阅读说明：本技术 一种基于轮轨耦合剪切力检测的计轴方法及计轴系统 (Axle counting method and axle counting system based on wheel-rail coupling shearing force detection ) 是由 张璐 王智新 林锦锋 吴春晓 王晟 王岁儿 张天赋 晋云功 闫秋吉 孙国营 潘建 于 2021-09-18 设计创作，主要内容包括：本发明涉及一种基于轮轨耦合剪切力检测的计轴方法及计轴系统,计轴方法包括以下步骤：测量并实时获取钢轨测点处的形变数据；根据所述形变数据得到测点处的轮轨耦合剪切力曲线；根据所述轮轨耦合剪切力曲线得到应变差值曲线；根据所述应变差值曲线进行计轴；计轴系统包括：多个光纤光栅敏感元件、弹性基片和计算单元,其中,所述弹性基片,用于固定所述光纤光栅敏感元件；所述光纤光栅敏感元件,用于测量并获取钢轨测点处的形变数据；所述计算单元,用于从所述光纤光栅敏感元件接收所述形变数据,并根据所述形变数据得到轮轨耦合剪切力曲线,根据所述轮轨耦合剪切力曲线得到应变差值曲线,最后根据所述应变差值曲线进行计轴。(The invention relates to an axle counting method and an axle counting system based on wheel-rail coupling shearing force detection, wherein the axle counting method comprises the following steps: measuring and acquiring deformation data at a steel rail measuring point in real time; obtaining a wheel-rail coupling shearing force curve at a measuring point according to the deformation data; obtaining a strain difference curve according to the wheel-rail coupling shearing force curve; calculating an axis according to the strain difference curve; the axle counting system comprises: the fiber bragg grating sensor comprises a plurality of fiber bragg grating sensitive elements, an elastic substrate and a calculating unit, wherein the elastic substrate is used for fixing the fiber bragg grating sensitive elements; the fiber bragg grating sensitive element is used for measuring and acquiring deformation data of a steel rail measuring point; and the calculation unit is used for receiving the deformation data from the fiber bragg grating sensitive element, obtaining a wheel-rail coupling shearing force curve according to the deformation data, obtaining a strain difference value curve according to the wheel-rail coupling shearing force curve, and finally carrying out axis counting according to the strain difference value curve.)

1. An axle counting method based on wheel-rail coupling shear force detection is characterized by comprising the following steps:

measuring and acquiring deformation data at a steel rail measuring point in real time;

obtaining a wheel-rail coupling shearing force curve at a measuring point according to the deformation data;

obtaining a strain difference curve according to the wheel-rail coupling shearing force curve;

and counting the axis according to the strain difference curve.

2. The axle counting method based on wheel-rail coupling shear force detection according to claim 1, wherein after the wheel-rail coupling shear force curve is obtained, the wheel-rail coupling shear force curve is low-pass filtered through a low-pass filter to obtain a smooth wheel-rail coupling shear force curve.

3. The axle counting method based on wheel-rail coupling shear force detection according to claim 1, wherein the obtaining of the wheel-rail coupling shear force curve at the measurement point according to the deformation data specifically comprises,

obtaining a wheel load Q according to the deformation data, wherein the wheel load Q is in direct proportion to the deformation amount of the deformation data;

obtaining the shearing force Fs at the measuring point according to the wheel load Q;

and obtaining a wheel-rail coupling shearing force curve according to the shearing force Fs.

4. The axle counting method based on wheel-rail coupling shear force detection according to claim 3, wherein the obtaining of the shear force Fs at the measuring point according to the wheel load Q specifically comprises,

taking a point A and a point B on the steel rail, and when a wheel runs from the point A to the point B and does not pass through a measuring point, obtaining the relation between the shearing force Fs and the wheel load Q at the measuring point as follows:

when the wheel runs through the measuring point, the relation between the shearing force Fs of the cross section of the measuring point and the wheel load Q is obtained as follows:

wherein X is the distance between the wheel and the point A, and L is the distance between the point A and the point B.

5. The axle counting method based on wheel-rail coupling shear force detection is characterized in that when a wheel runs from the point B to the point A and the wheel does not pass through the measuring point, the relationship between the shear force Fs and the wheel load Q at the measuring point is as follows:

when the wheel runs through the measuring point, the relation between the shearing force Fs of the cross section of the measuring point and the wheel load Q is as follows:

and L is the distance between the point A and the point B.

