] In this embodiment, the airborne part and the ground control part are connected by two wireless communication links;

[0092] The first wireless communication link is the自有data link of the multi-rotor UAV platform. The first wireless communication link is connected to the remote controller and is used to transmit the video information, status information, and remote control commands of the multi-rotor UAV platform;

[0093] The second wireless communication link includes the airborne end of the payload link and the ground end of the payload link; the second wireless communication link is an additional link and is connected to the mission computer for data interaction with the mission computer; specifically, it is used to transmit spectrum monitoring data, payload control commands, and payload synchronization data.

[0094] It should be noted that there may be an inaccuracy in the "自有data link" in the translation of item . It might be better to have a more accurate expression like "the native data link of the multi-rotor UAV platform" or other more appropriate terms depending on the actual context.In this embodiment, the multi-rotor UAV platform and the mission computer interact with each other, and the multi-rotor UAV platform supplies power to the power management module; the multi-rotor UAV platform is wirelessly connected to the remote controller through the first wireless communication link, receives remote control commands sent by the remote controller, and sends image information.

[0095] Specifically, the multi-rotor UAV platform receives instructions from the mission computer and the remote controller, and flies according to the instructions; the multi-rotor UAV platform outputs navigation and attitude information of the UAV for target positioning to the mission computer; the multi-rotor UAV platform includes a gimbal camera, navigation sensors, flight controller, adapter board and a first wireless communication link (the multi-rotor UAV platform's own data link); the multi-rotor UAV platform is electrically connected to the mission computer and the power management system through the adapter board.

[0096] In this embodiment, the direction-finding device includes a first directional antenna, a second directional antenna, and a three-axis gimbal; the first directional antenna and the second directional antenna are mounted on the three-axis gimbal to achieve three-axis rotation, and the first directional antenna and the second directional antenna form a specific angle θ between them, satisfying the following relationship.

[0097] The specific included angle θ satisfies the following relationship:

[0098]

[0099] In the formula, Δα is the angle measurement error of the direction finding device, in rad; e is the signal amplitude measurement error of the monitoring direction finding receiver, in dBm, which is determined by the receiver performance; φ(.) is the antenna horizontal plane radiation pattern function; the antenna radiation pattern function is a conventional technique, and all parameters except for the specific included angle θ are known.

[0100] The monitoring and direction-finding receiver simultaneously measures the signal amplitude information received by the two antennas, and obtains the angle between the electromagnetic target and the central symmetry plane of the two antennas by comparison, which is called the angle deviation angle.

[0101] like Figure 2As shown, the three-axis gimbal includes: an azimuth servo motor 1-1, a roll servo motor 1-3, and a pitch servo motor 1-5; the centers of mass of the three servo motors are located in the same plane; the azimuth servo motor 1-1 and the roll servo motor 1-3 are connected by a first bracket 1-2, and the roll servo motor 1-3 and the pitch servo motor 1-5 are connected by a second bracket 1-4; a third bracket 1-6 is mounted on the rotor of the pitch servo motor 1-5, specifically, the third bracket is mounted on the rotor of the pitch motor by screws, and the pitch servo motor 1-5 is used to control the pitch movement of the third bracket 1-6; the three-axis gimbal is connected to the multi-rotor UAV platform through the azimuth servo motor 1-1.

[0102] The third bracket 1-6 has a U-shaped structure, including a first side and a second side that are parallel to each other. A first directional antenna bracket and a second directional antenna bracket are fixedly connected to the first side and the second side respectively. A first directional antenna is installed on the first directional antenna bracket, and a second directional antenna is installed on the second directional antenna bracket.

[0103] When the UAV is stationary or moving, the three-axis gimbal is rotated according to the angle deviation angle and the UAV attitude to decouple the antenna from the UAV attitude and ensure that the center of the dual antenna beam always points to the target. By measuring the angles of the pitch servo motor 1-1, the roll servo motor 1-3 and the pitch motor 1-5, and combining the UAV attitude, the azimuth information of the target relative to the UAV is calculated, so as to realize continuous direction finding of electromagnetic targets in the flight state of the UAV.

