Three-dimensional reconstruction method and volume measurement method for expansive high polymer slurry based on Lidar point cloud

Abstract

The invention discloses a three-dimensional reconstruction method and a volume measurement method for expansive high polymer slurry based on Lidar point clouds, and the three-dimensional reconstruction method comprises the following steps: placing a container filled with slurry on a table top, and collecting three-dimensional point cloud data of the liquid level of the slurry and the table top by a sensor; performing rotation correction on the obtained point cloud data by taking the table top point cloud data as a reference plane; projecting the liquid surface point cloud to a two-dimensional plane, fitting an outer boundary based on convex hull boundary points and the shape of the container, and aligning the height of the outer boundary with an actual liquid surface point cloud height value to reconstruct a liquid surface outer boundary; generating a complete three-dimensional model by combining geometric information of the bottom surface and the side wall of the container based on the point cloud data of the liquid level and the outer boundary; the volume measurement method is based on a three-dimensional reconstruction method, and further comprises the steps of accumulating the volumes of the triangulation volume units and calculating the total volume of slurry; according to the method, the real three-dimensional shape of the slurry can be directly obtained, errors caused by model hypothesis are avoided, and the accuracy of volume measurement is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of expansive polymer slurries, and particularly to a three-dimensional reconstruction method and a volume measurement method for expansive polymer slurries based on Lidar point clouds. Background Technique

[0002] In recent years, as a new type of engineering repair material, expansive polyurethane polymer slurries have been widely used in the repair projects of infrastructure due to their advantages such as fast expansion, high early strength, waterproofing, durability, and environmental protection. For example, in the prevention and control of water disasters, foundation reinforcement, road maintenance, etc. in underground projects such as mines and tunnels, polymer grouting has become a very characteristic development direction in the field of geotechnical engineering.

[0003] The main components of the polymer slurry include isocyanate, polyol, foaming agent, catalyst, etc. After mixing, gel reaction and foaming reaction mainly occur. At the beginning of the reaction, the slurry is a reddish-brown viscous liquid. As the reaction progresses, a large number of bubble nuclei are gradually generated, the bubbles rapidly increase in size, the volume expands, and finally solidifies to form a polymer solid with a certain strength. The change in the expansion volume of the slurry is an important parameter for studying its curing reaction. By accurately measuring the volume change, reliable data support can be provided for the chemical kinetic model of slurry expansion, so as to establish an accurate numerical simulation model, reveal its expansion mechanism, predict the expansion behavior, and improve the accuracy and efficiency of actual engineering repair.

[0004] Currently, the common methods for measuring the expansion volume of polymers are based on an idealized model proposed by Ireka et al., assuming that the liquid surface shape is ellipsoidal, and indirectly estimating the volume through limited measurement data. However, this method depends on the assumption of the liquid surface shape and is difficult to reflect the complex geometric characteristics of the slurry during the actual expansion process, resulting in measurement errors. Summary of the Invention

[0005] The purpose of the invention is to provide a three-dimensional reconstruction method and a volume measurement method for expansive polymer slurries based on Lidar point clouds, which solve the problem that the three-dimensional model of the existing expansive polymer slurries is difficult to reflect the complex geometric characteristics of the slurry during the actual expansion process, resulting in measurement errors.

[0006] The present invention is implemented as follows. A three-dimensional reconstruction method for expansive polymer slurries based on Lidar point clouds, the method comprising the following steps:

[0007] S1. Place the container filled with the slurry on the tabletop, and the sensor collects the three-dimensional point cloud data of the slurry liquid surface and the tabletop;

[0008] S2. Using the tabletop point cloud data as the reference plane, perform rotation correction on the point cloud data obtained in step S1;

[0009] S3. Project the liquid surface point cloud onto a two-dimensional plane, fit the outer boundary based on the convex hull boundary points and the shape of the container, and align its height with the actual liquid surface point cloud height value to reconstruct the outer boundary of the liquid surface;

[0010] S4. Based on the liquid surface and outer boundary point cloud data obtained in step S3, and combined with the geometric information of the bottom and side walls of the container, generate a complete three-dimensional model.

[0011] A further technical solution of the present invention is that in step S1, a transparent cylindrical container filled with an expansive polymer slurry is placed on a horizontal tabletop, and a device with LiDAR is fixed above the transparent cylindrical glass container.

