Fiber bragg grating vibration sensor with temperature self-compensation function and preparation method of fiber bragg grating vibration sensor

Abstract

The invention relates to a fiber bragg grating vibration sensor with a temperature self-compensation function and a preparation method, the sensor comprises a mass block with a high thermal expansion coefficient, a base and an X-shaped flexible hinge with a low thermal expansion coefficient, the base is provided with a shell, the X-shaped flexible hinge is arranged between the mass block and the base, and the X-shaped flexible hinge is arranged between the mass block and the base. The two ends of the X-shaped flexible hinge are connected with the mass block and the base respectively, a fiber grating used for detecting vibration in the vertical direction is axially arranged at the central axis of the end faces of the same sides of the mass block and the base, and the fiber grating is located between the mass block and the base and applies prestress. According to the invention, the central wavelength variation of the fiber bragg grating caused by temperature change counteracts the central wavelength variation of the fiber bragg grating caused by stress generated by distance change due to thermal expansion between fiber bragg grating fixing points, so that the central wavelength of the fiber bragg grating is not influenced by temperature change; and the temperature self-compensation of the fiber grating vibration sensor is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber grating sensors, and in particular relates to a fiber grating vibration sensor with temperature self-compensation and a preparation method thereof. Background Art

[0002] The most significant advantage of fiber Bragg grating (FBG) sensors is that they can modulate the wavelength of the measured physical quantity, so that the sensor output signal is not affected by light intensity, connecting fiber and coupler losses, or light source energy.

[0003] Vibration measurement is an important means of monitoring the safety of structures. However, fiber Bragg grating vibration sensors face the problem of cross-sensitivity between temperature and strain during the measurement process. That is, the axial strain generated by the fiber Bragg grating vibration sensor when detecting stress causes the drift of the fiber Bragg grating center wavelength, and the fluctuation of the external ambient temperature will also cause the drift of the fiber Bragg grating center wavelength, thereby affecting the accuracy of the measurement data. In addition, changes in the external ambient temperature will also cause the internal thermal stress of the sensor structure to affect the sensor structure size and material elastic modulus, thereby affecting the sensor performance and reducing the measurement accuracy. Therefore, in order to reduce the temperature sensitivity of the fiber Bragg grating vibration sensor, the fiber Bragg grating must be temperature compensated and packaged to reduce the impact of temperature changes on the fiber Bragg grating center wavelength.

[0004] Publication No. CN 110531110 A discloses a fiber Bragg grating two-dimensional acceleration sensor based on a U-groove structure. The sensor realizes the design of the fiber Bragg grating vibration sensor conversion elastic body by opening two pairs of U-groove structures set in opposite directions on the upper and lower parts of the middle body of the core body. The inertial body and the circumferential outer surface of the base are evenly opened with four fiber grooves. Four fiber Bragg gratings are installed in the fiber grooves by applying a certain prestress. The four fiber Bragg gratings are in adjacent and perpendicular directions, which is convenient for detecting vibrations in two perpendicular directions. The sensor uses the wavelength drift difference between two fiber Bragg gratings as the output signal, thereby eliminating the influence of the same-direction wavelength drift caused by the common environmental temperature change on the measurement result, and has the effect of temperature compensation. However, this method is based on the ideal situation that the center wavelength shifts of the two fiber Bragg gratings caused by temperature changes are the same and synchronized with the temperature changes, so the differential output is theoretically close to zero. However, in practical applications, due to uncontrollable factors such as the thickness of the glue during the packaging process, the degree of colloid curing, and whether the fiber Bragg grating is arranged along the main vibration direction, there will be differences in heat conduction between the fiber Bragg gratings fixed at different positions. Therefore, the center wavelength shifts of the two fiber Bragg gratings caused by temperature changes cannot be completely offset, causing the measurement results to still be inaccurate. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a fiber Bragg grating vibration sensor with temperature self-compensation and a preparation method thereof, by offsetting the change in the center wavelength of the fiber Bragg grating caused by temperature change and the change in the center wavelength of the fiber Bragg grating caused by stress generated by distance change due to thermal expansion between the fixed points of the fiber Bragg grating, thereby making the center wavelength of the fiber Bragg grating unaffected by temperature change, thereby realizing temperature self-compensation of the fiber Bragg grating vibration sensor.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A fiber Bragg grating vibration sensor with temperature self-compensation comprises a mass block with a high thermal expansion coefficient, a base and an X-shaped flexible hinge with a low thermal expansion coefficient, wherein a shell is arranged on the base, the shell wraps the mass block and the X-shaped flexible hinge, the mass block and the base are arranged relative to each other with an upper and lower interval, the X-shaped flexible hinge is arranged between the mass block and the base, and the two ends of the X-shaped flexible hinge are respectively connected to the mass block and the base; a fiber Bragg grating is axially arranged on the same side periphery of the mass block and the base, the fiber Bragg grating is located between the mass block and the base and is applied with prestress, and is used to detect vibration in the vertical direction.

