Grating tilt angle sensor capable of realizing tilt correction in installation process

Abstract

The invention discloses a grating tilt angle sensor capable of realizing tilt correction in an installation process based on a strain sensitive principle of a fiber bragg grating, and belongs to the technical field of fiber sensing, the grating tilt angle sensor comprises a grating tilt angle sensor body and an installation component used for being connected with a detected body, and the installation component is connected with the sensor body through a universal shaft. A component for fixing the corrected sensor body is also arranged between the grating tilt angle sensor body and the mounting component, or a component for fixing the corrected sensor body is also arranged between the grating tilt angle sensor body and the detected body. According to the invention, the initial inclination angle generated in the installation process can be compensated, and the inclination angle of the inclination angle sensor after installation is ensured to be 0 degree, so that the inclination angle measurement of the device is more accurate, and the installation is more convenient.

Description

Technical Field

[0001] The present invention belongs to the field of optical fiber sensing technology, relates to the sensing and demodulation of optical fiber gratings, and the structural design of optical fiber sensors. Specifically, it relates to a grating inclination sensor capable of realizing tilt correction during installation. Background Art

[0002] Fiber Bragg grating (FBG)-based inclination sensors have attracted widespread attention from researchers due to their advantages over traditional electromagnetic inclination sensors, including long-range measurement, high sensitivity, resistance to high temperatures and corrosion, strong immunity to electromagnetic interference, and large-scale reuse. They are widely used in geological disaster monitoring and early warning, building structural health monitoring, aerospace, and medical fields.

[0003] Existing fiber Bragg grating-based inclination sensors don't account for tilt compensation during installation. If the sensor is already tilted when mounted on the object being measured, the accuracy and range of the final inclination measurement will be affected. Furthermore, most reported fiber Bragg grating-based inclination sensors are designed and manufactured using a cantilever beam structure. However, without increasing the cantilever beam length and counterweight mass, these inclination sensors have low sensitivity and insufficient linearity when measuring at large angles.

[0004] Therefore, there is an urgent need for a grating inclination sensor with high sensitivity and capable of realizing tilt correction during the installation process. Summary of the Invention

[0005] The object of the present invention is to provide a grating inclination sensor that can realize tilt correction during the installation process, so that the inclination sensor can self-compensate for the tilt angle generated during the installation process, ensuring that its tilt angle is 0° before the formal measurement begins, thereby improving the sensitivity of the inclination sensor and the linearity of the measurement results.

[0006] To achieve the purpose of the present invention, the technical solution adopted is: a grating inclination sensor that can realize tilt correction during the installation process, including a grating inclination sensor body and a mounting component for connecting to the object to be detected, the mounting component and the sensor body are connected by a universal joint, and a component to be fixed after the sensor body is corrected is also provided between the grating inclination sensor body and the mounting component, or a component to be fixed after the sensor body is corrected is also provided between the grating inclination sensor body and the object to be detected.

[0007] Furthermore, the grating inclination sensor body includes a base plate and a pendulum, the base plate is connected to the universal joint, the pendulum is mounted on the base plate through a bearing, and a counterweight is mounted at the lower end of the pendulum; the sensor body also includes a fiber Bragg grating element fixed to the pendulum and the base plate after applying a certain prestress, and the counterweight swings under the constraint of the fiber Bragg grating element.

[0008] Furthermore, there are two fiber Bragg gratings on the fiber Bragg grating element, and the two fiber Bragg gratings are respectively located on both sides of the pendulum.

[0009] Furthermore, the pendulum is T-shaped, and two optical fiber fixing holes are provided on the shoulder of the pendulum. Both ends of the fiber Bragg grating element pass through the optical fiber fixing holes and are fixed in the optical fiber fixing holes.

[0010] Furthermore, a plurality of optical fiber fixing seats are provided on the bottom plate, and the plurality of optical fiber fixing seats are respectively located at the periphery of the pendulum and the counterweight block, and the fiber Bragg grating element is fixed to the bottom plate through the optical fiber fixing seats.

