Fiber grating three-way strain sensor

Abstract

The application discloses a fiber grating three-way strain sensor, and belongs to the technical field of fiber sensing, which comprises a base and an optical fiber; the base comprises eight fan-shaped plate components which are uniformly distributed along the circumference of the base; every two fan-shaped plate components which are centrally symmetrical relative to the center of the base form a group, and four groups of the fan-shaped plate components correspond to form four grating areas; three of the four grating areas are strain measurement grating areas, and one is a temperature compensation grating area; the two fan-shaped plate components of each strain measurement grating area are independent split structures and are used for fixed connection with a structure to be measured; the two fan-shaped plate components of the temperature compensation grating area are integrated whole structures, and only one of them is used for fixed connection with the structure to be measured; the base is provided with an optical fiber positioning groove along the preset laying direction of the optical fiber; the optical fiber positioning groove has four positioning layers which correspond to the four grating areas one by one; each positioning layer is provided with a containing channel for containing the optical fiber of the corresponding grating area, and the containing channels are arranged along the same central axis.

Description

Technical Field

[0001] This application belongs to the field of fiber optic sensing technology, specifically relating to a fiber optic grating triaxial strain sensor. Background Technology

[0002] Existing fiber Bragg grating triaxial strain sensors are large in size and difficult to install, which limits their promotion and practical application in small spaces, confined installation environments, and high-density deployment scenarios. They are unable to meet the requirements for sensor miniaturization, integration, and ease of installation in such scenarios. Summary of the Invention

[0003] In view of this, this application provides a fiber optic grating triaxial strain sensor, the main purpose of which is to achieve miniaturization and integration of the sensor.

[0004] To achieve the above objectives, this application mainly provides the following technical solutions:

[0005] This application provides a fiber optic grating triaxial strain sensor, including a base and an optical fiber;

[0006] The base includes eight sector plate components, which are evenly distributed along the circumference of the base. Each pair of sector plate components is centrally symmetrical with respect to the center of the base and forms a group. The four groups of sector plate components respectively constitute four grating areas.

[0007] Of the four grating regions, three are strain measurement grating regions and one is a temperature compensation grating region; the two sector plate components of each strain measurement grating region are independent separate structures, and both of the two independent sector plate components are used for fixed connection with the structure under test; the two sector plate components of the temperature compensation grating region are integrally formed structures, and only one of the two integrally formed sector plate components is used for fixed connection with the structure under test;

[0008] The base has fiber positioning slots along the preset laying direction of the optical fiber. The fiber positioning slots have four positioning layers, each of which corresponds to one of the four grating areas. Each positioning layer has a receiving channel for accommodating the optical fiber corresponding to the grating area, and the receiving channels of each positioning layer are arranged along the same central axis, thereby forming a continuous optical fiber laying path.

[0009] Optionally, each of the sector plate components has at least one screw hole on the side away from the center of the base, the screw hole being used for detachable connection with the fixing bracket.

[0010] Optionally, the fixing bracket is an annular structure arranged coaxially with the base, the inner circumference of the annular structure is correspondingly fitted to the side of the eight fan-shaped plate components away from the center of the base, and is detachably connected to each of the fan-shaped plate components through the screw holes.

[0011] Optionally, the fixing bracket forms a detachable pre-positioning connection with all the sector plate components through screw holes on each sector plate component, which is used to limit the circumferential uniform distribution posture of each sector plate component during installation. After the sector plate component used for fixed connection with the structure under test is welded and fixed to the structure under test on the side away from the fixing bracket, the fixing bracket is removed, so that the welded and fixed sector plate component can independently maintain a fixed connection with the structure under test.

[0012] Optionally, the fan-shaped plate component used for fixed connection with the structure under test has spot weld grooves on the side away from the structure under test.

[0013] Optionally, each of the sector plate components used for fixed connection with the structure under test is provided with at least two spot weld grooves, and the at least two spot weld grooves are respectively located close to the two radial sides of the corresponding sector plate component.

[0014] Optionally, each of the accommodating channels of the four positioning layers is arranged radially along the angle bisector direction of the corresponding grating area.

