Integrated flexible optical fiber sensing device and in-vivo sensing method thereof

Abstract

The invention provides an integrated flexible optical fiber sensing device and an in-vivo sensing method thereof, and belongs to the technical field of crossing of intelligent sensing and additive manufacturing. Comprising two fixing mechanisms which are arranged in parallel and at an interval and used for being fixed to the surface of a detected structure, and first caulking grooves are correspondingly formed in the end faces of the two fixing mechanisms; the elastic base body is arranged in the area between the two fixing mechanisms and arranged in a bent shape, a second caulking groove is formed in the end face of the elastic base body, and the second caulking groove is further communicated with the first caulking grooves in the two fixing mechanisms; the metalized optical fiber is sequentially embedded in the first embedding groove and the second embedding groove, and FBG fiber gratings are arranged at the two ends, located in the first embedding groove, of the metalized optical fiber; the metalized optical fiber, the two fixing mechanisms and the elastic base body are integrally formed. Metal 3D printing processing is adopted to improve the manufacturing efficiency, optical fiber metallization and an optical fiber-metal integrated forming process are combined, rigid connection of the optical fiber and the metal matrix is achieved, and heat resistance and operability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of intersection of intelligent sensing and additive manufacturing, and in particular to an integrated flexible optical fiber sensing device and an on-body sensing method thereof. Background Art

[0002] In extreme environments such as aircraft engine turbine blades, which are subjected to high temperatures, complex aerodynamic loads, high-cycle fatigue, and other multi-field coupling effects for a long time, real-time monitoring of the temperature-strain field of turbine blades is crucial to structural safety. Fiber Bragg grating sensors are sensitive to both strain and temperature, meaning that temperature and strain can simultaneously cause the fiber coupling wavelength to shift. As a new type of sensing component, fiber Bragg gratings can effectively avoid electromagnetic interference compared to electrical sensors, and have advantages such as small size and distributed monitoring. They are easy to integrate into the sensor substrate and apply to complex environments. Currently, in terms of sensor packaging methods, traditional gluing and soldering connection methods have problems such as poor heat resistance and poor operability. Existing sensor layout schemes generally have significant problems such as large substrate size and complex preparation, and ignore the influence of substrate stiffness on the strain perception of the structure to be measured.

[0003] Therefore, it is very necessary to provide an integrated flexible optical fiber sensing device and its on-body sensing method, which can improve the shortcomings of conventional bonding and soldering methods, such as poor heat resistance and unsuitability for high-temperature environments, by integrating the base structure and the optical fiber Bragg grating into one molding, and improve the shortcomings of existing sensing and detection equipment, such as small range and low rigidity. Summary of the Invention

[0004] In view of this, the present invention proposes an integrated flexible optical fiber sensing device and an in-body sensing method thereof, which is 3D printed, does not use conventional bonding or welding methods, has good heat resistance, and is suitable for temperature-strain monitoring.

[0005] In one aspect, the present invention provides an integrated flexible optical fiber sensing device, comprising: Two fixing mechanisms are arranged in parallel and at intervals, and are used to be fixed to the surface of the structure to be measured, and the end surfaces of the two fixing mechanisms are correspondingly provided with first embedding grooves; The elastic base is provided in the area between the two fixing mechanisms and is arranged in a curved shape. A second embedding groove is provided on the end surface of the elastic base, and the second embedding groove is also interconnected with the first embedding grooves on the two fixing mechanisms; The metallized optical fiber is sequentially embedded in the first embedding groove and the second embedding groove. Both ends of the metallized optical fiber located in the first embedding groove are provided with FBG optical fiber gratings. The metallized optical fiber is integrated with the two fixing mechanisms and the elastic matrix.

[0006] On the basis of the above technical solution, preferably, the elastic matrix includes two first arc segments, two second arc segments and a connecting beam, and the connecting beam is located between the two fixing mechanisms and is set at an angle to the longitudinal center planes of the two fixing mechanisms; one end of the two first arc segments is respectively fixedly connected to the adjacent side surfaces of the two fixing mechanisms, and the other end of the two first arc segments is fixedly connected to one end of the two second arc segments one by one, and the other end of the two second arc segments is respectively fixedly connected to different ends of the connecting beam.