[0012] A further technical solution of the present invention is that in step S2, the normal vector of the tabletop point cloud coordinates is extracted, the rotation matrix with the positive Z direction is calculated, and the complete point cloud data including the tabletop and the liquid surface is rotationally corrected so that the tabletop point cloud data is located on the xy plane and the liquid surface point cloud data is located on the Z plane, and the liquid surface point cloud data is the actual height value.

[0013] A further technical solution of the present invention is that the container is cylindrical, the convex hull in step S3 is the outer boundary contour of the projected liquid surface point cloud, and the outer boundary is fitted with the geometric center of the convex hull as the center and the inner diameter of the container as the diameter.

[0014] A further technical solution of the present invention is that in step S3, aligning the height of the outer boundary circle with the actual liquid surface point cloud height value specifically means: matching each point of the fitted circle with the closest point of the liquid surface point cloud, and assigning the height of the matching point to the Z value of the fitted circle to determine the outer boundary of the liquid surface.

[0015] A further technical solution of the present invention is that in step S4, the liquid surface is triangulated to generate a three-dimensional grid of the liquid surface and visualize the shape of the liquid surface; the bottom surface is the projection of the liquid surface points on the xy plane and is triangulated to generate; the side wall is constructed by connecting the bottom surface projection of the outer boundary points and the outer boundary points of the liquid surface.

[0016] The present invention also provides a method for measuring the volume of an expansive polymer slurry based on Lidar point cloud. The measurement method includes the following steps: generating a three-dimensional model according to the three-dimensional reconstruction method, and the three-dimensional model is generated by using the triangulation method; then performing step S5, accumulating the volumes of the triangulation volume units to calculate the total volume of the slurry.

[0017] A further technical solution of the present invention is that in step S5, the space between each triangular patch and the bottom surface forms a triangular prism unit, and the volume is obtained by multiplying the bottom area by the height.

[0018] A further technical solution of the present invention is that the height is taken as the average value of the heights of the triangle vertices, and the bottom area is the projected area of the triangle patch on the xy plane.

[0019] Advantages of the present invention: The present invention provides a method for three-dimensional reconstruction and volume measurement of expansive polymer slurry based on LiDAR point cloud, which can accurately reconstruct the true geometric shape of the slurry liquid surface, generate a complete three-dimensional model by combining the bottom surface and side wall information, and calculate the true volume of the slurry through triangulation technology. This method avoids the errors caused by traditional model simplification, and can realize real-time monitoring of the change of expansion volume during the reaction process, and has certain practical application value.

[0020] The present invention collects three-dimensional point cloud data of the slurry liquid surface and the tabletop with a device equipped with LiDAR. Adjust the coordinate system of the liquid surface point cloud with the tabletop as the reference plane, project the liquid surface point cloud onto a two-dimensional plane, fit the parameters with the container as the reference as the outer boundary of the liquid surface, and perform alignment processing on the height. Based on the liquid surface point cloud, combined with the geometric information of the bottom surface and the side wall, use the triangulation method to generate a complete three-dimensional model. By accumulating the volumes of the triangulation volume units, the total volume of the slurry is accurately calculated. The present invention improves the assumption that the shape of the liquid surface is limited to an ellipsoid model in the traditional calculation of the volume of polymer slurry, can directly obtain the true three-dimensional shape of the slurry, avoids the errors caused by model assumptions, and improves the accuracy of volume measurement. Description of the Drawings

[0021] Figure 1 is a flowchart of a three-dimensional reconstruction method of expansive polymer slurry based on Lidar point cloud provided by the present invention;

[0022] Figure 2 is a flowchart of a method for measuring the volume of expansive polymer slurry based on Lidar point cloud provided by the present invention;

[0023] Figure 3 is the original diagram of the point cloud data obtained in step S1 provided by the present invention;

[0024] Figure 4 is the corrected point cloud distribution diagram after step S2 provided by the present invention;

[0025] Figure 5 is the outer boundary diagram fitted in step S3 provided by the present invention;

[0026] Figure 6 is the outer boundary diagram of the liquid surface after regression height in step S3 provided by the present invention;

[0027] Figure 7 is the three-dimensional visualization diagram and actual comparison diagram generated by using the method of the present invention. Detailed Embodiments

[0028] The following describes the implementation modes of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] Example 1:

[0030] Figure 1 and 3 FIG. -7 shows a three-dimensional reconstruction method for expansive polymer slurry based on Lidar point cloud, including the following steps:

[0031] S1. Place a transparent cylindrical beaker filled with expansive polymer slurry on a horizontal tabletop, and vertically fix a mobile phone with a LiDAR above the transparent cylindrical glass container to collect three-dimensional point cloud data of the slurry liquid level in the container and the tabletop. The collected data is as Figure 3 shown. It can be seen that there is a difference between the original point cloud coordinate system collected by Lidar and the physical reference coordinate system of the real world, and coordinate transformation processing is required.

