METHOD, DEVICE AND SYSTEM FOR ANALYZING TUNNEL CLEARANCE BASED ON LASER POINT CLOUD

Abstract

A point cloud of a tunnel is obtained. A cylinder is fitted using the point cloud of the tunnel. A central axis of the tunnel is extracted. A section of the tunnel is intercepted based on the central axis of the tunnel. Point cloud subsets of two rails are extracted. A base line of a contour of the tunnel clearance is constructed. A center of the section of the tunnel is extracted. A point cloud of the section of the tunnel is registered with a point cloud of the tunnel clearance based on a constraint condition. The point cloud of the section of the tunnel and the point cloud of the tunnel clearance which are registered with each other are analyzed to determine whether the tunnel clearance is intruded.

Claims

1. A method for analyzing tunnel clearance based on a laser point cloud, comprising: 1) obtaining a point cloud of a tunnel; 2) fitting a cylinder using the point cloud of the tunnel; extracting a central axis of the tunnel; and intercepting a section of the tunnel based on the central axis of the tunnel; 3) extracting point cloud subsets of two rails; 4) constructing a base line of a contour of the tunnel clearance; and extracting a center of the section of the tunnel; and registering a point cloud of the section of the tunnel and a point cloud of the tunnel clearance based on a constraint condition; and 5) analyzing the point cloud of the section of the tunnel and the point cloud of the tunnel clearance which a registered with each other to determine whether the tunnel clearance is intruded.

2. The method of claim 1, wherein the step 1 comprises: scanning the tunnel using a three-dimensional laser scanner to obtain the point cloud of the tunnel; and intercepting the point cloud of the tunnel in sections.

3. The method of claim 2, wherein each section containing 10 rings,

4. The method of claim 1, wherein the step 2 comprises: 21) fitting a cylinder using the point cloud of the tunnel through Gaussian mapping to extract a central axis of the tunnel; 22) intercepting the point cloud of a single section of the tunnel based on a point p in the point cloud and an axis direction of the point to construct a section plane; and 23) projecting the point cloud of the section of the tunnel along the extracted central axis of the tunnel to obtain two-dimensional section data.

5. The method of claim 1, wherein the step 3 comprises: extracting point clouds of the two rails from the point cloud of the tunnel; selecting points p.sub.i and p.sub.j from point clouds of the two rails; and clustering point cloud subsets of the two rails using Euclidean distance.

6. The method of claim 1, wherein the constraint condition in the step 4 is obtained is obtained by steps of: selecting the highest points z_max.sub.i and z_max.sub.j of the point clouds of the two rails to construct a straight line l; calculating a slope k of the straight line l; fitting a circle using Random Sample and Consensus (RANSAC) method according to the point cloud of the section of the tunnel to obtain a center c of the circle and an abscissa c.Math.x of the center of the circle; and setting two constraint conditions: a) a bottom edge of a bound box of a clearance contour coincides with the straight line l; and b) an abscissa c.sub.0.Math.x of a center of the clearance contour is the abscissa c.Math.x of the center of the circle.

7. The method of claim 1, wherein the step 5 comprises: for a point p_i in the center of the point cloud of the tunnel section, searching the closest point p_in in the point cloud of the clearance contour through K-Nearest Neighbors (KNN); and determining whether the tunnel clearance is intruded through an intrusion function:
S=∥p_i−c∥−∥p_in−c∥, wherein, p_i is any point in the point cloud of the section of the tunnel; p_in is the closest point searched by KNN in the point cloud of the clearance contour; when S<0, the tunnel clearance is intruded; otherwise, the tunnel clearance is not intruded.

8. A device for analyzing tunnel clearance based on a laser point cloud, comprising: a data acquisition module, configured to acquire a point cloud of a tunnel; a preprocessing module, configured to preprocess the point cloud of the tunnel, intercept segments, and extract a central axis of the tunnel and point cloud subsets of a rail; wherein the point cloud subsets are for registration of the point cloud; and an analysis module, configured to calculate a straight line and a center of the tunnel, and register a point cloud of a clearance contour with a point cloud of a section of the tunnel through constraint conditions to analyze the tunnel clearance.

9. The device of claim 8, wherein the preprocessing module comprises: an interception unit, configured to intercept the point cloud of the tunnel into segments; and an extraction unit, configured to extract the point cloud subsets of the rails from the point cloud of the tunnel and and perform clustering for the point cloud subsets of the two rails using Euclidean distance, so as to extract the point cloud subsets of the two rails.

