Portable 3D laser scanning tunnel monitoring device

Abstract

This invention relates to a portable 3D laser scanning tunnel monitoring device, belonging to the field of tunnel lining monitoring technology. The device includes an upper handheld stabilizer, a monitoring device housing, a small gyroscope at the bottom, and a front-end retractable laser head. The handheld stabilizer is fixed to the upper part of the monitoring device housing, the small gyroscope is fixed to the bottom of the monitoring device, and the front-end retractable laser head is fixed inside the monitoring device via a telescopic rod, a telescopic head base, and a telescopic head connecting post. The monitoring device contains a control circuit. This device performs real-time monitoring via a program set in the control circuit and external control buttons. It can be applied to monitoring in various tunnels and has advantages such as good portability, high stability, and high measurement accuracy.

Description

Technical Field

[0001] This invention belongs to the field of tunnel lining monitoring technology and relates to a portable 3D laser scanning tunnel monitoring device. Background Technology

[0002] With the development of construction engineering technology and the increasing requirements for construction and maintenance, various defects will appear in the tunnel structure over time during the operation of various tunnels. Typical defects include: structural dripping and seepage, concrete cracks, spalling, and spalling. These defects are generally characterized by short occurrence time, large impact, and long repair time, especially during operation. Therefore, high-frequency inspection of tunnels is required.

[0003] Traditional methods of manually measuring tunnel deformation, cracks, and other tunnel defects are inefficient and costly. These methods are increasingly unable to meet practical monitoring needs and are unsuitable for current subway tunnel measurements. Therefore, the use of 3D laser scanners for tunnel inspection has been developed. 3D laser scanning technology, also known as real-scene replication technology, utilizes the principle of laser ranging. It employs a stable and accurate horizontal automatic motor to record the 3D coordinates, reflectivity, and texture information of a large number of dense points on the surface of the object being measured. This allows for the rapid reconstruction of a 3D model of the target object, as well as various graphic data such as lines, surfaces, and volumes. The laser emitter lens of the 3D laser scanner rotates in a vertical plane, while the automatic motor drives the scanner body to rotate horizontally, completing a 360-degree 3D scene scan.

[0004] With the development of measurement technology, intelligent monitoring technology for tunnel construction has become a major trend in the development of information-based tunnel construction. Therefore, it is necessary to continuously improve the level of automation in tunnel monitoring. Currently, the tunnel surface after support is not suitable for automated robotic monitoring. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a portable 3D laser scanning tunnel monitoring device. This monitoring device obtains a 3D model of the tunnel lining by scanning it, and then compares it with the original lining data to truly reflect the changes in the lining surface, thereby further inferring the stress changes in the lining.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A portable 3D laser scanning tunnel monitoring device includes an upper handheld stabilizer, a monitoring device housing, a small gyroscope at the bottom, and a front-end retractable laser head. The handheld stabilizer is fixed to the upper part of the monitoring device housing, the small gyroscope is fixed to the bottom of the monitoring device, and the front-end retractable laser head is fixed inside the monitoring device via a telescopic rod, a telescopic head base, and a telescopic head connecting post. The monitoring device is equipped with a control circuit. This invention enables real-time monitoring through a program set in the control circuit and control buttons on the outside of the monitoring device, and can be applied to monitoring in various tunnels.

[0007] Furthermore, the handheld stabilizer is fixed to the upper part of the monitoring device housing, the yaw axis 28 is connected to the vertical arm 26 and the handheld stabilizer base 23, the horizontal arm 29 is connected to the connecting plate 27 and the roll axis 24, and the handheld grip 30 is connected to the connecting plate 27.

[0008] Furthermore, the small gyroscope is located at the bottom of the monitoring device, and the intelligent micro motor 101 is connected to the vertical connecting shaft 106 and the horizontal connecting shaft 107 respectively through the gear 108. During the movement, the intelligent micro motor 101 adjusts the movement of the rotating ring 102 and the balance ring 103 in real time through the auxiliary circuit 21 to counteract external interference, thereby ensuring the stability of the entire monitoring device during the monitoring process.