[0007] Preferably, the initial bending radius of the two first arc segments and the two second arc segments is the same, the central angle of the first arc segment is 90°, the central angle of the second arc segment is 180°, and the length of the connecting beam is twice the initial bending radius of the first arc segment.

[0008] Preferably, the deviation of the central wavelengths of the FBG fiber gratings at both ends of the metallized optical fiber is 2-5 nm.

[0009] Preferably, the process of integrating the metallized optical fiber with the two fixing mechanisms and the elastic matrix comprises the following steps: Using the fused tapered method, a precision motor is used under a microscope to control the drawing speed and displacement of the heated optical fiber, monitor the diameter of the optical fiber, and place fiber Bragg gratings (FBGs) at both ends of the tapered optical fiber. The tapered optical fiber and the FBGs are then fused together to produce a micro-nano optical fiber. The cladding is then removed, and a metal coating is formed on the surface of the micro-nano optical fiber through chemical plating and metal plating processes to produce a metallized optical fiber. Use CAD software to design the three-dimensional models of the two fixing mechanisms and the elastic base; Use the slicing tool to slice the 3D model and generate layer-by-layer 2D contour data; Plan the laser scanning path, set the laser power, scanning speed and powder layer thickness, select the appropriate substrate, and clean and preheat the substrate; Load the metal powder into the powder feeding device and use a scraper to evenly spread the powder on the substrate to achieve the set powder layer thickness; fill the printing chamber with inert gas; The laser scans and melts the powder layer according to the slice data. After each layer of powder is melted, the substrate decreases by one layer, and the powder-laying-scanning process is repeated. When printing reaches the powder layer of the first and second embedding grooves, the chamber door is opened to sweep away the metal powder on the top layer, and the bent metallized optical fiber is placed in the first and second embedding grooves. Printing is performed layer by layer again until printing is completely completed, resulting in an integrated metallized optical fiber, two fixing mechanisms and an elastic matrix.

[0010] Preferably, the depth of the first and second embedding grooves is 1.2-1.5 times the diameter of the metallized optical fiber, the width of the first and second embedding grooves is 1.1-1.3 times the diameter of the metallized optical fiber, and the cross-sectional shape of the first and second embedding grooves is elliptical.

[0011] Preferably, the elastic base and the two fixing mechanisms have the same height, and the width of the elastic base is greater than the height of the elastic base; and the angle between the connecting beam and the longitudinal center planes of the two fixing mechanisms is 30°.

[0012] In another aspect, the present invention provides an on-body sensing method using an integrated flexible optical fiber sensing device, comprising the following steps: S1: Configure the above-mentioned integrated flexible optical fiber sensing device; connect the fiber Bragg grating (FBG) at one end of the metallized optical fiber to the light source optical path; the metallized optical fiber is obtained by setting FBG fiber Bragg gratings at both ends of the tapered optical fiber to obtain a micro-nano optical fiber and further providing a metal coating; S2: Constructing a light intensity loss and strain measurement model; S3: By obtaining the light intensity difference of the fiber Bragg grating at both ends of the metallized optical fiber, the temperature and strain are solved by using the wavelength-intensity hybrid demodulation method of the dual fiber Bragg grating.

[0013] Preferably, the content of step S2 is to obtain the bending loss of the FBG fiber grating when it is not subjected to external force; obtain the bending loss of the metallized optical fiber at the first arc segment; x The elongation in the axial direction and the metallized optical fiber at the connecting beam are x The elongation in the axial direction, x The axial direction is the length extension direction of the fixing mechanism, the bending radius of the first arc segment when not subjected to an external load, and the bending radius of the first arc segment of the metallized optical fiber after being stretched by an external load, and a mapping relationship between strain and light intensity loss is constructed.

[0014] Preferably, the content of step S3 is to construct a mapping relationship between the light intensity loss and the bending radius of the first arc segment of the metallized optical fiber when subjected to an external load; obtain a relationship that the central wavelength of the FBG fiber grating is proportional to the change in temperature; and comprehensively calculate the mapping relationship between the light intensity loss and the bending radius of the first arc segment of the metallized optical fiber when subjected to an external load, the relationship between the temperature change and the wavelength drift, and the mapping relationship between strain and light intensity loss to obtain the strain change and the temperature change.

