Triaxial FBG acceleration sensing and demodulation integrated system based on edge calculation

Abstract

The invention provides a three-axis FBG acceleration sensing and demodulation integrated system based on edge calculation. A miniature FBG demodulator is packaged in a three-axis FBG acceleration sensor shell; the miniature fiber grating demodulator comprises a core control and data processing module, a light source module, a photoelectric conversion module and a communication display module. Output light of the light source module is respectively connected with the three single-axis FBG acceleration sensors through the 1 * 3 optical fiber coupler and the three optical fiber circulators; third ports of the three optical fiber circulators are respectively connected with three input ends of the photoelectric conversion module; the core control and data processing module processes the acquired three-axis acceleration signals through a powerful calculation function, and data transmission and display are carried out through the communication display module. According to the invention, the problem of high cost of the fiber bragg grating acceleration sensor and a matched traditional demodulator is solved, and simple, efficient and low-cost triaxial fiber bragg grating acceleration measurement and edge calculation processing are realized.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, and more particularly to an integrated three-axis FBG acceleration sensing and demodulation system based on edge computing. Background Technology

[0002] Fiber Bragg grating (FBG) sensors are fiber optic sensors based on the principle of wavelength modulation. Changes in external physical quantities (such as strain, temperature, and vibration) cause alterations in the grating's period or effective refractive index, resulting in a shift in the center wavelength of its reflection or transmission. By accurately measuring this wavelength shift, information about the measured physical quantity can be derived. FBG accelerometers based on this principle possess significant advantages, including inherent resistance to electromagnetic interference, corrosion resistance, and ease of forming distributed sensor networks. They demonstrate important application value in fields such as structural health monitoring, aerospace, and vibration analysis of precision equipment. A miniature fiber Bragg grating demodulator is the core device of the aforementioned sensing system. Its function is to quickly and accurately scan and capture the reflection spectrum of the fiber Bragg grating, thereby determining its center wavelength.

[0003] Currently, typical technical solutions for fiber Bragg grating (FBG) acceleration measurement usually consist of a discrete miniature FBG demodulator and a separately packaged FBG accelerometer sensor. Existing demodulators mostly use tunable lasers as scanning light sources, controlling their output wavelength through a driving circuit, and using photodetectors to receive the light signal reflected by the sensing grating. The wavelength value is then calculated by a data processing unit. For sensors, common FBG accelerometers often employ elastic structures such as cantilever beams to convert inertial force into axial strain of the fiber Bragg grating. In practical engineering applications, the demodulator and sensor are two separate products connected via fiber optic patch cords. While this approach is technically mature, it is increasingly unable to meet the growing market demand for low cost, high integration, and convenient deployment.

[0004] The existing discrete technology solutions described above have significant shortcomings. First, low system integration leads to high overall costs. High-performance benchtop demodulators are bulky, power-hungry, and expensive, while the structural design and precision packaging of the sensors themselves further increase the total system cost, limiting their application in large-scale and widespread scenarios. Second, installation and deployment are inconvenient. Traditional sensors often lack standardized, multi-scenario adaptable installation interfaces. When installing in complex environments such as bridges and large machinery, custom brackets or destructive drilling are often required, resulting in long deployment cycles, poor flexibility, and difficulty in ensuring consistent installation quality. Third, at the data processing and system architecture level, existing solutions heavily rely on host computers or remote servers for data computation, leading to limited system real-time performance, response delays, and difficulties in deployment and reduced reliability in edge scenarios with poor network conditions or unattended operation. Finally, system reliability and ease of use need improvement. The discrete design leads to complex field wiring and makes connection points susceptible to damage. Furthermore, traditional demodulators are complex to operate, often relying on host computer software, making independent on-site display and operation difficult, and unsuitable for applications requiring high convenience, such as outdoor or mobile inspections. Therefore, developing a low-cost, low-power, highly integrated fiber Bragg grating accelerometer demodulation system with real-time edge computing capabilities and easy installation and maintenance is urgently needed and has significant application value. Summary of the Invention

[0005] To address the aforementioned technical problems of traditional fiber Bragg grating (FBG) sensing systems, such as high cost, low integration, inconvenient installation and deployment, and insufficient real-time performance due to reliance on backend processing, this invention provides a triaxial FBG acceleration sensing and demodulation integrated system based on edge computing. This invention primarily utilizes a highly integrated dual-board demodulation circuit structure combined with an integrated packaged triaxial sensor mechanical structure to construct an integrated system with edge intelligent sensing capabilities. This allows for real-time signal acquisition, demodulation, and processing locally, significantly reducing system cost and power consumption, simplifying on-site installation, and improving overall reliability and portability.

