CN113834448B - Double-dynamic nested optical fiber space curvature sensor and preparation method thereof - Google Patents
Double-dynamic nested optical fiber space curvature sensor and preparation method thereof Download PDFInfo
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- CN113834448B CN113834448B CN202111087597.4A CN202111087597A CN113834448B CN 113834448 B CN113834448 B CN 113834448B CN 202111087597 A CN202111087597 A CN 202111087597A CN 113834448 B CN113834448 B CN 113834448B
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/255—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures for measuring radius of curvature
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
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Abstract
The invention discloses a dual-dynamic nested optical fiber space curvature sensor and a preparation method thereof. The invention adopts the double dynamic elastic composite matrix, the outer elastic matrix is sleeved outside the inner elastic matrix, a plurality of groups of fiber gratings are respectively arranged in the grooves of the two elastic matrixes with different cross section sizes, and the fiber gratings on the matrixes with different cross section sizes can bear different degrees of bending, so that the dynamic range of the curvature sensor is increased. The double dynamic nested space curvature sensor has the advantages of double dynamic curvature measurement, large observation range, high precision, sensitive response and the like, and is suitable for wide popularization.
Description
Technical Field
The invention belongs to the technical field of space curvature measurement, and particularly relates to a double-dynamic nested optical fiber space curvature sensor and a preparation method thereof.
Background
The space curvature measurement technology can be used for carrying out structural form recovery, plays an important role in the fields of machinery, aerospace engineering, biomedicine and medicine, and can realize structural health monitoring of civil structures and infrastructures (buildings, tunnels, bridges and roads). Currently common curvature sensors include electro-strain gauge based curvature sensors, capacitive curvature sensors, laser displacement sensors, and fiber optic curvature sensors. The electric strain sensor is subjected to the problems of a patch technology and the like, and the calculation accuracy cannot be accurately ensured; the capacitive sensor has high output impedance and poor load capacity, and is easily influenced by external interference to generate an unstable phenomenon; the laser displacement sensor has the problem that the large-scale measurement cannot be met; the optical fiber curvature sensor mainly focuses on a light intensity modulation type and an optical fiber grating type, and the light intensity modulation type has the problem of poor repeatability caused by easy environmental disturbance.
The fiber bragg grating has the advantages of light weight, small volume, good flexibility, easiness in attaching to a sensing device, no electromagnetic interference and the like, and a space curvature sensor manufactured based on the fiber bragg grating is widely applied to the morphological measurement field in recent years. At present, the curvature sensor based on the fiber grating has the limitation of the dynamic range by the grating response range and the breaking strain range, the drift amount of the central wavelength of the grating is limited and exceeds the bearable limit strain value, and the central wavelength of the grating does not drift along with the increase of strain and cannot be monitored any more, so that the monitoring requirement under the complex environment is required to be realized through the structural design of the sensor layout and the matrix.
Disclosure of Invention
The invention aims to solve at least one of the technical problems of engineering technology, dynamic measurement range, measurement precision, sensitivity and the like of the fiber bragg grating sensor in a monitoring environment to a certain extent. Therefore, the invention aims to provide a dual-dynamic nested optical fiber space curvature sensor and a preparation method thereof. The invention adopts the double dynamic elastic composite matrix, the outer elastic matrix is sleeved outside the inner elastic matrix, a plurality of groups of fiber gratings are respectively arranged in the grooves of the two elastic matrixes with different cross section sizes, and the fiber gratings on the matrixes with different cross section sizes can bear different degrees of bending, so that the dynamic range of the curvature sensor is increased. The dual-dynamic nested space curvature sensor has the advantages of dual-dynamic curvature measurement, large observation range, high precision, sensitive response, low cost, small volume, long-term monitoring and the like, is suitable for large-scale popularization, is particularly suitable for being applied to the landslide monitoring field, is beneficial to promoting the development of ocean engineering geological disaster placement in China, and ensures the safe production of submarine pipelines, ports, ocean facilities and the like.
In one aspect, the invention provides a dual dynamic nested fiber optic space curvature sensor. According to an embodiment of the present invention, the dual dynamic nested fiber optic space curvature sensor comprises:
the double dynamic elastic composite matrix comprises a hollow inner layer elastic matrix and an outer layer elastic matrix, wherein the outer layer elastic matrix is sleeved on the outer side of the inner layer elastic matrix, and grooves are formed in the outer circumferential edges of the inner layer elastic matrix and the outer layer elastic matrix;
the first fixing head is arranged at one end of the double dynamic elastic composite matrix;
the second fixing head is arranged at the other end of the double dynamic elastic composite matrix;
the fiber bragg grating is arranged in the groove, is tightly attached to the inner layer elastic matrix or the outer layer elastic matrix, penetrates through the second fixing head and is connected to the grating demodulator.
