A method for installing an optical fiber sensor

Abstract

This invention relates to the field of fiber optic grating monitoring of structural stress in crane machinery, and discloses a method for installing a fiber optic sensor, comprising: determining the installation direction of the fiber optic sensor at the measured point, thereby facilitating the determination of the installation position of the fiber optic sensor; pre-treating the surface of the measured point to keep the surface clean, facilitating the welding of the fiber optic sensor; wherein, the measured point is the location point measured by the fiber optic sensor; pre-treating the surface of the measured point of the fiber optic sensor includes pre-positioning the fiber optic sensor to ensure accurate subsequent installation; pre-positioning the fiber optic sensor includes: mounting the fiber optic sensor on a pre-positioning device; fixing the fiber optic sensor to the measured point using the pre-positioning device; and welding the fiber optic sensor. By using a pre-positioning device to temporarily position the fiber optic sensor, the accurate installation position of the fiber optic sensor can be ensured, thereby enabling long-term, reliable monitoring of the stress in the crane structure.

Description

Technical Field

[0001] This invention relates to the field of fiber optic grating monitoring of structural stress in lifting machinery, and in particular to a method for installing a fiber optic sensor. Background Technology

[0002] Fiber optic sensors have gained widespread attention and achieved remarkable results in recent years in fields such as civil engineering, aerospace, bridge and tunnel engineering, and marine exploration due to their advantages including light weight, small size, high sensitivity, strong resistance to electromagnetic interference, flexible multiplexing capabilities, and ease of implementing distributed or quasi-distributed measurements. However, in structural health monitoring systems, fiber optic sensors, as the primary instruments for signal acquisition, are typically attached to the structural surface or embedded within the structure. They are highly susceptible to harsh environments such as high temperature, high pressure, and strong corrosion, leading to performance degradation. Degraded fiber optic sensors will malfunction, resulting in discrepancies between the signals acquired by the monitoring system and the actual structural condition, potentially leading to incorrect assessments of the health status of the measured structure.

[0003] Currently, there are three main methods for installing fiber optic sensors on steel structure surfaces: bonding, riveting, and spot welding. Bonding is limited by the properties of the adhesive, resulting in low strain transfer efficiency and poor long-term stability, thus failing to meet long-term monitoring requirements. Riveting requires drilling into the structure being measured, damaging the original structure and is generally not permitted. Spot welding offers advantages such as stable strain transfer performance, high connection strength, and no damage to the measured structure, making it suitable for long-term monitoring in harsh environments and the most ideal installation method for engineering applications.

[0004] However, fiber optic sensors are small in size, lightweight, and highly sensitive, making spot welding very difficult, which leads to unsatisfactory installation results. Summary of the Invention

[0005] The purpose of this invention is to provide a method for installing fiber optic sensors to solve the technical problem of unsatisfactory installation results in existing fiber optic sensor installation methods.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A method for installing an optical fiber sensor, comprising:

[0008] Determine the installation orientation of the fiber optic sensor at the point being measured;

[0009] The surface of the measured point is pre-processed; wherein, the measured point is the location point measured by the fiber optic sensor;

[0010] The preprocessing of the surface of the measured point of the fiber optic sensor includes pre-positioning the fiber optic sensor; the pre-positioning of the fiber optic sensor includes:

[0011] The fiber optic sensor is installed on the pre-positioning device;

[0012] The fiber optic sensor is fixed to the point being measured using the pre-positioning device.

[0013] The fiber optic sensor is welded.

[0014] Preferably, mounting the fiber optic sensor on the pre-positioning device includes:

[0015] The sensor mounting welding column of the fiber optic sensor is coaxially aligned with the welding column extension sleeve of the prepositioning device.

[0016] The sensor mounting welding post is installed inside the extension bushing of the welding post.

[0017] Preferably, fixing the fiber optic sensor to the measured point using the pre-positioning device includes:

[0018] The prepositioning device is moved on the mounting surface where the fiber optic sensor is installed until the fiber optic sensor is placed on the measured point.

