CN111752308B - Method for correcting moving scanning posture in circular shield tunnel - Google Patents
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- CN111752308B CN111752308B CN201910230695.5A CN201910230695A CN111752308B CN 111752308 B CN111752308 B CN 111752308B CN 201910230695 A CN201910230695 A CN 201910230695A CN 111752308 B CN111752308 B CN 111752308B
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Abstract
The invention relates to a method for correcting a moving scanning posture in a circular shield tunnel, which comprises the following steps: step S1: the fixed mobile scanning equipment is connected with the scanner and used for scanning the point cloud of the circular shield tunnel at the current position in a spherical scanning mode; step S2: automatically reading the station point cloud after scanning is finished, eliminating obvious noise, performing cylindrical surface fitting on the station point cloud, and calculating an included angle between the projection of a fitted cylindrical central axis on an XY plane and a Y axis, namely an included angle theta between the 0-degree direction of the current scanner and the central axis of the tunnel, wherein the Z axis points to the vertical direction, the Y axis points to the horizontal direction, and the X axis points to the mileage direction; step S3: and controlling the scanner to rotate the angle theta calculated in the step S3, enabling the scanning section to be perpendicular to the central axis of the tunnel, and simultaneously recording the pitch angle and the rotation angle of the scanning equipment, thereby realizing posture correction of the mobile scanning equipment.
Description
Technical Field
The invention relates to the technical field of tunnel monitoring, in particular to a method for correcting a moving scanning posture in a circular shield tunnel.
Background
In urban traffic, the subway is one of the most important. With the development of new mapping technology, the construction and safety monitoring of subway tunnels has been developed from the traditional simple monitoring modes such as site survey and manual judgment to the high-precision semi-automatic and automatic monitoring stages, and the high-precision mapping means is used for safety monitoring of large urban public infrastructures.
Three-dimensional laser scanning equipment collection point cloud data does not need specific device, has advantages such as data acquisition is fast, the data bulk is big, efficient, not only can obtain the point cloud of high accuracy, high density, but also can obtain the positive shadowgraph inside the tunnel, through the infiltration of shadow graph can be fine the tunnel section of jurisdiction, the condition such as leak, wrong platform, reduced manual identification's the degree of difficulty and inaccuracy.
The tunnel mobile scanning is mobile scanning equipment which integrates various sensors such as a three-dimensional laser scanner and the like, can move rapidly on a track, and obtains the information of deformation and diseases inside the tunnel. Before the mobile scanning starts, the scanner is often required to be corrected in an initial posture, the scanning section is ensured to be perpendicular to the central axis of the tunnel, image forming deformation is reduced, and detection precision is improved.
Because no GPS signal exists in the subway tunnel, a GPS + inertial navigation combined positioning mode cannot be used, the traditional attitude adjustment means is generally carried out by means of approximate aiming of human eyes, assistance of a reference object and the like, and the precision is often difficult to meet the requirement. The utility model patent 201620811698.X uses and also can accomplish the confirmation of scanning gesture through the laser corrector, but has used external auxiliary assembly to carry out scanner gesture adjustment, has increased equipment cost.
Disclosure of Invention
The present invention is directed to a method for correcting a moving scanning posture in a circular tunnel, which is provided to overcome the drawbacks of the prior art, and the method does not require manual work or reference object collimation, and does not require external equipment assistance, and can rapidly complete the scanning of a section perpendicular to a central axis of the tunnel, thereby reducing the error of the scanning of the section perpendicular to the central axis of the tunnel.
The purpose of the invention can be realized by the following technical scheme, comprising the following steps:
step S1: the fixed mobile scanning equipment is connected with the scanner and used for scanning the point cloud of the circular shield tunnel at the current position in a spherical scanning mode;
step S2: automatically reading the station point cloud after scanning is finished, eliminating obvious noise, performing cylindrical surface fitting on the station point cloud, and calculating an included angle between the projection of a fitted cylindrical central axis on an XY plane and a Y axis, namely an included angle theta between the 0-degree direction of the current scanner and the central axis of the tunnel, wherein the Z axis points to the vertical direction, the Y axis points to the horizontal direction, and the X axis points to the mileage direction;
step S3: and controlling the scanner to rotate the angle theta calculated in the step S3, enabling the scanning section to be perpendicular to the central axis of the tunnel, and simultaneously recording the pitch angle and the rotation angle of the scanning equipment, thereby realizing posture correction of the mobile scanning equipment.
The point cloud acquisition software in the step 1 is self-development software on a PC (personal computer) terminal and is used for controlling and operating the scanner.
The cylindrical surface fitting in the step 2 is a function in the point cloud acquisition software.