[0104] The formula for calculating the target's position relative to the UAV is shown below:

[0105]

[0106] Where, q β The target azimuth angle, in rad, is defined as the angle between the line connecting the UAV and the target and true north. A positive angle is defined when the target is east of the UAV. 31 and a 33 For the corresponding element (a) in matrix A 31 and a 33 The selection is based on the derivation; the formula for calculating matrix A is as follows:

[0107]

[0108] In the formula, Let θ be the drone's pitch angle, ψ be the drone's yaw angle, and γ be the drone's roll angle. For the pitch servo motor, 1-5 rotations, q γ For the roll servo motor, 1-3 rotations, qψ For the azimuth servo motor 1-1 rotation angle, Δq β The angle deviation angle is given above, and all angles are in rad, which enables the system to have direction finding capability during maneuvering flight.

[0109] Among them, the azimuth servo motor is used to control the azimuth rotation of the antenna and measure the azimuth angle of the antenna rotation; the roll servo motors 1-3 are used to control the roll rotation of the antenna and measure the roll azimuth angle of the antenna roll; and the pitch servo motors 1-5 are used to control the pitch movement of the antenna and measure the pitch azimuth angle of the antenna pitch.

[0110] Specifically, the first directional antenna and the second directional antenna are electrically connected to the monitoring and direction-finding receiver via cables, and the received signals are input to the monitoring and direction-finding receiver for amplitude comparison and direction finding. The monitoring and direction-finding receiver is a dual-channel receiver, which can simultaneously measure the amplitude values ​​of the first directional antenna and the second directional antenna and output them to the mission computer.

[0111] Example 2: This invention also provides a multi-rotor electromagnetic signal direction finding and positioning method. This example uses the multi-rotor electromagnetic signal interference investigation system described in Example 1, such as... Figure 5 As shown, the direction finding and positioning method includes the following steps:

[0112] Step 1: After the multi-rotor UAV platform is powered on, it performs a self-test. If the self-test passes, it will enter the operation process. If the self-test fails, it will not be able to take off and troubleshooting is required.

[0113] Step 2: After entering the operation process, control the multi-rotor UAV platform to fly to the target airspace using the remote controller;

[0114] Step 3: The remote controller hands over control to the ground control equipment. The remote controller is in monitoring mode and can take over the drone in case of abnormality.

[0115] The ground-based telemetry and control equipment controls the airborne part to enter the target search mode. In the target search mode, the direction finding device is in the search mode and is in single-antenna amplitude comparison operation state. That is, the monitoring direction finding receiver only outputs the monitoring results of one directional antenna. The ground-based telemetry and control equipment sets the monitoring direction finding receiver parameters and controls the three-axis gimbal to perform scanning search. The gimbal can be manually controlled to search for targets or automatically scan targets.

[0116] Step 4: After the target signal is detected by the scan, select the signal frequency on the ground control equipment, enter the target positioning mode, monitor the direction finding payload to enter the target tracking state, and continuously output direction finding information.

[0117] Step 5: In target positioning mode, the ground control and measurement equipment includes two track generation modes: manual track generation or automatic track generation.

[0118] Step 6: The flight path is uploaded to the mission computer via the second wireless communication link, and the mission computer controls the flight of the multi-rotor UAV platform.

[0119] Step 7: The multi-rotor UAV platform flies along the flight path, and the direction-finding payload continuously tracks and determines the direction of electromagnetic interference sources during flight, continuously outputting direction-finding data and sending it to the ground control equipment; the positioning algorithm module of the ground control equipment performs target positioning based on the direction-finding data;

[0120] The mission is considered complete when the positioning reaches a certain accuracy or the distance between the drone and the target reaches a preset distance; the drone can approach to take pictures and upload the target information (including positioning results, frequency information, etc.) to the command and control center.

[0121] Step 8: After the mission is completed, the remote controller takes over the drone and controls it to return and land.

[0122] In step 5 of this embodiment, when the automatic track generation mode is in place and the direction finding only has target azimuth information, the track planning module of the ground telemetry and control equipment takes the target azimuth as input and automatically generates a track based on the maximum angular velocity criterion; when there is a preliminary positioning result, the track planning module of the ground telemetry and control equipment takes the target position as input and automatically generates a track based on the maximum determinant of the Fisher information matrix det (FIM).

