A fiber grating vibration sensor based on S-shaped elastomer and a sensitive wedge beam

Abstract

The application discloses a fiber grating vibration sensor based on S-shaped elastic bodies and sensitive wedge beams, which comprises a fixed base, two groups of counterweight mass blocks symmetrically arranged on the fixed base, S-shaped elastic bodies symmetrically arranged above and below each counterweight mass block, and the ends of two S-shaped elastic bodies in the same horizontal direction being connected; a sensitive wedge beam is arranged between each S-shaped elastic body and the counterweight mass block, and the sensitive wedge beam is used for amplifying the vibration pickup feedback displacement of the counterweight mass block; a double fiber grating string is arranged between the two counterweight mass blocks, one end of the double fiber grating string penetrates through the fixed base and is connected with a sealing end and an armored optical cable, and the other end of the double fiber grating string is arranged in the fixed base. The application realizes pickup of an ultralow-frequency vibration signal and has high sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic grating sensors, specifically relating to a fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitivity-enhancing wedge beam. Background Technology

[0002] Vibration exists in all aspects of production and daily life, such as in large buildings like bridges, high-rises, and mines; transportation vehicles like airplanes, high-speed trains, and ships; and various large instruments and equipment. When these projects experience abnormal vibrations, structural health problems are usually present. Low-frequency vibration monitoring plays an important role in vibration monitoring. For example, the operating speed of a large hydroelectric generator unit is approximately 60 r / min (rotation frequency of 1 Hz). The vibration caused by water eddies is about 1 / 3 of the rotational speed, or about 0.3 Hz. The natural frequency of highway and railway bridges with spans of 30–60 m is generally around 2 Hz; the natural frequency of a high-rise building reaching a height of 400 m is 0.16 Hz; the first-order natural frequency of a heavy gravity dam is around 3 Hz, while the first-order natural frequency of a lighter arch dam is around 1.5 Hz. Therefore, it is necessary to conduct real-time online monitoring of the key load-bearing components of large-scale projects through a series of detection and analysis methods.

[0003] In low-frequency vibration sensing and monitoring applications, compared to traditional electromagnetic sensors, fiber Bragg grating sensors offer advantages such as simple structure, high stability, high precision, wide dynamic range, and resistance to electromagnetic interference. Fiber Bragg grating sensors can utilize wavelength division multiplexing (WDM) technology to form fiber optic sensor networks, which, when connected to fiber Bragg grating demodulation equipment, enable large-scale, long-distance monitoring of various signals.

[0004] Research on low-frequency fiber Bragg grating vibration sensors currently focuses on enhancing sensitivity to low-frequency vibration signals through various elastic structures and encapsulation materials. The elastic structures primarily include embedded, cantilever beam, and spindle spring oscillator types. Each type of fiber Bragg grating vibration sensor has its advantages and disadvantages. Embedded structures have high resonant frequencies and low sensitivity, making them difficult to measure weak low-frequency vibration signals. Cantilever beam structures are simple and have become classic elastic elements for low-frequency vibration fiber Bragg grating sensors. Hollow beam, double cantilever beam, and U-beam structures have emerged, but because the sensitive grating is directly glued to the cantilever beam surface, chirping or multi-peak phenomena easily occur, leading to inaccurate measurements, low sensitivity, and poor stability. While spindle spring oscillator structures can pick up low-frequency vibration signals, their complex structure makes them difficult to encapsulate and they are susceptible to lateral interference. Based on the design concept of the main vibration elastic element, domestic and foreign experts have conducted extensive and in-depth research on the design of low-frequency vibration fiber Bragg grating (FBG) sensors. Flexible hinge-type FBG vibration sensors have also emerged. Zhang Faye designed an FBG accelerometer based on a flexible hinge structure with a response frequency of 10–240 Hz and a sensitivity of 236 pm / g, but it lacks temperature compensation functionality. Currently, the measurement frequency range of vibration sensors is mainly concentrated above 10 Hz, but sensors for picking up vibrations below 10 Hz or even ultra-low frequency signals are rarely reported. Therefore, developing high-sensitivity, ultra-low frequency vibration feedback, a wide response frequency range, strong lateral anti-interference ability, and temperature compensation capabilities has become the main direction for the design of low-frequency FBG vibration sensors. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitive wedge beam, which can pick up ultra-low frequency vibration signals with high sensitivity.

