Sensor device based on Bragg grating, and building structure displacement monitoring device and method
Through the combination of a sensor device based on the Bragg grating and a continuous laser, the problem of difficult to achieve high accuracy, high real-time and low interference in the existing technology is solved, and efficient and accurate monitoring of building structure displacement is achieved.
Patent Information
- Application Number
- CN202510321910.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-18
- Publication Date
- 2025-05-06
AI Technical Summary
The existing building structure displacement monitoring methods are difficult to meet the multiple requirements of high accuracy, high real-time and low interference at the same time, especially in the long-term and high-frequency monitoring of complex structures.
Using a sensor device based on Bragg grating, the combination of optical fiber bracket, signal transmitting fiber and signal receiving fiber is achieved by using a continuous laser and grating demodulator to realize real-time monitoring of building structure displacement.
It realizes high-precision and real-time monitoring of building structure displacement without damaging the integrity of the building structure, and has the advantages of strong anti-interference ability and high sensitivity.
Smart Images
Figure CN119935202A_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the technical field of building health monitoring, and specifically relates to a sensor device based on Bragg grating, a building structure displacement monitoring device and method. Background Art
[0002] The displacement of building structures is one of the important indicators to measure the stability and safety of building structures. Traditional methods for monitoring the displacement of building structures include: visual inspection, vibration testing, electrical detection, stress-strain detection, temperature detection, etc. The visual inspection method relies on experience, is highly subjective, and is difficult to detect problems with the building structure; the vibration testing method is greatly affected by environmental noise and has low sensitivity to minor damage; the electrical detection method, stress-strain detection method, temperature detection method, etc. require the installation of corresponding sensors, so it is necessary to partially modify or drill holes in the building structure, affecting the integrity of the building structure. The above common methods are difficult to simultaneously meet multiple requirements such as high accuracy, high real-time performance, and low interference when performing long-term and high-frequency monitoring of complex structures.
[0003] Acoustic detection methods can monitor the tiny displacements of building structures for a long time and at high frequencies without causing damage to the overall building structure. Commonly used acoustic detection methods include acoustic emission (AE) and ultrasonic detection (UT). Acoustic emission is a material damage detection method. Its principle is that the sound generated when a solid is deformed or damaged will be released as an elastic wave. This phenomenon is acoustic emission, and the elastic wave can be detected by an acoustic emission sensor. The occurrence and development of small deformations or tiny cracks in building structures are accompanied by the occurrence of acoustic emissions. Therefore, displacements caused by damage to building structures can be found based on acoustic emissions. The acoustic emission method relies on acoustic emissions caused by damage that has occurred. It is a passive monitoring method, and it also has shortcomings such as weak signals and susceptibility to noise interference, and the positioning of displacement sound sources is limited. Ultrasonic detection method belongs to active monitoring. The signal it generates is strong, and its anti-interference ability is also improved, which can accurately locate displacements.
[0004] However, in the current ultrasonic detection method, receivers, signal processing equipment, etc. are key issues that hinder the application of the technology. For ultrasonic detection methods, the receiver must have sufficient sensitivity and good resolution to detect tiny defects and distinguish defects. In addition, the current receivers generally have poor adaptability to the working environment, and the performance of the equipment is affected in high temperature or high humidity environments. For ultrasonic detection, noise and interference are common challenges when processing signals, so high requirements are also placed on the performance of signal processing equipment. Moreover, in the existing ultrasonic detection method, receivers, signal processing equipment and other equipment need to be highly coordinated and compatible, otherwise the detection effect will be poor. Summary of the invention
[0005] The purpose of the present application is to provide a sensor device based on Bragg grating, a building structure displacement monitoring device and method to solve the technical problems mentioned in the background technology.