[0009] Furthermore, the bottom of the miniature gyroscope, the outer shell of the monitoring device, the outer shell of the telescopic rod, and the base of the telescopic head contain cushioning material.

[0010] Furthermore, the telescopic laser head is installed inside the monitoring device, the telescopic head base 12 is fixed on the inner arm structure of the monitoring device, the telescopic head connecting column 13 fixes the telescopic head shell 14 on the base, the telescopic rod 16 is connected to the spring 15 and the laser head base 19, and the laser head base 19 is retracted through the telescopic rod 16 and the spring 15.

[0011] Furthermore, after the laser emitter 17 emits a laser, the laser receiver 18 receives the reflected laser and transmits the received information to the main circuit 31. The received information is then uploaded to the cloud in real time through the circuit program settings in the main circuit 31. The obtained tunnel lining data information is then used to create a 3D image through an algorithm.

[0012] Laser pulse signals are emitted by the built-in laser emitter 17. These laser pulse signals are reflected back by the target surface after traveling a certain distance and are received by the laser receiver 18 built into the laser scanner. Then, by measuring the propagation time or phase difference of the laser pulse signal, the distance d between the scanner position and the target point can be calculated. At the same time, the internal module of the laser scanner records the vertical angle α and horizontal angle β of the laser pulse signal. Finally, by calculating parameters such as distance d, vertical angle α, and horizontal angle β, the three-dimensional coordinates of the target point P can be determined. Then, the obtained point cloud data is input through the Poisson surface reconstruction algorithm to finally perform 3D reconstruction.

[0013] The beneficial effects of this invention are as follows: 1) The device of the present invention has a retractable laser scanning head at the front end of the laser scanner. By extending the scanning head, the scanning instrument is protected. At the same time, four laser emitters are set in the laser head. By working simultaneously with the four lasers, the scanning time is reduced, the error is reduced, and the accuracy is increased.

[0014] 2) The device of the present invention has a small gyroscope at the bottom of the laser scanner. The gyroscope, through the control system in the auxiliary circuit, controls the micro motor 101 to adjust the movement of the rotating ring 102 and the balance ring 103 in real time, thereby canceling external interference and ensuring the stability of the entire monitoring instrument during the monitoring process.

[0015] 3) The device of the present invention has a handheld stabilizer on the upper part of the laser scanner. During the walking measurement process, the handheld stabilizer reduces the shaking during walking by controlling the roll axis, pitch axis and yaw axis, thereby maintaining the stability of the laser scanner during measurement.

[0016] 4) The device of the present invention can further maintain the stability of the scanner during the measurement process by means of the joint control of the handheld stabilizer at the top of the laser scanner and the gyroscope at the bottom, thereby improving the accuracy of the measurement process.

[0017] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a front view of the portable 3D laser scanning tunnel monitoring device proposed in this invention; Figure 2 This is a schematic diagram of the internal structure of the portable 3D laser scanning tunnel monitoring device proposed in this invention; Figure 3 This is a diagram of the laser location of the portable 3D laser scanning tunnel monitoring device proposed in this invention; Figure 4 for Figure 1 A magnified view of a section at point A - a schematic diagram of the bottom gyroscope; Figure 5 for Figure 1 Enlarged view of section B - Front view of the upper handheld stabilizer; Figure 6 It is a three-dimensional coordinate system; Figure 7 Here is a flowchart of the data preprocessing process; In the diagram: 1. Monitoring device housing; 2. Telescopic laser head; 3. Soft pad; 4. Connecting post; 5. Support rod; 6. Rotary button; 7. Small display; 8. Control buttons; 9. Button connector; 10. Rotating disc; 11. Cushioning material; 12. Telescopic head base; 13. Telescopic head connecting post; 14. Telescopic head housing; 15. Spring; 16. Telescopic rod; 17. Laser emitter; 18. Laser receiver; 19. Laser head base; 20. Laser... 21. Bald head housing; 22. Auxiliary circuit; 23. Power supply; 24. Handheld stabilizer base; 25. Roll axis; 26. Pitch axis; 27. Vertical arm; 28. Connecting plate; 29. ​​Yaw axis; 30. Horizontal arm; 31. Handheld grip; 32. Main circuit; 103. Intelligent micro motor; 104. Rotating ring; 105. Balance ring; 106. Rotating wheel; 107. Gyroscope housing; 108. Vertical connecting shaft; 109. Horizontal connecting shaft; 100. Gear. Detailed Implementation

