Axle counting sensor and looseness detection method thereof

Abstract

The invention belongs to the technical field of rail transit, and discloses an axle counting sensor and a looseness detection method thereof.The axle counting sensor comprises N first fiber bragg gratings, a second fiber bragg grating and an elastic body, and N is larger than or equal to 2; n first containing cavities and a second containing cavity are formed in the elastomer, each first containing cavity is internally provided with a first fiber bragg grating, each second fiber bragg grating is arranged in the corresponding second containing cavity, the elastomer is provided with a boss above each first containing cavity, and the N bosses are all located on the top face, making contact with the bottom face of a steel rail, of the elastomer; the boss is used for extruding the first fiber bragg grating and changing the initial reflection wavelength of the first fiber bragg grating. According to the axle counting sensor, through the boss, the axle counting function and the looseness detection function of the fiber grating sensor in the sensor component can be achieved at the same time only by leading out one optical cable, and compared with the prior art in which multiple optical cables are led out, the structure is simplified, and the system availability is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of rail transportation, and in particular relates to an axle counting sensor and a looseness detection method thereof. Background Art

[0002] Axle counting equipment is an important signal detection device to ensure the safe operation of rail transit systems. It determines the occupied or idle state of a railway section by detecting the number of wheel axles. The principle of axle counting technology to determine the section occupancy is as follows: for a certain section, as long as the axle counting sensor counts the number of axles of trains entering the section and the number of axles of trains leaving the section, the section is considered to be occupied, otherwise it is considered to be idle.

[0003] Axle counting equipment usually consists of an axle counting sensor and an axle counting host. The axle counting sensor is installed on the rail. As a safety device, in addition to wheel detection, it must have corresponding detection capabilities when the axle counting sensor is loose or falls off the rail to prevent the axle counting sensor from posing a safety threat to passing trains.

[0004] According to the different sensing mechanisms, axle counters can be divided into electromagnetic axle counters and fiber grating axle counters. At present, electromagnetic axle counters are mainly used in rail transit systems as the mainstream solution for wheel passing detection. Electromagnetic axle counters require cables to be laid beside the track to power the sensors on the track. The transmission distance is short, the price is expensive, and the sensors are easily affected by electromagnetic interference.

[0005] The basic principle of fiber Bragg grating sensing is as follows: Fiber Bragg grating is a diffraction grating formed by axially periodically modulating the refractive index of the optical fiber core through a certain method, and is a passive filter device. Figure 1 As shown, Figure 1 This is a schematic diagram of the reflection characteristics of the fiber Bragg grating. For broadband light incident on the fiber Bragg grating, only the light with a wavelength that meets certain conditions can be reflected back, and the rest of the light is transmitted. The grating pitch of the fiber Bragg grating is related to the wavelength of the reflected light. When the grating pitch of the fiber Bragg grating changes due to changes in external parameters (strain, temperature, etc.), it will cause the wavelength of the reflected light to change. By detecting the change in the wavelength of the reflected light from the fiber Bragg grating, the strain and temperature can be measured.

[0006] The prior art has the following technical solutions: 1. A method for measuring axle count based on fiber grating (the grating is attached to the rail waist) to measure the change in shear force when the wheel passes.

[0007] 2. A method for measuring axle count based on fiber grating (the grating is fixed to the bottom of the rail) to measure the change in vertical force when the wheel passes by.

[0008] 3. The output of the forward and reverse axle numbers is realized according to the sequence composed of the state changes of the two strain detection gratings when the wheels pass by (similar to the electromagnetic axle counter). In actual use, when axles of different weights pass by continuously, the waveforms of some axles measured by the two strain detection gratings may overlap or be out of order. The original axle counting judgment method may result in missed axles, affecting driving safety.