[0006] On the one hand, the sensor device based on Bragg grating provided in the present application includes two optical fiber holders, a support rod, a signal transmitting optical fiber and a signal receiving optical fiber; wherein, the signal transmitting optical fiber is obtained by setting an ultrasonic signal transmitting segment on a single-mode optical fiber, and the ultrasonic signal transmitting segment is formed by stripping the cladding of the single-mode optical fiber and coating a photoacoustic conversion material in the stripping area; the signal receiving optical fiber is a fiber Bragg grating; the support rod and the signal transmitting optical fiber pass through the two optical fiber holders in parallel with each other, and the signal receiving optical fiber is fixed to one end face of the two optical fiber holders and is parallel to the signal transmitting optical fiber; and the ultrasonic signal transmitting segment of the signal transmitting optical fiber and the Bragg grating of the signal receiving optical fiber are located between the two optical fiber holders.
[0007] Furthermore, the optical fiber bracket includes a bracket body; the bracket body is provided with a first through channel and a second through channel parallel to each other, which are respectively used to insert the support rod and the signal transmitting optical fiber; a through groove parallel to the first through channel is opened at the top of the bracket body, which is used to install the signal receiving optical fiber.
[0008] Furthermore, the bracket body is also provided with an internal threaded hole extending from the side surface of the bracket body to the first through hole and perpendicular to the first through hole.
[0009] Furthermore, the photoacoustic conversion material is selected from a nano-gold composite material.
[0010] Furthermore, the nano-gold composite material is prepared by the following method:
[0011] The method comprises the following steps: mixing polydimethylsiloxane and Sylgard 184 curing agent in a mass ratio of 10:(1-3), stirring and standing for use; grinding gold salt HAuCl4·3H20 into powder in a drying oven heated to 90-100°C for use; adding the gold salt powder into the polydimethylsiloxane mixture after standing for use, stirring to disperse the gold salt powder, and obtaining a light yellow colloid mixture; wherein the mass of the gold salt powder is 3.75%-7.5% of the polydimethylsiloxane mixture; placing the light yellow colloid mixture in an ice-water mixture for ultrasonic water bathing to reduce the gold salt into gold nanospheres, thereby obtaining a nano-gold composite material; and placing the nano-gold composite material in a vacuum device for vacuum degassing.
[0012] On the other hand, the building structure displacement monitoring device provided by the present application includes a sensor device, a continuous laser, and a grating demodulator; the continuous laser is connected to the multimode optical fiber in the sensor device, used to emit laser to the multimode optical fiber, and stimulate the ultrasonic signal transmitting segment to generate an ultrasonic signal; the grating demodulator is connected to the signal receiving optical fiber, used to collect the optical signal of the signal receiving optical fiber.
[0013] Furthermore, there are multiple sensor devices, and the multiple sensor devices are connected in series through optical fibers. Specifically, the signal transmitting optical fibers are connected in series through optical fibers, and the signal receiving optical fibers are connected in series through optical fibers.
[0014] On the other hand, the present application provides a method for monitoring displacement of a building structure, using the above-mentioned building structure displacement monitoring device, comprising:
[0015] Connect the two optical fiber brackets of the sensor device to the wall to be measured; start the continuous laser to emit laser to the multimode optical fiber, and stimulate the ultrasonic signal transmitting section to generate ultrasonic signals; the grating demodulator collects the optical signal of the signal receiving optical fiber; and calculate the displacement of the wall to be measured according to the wavelength change of the optical signal of the signal receiving optical fiber.
[0016] Furthermore, before starting the continuous laser to emit laser to the multimode optical fiber, the relative positions of the two optical fiber brackets on the support rod are adjusted, so as to adjust the distance between the two optical fibers to reach a preset distance; the distance between the two optical fibers is the sensing length, which is related to the displacement monitoring sensitivity. The relationship between the sensing length and the displacement monitoring sensitivity is pre-calibrated, and the distance is preset based on the displacement monitoring sensitivity requirements.
