Fiber bragg grating strain sensor with temperature compensation

Abstract

The utility model relates to the technical field of sensors, and provides a fiber bragg grating strain sensor with temperature compensation, which comprises a fiber bragg grating, a sliding block and a prismatic base body, the prismatic base body is of a hollow structure, the sliding block is welded at one end of a diagonal line of the prismatic base body, the fiber bragg grating strain sensor further comprises a deformation plate, and the material of the deformation plate is consistent with that of a measured component. The two ends of the other diagonal line of the prismatic base body are welded with the deformation plate; the fiber bragg grating is welded to the sliding block and the other end, welded to the diagonal line of the sliding block, of the prismatic base body, and the fiber bragg grating is lengthened between the two welding points. Compared with the prior art, a compensation block which is inconsistent with the prismatic base body in material is abandoned, parameters influencing compensation are reduced, and the compensation effect can be better guaranteed.

Description

Technical Field

[0001] The utility model relates to the technical field of sensors, in particular to a fiber grating strain sensor with temperature compensation. Background Art

[0002] Fiber Bragg grating is a kind of diffraction grating formed by axially periodically modulating the refractive index of the fiber core through a certain method. It is a passive filter device. In actual application, as the external temperature changes, the effective refractive index and grating period of the fiber Bragg grating will change accordingly. Since the central wavelength of the fiber Bragg grating is related to its effective refractive index and grating period, its central wavelength will also drift accordingly. The drift is about 10pm / ℃, which seriously limits the practical application of fiber Bragg grating. Therefore, it is very necessary to perform temperature compensation on the fiber Bragg grating.

[0003] To this end, the applicant provides a fiber Bragg grating strain sensor with temperature compensation in a patent with publication number "CN219284226U", including a fiber Bragg grating, a compensation block, a slider and a prism-shaped base, the prism-shaped base is a hollow structure; the compensation block and the slider are respectively fixedly connected to the end points of a diagonal line of the prism-shaped base, the two ends of the fiber Bragg grating are respectively fixedly connected to the slider and the compensation block, and the two sides of the other diagonal line of the prism-shaped base are provided with outwardly extending structural members, and the ends of the structural members are set as long strips of adhesive structures, which are adhered to the measured component by the adhesive structure when in use. However, this compensation method requires multiple parameters to ensure the compensation effect of the sensor. Utility Model Content

[0004] The utility model aims to provide a fiber grating strain sensor with temperature compensation, so as to provide a compensation method different from the prior art and reduce the parameters affecting the compensation.

[0005] The utility model is realized by the following technical solutions:

[0006] A fiber grating strain sensor with temperature compensation, comprising a fiber grating, a slider and a prism-shaped base, wherein the prism-shaped base is a hollow structure, the slider is welded to one end of a diagonal line of the prism-shaped base, and further comprising a deformation plate, the material of the deformation plate is consistent with the material of the measured component, and both ends of the other diagonal line of the prism-shaped base are welded to the deformation plate;

[0007] The optical fiber Bragg grating is welded to the slider and to the other end of the diagonal line of the slider welded to the prism-shaped base body, and the optical fiber Bragg grating is stretched between the two welding points.

[0008] Optionally, a positioning column is provided on the prismatic base at the welding position with the deformation plate, and a welding pad hole cooperating with the positioning column is provided on the deformation plate.

[0009] Optionally, two positioning columns are respectively provided at two ends of the prismatic base.

[0010] Optionally, when the two diagonal lines of the prismatic base are not equal in length, the slider is welded on the long diagonal line of the prismatic base.

[0011] Optionally, the sliding block and the prismatic base are made of the same material.

[0012] Optionally, the prismatic base and the slider are both made of Invar steel.

[0013] Optionally, the deformable plate is made of glass fiber.

[0014] This practical technical solution has at least the following advantages and beneficial effects:

[0015] 1. In the present invention, the deformation plate is made of the same material as the component to be measured. When the ambient temperature rises, the thermal expansion of the deformation plate in the short diagonal direction drives the prismatic matrix to undergo tensile deformation in this direction, thereby causing the prismatic matrix to shrink in the direction of the fiber grating welding point connection line. The shrinkage amount and the thermal expansion elongation of the fiber grating effective grating area compensate each other, thereby ensuring the temperature compensation effect of the sensor. In addition, the present invention abandons the compensation block whose material is inconsistent with the prismatic matrix, reduces the parameters affecting the compensation, and facilitates better guarantee of the compensation effect.