[0123] In this embodiment, the optimal direction finding and positioning trajectory planning method based on maximizing det(FIM) is implemented. The ground control and measurement equipment has manual trajectory generation and automatic trajectory generation functions. The automatic trajectory generation function can generate the most favorable flight trajectory for target positioning based on the current estimated target position and the current state of the UAV.

[0124] The trajectory planning module of the ground-based telemetry and control equipment takes the target position as input and automatically generates a trajectory based on the maximum det (FIM) criterion, specifically:

[0125] Enter the current estimated target location information Current status of drone And the predicted number of waypoints K;

[0126] Using the current state X0 of the UAV as the starting point of the predicted trajectory, the UAV state at the k-th predicted trajectory point is... k represents the k-th predicted waypoint;

[0127] in, y0 and y0 are the estimated x and y coordinates of the target, respectively; V0 is the current velocity of the UAV; x0 and y0 are the x and y coordinates of the current position of the UAV, respectively; ψ0 is the current heading angle of the UAV. V is the current heading angular velocity of the drone;k Let the speed of the UAV at the k-th predicted waypoint be denoted as . Let ψ be the angular velocity of the heading at the position of the k-th predicted waypoint. k Let x be the heading angle of the k-th predicted waypoint position. k ,y k Let x and y be the x and y coordinates of the UAV at the kth predicted waypoint;

[0128] For k = 1:1:K

[0129] The sampling space for generating control quantities is based on the current UAV velocity and angular velocity:

[0130]

[0131] V max,k To calculate the upper limit of the UAV's flight speed at the k-th predicted waypoint, V min,k This is the lower limit for the drone's flight speed at the k-th predicted waypoint; To calculate the upper limit of the maximum heading angular velocity of the UAV at the k-th predicted waypoint, To calculate the lower bound of the minimum heading angular velocity of the UAV at the k-th predicted waypoint; V max V is the maximum flight speed of the drone. min The minimum flight speed for the drone, This is the maximum flight acceleration of the drone; This represents the maximum angular velocity of the drone's heading. This is the maximum heading angular acceleration of the drone. For angular velocity resolution; V step V represents velocity resolution, Δt represents the prediction time interval, and V k-1 Let k be the predicted flight speed of the UAV at the (k-1)th waypoint. Let ω be the angular velocity of the (k-1)th predicted track point of the UAV.

[0132] For V k =V min,k :V Step :V max,k

[0133]

[0134] make in The predicted state of the drone is used to calculate the predicted trajectory. and control quantity Substitute into the UAV's state equation: Calculate the predicted state of the drone at the next moment. The predicted flight path of the UAV is obtained by iterating n times and combining the predicted states into a set.

[0135] Based on the UAV predicted flight path Tr and the current estimated target location information Calculate the objective function for evaluating multi-step positioning tracks. Evaluate the predicted flight path;

[0136] End

[0137] End

[0138] Find the optimal control quantity U corresponding to maximizing the objective function of multi-step positioning trajectory evaluation. k =argmax(J FIM );

[0139] Update and record the drone's motion status: X k+1 =f(X) k U k );

[0140] End

[0141] Output the generated waypoints W = {X i |i=1,3,...,K};

[0142] in,

[0143] Maximizing the FIM determinant is used as the criterion for optimizing the orientation and positioning trajectory to improve the positioning accuracy of the target.

[0144] Among them, FIM k+n The Fisher information matrix is ​​calculated as follows, obtained by looping n times:

[0145]

[0146] In the formula, Φ k+1|k The target state transition matrix is ​​expressed as follows:

[0147]

[0148] R k To observe the covariance matrix of the noise sequence (which is a fixed value that can be set manually, a common technique), H k The Jacobian matrix of the observation equation is expressed as:

[0149]

[0150] In the formula, The x and y coordinates of the UAV at track point k in the predicted trajectory Tr; These are the x and y coordinates of the estimated target, respectively.

[0151] Based on the above method, the optimal direction-finding and positioning flight trajectory of the UAV based on the current estimated target position can be generated, which can effectively improve the direction-finding and positioning convergence process and the final positioning result, such as Figures 3-4 As shown in Table 1, flight paths 1-6 are the optimal flight paths based on the current estimated target position. The positioning effect of the UAV flying along these paths is significantly better than that of the straight flight paths 1-1 to 1-5.

