A trajectory planning method for automatic inspection of ultra-high arch dams by unmanned aerial vehicles

Abstract

The present invention provides an arch dam unmanned inspection route planning method, which is particularly applicable to the unmanned aerial vehicle automated inspection of large extra-high arch dams. Based on a large hyperbolic arch dam, the present invention constructs an arch dam function model; determines the flight altitude of the unmanned aerial vehicle according to the unmanned aerial vehicle parameters and the requirements of aerial photography, determines the photography baseline and the photography time interval, and calculates the photography track points of the arch dam body and the spillway area based on this; then the obtained aerial photography points are converted into coordinates to meet the input requirements of the unmanned aerial vehicle track points; then the edge position of the extra-high arch dam body is delineated, and the information of the aerial photography points outside the inspection range is removed; finally, the aerial photography points are allocated to each aircraft according to the unmanned aerial vehicle inspection operation time and flight speed. The present invention provides the steps and requirements of unmanned aerial photography of large arch dams on the scale of flight strips and inspection areas, solves the problem that the existing technology cannot be applied to hyperbolic arch dams due to the complex hyperbolic geometric structure of the arch dam, and fills the technical gap of the full-process automated unmanned detection of the arch dam surface.

Description

Technical Field

[0001] The invention relates to the technical field of track planning, and in particular to unmanned automatic inspection track planning of arch dams based on photogrammetry tasks. Background Art

[0002] With the increasing demand for water resources in recent years, my country has built many reservoirs and dam projects in recent years. Dam projects are large-scale, and the safety of reservoirs and dams is closely related to people's quality of life and safety. However, during the long-term service, due to changes in water level, temperature, creep and other factors, the arch dam concrete will produce defects such as cracks, erosion, seepage, etc. to varying degrees, affecting the safe operation of the arch dam. Therefore, regular inspection of the arch dam surface concrete and comprehensive analysis combined with relevant monitoring results are crucial to mastering the operating status of the arch dam and ensuring its safe operation.

[0003] In the past, dam surface defect detection could only rely on traditional detection by manual high-altitude hanging operations, human visual inspection, manual interpretation and identification. Traditional methods are often inefficient in detecting dam surface defects due to heavy tasks and human visual negligence, and it is difficult to detect concrete defects in a timely manner; they also have disadvantages such as long cycles, high costs, long distances from the dam surface, and high safety risks, which seriously endanger the stability and safe operation of hydropower station dams.

[0004] Existing drone trajectory planning has many different application scenarios, mainly used in power inspection, building crack detection and other fields. Unlike its regular structure, ultra-high arch dams often present a hyperbolic geometric structure, which makes it difficult to apply the currently proposed drone trajectory algorithm to the disease monitoring of arch dams, especially large ultra-high arch dams. In addition, most of the existing inspection algorithms are based on the assumption of ideal conditions and do not support multiple drone route planning, which is particularly important for later automated inspection operations. Therefore, it is urgent to explore new ultra-high arch dam surface inspection technologies to fill the technical gap in the full-process automated unmanned inspection of the arch dam surface.

[0005] In view of the above problems, a route planning method is designed, which is especially used for drone disease monitoring of large and extra-high arch dams. It solves the problem that the current technology cannot be used for hyperbolic arch dams and does not support multiple drone trajectory planning. Summary of the invention

[0006] In view of the above-mentioned defects, the technical problem solved by the present invention is to provide a trajectory planning method for automatic inspection of large-scale extra-high arch dams by unmanned aerial vehicles, so as to fill the technical gap in the full-process automated unmanned inspection of the arch dam surface.

[0007] The present invention provides a track planning for automatic inspection of a large-scale ultra-high arch dam by a UAV, and the specific steps include:

[0008] Step 1: According to the flight area information, the arch dam coordinate system is established to obtain the plane coordinate function of the hyperbolic arch dam, the arch ring body parameters (including the thickness of the arch crown beam, the thickness of the arch end, the semi-center angle, the chord length, the arch crown curvature radius) and the arch crown beam section parameters, and the arch dam is partitioned as a whole to construct the hyperbolic function model of the arch dam in different areas;

[0009] Step 2: Obtain relevant information of the drone and basic parameters of aerial photography, including camera parameters such as sensor size, image size, focal length, shutter speed, and photography parameters such as expected lateral overlap, expected heading overlap, flight speed, and flight distance from the arch dam body;