[0015] Optionally, when the optical fiber is laid along the accommodating channel, it forms measurement segments distributed along the angle bisector of the grating area, and adjacent measurement segments are connected by a turning segment located at the circumferential edge of the grating area to form a continuous optical fiber laying path.

[0016] Optionally, the fiber optic cable laying path is a continuous reciprocating bending path.

[0017] Optionally, the optical fiber laying path is composed of four measurement segments and three turning segments connected alternately in sequence; the four measurement segments are laid one-to-one in the accommodating channels of the four grating areas, and each measurement segment extends radially along the angle bisector of the corresponding grating area; the three turning segments are located at the circumferential edges of two adjacent grating areas, and each turning segment connects to the ends of two adjacent measurement segments, forming a closed and continuous optical fiber laying loop.

[0018] By employing the above technical solution, this application has at least the following beneficial effects:

[0019] The fiber Bragg grating triaxial strain sensor provided in this application, by setting the base as eight circumferentially evenly distributed sector plate components and grouping them into three strain measurement grating areas and one temperature compensation grating area, combines the differentiated structure of the two sector plate components in the strain measurement grating area being independent and fixed to the structure under test, and the two sector plate components in the temperature compensation grating area being integrated and individually fixed. This differentiated structure can accurately capture triaxial strain signals and effectively eliminate temperature interference through the temperature compensation structure, ensuring measurement accuracy. At the same time, the base integrates four layers of coaxially arranged fiber positioning slots, which makes the fiber laying form a continuous and regular path, reducing fiber transmission loss and achieving a high degree of integration of the sensor structure, significantly reducing the overall size of the sensor and simplifying the installation process. Thus, it effectively solves the problems of large size and difficult installation of existing fiber Bragg grating triaxial strain sensors. While meeting the requirements of miniaturization, integration, and convenient installation in small spaces, confined installation environments, and high-density deployment scenarios, it also takes into account the accuracy and stability of triaxial strain measurement, expanding the sensor's application range. Attached Figure Description

[0020] Figure 1 This is a front view of a fiber Bragg grating triaxial strain sensor according to an optional embodiment of this application.

[0021] Figure 2 This is a schematic diagram of the back structure of a fiber Bragg grating triaxial strain sensor according to an optional embodiment of this application.

[0022] The reference numerals in the attached figures are as follows:

[0023] 100. Base; 200. Fiber optic cable; 300. Mounting bracket;

[0024] 1. Sector-shaped plate component; 2. Fiber optic positioning groove; 3. Screw hole; 4. Spot welding groove. Detailed Implementation

[0025] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0026] 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 one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0027] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0028] The preferred embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0029] See Figure 1 and Figure 2 As shown, according to an embodiment of this application, a fiber optic grating triaxial strain sensor is provided, including a base 100 and an optical fiber 200. The base 100 includes eight sector plate components 1, which are evenly distributed along the circumference of the base 100. Each pair of sector plate components 1 arranged symmetrically with respect to the center of the base 100 forms a group, and the four groups of sector plate components 1 respectively constitute four grating regions. Of the four grating regions, three are strain measurement grating regions, and one is a temperature compensation grating region. The two sector plate components 1 in each strain measurement grating region are independent separate structures. The sector plate components 1 are all used for fixed connection with the structure under test; the two sector plate components 1 of the temperature compensation grating area are integrally formed, and only one of the two integrally formed sector plate components 1 is used for fixed connection with the structure under test; the base 100 has an optical fiber positioning groove along the preset laying direction of the optical fiber 200. The optical fiber positioning groove has four positioning layers, and the four positioning layers correspond one-to-one with the four grating areas. Each positioning layer has a receiving channel for accommodating the optical fiber 200 of the corresponding grating area, and the receiving channels of each positioning layer are arranged along the same central axis, thereby forming a continuous optical fiber laying path.

