A fiber grating magnetic field sensing device with temperature compensation

Abstract

The present invention belongs to the technical field of sensors for magnetic field measurement, and is specifically a fiber Bragg grating magnetic field sensing device with temperature compensation. The device solves the problem of cross-sensitivity between temperature and magnetic field in fiber Bragg grating magnetic field sensors, and comprises a first giant magnetostrictive material and a second giant magnetostrictive material whose expansion and contraction directions are perpendicular to each other, the first giant magnetostrictive material and the second giant magnetostrictive material are installed inside a shell, an elastic horizontal prestressed structure is arranged between the first giant magnetostrictive material and the second giant magnetostrictive material in the axial direction, a prestressed fine-tuning structure capable of adjusting the axial prestress is arranged at the outer ends of the first giant magnetostrictive material and the second giant magnetostrictive material, and a vertical micro-clamping structure capable of adjusting the position is arranged between the first giant magnetostrictive material and the second giant magnetostrictive material and the shell; a fiber magnetic field measurement grating and a fiber temperature compensation grating are arranged on the first giant magnetostrictive material and the second giant magnetostrictive material, respectively.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors for measuring magnetic fields, and in particular is a fiber grating magnetic field sensing device with temperature compensation. Background Art

[0002] In recent years, magnetic field sensors have been widely used in the fields of mechanical industry, military engineering, geophysics, biomedicine, etc. Although traditional magnetic field sensors, such as fluxgate magnetometers, Hall effect magnetometers, induction coil magnetometers, etc., can achieve high measurement accuracy, they generally have the characteristics of complex and expensive systems, weak anti-electromagnetic interference capabilities, and poor reusability.

[0003] Since 1966, the performance of optical fiber has been greatly improved, which has led to the rapid development of optical fiber sensing technology. Optical fiber sensors based on optical fiber sensing technology have the characteristics of low cost, simple production, and strong anti-electromagnetic interference ability, so they are favored by many researchers. As an important branch of optical fiber sensors, optical fiber magnetic field sensors have proposed a variety of magnetically sensitive functional materials with the development of materials science, which are mainly divided into three types: magnetostrictive materials, magneto-optical materials, and magnetic nanofluid materials. Among them, magnetostrictive materials are currently the functional materials with the fastest research, development and wide application. Under the action of the magnetic field, the shape, size and volume of the magnetostrictive material itself will change. Through the interaction between the material expansion and contraction deformation and the magnetic field, the mutual conversion of electromagnetic energy and mechanical energy or acoustic energy is realized. At present, the magnetostrictive material with the best magnetostrictive properties and practical value is TbDyFe alloy, also known as Terfenol-D. However, the optical fiber magnetic field sensor combined with magnetostrictive materials will affect the magnetic field measurement when the temperature changes, so the influence of temperature on the magnetic field measurement must be eliminated. Summary of the invention

[0004] The present invention provides a fiber grating magnetic field sensing device with temperature compensation in order to solve the problem of cross-sensitivity between temperature and magnetic field in a fiber grating magnetic field sensor.

[0005] The present invention adopts the following technical scheme: a fiber Bragg grating magnetic field sensing device with temperature compensation, comprising a first giant magnetostrictive material and a second giant magnetostrictive material whose expansion and contraction directions are perpendicular to each other, the first giant magnetostrictive material and the second giant magnetostrictive material are installed inside a shell, the first giant magnetostrictive material and the second giant magnetostrictive material are coaxially arranged, an elastic horizontal prestressed structure is arranged axially between the first giant magnetostrictive material and the second giant magnetostrictive material, a prestressed fine-tuning structure capable of adjusting the axial prestress is arranged at the outer ends of the first giant magnetostrictive material and the second giant magnetostrictive material, and a vertical micro-clamping structure capable of adjusting the position is arranged between the first giant magnetostrictive material and the second giant magnetostrictive material and the shell; a fiber magnetic field measuring grating and a fiber temperature compensation grating are respectively arranged on the first giant magnetostrictive material and the second giant magnetostrictive material, the fiber magnetic field measuring grating and the fiber temperature compensation grating are connected at one end close to each other through an optical fiber, and the other end is respectively connected to the outside of the shell through an optical fiber.

