阅读说明：本技术 一种轮轨接触几何参数测量方法 (Wheel-rail contact geometric parameter measuring method ) 是由 尹辉 许宏丽 黄华 白新宇 徐鹏 韩明 于 2021-07-02 设计创作，主要内容包括：本发明提供了一种轮轨接触几何参数测量方法,包括：对轮轨点云进行平面基元和圆柱体基元检测；提取轮缘内侧面所在基元,粗分割轮缘部分点云；进行圆环基元检测,提取轮缘部分以及轨底部分对应基元,得到对应基元参数；计算轮对中心点、轨底中心点,获取轮轴方向；测量轮对横移量、轮对侧滚角、轮对摇头角以及轮对沉浮量,并定位点云中属于铁轨踏面的点；对点云进行切片,去除各点云片中属于铁轨踏面的点；基于RANSAC算法对去除后的点进行切片圆结构信息拟合,得到切片圆的圆心和半径；计算每个切片中铁轨踏面上的点到切片圆圆心的距离,确定接触斑；测量接触斑的长短轴长。该方法可以精确地测量轮轨参数,为列车安全运行提供技术支持。(The invention provides a wheel-rail contact geometric parameter measuring method, which comprises the following steps: detecting plane elements and cylinder elements of the wheel-track point cloud; extracting elements where the inner side surfaces of the wheel rims are located, and roughly dividing point clouds of the wheel rims; detecting circular ring elements, extracting corresponding elements of the wheel rim part and the rail bottom part to obtain corresponding element parameters; calculating the central point of the wheel set and the central point of the rail bottom to obtain the direction of the wheel shaft; measuring the wheel set transverse displacement, the wheel set side rolling angle, the wheel set pan head angle and the wheel set sinking and floating amount, and positioning points belonging to the rail tread in the point cloud; slicing the point cloud, and removing points belonging to the rail tread in each point cloud slice; performing structural information fitting on the removed points on the slicing circle based on an RANSAC algorithm to obtain the circle center and the radius of the slicing circle; calculating the distance from a point on the rail tread in each slice to the center of a slice circle, and determining a contact patch; the long and short axis lengths of the contact patches were measured. The method can accurately measure the wheel track parameters and provide technical support for safe operation of the train.)

1. A wheel-rail contact geometric parameter measuring method is characterized by comprising the following steps:

s1, detecting the planar element and the cylindrical element of the wheel track point cloud;

s2 extracting the elements where the inner side surface of the rim is located from the detection result of the step S1, and roughly dividing the point cloud of the rim part according to the information of the elements where the inner side surface of the rim is located;

s3, performing circular ring element detection on the point cloud of the roughly divided rim part, and extracting corresponding elements of the rim part and the rail bottom part to obtain corresponding element parameters;

s4, calculating the wheel set central point and the rail bottom central point according to the element parameters to obtain the wheel axle direction;

s5 measuring wheel set transverse displacement, wheel set side rolling angle, wheel set rolling angle and wheel set sinking and floating amount according to the calculation result of S4, and positioning points belonging to the rail tread in the point cloud;

s6, slicing the point clouds, and removing points belonging to the rail tread in each point cloud slice;

s7, performing slicing circle structure information fitting on the point cloud points with the tread points removed based on a RANSAC algorithm to obtain the circle center and the radius of the slicing circle;

s8, calculating the distance from the point on the rail tread to the center of the slice circle in each slice, wherein the set of points smaller than a certain threshold value is the contact patch;

s9, the length of the long axis and the length of the short axis of the contact patch are measured according to the coordinates of the center point of the contact patch.

2. The method of claim 1, wherein said step S1 is preceded by processing the point cloud data of the wheel-track to establish two different coordinate systems for the wheel set and the track, and establishing O with the midpoint of the axle center of the wheel set as the origin when the wheel set is in the normal operating position_w-X_wY_wZ_wA wheelset coordinate system that moves with the wheelset relative to the track; establishing O by using the central point of the centers of the two side rail surfaces as the origin_r-X_rY_rZ_rA traveling coordinate system, a plane of the rail bottom and a traveling coordinate system O_r-X_rY_rZ_rX in (1)_rO_rY_rPlane parallel, wherein, X_rIs the horizontal extension direction of the rail surface，Y_rOn the plane of the rail foot and in contact with X_rPerpendicular, Z_rPerpendicular to the plane of the rail bottom. X_w、Y_w、Z_wAre each independently of X_r、Y_r、Z_rAnd establishing a coordinate system under a normal condition, wherein each coordinate axis of the wheel set coordinate system and the following coordinate system is pairwise parallel, and only Zr and Zw have a difference value in the Z-axis direction.