[0006] The technical means employed in this invention are as follows:

[0007] An edge computing-based triaxial FBG acceleration sensing and demodulation integrated system includes a miniature fiber Bragg grating demodulator encapsulated within the housing of a triaxial FBG acceleration sensor. The miniature fiber Bragg grating demodulator includes a core control and data processing module, a light source module, a photoelectric conversion module, and a communication and display module. The triaxial FBG accelerometer includes a sensor housing and three single-axis fiber Bragg grating accelerometers encapsulated inside the sensor housing. The light waves emitted by the light source module are connected to the first ports of three fiber optic circulators via 1x3 fiber optic couplers. The output of the second port of the fiber optic circulator is connected to the single-axis fiber optic grating accelerometer. The reflected light from the three-axis FBG accelerometer is optically connected to the three input ports of the photoelectric conversion module via the third port of the fiber optic circulator of the three-axis FBG accelerometer. The output terminal of the photoelectric conversion module is electrically connected to the input terminal of the core control and data processing module, and the photoelectric conversion module outputs a light intensity electrical signal to the core control and data processing module. The core control and data processing module converts spectral data into wavelength offsets using a lightweight wavelength demodulation algorithm. The control output terminal of the core control and data processing module is electrically connected to the control input terminal of the light source module, and the core control and data processing module outputs a wavelength scanning drive signal to the light source module. The data output terminal of the core control and data processing module is electrically connected to the input terminal of the communication display module, and the sensing data output by the core control and data processing module is sent to the communication display module.

[0008] Furthermore, the core control and data processing module includes a microcontroller unit, which is fixed on the main PCB base plate; The light source module includes a tunable laser and a high-precision multi-channel digitally controlled current source chip. The tunable laser is fixed to the laser base plate, and the high-precision multi-channel digitally controlled current source chip is fixed to the main PCB base plate. The high-precision multi-channel digitally controlled current source chip is connected to the microcontroller unit through an SPI interface, and the current output terminal of the high-precision multi-channel digitally controlled current source chip is electrically connected to the drive pin of the tunable laser through a wire. The photoelectric conversion module includes three photodetectors and three transimpedance amplifiers. The optical input end of the photodetector receives the reflected light signal from the fiber optic grating through an optical fiber. The electrical output end of the photodetector is electrically connected to the input end of the transimpedance amplifier. The output end of the transimpedance amplifier is electrically connected to the analog-to-digital conversion pin of the microcontroller unit. The communication display module includes a display screen, which is embedded and fixed on the surface of the housing of the micro fiber Bragg grating demodulator. The display screen is electrically connected to the display interface of the microcontroller unit.

[0009] Furthermore, the light source module also includes a temperature control module, which includes a temperature control chip and a heat sink. The temperature control chip is plugged into the main PCB board via a connector and is electrically connected to the thermistor pin of the tunable laser. The heat sink is attached to the surface of the tunable laser housing via a thermally conductive material.

[0010] Furthermore, the high-precision multi-channel digitally controlled current source chip is a five-channel current source chip, model LTC2662; the microcontroller unit is model STM32H750.

