CN209877907U - A Cam Structure Fiber Bragg Grating Large Range Inclination Sensor - Google Patents

Abstract

The utility model discloses a fiber grating large-range inclination sensor with a cam structure, which comprises: a mass block, a square boss, a box body, a cam, a box cover, a sealing cover, and a limit baffle; the inside of the box body is provided with two There are square bosses of equal size, and optical fiber access holes are opened on both sides of the outer longitudinal sides of the box; the box cover and the box body are connected by screws to form a closed space, and the lower surface of the box cover is provided with a limit baffle; The cam is supported by the transmission rod and is located in the middle between the two square bosses; one end of the threaded rod is connected to the mass block, the other end is connected to the transmission rod and the two are integrated; the cover is located on the upper and lower sides outside the box body. At the end, the cover axially fixes both ends of the transmission rod. The utility model has the advantages of simple structure, adjustable sensitivity and range, temperature self-compensation, etc., and can realize large-range, stable, accurate and high-sensitivity inclination measurement.

Description

A Cam Structure Fiber Bragg Grating Large Range Inclination Sensor

technical field

The utility model belongs to the technical field of optical fiber grating sensors and inclination angle measurement, in particular to an optical fiber grating large-range inclination sensor with a cam structure.

Background technique

As the sensing part of the monitoring system, the sensor is in a very important position. It has been a hot spot for R&D and application in various countries for many years. At present, inclination sensors are widely used in engineering practice. Various large-scale civil engineering projects such as buildings, bridges, slopes and tunnels often use inclination sensors to monitor their inclination. In addition, they can also be used in the electronic compass of aircraft , static self-correction of horizontal platforms, and detection of limb movement postures and other practical fields.

Most of the traditional inclination sensors are based on the electromagnetic effect and capacitive effect. Although they can achieve high accuracy and resolution during measurement, this weak current sensor has poor anti-electromagnetic interference performance and is greatly affected by temperature. , short measurement distance, and it is increasingly difficult to meet the current monitoring requirements in terms of continuity, real-time and measurement sensitivity, which undoubtedly brings great inconvenience to basic engineering measurement.

Fiber Bragg Grating has the advantages of high measurement sensitivity, anti-electromagnetic interference, long signal transmission distance, and corrosion resistance. It can remotely monitor the structure of buildings for a long time. It is very suitable for real-time monitoring in harsh outdoor environments such as tunnels and slopes. .

However, the existing fiber grating inclination sensor mainly adopts the technical solution of directly pasting the fiber grating on the beam surface of the cantilever pendulum. In practical application, there are the following problems: including small measurable range, low sensitivity, and easy to be affected by temperature In addition, the temperature cannot be self-compensated, the product is large in size, the optical fiber in the box is not easy to coil, and the range and sensitivity cannot be adjusted according to actual needs; it is not conducive to long-term accurate monitoring.

Utility model content

Aiming at the above-mentioned problems existing in the prior art, the utility model provides a fiber grating large-range inclination sensor with a cam structure, which has the advantages of simple structure, adjustable sensitivity and range, temperature self-compensation, etc., and can realize large-range, stable , Accurate, high-sensitivity inclination measurement.

For this reason, the utility model has adopted following technical scheme:

A fiber grating large-range inclination sensor with a cam structure, comprising: a mass block, a first fiber grating, a square boss, a box, a cam, a second fiber grating, a transmission rod, a threaded rod, a box cover, a cover, a limit Baffle plate, adhesive; the inside of the box is provided with two square bosses of equal size, and the outer longitudinal sides of the box are provided with optical fiber access holes; the box cover and the box are connected by screws A closed space is formed, and a limit baffle is provided on the lower surface of the box cover; the cam is supported by the transmission rod and is located in the middle between the two square bosses; the first fiber grating and the second fiber grating It is fixed on the surface of the square boss by adhesive; one end of the threaded rod is connected with the mass block, and the other end is connected with the transmission rod and the two are integrated; the cover is located at the upper and lower ends of the outside of the box , The cover fixes the two ends of the transmission rod in the axial direction to prevent sliding in the axial direction and affect the measurement accuracy.