6. The axle counting method based on wheel-rail coupling shear force detection according to claim 1, wherein the wheel-rail coupling shear force curves comprise a first wheel-rail coupling shear force curve, a second wheel-rail coupling shear force curve and a third wheel-rail coupling shear force curve; the strain difference curve comprises a first strain difference curve and a second strain difference curve; the first strain difference curve is obtained by difference of the first wheel-rail coupling shearing force curve and the second wheel-rail coupling shearing force curve, and the second strain difference curve is obtained by difference of the second wheel-rail coupling shearing force curve and the third wheel-rail coupling shearing force curve.

7. The axle counting method based on the wheel-rail coupling shear force detection according to claim 6, wherein the axle counting according to the strain difference curve specifically comprises,

dividing the first strain difference curve and the second strain difference curve into a state 0 or a state 1, wherein the state 0 indicates that the wheel is outside the measuring area, and the state 1 indicates that the wheel is inside the measuring area;

recording the state time sequence change of the state of the strain difference curve along with the time change;

and completing the axle counting according to the state time sequence change.

8. The axle counting method based on wheel-rail coupling shear force detection according to claim 7, wherein after obtaining the strain difference curve, the state of the strain difference curve is judged by threshold values th1 and th2, wherein th1> th 2;

the threshold th1 represents the entrance of the wheel bottom into the measurement area;

the threshold th2 indicates that the wheel bottom is out of the measurement area.

9. An axle counting system based on wheel-rail coupling shear force detection, characterized in that the axle counting system comprises: a plurality of fiber grating sensing elements, an elastic substrate and a computing unit, wherein:

the elastic substrate is used for fixing the fiber grating sensitive element;

the fiber bragg grating sensitive element is used for measuring and acquiring deformation data of a steel rail measuring point;

and the calculation unit is used for receiving the deformation data from the fiber bragg grating sensitive element, obtaining a wheel-rail coupling shearing force curve according to the deformation data, obtaining a strain difference value curve according to the wheel-rail coupling shearing force curve, and finally carrying out axis counting according to the strain difference value curve.

10. The axle counting system based on wheel-rail coupling shear force detection according to claim 9, further comprising a low pass filter, wherein the low pass filter is configured to perform low pass filtering on the wheel-rail coupling shear force curve after obtaining the wheel-rail coupling shear force curve, so as to obtain a smooth wheel-rail coupling shear force curve.

11. The axle counting system based on wheel-rail coupling shear force detection according to claim 9, wherein the calculating unit obtaining a wheel-rail coupling shear force curve at the measurement point according to the deformation data specifically comprises:

obtaining a wheel load Q according to the deformation data, wherein the wheel load Q is in direct proportion to the deformation amount of the deformation data;

obtaining the shearing force Fs at the measuring point according to the wheel load Q;

and obtaining a wheel-rail coupling shearing force curve according to the shearing force Fs.

12. The axle counting system based on wheel-rail coupling shear force detection according to claim 11, wherein the calculating unit obtains the shear force Fs at the measuring point according to the wheel load Q, and specifically comprises,

taking a point A and a point B on the steel rail, and when a wheel runs from the point A to the point B and does not pass through a measuring point, obtaining the relation between the shearing force Fs and the wheel load Q at the measuring point as follows:

when the wheel runs through the measuring point, the relation between the shearing force Fs of the cross section of the measuring point and the wheel load Q is obtained as follows:

wherein X is the distance between the wheel and the point A, and L is the distance between the point A and the point B;

and obtaining the shearing force Fs through the wheel load Q, the distance L and the distance X.

13. The axle counting system based on wheel-rail coupling shear force detection according to claim 9, further comprising a bottom plate, a transmission optical cable and a boss arranged on the bottom plate; the fiber grating sensing element and the elastic substrate are both arranged on the bottom plate, and the fiber grating sensing element and the elastic substrate are bonded to form a strain gauge; one end of the transmission optical cable is connected with the fiber bragg grating sensitive element; the bosses are arranged at two ends of the fiber bragg grating sensitive element;

the lug boss is used for being connected with a steel rail; the bottom of the fiber bragg grating sensitive element is fixedly connected in the bottom plate.

