CN101532827A - Deviation correction method for measurement of rail wear based on laser vision - Google Patents

Abstract

The invention discloses a deviation correction method for laser vision rail wear measurement, comprising: dividing the rail waist contour of the characteristic contour of the rail section measured by a laser vision sensor into a rail waist large circle and a rail waist small circle; The tangent point of the small waist circle is used to fit the longitudinal axis of the rail; the characteristic contour is projected onto the auxiliary plane perpendicular to the longitudinal axis of the rail to obtain the projected contour of the rail section; by aligning the standard contour of the rail section with the projected contour, the calculation The wear value of the rail section; based on the method of the present invention, the rail wear measurement error caused by the non-perpendicularity between the light plane projected by the laser vision sensor and the longitudinal axis of the rail can be eliminated.

Description

A deviation correction method for laser vision rail wear measurement

technical field

The invention relates to laser vision measurement technology, in particular to a deviation correction method for laser vision rail wear measurement.

Background technique

Regular inspection of rails is very important for reasonable planning and low-cost maintenance of railway transportation: on the one hand, in the early stages of rail wear and deformation, rail inspection helps to formulate a reasonable railway maintenance schedule to avoid dangerous situations; On the other hand, effective track inspection will lay the foundation for the transformation of track from periodic maintenance to condition-based maintenance, so that limited manpower and equipment resources can be better utilized, and track maintenance costs can be effectively saved.

At present, many research institutions and scholars at home and abroad have studied the detection methods of rail wear, and successfully developed various measuring devices. According to different detection methods, measuring devices can be divided into contact and non-contact. Among them, the contact measurement device has high measurement accuracy, but the operation is complicated and the measurement efficiency is low. It is only suitable for static measurement. It is mainly used in the laboratory to study the wear resistance of rails and is not suitable for online measurement. The non-contact measurement device is suitable for dynamic measurement. .

Regarding the non-contact measuring device, in the Chinese patent application whose application number is 200510123725.0, and the invention name is "Laser Vision Dynamic Measurement Device and Measurement Method for Rail Wear", a single-line laser vision sensor is only arranged on the inner side of the rail, which is convenient The device can complete the measurement of rail vertical wear and side wear. The device and measurement method improve the efficiency of rail wear measurement, reduce the cost of measurement equipment, and improve the operability and convenience of engineering applications. However, the laser vision sensor in this device only projects one light plane, so each image only contains the characteristic outline of a rail section, resulting in a waste of image information.

In addition, in the Chinese patent application with the application number 200710176429.6 and the title of the invention "a vehicle-mounted dynamic measurement device and method for comprehensive parameters of rail wear", a laser vision sensor based on a grating structure is disclosed to measure the vertical wear, horizontal wear and Apparatus and method for wave abrasion. The device and method described in this patent application can increase the acquisition density without improving the performance of image acquisition hardware, so as to meet the requirements of online dynamic measurement of wave wear.

The above two devices and measurement methods require that the light plane projected by the laser vision sensor be perpendicular to the longitudinal axis of the rail during the rail wear measurement process. However, during the installation process of the laser vision sensor, it is difficult to ensure that the light plane projected by it is perpendicular to the longitudinal axis of the rail. In addition, the laser vision sensor is installed at the bottom of the train. When the train is running, the light plane projected by the laser vision sensor is not perpendicular to the longitudinal axis of the rail due to the vibration of the train, thereby reducing the accuracy of rail wear measurement.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a method for correcting the wear of a laser vision rail, which can eliminate the measurement error of the rail wear caused by the non-perpendicularity between the light plane projected by the laser vision sensor and the longitudinal axis of the rail. Accuracy of rail wear measurement.