Preferably, the cam is mainly composed of two parts, including an upper part and a lower part; the upper part is a standard semicircle, and the circular arc profile of the lower part is left-right symmetrical. Starting at the critical point of the lower half, the length of the line connecting any point on the arc profile to the center of the cam circle increases with the increase of the acute angle between the line and the bottom diameter line of the standard semicircle in the upper half While increasing linearly, the acute angle starts at 0° and ends at 90°.

Preferably, the first fiber grating and the second fiber grating are arranged symmetrically on both sides of the cam. Tangent at the critical point of the part and the bottom half. When there is an inclination acting on the sensor, the mass block swings with the inclination angle, which drives the transmission rod to rotate, and then drives the cam to swing. The lower part of the cam will lift up one of the fiber gratings to stretch the fiber grating, while the other fiber grating The grating will move along the standard semi-circular arc without being affected by the change of inclination angle. As the temperature compensation of the stretched fiber grating, the difference of the wavelength drift of the two fiber gratings is used as the output signal of the sensor, so as to achieve the temperature self-control. The effect of compensation.

Preferably, according to the thickness of the cam or the distance between two square bosses, the requirements of different sensitivities, precisions and ranges in actual measurement applications can be met, and the grating will not be broken.

Preferably, the limit baffle is used to limit the swing angle of the mass within ±90°.

Preferably, the center of the cam is provided with a center hole, the transmission rod passes through the center hole of the cam through interference fit, and the two ends of the transmission rod are radially limited by self-lubricating bearings.

Preferably, a threaded hole is provided at the top center of the mass block, and the mass block and the transmission rod are connected by a threaded rod. The threaded rod is used as a connection between the mass block and the cylindrical transmission rod. When the sensor is tilted, the mass block will swing due to the inclination. Passed to the cam to ensure measurement accuracy and sensitivity.

Preferably, the box body and the square boss are an integrated structure.

Preferably, the square bosses are symmetrically distributed on both sides with the cam as the center; the first fiber grating and the second fiber grating are symmetrically tangent to both sides of the cam; Pre-stretching, pasting the pre-stretched fiber grating on the surface of the square boss.

Preferably, rounded corners are provided at the places where both sides of the cam are tangent to the fiber grating, so as to prevent the fiber from being cut.

Compared with the prior art, the beneficial effects of the utility model are:

(1) Temperature self-compensation can be realized. The sensor adopts a cam structure, and two fiber gratings are symmetrically distributed on both sides. When the grating on one side is stretched, the grating on the other side will move on a semicircular arc with a constant radius, and act as For the temperature compensation of the stretched grating, the problem of temperature and strain cross-sensitivity can be eliminated by using the differential output of the wavelength drift of two fiber gratings, so that it can adapt to complex and changeable external environments.

(2) Large measuring range and high measurement accuracy. It can be seen from the structural design that the optical fiber grating inclination sensor has a range of -90° to 90°, which can meet the requirements for the inclination range of large civil engineering structures. The inclination value measured by the sensor is used to calculate the deformation value through relevant calculation formulas, and the sensor of the utility model can carry out inclination calibration tests in the laboratory, and can realize accurate measurement of the inclination value.

(3) Various layout methods and wide application range. The utility model is a sealed box design, which can be directly arranged at the required monitoring position, and can also be pre-embedded in a prefabricated component, which can improve the survival rate of the sensor in construction detection.

(4) The utility model adopts optical signal transmission, which is not affected by electromagnetic interference in nature; it can realize remote real-time online monitoring, which greatly overcomes the influence of traditional electrical signal measuring inclination angles which are easily affected by electromagnetic interference.

(5) The accuracy and precision of measurement can be effectively adjusted by increasing the weight of the mass or changing the thickness of the cam, so as to meet the measurement requirements in different environments.