[0030] The fiber Bragg grating triaxial strain sensor (hereinafter referred to as the sensor) provided in the embodiments of this application, by setting the base 100 as eight circumferentially evenly distributed fan-shaped plate components 1 and grouping them to form three strain measurement grating areas and one temperature compensation grating area, combines the differentiated structure of the two fan-shaped plate components 1 of the strain measurement grating area being independent and fixed to the structure under test, and the two fan-shaped plate components 1 of the temperature compensation grating area being integrated and only individually fixed, which can accurately capture triaxial strain signals and effectively eliminate temperature interference through the temperature compensation structure, ensuring measurement accuracy. At the same time, the base 100 integrates four layers of coaxially arranged fiber positioning slots, so that the fiber optic cable 200 is laid in a continuous and regular path, which reduces the transmission loss of the fiber optic cable 200 and achieves the goal of high integration of the sensor structure, significantly reducing the overall size of the sensor and simplifying the installation process. Thus, it effectively solves the problems of large size and difficult installation of existing fiber Bragg grating triaxial strain sensors, while meeting the requirements of miniaturization, integration and convenient installation of sensors in small spaces, narrow installation environments and high-density layout scenarios, and taking into account the accuracy and stability of triaxial strain measurement, thus expanding the applicability of the sensor.

[0031] The base 100 serves as the mechanical support structure for the sensor, used to fix the optical fiber 200 and connect the structure to be measured. At the same time, it separates strain transmission and temperature compensation through its own structure.

[0032] Specifically, the fiber optic cable 200 has a built-in fiber optic grating. The fiber optic grating will shift its wavelength with changes in external strain and temperature. By detecting the wavelength change, the strain magnitude can be inferred. At the same time, the fiber optic cable 200 can also perform signal transmission without the need for additional wires.

[0033] The base 100 is roughly disc-shaped and consists of eight sector-shaped plate components 1, which are evenly distributed along the circumference of the base 100.

[0034] Specifically, the sector-shaped plate component 1 refers to a component that is fan-shaped in shape, with a thickness much smaller than its radial length and arc length, and without obvious three-dimensional protrusions or heavy block structures. In this embodiment, eight sector-shaped plate components 1 are evenly distributed around the center of the base 100 in a 360° circumferential direction. The central angle of a single sector-shaped plate component 1 is 45°, and the included angle between two adjacent sector-shaped plate components 1 is also 45°, ensuring the uniformity and symmetry of the circumferential layout of the base 100.

[0035] It should be noted that when the material of the structure under test is concrete, metal, or similar materials, the material of the sector plate component 1 is preferably stainless steel, epoxy resin, or other materials with a similar coefficient of thermal expansion to the structure under test. By matching the coefficient of thermal expansion of the sector plate component 1 with that of the structure under test, the problem of thermal deformation incompatibility caused by the difference in materials is reduced. This avoids signal distortion during the strain transfer from the structure under test to the sector plate component 1, ensuring that the strain data subsequently detected by the fiber optic grating is consistent with the actual strain state of the structure under test, and guaranteeing the accuracy of strain measurement.

[0036] In order to achieve sensor miniaturization and integration, the base 100 integrates four independent grating areas. Each grating area is composed of a set of two centrally symmetrical sector plate components 1, and each grating area corresponds to a fiber optic grating segment.

[0037] Specifically, a set of two centrally symmetrical sector plate components 1 refers to a set of two sector plate components 1 that, with the center of the base 100 as the origin, can be rotated 180° to completely coincide with the other sector plate component 1. For example, the sector plate component 1 at the 12 o'clock position and the sector plate component 1 at the 6 o'clock position form a group, the sector plate component 1 at the 3 o'clock position and the sector plate component 1 at the 9 o'clock position form a group, and so on. Centrally symmetrical grouping ensures that the stress and temperature environment of each group of grating areas is consistent, avoiding measurement deviations caused by positional offsets.

[0038] The four grating areas are divided into three strain measurement grating areas and one temperature compensation grating area. The three strain measurement grating areas are arranged adjacent to each other along the circumference of the base 100, and with the center of the base 100 as the reference, the detection directions corresponding to the three strain measurement grating areas are 0°, 45° and 90°, respectively, so as to realize the synchronous detection of strain in three orthogonal directions of the structure under test.

