阅读说明：本技术 一种磁浮轨道中心线提取方法 (Method for extracting central line of magnetic suspension track ) 是由 姚连璧 阮东旭 孙向东 郭海霞 袁琴 于 2020-12-22 设计创作，主要内容包括：本发明涉及一种磁浮轨道中心线提取方法,该方法包括以下步骤：获取轨道断面点云数据和磁浮轨道断面模型点集,磁浮轨道断面模型点集包括轨道模型平面中心点；从轨道断面点云数据中提取点云轨道断面初始匹配中心点；依据轨道模型平面中心点至点云轨道断面初始匹配中心点所需的平移参数平移磁浮轨道断面模型点集,基于距离最小化原则,利用轨道断面点云数据重构磁浮轨道断面模型点集,得到适应性模型点集；利用最小二乘改进的二维ICP算法计算适应性模型点集与轨道断面点云数据的匹配参数,得到最终点云轨道中心点；基于最终点云轨道中心点,利用拟合算法得到磁浮轨道的中心线。与现有技术相比,可有效提高磁浮轨道中心线提取的效率和精度。(The invention relates to a method for extracting a central line of a magnetic suspension track, which comprises the following steps: acquiring track section point cloud data and a magnetic suspension track section model point set, wherein the magnetic suspension track section model point set comprises a track model plane central point; extracting an initial matching center point of a point cloud track section from the point cloud data of the track section; translating the point set of the magnetic suspension track section model according to translation parameters required by the initial matching center point from the plane center point of the track model to the point cloud track section, and reconstructing the point set of the magnetic suspension track section model by using the point cloud data of the track section based on the distance minimization principle to obtain an adaptive model point set; calculating matching parameters of the adaptive model point set and the point cloud data of the track section by using a least square improved two-dimensional ICP algorithm to obtain a final point cloud track central point; and obtaining the central line of the magnetic suspension track by utilizing a fitting algorithm based on the final point cloud track central point. Compared with the prior art, the efficiency and the precision of extracting the central line of the magnetic suspension track can be effectively improved.)

1. A method for extracting a central line of a magnetic levitation track is characterized by comprising the following steps:

s1: acquiring track section point cloud data and a magnetic suspension track section model point set, wherein the magnetic suspension track section model point set comprises a track model plane central point;

s2: extracting an initial matching center point of a point cloud track section from the point cloud data of the track section;

s3: translating the point set of the magnetic suspension track section model according to translation parameters required by the initial matching center point from the plane center point of the track model to the point cloud track section, and reconstructing the point set of the magnetic suspension track section model by using the point cloud data of the track section based on the distance minimization principle to obtain an adaptive model point set;

s4: calculating matching parameters of the adaptive model point set and the point cloud data of the track section by using a least square improved two-dimensional ICP algorithm to obtain a final point cloud track central point;

s5: and obtaining the central line of the magnetic suspension track by utilizing a fitting algorithm based on the final point cloud track central point.

2. The method for extracting the centerline of the magnetic levitation track as claimed in claim 1, wherein the step of obtaining the point cloud data of the track section and the point set of the model of the magnetic levitation track section in S1 comprises the following steps:

acquiring magnetic levitation track scanning point cloud data, and acquiring a magnetic levitation track section model point set based on magnetic levitation track design parameters;

based on the moving scanning track data, slicing the magnetic suspension track scanning point cloud data by using vector projection to generate sliced point cloud data;

and projecting, rotating and translating the slice point cloud data to generate track section point cloud data.

3. The method of claim 2, wherein the calculation of slicing by vector projection based on the moving scanning track data is performedIn thatThe projection length L needs to be smaller than the slice thickness threshold h, and the expression of L is:

wherein, A and B are adjacent track points, C is a certain point in the point cloud data of the magnetic suspension track scanning point, and alpha isAndthe included angle of (a).

4. The method for extracting the center line of the magnetic levitation track as claimed in claim 2, wherein the track section point cloud data is represented as:

wherein the content of the first and second substances,is a point cloud coordinate of a track section, R is a rotation matrix from a plane passing through track points and a normal vector as a track direction vector to an xoy plane,is a point cloud coordinate of a plane passing through the track points and the normal vector is a track direction vector,and the average value of point cloud coordinates in the xoy plane after rotation.

