An optical fiber grating displacement sensor device

Abstract

A fiber Bragg grating displacement sensor device includes a housing, a fiber Bragg grating, a cam push rod mechanism, a clamping mechanism, a temperature compensator, a concentric pulley, an eccentric wheel, a cylindrical base, a deformable substrate, etc. The measuring probe extends into the housing and is tangent to the upper side of the cam, and the other end can move freely. A large pulley is provided on one side of the cam, and an active pulley is provided on the upper side of the pulley; a transmission belt is provided between the active pulley and the passive pulley, and the passive pulley is embedded in the straight groove of the clamping mechanism; the other side of the straight groove slide bar of the clamping mechanism is embedded with the eccentric wheel, and the eccentric wheel is fixed on the base to drive the eccentric wheel to rotate. A thin rope is connected to the outer side of the eccentric wheel and connected to the slider; the slider is placed on the sensing substrate, and four fiber Bragg gratings with different directions are built in the sensing substrate. The present invention uses fiber Bragg grating for displacement measurement, has good durability and is not affected by electromagnetic fields. It is equipped with a temperature compensator, which can fundamentally eliminate the interference of temperature on the fiber Bragg grating sensor, avoid the fiber Bragg grating displacement sensor from contacting with external corrosive substances, and can adapt to harsh environments.

Description

Technical Field

[0001] The present invention belongs to the field of optical fiber sensing, and relates to a displacement sensor device for detecting the depth of a ground collapse body. Background Art

[0002] Ground collapse refers to a geological phenomenon in which surface rocks, soil masses, etc. sink downward under the action of natural or human factors, and a collapse pit or collapse hole is formed on the ground. When this geological phenomenon occurs in an area with human activities, it may develop into a geological disaster. Due to the characteristics of suddenness, concealment, uncertainty, and spatio-temporal effect of ground collapse, the formed collapse area will also cause harm to above-ground or underground structures. At present, the treatment of ground collapse mainly focuses on preventive and protective measures. To effectively ensure the safe operation of projects and reduce the catastrophic consequences brought by ground collapse, it is very necessary to prevent and monitor ground collapse through monitoring and early warning.

[0003] With the development of optical fiber sensing technology, optical fiber grating sensors have been widely used in fields such as bridges, water conservancy, and construction engineering due to their advantages of anti-electromagnetic interference, corrosion resistance, high insulation, wide measurement range, and easy multiplexing into a network. It is mainly used to test information such as deformation, temperature, stress and strain. When the external force applied to the optical fiber grating changes, the strain distribution of the optical fiber grating itself changes accordingly, thereby causing a change in the central wavelength of the optical fiber grating; through an optical fiber grating demodulation device, the change in the central wavelength can be converted into a change in optical power, and by detecting the change in optical power, the detection of displacement can be achieved.

[0004] For the prevention and monitoring of geological disasters such as ground collapse, it is necessary to detect the deep displacement of the ground collapse body. Currently, the most commonly used sensor for deep displacement monitoring is the micro-electro-mechanical sensor (MEMS). After converting the mechanical displacement into a resistance or voltage output that is linearly or arbitrarily functionally related through internal components of the sensor, the displacement that has occurred can be calculated through conversion. This method uses electrical sensing, but it requires power supply on-site, the implementation cost is relatively high, and it is also relatively easy to wear, with low durability. Summary of the Invention