According to the dual-dynamic nested optical fiber space curvature sensor, firstly, the dual-dynamic elastic composite matrix is adopted, the outer elastic matrix is sleeved on the outer side of the inner elastic matrix, a plurality of groups of optical fiber gratings are respectively arranged in grooves of two elastic matrixes with different cross-section sizes, the optical fiber gratings on the matrixes with different cross-section sizes can bear different degrees of bending, and the dynamic range (namely, the observation range is large) of the curvature sensor is increased. And secondly, the plurality of groups of fiber gratings are respectively arranged in the grooves of the inner elastic matrix and the outer elastic matrix, so that the contact area between the fiber gratings and the elastic matrix is increased, and the protection of the fiber gratings is enhanced. Therefore, the dual-dynamic nested space curvature sensor has the advantages of dual-dynamic curvature measurement, large observation range, high precision, sensitive response and the like, and is suitable for wide-range popularization.
In addition, the dual-dynamic nested optical fiber space curvature sensor according to the embodiment of the invention can also have the following additional technical features:
in some embodiments of the present invention, the number of grooves provided on the inner elastic substrate is 3 to 4, and a plurality of the grooves are equally spaced along the outer circumferential direction of the inner elastic substrate.
In some embodiments of the present invention, the number of grooves provided on the outer elastic substrate is 3 to 4, and a plurality of the grooves are equally spaced along the outer circumferential direction of the outer elastic substrate.
In some embodiments of the invention, the inner elastic matrix has an outer diameter of 14 to 20mm.
In some embodiments of the invention, the thickness h of the inner elastic matrix at the thinnest point in the radial direction is 3 to 6mm.
In some embodiments of the invention, the outer diameter of the outer elastic matrix is 24 to 30mm.
In some embodiments of the invention, the thickness f of the outer elastic matrix at the thinnest point in the radial direction is 4 to 8mm.
In some embodiments of the present invention, the second fixing head includes an I-fixing head and a II-fixing head, the I-fixing head and the II-fixing head are connected by threads, a plurality of I-fiber holes are formed on the I-fixing head, and the plurality of I-fiber holes correspond to positions of the fiber gratings disposed in the grooves; the II-fixing head is provided with an II-optical fiber outlet hole, and the fiber grating is gathered in the II-optical fiber outlet hole after penetrating out from the I-optical fiber outlet hole and penetrates out from the II-optical fiber outlet hole.
In some embodiments of the invention, the curvature sensor further comprises: and the tensile rope penetrates through the inner layer elastic matrix through the hollow core and is used for distributing and recycling the sensor. From this, lay the stay cord in inlayer elastic matrix center, adopt first fixed head and second fixed head to fix it, when laying and retrieving the sensor, draw the stay cord, effectively avoided the sensor to receive the destruction at the laying and retrieving in-process.
In some embodiments of the invention, the curvature sensor further comprises: the protection pipe is sleeved on the outer side of the outer layer elastic matrix and used for protecting the outer layer elastic matrix. Therefore, the outer side of the outer layer elastic matrix is coated with the protection tube, and the protection tube can effectively prevent corrosion and water, so that the outer layer elastic matrix and the fiber bragg grating are protected.
In some embodiments of the invention, the curvature sensor further comprises: and the sleeve is arranged at the outer side of the fiber bragg grating penetrating out of the second fixing head and used for protecting the fiber bragg grating.
In another aspect, the present invention provides a method for preparing the dual-dynamic nested optical fiber space curvature sensor according to the above embodiment, comprising:
(1) Fixing the fiber grating in a straightened state in a groove of an inner elastic matrix, fixing the fiber grating in a straightened state in the groove of the outer elastic matrix, and sleeving the outer elastic matrix on the outer side of the inner elastic matrix so as to obtain a dual-dynamic elastic composite matrix;
(2) The tensile rope sequentially passes through the first fixing head, the inner elastic matrix and the second fixing head and is respectively fixed with the first fixing head and the second fixing head;
(3) One end of the double dynamic elastic composite matrix is embedded into a groove corresponding to the first fixing head, the tail fiber of the fiber bragg grating penetrates through the second fixing head, and the other end of the double dynamic elastic composite matrix is embedded into the groove corresponding to the second fixing head.