[0011] Furthermore, the optical fiber fixing hole is also filled with an adhesive, and the optical fiber Bragg grating element is fixed while passing through the optical fiber fixing hole through the adhesive.

[0012] Furthermore, the installation component is a box body, and the box body and the bottom plate are both provided with through holes for the optical fibers in the fiber Bragg grating element to pass through, and the box body and / or the bottom plate are also provided with line clips for fixing or winding the optical fibers.

[0013] Furthermore, the component is a slow-drying adhesive, and the box body is provided with a glue injection hole corresponding to the gap between the lower end of the grating inclination sensor body and the box body.

[0014] Furthermore, the pendulum and the counterweight are fixed by bonding with an adhesive.

[0015] The beneficial effects of the present invention are:

[0016] By connecting the mounting member to the grating inclination sensor body through a universal joint, after the mounting member is fixed on the object to be detected, the grating inclination sensor body can be vertically corrected by its own weight. By fixing the grating inclination sensor body after the correction, it is ensured that the vertical inclination angle of the grating inclination sensor is 0° before the formal measurement begins, thereby improving the sensitivity of the inclination sensor and the linearity of the measurement results.

[0017] The structural design of the present invention is compact and can be miniaturized; at the same time, the present invention focuses on practical engineering applications, so that the tilt sensor provided by the present invention is easy to produce, install and debug. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings illustrate exemplary embodiments of the present invention and together with the description serve to explain the principles of the present invention. These drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification.

[0019] Figure 1 This is a front view of the grating inclination sensor provided by the present invention that can achieve tilt correction during installation;

[0020] Figure 2 This is a three-dimensional view of the grating inclination sensor provided by the present invention that can achieve tilt correction during installation;

[0021] Figure 3 This is a packaging view of the grating inclination sensor provided by the present invention that can achieve tilt correction during installation;

[0022] Figure 4 This is the sensing system diagram of the tilt sensor;

[0023] Figure 5 This is a graph of the grating center wavelength data detected by the fiber Bragg grating demodulation device.

[0024] Markings and corresponding parts names in the accompanying drawings:

[0025] 1. Box body, 2. Bottom plate, 3. Pendulum, 4. Fiber fixing seat, 5. Counterweight, 6. Slow-drying adhesive, 7. Universal joint, 8. Stainless steel shaft, 9. Bearing, 10. Fiber Bragg grating, 11. Optical fiber, 12. Glue injection hole, 13. Fiber fixing hole. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It will be understood that the specific embodiments described herein are intended only to explain the relevant content and are not intended to limit the present invention. It should also be noted that, for ease of description, only portions relevant to the present invention are shown in the accompanying drawings.

[0027] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] like Figure 1 、 Figure 2As shown, the present invention provides a grating inclination sensor capable of achieving tilt correction during installation, comprising a grating inclination sensor body and a mounting member, wherein the mounting member and the sensor body are connected via a universal shaft 7. Specifically, the mounting member is used to install the present invention on the object to be detected, and the mounting member and the object to be detected are fixed by screws or the like. Furthermore, the universal shaft 7 can be a ball joint, a cross universal coupling, or the like. Both the universal shaft 7 and the mounting member, and the universal shaft 7 and the sensor body, can be hingedly connected by a stainless steel shaft 8. This ensures that after the mounting member is fixed to the object to be detected, the sensor body can swing to a vertical position on the mounting member due to gravity, enabling the present invention to achieve automatic correction of the sensor body after installation.

[0029] To prevent the sensor body from swinging freely during subsequent testing, which could affect the tilt angle detection, the sensor body must be secured after it is vertical. Specifically, if the mounting member is large enough, the sensor body can be secured directly to the mounting member using an assembly after it is vertical. If the mounting member is small, the sensor body can be secured directly to the object being tested using an assembly after it is vertical.

[0030] In the present invention, while ensuring that the sensor body can be swung to a vertical state on the mounting member by gravity after the mounting member is fixed on the object to be detected, the universal joint 7 in the present invention can also be replaced by other connecting devices that can rotate freely along the X-axis and the Y-axis. The sensor body is hoisted on the mounting member through the connecting device, so that after the mounting member is fixed on the object to be detected, the sensor body can also be swung to a vertical state by gravity. That is, the sensor body of the present invention can also achieve automatic correction after installation.