[0009] The above technical solutions mainly disclose the fiber Bragg grating axle counting method, but none of them disclose how to realize the looseness detection of the fiber Bragg grating axle counting sensor. Summary of the invention

[0010] In view of the above problems, the present invention provides an axle counter sensor and a looseness detection method thereof, which adopts the following technical solutions: An axle counting sensor comprises N first fiber gratings, second fiber gratings and an elastic body, where N is greater than or equal to 2; Among them, N first accommodating cavities and 1 second accommodating cavity are arranged inside the elastomer, each of the first accommodating cavity is arranged with a first fiber grating, and the second fiber grating is arranged in the second accommodating cavity. The elastomer is provided with a boss above each first accommodating cavity, and the N bosses are all located on the top surface of the elastomer in contact with the bottom surface of the rail; each of the first fiber grating is tightly fitted with the wall surface of the first accommodating cavity, and the second fiber grating has a gap with the wall surface of the second accommodating cavity, and the boss is used to squeeze the first fiber grating to change the initial reflection wavelength of the first fiber grating.

[0011] Furthermore, it also includes a clamping block and a fastening assembly, wherein the clamping blocks on both sides of the elastomer are detachably connected to the rail through the fastening assembly, and the clamping blocks press the top surface of the elastomer onto the bottom surface of the rail.

[0012] Furthermore, the installation directions of the N first fiber gratings are all parallel to the rail.

[0013] Furthermore, the clamping block includes an integrally formed U-shaped slot, a connecting plate and a connecting block, the two ends of the connecting plate are respectively connected to one side of the two U-shaped slots, the notches of the two U-shaped slots are flush, the bottom of the connecting block is connected to the connecting plate, and a through hole is provided on the connecting block.

[0014] Furthermore, the elastic body includes a rectangular body, and the rectangular body is provided with protrusions matching the U-shaped slot on both sides.

[0015] Furthermore, an optical cable connector is provided at a middle position on one side of the rectangular body.

[0016] Furthermore, an optical fiber channel is provided in the elastic body, and the inner optical fiber of the optical cable passes through the optical fiber channel and is respectively connected to the N first optical fiber gratings and the N second optical fiber gratings.

[0017] The present invention also provides a method for detecting looseness of the axle counter sensor, comprising the following steps: Acquire in real time the reflection wavelengths of N first fiber gratings and the reflection wavelengths of the second fiber gratings; Temperature compensation is performed on the reflection wavelengths of the N first fiber gratings by using the reflection wavelength collected in real time by the second fiber grating to obtain the reflection wavelengths of the N first fiber gratings after temperature compensation; According to the change amount of the reflection wavelength of the first fiber grating after temperature compensation and the looseness detection threshold of the first fiber grating, it is determined whether the axle counting sensor and the rail are loose or falling off.

[0018] Furthermore, the method further comprises the following steps: An axle counter sensor is installed between two rail sleepers, and a set preload force is applied between the elastic body and the rail to obtain N reflection wavelengths of the first fiber Bragg grating after installation and the second fiber Bragg grating after installation; The looseness detection threshold of each first fiber grating is determined according to the reflection wavelength of each first fiber grating after installation and the change of the reflection wavelength of each first fiber grating when the train passes the rail under different pre-tightening forces of the elastic body and the rail.

[0019] Further, according to the reflection wavelength of each first fiber Bragg grating after installation and the change amount of the reflection wavelength of each first fiber Bragg grating when the train passes the rail under different pre-tightening forces of the elastic body and the rail, the looseness detection threshold of each first fiber Bragg grating is determined, including: Acquire a first change in the reflection wavelength of the first fiber grating when a train passes over the rail at a set preload value; The preload force value applied by the fastening assembly to the clamping block is gradually reduced on the basis of the set preload force value, and the second change amount of the reflection wavelength of each first fiber Bragg grating when the train passes over the rail at the current preload force value is obtained in real time, wherein the first change amount and the second change amount are both the difference between the maximum value of the reflection wavelength of the first fiber Bragg grating when the train passes over the rail and the reflection wavelength after the first fiber Bragg grating is installed; When the difference between the first variation and the second variation reaches a set value, the difference between the reflection wavelength of each first fiber grating after installation and the reflection wavelength under the current preload value is determined as a looseness detection threshold.

