A grating tilt sensor capable of tilt correction during installation

Abstract

The application discloses a grating tilt sensor capable of realizing installation process tilt correction based on the strain sensitive principle of fiber Bragg grating and belongs to the technical field of optical fiber sensing, which comprises a grating tilt sensor body and a mounting component for being connected with a detected body, the mounting component is connected with the sensor body through a universal shaft, and a component to be fixed after correction of the sensor body is arranged between the grating tilt sensor body and the mounting component or between the grating tilt sensor body and the detected body. The application can compensate for the initial tilt angle generated in the installation process, so that the tilt angle of the tilt sensor after installation is ensured to be 0°, thereby making the tilt angle measurement of the device more accurate and the installation more convenient.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing technology, and relates to the sensing and demodulation of fiber optic gratings and the structural design of fiber optic sensors. Specifically, it relates to a grating tilt sensor that can realize tilt correction during the installation process. Background Technology

[0002] Fiber Bragg grating-based tilt sensors have attracted widespread attention from researchers due to their advantages over traditional electromagnetic tilt sensors, including longer measurement distances, higher sensitivity, resistance to high temperatures and corrosion, stronger resistance to electromagnetic interference, and large-scale reusability. They can be widely applied in fields such as geological disaster monitoring and early warning, building structural health monitoring, aerospace, and medicine.

[0003] Current fiber Bragg grating-based tilt sensors do not consider the compensation for tilt angle during installation. If the tilt sensor is tilted when installed on the object being measured, the accuracy and range of the final tilt measurement will be affected. Furthermore, most reported fiber Bragg grating-based tilt sensors are designed and manufactured using cantilever beam structures; however, tilt sensors based on this structure have low sensitivity without increasing the cantilever beam length and counterweight mass, and the linearity of the measurement results is also insufficient when measuring large angles.

[0004] Therefore, there is an urgent need for a grating tilt sensor with high sensitivity that can achieve tilt correction during installation. Summary of the Invention

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

[0006] To achieve the objective of this invention, the technical solution adopted is as follows: a grating tilt sensor capable of tilt correction during installation, comprising a grating tilt sensor body and a mounting component for connecting with the object being tested, the mounting component being connected to the sensor body via a universal joint, and a component for fixing the sensor body after calibration being provided between the grating tilt sensor body and the mounting component, or a component for fixing the sensor body after calibration being provided between the grating tilt sensor body and the object being tested.

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

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

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

[0010] Furthermore, the base plate is provided with multiple fiber optic mounting brackets, which are located around the pendulum and the counterweight, and the fiber Bragg grating element is fixed to the base plate through the fiber optic mounting brackets.

[0011] Furthermore, the fiber fixing hole is also filled with adhesive, which allows the fiber Bragg grating element to pass through the fiber fixing hole and be fixed at the same time.

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

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

[0014] Furthermore, the pendulum and the counterweight are bonded and fixed together with an adhesive.

[0015] The beneficial effects of this invention are:

[0016] By connecting the mounting component to the grating tilt sensor body via a universal joint, and fixing the mounting component to the object being measured, the grating tilt sensor body can be vertically corrected by its own weight. By fixing the grating tilt sensor body after correction, the vertical tilt angle of the grating tilt sensor is guaranteed to be 0° before the measurement begins, thus improving the sensitivity of the tilt sensor and the linearity of the measurement results.