5. The method for extracting the center line of the magnetic levitation track as claimed in claim 2, wherein the process of obtaining the point set of the magnetic levitation track profile model based on the design parameters of the magnetic levitation track comprises:

drawing a CAD (computer aided design) graph of the section of the magnetic levitation track according to the design parameters of the magnetic levitation track;

and equally dividing the line segments of the sections of the magnetic levitation track in a CAD graph of the sections of the magnetic levitation track to obtain a point set of the section model of the magnetic levitation track.

6. The method for extracting the center line of the magnetic levitation track as claimed in claim 1, wherein the step of extracting the initial matching center point of the point cloud track profile in S2 comprises:

extracting data larger than a height threshold value from the point cloud data of the track section to obtain a track plane point set;

and calculating the mean value of the point set of the orbit plane to obtain the initial matching center point of the point cloud orbit section.

7. The method for extracting the centerline of the magnetic levitation track as claimed in claim 1, wherein the step of obtaining the adaptive model point set in S3 comprises:

and extracting the model point closest to each point cloud data point in the translated magnetic levitation track section model point set, reconstructing the magnetic levitation track section model point set, and then reversely translating the reconstructed magnetic levitation track section model point set by utilizing the translation parameters to obtain the adaptive model point set.

8. The method for extracting the centerline of the magnetic levitation track as claimed in claim 1, wherein in S4, the objective function of the least squares improved two-dimensional ICP algorithm is:

wherein i is the ith data point, x'_i,y′_iAs reference data points, b₁And b₂And a is a translation parameter, a is a rotation matrix parameter, and n is the number of data points.

9. The method for extracting the centerline of a magnetic levitation track as claimed in claim 8, wherein in S4, the matching parameters a, b are calculated₁And b₂The formula of (1) is:

wherein, X' is represented as:

y' is represented by:

x is represented as:

y is represented by:

10. the method for extracting the centerline of a magnetic levitation track as claimed in claim 9, wherein the matching parameters a, b are obtained in S4₁And b₂Then, judge b₁And b₂If the difference value of the matching parameter of the previous iteration is larger than or equal to the threshold value, b is used₁And b₂And (5) executing S3 as a translation parameter, if not, calculating the central point of the final point cloud trackThe calculation formula of the final point cloud track central point is as follows:

wherein R is^-1Is a rotation matrix of the xoy plane rotated to a plane passing through the locus points and the normal vector is a locus direction vector,and the average value of point cloud coordinates in the xoy plane after rotation.

Technical Field

The invention relates to the field of magnetic levitation track measurement, in particular to a method for extracting a central line of a magnetic levitation track.

Background

The high-speed magnetic suspension train is a novel ground vehicle which utilizes electromagnetic force to realize suspension and guidance of the train, a linear motor realizes traction drive, a track of the high-speed magnetic suspension train is composed of a prestressed concrete beam, a connecting piece, a functional piece and a long stator which is provided with a tooth socket structure and is spliced in a segmented mode, and the train surrounds a sliding surface, a guiding surface and a stator surface to fly. The safe, stable and efficient operation of the high-speed train is mainly characterized in that whether the railway track meets the designed type and position, and the spatial position, the geometric state and the line attachment of the track can be accurately reflected by regular measurement and maintenance. The magnetic suspension track is used as a key element in the surveying and mapping positioning of the magnetic suspension infrastructure object, and due to the characteristics of planar track, long route and the like, the data obtained by the existing method is discrete and low-efficiency, can not accurately and quickly reflect each element of the track, and is difficult to meet the monitoring requirement of the operation and maintenance of the modern railway.