[0007] Furthermore, the X-shaped flexible hinge includes at least one pair, and the pair of X-shaped flexible hinges are arranged in parallel and spaced apart, and bosses are respectively provided at the upper and lower ends of the X-shaped flexible hinge, and grooves are provided at the lower end of the mass block and the upper end of the base, and the bosses are plugged into and matched with the corresponding grooves.

[0008] Furthermore, an upper optical fiber groove is axially arranged at the center axis of one side end surface of the mass block, and a lower optical fiber groove is axially arranged at the center axis of one side end surface of the base, the upper optical fiber groove and the lower optical fiber groove are coaxial, and the two end tail fibers of the optical fiber grating are respectively fixed in the upper optical fiber groove and the lower optical fiber groove.

[0009] Furthermore, the boss is a column pin, the groove is a column hole, and the column pin and the corresponding column hole are interference fit.

[0010] Furthermore, the base is provided with a fiber hole which is in communication with the lower optical fiber groove, and a pigtail at one end of the optical fiber grating passes through the fiber hole and extends out of the base.

[0011] Furthermore, the base includes an upper substrate and a lower substrate, the upper substrate is stacked on the lower substrate, and the outer periphery of the lower substrate extends beyond the outer periphery of the upper substrate.

[0012] Furthermore, the lower optical fiber groove is arranged on the upper substrate, and the fiber insertion hole is arranged on the lower substrate and is connected with the lower optical fiber groove.

[0013] Furthermore, the mass block and the base are both made of aluminum alloy, and the X-shaped flexible hinge is made of Invar.

[0014] Furthermore, the pigtails at both ends of the fiber grating are fixed in the upper fiber groove and the lower fiber groove respectively by epoxy resin, and at least the pigtail located in the epoxy resin is a bare fiber.

[0015] The present invention also provides a method for preparing a fiber grating vibration sensor with temperature self-compensation, comprising the following steps: Step S1: performing interference fit heat-fitting on the X-shaped flexible hinge, the mass block and the base; Step S2: after applying a certain prestress to the fiber Bragg grating, the pigtails at both ends of the fiber Bragg grating are fixed to the periphery of the mass block and the periphery of the base respectively, the fiber Bragg grating is located between the mass block and the base, and the pigtail at least one end of the fiber Bragg grating extends out of the base; Step S3: Assembling a shell on the base.

[0016] The present invention adopts the above technical solution, which has the following advantages and effects: The present invention provides a fiber Bragg grating vibration sensor with temperature self-compensation and a preparation method thereof, aiming to solve the problem of strain and temperature cross-sensitivity occurring in the fiber Bragg grating vibration sensor when performing vibration measurement. The present invention fixes the fiber Bragg grating between a mass block with a high thermal expansion coefficient and a base, and the mass block and the base are connected by an X-shaped flexible hinge with a low thermal expansion coefficient. By selecting the dimensions of the mass block, the base and the X-shaped flexible hinge and the thermal expansion coefficient of the material, the change in the center wavelength of the fiber Bragg grating caused by temperature change and the change in the center wavelength of the fiber Bragg grating caused by stress due to distance change caused by thermal expansion between the fiber Bragg grating fixed points are offset, and finally the center wavelength of the fiber Bragg grating is not affected by temperature change, thereby realizing temperature self-compensation of the fiber Bragg grating vibration sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a schematic diagram of the structure of a fiber grating vibration sensor with temperature self-compensation according to the present invention.