[0005] Aiming at the defects of the prior art, the present invention provides an optical fiber grating displacement sensor device. By applying optical fiber grating sensing technology to the monitoring of the deep displacement of a ground collapse body, compared with conventional electrical testing methods, no power supply is required at the test site, the installation is relatively convenient, the cost is relatively low, the displacement distribution at a certain depth inside the ground collapse body can be measured, and at the same time, the optical fiber grating sensor has no direct contact with the external environment and will not be rubbed and worn, so its service life is longer and the reliability is higher. Furthermore, it can provide prevention and reference for natural disasters such as ground collapse.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] An optical fiber grating displacement sensor device includes an external protection module, a cam push rod mechanism module, a clamping mechanism module, and an optical fiber grating deformation compensation module located inside the external protection module. The cam push rod mechanism module and the clamping mechanism module are connected by a transmission rod 36, which plays a transmission role in the whole device. The purpose is to drive the slider on the deformable sensing substrate 9 in the optical fiber grating deformation compensation module to move, so that the pressure on the deformable sensing substrate 9 changes and deforms, and then drives the optical fiber gratings in four different directions on the deformable sensing substrate 9 to change in wavelength. The optical fiber grating deformation compensation module is the core part of the whole device. It is connected to the cam push rod mechanism module and the clamping mechanism module through a thin string 24 and an eccentric wheel mechanism 6. The main purpose is to calculate the amount of deformation of the deformable sensing substrate 9, and at the same time eliminate the influence of temperature on the optical fiber grating, so that the measurement result is more accurate. The external protection module is located outside the whole device, mainly used to reduce the interference of external factors, improve the durability of the structure, protect the whole device, and make the service life of the structure longer.

[0008] The external protection module includes: a cuboid housing 1, a top cover 32, and a bottom plate 29. One end of the cuboid housing 1 is provided with a through hole 30 for passing through the measuring probe 10. The size of the through hole 30 matches the size of the top end of the measuring probe 10, so that the two can be closely connected. One end of the top cover 32 is provided with a vent hole 27 to keep the air inside and outside the device flowing. The bottom plate 29 is a plate-like structure without a through hole; the top cover 32, the cuboid housing 11, and the bottom plate 29 are assembled together using an adhesive; the cam push rod mechanism module, the clamping mechanism module, and the optical fiber grating deformation compensation module are arranged in sequence from left to right along the length direction inside the cuboid housing 1; a through hole for passing through the movable rocker 11 is provided below one side surface along the length direction (this side surface is perpendicular to the upper and lower surfaces). The materials of the external protection module are all aluminum alloy, and a layer of polyethylene protective film is also coated on its outer side, which can protect the metal shell, improve the durability of the structure, and make the service life of the structure longer.

[0009] The described cam push rod mechanism module 2 includes: a machine table 31, a movable rocker 11, a cam 12, a measuring probe 10, and a large fixed track 13. The machine table 31 is made of metal and consists of a horizontally arranged rectangular parallelepiped panel with polished edges and corners and vertically arranged connecting columns. The connecting columns are located at one end of the rectangular parallelepiped panel. The machine table 31 is fixed on the bottom plate 29 of the inner lower surface of the external protection module by bolts 28 and serves as the assembly base for the remaining parts; there are four through holes above the connecting columns. The movable rocker 11 passes through the through hole on the side of the rectangular outer shell 1 and extends into the interior of the shell and aligns and coincides with the through hole of the concentric disc 5. The large fixed track 13 is a block structure with a vertically arranged through hole in the center of the block structure and a horizontally arranged blind hole at each of the four corners. Align the side with the four blind holes with the through holes above the connecting columns of the machine table 31 and connect them by bolts 28. One end of the measuring probe 10 passes through the through hole 30 provided on the upper surface of the cubic outer shell 1 and extends into the interior of the shell. This end passes through the central through hole of the large fixed track 13 and makes fixed contact with the upper end of the cam 12. The measuring probe 10 is made of a plastic rod with relatively strong plasticity, and a steerable corner 39 is provided in the middle part. Through the steerable corner 39, the direction of the metal probe at one end of the measuring probe 10 outside the shell 1 can be changed, so as to realize the deep displacement measurement of the ground collapse body in the horizontal and vertical directions.