[0020] Furthermore, the method further comprises the following steps: The number of the passing train wheel axles and the passing direction of the wheels are determined according to the reflected wavelengths of the N first optical fiber gratings acquired in real time.

[0021] Further, temperature compensation is performed on the reflection wavelengths of the N first fiber gratings by using the reflection wavelength collected in real time by the second fiber grating to obtain the reflection wavelengths of the N first fiber gratings after temperature compensation, including the following steps: Determine a proportionality coefficient between the change in reflection wavelength after each first fiber grating is installed and the change in reflection wavelength after each second fiber grating is installed; According to the proportionality coefficient, the reflection wavelength collected in real time by the second fiber grating and the reflection wavelength after the second fiber grating is installed, the reflection wavelength of each first fiber grating is temperature compensated to obtain the reflection wavelengths of N first fiber gratings after temperature compensation.

[0022] Beneficial effects of the present invention: 1. The axle counter sensor of the present invention can realize the axle counting function and looseness detection function of the fiber grating sensor inside the sensor component simultaneously by leading out only one optical cable through the boss. Compared with the prior art of leading out multiple optical cables, the structure is simplified and the system availability is improved.

[0023] 2. The present invention sets the sensor loosening detection threshold in conjunction with a train passing over a rail, and can accurately determine whether the axle counter sensor is loose or fallen off.

[0024] 3. The axle counting working process of the axle counter sensor of the present invention can avoid partial overlap or disordered sequence of passing vehicle waveforms.

[0025] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 A schematic diagram showing the basic principle of fiber Bragg grating sensing is shown; Figure 2 A schematic structural diagram of an axle counter sensor according to an embodiment of the present invention is shown; Figure 3 A schematic structural diagram of an elastic body according to an embodiment of the present invention is shown; Figure 4 It shows a schematic structural diagram of a clamping block according to an embodiment of the present invention; Figure 5 A schematic flow chart of a looseness detection method for an axle counter sensor according to an embodiment of the present invention is shown; Figure 6 A schematic diagram of a working process of an axle counter sensor according to an embodiment of the present invention is shown; Figure 7 A schematic diagram showing the principle of setting the looseness detection threshold of the first fiber Bragg grating according to an embodiment of the present invention; Figure 8 A schematic diagram showing the principle of temperature compensation for the reflection wavelength of the first fiber grating according to an embodiment of the present invention is shown; Fig. 9 A schematic diagram of the axle counting process of fiber Bragg grating sensing according to an embodiment of the present invention is shown.

[0028] In the figure: 1, elastic body; 2, clamping block; 3, fastening assembly; 4, optical cable; 5, first fiber grating; 6, second fiber grating; 11, boss; 12, rectangular body; 13, protrusion; 14, optical cable connector; 21, U-shaped slot; 22, connecting plate; 23, connecting block; 24, through hole; 25, groove; 31, bolt; 32, nut. DETAILED DESCRIPTION In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second" etc. in the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged in appropriate circumstances, so that the embodiments of the present application described here. In the present application, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "middle", "vertical", "horizontal", "lateral", "longitudinal" etc. are based on the orientation or positional relationship shown in the accompanying drawings.

[0031] The invention provides an axle counting sensor and a looseness detection method thereof, which can detect the looseness or falling off of the sensor while counting the axle.