[0031] The grating inclination sensor body of the present invention includes a base plate 2 and a pendulum 3. The axial direction of the pendulum 3 is aligned with the axial direction of the base plate 2, and the central axis of the pendulum 3 and the central axis of the base plate 2 are in the same vertical plane. A universal joint 7, using a stainless steel shaft 8, is hingedly connected to the base plate 2, thereby connecting the grating inclination sensor body and the mounting structure via the universal joint 7. The pendulum 3 also has a mounting hole, and the base plate 2 also has an optical axis. The pendulum 3 is mounted on the optical axis through the mounting hole, allowing the pendulum 3 to swing around the optical axis after installation on the base plate 2. Furthermore, to minimize friction between the mounting hole wall and the outer wall of the optical axis, a bearing 9 is also mounted on the optical axis. The pendulum 3 is mounted on the bearing 9 through the mounting hole, connecting the pendulum 3 to the base plate 2 via the bearing 9, minimizing frictional resistance encountered by the pendulum 3 during its swing. A counterweight 5 is also fixedly mounted on the lower end of the pendulum 3.

[0032] The sensor body also includes a fiber Bragg grating (FBG) element, which includes an optical fiber 11 and a fiber Bragg grating (FBG) 10 mounted on the optical fiber 11. During installation, the FBG element of the present invention is first prestressed and then secured to the pendulum 3 and base plate 2, allowing the counterweight 5 to swing under the constraints of the FBG element. Once installed, since the FBG element is secured to the pendulum 3 and base plate 2, the pendulum 3 pulls on the FBG element as it swings, causing deformation of the FBG 10 therein, thereby detecting the tilt angle.

[0033] The fiber Bragg grating element of the present invention includes two fiber Bragg gratings 10, each having a different center wavelength. The two fiber Bragg gratings 10 are located on either side of a pendulum 3. When the tilt angle changes, the pendulum 3 swings relative to the base plate 2, causing the two fiber Bragg gratings 10 to be stretched and bent. Since the tension on the fiber Bragg grating 10 is proportional to the change in its wavelength, and the center wavelength of the fiber Bragg grating 10 remains unchanged when bent, the tilt direction and angle can be determined. Because the fiber Bragg grating 10 is also very sensitive to temperature changes, in order to eliminate temperature cross-sensitivity, the present invention subtracts the wavelength changes of the two fiber Bragg gratings 10 to eliminate temperature cross-sensitivity. In the present invention, the wavelength difference between the two fiber Bragg gratings 10 corresponds one-to-one to the tilt angle and tilt direction.

[0034] The pendulum 3 is T-shaped. When the pendulum 3 is installed, the horizontal portion of the pendulum 3 is mounted on the base plate 2 via the bearing 9, while the counterweight 5 is mounted on the lower end of the vertical portion of the pendulum 3. At the same time, two optical fiber fixing holes 13 are provided on the horizontal portion of the pendulum 3. The two optical fiber fixing holes 13 are respectively located at the two ends of the horizontal portion of the pendulum 3. When the fiber Bragg grating element is installed, the ends of the optical fibers 11 in the fiber Bragg grating element extend outward through the optical fiber fixing holes 13. After the ends of the optical fibers 11 pass through the optical fiber fixing holes 13, the portion of the optical fibers 11 located in the optical fiber fixing holes 13 is fixed within the optical fiber fixing holes 13, thereby achieving fixation between the fiber Bragg grating element and the pendulum 3.

[0035] In order to facilitate the fixation between the optical fiber 11 in the fiber Bragg grating element and the base plate 2, the base plate 2 is further provided with a plurality of optical fiber fixing seats 4. The plurality of optical fiber fixing seats 4 are arranged at intervals along the periphery of the pendulum 3 and the counterweight 5. When the fiber Bragg grating element is installed, the optical fiber 11 in the fiber Bragg grating element is fixed to the base plate 2 through the optical fiber fixing seats 4, which makes the fixation of the optical fiber 11 simpler. At the same time, when the fiber Bragg grating element is installed, the fiber Bragg grating 10 on the fiber Bragg grating element is located between the portion where the optical fiber 11 is fixed to the pendulum 3 and the portion where the optical fiber 11 is fixed to the base plate 2, thereby ensuring that the fiber Bragg grating 10 is deformed when the pendulum 3 swings.