[0010] The described clamping mechanism module 3 includes: a concentric disc 5, a central wheel 14, an active pulley 15, a passive pulley 16, a straight groove connecting rod 17, a straight groove sliding rod 18, a cylindrical convex rod 19, a common connecting rod 20, a small fixed track 21, a rotatable large pulley 22, a transmission belt 35, and a rotatable large pulley 22. The concentric disc 5 is fixed above the bottom plate 29, and its upper surface contacts the outer side surface of the active pulley 15 to provide support for the movement of the active pulley 15; a central wheel 14 is provided inside the active pulley 15, and the central wheel 14 rotates concentrically with the active pulley 15. A transmission rod 36 is connected between the central wheel 14 and the cam 12. The rotation of the cam 12 will cause the movement of the transmission rod 36 and then drive the central wheel 14 to rotate. At the same time, a transmission belt 35 is provided between the active pulley 15 and the passive pulley 16, and the passive pulley 16 is embedded in the straight groove of the straight groove connecting rod 17. That is, the rotation of the cam 12 drives the central wheel 14 to rotate. After the central wheel 14 rotates, it will drive the active pulley 15 to rotate. After the active pulley 15 rotates and generates a relative displacement through the transmission belt 35, the passive pulley 16 will slide in the chute on the straight groove connecting rod 17. One end of the straight groove connecting rod 17 is fixedly connected to one end of the common connecting rod 20 by a thread. The small fixed track 21 is nested on the connecting rod 20. The other end of the common connecting rod 20 is connected to one end of the straight groove sliding rod 18 by a thread. The other end of the straight groove sliding rod 18 is provided with a straight groove, and the convex rod 19 is embedded in this straight groove.

[0011] The fiber Bragg grating deformation compensation module includes: a temperature compensator 4, an eccentric wheel 6, a cylindrical base 7, four fiber Bragg gratings 8 in different directions, a deformable sensing substrate 9, a slider 23, a thin string 24, an angular displacement sensor 37, and a tensiometer 38. The eccentric wheel 6 includes a rotatable large pulley 22 and a convex rod 19. One end of the convex rod 19 is first fixed to the rotatable large pulley 22 by an adhesive, and the other end is then embedded in the straight groove opening of a straight groove slide rod 18. The straight groove slide rod 18 pulls the convex rod 19 to move, thereby driving the rotatable large pulley 22 to rotate. The rotatable large pulley 22 is of a disc structure with a square hole in the middle for connecting to the top of the cylindrical base 7 to fix the eccentric wheel 6. The cylindrical base 7 is threadedly connected to the eccentric wheel 6 through a threaded hole to provide support for the rotation of the eccentric wheel 6. A thin string 24 is wound around the outer side of the rotatable large pulley 22, and one end of the thin string 24 is connected to the slider 23, and the slider 23 is located at the upper end of the deformable sensing substrate 9. A groove is provided at the edge of the slider 23, and a small angular displacement sensor 37 is placed in the groove. One end of the angular displacement sensor 37 is fixed in the groove of the slider 23 by a bolt and optical glue, and the other end is connected to the metal hook of the tensiometer 38. The tensiometer 38 is also connected to the other end of the thin string 24 through the metal hook at the other end. At the same time, for the convenience of reading data, the small angular displacement sensor 37 and the slider 23 can be regarded as a whole during on-site operation. The horizontal inclination angle θ of the thin string 24 after the movement of the slider 23 is measured by the angular displacement sensor 37, and the tension F of the thin string 24 can be read by the tensiometer 38 connected to the end of the angular displacement sensor 37. The deformable sensing substrate 9 is a thin plate structure that can be deformed under force. Its left end is fixed to the upper surface of the bottom plate 29 by screws. A groove is also provided in the middle of the sensing substrate 9, and four fiber Bragg gratings 8 in different directions are fixed in the groove by optical glue. The four fiber Bragg gratings 8 form a cross-shaped structure, and the center of the cross-shaped structure coincides with the center of the deformable sensing substrate 9. The temperature compensator 4 is located on the left side of the deformable sensing substrate 9 and includes a bare free fiber 26, a thin straight rod 34, a fixed base 25, and a fixing nut 33: First, the bare free fiber 26 is encapsulated, and then it is wound around the thin straight rod 34 to improve its durability under harsh conditions. At the same time, the fiber splice is processed by an optical fiber fusion splicer and fixed to the fixed base 25 through the fixing nut 33 to obtain a bare fiber device. Finally, the connected bare fiber device is fixedly connected to the bottom plate 29 through an adhesive.