3. The method according to claim 2, wherein the S2 includes:

step S21: extracting the inner side surfaces omega of the two-side wheel rims from the element detection result in S1 according to the constraint conditions that the inner side distance of the wheel pair and the inner side surfaces of the wheel rims are parallel to each other₁As the inner side of the rim and omega for the left wheel set₂The inner side surface of the wheel rim is used as a right wheel set;

step S22: calculating the omega of the plane according to the thickness of the standard wheel rim₁And Ω₂Plane omega separated from the thickness of the standard rim₁' and omega₂The plane parameters of' correspond to the front view of the wheel-track point cloud data;

step S23: according toAnd roughly dividing the rim part in the wheel track original point cloud, whereinFrom any point p to plane omega in the wheel track point cloud_iThe Euclidean distance of (a) is,from any point p to plane omega in the wheel track point cloud_iThe euclidean distance of' i ═ 1, 2.

4. The method according to claim 2, wherein the extracting of the rim portion and the rail bottom portion corresponding cells in S3 and obtaining corresponding cell parameters comprises:

step S31: the extraction of the rail bottom element is carried out according to the following three conditions: 1) the type of the model element to be extracted is a plane; 2) extracting normal vector and Z of plane_rThe directions are parallel; 3) extracting the minimum z coordinate value of the plane;

step S32: the elements of the rim portion are extracted according to the following three conditions: 1) the extracted primitive type is a circular ring primitive, comprisingEight parameters, wherein,the method comprises the steps that three parameters are included in the direction of a circular ring shaft, Center is the Center of the circular ring shaft and comprises the three parameters, radiuMax is the large radius of the circular ring and comprises one parameter, and radiuMin is the small radius of the circular ring and comprises one parameter; 2) a wheel rim radius; 3) normal vector of extracted circular ring element ToNormal to the inner side of the rimAre parallel and satisfyWhere θ is a set threshold.

5. The method according to claim 2, wherein the calculating wheel set center point and rail base center point according to the primitive parameters to obtain wheel axle direction comprises:

s41: calculating the center of the wheel pair according to the center point coordinate of the intersection point of the straight line passing through the center point of the circular ring where the wheel rim is located and the inner side faces of the two wheel rims along the direction of the wheel shaft;

s42: calculating the center of the rail bottom according to the center point coordinate of the center point of the plane bounding box of the rail plane;

s43: the normal vector of the plane element of the inner side surface of the wheel rim is the wheel axle direction.

6. The method according to claim 2, wherein the S5 includes:

s61: measuring the transverse displacement of the wheel set, wherein the center of the wheel set and the center point of the rail bottom are in Y_rSpacing in the direction;

s62: measuring the sinking and floating amount of the wheel set, wherein the center of the wheel set and the center point of the rail bottom are in Z_rSpacing and initial position Z in axial direction_rThe difference in the amount of shaft traverse;

s63: measuring the side rolling angle of the wheel set, and taking the axis of the wheel set as O in a following coordinate system_r-X_rY_rZ_rX in (1)_rO_rY_rThe included angle of the plane;

s64: measuring the pan angle of the wheel pair, as the perpendicular to the wheel axis relative to X_rThe angle of the axes.

7. The method of claim 2, wherein in step S5, the points belonging to the rail tread in the point cloud are located according to a priori structural information of the rail, the priori structural information being determined according to railroad industry standards.

8. The method according to claim 2, wherein the S6 includes:

s61: estimating the point cloud density rho by adopting a nuclear density estimation method, wherein a slice thickness delta calculation formula is shown as the following formula (1);

δ＝M·ρ (1)

wherein M is an empirical value of 4-8;

s62: the coordinate system of the point cloud slice is that the X axis is along the central line direction of the point cloud at the bottom, the Y axis is parallel to the central line direction of the point cloud at the upper part of the combined point cloud, the Z axis is vertical to the bottom surface of the point cloud, and the Y axis direction is selected as the point cloud slice direction;

s63: and projecting the point set in each point cloud slice to the central plane to realize the dimension reduction processing of local data.

