A relative positioning method for drone swarms at night

Abstract

The present invention belongs to the field of aircraft navigation and positioning technology, and discloses a method for relative positioning of a swarm of drones at night. The present invention achieves distributed collaborative positioning and collision warning within a swarm of drones by installing a magnetic compass, a passive infrared reflective ball, and a two-dimensional turntable infrared camera on the drones, as well as a communication topology network. This method does not require the addition of additional equipment or reliance on external signal sources, thus avoiding external interference. Compared with traditional laser radar and ultrasonic positioning methods, the present invention effectively simplifies the system and reduces implementation costs. At the same time, by using passive infrared reflective balls as nighttime location markers for drones, the method has the advantages of low cost, low power consumption, and low detectability, making it beneficial for nighttime penetration, reconnaissance, strike and other combat missions.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft navigation and positioning, and relates to a relative positioning method for a group of unmanned aerial vehicles at night. Background Art

[0002] With the advancement of science and technology, drone swarms have broad application prospects in both military and civilian fields, particularly for low-altitude security within future ground-based security systems. Drone swarms, with their numerous advantages, including strong combat capability, high system survivability, and low attack costs, are of great significance to my country's industrial production, social economy, scientific research, education, and other areas of protection, production, safety, and rescue, as well as to national defense, social stability, and economic development. However, acquiring highly accurate and reliable relative spatiotemporal relationships between drones within a swarm is crucial for drone swarm flight safety and mission execution. Therefore, the demand and necessity for fast, cost-effective, and high-quality drone swarm collaborative localization technology is rapidly increasing.

[0003] Currently, domestic and international scholars have achieved significant results in the field of autonomous relative positioning of drone swarms and have proposed a series of methods, such as laser pulse ranging, UWB ranging, visual ranging, ultrasonic ranging, and radio ranging, which have been widely applied in various fields. Laser pulse ranging is extremely expensive; UWB ranging has poor stability and may interfere with other wireless communications; ultrasonic ranging has slow acquisition speeds and a limited scope of application; and radio ranging is susceptible to interference and has poor reliability. Compared to other methods, visual ranging offers advantages such as low cost, passive sensing, and low detectability, making it a key research direction for the future. Existing visual ranging methods, however, primarily rely on binocular cameras, which are computationally intensive and cannot meet the needs of nighttime use.

[0004] At the same time, the ultimate goal of drone swarm applications is to adapt to all-weather and all-scenario requirements. However, there is currently little research on relying on drones themselves for relative positioning perception under nighttime conditions, which is one of the most important application scenarios for drone swarms, especially in the military. Therefore, a nighttime visual collaborative positioning method within drone swarms is needed to ensure the normal operation of drone swarms in nighttime environments. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a method for relative positioning of a swarm of drones at night.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] The present invention is specifically achieved in this way:

[0008] A method for relative positioning of a drone swarm at night, wherein a drone swarm includes four drones, each of which includes a magnetic compass, a passive infrared reflective ball, and a two-dimensional turntable infrared camera, includes the following steps:

[0009] Step 1: Deployment of the unmanned swarm formation before takeoff

[0010] Arrange UAVs 1, 2, 4, and 3 in sequence at the takeoff site in a diamond-shaped geometric formation. Ensure that the initial distance between a pair of UAVs arranged on the diagonal of the diamond is equal to the initial distance between UAVs arranged at adjacent vertices of the diamond. Furthermore, the initial actual distance between each UAV should be at least greater than the sum of their safety radii and less than the maximum effective detection range of the infrared camera.

[0011] Step 2: Power on the unmanned swarm formation;

[0012] Step 3: UAV pre-takeoff benchmark construction, including positioning benchmark construction and time benchmark construction;