14. The axle counting system based on wheel-rail coupling shear force detection according to claim 13, wherein the strain gauge is arranged obliquely relative to the length direction of the steel rail, a gap is left between adjacent strain gauges, and the center lines of adjacent strain gauges are arranged in parallel.

Technical Field

The invention belongs to the technical field of train detection, and particularly relates to an axle counting method and an axle counting system based on wheel-rail coupling shearing force detection.

Background

With the continuous development of scientific technology, axle counting devices are widely applied to rail transit signal systems under different engineering environments and line conditions, and have a plurality of application schemes. The current scheme of axle counting in the railway system mainly comprises an electromagnetic axle counting scheme.

The electromagnetic induction axle counting is utilized, when a train passes through an axle counting point, the wheel axle cuts a magnetic induction line to cause induced electromotive force on an induction coil, and the induced electromotive force is changed compared with that without wheels, so that whether the train passes through the axle counting point or not is judged, the axle counting is realized, and the function of monitoring the occupation of a track is realized. However, in an actual railway system, a lot of interference faults exist in the electromagnetic induction meter shaft equipment, such as strong surge interference, metal foreign matter interference and other line magnetic field interference, and the application of the electromagnetic sensor in a high-speed train is seriously influenced.

Different from the traditional electromagnetic induction technology, the fiber grating sensing technology has been born, and has the characteristics of electric insulation, electromagnetic interference resistance, corrosion resistance, strong stability, small volume, light weight and the like, so that the fiber grating sensing technology is widely applied to environments with strong electromagnetic interference and variable humidity. And the axle counting product developed based on the fiber bragg grating does not need to place electromagnetic sensitive equipment in an outdoor environment, so that the problems of the electrical equipment can be avoided, and the product is not fatigued to cope with the influences of electromagnetic interference and the like of an application scene.

In the axle counting measurement method in the related art, the applicant thinks that there is a problem that interference from the external environment is easily received when measurement is performed, and stability of the axle counting and accuracy of the measurement result are affected. There is a need for an axle counting method and system that improves measurement accuracy and stability.

Disclosure of Invention

Aiming at the problems, the invention discloses an axle counting method and an axle counting system based on wheel-rail coupling shearing force detection.

In a first aspect, the invention discloses an axle counting method based on wheel-rail coupling shear force detection, which comprises the following technical scheme.

An axle counting method based on wheel-rail coupling shear force detection comprises the following steps:

measuring and acquiring deformation data at a steel rail measuring point in real time;

obtaining a wheel-rail coupling shearing force curve at a measuring point according to the deformation data;

obtaining a strain difference curve according to the wheel-rail coupling shearing force curve;

and counting the axis according to the strain difference curve.

Further, after the wheel-rail coupling shearing force curve is obtained, low-pass filtering is performed on the wheel-rail coupling shearing force curve through a low-pass filter, and a smooth wheel-rail coupling shearing force curve is obtained.

Further, the obtaining of the wheel-rail coupling shear force curve at the measurement point according to the deformation data specifically includes obtaining a wheel load Q according to the deformation data, where the wheel load Q is in direct proportion to the deformation amount of the deformation data; obtaining the shearing force Fs at the measuring point according to the wheel load Q; and obtaining a wheel-rail coupling shearing force curve according to the shearing force Fs.

Further, the obtaining of the shearing force Fs at the measurement point according to the wheel load Q specifically includes,

taking a point A and a point B on the steel rail, and when a wheel runs from the point A to the point B and does not pass through a measuring point, obtaining the relation between the shearing force Fs and the wheel load Q at the measuring point as follows:

when the wheel runs through the measuring point, the relation between the shearing force Fs of the cross section of the measuring point and the wheel load Q is obtained as follows:

wherein X is the distance between the wheel and the point A, and L is the distance between the point A and the point B;

and obtaining the shearing force Fs through the wheel load Q, the distance L and the distance X.

Further, when the wheel travels from the point B to the point a and when the wheel does not pass the measurement point, the relationship between the shear force Fs and the wheel load Q at the measurement point is:

when the wheel runs through the measuring point, the relation between the shearing force Fs of the cross section of the measuring point and the wheel load Q is as follows:

and L is the distance between the point A and the point B.