[0152] Table 1. Localization effect of different flight paths on fixed targets

[0153]

[0154] The multi-rotor electromagnetic signal interference investigation system provided by this invention includes a trajectory planning module deployed on the ground-based telemetry and control equipment. This trajectory planning module generates the optimal direction-finding and positioning trajectory based on the current positioning results, thereby improving the overall direction-finding and positioning convergence process and final positioning accuracy, and enhancing system efficiency. Specifically, the trajectory planning module is based on the currently estimated target position information... The current state X0 of the drone and the predicted number of waypoints K are used to... The trajectory optimization evaluation function generates the optimal trajectory that can improve the observability of direction finding and positioning. Controlling the UAV to fly along this trajectory can improve the convergence speed and final positioning accuracy of the system, thereby enhancing the overall performance of the system.

[0155] The multi-rotor electromagnetic signal interference investigation system provided by this invention mounts two directional antennas on a three-axis servo gimbal, with the two antennas at a specific angle. Through dual-antenna amplitude comparison direction finding combined with gimbal tracking control, the system enables continuous tracking and direction finding of electromagnetic signal interference sources by the UAV during flight, improving direction finding efficiency and accuracy. The monitoring direction finding receiver is a dual-channel receiver electrically connected to the two antennas, capable of simultaneously comparing the amplitudes of the signals received by the two antennas. This allows for direction finding of power fluctuation signals, expanding the system's application range. Furthermore, a trajectory planning module is deployed on the ground-based telemetry and control equipment, enabling the system to plan the optimal direction finding and positioning trajectory based on the current positioning results. By optimizing the UAV's flight trajectory, the observability of the direction finding and positioning algorithm is improved, the positioning convergence process and final positioning accuracy are enhanced, and system performance is increased. The system includes a differential positioning base station, which can significantly improve the UAV's own navigation and positioning accuracy, thereby further improving the system's positioning results.

[0156] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-rotor electromagnetic signal interference detection system, characterized in that, The system includes an aerial part and a ground control part; The aerial part includes a multi-rotor UAV platform and a monitoring and direction-finding payload, a mission computer, an aerial end of the payload link, and a power management module mounted on the multi-rotor UAV platform; The monitoring and direction-finding payload is used to receive electromagnetic signals, detect electromagnetic targets, and measure the azimuth of the targets; the monitoring and direction-finding payload includes a direction-finding device and a monitoring and direction-finding receiver; the direction-finding device combines amplitude comparison direction-finding of dual antennas with pan-tilt tracking control to achieve continuous tracking and direction-finding of electromagnetic signal interference sources by the UAV in flight; the monitoring and direction-finding receiver is a dual-channel monitoring and direction-finding receiver, and two directional antennas in the monitoring and direction-finding receiver are electrically connected; The mission computer is connected to the monitoring and direction-finding receiver, the multi-rotor UAV platform, and the aerial end of the payload link; The direction-finding device includes a first directional antenna, a second directional antenna, and a three-axis gimbal; the first directional antenna and the second directional antenna are mounted on the three-axis gimbal to achieve three-axis rotation, and the first directional antenna and the second directional antenna are at a specific angle to each other. The specific included angle The following relationship must be satisfied: ； In the formula, The angle measurement error of the direction finding device is expressed in rad. The signal amplitude measurement error of the monitoring direction-finding receiver is expressed in dBm. This is the antenna horizontal plane radiation pattern function; The monitoring and direction-finding receiver measures the signal amplitude information received by the two antennas simultaneously, and obtains the angle between the electromagnetic target and the central symmetry plane of the two antennas by comparison, which is called the angle measurement deviation angle; The three-axis pan-tilt includes: an azimuth servo motor (1-1), a roll servo motor (1-3), and a pitch servo motor (1-5); the centers of mass of the three servo motors are in the same plane; When the UAV is stationary or moving, the three-axis pan-tilt is controlled to rotate according to the angle measurement deviation angle and the UAV attitude, so as to achieve decoupling of the antenna and the UAV attitude, and make the beam center of the dual antennas always point to the target. By measuring the angles of the azimuth servo motor (1-1), the roll servo motor (1-3), and the pitch servo motor (1-5), and combining the UAV attitude, the azimuth information of the target relative to the UAV is calculated, so as to achieve continuous direction-finding of the electromagnetic target in the flight state of the UAV; Among them, the calculation formula for calculating the azimuth information of the target relative to the UAV is as follows: ； in, The target azimuth is expressed in rad. and For matrix Corresponding elements in the matrix; The calculation formula is as follows: In the formula, For the drone's pitch angle, For the yaw angle of the drone, For the drone's roll angle, For the pitch servo motors (1-5) rotation angle, For the rotation angle of the roll servo motors (1-3), For the rotation angle of the azimuth servo motor (1-1), To measure the angular deviation angle for antenna array measurements.

