A smart cable on-site calibration method with built-in fiber grating sensor

Abstract

The present invention discloses an on-site calibration method for a smart cable with a built-in fiber grating sensor. The smart cable is erected on-site to a certain height above an already placed ordinary cable so that it is in full contact with the environment and the stress of the reel is released. At the same time, an external temperature and humidity sensor arranged along the smart cable and the built-in fiber grating sensor are used to calibrate monitoring data. This can solve the problem that the super-long smart cable cannot be calibrated in the factory. The entire on-site calibration method is simple to operate, the reference wavelength data recorded by the calibration is accurate, the monitoring data converted subsequently is highly accurate, and the calibration process has little impact on the on-site construction progress, the on-site acceptance is high, and it is easy to promote and apply.

Description

Technical Field

[0001] The present invention relates to the technical field of suspension bridge construction, and more specifically, to a smart cable strand on-site calibration method with a built-in fiber grating sensor. Background Art

[0002] With the continuous breakthrough in the construction scale of domestic suspension bridges, the role of the main cable strand as the main load-bearing and non-replaceable component of the suspension bridge has become increasingly prominent. In order to accurately evaluate the working and environmental status of the main cable of the suspension bridge, many researchers at home and abroad have proposed to place fiber grating sensors inside the main cable to intuitively obtain various state parameter data of the main cable, thereby realizing the evaluation of the main cable status and ensuring the safety of the bridge structure.

[0003] During the factory manufacturing stage, it is obviously unreasonable to calibrate the smart cable strands with built-in fiber grating sensors directly in the factory to simulate the on-site installation state because the cables are several kilometers long. Calibration is performed on the entire smart cable strand after it is rolled, and the reference wavelength of each fiber grating sensor in the smart cable strand and the corresponding reference monitoring physical quantities such as temperature, strain, relative humidity, etc. are recorded. This is inconsistent with the actual state of the smart cable strand after it is installed on site, so in-factory calibration is not feasible. Summary of the invention

[0004] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0005] Another object of the present invention is to provide a method for on-site calibration of a smart cable with a built-in fiber grating sensor, so as to solve the technical problem that the existing method of calibrating a smart cable with a built-in fiber grating sensor in a factory cannot ensure that the data is consistent with reality and is not scientific enough.

[0006] In order to achieve these purposes and other advantages according to the present invention, a method for on-site calibration of a smart cable strand with a built-in fiber grating sensor is provided, comprising the following steps:

[0007] S1. Pull the smart cable with built-in fiber grating sensor into place according to the construction process of ordinary cable, put it into the saddle and anchor it. Before anchoring, lift the smart cable at the side span and middle span of the suspension bridge to avoid contact with the ordinary cable below.

[0008] S2. Arrange multiple external sensors along the surface of the smart cable strand. The external sensors are temperature and humidity sensors. The number of temperature and humidity sensors is not less than 9, covering the positions of the smart cable strands in the anchor room, loose cable saddle, side span, middle span, and main cable saddle. The temperature and humidity sensors monitor the same physical quantity type as the fiber Bragg grating sensor, and the measurement accuracy of the temperature and humidity sensors is better than that of the fiber Bragg grating sensor.

[0009] S3, collecting wavelength data of the fiber grating sensor and data of the temperature and humidity sensor in the smart cable strand at the same collection frequency, and the collection time is not less than 24 hours;

[0010] S4, analyzing and processing the data obtained in step S3, comparing the monitoring data of the fiber Bragg grating sensor and the temperature and humidity sensor, and when the data change patterns of the two are consistent, selecting the data of the current fiber Bragg grating sensor as the reference wavelength of the subsequent monitoring data and the reference value corresponding to the calculation of other physical quantities;

[0011] S5. Remove the temperature and humidity sensors on the surface of the smart cable along the line to complete the calibration of the smart cable.

[0012] Preferably, the number of the temperature and humidity sensors is calculated cumulatively by arranging one additional sensor for every 100 m increase in altitude.

[0013] Preferably, the height of the smart cable strand located at the side span relative to the ordinary cable strand installed below is greater than 10 cm, and the height of the smart cable strand located at the middle span relative to the ordinary cable strand installed below is greater than 20 cm.

