CN115183741A - Fiber grating tilt angle sensor - Google Patents

Abstract

The invention relates to a fiber grating tilt angle sensor which comprises an elastic body, sensitization connecting parts, a fiber grating and a mass block, wherein the two sensitization connecting parts are respectively connected to two ends of the elastic body in the extending direction, two ends of the fiber grating are respectively connected to the two sensitization connecting parts, the extending direction of the fiber grating is parallel to the extending direction of the elastic body, the fiber grating and the elastic body are arranged at intervals, and the mass block is connected to one sensitization connecting part. Because the fiber grating and the elastic body are arranged at intervals, the deformation of the fiber grating is larger than that of the elastic body, and the sensitization is further realized. Compared with the prior art, the invention has simple structure, can be realized by smaller volume, simultaneously realizes the sensitization effect, ensures the sensing precision and has good application prospect.

Description

A fiber grating tilt sensor

technical field

The invention relates to the technical field of optical fiber sensing, in particular to a fiber grating inclination sensor.

Background technique

When large-scale construction projects are carried out around large-scale civil structures such as tunnels, bridges, and houses, under the influence of various factors such as unloading and vibration, the foundation is prone to uneven settlement, causing tilting deformation of related structures. Therefore, it is often necessary to conduct real-time online tilt status monitoring of the affected structures during construction.

Most of the traditional inclination sensors are electrical sensors with high measurement accuracy and resolution, but the shortcoming of being susceptible to electromagnetic interference limits their use in complex environments. The fiber grating inclination sensor has the advantages of anti-electromagnetic interference, strong stability, and easy networking, and has been widely used in the field of structural health monitoring.

However, the current fiber grating inclination sensor has low precision, and it is difficult to meet the high-precision measurement requirements under the condition of small structure.

SUMMARY OF THE INVENTION

In view of this, it is necessary to provide a fiber grating inclination sensor to solve the problem of low precision of the existing fiber grating sensor.

In order to achieve the above-mentioned technical purpose, the present invention has adopted the following technical solutions:

The present invention provides a fiber grating inclination sensor, comprising:

an elastic body, which can be bent to both sides of its extension direction;

Two sensitization connecting parts are respectively connected to both ends of the elastic body in the extending direction;

Fiber grating, two ends of the fiber grating are respectively connected to the two sensitization connecting parts, the extension direction of the fiber grating is parallel to the extension direction of the elastic body, and the fiber grating and the elastic body are arranged at intervals ;

A mass block is connected to one of the sensitization connecting parts.

Further, the sensitization connecting part includes a connecting block and a sensitizing block, the connecting block is connected to one end of the elastic body in the extending direction, the sensitizing block is connected to the connecting block, and is connected to the elastic body. The bodies are arranged at intervals, and both ends of the fiber grating are respectively connected to the sensitization block.

Further, the sensitization block is a rigid structure.

Further, the sensitizing block extends toward the middle of the elastic body along the extending direction of the elastic body.

Further, each of the sensitization connecting parts includes two sensitization blocks, and the number of the fiber gratings is two, which are symmetrically arranged on both sides of the elastic body.

Further, the two fiber gratings are connected in series toward the end of the mass.

Further, it also includes a housing, the elastic body, the sensitization connecting part, the fiber grating and the mass block are all arranged in the housing, and the end of the elastic body facing away from the mass block is connected to the the housing, the fiber grating passes through and extends out of the housing away from the mass.

Further, the position where the fiber grating is inserted on the casing is sealed by a sealant to form a closed space.

Further, the closed space formed by the shell is filled with silicone oil.

Further, limit holes are opened on the casing.

The invention provides a fiber grating inclination sensor, which makes the fiber grating located on both sides of the elastic body through the sensitizing connection part. When the whole fiber grating inclination sensor is inclined with the object to be measured, the mass block drives the elastic body to bend, and the fiber grating is bent. It will deform along with the elastic body. At this time, the wavelength signal transmitted inside the fiber grating will change, and the inclination of the object to be measured can be obtained according to the wavelength signal. At the same time, because the fiber grating and the elastic body are spaced apart, the deformation of the fiber grating will be greater than that of the elastic body, thereby realizing sensitization. Compared with the prior art, the present invention has a simple structure, can be realized by a smaller volume, and also achieves a sensitization effect, ensures the accuracy of sensing, and has a good application prospect.

Description of drawings

1 is a schematic structural diagram of an embodiment of a fiber grating inclination sensor provided by the present invention;

2 is a schematic structural diagram of a fiber grating inclination sensor provided by the present invention without a casing and a mass block according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of calculation in an embodiment of the fiber grating tilt sensor provided by the present invention.

