Tunnel inner surface detection device and method based on three-dimensional laser scanning

Abstract

The present application belongs to the field of optical detection technology of rail transit, and particularly relates to a tunnel inner surface detection device and method based on three-dimensional laser scanning. The detection device comprises a UAV, a three-dimensional laser scanner, a central control platform and a plurality of optical guiding systems. An electronic laser target is also installed on the UAV. The detection method comprises the steps of BIM modeling, tunnel segmentation, import of planning path, detection device erection, planning path analysis, three-dimensional scanning, flight path monitoring and correction. The present application can perform high-precision three-dimensional scanning of the tunnel inner surface with the aid of the UAV. In a closed space, the UAV can accurately fly along the planned path at a fixed height without relying on satellite navigation signals. The present application can be carried out in parallel with other construction work in the tunnel and does not interrupt other construction work.

Description

Technical Field

[0001] This invention belongs to the field of optical inspection technology for rail transit, specifically relating to a tunnel interior surface inspection device and method based on three-dimensional laser scanning. Background Technology

[0002] Existing 3D laser scanning technology for tunnels is mostly used in subway tunnels or other rail-guided tunnels. A 3D laser scanner mounted on a railcar moves directionally along a track within the tunnel to create high-precision point cloud data of the tunnel's interior and fit a 3D model of the tunnel's interior. However, for tunnels still under excavation, tunnels with only initial supports completed, or connecting passages between tunnels, there is no track for the railcar to travel smoothly and with a defined trajectory. The laser scanner lacks a fixed directional track, resulting in chaotic and disorganized point cloud data with excessive errors. This makes it impossible to accurately fit a 3D model of the tunnel's interior, and consequently, to accurately determine the over- or under-excavation of the tunnel surface.

[0003] With the development of microelectromechanical systems (MEMS), navigation, and communication technologies, various intelligent automated vehicles with navigation, path planning, and remote control functions have emerged, among which drones and autonomous guided vehicles (AGVs) are the most representative. Some related technologies disclose solutions for using AAVs paired with 3D laser scanners to perform 3D laser scanning of tunnel interiors. However, AAVs rely on flat ground for movement, and the flatness of the ground cannot be guaranteed before the track is laid. This results in excessive vibration of the onboard 3D laser scanner, leading to chaotic point cloud data and making it impossible to fit a high-precision 3D model of the tunnel interior. This significantly limits the application of AAVs paired with 3D laser scanners for 3D laser scanning of tunnel interiors. Other related technologies disclose solutions for using drones paired with 3D laser scanners to perform 3D laser scanning of tunnel interiors. However, in tunnels, which are deeply buried and enclosed environments, satellite navigation signals are weak or even blocked. Drones cannot accurately locate themselves using satellite navigation, and cannot guarantee that they will fly precisely along the ideal path. This is especially true for tunnels with curves, where the accuracy of the flight trajectory cannot be guaranteed. Consequently, it is impossible to guarantee high-precision 3D scanning of the tunnel interior. This presents a significant challenge to the application of drones in the field of tunnel 3D laser scanning. Summary of the Invention

[0004] The present invention aims to provide a tunnel interior surface inspection device and method based on three-dimensional laser scanning, so as to use a drone to perform high-precision three-dimensional scanning of the tunnel interior surface.

[0005] To achieve the above objectives, one technical solution adopted by the present invention is to provide a tunnel interior surface inspection device based on three-dimensional laser scanning, including a drone, a three-dimensional laser scanner, a central control platform, and several sets of optical guidance systems:

[0006] The drone has path planning, remote control and hovering functions. The drone is equipped with a remote control receiver and an electronic laser target.

[0007] A 3D laser scanner, mounted on a drone;

[0008] The optical guidance system includes a support, a laser, and a high-precision rotary stage. The high-precision rotary stage is mounted on the support, and the electron laser target is connected to a signal transmitter. The laser is mounted on the high-precision rotary stage.

[0009] The central control platform includes an analysis module, a control module, a signal receiver, and a remote control transmitter. The high-precision rotary table and the remote control transmitter are electrically connected to the control module, and the analysis module is electrically connected to the signal receiver and the control module.