[0015] The present invention provides an integrated flexible optical fiber sensing device and an on-body sensing method thereof, which have the following advantages over the prior art: (1) This scheme proposes an integrated sensor structure with an elastic matrix, which has the advantages of low stiffness and large range. The elastic matrix used as the substrate and the two fixing mechanisms are processed by metal 3D printing to improve manufacturing efficiency. In combination with the optical fiber metallization and optical fiber-metal integrated molding process, a rigid connection between the optical fiber and the metal matrix is ​​achieved, overcoming the problems of poor heat resistance and poor operability brought about by traditional bonding and soldering connection methods. The metallized optical fiber coating process based on chemical plating and electroplating is used to enhance the interface bonding strength between the optical fiber and the metal matrix and enhance the high temperature resistance of the optical fiber. (2) In terms of signal demodulation mechanism, the sensing device provided by this scheme adopts a dual FBG wavelength-light intensity hybrid demodulation method to solve temperature and strain. It has good results in the static characteristics, dynamic response, cross-coupling and high temperature resistance tests of temperature-strain. It can realize the composite perception of temperature-strain under the condition of designing specific temperature-strain decoupling. (3) The sensing device provided by this scheme is particularly suitable for structural health monitoring of turbine blades and provides a reliable temperature-strain testing method. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 A top view of an integrated flexible optical fiber sensing device and an in-body sensing method thereof according to the present invention; FIG2( a ) is a bottom view of an integrated flexible optical fiber sensing device and an in-body sensing method thereof according to the present invention; FIG2( b ) is a left side view of an integrated flexible optical fiber sensing device and an in-body sensing method thereof according to the present invention; Figure 3 This is a schematic structural diagram of a metallized optical fiber of an integrated flexible optical fiber sensing device and an in-body sensing method thereof according to the present invention; Figure 4 A schematic diagram of the dimensions of an integrated flexible optical fiber sensing device and an in-body sensing method thereof according to the present invention; Figure 5 This is a schematic diagram of a structural force analysis of an integrated flexible optical fiber sensing device and an on-body sensing method thereof according to the present invention; Figure 6 A three-dimensional diagram of an integrated flexible optical fiber sensing device and an on-body sensing method thereof according to the present invention; Figure 7 A modeling strategy for a decoupling model of an integrated flexible optical fiber sensing device and an in-body sensing method thereof of the present invention; Figure 8 Schematic diagram of a multi-channel decoupling strategy for an integrated flexible optical fiber sensing device and an in-body sensing method thereof according to the present invention; Figure 9 This is a schematic diagram of the structure of a multi-layer perception extreme learning machine of an integrated flexible optical fiber sensing device and its in-body perception method of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] As a new type of sensing component, fiber Bragg grating can effectively avoid electromagnetic interference compared to electrical sensors, and has advantages such as small size and distributed monitoring. It is easy to integrate into the sensor substrate and apply to complex environments. At present, in terms of sensor packaging methods, traditional gluing and soldering connection methods have problems such as poor heat resistance and poor operability. In addition, existing sensor layout schemes generally have significant problems such as large substrate size and complex preparation, and ignore the influence of substrate stiffness on the strain perception of the structure to be measured. In view of this, Figure 1 Combined with Figure 2 (a), Figure 2 (b), Figure 3 、 Figure 5 and Figure 6 As shown, on the one hand, the present invention provides an integrated flexible optical fiber sensing device, comprising: The two fixing mechanisms 4 are arranged in parallel and at intervals for fixing to the surface of the structure to be measured. The end faces of the two fixing mechanisms 4 are correspondingly provided with first embedding grooves 100; the two fixing mechanisms 4 are respectively provided with fixing circular holes 1 for fixing to the structure to be measured.

[0020] The elastic base 3 is provided in the area between the two fixing mechanisms 4 and is arranged in a curved shape. A second embedding groove 200 is provided on the end surface of the elastic base 3. The second embedding groove 200 is also interconnected with the first embedding groove 100 on the two fixing mechanisms 4. The metallized optical fiber 2 is sequentially embedded in the first embedding groove 100 and the second embedding groove 200. FBG fiber gratings 5 ​​are provided at both ends of the metallized optical fiber 2 located in the first embedding groove 100. The metallized optical fiber 2 is integrally formed with the two fixing mechanisms 4 and the elastic base 3. In this embodiment, the FBG fiber gratings 5 ​​at both ends of the metallized optical fiber 2 are identical only in size; the center wavelengths of the two FBG fiber gratings 5 ​​differ by 2-5 nm.

