An automatic landing method and system for unmanned aerial vehicles

Abstract

This invention relates to an automatic landing method and system for unmanned aerial vehicles (UAVs). The method includes: acquiring and calculating the position of the UAV based on real-time visible light images and real-time infrared images to obtain a first calculated position and a second calculated position; fusing the ranging distance, the first calculated position, and the second calculated position according to a fusion strategy to obtain a fused position of the UAV, thereby guiding the UAV to land in a target area. The fusion strategy includes: when both the first and second calculated positions are obtained simultaneously, using either the first calculated position or the second calculated position as the fused position based on the error between the first calculated position and the ranging distance; when the real-time visible light images and real-time infrared images are incomplete, and the ranging distance of the UAV is less than a second preset value, using either the first calculated angle or the second calculated angle, along with the ranging distance, as the fused position. The method of this invention can improve the positioning and recognition accuracy and reliability during the UAV landing process.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) flight technology, and in particular to an automatic landing method and system for UAVs. Background Technology

[0002] The automatic landing function of multi-rotor drones enables them to land precisely and automatically on designated platforms without external human intervention or operation. It is a crucial component of fully autonomous drone operations, providing fundamental support for autonomous tasks such as automatic recovery and recharging. Currently, there are two main methods for implementing automatic drone landing technology: RTK (Real-time kinematic) carrier phase differential positioning and image recognition positioning. RTK positioning uses a data link to transmit GPS (Global Positioning System) differential positioning information, providing the drone's position relative to the landing platform. Image recognition positioning involves pre-deploying image tags on the takeoff and landing platform, which are then identified by the drone's onboard vision module to calculate the drone's position relative to the platform.

[0003] However, the aforementioned automatic landing technologies relying on single-source positioning methods still have shortcomings. On the one hand, in practical applications, these technologies often suffer from poor anti-interference capabilities and low terminal landing positioning accuracy, affecting position recognition accuracy during automatic landing. Specifically, existing RTK positioning methods require an additional air-to-ground communication link, and their positioning accuracy depends on the quality of the communication signal, making them susceptible to electromagnetic interference. Furthermore, when the UAV is too close to the platform during terminal landing, excessively strong communication signals can cause congestion, affecting the real-time nature of positioning information. Image recognition methods rely on ambient lighting; when ambient light is poor, the visual image recognition effect is significantly reduced. Moreover, at low flight altitudes, image recognition methods may suffer from insufficient field-of-view coverage, making image recognition impossible. Therefore, neither method can guarantee effective terminal landing accuracy, especially when the platform is moving, which further amplifies the sensitivity to terminal accuracy and degrades landing accuracy further.

[0004] On the other hand, to improve the accuracy of position recognition during automatic landing, the RTK positioning method requires the use of a high-precision GPS module and antenna, and necessitates the additional installation and deployment of data links, consuming valuable bandwidth resources of the drone and significantly impacting the original equipment installation layout. Image recognition positioning methods, in order to balance recognition accuracy at both high and low altitudes, place high demands on camera resolution and the hardware running the graphics algorithms, increasing equipment costs. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides an automatic landing method and system for unmanned aerial vehicles (UAVs), which solves the technical problems of low positioning accuracy during UAV landing, insufficient guidance capability in the terminal phase of landing, especially for automatic landing of mobile platforms, and significant environmental influence on the perception capability of the target landing area in the prior art.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0009] In a first aspect, embodiments of the present invention provide an automatic landing method for an unmanned aerial vehicle (UAV), used to guide the UAV to land in a target area, wherein the UAV is equipped with onboard components, the target area is equipped with a visible light beacon, and an infrared light beacon is configured in combination with the visible light beacon; the method includes:

[0010] The airborne components acquire real-time visible light and real-time infrared light images in the direction of the target area; the airborne components acquire the distance between the UAV and the target area based on the ranging sensor;

[0011] The airborne component performs position calculation based on the real-time visible light image to obtain a first calculated position of the UAV relative to the target area; the first calculated position includes a first calculated angle and a first calculated distance; the airborne component performs position calculation based on the real-time infrared light image to obtain a second calculated position of the UAV relative to the target area; the second calculated position includes a second calculated angle and a second calculated distance;

[0012] The airborne components fuse the ranging distance, the first calculated position, and the second calculated position according to a preset fusion strategy to obtain the fused position of the UAV, and guide the UAV to land in the target area based on the fused position;

[0013] The preset fusion strategy includes: when the airborne components simultaneously obtain the first calculated position and the second calculated position, calculating the error between the first calculated distance and the ranging distance; when the error is less than a first preset value, using the first calculated position as the fused position; when the error is greater than or equal to the first preset value, using the second calculated position as the fused position; and...

[0014] When the real-time visible light image and the real-time infrared light image are incomplete, and the ranging distance of the UAV is less than the second preset value, either the first solution angle or the second solution angle, and the ranging distance are used as the fusion position.

[0015] Optionally, the infrared beacon includes at least three infrared point light sources; the infrared point light sources include: a central point light source located at the geometric center of the visible light beacon, and at least two edge point light sources located at non-geometric center locations of the visible light beacon;

[0016] The airborne components perform position calculation based on the real-time infrared image, including:

[0017] The airborne component identifies infrared point light sources in the real-time infrared light image;

[0018] The airborne component determines the homography matrix corresponding to the real-time infrared point light source image based on the real-time infrared image and the orthophoto image corresponding to the infrared point light source; and determines the second solution angle of the UAV relative to the target area based on the homography matrix; wherein, the orthophoto image is an image pre-saved locally on the airborne component;

[0019] The airborne component obtains the second calculated distance of the UAV relative to the target area based on the pixel distance and actual distance between any two infrared point light sources in the real-time infrared light image and the transformation of the intrinsic and extrinsic parameters of the infrared light image acquisition device.