In order to achieve the above object, technical solution of the present invention is achieved in that way:

The invention provides a deviation correction method for laser vision rail wear measurement, the method comprising:

a. The rail waist profile of the characteristic profile of the rail section measured by the laser vision sensor is divided into a rail waist large circle and a rail waist small circle;

b. Fitting the longitudinal axis of the rail according to the tangent point of the large rail waist circle and the small rail waist circle;

c. Projecting the feature profile to an auxiliary plane perpendicular to the longitudinal axis of the rail to obtain a projected profile of the rail section;

d. Calculate the wear value of the rail section by aligning the standard profile of the rail section with the projected profile.

Wherein, the laser vision sensor in step a measures the characteristic contour of the rail section: the laser vision sensor projects a light plane inside the rail, and the light plane intersects with the rail to form the characteristic contour of the rail section.

The laser vision sensor includes two or more than two light plane projectors; the multiple light planes projected by the laser vision sensor are parallel to each other.

After the step a, the method also includes: based on the coordinates of the feature profile in the two-dimensional measurement coordinate system of the laser vision sensor mathematical model, using a radius-constrained nonlinear optimization method to respectively fit the rail waist great circle and rail waist The equation of the small circle; and calculate the tangent point coordinates of the large circle of the rail waist and the small circle of the rail waist based on the equations of the large circle of the rail waist and the small circle of the rail waist.

In step b, fitting the longitudinal axis of the rail according to the tangent point of the large rail waist circle and the small rail waist circle is: according to the coordinate fitting line of the tangent point in the camera coordinate system of the mathematical model of the laser vision sensor, the The straight line is used as the longitudinal axis of the rail.

In step d, aligning the standard profile of the rail section with the projected profile is: taking the rail waist profile of the projected profile as a reference, and aligning the standard profile with the projected profile on the auxiliary plane.

The wear values include: vertical wear values and horizontal wear values.

The wear value of the calculated rail section described in step d is:

The vertical wear value is the distance from the vertical wear measurement point of the standard profile to the projected profile in the vertical direction;

The horizontal wear value is the distance from the horizontal wear measurement point of the standard profile to the projected profile in the horizontal direction.

The deviation correction method for laser vision rail wear measurement of the present invention uses a multi-line laser vision sensor to collect images containing multiple cross-sectional feature profiles of the rail, thus improving the utilization rate of image information.

In addition, the present invention calculates the longitudinal axis of the rail based on the characteristic profile of the rail section measured by the laser vision sensor based on the mathematical model of the laser vision sensor; based on the auxiliary plane perpendicular to the longitudinal axis of the rail, the measured The feature contour is projected on the auxiliary plane to obtain the projected contour. The present invention aligns the standard contour with the projected contour benchmark to calculate the wear value in the rail section, which can eliminate the rail wear measurement caused by the non-perpendicularity between the light plane projected by the laser vision sensor and the longitudinal axis of the rail The error improves the accuracy of rail wear measurement.

Description of drawings

Fig. 1 is the schematic flow chart of the deviation correction method of the laser vision rail wear measurement of the present invention;

Fig. 2 is the characteristic contour image of the rail section captured by the laser vision sensor;

Fig. 3 is the data model of laser vision sensor;

Fig. 4 is a schematic diagram of determining the point of tangency between the large circle of the rail waist and the small circle of the rail waist in the two-dimensional measurement coordinate system;

Fig. 5 is a schematic diagram of the structural relationship between the longitudinal axis of the rail and the characteristic profile of the rail section and the auxiliary plane in the present invention;

Fig. 6 is a schematic diagram of the alignment of the projected contour and the standard contour of the rail section.

Detailed ways

The technical solutions of the present invention will be further elaborated below in conjunction with the accompanying drawings and specific embodiments.

A deviation correction method for laser vision rail wear measurement provided by the present invention, as shown in Figure 1, mainly includes the following steps:

In step 101, the multi-line laser vision sensor is used to collect images containing feature contours of multiple cross-sections of the rail, and the three-dimensional data of the feature contours in the camera coordinate system is obtained based on the mathematical model of the laser vision sensor.