[0010] The working principle and beneficial effects of this solution are as follows: The centerline of the tunnel to be measured is located through measurement. Then, combining BIM technology, the drone's flight path is planned along the tunnel centerline using its path planning function. The center of the electron laser target is located on the tunnel centerline, and the drone maintains a certain altitude throughout the flight. To achieve high-precision 3D scanning of the tunnel's interior surface using the drone, the center of the electron laser target must always be positioned on the tunnel centerline and the planned path. Therefore, this solution can:

[0011] For straight sections of the tunnel: An optical guidance system is set up at the tunnel centerline. A remotely controlled drone takes off and hovers at the starting point of the planned path. A high-precision rotary table rotates the laser, aligning its beam with the tunnel centerline and the drone. The laser beam illuminates the center of the electron laser target. The drone flies forward at a constant speed in a straight line, while a 3D laser scanner scans the tunnel interior during flight. The electron laser target senses the position of the laser beam and transmits this information to the analysis module via a signal transmitter. The analysis module analyzes the position of the laser beam relative to the target center. If the beam illuminates the target center, the drone continues flying forward without adjusting its trajectory. If the beam is to the right of the target center, the drone is veering to the left. Upon receiving the analysis results, the control module adjusts the drone to fly to the right until the beam illuminates the target center again. Conversely, if the beam is to the left, the drone flies to the left. Corrections are also made if the beam is too high or too low relative to the target center. Therefore, the drone can always be analyzed along the planned path, thereby achieving high-precision three-dimensional scanning of the inner surface of a straight tunnel.

[0012] For curved sections of the tunnel: Two optical guidance systems are installed on either side of the tunnel centerline. Two high-precision rotary tables are then used to rotate the lasers from the two lasers, causing the intersection point to lie on the planned path. The control module precisely controls the rotation of the two rotary tables, allowing the intersection point to move uniformly along the planned path at the speed of the drone. Once the remote-controlled drone takes off and hovers at the starting point of the planned path, the intersection point also illuminates the center of the electron laser target. If the electron laser target senses a deviation in the position of the laser intersection point, the remote-controlled drone can adjust until the intersection point returns to the center, ensuring the drone always flies along the planned path of the curve. This achieves high-precision three-dimensional scanning of the inner surface of the curved tunnel.

[0013] This solution enables drones to fly accurately along a planned path at a fixed altitude within a confined space without relying on satellite navigation signals. Even if deviations occur during flight, the flight path can be corrected quickly, in real time, and with high precision. Combined with a 3D laser scanner, it is highly suitable for high-precision 3D scanning of the inner surface of tunnels without the need for manual intervention, resulting in a high degree of automation.

[0014] This solution ensures the accuracy of the UAV's flight trajectory by combining the UAV with an optical guidance system. Moreover, the optical guidance system has the characteristics of long guidance distance, high guidance accuracy, and high degree of automation. A single UAV flight can scan 500m to 4000m (depending on the power of the laser and the direction of the tunnel), which is more than an order of magnitude higher than the existing technology. Under the same scanning accuracy, this solution can greatly improve work efficiency.

[0015] This solution occupies little space (especially for scanning straight tunnels, requiring only about 100cm of space along the tunnel centerline), and can scan the tunnel in segments. Therefore, it can be carried out in parallel with other construction work in the tunnel without interrupting or posing a safety threat to other construction work in the tunnel. It can be completed independently without relying on the cooperation of other construction trades, which is very conducive to its widespread use.

[0016] Optionally, a battery is also included, which is mounted on the drone. The battery can power the drone, as well as the onboard electronic laser target, signal transmitter, and 3D laser scanner.