Description of drawings

Fig. 1 is a schematic plan view of a fiber grating large-range inclination sensor with a cam structure provided by the present invention.

Fig. 2 is a schematic cross-sectional structure diagram of a fiber grating large-range inclination sensor with a cam structure provided by the utility model.

Fig. 3 is a schematic diagram of a three-dimensional structure of a fiber grating large-range inclination sensor with a cam structure provided by the present invention.

Fig. 4 is a three-dimensional structural schematic diagram of a cam in a fiber grating large-range inclination sensor with a cam structure provided by the present invention.

Fig. 5 is a schematic plan view of the cam in a fiber grating large-range inclination sensor with a cam structure provided by the present invention.

Explanation of reference signs: 1. mass block; 2. first fiber grating; 3. square boss; 4. box; 5. cam; 6. second fiber grating; 7. transmission rod; 8. threaded rod; 9 , box cover; 10, cover; 11, limit baffle; 12, adhesive; 5-1, upper half; 5-2, lower half.

Detailed ways

The utility model will be described in detail below in conjunction with the accompanying drawings and specific embodiments, wherein the specific embodiments and descriptions are only used to explain the utility model, but not as a limitation to the utility model.

As shown in Figures 1-3, the utility model discloses a fiber grating large-range inclination sensor with a cam structure, including: a mass block 1, a first fiber grating 2, a square boss 3, a box body 4, a cam 5, The second fiber grating 6, transmission rod 7, threaded rod 8, box cover 9, cover 10, limit baffle 11, adhesive 12; the inside of the box body 4 is provided with two square bosses of equal size 3. The outer longitudinal sides of the box body 4 are provided with optical fiber access holes; the box cover 9 and the box body 4 are connected by screws to form a closed space, and the lower surface of the box cover 9 is provided with a limit baffle 11; the cam 5 is supported by the transmission rod 7 and is located in the middle between the two square bosses 3; the first fiber grating 2 and the second fiber grating 6 are fixed on the square boss 3 by an adhesive 12 On the surface; one end of the threaded rod 8 is connected to the mass block 1, the other end is connected to the transmission rod 7 and the two are combined into one; the cover 10 is located at the upper and lower ends of the outside of the box body 4, and the cover 10 is a pair of The two ends of the transmission rod 7 are axially fixed to prevent sliding in the axial direction and affecting the measurement accuracy.

Specifically, as shown in Figures 4 and 5, the cam 5 is mainly composed of two parts, including an upper half 5-1 and a lower half 5-2; the upper half 5-1 is a standard semicircle shape, the arc profile of the lower part 5-2 is left-right symmetrical, starting from the critical point of the upper part 5-1 and the lower part 5-2, the line connecting any point on the arc profile with the center of the cam 5 The length of the line increases linearly with the increase of the acute angle of the angle between the connecting line and the bottom diameter line of the upper half 5-1 standard semicircle, and the acute angle starts from 0° and ends at 90°.

Specifically, the first fiber Bragg grating 2 and the second fiber Bragg grating 6 are symmetrically arranged on both sides of the cam 5, the grid area of which is located between the cam 5 and the square boss 3, and the first fiber Bragg grating 2 and the second fiber Bragg grating 6 are all tangent to the critical point of the upper half 5-1 and the lower half 5-2 of the cam 5.

Specifically, according to the thickness of the cam 5 or the distance between the two square bosses 3, the requirements of different sensitivities, precisions and ranges in actual measurement applications can be met, and the grating will not be broken.

Specifically, the limit baffle 11 is used to limit the swing angle of the mass 1 within ±90°.

Specifically, the center of the cam 5 is provided with a center hole, the transmission rod 7 passes through the center hole of the cam 5 through an interference fit, and the two ends of the transmission rod 7 are radially limited by self-lubricating bearings.