[0019] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0020] See Figures 1 to 5 The present invention provides a portable 3D laser scanning tunnel monitoring device, including a monitoring device housing 1. The monitoring device housing 1 contains a main circuit 31, an auxiliary circuit 21, a power supply 22, a connecting column 4, a support rod 5, a rotary button 6, a small display 7, control buttons 8, a button connector 9, a rotating disk 10, and the most important retractable laser head 2. The upper part of the monitoring device housing 1 is a handheld stabilizer, and the bottom of the monitoring device has a small gyroscope A, and also contains four support rods.

[0021] The upper part of the monitoring device housing 1 includes: a handheld stabilizer base 23, a roll axis 24, a pitch axis 25, a vertical arm 26, a connecting plate 27, a yaw axis 28, a horizontal arm 29, and a handheld grip 30. The handheld stabilizer base 23 is connected to the yaw axis 28 and the roll axis 24 via the vertical arm 26. The horizontal arm 29 is connected to the connecting plate 27 and the roll axis 24. The handheld grip 30 is connected to the connecting plate 27.

[0022] In the upper part of the outer casing 1 of the monitoring device, the roll axis 24 is mainly responsible for controlling the left and right rotation of the measuring device, so that the measuring instrument rotates horizontally, thereby keeping the measuring instrument horizontally stable during the walking measurement process. The pitch axis 25 is mainly responsible for controlling the up and down tilting movement of the measuring device, so that the measuring device can adjust the measurement angle up and down, thereby keeping the measuring device stable in the vertical direction. The yaw axis 28 is mainly responsible for controlling the horizontal rotation of the measuring device, so that the measuring device can adjust left and right, thereby keeping the measuring device stable in the horizontal direction.

[0023] The small gyroscope A at the bottom of the monitoring device includes: an intelligent micro motor 101, a rotating ring 102, a balance ring 103, a rotating wheel 104, a gyroscope housing 105, a vertical connecting shaft 106, a horizontal connecting shaft 107, and a gear 108. The intelligent micro motor 101 is connected to the vertical connecting shaft 106 and the horizontal connecting shaft 107 via the gear 108. During operation, the intelligent micro motor 101 adjusts the movement of the rotating ring 102 and the balance ring 103 in real time through the auxiliary circuit 21 to counteract external interference, thereby ensuring the stability of the entire monitoring device during the monitoring process.

[0024] The monitoring device internally includes: a telescopic head base 12, a telescopic head connecting column 13, a telescopic head housing 14, a spring 15, a telescopic rod 16, a laser emitter 17, a laser receiver 18, a laser head base 19, and a laser head housing 20. The telescopic head base 12 is fixed to the inner arm structure of the monitoring device, while the telescopic head connecting column 13 fixes the telescopic head housing 14 to the base. The telescopic rod 16 is connected to the spring 15 and the laser head base 19, and the laser head base 19 retracts via the telescopic rod 16 and the spring 15. After the laser emitter 17 emits a laser, the laser receiver 18 receives the reflected laser light and transmits the received information to the main circuit 31. The circuit program in the main circuit 31 then uploads the received information to the cloud in real time, and further uses algorithms to create a 3D image of the tunnel lining data.

[0025] The working principle of the device described in this invention is as follows: Laser pulse signals are emitted by the laser transmitter 17 built into the laser scanner. These laser pulse signals are reflected back from the target surface after traveling a certain distance and are received by the laser receiver 18 built into the laser scanner. Then, by measuring the propagation time or phase difference of the laser pulse signals, the distance d between the scanner position and the target point can be calculated. Simultaneously, the internal module of the laser scanner records the vertical angle α and horizontal angle β of the laser pulse signals. Finally, by calculating parameters such as distance d, vertical angle α, and horizontal angle β, the three-dimensional coordinates of the target point P can be determined. The calculation principle of the three-dimensional laser scanner acquiring the three-dimensional coordinates of the target is as follows: Figure 6 As shown. Figure 7 This is a flowchart of the data preprocessing process.