[0016] 2. In the present invention, the prismatic base is welded to the deformation plate to avoid creep at the connection point when stretched greatly and thus causing the sensor to become inaccurate. That is, the use of welding connection can enable the sensor to withstand greater strain changes, that is, the sensor has a larger measuring range. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the utility model and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A partial cross-sectional view of a fiber grating strain sensor with temperature compensation provided by the utility model;

[0019] Figure 2 for Figure 1 AA section view;

[0020] Figure 3 for Figure 1 Rear view of

[0021] Figure 4 It is a schematic diagram of the connection structure of the prismatic matrix, the fiber Bragg grating and the slider;

[0022] Figure 5 for Figure 4 Bottom view of

[0023] Icon: 1-fiber Bragg grating, 2-slider, 3-prismatic substrate, 301-positioning column, 4-deformation plate, 401-soldering pad hole, 5-protective cover, 6-protective tube. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Generally, the components of the embodiments of the utility model described and shown in the drawings here can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention to be protected, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] refer to Figure 1 and Figure 4 A fiber Bragg grating 1 strain sensor with temperature compensation includes a fiber Bragg grating 1, a slider 2, a prismatic substrate 3 and a deformation plate 4.

[0027] The prismatic base 3 is a hollow structure, and the slider 2 is welded to one end of a diagonal line of the prismatic base 3. In this embodiment, the four sides of the prismatic base 3 are of equal thickness, the structure is symmetrical, the acute angle is designed to be 60°, and the thickness does not exceed 2 mm. Of course, in other embodiments, the angle of the prismatic base can also be adjusted accordingly according to the sensitivity coefficient of the sensor.

[0028] The slider 2 is welded to one end of a diagonal line of the prismatic substrate 3, the fiber grating 1 is welded to the slider 2, and is welded to the other end of the diagonal line of the slider 2 welded to the prismatic substrate 3, and the fiber grating 1 is stretched between the two welding points. In practical applications, the fiber grating 1 is first welded to the prismatic substrate 3 and the slider 2. After welding, the grating is stretched to reach 6000με, and then the slider 2 is welded to the prismatic substrate 3. In this way, the positive and negative amounts of strain can be measured. When selecting solder, in addition to the melting temperature not being higher than 350℃, the linear expansion coefficient of the solder is required to be similar to the material selected for the prismatic structure to ensure good and reliable welding. The slider 2 and the prismatic substrate 3 are made of the same material. In this embodiment, the prismatic substrate and the slider 2 are both made of invar steel material, and its linear expansion coefficient is (1~3)×10-6 / ℃.

[0029] In addition, it is worth noting that the fiber Bragg grating 1 of this embodiment is fixed in the above manner, eliminating the compensation block whose material is inconsistent with the prismatic base 3, that is, avoiding the difficulty of welding the compensation block and the prismatic base 3.

[0030] The fiber grating 1 can be the same as the prior art, with a polyimide coating on the surface, which can meet the requirements of use in an environment below 350°C. The fiber grating 1 is made by a special process of femtosecond point-by-point writing. The coating layer of the grating area is not damaged during and after grating and remains attached to the surface of the optical fiber, which can provide good protection for the fiber grating 1.

[0031] The material of the deformation plate 4 is consistent with the material of the component to be measured, and both ends of the other diagonal of the prismatic matrix 3 are welded to the deformation plate 4. In this embodiment, taking the application on the wind turbine blade as an example, the deformation plate 4 is made of the same glass fiber as the blade material, and the linear expansion coefficient of the material is (10-14)×10-6 / ℃. Of course, in other embodiments, the material of the deformation plate 4 is selected according to the material of the component to be measured. In practical applications, when the ambient temperature rises, the thermal expansion of the deformation plate 4 in the short diagonal direction (that is, the L2 length direction) is used to drive the prismatic matrix to undergo tensile deformation in this direction, thereby causing the prismatic matrix to shrink in the long diagonal direction (that is, the L1 length direction). The shrinkage amount and the thermal expansion elongation of the effective grating of the fiber grating 1 (that is, the L1 part) compensate each other, thereby ensuring the temperature compensation effect of the sensor.