And 2, performing cylindrical surface fitting according to a least square method, obtaining seven undetermined parameters (a, b, c), (x, y, z) and R through the least square method, and fitting the scanning point cloud to the cylindrical surface according to the seven undetermined parameters, wherein (a, b, c) is a point on a central axis of the fitting cylinder, (x, y, z) is a unit vector of the central axis of the fitting cylinder, and R is the radius of the fitting cylindrical surface.
The fitting of the cylindrical surface in the step 2 specifically comprises the following steps: setting an initial value of the undetermined parameter, iterating to obtain a balance value of the undetermined parameter, deleting the point cloud with the residual error larger than a set value according to a fitting result to obtain new point cloud, and iterating the balance value of the undetermined parameter serving as the initial value to the new point cloud data until the correction value of the undetermined parameter is smaller than a set threshold value after certain iteration.
And 3, the angle of the scanner to be rotated in the step 3 is the included angle between the projection of the central axis of the cylindrical surface fitted for the scanning point cloud in the xy plane and the y axis.
And 3, automatically controlling the scanner to rotate through the rotation angle calculated by the point cloud acquisition software in the rotation of the scanner in the step 3.
Drawings
Fig. 1 is a flowchart illustrating a method for correcting a moving scanning posture in a circular shield tunnel according to the present invention;
FIG. 2 is a schematic view of a mobile scanning data acquisition of the present invention;
FIG. 3 is a schematic illustration of cylinder fitting;
fig. 4 is a schematic view of the angle over which the scanner is to be rotated in the xy plane.
Detailed Description
The invention is described in detail below with reference to the drawings and specific examples. The present example is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following examples.
The invention discloses a method for correcting a moving scanning posture in a circular tunnel, and relates to two aspects of field measurement and software processing. In the aspect of field measurement, any circular tunnel is taken as a scanning target, a three-dimensional laser scanning technology is adopted for measurement through a software control scanner, and point clouds are automatically transmitted and recorded into a specified directory of a PC (personal computer) end hard disk; in the software processing stage, software automatically reads recorded point cloud data, obvious noise is eliminated, the included angle between the 0-degree direction of the scanner and the central axis of the tunnel is obtained through an improved cylindrical surface fitting algorithm, and the scanner is controlled to rotate by the software to enable the scanning section of the scanner to be perpendicular to the central axis of the tunnel.
As shown in fig. 1, the method for correcting the moving scanning posture after determining a circular tunnel as the measurement object includes:
step S1: before the mobile scanning starts, the connection between a point cloud acquisition program and a scanner is established, and the scanner is controlled by software to complete the scanning of an inspection station in a spherical mode.
Step S2: after scanning is finished, software automatically reads recorded point cloud data, fits the point cloud data into a cylindrical surface according to an improved cylindrical surface fitting algorithm, and calculates to obtain an included angle between the scanner direction of 0 degree and the central axis of the tunnel.
As shown in fig. 3, in step S2, cylindrical surface fitting is performed according to the least square method, and seven undetermined parameters (a, b, c) and (x) are obtained by the least square method 0 , y 0 ,z 0 ) R, fitting the scanning point cloud to the cylindrical surface according to seven undetermined parameters, wherein (x) 0 , y 0 ,z 0 ) And (b) a point P on the central axis of the fitting cylinder, wherein (a, b and c) are unit vectors a of the central axis of the fitting cylinder, and r is the radius of the fitting cylinder.
The invention improves the fitting of the cylindrical surface: setting an initial value of the undetermined parameter, iterating to obtain a balance value of the undetermined parameter, deleting the point cloud with the residual error larger than a set value according to a fitting result to obtain new point cloud, and iterating the balance value of the undetermined parameter serving as the initial value to the new point cloud data until the correction value of the undetermined parameter is smaller than a set threshold value after certain iteration.
The specific derivation is as follows, to uniquely determine the cylinder, a circle is requiredThe direction vector (a, b, c) of the column axis and the coordinate (x) of a point on the axis 0 , y 0 ,z 0 ) And a cylinder radius r. From this, the parametric equation for the center axis of the cylinder can be found as:
wherein t is a parameter vector.
The cylindrical surface can be regarded as a set of points with a constant distance to an oriented straight line according to the geometrical characteristics of the cylindrical surface. The equation for a spatial cylinder can be expressed as:
wherein, (x, y, z) is a point on the spatial cylindrical surface, and (a, b, c) is a unit vector. Further developing and finishing the formula to obtain:
the error equation can be listed as:
linearization of the above equation is required. In the linearization process, because the correlation between the parameters of the above formula is relatively large, the calculation result of the parameters is relatively influenced by the omission of high-order terms, and the initial value of the parameters needs to be relatively high, otherwise, iteration may not converge or a wrong result may be converged.