9. The method according to claim 2, wherein the S7 includes:

s71: projecting points in each point cloud piece to a point cloud piece central plane to obtain a slice projection point set, then removing points on a bottom tread in the point cloud slice by using structure prior information, and only keeping point clouds of a wheel to perform parameter fitting of a circle;

s72: randomly selecting three non-collinear points in the slice projection point set as three points capable of forming a circle model, calculating the circle center and the radius of the circle model, calculating the absolute value of the difference between the distances from the other points except the three points of the circle model in the projection point set to the circle center of the circle model and the radius of the circle model, taking the points with the absolute values of the differences smaller than a set threshold value as local points of the current circle model, taking the circle model obtained when the number of the local points reaches a set proportion as a slice circle, and taking the circle center O and the radius R as the circle center and the radius of the slice circle.

10. The method according to claim 2, wherein the S8 includes: calculating the distance D from a point in the bottom rail tread in each slice to the center of the slice_iSetting a certain threshold value as R + T, T as elastic threshold value, R as radius of slice circle, if D_iSatisfies D_iAnd if the radius is less than or equal to R + T, the contact points are obtained by extraction, and the set of all the contact points is the contact spots, wherein the elastic threshold value T is 0.001-0.005 times of the radius R.

Technical Field

The invention relates to the technical field of three-dimensional vision measurement, in particular to a point cloud-based wheel-rail contact geometric parameter measurement method.

Background

The rapid development of high-speed trains enables the running speed and the density of the trains to be continuously improved, further the wheel-rail contact mechanism becomes more and more complex, the interaction between the wheel rails is stronger, particularly the wheel-rail rolling contact fatigue caused by abnormal contact postures between the wheel rails, so that the damages such as wheel-rail surface peeling, cracks and the like are caused, the service life of the track is shortened, the economy, the comfort and the running safety of the trains are seriously influenced, and the maintenance and replacement cost of the track is remarkably increased. The wheel-rail relationship is one of the leading subjects in the railway engineering research field, and the research on the wheel-rail contact relationship is the key. The attitude and position of the wheel set relative to the rail is a very important part of the wheel-rail contact geometry, and the wheel-rail contact geometry parameters reflect the three-dimensional space geometrical relationship formed between the wheel rails under different contact attitudes and different stresses. But at the wheel rail contact area is located at the wheel rail interface area. The traditional contact measurement method cannot directly measure the wheel rail contact geometric parameters.

Therefore, a method for measuring the geometrical parameters of wheel rail contact is needed.

Disclosure of Invention

The invention provides a wheel-rail contact geometric parameter measuring method, which aims to overcome the defects in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme.

The embodiment provides a wheel-rail contact geometric parameter measuring method, which comprises the following steps:

s1, detecting the planar element and the cylindrical element of the wheel track point cloud;

s2 extracting the elements where the inner side surface of the rim is located from the detection result of the step S1, and roughly dividing the point cloud of the rim part according to the information of the elements where the inner side surface of the rim is located;

s3, performing circular ring element detection on the point cloud of the roughly divided rim part, and extracting corresponding elements of the rim part and the rail bottom part to obtain corresponding element parameters;

s4, calculating the wheel set central point and the rail bottom central point according to the element parameters to obtain the wheel axle direction;

s5 measuring wheel set transverse displacement, wheel set side rolling angle, wheel set rolling angle and wheel set sinking and floating amount according to the calculation result of S4, and positioning points belonging to the rail tread in the point cloud;

s6, slicing the point clouds, and removing points belonging to the rail tread in each point cloud slice;

s7, performing slicing circle structure information fitting on the point cloud points with the tread points removed based on a RANSAC algorithm to obtain the circle center and the radius of the slicing circle;

s8, calculating the distance from the point on the rail tread to the center of the slice circle in each slice, wherein the set of points smaller than a certain threshold value is the contact patch;

s9, the length of the long axis and the length of the short axis of the contact patch are measured according to the coordinates of the center point of the contact patch.

Preferably, before S1, the point cloud data of the wheel-track needs to be processed, two different coordinate systems are established for the wheel set and the track, and when the wheel set is located at the normal operating position, O is established with the midpoint of the axle center of the wheel set as the origin_w-X_wY_wZ_wA wheelset coordinate system that moves with the wheelset relative to the track; establishing O by using the central point of the centers of the two side rail surfaces as the origin_r-X_rY_rZ_rA traveling coordinate system, a plane of the rail bottom and a traveling coordinate system O_r-X_rY_rZ_rX in (1)_rO_rY_rPlane parallel, wherein, X_rIn the direction of horizontal extension of the rail surface, Y_rOn the plane of the rail foot and in contact with X_rPerpendicular, Z_rPerpendicular to the plane of the rail bottom. X_w、Y_w、Z_wAre each independently of X_r、Y_r、Z_rAnd establishing a coordinate system under a normal condition, wherein each coordinate axis of the wheel set coordinate system and the following coordinate system is pairwise parallel, and only Zr and Zw have a difference value in the Z-axis direction.