[0018] Figure 2 It is a schematic diagram of the base structure of the present invention.

[0019] Figure 3 It is a schematic diagram of the mass block structure of the present invention.

[0020] Figure 4 It is a schematic diagram of the X-shaped flexible hinge structure of the present invention.

[0021] Figure 5 Schematic diagram of the temperature compensation principle of the present invention.

[0022] Figure 6 Schematic diagram of thermal deformation decomposition based on the temperature compensation principle of the invention.

[0023] Figure 7 A schematic diagram of the temperature compensation structure of the fiber Bragg grating vibration sensor of the present invention.

[0024] Among them, 1-shell, 2-mass block, 3-X-type flexible hinge, 4-fiber grating, 5-base, 6-bolt, 201-upper column hole, 202-upper fiber groove, 301-column pin, 501-lower base plate, 502-upper base plate, 503-fiber hole, 504-counter hole, 505-lower column hole, 506-lower fiber groove. DETAILED DESCRIPTION

[0025] The embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings so that the purpose, features and advantages of the present invention can be more clearly understood. It should be understood that the embodiments shown in the accompanying drawings are not intended to limit the scope of the present invention, but are only intended to illustrate the essential spirit of the technical solution of the present invention.

[0026] like Figure 1-Figure 4 As shown. The present invention provides a fiber Bragg grating vibration sensor with temperature self-compensation, comprising a mass block 2, a base 5 and an X-shaped flexible hinge 3. A shell 1 is arranged on the base 5, and the shell 1 wraps the mass block 2 and the X-shaped flexible hinge 3. The mass block 2 and the base 5 are spaced relative to each other in the upper and lower directions. The X-shaped flexible hinge 3 is arranged between the mass block 2 and the base 5, and the two ends of the X-shaped flexible hinge 3 are respectively connected to the mass block 2 and the base 5. A fiber Bragg grating 4 is axially arranged on the same side periphery of the mass block 2 and the base 5. The fiber Bragg grating 4 is located between the mass block 2 and the base 5 and is applied with prestress. The fiber Bragg grating 4 is used to detect vibration in the vertical direction. The fiber Bragg grating 4 has its tail fibers bonded and fixed to the mass block 2 and the base 5 at both ends by applying a certain prestress, and one end of the tail fiber passes through the base 5 and is connected to the demodulator.

[0027] Specifically, the mass block 2 and the base 5 are made of materials with high thermal expansion coefficient, such as aluminum alloy or beryllium bronze, the mass block 2 is a rectangular parallelepiped structure, and the base 5 is a plate structure. The X-shaped flexible hinge 3 is made of materials with low thermal expansion coefficient, such as quartz or invar.

[0028] The X-shaped flexible hinge 3 is an X-shaped structural member, and the X-shaped flexible hinge 3 is arranged between the mass block 2 and the base 5 to connect the mass block 2 and the base 5 as a whole. The bottom of the shell 1 is open, and screw holes are arranged around the bottom of the shell 1, and countersunk holes 504 are arranged around the edges of the upper end of the base 5. The bolts 6 pass through the countersunk holes 504 and are threadedly connected with the corresponding screw holes to realize the fixing of the shell 1 and the base 5.

[0029] Furthermore, the X-shaped flexible hinge 3 includes at least one pair, and the pair of X-shaped flexible hinges 3 are arranged in parallel and spaced apart, and bosses are respectively arranged at the upper and lower ends of the X-shaped flexible hinge 3, and grooves are provided at the lower end of the mass block 2 and the upper end of the base 5. After the bosses are plugged into the corresponding grooves, the X-shaped flexible hinge 3 is connected and fixed to the mass block 2 and the base 5. The bosses and the grooves are connected by a shrink-fit interference fit to realize a reliable and stable connection between the X-shaped flexible hinge 3, the mass block 2 and the base 5.

[0030] Specifically, in order to ensure the stability of the mass block 2 and the base 5 and reduce the torsional stiffness and lateral interference of the X-shaped flexible hinge 3, a plurality of X-shaped flexible hinges 3 may be provided, and the plurality of X-shaped flexible hinges 3 are parallel and spaced from each other.