[0032] S2. Using the tabletop point cloud data as the reference plane, perform rotation correction on the point cloud data.

[0033] Specifically, extract the normal vector of the tabletop point cloud coordinates, calculate the rotation matrix between it and the positive Z direction, and perform rotation correction on the complete point cloud data including the tabletop and the liquid level, so that the tabletop point cloud data is located on the xy plane, and the height value of the liquid level point cloud is the actual height value. The corrected point cloud distribution diagram is as Figure 4 shown.

[0034] S3. Project the liquid level point cloud onto a two-dimensional plane, and based on the convex hull boundary points, fit the outer boundary circle to obtain a fitted outer boundary diagram as Figure 5 shown; and align its height with the actual liquid level point cloud height value to reconstruct the outer boundary of the liquid level. The outer boundary diagram of the liquid level after regression of the height is as Figure 6 shown.

[0035] Among them, the convex hull is the outer boundary contour of the projected liquid level point cloud. The outer boundary circle is fitted with the geometric center of the convex hull as the center and the inner diameter of the container as the diameter.

[0036] S4. Based on the liquid level and outer boundary point cloud data, combined with the geometric information of the bottom surface and the side wall, use the triangulation method to generate a complete three-dimensional model.

[0037] In this embodiment, the LiDAR is a lidar depth sensor, which calculates the depth value by emitting infrared light and measuring the return time to generate three-dimensional point cloud data.

[0038] In this embodiment, in step S3, the convex hull is the outer boundary contour of the liquid surface point cloud after projection. The outer boundary circle is fitted with the geometric center of the convex hull as the center and the inner diameter of the container as the diameter. In this embodiment, the inner diameter of the container is 4.5 cm.

[0039] In this embodiment, in step S3, align the height of the outer boundary circle with the height value of the actual liquid surface point cloud. Specifically: match each point of the fitted circle with the nearest point of the liquid surface point cloud, assign the height of the matching point to the Z value of the fitted circle, and determine the outer boundary of the liquid surface. In this embodiment: in step S4, perform triangulation on the liquid surface to generate a three-dimensional mesh of the liquid surface, which can visualize the shape of the liquid surface. The bottom surface is the projection of the liquid surface points on the xy plane and is generated by triangulation. The side wall is constructed by connecting the bottom surface projection of the outer boundary points with the outer boundary points of the liquid surface. The obtained visualization diagram is shown in Figure 7 the left attached drawing of Figure 7 the right attached drawing of is the actual drawing of the expansive polymer slurry, and it can be seen from Figure 7 that the three-dimensional model diagram reconstructed by the method of the present invention is highly similar to the actual situation. The present invention improves the assumption that the shape of the liquid surface is limited to an ellipsoidal model in the traditional calculation of the volume of polymer slurry, and can directly obtain the true three-dimensional shape of the slurry.

[0040] Embodiment 2:

[0041] As Figures 1-7 described in a method for measuring the volume of an expansive polymer slurry based on Lidar point cloud, the measurement method includes the following steps: generate a three-dimensional model according to the method described in Embodiment 1, and the three-dimensional model is generated using the triangulation method; then perform step S5, accumulate the volumes of the triangulation volume units, and calculate the total volume of the slurry.

[0042] In this embodiment: in step S5, the space between each triangular patch and the bottom surface forms a triangular prism unit, and the volume is obtained by multiplying the bottom area by the height.

[0043] In this embodiment, the height is taken as the average value of the heights of the triangular vertices, and the bottom area is the projected area of the triangular patch on the xy plane.

[0044] In this embodiment: according to Figures 3-6 the data, the calculated result of the volume of the slurry is 95.12 cm 3 .