Preferably, S2 includes:

step S21: extracting the inner side surfaces omega of the two-side wheel rims from the element detection result in S1 according to the constraint conditions that the inner side distance of the wheel pair and the inner side surfaces of the wheel rims are parallel to each other₁As the inner side of the rim and omega for the left wheel set₂The inner side surface of the wheel rim is used as a right wheel set;

step S22: calculating the omega of the plane according to the thickness of the standard wheel rim₁And Ω₂Plane omega separated from the thickness of the standard rim₁' and omega₂The plane parameters of' correspond to the front view of the wheel-track point cloud data;

step S23: according toAnd32 roughly dividing the rim part in the wheel track original point cloud, whereinFrom any point p to plane omega in the wheel track point cloud_iThe Euclidean distance of (a) is,from any point p to plane omega in the wheel track point cloud_iThe euclidean distance of' i ═ 1, 2.

Preferably, extracting the rim part and the rail bottom part corresponding cells in S3 and acquiring corresponding cell parameters includes:

step S31: the extraction of the rail bottom element is carried out according to the following three conditions: 1) the type of the model element to be extracted is a plane; 2) extracting normal vector and Z of plane_rThe directions are parallel; 3) extracting the minimum z coordinate value of the plane;

step S32: the elements of the rim portion are extracted according to the following three conditions: 1) the extracted primitive type is a circular ring primitive, comprisingEight parameters, wherein,the method comprises the steps that three parameters are included in the direction of a circular ring shaft, Center is the Center of the circular ring shaft and comprises the three parameters, radiuMax is the large radius of the circular ring and comprises one parameter, and radiuMin is the small radius of the circular ring and comprises one parameter; 2) a wheel rim radius; 3) normal vector of extracted circular ring element ToNormal to the inner side of the rimAre parallel and satisfyWhere θ is a set threshold.

Preferably, calculating a wheel set center point and a rail bottom center point according to the element parameters to obtain a wheel axle direction, and the method comprises the following steps:

s41: calculating the center of the wheel pair according to the center point coordinate of the intersection point of the straight line passing through the center point of the circular ring where the wheel rim is located and the inner side faces of the two wheel rims along the direction of the wheel shaft;

s42: calculating the center of the rail bottom according to the center point coordinate of the center point of the plane bounding box of the rail plane;

s43: the normal vector of the plane element of the inner side surface of the wheel rim is the wheel axle direction.

Preferably, S5 includes:

s61: measuring the transverse displacement of the wheel set, wherein the center of the wheel set and the center point of the rail bottom are in Y_rSpacing in the direction;

s62: measuring the sinking and floating amount of the wheel set, wherein the center of the wheel set and the center point of the rail bottom are in Z_rSpacing and initial position Z in axial direction_rThe difference in the amount of shaft traverse;

s63: measuring the side rolling angle of the wheel set, and taking the axis of the wheel set as O in a following coordinate system_r-X_rY_rZ_rX in (1)_rO_rY_rThe included angle of the plane;

s64: measuring wheel pairAngle of yaw, perpendicular to the wheel axis, relative to X_rThe angle of the axes.

Preferably, in S5, the points belonging to the rail tread in the point cloud are located according to the structural prior information of the rail, which is determined according to the railroad industry standard.

Preferably, S6 includes:

s61: estimating the point cloud density rho by adopting a nuclear density estimation method, wherein a slice thickness delta calculation formula is shown as the following formula (1);

δ＝M·ρ (1)

wherein M is an empirical value of 4-8;

s62: the coordinate system of the point cloud slice is that the X axis is along the central line direction of the point cloud at the bottom, the Y axis is parallel to the central line direction of the point cloud at the upper part of the combined point cloud, the Z axis is vertical to the bottom surface of the point cloud, and the Y axis direction is selected as the point cloud slice direction;

s63: and projecting the point set in each point cloud slice to the central plane to realize the dimension reduction processing of local data.