Furthermore, the wheel-rail coupling shear force curve comprises a first wheel-rail coupling shear force curve, a second wheel-rail coupling shear force curve and a third wheel-rail coupling shear force curve; the strain difference curve comprises a first strain difference curve and a second strain difference curve; the first strain difference curve = the first wheel-rail coupling shear force curve-the second wheel-rail coupling shear force curve, and the second strain difference curve = the second wheel-rail coupling shear force curve-the third wheel-rail coupling shear force curve.

Furthermore, the axle counting according to the strain difference curve specifically includes,

dividing the first strain difference curve and the second strain difference curve into a state 0 or a state 1, wherein the state 0 indicates that the wheel is outside the measuring area, and the state 1 indicates that the wheel is inside the measuring area;

recording the state time sequence change of the state of the strain difference curve along with the time change;

and completing the axle counting according to the state time sequence change.

Further, after obtaining the strain difference curve, the state of the strain difference curve is judged by the threshold values th1 and th2, wherein th1> th 2;

the threshold th1 represents the entrance of the wheel bottom into the measurement area;

the threshold th2 indicates that the wheel bottom is out of the measurement area.

On the other hand, the invention discloses an axle counting system, which comprises the following technical scheme.

An axle counting system based on wheel-rail coupled shear force detection, the axle counting system comprising: a plurality of fiber grating sensing elements, an elastic substrate and a computing unit, wherein:

the elastic substrate is used for fixing the fiber grating sensitive element;

the fiber bragg grating sensitive element is used for measuring and acquiring deformation data of a steel rail measuring point;

and the calculation unit is used for receiving the deformation data from the fiber bragg grating sensitive element, obtaining a wheel-rail coupling shearing force curve according to the deformation data, obtaining a strain difference value curve according to the wheel-rail coupling shearing force curve, and finally carrying out axis counting according to the strain difference value curve.

Furthermore, the axle counting system further comprises a low-pass filter, and the low-pass filter is used for performing low-pass filtering on the wheel-rail coupling shear force curve after the wheel-rail coupling shear force curve is obtained, so as to obtain a smooth wheel-rail coupling shear force curve.

Furthermore, the step of obtaining a wheel-rail coupling shear force curve at the measurement point according to the deformation data by the calculation unit specifically includes:

obtaining a wheel load Q according to the deformation data, wherein the wheel load Q is in direct proportion to the deformation amount of the deformation data;

obtaining the shearing force Fs at the measuring point according to the wheel load Q;

and obtaining a wheel-rail coupling shearing force curve according to the shearing force Fs.

Further, the calculating unit obtains the shearing force Fs at the measuring point according to the wheel load Q, specifically including,

taking a point A and a point B on the steel rail, and when a wheel runs from the point A to the point B and does not pass through a measuring point, obtaining the relation between the shearing force Fs and the wheel load Q at the measuring point as follows:

when the wheel runs through the measuring point, the relation between the shearing force Fs of the cross section of the measuring point and the wheel load Q is obtained as follows:

wherein X is the distance between the wheel and the point A, and L is the distance between the point A and the point B;

and obtaining the shearing force Fs through the wheel load Q, the distance L and the distance X.

Furthermore, the axle counting system also comprises a bottom plate, a transmission optical cable and a boss which are arranged on the bottom plate; the fiber grating sensing element and the elastic substrate are both arranged on the bottom plate, and the fiber grating sensing element and the elastic substrate are bonded to form a strain gauge; one end of the transmission optical cable is connected with the fiber bragg grating sensitive element; the bosses are arranged at two ends of the fiber bragg grating sensitive element; the lug boss is used for being connected with a steel rail; the bottom of the fiber bragg grating sensitive element is fixedly connected in the bottom plate.

Furthermore, the strain gauges are obliquely arranged relative to the length direction of the steel rail, a gap is reserved between every two adjacent strain gauges, and the center lines of the adjacent strain gauges are arranged in parallel.