[0011] Furthermore, the lightweight wavelength demodulation algorithm includes the following steps: S1. The microcontroller unit controls a high-precision multi-channel digitally controlled current source to drive a tunable laser to output a linearly scanning laser wavelength, and synchronously triggers an analog-to-digital converter to acquire the light intensity voltage sequence V[i] obtained by the photodetector. According to the pre-calibrated wavelength-time mapping relationship, the acquired time sequence t[i] is converted into the corresponding instantaneous wavelength sequence λ[i], and the voltage-wavelength data pair (λ[i], V[i]) of the reflection spectrum is reconstructed. S2. Perform filtering preprocessing on the voltage-wavelength data pairs to reduce noise; traverse all data pairs, filter out three-point groups (λ[i-1], V[i-1]), (λ[i], V[i]), (λ[i+1], V[i+1]) among three consecutive sampling points with local maximum light intensity voltage values, and select the group with the largest light intensity voltage value V[i] as the target three-point group to locate the peak region of the fiber grating reflection peak; S3. Substitute the target three-point set into a quadratic function model for fitting, calculate the function coefficients, and solve for the precise peak wavelength of the fiber grating reflection peak using the quadratic function vertex formula. ; S4. Convert the peak wavelength shift Δλ into the axial strain ε of the fiber grating; then, combine the mechanical model of the cantilever beam structure to convert the strain ε into the measured acceleration value a, and complete the real-time calculation of the triaxial acceleration.

[0012] Furthermore, in S3, the quadratic function model is as follows:

[0013]

[0014] Precise peak wavelength The formula is as follows: λ[i]+

[0015] Where Δλ is the peak wavelength shift of FBG.

[0016] Furthermore, S4 specifically includes the following steps: When the sensor is subjected to external vibration, the peak wavelength of the fiber Bragg grating will drift with the vibration. The amount of drift Δλ and the axial strain ε of the fiber Bragg grating satisfy the core relationship of fiber Bragg grating sensing:

[0017] In the formula, ε is the effective elastic-optic coefficient of the quartz optical fiber, and ε is the axial strain generated by the fiber Bragg grating under vibration. Based on the cantilever beam mechanical structure of the sensor, the mechanical relationship between the cantilever beam strain ε and acceleration a is as follows:

[0018] In the formula, m is the mass of the mass block, L is the length of the cantilever beam, b is the width of the cantilever beam, h is the thickness of the cantilever beam, and E is the elastic modulus of the cantilever beam material; Substituting the expression for strain ε into the wavelength drift formula, we obtain the final formula for calculating acceleration a: .

[0019] Furthermore, the sensor housing is an aluminum alloy cubic structure; the three single-axis fiber grating accelerometers form the three coordinate axes of a three-dimensional rectangular coordinate system. Each single-axis fiber grating accelerometer includes a fiber grating and a cantilever beam structure for attaching and fixing the fiber grating. A mass block is provided at the free end of the cantilever beam structure.

[0020] Furthermore, the cantilever beam structure is an iso-strain beam, and the cantilever beam structure and the sensor housing are an integrated spliced ​​structure; the sensor housing is provided with an optical fiber routing groove for fixing optical fibers, and the end of the optical fiber routing groove is provided with a silicone buckle.

[0021] Furthermore, the cavity inside the sensor housing is a sealed cavity filled with dry gas.

[0022] Compared with the prior art, the present invention has the following advantages: This invention achieves miniaturization, low cost, and high portability of the sensing system by directly combining a highly integrated demodulation circuit with an integrated packaged triaxial sensor in terms of physical structure, thus solving the problems of high cost and complex deployment of traditional discrete systems.

[0023] The miniature fiber grating demodulator provided by this invention, by adopting a dual-board integrated hardware architecture with a high-precision multi-channel current source chip as the core, achieves high-precision, low-interference driving of tunable lasers, significantly simplifies the circuit structure, and improves the stability and reliability of wavelength scanning.

[0024] The triaxial FBG accelerometer provided by this invention achieves high sensitivity and anti-cross-interference measurement of triaxial acceleration by adopting an integrally machined cubic shell-cantilever beam mechanical structure and an internal fiber optic cable management design, while ensuring the robustness and long-term stability of the sensor itself.

[0025] The overall system provided by this invention, by setting standardized threaded holes on the sensor housing and adapting to a magnetic base, enables rapid, flexible and reliable installation in various complex scenarios such as large machinery, bridge structures and temporary inspections, greatly improving its engineering applicability.