[0017] Optionally, a light-shielding block is provided at the center of the electron laser target. The photosensitive surface of the electron laser target mainly consists of CCD photosensitive electronic components, and prolonged exposure to laser light will significantly shorten the lifespan of these components. With the light-shielding block installed, the laser will shine directly onto the block, and the electron laser target will not detect the irradiation point. Combined with the logic in the control system indicating that the laser is on, it can be determined that the drone has not deviated from the planned path. Only after the drone deviates will the laser irradiation point fall outside the edge of the light-shielding block and be detected by the electron laser target. Since the drone will not deviate from the planned path for most of its flight time, this ensures that the laser shines directly onto the light-shielding block, rather than the photosensitive surface of the electron laser target, thus extending the lifespan of the electron laser target. Furthermore, during tunnel construction, construction machinery in the environment may cause slight vibrations in the ground. These vibrations are transmitted to the laser through the support structure, causing the irradiation point to move back and forth on the electron laser target. This could lead the analysis module to misjudge that the drone has deviated from the planned path. By setting the shape and size of the shading blocks, the reciprocating movement of the irradiation point caused by the vibration of construction machinery can be completely placed on the shading blocks, thus avoiding misjudgment.

[0018] Another technical solution adopted by the present invention is to provide a method for detecting the inner surface of a tunnel based on three-dimensional laser scanning using the above-mentioned detection device, comprising the following steps:

[0019] BIM Modeling: Import the tunnel design data into BIM modeling software, and determine the tunnel centerline after completing the BIM modeling of the tunnel;

[0020] Tunnel segmentation: Based on the tunnel centerline, the tunnel is divided into several straight and curved segments along the direction of the tunnel centerline. The design data of the tunnel centerline position of each segment is obtained. Based on the design data of the tunnel centerline position, the flight path of the UAV at a height of 1.0m to 1.5m above the ground in each segment is planned. The planned path includes the starting point and the ending point.

[0021] Import the planned path: Import the planned path into the drone, place the drone at the starting point of the planned path, and set the drone's flight speed; import the planned path into the control module;

[0022] Setting up the detection device: Install the 3D laser scanner, electron laser target, and signal transmitter onto the drone, start the drone and hover it so that the center of the electron laser target coincides with the starting point; install the bracket at the starting position of the planned path, and adjust the height of the laser by the bracket so that the irradiation point of the laser beam coincides with the center of the target;

[0023] Path planning analysis: Based on the flight speed and path planning data, the control module analyzes the time-sharing control points of the illumination point on the path planning;

[0024] 3D scanning: The drone flies along the planned path at the set speed and starts the 3D laser scanner;

[0025] Flight path monitoring and correction: When the UAV starts flight, a high-precision rotary table is activated simultaneously. The high-precision laser beam drives the laser to illuminate the time-sharing control points sequentially at the same speed as the flight speed. The electronic laser target senses the laser illumination point and sends the illumination point position information to the analysis module through the signal transmitter. After receiving the signal through the signal receiver, the analysis module analyzes the position of the laser illumination point relative to the target center. Based on the direction and position of the deviation of the illumination point from the target center, the control module and remote transmitter adjust the UAV's flight direction until the target center coincides with the illumination point, and until the UAV flies to the destination.

[0026] Optionally, in the tunnel segmentation step, the slope of each tunnel segment remains constant, and the slope value of each tunnel segment is obtained. The slope value of the planned path is equal to the slope value of that tunnel segment. In this way, the high-precision rotary table only needs to rotate laterally, instead of longitudinally.

[0027] Optionally, the spacing between time-sharing control points is 0.5m to 1m, or the time interval between time-sharing control points is 0.1s to 0.5s.

[0028] Optionally, a test flight step is included before the flight path monitoring and correction steps: the UAV flies 50m to 100m along the planned path from the starting point to the ending point, observing whether the illumination point always coincides with the target center. This is used to verify whether the laser illumination point coincides with the planned path setting, thereby verifying whether the laser position is installed accurately. This test flight step can be repeated multiple times.

[0029] Optionally, in the flight path monitoring and correction step, for the straight section of the tunnel: an optical guidance system is set up at the starting point of the centerline of the tunnel section, and the direction of the laser illumination coincides with the planned path of the UAV; for the curved section of the tunnel: an optical guidance system is set up on both sides at the starting point of the centerline of the tunnel section, the lasers of the two lasers intersect, and the control module controls the high-precision rotary table to rotate in coordination to keep the intersection point on the planned path, and the displacement of the intersection point on the planned path coincides with and is synchronized with the displacement of the optical target.