[0014] Preferably, in step S4, when the monitoring data change patterns of the fiber Bragg grating sensor and the temperature and humidity sensor within 24 hours are inconsistent, add another set of collection cycles with a time of 24 hours to obtain the collected data for comparison, and the collection cycle is accumulated to 72 hours at most. When the monitoring data change patterns of the fiber Bragg grating sensor and the temperature and humidity sensor within 72 hours are still inconsistent, replace the current smart cable.

[0015] Preferably, in step S1, wire rope winches are respectively connected to both ends of the smart cable strand to achieve lifting of the smart cable strand.

[0016] The present invention includes at least the following beneficial effects: the on-site calibration method of the smart cable with built-in fiber grating sensors of the present invention is applicable to the calibration of cables with various built-in fiber grating sensors, and the smart cable is erected on-site to a certain height above the ordinary cable that has been placed, so that it is fully in contact with the environment and the stress of the reel is released, and at the same time, the external temperature and humidity sensors arranged along the smart cable and the built-in fiber grating sensors are used to calibrate the monitoring data, which can solve the problem that the super-long smart cable cannot be calibrated in the factory. The entire on-site calibration method is simple to operate, the reference wavelength data recorded by the calibration is accurate, the monitoring data converted subsequently is highly accurate, and the calibration process has little impact on the on-site construction progress, the on-site acceptance is high, and it is easy to promote and apply.

[0017] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the process of the present invention;

[0019] Figure 2 It is a schematic diagram of the longitudinal structure of the present invention when the temperature and humidity sensors are arranged;

[0020] Figure 3 It is a schematic diagram of the cross-sectional structure of the present invention when the temperature and humidity sensors are arranged;

[0021] Figure 4 The temperature-time curve diagram drawn by the present invention according to the grating sensor data in Table 1;

[0022] Figure 5 The temperature-time curve diagram drawn by the present invention according to the temperature and humidity sensor data in Table 3;

[0023] Figure 6 For this Figure 4 and Figure 5 Comparison graph of corresponding data;

[0024] Figure numerals in the specification: 1. smart cable strand, 2. ordinary cable strand, 3. fiber grating sensor, 4. temperature and humidity sensor, 5. collection equipment, 6. anchor chamber, 7. loose cable saddle, 8. side span, 9. main cable saddle, 10. middle span. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0026] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0027] like Figure 1-6 As shown, the present invention provides a smart cable strand on-site calibration method with a built-in fiber grating sensor, comprising the following steps:

[0028] S1. Combination Figure 2As shown, the smart cable strand 1 with built-in fiber Bragg grating sensors 3 is pulled into place and anchored according to the construction process of the common cable strand 2. Before anchoring, the smart cable strand 1 is raised at the side span 8 and the middle span 10 of the suspension bridge to avoid contact with the ordinary cable strand 2 installed below. The cable strand with the fiber Bragg grating sensor 3 installed inside for measuring various physical quantity parameters is called the smart cable strand 1. For the convenience of explanation, the raised height is set to H.

[0029] S2. Arrange multiple temperature and humidity sensors 4 along the surface of the smart cable strand 1 and temporarily fix them with tape or rope. The number of temperature and humidity sensors 4 is not less than 9, covering the positions of the smart cable strand 1 in the anchor chamber 6, the loose cable saddle 7, the side span 8, the middle span 10, and the main cable saddle 9. The probes of the temperature and humidity sensors 4 should be close to the surface of the smart cable strand 1. The radial cross-sectional diagram of the arrangement is as follows: Figure 3 As shown, the temperature and humidity sensor 4 monitors the same type of physical quantities as the fiber Bragg grating sensor 3 , and the measurement accuracy of the temperature and humidity sensor 4 is better than that of the fiber Bragg grating sensor 3 .

[0030] S3, collecting wavelength data of the fiber Bragg grating sensor 3 and the data of the temperature and humidity sensor 4 in the smart cable strand 1 at the same collection frequency, and the collection time is not less than 24 hours. The data of the fiber Bragg grating sensor 3 and the temperature and humidity sensor 4 are received by the collection device 5 connected by external communication, and the collected data is stored in the computer terminal.