[0026] This invention deeply integrates edge computing capabilities with fiber optic sensing demodulation technology, enabling real-time acquisition, spectral demodulation, and data processing of acceleration signals within an integrated system. This significantly reduces reliance on host computers or the cloud, minimizes data latency and transmission burden, and substantially lowers overall system power consumption and operating costs thanks to its highly integrated low-power hardware design and localized processing capabilities. Furthermore, the system's built-in display interface and dual-mode operation design support independent operation without a host computer and rapid deployment, allowing it to flexibly adapt to various edge computing scenarios, from long-term online monitoring of large machinery and bridge structures to temporary inspections and mobile detection. Ultimately, while ensuring high-precision measurement, this invention achieves a comprehensive improvement in cost, power consumption, real-time performance, and engineering applicability of the fiber optic accelerometer sensing system. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the module structure of the present invention. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0034] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0035] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0036] like Figure 1 As shown, the present invention provides an integrated triaxial FBG acceleration sensing and demodulation system based on edge computing, including a miniature fiber optic demodulator encapsulated in the housing of a triaxial FBG acceleration sensor. The miniature fiber Bragg grating demodulator includes a core control and data processing module, a light source module, a photoelectric conversion module, and a communication and display module. The triaxial FBG accelerometer includes a sensor housing and three single-axis fiber Bragg grating accelerometers encapsulated inside the sensor housing. The light waves emitted by the light source module are connected to the first ports of three fiber optic circulators via 1x3 fiber optic couplers. The output of the second port of the fiber optic circulator is connected to the single-axis fiber optic grating accelerometer. The reflected light from the three-axis FBG accelerometer is optically connected to the three input ports of the photoelectric conversion module via the third port of the fiber optic circulator of the three-axis FBG accelerometer. The output terminal of the photoelectric conversion module is electrically connected to the input terminal of the core control and data processing module, and the photoelectric conversion module outputs a light intensity electrical signal to the core control and data processing module. The core control and data processing module converts spectral data into wavelength offsets using a lightweight wavelength demodulation algorithm. The control output terminal of the core control and data processing module is electrically connected to the control input terminal of the light source module, and the core control and data processing module outputs a wavelength scanning drive signal to the light source module. The data output terminal of the core control and data processing module is electrically connected to the input terminal of the communication display module, and the sensing data output by the core control and data processing module is sent to the communication display module.

[0037] Specifically, the miniature fiber Bragg grating demodulator includes a core control and data processing module, a light source module, a photoelectric conversion module, and a communication and display module. The core control and data processing module serves as the system control core; the light source module emits wavelength-tunable optical signals; the photoelectric conversion module converts the optical signals into electrical signals; and the communication and display module displays and communicates the data. The triaxial FBG accelerometer includes a sensor housing and three single-axis fiber Bragg grating accelerometers encapsulated within the housing. The sensitive axes of the three sensing units form a three-dimensional Cartesian coordinate system.

[0038] The output of the light source module is optically connected to the input of the triaxial FBG accelerometer via a fiber optic connector. The three outputs of the triaxial FBG accelerometer are optically connected to the three inputs of the photoelectric conversion module via optical fibers. The output of the photoelectric conversion module is electrically connected to the input of the core control and data processing module, used to transmit the optical intensity signal to the core control and data processing module. The control output of the core control and data processing module is electrically connected to the control input of the light source module, used to output a wavelength scanning drive signal. The data output of the core control and data processing module is electrically connected to the input of the communication display module, used to output the processed sensor data.

[0039] Furthermore, the core control and data processing module includes a microcontroller unit fixed on the main PCB substrate. The light source module includes a tunable laser and a high-precision multi-channel digitally controlled current source chip. The tunable laser is fixed on the laser substrate, and the current source chip is fixed on the main PCB substrate and connected to the microcontroller unit via an SPI interface. Its current output terminal drives the tunable laser. The photoelectric conversion module includes three photodetectors and three transimpedance amplifiers. The photodetectors receive the reflected light signal from the fiber Bragg grating, which is then converted by the transimpedance amplifiers and sent to the analog-to-digital conversion pin of the microcontroller unit. The communication display module includes a display screen, embedded and fixed on the surface of the housing and electrically connected to the microcontroller unit.

