Transient displacement sensor based on optical fiber uniform macro-bending loss and elastic substrate tension and compression dynamic change and manufacturing method and application thereof

Abstract

The invention provides a transient displacement sensor based on optical fiber uniform macro-bending loss and elastic substrate tension and compression dynamic change and a manufacturing method and application thereof, and belongs to the field of optical fiber sensor design. Comprising an elastic substrate and an optical fiber arranged on the elastic substrate in a penetrating mode. The optical fibers are arranged on the elastic substrate in a penetrating mode at the same intervals and fixedly connected with the elastic substrate at the penetrating points, the optical fibers are bent in a continuous wave shape after penetrating, and the bent shapes are completely the same; the other end of the optical fiber is connected with the photodiode; when the elastic substrate deforms in the length direction of the optical fiber, the curvature of the optical fiber can be changed; and the width of the elastic substrate is 20-500 times of the diameter of the optical fiber. When the sensor is manufactured, the bonding mode is simple, the process is convenient, reliability is high, and operation is easy; the displacement range measured by the sensor is larger, continuous measurement can be achieved, and the dynamic monitoring range is larger. During application, the linear region is large, and the reliability is high.

Description

Technical Field

[0001] The present invention belongs to the field of optical fiber sensor design, and specifically relates to a transient displacement sensor based on uniform macrobending loss of optical fiber and dynamic changes of tension and compression of elastic substrate, and a manufacturing method and application thereof. Background Art

[0002] Optical fiber or optical fiber is a fiber material made of glass or plastic, which transmits light using the principle of "total reflection of light". The optical fiber itself has a small diameter and is easy to bend during use. When the curvature of the curved section of the optical fiber is large enough, the transmission path of the light will change, and a large number of conduction modes will be converted into radiation modes. The light enters the cladding and is absorbed by the coating layer, that is, part of the light will leak in the curved section of the optical fiber, or macrobending loss. In communication optical fibers, macrobending losses caused by routing turns and laying bends are generally regarded as unfavorable factors, because macrobending losses in optical fiber communications are not sensitive factors, and the lower the loss, the better. However, if this macrobending loss is reasonably predicted and used, macrobending sensors can be made.

[0003] Fiber optic sensors have become an important structural health monitoring method in the aerospace and automotive fields. The use of optical fibers to replace glass fibers or fiber bundles in fiber composite plates or pipelines has a high application possibility. Fiber optic sensors are light, small and highly sensitive, but ordinary fiber optic sensing methods are difficult to achieve large displacement monitoring, and the existing macro-bend fiber optic sensors have problems such as discontinuous displacement sensing, unstable fiber macro-bending rate, and difficulty in precise control of fiber macro-bending rate.

[0004] For the patent with publication number CN114993187A, the macrobending is achieved by embedding the entire bent optical fiber into an elastic substrate. The shrinkage deformation of the elastic substrate is affected by the deformation of the optical fiber, and the deformations of the two are coordinated with each other. However, due to the large contact surface between the two and the influence of boundary conditions, the deformation at the edge of the elastic substrate is very different from that in the middle. The deformation of the optical fiber in the middle is large, and the deformation of the optical fiber at the edge gradually decreases, and the reduction amplitude is uncontrollable and non-linear. In addition, due to the stress mismatch that will lead to an unstable state, the wavy optical fiber formed is limited by the full contact bonding method, and the shape of each wave is very different. The randomness of this difference will make the macrobending rate uncontrollable, and it is impossible to obtain a sensor with a target measurement range through curvature design.

[0005] Compared with the above-mentioned existing patents, the optical fiber is arranged as a whole on the surface of the elastic substrate, and is fixed and bonded to the substrate only with glue. Once the longitudinal width of the elastic substrate is not designed to reach a certain length, the sensor after prestress relaxation may be twisted or other complex deformations, and the desired flat state cannot be achieved. This requires that the width of the elastic substrate is much larger than the diameter of the optical fiber, which greatly increases the unnecessary mass of the sensor. The load on the surface to be measured increases, which not only increases the measurement error, but also loses the possibility of measuring the vibration of small structures. At the same time, when using the optical fiber sensor in the above-mentioned patent for measurement, it is impossible to achieve single-point displacement measurement on the surface of the structure to be measured, because the deformation of the optical fiber relies on the two short sides of the elastic substrate to clamp and fix and stretch. In actual applications, it is necessary to completely stick one short side on the surface to be measured, and the measurement range is the coupling of countless point displacements on this short side. It is not very meaningful in actual applications, and it is impossible to accurately obtain the displacement measurement result of a single point. Summary of the invention