[0021] Figure 1 and Figure 6 The elastic base 3 shown is similar to an 8-shaped or S-shaped. Specifically, the elastic base 3 mainly includes three parts: two first arc segments 31, two second arc segments 32 and a connecting beam 33. The connecting beam 33 is located between the two fixing mechanisms 4 and is set at an angle with the longitudinal center plane of the two fixing mechanisms 4. The angle is θ One end of the two first arc segments 31 is fixedly connected to the adjacent side surfaces of the two fixing mechanisms 4, and the other ends of the two first arc segments 31 are fixedly connected to one end of the two second arc segments 32 in a one-to-one correspondence, and the other ends of the two second arc segments 32 are fixedly connected to different ends of the connecting beam 33.

[0022] In this embodiment, in order to simplify the structure and reduce the amount of calculation, the initial bending radius of the two first arc segments 31 and the two second arc segments 32 are made the same, that is, Figure 4 The radius of R 2 and R 3 are equal, so R 2= R 3= R , and the central angle of the first arc segment 31 is 90°, the central angle of the second arc segment 32 is 180°, and the length of the connecting beam 33 is twice the initial bending radius of the first arc segment 31.

[0023] In order to better optimize the structure of the elastic base 3 and the two fixing mechanisms 4 used as the substrate, when the metal base is installed on the surface of the measured structure, the stiffness of the base will introduce a constraint reaction force to affect the deformation of the measured structure. In order to reduce and quantify this effect, the impact factor is defined as q .

[0024] Establish x External load F The mapping relationship between the impact factor and x The axial direction is the length extension direction of the fixing mechanism 4, wherein ,like Figure 5 As shown, based on the principle of material mechanics energy method, the elastic base 3 and the two fixing mechanisms 4 are x The total deformation in the direction is: ,in A is the cross-sectional area of ​​the elastic matrix 3, , b is the cross-sectional width of the elastic matrix 3, h is the height of the elastic base 3; E is the elastic modulus; I is the moment of inertia, ; L For the elastic matrix 3 x The total length in the axial direction, ; So the impact factor can be obtained as .

[0025] During the optimization of the elastic matrix structure, multi-objective constraints can be set according to actual needs, such as the angle between the connecting beam 33 and the vertical direction. θ , cross-sectional area A and the initial bending radius of the first arc segment 31 R etc., it is necessary to coordinate and optimize multiple parameters to adjust the substrate stiffness. For example, in this embodiment, after analysis, it can be known that the height of the elastic base 3 is h and cross-sectional width of elastic matrix 3 b The increase of the sensor's influence factor q will increase; angle θ and initial bending radius R Increase, impact factor q Will decrease.

[0026] In one embodiment, the overall size of the elastic base is 20 mm × 10.5 mm × 0.55 mm, and the initial bending radius is R 2mm, angle θ The angle is 30°, the elastic base 3 and the two fixing mechanisms 4 have the same height, and the width of the elastic base 3 is greater than the height of the elastic base 3. By limiting the inward deflection of the elastic base 3, the overall size of the elastic base can be reduced while maintaining sufficient sensitivity and ease of installation, thus achieving the requirement of a small-size configuration.

[0027] As shown in Figures 2(a) and 2(b), the depth of the first embedding groove 100 and the second embedding groove 200 is 1.2-1.5 times the diameter of the metallized optical fiber 2, the width of the first embedding groove 100 and the second embedding groove 200 is 1.1-1.3 times the diameter of the metallized optical fiber 2, and the cross-sectional shape of the first embedding groove 100 and the second embedding groove 200 is elliptical.