[0017] The present invention features a compact structural design that enables miniaturization; at the same time, the present invention focuses on practical engineering applications, making the tilt sensor provided by the present invention easy to manufacture, install and debug. Attached Figure Description

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

[0019] Figure 1 This is a front view of the grating tilt sensor provided by the present invention, which enables tilt correction during the installation process;

[0020] Figure 2 This is a three-dimensional view of the grating tilt sensor provided by the present invention, which enables tilt correction during the installation process;

[0021] Figure 3 This is a packaged view of the grating tilt sensor provided by the present invention, which enables tilt correction during the installation process;

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

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

[0024] The attached diagram shows the markings and corresponding component names:

[0025] 1. Box body, 2. Base plate, 3. Pendulum, 4. Fiber optic mounting base, 5. Counterweight, 6. Slow-drying adhesive, 7. Universal joint, 8. Stainless steel shaft, 9. Bearing, 10. Fiber Bragg grating, 11. Fiber optic cable, 12. Adhesive injection hole, 13. Fiber optic cable fixing hole. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] like Figure 1 , Figure 2As shown, the present invention provides a grating tilt sensor capable of tilt correction during installation, comprising a grating tilt sensor body and a mounting component, wherein the mounting component is connected to the sensor body via a universal joint 7. Specifically, the mounting component is used to mount the present invention onto the object being tested, and the mounting component is fixed to the object being tested using screws or the like; meanwhile, the universal joint 7 can be a ball joint, a universal joint, or the like, and the universal joint 7 can be connected to the mounting component and the sensor body using a stainless steel shaft 8, thereby ensuring that after the mounting component is fixed to the object being tested, the sensor body can swing to a vertical state by gravity on the mounting component, enabling the sensor body to automatically correct itself after installation.

[0029] To prevent the sensor body from swinging arbitrarily during subsequent detection processes and affecting the tilt angle detection, the sensor body needs to be fixed after it is in a vertical position. Specifically, when the mounting component is large enough, the sensor body can be directly fixed to the mounting component after it is in a vertical position using a component; when the mounting component is small, the sensor body can be directly fixed to the object being detected using a component after it is in a vertical position.

[0030] In this invention, after the mounting component is fixed on the object being tested, the sensor body can swing to a vertical position by gravity on the mounting component. In this invention, the universal joint 7 can also be replaced by other connecting devices that can rotate freely along the X and Y axes. The sensor body is hoisted onto the mounting component by the connecting device, so that after the mounting component is fixed on the object being tested, the sensor body can also swing to a vertical position by gravity. That is, after installation, the sensor body can also achieve automatic calibration.

[0031] The grating tilt sensor body of this invention includes a base plate 2 and a pendulum 3. The axial direction of the pendulum 3 is consistent 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 on the same vertical plane. A universal joint 7 is hinged to the base plate 2 using a stainless steel shaft 8, thereby connecting the grating tilt sensor body and the mounting components via the universal joint 7. The pendulum 3 also has mounting holes, and the base plate 2 has an optical axis. The pendulum 3 is mounted on the optical axis through the mounting holes, allowing it to swing around the optical axis on the base plate 2 after installation. Simultaneously, to minimize friction between the mounting hole wall and the outer wall of the optical axis, a bearing 9 can be installed on the optical axis. The pendulum 3 is then mounted on the bearing 9 through the mounting holes, connecting the pendulum 3 and the base plate 2 via the bearing 9, minimizing frictional resistance during the swing of the pendulum 3. A counterweight 5 is also fixedly installed at the lower end of the pendulum 3.

[0032] The sensor body also includes a fiber Bragg grating element, which comprises an optical fiber 11 and a fiber Bragg grating 10 mounted on the optical fiber 11. During installation, a certain prestress is applied to the fiber Bragg grating element before it is fixed together to the pendulum 3 and the base plate 2, causing the counterweight 5 to swing under the constraint of the fiber Bragg grating element. After installation, because the fiber Bragg grating element is fixed together to the pendulum 3 and the base plate 2, the pendulum 3 pulls on the fiber Bragg grating element during swing, causing the fiber Bragg grating 10 within it to deform, thereby detecting the tilt angle.