[0020] The airborne component uses the second calculated angle and the second calculated distance as the second calculated position.

[0021] Optionally, the visible light beacon is square, and the infrared light beacon includes four edge point light sources, with the four infrared point light sources being arranged one-to-one at the four right-angle positions of the visible light beacon.

[0022] Optionally, the visible light beacon is an AprilTag image;

[0023] The airborne components perform position calculation based on the real-time visible light image, including:

[0024] The airborne component identifies the real-time AprilTag image in the real-time visible light image, and based on the real-time AprilTag image and according to the actual size of the AprilTag image, uses the AprilTag algorithm to calculate the first calculated distance and the first calculated angle of the UAV relative to the target area, which are used as the first calculated position.

[0025] Optionally, the ranging sensor is a laser ranging sensor;

[0026] The airborne components acquire the distance between the UAV and the target area based on a ranging sensor, including:

[0027] The airborne components acquire the real-time ranging distance of the target area through the laser ranging sensor;

[0028] The airborne component determines the range (X0, Y0, z0) of the target area and the position (x, y, z) of the UAV based on the first or second solution position, and determines whether x∈X0 and y∈Y0 based on the first or second solution position.

[0029] If so, the real-time ranging distance is taken as the ranging distance of the UAV relative to the target area.

[0030] Optionally, guiding the drone to land in the target area based on the fused location includes:

[0031] S1. The airborne components determine, based on the current fusion position, whether the distance between the drone and the target area is within the first altitude range. If so,

[0032] The drone's current fused position is sent to the navigation controller, which then generates first navigation information based on the current fused position to guide the drone to align with the geometric center of the visible light beacon and descend.

[0033] S2. The onboard components determine whether the distance between the drone and the target area is within the second altitude range based on the drone's current fusion position. If so,

[0034] The onboard components stop acquiring visible light images, lock onto the center point light source of the infrared beacon, acquire the distance of the UAV through the ranging sensor, and send the distance to the navigation controller so that the navigation controller can generate second navigation information based on the distance, guide the UAV to align with the center point light source of the infrared beacon, and land in the target area.

[0035] Optionally, prior to S1, the method further includes:

[0036] S0. When a landing command is received, the onboard components identify visible light beacons or infrared light beacons in the real-time visible light image and the real-time infrared light image;

[0037] When either the visible light beacon or the infrared light beacon is detected, the visible light beacon or the infrared light beacon in the current field of view is locked, the first calculated position corresponding to the visible light beacon or the second calculated position corresponding to the infrared light beacon is calculated, the fusion position of the UAV is determined according to the fusion strategy and sent to the navigation controller, so that the navigation controller generates third navigation information based on the fusion position, guides the UAV to move directly above the target area and synchronizes with the horizontal movement speed of the target area.

[0038] Secondly, embodiments of the present invention provide an automatic landing system for a drone, used to guide the drone to land in a target area, the landing system comprising:

[0039] Visible light beacons are placed within the target area;

[0040] An infrared light beacon is configured in combination with the visible light beacon.

[0041] Airborne components, pluggably mounted on the UAV, said airborne components include:

[0042] Visible light image acquisition device, used to acquire real-time visible light images in the direction of a target area;

[0043] An infrared light image acquisition device is used to acquire real-time infrared light images in the direction of a target area;

[0044] Ranging sensors are used to obtain the distance of the drone relative to the target area;

[0045] A fusion controller is configured to perform position calculation based on the real-time visible light image to obtain a first calculated position of the UAV relative to a target area; the first calculated position includes a first calculated angle and a first calculated distance; the airborne components perform position calculation based on the real-time infrared light image to obtain a second calculated position of the UAV relative to the target area; the second calculated position includes a second calculated angle and a second calculated distance; and, according to a preset fusion strategy, fuse the ranging distance, the first calculated position, and the second calculated position to obtain a fused position of the UAV, and guide the UAV to land in the target area based on the fused position;

[0046] The preset fusion strategy includes: when the airborne components simultaneously obtain the first solution position and the second solution position, calculating the error between the first solution distance and the ranging distance; when the error is less than a first preset value, using the first solution position as the fusion position; when the error is greater than or equal to the first preset value, using the second solution position as the fusion position; and when the real-time visible light image and the real-time infrared light image are incomplete, and the ranging distance of the UAV is less than a second preset value, using either the first solution angle or the second solution angle, and the ranging distance as the fusion position.

[0047] Optionally, the airborne components further include:

[0048] An adjustment platform, rotatably connected to the UAV, is used to support the visible light image acquisition device, the infrared light image acquisition device, the ranging sensor, and the fusion controller.

[0049] The servo motor is communicatively connected to the fusion controller and is used to drive the adjustment platform to rotate relative to the UAV based on the rotation control commands sent by the fusion controller.

[0050] Optionally, the airborne components further include:

[0051] Status indicator lights are used to indicate the drone's flight status by their color and flashing pattern when the drone is landing.

[0052] A supplemental light is used to turn on based on a light control command sent by the fusion controller to provide supplemental light to the visible light beacon.