Detailed ways

The preferred embodiments of the present invention are specifically described below with reference to the accompanying drawings, wherein the accompanying drawings constitute a part of the present application, and together with the embodiments of the present invention, are used to explain the principles of the present invention, but are not used to limit the scope of the present invention.

The present invention utilizes the gravity component of the mass block to drive the elastic body 1 to swing, so that the fiber grating 3 on one side of the elastic body 1 stretches or shrinks. To achieve increased sensitivity and improve sensor accuracy. Further, in the present invention, the fiber grating 3 is arranged between the two sensitizing blocks 22, and the two sensitizing blocks 22 extend along the direction of the elastic body 1, so that the deformation on the sensitizing block 22 is better than that on the fiber grating 3. Ignoring, all the deformation is concentrated in the middle fiber grating 3 to achieve further sensitization of the structure, and the sensitivity of the fiber grating inclination sensor can be maximized through the combination of the two sensitization methods.

On the other hand, in the present invention, fiber gratings 3 are also arranged on both sides of the elastic body 1, and the inclination angle is jointly calculated by the change of the difference between the center wavelengths of the two fiber gratings 3, and the measurement accuracy of the sensor is improved by the differential method. The effect of temperature on fiber grating is eliminated.

With reference to FIGS. 1 and 2 , the present invention provides an embodiment of a fiber grating sensor. The fiber grating sensor includes an elastic body 1 , a sensitization connecting portion 2 , a fiber grating 3 and a mass 4 . The elastic body 1 can be bent to both sides of its extension direction, the two sensitization connecting parts 2 are respectively connected to the two ends of the elastic body 1 in the extension direction, and the two ends of the fiber grating 3 are respectively connected to the two In the sensitizing connection part 2, the extension direction of the fiber grating 3 is parallel to the extension direction of the elastic body 1, the fiber grating 3 and the elastic body 1 are spaced apart, and the mass 4 is connected to one of the sensitizers. connection part.

The present invention provides a fiber grating sensor. The fiber grating 3 is located on both sides of the elastic body 1 through the sensitizing connection part 2. When the entire fiber grating sensor tilts with the object to be measured, the mass block 4 drives the elastic body 1 to deform. , the fiber grating 3 will deform together with the elastic body 1, and the wavelength signal transmitted inside the fiber grating 3 will change at this time, and the inclination of the object to be measured can be obtained according to the wavelength signal. At the same time, since the fiber grating 3 and the elastic body 1 are arranged at intervals, the deformation degree of the fiber grating 3 will be greater than the deformation degree of the elastic body 1, thereby realizing sensitization. Compared with the prior art, the present invention has a simple structure, can be realized by a smaller volume, and also achieves a sensitivity enhancement effect, ensures the accuracy of sensing, and has a good application prospect.

As a preferred embodiment, the sensitizing connecting part 2 in this embodiment includes a connecting block 21 and a sensitizing block 22, the connecting block 21 is connected to one end of the elastic body 1 in the extending direction, and the sensitizing block 21 is connected to one end of the elastic body 1 in the extending direction. The block 22 is connected to the connection block 21 and is spaced apart from the elastic body 1 , and both ends of the fiber grating 3 are respectively connected to the sensitization block 22 .

The connection block 21 realizes the spaced setting of the sensitizing blocks 22, and further realizes the spaced setting of the fiber grating 3, which has the effect of increasing sensitivity and makes the fiber grating sensor more accurate. In practice, the connecting block 21 , the sensitizing block 22 and the elastic body 1 can be integrally formed using processing techniques such as wire cutting to meet the requirement of smaller volume, or can be manufactured separately and assembled together.

The present invention also provides a preferred embodiment, in which the sensitization block 22 is a rigid structure. The sensitizing block 22 of the rigid structure will not deform, so that the deformation following the elastic body 1 is all concentrated on the fiber grating 3. Under the condition that the deformation degree of the elastic body 1 is the same, the deformation degree of the fiber grating 3 can be increased, and the cost of the fiber grating 3 can be increased. Sensitivity and precision of fiber grating sensors.

Further, as a preferred embodiment, the sensitization block 22 in this embodiment extends toward the middle of the elastic body 1 along the extending direction of the elastic body 1 . In this way, the length of the fiber grating 3 can be shortened, so that the bending deformation of the fiber grating 3 is more concentrated in the middle thereof, which further improves the measurement sensitivity and accuracy of the fiber grating sensor. The above features cooperate with the spacing between the fiber grating 3 and the elastic body 1, and work together to achieve double sensitization.