[0006] In order to solve the problems in the prior art, the present invention proposes a transient displacement sensor based on uniform macrobending loss of optical fiber and dynamic changes of tension and compression of elastic substrate, as well as a manufacturing method and application thereof.

[0007] The technical solution adopted by the present invention is as follows:

[0008] In the first aspect, the present invention discloses a transient displacement sensor based on uniform macrobending loss of optical fiber and dynamic changes of tension and compression of an elastic substrate, comprising an elastic substrate and an optical fiber interspersed on the elastic substrate; the optical fibers are interspersed on the elastic substrate at the same spacing and fixedly connected to the elastic substrate at the interspersing points, and the optical fibers present continuous wavy bends after interspersing, and the bend shapes are exactly the same; one end of the optical fiber is connected to a light source, and the other end is connected to a photodiode; when the elastic substrate is deformed in the length direction of the optical fiber, it will drive the optical fiber to undergo a change in the optical fiber bending curvature; the width of the elastic substrate is 20-500 times the diameter of the optical fiber.

[0009] In a second aspect, the present invention discloses a method for manufacturing the transient displacement sensor, comprising the following steps:

[0010] 1) inserting optical fibers on an elastic substrate at the same interval, wherein the length direction of the optical fibers is consistent with the length direction of the elastic substrate; and taking the length direction of the elastic substrate as the direction of subsequent pre-stretching;

[0011] 2) stretching the elastic substrate to a maximum elongation ratio, in which the optical fiber is straightened and fits with the upper and lower surfaces of the elastic substrate, and the optical fiber and the elastic substrate are consolidated at the interlaced position of the optical fiber and the elastic substrate in the current state;

[0012] 3) The stretching of the elastic substrate is canceled, and the optical fibers originally attached to the elastic substrate are bent into identical arches as the elastic substrate contracts, and the optical fibers as a whole contract into a wavy shape; one end of the optical fiber is connected to a light source, and the other end is connected to a photodiode, to obtain the transient displacement sensor.

[0013] In a third aspect, the present invention discloses a method for displacement measurement using the transient displacement sensor, comprising the following steps:

[0014] The elastic substrate is pre-stretched in the length direction of the optical fiber, and the elongation ratio of the elastic substrate during pre-stretching is less than the maximum elongation ratio of the elastic substrate; then one end of the long side of the elastic substrate in the pre-stretched state is vertically fixed to the surface of the structure to be measured, and the other end is vertically fixed to the surface of any fixed structure; one end of the optical fiber is connected to a light source, and the other end is connected to a photodiode;

[0015] The displacement signal of the structure to be measured in the direction of the optical fiber arrangement will be converted into the curvature change of the optical fiber bending. The curvature change of the optical fiber bending will eventually change the optical power signal received by the photodiode. The photodiode converts the optical power signal into an electrical signal output, that is, the transient displacement change of the surface of the structure to be measured is obtained.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) Compared with the traditional fiber grating sensor, the displacement range that can be measured by the present invention is larger.

[0018] (2) Compared with the existing optical fiber macrobend sensors, the optical fiber sensor of the present invention can continuously measure the out-of-plane displacement of the structure to be measured, and its dynamic monitoring range is larger than that of the traditional optical fiber macrobend sensors. In addition, the present invention improves the line pasting method of the prior art to point pasting, so that the contact area between the optical fiber and the elastic substrate is reduced to a minimum. The size of the macrobend ring of the optical fiber is determined by the distance between the two arch feet, and the shape of the macrobend ring can be accurately controlled, thereby determining the curvature size. By perforating the prestressed elastic substrate and point-bonding the optical fiber, the optical fiber bending curvature can be well maintained in a uniform, regular and repeatable state change, further expanding the application of this type of macrobend optical fiber sensor, and can be applied to large-scale transient displacement measurement of tiny structures.

