Unmanned aerial vehicle fixed-point directional landing method and system

Abstract

The invention provides an unmanned aerial vehicle fixed-point directional landing method and system, and relates to the technical field of mine hole unmanned aerial vehicle inspection. The UWB base station and the positioning identifier are deployed on the hangar used for stopping and charging the unmanned aerial vehicle in the mine hole, the approximate position of the unmanned aerial vehicle in the mine hole and the relative position of the unmanned aerial vehicle to the hangar are obtained through UWB communication, preliminary positioning is achieved, then the positioning identifier is found through the visual sensor, and accurate positioning is achieved. The landing position, direction and posture of the unmanned aerial vehicle above the hangar are obtained, so that the unmanned aerial vehicle autonomously and accurately locates and lands in the preset hangar, the functions of charging, cleaning, data transmission and the like can be completed in the hangar, a basis is provided for autonomously and regularly polling the unmanned aerial vehicle in a mine hole, and the key problem of autonomously polling and charging the unmanned aerial vehicle in the mine hole is solved; and the application scene of the unmanned aerial vehicle system under the inspection task is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of mine tunnel unmanned aerial vehicle inspection, and in particular to a method and system for fixed-point directional landing of an unmanned aerial vehicle. Background Art

[0002] With the development and improvement of drone technology, drones have gradually become popular in mine inspection operations due to their advantages such as improving inspection efficiency and coverage, reducing safety risks, providing high-quality data, adapting to complex environments, and developing intelligence and automation.

[0003] Compared with the traditional manual inspection method, the use of drones in mine inspection operations has brought many advantages, but there are still some problems. In particular, the problem of drone endurance. Due to the limitations of battery technology, the battery endurance of drones is difficult to meet the needs of long-term and large-scale mine inspections. In order to extend the endurance of drone inspection operations, it is necessary to set up a specific hangar or cabin for the drone to automatically charge the drone under the mine. In order to realize the automatic charging of the drone in the hangar or cabin, the first thing to solve is the positioning and precise landing of the drone.

[0004] At present, the existing positioning by deploying base stations to obtain the distance and thus the position can only obtain the approximate position, with low positioning accuracy, which cannot meet the closed-loop control needs of the drone itself, and the SLAM-like algorithm based on laser radar can only obtain the position of the drone in the launch inertial system, and cannot obtain the position relationship between the drone and the hangar, making it difficult to accurately land in the hangar for charging and data transmission. This greatly limits the drone's ability to perform autonomous inspection tasks in extreme environments.

[0005] The present invention is proposed based on this. Summary of the invention

[0006] The purpose of the present invention is to provide a method and system for fixed-point directional landing of a UAV in the existing large-scale mine environment without changing the physical structure of the mine, so as to obtain the landing position, direction and posture of the UAV above the hangar, so that the UAV can autonomously and accurately locate and land in a preset hangar.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention provides a method for fixed-point directional landing of an unmanned aerial vehicle, comprising: S1 base station and positioning mark deployment, deploying UWB base stations on each hangar in a mine cave, and deploying multiple positioning marks on the apron of each hangar; S2 preliminary positioning, communicating with each UWB base station through the UWB tag on the unmanned aerial vehicle, obtaining the distance between the unmanned aerial vehicle and different UWB base stations, obtaining the preliminary position information of the unmanned aerial vehicle, finding and approaching the nearest hangar; S3 precise positioning, finding the positioning mark through the visual sensor on the unmanned aerial vehicle, and adjusting the landing position, direction and posture of the unmanned aerial vehicle according to the positioning mark.

[0009] The present invention provides a preferred solution in a first aspect, wherein the S1 base station and the positioning marker are deployed, and the positioning marker is a self-luminous object with color.

[0010] More preferably, in the deployment of the S1 base station and the positioning mark, the positioning mark uses at least three self-luminous objects of different colors, and the color one light-emitting object, the color two light-emitting object and the color three light-emitting object are respectively placed at the center of the hangar apron, the edge in the direction of the nose, and the edge in the direction of the tail; in the S3 precise positioning, the self-luminous objects are found by visual sensors, and the drone is adjusted to be directly above the color one light-emitting object by judging the color, and at the same time, the heading is adjusted so that the nose direction points to the color two light-emitting object and the tail direction points to the color three light-emitting object.

[0011] In a first aspect, the present invention provides a preferred solution, in which, in the S2 preliminary positioning, preliminary position information of the UAV relative to each hangar is obtained according to the least squares method or numerical optimization algorithm.