[0012] The usage process of the present invention:

[0013] In the initial state, the slider 23 is statically placed on the deformable sensing substrate 9, and the tension of the thin string 24 on the slider 23 is zero. At this time, the deformable sensing substrate 9 does not deform. At this time, the initial wavelength of the fiber Bragg grating 8 is recorded as λ.

[0014] The outer circumferential plane of the cam 12 coincides and mates with the contact point of the end of the push rod on the inner side of the housing 1. When the movable rocker 11 is rotated under force, the cam 5 can be rotated, so that one end of the measuring probe 10 located outside the housing 1 starts to move. When the metal tip of the probe on the outside of the measuring probe 10 reaches the required test point, the transmission rod 36 embedded in the cam 12 will drive the central wheel 14 on the concentric disc 5 to rotate, and then drive the driving pulley 15 to rotate. Then, due to the action of the transmission belt 35, the driven pulley 16 will also start to rotate. The clamping mechanism 3 undergoes a rigid body motion, thereby driving the rotatable large pulley 22 on the eccentric wheel 6 to rotate. As the rotatable large pulley 22 rotates, the thin rope 24 will be pulled to drive the slider 23 to move, so that the pressure on the deformable sensing substrate 9 exerted by the slider 23 will change, so that the deformable sensing substrate deforms, and then drives the fiber Bragg gratings 8 in four different directions on the sensing substrate 9 to change. The horizontal tilt angle θ of the thin rope 24 after the slider 23 moves can be measured by the angular displacement sensor 37, and the tension F of the thin rope 24 can be read by the tensiometer 38 connected to the end of the angular displacement sensor 37. After measuring the change amount of the central wavelength of the fiber Bragg grating 8 and knowing the mass of the slider 23 and the above parameters, through formula (1), the deformation amount of the deformable sensing substrate 9 can be calculated, and then combined with the displacement sizes in four directions of the fiber Bragg grating 8, the depth displacement size and direction of the ground collapse body can be obtained through vector synthesis.

[0015]

[0016] Among them, Δλ represents the change amount of the central wavelength of the fiber Bragg grating 8; F represents the tension of the thin rope 24; θ represents the horizontal tilt angle θ of the thin rope 24; mg represents the mass of the slider 23; L represents the length of the deformable substrate, x represents the distance from the upward bending point to the fixed point when the deformable sensing substrate 9 deforms; t represents the thickness of the deformable substrate; h represents the upward bending deformation amount of the deformable substrate; λ represents the initial wavelength of the fiber Bragg grating 8.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) The present invention combines the mature fiber optic sensing technology with traditional mechanical structures such as pulleys and connecting rods to complete the measurement of the displacement. It does not require a power supply on site, is not affected by electromagnetic interference, does not affect the external electromagnetic field, has good electrical insulation performance, good durability, wide application range, and is safe and reliable.

[0019] (2) When the present invention is used, the signal comes from the change of the wavelength of the fiber Bragg grating. The fluctuation of the on-site power size will not affect the change of the result. The fiber Bragg fiber optic sensor is adopted, which effectively reduces the cost.

[0020] (3) The deep displacement measurement range of the ground collapse body can be increased by changing the size of the deformable sensing substrate and the rotation speed of the cam in the present invention. It can be widely used in on-site construction measurement and displacement measurement in harsh environments. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the overall structural device of the present invention;

[0022] Figure 2 It is a schematic diagram of the cam push rod mechanism device of the present invention;

[0023] Figure 3 It is a schematic diagram of the clamping mechanism device of the present invention;

[0024] Figure 4 It is a schematic diagram of the temperature compensator device of the present invention;

[0025] Figure 5 It is a deformation diagram of the deformable sensing substrate before and after being stressed in the present invention;

[0026] Figure 6 It is a partial enlarged view of the internal angular displacement sensor of the slider in the present invention;