The invention has at least the following technical effects:

1. the fiber grating sensing element and the elastic substrate are combined into a strain gauge structure, and the fiber grating sensing element is arranged at a specified position on a track in an installation mode of fixedly connecting and encapsulating the bottom of the fiber grating in the bottom plate, so that the influence of the external environment on the measurement of the fiber grating sensing element can be reduced, and the sensitivity and the accuracy of the axle counting are improved;

2. by adopting a double-threshold mode, the axis can be counted only when the state time sequence change process of the two strain difference value curves meets a specific condition (the strain difference value curves v1 and v2 meet the preset time sequence change), so that the fault-tolerant capability, the stability and the accuracy are improved.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of a fiber grating sensor and a substrate according to the present application;

FIG. 2(a) is a schematic front view of a steel rail after the fiber grating sensor is installed in the present application;

FIG. 2(b) is a schematic side view of a steel rail after the fiber grating sensor is installed in the present application;

FIG. 3(a) is a wheel-rail coupled shear force curve for forward driving in the present application;

FIG. 3(b) is a wheel-rail coupled shear force curve for the reverse driving case of the present application;

FIG. 4 is a schematic view of a station arrangement in the present application;

FIG. 5 is a schematic view of a wheel-rail force analysis in the present application;

FIG. 6(a) is a graph illustrating differential strain curves in a forward driving mode;

fig. 6(b) is a diagram illustrating a strain difference curve in the case of reverse driving in the present application.

Reference numerals: 1. a fiber grating sensing element; 2. an elastic substrate; 3. a base plate; 4. a transmission optical cable; 5. and (4) a boss.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

The embodiment of the application discloses an axle counting system based on wheel-track coupling shearing force detection, which comprises a fiber grating sensitive element, an elastic substrate and a calculating unit, wherein the elastic substrate is used for fixing the grating sensitive element; the grating sensitive element is used for measuring and acquiring deformation data at a steel rail measuring point;

and the calculation unit is used for receiving the deformation data from the fiber bragg grating sensitive element, drawing a wheel-track coupling shearing force curve according to the deformation data, obtaining a strain difference curve according to the wheel-track coupling shearing force curve, and finally carrying out axis counting according to the strain difference curve.

Referring to fig. 1, the axle counting system further comprises a base plate 3, a transmission cable 4 mounted on the base plate 3, and a boss 5 mounted on the base plate 3. The boss 5 is used for being connected with a steel rail on which the fiber bragg grating sensing elements 1 are installed, the exposed end part of the boss 5 is used for being installed on the steel rail, the elastic substrate 2 is installed at three positions on the bottom plate 3, and the number of the fiber bragg grating sensing elements 1 is the same as that of the elastic substrate 2. The fiber bragg grating sensitive elements 1 correspond to the elastic substrates 2 one by one, and the fiber bragg grating sensitive elements 1 are bonded with the elastic substrates 2 to form strain gauges.

After the boss 5 is fixed on the steel rail, the strain gauge is mounted on the steel rail. The mounting position for mounting the strain gauge on the steel rail is located in the middle of the tie gap of the steel rail and at the symmetrical positions of the two ends of the steel rail, and the mounting position on the steel rail is designated, so that the mounting is more stable.

The middle part of the fiber grating sensitive element 1 is punched or thinned, so that the interference generated between the fiber grating sensitive elements 1 is reduced. When the steel rail is installed, the central lines of the three strain gauges at the measuring point are parallel to each other and form an included angle of 45 degrees with the length direction of the steel rail. After the strain gauge is formed, the magnitude of a single output signal is low, the mounting position on the steel rail is selected, the strain gauge is inclined by 45 degrees, the signal-to-noise ratio is low, and the sensitivity, the accuracy and the measurement precision of the test can be improved.

Referring to fig. 2(a) and 2(b), the installation of the fiber bragg grating sensor 1 is schematically illustrated, fig. 2(a) is an observation diagram of the front surface of the steel rail, fig. 2(b) is an observation diagram of the side surface of the steel rail, and the measuring points in fig. 2(a) and 2(b) correspond to strain gauges for measurement.

