A tethered UAV precision assisted landing device, method and system

Abstract

The present invention discloses a tethered UAV precision assisted landing device, method, and system, comprising: a host computer communicating with a camera and a power unit; the camera collecting image information of the tethered platform and transmitting it to the host computer; the host computer processing the received information and issuing control instructions to the power unit to control the operating state of the power unit; a tethered cable retracting device and a lower computer both located within a housing; a through hole provided in the middle of the top of the housing, through which the tethered cable is connected to the UAV; the tethered cable retracting device connected to the tethered cable; the lower computer connected to the tethered cable retracting device and simultaneously receiving signals transmitted by the host computer to control the operating state of the tethered cable retracting device. The present invention discloses a method for pulling a UAV using a tethered cable retracting device when the UAV's altitude is less than a certain altitude threshold. This method can ensure that the UAV accurately lands at a preset parking position, eliminating the centimeter-level error associated with single-view landing.

Description

Technical Field

[0001] The present invention belongs to the technical field of unmanned aerial vehicle (UAV) navigation and positioning, and relates to a tethered UAV precision assisted landing device, method and system. Background Art

[0002] Tethered drones use ground-based electricity transmitted via tethered cables as their power source, replacing traditional lithium batteries, enabling them to hover for extended periods of time. Currently, tethered drones are primarily used for fixed-point communications support, image telemetry, and television broadcasting.

[0003] As drones become increasingly widely used in production and life, the requirements for precise drone identification and landing are becoming increasingly stringent. Currently, the most widely used solutions for precise drone landing include RTK GPS and image recognition (vision). RTK GPS-based precision landing technology uses an RTK base station to transmit the drone's precise position in a geodetic coordinate system. This approach to precise drone landing relies primarily on RTK GPS's centimeter-level positioning accuracy. Simply providing a precise target landing location, combined with the drone's own precise real-time position, allows for precise landing. However, the system relies on numerous components (mobile stations, fixed stations, antennas, wireless data transmission, etc.), resulting in high costs. Image recognition technology uses onboard drone image recognition equipment to identify the target landing point on the ground and determine the relative position between the target landing point and the drone. This approach, for example, uses QR code recognition for landing. This solution offers significant advantages over RTK GPS landing technology, achieving centimeter-level accuracy, but suffers from significant errors during the single-vision landing process. Summary of the Invention

[0004] The present invention aims to provide a tethered drone precision-assisted landing device, method, and system to address two issues: 1) the high cost and numerous components of existing RTK GPS positioning systems; and 2) the large errors in image recognition positioning systems during single-view landing.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A tethered UAV precision assisted landing device, comprising: a UAV and a tethered platform;

[0007] The drone includes a host computer, a camera, and a power unit. The host computer is connected to the camera and the power unit respectively. The camera collects image information of the tethered platform and sends it to the host computer. The host computer processes the received information and sends instructions to the power unit to control its working status.

[0008] The tethered platform includes a shell, a tethered cable retracting device, an AGV trolley; a lower computer and a tethered cable; the AGV trolley, the tethered cable retracting device and the lower computer are all located inside the shell; a through hole is provided in the middle position of the top of the shell, and the tethered cable is connected to the drone through the through hole; the tethered cable retracting device is connected to the tethered cable; the lower computer is connected to the tethered cable retracting device and the AGV trolley, and the lower computer is electrically connected to the upper computer. The lower computer receives signals sent by the upper computer and controls the working status of the tethered cable retracting device.

[0009] A further improvement of the present invention is:

[0010] Furthermore, both the drone and the tethered platform include batteries. The drone's battery is connected to the host computer, camera and power unit to supply power to the host computer, camera and power unit; the tethered platform's battery is connected to the lower computer, AGV trolley and tethered cable retraction device to supply power to the lower computer, AGV trolley and tethered cable retraction device; the lower computer determines the battery power of the tethered platform's battery. If it is less than the minimum power, the lower computer drives the AGV trolley to move to the charging point to charge the tethered platform's battery.

[0011] Furthermore, a red light and a green light are provided on the top of the shell; there are two red lights and two green lights, and the red lights and the green lights are evenly arranged around the through hole; the camera is a monocular camera; the minimum power is set manually; the battery of the tethered platform supplies power to the battery of the drone through the tethered cable.