[0028] The process of integrating the metallized optical fiber 2, the two fixing mechanisms 4 and the elastic base 3 includes the following steps: Using the fusion taper method, a precision motor is used under a microscope to control the stretching speed and displacement of the heated optical fiber, the diameter of the optical fiber is monitored, FBG fiber gratings are respectively arranged at both ends of the tapered optical fiber, and the tapered optical fiber and the fiber grating are fused to obtain a micro-nano optical fiber; the cladding on the surface of the micro-nano optical fiber is removed, and a metal coating is formed on the surface of the micro-nano optical fiber through chemical plating and metal plating processes to obtain a metallized optical fiber 2; for example, a wire stripper is used to remove the coating layer of the optical fiber, and a metal nickel layer is plated on the surface of the optical fiber by activating, sensitizing, chemically plating and electroplating the decoated optical fiber. The diameter of the tapered optical fiber is 5μm, and the coating thickness at the tapered optical fiber is 45μm, that is, the diameter after coating is 50μm; the length of the FBG fiber grating is 1mm, and the diameter after coating is 125μm; the metal nickel layer is used to enhance the interface bonding strength between the metallized optical fiber and the substrate, and enhance the high temperature resistance of the metallized optical fiber; Use CAD software to design a three-dimensional model of the two fixing mechanisms 4 and the elastic base 3; and export it into an STL format file; Use SLM-specific software to slice the 3D model and generate layer-by-layer 2D contour data; Use aluminum alloy powder (AlSi10Mg) to prepare the substrate structure, plan the laser scanning path, set the laser power, scanning speed and powder layer thickness, select the appropriate substrate, and clean and preheat the substrate; The metal powder is loaded into the powder feeding device and the powder is evenly spread on the substrate using a scraper to achieve the set powder layer thickness. The printing chamber is filled with inert gas. The high-purity inert gas atmosphere can prevent metal oxidation. The laser scans and melts the powder layer according to the slice data. After each layer of powder is melted, the substrate decreases by one layer, and the powder spreading-scanning process is repeated. When printing reaches the powder layer of the first embedding groove 100 and the second embedding groove 200, the chamber door is opened to sweep away the metal powder on the top layer, and the bent metallized optical fiber 2 is placed in the first embedding groove 100 and the second embedding groove 200. Printing is performed layer by layer again until printing is completely completed, thereby obtaining an integrated metallized optical fiber 2, two fixing mechanisms 4 and elastic matrix 3.

[0029] In this embodiment, a laser power of 350 W, a scanning speed of 1000 mm / s, and a layer thickness of 50 μm were used to ensure the interfacial bonding performance and high-temperature stability between the optical fiber and the metal substrate. The laser scanning path was set to a checkerboard pattern. The depth of the first and second beaded grooves 100 and 200 was 0.3 mm.

[0030] After the metallized optical fiber of the dual FBG fiber Bragg grating structure is implanted into the substrate, the temperature-strain in-body sensing of the structure under test can be realized. When the light passes through the curved structure of the elastic matrix 3 and reaches the second FBG fiber Bragg grating, there is a light intensity loss, forming a light intensity difference. The strain is measured in-body through the light intensity difference, and the temperature is measured in-body through the wavelength drift of the FBG fiber Bragg grating. Figure 1 and Figure 5 As shown in the figure, the light intensity variation of the first FBG fiber Bragg grating on the left is caused by the power fluctuation of the light source and the bending disturbance of the transmission fiber, while the light intensity fluctuation of the second FBG fiber Bragg grating on the right is coupled with the light intensity variation of the first FBG fiber Bragg grating and the light intensity variation caused by the bending of the fiber between the two FBG fiber Bragg gratings. The light intensity difference between the two can effectively measure strain.

[0031] According to the Marcuse principle, the initial optical fiber bending loss coefficient is expressed as: , is a constant, p 0 o'clock is 2, p When not 0 is 1; and are the radial normalized phase constant and radial normalized attenuation constant, respectively. V is the normalized frequency, d is the radius of the tapered fiber, is the axial propagation constant, and They are v -1st order sum v +1st order modified Bessel function.

[0032] In another aspect, the present invention provides an on-body sensing method using an integrated flexible optical fiber sensing device, comprising the following steps: S1: Configuring the aforementioned integrated flexible fiber optic sensing device; connecting the fiber Bragg grating (FBG) at one end of a metalized fiber 2 to the light source optical path. Metalized fiber 2 is obtained by attaching fiber Bragg gratings (FBGs) 5 at each end of a tapered fiber, creating a micro-nano fiber, and then further metallizing it. The optimization of the substrate structure, preparation of the metallization layer, and 3D printing to create the integrated flexible fiber optic sensing device are as previously described.