[0039] Specifically, the two centrally symmetrical sector plate components 1 in the same strain measurement grating area are completely separate structures with no mechanical connection between them. Each sector plate component 1 can independently deform in response to the strain of the structure under test. Both sector plate components 1 are fixed to the surface of the structure under test by bonding, welding, or bolting. This effectively avoids mechanical interference between the two sector plate components 1, ensuring that the strain generated by the structure under test is directly and without attenuation transmitted to the sector plate component 1, and then transmitted to the fiber optic grating laid on it. This allows the strain measurement grating area to accurately capture the strain component of the structure under test in the centrally symmetrical direction. In contrast, the two centrally symmetrical sector plate components 1 in the temperature compensation grating area are integral structures manufactured by injection molding, machining, or other processing methods. This integral structure has high mechanical strength and will not undergo relative deformation due to external strain. Only one sector plate component 1 is fixedly connected to the structure under test, while the other sector plate component 1 is suspended. Therefore, the overall structure of the temperature-compensated grating region will not undergo local deformation due to the strain of the structure under test. Consequently, the fiber grating laid on this overall structure will not sense the strain signal. Simultaneously, the sector plate component 1, fixedly connected to the structure under test, can transfer the temperature of the structure to the fiber grating. Since the sector plate component 1 is suspended, it will not bear strain. Therefore, the fiber grating in the temperature-compensated grating region will only experience wavelength shift due to temperature changes. In this embodiment, by comparing the wavelength changes produced by the fiber gratings in the three strain measurement grating regions with those produced by the fiber grating in the temperature-compensated grating region, it is found that the fiber grating in the strain measurement grating region is affected by both strain and temperature, while the fiber grating in the temperature-compensated grating region is only affected by temperature. This allows temperature interference to be eliminated from the total signal of the strain measurement grating region, obtaining a pure strain signal. Ultimately, this solves the common problem of cross-sensitivity between temperature and strain in fiber grating sensors, effectively improving the accuracy of strain measurement.

[0040] To secure the optical fiber 200 and prevent it from loosening or shifting, a groove, known as an optical fiber positioning groove, is provided on one side of the base 100. This groove extends along the preset laying direction of the optical fiber 200. Here, the preset laying direction of the optical fiber 200 refers to the direction it follows after being laid on the base 100.

[0041] Specifically, taking any set of two centrally symmetrical sector plate components 1 as an example, the preset laying direction of the optical fiber 200 in the grating area corresponding to the set of sector plate components 1 is as follows: first, it extends along the radial direction of one of the sector plate components 1 in the set towards the central axis of the base 100; then, starting from the central axis of the base 100, it extends along the radial direction of the other sector plate component 1 in the set that is centrally symmetrical with the previous sector plate component 1 towards the other sector plate component 1, so that the optical fiber 200 can completely cover the two sector plate components 1 in the set and realize the signal sensing function of the corresponding grating area. For the grating area corresponding to another set of centrally symmetrical sector plate components 1 adjacent to the two centrally symmetrical sector plate components 1 of the base 100 along the circumference, the preset laying direction of the optical fiber 200 is consistent with the aforementioned grating area and is continuously connected: after completing the laying of the previous set of grating areas, that is, extending to the end of another sector plate component 1 in the set, the optical fiber 200 extends naturally along the circumferential direction of the base 100 and connects to the starting end of one of the sector plate components 1 corresponding to the adjacent set of grating areas. This extension path fits the circumferential tangent direction of the base 100 and is consistent with the circumferential distribution trajectory of the sector plate components 1. Subsequently, the optical fiber 200 extends along the radial direction of the sector plate component 1 in the adjacent set towards the central axis position of the base 100. Then, starting from the central axis position of the base 100, it extends along the radial direction of another sector plate component 1 in the adjacent set that is centrally symmetrical with the previous sector plate component 1 towards the other sector plate component 1, thereby completely covering the two sector plate components 1 of the adjacent set.