[0019] (3) The present invention uses a plurality of macrobends to simultaneously pull and compress to jointly measure transient displacement, and has a large linear region and strong reliability. The width of the elastic substrate of the present invention is 20-500 times the diameter of the optical fiber. If the width of the elastic substrate is less than 20 times the diameter of the optical fiber, the width of the elastic substrate is too small to achieve stable consolidation. If the width of the elastic substrate is greater than 500 times the diameter of the optical fiber, the width of the elastic substrate is too wide and the width of the short side is too large, which increases the load and loses the possibility of measuring single-point displacement. The instantaneous displacement sensor of the present invention can fix one end of the elastic substrate on the surface of the object to be measured, and the bonding area is a circle with a diameter of 3 mm. At the same time, by adjusting the orientation of the elastic substrate in the direction of the optical fiber, the movement of the measured system in a selected direction at a selected point can be collected.

[0020] (4) Compared with the traditional optical fiber macrobending sensor, the present invention has a simple bonding method, a convenient manufacturing process, strong reliability and easy operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of a one-dimensional displacement sensor of the present invention;

[0022] Figure 2 This is a flow chart of manufacturing a one-dimensional displacement sensor of the present invention;

[0023] Figure 3 This is a linear region verification experiment diagram of the one-dimensional displacement sensor of the present invention;

[0024] Figure 4 for Figure 3 The oscilloscope measures the signal;

[0025] Figure 5 This is a diagram of the application example of the one-dimensional displacement sensor of the present invention;

[0026] Figure 6 for Figure 5 Comparison chart of oscilloscope measurement signal and Doppler vibrometer signal of reliable equipment in sensing example;

[0027] Figure 7 This is a flow chart of the design scheme of the one-dimensional displacement sensor of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0031] In addition, in the description of the present invention, “plurality” means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0032] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0034] like Figure 1 As shown, it is a schematic diagram of the device of the one-dimensional displacement sensor of optical fiber macrobending loss of the present invention. The present invention discloses a transient displacement sensor based on uniform macrobending loss of optical fiber and dynamic change of tension and compression of elastic substrate, which includes an elastic substrate and an optical fiber interspersed and arranged on the elastic substrate; the optical fiber is interspersed and arranged on the elastic substrate at the same spacing, and is fixedly connected to the elastic substrate at the interspersing point, and the optical fiber presents continuous wavy bending after interspersing, and the bending shape is exactly the same; one end of the optical fiber is connected to a light source, and the other end is connected to a photodiode; when the elastic substrate is deformed in the direction of optical fiber arrangement, it will drive the optical fiber to change the curvature of the optical fiber bending; the width of the elastic substrate is 20-500 times the diameter of the optical fiber.

[0035] In the present invention, the number of continuous wavy bends is 5-15; the continuous wavy bends use the elastic base as the reference plane; of two adjacent bends, one is located above the reference plane and the other is located below the reference plane; and during the deformation of the elastic base, the distance between any two adjacent interlaced points is equal.

[0036] When the elastic substrate is not stretched, the distance between the two interpenetration points is l, and the maximum stretching ratio is a. Then, at the maximum elongation ratio, the distance between the two interpenetration points is a×l. When the transient displacement sensor of the present invention is used for displacement monitoring, in order to simultaneously detect the dynamic changes of tension and compression, it is necessary to arrange the transient displacement sensor to stretch the elastic substrate at a ratio of b (0<b<a). At this time, the distance between the two interpenetration points is b×l. In a specific embodiment of the present invention, when the transient displacement sensor is manufactured, the maximum pre-stretching ratio a is selected to be 150%, b is preferably 120%-135%, and l is preferably 10mm. When measuring, in order to ensure the measurement accuracy, it is hoped that the change value of the stretching ratio of the elastic substrate relative to b is controlled within the range of 1.5%. Then, the displacement measurement range of the dynamic change of tension and compression of the sensor is 0-1.5mm; at the same time, the distance range between the vertex of the optical fiber bending and the elastic substrate is 4.925mm-5.075mm.