[0030] Optionally, the laser also includes a laser rangefinder. During flight path monitoring, the laser rangefinder can measure the distance the target travels alongside the drone and compare it with the distance recorded by the drone to observe synchronization. This helps determine whether the drone is flying normally and following the planned path.

[0031] Optionally, for curved sections of the tunnel, during the flight path monitoring and correction step, if illumination points appear simultaneously on both sides of the target, the UAV gradually decelerates. If the electronic laser target senses that the two illumination points are moving towards the center until they coincide with the target, the UAV resumes its set flight speed. If, after the UAV decelerates, the electronic laser target senses that the distance between the two illumination points has increased, the UAV gradually accelerates until the two illumination points move towards the center and coincide with the target, at which point the UAV resumes its set flight speed. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the operation of the tunnel interior surface detection device based on three-dimensional laser scanning in Embodiment 1 of the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of the three-dimensional laser scanner and the electron laser target mounted on the UAV in Embodiment 1 of the present invention;

[0034] Figure 3 This is a schematic diagram of the optical guidance system in Embodiment 1 of the present invention;

[0035] Figure 4 This is a schematic diagram of the structure of the electron laser target in Embodiment 1 of the present invention;

[0036] Figure 5 This is a schematic diagram of the operation of the tunnel interior surface detection device based on three-dimensional laser scanning in Embodiment 2 of the present invention. Detailed Implementation

[0037] The following detailed description illustrates the specific implementation method:

[0038] The markings in the accompanying drawings include: 1. Straight section of the tunnel; 2. Curved section of the tunnel; 3. Centerline of the tunnel; 4. Hexacopter UAV; 5. 3D laser scanner; 6. Electron laser target; 6. Cover 601; 602. Convex lens; 603. Light-shielding block; 604. Mounting bracket; 605. Mounting box; 7. Optical guidance system; 7. Laser; 701. High-precision rotary table; 702. Support; 703. Time-sharing control point; 8.

[0039] Example 1

[0040] This embodiment applies to the straight section 1 of the tunnel:

[0041] This embodiment is basically as follows: Figure 1 , Figure 2 As shown: A device and method for detecting the interior surface of a tunnel based on three-dimensional laser scanning.

[0042] The detection equipment includes a drone, a 3D laser scanner, a central control platform, and several optical guidance systems.

[0043] The drone is a multi-rotor drone, specifically a hexacopter drone 4 in this embodiment, possessing stable and excellent hovering and level flight capabilities. The drone is equipped with a flight control module and a remote control receiver. The flight control module can autonomously write flight control programs; the planned path is written into the flight control module in the form of a flight control program. Executing the flight control program allows the drone to fly roughly along the designed planned path. The drone also includes a gravity sensor, accelerometer, electronic gyroscope, and magnetic compass, all electrically connected to the flight control module. The gravity sensor measures the acceleration caused by gravity, allowing the calculation of the drone's tilt angle relative to the horizontal plane; the accelerometer measures the drone's linear acceleration in both horizontal and vertical directions, used by the flight control module to calculate the drone's flight speed; the electronic gyroscope measures the drone's rotation and yaw; and the magnetic compass provides the drone with a sense of direction.

[0044] The FARO 3D Laser Scanner 5 is used, offering fast scanning speed, high accuracy, and a wide scanning range. The 3D Laser Scanner 5 is mounted on the back of the drone's fuselage. A lithium battery is installed under the drone's fuselage, providing power to the drone and all recording equipment.

[0045] The optical guidance system 7 includes a bracket 703, a laser 701, and a high-precision rotary stage 702. The bracket 703 is a tripod with adjustable height and horizontal rotation. The high-precision rotary stage 702 is mounted on the bracket 703 and is a Huatian Keyuan MRSA100 precision electronically controlled rotary stage with a rotational accuracy resolution of 0.01°. The laser 701 is an INTRUMAX laser instrument or other similar laser instruments with laser aiming and ranging functions, and is mounted on the high-precision rotary stage 702.