According to the method provided by the embodiment of the invention, firstly, the double dynamic elastic composite matrix is adopted, the outer elastic matrix is sleeved on the outer side of the inner elastic matrix, a plurality of groups of fiber gratings are respectively arranged in grooves of two elastic matrixes with different cross section sizes, and the fiber gratings on the matrixes with different cross section sizes can bear different degrees of bending, so that the dynamic range of the curvature sensor is enlarged. And secondly, the plurality of groups of fiber gratings are respectively arranged in the grooves of the inner elastic matrix and the outer elastic matrix, so that the contact area between the fiber gratings and the elastic matrix is increased, and the protection of the fiber gratings is enhanced. And thirdly, the outer side of the outer layer elastic matrix is coated with a protection tube which can effectively prevent corrosion and water, so that the outer layer elastic matrix and the fiber grating are protected. Fourthly, lay the stay cord that resists at inlayer elastic substrate center, adopt first fixed head and second fixed head to fix it, when laying and retrieving the sensor, pull the stay cord, effectively avoided the sensor to suffer the destruction at the laying and retrieving in-process. Therefore, the dual-dynamic nested space curvature sensor has the advantages of dual-dynamic curvature measurement, large observation range, high precision, sensitive response and the like, and is suitable for wide-range popularization.
In addition, the method according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the invention, the method further comprises: (4) The protection pipe is sleeved on the outer side of the outer elastic matrix, one end of the protection pipe is embedded into the corresponding groove of the first fixing head, and the other end of the protection pipe is embedded into the corresponding groove of the second fixing head.
In some embodiments of the invention, the method further comprises: (5) The sleeve is arranged on the outer side of the fiber grating penetrating out of the second fixing head, the fiber grating is wrapped, the fiber grating penetrating out of the second fixing head is used for protecting the fiber grating penetrating out of the second fixing head, and the fiber grating penetrating out of the second fixing head is connected to the demodulator.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is an axial cross-sectional view of a dual dynamic nested spatial curvature sensor according to one embodiment of the present invention.
FIG. 2 is a cross-sectional view of a dual dynamically nested spatial curvature sensor without a stationary head package, in accordance with one embodiment of the present invention.
FIG. 3 is a cross-sectional view of an I-clamp head of one embodiment of the invention.
Fig. 4 is a rear side view of a second stationary head according to an embodiment of the invention.
Fig. 5 is a front side view of a second stationary head according to an embodiment of the invention.
FIG. 6 is a schematic cross-sectional view of a cylindrical elastomeric matrix including three sets of gratings according to one embodiment of the present invention when bent.
FIG. 7 is a force analysis diagram of a dual dynamic nested spatial curvature sensor when flexed in accordance with one embodiment of the present invention.
The anti-pulling rope comprises a 1-anti-pulling rope, a 2-fiber grating, a 3-inner elastic matrix, a 4-outer elastic matrix, a 5-protection tube, a 6-first fixing head, a 7-second fixing head, an 8-sleeve, a 7-I-I-fixing head, a 7-II-II-fixing head, a 7-1-protection tube fixing slot position, a 7-2-outer elastic matrix fixing slot position, a 7-3-inner elastic matrix fixing slot position, a 7-4-I-fiber outlet, a 7-5-II-fiber outlet, a 7-6-I-anti-pulling rope outlet and a 7-7-II-anti-pulling rope outlet.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and to simplify the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the present invention, unless explicitly specified and limited otherwise, terms such as "mounted," "connected," "secured," and the like are to be construed broadly and may be, for example, fixedly attached, detachably attached, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.
In one aspect of the present invention, a dual dynamic nested fiber optic space curvature sensor is provided, with reference to fig. 1 and 2, comprising: the optical fiber grating comprises a double dynamic elastic composite matrix, a first fixing head 6, a second fixing head 7 and an optical fiber grating 2.
According to an embodiment of the present invention, referring to fig. 1 and 2, the dual-dynamic elastic composite matrix includes a hollow inner elastic matrix 3 and an outer elastic matrix 4, the outer elastic matrix 4 is sleeved on the outer side of the inner elastic matrix 3, and the outer circumferential edges of the inner elastic matrix 3 and the outer elastic matrix 4 are respectively provided with a groove, and the grooves penetrate through the length direction of the inner elastic matrix 3 or the outer elastic matrix 4. The inner elastic matrix 3 and the outer elastic matrix 4 are hollow cylinders. Therefore, the dual-dynamic elastic composite matrix is adopted, the plurality of groups of fiber gratings 2 are respectively arranged in the grooves of the two elastic matrixes with different cross section sizes, and the fiber gratings 2 on the matrixes with different cross section sizes can bear different degrees of bending, so that the dynamic range of the curvature sensor is enlarged.
In an embodiment of the present invention, the cross-section of the opening of the groove is semi-elliptical, the semi-major axis is the opening size, and the semi-minor axis is the groove depth.