[0037] The elastic base is a braided elastic flat rope base, and the optical fiber is vertically inserted into the elastic base at the same interval, and is divided into a suspended part and a fixed part, and the suspended part presents a continuous macro-bend ring; the optical fibers at both ends are tightly bonded to the stretched elastic rope only at the insertion point, and after relaxation, the optical fiber forms a plurality of out-of-plane macro-bend arches as the elastic rope is stretched, and an optical fiber inserted thereon has several out-of-plane macro-bend arches (macro-bend rings, macro-bend arches); the surface normal of each out-of-plane macro-bend arch is perpendicular to the direction of the optical fiber, and it is evenly distributed outside the upper and lower surfaces of the elastic base; when the elastic base transmits the vibration of the surface to be measured, it drives the left and right arch feet of the macro-bend arch of each optical fiber to approach and move away from each other, thereby changing the curvature of the macro-bend arch.

[0038] Based on the compression rod stability theory, the optical fiber macrobend arch is a fixed rod at both ends. After the prestress of the elastic base is released, the deformation is symmetrical about the midpoint, and the reaction moment of the two arch feet is the same as M. e , the approximate differential equation of the deflection curve is

[0039]

[0040] Wherein, w is the deflection of any section of the optical fiber; x is the horizontal distance from any section of the optical fiber to the arch foot; M(x) is the bending moment of any section at a horizontal distance x from the arch foot; E is the Young's modulus of the optical fiber; I is the moment of inertia of the section; F is the horizontal force on the optical fiber arch foot;

[0041] Reference notation The above formula can be written as

[0042]

[0043] That is the shape deflection curve of the optical fiber macrobend; where k is an intermediate variable.

[0044] Preferably, the spacing of the optical fibers inserted into the braided elastic flat rope base is adjusted and designed to present different sizes of arch curvatures at different spacings.

[0045] Preferably, a plurality of parallel optical fibers can be arranged in the width direction of the base of the braided elastic flat rope, and the distance between the optical fibers can be adjusted as required. Preferably, the elastic flat rope can be freely deformed in the direction of the optical fiber arrangement.

[0046] Preferably, the base of the braided elastic flat rope should be elastic, and the plastic deformation produced during use is small or almost non-existent. It can be glued together with the optical fiber material at the insertion point. The material can be selected from braided rubber rope, Ecoflex, TPU, etc. The base width of the braided elastic flat rope can be set at 1mm to 3mm to ensure that the displacement signal of a single point can be collected at its end. When using quick-drying glue to stick the elastic flat rope to the surface to be measured, a narrower elastic flat rope can be selected due to the stronger fluidity of the glue. It is recommended to be between 20-500 times the diameter of the optical fiber. The narrower short side width will further improve the measurement accuracy; in a specific embodiment of the present invention, the width of the tested elastic base is about 3mm, which is about 365 times the diameter of the SMF28 optical fiber used at this time.

[0047] More preferably, the braided elastic flat rope base is in a completely relaxed state in the initial state of the sensor, and can be partially stretched to the measurement linear region when placed on the surface of the object to be measured, and shrink or elongate along with the surface of the object to be measured.

[0048] The optical fiber model can be SMF28; the insertion directions of the multiple optical fibers on the elastic base are kept as straight lines parallel to each other as much as possible and consistent with the tension and compression direction of the elastic rope.

[0049] The range and sensitivity of the transient displacement sensor can be determined by the pre-stretching rate of the elastic substrate and the number of arched suspended areas through which the optical fiber is inserted. However, the maximum pre-stretching rate limit of the elastic substrate and the linear region limitation of the sensor itself need to be considered. Excessive tension and compression will exceed the measurement range of the sensor itself, and may also cause glue bonding failure and optical fiber slippage and breakage.

[0050] The present invention also discloses a method for manufacturing the transient displacement sensor; the method comprises the following steps:

[0051] 1) The optical fibers are vertically interspersed with the upper and lower surfaces of the braided elastic flat rope base at the same interval, and the interspersed extension direction is the stretching direction (i.e., the length direction) of the braided elastic flat rope base, and the optical fibers are arranged in a straight line.