[0033] S2: Construct a light intensity loss and strain measurement model.

[0034] The content of step S2 is to set the FBG fiber grating 5 at both ends of the metallized optical fiber 2 to be FBG1 and FBG2 respectively, and the reflected light intensities of the FBG fiber grating 5 of the metallized optical fiber 2 in the initial state after the integrated molding are respectively The reflected light intensities of the FBG fiber grating 5 in the unbent state before the metallized optical fiber 2 is embedded in the two fixing mechanisms 4 and the elastic matrix 3 are respectively , the bending loss of FBG fiber Bragg grating 5 when it is not subjected to external force is: ,in, r is the initial bending radius of the metallized optical fiber 2 embedded in the first embedding groove 100 and the second embedding groove 200; is the ratio of the length of the metallized optical fiber 2 corresponding to the initial bending radius of the first arc segment 31 to the circumference of the virtual circle corresponding to the initial bending radius, is the optical fiber bending loss coefficient in the initial state, then the bent metallized optical fiber 2 at the first arc segment 31 is x Axial elongation , and the metallized optical fiber 2 at the connecting beam 33 is x Axial elongation , satisfying the following relationship, x The axial direction is the length extension direction of the fixing mechanism 4, R 0 is the bending radius of the first arc segment 31 of the metallized optical fiber 2 after being stretched by the external load, is the included angle between the two ends of the first arc segment 31, ;strain The relationship between the bending radius of the metallized optical fiber 2 is: , L For the elastic matrix 3 x The total length in the axial direction, R is the bending radius of the first arc segment 31 when there is no external load, , is the angle between the connecting beam 33 and the longitudinal center plane of the two fixing mechanisms 4; and light intensity loss The mapping relationship is: .

[0035] S3: By obtaining the light intensity difference of the fiber Bragg grating at both ends of the metallized optical fiber 2, the temperature and strain are solved by using the wavelength-light intensity hybrid demodulation method of the dual fiber Bragg grating.

[0036] The content of step S3 is that when subjected to external load, the light intensity loss coefficient of the metallized optical fiber 2 is The relationship between the optical intensity loss and the bending radius of the first arc segment 31 of the current metallized optical fiber 2 is: ,in are the peak light intensities of the FBG fiber grating 5 at both ends of the metallized optical fiber 2 under external load; is the current bending radius of the first arc segment 31 after being subjected to external load RThe ratio of the length of the metallized optical fiber 2 corresponding to 0 to the circumference of the virtual circle corresponding to the initial bending radius; is the bending loss coefficient of the optical fiber under external load ;make , ; Changes in the central wavelength of the FBG fiber grating 5 and temperature Proportional, , are the center wavelength drifts of the FBG fiber grating 5 at both ends of the metallized optical fiber 2, are the center wavelengths of the FBG fiber grating 5 at both ends of the metallized optical fiber 2, is the coefficient of thermal expansion, is the thermo-optical coefficient, is the temperature change, the relationship between the comprehensive temperature change and wavelength drift, strain and light intensity loss The mapping relationship is obtained , and is a constant, and the strain variation is obtained by obtaining the center wavelength drift of the FBG fiber grating 5. and temperature change . It can be seen that we only need to determine the constant K T 、 K ε 、 and , we can determine ∆ according to the change in the central wavelength of the reflected light from the fiber Bragg grating. ε ,∆ T That is, it can realize the composite measurement of structural temperature and strain under different environments.

[0037] The operating temperature range of the integrated flexible optical fiber sensing device of this embodiment is 20°C to 500°C. Within the operating temperature range of 500°C, the temperature linearity is better than 0.9878, and the temperature and strain decoupling performance is good. By constructing light intensity-wavelength composite perception data and processing it through a neural network algorithm, the maximum decoupling error is less than 8%.