[0032] like Figure 2As shown, an axle counter sensor includes a fiber Bragg grating assembly, an elastic body 1, a clamping block 2, a fastening assembly 3 and an optical cable 4, wherein the fiber Bragg grating assembly includes N first fiber Bragg gratings 5 ​​and second fiber Bragg gratings 6, wherein N ≥ 2, and the elastic body 1 is provided with N first accommodating cavities and 1 second accommodating cavity, each first accommodating cavity is provided with a first fiber Bragg grating 5, and the second fiber Bragg grating 6 is provided in the second accommodating cavity, as shown in FIG. Figure 3 As shown, the elastic body 1 is provided with a boss 11 above each first accommodating cavity, wherein the N bosses 11 are all located on the top surface of the elastic body 1 in contact with the bottom surface of the rail.

[0033] The N first FBGs 5 are installed in parallel to the rails, and each first FBG 5 is closely attached to the wall of the first accommodating cavity, so that the strain of the elastic body 1 can be transmitted to the N first FBGs 5. The first FBG 5 is used to collect strain signals when the train passes over the rails.

[0034] There is a gap between the second fiber Bragg grating 6 and the wall of the second accommodating cavity, so the strain of the elastic body 1 cannot be transmitted to the second fiber Bragg grating 6. The second fiber Bragg grating 6 is used to measure temperature.

[0035] The clamping blocks 2 on both sides of the elastic body 1 are detachably connected to the rail through the fastening assembly 3. The clamping blocks 2 press the top surface of the elastic body 1 onto the bottom surface of the rail so that the top surface of the elastic body 1 fits tightly with the bottom surface of the rail. When the elastic body 1 is fastened to the rail, the boss 11 is used to squeeze the first fiber grating 5 to change the initial reflection wavelength of the first fiber grating 5.

[0036] An optical fiber channel is provided in the elastic body 1 , and the inner optical fiber of the optical cable 4 passes through the optical fiber channel and is connected to the N first optical fiber gratings 5 ​​and the N second optical fiber gratings 6 respectively.

[0037] For example, Figure 4 As shown, the clamp block 2 includes an integrated U-shaped slot 21, a connecting plate 22 and a connecting block 23, the two ends of the connecting plate 22 are respectively connected to one side of the two U-shaped slots 21, the notches of the two U-shaped slots 21 are flush, the width of the U-shaped slot 21 is determined according to the thickness of the elastic body 1 and the rail bottom size of the rail, the bottom of the connecting block 23 is connected to the connecting plate 22, and a through hole 24 is provided on the connecting block 23. Each U-shaped slot 21 is provided with a chamfer at its corners.

[0038] For example, Figure 2As shown, the fastening assembly 3 includes a bolt 31 and a nut 32, two clamping blocks 2 are arranged at both ends of the elastomer 1, the first clamping block 2 and the second clamping block 2 are respectively located on both sides of the first end of the elastomer 1, the U-shaped groove 21 of the first clamping block 2 and the U-shaped groove 21 of the second clamping block 2 clamp the first end of the elastomer 1 to the bottom of the rail, the bolt 31 passes through the through hole 24 on the connecting block 23 of the first clamping block 2 and the through hole 24 on the connecting block 23 of the second clamping block 2 in sequence and is threadedly connected with the nut 32, and a pre-tightening force is applied after the nut 32 is tightened, so that the first end of the elastomer 1 is fixedly connected to the bottom of the rail.

[0039] The U-shaped slot 21 of the third clamping block 2 and the U-shaped slot 21 of the fourth clamping block 2 clamp the second end of the elastomer 1 to the bottom of the rail, and the bolt 31 passes through the through hole 24 on the connecting block 23 of the third clamping block 2 and the through hole 24 on the connecting block 23 of the fourth clamping block 2 in sequence and is threadedly connected with the nut 32. After tightening the nut 32, a pre-tightening force is applied to fix the second end of the elastomer 1 to the bottom of the rail.

[0040] For example, Figure 2 As shown, the connecting blocks 23 of the first clamping block 2 and the third clamping block 2 are both provided with a groove 25 on one side of the through hole 24, and the groove 25 is used to accommodate the head of the bolt 31, so that the outer surface of the axle counter sensor and the rail is flat after installation.