2. The multi-rotor electromagnetic signal interference investigation system according to claim 1, characterized in that, The ground control part includes ground measurement and control equipment, an RTK base station, a ground end of the payload link, and a remote controller supporting the multi-rotor UAV platform.

3. The multi-rotor electromagnetic signal interference investigation system according to claim 2, characterized in that, The aerial part and the ground control part are connected by two wireless communication links; The first wireless communication link is the own data link of the multi-rotor UAV platform. The first wireless communication link is connected to the remote controller and is used to transmit video information, status information, and remote control commands of the multi-rotor UAV platform; The second wireless communication link includes the aerial end and the ground end of the payload link; The second wireless communication link is connected to the mission computer and is used for data interaction with the mission computer.

4. The multi-rotor electromagnetic signal interference investigation system according to claim 3, characterized in that, The multi-rotor UAV platform conducts data interaction with the mission computer, and the multi-rotor UAV platform outputs power supply to the power management module; the multi-rotor UAV platform is wirelessly connected to the remote controller through the first wireless communication link. The multi-rotor UAV platform receives the remote control commands sent by the remote controller through the first wireless communication link and sends down image information.

5. The multi-rotor electromagnetic signal interference investigation system according to claim 1, characterized in that, The three-axis gimbal includes: an azimuth servo motor (1-1), a roll servo motor (1-3), and a pitch servo motor (1-5); the centers of mass of the three servo motors are located in the same plane; the azimuth servo motor (1-1) and the roll servo motor (1-3) are connected by a first bracket (1-2), the roll servo motor (1-3) and the pitch servo motor (1-5) are connected by a second bracket (1-4), and a third bracket (1-6) is installed on the rotor of the pitch servo motor (1-5); the three-axis gimbal is connected to the multi-rotor UAV platform through the azimuth servo motor (1-1); The third bracket (1-6) is a U-shaped structure, including a first side and a second side that are parallel to each other. A first directional antenna bracket and a second directional antenna bracket are fixedly connected to the first side and the second side respectively. A first directional antenna is installed on the first directional antenna bracket and a second directional antenna is installed on the second directional antenna bracket.

6. A method for determining and locating direction using electromagnetic signals from a multi-rotor aircraft, employing the multi-rotor electromagnetic signal interference detection system described in any one of claims 1-5, characterized in that, The direction finding and positioning method includes the following steps: Step 1: After the multi-rotor UAV platform is powered on, it performs a self-test. If the self-test passes, it will proceed with the operation process. If the self-test fails, it will not be able to take off and troubleshooting will be required. Step 2: After entering the operation process, control the multi-rotor UAV platform to fly to the target airspace using the remote controller; Step 3: The remote controller transfers control to the ground control equipment; the ground control equipment controls the airborne part to enter the target search mode. In the target search mode, the direction finding device is in the search mode. The direction finding device is in single-antenna operation mode, that is, the monitoring direction finding receiver only outputs the monitoring results of one directional antenna. The monitoring direction finding receiver parameters are set on the ground control equipment, and the three-axis gimbal is controlled to perform scanning search. Step 4: After the target signal is detected by the scan, select the signal frequency on the ground control equipment and enter the target positioning mode; Step 5: In target positioning mode, the ground control and measurement equipment generates a flight track; Step 6: Upload the flight path generated in Step 5 to the mission computer via the second wireless communication link, and the mission computer controls the flight of the multi-rotor UAV platform. Step 7: The multi-rotor UAV platform flies along the flight path, and the direction-finding payload continuously tracks and determines the direction of electromagnetic interference sources during flight, continuously outputting direction-finding data and sending it to the ground control equipment; the positioning algorithm module of the ground control equipment performs target positioning based on the direction-finding data; The mission is considered complete when the positioning reaches a certain accuracy or when the distance between the drone and the target reaches a preset distance. Step 8: After the mission is completed, the remote controller takes over the drone and controls it to return and land.