[0013] Step 4: Acquisition of relative coordinate position information of each drone: Based on the directed communication topology, drone 2 and drone 3 can obtain the pixel coordinate information before takeoff stored in the pixel coordinate values ​​of the infrared camera imaging plane of drone 1 and drone 4, as well as the real-time detected pixel coordinate information, and then obtain the real-time position coordinates of drone 2 and drone 3 in their respective obtuse angle relative coordinate systems, and use the real-time position coordinates to coordinate the relative coordinates as the position feedback of drone 2 and drone 3 for the position closed-loop control of drone 2 and drone 3; drone 1 and drone 4 are respectively (x 14 ,θ 14 ) and (x 41 ,θ 41 ) as its relative coordinate reference, and maintain its posture through its respective position closed-loop control, where x 14 The horizontal coordinate of the pixel coordinate information of drone 4 before takeoff stored in the infrared camera imaging plane of drone 1 is θ 14 is the diameter pixel value of the maximum contour of the passive infrared reflective ball of UAV 4 on the imaging plane of UAV 1; 41 The horizontal coordinate of the pixel coordinate information of drone 1 before takeoff stored in the infrared camera imaging plane of drone 4, θ 41 is the pixel value of the diameter of the maximum contour of the passive infrared reflective ball of UAV 1 on the imaging plane of UAV 4;

[0014] Step 5: UAV 1 and UAV 4 respectively compare the changes in the diameter pixel values ​​of the maximum imaging contours of the passive infrared reflective balls of UAV 2 and UAV 3 on the imaging plane of UAV 1 and UAV 4 in real time with the threshold to determine the cluster collision risk, and send anti-collision warning instructions to UAV 2 and / or UAV 3 through the directed communication topology.

[0015] Furthermore, during the flight, UAV 1 shares its magnetic compass information with UAVs 2 to 4 in real time through a directed communication topology.

[0016] Furthermore, the positioning reference construction in step 3 specifically includes the following steps:

[0017] Step 3.1: Set the angle α1 between the axis of the 2D turntable infrared camera of UAV 1 and its heading to 180°, and the angle between the axis of the 2D turntable infrared camera of the remaining UAVs and their heading to zero;

[0018] Step 3.2: Adjust the angles between the axes of the 2D turntable infrared cameras of UAV 1 and UAV 4 and their headings so that the passive infrared reflective balls of UAV 1 and UAV 4 are horizontally centered on each other's imaging planes, and the passive infrared reflective balls of UAV 2 and UAV 3 are within the imaging planes of the 2D turntable infrared cameras of UAV 1 and UAV 4.

[0019] Step 3.3: Record and store the angles α1 to α4 between the axis of the 2D turntable infrared camera of UAV 1 to UAV 4 and its heading;

[0020] Step 3.4: Start the closed-loop control program for the 2D turntable infrared camera angle, so that the angle values ​​α1 to α4 remain consistent with the recorded and stored values ​​before takeoff throughout the entire subsequent flight process;

[0021] Step 3.5: Record and store the pixel coordinate values ​​of the passive infrared reflective balls of UAV 2, UAV 3, and UAV 4 in the imaging plane of UAV 1's infrared camera; the pixel coordinate values ​​of the passive infrared reflective balls of UAV 1, UAV 2, and UAV 3 in the imaging plane of UAV 4's infrared camera; the pixel diameter values ​​of the maximum imaging contours of the passive infrared reflective balls of UAV 1 and UAV 4 in each other's imaging planes; and the pixel diameter values ​​of the maximum imaging contours of UAV 2 and UAV 3 in the imaging planes of UAV 1 and UAV 4, respectively; and use the above information as the collaborative relative positioning reference information;

[0022] Step 3.6: Construct the obtuse angle relative coordinate system of UAV 2 and UAV 3.

[0023] Furthermore, the time reference construction includes synchronizing the communication clocks between the drones.

[0024] Preferably, the viewing angle of the infrared camera is 90°.

[0025] Preferably, in step 3.2, the passive infrared reflective balls of UAV 2 and UAV 3 are located in the imaging plane of the two-dimensional turntable infrared camera of UAV 1 and UAV 4, and are as far away from the boundary of the imaging plane as possible and as symmetrical as possible about the horizontal center of the imaging plane.

[0026] Furthermore, the construction of the obtuse angle relative coordinate system includes: constructing the χ3-ζ3 obtuse angle relative coordinate system of UAV 3, with the relative position S3 of UAV 3 in the cluster formation before takeoff as the coordinate origin (0, 0), when UAV 3 moves to the position S'3 after takeoff, its coordinates become (χ'3, ζ'3), and the pixel coordinate values ​​of the corresponding passive infrared reflective ball of UAV 3 on the imaging plane of the infrared camera of UAV 1 and UAV 4 become (x'3, ζ'3) respectively. 13 , y' 13 ) and (x' 43 , y' 43 ), according to the coordinate geometry relationship, we can get: χ'3=x 43 -x' 43 ,ζ'3=x' 13 -x 13 Similarly, the relative coordinates of the cluster formation of UAV 2 in its χ2-ζ2 obtuse angle relative coordinate system are (χ'2, ζ'2), where χ'2 = x' 42 -x 42 ,ζ'2=x 12 -x' 12 .

