Fiber grating cable force sensor

Abstract

The utility model relates to a fiber bragg grating cable force sensor, which is provided with a fiber connector, a temperature matrix serving as a second temperature compensation and an output block, and is characterized in that a plurality of elastic components are arranged on a ring body along the circumferential direction, and the elastic components serving as a first temperature compensation are used for accommodating a grating, so that the grating and a fiber are arranged along the circumferential direction of the ring body; the two ends of the ring body are respectively provided with a backing plate, the periphery of the ring body is provided with a protective cover and a cover plate for protecting the optical fiber, the elastic assembly comprises a hollow grating fixing block, a grating is located in the grating fixing block, and the two sides of the grating fixing block are provided with optical fiber grooves in the circumferential direction of the ring body for fixing the optical fiber. According to the utility model, the influence of sensor installation on the anchorage device structure can be effectively reduced, optical fiber bending is avoided, the crest value definition is effectively protected, and the generation of secondary waves is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of sensors, and in particular relates to a fiber grating cable force sensor. Background Art

[0002] In order to ensure the safety of bridges during construction and operation, it is necessary to conduct cable health monitoring on some large-span bridges that meet the monitoring requirements to ensure the safety of people and property.

[0003] At present, the commonly used bridge cable force monitoring methods include magnetic flux method, frequency method, etc. These methods are not applicable to some bridges subject to power supply constraints due to the limitation of the principle, and have the disadvantages of low accuracy, poor stability, and troublesome measurement. In order to meet the versatility of bridge cable force monitoring and ensure monitoring accuracy, use stability and measurement convenience, the present invention adopts fiber grating technology, and makes use of the advantages of fiber grating technology such as strong anti-electromagnetic interference, stability, corrosion resistance, waterproofness, and anti-accumulation to make a fiber grating cable force sensor.

[0004] There are many cable tension sensors based on fiber Bragg grating technology on the market. The essence is to calculate the cable tension by converting the micro-strain generated by the grating force. The fiber Bragg grating through-type cable tension sensors on the market have the following problems:

[0005] (1) Difficulty in production. Optical fiber is a precision component that is sensitive to tiny strains. It is necessary to ensure the stability of sensor performance while also ensuring the accuracy of mass production.

[0006] (2) Most of the wires are inserted in the axial direction, which will affect the installation and increase the overall size, which may affect the dimensional parameters of the original structure of the anchor.

[0007] (3) It is difficult to ensure concentricity without affecting the force. The through-type cable tension sensor on the market is embedded, that is, part of the anchor nut is embedded in the cable tension sensor to ensure concentricity, but embedding will increase the friction area between the sensor and the anchor nut, and the nut surface roughness is large, which will affect the accuracy of the sensor when in use.

[0008] (4) The large outer diameter has an impact on the protective cover. Also because of the embedded cable tension sensor, the outer diameter of the sensor will be larger than the anchor, which affects the design size of the protective cover of the anchor itself.

[0009] Most optical fibers on the market are placed along the axis of the core, which causes the following main disadvantages: ① It affects the height of the entire sensor, and thus affects the size and cost of the anchor; ② Temperature compensation requires an additional temperature matrix, and the temperature compensation error is large, because there will be wavelength loss due to fusion splicing; ③ The optical fiber is placed along the axial direction, and the fusion splicing of multiple sections of optical fiber for the same sensor requires bending the optical fiber. Bending the optical fiber will affect the wave peak, the value will be smaller, and the number of secondary waves will increase; ④ The sensor is under pressure when used, so the grid area is compressed and short, so the sensor optical fiber needs to be in a pre-tensioned state before leaving the factory. The measuring range will be affected by the pre-tensioning amount, and the processing and production difficulty is also high. Utility Model Content

[0010] In view of the various shortcomings of the existing technology, a fiber grating cable tension sensor is proposed, which can effectively reduce the impact of installing the sensor on the anchor structure, avoid bending of the optical fiber, effectively protect the clarity of the wave peak value, and reduce the generation of secondary waves.

[0011] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0012] A fiber grating cable force sensor comprises a ring body, on which a fiber optic connector, a temperature substrate as a second temperature compensation and an output block are arranged. A plurality of elastic components are arranged along the circumferential direction of the ring body. The elastic components serve as a first temperature compensation and are used to accommodate the grating, so that the grating and the optical fiber are arranged along the circumferential direction of the ring body. Pads are arranged at both ends of the ring body respectively, and a protective cover and a cover plate are arranged on the periphery of the ring body to protect the optical fiber.