In the embodiment of the present invention, the material of the above-mentioned dual dynamic elastic composite matrix is not particularly limited, and for example, may be at least one selected from polyoxymethylene, polyethylene, fiber reinforced plastic, acrylonitrile-butadiene-styrene, and polypropylene.
According to one embodiment of the present invention, the outer diameter of the inner elastic matrix 3 is 14-20 mm, thereby further making the bending range that the inner elastic matrix 3 can withstand reasonable, and thus increasing the dynamic range of the curvature sensor. The inventors found that if the outer diameter of the inner elastic matrix 3 is too small, the sensitivity of the sensor is too low, and the sensor is insensitive to small curvature bending, and if the outer diameter is too large, the outer diameter of the outer elastic matrix 4 is indirectly caused to be too large, so that the bending range that the outer elastic matrix 4 can bear is too small, the measuring range of the sensor is small, and the sensor is easy to damage.
According to a further embodiment of the present invention, the thickness h of the inner elastic base 3 at the thinnest point in the radial direction is 3 to 6mm, thereby further making the bending range that the inner elastic base 3 can withstand reasonable, and thus increasing the dynamic range of the curvature sensor. The inventors found that if the thickness of the inner elastic matrix 3 at the thinnest point in the radial direction is too small, the sensitivity of the sensor is too low, the sensor is not sensitive to small curvature bending, and the inner elastic matrix is easily broken.
According to a further embodiment of the present invention, the outer diameter of the outer elastic matrix 4 is 24-30 mm, thereby further making the bending range that the outer elastic matrix 4 can withstand reasonable, and thus increasing the dynamic range of the curvature sensor. The inventors found that if the outer diameter of the outer elastic base 4 is too small, the outer diameter of the inner elastic base 3 is too small, resulting in too low sensitivity of the sensor, and that it is insensitive to small curvature bending, and if the outer diameter of the outer elastic base 4 is too large, the bending range that the outer elastic base 4 can withstand is too small, resulting in a small measurement range of the sensor, and that it is vulnerable.
According to a further embodiment of the present invention, the thickness f of the outer elastic base 4 at the thinnest point in the radial direction is 4-8 mm, thereby further making the bending range that the outer elastic base 4 can withstand reasonable, and thus increasing the dynamic range of the curvature sensor. The inventors found that if the thickness of the outer elastic matrix 4 in the radial direction is too small, the sensitivity of the sensor is too low, the sensor is not sensitive to bending with a small curvature, and the outer elastic matrix is easily broken.
According to a further specific embodiment of the present invention, the distance between the outer surface of the inner elastic matrix and the inner surface of the outer elastic matrix in the radial direction is 2-10mm.
According to an embodiment of the present invention, referring to fig. 2, the fiber bragg grating 2 is disposed in the groove of the dual-dynamic elastic composite matrix in a straight line along the length direction of the dual-dynamic elastic composite matrix, and the fiber bragg grating 2 is disposed closely to the inner elastic matrix 3 or the outer elastic matrix 4, and the fiber bragg grating 2 is in a straightened state, one end of the fiber bragg grating 2 is flush with the dual-dynamic elastic composite matrix, and the other end passes through the second fixing head 7 and is connected to a grating demodulator (not shown in the figure). The demodulator is a fiber grating demodulator, and is a device capable of demodulating optical wavelength information by means of mutual conversion of wavelength and voltage.
According to another embodiment of the present invention, the number of grooves provided on the inner elastic substrate 3 is 3-4, a plurality of the grooves are distributed at equal intervals along the outer circumferential direction of the inner elastic substrate 3, and the fiber gratings 2 are provided in the grooves, so that the fiber gratings 2 on the inner elastic substrate 3 are distributed at equal intervals to obtain more uniform discrete curvature data, and the distribution interval is adjusted to adapt to different measurement conditions.
Thus, the double dynamic elastic composite matrix is composed of two layers of three/four leaf grass-shaped elastic matrixes with different cross-section sizes.
It should be noted that, for prevention, damage or degumming of a certain fiber grating 2 may be caused during packaging, testing, construction and use, and measurement accuracy is affected, so 2 to 8 fibers are generally disposed in one groove.
According to another embodiment of the present invention, the number of grooves provided on the outer elastic substrate 4 is 3-4, a plurality of the grooves are distributed at equal intervals along the outer circumferential direction of the outer elastic substrate 4, and the fiber gratings 2 are provided in the grooves, so that the fiber gratings 2 on the outer elastic substrate 4 are distributed at equal intervals, more uniform discrete curvature data is obtained, and the distribution interval is adjusted to adapt to different measurement conditions.