[0010] Step 3: Calculate the ground resolution of the image, the aerial photography baseline, the lateral photography baseline, and the photography time interval according to the given parameters;

[0011] Step 4: Based on the aerial photography parameters and the hyperbolic function model of the ultra-high arch dam, the flight altitude of the UAV is determined, and the photography track points of the arch dam body and the spillway area are calculated accordingly;

[0012] Step 5: Based on the route shooting point in the arch dam coordinate system, coordinate conversion is performed on the shooting point to obtain the position information of the shooting point in the WGS84 coordinate system;

[0013] Step 6: Considering the difference between the design drawings and the actual construction, the edge position of the main body of the ultra-high arch dam is delineated, and the information of the aerial photography points outside the range is removed to obtain the longitude, latitude and elevation information of all photography points in the inspection area;

[0014] Step 7: Estimate the number of photography points based on the inspection time and flight speed of the drone, and allocate the aerial photography points to each aircraft according to the actual situation;

[0015] Step 8: Determine the rationality of the track planning result information, and finally obtain the target flight area track information and the inspection mission results of each UAV under the correct basic parameters.

[0016] Preferably, the step 1 is to construct a hyperbolic function model of the arch dam, and the specific steps include:

[0017] Step 1.1. According to the flight area information, establish the arch dam coordinate system with the center point of the upstream dam surface as the coordinate origin, the symmetry axis direction of the downstream arch dam as the y-axis, the direction perpendicular to the y-axis as the x-axis, and the dam axis vertically downward as the z-axis;

[0018] Step 1.2: Analyze the area where the spillway is located based on the design drawings, and divide the operating area into three parts: the arch dam body-left bank, the spillway area, and the arch dam body-right bank based on the distribution of the spillway of the large extra-high arch dam.

[0019] Preferably, the step 3, calculating specific parameters of aerial photography, comprises the following specific steps:

[0020] Step 3.1, according to the sensor size, focal length and flight distance from the arch dam body given in step 2, calculate the actual ground range of the image as formula 1;

[0021] Step 3.2, combined with the image size of the drone photography, calculate the ground resolution of the image as formula 2;

[0022] Step 3.3, based on the actual imaging length and the expected heading overlap, the heading photography baseline is calculated as Formula 3; based on the actual imaging width and the expected lateral overlap, the lateral photography baseline is calculated as Formula 4;

[0023] Step 3.4: Calculate the photography time interval as Formula 5 based on the heading overlap and the flight speed of the drone relative to the ground.

[0024] Preferably, the step 4, calculating the photography track points in each area, specifically comprises the following steps:

[0025] Step 4.1, combining the arch dam crest elevation and the actual imaging width, obtain the flight altitude of the first flight strip as Formula 6;

[0026] Step 4.2, based on the flight altitude of the flight strip, combined with the plane coordinate function of the hyperbolic arch dam, the arch ring body parameters and the arch crown beam section parameters, linear interpolation is performed to obtain the arch end thickness, centerline chord length and arch end curvature radius at the desired altitude;

[0027] Step 4.3, based on the arch dam parameters at this elevation, calculate the aerial photography points of a single flight strip;

[0028] Step 4.4, based on the calculated lateral photography baseline, determine the specific altitude of the next flight strip of the arch dam body as Formula 12;

[0029] Step 4.5: Determine whether the elevation of the next navigation zone is within the elevation range of the arch dam. If so, return to step 4.2. If not, complete the route calculation in the area.

[0030] Preferably, the specific steps of converting the arch dam coordinate system to the WGS84 latitude and longitude coordinate system in step 5 include:

[0031] Step 5.1, obtain the coordinates of the control points of the coordinate system transformation;

[0032] Step 5.2: Use the known control point coordinates to solve the coordinate transformation parameters as formula 13, and transform the arch dam coordinates into geodetic coordinates (X, Y, Z) in the WGS84 coordinate system;

[0033] Step 5.3: Use the geodetic coordinate system conversion parameters to convert the geodetic coordinates to the longitude and latitude of the aerial photography point to meet the input requirements of the drone aerial photography point.