[0031] As a preferred embodiment, the X-shaped flexible hinge 3 in the present invention includes a pair, and the pair of X-shaped flexible hinges 3 are arranged in parallel and spaced apart between the mass block 2 and the base 5. The lower end surface of the mass block 2 and the upper end surface of the base 5 are both provided with four grooves, and the upper and lower end surfaces of the X-shaped flexible hinge 3 are both provided with bosses, and the four bosses on the upper end surfaces of the pair of X-shaped flexible hinges 3 are plugged and matched with the four grooves on the lower end surface of the mass block 2, and the four bosses on the lower end surfaces of the pair of X-shaped flexible hinges 3 are plugged and matched with the four grooves on the upper end surface of the base 5.

[0032] Furthermore, in order to facilitate the fixation of the fiber grating 4, an upper fiber groove 202 is axially arranged at the center axis of one side end face of the mass block 2, and a lower fiber groove 506 is axially arranged at the center axis of one side end face of the base 5. The upper fiber groove 202 and the lower fiber groove 506 are coaxial, and the pigtails at both ends of the fiber grating 4 are bonded and fixed in the upper fiber groove 202 and the lower fiber groove 506 respectively.

[0033] Specifically, the upper fiber groove 202 and the lower fiber groove 506 are respectively located on the same side of the mass block 2 and the base 5 and are relatively coaxially connected vertically. The cross-sections of the upper fiber groove 202 and the lower fiber groove 506 are preferably U-shaped structures.

[0034] Furthermore, the boss is a column pin 301, the groove is a column hole, and the column pin 301 and the corresponding column hole are interference fit.

[0035] Specifically, the column pin 301 is preferably a cylindrical pin, and the column hole is preferably a cylindrical hole. The column pin 301 is respectively arranged on the upper and lower ends of the X-shaped flexible hinge 3 and is integrated therewith. The column hole on the lower surface of the mass block 2 is an upper column hole 201, and the upper column hole 201 is respectively matched with the four column pins 301 on the upper end surface of a pair of X-shaped flexible hinges 3 in a hole-shaft connection mode. The column hole on the upper surface of the base 5 is a lower column hole 505, and the lower column hole 505 is respectively plugged and matched with the four column pins 301 on the lower end surface of a pair of X-shaped flexible hinges 3.

[0036] Furthermore, the base 5 is provided with a fiber hole 503 which penetrates the lower fiber groove 506 . The pigtail of the FBG 4 passes through the fiber hole 503 and extends out of the lower end surface of the base 5 . The extended pigtail is connected to the fiber jumper and then connected to the demodulator.

[0037] Furthermore, the base 5 includes an upper substrate 502 and a lower substrate 501 . The upper substrate 502 is stacked on the lower substrate 501 , and the outer periphery of the lower substrate 501 extends beyond the outer periphery of the upper substrate 502 .

[0038] Specifically, the outer peripheral size of the upper substrate 502 is smaller than the outer peripheral size of the lower substrate 501. The upper substrate 502 and the lower substrate 501 are integrally arranged. When the upper substrate 502 is arranged on the lower substrate 501, the outer peripheral surface of the upper substrate 502 is coaxial with the outer peripheral surface of the lower substrate 501. The shell 1 is arranged on the lower substrate 501 to surround the upper substrate 502.

[0039] Furthermore, the lower fiber slot 506 is axially arranged on the central axis of one side end surface of the upper substrate 502, and the fiber hole 503 is arranged on the lower substrate 501 and penetrates the lower fiber slot 506. One end of the fiber grating 4 passes through the lower fiber slot 506 through the fiber hole 503 and then extends out of the lower substrate 501.

[0040] Furthermore, the pigtails at both ends of the fiber grating 4 are respectively bonded and fixed in the upper fiber groove 202 and the lower fiber groove 506 by epoxy resin, and at least the pigtail located in the epoxy resin is a bare fiber.

[0041] Specifically, in order to prevent the prestress on the fiber grating 4 from disappearing, the fiber pigtail bonded and fixed in the epoxy resin is a bare fiber segment. By bonding and fixing the bare fiber segment, the fiber pigtail coating layer can be prevented from delamination and the prestress pre-applied to the fiber grating 4 can be released.