[0040] Furthermore, the light source module also includes a temperature control module for stabilizing the operating temperature of the tunable laser.

[0041] Furthermore, the sensor housing is an aluminum alloy cubic structure. Each single-axis sensing unit includes a fiber Bragg grating and a cantilever beam structure for attaching it, with a mass block at the free end of the cantilever beam. The cantilever beam is a constant strain beam and is an integrated, spliced ​​structure with the sensor housing. The sensor housing has fiber optic cable routing channels and silicone clips to secure the fiber optic cables. The housing chamber is a sealed chamber that can be filled with dry gas. The sides and bottom of the sensor housing have standard mounting threaded holes for screw fixing or connection to a magnetic base.

[0042] The miniature fiber Bragg grating demodulator integrates a core control and data processing module, a light source module, a photoelectric conversion module, and a communication and display module.

[0043] The core control and data processing module uses an STM32H750 microcontroller unit as the main controller, which integrates a multi-channel ADC module with a sampling rate of 1MHz. The microcontroller unit is fixed to the 4-layer FR-4 material main PCB baseboard via pin headers.

[0044] The core control and data processing module adopts a lightweight wavelength demodulation algorithm, which directly converts the acquired spectral data into wavelength offsets instead of uploading the original spectral data, thereby processing the three-channel reflection spectrum and obtaining the acceleration solution of the three-axis FBG accelerometer.

[0045] During system operation, the MCU of the core control and data processing module completes the acquisition, processing, and acceleration calculation of the fiber optic grating (FBG) reflection signal through the following demodulation algorithm. The specific process is as follows: 1. Wavelength scanning and synchronous signal acquisition; The MCU controls the high-precision multi-channel numerically controlled current source of the light source module to output drive signals, thereby regulating the tunable laser to output scanning laser with a wavelength that changes linearly with time within a preset tuning range. After the laser is transmitted to the three-axis FBG accelerometer via the optical path, it is reflected by the sensor to form a reflected light signal. This reflected light signal is transmitted to the photodetector of the photoelectric conversion module through the optical circulator.

[0046] Simultaneously with the start of wavelength scanning, the MCU triggers the ADC module to start synchronous acquisition: the photodetector converts the reflected light signal into photocurrent, which is then amplified into a voltage signal V(t) by the transimpedance amplifier. The ADC module then digitally samples this voltage signal to obtain the reflected light intensity voltage sequence V[i] that strictly corresponds to the scanning time sequence t[i].

[0047] Based on the wavelength-time linear mapping relationship of the laser (pre-calibrated), the time series t[i] is transformed into the instantaneous wavelength series λ[i], and finally the voltage-wavelength data pair (λ[i], V[i]) characterizing the reflection spectrum of the FBG is reconstructed.

[0048] 2. Spectral data preprocessing and peak region localization; Preprocessing is performed on the reconstructed voltage-wavelength data pairs. Filtering algorithms (such as moving average filtering) are used to reduce signal glitches caused by circuit noise and environmental interference, while retaining the core characteristics of the FBG reflection peak, thus providing high signal-to-noise ratio data for subsequent peak position detection.

[0049] After preprocessing, all voltage-wavelength data pairs are traversed, and groups of three consecutive points that meet the following conditions are selected: Let the consecutive sampling points be (λ[i-1], V[i-1]), (λ[i], V[i]), and (λ[i+1], V[i+1]), where Δλ is the wavelength interval between adjacent sampling points (Δλ=λ[i]-λ[i-1]=λ[i+1]-λ[i], a preset fixed value), which must satisfy: V[i]>V[i-1] and V[i]>V[i+1] (the middle point is a local maximum value).

[0050] From all the three-point groups that meet the conditions, select the group with the largest V[i] as the target three-point group. This three-point group corresponds to the true peak region of the FBG reflection peak, ensuring the accuracy of peak position detection.