[0053] (III) Beneficial Effects

[0054] The automatic landing method for unmanned aerial vehicles (UAVs) proposed in this invention fuses the distance measured by the UAV relative to the target area, a first calculated position, and a second calculated position to obtain the fused position of the UAV, and guides the UAV to land based on this fused position. Compared with existing single-source positioning methods, this method can comprehensively determine the UAV's position information based on position information obtained from multiple data sources, expand the range of the UAV's sensing distance to the platform, and the measurement results have better stability. This improves the positioning and recognition accuracy and reliability during the UAV landing process, and reduces the collision risk that may be caused by the UAV flying at low altitudes. In particular, for the automatic landing process of UAVs on moving platforms, a larger upper limit of sensing distance can identify the position of the moving platform earlier, while a smaller lower limit of sensing distance can effectively improve the UAV's following ability and landing accuracy on the moving platform.

[0055] Secondly, the automatic landing method for UAVs proposed in this embodiment of the invention, when simultaneously obtaining the first calculated position and the second calculated position, prioritizes the first calculated position based on real-time visible light images as the fusion position. However, when lighting conditions are poor, resulting in a large error in the first calculated position, it switches to the second calculated position based on real-time infrared light images to ensure accurate positioning and recognition of the UAV under various complex lighting environments. Furthermore, based on the actual positioning characteristics corresponding to different landing altitudes during the UAV's landing process, the most accurate position information corresponding to different landing altitudes is used as the fusion position to maintain high positioning and recognition accuracy throughout the UAV's landing process and increase its resistance to environmental interference.

[0056] Then, in the UAV automatic landing system proposed in this embodiment of the invention, the airborne component is an independent pluggable module integrated on the adjustment platform. When using it, the user only needs to install the adjustment platform on the UAV and make the airborne component communicate with the UAV. The airborne component can then work normally and provide accurate positioning information to the UAV. The user does not need to understand the underlying working principle of the airborne component, thus effectively improving the independence and versatility of the airborne component, simplifying the debugging and maintenance of the UAV, and improving the development efficiency of UAV flight control technology. Attached Figure Description

[0057] Figure 1 This is a flowchart illustrating an automatic landing method for a drone provided in this embodiment;

[0058] Figure 2 This is a schematic diagram of the visible light beacon and infrared light beacon provided in the embodiment;

[0059] Figure 3 This is a schematic diagram of the structure of the airborne components provided in the embodiment;

[0060] Figure 4 for Figure 3 A schematic diagram of direction A.

[0061] [Explanation of Labels in the Attached Image]

[0062] 1. Visible light image acquisition device; 2. Infrared light image acquisition device; 3. Ranging sensor; 4. Fusion controller; 5. Adjustment platform; 501. Bracket; 502. Carrier plate; 6. Servo motor; 7. Rotating shaft; 8. Status indicator light; 9. Complementary light; 10. Visible light beacon; 11. Infrared light beacon; 111. Center point light source; 112. Edge point light source; 12. Attitude controller. Detailed Implementation

[0063] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0064] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0065] It should be noted that the first real-time distance, second real-time distance, and ranging distance of the UAV relative to the target area involved in the embodiments can specifically be the distance from the UAV to a specified location in the target area. The specified location can be the center of the target area, the center of the visible light beacon, or the center of the infrared light beacon. Preferably, the above three locations are the same point within the target area.

[0066] Example 1

[0067] This embodiment provides an automatic landing method for unmanned aerial vehicles (UAVs) to guide them to land in a target area. The UAV is equipped with onboard components, and the target area is equipped with a visible light beacon and an infrared light beacon configured in combination with the visible light beacon. Specifically, the target area can be a designated ground area, a fixed platform, or a mobile platform. The visible light beacon can be a horizontally positioned plane in the target area, with a QR code image label printed on it. The QR code image label can specifically be ArUco or AprilTag. The infrared light beacon can specifically be an active infrared light emitting module that emits infrared light through an infrared point light source to indicate the location of the target area to the onboard components. The geometric centers of the visible light beacon and the infrared light beacon coincide for combined configuration, thereby facilitating the positioning of the onboard components.

[0068] like Figure 1 As shown, the automatic landing method for the drone includes:

[0069] A10. The airborne component acquires real-time visible light images and real-time infrared light images in the direction of the target area; the airborne component acquires the distance between the UAV and the target area based on the ranging sensor.

[0070] A20. The airborne component performs position calculation based on the real-time visible light image to obtain a first calculated position of the UAV relative to the target area; the first calculated position includes a first calculated angle and a first calculated distance; the airborne component performs position calculation based on the real-time infrared light image to obtain a second calculated position of the UAV relative to the target area; the second calculated position includes a second calculated angle and a second calculated distance.

[0071] A30. The airborne component fuses the ranging distance, the first calculated position, and the second calculated position according to a preset fusion strategy to obtain the fused position of the UAV, and guides the UAV to land in the target area based on the fused position.

[0072] The preset fusion strategy includes: when the airborne components simultaneously obtain the first solution position and the second solution position, calculating the error between the first solution distance and the ranging distance; when the error is less than a first preset value, using the first solution position as the fusion position; when the error is greater than or equal to the first preset value, using the second solution position as the fusion position; and when the real-time visible light image and the real-time infrared light image are incomplete, and the ranging distance of the UAV is less than a second preset value, using either the first solution angle or the second solution angle, and the ranging distance as the fusion position.

[0073] The first preset value is set according to actual needs. Generally, the smaller the first preset value, the higher the requirement for positioning and recognition accuracy.

[0074] Furthermore, the preset fusion strategy may also include: when the airborne components obtain only one of the first or second calculated positions, the obtained first or second calculated position is directly used as the fusion position. If neither the first nor the second calculated position is obtained, and the UAV's ranging distance is greater than a second preset value, it indicates that the airborne components have not yet searched for the target area, and fusion is not performed in this case. The second preset value can be set according to the actual landing process control parameters; preferably, the second preset value is 5m.