The traditional track center line measurement mainly adopts the following modes: 1) manual on-line measurement, measuring mileage by a steel ruler, measuring and setting a curve by a total station instrument vector distance method or an angle deviation method, and directly adopting coordinates of each element by using a total station instrument and a GPS RTK method. However, the methods require manual work, which results in poor safety and large workload, and require a large amount of manpower and material resources to cause resource loss, and meanwhile, the methods have the disadvantages of incomplete information collection, low operation efficiency and the like. 2) The method has the advantages that the high-resolution image is used, the railway area can be effectively extracted based on the grid image processing method, the occurrence of railway track line false alarm targets is reduced, the accurate railway track line extraction is realized through a differential geometric algorithm, but the extraction rate does not reach one hundred percent at present, and the measurement precision is lower than that of a traditional mode. 3) The method for extracting the railway track based on the airborne LiDAR comprises the steps of establishing an object-oriented railway area extraction algorithm by utilizing the airborne LiDAR and image data, eliminating the influence of interference factors through mathematical morphology processing, obtaining LiDAR point cloud data of a rail area, further separating the point cloud of the track according to the height characteristics of the point cloud of the railway track, and finally accurately fitting the point cloud data of the track through a least square method to obtain track information. However, the existing method has the defects that the precision cannot meet the engineering requirement and the recognition effect in the track curve direction is poor.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for extracting the center line of a magnetic levitation track.

The purpose of the invention can be realized by the following technical scheme:

a method for extracting a central line of a magnetic levitation track comprises the following steps:

s1: acquiring track section point cloud data and a magnetic suspension track section model point set, wherein the magnetic suspension track section model point set comprises a track model plane central point;

s2: extracting an initial matching center point of a point cloud track section from the point cloud data of the track section;

s3: translating the point set of the magnetic suspension track section model according to translation parameters required by the initial matching center point from the plane center point of the track model to the point cloud track section, and reconstructing the point set of the magnetic suspension track section model by using the point cloud data of the track section based on the distance minimization principle to obtain an adaptive model point set;

s4: calculating matching parameters of the adaptive model point set and the point cloud data of the track section by using a least square improved two-dimensional ICP algorithm to obtain a final point cloud track central point;

s5: and obtaining the central line of the magnetic suspension track by utilizing a fitting algorithm based on the final point cloud track central point.

In S1, the method for acquiring the point cloud data of the track section and the point set of the magnetic suspension track section model comprises the following steps:

acquiring magnetic levitation track scanning point cloud data, and acquiring a magnetic levitation track section model point set based on magnetic levitation track design parameters;

based on the moving scanning track data, slicing the magnetic suspension track scanning point cloud data by using vector projection to generate sliced point cloud data;

and projecting, rotating and translating the slice point cloud data to generate track section point cloud data.

Based on the moving scanning track data, the calculation of slicing by using vector projectionIn thatThe projection length L needs to be smaller than the slice thickness threshold h, and the expression of L is:

wherein, A and B are adjacent track points, C is a certain point in the point cloud data of the magnetic suspension track scanning point, and alpha isAndthe included angle of (a).

The track section point cloud data is expressed as:

wherein the content of the first and second substances,is a point cloud coordinate of a track section, R is a rotation matrix from a plane passing through track points and a normal vector as a track direction vector to an xoy plane,is a point cloud coordinate of a plane passing through the track points and the normal vector is a track direction vector,and the average value of point cloud coordinates in the xoy plane after rotation.

The process of obtaining the point set of the magnetic levitation track section model based on the magnetic levitation track design parameters comprises the following steps:

drawing a CAD (computer aided design) graph of the section of the magnetic levitation track according to the design parameters of the magnetic levitation track;

and equally dividing the line segments of the sections of the magnetic levitation track in a CAD graph of the sections of the magnetic levitation track to obtain a point set of the section model of the magnetic levitation track.

In S2, the process of extracting the initial matching center point of the point cloud track cross section includes:

extracting data larger than a height threshold value from the point cloud data of the track section to obtain a track plane point set;

and calculating the mean value of the point set of the orbit plane to obtain the initial matching center point of the point cloud orbit section.

The process of obtaining the adaptive model point set in S3 includes:

and extracting the model point closest to each point cloud data point in the translated magnetic levitation track section model point set, reconstructing the magnetic levitation track section model point set, and then reversely translating the reconstructed magnetic levitation track section model point set by utilizing the translation parameters to obtain the adaptive model point set.

In S4, the objective function of the least squares modified two-dimensional ICP algorithm is:

wherein i is the ith data point, x'_i,y′_iAs reference data points, b₁And b₂Alpha is a translation parameter, alpha is a rotation matrix parameter, and n is the number of data points.