[0012] A tethered UAV precision assisted landing method, comprising:

[0013] Receive image information of the tethered platform captured by the camera;

[0014] Based on the received image information of the tethered platform, the relative height information and heading information of the UAV and the system platform are obtained;

[0015] Based on the relative altitude information and heading information, the driving device adjusts the flight attitude of the UAV for landing;

[0016] Determine whether the relative height between the UAV and the system platform is greater than the set height threshold. If so, drive the tethered cable retraction device to keep the tethered cable straight; if not, drive the tethered cable retraction device to retract the cable to complete the landing of the UAV.

[0017] Furthermore, based on the received image information of the tethered platform, the relative height information of the UAV and the system platform is obtained; specifically:

[0018] The image of the tethered platform is calibrated using a checkerboard grid to identify the characteristic intensities of red and green lights. The position of the drone is then determined by determining the positions of the corresponding pixels on the image.

[0019] Based on the grayscale reconstruction algorithm, the coordinates of the red and green lights in the image are obtained;

[0020] Based on the Perspective-n-Point algorithm, the real coordinates of the built-in light points are compared, and the coordinate transformation of the world coordinate system, camera coordinate system, image coordinate system and pixel coordinate system is performed to obtain the camera position, that is, the height of the drone relative to the apron.

[0021] Furthermore, based on the grayscale reconstruction algorithm, the coordinates of the red and green lights in the image are obtained; specifically:

[0022] Identify the red and green colors of the image to obtain the red light image ImgRedLight and the green light image ImgGreenLight. Based on the grayscale centroid algorithm, the centroid of the bright spot is obtained. For targets with uneven brightness, the extreme value method is used to obtain the point with the maximum light intensity g. max , and determine a threshold K = g max -g; Determine the elements larger than K on both sides of the threshold and obtain their center of gravity as the center of the target; for an image f of size M*N, the gray value of the pixel f ij All those exceeding the threshold K participate in the center of gravity processing, so the center of gravity coordinates are:

[0023]

[0024] in

[0025] You can get the red feature point coordinates maxR1, maxR2, and the green feature point coordinates maxG1, maxG2.

[0026] Furthermore, the heading information of the drone is obtained, specifically:

[0027] The heading information of the UAV, i.e. the angle of the UAV relative to the tethered platform, sets the positive direction of the tethered platform; the number of light points in the image is greater than or equal to 3;

[0028] If there is only one green dot, let the coordinates of the red light R1 in the image be (x0, y0), and R2 be (x1, y1). The relative angle of the drone is:

[0029]

[0030] If there is only one red dot, let the coordinates of the green light G1 in the image be (x1, y1), and G2 be (x2, y2). The relative angle of the drone is:

[0031]

[0032] The number of light points in the image is 4:

[0033] Based on the Perspective-n-Point algorithm, compare the coordinates of the four lights in the world coordinate system with the coordinates of the image coordinate system to obtain the rotation matrix nX, whose direction vector is (x, y, z);

[0034] The relative angle of the drone is:

[0035]

[0036] Furthermore, it is determined whether the relative height between the UAV and the system platform is greater than the set height threshold. If so, the tethered cable retraction device is driven to keep the tethered cable in a straight state. Specifically, when the relative height between the UAV and the system platform is greater than 0.5m, the height of the UAV continues to drop, the upper computer sends a signal to the lower computer, and the lower computer drives the tethered cable retraction device to keep the tethered cable in a straight state, but does not generate tension on the UAV.

[0037] Furthermore, the tethered cable retracting device is driven to retract the cable to complete the landing of the UAV; specifically:

[0038] When the relative height between the UAV and the system platform is less than 0.5m, the upper computer sends a signal to the lower computer, and the lower computer drives the tethered cable retraction device to retract the cable. The retraction force of the tethered cable retraction device is greater than the lift of the UAV, causing the UAV to land accurately.

[0039] A tethered UAV precision assisted landing system, comprising:

[0040] A receiving module, configured to receive image information of the tethered platform captured by the camera;

[0041] an acquisition module, wherein the acquisition module acquires relative height information and heading information of the UAV and the system platform based on the received image information of the tethered platform;

[0042] A driving module, which drives a driving device to adjust the flight attitude of the UAV for landing based on the relative height information and the heading information;

[0043] The judgment module is used to determine whether the relative height between the UAV and the system platform is greater than a set threshold. If so, the tethered cable retraction device is driven to keep the tethered cable straight; if not, the tethered cable retraction device is driven to retract the cable to complete the landing of the UAV.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention uses a camera to capture images of the tethered platform and transmits them to a host computer for processing. The host computer then issues commands to the power unit to control its operating status. A lower computer is electrically connected to the host computer and receives signals from the host computer to control the operating status of the tethered cable retracting and extending device. The present invention has a simple structure and lacks complex components, significantly reducing costs.