In the present invention, a multi-line laser vision sensor is used to measure multiple sections of the inner rail waist and rail head of the rail. The multi-line laser vision sensor contains two or more than two light plane projectors, which can project a plurality of parallel light plane. Preferably, a laser vision sensor capable of projecting three light planes may be used, wherein the three projected light planes are parallel to each other. The laser projector in the laser vision sensor projects a light plane aimed at the inner side of the rail. The light plane intersects with the rail to form a rail section, and the rail section coincides with the light plane. After being imaged by the rail section imaging system, an image of the characteristic outline of the rail section is obtained. Among them, the rail section imaging system is mainly composed of cameras, lenses and image acquisition systems.

It should be pointed out that, in principle, the laser projector in the laser vision sensor needs to be aligned with the inner side of the rail to project the light plane perpendicular to the longitudinal axis of the rail, but in practical applications, it is difficult to ensure that its The projected light plane is absolutely perpendicular to the longitudinal axis of the rail; in addition, the laser vision sensor is installed at the bottom of the train. When the train is running, the light plane projected by the laser vision sensor is not perpendicular to the longitudinal axis of the rail due to the vibration of the train. . In view of the above factors, the present invention can measure the wear of the rail based on the condition that the optical plane is not perpendicular to the longitudinal axis of the rail, and can eliminate the non-perpendicular band between the optical plane projected by the laser vision sensor and the longitudinal axis of the rail in the prior art. The measurement error of rail wear. The present invention can accurately measure rail wear through subsequent processing.

A laser vision sensor capable of projecting three mutually parallel light planes is used to project light planes on the inner side of the rail to form three rail sections, namely rail section 1, rail section 2 and rail section 3. After being imaged by the rail section imaging system, images containing the characteristic contours of three rail sections are obtained, as shown in Figure 2, where characteristic contour 1 corresponds to rail section 1, characteristic contour 2 corresponds to rail section 2, and characteristic contour 3 corresponds to rail section 3. Each feature profile includes two parts: rail head profile and rail waist profile.

The image of the feature contour is collected into the computer memory by a high-speed image acquisition card, and the image is analyzed to obtain the coordinates of the feature contour in the image coordinate system, that is, the image coordinates. Then, through the mathematical model of the laser vision sensor, the image coordinates are transformed into the camera coordinate system to obtain the three-dimensional coordinates of the feature contour in the camera coordinate system.

Among them, the mathematical model of the laser vision sensor is shown in Figure 3: the camera coordinate system is o _c -x _c y _c z _c ; the image coordinate system of the image coordinate plane 31 is o _u -x _u y _u ; the light plane 30, namely Aim the light plane projected by the laser projector at the inner side of the rail, take any point o _m of the light plane 30 as the origin, establish a three-dimensional reference coordinate system o _m -x _m y _m z _m , set z _m = 0, and then obtain the light plane The two-dimensional measurement coordinate system of is o _m -x _m y _m .

Based on the above-mentioned mathematical model of the laser vision sensor, the image coordinates of the feature contour are converted between the image coordinate system and the camera coordinate system to obtain the three-dimensional coordinates of the feature contour in the camera coordinates. Among them, the conversion between various coordinate systems in the mathematical model of the laser vision sensor can refer to the Chinese patent application with the application number 03142658.1 and the title of the invention "a calibration method for structured light vision sensors based on planar targets". Table 1, Table 2, and Table 3 respectively give the three-dimensional coordinate data of the rail waist contours of the three characteristic contours in Fig. 2 in the camera coordinate system o _c -x _{cy c} z _c , and the unit is millimeter (mm).