[0031] S4, analyzing and processing the data obtained in step S3, comparing the monitoring data of the fiber Bragg grating sensor 3 and the temperature and humidity sensor 4, when the data change patterns of the two are consistent, selecting the data of the current fiber Bragg grating sensor 3 as the reference wavelength of the subsequent monitoring data and the reference value corresponding to the calculation of other physical quantities.

[0032] S5. Remove the temperature and humidity sensors 4 on the surface of the smart cable 1 along the line to complete the calibration of the smart cable 1.

[0033] This embodiment provides a specific data analysis case, such as Figure 2 As shown, the two ends of the bridge are symmetrically arranged, divided into anchor room, loose cable saddle, side span, middle span, and main cable saddle, and a total of at least 9 areas. Taking one of the anchor room areas as an example, there are a total of 5 measuring points of the built-in fiber grating sensor corresponding to the anchor room area on the smart cable strand, which are numbered and the reference wavelength is also called the initial wavelength. The data is shown in Table 1 below:

[0034] Table 1 Wavelength data collected by the built-in fiber Bragg grating sensor

[0035] Time / raster number 1 2 3 4 5 00:00 1550324 1552335 1550317 1552333 1550348 01:00 1550322 1552334 1550315 1552331 1550345 02:00 1550322 1552333 1550315 1552329 1550344 …… 22:00 1550317 1552325 1550307 1552322 1550337 23:00 1550313 1552323 1550303 1552320 1550335 24:00 1550312 1552320 1550302 1552317 1550333

[0036] Assume that the reference wavelength and reference temperature corresponding to grating numbers 1 to 5 are the data in the table below, and the temperature sensitivity coefficient is K. K is determined according to the specific fiber grating sensor selected. Here, K=10.6pm / °C.

[0037] Table 2 Assumed grating reference wavelength and reference temperature

[0038] Raster number 1 2 3 4 5 Reference wavelength 1550324 1552335 1550317 1552333 1550348 Reference wavelength corresponding to temperature 23.2 23.2 23.2 23.2 23.2

[0039] After linear conversion, the wavelength change is converted into temperature, and the curve is as follows Figure 4 As shown, in Figure 4 The curves corresponding to the grating numbers 1-5 are also the curves corresponding to the time from top to bottom at 14:24. The temperature data recorded by the temperature and humidity sensors installed in the anchor room area are shown in Table 3 below. Figure 5 shown.

[0040] Table 3 Temperature data collected by external sensors

[0041] time temperature 00:00 23.2 01:00 23 02:00 23 …… 22:00 23.5 23:00 23.5 24:00 23.4

[0042] The curve Figure 4 Data and curves Figure 5 By comparing the data, we can get Figure 6 From the comparison shown, we can see that in the early morning when the ambient temperature is relatively constant, the temperature difference measured by the built-in fiber grating sensor and the temperature and humidity sensor in the same area is controlled within 1°C, and the time patterns of temperature rise, temperature drop and maximum value are also consistent, indicating that the assumptions in Table 2 above are established, that is, the data in Table 2 can be used as the reference wavelength and reference temperature expressed by the smart cable.

[0043] In another technical solution, Figure 1-3 As shown, the number of temperature and humidity sensors is calculated cumulatively with one additional sensor for every 100m increase in altitude. On the basis of setting a minimum of 9 temperature and humidity sensors, additional temperature and humidity sensors are added according to the altitude change of the entire smart cable strand to improve the scientific nature of monitoring, improve data reliability, and ensure that the monitoring covers the entire length range of the smart cable strand normally and completely.

[0044] In another technical solution, Figure 1-3 As shown, the height of the smart cable strand located at the side span relative to the ordinary cable strand installed below is greater than 10 cm, and the height of the smart cable strand located at the middle span relative to the ordinary cable strand installed below is greater than 20 cm. The length of the smart cable strand located at the middle span is greater, and there are curvatures on both sides. By setting a certain height difference range, it is ensured that the smart cable strand does not contact the ordinary cable strand below, so as not to affect the accuracy of the monitoring data.