[0006] Technical Solution: The fiber Bragg grating vibration sensor of the present invention, based on an S-shaped elastomer and a sensitivity-enhancing wedge beam, includes a fixed base, two sets of counterweights symmetrically arranged on the fixed base, an S-shaped elastomer symmetrically arranged above and below each counterweight, and the ends of two S-shaped elastomers in the same horizontal direction connected together; a sensitivity-enhancing wedge beam is arranged between each S-shaped elastomer and the counterweight, the sensitivity-enhancing wedge beam being used to amplify the vibration feedback displacement of the counterweight; a double fiber Bragg grating string is arranged between the two counterweights, one end of the double fiber Bragg grating string passing through the fixed base and connected to the end cap and armored optical cable, the other end being located inside the fixed base.

[0007] Furthermore, the fixed base, S-shaped elastomer, and sensitive wedge beam are all made of the same elastic alloy material by wire cutting. Therefore, the elastic sensitive component has no other related components, which reduces redundant errors and improves the stability of the sensor.

[0008] Furthermore, all the S-shaped elastomers and all the sensitive-enhancing wedge beams on the fixed base constitute the vibration elastic system of the sensor. The elastic coefficient K of the vibration elastic system has a direct impact on the sensor's sensitivity S and natural resonant frequency f0, and the elastic coefficient K of the vibration elastic system is determined by its material elastic modulus E, the structural parameters of the S-shaped elastomers and the sensitive-enhancing wedge beams.

[0009] Furthermore, the calculation formulas for the elastic coefficient K of the vibration elastic system, the sensitivity S of the sensor, and the natural resonant frequency f0 are as follows:

[0010]

[0011]

[0012]

[0013] In the formula, L represents S-type elasticity. body Length; t represents the height of the S-shaped elastic body; b represents the width of the cross-section of the S-shaped elastic body; h represents the thickness; n represents the number of elastic units; W represents the length of the wedge beam; m represents the total mass of the central component of the fixed base and all counterweights; λ B The wavelength of the Bragg grating is given; L, t, b, h, n, and W are obtained through optimization analysis based on the required parameters of sensitivity S and natural resonant frequency f0.

[0014] Furthermore, the counterweight mass block is made of hard alloy material and is fixed to the central component of the fixed base by fixing screws to form a vibrating mass block.

[0015] Furthermore, the dual fiber gratings are etched onto a single optical fiber and arranged in a symmetrical package, with wavelengths between 1525 and 1565 nm selected, and the wavelength difference between the two gratings exceeding 5 nm.

[0016] Furthermore, the fixed base is provided with a first groove and a second groove distributed vertically in the middle, and the two gratings of the dual fiber grating string are respectively placed in the first groove and the second groove.

[0017] Furthermore, the fixed base is provided with a third groove, a fourth groove, and a fifth groove, and the bare fiber portions at both ends and in the middle of the dual fiber grating string are encapsulated in the third groove, the fourth groove, and the fifth groove of the fixed base by optical adhesive.

[0018] Furthermore, the mounting surface of the fixed base is machined with threaded holes and fixed to the sensor vibration measurement mounting surface by a variable diameter adapter screw.

[0019] Furthermore, a groove is formed between the vibrating mass block and the fixed base, so that there is an elastic buffer area when the vibrating mass block and the optical fiber deform and move up and down. This allows the vibrating mass block to have a large displacement in the vertical direction, and also ensures that the sensor will not break the optical fiber when subjected to large vibration impact.

