阅读说明：本技术 一种温度不敏感的椭圆铰链光纤光栅加速度传感器 (Temperature-insensitive elliptical hinge fiber grating acceleration sensor ) 是由 梁磊 李自闯 王慧 许儒泉 徐刚 罗裴 吴慧峰 王永皎 于 2020-04-30 设计创作，主要内容包括：本发明公开了一种温度不敏感的椭圆铰链光纤光栅加速度传感器,包括传感器壳体、芯体与两根光纤光栅,芯体由惯性质量块、椭圆柔性铰链和基座构成,惯性质量块关于柔性铰链对称且高于柔性铰链连接的另一侧,惯性质量块和与之相对的基座上下顶部均设有光纤沟槽,光纤穿过光纤沟槽从两边壳体的孔中出来,光纤在惯性质量块和基座中间刻写有光栅,柔性铰链为椭圆形柔性铰链,惯性质量块绕着柔性铰链发生相对位移,从而使光纤光栅产生相对位移。本设计体积小易于封装,具有较高的频率测量范围,且对温度不敏感。(The invention discloses a temperature-insensitive elliptical hinge fiber grating acceleration sensor, which comprises a sensor shell, a core body and two fiber gratings, wherein the core body consists of an inertial mass block, an elliptical flexible hinge and a base, the inertial mass block is symmetrical relative to the flexible hinge and is higher than the other side connected with the flexible hinge, the inertial mass block and the upper top and the lower top of the base opposite to the inertial mass block are respectively provided with a fiber groove, an optical fiber passes through the fiber grooves and comes out from holes of the shells at two sides, the optical gratings are engraved between the inertial mass block and the base, the flexible hinge is an elliptical flexible hinge, and the inertial mass block generates relative displacement around the flexible hinge, so that the fiber gratings generate relative displacement. The design has small volume, easy encapsulation, higher frequency measurement range and insensitivity to temperature.)

1. The elliptical hinge fiber grating sensor insensitive to temperature is characterized by comprising a sensor shell, a core body and two fiber gratings, wherein the core body comprises an inertia mass block and an elliptical flexible hinge, the inertia mass block is symmetrical relative to the flexible hinge and is higher than the other side connected with the flexible hinge, fiber grooves are formed in the upper top and the lower top of the inertia mass block, wire outlets are formed in two sides of the sensor shell, the wire outlets and the fiber grooves are located on the same straight line, optical fibers penetrate through the base and the fiber grooves in the inertia mass block from the wire outlet on one side of the base and penetrate out from the wire outlet on the other side of the base, the fiber gratings are engraved in the middles of the inertia mass block and the base, and the optical fibers on two sides of; the flexible hinge is an elliptical flexible hinge which is symmetrical to the inertial mass block and generates relative displacement around the flexible hinge, so that the two fiber gratings generate strain simultaneously.

2. The elliptical hinge fiber grating acceleration sensor of claim 1, wherein: the fiber bragg grating is a fiber bragg grating.

3. The elliptical hinge fiber grating acceleration sensor of claim 2, wherein: the grating region length of the fiber grating is 5mm, and the central wavelength is 1535-1565 nm.

4. The elliptical hinge fiber grating acceleration sensor of claim 2, wherein: the interval between the central wavelengths of the upper fiber Bragg grating and the lower fiber Bragg grating is more than 5 nm.

5. The elliptical hinge fiber grating acceleration sensor of any one of claims 1-4, wherein: the optical fiber is fixed in the optical fiber groove through a glue binder, the grating is positioned between the top of the base and the inertial mass block, and the distance between the top of the base and the inertial mass block is 6 mm.

6. The elliptical hinge fiber grating acceleration sensor of claim 5, wherein: the thickness of the thin wall of the elliptic flexible hinge is 0.5-3 mm.

7. The elliptical hinge fiber grating acceleration sensor of claim 6, wherein: the height of the inertial mass block on one side of the flexible hinge is higher than that on the other side of the flexible hinge, so that sensitization is realized.

8. The elliptical hinge fiber grating acceleration sensor of claim 7, wherein: the core body and the end cover are connected through threads.

9. The elliptical hinge fiber grating acceleration sensor of claim 8, wherein: the sensor core body is made of stainless steel.

10. The elliptical hinge fiber grating acceleration sensor of claim 9, wherein: the optical fiber groove is formed in the center of the top of the upper end and the lower end of the inertial mass block, and the optical fiber groove is correspondingly formed in the top of the base.

Technical Field

The invention relates to an acceleration sensor, belongs to the technical field of optical fiber sensing, and particularly relates to an elliptical hinge optical fiber grating acceleration sensor insensitive to temperature.