[0027] In the figure: 1 cuboid housing, 2 cam push rod mechanism, 3 clamping mechanism, 4 temperature compensator, 5 concentric disc, 6 eccentric wheel, 7 cylindrical base, 8 fiber Bragg gratings in four different directions, 9 deformable sensing substrate, 10 measuring probe, 11 movable rocker, 12 cam, 13 large fixed track, 14 central wheel, 15 driving pulley; 16 driven pulley, 17 straight groove connecting rod, 18 straight groove sliding rod, 19 cylindrical convex rod, 20 ordinary connecting rod, 21 small fixed track, 22 rotatable large pulley, 23 slider, 24 thin rope, 25 fixed support, 26 bare free optical fiber, 27 ventilation hole, 28 bolt, 29 bottom plate, 30 through hole, 31 machine table, 32 top cover, 33 fixing nut, 34 thin straight rod, 35 conveyor belt, 36 transmission rod, 37 angular displacement sensor, 38 tensiometer, 39 steerable corner. Detailed Implementation Modes

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0029] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0030] As Figure 1 and Figure 2 shown, a fiber Bragg grating displacement sensor device involved in this embodiment includes: a cam push rod mechanism module, a clamping mechanism module, a fiber Bragg grating deformation compensation module, and an external protection module. The machine table 32 is fixed on the bottom plate 30. The movable rocker 11 passes through the through hole on the housing and extends into the interior of the housing, aligning and overlapping with the through hole of the cam 5. The large fixed track 13 is a cube with four small holes of the same size that do not completely penetrate in the middle and a small hole that completely penetrates in the middle. Align the side with the four small holes with the through hole above the machine table 31 and connect them by threading. One end of the measuring probe 10 passes through the through hole 30 provided on the housing and extends into the rectangular parallelepiped housing 1, and the end thereof located inside the housing passes through the large fixed track 13 and is fixedly contacted with the upper end of the cam 12.

[0031] The top cover 32 is a rectangular parallelepiped with holes 30 and 27 in the middle. The size of the through hole 30 is consistent with the size of the top end of the measuring probe 10, so that the two can be tightly connected. The size of the top cover 32 can be adjusted according to the on-site measurement requirements. In addition, the material of the top cover 32 is aluminum alloy, and its outer side is also coated with a polyethylene protective film, which can protect the metal shell, improve the durability of the structure, and make the service life of the structure longer.

[0032] The concentric disc 5 is located on the right side of the cam 12. A driving pulley 15 is provided on the upper side of the concentric disc 5. There is a central wheel 14 inside the driving pulley 15, and the central wheel 14 rotates concentrically with the driving pulley 15. The central wheel 14 is connected to the cam 12 through a transmission rod 36. The rotation of the cam 12 will cause the movement of the transmission rod and then drive the central wheel 14 to rotate. The concentric disc 5 is fixed on the upper end of the base. At the same time, a transmission belt 35 is provided between the driving pulley 15 and the driven pulley 16, and the driven pulley 16 is embedded in the straight groove of the straight groove link 17. That is, the rotation of the cam 12 drives the central wheel 14 to rotate. After the central wheel 14 rotates, it will drive the driving pulley 15 to rotate. After the driving pulley 15 rotates and generates a relative displacement through the transmission belt, the driven pulley 16 will slide in the chute of the straight groove link 17.

[0033] The clamping mechanism 3 includes a set of straight groove linkages 17, a set of straight groove sliders 18, a set of linkages 20, and a small fixed track 21. One end of the straight groove linkage is fixedly connected to the linkage by a thread. The small fixed track is nested on the linkage. The other end of the linkage is threadedly connected to one end of the straight groove slider. The other side of the straight groove slider is fixedly engaged with the convex rod on the eccentric wheel.

[0034] The bottom plate 29 is of a square structure. The eccentric wheel 6 is fixed on the cylindrical base 7. The rotation of the straight groove slider 18 and the small pulley on the eccentric wheel can drive the eccentric wheel to rotate. The eccentric wheel is of a disc structure with a square hole in the middle, which can be connected to the bottom base to fix the eccentric wheel. The eccentric wheel is threadedly connected to the cylindrical base through a threaded hole, and its diameter should be larger than the diameter of the circular hole on the central column.