[0027] Furthermore, the directed communication topology is specifically as follows: there is a one-way communication relationship between UAV 1 and UAV 2, UAV 3 and UAV 4; there is a one-way communication relationship between UAV 4 and UAV 2 and UAV 3; there is a two-way communication relationship between UAV 2 and UAV 3, in which UAV 1 is the information sender.

[0028] The safety radius described in this application is twice the radius of the circumscribed circle of the maximum outline of the drone body.

[0029] Compared to existing technologies, this invention achieves visual relative positioning of drone swarms at night through the use of drone magnetic compasses, passive infrared reflective balls, and a two-dimensional turntable infrared camera. This eliminates the need for additional equipment and relies on GPS, lidar, ultrasonic radar, and other technologies. Compared to traditional positioning methods, this invention effectively simplifies the system and reduces implementation costs. Furthermore, by using passive infrared reflective balls as drone nighttime location markers, this method offers advantages such as low cost, low power consumption, and low detectability, making it beneficial for nighttime penetration, reconnaissance, and strike missions. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0031] Figure 1 It is a technical solution diagram of an embodiment.

[0032] Figure 2 Schematic diagram of the obtuse angle coordinate system of the embodiment.

[0033] Figure 3 Schematic diagram of the communication topology.

[0034] Figure 4 2 is a flowchart of the working process of the embodiment. DETAILED DESCRIPTION

[0035] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0036] A relative positioning method for drone swarms at night, as shown in the attached Figure 1 As shown, it mainly includes 4 UAVs, each of which is equipped with a magnetic compass, a passive infrared reflective ball and a two-dimensional turntable infrared camera. The magnetic compass is used for each UAV to obtain its heading direction information, the passive infrared reflective ball is used as a marker for night vision positioning, and the infrared camera has a viewing angle of 90°. The relative positioning of the UAV group only requires the infrared cameras of UAV 1 and UAV 4 to achieve the coordinated positioning of the formation. The infrared cameras of UAV 2 and UAV 3 can be used for formation mission payloads, such as obtaining information such as search, reconnaissance, and obstacle avoidance.

[0037] The specific implementation flow chart is as attached Figure 4 As shown, the following steps are included:

[0038] Step 1: Deployment of the unmanned swarm formation before takeoff.

[0039] Each drone group will be assigned according to the Figure 1The diamond-shaped geometric formation shown is arranged at the takeoff site. Specifically, UAV 1, UAV 2, UAV 4, and UAV 3 are arranged sequentially at the takeoff site in a diamond-shaped geometric formation. The initial distance (γ5) between a pair of UAVs arranged on the diagonal of the diamond should be equal to the initial distance (γ1 or γ2 or γ3 or γ4) between UAVs arranged at adjacent vertices of the diamond. In this embodiment, the initial actual distance between each UAV satisfies γ1 = γ2 = γ3 = γ4 = γ5. The initial actual distance between each UAV should be at least greater than the sum of their safety radii to avoid collision risks. At the same time, it should also be less than the maximum effective detection range of the infrared camera. Step 2: Power on the unmanned cluster formation.

[0040] Step 3: Baseline construction before the drone takes off.

[0041] Step 3.1: Positioning benchmark construction:

[0042] Step 3.1.1: Set the angle α1 between the axis of the 2D turntable infrared camera of UAV 1 and its heading to 180°. Set the angles α2 to α4 between the axis of the 2D turntable infrared camera of the remaining UAVs and their headings to zero.