[0017] Compared with the prior art, this application has the following advantages and beneficial effects:
[0018] It has a simple structure, small size, light weight, good corrosion resistance, strong anti-interference, high sensitivity, and can realize real-time continuous monitoring; by bonding it to the surface of the building, the displacement of the building surface can be monitored without destroying the overall structure of the building; by adjusting the distance between the two optical fiber brackets, the displacement monitoring sensitivity can be adjusted; it can be widely used in health monitoring of building structures such as houses, bridges, dams, power plants, and nuclear power plants. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0020] Figure 1 is a schematic structural diagram of a sensor device in an embodiment;
[0021] Figure 2 Schematic diagram of the structure of the optical fiber bracket in the embodiment;
[0022] Figure 3 This is a schematic diagram of the structure of the signal transmitting optical fiber in the embodiment;
[0023] Figure 4 This is a schematic diagram of the structure of the signal receiving optical fiber in the embodiment;
[0024] Figure 5 Schematic diagram of the application of the sensor device in the embodiment.
[0025] Figure numerals: first optical fiber bracket 1, bracket body 11, first through channel 12, second through channel 13, through groove 14, internal threaded channel 15, second optical fiber bracket 2, support rod 3, signal transmitting optical fiber 4, ultrasonic signal transmitting segment 41, single-mode optical fiber core 42, photoacoustic conversion material cladding 43, single-mode optical fiber cladding 44, signal receiving optical fiber 5, second single-mode optical fiber core 51, second single-mode optical fiber cladding 52, Bragg grating 53, wall 6. DETAILED DESCRIPTION
[0026] The following will be combined with the specific implementation methods of the present application to clearly and completely describe the technical solution of the present application. Obviously, the specific implementation methods described are only part of the specific implementation methods of the present application, rather than all of the specific implementation methods. Based on the implementation methods in the present application, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.
[0027] Example 1
[0028] The sensor device based on Bragg grating provided in this embodiment has a specific structure. Figure 1 It includes a first optical fiber bracket 1, a second optical fiber bracket 2, a support rod 3, a signal transmitting optical fiber 4 and a signal receiving optical fiber 5; the support rod 3 and the signal transmitting optical fiber 4 are parallel to each other and pass through the first optical fiber bracket 1 and the second optical fiber bracket 2; the signal receiving optical fiber 5 is fixed to the top of the first optical fiber bracket 1 and the second optical fiber bracket 2 and is parallel to the signal transmitting optical fiber 4.
[0029] The first optical fiber bracket 1 and the second optical fiber bracket 2 have the same structure, see Figure 2, which is a schematic diagram of the structure of the first optical fiber bracket 1 and the second optical fiber bracket 2 in a specific embodiment. The structures of the first optical fiber bracket 1 and the second optical fiber bracket 2 both include a bracket body 11. In the present specific embodiment, the bracket body 11 is in a square shape, 10 mm long, 10 mm wide, and 5 mm high; the bracket body 11 is provided with a first through hole 12 and a second through hole 13 parallel to each other, the first through hole 12 is used to insert the support rod 3, and the second through hole 13 is used to insert the signal transmitting optical fiber 4. In the present specific embodiment, the aperture of the first through hole 12 is 3 mm, and the aperture of the second through hole 13 is 1 mm; a through groove 14 parallel to the first through hole 12 is provided at the top of the bracket body 11, and the through groove 14 is used to install the signal receiving optical fiber 5. In the present specific embodiment, the width and depth of the through groove 14 are both 1 mm.
[0030] The support rod 3 passes through the first through-hole 12 of the two optical fiber brackets, the signal transmitting optical fiber 4 passes through the second through-hole 13 of the two optical fiber brackets, and the signal receiving optical fiber 5 is installed in the through-groove 14 at the top of the two optical fiber brackets, and the signal transmitting optical fiber 4 and the signal receiving optical fiber 5 remain parallel. In the present application, the support rod 3 plays a supporting role for the two optical fiber brackets, and its material is preferably a high-strength, high-toughness, corrosion-resistant, and high-temperature-resistant material, such as stainless steel, aluminum alloy, engineering plastics, ceramics, titanium alloy, etc.