[0013] Furthermore, the elastic component includes a hollow grating fixing block, the grating is located in the grating fixing block, and optical fiber grooves are provided on both sides of the grating fixing block along the circumferential direction of the ring body for fixing the optical fiber.

[0014] Furthermore, the cross section of the grating fixing block is in a rhombus shape, and the optical fiber grooves are arranged along two opposite corners of the rhombus.

[0015] Furthermore, the cross section of the temperature matrix is ​​rectangular, a grating groove is arranged in the center of the rectangle along the circumferential direction of the ring body, and a grating capable of sensing temperature is arranged in the grating groove.

[0016] Furthermore, the backing plate is arranged in a circular ring shape, and its longitudinal section is L-shaped, and the backing plate is matched with the inner side thread of the ring body.

[0017] Furthermore, a backing plate groove is arranged on one side surface of the backing plate, and a boss matching with the backing plate groove is arranged on the ring body.

[0018] Furthermore, the cover plate and the protective cover are arranged in an arc shape, the cover plate is arranged outside the protective cover, and the arc radius of the cover plate is larger than the arc radius of the protective cover.

[0019] Further, the cover plate is arranged above the output block and the elastic component adjacent to the output block.

[0020] Furthermore, a notch is provided on one side of the protective cover to match the output block, and the optical fiber connector and the output block are embedded with each other and fixed on the ring body.

[0021] Furthermore, the distance between the top of the pad at one end of the ring body and the bottom of the other pad is 50 to 80 mm.

[0022] Fiber Bragg Bragg gratings are very sensitive to stress and temperature. Whether the fiber Bragg grating is subjected to stress or the ambient temperature changes, it is reflected in the fiber Bragg grating wavelength as a change. Therefore, when the fiber Bragg grating tension sensor senses stress during operation, it is also necessary to eliminate the influence of ambient temperature on the reflected wavelength, that is, to make ΔT = 0 or ΔT known. The sensor is equipped with multiple elastic components, and the grating segment that senses stress is encapsulated on the elastic component to form the first temperature compensation.

[0023] First temperature compensation: the elastic component has a diamond structure, and the ring body 1 is made of 40Cr. Affected by the thermal expansion coefficient of 40Cr itself, when the temperature T rises, the ring body can be regarded as expanding. Affected by the solder joint, the elastic component will stretch along the axial direction of the ring body. At this time, the optical fiber fixed in the optical fiber groove of the elastic component will be compressed, and the optical fiber wavelength Δλ1 of the elastic component will decrease, that is, -Δλ1; and affected by the temperature T, the optical fiber will also expand under the action of its own thermal expansion coefficient. At this time, the wavelength Δλ2 of the optical fiber itself will increase, that is, +Δλ2. The drift of the optical fiber affected by temperature is its inherent property and cannot be adjusted, but Δλ1 can be controlled by adjusting the diamond structure of the elastic component, so that the stretched |Δλ1|≈|Δλ2| of the elastic component can be made, (-Δλ1)+Δλ2≈0, so temperature compensation can be achieved.

[0024] Second temperature compensation: A temperature-sensing grating is set in the temperature matrix as the second temperature compensation. The grating in the elastic component and the grating in the temperature matrix are fused together. When collecting data, a series of wavelength values ​​can be obtained, among which there will be a known ΔT. The temperature compensation of the fiber grating cable tension sensor can be achieved by eliminating ΔT using the factory calibration formula.

[0025] The formula for measuring strain and temperature with fiber Bragg grating is: ΔλB=ΔλB0[(1-pe)ε+(α+ξ)ΔT]

[0026] ΔλB is the wavelength offset of the fiber Bragg grating; ΔλB0 is the free wavelength at ambient temperature; pe is the effective elastic-optic coefficient of the fiber; ΔT is the temperature change; α is the thermal expansion coefficient of the fiber, which represents the rate of change of the grating period with temperature; ξ is the thermo-optic coefficient of the fiber Bragg grating, which represents the rate of change of the refractive index with temperature.

[0027] The formula for calculating the temperature change is: Δλ / λ=(α+ξ)ΔT

[0028] The temperature compensation of this sensor uses the hardware compensation method, that is, measuring the peak wavelength difference. The second temperature compensation is arranged outside the elastic component of the cable force sensor, so that it is in a free state and is not subject to external stress. The measured wavelength is the temperature wavelength; the wavelength measured by the fiber grating encapsulated in the elastic component is sensitive to temperature and stress. The influence of temperature is eliminated by measuring the peak wavelength difference of the two parts of the fiber grating.