Preferably, S7 includes:

s71: projecting points in each point cloud piece to a point cloud piece central plane to obtain a slice projection point set, then removing points on a bottom tread in the point cloud slice by using structure prior information, and only keeping point clouds of a wheel to perform parameter fitting of a circle;

s72: randomly selecting three non-collinear points in the slice projection point set as three points capable of forming a circle model, calculating the circle center and the radius of the circle model, calculating the absolute value of the difference between the distances from the other points except the three points of the circle model in the projection point set to the circle center of the circle model and the radius of the circle model, taking the points with the absolute values of the differences smaller than a set threshold value as local points of the current circle model, taking the circle model obtained when the number of the local points reaches a set proportion as a slice circle, and taking the circle center O and the radius R as the circle center and the radius of the slice circle.

Preferably, S8 includes: calculating the distance D from a point in the bottom rail tread in each slice to the center of the slice_iSetting a certain threshold value as R + T, T as elastic threshold value, R as radius of slice circle, if D_iSatisfies D_i≤RAnd + T, the contact points are extracted, the set of all the contact points is the contact spot, and the elastic threshold value T is 0.001-0.005 times of the radius R.

The technical scheme provided by the wheel-rail contact geometric parameter measuring method is that based on the machine vision theory, the wheel-rail point cloud is generated by using a structured light non-contact three-dimensional reconstruction technology, and on the basis, the wheel-rail contact geometric parameters are measured, so that the transverse displacement, the sinking displacement, the pan angle and the side rolling angle of a wheel pair relative to a rail can be accurately measured, a wheel-rail contact spot area is extracted, and the long axis and short axis parameters of the wheel-rail contact spot are obtained through calculation, so that the rapid, accurate and reliable technical support is provided for the safe operation of a train, an experimental means is provided for the theoretical research of the wheel-rail contact relationship, and the method has important practical significance for the theoretical research of the safe operation and the wheel-rail contact relationship.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic flow chart of a wheel-rail contact geometric parameter measurement method provided in this embodiment;

FIG. 2 is a schematic structural diagram of two coordinate systems of the present embodiment;

FIG. 3 is a diagram illustrating the result of rough segmentation;

FIG. 4 is a schematic diagram of positions of variables of a wheel set lateral shift amount, a wheel set side roll angle, a wheel set rock angle, and a wheel set heave amount, which are designed by the wheel-rail contact geometric parameter measurement method of the embodiment;

FIG. 5 is a schematic diagram of removing tread points from a slice point cloud and fitting circle information;

FIG. 6 is a schematic diagram of computing contact points in a slice using structural information;

fig. 7 is a schematic view of a wheel-rail contact patch measurement scenario.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

For the convenience of understanding the embodiments of the present invention, the following description will be further explained by taking several specific embodiments as examples in conjunction with the drawings, and the embodiments are not to be construed as limiting the embodiments of the present invention.

Examples

Fig. 1 is a schematic flow chart of a wheel-rail contact geometric parameter measurement method provided in this embodiment, and referring to fig. 1, the method includes the following steps:

processing the point cloud data of the wheel track to establish two different coordinate systems for the wheel set and the track, wherein fig. 2 is a schematic structural diagram of the two coordinate systems of the embodiment, and referring to fig. 2, the point cloud data of the wheel set is used as an origin to establish an O_w-X_wY_wZ_wA wheelset coordinate system that moves with the wheelset relative to the track; establishing O by using the central point of the centers of the two side rail surfaces as the origin_r-X_rY_rZ_rA traveling coordinate system, a plane of the rail bottom and a traveling coordinate system O_r-X_rY_rZ_rX in (1)_rO_rY_rPlane parallel, wherein, X_rIn the direction of horizontal extension of the rail surface, Y_rOn the plane of the rail foot and in contact with X_rPerpendicular, Z_rPerpendicular to the plane of the rail bottom. X_w、Y_w、Z_wAre each independently of X_r、Y_r、Z_rParallel. The coordinate system is established under normal conditions, coordinate axes of the wheel set coordinate system and the following coordinate system are pairwise parallel, and only Zr and Zw have difference values in the Z-axis direction. At any position where the attitude of the wheelset changes, if the wheelset deviates from the normal position, the wheelset coordinate system is relative to Y_rAnd Z_rDeviation DeltaY_rAnd Δ Z_rRotated by ψ about the X axis and θ about the Z axis.