[0031] Furthermore, the bracket body 11 is also provided with an internal threaded hole 15 extending from the side surface of the bracket body 11 to the first through hole 12 and perpendicular to the first through hole 12. The bracket body 11 can be fixed to the support rod 3 by screwing a screw into the internal threaded hole 15.
[0032] In this specific embodiment, the first optical fiber bracket 1 and the second optical fiber bracket 2 are prepared with polycarbonate as raw material, and a specific preparation method thereof is provided below: first, polycarbonate particles or granules are placed in an injection molding machine for heating, and the heated and melted polycarbonate is injected into an injection mold of the optical fiber bracket, and a molded optical fiber bracket is obtained after cooling; then, a deburring tool is used to clean the burrs of the optical fiber bracket to ensure its smooth surface; finally, the internal threaded hole 15 is processed in a direction perpendicular to the first through hole 12 until the internal threaded hole 15 reaches the first through hole 12.
[0033] See also Figure 3, shown is a schematic diagram of the structure of the signal transmitting optical fiber 4 in the embodiment, the signal transmitting optical fiber 4 is obtained by setting an ultrasonic signal transmitting segment 41 on a single-mode optical fiber, the ultrasonic signal transmitting segment 41 is obtained by stripping the cladding of the single-mode optical fiber and coating the photoacoustic conversion material in the stripping area to form a photoacoustic conversion material cladding 43, that is, the ultrasonic signal transmitting segment 41 includes a single-mode optical fiber core 42 and a photoacoustic conversion material cladding 43 wrapping the single-mode optical fiber core 42, and the structure of other parts on the single-mode optical fiber includes a single-mode optical fiber core 42 and a single-mode optical fiber cladding 44 covering the single-mode optical fiber core 42.
[0034] In this specific embodiment, the photoacoustic conversion material is prepared by the following method: polydimethylsiloxane PDMS and Sylgard 184 curing agent are mixed in a mass ratio of 10: (1-3), preferably in a mass ratio of 10: 3; then stirred with a glass rod for 2 minutes and allowed to stand for 1 minute for use; gold salt HAuCl4·3H20 with a purity of 99.9% is ground into powder in a drying oven heated to 90°C-100°C for use; the gold salt powder is added to the PDMS mixture after standing, and stirred with a glass rod for 20 minutes to fully disperse the gold salt powder to obtain a light yellow colloidal mixture; wherein the mass of the gold salt powder is 3.75%-7.5% of the PDMS mixture; the light yellow colloidal mixture is placed in an ice-water mixture and subjected to an ultrasonic water bath for 30 minutes to reduce the gold salt to gold nanospheres; when the mixture gradually changes from light yellow to ruby red during the reaction, the photoacoustic conversion material is obtained; the photoacoustic conversion material is placed in a vacuum device for vacuum degassing to eliminate bubbles in the photoacoustic conversion material.
[0035] See also Figure 4 , shown is a schematic structural diagram of a signal receiving optical fiber 5 in an embodiment, wherein the signal receiving optical fiber 5 is obtained by stripping off a cladding corresponding to a Bragg grating in a fiber Bragg grating, wherein the fiber Bragg grating comprises a second single-mode optical fiber core 51, a second single-mode optical fiber cladding 52 wrapping the second single-mode optical fiber core 51, and a Bragg grating 53 prepared on the second single-mode optical fiber core 51 by a phase mask method.
[0036] Example 2
[0037] This embodiment will provide a building structure displacement monitoring device and a monitoring method thereof. The building structure displacement monitoring device of this embodiment includes the sensor device of embodiment 1 and a continuous laser and a grating demodulator; the continuous laser is connected to the multimode optical fiber in the sensor device to emit laser to the multimode optical fiber and excite the ultrasonic signal emitting section 41 to generate an ultrasonic signal; the grating demodulator is connected to the signal receiving optical fiber 5, and the grating demodulator is used to send a monitoring laser to the signal receiving optical fiber 5 and collect the optical signal reflected by the signal receiving optical fiber 5.