Specifically, a threaded hole is provided at the top center of the mass block 1 , and the mass block 1 and the transmission rod 7 are connected by a threaded rod 8 .

Specifically, the box body 4 and the square boss 3 are an integrated structure.

Specifically, the square bosses 3 are symmetrically distributed on both sides with the cam 5 as the center; the first fiber grating 2 and the second fiber grating 6 are symmetrically tangent to both sides of the cam 5; The fiber hole pre-stretches the fiber grating, and pastes the pre-stretched fiber grating on the surface of the square boss 3 .

Specifically, rounded corners are provided at the places where both sides of the cam 5 are tangent to the fiber grating to prevent the fiber from being cut.

Example

A kind of fiber grating large range inclination sensor of cam structure, as shown in Figure 1, comprises: casing 4, case cover 9, cam 5, cover 10, transmission rod 7, mass block 1 and threaded rod 8; Wherein cam 5 Both sides of the fiber grating are closely tangent to the symmetrically placed fiber grating, and when arranging the position of the grating, the tangent places on both sides are rounded to prevent cutting the optical fiber; the sensor is connected between the box cover 9 and the box body 4 by screws A closed space is formed, and a limit baffle 11 is also provided on the lower surface of the box cover 9 to prevent the mass block 1 from breaking the optical fiber due to excessive force swing; 7 is fixed in the axial direction, and at the same time, when the mass block 1 swings, it can prevent the self-lubricating bearing from falling off; it should be noted that: the threaded rod 8 is the connecting piece between the mass block 1 and the transmission rod 7, or is it the same amount of transmission of the mass block 1 component force By changing the length of the threaded rod 8, the stress on the cam 5 can be changed, thereby affecting the measuring range and precision of the sensor.

In this embodiment, two square bosses 3 of equal size are arranged inside the box body 4, and are symmetrically distributed on both sides with the cam 5 as the center; threaded fiber hole, when the first fiber grating 2 and the second fiber grating 6 are symmetrically tangent to both sides of the cam 5, the fiber grating is pre-stretched through the fiber hole on both sides of the box body 4, and finally glued The pre-stretched optical fiber is pasted on the surface of the square boss 3; as a preference, the first fiber grating 2, the second fiber grating 6, the square boss 3 and the threaded hole for fiber outlet are all on the same central line.

In specific implementation, in order to realize the cooperative connection of each part, corresponding connectors can be provided or provided on each part; Consistent threads, the threaded rod 8 combines the mass block 1 and the transmission rod 7 through threaded connection, and realizes the fixing of the corresponding positions of the three; The position is a vertical relationship. When the mass 1 swings to the maximum range due to the force, it will be blocked by the limit baffle 11, so as to ensure that the optical fiber will not be broken.

During specific use, the sensor of the utility model is vertically fixed on the structure to be measured. When the inclination angle of the structure changes, the sensor also changes in the same inclination angle. At this time, the mass block 1 swings due to the effect of gravity, then The threaded rod 8 transmits the component force of the mass block 1 to the cam 5 in equal amounts, so that the cam 5 will swing differently due to different inclination angles, and stick to the fixed position on the surface of the two square bosses 3 inside the box body 4 The first fiber grating 2 and the second fiber grating 6 will have different radial expansion and contraction due to the different swings of the cam 5, which will cause the center wavelength of the fiber grating to drift, which can be detected according to the corresponding relationship between the change of the center wavelength and the inclination angle The magnitude and direction of the inclination.