[0042] In order to realize the multi-purpose function of a single optical fiber 200 connecting multiple grating areas and to avoid mutual interference between the optical fiber 200 segments corresponding to each grating area, the optical fiber positioning groove on the base 100 is set as four positioning layers along the thickness direction of the base 100, and the four positioning layers correspond one-to-one with the four grating areas.

[0043] It should be noted that each positioning layer consists of grooves of varying depths, forming accommodating channels for the optical fiber 200. The inner diameter of these channels matches the outer diameter of the optical fiber 200, ensuring stable clamping and positioning. Through this layered structure, the optical fiber 200 segments corresponding to the four grating regions can be independently laid within their respective positioning layer accommodating channels. This achieves an integrated layout where a single optical fiber 200 sequentially connects the four grating regions, eliminating the need for multiple optical fibers 200 to connect each grating region separately. It also effectively prevents entanglement, crossing, or mechanical interference between the optical fiber 200 segments from different grating regions, while preventing mutual interference during signal transmission and ensuring the independence and stability of signal sensing in each grating region. Furthermore, to improve the stability of the optical fiber 200 laying, connection reliability, and signal transmission stability, the optical fiber 200 segments corresponding to the four grating regions can be independently laid within their respective positioning layer accommodating channels via glass welding, forming a robust connection structure.

[0044] Specifically, the four positioning layers are arranged coaxially with their respective accommodating channels, and their centers are all located on the same straight line. This straight line is completely coincident with the central axis of the base 100, that is, the central axis of each accommodating channel is collinear with the central axis of the base 100.

[0045] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 1 and Figure 2 As shown, each sector plate component 1 has at least one screw hole 3 on the side away from the center of the base 100, and the screw hole 3 is used for detachable connection with the fixed bracket 300.

[0046] Specifically, in this embodiment, each sector plate component 1 has two screw holes 3 at its edge facing outward from the geometric center of the base 100 and toward the circumferential outer edge of the sensor, and the two screw holes 3 are evenly distributed along the circumference of the base 100.

[0047] In the above embodiments, see Figure 1 and Figure 2 As shown, the fixed bracket 300 is a ring structure arranged coaxially with the base 100. The inner circumference of the ring structure is correspondingly attached to the side of the eight sector plate components 1 away from the center of the base 100, and is detachably connected to each sector plate component 1 through screw holes 3.

[0048] Here, the fixed bracket 300 forms a detachable pre-positioned connection with all the sector plate components 1 through the screw holes 3 on each sector plate component 1. This connection is used to limit the circumferential uniform distribution posture of each sector plate component 1 during installation. After the sector plate component 1, which is used to be fixedly connected to the structure under test, is welded and fixed to the structure under test on the side away from the fixed bracket 300, the fixed bracket 300 is removed, so that the welded and fixed sector plate component 1 can independently maintain a fixed connection with the structure under test.

[0049] It should be noted that the fixing bracket 300 is synchronously attached and fixed to all the sector plate components 1 through the screw holes 3. This can force the eight sector plate components 1 to maintain a preset posture of uniform circumferential distribution, avoiding the disruption of the centrally symmetrical grouping and 360° uniform distribution structural features due to the displacement of a single sector plate component 1 during installation. This ensures the precise alignment of the 0°, 45°, and 90° detection directions of the three strain measurement grating areas, while also ensuring the consistency of the stress and temperature environment of each group of grating areas. This provides a structural prerequisite for the directional accuracy and signal stability of subsequent triaxial strain detection. Based on this, there is no need to adjust the angle and spacing of each sector plate component 1 individually during installation. The fixing bracket 300 can complete the posture fixation of all sector plate components 1 at once, greatly reducing the installation difficulty. It is especially suitable for small spaces, narrow installation environments, and high-density layout scenarios, which is consistent with the goal of sensor miniaturization and integration, further realizing the purpose of convenient installation.