[0029] The beneficial effects of the utility model are:

[0030] 1. The optical fiber is arranged along the circumferential direction of the ring body, exits the line tangent to the ring body, and then passes through the protective cover, which can effectively reduce the impact of installing the sensor on the anchor structure. This arrangement avoids bending of the optical fiber, effectively protects the clarity of the wave peak value, and reduces the generation of secondary waves.

[0031] 2. Use universal fiber optic connectors to output cables, which can effectively solve the problem of traditional direct output cables accidentally breaking the optical cable during sensor installation and cable tensioning, thereby ensuring the survival rate of the sensor and facilitating network debugging. The subsequent connection to the fiber grating demodulation device can effectively ensure the wavelength clarity and is conducive to remote data transmission.

[0032] 3. The optical fiber is arranged along the circumferential direction of the ring body, which reduces the height requirement of the ring body. Therefore, the distance from the top of the pad at one end of the ring body to the bottom of the other pad is set to 50-80 mm, that is, the overall height of the sensor is 50-80 mm, and the outer diameter is consistent with the matching nut, which can effectively reduce the impact on the anchor.

[0033] 4. The ring body, pad, protective cover and cover plate are all split structure processing, which can reduce the processing difficulty, ensure the precision and consistency of the same batch of sensors, and can make the structure tempered separately to control the hardness difference.

[0034] 5. The first temperature compensation and the second temperature compensation are set as temperature compensation, which greatly reduces the influence of temperature on the sensor.

[0035] 6. The sensor is provided with a cover plate, which is arranged above the output block and the elastic component adjacent to the output block. The output block and the elastic component can be inspected and repaired while collecting the missing data. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the structure of the utility model without the protective cover and the cover plate;

[0037] Figure 2 It is a schematic diagram of the overall structure of the utility model.

[0038] In the accompanying drawings: 1-ring body, 2-optical fiber connector, 3-temperature matrix, 4-output block, 5-elastic component, 501-grating fixing block, 502-optical fiber groove, 6-pad, 7-protective cover, 8-cover plate. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the drawings of the present invention. Based on the embodiments in this application, other similar embodiments obtained by ordinary technicians in this field without making creative work should all fall within the scope of protection of this application. In addition, the directional words mentioned in the following embodiments, such as "up", "down", "left", "right", etc., are only referenced to the directions of the drawings. Therefore, the directional words used are used to illustrate rather than limit the invention.

[0040] The utility model is further described below in conjunction with the accompanying drawings and preferred embodiments.

[0041] like Figure 1 and Figure 2 As shown, a fiber grating cable force sensor includes a ring body 1, on which a fiber connector 2, a temperature matrix 3 as a second temperature compensation, an output block 4, and an elastic component 5 as a first temperature compensation are arranged, and the elastic component 5 is used to accommodate a grating. The elastic components 5 are provided in plurality, and the plurality of elastic components 5 are arranged along the circumferential direction of the ring body, and include a grating fixing block 501 and a fiber groove 502 in an integrated structure, the grating fixing block 501 is a diamond-shaped hollow structure, and the hollow part is used to accommodate the grating, and each grating fixing block 501 is provided with a section of grating for sensing stress. The grating fixing block 501 is fixed to the ring body at both ends along the axial direction of the ring body 1, and the fiber groove 502 is a free end, which extends along the two diagonal angles of the diamond and is arranged along the circumference of the ring body 1. In this embodiment, the cross-section of the fiber groove 502 is rectangular, and a groove is arranged in the middle of the rectangle for accommodating the optical fiber. Multiple grating fixing blocks 501 are provided. In the present embodiment, four grating fixing blocks 501 are provided. The multiple grating fixing blocks 501 are arranged at intervals. The optical fibers between adjacent grating fixing blocks 501 are connected in series by fusion splicing. The elastic component is made of low thermal expansion coefficient material, and the ring body 1 is made of 40Cr material.

[0042] The optical fiber connector 2 and the output block 4 are used in conjunction with each other. Specifically, the optical fiber connector 2 and the output block 4 are fixed on the ring body 1 after being interlocked with each other, and are used for the access and output of the optical fiber. The cross section of the temperature matrix 3 is rectangular, and a grating groove for accommodating the grating is arranged in the center of the rectangle along the circumferential direction of the ring body, and bolt holes are arranged on both sides of the rectangle to facilitate the fixing of the temperature matrix 3 on the ring body. The temperature matrix 3 can reduce the influence of temperature on the grating optical fiber as a grating temperature compensation. A grating that can sense temperature is arranged in the grating groove, and the temperature matrix 3 and the elastic component 5 are located on the same circumference.