The working principle of the utility model is as follows: the sensor of the utility model is vertically fixed on the structure to be tested. In the initial state of the sensor, the mass block 1 is only subjected to gravity, perpendicular to the horizontal plane, and the cam 5 is in an unstressed state. When the sensor itself has an inclination angle, due to the component force generated by the gravity of the mass block 1 itself, and the mass block 1 and the cam 5 are integrated, the cam 5 subjected to the force component will swing; It consists of parts, the upper part 5-1 is a standard semicircle, and the arc profile of the lower part 5-2 is left-right symmetrical, starting from the critical point of the upper part 5-1 and the lower part 5-2, the circle The length of the connection line between any point on the arc profile and the center of the cam 5 linearly increases along with the increase of the acute angle of the included angle between the connection line and the bottom diameter line of the upper half 5-1 standard semicircle. The acute angle starts from 0° and ends at 90°; the cam 5 is supported by the drive rod 7 through the center hole of the cam 5 and is positioned in the middle between the two square bosses 3, and is tangent to each other in the vertical direction on both sides. 2 fiber gratings; when one side of the grating is stretched, the other side of the grating will move on a semi-circular arc with a constant radius, and it will be used as temperature compensation for the stretched grating, resulting in a shift in the central wavelength of the grating , by detecting the change of the central wavelength of the fiber grating, the change of the tilt angle of the structure under test can be measured. This new type of fiber grating tilt sensor has a good linear relationship.

The measurement principle of the present utility model is as follows:

For a fiber grating with an initial center wavelength of λ, the relationship between its wavelength shift Δλ, its axial strain Δε and the ambient temperature change ΔT is:

Where α _f is the thermal expansion coefficient of the optical fiber, ζ is the thermo-optic coefficient of the optical fiber, and Pe is the effective _elasto -optic coefficient of the optical fiber. At room temperature, _Pe is approximately equal to 0.22. It is known that the length of the initial half of the optical fiber is L, and the length of the optical fiber after being stressed is L′, then the transformation relation is:

The maximum stroke of the cam 5 in the radial direction is S, and the relationship between it and the inclination angle θ of the measured structure away from the vertical plane is:

The parameters in the above formula are shown in Figure 5.

The length L' of the fiber after deformation is expressed as:

Optical fiber is stressed and strained Combining formulas (1, 2, 3, 4) can be obtained:

Since the sensor uses a cam structure, and the two fiber gratings are symmetrically distributed on both sides, when the grating on one side is stretched, the grating on the other side will move on a semicircular arc with a constant radius. And as the temperature compensation of the stretched grating, the problem of temperature and strain cross-sensitivity can be eliminated by using the differential method, and the difference Δλ of the wavelength offset of the fiber Bragg grating after temperature self-compensation can be expressed as:

According to the above formula (6), the wavelength drift difference between FBG1 and FBG2 can be calculated as:

Δλ _1-2 = Δλ ₁ -Δλ ₂ = (1-P _e )λΔε (7)

From this, the relationship between the inclination angle θ and the FBG wavelength drift Δλ _1-2 can be obtained:

The theoretical relationship between the inclination angle θ and the wavelength change Δλ _1-2 is obtained from the above equation, and L in the formula is half the length of the optical fiber, as a known value; by demodulating the wavelength change of the fiber grating inclination sensor, the cam 5 can be obtained The change value of the inclination angle of the structure realizes the real-time online monitoring of the inclination of the measured structure.

The advantage of this embodiment is that it can overcome the problem of temperature crosstalk, and its measurement results are not affected by temperature. Since the reflection wavelength of a fiber Bragg grating also depends on temperature, if the measured information is determined by monitoring the change of the reflection wavelength of a single fiber Bragg grating, the measurement result will inevitably be affected by the temperature, and the change of the ambient temperature will also cause measurement errors. In this embodiment, the measured information is determined by monitoring the difference between the reflected wavelengths of the two fiber gratings. Due to the temperature change, the wavelength change of the two fiber gratings is determined. The difference in wavelength depends only on the tilt angle, which is independent of temperature. Therefore, the measurement results of this embodiment are not affected by temperature.

The above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements and improvements made within the scope of the spirit and principle of the present utility model shall be included in this utility model. within the scope of protection of utility models.