[0006] Furthermore, the horizontal prestressed structure includes a first prestressed baffle in contact with the first giant magnetostrictive material and a second prestressed baffle in contact with the second giant magnetostrictive material. The first giant magnetostrictive material and the second giant magnetostrictive material can slide left and right in a space set inside the shell, and a prestressed spring is set between the first prestressed baffle and the second prestressed baffle.

[0007] Furthermore, the left side of the first prestressed baffle is a raised block for applying prestress to the first giant magnetostrictive material, and the right side is a cylindrical spring sleeve in which the prestressed spring portion is placed; the left side of the second prestressed baffle is a cylindrical spring push shaft with a spring washer and a prestressed spring, and the right side is a raised block for applying prestress to the second giant magnetostrictive material.

[0008] Furthermore, the vertical micro-clamping structure includes fixed baffles symmetrically arranged on the front and rear sides of the first giant magnetostrictive material and the second giant magnetostrictive material. The fixed baffle is installed in a rectangular baffle placement groove. The rectangular baffle placement groove is a structure symmetrically arranged on the front and rear inner walls of the shell. Two rectangular screw grooves are also arranged in the rectangular baffle placement groove. The two screw grooves are in the baffle placement groove and fixed on the inner wall of the shell. A leveling screw is arranged in the screw groove. The groove edge of the screw groove close to the fixed baffle is thicker and has an internal threaded hole. There is also a cylindrical opening on one side of the fixed baffle. The internal threaded hole and the cylindrical opening are penetrated with a leveling screw. Screw holes are opened at the front and rear walls of the shell corresponding to the screw grooves. The screw holes on the shell, the internal threaded holes of the screw grooves and the cylindrical opening of the fixed baffle are on the same axis for adjusting the leveling screws.

[0009] Furthermore, the prestressed fine-tuning structure includes a pair of rectangular slider grooves symmetrically arranged on the left and right, a concave slider is placed in the rectangular slider groove, a side of the concave slider close to the inner wall of the shell has a groove, and cylindrical threaded holes are symmetrically opened on the left and right walls of the shell corresponding to the groove of the concave slider. The prestressed fine-tuning screw is screwed into the threaded holes on the left and right walls of the shell from the outside and passes through the groove of the concave slider, and the other side of the concave slider is in contact with the first giant magnetostrictive material or the second giant magnetostrictive material.

[0010] Furthermore, the first giant magnetostrictive material and the second giant magnetostrictive material are rectangular structures of the same shape, the expansion direction of the first giant magnetostrictive material is parallel to the axis of the optical fiber magnetic field measurement grating, and the expansion direction of the second giant magnetostrictive material is perpendicular to the axis of the optical fiber temperature compensation grating.

[0011] Furthermore, the central wavelengths of the optical fiber magnetic field measurement grating and the optical fiber temperature compensation grating are the same.

[0012] Furthermore, through holes are symmetrically opened on the left and right walls of the shell, polytetrafluoroethylene sleeves are inserted into the holes, and the optical fiber passes through the polytetrafluoroethylene sleeves.

[0013] Furthermore, the optical fiber magnetic field measurement grating and the optical fiber temperature compensation grating are respectively fixed on the surface of the first giant magnetostrictive material and the second giant magnetostrictive material by UV fixing glue.

[0014] Compared with the prior art, the present invention increases the strain under the action of the magnetic field by applying a certain prestress to the giant magnetostrictive material, thereby increasing the central wavelength change of the fiber grating, so that the device has a higher sensitivity. At the same time, two pieces of giant magnetostrictive material are integrated inside the shell, which can be used in a more severe environment. The device also uses the relationship between the expansion and contraction direction of the giant magnetostrictive material and the magnetic field direction, and eliminates the influence of temperature on the magnetic field measurement of the fiber grating magnetic field sensor device by setting a fiber temperature compensation grating, thereby improving the accuracy of the magnetic field measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the present invention;

[0016] Figure 2 It is the measurement principle diagram of the present invention;