[0075] It should be noted that the above fusion strategy is based on the situations that may occur during the drone's landing. Under sufficient ambient light, the first calculated position based on the real-time visible light image has high accuracy, and the error between the first calculated distance and the measured distance is usually small, making it directly usable as the fusion position. When the ambient light intensity is insufficient, the obtained real-time visible light image is unclear, easily causing a decrease in the accuracy of the calculated first position, resulting in an error greater than the first preset value. However, the real-time infrared light image is not sensitive to ambient light intensity at this time, and even in low-light conditions, a second calculated position with relatively better accuracy can still be calculated based on the real-time infrared light image, which can replace the first calculated position as the fusion position. Based on this, the above fusion strategy can effectively improve the positioning accuracy of the drone under different light intensities.

[0076] In addition, when the drone lands in an area close to the target area (where the drone's ranging distance is less than the second preset value), the visible light image acquisition device and the infrared light image acquisition device will be unable to acquire complete real-time visible light images and real-time infrared light images due to the limited field of view. Therefore, they cannot calculate the first or second calculated distance. In this case, either the first or second calculated angle is used as the fusion position along with the ranging distance measured by the ranging sensor. This can extend the lower limit of the drone's perception distance of the target area, enabling accurate positioning even when the drone is close to the target area, guiding the drone to land, and thus ensuring the positioning and recognition accuracy of the drone in the final stage of landing.

[0077] The automatic landing method for unmanned aerial vehicles (UAVs) proposed in this embodiment obtains the fused position of the UAV by fusing the distance measured relative to the target area, the first calculated position, and the second calculated position, and guides the UAV to land based on the fused position. Compared with existing single-source positioning methods, this method can comprehensively determine the UAV's position information based on position information obtained from multiple data sources, resulting in better stability. Moreover, the combination of visible light beacons and infrared light beacons can basically cover all-weather lighting conditions. During the day when lighting conditions are good, visible light beacons are used as the primary method, while infrared light beacons can be used as a supplement when lighting conditions are poor, such as at night or on cloudy days, resulting in a large error between the first calculated position and the distance measured. This improves the positioning and identification accuracy during the UAV landing process and reduces the collision risk that may occur when the UAV is flying at low altitudes.

[0078] In a first preferred embodiment of this invention, the infrared beacon includes at least three infrared point light sources; each infrared point light source includes: a center point light source located at the geometric center of the visible light beacon, and at least two edge point light sources located at non-geometric center locations of the visible light beacon. These at least three infrared point light sources can form a simple geometric pattern, enabling airborne components to perform position calculations based on this geometric pattern.

[0079] Preferably, the visible light beacon is square, and the infrared light beacon includes four edge point light sources, which are arranged one-to-one at the four right-angle positions of the visible light beacon, so that the geometric pattern formed by the edge point light sources is consistent with the outline of the visible light beacon, thereby unifying their sizes.

[0080] Specifically, in step A20, the airborne component performs position calculation based on the real-time infrared light image, specifically including sub-steps M1 to M4:

[0081] M1, the airborne component identifies infrared point light sources in the real-time infrared light image.

[0082] M2. The airborne component determines the homography matrix corresponding to the real-time infrared point light source image based on the real-time infrared image and the orthophoto image corresponding to the infrared point light source; and determines the second solution angle of the UAV relative to the target area based on the homography matrix.

[0083] The orthogonal image is an orthogonal image of an infrared beacon that is pre-stored locally on the airborne components.

[0084] M3. The airborne component obtains the second calculated distance of the UAV relative to the target area based on the pixel distance and actual distance between any two infrared point light sources in the real-time infrared light image and the transformation of the intrinsic and extrinsic parameters of the infrared light image acquisition device.

[0085] M4, the airborne component uses the second calculated angle and the second calculated distance as the second calculated position.

[0086] In a second preferred embodiment of this example, the visible light beacon is an AprilTag image.

[0087] Specifically, in step A20, the airborne component performs position calculation based on the real-time visible light image, including:

[0088] The airborne component identifies the real-time AprilTag image in the real-time visible light image, and based on the real-time AprilTag image and according to the actual size of the AprilTag image, uses the AprilTag algorithm to calculate the first calculated distance and the first calculated angle of the UAV relative to the target area, which are used as the first calculated position.

[0089] More specifically, the AprilTag algorithm can be implemented directly using the AprilTag algorithm package in the existing OpenCV library, or it can be a tool or functional module in other existing tool libraries used to implement the AprilTag algorithm.

[0090] In the third preferred embodiment of this example, when the airborne component obtains the first calculated position or the second calculated position, the reliability of the ranging distance obtained by the ranging sensor can be judged. When the ranging distance obtained is reliable enough, it is then used for position fusion to further improve the positioning and recognition accuracy.

[0091] In this embodiment, the ranging sensor is a laser ranging sensor. The principle behind its reliability in determining the ranging distance is as follows: the distance measured by the laser ranging sensor is the distance between the drone and an object below it. When the drone is horizontally far from the target area, the obtained ranging result has a large error compared to the drone's true position, resulting in low reliability. Conversely, when the drone is horizontally close to the target area, the distance measured by the laser ranging sensor is closer to the drone's true position, exhibiting higher reliability. Specifically, in the NED (North-East-Down) coordinate system with the ground as the reference frame, the target area is a horizontal plane region with the same vertical coordinate, which can be represented by coordinates (X0, Y0, z0), where the horizontal coordinate X0 and vertical coordinate Y0 are both numerical intervals. The drone is represented as a point mass, which can be represented by coordinates (x, y, z). When x∈X0 and y∈Y0, the drone is determined to be horizontally close to the target area; otherwise, the drone is determined to be horizontally far from the target.