[0046] Furthermore, the present invention calculates the relative height and heading information of the UAV and the system platform based on the image information obtained by the monocular camera, and then uses a tethered cable retraction device to pull the UAV when the relative height information is less than the height threshold, ensuring that the UAV lands accurately at the preset parking position, thereby eliminating the centimeter-level error of single visual landing. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0048] Figure 1 A schematic diagram of the drone and tethered platform of the present invention;

[0049] Figure 2 A schematic diagram of the connection relationship between the components of the drone and the tethered platform of the present invention;

[0050] Figure 3 A schematic diagram of the relative positions and prescribed directions of the UAV and the tethered platform of the present invention;

[0051] Figure 4 The image captured by the camera;

[0052] Figure 5 A diagram of a mooring cable retracting and releasing device according to the present invention;

[0053] Figure 6 This is a flow chart of the tethered UAV precision assisted landing method of the present invention;

[0054] Figure 7 This is a structural diagram of the tethered UAV precision assisted landing system of the present invention;

[0055] Figure 8 Schematic diagram of the Perspective-n-Point algorithm used in the present invention;

[0056] Figure 9 This is a design diagram of the autonomous landing system framework of the present invention.

[0057] Among them, 1-UAV; 2-tethered cable; 3-tethered platform; 4-AGV car; 5-first red light; 6-first green light; 7-second green light; 8-second red light; 9-tethered cable retracting device; 10-upper computer; 11-camera; 12-power unit; 13-lower computer; 15-tethered platform battery; 16-UAV battery. DETAILED DESCRIPTION

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0059] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0060] 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.

[0061] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0062] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0063] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0064] The present invention is described in further detail below with reference to the accompanying drawings:

[0065] See also Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 and Figure 5 , the present invention discloses a tethered UAV precision assisted landing device, comprising: a UAV 1 and a tethered platform 3;

[0066] The drone 1 includes a host computer 10, a camera 11, and a power unit 12; the host computer 10 is connected to the camera 11 and the power unit 12 respectively; the camera 11 collects image information of the tethered platform 3 and sends it to the host computer 10; the host computer 10 processes the received information and issues instructions to the power unit 12 to control the working state of the power unit 12;

[0067] The tethering platform 3 includes a shell, a tethering cable retracting device 9, an AGV trolley 4, a lower computer 13 and a tethering cable 2; the AGV trolley 4, the tethering cable retracting device 9 and the lower computer 13 are all located inside the shell; a through hole is provided in the middle position of the top of the shell, and the tethering cable 2 is connected to the drone 1 through the through hole; the tethering cable retracting device 9 is connected to the tethering cable 2; the lower computer 13 is connected to the tethering cable retracting device 9 and the AGV trolley 4, and the lower computer 13 is electrically connected to the upper computer 10, and the lower computer 13 receives the signal sent by the upper computer 10 to control the working state of the tethering cable retracting device 9.

[0068] Both the drone 1 and the tethered platform 3 include batteries. The drone's battery 16 is connected to the host computer 10, camera 11, and power unit 12, providing power to these three components. The tethered platform's battery 15 is connected to the lower computer 13, the AGV 4, and the tethered cable retractor 9, providing power to these components. The lower computer 13 determines the battery level of the tethered platform's battery 15. If the battery level is below the minimum, the lower computer 13 drives the AGV 4 to a charging station to charge the tethered platform's battery 15. This minimum level is manually set. The tethered platform's battery 15 supplies power to the drone's battery 16 via the tethered cable 2.

[0069] A red light and a green light are provided on the top of the housing; there are two red lights and two green lights; the red light includes a first red light 5 and a first red light 8, and the green light includes a first green light 6 and a second green light 7;

[0070] The first red light 5, the second red light 8, the first green light 6 and the second green light 7 are evenly arranged around the through hole; the camera 11 is a monocular camera.