[0038] The following will be combined Figure 5The specific implementation process of monitoring in this embodiment is provided.
[0039] (1) Adjust the relative positions of the first optical fiber bracket 1 and the second optical fiber bracket 2 on the support rod 3 to obtain the required sensing length, which is the distance between the first optical fiber bracket 1 and the second optical fiber bracket 2; screw the screw into the internal threaded hole 15 to fix the first optical fiber bracket 1 and the second optical fiber bracket 2 on the support rod 3;
[0040] The sensing length value is related to the displacement sensitivity. Different displacement sensitivities can be obtained by adjusting the sensing length. The relationship between the sensing length and the displacement sensitivity is pre-calibrated. In actual use, the sensing length value is determined according to the demand for displacement sensitivity.
[0041] (2) Install the signal receiving optical fiber 5 in the through groove 14 at the top of the first optical fiber bracket 1 and the second optical fiber bracket 2, ensure that the Bragg grating 53 is located between the first optical fiber bracket 1 and the second optical fiber bracket 2, and use epoxy resin glue to glue the signal receiving optical fiber 5 to the first optical fiber bracket 1 and the second optical fiber bracket 2; because the ultrasonic signal transmitting segment 41 (which can be one or more) is less affected by the working range, the movement of the signal transmitting optical fiber 4 in the first optical fiber bracket 1 and the second optical fiber bracket 2 is not restricted.
[0042] (3) Glue the bottom ends of the first optical fiber bracket 1 and the second optical fiber bracket 2 to the wall 6, unscrew the screws from the internal threaded hole 15, and remove the support rod 3;
[0043] (4) The continuous laser and the optical power meter are respectively connected to the two ends of the signal transmitting optical fiber 4, and the grating demodulator is connected to the signal receiving optical fiber 5;
[0044] (5) Start the continuous laser and the grating demodulator. The continuous laser emits laser to excite the ultrasonic signal emitting section 41 to generate ultrasonic waves. The grating demodulator emits laser to monitor the change in wavelength of the emitted light of the Bragg grating 53 caused by the ultrasonic waves, and receives the reflected light. The displacement of the wall 6 can be inferred based on the change in wavelength of the generated light.
[0045] The working principle of the building structure displacement monitoring device of this application is:
[0046] The laser emitted by the continuous laser enters the signal transmitting optical fiber 4 and propagates. When it propagates to the ultrasonic signal transmitting section 41, a plasma resonance phenomenon occurs, thereby generating ultrasonic waves. During the propagation of ultrasonic waves on the wall 6, the displacement of the wall 6 will disturb the propagation path of the ultrasonic waves, causing the waveform to change. The ultrasonic wave changes will be monitored by the Bragg grating 53. The ultrasonic wave will cause a slight strain or displacement in the signal receiving optical fiber 5 where the Bragg grating 53 is located, affecting the reflection wavelength of the signal receiving optical fiber 5, that is, the shift of the Bragg wavelength. The grating demodulator emits a laser of a specific wavelength to the signal receiving optical fiber 5, and detects the wavelength change of the reflected light of the Bragg grating 53. The displacement degree of the wall 6 can be inferred based on the wavelength change.
[0047] Furthermore, there may be multiple sensor devices, and the multiple sensor devices are connected in series through optical fibers. Specifically, the signal transmitting optical fibers 4 are connected in series through optical fibers, and the signal receiving optical fibers 5 are connected in series through optical fibers.
[0048] Note that the above are only preferred embodiments of the present application and the technical principles used. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present application. Therefore, although the present application is described in more detail through the above embodiments, the present application is not limited to the above embodiments, and may also include more other equivalent embodiments without departing from the concept of the present application, all of which belong to the protection scope of the present application.