[0012] In a second aspect, the present invention provides a UAV fixed-point directional landing system, which is based on the above method and includes: a base station and a positioning identifier, a UWB base station deployed on each hangar in the mine, and multiple positioning identifiers deployed on the apron of each hangar; a preliminary positioning module, which is used to communicate with each UWB base station through the UWB tag on the UAV, obtain the distance between the UAV and different UWB base stations, obtain the preliminary location information of the UAV, find and approach the nearest hangar; a precise positioning module, which is used to find the positioning identifier through the visual sensor on the UAV, and adjust the landing position, direction and posture of the UAV according to the positioning identifier.

[0013] Compared with the prior art, the above technical solution has the following advantages:

[0014] The fixed-point directional landing method for a UAV of the present invention deploys a UWB base station and a positioning mark on a hangar in a mine cave for parking and charging the UAV, obtains the approximate position of the UAV in the mine cave and its relative position to the hangar through UWB communication, realizes preliminary positioning, and then uses a visual sensor to find the positioning mark to realize precise positioning, obtains the landing position, direction and posture of the UAV above the hangar, and enables the UAV to autonomously and accurately locate and land in a preset hangar, and can complete functions such as charging, cleaning and data transmission in the hangar, providing a basis for realizing autonomous and regular inspections of UAVs in mine caves, solving the key problem of autonomous inspection and charging of UAVs in mine caves, and expanding the application scenarios of UAV systems under inspection tasks. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0016] Figure 1 A flowchart of a method for fixed-point directional landing of a UAV provided by a specific embodiment of the present invention;

[0017] Figure 2 A schematic diagram of a UAV fixed-point directional landing system provided by a specific embodiment of the present invention;

[0018] Figure 3 A schematic diagram of precise positioning and directional landing of a hangar in a UAV fixed-point directional landing system provided in a specific embodiment of the present invention.

[0019] Figure numerals: UAV 1, UWB base station 2, hangar apron 3, positioning mark 4, preliminary positioning module 5, precise positioning module 6, mine cave 7, UWB tag 8. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Embodiment 1

[0022] Please refer to Figure 1 This embodiment provides a method for fixed-point directional landing of a UAV, which mainly includes the following steps:

[0023] S1 Base station and positioning mark deployment, UWB base stations are deployed on each hangar in the mine, and multiple positioning marks are deployed on each hangar apron. In this embodiment, the positioning mark preferably adopts a self-luminous object with color.

[0024] S2 performs preliminary positioning, communicates with each UWB base station through the UWB tag on the drone, obtains the distance between the drone and different UWB base stations, obtains the preliminary location information of the drone, and finds and approaches the nearest hangar.

[0025] S3 accurately locates the drone by using the visual sensor on the drone to find the positioning mark and adjust the landing position, direction and posture of the drone according to the positioning mark.

[0026] In a preferred embodiment, in step S2, preliminary positioning, the preliminary position information of the drone is obtained according to the least squares method, which is specifically achieved by the following steps:

[0027] S21 Since the propagation speed of UWB signals is close to the speed of light c, the distance d between the drone and each UWB base station is calculated using the formula d=c×t / 2, where t is the round-trip time of the signal.

[0028] S22 Assume that there are n UWB base stations in the mine, and the coordinates of each base station are known, denoted as (x i ,y i ,z i ),i=1,2,…,n, the distance between the UWB tag on the drone and the i-th base station is d i .

[0029] S23 Assume the coordinates of the drone are (x, y, z). For each base station, establish an equation about the drone position (x, y, z):

[0030] (xx i ) 2 +(yy i ) 2 +(zz i ) 2 =d i 2

[0031] Therefore, n nonlinear equations are obtained, and a nonlinear equation system is obtained.

[0032] S24 linearizes the above nonlinear equations, which can be achieved by Taylor series expansion or first-order linear approximation.

[0033] S25 uses the least squares method or solves the linearized equations to obtain the initial position of the drone.

[0034] In the method for fixed-point directional landing of unmanned aerial vehicles in this embodiment, the initial position information of the unmanned aerial vehicle is obtained according to the least square method, which has the advantages of high-precision positioning capability, strong adaptability, efficient data processing, easy implementation and integration, and high robustness. These advantages make the least square method an effective choice for the initial positioning method of fixed-point directional landing of unmanned aerial vehicles.

[0035] In a preferred embodiment, in the initial positioning of S2, the drone obtains multiple drone position information through UWB ranging, 360 laser radar, downward laser ranging radar, optical flow sensor and inertial navigation system, and then performs data fusion to obtain accurate drone position information. By fusing the position data obtained by multiple sensors, more accurate drone position information can be obtained, which is more conducive to accurate initial positioning and more adaptable to the dim light and dusty mine environment.