[0038] The neural network algorithm mentioned here is to measure temperature and strain simultaneously in practical applications. However, due to the coupling effect between the two, decoupling processing needs to be achieved through neural network and other algorithms. In this embodiment, the sensor adopts a dual FBG fiber grating structure: the incident light is first reflected by the left FBG fiber grating FBG1 to form a light intensity signal. I 1, and then transmitted to the FBG fiber Bragg grating FBG2 on the right through the flexible bending structure defined by the elastic matrix. The bending deformation of the flexible structure will cause light loss, resulting in the light intensity signal of the FBG fiber Bragg grating FBG2 on the right I2 produces strain-related attenuation, so the light intensity difference and the strain present a nonlinear mapping relationship. At the same time, the central wavelength drift of any FBG fiber grating Δ λ It can characterize temperature changes, but the thermal expansion effect will cause wavelength drift and thermal strain at the same time, forming cross-coupling interference. To this end, it is necessary to establish a I and Δ λ The decoupling algorithm takes θ as input and θ and θ as output. The following is a detailed introduction to the neural network decoupling algorithm.

[0039] In the modeling of algorithm structure, since temperature can also cause thermal strain, but strain is mainly caused by external force, there is both correlation and difference between the two output variables, namely strain and temperature. Therefore, it is not a good method to adopt independent modeling strategy and coupled modeling strategy in algorithm structure modeling. In this paper, a decoupling algorithm modeling strategy is proposed to improve the decoupling accuracy. Figure 1 As shown in FIG, in this strategy, the established model includes a shared part and multiple decoupled parts, where the decoupled part corresponds to the output variable, and the shared part and the decoupled part in the model represent the correlation and difference between the output variables to a certain extent.

[0040] Depend on Figure 7 The decoupling strategy described above constructs a decoupling model of the embodiment. In the embodiment, the inputs are the same, namely, the light intensity difference and the center wavelength drift, and the outputs are both strain and temperature, such as Figure 8 and Figure 9 As shown in the figure, a multi-layer perceptron multi-channel extreme learning machine decoupling network is established. This model primarily consists of three channels of an extreme learning machine with the same multi-layer perceptron. Each channel outputs strain and temperature predictions, and the final strain and temperature are the weighted averages of the outputs of these three channels. The multi-channel architecture facilitates more stable predictions. For a specific channel, the multi-layer perceptron extreme learning machine structure has two hidden layers. The first layer serves as a shared component with 100 neurons. The second layer contains two decoupling components, corresponding to strain and temperature, with 50 and 35 neurons, respectively. Reinforced linear unit (ReLU) activation function is used.

[0041] A dual-FBG wavelength-intensity hybrid demodulation method is used to resolve temperature and strain. By constructing a light intensity loss and strain measurement model, the strain measurement range is extended to 37.520με, and the FBG wavelength can accurately map the ambient temperature.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An integrated flexible optical fiber sensing device, characterized in that: include: Two fixing mechanisms are arranged in parallel and at intervals, and are used to be fixed to the surface of the structure to be measured, and the end surfaces of the two fixing mechanisms are correspondingly provided with first embedding grooves; The elastic base is provided in the area between the two fixing mechanisms and is arranged in a curved shape. A second embedding groove is provided on the end surface of the elastic base, and the second embedding groove is also interconnected with the first embedding grooves on the two fixing mechanisms; The metallized optical fiber is sequentially embedded in the first embedding groove and the second embedding groove. Both ends of the metallized optical fiber located in the first embedding groove are provided with FBG optical fiber gratings. The metallized optical fiber is integrated with the two fixing mechanisms and the elastic matrix.

2. The integrated flexible optical fiber sensing device according to claim 1, characterized in that: The elastic base includes two first arc segments, two second arc segments and a connecting beam. The connecting beam is located between the two fixing mechanisms and is set at an angle to the longitudinal center planes of the two fixing mechanisms. One end of the two first arc segments is fixedly connected to the adjacent side surfaces of the two fixing mechanisms, and the other end of the two first arc segments is fixedly connected to one end of the two second arc segments in a one-to-one correspondence. The other end of the two second arc segments is fixedly connected to different ends of the connecting beam.

3. The integrated flexible optical fiber sensing device according to claim 2, characterized in that: The two first arc segments and the two second arc segments have the same initial bending radius, the central angle of the first arc segment is 90°, the central angle of the second arc segment is 180°, and the length of the connecting beam is twice the initial bending radius of the first arc segment.

4. The integrated flexible optical fiber sensing device according to claim 2, characterized in that: The deviation of the central wavelength of the FBG fiber grating at both ends of the metallized optical fiber is 2-5nm.