According to an embodiment of the present invention, referring to fig. 1, a first fixing head 6 is provided at one end of the dual-dynamic elastic composite matrix, where the first fixing head 6 is used for fixing the dual-dynamic elastic composite matrix, and a groove corresponding to the dual-dynamic elastic composite matrix is provided on the first fixing head 6. If the sensor further comprises a protection tube 5, the first fixing head 6 is provided with a groove corresponding to the protection tube 5.
According to an embodiment of the present invention, referring to fig. 3-5, a second fixing head 7 is disposed at the other end of the dual-dynamic elastic composite matrix, and is used for fixing the dual-dynamic elastic composite matrix, and the second fixing head 7 is provided with a slot corresponding to the dual-dynamic elastic composite matrix. If the sensor further comprises a protection tube 5, the second fixing head 7 is provided with a groove corresponding to the protection tube 5.
According to the embodiment of the present invention, paint can be sprayed on the surfaces of the first and second fixed heads 6 and 7 to prevent corrosion. The first fixing head 6 and the second fixing head 7 are made of anti-corrosion stainless steel, and the circular section is designed with grooves which meet the requirement that the protection pipe and the elastic matrix are embedded into the fixing heads so as to meet the requirement that the tensile steel wire rope, the double dynamic elastic composite matrix and the protection pipe 4 are fixed. The structural design of the first fixing head 6 differs from that of the second fixing head 7 in that the components of the first fixing head 6 are independent and have no optical fiber outlet.
According to yet another embodiment of the present invention, referring to fig. 4-5, the second fixing head 7 includes an I-fixing head 7-I and an II-fixing head 7-II, the I-fixing head 7-I and the II-fixing head 7-II are connected by threads, a plurality of I-fiber holes 7-4 are provided on the I-fixing head 7-I, and the plurality of I-fiber holes 7-4 correspond to the positions of the fiber bragg gratings 2 provided in the grooves; the II-fixing head 7-II is provided with a II-optical fiber outlet 7-5, and the fiber grating 2 is gathered in the II-optical fiber outlet 7-5 after penetrating out from the I-optical fiber outlet 7-4 and penetrates out from the II-optical fiber outlet 7-5. The I-fixed head 7-I is also provided with an I-pull-resistant rope outlet 7-6, the II-fixed head 7-II is provided with an II-pull-resistant rope outlet 7-7, and the pull-resistant rope 1 sequentially passes through the I-pull-resistant rope outlet 7-6 and the II-pull-resistant rope outlet 7-7 to penetrate out of the second fixed head 7. In addition, the I-fixing head 7-I also comprises an inner elastic matrix fixing groove 7-3, an outer elastic matrix fixing groove 7-2 and a protective tube fixing groove 7-1, which are used for fixing the inner elastic matrix 3, the outer elastic matrix 4 and the protective tube 5.
According to a further embodiment of the invention, the fixed connection and the through hole positions of the first fixed head 6 and the second fixed head 7 are all subjected to waterproof sealing treatment.
Further, referring to fig. 1, the curvature sensor further includes: the anti-pulling rope 1 penetrates through the inner layer elastic matrix 3 through the hollow structure, the anti-pulling rope 1 is fixed through the first fixing head and the second fixing head, and when the sensor is distributed and recovered, the anti-pulling rope is pulled, so that the sensor is effectively prevented from being damaged in the distribution and recovery process.
Further, referring to fig. 1, the curvature sensor further includes: the protection tube 5 is made of a composite material, the protection tube 5 is sleeved on the outer side of the outer layer elastic matrix 4, and the protection tube 5 can effectively prevent corrosion and water, so that the outer layer elastic matrix 4 and the fiber bragg grating 2 are protected.
According to the embodiment of the invention, the protection tube 5 is a flexible waterproof plastic sleeve or a telescopic metal tube, and has a thickness of at least 1mm, so that the fiber bragg grating 2 is protected from being damaged by external factors.
Further, referring to fig. 1, the curvature sensor further includes: and the sleeve 8 is arranged at the outer side of the fiber grating 2 penetrating out of the second fixing head 7 and is used for protecting the fiber grating 2.