[0036] Please refer to Figure 2 This embodiment provides a UAV fixed-point directional landing system, based on the above method, mainly including the following: base station and positioning mark, UWB base station 2 deployed on each hangar in the mine cave 7, and multiple positioning marks 4 deployed on each hangar apron 3. The preliminary positioning module 5 is used to communicate with each UWB base station 2 through the UWB tag 8 on the UAV 1, obtain the distance between the UAV and different UWB base stations, obtain the preliminary location information of the UAV, find and approach the nearest hangar. The precise positioning module 6 is used to find the positioning mark through the visual sensor on the UAV, and adjust the landing position, direction and posture of the UAV according to the positioning mark.

[0037] In a preferred embodiment, in the S2 preliminary positioning, the UWB tag on the drone communicates with each UWB base station, obtains the instructions of the UWB base station through communication and sends them to the host computer of the drone for analysis; after analysis, the host computer generates a position control instruction and sends it to the drone actuator to perform the corresponding action. The execution of the drone's mission can be controlled by the central control platform to achieve the setting of the drone's mission. The instructions sent by the central control platform are transmitted through the UWB base station. The drone receives the instructions from the base station through the UWB tag and sends them to the host computer for analysis. The protocol used for the information is shown in Table 1:

[0038] Table 1

[0039]

[0040] The data content is shown in Table 2:

[0041] Table 2

[0042]

[0043] In order to realize autonomous inspection of drones in mines, the following instructions are preset:

[0044] 0 No command, only read the number and distance content. The distance L and the task are meaningless. But it indicates that the UART command from the aircraft to the identification card can be received

[0045] 1 forward forward distance L task 0

[0046] 2 Backwards Flying distance L Mission 0

[0047] 3 Turn on the spot. The turning angle is the distance L. This angle will only be 90, 180, 270. During the subsequent movement of Task 0, a forward command will be sent, which together will be the command to turn left, turn right, and retreat.

[0048] 4 Turn left after going forward for a certain number of centimeters. From the current position, turn left when a left-turning lane is found within the detection distance L. Send a response when a left-turning lane is found.

[0049] 5 Turn right after moving forward a certain number of centimeters. Starting from the current position, turn right when a right-turning lane is found within the detection distance L. Send a response when a right-turning lane is found.

[0050] 6. Back up how many centimeters before turning left. From the current position, turn left when a left-turning lane is found within the detection distance L. Send a response when a left-turning lane is found.

[0051] 7 Back up how many centimeters before turning right. Counting from the current position, turn right when a right-turning lane is found within the detection distance L. Send a response when a right-turning lane is found.

[0052] 0x10 Search for a charging device within a distance of L ahead to charge, that is, there is a charging device at a distance of L ahead, and the aircraft is required to go there to charge. A response must be sent before finding a charging location and preparing to enter and charge by itself. A response must also be sent when charging is completed and ready to continue the mission.

[0053] 0x11 This command is used when there is a device failure or other abnormal situation, requiring the aircraft to wait for the next instruction at a fixed time when the charging station is fully charged. After receiving this command, the aircraft can enter the charging state or rest and wait for the required distance L for a certain number of seconds before requesting the base station to continue the mission again. This command will only be sent at the charging station.

[0054] 0x20 Search for the corresponding device with the task specified number within the distance L, and respond after the shooting task is completed.

[0055] Task 1: Default task equipment search and shooting

[0056] Task 2: 120-degree circular shooting. Observe the environment at the designated location.

[0057] Tasks.....We will discuss and define which tasks can be completed later.

[0058] 0x40 can communicate with the identification card through UART,

[0059] 0x80 Distance L is 0, Task is 0 The tag card has closed the UAER communication and entered the deep sleep period. When receiving this command, stop sending the UAER command. Wait for the next 0x40 or other command to send again. Features: When the tag card sends UART data (except this command), it will not enter the sleep period within 3 milliseconds. Under normal circumstances, it will wake up once per second.

[0060] Therefore, the mission execution of the drone can be controlled by the central control platform to realize the setting of the drone mission. At the same time, the drone can obtain the position coordinates in the mine and the position relative to the hangar, so as to prepare for the drone to autonomously find the hangar and land.