Table 1 shows part of the three-dimensional data of the feature contour 1 rail waist contour in the camera coordinate system:

Table 1

Table 2 shows part of the three-dimensional data of the feature contour 2 rail waist contour in the camera coordinate system:

Table 2

Table 3 shows part of the three-dimensional data of the feature contour 3-track waist contour in the camera coordinate system:

table 3

Step 102, fitting the large rail waist circle and the small rail waist circle of the characteristic contour in the two-dimensional measurement coordinate system of the light plane; and fitting the three-dimensional data in the camera coordinate system according to the tangent point of the large rail waist circle and the small rail waist circle A straight line, as the longitudinal axis of the rail.

Establish the measurement coordinate system o _n -x _n y _n of the rail section, as shown in Figure 4, take the symmetry axis of the rail as the yn axis, and take the rail bottom as the x _n axis, and the profile of section AB represents the profile of the large circle on the rail waist, Section BC represents the outline of the small circle on the rail waist. Point B is the point of tangency between the large circle and the small circle.

Since the rail section coincides with the optical plane 30 in Fig. 3, the above measurement coordinate system o _n -x _n y _n coincides with the two-dimensional measurement coordinate system o _m -x _m y _m of the optical plane in Fig. 3 .

Based on the mathematical model of the laser vision sensor, through the conversion of the camera coordinate system and the two-dimensional measurement coordinate system, the three-dimensional camera coordinates of the rail waist shown in Table 1, Table 2, and Table 3 can be mapped to the two-dimensional measurement coordinate system to obtain the characteristics The two-dimensional measurement coordinates of the profile on the light plane. Then, in the two-dimensional measurement coordinate system, the rail waist profile of the characteristic contour is divided into a large rail waist circle and a small rail waist circle, and the equations of the large rail waist circle and the small rail waist circle are respectively fitted by a radius-constrained nonlinear optimization method. Among them, the radius-constrained nonlinear optimization method and fitting algorithm are prior art, and will not be repeated here.

The equations of the large rail waist circle and the rail waist small circle of feature profile 1 in the two-dimensional measurement coordinate system are:

Rail waist great circle: (x-266.129) ² +(y+195.365) ² ＝122500

Rail waist small circle: (x+40.363) ² +(y+62.060) ² ＝225

The equations of the large rail waist circle and the rail waist small circle of the feature profile 2 in the two-dimensional measurement coordinate system are:

Rail waist great circle: (x-255.818) ² +(y+170.034) ² ＝122500

Rail waist small circle: (x+49.864) ² +(y+35.912) ² ＝225

The equations of the large rail waist circle and the rail waist small circle of the characteristic contour 3 in the two-dimensional measurement coordinate system are:

Rail waist great circle: (x-244.819) ² +(y+147.468) ² ＝122500

Rail waist small circle: (x+59.009) ² +(y+8.736) ² ＝225

According to the above equations of the large rail waist circle and the small rail waist circle, the point of tangency between the large rail waist circle and the small rail waist circle can be calculated. The coordinates of the tangent points of the large rail waist circle and the small rail waist circle of feature contour 1, feature contour 2 and feature contour 3 in the two-dimensional measurement coordinate system are: Q1 _m (-54.118, -56.078), Q2 _m (-63.600, -29.885), Q3 _m (-72.654, -2.506).

Based on the conversion between the two-dimensional measurement coordinate system and the image coordinate system, the coordinates of the three tangent points in the image coordinates are: Q1 _u (359.410,381.806), Q2 _u (459.433,381.008), Q3 _u (545.057,376.976 ).

Based on the conversion between the image coordinate system and the camera coordinate system, the coordinates of the three tangent points in the camera coordinate system are: Q1 _c (-2.569, 27.387, 410.542), Q2 _c (24.995, 27.709, 418.689), Q3 _c (49.848, 27.256, 429.129).

Then, according to the coordinates of the three tangent points in the camera coordinate system, a straight line is obtained through a fitting algorithm, which is the longitudinal axis of the rail. Wherein, the algorithm of fitting a straight line through three points in space is a prior art, and will not be repeated here.