10. A system for analyzing tunnel clearance based on a laser point cloud, comprising: a three-dimensional scanner; a processor; a storage; and a program, stored on the storage, for executing the method of claim 1; wherein the system is mounted on a tunnel inspection vehicle; and the three-dimensional scanner is connected to the processor, and is configured to scan the tunnel to obtain point cloud of the tunnel and send the obtained point cloud of the tunnel to the processor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The drawings are illustrative in nature and are not drawn to scale. Throughout the drawings, like reference numerals refer to identical or functionally similar elements. For clarity, not every component is labeled in every figure. The embodiments of the present disclosure are illustrated below with reference to the accompanying drawings.

[0056] FIG. 1 is a flowchart of a method for analyzing tunnel clearance based on laser point clouds according to at least one embodiment of the present disclosure.

[0057] FIG. 2 is a schematic diagram of a point cloud of a segment containing 10 rings obtained by using the method according to at least one embodiment of the present disclosure.

[0058] FIG. 3 is a schematic diagram of a point cloud of rails in a section of the tunnel according to at least one embodiment of the present disclosure.

[0059] FIG. 4 shows results of the clearance analysis of the tunnel using the method according to at least one embodiment of the present disclosure.

[0060] FIG. 5 is a schematic diagram of a device for analyzing tunnel clearance based on laser point clouds according to at least one embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0061] The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings, from which technical solutions of the present disclosure become clear.

Embodiment 1

[0062] This embodiment illustrates a method for analyzing tunnel clearance based on laser point clouds, which can be directly applied to various laser point clouds based clearance analysis devices of subway tunnels. In specific implementation, the application can be realized by writing corresponding programs in controllers of clearance analysis device of the subway tunnel. As shown in FIG. 1, the method includes the following steps.

[0063] 1) A point cloud of a subway tunnel is obtained. Specifically, the tunnel is scanned by a three-dimensional scanner based tunnel inspection vehicle to obtain the point cloud of the subway tunnel.

[0064] 2) A cylinder is fitted using the point cloud of the tunnel. A central axis of the tunnel is extracted. A section of the tunnel is intercepted based on the central axis of the tunnel. Specifically, the cylinder is fitted using the point cloud through Gaussian mapping. The central axis of the subway tunnel is extracted, and the point cloud data of a single section of a tunnel is intercepted. A section plane is constructed based on a point p in the point cloud and the axis direction of the point.

[0065] 3) Point cloud subsets of rails are extracted. Specifically, point p.sub.i and point p.sub.j are respectively selected from the point clouds of the two rails. The point cloud subsets of the two rails are clustered using Euclidean distance. A threshold of clustering distances is set to 0.02 m, and the point cloud subset of the rail is extracted.

[0066] 4) A base line of a contour of tunnel clearance is constructed, and a center of the section of the tunnel is extracted. The point cloud of the section of the tunnel is registered with the point cloud of the tunnel clearance based on constraint conditions. Specifically, the highest points z_max.sub.i and z_max.sub.j of the point clouds of the two rails are selected to construct a straight line l, and a slope k of the straight line l is calculated. A circle is fitted for the section of the tunnel using Random Sample And Consensus (RANSAC) method, and a threshold of the RANSAC bandwidth set to 0.04 m, and a circle center c is obtained. The point cloud of the contour of the tunnel clearance is registered with the point cloud of the tunnel section, in which the following two constraint conditions should be satisfied. One is that a bottom edge of a bounding box of a clearance contour coincides with the straight line l. The other constraint is that an abscissa of a center of the clearance contour c0.Math.x is the abscissa c.Math.x of the center of the circle.

[0067] 5) Data analysis is carried out to determine the invasion. Specifically, for any point p_i in the center of the point cloud of the tunnel section, the closest point p_in in the point cloud of the clearance contour is searched through KNN, and then whether the clearance is intruded is judged by an intrusion function. The intrusion function is defined as:

S=∥p_i−c∥−∥p_in−c∥,

[0068] where, p_i is any point in the point cloud of the tunnel section; p_in is the closest point searched by KNN in the point cloud of the clearance contour; when S<0, the tunnel clearance is intruded; otherwise, the tunnel clearance is not intruded.

[0069] In this embodiment, an accurate calculation and analysis method is provided to determine whether the tunnel intrudes the clearance contour. Specifically, the point cloud of a subway tunnel is obtained. A cylinder is fitted using the point cloud of the tunnel. The central axis of the tunnel is extracted. The section of the tunnel is intercepted based on the central axis of the tunnel. A point cloud subset of a rail is extracted. The base line of a clearance contour is constructed, and the center of the section of the tunnel is extracted. The point cloud of the section of the tunnel is registered with the point cloud of the tunnel clearance based on constraint conditions. Data analysis is carried out to determine the intrusion. The above method is a simple and feasible method for clearance analysis of subway tunnels, which can effectively reduce the difficulty in the clearance analysis of subway tunnel, avoid analysis errors caused by complex analysis and calculation, and improve the efficiency and accuracy of the clearance analysis.