[0061] In a preferred embodiment, please refer to Figure 3 , the positioning mark uses at least three self-luminous objects of different colors, and the color one (blue) luminous object, the color two (red) luminous object and the color three (green) luminous object are placed at the center of the hangar apron, the edge of the nose direction and the edge of the tail direction respectively; in the precise positioning of S3, the self-luminous object is found by the visual sensor, and the drone is adjusted to the top of the color one luminous object by judging the color, and the heading is adjusted to point to the color two luminous object in the nose direction and the color three luminous object in the tail direction at the same time. More specifically, in order to achieve the precise and directional landing of the drone, it is necessary to identify the position and relative heading angle of the drone above the hangar. In this embodiment, three self-luminous objects of different colors are placed at the center of the hangar and the edge of the nose direction and the edge of the tail direction respectively. When the drone needs to return to the hangar, it will first find and approach the nearest hangar according to the preliminary positioning method in S2. After approaching the hangar, it will find the luminous object through the camera, and adjust the drone to the top of the blue by judging the color, and at the same time adjust the heading to point to the red target in the nose direction and the green target in the tail direction. This can ensure the accuracy of the position and direction of the drone after landing, and ensure that the landing direction and position of the drone meet the preset requirements.

[0062] Embodiment 2

[0063] This embodiment provides another preferred method for preliminary positioning of a UAV for fixed-point directional landing, wherein preliminary position information of the UAV is obtained according to a numerical optimization algorithm, wherein the numerical optimization algorithm adopts a Gauss-Newton method or a Levenberg-Marquardt algorithm, and is specifically implemented by the following steps:

[0064] S21 Since the propagation speed of UWB signals is close to the speed of light c, the distance d between the drone and each UWB base station is calculated using the formula d = c × t / 2, where t is the round-trip time of the signal;

[0065] S22 Assume that there are n UWB base stations in the mine, and the coordinates of each base station are known, denoted as (x i ,y i ,z i ),i=1,2,…,n, the distance between the UWB tag on the drone and the i-th base station is d i ;

[0066] S23 Assume the coordinates of the drone are (x, y, z). For each base station, establish an equation about the drone position (x, y, z):

[0067] (xx i ) 2 +(yy i ) 2 +(zz i ) 2 =d i 2

[0068] Therefore, n nonlinear equations are obtained, and a nonlinear equation system is obtained;

[0069] S24' Initial guess: Provide an initial position guess of a drone;

[0070] S25' parameter setting: set the parameters of the numerical optimization algorithm, including the number of iterations, convergence tolerance and damping factor;

[0071] S26' Calculate Jacobian matrix: Calculate the Jacobian matrix of the nonlinear equations relative to the position based on the current position estimate;

[0072] S27' Update step size: Use the Gauss-Newton method or Levenberg-Marquardt algorithm, combined with the Jacobian matrix and residual, to solve the update step size;

[0073] S28' Position update: adjust the drone's position estimate according to the update step size;

[0074] S29' Convergence check: Check whether the change in the position estimate is less than the convergence tolerance, or whether the number of iterations has reached the maximum limit; if the convergence condition is met, output the final position; otherwise, continue to iterate; when the algorithm converges, output the final drone position estimate.

[0075] In the method for fixed-point directional landing of unmanned aerial vehicles in this embodiment, the preliminary positioning of the unmanned aerial vehicle is performed by using a numerical optimization algorithm to obtain the preliminary position information of the unmanned aerial vehicle relative to each hangar, which has the advantages of high-precision positioning, real-time performance and flexibility, strong anti-interference ability, optimized resource utilization, scalability and adaptability, etc. These advantages enable the unmanned aerial vehicle to achieve fixed-point directional landing in various complex environments, and improve the safety and efficiency of landing.

[0076] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the above-mentioned embodiments of the methods. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0077] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] The above-described embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for fixed-point directional landing of an unmanned aerial vehicle, characterized in that: include: S1 base station and positioning mark deployment: UWB base stations are deployed on each hangar in the mine, and multiple positioning marks are deployed on the apron of each hangar; S2: Initial positioning: The UWB tag on the drone communicates with each UWB base station to obtain the distance between the drone and different UWB base stations, obtain the initial location information of the drone, and find and approach the nearest hangar; S3 accurately locates the drone by using the visual sensor on the drone to find the positioning mark and adjust the landing position, direction and posture of the drone according to the positioning mark.

2. The method for fixed-point directional landing of an unmanned aerial vehicle according to claim 1, characterized in that: In the deployment of the S1 base station and the positioning mark, the positioning mark adopts a self-luminous object with color.

3. The method for fixed-point directional landing of an unmanned aerial vehicle according to claim 1, characterized in that: In the deployment of the S1 base station and the positioning mark, the positioning mark uses at least three self-luminous objects of different colors, and the color one light-emitting object, the color two light-emitting object and the color three light-emitting object are respectively placed at the center of the hangar apron, the edge of the nose direction and the edge of the tail direction; in the S3 precise positioning, the self-luminous object is found through the visual sensor, and the drone is adjusted to be directly above the color one light-emitting object by judging the color, and at the same time, the heading is adjusted so that the nose direction points to the color two light-emitting object and the tail direction points to the color three light-emitting object.