[0043] Pads 6 are provided at both ends of the ring body 1. Pads 6 are provided in a circular ring shape, and their outer diameter is the same as the inner diameter of the ring body 1. The longitudinal section of the ring body 1 is L-shaped. The side of pad 6 in contact with the ring body 1 is provided with an external thread, and the ring body is provided with an internal thread. Pad 6 and ring body 1 are threadedly matched. At the same time, pad grooves are provided on the other side of pad 6, and bosses matching the pad grooves are provided on the end face of the ring body 1. Pad grooves and bosses are interlocked to further fix the ring body 1 and pad 6. In this embodiment, the spacing from the top of the pad at one end of the ring body to the bottom of the other pad is 50 to 80 mm, that is, the overall height of the sensor is 50 to 80 mm.

[0044] The periphery of the ring body 1 is provided with a protective cover 7 and a cover plate 8, and the protective cover 7 and the cover plate 8 are arranged in an arc shape. The protective cover 7 is arranged on the outside of the ring body 1, and the cover plate 8 is arranged on the outside of the protective cover 7, and its arc radius is greater than the arc radius of the protective cover 7. Both ends of the protective cover 7 and both ends of the cover plate 8 are connected to the pad 6 by threads, and the cover plate 8 is also connected to the protective cover 7 by threads. Specifically, threads are arranged on the pad 6, and threads matching with the pad 6 are arranged at both ends of the protective cover 7 and both ends of the cover plate 8. At the same time, threads are arranged at the abutment between the protective cover 7 and the cover plate 8. A notch is arranged on one side of the protective cover 7 to match with the output block 4. The cover plate 8 is arranged above the output block 4 and an elastic component 5 adjacent to the output block 4, which can effectively protect the grating optical fiber and facilitate subsequent maintenance and repair.

[0045] The present invention has been described in detail above. The above description is only a preferred embodiment of the present invention and should not limit the scope of implementation of the present invention. That is, all equivalent changes and modifications made within the scope of this application should still fall within the scope of the present invention.

Claims

1. A fiber grating cable force sensor, comprising a ring body, on which a fiber connector, a temperature matrix as a second temperature compensation and an output block are arranged, characterized in that: A plurality of elastic components are arranged on the ring body along the circumferential direction. The elastic components serve as the first temperature compensation to accommodate the grating, so that the grating and the optical fiber are arranged along the circumferential direction of the ring body. Pads are arranged at both ends of the ring body respectively, and a protective cover and a cover plate are arranged on the periphery of the ring body to protect the optical fiber.

2. A fiber grating cable force sensor according to claim 1, characterized in that: The elastic component comprises a hollow grating fixing block, the grating is located in the grating fixing block, and optical fiber grooves are arranged on both sides of the grating fixing block along the circumferential direction of the ring body for fixing the optical fiber.

3. A fiber grating cable force sensor according to claim 2, characterized in that: The cross section of the grating fixing block is in a rhombus shape, and the optical fiber grooves are arranged along two opposite corners of the rhombus.

4. The fiber grating cable force sensor according to claim 3, characterized in that: The cross section of the temperature matrix is ​​rectangular, a grating groove is arranged in the center of the rectangle along the circumferential direction of the ring body, and a grating capable of sensing temperature is arranged in the grating groove.

5. The fiber grating cable force sensor according to claim 4, characterized in that: The backing plate is arranged in a circular ring shape, and its longitudinal section is L-shaped. The backing plate is matched with the inner thread of the ring body.

6. The fiber grating cable force sensor according to claim 5, characterized in that: A backing plate groove is arranged on one side surface of the backing plate, and a boss matched with the backing plate groove is arranged on the ring body.

7. A fiber grating cable force sensor according to any one of claims 1 to 6, characterized in that: The cover plate and the protective cover are arranged in an arc shape. The cover plate is arranged outside the protective cover, and the arc radius of the cover plate is larger than the arc radius of the protective cover.

8. The fiber grating cable force sensor according to claim 7, characterized in that: The cover plate is arranged above the output block and the elastic component adjacent to the output block.

9. The fiber grating cable force sensor according to claim 8, characterized in that: A notch is arranged on one side of the protective cover to match the output block, and the optical fiber connector and the output block are embedded with each other and fixed on the ring body.

10. The fiber grating cable force sensor according to claim 9, characterized in that: The distance from the top of the pad at one end of the ring body to the bottom of the other pad is 50 to 80 mm.

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