[0050] Furthermore, during installation, all sector plate components 1 are first fixed to the fixed bracket 300 via screw holes 3. Then, the side of each sector plate component 1 away from the fixed bracket 300 is welded to the structure under test. After welding, the fixed bracket 300 is removed. This installation method not only uses the fixed bracket 300 to fix the posture of each sector plate component 1 during the installation stage, but also eliminates additional mechanical constraints by subsequently removing the fixed bracket 300. When both sector plate components 1 in the strain measurement grating area are fixed to the structure under test, and only a single sector plate component 1 in the temperature compensation grating area is fixed to the structure under test and welded, removing the fixed bracket 300 will not interfere with the sector plate component 1 already fixed to the structure under test, while ensuring that the unfixed sector plates in the temperature compensation grating area remain unconstrained. This ensures that the strain in the strain measurement grating area is transmitted to the fiber optic grating without attenuation, and also ensures the functional independence of the temperature compensation grating area, which only senses temperature and not strain. This further avoids the risk of signal distortion during installation and effectively improves the accuracy of strain measurement.

[0051] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 1 As shown, the fan-shaped plate component 1, which is used to fix the structure to be tested, has spot weld grooves 4 on the side away from the structure to be tested.

[0052] In this embodiment, by opening a spot welding groove 4 on the side of the sector plate component 1 used for fixed connection with the structure under test away from the structure under test, a precise positioning reference and convenient operating space are provided for the welding operation. This facilitates the rapid completion of spot welding operations in small spaces, confined installation environments, and high-density layout scenarios, avoiding accidental welding to the fiber positioning groove or adjacent sector plate components 1 during the welding process, thus ensuring installation accuracy and efficiency. Furthermore, it concentrates the welding points within the spot welding groove 4, improving the stability and reliability of the welding connection, effectively avoiding problems such as incomplete welding and detachment, and ensuring a stable connection between the sector plate component 1 and the structure under test. This ensures that the strain of the structure under test can be directly and without attenuation transmitted to the sector plate component 1 and the fiber grating laid on it. At the same time, it meets the design goals of sensor miniaturization and integration without increasing the structural volume. In addition, the disassembly and assembly process of the fixed bracket 300 further avoids interference of the installation process on the measurement signal, providing process-level assurance for the accuracy and stability of strain measurement.

[0053] In this embodiment, the sector plate component 1 used for fixed connection with the structure under test refers to each sector plate component 1 in the three strain measurement grating areas, as well as the sector plate component 1 used for fixed connection with the structure under test in the temperature compensation grating area.

[0054] In the above embodiments, see Figure 1 and Figure 2 As shown, each of the sector plate components 1 used for fixed connection with the structure under test is provided with at least two spot weld grooves 4, and the at least two spot weld grooves 4 are respectively set close to the two radial sides of the corresponding sector plate component 1.

[0055] Here, a two-point symmetrical weld point layout forms a stable bidirectional fixing structure, effectively limiting the deflection, loosening, or displacement of the sector plate component 1 under stress, significantly improving the reliability and anti-detachment capability of the connection with the structure under test, and avoiding stress concentration or connection failure problems that may occur with single-point welding; at the same time, it enables the strain of the structure under test to be uniformly transmitted along the radial direction of the sector plate component 1, ensuring that the strain is efficiently and without distortion transmitted from the radial edge through the weld points to the entire sector plate component 1 and the fiber grating laid on it, avoiding strain transmission path deviation caused by improper weld point position. The layout avoids displacement or attenuation; at the same time, it does not require increasing the volume of the sector plate component 1, which fits the design goals of sensor miniaturization and integration. The two-point positioning further improves the accuracy of welding operations, avoiding accidental welding to the fiber positioning slot or adjacent components. Combined with the disassembly and assembly process of the fixed bracket 300, it not only ensures the independent deformation capability of the strain measurement grating area sector plate component 1, but also maintains the functional independence of the temperature compensation grating area. From the perspective of structural layout and process adaptation, it further consolidates the accuracy and stability of strain measurement, and adapts to the installation requirements of small space and high-density layout scenarios.

[0056] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 2 As shown, each of the four positioning layers has a accommodating channel that extends radially along the angle bisector of the corresponding grating area.