[0019] Preferably, the pre-positioning device includes the welding column extension sleeve, a guide plate, a compression spring, a bracket, and a positioning magnet. The guide plate, the compression spring, and the bracket are sequentially sleeved on the welding column extension sleeve. A guide shaft is provided on the guide plate, and the bracket is sleeved on the guide shaft. A retaining spring is provided on the upper part of the guide shaft to limit the axial distance between the guide plate and the bracket. The compression spring is provided on the guide plate, and the positioning magnet is fixedly connected to the end of the bracket by bolts. The number of the welding column extension sleeve, the compression spring, and the positioning magnet are all two.

[0020] Preferably, determining the installation direction of the fiber optic sensor includes:

[0021] Establish a finite element model of the device under test;

[0022] The direction of the maximum principal stress is determined based on the finite element model as the installation direction of the fiber optic sensor.

[0023] Preferably, before pre-positioning the fiber optic sensor, the pre-processing of the surface of the measured point further includes:

[0024] Rust removal was performed on the measured points;

[0025] The test point is polished;

[0026] The test points are cleaned.

[0027] Preferably, welding the fiber optic sensor includes:

[0028] Set the parameters for the spot welding machine;

[0029] Wipe the polished surface of the test point clean with an alcohol swab.

[0030] The fiber optic sensor is spot-welded to the point being measured using the spot welding machine.

[0031] Preferably, the method further includes:

[0032] The optical fiber cable for the fiber optic sensor is laid.

[0033] The laying of the optical cable for the fiber optic sensor includes:

[0034] Determine the bending radius of the optical cable;

[0035] The fiber optic sensor and fiber optic connector are protected by a cover plate;

[0036] Secure the optical cable with cable ties, thread the secured optical cable into the flexible tube, and place the flexible tube inside.

[0037] Preferably, the method further includes:

[0038] The welding quality of the fiber optic sensor was inspected using a fiber optic grating demodulator, and the inspection results were obtained.

[0039] If the inspection results are unsatisfactory, the fiber optic sensor shall be re-welded.

[0040] If the test results are satisfactory, there is no need to re-weld the fiber optic sensor.

[0041] Preferably, the step of using a fiber optic grating demodulator to inspect the welding quality of the fiber optic sensor and obtaining the inspection results includes:

[0042] The initial reading of the center wavelength of the fiber optic sensor is measured using the fiber optic grating demodulator.

[0043] The post-welding center wavelength of the fiber optic sensor was measured using the fiber optic grating demodulator.

[0044] Determine the difference between the post-weld center wavelength and the initial reading;

[0045] If the difference is greater than the maximum allowable value, the test result is unqualified.

[0046] If the difference is not greater than the maximum allowable value, then the test result is qualified.

[0047] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0048] The fiber optic sensor installation method provided by this invention includes: determining the installation direction of the fiber optic sensor at the measured point; pre-processing the surface of the measured point; pre-processing the surface of the measured point of the fiber optic sensor includes pre-positioning the fiber optic sensor; pre-positioning the fiber optic sensor includes: installing the fiber optic sensor on a pre-positioning device; fixing the fiber optic sensor to the measured point using the pre-positioning device; and welding the fiber optic sensor. The pre-positioning device provides temporary positioning of the fiber optic sensor, ensuring accurate installation and enabling long-term, reliable monitoring of the stress on the crane structure. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 A schematic diagram of the fiber optic sensor mounting pre-positioning device provided by the present invention;

[0051] Figure 2 Exploded view of the fiber optic sensor mounting pre-positioning device provided by the present invention;

[0052] Figure 3 This is a half-sectional view of the welding column extension bushing provided by the present invention;

[0053] in:

[0054] 1-Bracket; 2-Welding column extension sleeve; 3-Guide plate; 4-Compression spring; 5-Positioning magnet; 6-Fiber optic sensor; 101-First bracket hole; 102-Second bracket hole; 104-Third bracket hole; 201-Upper shaft; 202-Lower hole; 301-Snap ring; 302-Guide shaft; 303-Guide pressure plate; 304-Guide hole; 502-Nut; 503-Washer; 504-Bolt; 602-Sensor mounting welding column. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] The purpose of this invention is to provide an installation method for fiber optic sensors to solve the technical problem that the installation effect of existing fiber optic sensors is not ideal.