Background

Compared with various traditional sensors, the fiber Bragg grating has the advantages of small size, light weight, high precision, electromagnetic interference resistance, wavelength division multiplexing, corrosion resistance, long transmission distance, intrinsic explosion resistance, suitability for severe environments and the like, and has great application prospects in the fields of aerospace, national defense construction, health detection and the like. The acceleration sensor takes the fiber Bragg grating as a sensing element, inherits a series of advantages of the fiber Bragg grating, and realizes distributed measurement of acceleration signals by converting external acceleration signals into drift of the wavelength of the fiber Bragg grating.

Most of the existing fiber grating acceleration sensors are cantilever beam type, diaphragm type and hinge type, but the former two have low natural frequencies, so that the sensors are only suitable for measuring low-frequency signals in the building field, the hinge type can meet the requirement of high-frequency-band measurement, but the sensitivity is low, the volume and the weight are often too large after packaging, and the miniaturization and the high sensitivity are the development directions of the sensors. In addition, the fiber grating is sensitive to temperature and strain at the same time, and the single-grating sensor needs additional temperature compensation to eliminate temperature influence, so that the signal detection difficulty is increased.

The above technical information is only intended to increase the understanding of the general background of the present patent application and should not be taken as an acknowledgement or any form of suggestion that this information constitutes prior art already known to a person skilled in the art.

Disclosure of Invention

The invention aims to solve the technical problem that the elliptical hinge fiber grating acceleration sensor insensitive to temperature is provided aiming at the defects in the prior art, has the advantages of simple structure, easy packaging, reduction of the whole packaging process of the sensor, small overall dimension, higher frequency detection range and higher sensitivity, and is insensitive to temperature.

The solution adopted by the invention to solve the technical problems is as follows: a temperature insensitive elliptical hinge fiber grating sensor comprises a sensor shell, a core body and two fiber gratings, wherein the core body comprises an inertia mass block and an elliptical flexible hinge, the inertia mass block is symmetrical relative to the flexible hinge and is higher than the other side connected with the flexible hinge, fiber grooves are formed in the upper top and the lower top of the inertia mass block, wire outlet holes are formed in two sides of the sensor shell, the wire outlet holes and the fiber grooves are located on the same straight line, optical fibers penetrate through the base and the fiber grooves in the inertia mass block from the wire outlet hole in one side of the base and penetrate out from the wire outlet holes in the other side of the base, the gratings are engraved in the middles of the inertia mass block and the base, and the optical fibers on; the flexible hinge is an elliptical flexible hinge which is symmetrical to the inertial mass block and generates relative displacement around the flexible hinge, so that the two fiber gratings generate strain simultaneously.

In one or more embodiments of the present invention, the fiber grating is a fiber bragg grating.

In one or more embodiments of the present invention, the grating region length of the fiber grating is 5mm, and the center wavelength is 1535-1565 nm.

In one or more embodiments of the present invention, the upper fiber bragg grating and the lower fiber bragg grating center wavelength are spaced apart by greater than 5 nm.

In one or more embodiments of the invention, the optical fiber is fixed in the optical fiber groove by glue adhesive, the grating is located between the top of the base and the inertial mass, and the distance between the top of the base and the inertial mass is 6 mm.

In one or more embodiments of the invention, the thin wall thickness of the elliptical flexible hinge is 0.5-3 mm.

In one or more embodiments of the present invention, the height of the inertial mass on one side of the flexible hinge is higher than that on the other side of the flexible hinge, so as to realize sensitization.

In one or more embodiments of the invention, the core and the end caps are connected by threads.

In one or more embodiments of the present invention, the sensor core material is stainless steel.

In one or more embodiments of the present invention, the optical fiber groove is disposed in the center of the top of the upper and lower ends of the inertial mass, and the optical fiber groove is correspondingly disposed on the top of the base.

The invention has the following beneficial effects:

the invention is based on the elliptical flexible hinge structure, has simple structure, reduces the whole packaging process of the sensor, has small overall dimension, saves the installation space, has a higher frequency measurement range, has lever effect by increasing the height of one end of the elliptical single-shaft flexible hinge, has sensitization function, is beneficial to increasing the sensitivity of the sensor, has the distance between the top of the base and the inertial mass block which is equivalent to the length of the grating, only allows the strain of the grating, avoids the strain transfer and reduces the sensitivity, and under the action of an external excitation source, the vertically symmetrical inertial mass block generates micro-amplitude vibration around the elliptical flexible hinge to drive the upper fiber grating and the lower fiber grating to move reversely, uses the symmetrical flexible hinge to replace the traditional cantilever beam or other elastomer structures, is beneficial to increasing the resonance frequency of the sensor, and can multiply the sensitivity of the sensor by measuring the relative variation of the central, the influence of temperature on the sensor can be avoided, so that the sensor is insensitive to the temperature and is particularly suitable for acceleration measurement in a high-frequency domain range.