In order to arbitrarily select the initial values of the parameters in the adjustment process on the premise of ensuring the optimal parameter solution, the error equation needs to be correspondingly transformed, and the conditions are considered
. Let the error equation be:
linearizing the above equation to obtain:
in the above formula, the first and second carbon atoms are,
wherein,
calculating partial derivatives of 7 parameters; r is 0 And R 0 The radius of the cylinder after the parameter approximation is substituted.
Due to x 0 , y 0 ,z 0 These 3 parameters are related, and a, b, c are also related, requiring constraints on the parameters. And the central axis of the cylinder needs to be specified in size and direction. Therefore, provision is made for:
wherein,
。
and (4) taking the constraint conditions and the error equation into consideration, and performing iterative solution to converge to obtain the optimal approximate parameter estimation value.
Step S3: the scanner is controlled by software to rotate by the angle, so that the scanning section of the scanner is perpendicular to the central axis of the tunnel. The rotation angle θ is an included angle between the xy plane projected by the central axis of the fitting cylindrical surface and the y axis, as shown in fig. 4.
And after the posture of the scanner is adjusted, the scanner can be used for scanning the tunnel section.
Claims (3)
1. A method for correcting a moving scanning attitude in a circular shield tunnel is characterized by comprising the following steps:
step S1: the fixed mobile scanning equipment is connected with the scanner and used for scanning the point cloud of the circular shield tunnel at the current position in a spherical scanning mode;
step S2: automatically reading the 'point cloud of the circular shield tunnel at the current position' in the step S1 after scanning is finished, eliminating obvious noise and performing cylindrical surface fitting on the point cloud, and calculating an included angle between the projection of a fitted cylindrical central axis on an XY plane and a Y axis, namely an included angle theta between the 0-degree direction of the current scanner and the central axis of the tunnel, wherein the Z axis points to the vertical direction, the Y axis points to the horizontal direction, and the X axis points to the mileage direction;
step S3: and controlling the scanner to rotate the angle theta calculated in the step S3, enabling the scanning section to be perpendicular to the central axis of the tunnel, and simultaneously recording the pitch angle and the rotation angle of the scanning equipment, thereby realizing posture correction of the mobile scanning equipment.
2. The method for correcting the mobile scanning attitude in the circular shield tunnel according to claim 1, wherein the step S1 is characterized in that the tunnel point cloud collecting device is a tunnel mobile scanning device and does not include an external attitude auxiliary adjusting module.
3. The method for correcting the moving scanning posture in the circular shield tunnel according to claim 1, wherein the step S2 is characterized in that the least square fitting algorithm is used to perform the cylindrical surface fitting on the whole point cloud to obtain seven parameters of the cylindrical surface.
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| CN112923869A (en) * | 2021-02-03 | 2021-06-08 | 南京市测绘勘察研究院股份有限公司 | Subway tunnel clearance detection method based on point cloud |
| CN116164754B (en) * | 2023-04-25 | 2023-06-23 | 中国电子科技集团公司第五十四研究所 | Cloud deck virtualization method based on unmanned aerial vehicle motion state |
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| CN103175510A (en) * | 2013-03-13 | 2013-06-26 | 华中科技大学 | Smart laser profiler automatic in leveling and direction adjustment |
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| EP2620746A1 (en) * | 2012-01-30 | 2013-07-31 | Hexagon Technology Center GmbH | Surveying device with scan functionality and single-point measuring mode |
| CN104392476B (en) * | 2014-12-04 | 2017-07-21 | 上海岩土工程勘察设计研究院有限公司 | The method that tunnel three-dimensional axis is extracted based on minimum bounding box algorithm |
| CN104792274B (en) * | 2015-04-02 | 2017-12-26 | 同济大学 | A kind of measuring method of circular tunnel convergent deformation |
| CN104990501B (en) * | 2015-07-14 | 2018-01-26 | 华中科技大学 | A system parameter calibration method of a three-dimensional laser scanning device |
| CN205910600U (en) * | 2016-07-29 | 2017-01-25 | 上海岩土工程勘察设计研究院有限公司 | Rectify device of scanning gesture |
| CN107830839B (en) * | 2017-10-11 | 2020-06-26 | 北京工业大学 | Ground three-dimensional laser scanning data processing method and device |
| CN107796363A (en) * | 2017-10-13 | 2018-03-13 | 北京工业大学 | A kind of method based on the extraction of continental rise LiDAR radians tunnel cross-section |
| CN109372545B (en) * | 2018-12-19 | 2020-06-05 | 上海勘察设计研究院(集团)有限公司 | Method for evaluating opening degree of bottom joint of circular shield through joint tunnel segment |
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