[0042] Furthermore, in order to prevent the overflow of epoxy resin, glue dispensing grooves are provided at the bottom of the upper optical fiber groove 202 and the lower optical fiber groove 506 for bonding and fixing the pigtail. By filling the epoxy resin into the glue dispensing grooves at the bottom of the upper optical fiber groove 202 and the lower optical fiber groove 506, the epoxy resin can be prevented from overflowing along the upper optical fiber groove 202 or the lower optical fiber groove 506 when bonding and fixing the pigtail.

[0043] like Figure 5 , Figure 6 The temperature compensation principle of the fiber Bragg grating vibration sensor of the present invention is as follows: the X-shaped flexible hinge 3 of the fiber Bragg grating vibration sensor is simplified to a hypotenuse component, and the mass block 2 and the base 5 are simplified to a base component.

[0044] With the X-axis as the horizontal direction and the Y-axis as the vertical direction, the length of the hypotenuse member is set to L1, the thermal deformation after heating is dL1, the length of the hypotenuse member after heating is L1+dL1, the length of the base member is L2, the thermal deformation after heating is dL2, the length of the base member after heating is L2+dL2, the thermal expansion coefficients of the mass block 2 and the base 5 are both α1, the thermal expansion coefficient of the X-type flexible hinge 3 is α2, the distance between the top of the base 5 and the bottom of the mass block 2 in the base member is h, the angle between the base member and the hypotenuse member when not rotated is θ, the thermal expansion of the hypotenuse member causes the base member and the hypotenuse member to rotate relative to each other at an angle of dθ, and the angle between the base member and the hypotenuse member after heating is θ+dθ.

[0045] When the ambient temperature rises, the base member expands horizontally due to heat, which reduces the distance h between the top of the base 5 and the bottom of the mass block 2. The base member and the bevel member rotate relative to each other due to the thermal expansion of the bevel member, which increases the distance h between the top of the base 5 and the bottom of the mass block 2. At this time, the temperature-sensitive change in the distance between the top of the base 5 and the bottom of the mass block 2 is dh, and the axial strain of the fiber Bragg grating 4 is for: ; (1) When the ambient temperature changes, the bevel member and the base member rotate relative to each other, and the thermal deformation of the bevel member can be Decomposed on the XY axes of the rectangular coordinate system, the thermal deformation of the bevel component is The vector expression of is: ; (2) In formula (2), is the unit vector on the X-axis, is the unit vector on the Y axis, is the angle between the bevel member and the base member; Then the change of ambient temperature of the bevel component is Thermal deformation under It is expressed as: ; (3) In formula (3), for Coefficient of thermal expansion in direction (transverse), for Coefficient of thermal expansion in the longitudinal direction.

[0046] At this time, the thermal expansion coefficient of the bevel member is defined in the rectangular coordinate system as for: ; (4) Combining formulas (2)-(4), we can get: ; (5) The longitudinal thermal expansion coefficient of the beveled edge component (i.e., X-shaped flexible hinge 3) can be obtained by sorting out: for: ; (6) Since the fiber Bragg grating 4 can directly measure the strain and temperature, the central wavelength of the fiber Bragg grating 4 and the center wavelength drift of the fiber Bragg grating It is expressed as: ; (7) In formula (7), represents the strain sensitivity of the fiber Bragg grating 4 measured, is the measured temperature sensitivity of fiber Bragg grating 4, is the effective elastic-optical coefficient of the optical fiber, is the thermo-optical coefficient of the optical fiber, is the thermal expansion coefficient of the optical fiber.

[0047] In order to achieve the temperature compensation effect, the fiber Bragg grating vibration sensor should be subjected to only the change of ambient temperature. Under the influence of is 0, which satisfies: ; (8) The strain part of the center wavelength drift of the fiber Bragg grating 4 is the center wavelength change caused by the negative displacement compression of the fiber Bragg grating 4 between two fixed points affected by temperature.