[0057] In this embodiment, by setting up four positioning layers, each accommodating channel extends radially along the angle bisector of the corresponding grating area. This allows the accommodating channel to adapt to the central symmetry structure and detection direction of the grating area, ensuring that the optical fiber 200 can completely fit the force transmission path of the fan-shaped plate component 1 when laid radially along the angle bisector, avoiding bending or twisting of the optical fiber 200, further reducing transmission loss and improving the stability of the fixed optical fiber 200. It also ensures that the fiber gratings of each strain measurement grating area are accurately aligned with the corresponding detection direction, so that the strain of the structure under test is transmitted to the optical fiber 200 radially along the angle bisector without offset or distortion, significantly improving the directional accuracy of the three-dimensional strain detection.

[0058] Specifically, in this embodiment, each grating area is composed of two fan-shaped plate members 1 that are centrally symmetrical with respect to the center of the base 100. The angle bisector of the member is the axis of symmetry of the overall fan-shaped area of ​​the grating area. Each accommodating channel extends along this axis of symmetry from the area near the center of the base 100 to the circumferential edge of the corresponding grating area.

[0059] In the above embodiments, see Figure 2 As shown, when the optical fiber 200 is laid along the accommodating channel, it forms measurement segments distributed along the angle bisector of the grating area. Adjacent measurement segments are connected by turning segments located at the circumferential edge of the grating area, forming a continuous optical fiber laying path.

[0060] Here, the measurement segments formed by the fiber optic cable 200 laid along the accommodating channel are distributed along the angle bisector of the grating area and connected into a continuous path by the turning segments at the circumferential edge of the grating area. This ensures that the measurement segments in each grating area precisely fit the main strain transmission path, guaranteeing that strain is transmitted to the fiber optic grating without distortion, further improving the directional accuracy and signal stability of triaxial strain detection. Simultaneously, it allows the turning segments to avoid the concentrated area of ​​the coaxial accommodating channel at the center of the base 100, preventing adjacent measurement segments from intersecting or causing mechanical interference in the central area. Furthermore, the curvature of the turning path at the circumferential edge is gentler. This reduces the bending stress and transmission loss of the optical fiber 200, ensuring the stable realization of the integrated layout of four grating areas connected in series by a single optical fiber 200; it also makes the entire optical fiber laying path highly compatible with the circumferential distribution of the fan-shaped plate component 1 and the layered structure of the four positioning layers, without the need for additional expansion of the base 100 space, which fits the miniaturization goal. Moreover, the regular measurement section and turning section path facilitates the laying, positioning and glass welding and fixing of the optical fiber 200, reducing the processing and installation difficulty, while maintaining the independence of signal sensing in each grating area and ensuring that the temperature compensation function is not affected.

[0061] In the above embodiments, see Figure 2 As shown, the fiber optic cable laying path is a continuous reciprocating bend.

[0062] Here, by setting the fiber optic laying path as a continuous reciprocating bending path, the reciprocating layout allows a single fiber 200 to form a compact and continuous connection between the four positioning layers and the four grating areas. This allows for complete coverage of all grating areas without additional path length extension, perfectly aligning with the sensor's miniaturization and integration design goals and effectively controlling the overall volume of the base 100. Furthermore, the reciprocating bending turning segments are concentrated at the circumferential edge of the grating area, maintaining the radial extension of the measuring segment along the angle bisector, and avoiding path intersections or excessive bending. The design addresses issues such as stress concentration and increased transmission loss in the Fiber 200, ensuring stable signal transmission. Simultaneously, the well-organized reciprocating path and the circumferentially distributed fan-shaped plate with layered coaxial accommodating channels are highly compatible with the structure. This facilitates precise laying, positioning, and glass welding of the Fiber 200, reducing processing and installation difficulty. It also ensures that each grating area measurement segment independently conforms to the strain transmission path, without interfering with the directional accuracy of strain measurement and the functional independence of the temperature compensation grating area. This further enhances the sensor's adaptability in small spaces and high-density deployment scenarios, as well as the reliability of triaxial strain measurement.