[0071] See also Figure 6 The present invention discloses a tethered UAV precision assisted landing method, comprising:

[0072] S101, receiving image information of the tethered platform 3 captured by the camera 11;

[0073] S102, based on the received image information of the tethered platform 3, obtaining relative height information and heading information between the UAV 1 and the system platform 3;

[0074] S102.1, calibrate the image of tethered platform 3 using a checkerboard grid to identify the characteristic intensities of red and green lights, and determine the position of the drone by determining the positions of the corresponding pixels of the red and green lights on the image;

[0075] S102.2, based on the grayscale reconstruction algorithm, obtain the coordinates of the red light and the green light in the image;

[0076] Identify the red and green colors of the image to obtain the red light image ImgRedLight and the green light image ImgGreenLight. Based on the grayscale centroid algorithm, obtain the centroid of the bright spot. For targets with uneven brightness, use the extreme value method to obtain the point with the maximum light intensity and determine a threshold. Determine the elements on both sides of the threshold that are greater than the threshold and obtain their centroid position as the center of the target. For an image f of size M*N, the grayscale value of the pixel f ij All those exceeding the threshold participate in the center of gravity processing, so the center of gravity coordinates are:

[0077]

[0078] You can get the red feature point coordinates maxR1, maxR2, and the green feature point coordinates maxG1, maxG2.

[0079] S102.3, based on the Perspective-n-Point algorithm, compare the real coordinates of the built-in light points and perform coordinate transformations on the world coordinate system, camera coordinate system, image coordinate system, and pixel coordinate system to obtain the camera position, that is, the height of the drone relative to the landing pad.

[0080] Get the heading information of UAV 1, specifically:

[0081] The heading information of the UAV, i.e. the angle of the UAV relative to the tethered platform (3), sets the positive direction of the tethered platform; the number of light points in the image is greater than or equal to 3;

[0082] If there is only one green dot, let the coordinates of the red light R1 in the image be (x0, y0), and R2 be (x1, y1). The relative angle of the drone is:

[0083]

[0084] If there is only one red dot, let the coordinates of the green light G1 in the image be (x1, y1), and G2 be (x2, y2). The relative angle of the drone is:

[0085]

[0086] The number of light points in the image is 4:

[0087] Based on the Perspective-n-Point algorithm, compare the coordinates of the four lights in the world coordinate system with the coordinates of the image coordinate system to obtain the rotation matrix nX, whose direction vector is (x, y, z);

[0088] The relative angle of the drone is:

[0089]

[0090] S103 , based on the relative altitude information and the heading information, the driving device 12 is driven to adjust the flight attitude of the UAV 1 for landing.

[0091] S104, determine whether the relative height between the UAV 1 and the system platform 3 is greater than the set threshold. If so, drive the tethered cable retracting device 9 to keep the tethered cable 2 straightened; if not, drive the tethered cable retracting device 9 to retract the cable to complete the landing of the UAV.

[0092] When the relative height between drone 1 and system platform 3 exceeds 0.5m, drone 1 continues to descend. Host computer 10 sends a signal to slave computer 13, which activates tether cable retraction and unwinding device 9 to keep tether cable 2 straightened without exerting tension on the drone. When the relative height between drone 1 and system platform 3 drops below 0.5m, host computer 10 sends a signal to slave computer 13, which activates tether cable retraction and unwinding device 9 to retract the cable. The retraction force from the tether cable retraction and unwinding device 9 exceeds the drone's lift, allowing the drone to land precisely.

[0093] See also Figure 7 The present invention discloses a tethered UAV precision assisted landing system, comprising:

[0094] A receiving module, which is used to receive image information of the tethered platform 3 collected by the camera 11;

[0095] An acquisition module, which acquires relative height information and heading information between the UAV 1 and the system platform 3 based on the received image information of the tethered platform 3;

[0096] The driving module drives the driving device 12 to adjust the flight attitude of the UAV for landing based on the relative height information and the heading information;

[0097] The judgment module is used to judge whether the relative height between the UAV 1 and the system platform 3 is greater than the set threshold. If so, the tethered cable retracting device 9 is driven to keep the tethered cable 2 straightened; if not, the tethered cable retracting device 9 is driven to retract the cable to complete the landing of the UAV.

[0098] Example:

[0099] The present invention discloses a tethered UAV precision assisted landing method, comprising the following steps:

[0100] Step S1: The camera at the bottom of the drone captures the image of two red and two green lights at the top of the landing pad and transmits it to the host computer;

[0101] Step S2: Calculate the relative height between the drone and the landing pad and the heading of the drone through a visual algorithm;

[0102] Step S3: The host computer communicates with the flight control system to achieve visual control of the UAV to adjust its attitude and land. At the same time, the tethered cable retraction device is in a low torque retraction mode to keep the cable straight at all times.