5. The integrated flexible optical fiber sensing device according to claim 2, characterized in that: The process of integrating the metallized optical fiber with the two fixing mechanisms and the elastic matrix includes the following steps: Using the fused tapered method, a precision motor is used under a microscope to control the drawing speed and displacement of the heated optical fiber, monitor the diameter of the optical fiber, and place fiber Bragg gratings (FBGs) at both ends of the tapered optical fiber. The tapered optical fiber and the FBGs are then fused together to produce a micro-nano optical fiber. The cladding is then removed, and a metal coating is formed on the surface of the micro-nano optical fiber through chemical plating and metal plating processes to produce a metallized optical fiber. Use CAD software to design the three-dimensional models of the two fixing mechanisms and the elastic base; Use the slicing tool to slice the 3D model and generate layer-by-layer 2D contour data; Plan the laser scanning path, set the laser power, scanning speed and powder layer thickness, select the appropriate substrate, and clean and preheat the substrate; Load the metal powder into the powder feeding device and use a scraper to evenly spread the powder on the substrate to achieve the set powder layer thickness; fill the printing chamber with inert gas; The laser scans and melts the powder layer according to the slice data. After each layer of powder is melted, the base plate decreases by one layer, and the powder spreading-scanning process is repeated. When printing reaches the powder layer of the first and second embedding grooves, the chamber door is opened to sweep away the metal powder on the top layer, and the bent metallized optical fiber is placed in the first and second embedding grooves, and printing is performed layer by layer again until printing is completely completed, obtaining an integrated metallized optical fiber, two fixing mechanisms and elastic matrix.

6. The integrated flexible optical fiber sensing device according to claim 5, characterized in that: The depth of the first and second embedding grooves is 1.2-1.5 times the diameter of the metallized optical fiber, the width of the first and second embedding grooves is 1.1-1.3 times the diameter of the metallized optical fiber, and the cross-section of the first and second embedding grooves is elliptical.

7. The integrated flexible optical fiber sensing device according to claim 2, characterized in that: The elastic base and the two fixing mechanisms have the same height, and the width of the elastic base is greater than the height of the elastic base; the angle between the connecting beam and the longitudinal center plane of the two fixing mechanisms is 30 degrees.

8. An on-body sensing method using an integrated flexible optical fiber sensing device, characterized in that: The steps include: S1: An integrated flexible optical fiber sensing device as described in any one of claims 3 to 7 is configured; a fiber Bragg grating (FBG) at one end of a metallized optical fiber is connected to a light source optical path; the metallized optical fiber is obtained by providing a fiber Bragg grating (FBG) at each end of a tapered optical fiber to obtain a micro-nano optical fiber and further providing a metal coating; S2: Constructing a light intensity loss and strain measurement model; S3: By obtaining the light intensity difference of the fiber Bragg grating at both ends of the metallized optical fiber, the temperature and strain are solved by using the wavelength-intensity hybrid demodulation method of the dual fiber Bragg grating.

9. The on-body sensing method of the integrated flexible optical fiber sensing device according to claim 8, characterized in that: The content of step S2 is to obtain the bending loss of the FBG fiber grating when it is not subjected to external force; obtain the bending loss of the metallized optical fiber at the first arc segment; x The elongation in the axial direction and the metallized optical fiber at the connecting beam are x The elongation in the axial direction, x The axial direction is the length extension direction of the fixing mechanism, the bending radius of the first arc segment when not subjected to an external load, and the bending radius of the first arc segment of the metallized optical fiber after being stretched by an external load, and a mapping relationship between strain and light intensity loss is constructed.

10. The on-body sensing method of the integrated flexible optical fiber sensing device according to claim 9, characterized in that: Step S3 includes constructing a mapping relationship between light intensity loss and the bending radius of the first arc segment of the metallized optical fiber when subjected to an external load; obtaining a relationship that the central wavelength of the FBG fiber grating is proportional to the temperature change; and comprehensively calculating the mapping relationship between light intensity loss and the bending radius of the first arc segment of the metallized optical fiber when subjected to an external load, the relationship between the temperature change and the wavelength drift, and the mapping relationship between strain and light intensity loss to obtain the strain change and the temperature change.

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