[0043] Step 3.1.2: Fine-tune the angles α1 and α4 between the axis of the 2D turntable infrared camera of UAV 1 and UAV 4 and their headings, and make the passive infrared reflective balls meet the following requirements in the imaging plane of their respective infrared cameras. Figure 1 The requirements shown are that the passive infrared reflective balls of UAV 1 and UAV 4 should be positioned at the horizontal center of each other's imaging planes, and the passive infrared reflective balls of UAV 2 and UAV 3 should both be positioned within the imaging planes of the two-dimensional turntable infrared cameras of UAV 1 and UAV 4, as far away from the boundaries of the imaging planes as possible, and as symmetrically as possible about the horizontal center of the imaging planes.

[0044] Description: Attached Figure 1 Where a is the pixel width of the infrared camera imaging plane, and b is the pixel height. The specific values ​​are determined by the performance of the actual infrared camera used.

[0045] Step 3.1.3: Record and store the angles α1 to α4 between the axis of the 2D turntable infrared camera of UAV 1 to UAV 4 and their headings at this time;

[0046] Step 3.1.4: Start the closed-loop control program for the 2D turntable infrared camera angle, so that the angle values ​​α1 to α4 remain consistent with the recorded and stored values ​​before takeoff throughout the entire subsequent flight process;

[0047] Step 3.1.5: Record and store the pixel coordinates (x 12 ,y12 )、(x 13 ,y 13 ) and (x 14 ,y 14 ); At the same time, record and store the pixel coordinate values ​​(x 41 ,y 41 )、(x 42 ,y 42 ) and (x 43 ,y 43 ), the coordinates are shown in the attached Figure 1 At the same time, the diameter pixel value of the maximum imaging contour of the passive infrared reflective balls of UAV 1 and UAV 4 on the imaging plane of each other is stored and recorded, and recorded as: θ 41 and θ 14 , and the diameter pixel values ​​of the maximum imaging contours of UAV 2 and UAV 3 on the imaging planes of UAV 4 and UAV 1, respectively, are recorded as: θ 42 ,θ 12 and θ 43 ,θ 13 ; and use the above as collaborative relative positioning benchmark information.

[0048] Step 3.1.6: Follow the instructions in the attached Figure 2 As shown in the figure, taking UAV 3 as an example, its χ3-ζ3 obtuse angle relative coordinate system is constructed. The coordinate system takes the relative position S3 of UAV 3 in the cluster formation before takeoff as the coordinate origin (0, 0). Figure 2 After the S'3 position is shown, its coordinates become (χ'3, ζ'3), and the pixel coordinates of the passive infrared reflective ball of UAV 3 on the imaging plane of the infrared camera of UAV 1 and UAV 4 become (x' 13 , y' 13 ) and (x' 43 , y' 43 ), therefore, according to the attached Figure 2 The coordinate geometry relationship shown in the figure shows that: χ'3=x 43 -x' 43 ,ζ'3=x' 13 -x 13 Similarly, the relative coordinates of the UAV 2 in its χ2-ζ2 obtuse angle relative coordinate system are (χ'2, ζ'2), where χ'2 = x' 42 -x 42 ,ζ'2=x 12 -x' 12 .

[0049] Step 3.2: Time base construction: Synchronize the communication clocks between drones to ensure the consistency of collaborative positioning of drones in the cluster.

[0050] Step 4: Obtain information such as the relative coordinates of each drone: Figure 3 The directional communication topology shown in FIG2 and FIG3 can obtain the pixel coordinate information (x) stored before takeoff of the pixel coordinate values ​​of the infrared camera imaging plane of UAV 1 and UAV 4. 13 ,y 13 )、(x 12 ,y 12 )、(x 42 ,y 42 ) and (x 43 ,y 43 ), and the real-time detected pixel coordinate information (x' 13 , y' 13 )、(x' 12 , y' 12 )、(x' 42 , y' 42 ) and (x' 43 , y' 43 ), and then the real-time position coordinates (χ'2, ζ'2) and (χ'3, ζ'3) of UAVs 2 and 3 in their respective obtuse angle relative coordinate systems can be obtained, and the collaborative positioning relative coordinates are used as the position feedback of UAVs 2 and 3 for the position closed-loop control of UAVs 2 and 3; for UAVs 1 and 4, ... Figure 2 As shown (x 14 ,θ 14 ) and (x 41 ,θ 41 ) as their relative coordinate reference, and maintain their attitude through closed-loop position control. The directed communication topology is as follows: UAV 1 has one-way communication with UAV 2, UAV 3, and UAV 4; UAV 4 has one-way communication with UAV 2 and UAV 3; and UAV 2 and UAV 3 have two-way communication, with UAV 1 being the information sender.