[0051] 3. Quadratic function fitting and accurate peak wavelength determination; Substitute the target three-point set (λ[i-1], V[i-1]), (λ[i], V[i]), and (λ[i+1], V[i+1]) into the quadratic function model y=ax²+bx+c for fitting, and solve for the function coefficients a and b using the following formula:

[0052]

[0053] Based on the vertex characteristics of a quadratic function (where the x-coordinate of the vertex represents the peak position), the precise peak wavelength of the FBG reflection peak is derived. : λ[i]+

[0054] 4. Wavelength drift-strain-acceleration conversion When the sensor is subjected to external vibration, the peak wavelength of the FBG will drift with the vibration. The drift amount Δλ (Δλ=λ_B-λ0, where λ0 is the initial peak wavelength under zero strain) satisfies the core relationship between the FBG axial strain ε and the FBG:

[0055] In the formula, ε is the effective elastic-optic coefficient of the silica fiber (a fixed constant, with a value of ≈0.22), and ε is the axial strain generated by the FBG under vibration.

[0056] Based on the cantilever beam mechanical structure of the sensor, the mechanical relationship between the cantilever beam strain ε and acceleration a is as follows:

[0057] In the formula, m is the mass of the mass block, L is the length of the cantilever beam (distance from the fixed end to the FBG bonding point), b is the width of the cantilever beam, h is the thickness of the cantilever beam, and E is the elastic modulus of the cantilever beam material.

[0058] Substituting the expression for strain ε into the wavelength drift formula, and simplifying, we obtain the final formula for calculating acceleration a:

[0059] Using the above formula, the MCU can directly convert the accurately calculated peak wavelength drift Δλ into the corresponding acceleration value, realizing real-time, high-precision measurement of triaxial vibration acceleration.

[0060] The light source module includes a domestically produced narrowband tunable laser and an LTC2662 five-channel high-precision digitally controlled current source chip. The laser is soldered onto a separate laser base plate, and the optical output is led out through an FC / APC fiber optic adapter. The current source chip is soldered onto the main PCB base plate and is controlled by the microcontroller unit via an SPI interface, outputting five channels of current with an accuracy within ±0.1 mA, which drive the laser to achieve wavelength scanning via wires. The light source module also includes a TCM1040 temperature control chip and a matching heat sink. The temperature control chip is inserted into the main PCB base plate via a gold finger connector and connected to the laser's thermistor. The heat sink is attached to the laser housing with thermal grease to stabilize the operating temperature.

[0061] The photoelectric conversion module consists of three InGaAs photodetectors and three transimpedance amplifier circuits. The detectors are fixed by clip brackets, and their optical input terminals receive reflected light signals from the sensors. Their electrical output terminals are connected to the input terminals of the transimpedance amplifiers via wiring terminals, and the output terminals of the transimpedance amplifiers are connected to the ADC input pin of the microcontroller unit.

[0062] The communication display module includes a 7.0-inch LCD screen, which connects to the display interface of the microcontroller unit via an FFC cable and is embedded in the opening on the front panel of the demodulator for real-time display of spectral and acceleration data. The demodulator housing also features a USB Type-C interface for data transfer with a host computer.

[0063] The housing of the three-axis FBG accelerometer is made of 6061-T6 aluminum alloy and is machined into a cubic structure. Inside, it encapsulates three spatially orthogonally arranged single-axis sensing units.

[0064] At the core of each single-axis sensing unit is a cantilever beam structure, which is a constant-strain beam integrally machined with an aluminum alloy housing. The cantilever beam is wider at the fixed end and narrower at the free end, with optimized dimensions. A fiber grating is attached to the surface of the cantilever beam, and a hollow stainless steel mass block is attached to the free end. The sensing axes of the three such units are aligned with the X, Y, and Z axes of a three-dimensional Cartesian coordinate system, respectively.

[0065] The sensor housing has internally milled fiber optic cable channels to guide and protect the three optical fibers entering the housing. Silicone clips at the ends of the channels secure the fibers approximately 5 mm from the grating bonding point, preventing interference caused by fiber movement. The sensor housing cavity is sealed and can be filled with dry nitrogen to reduce the influence of ambient humidity.