The dual-dynamic nested optical fiber space curvature sensor according to the embodiment of the invention has at least one of the following advantages:
firstly, the dual-dynamic elastic composite matrix is adopted, the outer elastic matrix 4 is sleeved on the outer side of the inner elastic matrix 3, a plurality of groups of fiber gratings 2 are respectively arranged in grooves of two elastic matrices with different cross section sizes, and the fiber gratings 2 on the matrices with different cross section sizes can bear different degrees of bending, so that the dynamic range (namely, the observation range is large) of the curvature sensor is increased. Secondly, the optical fiber gratings 2 are respectively arranged in the grooves of the inner layer elastic matrix 3 and the outer layer elastic matrix 4, so that the contact area between the optical fiber gratings 2 and the elastic matrix is increased, and the protection of the optical fiber gratings 2 is enhanced. Thirdly, the outer side of the outer elastic matrix 4 is coated with a protection tube 5, and the protection tube 5 can effectively prevent corrosion and water, thereby playing a role in protecting the outer elastic matrix 4 and the fiber bragg grating 2. Fourthly, lay the tensile rope in inlayer elastic matrix 3 center, adopt first fixed head 6 and second fixed head 7 to fix it, when laying and retrieving the sensor, pull tensile rope, effectively avoided the sensor to suffer the destruction at laying and retrieving the in-process.
In another aspect, the present invention provides a method for preparing the dual-dynamic nested optical fiber space curvature sensor according to the above embodiment, comprising:
(1) The fiber bragg grating 2 in a straightened state is fixed in a groove of the inner elastic matrix 3, the fiber bragg grating 2 in a straightened state is fixed in a groove of the outer elastic matrix 4, and the outer elastic matrix 4 is sleeved on the outer side of the inner elastic matrix 3 so as to obtain a double dynamic elastic composite matrix.
As a specific example, the method of fixing the fiber grating 2 in the groove of the inner layer elastic substrate 3 is as follows:
the inner layer elastic matrix 3 is fixed on a manufacturing table, one end of the fiber bragg grating is fixed at one end of the inner layer elastic matrix, which is close to the second fixing head 7, through glue, a horn mouth is arranged at the other end of the inner layer elastic matrix, a plurality of groups of grooves are formed in the horn mouth and correspond to the grooves of the inner layer elastic matrix, the fiber bragg grating is arranged along the grooves of the inner layer elastic matrix until the fiber bragg grating passes through the horn mouth, after the fiber bragg grating 2 passing through the horn mouth is guided by a plurality of groups of pulleys, proper tension is applied to the fiber bragg grating between the pulleys, so that the central wavelength of the fiber bragg grating 2 deviates by 2-3nm, the fiber bragg grating 2 is in a straightened state in the working process of the sensor, and the fiber bragg grating 2 positioned and fixed in the grooves of the inner layer elastic matrix 3 by using glue.
It should be noted that the center wavelength shift of the fiber grating 2 can be obtained by a demodulator test.
The fiber grating 2 is fixed in the groove of the outer elastic matrix 4 by the same method, and then the outer elastic matrix 4 is sleeved outside the inner elastic matrix 3, so that a dual-dynamic elastic composite matrix is obtained.
After the fiber bragg grating 2 is laid, a white sleeve is sleeved at one end of the fiber pigtail corresponding to the second fixing head 7.
(2) The tensile cord sequentially passes through the first fixing head 6, the inner layer elastic matrix 3 and the second fixing head 7 and is respectively fixed with the first fixing head 6 and the second fixing head 7.
In this step, the tail ends of the first fixing head 6 and the second fixing head 7 are provided with a plurality of fixing hole sites for fixing the anti-pulling rope so as to prevent the anti-pulling rope from falling off the sensor when being laid, fished and recovered, and all the through holes are subjected to water seepage prevention treatment after being packaged.
(3) One end of the dual-dynamic elastic composite matrix is embedded into a groove corresponding to the first fixing head 6, the tail fiber of the fiber bragg grating 2 passes through the second fixing head 7, and the other end of the dual-dynamic elastic composite matrix is embedded into a groove corresponding to the second fixing head 7.
Further, the method further comprises: (4) The protection tube 5 is sleeved on the outer side of the outer elastic matrix 4, one end of the protection tube 5 is embedded into the corresponding groove of the first fixing head 6, and the other end of the protection tube 5 is embedded into the corresponding groove of the second fixing head 7.
Further, the method further comprises: (5) The sleeve is arranged on the outer side of the fiber grating 2 penetrating out of the second fixing head 7, and wraps the fiber grating, so that the fiber grating penetrating out of the second fixing head is protected, and the fiber grating penetrating out of the second fixing head is connected to a demodulator.