Drawings

Fig. 1 is a schematic structural view of the present invention.

In the figure, 1-an elliptical flexible hinge, 2-an inertial mass block, 3-an optical fiber groove, 4-an optical fiber, 5-a sensor shell, 6-a shell end cover and 7-a wire outlet hole.

Fig. 2 is a schematic structural view of the core of the present invention.

Fig. 3 is a graph of the dimensional parameters of a sensing unit of the present invention.

FIG. 4 is a diagram of a mechanical model of the present invention.

Detailed Description

The technical scheme and the beneficial effects of the invention are clearer and clearer by further describing the specific implementation mode of the invention with the accompanying drawings of the specification; and are intended to be illustrative of the invention and not to be construed as limiting the invention.

As shown in fig. 1 to 4, the embodiments of the present invention preferably provide a temperature insensitive elliptical hinge fiber grating acceleration sensor, which includes a sensor housing 5, a core and two optical fibers 4, the core includes an inertial mass 2 and an elliptical flexible hinge 1, and the inertial mass 2 is symmetric with respect to the flexible hinge and is higher than the other side of the flexible hinge connection to realize sensitivity enhancement. The inertial mass block 2 and the top portion about the relative base all are equipped with optic fibre slot 3, and 6 both sides of sensor casing are equipped with wire hole 7, and wire hole 7 and optic fibre slot 3 are located same straight line, and optic fibre 4 is worn 7 into through the optic fibre slot 3 on base and the inertial mass block from base one side wire hole, and is worn out from the opposite side wire hole, and optic fibre has carved with the grating in the middle of inertial mass block 2 and the base, and optic fibre 4 and the optic fibre slot 3 of grating both sides are connected fixedly.

The elliptical flexible hinge 1 is symmetrically distributed with inertial mass blocks 2 and relatively displaces around the flexible hinge, so that two optical fibers 4 are simultaneously strained. The invention is based on the elliptical flexible hinge structure, has simple structure, reduces the whole packaging process of the sensor, has small overall dimension, saves the installation space, has a higher frequency measurement range, has lever effect by increasing the height of one end of the elliptical single-shaft flexible hinge, has sensitization function, is beneficial to increasing the sensitivity of the sensor, has the distance between the top of the base and the inertial mass block which is equivalent to the length of the grating, only allows the strain of the grating, avoids the strain transfer and reduces the sensitivity, and under the action of an external excitation source, the vertically symmetrical inertial mass block generates micro-amplitude vibration around the elliptical flexible hinge to drive the upper fiber grating and the lower fiber grating to move reversely, uses the symmetrical flexible hinge to replace the traditional cantilever beam or other elastomer structures, is beneficial to increasing the resonance frequency of the sensor, and can multiply the sensitivity of the sensor by measuring the relative variation of the central, the influence of temperature on the sensor can be avoided, so that the sensor is insensitive to temperature and is particularly suitable for acceleration measurement in a high-frequency domain range, and on the basis, the sensitivity of the sensor can be increased by increasing the weight of the inertia mass block or changing the thickness of the flexible hinge.

By way of further example with the above embodiments, the schemes that can be combined in the above embodiments in a single or combined manner are as follows:

in some examples, the fiber bragg grating is a fiber bragg grating, and the fiber 4 bragg grating is fixed on one side of the base, then is pre-stretched appropriately, and then is fixed on the other side of the base at the end of the inertial mass, and is fixed in the fiber groove by using an adhesive 353 ND.

In some examples, the fiber bragg grating has a length of 5mm and a center wavelength of 1535 and 1565 nm.

In some examples, the upper and lower fiber bragg gratings center wavelength spacing is greater than 5 nm.

In some examples, the optical fiber is secured within the fiber groove by an adhesive. The grating is located between the top of the base and the inertial mass block, and the distance between the top of the base and the inertial mass block is 6 mm.

In some examples, the thin wall thickness of the elliptical-type flexible hinge is 0.5-3 mm.

In some examples, the inertial mass is symmetric about the elliptical compliant hinge.

In some examples, the core and the end cap are connected by threads.

In some examples, the sensor cell material is stainless steel.