The two ends of the bottom plate 3 are provided with optical cable grooves, the transmission optical cable 4 enters the bottom plate 3 from the optical cable grooves of the bottom plate 3 and is welded with the three fiber bragg grating sensitive elements 1, tail fiber discs of the three fiber bragg grating sensitive elements 1 are placed in the stainless steel rail bottom plate 3, liquid silicon rubber is injected for encapsulation treatment, the three fiber bragg grating sensitive elements are fixed on the bottom plate 3, only the bosses 5 at the two ends of the fixed fiber bragg grating sensitive elements 1 are exposed, and then the installation connection between the two fiber bragg grating sensitive elements and a steel rail is carried out by using the raised lines. By adopting the installation mode, only the two ends of the fiber grating sensitive element 1 are in direct contact with the rail web of the steel rail, and the fiber grating sensitive element 1 is directly driven to deform when the steel rail deforms under stress, so that the steel rail is not easily influenced by the rigidity of the shell. Therefore, the sensitivity of the detection area of the fiber grating sensing element 1 is higher while the fiber grating sensing element 1 is more stably installed.

By adopting the installation mode, the fiber bragg grating sensitive element 1 can be well protected when in use, the fiber bragg grating sensitive element 1 keeps high sensitivity and accuracy, and wheel-rail coupling shearing force can be conveniently and better measured to realize axle counting operation.

The embodiment of the application also discloses an axle counting method based on wheel-rail coupling shearing force detection, which comprises the following steps:

s1, measuring and acquiring deformation data at the steel rail measuring point by the fiber bragg grating sensing element 1.

And mounting the base plate and the strain gauge on the mounting position of the steel rail through the boss, and detecting the deformation data of the steel rail through the fiber bragg grating sensitive element.

After the fiber grating sensing element 1 is installed, when a wheel of a train passes through a monitoring area distributed with the fiber grating sensing element 1, a steel rail generates stress change under the action of gravity of a carriage and also generates deformation, because the fiber grating sensing element 1 is solidified on the elastic substrate 2 and is closely attached to the steel rail without relative displacement, the fiber grating sensing element 1 also generates deformation, when strain is transmitted to the fiber grating sensing element 1 through the steel rail, the central wavelength of reflected light shifts, and the reflected light intensity of continuous light in a waveband regularly changes. The deformation of the steel rail when the train passes through is mapped to the change of the central wavelength of the grating reflected light, so that the sensing of the fiber grating sensing element 1 on the coupling of the steel rail is realized. The fiber bragg grating sensing element 1 reflects deformation data of the wheel after passing, and the deformation quantity of the deformation data is in positive correlation with the magnitude of the wheel load Q passing through the steel rail.

And S2, obtaining a wheel-rail coupling shearing force curve according to the steel rail deformation data detected by the fiber bragg grating sensitive element 1 by the calculation unit.

The three fiber bragg grating sensitive elements 1 are divided into a first fiber bragg grating sensitive element, a second fiber bragg grating sensitive element and a third fiber bragg grating sensitive element. As the wheel deforms through the steel rail, deformation data are measured by the three fiber bragg grating sensitive elements 1, and the deformation quantity of the deformation data is in direct proportion to the wheel load Q at the measuring point.

The wheel load Q is in direct proportion to the deformation quantity of the deformation data, the shearing force Fs at the measuring point is obtained through the wheel load Q, and then a wheel-rail coupling shearing force curve is obtained through the change of the shearing force Fs. And finally, three wheel-rail coupling shear force curves are obtained, namely a first wheel-rail coupling shear force curve s1, a second wheel-rail coupling shear force curve s2 and a third wheel-rail coupling shear force curve s 3.

The axle counting system further comprises a low-pass filter, the low-pass filter performs low-pass filtering on the wheel-rail coupling shearing force curve measured in real time to obtain a smoother wheel-rail coupling shearing force curve, wheel axle counting (axle counting) is facilitated by the calculating unit, and the obtained wheel-rail coupling shearing force curve is shown in fig. 3(a) and fig. 3 (b). Fig. 3(a) shows a wheel-rail coupling shear force curve in the case of forward running, and fig. 3(b) shows a wheel-rail coupling shear force curve in the case of reverse running.