According to the method provided by the embodiment of the invention, firstly, the dual-dynamic elastic composite matrix is adopted, the outer elastic matrix 4 is sleeved on the outer side of the inner elastic matrix 3, the plurality of groups of fiber gratings 2 are respectively arranged in the grooves of the two elastic matrices with different cross section sizes, and the fiber gratings 2 on the matrices with different cross section sizes can bear different degrees of bending, so that the dynamic range of the curvature sensor is enlarged. Secondly, the optical fiber gratings 2 are respectively arranged in the grooves of the inner layer elastic matrix 3 and the outer layer elastic matrix 4, so that the contact area between the optical fiber gratings 2 and the elastic matrix is increased, and the protection of the optical fiber gratings 2 is enhanced. Thirdly, the outer side of the outer elastic matrix 4 is coated with a protection tube 5, and the protection tube 5 can effectively prevent corrosion and water, thereby playing a role in protecting the outer elastic matrix 4 and the fiber bragg grating 2. Fourthly, lay the tensile rope in inlayer elastic matrix 3 center, adopt first fixed head 6 and second fixed head 7 to fix it, when laying and retrieving the sensor, pull tensile rope, effectively avoided the sensor to suffer the destruction at laying and retrieving the in-process. Therefore, the dual-dynamic nested space curvature sensor has the advantages of dual-dynamic curvature measurement, large observation range, high precision, sensitive response and the like, and is suitable for wide-range popularization.
The testing method of the double-dynamic nested space curvature sensor comprises the following steps:
taking landslide monitoring as an example, a sensor is buried in a soil layer through penetrating equipment, a soil layer is led out from the upper side of the sensor through optical fibers, and the sensor is connected with a demodulator, so that wireless equipment can be controlled by a raspberry group microcomputer, information is transmitted to a remote upper computer, and remote monitoring is achieved.
The principle of realizing the double dynamic curvature measurement is as follows:
the central reflection wavelength of the fiber grating is in direct proportion to the grating period and the effective refractive index of the fiber core, so when the fiber grating is strained and the temperature fluctuates due to the external environment, the change of the grating period and the effective refractive index can be directly caused, and the central wavelength of the reflection can be changed. The measurement of physical quantities such as temperature, strain, etc. can be achieved by using such wavelength drift. By means of the linear relation between the offset and the matrix radius and bending radius, the bending radius and bending direction angle of the grating point can be obtained, namely, the bending radius and bending direction angle of the elastic matrix where the grating point is located can be obtained. The data obtained by measuring a plurality of gratings at the same time can be used for reconstructing the bending condition graph of the sensor by utilizing an algorithm.
The specific calculation process is as follows:
as a specific example, referring to fig. 6 and 7, three points a and B, C represent the positions of the three sets of gratings in the cross section, respectively. The x-axis is defined as the direction of connecting the center O of the circular section of the elastic matrix to one of the grooves, the y-axis is defined as the direction perpendicular to the x-axis on the circular section, and the z-axis is perpendicular to the x-axis and the y-axis, namely the axial direction of the matrix. Theta represents that the azimuth vector from the origin O to the point (A, B or C) forms an angle with the positive direction of the x-axis, which is called azimuth angle, and then the theta of the point A is 0, and the theta of the point B and the point C are respectivelyAnd->Beta is the angle between the principal normal vector of the O point and the positive direction of the x axis when the cylindrical elastic matrix is bent, and is called the bending direction angle. The bending radius of the cylindrical elastic matrix is R. When the cylindrical elastic matrix is bent, the axis where the O point is located is the central axis, and the length is unchanged, so that the central angle corresponding to the bending of the cylindrical elastic matrix is +.>The bending angle of the busbar at which this point (A, B or C) is located is also γ.
For example, the bending radius R of the elastic matrix at point A A Satisfy the relation
R A ＝R-rcos(β-θ) (1)
Therefore, the A-point strain ε A The method comprises the following steps:
similarly, when the bending radius of the cylindrical elastic matrix with the cross-section radius R is R, the point corresponding to the arbitrary azimuth angle theta of the cylindrical surface is strained as
Since Δλ=k e * Epsilon, thus causing a shift in the center wavelength of the a-point fiber grating:
K e for the strain sensitivity coefficient, K e 1.2 pm/. Mu.epsilon.was taken. Δλ represents the shift of the center wavelength, and the interpolation of the center wavelength after the bending is the shift after the center wavelength before the bending is measured and the center wavelength before the bending is measured.
Maximum shift delta lambda bearable by central wavelength of fiber grating max Radius r of inner elastic matrix 1 The minimum bending radius corresponding to the elastic matrix of the inner layer is R1 min The method comprises the steps of carrying out a first treatment on the surface of the Radius r of outer elastic matrix 2 The minimum bending radius corresponding to the outer elastic matrix is R2 min 。
R when the elastic composite matrix is bent 1 <r 2 Thus R2 min >R1 min 。
The dual-dynamic sensor is bent and deformed due to external force, when the bending radius is smaller than R2 min At this time, the fiber grating arranged on the outer layer elastic matrix is destroyed due to the fact that the fiber grating exceeds the maximum drifting amount of the central wavelength, and the fiber grating arranged on the inner layer elastic matrix works normally, so that the effect of double dynamic curvature measurement is achieved.