The axis equation of the longitudinal axis of the rail is expressed as: $\frac{x+2.569}{1}=\frac{\mathrm{the\; y}-27.387}{-0.003}=\frac{z-410.452}{0.357};$ Expressed parametrically as: $\left\{\begin{array}{c}x=t-2.569\\ \mathrm{the\; y}=-0.003\·t+27.387\\ z=0.357\·t+410.542\end{array}\right.,$ Where t∈R, t is a parameter, and R is the radius of the large rail waist circle or the rail waist small circle.

In step 103, a plane perpendicular to the longitudinal axis of the rail is drawn through any point on the longitudinal axis of the rail to obtain an auxiliary plane.

Preferably, the tangent point Q1 of the large circle of the rail waist and the small circle of the rail waist corresponding to the characteristic contour 1 on the longitudinal axis of the rail can be taken, as shown in Figure 5, and a plane perpendicular to the longitudinal axis of the rail is drawn through Q1 to obtain auxiliary Plane F. Based on the point-to-point equation or parametric equation of the longitudinal axis of the rail, the equation of the auxiliary plane F perpendicular to the longitudinal axis of the rail at the tangent point Q1 _c (-2.569, 27.387, 410.542) is obtained: x-0.003y+0.357z -143.789=0.

Step 104, taking the direction of the longitudinal axis of the rail as the projection direction, projecting the characteristic contour onto the auxiliary plane to obtain the projected contour of the rail section.

The projection of the feature contour on the auxiliary plane is used as the projected contour of the rail section.

According to the three-dimensional data of the feature contour in the camera coordinate system, the three-dimensional data of the projected contour in the camera coordinate system are obtained through calculation. Among them, the relationship between a point on the feature contour and its corresponding point on the projected contour, i.e. the projected point, is: draw a straight line perpendicular to the auxiliary plane through a certain point on the characteristic contour, and the intersection of the straight line and the auxiliary plane is the point Projection point on construction plane. Then, according to the three-dimensional coordinates of the point in the camera coordinate system, the coordinates of the projected point of the point in the camera coordinate system can be obtained. Similarly, other points on the feature contour use this method to obtain the projection points on the auxiliary plane. The combination of the various projection points is the projection contour.

Table 4, Table 5 and Table 6 show the three-dimensional data of the projected contour corresponding to the rail waist contour of each rail section in Fig. 2 in the camera coordinate system. Feature profile 1 corresponds to projected profile 1, feature profile 2 corresponds to projected profile 2, and feature profile 3 corresponds to projected profile 3.

Table 4 shows the three-dimensional data of the rail waist profile of projected profile 1 in the camera coordinate system:

Table 4

Table 5 shows the three-dimensional data of the rail waist profile of projected profile 2 in the camera coordinate system:

table 5

Table 6 shows the three-dimensional data of the rail waist profile of projected profile 3 in the camera coordinate system:

Table 6

Step 105: Aligning the projected profile of the rail section with the standard profile based on the waist profile of the projected profile of the rail section, thereby calculating the wear value of the rail section.

The so-called standard profile refers to the standard geometric profile of the cross-section of the rail under the condition that the rail has no wear and the specifications are regular. Since the wear of the rail in use mainly occurs at the rail head part, and the rail waist part is basically not worn, therefore, the present invention aligns the projected profile of the rail section with the rail waist profile of the standard profile on the auxiliary plane, and then calculates the Individual wear values for the head profile, including horizontal wear values and vertical wear values.

Figure 6 is a schematic diagram of the alignment of the projected profile and the standard profile of the rail section. Point G is the horizontal wear measurement point, and H point is the vertical wear measurement point. According to the "Railway Line Maintenance Rules", point G is located at a distance of 16mm from the top surface of the rail on the standard section, and point H is located at 1/3 of the width of the top surface of the rail. By aligning the projected profile of the rail section with the standard profile and taking the rail waist profile as the benchmark, the vertical wear value W _v and the horizontal wear value W _h of the rail section can be obtained.