[0034] Preferably, the specific steps of calculating the aerial photography points of a single flight strip in step 4.3 include:

[0035] Step 4.3.1, according to the actual imaging length of the image, obtain the arc length of the center line of the first image of the current flight strip as formula 7;

[0036] Step 4.3.2: According to the calculation formula of the arc length of the arch ring centerline of the arch dam, use Newton's method to solve the nonlinear equation to obtain the coordinates of the corresponding position of the aerial photography point on the centerline;

[0037] Step 4.3.3, based on the coordinates of the aerial photography point and the radius of curvature of the crown, calculate the radial angle of the position relative to the symmetry axis (y axis) of the dam body as Formula 8;

[0038] Step 4.3.4, combining the flight distance from the arch dam body and the radial angle, calculate the actual coordinates of the aerial photography point in the arch dam coordinate system as Formula 9;

[0039] Step 4.3.5, based on the aerial photography baseline, calculate the arc length of the centerline of the next aerial photography point as Formula 10;

[0040] Step 4.3.6, determine whether the next aerial point is within the current area. If so, return to step 4.3.2. If not, complete the calculation of the aerial points in the current flight zone.

[0041] Step 4.3.7: Based on the calculated coordinates of the aerial photography points, calculate the yaw angle of each aerial photography point as Formula 11.

[0042] It can be seen from the above scheme that the arch dam unmanned inspection route planning method provided by the present invention is particularly applicable to the unmanned inspection of large and extra-high arch dams. On the basis of a large hyperbolic arch dam, the present invention constructs an arch dam function model; determines the drone flight altitude according to the drone parameters and aerial photography requirements, determines the photography baseline and photography time interval, and calculates the photography track points of the arch dam body and the spillway area based on this; then the obtained aerial points are converted into coordinates to meet the drone track point input requirements; then the edge position of the extra-high arch dam body is delineated, and the aerial photography point information outside the inspection range is removed; finally, the aerial photography points are allocated to each aircraft according to the drone inspection operation time and flight speed. The present invention provides the steps and requirements for drone aerial photography of large arch dams on the scale of flight strips and inspection areas, which solves the problem that the current technology cannot be used for hyperbolic arch dams and does not support drone track planning for multiple flights. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] 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 some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 is an overall flow chart of an embodiment of the present invention;

[0045] Figure 2 This is a flow chart of calculating aerial photography points in each area in an embodiment of the present invention;

[0046] Figure 3 This is a flow chart of calculating aerial photography points for a single flight strip according to an embodiment of the present invention;

[0047] Figure 4 This is a schematic diagram of the coordinates of a plane arch ring according to an embodiment of the present invention;

[0048] Figure 5 This is a schematic cross-sectional view of a crown beam according to an embodiment of the present invention;

[0049] Figure 6 A schematic diagram of the rotation of a three-dimensional coordinate system according to an embodiment of the present invention;

[0050] Figure 7 The cross section and zoning operation diagram of the arch dam according to the embodiment of the present invention;

[0051] Figure 8 This is a design diagram of an unmanned inspection according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The present invention proposes a trajectory planning method for UAV disease monitoring of extra-high arch dams, and has been successfully applied to the unmanned inspection of the downstream dam surface of the extra-high arch dam of Xiaowan Hydropower Plant in Yunnan Province. Regular inspection of the arch dam surface concrete helps to understand the operating status of the arch dam, thereby ensuring the safe and normal operation of the arch dam.

[0053] 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.

[0054] Please also read Figures 1 to 8 Now, a specific implementation method of the large-scale extra-high arch dam UAV disease monitoring trajectory planning method provided by the present invention is described, and the specific steps include:

[0055] Step 1: According to the flight area information, the arch dam coordinate system is established to obtain the plane coordinate function of the hyperbolic arch dam, the arch ring body parameters (including arch crown beam thickness, arch end thickness, semi-center angle, chord length, arch crown curvature radius) and arch crown beam section parameters, and the arch dam is partitioned as a whole to construct the hyperbolic function model of the arch dam in different areas.

[0056] Step 1.1, see Figure 5 According to the inspection area information, the arch dam coordinate system is established with the center point of the upstream dam surface as the coordinate origin, the symmetry axis direction of the downstream arch dam as the y-axis, the direction perpendicular to the y-axis as the x-axis, and the dam axis vertically downward as the z-axis;

[0057] Step 1.2, see Figure 8 According to the design drawings, the area where the spillway is located is analyzed, and the coordinate range of each area in the arch dam coordinate system is determined; according to the distribution of spillways of large extra-high arch dams, the operating area is divided into three parts: the arch dam body-left bank, the spillway area and the arch dam body-right bank.