[0020] The technical solution of this invention utilizes a vibration response system composed of S-shaped elastic bodies, sensitive wedge beams, and vibrating mass blocks symmetrically distributed on the upper and lower and left and right sides to pick up external excitations, and employs dual gratings as vibration sensing elements. When the vibration response system is subjected to external excitation acceleration along the vertical direction, the vibrating mass block, due to inertia, applies tensile and compressive forces to the elastic components composed of the symmetrical S-shaped elastic bodies and wedge beams respectively. Consequently, the upper and lower gratings are stretched and compressed respectively, experiencing strains of equal amplitude and opposite direction. The grating wavelength drifts are opposite, and the vibration sensitivity is multiplied, thereby converting the external vibration signal into a wavelength modulation signal of the fiber optic grating, which is then connected to a fiber optic grating demodulation device for demodulation of the vibration wavelength signal.

[0021] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0022] (1) The sensor improves vibration sensitivity in many ways by using an S-shaped elastic structure with reduced structural stiffness, a wedge beam to amplify vibration feedback, and increasing the mass of the mass block. Temperature compensation is achieved by using a dual grating packaging method. This makes the sensor have advantages such as high sensitivity, good ultra-low frequency vibration pickup capability, wide response frequency band, stable signal output, strong lateral anti-interference capability, simple structure, and easy realization of multi-dimensional vibration measurement.

[0023] (2) This invention reduces the structural elastic coefficient through parametric design of S-shaped elastomer, amplifies the vibration feedback displacement of mass block by wedge beam, and increases vibration sensitivity by adding vibration response mass, thereby achieving the pickup of ultra-low frequency vibration signals with a sensitivity of about 840 pm / g and a minimum pickup frequency of 0.5 Hz.

[0024] (3) The present invention uses the same elastic alloy material to integrally process the fixed base and the elastic structure. The elastic sensitive component has no other related components, which reduces redundant error and improves the stability of the sensor.

[0025] (4) There are grooves of a certain width between the S-shaped elastic structures, which makes the vibrating mass block and the optical fiber have an elastic buffer area, so that the excitation mass block has a large displacement along the vertical direction, and also ensures that the sensor will not break the optical fiber when subjected to large vibration impact, thus improving the reliability of the sensor.

[0026] (5) The present invention achieves temperature compensation self-compensation through a dual grating structure. Since the dual gratings are symmetrically packaged with the same optical fiber, the strain of external vibration is exactly opposite and equal in amplitude. The temperature environment of the two packaged gratings is the same. Therefore, the influence of temperature drift (the difference in wavelength signal of the demodulated symmetrical grating) can be eliminated and the sensitivity can be multiplied by signal matching of the dual sensing gratings. This can effectively improve the low-frequency vibration pickup capability of the sensor. Attached Figure Description

[0027] Figure 1 This is the front view of the present invention;

[0028] Figure 2 This is the left view of the present invention;

[0029] Figure 3 This is a schematic diagram of the structure of the S-shaped elastomer (1 / 4 basic elastic unit) and the sensitive wedge beam of the present invention;

[0030] Figure 4 The time-domain response diagram of the fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitive wedge beam of the present invention is shown.

[0031] Figure 5 This is a linear response diagram of the fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitive wedge beam according to the present invention. Detailed Implementation

[0032] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0033] like Figure 1-2As shown, the fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitivity-enhancing wedge beam of the present invention includes a fixed base 1, a set screw 2, an S-shaped elastomer 31, a sensitivity-enhancing wedge beam 32, a counterweight block 4, a fixing screw 5, a central component 6, a dual fiber optic grating string 7, an elastic buffer region 8, an end cap 9, a plastic sleeve 10, an armored optical cable 11, a first groove 12, a second groove 13, a third groove 14, a fourth groove 15, a fifth groove 16, and a vibrating mass block 17. The fixed base 1, the S-shaped elastomer 31, the sensitivity-enhancing wedge beam 32, and the central component 6 are all made of the same elastic alloy material and are wire-cut. There are four counterweight blocks 4, which are symmetrically arranged on the horizontal center line of the fixed base 1. In this embodiment, the counterweight blocks 4 are fixed to the threaded holes machined in the middle of the fixed base 1 by fixing screws 5. Each counterweight mass 4 has symmetrically arranged wire-cut S-shaped elastic bodies 31 above and below it. The ends of two S-shaped elastic bodies 31 in the same horizontal direction are connected. A sensitivity-enhancing wedge beam 32 is arranged between each S-shaped elastic body 31 and the counterweight mass 4. The two sensitivity-enhancing wedge beams 32 in the vertical direction are symmetrical, and the two sensitivity-enhancing wedge beams 32 in the horizontal direction are symmetrical. The two S-shaped elastic bodies 31 in the horizontal direction are symmetrical. The four counterweight mass blocks 4 distributed on the left and right sides and front and back are located between the upper and lower S-shaped elastic bodies 31.