[0051] Note: The above description is based on the relative positioning of the drone in the horizontal plane. Figure 1 and 2 The pixel height coordinate y is shown in 12 、y 13 、y 14 、y 41 、y 42 and y 43 It is used for collaborative positioning of the cluster in the height direction. The principle is similar to the horizontal plane control of the drone, so I will not go into details here.

[0052] Step 5: UAV 1 and UAV 4 respectively use θ 42 ,θ 12 and θ 43 ,θ 13 The change of is compared with the threshold to determine the cluster collision risk, and the anti-collision warning instruction is sent to UAV 2 or UAV 3 through the communication topology to avoid the collision risk between UAVs. 42 ,θ 43 are the pixel values ​​of the diameter of the maximum contour of the passive infrared reflective balls of UAV 2 and UAV 3 on the imaging plane of UAV 4; θ 12 ,θ 13 are the pixel values ​​of the diameter of the maximum contour of the passive infrared reflective balls of UAV 2 and UAV 3 on the imaging plane of UAV 1;

[0053] Step 6: Drone 1 receives control commands from the external system to ensure the entire formation operates as directed. During flight, Drone 1 shares its magnetic compass information with Drones 2-4 in real time via the communication topology, ensuring consistent orientation across the entire formation, facilitating formation maintenance and flight.

[0054] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0055] It should be noted that, in this application, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0056] The above is only an embodiment of the present invention. Common knowledge such as the known specific structures and characteristics in the scheme is not described in detail here. Ordinary technicians in the field are aware of all common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the field can improve and implement this scheme in combination with their own abilities under the inspiration given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for relative positioning of a group of drones at night, characterized in that: A drone swarm consists of four drones, each equipped with a magnetic compass, a passive infrared reflector, and a two-dimensional turntable infrared camera. The following steps are involved: Step 1: Deployment of the unmanned swarm formation before takeoff Arrange UAVs 1, 2, 4, and 3 in sequence at the takeoff site in a diamond-shaped geometric formation. Ensure that the initial distance between a pair of UAVs arranged on the diagonal of the diamond is equal to the initial distance between UAVs arranged at adjacent vertices of the diamond. Furthermore, the initial actual distance between each UAV should be at least greater than the sum of their safety radii and less than the maximum effective detection range of the infrared camera. Step 2: Power on the unmanned swarm formation; Step 3: UAV pre-takeoff benchmark construction, including positioning benchmark construction and time benchmark construction; Step 4: Acquisition of relative coordinate position information of each drone: Based on the directed communication topology, drone 2 and drone 3 can obtain the pixel coordinate information before takeoff stored in the pixel coordinate values ​​of the infrared camera imaging plane of drone 1 and drone 4, as well as the real-time detected pixel coordinate information, and then obtain the real-time position coordinates of drone 2 and drone 3 in their respective obtuse angle relative coordinate systems, and use the real-time position coordinates to coordinate the relative coordinates as the position feedback of drone 2 and drone 3 for the position closed-loop control of drone 2 and drone 3; drone 1 and drone 4 are respectively (x 14 ,θ 14 ) and (x 41 ,θ 41 ) as its relative coordinate reference, and maintain its posture through its respective position closed-loop control, where x 14 The horizontal coordinate of the pixel coordinate information of drone 4 before takeoff stored in the infrared camera imaging plane of drone 1 is θ 14 is the diameter pixel value of the maximum contour of the passive infrared reflective ball of UAV 4 on the imaging plane of UAV 1; 41 The horizontal coordinate of the pixel coordinate information of drone 1 before takeoff stored in the infrared camera imaging plane of drone 4, θ 41 is the pixel value of the diameter of the maximum contour of the passive infrared reflective ball of UAV 1 on the imaging plane of UAV 4; Step 5: UAV 1 and UAV 4 respectively compare the changes in the diameter pixel values ​​of the maximum imaging contours of the passive infrared reflective balls of UAV 2 and UAV 3 on the imaging plane of UAV 1 and UAV 4 in real time with the threshold to determine the cluster collision risk, and send anti-collision warning instructions to UAV 2 and / or UAV 3 through the directed communication topology.