[0057] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] like Figures 1-3 As shown in the embodiments of this specification, an installation method for an optical fiber sensor 6 is provided, including: determining the installation direction of the optical fiber sensor 6 at the measured point to facilitate the reasonable setting of the number of optical fiber sensors; pre-treating the surface of the measured point to keep it clean for subsequent welding of the optical fiber sensor 6, wherein the measured point is the position point measured by the optical fiber sensor 6; pre-treating the surface of the measured point of the optical fiber sensor 6 includes pre-positioning the optical fiber sensor 6 to ensure accurate installation position of the optical fiber sensor; pre-positioning the optical fiber sensor 6 includes: mounting the optical fiber sensor 6 on a pre-positioning device; fixing the optical fiber sensor 6 to the measured point using the pre-positioning device; and welding the optical fiber sensor, mainly using spot welding. By using the pre-positioning device to temporarily position the optical fiber sensor 6, accurate installation position can be ensured, thereby enabling long-term, reliable monitoring of the structural stress of the device under test.

[0059] Installing the fiber optic sensor 6 on the pre-positioning device includes: aligning the sensor mounting welding post 602 of the fiber optic sensor 6 coaxially with the welding post extension sleeve 2 of the pre-positioning device; and installing the sensor mounting welding post 602 inside the welding post extension sleeve 2.

[0060] Fixing the fiber optic sensor 6 to the measured point using a pre-positioning device includes: moving the pre-positioning device on the mounting surface of the fiber optic sensor 6; the pre-positioning device is attracted to the steel structure surface of the lifting machinery by the attraction of a positioning magnet until the fiber optic sensor 6 is placed on the measured point.

[0061] The pre-positioning device includes a welding column extension sleeve 2, a guide plate 3, a compression spring 4, a bracket 1, and a positioning magnet 5. The guide plate 3, the compression spring 4, and the bracket 1 are sequentially mounted on the welding column extension sleeve 2. A guide shaft 302 is provided on the guide plate 3, and the bracket 1 is mounted on the guide shaft 302. A retaining ring 301 is provided on the upper part of the guide shaft 302 to limit the axial distance between the guide plate 3 and the bracket 1. The compression spring 4 is provided on the guide plate 3, and the positioning magnet 5 is fixedly connected to the end of the bracket 1 by bolts 504. There are two welding column extension sleeves 2, two compression springs 4, and two positioning magnets 5.

[0062] The specific relative positions of the components of the pre-positioning device include: the upper shaft 201 of the welding column extension sleeve 2 passes through the second bracket hole 102 on the bracket 1; the lower hole 202 of the welding column extension sleeve 2 is fitted into the sensor mounting welding column 602 of the fiber optic sensor 6; the sensor mounting welding column 602 passes through the guide hole 304 on the guide pressure plate 303; the guide shaft 302 on the guide pressure plate 3 passes through the first bracket hole 101 on the bracket 1; the compression spring 4 is sleeved on the welding column extension sleeve 2 and placed between the guide pressure plate 3 and the bracket 1; the guide shaft 302 on the guide plate 3 is equipped with a snap ring 301, which is used to limit the displacement of the bracket 1 and the guide plate 3 along the axial direction of the guide shaft 302 within a certain range; the bolt 504 passes through the third bracket hole 104 on the bracket 1; and the positioning magnet 5 is fixed to the bracket 1 by the nut 502, the washer 503, and the bolt 504.

[0063] The specific usage method of the sensor pre-positioning device includes: after placing the fiber optic sensor on the device under test, aligning the welding post extension sleeve 2 on the sensor pre-positioning device coaxially with the sensor mounting welding post 602, fitting the welding post extension sleeve 2 onto the sensor mounting welding post 602, and then moving the sensor pre-positioning device toward the mounting surface until the fiber optic sensor reaches the measured point. The optical fiber sensor is then attracted to the measured point using the attraction force of the positioning magnet 5. The sensor is pre-positioned in the mounting position by the attraction force of the positioning magnet 5 and the spring force of the compression spring 4. The sensor pre-positioning device can be removed after welding is completed.