[0034] The mounting surface of the fixed base 1 has threaded holes, and the sensor needs to be fixed to the vibration measurement mounting surface by means of a variable diameter adapter screw.

[0035] A double fiber Bragg grating string 7 is arranged between the two counterweight blocks 4. The double fiber Bragg grating string 7 is etched onto a single optical fiber and arranged symmetrically in a top-bottom configuration. The wavelength is selected between 1525 and 1565 nm, and the wavelength difference between the two gratings exceeds 5 nm. A first groove 12 and a second groove 13 are machined in the middle of the fixing base 1, and the first groove 12 and the second groove 13 are distributed vertically. The two gratings of the double fiber Bragg grating string 7 are placed in the first groove 12 and the second groove 13, respectively. A third groove 14, a fourth groove 15, and a fifth groove 16 are also machined on the fixing base 1. The two ends and the bare fiber portion in the middle of the double fiber Bragg grating string 7 are sealed in the third groove 14, the fourth groove 15, and the fifth groove 16 of the fixing base 1 using optical adhesive. One end of the dual fiber Bragg grating string 7 passes through the fixed base 1 and is connected to the end cap 9 and the armored optical cable 11, while the other end is located inside the fixed base 1. Specifically, the optical fiber at one end of the tension-fixed dual fiber Bragg grating string 7 passes through the threaded hole of the fixed base 1, the end cap 9, and the armored optical cable 11, respectively. The bare fiber at the other end is glued and terminated inside the groove 14 of the fixed base 1. It is tightened into the threaded hole on the mounting surface of the fixed base 1 by the set screw 2. One end of the end cap 9 is fixed in the threaded hole machined on the upper surface of the fixed base 1. The other end of the end cap 9 is extruded and fixed to the armored optical cable 11 by cold pressing tube. The plastic sleeve 10 passes through the armored optical cable 11 and is connected to the end cap 9 by sealing silicone.

[0036] All the S-shaped elastic bodies 31 and all the sensitivity-enhancing wedge beams 32 on the fixed base 1 constitute the vibration elastic system of the sensor. The elastic coefficient K of the vibration elastic system directly affects the sensor's sensitivity S and natural resonant frequency f0, and the elastic coefficient K of the vibration elastic system is mainly determined by its material elastic modulus E, the structural parameters of the S-shaped elastic bodies 31 and the sensitivity-enhancing wedge beams 32. Among them, the S-shaped elastic body 31 has a relatively symmetrical structure, so 1 / 4 of the basic unit is taken for structural mechanics research, such as... Figure 3 As shown, the following analysis uses the energy method in mechanics of materials to divide the unit into two parts and analyze the displacement under the action of a vertically upward force F applied along the axis of symmetry.

[0037] Part 1: M1(x) = Fx, N1(x) = 0, 0 ≦x ≦Lb;

[0038]

[0039] Part 2: M2(x)=F(Lb / 2), N2(x)=F, 0≦x≦tb;

[0040]

[0041] The total displacement δ of the 1 / 4 basic unit of the S-type elastic body 1 / 4总 Let A = bh, I = b3h / 12:

[0042]

[0043] The total displacement of a basic element under the action of an axial force F is:

[0044]

[0045] According to the linear elasticity theory K = F / δ, the axial elastic coefficient K of an S-shaped elastic body with n basic units is... S for:

[0046]