[0052] 2) The elastic substrate is stretched to the maximum elongation ratio. When the braided elastic flat rope substrate is stretched to the maximum stretching ratio, the optical fiber is straightened, and the tensioned optical fiber (i.e., the straightened optical fiber) is attached to the upper and lower surfaces of the elastic substrate. 406 glue is used to fix the optical fiber and the elastic substrate at the insertion position of the optical fiber and the elastic rope in the current state;

[0053] 3) The stretching of the braided elastic flat rope base is canceled, and the optical fibers originally attached to the elastic base are bent into identical arches as the braided elastic flat rope base contracts; one end of the optical fiber is connected to a light source, and the other end is connected to a photodiode to obtain the transient displacement sensor.

[0054] Preferably, when it is necessary to arrange multiple optical fibers on a braided elastic flat rope base or the arranged optical fibers have macrobend rings of different sizes, multiple optical fibers in the same direction can be arranged in parallel when inserting the optical fibers in step 1), or the size of the optical fiber macrobend arch can be controlled by adjusting the spacing distance when inserting the optical fibers.

[0055] Preferably, in the step 2), the consolidation method of the optical fiber and the elastic substrate at the insertion point can be determined according to different elastic substrate materials. When the braided rubber rope or TPU is used as the elastic substrate, glue can be used for consolidation, such as 406 glue; when Ecoflex is used as the elastic substrate, UV-curing glue can be used for bonding.

[0056] The present invention further discloses a method for using the sensor to perform transient displacement measurement, and the specific method is as follows: pre-stretch the braided elastic flat rope base along the direction of the optical fiber; during stretching, the elongation ratio of the elastic base is less than the maximum elongation ratio of the elastic base, so as to avoid excessive stretching and breakage of the optical fiber or slip failure at the glue consolidation point; then the two ends of the long side of the elastic base of the sensor are respectively vertically bonded to the surface of the structure to be measured and the surface of a fixed structure; one end of the optical fiber is connected to a light source, and the other end is connected to a photodiode; the vibration signal of the surface of the structure to be measured in the direction of the optical fiber sensor is converted into a change in the curvature of the optical fiber macrobend arch, and the macrobend loss changes. The change in curvature of several macrobend arches will cause the light power received by the photodiode end to change. The photodiode converts the optical signal at the optical fiber end into an electrical signal, and the change in the electrical signal can be used to convert the transient displacement change of the surface of the structure to be measured. Figure 2 As shown, in a specific embodiment of the present invention, the specific steps of the manufacturing process of the transient displacement sensor are as follows:

[0057] (1) Figure 2As shown in (a), a braided rubber wire rope is first taken as an elastic base, the length of which should be greater than the number of required macrobend arches multiplied by the distance between arch feet, and optical fibers are inserted at the same distance at the longitudinal axis of the upper surface; for the SMF28 optical fiber used in this example, it is recommended that the arch foot spacing is between 7mm and 13mm, and it is recommended to use a manufacturing method with an arch foot spacing of 10mm;

[0058] (2) Figure 2 As shown in (b), the two ends of the elastic base with inserted optical fibers are fixed with clamps to the maximum elongation ratio, and care is taken to keep it straight and not twisted; the two ends of the optical fiber are tensioned so that the macrobend arch is close to the upper and lower surfaces of the flat rope in this step; and for the common braided rubber flat rope used in this example as the elastic base, its maximum elongation ratio is 150%.

[0059] (3) Figure 2 As shown in (b), for the two macrobend half rings at the beginning and end of the braided rubber flat rope, the optical fiber of the arch foot extension section needs to be in contact with the braided rubber flat rope and consistent with the longitudinal axis direction of the braided rubber flat rope. It is recommended to use a small amount of instant adhesive to consolidate the optical fiber and the braided rubber flat rope at the arch foot of each macrobend arch. A small amount of glue can avoid a significant impact on the shrinkage of the woven rubber flat rope; the instant adhesive used here can be 502, 406, etc., and adhesives with different properties can be selected according to the elastic base material used.

[0060] (4) Figure 2 As shown in (c)-(d) in the figure, the stretching at both ends of the braided rubber wire flat rope is cancelled. Due to the contraction of the braided rubber wire flat rope, the part not fixed to the braided rubber wire flat rope is suspended and bent to form macro-arches. The curvature and shape of the macro-arches are determined by the distance between the arch feet. When the braided rubber wire flat rope is stretched again, the distance between the arch feet increases, and the curvature of the macro-arch decreases until it is stretched again to a flat state that is completely fitted with the braided rubber wire flat rope. At this time, the curvature is almost reduced to 0.