[0017] Among them, 1-polytetrafluoroethylene sleeve, 2-optical fiber, 3-screw hole, 4-leveling screw, 5-UV fixing glue, 6-optical fiber magnetic field measurement grating, 7-fixed baffle, 8-first giant magnetostrictive material, 9-first prestressed baffle, 10-prestressed spring, 11-spring washer, 12-second prestressed baffle, 13-second giant magnetostrictive material, 14-optical fiber temperature compensation grating, 15-housing, 16-fixing hole, 17-concave slider, 18-screw slot, 19-baffle placement slot, 20-prestressed fine-tuning screw, 21-slider placement slot. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] like Figure 1As shown, a fiber grating magnetic field sensing device with temperature compensation mainly includes a first giant magnetostrictive material 8, a second giant magnetostrictive material 13, a fiber magnetic field measurement grating 6, a fiber temperature compensation grating 14, a UV fixing glue 5, a shell 15 and a fixing structure. The fixed structure includes a horizontal prestressed structure and a vertical micro-clamping structure, wherein the horizontal prestressed structure includes a first prestressed baffle 9, a second prestressed baffle 12, a prestressed spring 10, a spring washer 11, a concave slider 17, and a prestressed fine-tuning screw 20; the vertical micro-clamping structure includes a fixed baffle 7, a rectangular screw groove 18 and a leveling screw 4; the shell 15 is a rectangular box-shaped structure, and is integrated with the shell 15 and has two pairs of rectangular baffle placement grooves 19 symmetrical in front and back on the inner wall of the shell and a pair of rectangular slider grooves 21 symmetrical in left and right; a fixed baffle 7 and two rectangular screw grooves 18 are placed in the baffle placement groove 19, the two screw grooves 18 are located at both ends of the baffle placement groove 19 and are adhered to the inner wall of the shell 15, and there is a leveling screw 4 in the screw groove, and the screw groove is close to the fixed The groove edge on one side of the fixed baffle is thicker and has an internally threaded cylindrical opening. There is also a cylindrical opening on the side of the fixed baffle close to the screw groove. Screw holes 3 are opened on the front and rear walls of the shell 15 corresponding to the screw groove 18, and the screw holes on the shell, the internally threaded holes of the screw groove and the cylindrical opening of the fixed baffle are on the same axis, which is convenient for adjusting the leveling screw 4; a concave slider 17 is placed in the rectangular slider groove 21. The concave slider 17 is a rectangular parallelepiped with a groove on one side close to the inner wall of the shell. Cylindrical threaded holes are symmetrically opened on the left and right walls of the shell corresponding to the groove of the concave slider 17. The prestressed fine-tuning screw 20 is screwed into the threaded holes on the left and right walls of the shell from the outside and penetrates into the groove of the concave slider 17; through holes are also symmetrically opened on the left and right walls of the shell, and a polytetrafluoroethylene sleeve 1 is inserted into the hole. The first giant magnetostrictive material 8 and the second giant magnetostrictive material 13 are in the shape of a cuboid, and the two have the same shape but their expansion and contraction directions are perpendicular to each other. The two are placed horizontally and symmetrically at the bottom of the housing 15, wherein the first giant magnetostrictive material 8 is placed horizontally between the two fixed baffles 7 in the left half of the housing, and the left side of the first giant magnetostrictive material 8 is close to the concave slider 17 in the slider groove 21 on the left side of the housing inner wall, and the second giant magnetostrictive material 13 is placed horizontally between the two fixed baffles 7 in the right half of the housing, and the right side of the second giant magnetostrictive material 13 is close to the concave slider 17 in the slider groove 21 on the left side of the housing inner wall. A concave slider 17 in the slider groove 21 on the right side of the inner wall of the housing, a first prestressed baffle 9, a prestressed spring 10, a spring washer 11 and a second prestressed baffle 12 are sequentially arranged between the first giant magnetostrictive material 8 and the second giant magnetostrictive material 13; the first prestressed baffle 9 and the second prestressed baffle 12 can slide to their respective adjacent horizontal baffle grooves, the left side of the first prestressed baffle 9 is a raised block for applying prestress to the first giant magnetostrictive material 8, and the right side is a cylindrical spring sleeve in which a part of the prestressed spring 10 can be placed.On the left side of the second prestressed baffle 12 is a cylindrical spring push shaft with a spring washer 11 and a prestressed spring 10, which is used to cooperate with the spring sleeve to fix the prestressed spring to prevent the spring from twisting and deformation. On the right side is a block identical to the left side of the first prestressed baffle 9, which can apply prestress to the second giant magnetostrictive material 13.