7. The multi-rotor electromagnetic signal direction finding and positioning method according to claim 6, characterized in that, In step 5, the ground-based telemetry and control equipment includes two track generation modes: manual track generation and automatic track generation. In automatic trajectory generation mode, when the direction finding only has the target's azimuth information relative to the UAV at the beginning, the trajectory planning module of the ground telemetry and control equipment takes the target's azimuth information relative to the UAV as input and automatically generates a trajectory based on the maximum angular velocity. Once preliminary positioning results are available, the trajectory planning module of the ground-based telemetry and control equipment uses the current estimated target position as input and automatically generates a trajectory based on the maximum determinant (det) criterion of the Fisher information matrix.

8. The multi-rotor electromagnetic signal direction finding and positioning method according to claim 7, characterized in that, The trajectory planning module of the ground-based telemetry and control equipment takes the current estimated target position as input and automatically generates a trajectory based on the maximum det criterion, specifically: (1) Input the current estimated target location information Current status of the drone and the number of predicted waypoints ; Current status of the drone As the starting point of the predicted trajectory, the UAV state at the k-th predicted trajectory point is: , k Indicates the first k One predicted waypoint, ; in, These are the estimated x and y coordinates of the target, respectively; This is the drone's current speed; These are the horizontal and vertical coordinates of the drone's current location; The current heading angle of the drone. This represents the current heading angular velocity of the drone; Let the speed of the UAV at the k-th predicted waypoint be denoted as . Let be the heading angular velocity at the position of the k-th predicted waypoint. Let the heading angle be the position of the k-th predicted waypoint. Let x and y be the x and y coordinates of the UAV at the kth predicted waypoint; (2) Generate the sampling space of control quantities based on the current speed and angular velocity of the UAV: ； Based on the control quantity sampling space and velocity resolution, the control quantity used for predicting the trajectory is generated and calculated. ; , ; To calculate the upper limit of the UAV's flight speed at the k-th predicted waypoint, This is the lower limit for the drone's flight speed at the k-th predicted waypoint; To calculate the upper limit of the maximum heading angular velocity of the UAV at the k-th predicted waypoint, This is the lower bound for calculating the minimum heading angular velocity of the UAV at the k-th predicted waypoint; The maximum flight speed of the drone, The minimum flight speed for the drone, This is the maximum flight acceleration of the drone; This represents the maximum angular velocity of the drone's heading. This is the maximum heading angular acceleration of the drone. Angular velocity resolution; For speed resolution, For predicting time intervals, Let k be the predicted flight speed of the UAV at the (k-1)th waypoint. Let ω be the angular velocity of the (k-1)th predicted track point of the UAV. (3) Let ,in The predicted state of the drone is used to calculate the predicted trajectory. and control quantity Substitute into the UAV's state equation: Calculate the predicted state of the UAV at the next moment. The predicted flight path of the UAV is obtained by iterating n times and combining the predicted states into a set. ; Based on the predicted flight path of the UAV and current estimated target location information Calculate the objective function for evaluating multi-step positioning tracks. The predicted flight path is evaluated: ； in, The Fisher information matrix is ​​calculated as follows, obtained by looping n times: In the formula, The target state transition matrix is ​​expressed as follows: To observe the covariance matrix of the noise sequence, The Jacobian matrix of the observation equation is expressed as: In the formula, , For predicting trajectories The horizontal and vertical coordinates of the UAV at point k on the flight path; These are the estimated x and y coordinates of the target, respectively; (4) Find the optimal control quantity corresponding to the maximum of the multi-step positioning trajectory evaluation objective function. ; Update and record the drone's motion status: ; (5) Output the generated waypoints .

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