[0033] In this invention, the fiber Bragg grating element comprises two fiber Bragg gratings 10, each with a different center wavelength. These two gratings 10 are located on opposite sides of a pendulum 3. When the tilt angle changes, the pendulum 3 oscillates relative to the base plate 2, causing the two gratings 10 to be stretched and bent. Since the tension on the grating 10 is proportional to its wavelength change, and the center wavelength remains constant during bending, the tilt direction and angle can be determined. Because the grating 10 is also highly sensitive to temperature changes, this invention eliminates temperature cross-sensitivity by subtracting the wavelength changes of the two gratings 10. In this invention, the wavelength difference between the two gratings 10 corresponds one-to-one with the tilt angle and tilt direction.

[0034] The pendulum 3 is T-shaped. During installation, the horizontal part of the pendulum 3 is mounted on the base plate 2 via bearing 9, while the counterweight 5 is mounted on the lower end of the vertical part of the pendulum 3. At the same time, two fiber optic fixing holes 13 are also provided on the horizontal part of the pendulum 3. The two fiber optic fixing holes 13 are located at both ends of the horizontal part of the pendulum 3, respectively. During installation, the fiber optic grating element has both ends of the fiber optic 11 extending outward through the fiber optic fixing holes 13. After both ends of the fiber optic 11 have passed through the fiber optic fixing holes 13, the part of the fiber optic 11 located in the fiber optic fixing holes 13 is fixed inside the fiber optic fixing holes 13, so that the fiber optic grating element and the pendulum 3 are fixed together.

[0035] To facilitate easier fixing of the fiber 11 in the fiber Bragg grating element to the base plate 2, the base plate 2 is also provided with multiple fiber fixing seats 4. The multiple 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 fiber 11 in the fiber Bragg grating element is fixed to the base plate 2 through the fiber fixing seats 4, making the fixing method of the 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 part where the fiber 11 is fixed on the pendulum 3 and the part where the fiber 11 is fixed on the base plate 2, thereby ensuring that the fiber Bragg grating 10 deforms when the pendulum 3 swings.

[0036] In this invention, to facilitate the fixing of redundant optical fibers 11, both the housing and the base plate are provided with wire clips for fixing or winding the optical fibers 11. Multiple wire clips are provided on both the housing 1 and the base plate 2. The multiple wire clips on the housing 1 are arranged at intervals around the back of the housing 1, while the multiple wire clips on the base plate 2 are arranged at intervals around the base plate 2. This allows the redundant optical fibers 11 in the fiber Bragg grating element to be wound together on multiple wire clips in the housing or on multiple wire clips on the base plate 2 during the arrangement of the fiber Bragg grating element. In this invention, the optical fiber fixing base 4 can also be directly a wire clip. Furthermore, since the base plate 2 already has an optical fiber fixing base 4, the wire clips can be omitted from the base plate 2 when there is insufficient space for them.

[0037] During installation, after a certain prestress is applied to the fiber Bragg grating element, adhesive 6 is injected into the fiber fixing hole 13 and the fiber fixing base 4. After the adhesive 6 cures, the fiber Bragg grating element is fixed together in the fiber fixing hole 13 and the fiber fixing base 4, thereby achieving the fixation of the fiber Bragg grating element. This makes the installation of the fiber Bragg grating element more convenient without damaging it.

[0038] In this invention, since the counterweight 5 has an optical fiber fixing seat 4 on its outer side, the swing range of the counterweight 5 can be further limited by the optical fiber fixing seat 4. This design can prevent the fragile fiber Bragg grating 10 from breaking due to large-angle tilting and vibration during installation and transportation.

[0039] In this invention, the counterweight 5 can be made of copper, iron, stainless steel, etc. The material and shape of the counterweight 5 can be arbitrarily selected as long as it can be used for counterweighting. At the same time, in this invention, the pendulum 3 and the counterweight 5 can be fixed with an adhesive, such as acrylic AB glue. Of course, without affecting the accuracy of the grating tilt sensor, the connection between the counterweight 5 and the pendulum 3 can also be made by plugging, threaded connection, bolt connection, etc.