2. The method for relative positioning of a swarm of drones at night according to claim 1, characterized in that: During the flight, UAV 1 shares its magnetic compass information with UAVs 2 to 4 in real time through a directed communication topology.

3. The method for relative positioning of a swarm of drones at night according to claim 1, characterized in that: The positioning reference construction in step 3 specifically includes the following steps: Step 3.1: Set the angle α1 between the axis of the 2D turntable infrared camera of UAV 1 and its heading to 180°, and the angle between the axis of the 2D turntable infrared camera of the remaining UAVs and their heading to zero; Step 3.2: Adjust the angles between the axes of the 2D turntable infrared cameras of UAV 1 and UAV 4 and their headings so that the passive infrared reflective balls of UAV 1 and UAV 4 are horizontally centered in each other's imaging planes, and the passive infrared reflective balls of UAV 2 and UAV 3 are within the imaging planes of the 2D turntable infrared cameras of UAV 1 and UAV 4. Step 3.3: Record and store the angles α1 to α4 between the axis of the 2D turntable infrared camera of UAV 1 to UAV 4 and its heading; Step 3.4: Start the closed-loop control program for the 2D turntable infrared camera angle, so that the angle values ​​α1 to α4 remain consistent with the recorded and stored values ​​before takeoff throughout the entire subsequent flight process; Step 3.5: Record and store the pixel coordinate values ​​of the passive infrared reflective balls of UAV 2, UAV 3, and UAV 4 in the imaging plane of UAV 1's infrared camera; the pixel coordinate values ​​of the passive infrared reflective balls of UAV 1, UAV 2, and UAV 3 in the imaging plane of UAV 4's infrared camera; the pixel diameter values ​​of the maximum imaging contours of the passive infrared reflective balls of UAV 1 and UAV 4 in each other's imaging planes; and the pixel diameter values ​​of the maximum imaging contours of UAV 2 and UAV 3 in the imaging planes of UAV 1 and UAV 4, respectively; and use the above information as the collaborative relative positioning reference information; Step 3.6: Construct the obtuse angle relative coordinate system of UAV 2 and UAV 3.

4. The method for relative positioning of a swarm of drones at night according to claim 1, characterized in that: The time base construction includes synchronizing the communication clocks between the drones.

5. The method for relative positioning of a swarm of drones at night according to claim 1, characterized in that: The viewing angle of the infrared camera is 90°.

6. The method for relative positioning of a swarm of drones at night according to claim 3, characterized in that: In step 3.2, the passive infrared reflective balls of UAV 2 and UAV 3 are located within the imaging plane of the two-dimensional turntable infrared camera of UAV 1 and UAV 4, as far away from the boundary of the imaging plane as possible, and as symmetrical as possible about the horizontal center of the imaging plane.

7. The method for relative positioning of a swarm of drones at night according to claim 3, characterized in that: The construction of the obtuse angle relative coordinate system includes: constructing the χ3-ζ3 obtuse angle relative coordinate system of UAV 3, with the relative position S3 of UAV 3 in the cluster formation before takeoff as the coordinate origin (0, 0), when UAV 3 moves to the position S'3 after takeoff, its coordinates become (χ'3, ζ'3), and the pixel coordinate values ​​of the corresponding passive infrared reflective ball of UAV 3 on the imaging plane of the infrared camera of UAV 1 and UAV 4 become (x' 13 , y' 13 ) and (x' 43 , y' 43 ), according to the coordinate geometry relationship, we can get: χ'3=x 43 -x' 43 ,ζ'3=x' 13 -x 13 Similarly, the relative coordinates of the cluster formation of UAV 2 in its χ2-ζ2 obtuse angle relative coordinate system are (χ'2, ζ'2), where χ'2 = x' 42 -x 42 ,ζ'2=x 12 -x' 12 .

8. The method for relative positioning of a swarm of drones at night according to claim 1, characterized in that: The directed communication topology is specifically as follows: drone 1 has a one-way communication relationship with drone 2, drone 3 and drone 4; drone 4 has a one-way communication relationship with drone 2 and drone 3; drone 2 has a two-way communication relationship with drone 3, in which drone 1 is the information sender.

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