[0103] Step S4: When the visual control lands at a height of 0.5m, the system switches to the tethered cable assisted landing mode. The tethered cable retracting device provides a lift greater than that of the drone, enabling the drone to land accurately.

[0104] Step S1 includes: transmitting the image of the monocular camera at the bottom of the drone to the host computer in real time.

[0105] Step S2 includes:

[0106] Step S21: Process the camera image and calibrate it using a checkerboard to obtain a processed image. The camera image is as follows: Figure 4 As shown;

[0107] Step S22: Identify the red and green colors of the image to obtain the red light image ImgRedLight and the green light image ImgGreenLight. Use the grayscale centroid algorithm to obtain the centroid of the bright spot. For the target with uneven brightness (the light spot in this invention), first use the extreme value method to find the point with the maximum light intensity g. max, then determine a threshold K = g max -g (parameter g is 10-20), judge the elements larger than K on both sides of the threshold, and find their center of gravity as the center of the target. For an image f of size M*N, the grayscale f of the pixel ij All values ​​exceeding the threshold K are processed as the center of gravity, so the coordinates of the center of gravity are:

[0108]

[0109] in,

[0110] Use this method to obtain the coordinates of the red feature points maxR1, maxR2, and the coordinates of the green feature points maxG1, maxG2;

[0111] Step S23: Use the Perspective-n-Point algorithm, that is, the real coordinates of N spatial points in the world coordinate system (3-4 spatial points in this invention) and the projection of these spatial points on the image are known, and the position of the camera can be obtained. Compare the real coordinates of the built-in light point, and perform coordinate transformation on the world coordinate system, camera coordinate system, image coordinate system, and pixel coordinate system to obtain the camera position, that is, the height of the drone. The algorithm principle is as follows: Figure 8 shown.

[0112] Step S24 calculates the drone's heading, i.e., the drone's angle relative to the landing pad, droneOrientation, and specifies the positive direction as Figure 3 As shown, the calculation is divided into three cases:

[0113] The number of light points in the image is greater than or equal to 3:

[0114] If there is only one green dot, let the coordinates of the red light R1 in the image be (x0, y0), R2 be (x1, y1), and the relative angle of the drone be

[0115]

[0116] If there is only one red dot, let the coordinates of the green light G1 in the image be (x1, y1), G2 be (x2, y2), and the relative angle of the drone be

[0117]

[0118] The number of light points in the image is 4:

[0119] Use the Perspective-n-Point algorithm to compare the world coordinates of the four lights with the image coordinates to solve the rotation matrix nX, whose direction vector is (x, y, z)

[0120] Relative angle of drone

[0121]

[0122] Step S3 includes: when the relative height of the UAV is greater than 0.5m, the height of the UAV continues to decrease, and at the same time, Figure 5 The mooring cable retracting device in the mooring mechanism shown maintains low torque and continuously reels the line.

[0123] In step S4, when the UAV is less than 0.5m in height, the tethered cable retracting device switches to high torque, pulling the UAV to land completely. Figure 9 As shown in the figure, the entire system architecture combines the MVC framework with the ROS framework. The top-level view layer displays camera images, displays aircraft attitude messages, and provides a user interface for GUI interaction. The model layer encapsulates the logical control of the drone, including operations such as position, speed, and attitude control. The control layer encapsulates the general drone flight control layer, enabling communication with the flight control system to control the drone. A further layer, a visual algorithm toolkit, encapsulates various visual algorithms. These algorithms use camera images as input, perform visual processing, and then hand off logical control to the model layer. The model layer then outputs to the control layer to implement automatic visual control of the drone. The layers are loosely coupled and adhere to the ROS framework. Communication between the layers is implemented according to ROS communication mechanism standards.