Specifically, as shown in Figure 6, the vertical wear value W _v is the distance from the vertical wear measurement point H of the standard profile of the rail section to the projected profile in the vertical direction; the horizontal wear value W _h is the horizontal wear measurement point of the standard profile of the rail section G is the distance from the projected contour in the horizontal direction.

Based on the conversion between the camera coordinate system and the two-dimensional measurement coordinate system of the light plane, the two-dimensional measurement coordinate data of the projection profile on the light plane is obtained; since the angle between the light plane and the auxiliary plane is known, it can be calculated by cosine Obtain the coordinate data of the projected contour on the auxiliary plane. Then, after aligning the projected contour and the standard contour with the rail waist contour as the reference, the coordinates of the vertical wear measurement point and the horizontal wear measurement point on the standard contour can be obtained, thereby obtaining the wear values of the three rail sections:

Rail section 1: vertical wear value: 3.862mm, horizontal wear value: -1.550mm;

Rail section 2: vertical wear value: 3.894mm, horizontal wear value: -1.696mm;

Rail section 3: vertical wear value: 3.840mm, horizontal wear value: -1.716mm.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention.

Claims (8)

1. A deviation correction method for laser vision rail wear measurement, characterized in that the method comprises: a. The rail waist profile of the characteristic profile of the rail section measured by the laser vision sensor is divided into a rail waist large circle and a rail waist small circle; b. Fitting the longitudinal axis of the rail according to the tangent point of the large rail waist circle and the small rail waist circle; c. Projecting the feature profile to an auxiliary plane perpendicular to the longitudinal axis of the rail to obtain a projected profile of the rail section; d. Calculate the wear value of the rail section by aligning the standard profile of the rail section with the projected profile. 2. The deviation correction method for laser vision rail wear measurement according to claim 1, characterized in that the characteristic profile of the rail section measured by the laser vision sensor in step a is: the laser vision sensor projects a light plane on the inner side of the rail, and the light plane Intersects with the rail to form the characteristic profile of the rail section. 3. The deviation correction method for laser vision rail wear measurement according to claim 2, characterized in that, the laser vision sensor includes two or more light plane projectors; the plurality of light beams projected by the laser vision sensor The planes are parallel to each other. 4. The deviation correction method for laser vision rail wear measurement according to claim 1, characterized in that, after the step a, the method further comprises: based on the characteristic profile in the two-dimensional measurement coordinate system of the mathematical model of the laser vision sensor The coordinates of the radius constraint nonlinear optimization method are used to fit the equations of the large rail waist circle and the rail waist small circle respectively; and the rail waist large circle and the rail waist are calculated based on the equations of the rail waist large circle and the rail waist small circle The coordinates of the tangent point of the small circle. 5. The deviation correction method for laser vision rail wear measurement according to claim 1 or 4, characterized in that in step b, fitting the longitudinal axis of the rail according to the tangent point of the large circle of the rail waist and the small circle of the rail waist is: according to the A straight line is fitted to the coordinates of the tangent point in the camera coordinate system of the mathematical model of the laser vision sensor, and the straight line is used as the longitudinal axis of the rail. 6. The deviation correction method for laser vision rail wear measurement according to claim 1, characterized in that, in step d, aligning the standard contour of the rail section with the projected contour is: taking the rail waist contour of the projected contour as a reference , align the standard contour and projected contour on the auxiliary plane. 7. The deviation correction method for laser vision rail wear measurement according to claim 1, wherein the wear value includes: a vertical wear value and a horizontal wear value. 8. The deviation correction method for laser vision rail wear measurement according to claim 1 or 7, characterized in that, the wear value of the calculated rail section in step d is: The vertical wear value is the distance from the vertical wear measurement point of the standard profile to the projected profile in the vertical direction; The horizontal wear value is the distance from the horizontal wear measurement point of the standard profile to the projected profile in the horizontal direction.

Images