[0046] The electron laser target 6 is a self-made structure, comprising a frustum-shaped housing 601. A CCD electronic photosensitive element is mounted on the top surface of the housing 601, and a convex lens 602 is mounted on the bottom surface of the housing 601. A circular light-blocking block 603 is bonded to the center of the convex lens 602. A mounting bracket 604 is provided on the housing 601. The entire electron laser target 6 is mounted to the underside of the UAV via the mounting bracket 604. A mounting box 605 is also provided on the top surface of the housing 601. The mounting box 605 contains a circuit board for the CCD electronic photosensitive element. The circuit board has a photosensitive analysis module and a signal transmitter, which uses a WIFI communication module.

[0047] The central control platform includes an analysis module, a control module, a signal receiver, and a remote control transmitter. The high-precision rotary table 702 and the remote control transmitter are electrically connected to the control module, and the analysis module is electrically connected to the signal receiver and the control module.

[0048] The signal receiver also uses a WIFI communication module to establish a connection with the signal transmitter via WIFI. In other embodiments, if the drone manufacturer opens its dedicated communication link, the signal transmitter can also establish a connection with the drone's remote control receiver, which can then transmit the illumination point location information back to the remote control transmitter, thereby eliminating the need for a separate signal receiver.

[0049] In this embodiment, an STM32 development board is used for data processing. The functions of the analysis module and the control module are both implemented by the STM32 microcontroller chip mounted on the STM32 development board.

[0050] A method for detecting the interior surface of a tunnel based on three-dimensional laser scanning includes the following steps:

[0051] BIM Modeling: Import the tunnel design data into the BIM modeling software, and determine the tunnel centerline after completing the BIM modeling of the tunnel.

[0052] Tunnel Segmentation: Based on the tunnel centerline 3, the tunnel is divided into several straight and curved segments along the direction of the tunnel centerline 3. Each segment has the same slope. The design data of the tunnel centerline 3 position and slope of each straight segment are obtained. Based on the design data of the tunnel centerline 3 position, the flight path of the UAV at a height of 1.5m above the ground (the height of the electron laser target 6 center point from the tunnel design road surface) in the straight segment is planned. The planned path includes the start point and the end point.

[0053] Import the planned path: Write the planned path into a flight control program, then import the flight control program into the UAV's flight control module, place the UAV at the starting point of the planned path, and set the UAV's flight speed to 1m / s; then import the planned path into the control module for subsequent planned path parsing.

[0054] Detection device setup: The 3D laser scanner 5, electron laser target 6, and signal transmitter are installed on the drone. The drone is started and hovered, ensuring the center of the electron laser target 6 coincides with the starting point. Using pre-set measurement control points within the tunnel, the centerline 3 of the tunnel section and the starting point of the planned path are located through measurement. Using an optical guidance system 7, the bracket 703 is installed at the starting point of the planned path. The height of the laser 701 is adjusted using the bracket 703 to ensure the laser beam's direction coincides with the drone's planned path, and the illumination point coincides with the target center. For tunnels with slopes, the laser beam is tilted by adjusting the extension and retraction of the three legs of the bracket 703, with the tilt angle matching the slope of the tunnel section.

[0055] Path planning analysis: Based on the flight speed and planned path data, the control module analyzes the time-sharing control points 8 on the planned path, with a spacing of 1m between each time-sharing control point 8. For straight sections of the tunnel, all time-sharing control points 8 are on a straight line, so it is only necessary to find the correct direction of the laser 701 and maintain continuous illumination.

[0056] Test Flight: The UAV flies 50m along the planned path from the starting point to the endpoint, observing whether the illumination point consistently coincides with the target center. The first 100m is typically the distance where the UAV flies with high accuracy along the planned path. Subsequent distances are affected by errors from various sensors, flight control programs, and other factors in the flight environment, resulting in significant accumulated errors. Therefore, fine-tuning is required using the optical guidance system 7. The test flight process verifies the accuracy of the entire system's installation and integration. Especially for sloping tunnel sections, it is necessary to verify whether the tilt angle of the laser 701 matches the slope, because the high-precision rotary table 702 selected in this embodiment can only rotate left and right, not pitch.

[0057] 3D scanning: Start the drone to fly along the planned path at the set speed and start the 3D laser scanner 5.