型结构，增敏块22与弹性体1之间形成镂空细槽。这样使得本光纤光栅传感器在两个弯曲方向上均具备光纤光栅3进行增敏与检测，增加本光纤光栅传感器的实用性，同时两个光纤光栅3的配合能够降低测量误差的影响，提高测量精度。In a preferred embodiment, each of the sensitization connecting parts 2 includes two sensitization blocks 22 , and the number of the fiber gratings 3 is two, which are symmetrically arranged on both sides of the elastic body 1 . The connecting block 21, the sensitizing block 22 and the elastic body 1 together form a symmetrical

type structure, a hollowed slot is formed between the sensitizing block 22 and the elastic body 1 . In this way, the fiber grating sensor is equipped with fiber gratings 3 in both bending directions for sensitization and detection, which increases the practicability of the fiber grating sensor. At the same time, the cooperation of the two fiber gratings 3 can reduce the influence of measurement errors and improve the measurement accuracy. .

Referring to FIG. 2 again, as a preferred embodiment, in the fiber grating sensor in this embodiment, the two fiber gratings 3 are connected in series toward the end of the mass block 4 . This design step is convenient for manufacturing and installation, and it can also facilitate the subsequent calculation of the inclination angle.

The fiber grating 3 in this embodiment is pasted on both sides of the sensitizing block 22 by epoxy resin, and in order to more accurately perceive the wavelength shift that occurs when the fiber grating 3 is deformed, it is necessary to attach the fibers at both ends of the fiber grating 3 before pasting the fibers A pre-stretching operation is performed on the fiber grating 3, and the pre-stretching amount is about 2 nm to ensure that the fiber grating can sense shrinkage.

As a preferred embodiment, the fiber grating sensor in this embodiment further includes a housing 5, and the elastic body 1, the sensitization connecting part 2, the fiber grating 3 and the mass 4 are all disposed in the housing 5 , the end of the elastic body 1 facing away from the mass block 4 is connected to the housing 5 , and the fiber grating 3 passes through and extends out of the housing 5 away from the mass block 4 . The casing 5 encapsulates the above-mentioned parts together to form a complete independent device.

In this embodiment, the position where the fiber grating 3 is inserted into the casing 5 is sealed by a sealant to form a closed space.

Further, as a preferred embodiment, the closed space formed by the casing 5 in this embodiment is filled with silicone oil. The fiber grating sensor is susceptible to external interference when used. For example, when it is affected by external factors such as environmental noise and equipment vibration, the mass block 4 is prone to vibrate, which affects the measurement accuracy. Silicon oil has a certain damping, and filling with silicone oil can reduce the random vibration caused by this kind of vibration. The use of different damping silicone oils can further adjust the anti-disturbance ability of the sensor.

In a preferred embodiment, the casing 5 in the fiber grating sensor is provided with a limit hole 6, and the limit hole 6 can limit the position of the mass block 4, for example: fix the installed fiber grating sensor on the fine-tuning platform Make sure that the sensor is installed vertically, adjust the fine-tuning platform to the left to the preset angle, use the limit device to extend into the limit hole 6 to limit the left side of the mass block 4, complete the left-side limit, and adjust the fine-tuning platform to the right to the preset angle , use the limit device to extend into the limit hole 6 to limit the right side of the mass block 4, complete the right side limit, ensure that the mass block 4 is in a suitable posture, and eliminate the measurement error. And after adjustment, sealant can be applied to the pores on the casing 5 to ensure the sealing.

3, the present invention also provides a method for using the above-mentioned fiber grating sensor, the specific process is as follows:

Considering the sensitizing block 22 as a cantilever beam, the gravity component F of the mass block 4 is applied to the free end of the sensitizing block 22, satisfying:

F=mg sinθ

In the formula, m is the mass of the mass block 4, g is the acceleration of gravity, and θ is the inclination angle of the object to be measured.

Assuming that the elastic body 1 is bent downward in Figure 3, it can be seen from the material mechanics that the upper surface of the elastic body stretches and the lower surface contracts, and the axial average strain ε of the upper surface of the elastic body 1 is:

In the formula, is the required axial average strain of the upper surface of the elastic body 1, L is the length of the elastic body 1 in the extending direction, E is the elastic modulus of the elastic body 1, and n is the cross-section of the elastic body 1 in the extending direction. Width, h is the width of the cross section of the elastic body 1 in the extending direction.

When the elastic body 1 is bent, the distance between the two points A and B in Fig. 3 from the elastic body is always the same, so the two points A and B are respectively in the same plane as the two ends of the elastic body 1. It can be seen from the material mechanics, The strain at a point on a cantilever beam section is proportional to the point's distance from the neutral axis.

If the fiber bonding points are set at points A and B, and the fiber grating 3 is suspended between AB, the strain at the fiber grating 3 amplifies the average strain on the upper surface of the elastic body 1, and the amplification factor K ₁ is:

In the formula, c is the distance between the neutral layer of the elastomer 1 and the bonding point of the optical fiber, and h is the thickness of the elastomer 1.