Claims (10)

1. A fiber grating wide-range inclination angle sensor with a cam structure is characterized in that: the method comprises the following steps: the mass block (1), a first fiber bragg grating (2), a square boss (3), a box body (4), a cam (5), a second fiber bragg grating (6), a transmission rod (7), a threaded rod (8), a box cover (9), a sealing cover (10), a limiting baffle (11) and an adhesive (12); two square bosses (3) with the same size are arranged inside the box body (4), and optical fiber access holes are formed in the longitudinal two sides of the outer part of the box body (4); the box cover (9) is connected with the box body (4) through screws to form a closed space, and a limit baffle (11) is arranged on the lower surface of the box cover (9); the cam (5) is supported by the transmission rod (7) and then is positioned in the middle between the two square bosses (3); the first fiber grating (2) and the second fiber grating (6) are fixed on the surface of the square boss (3) through an adhesive (12); one end of the threaded rod (8) is connected with the mass block (1), and the other end of the threaded rod is connected with the transmission rod (7) and combines the mass block and the transmission rod into a whole; the sealing covers (10) are located at the upper end and the lower end of the outer portion of the box body (4), the two ends of the transmission rod (7) are axially fixed through the sealing covers (10), and the influence on measurement accuracy due to sliding in the axial direction is avoided.

2. The fiber grating wide-range tilt sensor of claim 1, wherein: the cam (5) mainly comprises two parts, including an upper half part (5-1) and a lower half part (5-2); the upper half part (5-1) is a standard semicircle, the circular arc profile of the lower half part (5-2) is bilaterally symmetrical, the length of a connecting line between any point on the circular arc profile and the circle center of the cam (5) is linearly increased along with the increase of an acute angle of an included angle between the connecting line and the bottom diameter line of the standard semicircle of the upper half part (5-1) from 0 degree to 90 degrees from the critical point of the upper half part (5-1) and the lower half part (5-2).

3. The fiber grating wide-range tilt sensor of claim 2, wherein: the first fiber bragg grating (2) and the second fiber bragg grating (6) are symmetrically arranged on two sides of the cam (5), the grating area of the first fiber bragg grating is located between the cam (5) and the square boss (3), and the first fiber bragg grating (2) and the second fiber bragg grating (6) are tangent to critical points of the upper half portion (5-1) and the lower half portion (5-2) of the cam (5).

4. The fiber grating wide-range tilt sensor of claim 1, wherein: the requirements of different sensitivity, precision and measuring range in actual measurement application can be met according to the thickness of the cam (5) or the distance between the two square bosses (3), and the grating is prevented from being broken.

5. The fiber grating wide-range tilt sensor of claim 1, wherein: the limiting baffle (11) is used for limiting the swing angle of the mass block (1) within +/-900.

6. The fiber grating wide-range tilt sensor of claim 1, wherein: the center of the cam (5) is provided with a central hole, the transmission rod (7) penetrates through the central hole of the cam (5) in an interference fit mode, and two ends of the transmission rod (7) are radially limited by self-lubricating bearings.

7. The fiber grating wide-range tilt sensor of claim 1, wherein: the center of the top of the mass block (1) is provided with a threaded hole, and the mass block (1) is connected with the transmission rod (7) through a threaded rod (8).

8. The fiber grating wide-range tilt sensor of claim 1, wherein: the box body (4) and the square boss (3) are of an integrated structure.

9. The fiber grating wide range tilt sensor of a cam structure according to any one of claims 1 to 8, wherein: the square bosses (3) are symmetrically distributed on two sides by taking the cam (5) as a center; the first fiber bragg grating (2) and the second fiber bragg grating (6) are symmetrically tangent to two sides of the cam (5); the fiber bragg grating is pre-stretched through fiber outlet holes on two sides of the box body (4), and the pre-stretched fiber bragg grating is adhered to the surface of the square boss (3).

10. The fiber grating wide range tilt sensor of claim 9, wherein: and the two sides of the cam (5) are provided with rounded corners at the positions tangent to the fiber bragg grating, so that the optical fiber is prevented from being cut.