[0058] Flight path monitoring and correction: When the UAV starts flight, the high-precision rotary table 702 is started simultaneously, and the laser beam of the high-precision laser 701 is used to sequentially irradiate the time-sharing control point 8 at the same speed as the flight speed. The electronic laser target 6 senses the laser irradiation point and sends the irradiation point position information to the analysis module via a signal transmitter. The analysis module receives the signal via a signal receiver and analyzes the position of the laser irradiation point relative to the target center. A two-dimensional coordinate system is constructed with the target center as the origin. After the laser irradiation point illuminates the outside of the light-blocking block 603, the electronic laser target 6 senses the position coordinates (x, y) of the irradiation point. When the coordinates are (-x, 0), it indicates that the irradiation point has deviated to the left of the target center. The control module and remote transmitter then adjust the drone's flight to the left (|x|) until the target center coincides with the irradiation point. When the coordinates are (x, 0), the drone flies to the right. When the coordinates are (0, -y), the drone flies downwards. When the coordinates are (0, y), the drone flies upwards. When the coordinates are (x, y), it indicates that the irradiation point has deviated to the upper right of the target center. The drone then flies diagonally downwards to the left. The diagonal flight angle is calculated using trigonometric functions, and the diagonal flight distance is calculated using the Pythagorean theorem. Diagonal flight in other directions follows the same principle. Finally, the drone flew to the destination and collected all the point cloud data acquired by the 3D laser scanner 5.

[0059] Example 2

[0060] This embodiment applies to curved segment 2 of the tunnel:

[0061] The difference between this embodiment and Embodiment 1 is that two optical guidance systems 7 are used in the detection device. One optical guidance system 7 is set up on each side of the starting point of the tunnel centerline 3, and the lasers of the two lasers 701 intersect. During path planning and analysis, time-division control points 8 are evenly distributed on the planned path. When the intersection point of the two lasers 701 falls on the starting position, the rotation angle of the two high-precision rotary stages 702 is zeroed. Then, the position of each subsequent time-division control point 8 is analyzed into the angle that the two high-precision rotary stages 702 need to rotate. During UAV flight, the control system only needs to control the two high-precision rotary stages 702 to rotate simultaneously to the corresponding analyzed angle. This ensures that the intersection point is always located on the planned path, and the displacement of the intersection point on the planned path coincides with and is synchronized with the displacement of the optical target.

[0062] To determine whether the drone is flying along the planned path, the distance between the time-sharing control point 8 and the two lasers 701 can be calculated during the path analysis. Then, the laser ranging function on the laser 701 is used to detect the actual distance between the target center and the laser 701 when the drone arrives at each time-sharing control point 8 in real time. By comparing the actual distance with the analyzed distance, a large difference can be found to help determine whether the drone is flying normally and whether it is flying along the planned path.

[0063] During the flight path monitoring and correction process, if illumination points appear simultaneously on both sides of the target, the drone gradually decelerates. If the electronic laser target 6 senses that the two illumination points are moving towards the center until they coincide with the target, the drone resumes its set flight speed. For example, if illumination points (-x1,0) and (x2,0) are sensed on both sides of the target, and the difference between x2 and (-x1) gradually decreases until it becomes 0, it proves that the two illumination points are moving towards the center until they coincide with the target. If the drone decelerates and the electronic laser target 6 senses that the distance between the two illumination points increases, the drone gradually accelerates until the two illumination points move towards the center and coincide with the target, at which point the drone resumes its set flight speed.