At the same time, the distance between the bonding points C and D at both ends of the fiber grating 3 is smaller than the length of the elastic body 1. If the fiber grating 3 is suspended between AB and CD respectively, the axial strain of the two fiber gratings 3 ε ₂ and ε ₃ satisfy respectively:

Among them, ΔL _AC is the distance change of the two points AC on the sensitizing block 22, ΔL _CD is the distance change of CD, ΔL _DB is the distance change of the two points DB on the sensitization block 22, and ΔL _AB is the distance change of AB L _f is the suspension length of the fiber grating 3 .

Then, the fiber grating 3 is suspended between CDs to achieve further sensitization, and the sensitization coefficient K ₂ satisfies:

When the fiber grating 3 is suspended between CDs, the deformation of the sensitizing block 22 is much smaller than the deformation of the fiber grating 3, so ΔL _AC <<ΔL _CD , ΔL _DB <<ΔL _CD , then take:

After secondary sensitization, the total sensitization factor of the sensor is:

The wavelength change Δλ ₁ of the fiber grating 3 on the upper side of the elastic body 1 is:

Δλ ₁ =K _T ΔT+K _ε ε ₃

Among them, K _T is the temperature sensitivity coefficient of the sensor, K _ε is the strain sensitivity coefficient of the sensor, and ΔT is the temperature change.

The lower fiber grating 3 of the elastomer 1 and the upper fiber grating 3 are in the same temperature field, so the temperature coefficients are the same, and it can be seen from the material mechanics that the axial strains of the two are the same and opposite, and the wavelength change of the lower fiber grating 3 Δλ ₂ is:

Δλ ₂ =K _T ΔT-K _ε ε ₃

When the fiber grating 3 is in the 1500nm band, the strain sensitivity of the bare grating is 1.2pm/με, and the tilt angle satisfies:

The present invention provides a fiber grating sensor. The fiber grating 3 is located on both sides of the elastic body 1 through the sensitizing connection part 2. When the entire fiber grating sensor tilts with the object to be measured, the mass block 4 drives the elastic body 1 to deform. , the fiber grating 3 will bend with the elastic body 1, and the wavelength signal transmitted from the fiber grating 3 will change at this time, and the inclination of the object to be measured can be obtained according to the wavelength signal. At the same time, since the fiber grating 3 and the elastic body 1 are arranged at intervals, the deformation degree of the fiber grating 3 will be greater than the deformation degree of the elastic body 1, thereby realizing sensitization. Compared with the prior art, the present invention has a simple structure, can be realized by a smaller volume, and also achieves a sensitivity enhancement effect, ensures the accuracy of sensing, and has a good application prospect.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts of the various embodiments may be referred to each other.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Substitutions should be covered within the protection scope of the present invention.

Claims (10)

1. A fiber grating tilt sensor, comprising:

an elastic body capable of bending to both sides in an extending direction thereof;

the two sensitization connecting parts are respectively connected to two ends of the elastic body in the extending direction;

the two ends of the fiber bragg grating are respectively connected to the two sensitization connecting parts, the extending direction of the fiber bragg grating is parallel to the extending direction of the elastic body, and the fiber bragg grating and the elastic body are arranged at intervals;

and the mass block is connected with one sensitization connecting part.

2. The fiber grating tilt angle sensor of claim 1, wherein the sensitization connecting portion includes a connecting block and a sensitization block, the connecting block is connected to one end of the elastic body in the extending direction, the sensitization block is connected to the connecting block and spaced from the elastic body, and two ends of the fiber grating are respectively connected to the sensitization blocks.

3. The fiber grating inclination angle sensor according to claim 2, characterized in that the sensitization block is a rigid structure.

4. The fiber grating tilt sensor of claim 3, wherein the sensitization block extends towards the middle of the elastic body along the extension direction of the elastic body.

5. The fiber grating tilt angle sensor according to claim 4, wherein each of the sensitization connecting portions comprises two sensitization blocks, and the two fiber gratings are symmetrically arranged on two sides of the elastic body.

6. The fiber grating tilt angle sensor according to claim 5, wherein two of the fiber gratings are connected in series towards an end of the mass.

7. The FBG tilt angle sensor of claim 1, further comprising a housing, wherein the elastomer, the sensitization connection, the FBG, and the mass are disposed within the housing, wherein an end of the elastomer facing away from the mass is connected to the housing, and the FBG passes away from the mass and extends out of the housing.

8. The fiber grating tilt angle sensor according to claim 7, wherein the position of the housing where the fiber grating is inserted is sealed by a sealant to form a closed space.

9. The fiber grating tilt angle sensor according to claim 8, wherein the enclosed space formed by the housing is filled with silicone oil.

10. The fiber grating tilt angle sensor according to claim 7, wherein the housing is provided with a limiting hole.

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