[0092] Specifically, taking the aforementioned NED coordinate system as an example, in step A20, the airborne component obtains the distance between the UAV and the target area based on the ranging sensor, specifically including sub-steps N1 to N2:

[0093] N1. The airborne components obtain the real-time distance to the target area through the ranging sensor.

[0094] N2. The airborne component determines the range (X0, Y0, z0) of the target area and the position (x, y, z) of the UAV based on the first or second solution position, and determines whether x∈X0 and y∈Y0 based on the first or second solution position.

[0095] If so, the real-time ranging distance shall be used as the ranging distance of the UAV relative to the target area;

[0096] If not, ignore the current real-time distance measurement.

[0097] To further improve the accuracy of the ranging distance, before using the real-time ranging distance as the ranging distance of the UAV relative to the target area, an error matrix can be generated based on the errors of the first solution position, the second solution position, and the real-time ranging distance. An extended Kalman filter can then be used to correct the real-time ranging distance, and the corrected real-time ranging distance can be used as the ranging distance.

[0098] Example 2

[0099] To better understand Embodiment 1, this embodiment will provide a detailed explanation of the specific steps of step A30 in conjunction with the overall landing process of the UAV.

[0100] This embodiment provides an automatic landing method for unmanned aerial vehicles (UAVs). Based on the ranging distance, first calculated position, and second calculated position obtained in steps A10 to A20 of Embodiment 1, the ranging distance, first calculated position, and second calculated position are fused according to a preset fusion strategy to obtain the fused position of the UAV. Based on the fused position, the UAV is guided to land in the target area.

[0101] To meet the navigation requirements of drones, after obtaining the fused position of the drone, the following may also be included:

[0102] Multiple fused positions within a preset time period forward from the current moment are obtained to form a position sequence. Differential filtering and delay compensation are performed on the position sequence to obtain the relative motion speed between the UAV and the target area. The relative motion speed is sent to the navigation controller so that the navigation controller can determine the UAV's desired speed based on the relative motion speed.

[0103] Based on the fused position and relative motion speed obtained above, step A30 in this embodiment, guiding the UAV to land in the target area based on the fused position, includes sub-steps S0 to S2:

[0104] S0, Search and First Landing Phase:

[0105] When a flying UAV receives a landing command, it lowers its flight altitude to 20-30m. The onboard components acquire real-time visible light and real-time infrared light images in the direction of the target area and identify whether there are visible light or infrared light beacons in the real-time visible light and real-time infrared light images.

[0106] When the onboard components detect either the visible light beacon or the infrared light beacon, they lock onto the visible light beacon or the infrared light beacon in the current field of view, calculate the first calculated position corresponding to the visible light beacon or the second calculated position corresponding to the infrared light beacon, determine the fused position of the UAV according to the fusion strategy, and send it to the navigation controller. This allows the navigation controller to generate third navigation information based on the fused position, guiding the UAV to move directly above the target area and synchronize with the horizontal movement speed of the target area. In other words, the UAV and the target area are relatively stationary in the horizontal direction.

[0107] Specifically, when the target area is stationary relative to the ground, it is actually necessary to control the drone's horizontal speed to be reduced to 0. If the target area is a moving platform, it is necessary to control the drone to move at the same speed as the moving platform in the horizontal direction.

[0108] When the target area is a mobile platform, in order to further evaluate the synchronization effect between the UAV and the mobile platform, the airborne components can perform a Fourier transform based on the relative motion speed between the UAV and the target area to obtain the frequency domain information of the relative motion speed. Based on this, the relative speed maintenance between the platform and the aircraft can be determined, or the frequency domain information can be fed back to the UAV's flight control system to enable it to control the UAV's flight state more accurately.

[0109] S1, Second Landing Phase:

[0110] As the drone descends, its onboard components determine, based on the current fusion position, whether the distance between the drone and the target area is within the first altitude range.

[0111] If not, continue descending;

[0112] If so, the current fused position of the drone is sent to the navigation controller, so that the navigation controller can generate first navigation information based on the current fused position and guide the drone to land on the visible light beacon.

[0113] Specifically, the second-stage landing mainly relies on visible light images and / or infrared images for positioning. It is necessary to ensure that the visible light and infrared image acquisition devices can obtain clear and complete images of the visible light beacons and infrared beacons. Therefore, the first altitude range can be set according to the parameters of the visible light and infrared image acquisition devices and the actual size of the visible light and infrared beacons.

[0114] Preferably, in this embodiment, the visible light beacon has a size of 0.8m × 0.8m, and the first height range is greater than 5 meters and less than or equal to 15 meters.

[0115] S2, Terminal Descending Phase:

[0116] The drone continues its descent, and its onboard components determine, based on the drone's current merged position, whether the distance between the drone and the target area is within the second altitude range.

[0117] If not, continue descending;

[0118] If so, the onboard components stop acquiring visible light images, lock the center point light source of the infrared beacon to the center of the real-time infrared light image, acquire the range of the UAV through the range sensor, and send the range to the navigation controller so that the navigation controller generates second navigation information based on the range, guides the UAV to align with the center point light source of the infrared beacon, and lands in the target area.

[0119] Specifically, during the final stage of descent, because the visible light and infrared image acquisition devices are too close to the target area, complete images of the visible light and infrared beacons cannot be obtained. Therefore, the distance between the UAV and the target area cannot be calculated from the images, and the UAV's position can only be determined using a ranging sensor. Thus, acquiring visible light images can be stopped, and the UAV's position can be adjusted to lock the center point light source of the infrared beacon at the center of the real-time infrared image, ensuring that the UAV aligns with the center point light source of the infrared beacon and lands within the target area. Preferably, the second altitude range is less than or equal to 5 meters.