[0064] The above are merely embodiments of the present invention. The invention is not limited to the fields covered by these embodiments. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are able to access all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for tunnel interior surface inspection based on 3D laser scanning, applied to a tunnel interior surface inspection device based on 3D laser scanning. The device includes a drone, a 3D laser scanner, a central control platform, and several optical guidance systems. The drone has path planning, remote control and hovering functions. The drone is equipped with a remote control receiver and an electronic laser target. A 3D laser scanner, mounted on a drone; The optical guidance system includes a support, a laser, and a high-precision rotary stage. The high-precision rotary stage is mounted on the support, and the electron laser target is connected to a signal transmitter. The laser is mounted on the high-precision rotary stage. The central control platform includes an analysis module, a control module, a signal receiver, and a remote control transmitter. The high-precision rotary table and the remote control transmitter are electrically connected to the control module, and the analysis module is electrically connected to the signal receiver and the control module. It also includes a battery, which is installed on the drone; A light-shielding block is provided at the center of the electron laser target; Its features are: The method includes the following steps: BIM Modeling: Import the tunnel design data into BIM modeling software, and determine the tunnel centerline after completing the BIM modeling of the tunnel; Tunnel segmentation: Based on the tunnel centerline, the tunnel is divided into several straight and curved segments along the direction of the tunnel centerline. The design data of the tunnel centerline position of each segment is obtained. Based on the design data of the tunnel centerline position, the flight path of the UAV at a height of 1.0m to 1.5m above the ground in each segment is planned. The planned path includes the starting point and the ending point. Import the planned path: Import the planned path into the drone, place the drone at the starting point of the planned path, and set the drone's flight speed; import the planned path into the control module; Setting up the detection device: Install the 3D laser scanner, electron laser target, and signal transmitter onto the drone, start the drone and hover it so that the center of the electron laser target coincides with the starting point; install the bracket at the starting position of the planned path, and adjust the height of the laser by the bracket so that the irradiation point of the laser beam coincides with the center of the target; Path planning analysis: Based on the flight speed and path planning data, the control module analyzes the time-sharing control points of the illumination point on the path planning; 3D scanning: The drone flies along the planned path at the set speed and starts the 3D laser scanner; Flight path monitoring and correction: When the UAV starts flight, a high-precision rotary table is activated simultaneously. The high-precision laser beam drives the laser to illuminate the time-sharing control points sequentially at the same speed as the flight speed. The electronic laser target senses the laser illumination point and sends the illumination point position information to the analysis module through the signal transmitter. After receiving the signal through the signal receiver, the analysis module analyzes the position of the laser illumination point relative to the target center. Based on the direction and position of the deviation of the illumination point from the target center, the control module and remote transmitter adjust the UAV's flight direction until the target center coincides with the illumination point, and until the UAV flies to the destination.

2. The tunnel interior surface detection method based on three-dimensional laser scanning according to claim 1, characterized in that: In the tunnel segmentation process, the gradient of each tunnel segment remains constant, and the gradient value of each tunnel segment is obtained. The gradient value of the planned path is equal to the gradient value of that tunnel segment.

3. The tunnel interior surface detection method based on three-dimensional laser scanning according to claim 2, characterized in that: The spacing between time-sharing control points is 0.5m to 1m, or the time interval between time-sharing control points is 0.1s to 0.5s.

4. The tunnel interior surface detection method based on three-dimensional laser scanning according to claim 3, characterized in that: Before the flight path monitoring and correction steps, a test flight step is also included: the UAV flies 50m to 100m along the planned path from the starting point to the end point to observe whether the illumination point always coincides with the target center.

5. The tunnel interior surface detection method based on three-dimensional laser scanning according to claim 4, characterized in that: In the flight path monitoring and correction step, for the straight section of the tunnel: an optical guidance system is set up at the starting point of the centerline of the tunnel, and the direction of the laser beam coincides with the planned path of the UAV; for the curved section of the tunnel: an optical guidance system is set up on both sides at the starting point of the centerline of the tunnel, the laser beams of the two lasers intersect, and the control module controls the high-precision rotary table to rotate in coordination to keep the intersection point on the planned path, and the displacement of the intersection point on the planned path coincides with and is synchronized with the displacement of the optical target.

6. The tunnel interior surface detection method based on three-dimensional laser scanning according to claim 5, characterized in that: The laser also has a laser rangefinder.

7. The tunnel interior surface detection method based on three-dimensional laser scanning according to claim 6, characterized in that: For the curved sections of the tunnel, during the flight path monitoring and correction process, if illumination points appear simultaneously on both sides of the target, the drone gradually decelerates. If the electronic laser target senses that the two illumination points are moving towards the center until they coincide with the target, the drone resumes its set flight speed. If, after the drone decelerates, the electronic laser target senses that the distance between the two illumination points has increased, the drone gradually accelerates until the two illumination points move towards the center and coincide with the target, at which point the drone resumes its set flight speed.

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