[0026] Taking the location of the 3D laser scanner as the origin, the formula for calculating the 3D coordinates of the target point P is shown in Figure 1.1: (1.1) In equation (1.1): α is the vertical angle; β is the horizontal angle; d is the distance between the scanner position and the target point.

[0027] The original instrument coordinates obtained from the scanner are converted into a commonly used geodetic coordinate system to determine the true three-dimensional coordinates of the scanned data in the geodetic coordinate system. The coordinate system normalization and transformation algorithm is as follows: (1.2) (1.3) (1.4) (1.5) In equations (1.2) to (1.5): α, β, and γ are rotation parameters; Δx, Δy, and Δz are translation parameters.

[0028] The algorithm formula for smoothing and denoising point cloud data is as follows: (1.6) (1.7) In equations (1.6) to (1.7): d i Let point p and point p i The distance, where p i Let p be a point in the neighborhood of point p (i=1,2,3,...,n). This represents the average distance.

[0029] Assume the average distance between a point in a point cloud and its neighboring points. It statistically follows a normal distribution, as shown in formula (1.8): (1.8) For formula (1.8), we have the following expression: (1.9) (1.10) In equations (1.8) to (1.10): µ is the expected value; σ is the standard deviation; m is the number of points in the point cloud; Let be the average distance from the i-th point in the point cloud to other points in its neighborhood.

[0030] If the distance from a point to its nearest neighbor in its neighborhood is greater than a set threshold ε, then that point is treated as an outlier and deleted. (1.11) In equation (1.11), θ is the proportionality coefficient, which is related to the number of points in the neighborhood, and ε is the threshold.

[0031] The point cloud data obtained is input using the Poisson surface reconstruction algorithm, and a 3D reconstruction is finally performed. The algorithm is as follows: (1.12) In equation (1.12) Calculate the spatial coordinates of each point within the solution domain Ω of point x. For undetermined coefficients, Let m be the basis functions, and m be the number of basis functions.

[0032] By solving the discrete weighted L2 normal form of the residuals, an accurate local approximation is obtained, as shown in equation (1.13): (1.13) In the formula, n is the number of nodes in the solution region. It is a node The weight function. Equation (1.13) can be expressed in matrix form as: (1.14) in: (1.15) (1.16) (1.17) To find the undetermined coefficients a(x), we must first minimize J, that is: (1.18) Right now: (1.19) In the formula matrix and They are respectively: (1.20) (1.21) (1.22) From the above equation, we can obtain the approximation function. The expression is: (1.23) In the formula, For shape functions: (1.24) The adaptive octree partitioning method represents implicit functions as follows: (1.25) In the formula, For sampling points, Represents the center position of the node. Represents the width of the node.

[0033] Define a basis function to make the vector field Can be effectively expressed as a node function Linear summation: (1.26) In the formula, The maximum depth of the octree. The sampling interval is denoted as .

[0034] The reconstruction problem can be transformed into a high-dimensional Poisson problem using the following function: (1.27) (1.28) In the formula, Represents the convolution symbol. This means that n identical functions have undergone convolution operations. Definition for each sub-item.

[0035] The vector field is calculated as follows: (1.29) In the formula, S is the set of all point clouds, and s is the k-nearest neighbor region of the current point in the point set. It is the nearest neighbor of an octree of depth D. The node, These are the weight coefficients of cubic linear interpolation. yes The vertex normal vector.

[0036] Solving the Poisson equation to determine the vector field Then, in the function space Solving indicator functions , make the function The gradient best approximates the vector field. That is, to obtain the Poisson equation One solution. Solving this problem directly is quite difficult; it requires constructing equations. We can solve this problem by minimizing the equation, as shown in equation (1.30): (1.30) For a given dimensional vector Let be the coordinates of node O. For ease of calculation, this relationship is usually first expressed in matrix form, i.e., let , Then, define A matrix L of dimension, such that Return each The scalar product of the Laplace operator and the Laplace operator. That is, for each L's The element at that location is set to: (1.31) In the formula, the solution is obtained through the above formula. The problem boils down to finding a solution. .