[0040] like Figure 3 As shown, the mounting component is a housing 1 with dimensions of 68mm × 45mm × 139mm. The base plate 2, pendulum 3, counterweight 5, fiber Bragg grating elements, etc. are all encapsulated within the housing 1, effectively protecting the fiber Bragg grating elements and improving the service life of the invention. At the same time, both the housing 1 and the base plate 2 have through holes corresponding to the fiber fixing holes 13, so that after the fiber Bragg grating elements are installed, the two ends of the fiber 11 in the fiber Bragg grating elements can extend outward by passing through the through holes on the base plate 2 and the housing 1 in sequence.

[0041] The component used to fix 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 6-8 hours, and the complete curing time is approximately 24 hours. Simultaneously, the box body 1 is provided with an injection hole 12. The injection hole 12 must be positioned below the position of the counterweight 5, and preferably correspond to the gap between the base plate 2 and the inner wall of the box body 1. This ensures that when the slow-drying adhesive 6 is injected into the box body 1 through the injection hole 12, it is located between the lower end of the base plate 2 and the inner wall of the box body 1. Since the initial state of the slow-drying adhesive 6 is liquid, after the box body 1 is fixed to the object being tested, the base plate 2 and the pendulum 3 mounted on the base plate 2 can still maintain a vertical state under the influence of gravity. That is, within 1-3 hours after the slow-drying adhesive 6 is injected into the box body 1, it can compensate for the tilt angle generated during installation. As the slow-drying adhesive 6 cures, the vertically positioned base plate 2 is fixed, and the tilt angle can then be measured.

[0042] To prevent the counterweight 5 from being fixed to the base plate 2 due to excessive slow-drying adhesive 6 injected into the box body 1, the amount of slow-drying adhesive 6 injected 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 is 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 injection hole 12. When the slow-drying adhesive 6 injected into the box body 1 through the injection hole 12 overflows from the overflow hole, the injection of adhesive into the box body 1 is stopped.

[0043] The housing 1, base plate 2, pendulum 3, and universal joint 7 can be manufactured by 3D printing, injection molding, or metal processing (including but not limited to CNC machining, stamping, casting, etc.). The materials and molding methods of the housing 1, base plate 2, pendulum 3, and universal joint 7 can be adjusted according to requirements, provided that the grating tilt sensor can function properly.

[0044] During installation, the present invention first fixes the box body 1 onto the object being tested. After the box body 1 is fixed, the base plate 2 and the pendulum 3 on the base plate 2 remain vertical under the action of gravity, thus achieving the function of compensating for the installation tilt angle. Next, a slow-drying adhesive 6 is injected into the box body 1 through the injection hole 12. The slow-drying adhesive 6 is initially in a liquid state. Therefore, during the injection process and for 1 to 3 hours after injection, the base plate 2 and the pendulum 3 on the base plate 2 will also remain vertical under the action of gravity. The slow-drying adhesive 6 initially cures within 6 to 8 hours after injection and is initially fully cured within 24 hours after injection, thereby achieving the function of compensating for the installation tilt angle.

[0045] When the tilt angle of the object being tested 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 center wavelength of the fiber Bragg grating 10 remains unchanged when it is bent, the tilt direction and angle of the object being tested can be determined.

[0046] When using this invention, as 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 demodulation device, and a computer. 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 cascaded fiber Bragg gratings 10 of the tilt sensor described in this invention. The center wavelength reflected by the fiber Bragg gratings 10 passes through the optical circulator and reaches the fiber Bragg grating demodulation device. Finally, the computer receives the center wavelength data output by the fiber Bragg grating demodulation device, thereby completing the measurement of tilt angle changes. In this system, the optical attenuator adjusts the laser power emitted by the broadband light source to prevent distortion of the reflected signal from the fiber Bragg gratings 10 detected by the fiber Bragg grating demodulation device. The optical circulator ensures that the signal emitted by the broadband light source can only propagate clockwise within the circulator, guaranteeing that the light signal reflected by the fiber Bragg gratings can only be received by the fiber Bragg grating demodulation device and cannot return to the broadband light source. A grating demodulator can receive light signals reflected by fiber Bragg gratings and detect their center wavelength, and then send the data to a computer to complete the tilt sensing detection.