In S4, a matching parameter a is calculated,b₁and b₂The formula of (1) is:

wherein, X' is represented as:

y' is represented by:

x is represented as:

y is represented by:

in S4, matching parameters alpha, b are obtained₁And b₂Then, judge b₁And b₂If the difference value of the matching parameter of the previous iteration is larger than or equal to the threshold value, b is used₁And b₂And (5) executing S3 as a translation parameter, if not, calculating the central point of the final point cloud trackThe calculation formula of the final point cloud track central point is as follows:

wherein R is^-1Is a rotation matrix of the xoy plane rotated to a plane passing through the locus points and the normal vector is a locus direction vector,and the average value of point cloud coordinates in the xoy plane after rotation.

Compared with the prior art, the invention has the following advantages:

(1) the method comprises the steps of extracting the center line of the magnetic suspension track by applying template point cloud matching, obtaining the plane center point of the dense point cloud track by matching and searching point cloud data of the track section, fitting the center line equation of the magnetic suspension track by using a fitting mode, overcoming the defects of high working intensity, low efficiency and the like of manual detection, and providing a data base for the safe operation and maintenance of magnetic suspension.

(2) In the actually scanned magnetic suspension track scanning point cloud data, due to the fact that the position and the scanning line of a scanner are equiangular distribution, the obtained track section point cloud data density is uneven along with the position distribution, if a model point set with even distribution density is directly adopted, the matching effect is inevitably limited, the model point set adopts the adaptive density based on distance minimization to establish an adaptive model point set, and the model point set is continuously subjected to adaptive density reconstruction based on the iteration and distance minimization principle, so that the method is suitable for the scene with uneven track section point cloud distribution, and the precision of template point cloud matching can be effectively improved.

Drawings

FIG. 1 is a flow chart of the present invention;

FIG. 2 is a schematic view of the present invention using vector projection for slicing;

FIG. 3 is a schematic diagram of the track cross-section point cloud data of the present invention;

FIG. 4 is a schematic diagram of a magnetic levitation track structure according to the present invention;

FIG. 5 is a schematic diagram of a magnetic levitation track section model point set according to the present invention;

FIG. 6 is a diagram of the result of matching the adaptive model point set with the point cloud data of the rail section according to the present invention.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment 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 embodiments.

Examples

The embodiment provides a method for extracting a magnetic levitation track center line based on template point cloud matching, as shown in fig. 1, the method comprises the following steps:

s1: acquiring track section point cloud data and a magnetic suspension track section model point set, wherein the magnetic suspension track section model point set comprises a track model plane central point;

s2: extracting an initial matching center point of a point cloud track section from the point cloud data of the track section;

s3: translating the point set of the magnetic suspension track section model according to translation parameters required by the initial matching center point from the plane center point of the track model to the point cloud track section, and reconstructing the point set of the magnetic suspension track section model by using the point cloud data of the track section based on the distance minimization principle to obtain an adaptive model point set;

s4: calculating matching parameters of the adaptive model point set and the point cloud data of the track section by using a least square improved two-dimensional ICP algorithm to obtain a final point cloud track central point;

s5: and obtaining the central line of the magnetic suspension track by utilizing a fitting algorithm based on the final point cloud track central point.

Compared with the prior art, the method for extracting the center line of the magnetic suspension track based on template point cloud matching has the characteristics of accurate positioning, high efficiency, high safety and the like.

Specifically, the method comprises the following steps:

1) in S1, the method for acquiring the point cloud data of the track section and the point set of the magnetic suspension track section model comprises the following steps:

acquiring magnetic levitation track scanning point cloud data, and acquiring a magnetic levitation track section model point set based on magnetic levitation track design parameters; based on the moving scanning track data, slicing the magnetic suspension track scanning point cloud data by using vector projection to generate sliced point cloud data; and projecting, rotating and translating the slice point cloud data to generate track section point cloud data.

The magnetic suspension track scanning point cloud data comprises moving scanning track data, a track point set with the interval of 1m is generated by interpolating the moving scanning track data, point cloud slicing is carried out by utilizing adjacent track points and adopting a vector projection method, the specific principle is as shown in figure 2, A, B are the adjacent track points, and track direction vector is formedAny point in the magnetic suspension track scanning point cloud data is a point C, and forms a vector with the point AThe distance from point C to the plane passing through point a and perpendicular to the trajectory direction vector is L, which is given by the relation:

wherein alpha is a vectorAndthe included angle of (a).