[0120] In step S2, the airborne components rely on the ranging sensor to obtain the precise relative distance between the UAV and the target area, so as to further improve the positioning and identification accuracy and avoid potential collision risks between the UAV and the target area.

[0121] It should be noted that the function of controlling the UAV to move to the designated location based on the first navigation information, the second navigation information, and the third navigation information in steps S0 to S2 above can be implemented by the UAV's existing flight control system. The navigation controller can be a navigation controller carried by the UAV itself, or a navigation controller included in an onboard component.

[0122] Example 3

[0123] This embodiment provides an automatic landing system for a drone, used to guide the drone to land in a target area. The landing system includes: a visible light beacon 10, an infrared light beacon 11, and onboard components; specifically as follows:

[0124] Visible light beacon 10 is placed within the target area.

[0125] Infrared light beacon 11 is configured in combination with the visible light beacon.

[0126] Specifically, such as Figure 2 As shown, the visible light beacon 10 is square, specifically an 80cm*80cm KT board 10, with one side of the KT board 10 printed with an AprilTag image (not shown in the figure). The KT board is placed within the target area, or the KT board itself can be used as the target area. The infrared light beacon 11 includes a central point light source 111 and four edge point light sources 112. The central point light source 111 is located at the geometric center of the KT board, and the four infrared point light sources 112 are correspondingly located at the four right-angle positions of the KT board.

[0127] Airborne components, which can be plugged into the drone, such as Figures 3 to 4 As shown, the airborne components include: a visible light image acquisition device 1, an infrared light acquisition device 2, a ranging sensor 3, and a fusion controller 4, as detailed below:

[0128] Visible light image acquisition device 1 is used to acquire real-time visible light images in the direction of the target area. Specifically, the visible light image acquisition device 1 transmits the real-time visible light images to the fusion controller 4 at a frame rate of 30 FPS.

[0129] Infrared image acquisition device 2 is used to acquire real-time infrared images in the direction of the target area. Specifically, the infrared image acquisition device 2 transmits the real-time infrared images to the fusion controller 4 at a frame rate of 30 FPS.

[0130] Ranging sensor 3 is used to obtain the distance between the UAV and the target area.

[0131] The fusion controller 4 is used to calculate the position of the UAV relative to the target area based on the real-time visible light image, and to calculate the position of the UAV relative to the target area based on the real-time infrared light image. It then fuses the ranging distance, the first calculated position, and the second calculated position according to a preset fusion strategy to obtain the fused position of the UAV, guiding the UAV to land in the target area based on this fused position. The fusion controller can interact with the UAV's flight control system via serial communication, providing the flight control system with information such as the fused position. The preset fusion strategy includes: when the onboard components simultaneously obtain the first and second calculated positions, calculating the error between the first calculated position and the ranging distance; if the error is less than a preset value, using the first calculated position as the fused position; if the error is greater than or equal to the preset value, using the second calculated position as the fused position.

[0132] Specifically, the fusion controller 4 can be a main circuit board that integrates a microprocessor unit (MCU), and the visible light image acquisition device, infrared light acquisition device, and ranging sensor are directly mounted on the main circuit board.

[0133] In a preferred embodiment of this invention, to improve the search range of the visible light image acquisition device and the infrared light acquisition device, the airborne component further includes: an adjustment platform 5 and a servo motor 6, as detailed below:

[0134] An adjustment platform 5, rotatably connected to the UAV, is used to support the visible light image acquisition device 1, the infrared light image acquisition device 2, the ranging sensor 3, and the fusion controller 4. Specifically, the UAV can be rotatably connected to the bottom of the UAV with multiple degrees of freedom to expand the search range of the visible light image acquisition device and the infrared light acquisition device. Preferably, for economic reasons, the adjustment platform 5 includes a bracket 501 fixedly connected to the bottom of the UAV, a support plate 502 rotatably connected to the bracket 501 via a rotating shaft 7 with a single degree of freedom, and the fusion controller 4 is located on the side of the support plate 502 away from the UAV. Driven by a servo motor 6, the fusion controller 4 rotates along the pitch direction of the UAV to expand the search range of the visible light image acquisition device 1 and the infrared light acquisition device 2.

[0135] Servo motor 6, communicatively connected to the fusion controller, drives the support plate 502 of the adjustment platform 5 to rotate relative to the UAV based on rotation control commands sent by the fusion controller 4. This facilitates the visible light image acquisition device 1 and the infrared image acquisition device 2 in searching for or locking onto the visible light beacon 10 or the infrared beacon 11. Specifically, the output of servo motor 6 can be connected to a rotating shaft. When servo motor 6 rotates a specified angle according to the rotation control command, it can drive the support plate 502 to rotate by the same angle, thereby expanding the field of view of the visible light image acquisition device 1 and the infrared image acquisition device 2 carried by the adjustment platform 5. Preferably, single-axis stabilization processing can be further applied to servo motor 6 to eliminate the influence of changes in the aircraft's pitch angle and improve imaging quality.

[0136] In another preferred embodiment of this invention, the airborne components further include: a status indicator light 8 and a supplementary light 9.

[0137] The status indicator light 8 is used to indicate the drone's flight status by its color and flashing pattern when the drone lands, allowing the user to visually observe the drone's flight status. Specifically, the correspondence between the color and flashing pattern of the status indicator light 8 and the drone's flight status is shown in Table 1:

[0138] Table 1. Correspondence between the color and flashing status of the status indicator lights and the flight status of the UAV.