[0066] For easy installation, the sensor housing has M5 standard mounting threaded holes machined on all four sides and the bottom. Users can choose to use screws to directly fix the sensor to the monitoring location through the threaded holes. In addition, a magnetic base is available as an option. This base connects to the threaded holes on the bottom of the sensor housing with screws, allowing the sensor to be quickly attached to ferromagnetic surfaces such as bridge steel components or mechanical equipment, suitable for temporary inspection scenarios.

[0067] In use, connect the demodulator to the sensor using a fiber optic patch cord. After powering on the demodulator, the microcontroller unit starts up, driving the laser to output a scanning laser beam via a current source chip. The laser beam is reflected by the fiber grating inside the sensor and received by the photodetector inside the demodulator, converting it into an electrical signal. The microcontroller unit simultaneously acquires three electrical signals, processes them using internal algorithms, calculates the acceleration values ​​along the three axes in real time, and displays them locally on the screen or uploads them to the host computer software via USB.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A triaxial FBG acceleration sensing and demodulation integrated system based on edge computing, characterized in that, This includes a miniature fiber Bragg grating demodulator encapsulated within the housing of a triaxial FBG accelerometer; The miniature fiber Bragg grating demodulator includes a core control and data processing module, a light source module, a photoelectric conversion module, and a communication and display module. The triaxial FBG accelerometer includes a sensor housing and three single-axis fiber Bragg grating accelerometers encapsulated inside the sensor housing. The light waves emitted by the light source module are connected to the first ports of three fiber optic circulators via 1x3 fiber optic couplers. The output of the second port of the fiber optic circulator is connected to the single-axis fiber optic grating accelerometer. The reflected light from the three-axis FBG accelerometer is optically connected to the three input ports of the photoelectric conversion module via the third port of the fiber optic circulator of the three-axis FBG accelerometer. The output terminal of the photoelectric conversion module is electrically connected to the input terminal of the core control and data processing module, and the photoelectric conversion module outputs a light intensity electrical signal to the core control and data processing module. The core control and data processing module converts spectral data into wavelength offsets using a lightweight wavelength demodulation algorithm. The control output terminal of the core control and data processing module is electrically connected to the control input terminal of the light source module, and the core control and data processing module outputs a wavelength scanning drive signal to the light source module. The data output terminal of the core control and data processing module is electrically connected to the input terminal of the communication display module, and the sensing data output by the core control and data processing module is sent to the communication display module.

2. The triaxial FBG acceleration sensing and demodulation integrated system based on edge computing according to claim 1, characterized in that, The core control and data processing module includes a microcontroller unit, which is fixed on the main PCB base plate; The light source module includes a tunable laser and a high-precision multi-channel digitally controlled current source chip. The tunable laser is fixed to the laser base plate, and the high-precision multi-channel digitally controlled current source chip is fixed to the main PCB base plate. The high-precision multi-channel digitally controlled current source chip is connected to the microcontroller unit through an SPI interface, and the current output terminal of the high-precision multi-channel digitally controlled current source chip is electrically connected to the drive pin of the tunable laser through a wire. The photoelectric conversion module includes three photodetectors and three transimpedance amplifiers. The optical input end of the photodetector receives the reflected light signal from the fiber optic grating through an optical fiber. The electrical output end of the photodetector is electrically connected to the input end of the transimpedance amplifier. The output end of the transimpedance amplifier is electrically connected to the analog-to-digital conversion pin of the microcontroller unit. The communication display module includes a display screen, which is embedded and fixed on the surface of the housing of the micro fiber Bragg grating demodulator. The display screen is electrically connected to the display interface of the microcontroller unit.

3. The triaxial FBG acceleration sensing and demodulation integrated system based on edge computing according to claim 2, characterized in that, The light source module also includes a temperature control module, which includes a temperature control chip and a heat sink. The temperature control chip is plugged into the main PCB board via a connector and is electrically connected to the thermistor pin of the tunable laser. The heat sink is attached to the surface of the tunable laser housing via a thermally conductive material.