[0061] like Figure 3 Shown Figure 2 Calibration method and linear region verification of the sensor. The displacement sensor proposed in the present invention is arranged on a one-dimensional displacement table. The maximum elongation ratio of this example is 150%. The linearity of the sensor with 10 macrobending loss arches was tested on the sensor. The arch foot spacings of the three sensors were 7mm, 10mm and 13mm respectively; the light source and the photodiode were connected to both ends of the optical fiber respectively. In order to record the change of optical power in the optical fiber with the tension and compression of the sensor, an oscilloscope was connected to the end of the photodiode to record the change of the oscilloscope voltage under one tension and compression of the sensor. Figure 4 As shown. Figure 4It can be seen that the optical power change and displacement of the transient displacement sensors with three different arch foot spacings have a linear region during the stretching and contraction process. The R 2 The value close to 1 indicates good linearity. The calibration example can prove the accuracy and linearity of the sensor and its basic function of large deformation transient displacement measurement.

[0062] like Figure 5 The present invention shows a sensing example of measuring the transient response of a cantilever beam under the impact of a steel ball. One end of the elastic base of the one-dimensional sensor with a foot-arch spacing of 10 mm is fixed to the point to be measured on the upper surface of the cantilever beam, and the other end is fixed to a relatively static reference surface, keeping the direction of the optical fiber parallel to the normal direction of the upper surface of the cantilever beam. Use a steel ball to lightly hit the position A on the upper surface of the cantilever beam. When the cantilever beam vibrates, the vibration of the upper surface drives the sensor to expand and contract. During the expansion and contraction process of the elastic base of the sensor, the spacing between the arch feet of the macro-bend arch of the optical fiber increases and decreases accordingly. During the whole process, the macro-bending rate of the optical fiber between the arch feet changes with the vibration of the cantilever beam and the up and down displacement of the upper surface. The change in curvature changes the amount of light leaked from the bend. Therefore, the transient displacement of the vibration of the cantilever beam can be obtained by real-time monitoring of the optical power in the optical fiber. One end of the optical fiber is connected to a light source, and the other end is connected to a photodiode. The photodiode converts the optical signal into an electrical signal and displays it through an oscilloscope. At the same time, a Polytec Doppler vibrometer is set up, and a non-contact laser point is used to measure the out-of-plane displacement signal of the same point on the cantilever beam. A steel ball with a diameter of 8 mm was dropped from a height of 1 cm and hit the upper surface position B of the cantilever beam as an external impact load, and the oscilloscope signal and the Doppler vibrometer signal were collected at the same time.

[0063] Figure 6 for Figure 5 The comparison chart of the oscilloscope measurement signal and the Doppler vibrometer signal of the reliable equipment in the sensing example. The signal measured in the oscilloscope is the real-time situation of the optical power signal of the optical fiber being converted into an electrical signal. Through the linear relationship, it can be used as the real-time displacement signal of the position where the sensor is attached on the surface of the cantilever beam. The linear performance of the sensor has been Figure 4 Reflected in. Figure 6 It can be seen that in the measurement of the transient displacement of the entire cantilever beam upper surface, the entire measurement has good linearity and high repeatability. This proves the precision and accuracy of the invented sensor in transient displacement measurement, and proves that the invented sensor can detect single-point displacement.

[0064] like Figure 7As shown, the design of the present invention is biased towards practical applications. When the user faces measurement requirements, the specific range and accuracy requirements of the required measurement scale should be determined according to the work scenario. Then, according to the required measurement range, the initial size of the elastic substrate, the maximum elongation ratio and the distance between the arches of the optical fiber macrobends are selected to ensure that the stretching range covers the required measurement range, and according to Figure 2 The sensor is manufactured according to the manufacturing process shown in the figure. Figure 3 The experimental arrangement shown in the figure uses a one-dimensional displacement platform to check whether the linear region of the sensor covers the displacement range required for measurement. If the conditions are met, the design is completed; if the conditions are not met, first change the initial size of the elastic substrate to adjust the range of the linear sensitive region. If it is still not met, change the stretching ratio of the elastic substrate. If it still cannot be adjusted to the required range, you can choose to change the arch foot spacing of the optical fiber macrobend arch or the number of macrobend arches to adjust the linear region range to meet the measurement requirements.