[0036] In the present invention, to facilitate the securing of redundant optical fibers 11, both the box body and the base plate are provided with wire clips for securing or winding the optical fibers 11. Multiple wire clips are provided on both the box body 1 and the base plate 2. The multiple wire clips on the box body 1 are spaced apart along the four sides of the back of the box body 1, while the multiple wire clips on the base plate 2 are spaced apart along the four sides of the base plate 2. This allows the redundant optical fibers 11 in the fiber Bragg grating (FBG) element to be wound together on the multiple wire clips in the box body or on the multiple wire clips on the base plate 2 when the fiber Bragg grating element is arranged. In the present invention, the optical fiber fixing seat 4 can also directly serve as a wire clip. Furthermore, since the optical fiber fixing seat 4 is already provided on the base plate 2, the wire clips can be omitted from the base plate 2 if there is insufficient space for wire clips.

[0037] When installing the fiber Bragg grating element, after a certain prestress is applied to the fiber Bragg grating element, an adhesive 6 is injected into the fiber fixing hole 13 and onto the fiber fixing seat 4. After the adhesive 6 is cured, the fiber Bragg grating element is fixed together in the fiber fixing hole 13 and the fiber fixing seat 4, thereby achieving the fixation of the fiber Bragg grating element. This makes the installation of the fiber Bragg grating element more convenient without causing damage to the fiber Bragg grating element.

[0038] In the present invention, since the outer side of the counterweight block 5 is provided with a fiber fixing seat 4, the swing range of the counterweight block 5 can be further limited by the fiber fixing seat 4. This design can prevent the fragile fiber Bragg grating 10 from being broken due to large-angle tilt and vibration during installation and transportation.

[0039] In the present invention, the counterweight 5 can be a copper block, an iron block, a stainless steel block, etc., and the material and shape of the counterweight 5 can be selected at will while ensuring that the counterweight 5 can be used as a counterweight. At the same time, in the present invention, the pendulum 3 and the counterweight 5 can be fixed with an adhesive, which can be an acrylic structure AB glue, etc. Of course, without affecting the accuracy of the grating inclination sensor, the connection between the counterweight 5 and the pendulum 3 can also be achieved by plugging, threading, bolting, etc.

[0040] like Figure 3 As shown, the mounting member is a box body 1 having dimensions of 68 mm × 45 mm × 139 mm, so that the base plate 2, the pendulum 3, the counterweight 5, the fiber Bragg grating element, etc. are all encapsulated in the box body 1, effectively protecting the fiber Bragg grating element, etc., and improving the service life of the present invention; at the same time, through holes corresponding to the optical fiber fixing holes 13 are opened on the box body 1 and the base plate 2, so that after the fiber Bragg grating element is installed, the ends of the optical fibers 11 in the fiber Bragg grating element can sequentially extend outward through the through holes on the base plate 2 and the through holes on the box body 1.

[0041] The component used to secure the base plate 2 to the box body 1 is a slow-drying adhesive 6. The initial curing time of the slow-drying adhesive 6 is 6 to 8 hours, and the complete curing time of the slow-drying adhesive 6 is approximately 24 hours. Furthermore, the box body 1 is provided with an injection hole 12. The injection hole 12 is positioned below the position of the counterweight 5 and preferably corresponds to the gap between the base plate 2 and the inner wall of the box body 1. When the slow-drying adhesive 6 is injected into the box body 1 through the injection hole 12, the slow-drying adhesive 6 is located between the lower end of the base plate 2 and the inner wall of the box body 1. Since the slow-drying adhesive 6 is initially liquid, after the box body 1 is secured to the object being tested, the base plate 2 and the pendulum 3 mounted on the base plate 2 can still be maintained in a vertical position due to gravity. That is, within 1 to 3 hours after the slow-drying adhesive 6 is injected into the box body 1, the tilt angle generated during the installation process can be compensated. As the slow-drying adhesive 6 cures, the base plate 2, which remains in a vertical position, is secured, and tilt angle measurement can then begin.