Conversely, if the point C in the point cloud is located in a slice, the vector isIn the track direction vectorA projected value of (i), i.eThe value L is inevitably smaller than a slice thickness threshold value h, the slice thickness is related to the distribution density of the point cloud data, the slice thickness is set within an allowable error range, and according to a general condition, h can be set to be 2 cm.

The method comprises the steps of generating two-dimensional point cloud (namely the point cloud data of the track section) by projecting, rotating and translating the point cloud data of the slice, projecting each point in the slice to a plane passing through a track point and taking a normal vector as a track direction vector according to a point-to-point normal plane projection method, calculating a rotation matrix R for rotating the plane to the xoy plane according to the normal vector of the plane, and calculating the average value of point coordinates in the xoy plane after rotationThen the generated point cloud coordinates (x) of the track section_i,y_iAnd 0) is:

according to the structure and related design parameters of the magnetic levitation track, as shown in fig. 4, a section CAD graph is drawn, as shown in fig. 5, wherein the central point of the section CAD graph is located at the original point position in the graph, the section line segments of the magnetic levitation track are divided into point sets in a 'fixed distance equal division' mode through drawing processing in CAD, and the point set coordinates are extracted by a CAD tool to be made into a magnetic levitation track model point set file.

2) The process of extracting the initial matching center point of the point cloud track section comprises the following steps: aiming at the point cloud data of the track section, a highest point set, namely a track plane point set, in the point cloud data of the track section is calculated in a comparison mode, the track plane point set is roughly extracted according to a certain height threshold value, and based on the symmetry of a magnetic suspension track plane, the track plane center of the section is replaced by the coordinate average value of the track plane point set, so that the initial matching center point of the point cloud track section is obtained.

3) Translating the magnetic levitation track section model point set by using the point cloud track section initial matching center point calculated in the step 2), calculating a model point reconstruction model point set closest to each point cloud data point in the track section point cloud data in the magnetic levitation track section model point set by using the principle of distance minimization, and after the seeking is finished, reversely translating the model point set by using translation parameters to obtain an adaptive model point set.

4) In order to accurately calculate the matching parameters of the adaptive model point set and the point cloud data of the track section, a two-dimensional ICP algorithm based on least square improvement is adopted, and the specific steps are as follows: 4.1 setting a reference data set (point cloud data of a track section) and a target data set (an adaptive model point set); 4.2 for each point in the target data set, searching a point with the shortest distance corresponding to each point in the reference data set; and 4.3, establishing a matching target function, optimizing the target function, solving the optimal solution of the target function, and obtaining a new target data set.

The specific process of establishing the objective function is as follows:

for a point P in the target dataset_i(x_i,y_i) Finding a point M in the reference dataset_i(x′_i,y′_i) Let point P_iTo M_iThe distance is minimal. To P_i(x_i，y_i) Making a transformation to obtain pointsThe two corresponding relations are as follows:

wherein α, b₁，b₂Is a matching parameter;is a rotation matrix;transforming target data points for translation vectorsTo P_i(x_i，y_i) Corresponding reference data point M_i(x′_i，y′_i) The least square sum of the distances of (a) is the principle, and the objective function is established as follows:

wherein i is the ith data point, x'_i，y′_iAs reference data points, b₁And b₂Solving matching parameters alpha and b for translation parameters, alpha is a rotation matrix parameter, n is the number of data points₁，b₂So that f is minimized.

The three matching parameters are solved as:

order to

Then:

in this embodiment, the threshold of the translation vector is selected to be 1mm, the matching result is shown in FIG. 6, if b is₁Or b₂The difference value of the matching parameter of the previous iteration is greater than or equal to a threshold value, and b₁And b₂As a translation parameter, execute 3), otherwise, calculate the point cloud orbit center pointThe calculation formula is as follows:

wherein R is^-1And the rotation matrix is a rotation matrix of the xoy plane to a plane passing through the track point and the normal vector of the xoy plane is the track direction vector.

5) And calculating the central line of the magnetic suspension track by using a fitting algorithm based on the extracted final point cloud track central point.