It should be noted that the other parts of the present invention are not exhaustive, and are all known in the art.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (8)
1. A dual dynamic nested fiber optic space curvature sensor, comprising:
the double dynamic elastic composite matrix comprises a hollow inner layer elastic matrix and an outer layer elastic matrix, wherein the outer layer elastic matrix is sleeved on the outer side of the inner layer elastic matrix, and grooves are formed in the outer circumferential edges of the inner layer elastic matrix and the outer layer elastic matrix; the outer diameter of the inner-layer elastic matrix is 14-20 mm, and the thickness h of the thinnest part of the inner-layer elastic matrix along the radial direction is 3-6 mm; the outer diameter of the outer elastic matrix is 24-30 mm, and the thickness f of the thinnest part of the outer elastic matrix along the radial direction is 4-8 mm;
the first fixing head is arranged at one end of the double-dynamic elastic composite matrix and is used for fixing the double-dynamic elastic composite matrix, and a groove position corresponding to the double-dynamic elastic composite matrix is formed in the first fixing head;
the second fixing head is arranged at the other end of the double-dynamic elastic composite matrix and is used for fixing the double-dynamic elastic composite matrix, and a groove position corresponding to the double-dynamic elastic composite matrix is formed in the second fixing head;
the fiber bragg grating is arranged in the groove, is respectively clung to the inner layer elastic matrix and the outer layer elastic matrix, passes through the second fixing head and is connected to the grating demodulator;
the tensile rope penetrates through the inner layer elastic matrix through the hollow core and is used for distributing and recycling the sensor;
the second fixing head comprises an I-fixing head and a II-fixing head, the I-fixing head and the II-fixing head are connected through threads, a plurality of I-optical fiber outlet holes are formed in the I-fixing head, and the I-optical fiber outlet holes correspond to the positions of the optical fiber gratings arranged in the grooves; the II-fixing head is provided with an II-optical fiber outlet hole, and the fiber grating is gathered in the II-optical fiber outlet hole after penetrating out from the I-optical fiber outlet hole and penetrates out from the II-optical fiber outlet hole.
2. The dual dynamic nested optical fiber space curvature sensor according to claim 1, wherein the number of grooves provided on the inner elastic substrate is 3-4, and a plurality of the grooves are equally spaced along the outer circumferential direction of the inner elastic substrate.
3. The dual dynamic nested optical fiber space curvature sensor according to claim 1, wherein the number of grooves provided on the outer elastic substrate is 3-4, and a plurality of the grooves are equally spaced along the outer circumferential direction of the outer elastic substrate.
4. A dual-dynamic nested fiber optic space curvature sensor according to any of claims 1-3,
further comprises: the protection pipe is sleeved on the outer side of the outer layer elastic matrix and used for protecting the outer layer elastic matrix.
5. A dual-dynamic nested fiber optic space curvature sensor according to any of claims 1-3,
further comprises: and the sleeve is arranged at the outer side of the fiber bragg grating penetrating out of the second fixing head and used for protecting the fiber bragg grating.
6. A method of making the dual dynamically nested fiber optic space curvature sensor of any of claims 1-5, comprising:
(1) Fixing the fiber grating in a straightened state in a groove of an inner elastic matrix, fixing the fiber grating in a straightened state in the groove of the outer elastic matrix, and sleeving the outer elastic matrix on the outer side of the inner elastic matrix so as to obtain a dual-dynamic elastic composite matrix;
(2) The tensile rope sequentially passes through the first fixing head, the inner elastic matrix and the second fixing head and is respectively fixed with the first fixing head and the second fixing head;
(3) One end of the double dynamic elastic composite matrix is embedded into a groove corresponding to the first fixing head, the tail fiber of the fiber bragg grating penetrates through the second fixing head, and the other end of the double dynamic elastic composite matrix is embedded into the groove corresponding to the second fixing head.
7. The method as recited in claim 6, further comprising:
(4) The protection pipe is sleeved on the outer side of the outer elastic matrix, one end of the protection pipe is embedded into the corresponding groove of the first fixing head, and the other end of the protection pipe is embedded into the corresponding groove of the second fixing head.
8. The method as recited in claim 6, further comprising:
(5) And arranging a sleeve on the outer side of the fiber bragg grating penetrating out of the second fixing head.
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