[0035] In the specific implementation process, a corner-polished smooth sensing substrate is adopted to reduce the resistance during its sliding. Here, the deformable sensing substrate can be regarded as a cantilever beam structure. Its left end is fixed, and its right end can be compressed and deformed under the action of pressure. Its working principle is as follows: Rotate the cam, and the measuring probe starts to move. When it reaches the position of the test point, the transmission rod in contact with the cam will drive the central wheel on the concentric disc to rotate, and then drive the concentric disc and the driving pulley to rotate. Then, through the action of the transmission belt, the driven pulley will also start to rotate. This causes the clamping device to perform a rigid body motion, thereby driving the rotatable large pulley on the eccentric wheel to rotate. Generally, the slider is statically placed on the deformable sensing substrate, and the tensile force of the thin rope on the slider is zero. At this time, the substrate does not deform. As the eccentric wheel rotates, it will pull the thin rope to drive the slider to move, so that the pressure of the slider on the sensing substrate will change, and thus the deformable sensing substrate will deform, and then drive the fiber Bragg gratings in four different directions on the sensing substrate to change. The magnitude of the tensile force value of the thin rope can be obtained through a tensile force sensor, and the amount of deformation of the deformable sensing substrate can be obtained through the wavelength change of the fiber Bragg grating. The wavelength change of the fiber Bragg grating 8 is only related to the following parameters: the length L of the deformable sensing substrate 9, the distance x from the upward bending point to the fixed point when the deformable sensing substrate 9 deforms, the thickness t of the deformable sensing substrate 9, the initial wavelength λ of the fiber Bragg grating, the magnitude of the deformation amount h, the magnitude of the tensile force F on the slider, the horizontal inclination angle θ of the thin rope, and the mass m of the slider. The formula for the change in the central wavelength corresponding to the deformable sensing substrate 9 and the fiber Bragg grating 8 satisfies the following formula:

[0036]

[0037] By measuring the change in the central wavelength of the fiber Bragg grating 8, the deformation of the deformable sensing substrate is calculated, and then combined with the displacement of the fiber Bragg grating in four directions, the depth displacement and direction of the ground collapse body are obtained through vector synthesis. It can be considered that the change in the central wavelength of the fiber Bragg grating and the deformation of the deformable sensing substrate are in a one-to-one linear relationship, and by constantly changing the size of the deformable sensing substrate 9, the mass of the slider 23 and the rotation speed of the cam 12, the deep horizontal displacement test range of the ground collapse body reaches 50mm.

[0038] The eccentric wheel includes a rotatable large pulley and a cylindrical protruding rod bonded to the upper part thereof, and then a thin rope is wound around the outer side of the large pulley. The thin rope is also connected to a slider, and the slider is located at the upper end of the deformable sensing substrate.

[0039] After the structure is stable, the fiber Bragg gratings in four directions can be pasted on the deformable sensing substrate. When pasting, pay attention to keeping the thickness of the paste uniform to avoid causing too much structural change to the original structure. At the same time, pay attention to avoid bubbles in the packaging glue at the fiber Bragg grating, otherwise it will easily cause the multi-peak phenomenon of the sensor.

[0040] Then the bare free optical fiber in the temperature compensator is packaged and wound on a thin straight rod to improve its durability in harsh conditions. At the same time, the optical fiber joint is processed by a fiber fusion splicer to facilitate the connection of the sensor. Finally, the connected bare optical fiber device is fixedly connected to the bottom plate.

[0041] Finally, after the fiber grating packaging is completed on the deformable sensing substrate, the top cover can be assembled with the shell and the bottom plate, and the two parts can be combined with an adhesive at the bottom to limit the lateral movement between the top cover and the bottom plate; then a layer of polyethylene protective film is added to the outside of the shell, the top cover and the bottom plate to improve the durability of the structure and extend the service life of the structure.