4. The method for fixed-point directional landing of an unmanned aerial vehicle according to claim 5, characterized in that: In the S2 preliminary positioning, the drone obtains the position information of multiple drones through UWB ranging, 360 laser radar, downward-looking laser ranging radar, optical flow sensor and inertial navigation system, and then performs data fusion to obtain accurate drone position information.

5. The method for fixed-point directional landing of an unmanned aerial vehicle according to claim 1, characterized in that: In the S2 preliminary positioning, preliminary position information of the UAV is obtained according to the least squares method or numerical optimization algorithm.

6. The method for fixed-point directional landing of an unmanned aerial vehicle according to claim 5, characterized in that: In the S2 preliminary positioning, the preliminary position information of the drone is obtained according to the least squares method, which specifically includes the following: S21 Since the propagation speed of UWB signals is close to the speed of light c, the distance d between the drone and each UWB base station is calculated using the formula d = c × t / 2, where t is the round-trip time of the signal; S22 Assume that there are n UWB base stations in the mine, and the coordinates of each base station are known, denoted as (x i ,y i ,z i ),i=1,2,…,n, the distance between the UWB tag on the drone and the i-th base station is d i ; S23 Assume the coordinates of the drone are (x, y, z). For each base station, establish an equation about the drone position (x, y, z): Therefore, n nonlinear equations are obtained, and a nonlinear equation system is obtained; S24 linearizes the above nonlinear equations; S25 uses the least squares method or solves the linearized equations to obtain the initial position of the drone.

7. The method for fixed-point directional landing of an unmanned aerial vehicle according to claim 6, characterized in that: S24 linearizes the above nonlinear equations by Taylor series expansion or first-order linear approximation.

8. The method for fixed-point directional landing of an unmanned aerial vehicle according to claim 5, characterized in that: In the S2 preliminary positioning, the preliminary position information of the UAV relative to each hangar is obtained according to the numerical optimization algorithm, and the numerical optimization algorithm adopts the Gauss-Newton method or the Levenberg-Marquardt algorithm, which specifically includes the following: S21 Since the propagation speed of UWB signals is close to the speed of light c, the distance d between the drone and each UWB base station is calculated using the formula d = c × t / 2, where t is the round-trip time of the signal; S22 Assume that there are n UWB base stations in the mine, and the coordinates of each base station are known, denoted as (x i ,y i ,z i ),i=1,2,…,n, the distance between the UWB tag on the drone and the i-th base station is d i ; S23 Assume the coordinates of the drone are (x, y, z). For each base station, establish an equation about the drone position (x, y, z): Therefore, n nonlinear equations are obtained, and a nonlinear equation system is obtained; S24' Initial guess: Provide an initial position guess of a drone; S25' parameter setting: set the parameters of the numerical optimization algorithm, including the number of iterations, convergence tolerance and damping factor; S26' Calculate Jacobian matrix: Calculate the Jacobian matrix of the nonlinear equations relative to the position based on the current position estimate; S27' Update step size: Use the Gauss-Newton method or Levenberg-Marquardt algorithm, combined with the Jacobian matrix and residual, to solve the update step size; S28' Position update: adjust the drone's position estimate according to the update step size; S29' Convergence check: Check whether the change in the position estimate is less than the convergence tolerance, or whether the number of iterations has reached the maximum limit; if the convergence condition is met, output the final position; otherwise, continue to iterate; when the algorithm converges, output the final drone position estimate.

9. The method for fixed-point directional landing of an unmanned aerial vehicle according to claim 1, characterized in that: In the S2 preliminary positioning, the UWB tag on the drone communicates with each UWB base station, obtains the instructions of the UWB base station through communication and sends them to the host computer of the drone for analysis; after analysis, the host computer generates a position control instruction and sends it to the drone actuator for execution.

10. A UAV fixed-point directional landing system, based on the method according to any one of claims 1 to 9, characterized in that: include: Base stations and positioning markers, UWB base stations deployed on each hangar in the mine, and multiple positioning markers deployed on the aprons of each hangar; The preliminary positioning module is used to communicate with each UWB base station through the UWB tag on the drone, obtain the distance between the drone and different UWB base stations, obtain the preliminary location information of the drone, and find and approach the nearest hangar; The precise positioning module is used to find the positioning mark through the visual sensor on the drone and adjust the landing position, direction and posture of the drone according to the positioning mark.

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