[0058] Step 2: Obtain the relevant information of the UAV and the basic parameters of aerial photography, where the basic parameters include the inspection area (downstream surface of the extra-high arch dam), aircraft parameters, camera parameters and aerial photography parameters.

[0059] Aircraft parameters include aircraft name, maximum flight speed, minimum flight speed, recommended flight speed, maximum flight altitude, minimum flight altitude, and maximum flight range (need to be considered when planning a single route for the aircraft).

[0060] The camera parameters include the camera name, focal length (the camera is fixed-focus, which requires the resolution and aircraft altitude to be calculated), whether it supports focus adjustment (confirm the objective conditions of the camera, and if so, obtain the focal length range), the minimum shooting time interval (the heading distance between two adjacent images should not be less than the minimum shooting time interval multiplied by the actual flight speed of the aircraft), the pixel size (calculate the actual ground size of a single pixel), the sensor size (used to calculate the actual ground imaging range of the image frame), the number of pixels on the x-axis (the number of pixels horizontally in the photo), and the number of pixels on the y-axis (the number of pixels vertically in the photo).

[0061] Aerial photography parameters include the expected heading overlap (the overlap between two adjacent images along the flight direction of the aircraft, that is, the overlap percentage between two adjacent images on the same flight strip, between 60% and 65%), the expected lateral overlap (the overlap between two adjacent images perpendicular to the flight direction of the aircraft, that is, the overlap percentage between two adjacent strips, between 30% and 35%), the flight distance from the main body of the arch dam, the flight speed (calculating the photography exposure time and the operating range of each aircraft), the number of aircraft (a natural number for flight sortie arrangement), wind direction, and wind speed (to confirm whether the flight conditions are met).

[0062] Step 3: Based on the given parameters, calculate the ground resolution of the image, the aerial photography baseline, the lateral photography baseline, and the photography time interval.

[0063] Step 3.1: Based on the camera sensor size (lx, ly), focal length (f), and flight distance (D) from the arch dam body, calculate the actual ground range of the image:

[0064]

[0065] Step 3.2: Calculate the ground resolution μ (the ratio of the pixel size on the image to the actual geographic distance) of the image based on the image size (px, py) of the drone photography:

[0066] μ=dx / px=dy / py (Formula 2)

[0067] Step 3.3, based on the actual imaging length dx and the expected heading overlap qx, calculate the heading photography baseline Bx as:

[0068] Bx=(1-qx)×dx. (Formula 3)

[0069] According to the actual imaging width dy and the expected lateral overlap qy, the lateral imaging baseline By is calculated as:

[0070] By=(1-qy)×dy. (Formula 4)

[0071] Step 3.4: Calculate the photography time interval τ based on the heading overlap qx and the flight speed W of the drone relative to the ground:

[0072] The main factors affecting the later image stitching are heading overlap and lateral overlap. Aerial images should have sufficient heading overlap and lateral overlap to effectively ensure the correct stitching of the images obtained by the drone in the later stage. This kind of aerial photography task needs to be carried out by fixed-point shooting, and the drone track planning algorithm needs to give specific aerial points; coupled with the complex geometric structure and function model of the hyperbolic arch dam, this also makes it difficult to apply the currently proposed drone track algorithm to the disease monitoring of arch dams, especially large and extra-high arch dams.

[0073] Step 4: See Figure 2 Based on the determined aerial photography parameters and the hyperbolic function model of the ultra-high arch dam, the UAV flight altitude (determined by the lateral photography baseline) is determined, and the photography tracks of the arch dam body and the spillway are calculated accordingly. It should be noted that due to the flight altitude of the aerial photography in the spillway area, attention should be paid to avoiding obstacles such as diversion holes and spillways, that is, the aerial photography distance D' in this area should generally be greater than that of the arch dam body.

[0074] Step 4.1, combine the arch dam crest elevation H0 and the actual imaging width dy to obtain the first flight strip flight elevation H1:

[0075] H1=dy / 2 (Formula 6)

[0076] Step 4.2: Based on the flight altitude of the flight strip, combined with the plane coordinate function of the hyperbolic arch dam, the arch ring shape parameters and the arch crown beam section parameters, linear interpolation is performed to obtain the expected elevation H i The thickness of the arch end, the length of the centerline chord and the radius of curvature of the arch end are calculated.

[0077] Step 4.3, see Figure 3 , based on the arch dam parameters at this elevation, the aerial photography points of a single flight strip are calculated.