4. The edge computing-based triaxial FBG acceleration sensing and demodulation integrated system according to claim 2, characterized in that, The high-precision multi-channel digitally controlled current source chip is a five-channel current source chip, model LTC2662; the microcontroller unit is model STM32H750.

5. The triaxial FBG acceleration sensing and demodulation integrated system based on edge computing according to claim 1, characterized in that, The lightweight wavelength demodulation algorithm includes the following steps: S1. The microcontroller unit controls a high-precision multi-channel digitally controlled current source to drive a tunable laser to output a linearly scanning laser wavelength, and synchronously triggers an analog-to-digital converter to acquire the light intensity voltage sequence V[i] obtained by the photodetector. According to the pre-calibrated wavelength-time mapping relationship, the acquired time sequence t[i] is converted into the corresponding instantaneous wavelength sequence λ[i], and the voltage-wavelength data pair (λ[i], V[i]) of the reflection spectrum is reconstructed. S2. Perform filtering preprocessing on the voltage-wavelength data pairs to reduce noise; traverse all data pairs, filter out the three-point groups (λ[i-1], V[i-1]), (λ[i], V[i]), (λ[i+1], V[i+1]) among three consecutive sampling points with local maximum light intensity voltage values, and select the group with the largest light intensity voltage value V[i] as the target three-point group to locate the peak region of the fiber grating reflection peak; S3. Substitute the target three-point set into a quadratic function model for fitting, calculate the function coefficients, and solve for the precise peak wavelength of the fiber grating reflection peak using the quadratic function vertex formula. ; S4. Convert the peak wavelength shift Δλ into the axial strain ε of the fiber grating; then, combine the mechanical model of the cantilever beam structure to convert the strain ε into the measured acceleration value a, and complete the real-time calculation of the triaxial acceleration.

6. The triaxial FBG acceleration sensing and demodulation integrated system based on edge computing according to claim 5, characterized in that, In S3, the quadratic function model is as follows: Precise peak wavelength The formula is as follows: λ[i]+ Where Δλ is the peak wavelength shift of FBG.

7. The triaxial FBG acceleration sensing and demodulation integrated system based on edge computing according to claim 6, characterized in that, S4 specifically includes the following steps: When the sensor is subjected to external vibration, the peak wavelength of the fiber Bragg grating will drift with the vibration. The amount of drift Δλ and the axial strain ε of the fiber Bragg grating satisfy the core relationship of fiber Bragg grating sensing: In the formula, ε is the effective elastic-optic coefficient of the quartz optical fiber, and ε is the axial strain generated by the fiber Bragg grating under vibration. Based on the cantilever beam mechanical structure of the sensor, the mechanical relationship between the cantilever beam strain ε and acceleration a is as follows: In the formula, m is the mass of the mass block, L is the length of the cantilever beam, b is the width of the cantilever beam, h is the thickness of the cantilever beam, and E is the elastic modulus of the cantilever beam material; Substituting the expression for strain ε into the wavelength drift formula, we obtain the final formula for calculating acceleration a: 。 8. The triaxial FBG acceleration sensing and demodulation integrated system based on edge computing according to claim 1, characterized in that, The sensor housing is an aluminum alloy cubic structure; three single-axis fiber grating accelerometers form the three coordinate axes of a three-dimensional rectangular coordinate system. Each single-axis fiber grating accelerometer includes a fiber grating and a cantilever beam structure for attaching and fixing the fiber grating. A mass block is provided at the free end of the cantilever beam structure.

9. The edge computing-based triaxial FBG acceleration sensing and demodulation integrated system according to claim 8, characterized in that, The cantilever beam structure is an equal strain beam, and the cantilever beam structure and the sensor housing are an integrated spliced ​​structure; the sensor housing is provided with an optical fiber routing groove for fixing optical fibers, and the end of the optical fiber routing groove is provided with a silicone buckle.

10. The triaxial FBG acceleration sensing and demodulation integrated system based on edge computing according to claim 8, characterized in that, The cavity inside the sensor housing is a sealed cavity filled with dry gas.

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