[0042] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A fiber Bragg grating displacement sensor device, characterized in that, the fiber Bragg grating displacement sensor device includes an external protection module and a cam push rod mechanism module, a clamping mechanism module, and a fiber Bragg grating deformation compensation module located inside the external protection module; the cam push rod mechanism module and the clamping mechanism module are connected by a transmission rod (36), which plays a transmission role in the whole device and is used to drive the slider on the deformable sensing substrate (9) in the fiber Bragg grating deformation compensation module, so that the pressure on the deformable sensing substrate (9) changes and deforms, and then drives the fiber Bragg gratings in four different directions on the deformable sensing substrate (9) to change in wavelength; the fiber Bragg grating deformation compensation module is the core part of the whole device, which is connected to the cam push rod mechanism module and the clamping mechanism module through a thin rope (24) and an eccentric wheel (6). The main purpose is to calculate the deformation amount of the deformable sensing substrate (9), and at the same time eliminate the influence of temperature on the fiber Bragg grating, so that the measurement result is more accurate; the external protection module is located on the outside of the whole device; the external protection module includes a cuboid housing (1), a top cover (32), and a bottom plate (29); one end of the cuboid housing (1) is provided with a through hole (30) for passing through the measurement probe rod (10); one end of the top cover (32) is provided with a ventilation hole (27); the bottom plate (29) is a plate-like structure without a through hole; the cam push rod mechanism module, the clamping mechanism module, and the fiber Bragg grating deformation compensation module are arranged in sequence from left to right along the length direction inside the cuboid housing (1); a through hole for passing through the movable rocker (11) is provided below one surface of the long side; the cam push rod mechanism module (2) includes a machine table (31), a movable rocker (11), a cam (12), a measurement probe rod (10), and a large fixed track (13); the machine table (31) is fixed on the bottom plate (29) of the inner lower surface of the external protection module, and four through holes are provided above the connecting column; the movable rocker (11) passes through the through hole on the side surface of the cuboid housing (1) and extends into the cuboid housing (1) and aligns with the through hole of the concentric disc (5) and overlaps together; the large fixed track (13) is a block structure, and a vertically arranged through hole runs through the center of the block structure, and a horizontally arranged blind hole is provided at each of the four corners, and the side of the blind hole is aligned with the through hole above the connecting column of the machine table (31) for connection; one end of the measurement probe rod (10) passes through the through hole (30) provided on the upper surface of the cuboid housing (1) and extends into the cuboid housing (1), and this end passes through the central through hole of the large fixed track (13) and is fixedly contacted with the upper end of the cam (12); a steerable corner (39) is arranged in the middle of the measurement probe rod (10), and the direction of the metal probe at one end of the measurement probe rod (10) located outside the cuboid housing (1) is changed through the steerable corner (39), so as to realize the measurement of the deep displacement in the horizontal and vertical directions of the ground collapse body; The described clamping mechanism module (3) includes a concentric disc (5), a central wheel (14), a driving pulley (15), a driven pulley (16), a straight groove connecting rod (17), a straight groove sliding rod (18), a cylindrical convex rod (19), a common connecting rod (20), a small fixed track (21), a rotatable large pulley (22), a conveyor belt (35), and a rotatable large pulley (22); the concentric disc (5) is fixed above the bottom plate (29), and its upper surface contacts the outer side of the driving pulley (15) to provide support for the movement of the driving pulley (15); a central wheel (14) is arranged inside the driving pulley (15), and the central wheel (14) rotates concentrically with the driving pulley (15); the central wheel (14) is connected to the cam (12) through a transmission rod (36), and the rotation of the cam (12) will cause the movement of the transmission rod (36) and then drive the central wheel (14) to rotate; at the same time, a conveyor belt (35) is arranged between the driving pulley (15) and the driven pulley (16), and the driven pulley (16) is embedded in the straight groove of the straight groove connecting rod (17); that is, the rotation of the cam (12) drives the central wheel (14) to rotate, and after the central wheel (14) rotates, it will drive the driving pulley (15) to rotate. After the driving pulley (15) rotates and generates a relative displacement through the conveyor belt (35), the driven pulley (16) will slide in the chute on the straight groove connecting rod (17); one end of the straight groove connecting rod (17) is fixedly connected to one end of the common connecting rod (20), the small fixed track (21) is nested on the connecting rod (20), the other end of the common connecting rod (20) is connected to one end of the straight groove sliding rod (18), and a straight groove is provided at the other end of the straight groove sliding rod (18), and the convex rod (19) is embedded in the straight groove; The fiber Bragg grating deformation compensation module includes a temperature compensator (4), an eccentric wheel (6), a cylindrical base (7), four fiber Bragg gratings (8) in different directions, a deformable sensing substrate (9), a slider (23), a thin string (24), an angular displacement sensor (37), and a tensiometer (38); the eccentric wheel (6) includes a rotatable large pulley (22) and a convex rod (19), one end of the convex rod (19) is fixed on the rotatable large pulley (22), and the other end is embedded in the straight groove opening of a straight groove slide rod (18); the straight groove slide rod (18) pulls the convex rod (19) to move and thus drives the rotatable large pulley (22) to rotate; the rotatable large pulley (22) is of a disc structure with a square hole in the middle for connecting to the top of the cylindrical base (7) to fix the eccentric wheel (6); the cylindrical base (7) is threadedly connected to the eccentric wheel (6) to provide support for the rotation of the eccentric wheel (6); a thin string (24) is wound around the outer side of the rotatable large pulley (22), one end of the thin string (24) is connected to the slider (23), and the slider (23) is located at the upper end of the deformable sensing substrate (9); a groove is provided at the edge of the slider (23), and a small angular displacement sensor (37) is placed in the groove. One end of the angular displacement sensor (37) is fixed in the groove of the slider (23), and the other end is connected to the metal hook of the tensiometer (38). The tensiometer (38) is also connected to the other end of the thin string (24) through the metal hook at the other end; the horizontal tilt angle θ of the thin string (24) after the movement of the slider (23) is measured by the angular displacement sensor (37), and the tension F of the thin string (24) can be read by the tensiometer (38) connected to the end of the angular displacement sensor (37); the deformable sensing substrate (9) is a thin plate structure that can be deformed under force. Its left end is fixed on the upper surface of the bottom plate (29), and a groove is also provided in the middle. Four fiber Bragg gratings (8) in different directions are fixed in the groove by optical glue; the temperature compensator (4) is located on the deformable sensing substrate (9).