[0078] Step 4.3.1. According to the actual imaging length dx of the image, obtain the arc length of the center line of the first image of the current flight strip:

[0079]

[0080] in, Indicates the arc length of the centerline corresponding to the position of the j-th image of the i-th flight strip.

[0081] Step 4.3.2: According to the calculation formula of the arc length of the arch ring centerline of the arch dam, use Newton's method to solve the nonlinear equation to obtain the coordinates of the corresponding position of the aerial point on the centerline. in Y i j Respectively represent the X-axis and Y-axis coordinates of the j-th image of the ith flight strip;

[0082] Step 4.3.3: Based on the coordinates of the aerial photography point and the crown curvature radius RC, calculate the radial angle of the position relative to the symmetry axis (y axis) of the dam body.

[0083]

[0084] Step 4.3.4: Combine the flight distance D from the main arch dam and the thickness T of the arch dam at that location. i , radial angle The actual coordinates of the aerial photography point in the arch dam coordinate system are calculated as follows:

[0085]

[0086] Step 4.3.5, according to the aerial photography baseline Bx, calculate the centerline arc length of the next aerial photography point:

[0087]

[0088] Step 4.3.6, determine whether the next aerial point is within the current area. If so, return to step 4.3.2. If not, complete the calculation of the aerial points in the current flight zone.

[0089] Step 4.3.7, based on the calculated coordinates of the aerial photography points, calculate the yaw angle θ of each aerial photography point:

[0090]

[0091] Among them, N i is the total number of aerial points in the i-th flight strip. In other words, the present invention adopts the deflection angle of the line connecting the positions of the previous and next aerial points relative to the y-axis direction as the yaw angle of the current aerial point; if it is the first aerial point of the flight strip, the current aerial point and the next aerial point are used for calculation; if it is the last aerial point of the current flight strip, the current aerial point and the previous aerial point are used for calculation. The present invention stipulates that the yaw angle on the left side of the symmetry axis (y-axis) of the arch dam is set to a negative number, and the yaw angle on the right side is set to a positive number.

[0092] Step 4.4: Based on the calculated lateral photography baseline, determine the specific altitude of the next flight strip of the arch dam body:

[0093] H i =H1+(i-1)×By,(i≥1) (Formula 12)

[0094] Among them, H i Indicates the shooting altitude of the i-th flight strip.

[0095] Step 4.5: Determine whether the next navigation zone elevation is within the arch dam elevation range. If so, return to step 4.2; if not, complete the route calculation within the area.

[0096] Step 5: Based on the route shooting point in the arch dam coordinate system, the coordinates of the shooting point are transformed to obtain the position information of the shooting point in the WGS84 coordinate system.

[0097] Step 5.1, obtain the coordinates of the control points of the coordinate system transformation;

[0098] Step 5.2: Use the known control point coordinates to solve the coordinate transformation parameters. The coordinate transformation step is to transform the initial coordinate system OX G Y G Z G ε around the three coordinate axes x ,ε y ,ε z After the rotation, the origin of the rotation system is translated to the origin of the next coordinate system O-X0Y0Z0. At this time, the transformation can be described as:

[0099]

[0100] See attached Figure 6 The rotation order shown corresponds to three transformation matrices. Multiplying the three rotation matrices together can get the total rotation matrix:

[0101]

[0102] It is explained here that the large arch dam targeted by the present invention is often regarded as a rigid body during parameter transformation, that is, no scale scaling parameters are involved during three-dimensional coordinate transformation.

[0103] Step 5.3, using the calculated conversion parameters, convert the coordinates of the aerial point in the arch dam coordinate system into the geodetic coordinates (X, Y, Z) in the WGS84 coordinate system;

[0104] Step 5.4: Use the geodetic coordinate system conversion parameters to convert the geodetic coordinates to the longitude and latitude of the aerial photography point to meet the input requirements of the drone aerial photography point (B, L, H).

[0105] Step 6: Considering the difference between the design drawings and the actual construction, the edge position of the main body of the ultra-high arch dam is delineated, and the aerial photography point information outside the range is removed to obtain the longitude, latitude and elevation information of all photography points in the inspection area. In the embodiment, since the angle between the central axis of the ultra-high arch dam and the true north direction is 178°, the downstream surface of the main body of the arch dam is distributed in the south direction; therefore, when the edge points are removed, the longitude must be within the left bank-right bank range.