[0047] The sensitive-enhanced wedge beam 32 is simplified into an isotropic cantilever beam with a uniform cross-section. From this, the axial elastic modulus K of the end face of the wedge beam can be obtained. L for:

[0048]

[0049] The axial elastic coefficient K of the sensor elastic system 总 for:

[0050]

[0051] According to the definition of accelerometer sensitivity, the sensor sensitivity S is the ratio of the change in the center wavelength of the fiber optic grating to the acceleration a, i.e.: S = Δλ / a, where Δλ is the change in the center wavelength of the sensing grating due to strain, which can be expressed as:

[0052] Δλ B =(1-P e )δ αx λ B (8)

[0053] In the formula P e The effective photoelastic coefficient is related to the photoelastic effect of the optical fiber; δ αx Let be the strain experienced by the fiber grating along its axial direction. Equations (7), (8), and δ αx Substituting F / K and F=ma into S=Δλ / a, we obtain the expression for the sensitivity S1 of the single-sided strain grating of the sensor:

[0054]

[0055] According to the formula for the natural frequency of a structure, the resonant frequency f0 of the sensor can be obtained as follows:

[0056]

[0057] In the formula, L represents the length of the S-shaped elastic body; t represents the height of the S-shaped elastic body; b represents the width of the cross-section of the S-shaped elastic body; h represents the thickness; n represents the number of elastic units; W represents the length of the wedge beam; m represents the total mass of the central component of the fixed base and all counterweights; λ B The wavelength of the Bragg grating is given; L, t, b, h, n, and W are obtained through optimization analysis based on the required parameters of sensitivity S and natural resonant frequency f0.

[0058] Combination Figure 2 The central component 6 has four rectangular grooves of a certain depth symmetrically machined in the front, back, left, and right. A through threaded hole is machined in the middle of the rectangular grooves on the left and right sides. Four counterweights 4 are embedded in the rectangular grooves and are fixed to the central component 6 by fixing screws 5 to form a vibrating mass block 17. The counterweights 4 are made of hard alloy material with a density of 14.7 g / cm3, which is heavier than the density of the fixed base substrate (8.0 g / cm3). As can be seen from equation (10), the heavier the vibrating mass block 17, the higher the sensor sensitivity.

[0059] like Figure 1 As shown, a groove of a certain width is formed between the vibrating mass block 17 and the fixed base 1, so that there is an elastic buffer area 8 when the vibrating mass block 17 and the optical fiber deform and move up and down. In this embodiment, the width of the groove is more than 3 times the width b of the cross section of the S-shaped elastic body.

[0060] During the packaging process, the dual fiber Bragg grating string 7 needs to be clamped on a displacement fixture under a certain tension. The bare fiber portions on both sides and in the middle of the dual grating are encapsulated in the grooves of the fixing base using optical adhesive. When the sensor receives external excitation and vibrates, the center wavelength changes of FBG1 and FBG2 are as follows:

[0061]

[0062]

[0063] In equations (11) and (12), Δλ B1 , Δλ B2 , λ B1 , λ B2 α1 and α2 are the changes in center wavelength and center wavelength of FBG1 and FBG2, respectively; P is the photoelastic coefficient; α1 and α2 are the coefficients of thermal expansion of FBG1 and FBG2, respectively; ξ1 and ξ2 are the thermo-optic coefficients of FBG1 and FBG2, respectively; ΔT is the temperature change; ε1 and ε2 are the strains of FBG1 and FBG2, respectively.

[0064] Since the two Bragg gratings have the same temperature sensitivity coefficient, when the elastic body vibrates up and down, the strain of the two gratings is equal in magnitude and opposite in direction, i.e., ε1=-ε2=ε. Therefore, subtracting equation (12) from equation (11) yields:

[0065]

[0066] According to the vibration acceleration sensitivity formula S=Δλ / a, the wavelength difference of a dual fiber grating string is twice that of a single fiber grating. Therefore, the sensitivity of a vibration sensor using a dual fiber grating string will be doubled, and the influence of external temperature on the measurement results can be compensated.