[0124] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A tethered UAV precision assisted landing device, characterized in that: include: UAV (1) and tethered platform (3); The unmanned aerial vehicle (1) comprises a host computer (10), a camera (11) and a power unit (12); the host computer (10) is connected to the camera (11) and the power unit (12) respectively; the camera (11) collects image information of the tethered platform (3) and sends it to the host computer (10); the host computer (10) processes the received information and sends instructions to the power unit (12) to control the working state of the power unit (12); The mooring platform (3) includes a shell, a mooring cable retracting device (9), and an AGV trolley (4); a lower computer (13) and a mooring cable (2); the AGV trolley (4), the mooring cable retracting device (9), and the lower computer (13) are all located inside the shell; a through hole is provided at the middle position of the top of the shell, and the mooring cable (2) is connected to the drone (1) through the through hole; the mooring cable retracting device (9) is connected to the mooring cable (2); the lower computer (13) is connected to the mooring cable retracting device (9) and the AGV trolley (4), and the lower computer (13) is electrically connected to the upper computer (10), and the lower computer (13) receives a signal sent by the upper computer (10) to control the working state of the mooring cable retracting device (9); A red light and a green light are arranged on the top of the shell; there are two red lights and two green lights, and the red lights and the green lights are evenly arranged around the through hole.

2. The tethered UAV precision assisted landing device according to claim 1, characterized in that: The drone (1) and the mooring platform (3) both include batteries. The battery (16) of the drone (1) is connected to a host computer (10), a camera (11), and a power unit (12) to supply power to the host computer (10), the camera (11), and the power unit (12); the battery (15) of the mooring platform (3) is connected to a lower computer (13), an AGV trolley (4), and a mooring cable retracting and releasing device (9); and supplies power to the lower computer (13), the AGV trolley (4), and the mooring cable retracting and releasing device (9); the lower computer (13) determines the battery power of the battery (15) of the mooring platform. If the battery power is less than the minimum power, the lower computer (13) drives the AGV trolley (4) to move to a charging location to charge the battery (15) of the mooring platform.

3. The tethered UAV precision assisted landing device according to claim 2, characterized in that: The camera (11) is a monocular camera; the minimum power is set manually; the battery (15) of the tethered platform supplies power to the battery (16) of the drone via a tethered cable (2).

4. A landing method based on the tethered UAV precision assisted landing device according to any one of claims 1 to 3, characterized in that: include: receiving image information of the moored platform (3) collected by the camera (11); Based on the received image information of the tethered platform (3), relative height information and heading information of the UAV (1) and the tethered platform (3) are obtained; Based on the relative height information and the heading information, the driving power device (12) adjusts the flight attitude of the UAV (1) to land; Determine whether the relative height between the UAV (1) and the tethered platform (3) is greater than a set height threshold; if so, drive the tethered cable retracting device (9) to keep the tethered cable (2) in a straightened state; if not, drive the tethered cable retracting device (9) to retract the cable, thereby completing the landing of the UAV; The method of obtaining relative height information between the drone (1) and the tethered platform (3) based on the received image information of the tethered platform (3) is as follows: The image of the tethered platform (3) is calibrated using a checkerboard grid to identify the characteristic intensities of the red and green lights, and the position of the drone is obtained by determining the positions of the corresponding pixels of the red and green lights on the image; Based on the grayscale reconstruction algorithm, the coordinates of the red and green lights in the image are obtained; Based on the Perspective-n-Point algorithm, the real coordinates of the built-in light points are compared, and the coordinate transformation of the world coordinate system, camera coordinate system, image coordinate system and pixel coordinate system is performed to obtain the camera position, that is, the relative height of the drone to the landing pad; The grayscale reconstruction algorithm is used to obtain the coordinates of the red and green lights in the image; specifically: Identify the red and green colors of the image to obtain the red light image ImgRedLight and the green light image ImgGreenLight. Based on the grayscale centroid algorithm, the centroid of the bright spot is obtained. For targets with uneven brightness, the extreme value method is used to obtain the point with the maximum light intensity g. max , and determine a threshold K = g max -g, parameter g is 10-20; determine the elements larger than K on both sides of the threshold, and obtain their center of gravity as the center of the target; for an image f of size M*N, the gray value of the pixel f ij All those exceeding the threshold K participate in the center of gravity processing, so the center of gravity coordinates are: in, You can get the red feature point coordinates maxR1, maxR2, and the green feature point coordinates maxG1, maxG2.

5. The tethered UAV precision assisted landing method according to claim 4, characterized in that: The method of obtaining relative height information between the drone (1) and the tethered platform (3) based on the received image information of the tethered platform (3) is as follows: The image of the tethered platform (3) is calibrated using a checkerboard grid to identify the characteristic intensities of the red and green lights, and the position of the drone is obtained by determining the positions of the corresponding pixels of the red and green lights on the image; Based on the grayscale reconstruction algorithm, the coordinates of the red and green lights in the image are obtained; Based on the Perspective-n-Point algorithm, the real coordinates of the built-in light points are compared, and the coordinate transformation of the world coordinate system, camera coordinate system, image coordinate system and pixel coordinate system is performed to obtain the camera position, that is, the height of the drone relative to the apron.