Referring to fig. 4 and 5, the way of obtaining the wheel-rail coupling shear force Fs from the wheel load Q is specifically as follows,

when the train passes through the steel rail, the stress analysis of the detection point is as follows,

the method comprises the following steps that a first fiber grating sensitive element is arranged in the middle of a beam, a first measuring point is defined, a second fiber grating sensitive element and a third fiber grating sensitive element are arranged at symmetrical positions of two ends of the first fiber grating sensitive element at a certain distance, the two positions are respectively defined as a second measuring point and a third measuring point, and when a wheel runs through a monitoring area along different directions, the mechanical analysis of the shearing force Fs of the cross sections of the first measuring point, the second measuring point and the third measuring point is different. In fig. 4 and 5, points one, two, and three are represented using S1, S2, and S3, respectively. And wheel-rail coupling shear force curves at the first measuring point, the second measuring point and the third measuring point respectively correspond to a first wheel-rail coupling shear force curve s1, a second wheel-rail coupling shear force curve s2 and a third wheel-rail coupling shear force curve s 3. After obtaining the magnitude of the shearing force Fs at each measurement point, the calculation unit plots the wheel-rail coupling shearing force curves shown in fig. 3(a) and 3(b) according to the change in the magnitude of the shearing force Fs with time.

A section of steel rail between two sleepers A and B is regarded as a section of simply supported beam, and when a wheel runs on the steel rail from the end A to the end B (hereinafter referred to as forward running), the position where the wheel does not pass a measuring point is analyzed according to the mechanical principle of the beam;

the simply supported beam is in a balanced state under the action of the external force of the wheel, the counter force of the support is obtained according to a static equilibrium equation,

by

To obtain

Wherein, Sigma F_xFor resultant force in X direction, Σ F_yFor resultant force in Y direction, ∑ M_AIs the sum of the moments at points A, F_AYThe counter force of the support with point A upward, F_BYThe reaction force of the support with the point B upward is shown, Q is the load of the wheel, X is the distance from the bottommost part of the wheel to be detected to the point A, and L is the distance between the point AB and the point A.

When the first measuring point is analyzed, the beam is cut into a left section and a right section at the first measuring point by using the cross section, as shown in fig. 5, the left section of the beam is taken as a separation body, and the left section of the beam is in a balanced state because the beam is originally in the balanced state, so that the left section of the beam is also kept in the balanced state. The left section beam has the functions of upward support counter force and downward known force Q, and if the left section beam does not vertically move, a vertical internal force is always balanced with the vertical internal force on the section.

Wherein the content of the first and second substances,the shear force at point one is measured.

From the above analysis, it is known that the beam is divided into two sections by a cross-sectional method, and the results obtained by taking the internal force on the same cross section as the release body for the left-hand beam and the release body for the right-hand beam are equal in value but opposite in direction, and therefore the signs of the beams are defined according to the deformation of the beams caused by the shear force. Taking out a small section from the beam at the cross section, wherein if the shear force enables the small section to rotate clockwise, the shear force on the cross section is positive; otherwise, it is negative. Therefore, when the bottom of the wheel does not pass through the position of the measuring point, the shearing force F of the cross section of the measuring point is measured_SThe relationship with the wheel load Q is:

similarly, when the wheel runs through the position of the measuring point I, the relation between the shearing force Fs of the cross section of the measuring point I and the wheel load Q is as follows:

and for the second measuring point and the third measuring point, when the wheel does not pass or passes through the second measuring point and the third measuring point, the relation between the shearing force Fs and the wheel load Q at the cross sections of the second measuring point and the third measuring point is the same as that at the first measuring point.

When the wheel runs from the B end to the A end on the steel rail (hereinafter referred to as reverse running), the wheel passes through the measuring point III, and the relationship between the shearing force Fs of the cross section of the measuring point III and the wheel load Q is as follows:

when the wheel runs through the three positions of the measuring points, the relation between the shearing force Fs of the three cross sections of the measuring points and the wheel load Q is

From the above analysis, the magnitude of the shear force Fs can be clearly obtained, and three rail-coupled shear force curves s1, s2, and s3 shown in fig. 3(a) and 3(b) are obtained by the change in the shear force Fs.

S3, the calculating unit obtains a strain difference curve of the wheel rail shearing force according to the wheel rail coupling shearing force curve, and the strain difference curve comprises a first strain difference curve v1 and a second strain difference curve v 2.