[0037] Solve for the indicator function of the model surface. Then, by selecting relevant isovalues, the isosurfaces corresponding to the selected isovalues ​​are obtained, thus obtaining the reconstructed surface. To ensure that the selected isosurface closely approximates the location of the input sample points, this embodiment utilizes sample point location estimation. Then, the average value of the estimation results of all points is taken as the isosurface to extract the isosurface, as shown in equation (1.32).

[0038] (1.32) Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the scope and spirit of the invention, the scope of which is defined by the claims and their equivalents.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications should be covered within the scope of the claims of the present invention.

Claims

1. A portable 3D laser scanning tunnel monitoring device, characterized by: It includes an upper handheld stabilizer, a monitoring device housing, a small gyroscope at the bottom, and a retractable laser head; The handheld stabilizer is fixed to the upper part of the monitoring device housing and includes a handheld stabilizer base (23), a roll axis (24), a pitch axis (25), a vertical arm (26), a connecting plate (27), a yaw axis (28), a horizontal arm (29), and a handheld grip (30). The handheld stabilizer base (23) is connected to the yaw axis (28) and the roll axis (24) through the vertical arm (26). The horizontal arm (29) is connected to the connecting plate (27) and the roll axis (24), and the handheld grip (30) is connected to the connecting plate (27). The small gyroscope is fixed at the bottom of the monitoring device and includes a smart micro motor (101), a rotating ring (102), a balance ring (103), a rotating wheel (104), a gyroscope housing (105), a vertical connecting shaft (106), a horizontal connecting shaft (107), and a gear (108). The smart micro motor (101) is connected to the vertical connecting shaft (106) and the horizontal connecting shaft (107) respectively through the gear (108). During the movement, the smart micro motor (101) adjusts the movement of the rotating ring (102) and the balance ring (103) in real time through the auxiliary circuit (21). The retractable laser head is installed inside the monitoring device and includes a retractable head base (12), a retractable head connecting column (13), a retractable head shell (14), a spring (15), a retractable rod (16), a laser emitter (17), a laser receiver (18), a laser head base (19), and a laser head shell (20). The retractable head base (12) is fixed on the inner arm structure of the monitoring device, and the retractable head connecting column (13) fixes the retractable head shell (14) on the base. The retractable rod (16) is connected to the spring (15) and the laser head base (19), and the laser head base (19) retracts through the retractable rod (16) and the spring (15). The monitoring device has an internal control circuit; the device monitors the tunnel in real time through the program set in the control circuit and the control buttons on the outside of the device.

2. The portable 3D laser scanning tunnel monitoring device according to claim 1, characterized in that The bottom of the miniature gyroscope, the outer shell of the monitoring device, the outer shell of the telescopic rod, and the base of the telescopic head contain cushioning material.

3. The portable 3D laser scanning tunnel monitoring device according to claim 2, characterized in that: After the laser emitter (17) emits a laser, the laser receiver (18) receives the reflected laser and transmits the received information to the main circuit (31). The received information is then uploaded to the cloud in real time through the circuit program settings in the main circuit (31), and the obtained tunnel lining data information is 3D imaged through the algorithm.

4. The portable 3D laser scanning tunnel monitoring device according to claim 3, characterized in that: Laser pulse signals are emitted by the built-in laser emitter (17), which are reflected back by the target surface and received by the built-in laser receiver (18). The distance d between the monitoring device and the target point is calculated by measuring the propagation time or phase difference of the laser pulse signal. At the same time, the vertical angle α and horizontal angle β of the laser pulse signal are recorded. Finally, the three-dimensional coordinates of the target point P are determined by calculating the distance d, vertical angle α and horizontal angle β. Then, the point cloud data obtained is input through the Poisson surface reconstruction algorithm, and finally 3D reconstruction is performed.

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