[0020] The specific installation steps of the device of the present invention are as follows:

[0021] S1. First, place the fixed structure at the corresponding position of the housing 15. Then select two giant magnetostrictive materials with the same shape and perpendicular expansion and contraction directions: the first giant magnetostrictive material 8 and the second giant magnetostrictive material 13, and place them symmetrically on the bottom of the housing 15, and fix them under the action of the first prestressed baffle 9, the prestressed spring 10 and the second prestressed baffle 12.

[0022] S2. Adjust the prestress fine-tuning screws 20 on the left and right sides of the housing 15, and push the concave slider 17 in the housing slider groove 21 to fine-tune the prestress applied to the two giant magnetostrictive materials to improve the accuracy of magnetic field measurement. Since the first prestress baffle 9 and the second prestress baffle 12 can slide smoothly, it is ensured that the prestress applied to the first giant magnetostrictive material 8 and the second giant magnetostrictive material 13 is the same. Use a screwdriver to pass through the cylindrical screw hole 3 on the housing to turn the leveling screws 4 placed in the screw groove 18 in turn, and push the fixed baffle 7 horizontally. By observing the length of the leveling screws 4 exposed in the screw groove 18, it is determined whether the fixed baffle 7 is horizontal, so that the two giant magnetostrictive materials are slightly clamped, and the first giant magnetostrictive material 8 and the second giant magnetostrictive material 13 are prevented from sliding without constraining the giant magnetostrictive material from deforming in the magnetic field.

[0023] S3. Select two gratings with the same central wavelength, namely, the optical fiber magnetic field measurement grating 6 and the optical fiber temperature compensation grating 14, and observe on the spectrometer that when the central wavelengths of the two gratings are the same in the tensioned state, fix the optical fiber magnetic field measurement grating 6 and the optical fiber temperature compensation grating 14 on the surface of the first giant magnetostrictive material 8 and the second giant magnetostrictive material 13 respectively using UV fixing glue 5 to improve the strain transmission efficiency. The two gratings are connected by optical fiber, and the optical fibers connected to the other ends of the two gratings are led out through the polytetrafluoroethylene sleeve 1 on the left and right walls of the outer shell 15. After the installation is completed, a shell cover is added to the top of the outer shell 15 to protect the internal structure of the device to ensure that the device of the present invention can be used in harsh environments.

[0024] The measurement principle of a fiber grating magnetic field sensing device with temperature compensation of the present invention is as follows:

[0025] Fiber Bragg grating is an optical waveguide device that uses ultraviolet light to expose a photosensitive optical fiber through a phase mask method to make the core refractive index change periodically or non-periodically on the axis, and for a central wavelength of The light waves of the fiber grating are strongly reflected, and the rest of the light waves are all transmitted. This makes the fiber grating a narrowband filter or reflection device. The central wavelength of the fiber grating is It can be expressed as: ;(in is the effective refractive index of the core mode, is the grating period).

[0026] When a magnetic field is applied, the expansion and contraction of the first giant magnetostrictive material 8 drives the optical fiber magnetic field measurement grating 6 to produce axial strain, resulting in a change in the central wavelength of the optical fiber grating. It can be expressed as (in is the effective elastic-optical coefficient, is the axial strain). The expansion and contraction strain of magnetostrictive materials in the linear region under the action of a magnetic field satisfy (where c is a constant, H is the magnetic field strength), the above formula can be obtained .

[0027] Therefore, when only the magnetic field acts, the change in the central wavelength of the optical fiber magnetic field measurement grating 6 is The expansion direction of the second giant magnetostrictive material 13 is perpendicular to the axis of the fiber temperature compensation grating 14, and the central wavelength change of the fiber temperature compensation grating 14 is , the difference between the central wavelength changes of the two gratings It only contains magnetic field information.