[0063] Specifically, in this embodiment, see Figure 2 As shown, the fiber optic laying path consists of four measurement segments and three turning segments connected alternately in sequence. The four measurement segments are laid one-to-one in the accommodating channels of the four grating areas, and each measurement segment extends radially along the angle bisector of the corresponding grating area. The three turning segments are located at the circumferential edges of two adjacent grating areas, and each turning segment connects to the ends of two adjacent measurement segments, forming a closed and continuous fiber optic laying loop.

[0064] It will be readily understood by those skilled in the art that the aforementioned advantageous methods can be freely combined and superimposed without conflict.

[0065] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the protection scope of this application.

Claims

1. A fiber optic grating triaxial strain sensor, characterized in that, Includes base and optical fiber; The base includes eight sector plate components, which are evenly distributed along the circumference of the base. Each pair of sector plate components is centrally symmetrical with respect to the center of the base and forms a group. The four groups of sector plate components respectively constitute four grating areas. Of the four grating regions, three are strain measurement grating regions and one is a temperature compensation grating region; the two sector plate components of each strain measurement grating region are independent separate structures, and both of the two independent sector plate components are used for fixed connection with the structure under test; the two sector plate components of the temperature compensation grating region are integrally formed structures, and only one of the two integrally formed sector plate components is used for fixed connection with the structure under test; The base has an optical fiber positioning groove along the preset laying direction of the optical fiber. The optical fiber positioning groove has four positioning layers, and the four positioning layers correspond one-to-one with the four grating areas. Each positioning layer has a receiving channel for accommodating the optical fiber corresponding to the grating area, and the receiving channels of each positioning layer are arranged along the same central axis, thereby forming a continuous optical fiber laying path. Each of the four positioning layers has a accommodating channel that extends radially along the angle bisector of the corresponding grating area. When the optical fiber is laid along the accommodating channel, it forms measurement segments distributed along the angle bisector of the grating area. Adjacent measurement segments are connected by a turning segment located at the circumferential edge of the grating area to form a continuous optical fiber laying path. The fiber optic cable laying path is a continuous reciprocating bending path.

2. The fiber optic grating triaxial strain sensor according to claim 1, characterized in that, Each of the fan-shaped plate components has at least one screw hole on the side away from the center of the base, the screw hole being used for detachable connection with the fixed bracket.

3. The fiber optic grating triaxial strain sensor according to claim 2, characterized in that, The fixed bracket is a ring structure arranged coaxially with the base. The inner circumference of the ring structure is correspondingly attached to the side of the eight fan-shaped plate components away from the center of the base, and is detachably connected to each of the fan-shaped plate components through the screw holes.

4. The fiber optic grating triaxial strain sensor according to claim 3, characterized in that, The fixed bracket forms a detachable pre-positioned connection with all the sector plate components through screw holes on each sector plate component. It is used to limit the circumferential uniform distribution posture of each sector plate component during installation. After the sector plate component used for fixed connection with the structure under test is welded and fixed to the structure under test on the side away from the fixed bracket, the fixed bracket is removed, so that the welded and fixed sector plate component can independently maintain a fixed connection with the structure under test.

5. The fiber optic grating triaxial strain sensor according to claim 1, characterized in that, Each of the fan-shaped plate components used for fixed connection with the structure under test has a spot weld groove on the side away from the structure under test.

6. The fiber optic grating triaxial strain sensor according to claim 5, characterized in that, Each of the sector plate components used for fixed connection with the structure under test has at least two spot weld grooves, and the at least two spot weld grooves are respectively located close to the two radial sides of the corresponding sector plate component.

7. The fiber optic grating triaxial strain sensor according to claim 1, characterized in that, The optical fiber laying path is composed of four measurement segments and three turning segments connected alternately in sequence; the four measurement segments are laid one-to-one in the receiving channel of the four grating areas, and each measurement segment extends radially along the angle bisector of the corresponding grating area; The three turning segments are located at the circumferential edges of two adjacent grating areas, and each turning segment connects to the ends of two adjacent measurement segments to form a closed and continuous optical fiber laying loop.

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