[0064] Determining the installation direction of the fiber optic sensor 6 includes: establishing a finite element model of the device under test, which is mainly a lifting machine; determining the direction of the maximum principal stress as the installation direction of the fiber optic sensor 6 based on the finite element model, in order to reduce the number of fiber optic sensors 6 to be arranged.

[0065] Before pre-positioning the fiber optic sensor 6, the surface of the measured point is pre-treated, which also includes: removing rust from the measured point; specifically, using a grinder or angle grinder to remove paint, electroplating, oxide film, oil stains, rust spots and other covering layers at the measuring point location of the lifting machinery structure.

[0066] The measurement point needs to be polished; specifically, this involves polishing with sandpaper of 220-400 grit, ensuring the sandpaper marks are at a 45° angle to the sensor's orientation and are applied intersectingly. The polished area depends on the actual sensor size and installation method. If the sensor is not to be installed immediately, protective measures must be taken, or the area should be polished again during installation.

[0067] Clean the test point. Specifically, surface cleaning can be done using organic solvents such as acetone, anhydrous ethanol, trichloroethane, and isopropanol. First, use a cotton swab (or cloth) to remove any debris and rust from the grinding process around the test point; then, use a clean cotton swab dipped in organic solvent to wipe away stains and oil from the test point surface; next, repeatedly clean the test point surface with a clean cotton ball soaked in organic solvent, using a unidirectional or spiral cleaning method from the inside out until there are no stains on the cotton ball. Then, dry the surface with a clean cotton ball or by baking.

[0068] The process of welding the fiber optic sensor 6 includes: setting the parameters of the spot welding machine; specifically, selecting a voltage output of 70-75V, a welding time of approximately 3 milliseconds, and ensuring the electrode head is perpendicular to the surface of the crane's structure under test and applying a certain pressure (50-100N). The surface of the test point, after polishing, is cleaned with an alcohol swab; the fiber optic sensor 6 is then spot-welded to the test point using the spot welding machine.

[0069] The method also includes laying the optical cable for the optical fiber sensor 6. Laying the optical cable for the optical fiber sensor 6 specifically includes determining the bending radius of the optical cable. The smaller the bending radius of the optical fiber, the greater the impact on the reflection spectrum of the optical fiber sensor. When the optical fiber radius decreases to a certain extent, the spectrometer cannot scan the true reflection spectrum of the optical fiber sensor, and the center wavelength of the optical fiber sensor cannot be read, causing the optical fiber sensor to fail. When the bending radius of the optical fiber increases to a certain extent, the reflection spectrum of the optical fiber sensor is not affected by the change in bending radius. Therefore, it is necessary to bend the optical cable and adjust it according to the spectrum until the spectrum stabilizes, thereby determining the bending radius of the optical cable. The bending radius of the optical cable should be controlled within an appropriate range, R>10cm.

[0070] The fiber optic sensor 6 and the fiber optic cable connector are protected by a cover plate. Specifically, the fiber optic sensor is protected by a cover plate made of angle steel or channel steel. The fiber optic cable is secured with cable ties, and then the secured cable is threaded into a flexible conduit. The purpose of this arrangement is to protect the fiber optic cable.

[0071] The method also includes: using a fiber optic grating demodulator to inspect the welding quality of the fiber optic sensor 6 and obtaining the inspection result; if the inspection result is unqualified, the fiber optic sensor 6 is re-welded; if the inspection result is qualified, there is no need to re-weld the fiber optic sensor 6.

[0072] The welding quality of fiber optic sensor 6 is inspected using a fiber optic grating demodulator, and the inspection results are obtained, including: measuring the initial reading of the center wavelength of fiber optic sensor 6 using the fiber optic grating demodulator; measuring the center wavelength of fiber optic sensor 6 after welding using the fiber optic grating demodulator; determining the difference between the center wavelength after welding and the initial reading; if the difference is greater than the maximum allowable value, the inspection result is unqualified; if the difference is not greater than the maximum allowable value, the inspection result is qualified.