[0065] The above-mentioned embodiments only express several implementation modes of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A transient displacement sensor based on uniform macrobending loss of optical fiber and dynamic changes of tension and compression of elastic substrate, characterized in that: It comprises an elastic substrate and an optical fiber interspersed on the elastic substrate; the optical fiber is interspersed on the elastic substrate at the same interval and fixedly connected to the elastic substrate at the interspersed point; after the optical fiber is interspersed, it presents continuous wavy bending, and the bending shape is exactly the same; one end of the optical fiber is connected to a light source, and the other end is connected to a photodiode; When the elastic substrate is deformed in the length direction of the optical fiber, the optical fiber will be driven to change its bending curvature; the width of the elastic substrate is 20-500 times the diameter of the optical fiber.

2. The transient displacement sensor according to claim 1, characterized in that: The number of the continuous wavy bends is 5-15.

3. The transient displacement sensor according to claim 1, characterized in that: The continuous wavy bends take the elastic base as a reference plane; of two adjacent bends, one is located above the reference plane and the other is located below the reference plane.

4. The transient displacement sensor according to claim 1, characterized in that: The elastic base is made of braided rubber rope, Ecoflex or TPU.

5. The transient displacement sensor according to claim 1, characterized in that: During the elastic base deformation process, the distance between any two adjacent penetration points is equal.

6. The transient displacement sensor according to claim 1, characterized in that: The elastic substrate is in a partially stretched state in an initial state during application, and the elastic substrate can shrink or stretch based on the initial state.

7. A method for manufacturing the transient displacement sensor according to claim 1, characterized in that: The steps include: 1) inserting optical fibers on an elastic substrate at the same interval, wherein the length direction of the optical fibers is consistent with the length direction of the elastic substrate; and the length direction of the elastic substrate is used as the direction of subsequent stretching; 2) stretching the elastic substrate to a maximum elongation ratio, in which the optical fiber is straightened and fits with the upper and lower surfaces of the elastic substrate, and the optical fiber and the elastic substrate are consolidated at the interlaced position of the optical fiber and the elastic substrate in the current state; 3) The stretching of the elastic substrate is canceled, and the optical fibers originally attached to the elastic substrate are bent into identical arches as the elastic substrate shrinks, and the optical fibers shrink as a whole into a wave shape; One end of the optical fiber is connected to a light source, and the other end is connected to a photodiode to obtain the transient displacement sensor.

8. The method according to claim 7, characterized in that: In the step 2), when the elastic substrate is made of braided rubber rope or TPU, glue is used for consolidation; when the elastic substrate is made of Ecoflex, UV curing glue is used for consolidation.

9. A method for displacement measurement using the transient displacement sensor according to claim 1, characterized in that: The steps include: The elastic substrate is pre-stretched in the length direction of the optical fiber, and the elongation ratio of the elastic substrate during pre-stretching is less than the maximum elongation ratio of the elastic substrate; then one end of the long side of the elastic substrate in the pre-stretched state is vertically fixed to the surface of the structure to be measured, and the other end is vertically fixed to the surface of any fixed structure; one end of the optical fiber is connected to a light source, and the other end is connected to a photodiode; The displacement signal of the structure to be measured in the direction of the optical fiber arrangement will be converted into the curvature change of the optical fiber bending. The curvature change of the optical fiber bending will eventually change the optical power signal received by the photodiode. The photodiode converts the optical power signal into an electrical signal output, that is, the transient displacement change of the surface of the structure to be measured is obtained.

10. The method according to claim 9, characterized in that During pre-stretching, the elongation ratio of the elastic substrate is 80%-90% of the maximum elongation ratio of the elastic substrate; during displacement measurement, the change value of the elongation ratio of the elastic substrate relative to the elongation ratio of the elastic substrate during pre-stretching is controlled within 1.5%.

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