[0047] The following example uses a tilt sensing experimental device composed of three angular displacement platforms capable of generating tilt angles of ±20°, ±15°, and ±15° respectively. The middle and lower angular displacement platforms are used to simulate the tilt errors along the X and Y axes when the tilt sensor is mounted on the object being measured. Experimental results show that the proposed tilt angle compensation scheme using the universal joint 7 and epoxy resin can correct the ±5° tilt angle error generated by the tilt sensor along the X and Y axes respectively. Subsequently, the middle and lower angular displacement platforms are fixed, and the tilt angle of the upper angular displacement platform is changed to test the tilt measurement performance of the tilt sensor. At this time, the grating center wavelength data acquired by the grating demodulation device is as follows: Figure 5 As shown in the figure. The final experimental results show that the sensor can achieve tilt angle measurement of ±20°, and the measured tilt angle sensing data has good linearity.

[0048] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0050] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A grating tilt sensor capable of tilt correction during installation, characterized in that, The sensor body includes a grating tilt sensor body and a mounting component for connecting to the object being tested. The mounting component is connected to the sensor body via a universal joint (7). A component for fixing the sensor body after calibration is also provided between the grating tilt sensor body and the mounting component, or a component for fixing the sensor body after calibration is also provided between the grating tilt sensor body and the object being tested. The grating tilt sensor body includes a base plate (2) and a pendulum (3). The base plate (2) is connected to the universal joint (7). The pendulum (3) is mounted on the base plate (2) via a bearing (9), and a counterweight (5) is installed at the lower end of the pendulum (3). The sensor body also includes components that are fixed together to the pendulum (3) and the base plate (2) after a certain prestress is applied. The counterweight (5) swings under the constraint of the fiber Bragg grating element; the mounting component is a box (1), and the box (1) and the base plate (2) are provided with through holes for the fiber (11) in the fiber Bragg grating element to pass through, and the box (1) and / or the base plate (2) are also provided with wire clips for fixing or winding the fiber (11); the component is a slow-drying adhesive (6), and the box (1) is also provided with a glue injection hole (12) corresponding to the gap between the lower end of the grating tilt sensor body and the box (1). The position of the glue injection hole (12) must be lower than the position of the counterweight (5), and the gap between the glue injection hole (12) and the base plate (2) and the inner wall of the box (1) corresponds to the gap between the base plate (2) and the inner wall of the box (1).

2. The grating tilt sensor capable of tilt correction during installation according to claim 1, characterized in that, The fiber Bragg grating (10) on the fiber Bragg grating element consists of two fiber Bragg gratings (10), which are located on both sides of the pendulum (3).

3. The grating tilt sensor capable of tilt correction during installation according to claim 1, characterized in that, The pendulum (3) is T-shaped, and two fiber optic fixing holes (13) are opened on the shoulder of the pendulum (3). The two ends of the fiber Bragg grating element pass through the fiber optic fixing holes (13) and are fixed in the fiber optic fixing holes (13).

4. The grating tilt sensor capable of tilt correction during installation according to claim 3, characterized in that, The fiber fixing hole (13) is also filled with adhesive, which allows the fiber Bragg grating element to pass through the fiber fixing hole (13) and be fixed at the same time.

5. The grating tilt sensor capable of tilt correction during installation according to claim 1, characterized in that, The base plate (2) is provided with multiple fiber optic mounting bases (4), which are located around the pendulum (3) and the counterweight (5), and the fiber Bragg grating element is fixed on the base plate (2) through the fiber optic mounting bases (4).

6. The grating tilt sensor capable of tilt correction during installation according to claim 1, characterized in that, The pendulum (3) and the counterweight (5) are bonded together with an adhesive.

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