6. The tethered UAV precision assisted landing method according to claim 4, characterized in that: The obtaining of the heading information of the UAV (1) is specifically as follows: The UAV heading information, i.e. the angle of the UAV relative to the tethered platform (3), sets the positive direction of the tethered platform; the number of light points in the image is greater than or equal to 3; If there is only one green dot, let the coordinates of the red light R1 in the image be (x0, y0), and R2 be (x1, y1). The relative angle of the drone is: If there is only one red dot, let the coordinates of the green light G1 in the image be (x1, y1), and G2 be (x2, y2). The relative angle of the drone is: The number of light points in the image is 4: Based on the Perspective-n-Point algorithm, compare the coordinates of the four lights in the world coordinate system with the coordinates of the image coordinate system to obtain the rotation matrix nX, whose direction vector is (x, y, z); The relative angle of the drone is:

7. The tethered UAV precision assisted landing method according to claim 6, characterized in that: The method comprises judging whether the relative height between the UAV (1) and the mooring platform (3) is greater than a set height threshold, and if so, driving the mooring cable retracting and releasing device (9) so that the mooring cable (2) remains in a straightened state; specifically, when the relative height between the UAV (1) and the mooring platform (3) is greater than 0.5 m, the height of the UAV (1) continues to decrease, the upper computer (10) sends a signal to the lower computer (13), and the lower computer (13) drives the mooring cable retracting and releasing device (9) so that the mooring cable (2) remains in a straightened state, but does not generate a pulling force on the UAV.

8. The tethered UAV precision assisted landing method according to claim 7, characterized in that: The driving tethered cable retracting device (9) is used to retract the cable to complete the landing of the UAV; specifically: When the relative height between the UAV (1) and the mooring platform (3) is less than 0.5 m, the upper computer (10) sends a signal to the lower computer (13), and the lower computer (13) drives the mooring cable retracting device (9) to retract the cable. The retracting force of the mooring cable retracting device (9) is greater than the lift of the UAV, so that the UAV can be dragged and landed accurately.

9. A tethered UAV precision assisted landing system, characterized in that: include: A receiving module, the receiving module being used to receive image information of the moored platform (3) collected by the camera (11); an acquisition module, wherein the acquisition module acquires relative height information and heading information of the UAV (1) and the tethered platform (3) based on the received image information of the tethered platform (3); A driving module, wherein the driving module drives a power device (12) to adjust the flight attitude of the UAV for landing based on the relative height information and the heading information; A judgment module, the judgment module is used to judge whether the relative height between the UAV (1) and the mooring platform (3) is greater than a set threshold value, and if so, drive the mooring cable retracting device (9) to keep the mooring cable (2) in a straightened state; if not, drive the mooring cable retracting device (9) to retract the cable to complete the landing of the UAV; The method of obtaining relative height information between the drone (1) and the tethered platform (3) based on the received image information of the tethered platform (3) is as follows: The image of the tethered platform (3) is calibrated using a checkerboard grid to identify the characteristic intensities of the red and green lights, and the position of the drone is obtained by determining the positions of the corresponding pixels of the red and green lights on the image; Based on the grayscale reconstruction algorithm, the coordinates of the red and green lights in the image are obtained; Based on the Perspective-n-Point algorithm, the real coordinates of the built-in light points are compared, and the coordinate transformation of the world coordinate system, camera coordinate system, image coordinate system and pixel coordinate system is performed to obtain the camera position, that is, the relative height of the drone to the landing pad; The grayscale reconstruction algorithm is used to obtain the coordinates of the red and green lights in the image; specifically: Identify the red and green colors of the image to obtain the red light image ImgRedLight and the green light image ImgGreenLight. Based on the grayscale centroid algorithm, the centroid of the bright spot is obtained. For targets with uneven brightness, the extreme value method is used to obtain the point with the maximum light intensity g. max , and determine a threshold K = g max -g, parameter g is 10-20; determine the elements larger than K on both sides of the threshold, and obtain their center of gravity as the center of the target; for an image f of size M*N, the gray value of the pixel f ij All those exceeding the threshold K participate in the center of gravity processing, so the center of gravity coordinates are: in, You can get the red feature point coordinates maxR1, maxR2, and the green feature point coordinates maxG1, maxG2.

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