2. The fiber Bragg grating displacement sensor device according to claim 1, characterized in that, the temperature compensator (4) is located on the deformable sensing substrate (9) and includes a bare free fiber (26), a thin straight rod (34), a fixed base (25), and a fixing nut (33): First, the bare free fiber (26) is encapsulated and then wound around the thin straight rod (34) to improve its durability under harsh conditions. At the same time, the fiber joint is processed by an optical fiber fusion splicer and fixed to the fixed base (25) through the fixing nut (33) to obtain a bare fiber device; finally, the connected bare free fiber (26) and the bottom plate (29) are fixedly connected together by an adhesive agent.

3. The fiber Bragg grating displacement sensor device according to claim 1, characterized in that, the materials of the external protection module are all aluminum alloy, and a layer of polyethylene protective film is further coated on the outside, which can protect the metal shell, improve the durability of the structure, and make the service life of the structure longer.

4. A fiber Bragg grating displacement sensor device according to claim 1, characterized in that, the machine table (31) is made of metal and consists of a horizontally arranged rectangular panel with polished edges and corners and vertically arranged connecting columns. The connecting columns are located at one end of the rectangular panel. The machine table (31) is fixed on the bottom plate (29) of the inner lower surface of the external protection module through bolt rods and serves as an assembly base for the remaining parts.

5. A fiber Bragg grating displacement sensor device according to claim 1, characterized in that, the measuring probe rod (10) is made of a plastic rod with strong plasticity.

6. A fiber Bragg grating displacement sensor device according to claim 1, characterized in that, the four fiber Bragg gratings (8) form a cross-shaped structure, and the center of the cross-shaped structure coincides with the center of the deformable sensing substrate (9).

Images