[0139]

[0140]

[0141] The supplementary light 9 is mounted on the adjustment platform 5, specifically on any side of the bracket 501, and is turned on based on the light control command sent by the fusion controller 4 to supplement the visible light beacon 11.

[0142] Specifically, the lighting control command is determined by the fusion controller 4 based on the real-time visible light image. Specifically, the fusion controller 4 determines whether the global grayscale value of the real-time visible light image is less than a preset threshold based on the global grayscale perception of the ambient light conditions of the real-time visible light image. If so, the fusion controller 4 turns on the supplementary light through the lighting control command to supplement the light for the visible light image acquisition device; otherwise, no action is taken.

[0143] Furthermore, the adjustment platform 5 can also be equipped with other auxiliary components to provide the onboard components with richer auxiliary information to the UAV. For example, the adjustment platform can also be equipped with an attitude sensor 12, and the fusion controller 4 includes a cascade PID controller component. The attitude controller 12 is used to acquire the attitude of the support plate 502 relative to the UAV fuselage, so that the fusion controller 4 can determine the rotation angle output by the servo motor 6 based on the attitude of the support plate 502 relative to the fuselage, thereby adjusting the search range of the visible light image acquisition device 1 or infrared light acquisition device 2 carried on the support plate 502, or ensuring that the visible light image acquisition device 1 or infrared light acquisition device 2 continuously locks the geometric center of the KT board. The cascade PID controller component is loaded into the fusion controller 4 in the form of a computer program and can replace the navigation controller for precise landing guidance. It can acquire the relative speed between the current UAV and the target area, and superimpose the control results of precise landing guidance to return the desired speed in the NED coordinate system to the UAV's flight control system, so as to guide the UAV to land in the target area.

[0144] The autonomous landing system for unmanned aerial vehicles (UAVs) provided in this embodiment obtains its fused position primarily through two methods: identifying infrared beacons in the target area using an infrared image acquisition device, and identifying visible light beacons in the target area using a visible light image acquisition device. To ensure data accuracy and positioning precision during the final landing phase, the ranging distance collected by a ranging sensor is used to check and calibrate the position calculation results based on these two image recognition methods, while also providing terminal landing guidance. These two image recognition-based position calculation methods can cover all lighting conditions. Furthermore, supplementary lighting is used to improve the accuracy of visible light recognition during the landing phase and to enable the visible light image acquisition device to operate in nighttime environments, thereby improving the overall robustness of the system.

[0145] The airborne component is an independent, pluggable module integrated into the adjustment platform, offering the advantage of being ready to use immediately. Users simply need to install the adjustment platform on the drone and establish a communication connection between the airborne component and the drone. The airborne component will then function normally, providing the drone with accurate positioning information. Users do not need to understand the underlying working principles of the airborne component. The various stages of drone landing are independently determined by the airborne component, which improves compatibility with flight control systems of different drone platforms. This effectively ensures the independence and versatility of the airborne component, simplifies drone debugging and maintenance, and improves the development efficiency of drone flight control technology.

[0146] Since the systems / devices described in the above embodiments of the present invention are systems / devices used to implement the methods of the above embodiments of the present invention, those skilled in the art can understand the specific structure and modifications of the systems / devices based on the methods described in the above embodiments of the present invention, and therefore will not be repeated here. All systems / devices used in the methods of the above embodiments of the present invention fall within the scope of protection of the present invention.

[0147] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, EEPROM, optical storage, etc.) containing computer-usable program code.

[0148] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, as well as combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions.

[0149] It should be noted that any reference numerals placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In claims that enumerate several means, several of these means may be embodied by the same hardware. The use of the terms first, second, third, etc., is merely for convenience of expression and does not indicate any order. These terms can be understood as part of the component names.

[0150] Furthermore, it should be noted that in the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0151] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the claims should be interpreted to include both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0152] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, then this invention should also include these modifications and variations.

Claims

1. An automatic landing method for unmanned aerial vehicles (UAVs), used to guide the UAV to land in a target area, characterized in that, The drone is equipped with onboard components, the target area is equipped with a visible light beacon, and an infrared light beacon is configured in combination with the visible light beacon; the method includes: The airborne components acquire real-time visible light and real-time infrared light images in the direction of the target area; the airborne components acquire the distance between the UAV and the target area based on the ranging sensor; The airborne component performs position calculation based on the real-time visible light image to obtain a first calculated position of the UAV relative to the target area; the first calculated position includes a first calculated angle and a first calculated distance; the airborne component performs position calculation based on the real-time infrared light image to obtain a second calculated position of the UAV relative to the target area; the second calculated position includes a second calculated angle and a second calculated distance; The airborne components fuse the ranging distance, the first calculated position, and the second calculated position according to a preset fusion strategy to obtain the fused position of the UAV, and guide the UAV to land in the target area based on the fused position; The preset fusion strategy includes: when the airborne components simultaneously obtain the first calculated position and the second calculated position, calculating the error between the first calculated distance and the ranging distance; when the error is less than a first preset value, using the first calculated position as the fused position; when the error is greater than or equal to the first preset value, using the second calculated position as the fused position; and... When the real-time visible light image and the real-time infrared light image are incomplete, and the ranging distance of the UAV is less than the second preset value, either the first solution angle or the second solution angle, and the ranging distance are used as the fusion position.