[0045] The mobile phone with LiDAR in the present invention collects the three-dimensional point cloud data of the slurry liquid surface and the tabletop. Taking the tabletop as the reference plane, the coordinate system of the liquid surface point cloud is adjusted, the liquid surface point cloud is projected onto a two-dimensional plane, a circle with a diameter equal to the inner diameter of the container is fitted as the outer boundary of the liquid surface, and the height is aligned. Based on the liquid surface point cloud, combined with the geometric information of the bottom surface and the side wall, the triangulation method is used to generate a complete three-dimensional model. By accumulating the volumes of the triangulation volume units, the total volume of the slurry is accurately calculated. The present invention improves the assumption that the shape of the liquid surface is limited to the ellipsoid model in the traditional calculation of the volume of the high-polymer slurry, can directly obtain the true three-dimensional shape of the slurry, avoids the error caused by the model assumption, and improves the accuracy of volume measurement.

[0046] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A three-dimensional reconstruction method for expansive polymer slurry based on Lidar point cloud, characterized in that: The method includes the following steps: S1. Place the container filled with slurry on the tabletop, and the sensor collects the three-dimensional point cloud data of the slurry liquid level and the tabletop; S2. Using the tabletop point cloud data as the reference plane, perform rotation correction on the point cloud data obtained in step S1; S3. Project the liquid level point cloud onto a two-dimensional plane, and based on the convex hull boundary points and the shape of the container, fit the outer boundary, and align its height with the actual liquid level point cloud height value to reconstruct the outer boundary of the liquid level; S4. Based on the liquid level and outer boundary point cloud data obtained in step S3, combined with the geometric information of the bottom surface and side wall of the container, generate a complete three-dimensional model.

2. The three-dimensional reconstruction method of the expansive polymer slurry based on Lidar point cloud according to claim 1, characterized in that: In step S1, a transparent cylindrical container filled with a swellable polymer slurry is placed on a horizontal tabletop, and the device with LiDAR is fixed above the transparent cylindrical glass container.

3. A three-dimensional reconstruction method for expansive polymer slurry based on Lidar point cloud according to claim 1 or 2, characterized in that: In step S2, extract the normal vector of the tabletop point cloud coordinates, calculate the rotation matrix between it and the positive Z direction, and perform rotation correction on the complete point cloud data including the tabletop and the liquid level, so that the tabletop point cloud data is located on the xy plane, and the liquid level point cloud data is located on the Z plane, and the liquid level point cloud data is the actual height value.

4. A three-dimensional reconstruction method of expansive polymer slurry based on Lidar point cloud according to claim 1 or 2, characterized in that: The container is cylindrical. In step S3, the convex hull is the outer boundary contour of the projected liquid level point cloud, and the outer boundary is fitted with the geometric center of the convex hull as the center and the inner diameter of the container as the diameter.

5. A three-dimensional reconstruction method of a swelling polymer slurry based on Lidar point cloud according to claim 4, characterized in that: In step S3, align the height of the outer boundary circle with the actual liquid level point cloud height value. Specifically: match each point of the fitted circle with the nearest point of the liquid level point cloud, and assign the height of the matching point to the Z value of the fitted circle to determine the outer boundary of the liquid level.

6. A three-dimensional reconstruction method for expansive polymer slurry based on Lidar point cloud according to claim 1 or 2, characterized in that: In step S4, perform triangulation on the liquid level to generate a three-dimensional mesh of the liquid level, and visualize the shape of the liquid level; the bottom surface is the projection of the liquid level points on the xy plane and is generated by triangulation; the side wall is constructed by connecting the bottom surface projection of the outer boundary points and the liquid level outer boundary points.

7. A method for measuring the volume of expansive polymer slurry based on Lidar point cloud, characterized in that: The measurement method includes the following steps: generate a three-dimensional model according to the method described in any one of claims 1-6, and the three-dimensional model is generated using the triangulation method; then perform step S5, accumulate the volumes of the triangulation volume units, and calculate the total volume of the slurry.

8. A method for measuring the volume of a swelling polymer slurry based on Lidar point cloud according to claim 7, characterized in that: In step S5, the space between each triangular patch and the bottom surface forms a triangular prism unit, and the volume is obtained by multiplying the bottom area by the height.

9. A method for measuring the volume of a swelling polymer slurry based on Lidar point cloud according to claim 8, characterized in that: The height takes the average value of the heights of the triangular vertices, and the bottom area is the projected area of the triangular patch on the xy plane.

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