[0048] like Figure 7 When the ambient temperature changes by , the length change of the X-type flexible hinge 3 in the Y-axis direction for: ; (9) In formula (9), is the torsion radius of the X-shaped flexible hinge 3, is the half angle between the two straight beams of the X-shaped flexible hinge 3, and They are complementary angles.

[0049] At this time, the equivalent effect variable generated by the axial compression of the fiber Bragg grating 4 is for: ; (10) At this time, the overall thermal expansion coefficient of the compensation part between the two fixed points of the fiber Bragg grating can be obtained from formula (10), that is, the longitudinal thermal expansion coefficient of the X-shaped flexible hinge 3 for: ; (11) In formula (11), is the distance between the two fixed points of the fiber Bragg grating. Based on formula (11), by selecting the appropriate sizes and thermal expansion coefficients of the mass block 2, the base 5 and the X-shaped flexible hinge 3, the central wavelength of the fiber Bragg grating 4 is not affected by temperature changes, and the temperature self-compensation of the fiber Bragg grating vibration sensor is realized.

[0050] When verifying the feasibility of temperature compensation of fiber Bragg grating vibration sensor, the present invention performs steady-state thermal simulation on the fiber Bragg grating vibration sensor model through the simulation software Ansys Workbench. During the simulation, the initial ambient temperature during steady-state thermal simulation is set to 22°C, and the working temperature of 42°C is applied to the fiber Bragg grating vibration sensor model. The temperature environment of the fiber Bragg grating vibration sensor model is brought into the static analysis module, and the thermal deformation of the fiber Bragg grating vibration sensor model under the condition of 20°C temperature rise can be obtained. At the same time, the boundary condition to be solved is set to be frictionless at the bottom of the fiber Bragg grating vibration sensor model. After applying the weak spring condition, the relative displacement of the fiber Bragg grating vibration sensor model at the two ends of the fiber Bragg grating is solved, and the temperature compensation result of the fiber Bragg grating vibration sensor model can be obtained.

[0051] Through comparative simulation, the temperature drift of the fiber Bragg grating vibration sensor of the present invention can reach 0.64 pm / °C, which is effectively reduced compared with the temperature drift of 10 pm / °C of the traditional single-mode fiber Bragg grating.

[0052] When the fiber grating vibration sensor provided by the present invention is measured, the fiber grating vibration sensor is fixed on the surface of the object to be measured, and the bottom surface of the fiber grating vibration sensor is kept in a vertical position. When the fiber grating vibration sensor is subjected to external vibration excitation, under the action of inertia, the mass block 2 of the fiber grating vibration sensor rotates slightly around the center of the X-shaped flexible hinge 3, and the vertical displacement generated by the mass block 2 causes the fiber grating 4 to stretch or compress, causing the center wavelength of the fiber grating 4 to drift. The drift of the center wavelength of the fiber grating 4 is measured by a demodulator, thereby establishing a corresponding relationship between the external excitation acceleration and the drift of the center wavelength of the fiber grating, thereby obtaining vibration information of the vibration acceleration.

[0053] The present invention also provides a method for preparing a fiber grating vibration sensor with temperature self-compensation, comprising the following steps: Step S1: The X-shaped flexible hinge 3, the mass block 2 and the base 5 are heat-assembled by interference fit.

[0054] Specifically, during the hot-installation assembly, first clean the oil and dust on the mating surfaces of the base 5, the mass block 2 and the X-shaped flexible hinge 3; then heat the base 5 and the mass block 2 for 15-20 minutes, raise the temperature of both to about 1000°C, and keep them warm for 10 minutes. After eliminating the interference between the two and the upper and lower ends of the X-shaped flexible hinge 3, hot-installation can be performed immediately.

[0055] Step S2: After applying a certain prestress to the fiber grating 4, use epoxy resin to fix the pigtails at both ends of the fiber grating 4 in the upper fiber groove 202 on the periphery of the mass block 2 and the lower fiber groove 506 on the periphery of the base 5 respectively. The fiber grating 4 is located between the mass block 2 and the base 5, and at least one end of the pigtail of the fiber grating 4 extends out of the base 5.

[0056] Step S3: assembling the housing 1 on the base 5 ; during assembly, the housing 1 is fixed to the base 5 by bolts 6 .