[0028] When only the temperature changes, the central wavelength changes of the optical fiber magnetic field measurement grating 6 and the optical fiber temperature compensation grating 14 are equal, that is, ,(in is the thermal expansion coefficient of the giant magnetostrictive material, is the thermal expansion coefficient of the optical fiber, is the thermo-optic coefficient). Therefore, the difference in the change in the central wavelength is .

[0029] When the magnetic field and temperature change simultaneously, the change in the central wavelength of the optical fiber magnetic field measurement grating 6 contains the magnetic field and temperature information. The central wavelength variation of the fiber temperature compensation grating 14 only contains temperature information. At this time, the difference in the central wavelength change only contains information about the magnetic field. Therefore, the invented device can eliminate the cross sensitivity of temperature to magnetic field and improve the measurement accuracy.

[0030] Attached Figure 2The schematic diagram of the device of the present invention for simulating measurement in a laboratory includes the device of the present invention, a laser, a circulator, a coil, an optical fiber, a Tesla meter, a digital power supply, a photodetector and a computer.

[0031] In the laboratory, a magnetic field is generated by connecting a coil to an external digital power supply, and the size of the applied magnetic field is changed by changing the input current. The device of the present invention is placed inside the energized coil, the output end of the laser is connected to the first port of the circulator, the second port of the circulator is connected to the optical fiber led out of the device of the present invention, and the third port of the circulator is connected to the computer via a photodetector. When the light emitted by the laser passes through the circulator and the optical fiber and enters the fiber grating magnetic field sensing device, the optical signal carrying the magnetic field and temperature information is returned, and then transmitted to the computer for demodulation through the photodetector to obtain the size of the applied magnetic field. The Tesla meter can monitor the magnetic field inside the coil and calibrate and verify the demodulated data. The demodulation of the device of the present invention is achieved by writing a computer demodulation program, which is more in line with practical applications compared to the traditional spectrometer demodulation scheme.

[0032] When used in an actual magnetic field environment, the coil and digital power supply are not required, and the device of the present invention can be fixed on a fixed object in the magnetic field environment through the fixing hole 16 at the bottom of the shell for measurement. At the same time, multiple sensing devices with different central wavelengths can be made and used in series, and multi-channel data demodulation can be set to achieve multi-point measurement.

[0033] 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 replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fiber grating magnetic field sensing device with temperature compensation, characterized in that: The invention comprises a first giant magnetostrictive material (8) and a second giant magnetostrictive material (13) whose expansion and contraction directions are perpendicular to each other. The first giant magnetostrictive material (8) and the second giant magnetostrictive material (13) are installed inside a shell (15). The first giant magnetostrictive material (8) and the second giant magnetostrictive material (13) are coaxially arranged. An elastic horizontal prestressed structure is arranged axially between the first giant magnetostrictive material (8) and the second giant magnetostrictive material (13). A prestressed fine-tuning structure capable of adjusting the axial prestress is arranged at the outer ends of the first giant magnetostrictive material (8) and the second giant magnetostrictive material (13) close to the side surface of the shell. 8) and a vertical micro-clamping structure capable of adjusting the position is symmetrically arranged between the first giant magnetostrictive material (8) and the second giant magnetostrictive material (13) and the housing (15); an optical fiber magnetic field measurement grating (6) and an optical fiber temperature compensation grating (14) are respectively arranged on the first giant magnetostrictive material (8) and the second giant magnetostrictive material (13); the optical fiber magnetic field measurement grating (6) and the optical fiber temperature compensation grating (14) are connected at one end thereof by an optical fiber, and the other end thereof is respectively connected to the outside of the housing (15) by an optical fiber; the vertical micro-clamping structure prevents the first giant magnetostrictive material (8) and the second giant magnetostrictive material (13) from sliding without constraining the deformation of the giant magnetostrictive material in the magnetic field; The horizontal prestressed structure comprises a first prestressed baffle (9) in contact with a first giant magnetostrictive material (8) and a second prestressed baffle (12) in contact with a second giant magnetostrictive material (13); the first giant magnetostrictive material (8) and the second giant magnetostrictive material (13) can slide left and right in a space provided inside the housing (15); and a prestressed spring (10) is provided between the first prestressed baffle (9) and the second prestressed baffle (12).