[0067] To verify the beneficial effects of the present invention, an experimental study was conducted on a vibration testing environment built using the fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitive wedge beam according to the present invention. The experimental results are as follows:

[0068] The experimental instruments used included: a standard vertical vibration table, an ultra-low frequency vibration table motion quantity tester, a vibration calibration device control instrument, and a dynamic fiber optic grating demodulator.

[0069] 1. Sensitivity Test

[0070] According to the operating procedures of the low-frequency standard vibration table system, an external excitation of 10Hz and 1g is applied to the standard vibration table, causing a drift in the center wavelength of the two vibration gratings of the fiber optic vibration sensor based on an S-shaped elastomer and a sensitive wedge beam fixed on the vibration table surface. The amount of wavelength drift of the two gratings is detected using a dynamic fiber optic demodulator. Figure 4 The figure shown is the vibration time-domain wavelength response diagram of the fiber optic grating vibration sensor based on the S-shaped elastomer and the sensitive wedge beam of this invention.

[0071] from Figure 4 As can be seen from the above, the fiber optic grating vibration sensor based on S-shaped elastomer and sensitive wedge beam of this invention has equal waveform amplitudes on both sides of the grating when excited in the vertical direction, and is symmetrical from top to bottom. The wavelength change of one side of the grating is 420 pm / g, and the wavelength change of the other side of the grating is 419.5 pm / g. According to formula (11), the sensitivity of the vibration sensor is twice the grating change, and the sensitivity of the vibration sensor is about 840 pm / g.

[0072] 2. Amplitude-frequency response

[0073] According to the operating procedures of the low-frequency standard vibration table system, the standard vibration table is controlled to apply external excitation of the same amplitude but different frequencies. The excitation amplitude is set to 0.02g, and the excitation frequency is continuously adjusted from 0.5, 1, 2, 4, 6, 8, 10, 20, 40, 60, and 80Hz. This causes the center wavelength of the vibration gratings on both sides of the fiber optic vibration sensor based on an S-shaped elastomer and a sensitive wedge beam, which is fixed on the surface of the vibration table, to drift. The wavelength drift of the gratings on both sides is detected by a dynamic fiber optic demodulator. Table 1 below shows the dynamic characteristic data of the fiber optic vibration sensor based on an S-shaped elastomer and a sensitive wedge beam at different frequencies with the same amplitude.

[0074]

[0075]

[0076] As can be seen from the table above, the fiber optic grating vibration sensor based on the S-shaped elastomer and the sensitive wedge beam of this invention exhibits relatively stable wavelength changes under external excitation of the same amplitude but different frequencies. The lowest responsive operating frequency can reach 0.5Hz, and the highest responsive operating frequency can reach 80Hz. That is, the vibration response operating range is 0.5Hz to 80Hz, and the response flatness is <3dB.

[0077] 3. Linear response characteristics

[0078] According to the operating procedures of the low-frequency standard vibration table system, the standard vibration table is controlled to apply external excitation of the same frequency but different amplitudes. The excitation amplitude is set to 10Hz and continuously adjusted within the range of 0.2, 0.4, 0.6, 0.8, and 1g. This causes a drift in the center wavelength of the vibration gratings on both sides of the fiber optic vibration sensor based on an S-shaped elastomer and a sensitive wedge beam, which is fixed on the surface of the vibration table. The wavelength drift of the gratings on both sides is detected using a dynamic fiber optic demodulator. Figure 5 The graph shows the linear response of the fiber optic grating vibration sensor based on the S-shaped elastomer and the sensitive wedge beam under external excitation of the same frequency but different amplitudes.

[0079] from Figure 5 As can be seen, the linear response fitting curve of the vibration sensor has an R² value of 0.9955 and a nonlinearity of 0.06%, indicating that the fiber optic grating vibration sensor has a good linear response.

[0080] In summary, the technical solution of this invention employs a symmetrically packaged dual-grating structure that achieves identical amplitude and reverse direction when sensing external vibration strain. Signal matching through the dual sensing gratings eliminates the influence of temperature drift and improves sensitivity, effectively enhancing the sensor's low-frequency vibration pickup capability. This invention offers a wide operating response range, achieving high sensitivity and linearity while eliminating the effects of temperature drift and realizing low-frequency vibration pickup capability, making it easily expandable into a three-dimensional vibration sensor.