The first strain difference curve is obtained by difference of a first wheel-rail coupling shearing force curve and a second wheel-rail coupling shearing force curve, and the second strain difference curve is obtained by difference of a second wheel-rail coupling shearing force curve and a third wheel-rail coupling shearing force curve. That is, the first strain difference curve v1= s1-s2, and the second strain difference curve v2= s2-s 3. After the wheel-rail coupling shearing force curve is obtained, pairwise difference is carried out on the wheel-rail coupling shearing force curve, and a strain difference value curve can be obtained.

And S4, the calculation unit calculates the axis according to the strain difference curve.

The calculating unit is used for calculating the axis according to the strain difference curve and specifically comprises the following steps:

firstly, a strain difference curve is divided into a state 0 and a state 1, wherein the state 0 is that the wheel is positioned outside a sensitive area monitored by the fiber grating sensitive element 1, and the state 1 indicates that the wheel is positioned in the sensitive area monitored by the fiber grating sensitive element 1. Referring to fig. 6(a) and 6(b), the states of the strain difference curves are determined using the thresholds th1 and th 2. The threshold th1 represents that the train enters the sensitive area (i.e. enters the measuring area) monitored by the fiber grating sensor 1, and the strain difference curve enters the state 1. th2 represents the sensing zone (i.e. the outgoing measurement zone) monitored by the fiber grating sensor 1, and the strain difference curve enters the state 0, where th1> th 2. Fig. 6(a) is a graph showing the difference in strain between t1 and t2 and between t2 and t3 in the case of forward running, and fig. 6(b) is a graph showing the difference in strain between t1 and t2 and between t2 and t3 in the case of reverse running.

Then, as the train passes through the monitoring area of the fiber grating sensor 1, the state time sequence changes of the states of v1 and v2 changing with the time change are recorded.

When the train runs in the forward direction, the states of the strain difference curves v1 and v2 within the time period of 0-t1 are 0, the values are both smaller than th1, at the moment, the state of v1 is 0, the state of v2 is 0, and the combined state of v1 and v2 is 00. After the time t1, the value of v1 is greater than th1, at which time the v1 state becomes 1, the v2 state is 0, and the combined state of v1 and v2 is 10 in the time period t1-t 2. After the time t2, the value of v2 is greater than the threshold th1, the state of v2 is 1, the value of v1 is less than the threshold th2, the state of v1 is 0, and the combined state of v1 and v2 is 01 in the time period t1-t 2.

After the time t3, the value of v2 is smaller than the threshold th2, the state of v2 is 0, the state of v1 is 0, and the combined state of v1 and v2 after the time t3 is 00.

Finally, counting the axes according to the state time sequence change of the strain difference curve, which specifically comprises the following steps: when the wheel of the train passes from the first fiber grating sensitive element to the third fiber grating sensitive element, the state time sequence of v1 and v2 is 00, 10, 01 and 00; on the contrary, when the train passes from the third fiber grating sensing element to the first fiber grating sensing element, the state time sequences of v1 and v2 are 00, 01, 10 and 00.

If the state time sequences of v1 and v2 are 00, 10, 01 and 00, judging that the wheels of the train pass through the first fiber bragg grating sensitive element to the third fiber bragg grating sensitive element; if the state time sequences of v1 and v2 are 00, 01, 10 and 00, judging that the wheels of the train pass through the first fiber grating sensitive element from the third fiber grating sensitive element, thus finishing the direction judgment of the train, simultaneously recording the times of state time sequence changes, and finishing axle counting (namely axle counting). And, only when certain conditions (00, 10, 01, 00 or 00, 01, 10, 00) are met will one wheel axle count be completed, and fault-tolerant capability is improved.

The axle counting and the direction judging can be completed through the state time sequence change of the v1 and the v2 along with the time change. The accuracy and stability of the axle counting method can be improved through the double thresholds, the vibration impact generated when a train runs is large, the grating wavelength fluctuates along with the external vibration, the error axle counting can be possibly caused under the conditions of vibration and impact by adopting the mode of the single threshold, and the axle counting can be carried out only when specific conditions (00, 10, 01, 00 or 00, 01, 10 and 00) are met according to the state change process of two grating shearing force strain difference curves by adopting the mode of the double thresholds, so that the fault-tolerant capability and the stability and accuracy are improved.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.