[0042] In order to prevent the slow-drying adhesive 6 injected into the box body 1 from being excessive and fixing the counterweight 5 on the base plate 2, on the one hand, the amount of the injected slow-drying adhesive 6 can be controlled. On the other hand, an overflow hole can be opened on the box body 1, and the height of the overflow hole can be made between the lowest position of the counterweight 5 and the lowest position of the base plate 2, and the position of the overflow hole is higher than the position of the glue injection hole 12. When the slow-drying adhesive 6 injected into the box body 1 through the glue injection hole 12 overflows from the overflow hole, the injection of glue into the box body 1 is stopped.

[0043] The housing 1, base plate 2, pendulum 3, and universal joint 7 can be made by 3D printing, injection molding, or metal processing (including but not limited to CNC processing, stamping, casting, etc.). The material and molding method of the housing 1, base plate 2, pendulum 3, and universal joint 7 can be adjusted according to needs while ensuring the normal use of the grating inclination sensor.

[0044] During installation, the present invention first fixes the box body 1 on the object to be tested. After the box body 1 is fixed, the bottom plate 2 and the pendulum 3 on the bottom plate 2 are kept in a vertical state by gravity, thereby realizing the function of compensating for the installation tilt angle. Then, a slow-drying adhesive 6 is injected into the box body 1 through the glue injection hole 12. The initial state of the slow-drying adhesive 6 is liquid. Therefore, during the glue injection process and within 1 to 3 hours after the glue injection, the bottom plate 2 and the pendulum 3 on the bottom plate 2 will also be kept in a vertical state due to gravity. The slow-drying adhesive 6 will be initially cured within 6 to 8 hours after the glue injection, and the slow-drying adhesive 6 will be initially and completely cured 24 hours after the glue injection, thereby realizing the function of compensating for the installation tilt angle.

[0045] When the tilt angle of the object being detected changes, the two fiber Bragg gratings 10 are stretched and bent respectively. Since the tension on the fiber Bragg grating 10 is proportional to the change in its wavelength, and the central wavelength of the fiber Bragg grating 10 remains unchanged when it is bent, the tilt direction and angle of the object being detected can be determined.

[0046] When the present invention is used, Figure 4 As shown, the tilt sensor system includes a broadband light source, an optical isolator, an optical circulator, a tilt sensor, a fiber Bragg grating (FBG) demodulator, and a computer. The broadband laser light emitted by the broadband light source passes through the optical isolator and is connected to the optical circulator. The optical circulator transmits the broadband laser light into two serially connected fiber Bragg gratings (FBGs) 10 of the tilt sensor described herein. The center wavelength reflected by the FBGs 10 passes through the optical circulator and reaches the FBG demodulator. Finally, the computer receives the center wavelength data output by the FBG demodulator, thereby completing the measurement of tilt changes. In this system, the optical attenuator regulates the laser power emitted by the broadband light source to prevent distortion of the reflected signal from the FBG 10 detected by the FBG demodulator. The optical circulator ensures that the signal emitted by the broadband light source propagates only in a clockwise direction within the circulator, ensuring that the light signal reflected by the FBG is received only by the FBG demodulator and cannot return to the broadband light source. The grating interrogator can receive the light signal reflected by the fiber Bragg grating and detect its central wavelength, and then send the data to the computer to complete the tilt sensing detection.