[0041] For example, Figure 3 As shown, the elastic body 1 includes a rectangular body 12, and the rectangular body 12 is provided with protrusions 13 matching the U-shaped card slot 21 on both sides. For example, if there are 4 card blocks, the protrusions 13 on the rectangular body 12 are provided with 8. Figure 2 As shown, the two U-shaped slots 21 of each clamping block clamp the two protrusions 13 on the bottom of the rail respectively.

[0042] For example, Figure 3 As shown, an optical cable connector 14 is provided at a middle position on one side of the rectangular body 12 , and the optical cable connector 14 is used to fix the optical cable 4 .

[0043] For example, two first fiber gratings 5 ​​are provided, the two first fiber gratings 5 ​​are respectively provided at the two ends of the elastomer 1, the second fiber grating 6 is located between the two first fiber gratings 5, two bosses 11 are provided on the top surface of the elastomer 1, the two bosses 11 are respectively located above the two first fiber gratings 5, the two first fiber gratings 5 ​​are tightly fitted to the wall of the first accommodating cavity, so that the strain of the elastomer 1 can be transmitted to the two first fiber gratings 5, the two first fiber gratings 5 ​​are used to collect strain signals when the train passes over the rails, the second fiber grating 6 has a gap with the wall of the accommodating cavity, and the second fiber grating 6 is used to measure temperature.

[0044] When the elastic body 1 is fastened to the rail, the two bosses 11 squeeze the positions of the two first optical fiber gratings 5 ​​respectively, thereby changing the initial reflection wavelength of the first optical fiber gratings 5 ​​.

[0045] Based on the above axle counter sensor, such as Figure 5 As shown, the present invention also provides a looseness detection method for an axle counter sensor, comprising the following steps: S1. Before installing the axle counter sensor on the rail, obtain the initial wavelengths of N first fiber gratings 5 ​​and the initial wavelengths of the second fiber gratings 6.

[0046] S2, installing the axle counter sensor between the two rail sleepers, and applying a set preload force between the elastic body 1 and the rail, obtaining N reflection wavelengths of the first fiber Bragg grating 5 after installation and the reflection wavelengths of the second fiber Bragg grating 6 after installation, as follows: The elastomer 1 is clamped between two rail sleepers by a clamping block, wherein the top surfaces of the N bosses 11 of the elastomer 1 are in contact with the bottom surface of the rail, a set preload value is applied to the clamping block 2 by the fastening assembly 3, and the reflection wavelengths of the N first fiber gratings 5 ​​after installation and the reflection wavelengths of the N second fiber gratings 6 after installation are obtained.

[0047] S3, determining the looseness detection threshold of each first fiber Bragg grating 5 according to the reflection wavelength of each first fiber Bragg grating 5 after installation and the change of the reflection wavelength of each first fiber Bragg grating 5 when the train passes the rail under different pre-tightening forces of the elastic body 1 and the rail, comprising the following steps: Obtain a first change in the reflection wavelength of the first fiber grating 5 when a train passes over the rail at a set preload value; gradually reduce the preload value between the elastic body 1 and the rail on the basis of the set preload value, and obtain in real time a second change in the reflection wavelength of the first fiber grating 5 when a train passes over the rail at a current preload value; when the difference between the first change and the second change reaches a set value, determine the difference between the reflection wavelength of the first fiber grating 5 after installation and the reflection wavelength at the current preload value as a looseness detection threshold.

[0048] The first variation and the second variation are both the difference between the maximum value of the reflection wavelength of the first fiber grating 5 when the train passes over the rail and the reflection wavelength after the first fiber grating 5 is installed.

[0049] S4. During the operation of the axle counter sensor, the reflection wavelengths of the N first fiber gratings 5 ​​and the reflection wavelengths of the second fiber gratings 6 are obtained in real time, and the number of the passing train wheel axles and the direction in which the wheels pass are determined based on the reflection wavelengths of the N first fiber gratings 5 ​​obtained in real time.