[0106] Step 7: Estimate the number of photography points based on the UAV inspection operation time T, flight speed V and heading photography baseline length Bx:

[0107]

[0108] See attached Figure 8 In the unmanned inspection of the extra-high arch dam, the aircraft uses a cyclic operation to reduce unnecessary round trips of the drone. It is particularly important to note that the number of aerial photography points for each flight is obtained by estimation; when allocating the track points of each drone flight, the number of planned flight strips should be rounded to avoid repeated scanning of some areas during automated operations.

[0109] Step 8: Determine the rationality of the track planning result information, and finally obtain the target flight area track information and the inspection mission results of each UAV under the correct basic parameters.

[0110] The present invention constructs an arch dam function model based on a large-scale hyperbolic arch dam; determines the UAV flight altitude, the photography baseline and the photography time interval according to the UAV parameters and the aerial photography requirements, and calculates the photography track points of the arch dam body and the spillway area; then performs coordinate conversion on the obtained aerial photography points to meet the UAV track point input requirements; then delimits the edge position of the ultra-high arch dam body, and removes the aerial photography point information outside the inspection range; finally, distributes the aerial photography points to each aircraft according to the UAV inspection operation time and flight speed.

[0111] Compared with the prior art, the present invention takes into account the particularity of the geometric structure of large arch dams and divides the inspection area of ​​ultra-high arch dams into different areas. Different aerial photography distances are adopted for different arch dam bodies and different construction structures of spillways, ensuring the safety and reliability of automated operations while maximizing photography accuracy. The present invention fully considers the requirements of ground resolution, heading overlap and lateral overlap in aerial photography operations, effectively ensuring the accuracy of drone aerial images and the image stitching and disease monitoring of aerial photography in the later stage.

[0112] Based on the present invention, the track planning of automatic inspection of arch dams, especially large and extra-high arch dams by drones can be completed, which can ensure regular inspection of the arch dam surface concrete, help to understand the operating status of the arch dam, and thus ensure the safe and normal operation of the arch dam.

[0113] The specific embodiments described herein are merely examples of the spirit of the present invention. A person skilled in the art of the present invention may make various modifications or additions to the specific embodiments described or replace them in a similar manner, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for track planning of automatic inspection of ultra-high arch dam by unmanned aerial vehicle, characterized in that: The following steps are included: Step 1: According to the flight area information, the arch dam coordinate system is established to obtain the plane coordinate function of the hyperbolic arch dam, the arch ring body parameters and the arch crown beam section parameters, wherein the arch ring body parameters include the thickness of the arch crown beam, the thickness of the arch end, the semi-center angle, the chord length and the arch crown curvature radius; and the arch dam is partitioned as a whole to construct the hyperbolic function model of the arch dam in different areas; Step 2: Obtain relevant information of the drone and basic parameters of aerial photography, including camera parameters such as sensor size, image size, focal length, shutter speed, and photography parameters such as expected lateral overlap, expected heading overlap, flight speed, and flight distance from the main body of the arch dam; Step 3: Calculate the ground resolution of the image, the aerial photography baseline, the lateral photography baseline, and the photography time interval according to the given parameters; Step 4: Based on the aerial photography parameters and the hyperbolic function model of the ultra-high arch dam, the flight altitude of the UAV is determined, and the photography track points of the arch dam body and the spillway area are calculated accordingly; Step 5: Based on the route shooting point in the arch dam coordinate system, coordinate conversion is performed on the shooting point to obtain the position information of the shooting point in the WGS84 coordinate system; Step 6: Considering the difference between the design drawings and the actual construction, the edge position of the main body of the ultra-high arch dam is delineated, and the information of the aerial photography points outside the range is removed to obtain the longitude, latitude and elevation information of all photography points in the inspection area; Step 7: Estimate the number of photography points based on the inspection time and flight speed of the drone, and allocate the aerial photography points to each aircraft according to the actual situation; Step 8: Determine the rationality of the track planning result information, and finally obtain the target flight area track information and the inspection task results of each UAV under the correct basic parameters; The specific steps of step 4 include: Step 4.1, combine the arch dam crest elevation H0 and the actual imaging width dy to obtain the first flight strip flight elevation H1: H1=dy / 2 (Formula 6) Step 4.2: Based on the flight altitude of the flight strip, combined with the plane coordinate function of the hyperbolic arch dam, the arch ring shape parameters and the arch crown beam section parameters, linear interpolation is performed to obtain the expected elevation H i The thickness of the arch end, the length of the centerline chord, and the radius of curvature of the arch end; Step 4.3, based on the arch dam parameters at this elevation, calculate the aerial photography points of a single flight strip; Step 4.4: Based on the calculated lateral photography baseline, determine the specific altitude of the next flight strip of the arch dam body: H i =H1+(i-1)×By,(i≥1) (Formula 7) Among them, H i represents the shooting altitude of the ith flight strip; Step 4.5: Determine whether the next navigation zone elevation is within the arch dam elevation range. If so, return to step 4.2; if not, complete the route calculation within the area.