[0070] FIG. 2 is a schematic diagram of a point cloud of a segment containing 10 rings obtained by using the method of the present disclosure. The tunnel is scanned by a three-dimensional scanner based tunnel inspection vehicle to obtain the point cloud of the subway tunnel. In this embodiment, the point cloud of the subway tunnel is the point cloud of the segment containing 10 rings.

[0071] FIG. 3 is a schematic diagram of a point cloud of rails in a section of the tunnel. Specifically, the point p.sub.i and the point p.sub.j are respectively selected from the point clouds of the two rails. The point cloud subsets of the two rails are clustered using Euclidean distance. A threshold of clustering distances is set to 0.02 m, and the point cloud subset of the rail is extracted. The point cloud data in the wireframe shown in FIG. 3 is the extracted point cloud subsets of the two rails.

[0072] FIG. 4 shows the result of the clearance analysis of the tunnel using the method of this embodiment, in which the distance between the clearance contour and the closest point of the section of the tunnel is calculated and displayed. The method of the present disclosure can accurately analyze the tunnel clearance and inspect the clearance intrusion of subway tunnels.

Embodiment 2

[0073] Based on the method for analyzing tunnel clearance based on the laser point cloud, this embodiment provides a device for analyzing tunnel clearance based on a laser point cloud. Specifically, FIG. 2 shows an optional structural diagram of the device. As shown in FIG. 5, the device includes a data acquisition module, a preprocessing module, and an analysis module.

[0074] The data acquisition module is configured to acquire 3D point cloud data of a subway tunnel. The subway tunnel is scanned through a tunnel detection vehicle based 3D laser scanner system, and 3D point cloud data of the subway tunnel is exported for subsequent preprocessing and analysis calculation.

[0075] The preprocessing module is connected to the data acquisition module, and is configured to pre-process the point cloud data of the subway tunnel, intercept the segment, and extract the central axis of the tunnel and the point cloud subsets of rails. The preprocessing module includes an interception unit and an extraction unit. The interception unit is configured to intercept the point cloud data for segments containing 10 rings, which is convenient for subsequent batch processing. The extraction unit is configured to extract the point cloud subsets of the rails from the point cloud data of the tunnel, and perform clustering for the point cloud subsets of the two rails using Euclidean distance, so as to extract the point cloud subsets of the two rails.

[0076] The analysis module is connected to the preprocessing module, and is configured to calculate a straight line and a center of the tunnel, and register the point cloud of the clearance contour with the point cloud of the section of the tunnel through constraint conditions to carry out the clearance analysis.

[0077] In this embodiment, an accurate calculation and analysis method is provided to determine whether the tunnel intrude the clearance contour. Specifically, the point cloud of a subway tunnel is obtained. A cylinder is fitted using the point cloud of the tunnel. The central axis of the tunnel is extracted. The section of the tunnel is intercepted based on the central axis of the tunnel. A point cloud subset of a rail is extracted. The base line of a clearance contour is constructed, and the center of the section of the tunnel is extracted. The point cloud of the section of the tunnel is registered the point cloud of the tunnel clearance based on constraint conditions. Data analysis is carried out to determine the invasion. The above method is a simple and feasible method for clearance analysis of subway tunnels, which can effectively reduce the difficulty in the clearance analysis of subway tunnel, avoid analysis errors caused by complex analysis and calculation, and improve the efficiency and accuracy of the clearance analysis.

[0078] In some embodiments, the preprocessing module includes an interception unit and an extraction unit. The interception unit is configured to intercept the point cloud data into segments containing 10 rings, which is convenient for subsequent batch processing. The extraction unit is configured to extract the point cloud subsets of the rails from the point cloud data of the tunnel, and perform clustering for the point cloud subsets of the two rails using Euclidean distance, so as to extract the point cloud subsets of the two rails.

[0079] In some embodiments, the analysis module includes: a constraint calculation unit, a point cloud registration unit and an intrusion calculation unit. The constraint calculation unit is configured to construct the characteristic straight line of the rail and fit a circle through RANSAC, and calculate the slope of the straight line and the constraint conditions such as the center of the tunnel. The point cloud registration unit, based on the above constraints, the clearance contour is registered with the point cloud of the section of the tunnel. The intrusion calculation unit is configured to determine whether the segments of the tunnel intrude the tunnel clearance using the defined intrusion function.

[0080] The above embodiments are illustrative of the present disclosure and not intended to limit the scope of the present disclosure. Various modifications and changes made by those of ordinary skill in the art without departing from the spirit and scope of the present disclosure shall fall within the scope of the application defined by the appended claims.