[0050] S5, performing temperature compensation on the reflection wavelengths of the N first fiber gratings 5 ​​by using the reflection wavelength collected in real time by the second fiber grating 6 to obtain the reflection wavelengths of the N first fiber gratings 5 ​​after temperature compensation, comprising the following steps: S51, determine the proportionality coefficient between the change in reflection wavelength of each first fiber grating 5 after installation and the change in reflection wavelength of the second fiber grating 6 after installation. S52, performing temperature compensation on the reflection wavelength of each first fiber grating 5 according to the proportional coefficient, the reflection wavelength collected in real time by the second fiber grating 6, and the reflection wavelength after the second fiber grating 6 is installed, to obtain the reflection wavelengths of N first fiber gratings 5 ​​after temperature compensation.

[0051] S6. Determine whether the axle counter sensor is loose or detached from the rail according to the change in the reflection wavelength of the first fiber grating 5 after temperature compensation and the loose detection threshold of the first fiber grating 5.

[0052] When the change in the reflection wavelength of the temperature-compensated first fiber grating 5 is greater than the loose detection threshold of the first fiber grating 5, it is determined that the axle counting sensor is loose or detached from the rail, and the axle counting is stopped.

[0053] For example, if two first fiber gratings 5 ​​are provided, the initial wavelengths of the two first fiber gratings 5 ​​and the second fiber gratings 6 are recorded as , , .

[0054] like Figure 6 As shown, after the installation is completed, the reflection wavelengths of the first fiber grating 5 and the second fiber grating 6 after installation are recorded as follows: , , .

[0055] It should be noted that, since the two bosses 11 of the elastic body 1 will cause the tensile strain of the two first fiber gratings 5, the reflection wavelength increases, and the wavelength corresponding to the two first fiber gratings 5 ​​changes to , ,in , , and The value of is related to the thickness of the boss 11. When the thickness of the boss 11 is 0.1 mm, and The value is about 1000pm; the second fiber Bragg grating 6 is not affected by the strain generated during installation. When the temperature before and after installation remains unchanged, .

[0056] like Figure 7As shown, the process of setting the loose detection threshold is described by taking one of the first fiber gratings 5 ​​as an example: the loose detection threshold The setting needs to be combined with the vehicle passing process. Too small may cause false alarm. Too large will result in missed axes. Figure 7 The solid line in the middle is the change in the reflection wavelength of the first fiber grating 5 during the vehicle passing process. It is the first change in the reflection wavelength of the first fiber grating when the train passes the rail under the set preload value. Gradually reduce the preload value and install the axle counter sensor. When it drops by 30% (it can also be set to other values ​​as needed, and can be adjusted up and down during actual application), the preload force decreases at this time. The difference between the preload value and the normal preload value is the looseness detection threshold. The loose detection threshold processing process of the other first fiber grating 5 is the same as above and will not be repeated here.

[0057] When setting the looseness detection threshold, if the set decrease ratio is small, the preload force does not decrease significantly, and the corresponding value is also small. When abnormal fluctuations occur, the looseness detection threshold is easily triggered, causing a false alarm; if the set decrease ratio is large, the preload force is significantly reduced, that is, the looseness is already more obvious, and the corresponding value is large. When a train passes by, especially a train with a lighter axle weight, if the looseness detection threshold is not triggered, the threshold required for the above-mentioned axle counting cannot be reached due to the passing of the train, resulting in missed axle counting.

[0058] The reflection wavelengths of the two first optical fiber gratings 5 ​​are temperature compensated by the reflection wavelength collected in real time by the second optical fiber grating 6 to obtain the reflection wavelengths of the two first optical fiber gratings 5 ​​after temperature compensation.