2. According to claim 1, a method for track planning of automatic inspection of ultra-high arch dam by unmanned aerial vehicle is characterized in that: The specific steps of step 1 include: Step 1.

1. According to the flight area information, establish the arch dam coordinate system with the center point of the upstream dam surface as the coordinate origin, the symmetry axis direction of the downstream arch dam as the y-axis, the direction perpendicular to the y-axis as the x-axis, and the dam axis vertically downward as the z-axis; Step 1.2: Analyze the area where the spillway is located based on the design drawings, and divide the operating area into three parts: the arch dam body-left bank, the spillway area, and the arch dam body-right bank based on the distribution of the spillway of the large extra-high arch dam.

3. The method for track planning of automatic inspection of ultra-high arch dam by unmanned aerial vehicle according to claim 1 is characterized in that: The specific steps of step 3 include: Step 3.1, based on the camera's sensor size (lx, ly), focal length (f), and flight distance (D) from the main arch dam, calculate the actual ground range of the image: dx=lx×D / f dy=ly×D / f (Formula 1) Step 3.2: Calculate the ground resolution μ (the ratio of the pixel size on the image to the actual geographic distance) of the image based on the image size (px, py) of the drone photography: μ=dx / px=dy / py (Formula 2) Step 3.3, based on the actual imaging length dx and the expected heading overlap qx, calculate the heading photography baseline Bx as: Bx=(1-qx)×dx. (Formula 3) According to the actual imaging width dy and the expected lateral overlap qy, the lateral imaging baseline By is calculated as: By=(1-qy)×dy. (Formula 4) Step 3.4: Calculate the photography time interval τ based on the heading overlap qx and the flight speed W of the drone relative to the ground:

4. The method for track planning of automatic inspection of ultra-high arch dam by unmanned aerial vehicle according to claim 1 is characterized in that: The specific steps of step 5 include: Step 5.1, obtain the coordinates of the control points of the coordinate system transformation; Step 5.2: Use the known control point coordinates to solve the coordinate conversion parameters and convert the arch dam coordinates into geodetic coordinates (X, Y, Z) in the WGS84 coordinate system; Step 5.3: Use the geodetic coordinate system conversion parameters to convert the geodetic coordinates to the longitude and latitude of the aerial photography point to meet the input requirements of the drone aerial photography point.

5. The method for track planning of automatic inspection of ultra-high arch dam by unmanned aerial vehicle according to claim 1 is characterized in that: The specific steps of step 4.3 include: Step 4.3.

1. According to the actual imaging length dx of the image, obtain the arc length of the center line of the first image of the current flight strip: in, Indicates the arc length of the centerline corresponding to the position of the jth image of the i-th flight strip; Step 4.3.2: According to the calculation formula of the arc length of the arch ring centerline of the arch dam, use Newton's method to solve the nonlinear equation to obtain the coordinates of the corresponding position of the aerial point on the centerline. in They represent the X-axis and Y-axis coordinates of the j-th image of the ith flight strip respectively; Step 4.3.3: Based on the coordinates of the aerial photography point and the crown curvature radius RC, calculate the radial angle of the position relative to the symmetry axis (y axis) of the dam body. Step 4.3.4: Combine the flight distance D from the main arch dam and the thickness T of the arch dam at that location. i , radial angle The actual coordinates of the aerial photography point in the arch dam coordinate system are calculated as follows: Step 4.3.5, according to the aerial photography baseline Bx, calculate the centerline arc length of the next aerial photography point: Step 4.3.6, determine whether the next aerial point is within the current area. If so, return to step 4.3.

2. If not, complete the calculation of the aerial points in the current flight zone. Step 4.3.7: Calculate the yaw angle θ of each aerial point based on the calculated aerial point coordinates.

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