Claims

1. A fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitivity-enhancing wedge beam, characterized in that: Includes a fixed base (1), two sets of counterweight blocks (4) symmetrically arranged on the fixed base (1), and S-shaped elastic bodies (31) symmetrically arranged above and below each counterweight block (4), with the ends of the two S-shaped elastic bodies (31) on the same horizontal plane connected together; A sensitive-enhancing wedge beam (32) is provided between each of the S-shaped elastic bodies (31) and the counterweight mass block (4). The sensitive-enhancing wedge beam (32) is used to amplify the vibration feedback displacement of the counterweight mass block (4). A double fiber grating string (7) is set between the two counterweight mass blocks (4). One end of the double fiber grating string (7) passes through the fixed base (1) and is connected to the end cap (9) and the armored optical cable (11). The other end is set inside the fixed base (1). The counterweight mass blocks (4) are all fixedly connected to the central component (6) in the fixed base (1) by fixing screws (5) to form a vibrating mass block (17). The fixed base (1) is provided with a first groove (12) and a second groove (13) distributed vertically in the middle, and the two gratings of the double fiber grating string (7) are respectively placed in the first groove (12) and the second groove (13); The fixed base (1) is provided with a third groove (14), a fourth groove (15), and a fifth groove (16). The bare fiber portions at both ends and in the middle of the double fiber grating string (7) are sealed in the third groove (14), the fourth groove (15), and the fifth groove (16) of the fixed base (1) by optical adhesive.

2. The fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitivity-enhancing wedge beam according to claim 1, characterized in that: The fixed base (1), S-shaped elastomer (31), and sensitive wedge beam (32) are all made of the same elastic alloy material by wire cutting.

3. The fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitivity-enhancing wedge beam according to claim 1, characterized in that: All the S-shaped elastic bodies (31) and all the sensitive-enhancing wedge beams (32) on the fixed base (1) constitute the vibration elastic system of the sensor. The elastic coefficient of the vibration elastic system is... Sensitivity of the sensor and inherent resonant frequency It has a direct impact, and the elastic coefficient of the vibrating elastic system Due to its material elastic modulus The structural parameters of the S-shaped elastomer (31) and the sensitive wedge beam (32) are determined.

4. The fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitivity-enhancing wedge beam according to claim 3, characterized in that: The elastic coefficient of the vibration elastic system Sensor sensitivity and inherent resonant frequency The calculation formula is as follows: ； ； ； In the formula, Indicates S-shaped elasticity body length; Indicates the height of the S-shaped elastomer; Indicates the width of the cross-section of the S-shaped elastomer; Expressed as thickness; This is expressed as the number of elastic units; Expressed as the length of the wedge-shaped beam; This represents the total mass of the central component of the fixed base and all the counterweight blocks. The wavelength of the Bragg grating; , , , , , Based on sensitivity and inherent resonant frequency The required parameters were obtained through optimization analysis.

5. The fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitivity-enhancing wedge beam according to claim 1, characterized in that: The counterweight (4) is made of hard alloy material.

6. The fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitivity-enhancing wedge beam according to claim 1, characterized in that: The dual fiber grating string (7) is engraved on a single optical fiber and arranged in a symmetrical package. The wavelength is selected between 1525 and 1565 nm, and the wavelength difference between the two gratings exceeds 5 nm.

7. The fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitivity-enhancing wedge beam according to claim 1, characterized in that: The mounting surface of the fixed base (1) is machined with threaded holes and fixed to the sensor vibration measurement mounting surface by a variable diameter adapter screw.

8. The fiber optic grating vibration sensor based on an S-shaped elastomer and a sensitivity-enhancing wedge beam according to claim 1, characterized in that: A groove is formed between the vibrating mass block (17) and the fixed base (1), so that there is an elastic buffer area (8) between the vibrating mass block and the optical fiber when they deform up and down.

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