S1 performs plane element and cylinder element detection on the wheeltrack point cloud.

S2, extracting the element of the inner side of the rim from the detection result of the step S1, and roughly dividing the point cloud of the rim part according to the information of the element of the inner side of the rim.

Step S21: according to the constraint condition that the inner side distance of the wheel sets and the inner side surfaces of the wheel rims are parallel to each other, the inner side distance of the wheel sets in the embodiment is 1353 +/-2 mm,extracting the inner side surface omega of the double-side rim from the element detection result in S1₁As the inner side of the rim and omega for the left wheel set₂The inner side surface of the wheel rim is used as a right wheel set;

step S22: calculating the omega of the plane according to the thickness of the standard wheel rim₁And Ω₂Plane omega separated from the thickness of the standard rim₁' and omega₂' the plane parameters, in this embodiment, the standard rim thickness is 32 + -2 mm, corresponding to the front view of the point cloud data of the wheel track, specifically, omega₁' is on the left side of the plane and on the plane omega₁Planes spaced apart by 32mm, omega₂Is on the right side of the plane and omega on the plane₂Planes 32mm apart;

step S23: according toAnd32 roughly dividing the rim part in the wheel track original point cloud, whereinFrom any point p to plane omega in the wheel track point cloud_iThe Euclidean distance of (a) is,from any point p to plane omega in the wheel track point cloud_iThe euclidean distance of' i ═ 1, 2. Fig. 3 is a schematic diagram of the rough segmentation result.

S3, performing circular ring element detection on the point cloud of the roughly divided rim part, and extracting corresponding elements of the rim part and the rail bottom part to obtain corresponding element parameters.

The method specifically comprises the following steps:

step S31: the extraction of the rail bottom element is carried out according to the following three conditions: 1) the type of the model element to be extracted is a plane; 2) extracting normal vector and Z of plane_rThe directions are parallel; 3) extracting the minimum z coordinate value of the plane;

step S32: according to the following three conditionsExtracting the elements of the rim part: 1) the extracted primitive type is a circular ring primitive, comprisingEight parameters, wherein,the method comprises the steps that three parameters are included in the direction of a circular ring shaft, Center is the Center of the circular ring shaft and comprises the three parameters, radiuMax is the large radius of the circular ring and comprises one parameter, and radiuMin is the small radius of the circular ring and comprises one parameter; 2) the radius of the wheel rim is 458 +/-2 mm; 3) normal vector of extracted circular ring element ToNormal to the inner side of the rimAre parallel and satisfy Where θ is a set threshold, specifically, θ is 2.

S4, calculating the wheel set central point and the rail bottom central point according to the element parameters to obtain the wheel axle direction.

The method specifically comprises the following steps:

s41: calculating the center of the wheel pair according to the center point coordinate of the intersection point of the straight line passing through the center point of the circular ring where the wheel rim is located and the inner side faces of the two wheel rims along the direction of the wheel shaft;

s42: calculating the center of the rail bottom according to the center point coordinate of the center point of the plane bounding box of the rail plane;

s43: the normal vector of the plane element of the inner side surface of the wheel rim is the wheel axle direction.

S5, measuring wheel pair transverse displacement, wheel pair side rolling angle, wheel pair rolling angle and wheel pair sinking and floating amount according to the calculation result of S4, and positioning points belonging to the rail tread in the point cloud according to the structure prior information of the rail.

Fig. 4 is a schematic diagram of positions of variables of a wheel set transverse displacement amount, a wheel set side rolling angle, a wheel set rock angle and a wheel set sinking and floating amount, which are designed by the wheel-rail contact geometric parameter measurement method of the embodiment, and referring to fig. 4, the wheel set transverse displacement amount is Δ y; the sinking and floating amount of the wheel set is delta z; the side rolling angle of the wheel pair is psi; the wheelset yaw angle is θ.

S51: measuring the transverse displacement of the wheel set, wherein the center of the wheel set and the center point of the rail bottom are in Y_rSpacing in the direction;

s52: measuring the sinking and floating amount of the wheel set, wherein the center of the wheel set and the center point of the rail bottom are in Z_rSpacing and initial position Z in axial direction_rThe difference in the amount of shaft traverse;

s53: measuring the side rolling angle of the wheel set, and taking the axis of the wheel set as O in a following coordinate system_r-X_rY_rZ_rX in (1)_rO_rY_rThe included angle of the plane;

s54: measuring the pan angle of the wheel pair, as the perpendicular to the wheel axis relative to X_rThe angle of the axes.