Claims
1. A sensor device based on a Bragg grating, characterized in that: It includes two optical fiber brackets, a support rod, a signal transmitting optical fiber and a signal receiving optical fiber; wherein the signal transmitting optical fiber is obtained by arranging an ultrasonic signal transmitting section on a single-mode optical fiber, and the ultrasonic signal transmitting section is formed by stripping the cladding of the single-mode optical fiber and coating a photoacoustic conversion material in the stripping area; the signal receiving optical fiber is a fiber Bragg grating; the support rod and the signal transmitting optical fiber are parallel to each other and penetrate the two optical fiber brackets, the signal receiving optical fiber is fixed to one end face of the two optical fiber brackets and is parallel to the signal transmitting optical fiber; and the ultrasonic signal transmitting section of the signal transmitting optical fiber and the Bragg grating of the signal receiving optical fiber are located between the two optical fiber brackets.
2. The sensor device based on Bragg grating according to claim 1, characterized in that: The optical fiber bracket includes a bracket body; the bracket body is provided with a first through-hole and a second through-hole parallel to each other, which are respectively used to insert the support rod and the signal transmitting optical fiber; the top of the bracket body is provided with a through groove parallel to the first through-hole, which is used to install the signal receiving optical fiber.
3. The sensor device based on Bragg grating according to claim 2, characterized in that: The bracket body is also provided with an internal threaded hole extending from the side surface of the bracket body to the first through hole and perpendicular to the first through hole.
4. The sensor device based on Bragg grating according to claim 1, characterized in that: The photoacoustic conversion material is a nano-gold composite material.
5. The sensor device based on optical fiber ultrasonic sensing as claimed in claim 4, characterized in that: The nano-gold composite material is prepared by the following method: The method comprises the following steps: mixing polydimethylsiloxane and Sylgard 184 curing agent in a mass ratio of 10:(1-3), stirring and standing for use; grinding gold salt HAuCl4·3H20 into powder in a drying oven heated to 90-100°C for use; adding the gold salt powder into the polydimethylsiloxane mixture after standing for use, stirring to disperse the gold salt powder, and obtaining a light yellow colloid mixture; wherein the mass of the gold salt powder is 3.75%-7.5% of the polydimethylsiloxane mixture; placing the light yellow colloid mixture in an ice-water mixture for ultrasonic water bathing to reduce the gold salt into gold nanospheres, thereby obtaining a nano-gold composite material; and placing the nano-gold composite material in a vacuum device for vacuum degassing.
6. A building structure displacement monitoring device, characterized in that: A sensor device comprising any one of claims 1 to 5, a continuous laser and a grating demodulator; The continuous laser is connected to the multimode optical fiber in the sensor device to emit laser to the multimode optical fiber and stimulate the ultrasonic signal transmitting section to generate ultrasonic signals; the grating demodulator is connected to the signal receiving optical fiber to collect the optical signal of the signal receiving optical fiber.
7. The building structure displacement monitoring device according to claim 6, characterized in that: There are multiple sensor devices, and the multiple sensor devices are connected in series through optical fibers. Specifically, the signal transmitting optical fibers are connected in series through optical fibers, and the signal receiving optical fibers are connected in series through optical fibers.
8. A method for monitoring displacement of a building structure, characterized by: The building structure displacement monitoring device according to any one of claims 6 to 7 comprises: Connect the two optical fiber brackets of the sensor device to the wall to be measured; start the continuous laser to emit laser to the multimode optical fiber, and stimulate the ultrasonic signal transmitting section to generate ultrasonic signals; the grating demodulator collects the optical signal of the signal receiving optical fiber; and calculate the displacement of the wall to be measured according to the wavelength change of the optical signal of the signal receiving optical fiber.
9. The method for monitoring displacement of a building structure as claimed in claim 8, characterized in that: Before starting the continuous laser to emit laser light to the multimode optical fiber, the relative positions of the two optical fiber brackets on the support rod are adjusted, thereby adjusting the distance between the two optical fibers to reach a preset distance; The distance between the two optical fibers is the sensing length, which is related to the displacement monitoring sensitivity. The relationship between the sensing length and the displacement monitoring sensitivity is pre-calibrated, and the distance is preset based on the displacement monitoring sensitivity requirements.