[0059] like Figure 8 As shown, the process of eliminating the temperature influence is described by taking one of the first fiber Bragg gratings 5 ​​as an example: the reflection wavelength of the second fiber Bragg grating 6 after installation Only affected by temperature changes, so it can be used Eliminate the effect of temperature on the reflection wavelength of the two first fiber Bragg gratings 5 ​​after installation , After the axle counter sensor is installed, due to changes in ambient temperature, , , will change, Figure 8 Taking one fiber Bragg grating and the second fiber Bragg grating 6 as an example, the change trends of the two first fiber Bragg gratings 5 ​​are consistent. After the installation process is completed, and will change with the change of ambient temperature, and the changes are and The proportionality coefficient between the two is During the operation of the axle counter sensor, the reflection wavelength data of the first fiber grating 5 and the second fiber grating 6 are collected in real time. and ,right The part that eliminates the temperature effect, that is ,but What is reflected is the reflection wavelength of the first fiber grating 5 after temperature compensation, and the reflection wavelength processing process of another first fiber grating 5 is the same as above.

[0060] Working process of axle counter sensor: After the axle counter sensor is installed, the reflection wavelengths of the first fiber grating 5 and the second fiber grating 6 are recorded as follows: , , The reflection wavelengths of the first fiber Bragg grating 5 and the second fiber Bragg grating 6 of the two axle counter sensors collected in real time are , , , divided into 2 paths for processing, the first path is based on , Data to achieve axle counting function, the second route is based on , , Realize the looseness detection function of the axle counter sensor.

[0061] like Fig. 9 As shown, when a wheel passes by, the two first fiber gratings 5 ​​react in sequence, and the direction of the wheel passing can be determined according to the order of the reactions. The solid curve and the dotted curve represent the reaction curves of the two first fiber gratings 5 ​​when the axle passes by, respectively. The initial state bit is 0, and a change threshold is set. When the change of the first fiber grating 5 reaches the threshold, the state bit is 1, and when the change falls back to the threshold, the state bit returns to 0. When the state bit combination sequence of the two first fiber gratings 5 ​​is 00-10-11-01-00, the number of axles is increased by 1; if the above sequence is specified as the positive direction, the state bit combination sequence is 00-01-11-10-00, and the number of reverse axles is increased by 1.

[0062] The axle counter sensor of the present invention can be realized by leading out only one optical cable 4 through the boss 11, and at the same time realizes the axle counting function and looseness detection function of the fiber grating sensor inside the sensor component. Compared with the prior art of leading out multiple optical cables 4, the structure is simplified and the system availability is improved.

[0063] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An axle counter sensor, characterized in that: It includes N first fiber Bragg gratings, second fiber Bragg gratings and an elastic body, where N is greater than or equal to 2; Among them, N first accommodating cavities and 1 second accommodating cavity are arranged inside the elastomer, each of the first accommodating cavity is arranged with a first fiber grating, and the second fiber grating is arranged in the second accommodating cavity. The elastomer is provided with a boss above each first accommodating cavity, and the N bosses are all located on the top surface of the elastomer in contact with the bottom surface of the rail; each of the first fiber grating is tightly fitted with the wall surface of the first accommodating cavity, and the second fiber grating has a gap with the wall surface of the second accommodating cavity, and the boss is used to squeeze the first fiber grating to change the initial reflection wavelength of the first fiber grating.

2. The axle counter sensor according to claim 1, characterized in that: It also includes a clamping block and a fastening assembly. The clamping blocks on both sides of the elastic body are detachably connected to the rail through the fastening assembly, and the clamping blocks press the top surface of the elastic body onto the bottom surface of the rail.

3. The axle counter sensor according to claim 1, characterized in that: The installation directions of the N first fiber gratings are all parallel to the rail.

4. The axle counter sensor according to claim 2, characterized in that: The clamping block includes an integrally formed U-shaped slot, a connecting plate and a connecting block, the two ends of the connecting plate are respectively connected to one side of the two U-shaped slots, the notches of the two U-shaped slots are flush, the bottom of the connecting block is connected to the connecting plate, and a through hole is provided on the connecting block.