And positioning points belonging to the rail tread in the point cloud according to the structure prior information of the rail, wherein the structure prior information is determined according to the rail industry standard, and specifically the TB/T2341.3-9360 kg/m steel rail type standard.

S6, slicing the point clouds, and removing points belonging to the rail treads in each point cloud slice.

S61: estimating the point cloud density rho by adopting a nuclear density estimation method, wherein a slice thickness delta calculation formula is shown as the following formula (1);

δ＝M·ρ (1)

wherein M is an empirical value of 4-8;

s62: the coordinate system of the point cloud slice is as follows: the X axis is along the central line direction of the bottom point cloud, the Y axis is parallel to the central line direction of the upper point cloud of the combined point cloud, and the Z axis is perpendicular to the bottom surface of the point cloud. Selecting a Y-axis direction from the point cloud slicing direction;

s63: and projecting the point set in each point cloud slice to the central plane to realize the dimension reduction processing of local data.

S7, performing slicing circle structure information fitting on the point cloud points with the tread points removed based on the RANSAC algorithm to obtain the circle center and the radius of the slicing circle.

S71: and projecting the points in the cloud slices to the central plane of the cloud slices to obtain a slice projection point set, removing the points on the bottom tread in the cloud slices by using the structure prior information, and only keeping the point cloud of the wheel to perform the parameter fitting of the circle.

S72: randomly selecting three non-collinear points from the projection point set of the slice as three points capable of forming a circular model, calculating the center and radius of the circular model, and calculating the distances D from the other points except the three points of the circular model in the projection point set to the center of the circular model_iAbsolute value of difference abs (D) from radius R of circular model_i-R), when the absolute value of the difference is smaller than a set threshold value and the number of the points meeting the set threshold value reaches a set proportion point, the obtained circular model is taken as a slicing circle, and the circle center O and the radius R are the circle center and the radius of the slicing circle.

To ensure that the fitting results in a suitable model, the difference threshold T is set to ensure that most points are on the fitted circle₁When abs (D)_i-R)<T₁Considering the current point as the local point, obtaining the total number of the local points under the current model parameter after completely traversing, if the proportion of the total number of the local points is not less than the threshold value T₂Then, a better model is found, and the center O and the radius R are recorded, and fig. 5 is a schematic diagram of removing tread points from the slice point cloud and fitting circle information. The difference threshold value T₁Generally, the radius of the circular model R can be set to be about one thousandth of the radius R of the circular model, and in order to obtain a more accurate model proportion threshold value T₂Not less than 85%.

S8, calculating the distance between the point on the rail tread surface in each slice and the center of the circle of the slice, wherein the set of the points smaller than a certain threshold value is the contact patch.

Calculating the distance D from the point in the bottom rail surface determined by the structure prior information to the center of the slice in each slice_iSetting a certain threshold value as R + T, T as elastic threshold value, R as radius of slice circle, if D_iSatisfies D_iR + T or less, the contact point obtained by extraction, FIG. 6 is utilized in slicingAnd (3) calculating a contact point schematic diagram by the structural information, wherein the set of all contact points is a contact spot, and the elasticity threshold T is 0.001-0.005 times of the radius R.

S9, the length of the long axis and the length of the short axis of the contact patch are measured according to the coordinates of the center point of the contact patch.

The maximum value of the component (i.e., abscissa) of the coordinates of all the points in the contact patch in the X-axis direction is X_maxMinimum value of X_minAnd then the long axis length XLEN of the contact spot is calculated as XLEN ═ X_max-X_min. Similarly, the minor axis length YLen can be obtained by the component (i.e. ordinate) of the coordinates of all points in the contact patch in the Y-axis direction, and the calculation formula is that YLen is Y_max-Y_min. Fig. 7 is a schematic view of a wheel track contact patch measurement scene, and length of a long axis and a short axis in the X, Y direction of a contact patch is measured according to coordinates of a midpoint of the contact patch to obtain XLen and YLen, which are lengths of the long axis and the short axis of the contact patch.

From the above description of the embodiments, it is clear to those skilled in the art that the present invention can be implemented by software plus necessary general hardware platform. Based on such understanding, the technical solutions of the present invention may be embodied in the form of a software product, which may be stored in a storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the method according to the embodiments or some parts of the embodiments.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.