In some examples, the optical fiber groove is arranged in the center of the top of the upper end and the lower end of the inertial mass block, the optical fiber groove is correspondingly arranged on the top of the base, the length of the optical fiber groove on the inertial mass block and the base is not less than 6mm, the depth of the optical fiber groove is 0.5mm, and the coating layers of the pasting areas at the two ends are stripped by using a wire stripper, the length is about 6mm but not more than the length of the glue coating, so that the pasting is convenient and firm, and the long-. The thinnest place of the inertia mass block is larger than the thin wall thickness of the flexible hinge. The thickness of the inertia mass block is consistent with that of the flexible hinge, the thickness is 8-13mm, and the thickness is smaller than the width of the end cover.

When the fiber bragg grating acceleration sensor works, the fiber bragg grating acceleration sensor is fixed on an object to be tested, when external excitation is generated, the acceleration sensor vibrates along with the object to be tested, so that the inertia mass block slightly rotates relative to the flexible hinge, one fiber bragg grating is stretched along the axial direction when the inertia mass block rotates, the other fiber bragg grating is compressed along the axial direction, the central wavelengths of the two fiber bragg gratings are changed due to the change of axial strain, an external acceleration signal is converted into the relative drift amount of the central wavelengths of the two fiber bragg gratings, through the establishment of the linear relation between the relative drift amount of the central wavelengths of the two fiber bragg gratings and the acceleration, the acceleration value of an external excitation source can be determined when the relative drift amount of the central wavelengths of the two fiber bragg gratings is demodulated, and meanwhile vibration spectrum analysis can.

The working principle of the temperature-insensitive elliptical hinge FBG acceleration sensor is as follows: the fiber bragg grating acceleration sensor is fixed on an object to be tested, when external excitation is generated, the acceleration sensor vibrates along with the object to be tested, so that the inertia mass block slightly rotates relative to the flexible hinge, one fiber bragg grating is axially stretched when the inertia mass block rotates, the other fiber bragg grating is axially compressed, the central wavelengths of the two fiber bragg gratings are changed due to the change of axial strain, an external acceleration signal is converted into the relative drift amount of the central wavelengths of the two fiber bragg gratings, the linear relation between the relative drift amount of the central wavelengths of the two fiber bragg gratings and the acceleration is established, the acceleration value of an external excitation source can be determined when the relative drift amount of the central wavelengths of the two fiber bragg gratings is demodulated, and meanwhile vibration spectrum analysis can be carried out.

And establishing a relation model between the acceleration of the measured object and the relative wavelength drift amounts of the two fiber gratings.

The sensitivity S of the fiber grating acceleration sensor is the ratio of the relative change quantity delta lambda of the central wavelength of the fiber grating to the acceleration a:

the whole system is analyzed, and the moment balance equation can obtain:

the distance from the mass center of the inertia mass block to the center of the elliptical hinge is d, the height of the inertia mass block is h, the elastic coefficient of the optical fiber is K, the rigidity of the elliptical flexible hinge is K, the rotation angle of the elliptical hinge is theta, and l is the distance between the two optical fiber fixing points on the base and the inertia mass block.

The elastic coefficient k of the optical fiber is:

the stiffness K of the elliptical flexible hinge is:

wherein

E denotes the modulus of elasticity of the material, w denotes the thickness of the hinge, b denotes the chain half-axis of the elliptical hinge, s ═ c/t, c denotes the minor half-axis of the elliptical hinge, and t denotes the minimum thickness between the hinges.

The relational expression of the variation of the central wavelength of the fiber grating and the variation of the strain is as follows:

for a common single mode fiber, the effective elastic-optical coefficient is P_e＝0.22

Since the inertial mass is symmetrical about the flexible hinge, Δ₁＝-Δ₂＝Δ

Δλ＝Δλ₁-Δλ₂＝(1-P_e)(λ₁+λ₂)Δ (9)

Since theta is very small, theta is approximately equal to sin theta, so

Sensitivity S of simultaneous (1), (2) and (9):

according to the formula (11), the change of the acceleration of the object to be measured can be obtained from the relative drift amounts of the central wavelengths of the two fiber gratings, so that a vibration signal is obtained.

While this invention has been described in terms of the preferred embodiments, there may be alterations, permutations, and equivalents, which fall within the scope of this invention; there may be many alternative ways of implementing the invention; it is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention; it will be appreciated by persons skilled in the art that the present invention is not limited to the specific embodiments described above. Modifications and substitutions that are known in the art to which this invention pertains are deemed to lie within the scope and spirit of the invention as defined by the appended claims.