5. The axle counter sensor according to claim 4, characterized in that: The elastic body comprises a rectangular body, and protrusions matching the U-shaped slot are arranged on two sides of the rectangular body.

6. The axle counter sensor according to claim 5, characterized in that: An optical cable connector is also provided at a middle position on one side of the rectangular body.

7. The axle counter sensor according to any one of claims 1 to 6, characterized in that: An optical fiber channel is provided in the elastic body, and the inner optical fiber of the optical cable passes through the optical fiber channel and is respectively connected to the N first optical fiber gratings and the N second optical fiber gratings.

8. A method for detecting looseness of an axle counter sensor according to any one of claims 1 to 7, characterized in that: The following steps are involved: Acquire in real time the reflection wavelengths of N first fiber gratings and the reflection wavelengths of the second fiber gratings; Temperature compensation is performed on the reflection wavelengths of the N first fiber gratings by using the reflection wavelength collected in real time by the second fiber grating to obtain the reflection wavelengths of the N first fiber gratings after temperature compensation; According to the change amount of the reflection wavelength of the first fiber grating after temperature compensation and the looseness detection threshold of the first fiber grating, it is determined whether the axle counting sensor and the rail are loose or falling off.

9. The method for detecting looseness of an axle counter sensor according to claim 8, characterized in that: The following steps are also included: An axle counter sensor is installed between two rail sleepers, and a set preload force is applied between the elastic body and the rail to obtain N reflection wavelengths of the first fiber Bragg grating after installation and the second fiber Bragg grating after installation; The looseness detection threshold of each first fiber grating is determined according to the reflection wavelength of each first fiber grating after installation and the change of the reflection wavelength of each first fiber grating when the train passes the rail under different pre-tightening forces of the elastic body and the rail.

10. The method for detecting looseness of an axle counter sensor according to claim 9, characterized in that: According to the reflection wavelength of each first fiber Bragg grating after installation and the change amount of the reflection wavelength of each first fiber Bragg grating when the train passes the rail under different pre-tightening forces of the elastic body and the rail, the looseness detection threshold of each first fiber Bragg grating is determined, including: Acquire a first change in the reflection wavelength of the first fiber grating when a train passes over the rail at a set preload value; The preload force value applied by the fastening assembly to the clamping block is gradually reduced on the basis of the set preload force value, and the second change amount of the reflection wavelength of each first fiber Bragg grating when the train passes over the rail at the current preload force value is obtained in real time, wherein the first change amount and the second change amount are both the difference between the maximum value of the reflection wavelength of the first fiber Bragg grating when the train passes over the rail and the reflection wavelength after the first fiber Bragg grating is installed; When the difference between the first variation and the second variation reaches a set value, the difference between the reflection wavelength of each first fiber grating after installation and the reflection wavelength under the current preload value is determined as a looseness detection threshold.

11. The method for detecting looseness of an axle counter sensor according to any one of claims 8 to 10, characterized in that: The following steps are also included: The number of the passing train wheel axles and the passing direction of the wheels are determined according to the reflected wavelengths of the N first optical fiber gratings acquired in real time.

12. The method for detecting looseness of an axle counter sensor according to any one of claims 8 to 10, characterized in that: The method comprises the following steps: performing temperature compensation on the reflection wavelengths of N first fiber gratings by using the reflection wavelength collected in real time by the second fiber grating to obtain the reflection wavelengths of the N first fiber gratings after temperature compensation: Determine a proportionality coefficient between the change in reflection wavelength after each first fiber grating is installed and the change in reflection wavelength after each second fiber grating is installed; According to the proportionality coefficient, the reflection wavelength collected in real time by the second fiber grating and the reflection wavelength after the second fiber grating is installed, temperature compensation is performed on the reflection wavelength of each first fiber grating to obtain the reflection wavelengths of N first fiber gratings after temperature compensation.

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