[0073] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0074] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for installing an optical fiber sensor, characterized in that, include: Determine the installation orientation of the fiber optic sensor at the point being measured; The surface of the measured point is pre-processed; wherein, the measured point is the location point measured by the fiber optic sensor; The preprocessing of the surface of the measured point of the fiber optic sensor includes pre-positioning the fiber optic sensor; the pre-positioning of the fiber optic sensor includes: The fiber optic sensor is mounted on the pre-positioning device, and the sensor mounting welding post of the fiber optic sensor is coaxially aligned with the welding post extension sleeve of the pre-positioning device; the sensor mounting welding post is installed inside the welding post extension sleeve. The fiber optic sensor is fixed to the measured point using the pre-positioning device. The pre-positioning device is moved along the mounting surface of the fiber optic sensor until the fiber optic sensor is placed on the measured point. The pre-positioning device includes a welding column extension sleeve, a guide plate, a compression spring, a bracket, and a positioning magnet. The guide plate, the compression spring, and the bracket are sequentially sleeved on the welding column extension sleeve. A guide shaft is provided on the guide plate, and the bracket is sleeved on the guide shaft. A retaining ring is provided on the upper part of the guide shaft to limit the axial distance between the guide plate and the bracket. The compression spring is provided on the guide plate, and the positioning magnet is fixedly connected to the end of the bracket by bolts. The welding column extension sleeve, the compression spring, and the bracket are all part of the pre-positioning device. The number of springs and positioning magnets are both two; the upper shaft of the welding column extension sleeve passes through the second bracket hole on the bracket, the lower hole of the welding column extension sleeve is fitted into the sensor mounting welding column of the fiber optic sensor, the sensor mounting welding column passes through the guide hole on the guide plate, the guide shaft on the guide plate passes through the first bracket hole on the bracket, the compression spring is sleeved on the welding column extension sleeve and placed between the guide plate and the bracket, the guide shaft on the guide plate is equipped with the snap ring, which is used to limit the displacement between the bracket and the guide plate along the axial direction of the guide shaft within a certain range, the bolt passes through the third bracket hole on the bracket, and the positioning magnet is fixed on the bracket by a nut, a washer, and the bolt; The fiber optic sensor is welded.

2. The installation method of the fiber optic sensor according to claim 1, characterized in that, Determining the installation orientation of the fiber optic sensor at the measured point includes: Establish a finite element model of the device under test; The direction of the maximum principal stress is determined based on the finite element model as the installation direction of the fiber optic sensor.

3. The installation method of the fiber optic sensor according to claim 1, characterized in that, Before pre-positioning the fiber optic sensor, the pre-processing of the surface of the measured point further includes: Rust removal was performed on the measured points; The test point is polished; The test points are cleaned.

4. The installation method of the fiber optic sensor according to claim 3, characterized in that, The welding of the fiber optic sensor includes: Set the parameters for the spot welding machine; Wipe the polished surface of the test point clean with an alcohol swab. The fiber optic sensor is spot-welded to the point being measured using the spot welding machine.

5. The method for installing an optical fiber sensor according to claim 1, characterized in that, The method further includes: The optical cable for the optical fiber sensor is laid. The laying of the optical cable for the optical fiber sensor includes: Determine the bending radius of the optical cable; The fiber optic sensor and fiber optic connector are protected by a cover plate; Secure the optical cable with cable ties, thread the secured optical cable into the flexible tube, and place the flexible tube inside.

6. The method for installing an optical fiber sensor according to claim 1, characterized in that, The method further includes: The welding quality of the fiber optic sensor was inspected using a fiber optic grating demodulator, and the inspection results were obtained. If the inspection results are unsatisfactory, the fiber optic sensor shall be re-welded. If the test results are satisfactory, there is no need to re-weld the fiber optic sensor.

7. The method for installing an optical fiber sensor according to claim 6, characterized in that, The process of inspecting the welding quality of the fiber optic sensor using a fiber optic grating demodulator, and obtaining the inspection results, includes: The initial reading of the center wavelength of the fiber optic sensor is measured using the fiber optic grating demodulator. The post-welding center wavelength of the fiber optic sensor was measured using the fiber optic grating demodulator. Determine the difference between the post-weld center wavelength and the initial reading; If the difference is greater than the maximum allowable value, the test result is unqualified. If the difference is not greater than the maximum allowable value, then the test result is qualified.

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