[0045] In another technical solution, Figure 1-3 As shown, in step S4, when the monitoring data change patterns of the fiber Bragg grating sensor and the temperature and humidity sensor within 24 hours are inconsistent, a group of collection cycles with a time of 24 hours is added to obtain the collected data for comparison, and the collection cycle is accumulated to 72 hours at most. When the monitoring data change patterns of the fiber Bragg grating sensor and the temperature and humidity sensor within 72 hours are still inconsistent, it indicates that the smart cable with the built-in fiber Bragg grating sensor cannot measure the external environment state, and the current smart cable needs to be replaced.

[0046] In another technical solution, Figure 1-3 As shown, in step S1, wire rope winches are respectively connected to both ends of the smart cable strand to achieve the lifting of the smart cable strand. For the operation of the smart cable strand, the wire rope is retracted by the wire rope winch and the conventional cable strand lifting process can be performed.

[0047] The on-site calibration method of the smart cable with built-in fiber grating sensor of the present invention is to set up the smart cable on-site to a certain height above the ordinary cable that has been placed, so that it is fully in contact with the environment and releases the stress of the reel. At the same time, the external temperature and humidity sensor arranged on the smart cable along the line and the built-in fiber grating sensor are used to calibrate the monitoring data, which can solve the problem that the super-long smart cable cannot be calibrated in the factory. The whole on-site calibration method is simple to operate, the reference wavelength data recorded by the calibration is accurate, the monitoring data converted subsequently is highly accurate, and the calibration process has little impact on the on-site construction progress, the on-site acceptance is high, and it is easy to promote and apply.

[0048] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for on-site calibration of a smart cable with a built-in fiber grating sensor, characterized in that: The steps include: S1. Pull the smart cable with built-in fiber grating sensor into place according to the construction process of ordinary cable, put it into the saddle and anchor it. Before anchoring, lift the smart cable at the side span and middle span of the suspension bridge to avoid contact with the ordinary cable below. S2. Arrange multiple external sensors along the surface of the smart cable strand. The external sensors are temperature and humidity sensors. The number of temperature and humidity sensors is not less than 9, covering the positions of the smart cable strands in the anchor room, loose cable saddle, side span, middle span, and main cable saddle. The temperature and humidity sensors monitor the same physical quantity type as the fiber Bragg grating sensor, and the measurement accuracy of the temperature and humidity sensors is better than that of the fiber Bragg grating sensor. S3, collecting wavelength data of the fiber grating sensor and data of the temperature and humidity sensor in the smart cable strand at the same collection frequency, and the collection time is not less than 24 hours; S4, analyzing and processing the data obtained in step S3, comparing the monitoring data of the fiber Bragg grating sensor and the temperature and humidity sensor, and when the data change patterns of the two are consistent, selecting the data of the current fiber Bragg grating sensor as the reference wavelength of the subsequent monitoring data and the reference value corresponding to the calculation of other physical quantities; In step S4, when the monitoring data change patterns of the fiber Bragg grating sensor and the temperature and humidity sensor within 24 hours are inconsistent, add another set of 24-hour collection cycles to obtain the collected data for comparison. The collection cycle is accumulated to 72 hours at most. When the monitoring data change patterns of the fiber Bragg grating sensor and the temperature and humidity sensor within 72 hours are still inconsistent, replace the current smart cable strand; S5. Remove the temperature and humidity sensors on the surface of the smart cable along the line to complete the calibration of the smart cable.

2. The on-site calibration method of a smart cable with a built-in fiber grating sensor as claimed in claim 1, characterized in that: The number of the temperature and humidity sensors is calculated cumulatively by arranging one additional sensor for every 100 m increase in altitude.

3. The on-site calibration method of a smart cable with a built-in fiber grating sensor as claimed in claim 1, characterized in that: The height of the smart cable strand located at the side span relative to the ordinary cable strand installed below is greater than 10 cm, and the height of the smart cable strand located at the middle span relative to the ordinary cable strand installed below is greater than 20 cm.

4. The on-site calibration method of a smart cable with a built-in fiber grating sensor as claimed in claim 1, characterized in that: In step S1, wire rope winches are respectively connected to both ends of the smart cable strand to achieve the lifting of the smart cable strand.

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