[0032] On this basis, it is easy to understand that according to the expansion coefficient of the material and the sensitivity coefficient of the sensor, the ratio of L1 / L2 is reasonably set. Under ideal conditions, the thermal expansion of the deformation plate 4 in the short diagonal direction (that is, the length direction of L2) drives the prismatic base 3 to undergo tensile deformation in this direction, thereby causing the prismatic base 3 to contract in the long diagonal direction (that is, the length direction of L1). When the amount of contraction just offsets the thermal expansion tensile deformation of the effective grating area of ​​the fiber grating 1 (that is, the L1 part), the sensor has zero temperature drift and achieves the best compensation effect.

[0033] refer to Figure 3-Figure 5 On the prismatic base 3, a positioning column 301 is provided at the welding point with the deformation plate 4, and a welding pad hole 401 matching with the positioning column 301 is provided on the deformation plate 4. With such a configuration, the fixing effect between the deformation plate 4 and the prismatic base 3 is better, and creep of the connection point during large stretching is avoided, which causes the sensor to be misaligned, that is, the use of welding connection can make the sensor withstand greater strain changes, that is, the sensor has a larger range. Furthermore, two positioning columns 301 are provided at each end of the prismatic base 3, that is, the prismatic base 3 and the deformation plate 4 have four welding points in total, which ensures the connection effect between the two.

[0034] In this embodiment, the two diagonals of the prismatic base are of unequal lengths, the slider 2 is welded on the long diagonal of the prismatic base, and the positioning posts 301 are arranged at both ends of the short diagonal of the prismatic base 3 .

[0035] In practical applications, the protective cover 5 is fixedly connected to the deformation plate 4 to form a sensor (refer to Figure 1 and Figure 2 ), the fiber Bragg grating 1 passes through the inside of the protective cover 5, and a protective tube 6 for protecting the fiber Bragg grating 1 can also be provided on the protective cover 5. When in use, the deformation plate 4 is pasted on the component to be measured by an adhesive, and the deformation of the component to be measured is transmitted to the prismatic base 3 through the deformation plate 4, and the distance L2 between the welding points at the two ends of the short diagonal of the prismatic base 3 changes, causing the length of the long diagonal of the prismatic base 3 to change, that is, causing the distance L1 between the two welding points of the fiber Bragg grating 1 to change, and the force on the fiber Bragg grating 1 increases or decreases when it has been subjected to pre-tension, causing the central wavelength of the reflected light of the fiber Bragg grating 1 to change, and the change in the central wavelength is linearly related to the change in L2. By detecting the change in wavelength, the purpose of measuring strain is achieved.

[0036] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may be subject to various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fiber Bragg grating strain sensor with temperature compensation, comprising a fiber Bragg grating, a slider and a prism-shaped substrate, wherein the prism-shaped substrate is a hollow structure, and the slider is welded to one end of a diagonal line of the prism-shaped substrate, characterized in that: It also includes a deformation plate, the material of the deformation plate is consistent with the material of the component to be measured, and both ends of the other diagonal line of the prism-shaped base are welded to the deformation plate; The optical fiber Bragg grating is welded to the slider and to the other end of the diagonal line of the slider welded to the prism-shaped base body, and the optical fiber Bragg grating is stretched between the two welding points.

2. The fiber Bragg grating strain sensor with temperature compensation according to claim 1, characterized in that: The prismatic base is provided with a positioning column at a welding position with the deformation plate, and the deformation plate is provided with a welding pad hole matched with the positioning column.

3. The fiber Bragg grating strain sensor with temperature compensation according to claim 2, characterized in that: Two positioning columns are respectively arranged at two ends of the prismatic base.

4. The fiber Bragg grating strain sensor with temperature compensation according to any one of claims 1 to 3, characterized in that: When the two diagonal lines of the prismatic base are not equal in length, the slider is welded on the long diagonal line of the prismatic base.

5. The fiber Bragg grating strain sensor with temperature compensation according to any one of claims 1 to 3, characterized in that: The sliding block and the prismatic base are made of the same material.

6. The fiber Bragg grating strain sensor with temperature compensation according to claim 5, characterized in that: The prismatic base and the sliding block are both made of Invar steel.

7. The fiber Bragg grating strain sensor with temperature compensation according to any one of claims 1 to 3, characterized in that: The deformation plate is made of glass fiber.

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