2. The method according to claim 1, characterized in that, The infrared beacon includes at least three infrared point light sources; the infrared point light sources include: a center point light source located at the geometric center of the visible light beacon, and at least two edge point light sources located at non-geometric center locations of the visible light beacon; The airborne components perform position calculation based on the real-time infrared image, including: The airborne component identifies infrared point light sources in the real-time infrared light image; The airborne component determines the homography matrix corresponding to the real-time infrared image based on the real-time infrared image and the orthophoto image corresponding to the infrared point light source; and determines the second solution angle of the UAV relative to the target area based on the homography matrix; wherein, the orthophoto image is an image pre-saved locally on the airborne component; The airborne component obtains the second calculated distance of the UAV relative to the target area based on the pixel distance and actual distance between any two infrared point light sources in the real-time infrared light image and the transformation of the intrinsic and extrinsic parameters of the infrared light image acquisition device. The airborne component uses the second calculated angle and the second calculated distance as the second calculated position.

3. The method according to claim 2, characterized in that, The visible light beacon is square, and the infrared light beacon includes four edge point light sources, which are respectively arranged at the four right-angle positions of the visible light beacon.

4. The method according to claim 1, characterized in that, The visible light beacon is an AprilTag image; The airborne components perform position calculation based on the real-time visible light image, including: The airborne component identifies the real-time AprilTag image in the real-time visible light image, and based on the real-time AprilTag image and according to the actual size of the AprilTag image, uses the AprilTag algorithm to calculate the first calculated distance and the first calculated angle of the UAV relative to the target area, which are used as the first calculated position.

5. The method according to claim 1, characterized in that, The ranging sensor is a laser ranging sensor; The airborne components acquire the distance between the UAV and the target area based on a ranging sensor, including: The airborne components acquire the real-time ranging distance of the target area through the laser ranging sensor; The airborne component determines the range (X0, Y0, z0) of the target area and the position (x, y, z) of the UAV based on the first or second solution position, and determines whether x∈X0 and y∈Y0 based on the first or second solution position. If so, the real-time ranging distance is taken as the ranging distance of the UAV relative to the target area.

6. The method according to any one of claims 1 to 5, characterized in that, The step of guiding the drone to land in the target area based on the fused location includes: S1. The airborne components determine, based on the current fusion position, whether the distance between the drone and the target area is within the first altitude range. If so, The drone's current fused position is sent to the navigation controller, which then generates first navigation information based on the current fused position to guide the drone to align with the geometric center of the visible light beacon and descend. S2. The onboard components determine whether the distance between the drone and the target area is within the second altitude range based on the drone's current fusion position. If so, The onboard components stop acquiring visible light images, lock onto the center point light source of the infrared beacon, acquire the distance of the UAV through the ranging sensor, and send the distance to the navigation controller so that the navigation controller can generate second navigation information based on the distance, guide the UAV to align with the center point light source of the infrared beacon, and land in the target area.

7. The method according to claim 6, characterized in that, Prior to S1, the method further includes: S0. When a landing command is received, the onboard components identify visible light beacons or infrared light beacons in the real-time visible light image and the real-time infrared light image; When either the visible light beacon or the infrared light beacon is detected, the visible light beacon or the infrared light beacon in the current field of view is locked, the first calculated position corresponding to the visible light beacon or the second calculated position corresponding to the infrared light beacon is calculated, the fusion position of the UAV is determined according to the fusion strategy and sent to the navigation controller, so that the navigation controller generates third navigation information based on the fusion position, guides the UAV to move directly above the target area and synchronizes with the horizontal movement speed of the target area.

8. An automatic landing system for unmanned aerial vehicles (UAVs) for guiding the UAV to land in a target area, characterized in that, The landing system includes: Visible light beacons are placed within the target area; An infrared light beacon is configured in combination with the visible light beacon. Airborne components, pluggably mounted on the UAV, said airborne components include: Visible light image acquisition device, used to acquire real-time visible light images in the direction of a target area; An infrared light image acquisition device is used to acquire real-time infrared light images in the direction of a target area; Ranging sensors are used to obtain the distance of the drone relative to the target area; A fusion controller is configured to perform position calculation based on the real-time visible light image to obtain a first calculated position of the UAV relative to a target area; the first calculated position includes a first calculated angle and a first calculated distance; the airborne components perform position calculation based on the real-time infrared light image to obtain a second calculated position of the UAV relative to the target area; the second calculated position includes a second calculated angle and a second calculated distance; and, according to a preset fusion strategy, fuse the ranging distance, the first calculated position, and the second calculated position to obtain a fused position of the UAV, and guide the UAV to land in the target area based on the fused position; The preset fusion strategy includes: when the airborne components simultaneously obtain the first solution position and the second solution position, calculating the error between the first solution distance and the ranging distance; when the error is less than a first preset value, using the first solution position as the fusion position; when the error is greater than or equal to the first preset value, using the second solution position as the fusion position; and when the real-time visible light image and the real-time infrared light image are incomplete, and the ranging distance of the UAV is less than a second preset value, using either the first solution angle or the second solution angle, and the ranging distance as the fusion position.

9. The landing system according to claim 8, characterized in that, The airborne components also include: An adjustment platform, rotatably connected to the UAV, is used to support the visible light image acquisition device, the infrared light image acquisition device, the ranging sensor, and the fusion controller. The servo motor is communicatively connected to the fusion controller and is used to drive the adjustment platform to rotate relative to the UAV based on the rotation control commands sent by the fusion controller.

10. The landing system according to claim 9, characterized in that, The airborne components also include: Status indicator lights are used to indicate the drone's flight status by their color and flashing pattern when the drone is landing. A supplemental light is used to turn on based on a light control command sent by the fusion controller to provide supplemental light to the visible light beacon.

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