[0047] The following is an example of a tilt sensing experimental device composed of three angular displacement platforms that can generate tilt angles of ±20°, ±15°, and ±15° respectively. The angular displacement platforms in the middle layer and the lower layer are used to simulate the tilt errors along the X-axis and Y-axis when the tilt sensor is installed on the object to be measured. The experimental results show that the proposed tilt angle compensation scheme of the universal joint 7 combined with epoxy resin can correct the ±5° tilt error generated by the tilt sensor along the X-axis and Y-axis respectively; then, the angular displacement platforms in the middle layer and the lower layer are fixed, and the tilt angle of the angular displacement platform in the upper layer is changed to test the tilt measurement performance of the tilt sensor. At this time, the grating center wavelength data obtained by the grating demodulation device is as follows: Figure 5 The final experimental results show that the sensor can achieve ±20° tilt angle measurement, and the measured tilt sensing data has good linearity.

[0048] In the description of this specification, the description with reference to the terms "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine different embodiments / methods or examples described in this specification and the features of different embodiments / methods or examples, unless they are contradictory.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0050] It should be understood by those skilled in the art that the above embodiments are merely for the purpose of illustrating the present invention clearly, and are not intended to limit the scope of the present invention. For those skilled in the art, other changes or modifications may be made based on the above disclosure, and such changes or modifications are still within the scope of the present invention.

Claims

1. A grating inclination sensor capable of realizing tilt correction during installation, characterized in that: The invention comprises a grating inclination sensor body and a mounting component for connecting with a detected object, wherein the mounting component is connected to the sensor body via a universal shaft (7), and a component to be fixed after the sensor body is calibrated is provided between the grating inclination sensor body and the mounting component, or a component to be fixed after the sensor body is calibrated is provided between the grating inclination sensor body and the detected object.

2. The grating inclination sensor capable of realizing tilt correction during installation according to claim 1, characterized in that: The grating inclination sensor body comprises a base plate (2) and a pendulum (3), wherein the base plate (2) is connected to a universal joint (7), the pendulum (3) is mounted on the base plate (2) via a bearing (9), and a counterweight (5) is mounted on the lower end of the pendulum (3); the sensor body also comprises a fiber Bragg grating element fixed to the pendulum (3) and the base plate (2) after a certain prestress is applied, and the counterweight (5) swings under the constraint of the fiber Bragg grating element.

3. The grating inclination sensor capable of achieving tilt correction during installation according to claim 2, characterized in that: There are two fiber Bragg gratings (10) on the fiber Bragg grating element, and the two fiber Bragg gratings (10) are respectively located on both sides of the pendulum (3).

4. The grating inclination sensor capable of achieving tilt correction during installation according to claim 2, characterized in that: The pendulum (3) is T-shaped, and two optical fiber fixing holes (13) are provided on the shoulder of the pendulum (3). Both ends of the optical fiber Bragg grating element pass through the optical fiber fixing holes (13) and are fixed in the optical fiber fixing holes (13).

5. The grating inclination sensor capable of realizing tilt correction during installation according to claim 4, characterized in that: The optical fiber fixing hole (13) is also filled with an adhesive, and the optical fiber Bragg grating element is fixed while passing through the optical fiber fixing hole (13) through the adhesive.

6. The grating inclination sensor capable of achieving tilt correction during installation according to claim 2, characterized in that: A plurality of optical fiber fixing seats (4) are provided on the base plate (2), the optical fiber fixing seats (4) are respectively located on the periphery of the pendulum (3) and the counterweight (5), and the optical fiber Bragg grating element is fixed on the base plate (2) via the optical fiber fixing seats (4).

7. The grating inclination sensor capable of achieving tilt correction during installation according to claim 2, characterized in that: The mounting member is a box body (1), and the box body (1) and the bottom plate (2) are both provided with through holes for the optical fiber (10) in the fiber Bragg grating element to pass through, and the box body (1) and / or the bottom plate (2) are also provided with line clips for fixing or winding the optical fiber (11).

8. The grating inclination sensor capable of achieving tilt correction during installation according to claim 8, characterized in that: The component is a slow-drying adhesive (6), and the box body (1) is also provided with a glue injection hole (12) corresponding to the gap between the lower end of the grating inclination sensor body and the box body (1).

9. The grating inclination sensor capable of achieving tilt correction during installation according to claim 2, characterized in that: The pendulum (3) and the counterweight (5) are bonded and fixed by an adhesive.

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