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fiber Bragg grating vibration sensor with temperature self-compensation, characterized in that: The invention comprises a mass block (2) with a high thermal expansion coefficient, a base (5) and an X-shaped flexible hinge (3) with a low thermal expansion coefficient. The base (5) is provided with a shell (1), the shell (1) wraps the mass block (2) and the X-shaped flexible hinge (3), the mass block (2) and the base (5) are arranged relative to each other with an interval up and down, the X-shaped flexible hinge (3) is arranged between the mass block (2) and the base (5), and the two ends of the X-shaped flexible hinge (3) are respectively connected to the mass block (2) and the base (5); a fiber Bragg grating (4) is axially arranged on the same side periphery of the mass block (2) and the base (5), the fiber Bragg grating (4) is located between the mass block (2) and the base (5) and is applied with a prestress, and is used to detect vibration in the vertical direction.

2. The fiber Bragg grating vibration sensor with temperature self-compensation according to claim 1, characterized in that: The X-shaped flexible hinges (3) include at least one pair, the pair of X-shaped flexible hinges (3) are arranged in parallel and spaced apart, the upper and lower ends of the X-shaped flexible hinges (3) are respectively provided with bosses, the lower end of the mass block (2) and the upper end of the base (5) are both provided with grooves, and the bosses are plug-fitted into the corresponding grooves.

3. A fiber Bragg grating vibration sensor with temperature self-compensation according to claim 1 or 2, characterized in that: An upper optical fiber groove (202) is axially arranged at the center axis of one end surface of the mass block (2), and a lower optical fiber groove (506) is axially arranged at the center axis of one end surface of the base (5), the upper optical fiber groove (202) and the lower optical fiber groove (506) are coaxial, and the tail fibers at both ends of the optical fiber grating (4) are respectively fixed in the upper optical fiber groove (202) and the lower optical fiber groove (506).

4. The fiber Bragg grating vibration sensor with temperature self-compensation according to claim 2, characterized in that: The boss is a column pin (301), the groove is a column hole, and the column pin (301) and the corresponding column hole are interference fit.

5. The fiber Bragg grating vibration sensor with temperature self-compensation according to claim 3, characterized in that: The base (5) is provided with a fiber hole (503) that penetrates the lower optical fiber groove (506); a pigtail at one end of the optical fiber grating (4) passes through the fiber hole (503) and extends out of the base (5).

6. The fiber Bragg grating vibration sensor with temperature self-compensation according to claim 5, characterized in that: The base (5) comprises an upper substrate (502) and a lower substrate (501), wherein the upper substrate (502) is stacked on the lower substrate (501), and the periphery of the lower substrate (501) extends beyond the periphery of the upper substrate (502).

7. The fiber Bragg grating vibration sensor with temperature self-compensation according to claim 6, characterized in that: The lower optical fiber groove (506) is arranged on the upper substrate (502), and the fiber insertion hole (503) is arranged on the lower substrate (501) and is connected to the lower optical fiber groove (506).

8. The fiber Bragg grating vibration sensor with temperature self-compensation according to claim 7, characterized in that: The mass block (2) and the base (5) are both made of aluminum alloy, and the X-shaped flexible hinge (3) is made of Invar.

9. The fiber Bragg grating vibration sensor with temperature self-compensation according to claim 8, characterized in that: The pigtails at both ends of the fiber grating (4) are fixed in the upper fiber groove (202) and the lower fiber groove (506) respectively by epoxy resin, and at least the pigtail located in the epoxy resin is a bare fiber.

10. A method for preparing a fiber Bragg grating vibration sensor with temperature self-compensation according to any one of claims 1 to 9, characterized in that: The following steps are included: Step S1: performing interference fit heat-insertion on the X-shaped flexible hinge (3), the mass block (2) and the base (5); Step S2: after applying a certain prestress to the optical fiber Bragg grating (4), the pigtails at both ends of the optical fiber Bragg grating (4) are fixed to the periphery of the mass block (2) and the periphery of the base (5), respectively, the optical fiber Bragg grating (4) is located between the mass block (4) and the base (5), and the pigtail at least one end of the optical fiber Bragg grating (4) extends out of the base (5); Step S3: Assembling the housing (1) on the base (5).

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