2. The fiber Bragg grating magnetic field sensor with temperature compensation according to claim 1, characterized in that: The first prestressed baffle (9) has a protruding block on the left side for applying prestress to the first giant magnetostrictive material (8), and a cylindrical spring sleeve with a prestressed spring (10) partially placed inside it on the right side; the second prestressed baffle (12) has a cylindrical spring push shaft with a spring washer (11) and a prestressed spring (10) on the left side, and a protruding block on the right side for applying prestress to the second giant magnetostrictive material (13).

3. The fiber Bragg grating magnetic field sensor with temperature compensation according to claim 1, characterized in that: The vertical micro-clamping structure comprises fixed baffles (7) symmetrically arranged on the front and rear sides of the first giant magnetostrictive material (8) and the second giant magnetostrictive material (13), the fixed baffles (7) being installed in rectangular baffle placement grooves (19), the rectangular baffle placement grooves (19) being a structure symmetrically arranged on the front and rear inner walls of the housing, and two rectangular screw grooves (18) being arranged in the rectangular baffle placement grooves (19), the two screw grooves (18) being located in the baffle placement grooves (19) and fixed to the housing (15). On the inner wall, a leveling screw (4) is provided in the screw groove (18), the groove edge of the screw groove (18) close to the fixed baffle (7) is thicker and has an internal thread hole, and the fixed baffle (7) also has a cylindrical opening on one side, and the internal thread hole and the cylindrical opening are penetrated by the leveling screw (4), and the front and rear walls of the housing (15) are provided with screw holes (3) corresponding to the screw groove (18), and the screw hole on the housing, the internal thread hole of the screw groove and the cylindrical opening of the fixed baffle are on the same axis for adjusting the leveling screw (4).

4. The fiber Bragg grating magnetic field sensor with temperature compensation according to claim 1, characterized in that: The prestress fine-tuning structure comprises a pair of rectangular slider grooves (21) symmetrically arranged on the left and right sides, a concave slider (17) is placed in the rectangular slider groove (21), a concave slider (17) has a groove on one side close to the inner wall of the shell, cylindrical threaded holes are symmetrically opened on the left and right walls of the shell corresponding to the groove of the concave slider (17), the prestress fine-tuning screw (20) is screwed into the threaded holes on the left and right walls of the shell from the outside and penetrates into the groove of the concave slider (17), and the other side of the concave slider (17) is in contact with the first giant magnetostrictive material (8) or the second giant magnetostrictive material (13).

5. The fiber Bragg grating magnetic field sensor with temperature compensation according to claim 1, characterized in that: The first giant magnetostrictive material (8) and the second giant magnetostrictive material (13) are rectangular parallelepiped structures of the same shape; the expansion and contraction direction of the first giant magnetostrictive material (8) is parallel to the axis of the optical fiber magnetic field measurement grating (6), and the expansion and contraction direction of the second giant magnetostrictive material (13) is perpendicular to the axis of the optical fiber temperature compensation grating (14).

6. The fiber Bragg grating magnetic field sensor with temperature compensation according to claim 1, characterized in that: The optical fiber magnetic field measurement grating (6) and the optical fiber temperature compensation grating (14) have the same central wavelength.

7. The fiber Bragg grating magnetic field sensor with temperature compensation according to claim 1, characterized in that: The left and right walls of the housing (15) are symmetrically provided with through holes, a polytetrafluoroethylene sleeve (1) is inserted into the through hole, and the optical fiber (2) passes through the polytetrafluoroethylene sleeve (1).

8. The fiber Bragg grating magnetic field sensor with temperature compensation according to claim 1, characterized in that: The optical fiber magnetic field measurement grating (6) and the optical fiber temperature compensation grating (14) are respectively fixed on the surface of the first giant magnetostrictive material (8) and the second giant magnetostrictive material (13) by means of UV fixing glue (5).

Images