A novel fiber Bragg grating sensor for one-dimensional angle measurement

Abstract

This application provides a novel fiber Bragg grating sensor for one-dimensional angle measurement. A first truncated cone is provided in the first rotating part, and a first connector is provided in the second rotating part to connect with the first truncated cone. The first and second rotating parts can rotate relative to each other around the axis of the first truncated cone, avoiding the use of other rotating structures, simplifying the sensor structure and improving the compactness of the device. In addition to its connector function, the outer peripheral wall of the first truncated cone has a first groove to securely hold the first optical fiber within the groove, preventing the fiber from slipping out of the truncated cone and causing sensor malfunction. Furthermore, the first truncated cone radially compresses the first optical fiber, causing strain in the fiber Bragg grating mounted on it, which in turn causes a change in the Bragg wavelength of the grating, thus achieving angle monitoring. This angle sensor has a simple and reliable monitoring principle and a compact structure.

Description

Technical Field

[0001] This application relates to the field of sensor technology, and in particular to a novel fiber Bragg grating sensor for one-dimensional angle measurement. Background Technology

[0002] With the development of modern industrial automation, intelligent structural health monitoring, and precision mechanical control, the demand for high-precision, real-time, long-term, and non-electrical angle sensing is increasing. Traditional angle sensors mostly use electronic devices such as potentiometers, encoders, or inertial measurement units (IMUs). Although these devices meet the measurement requirements to some extent, they generally suffer from problems such as susceptibility to electromagnetic interference, poor corrosion resistance, insufficient long-term stability, and difficulty in embedding in complex structures, which limit their application in harsh environments or scenarios with high reliability requirements.

[0003] However, existing one-dimensional angle sensor structures based on fiber optic cables (FBGs) often suffer from problems such as insufficient sensitivity, poor linearity, complex structure, or inconvenient installation. Traditional solutions often rely on cantilever beams or pendulum structures to transfer angular displacement to the FBG, resulting in response lag or nonlinear errors. Other solutions, while employing rotation mechanisms, fail to effectively ensure the consistency of fiber tension and strain during rotation, easily causing signal drift or poor repeatability. Furthermore, how to achieve reliable and stable radial compression within a limited space to accurately modulate FBG strain remains a current technical challenge. Summary of the Invention

[0004] In view of this, this application provides a novel fiber Bragg grating sensor for one-dimensional angle measurement. The sensor can monitor the angle by not only connecting to the second rotating part through the first frustum set on the first rotating mechanism, but also by radially compressing the first optical fiber. This configuration enables the angle sensor to monitor the angle within a limited space, thus improving the compactness of the sensor.

[0005] To achieve the above objectives, this application provides the following technical solution: A novel fiber Bragg grating sensor for one-dimensional angle measurement includes: The first rotating mechanism includes a first rotating part and a second rotating part. The first rotating part is provided with a first frustum, and the second rotating part is provided with a first connector that is plugged into and connected to the first frustum. The first rotating part and the second rotating part can rotate relative to each other around the axis of the first frustum. The first optical fiber is equipped with a fiber Bragg grating; The first fixing mechanism includes a first fixing member disposed on the first rotating part and a second fixing member disposed on the second rotating part. The first truncated cone is located between the first fixing member and the second fixing member. Both the first fixing member and the second fixing member are used to fix the first optical fiber, and the first optical fiber located between the first fixing member and the second fixing member is always in a tensioned state. The first truncated cone has a first groove, and a portion of the first optical fiber is located in the first groove. When the first rotating part and the second rotating part rotate relative to each other, the first optical fiber located between the first fixing member and the second fixing member is radially squeezed by the first truncated cone, causing the first optical fiber to be elongated, thereby changing the grating pitch of the fiber Bragg grating, and thus causing a change in the Bragg wavelength of the fiber Bragg grating.

[0006] Optionally, the novel fiber Bragg grating sensor for one-dimensional angle measurement described above further includes a second rotation mechanism. The second rotation mechanism includes a third rotation part and a fourth rotation part. The third rotation part is provided with a second frustum, and the fourth rotation part is provided with a second connector that is plugged into and connected to the second frustum. The third rotation part and the fourth rotation part can rotate relative to each other around the axis of the second frustum. The second optical fiber is equipped with a fiber Bragg grating; The second fixing mechanism includes a third fixing member disposed on the third rotating part and a fourth fixing member disposed on the fourth rotating part. The second truncated cone is located between the third fixing member and the fourth fixing member. Both the third fixing member and the fourth fixing member are used to fix the second optical fiber, and the second optical fiber located between the third fixing member and the fourth fixing member is always in a tensioned state. The second truncated cone has a second groove, and a portion of the second optical fiber is located in the second groove. When the first rotating mechanism and the second rotating mechanism rotate relative to each other, one of the first optical fiber and the second optical fiber is stretched, and the other is relaxed.

[0007] Optionally, in the novel fiber Bragg grating sensor for one-dimensional angle measurement described above, the first rotating part is located on top of the third rotating part, the second rotating part is located on top of the fourth rotating part, and the first rotating part, the second rotating part, the third rotating part, and the fourth rotating part enclose a sealed cavity, wherein the sealed cavity is provided with through holes that match the first optical fiber and the second optical fiber.

[0008] Optionally, in the novel fiber Bragg grating sensor for one-dimensional angle measurement described above, both the first frustum and the second frustum include multiple stacked and coaxially arranged cylindrical structures, the outer diameters of the multiple cylindrical structures are different, and the outer peripheral wall of each cylindrical structure is provided with a groove.

[0009] Optionally, the novel fiber Bragg grating sensor for one-dimensional angle measurement described above also includes: A first prestress adjustment component is provided on the first rotating mechanism. The first prestress adjustment component is used to adjust the prestress of the first optical fiber provided between the first fixing member and the second fixing member, so that the first optical fiber is always in a taut state during the rotation of the first rotating mechanism. A second prestress adjustment component is provided on the second rotating mechanism. The second prestress adjustment component is used to adjust the prestress of the second optical fiber disposed between the third fixing member and the fourth fixing member, so that the second optical fiber is always in a taut state during the rotation of the second rotating mechanism.

[0010] Optionally, the novel fiber Bragg grating sensor for one-dimensional angle measurement described above also includes: A first elastic member is disposed between the first frustum and the first fixing member or the second fixing member, the first elastic member being configured to compensate for part of the elongation of the first optical fiber when the first optical fiber is stretched. A second elastic member is disposed between the second frustum and the third or fourth fixing member, the second elastic member being configured to compensate for a portion of the elongation of the second optical fiber when the second optical fiber is stretched.

[0011] Optionally, in the novel fiber Bragg grating sensor for one-dimensional angle measurement described above, the first rotating mechanism is provided with a first guiding component for guiding the first optical fiber located in the first groove, so that the first optical fiber extends to the first fixing position and the second fixing position respectively. The second rotating mechanism is provided with a second guide component for guiding the second optical fiber located in the second groove, so that the second optical fiber extends to the third fixing position and the fourth fixing position respectively.

[0012] Optionally, in the novel fiber Bragg grating sensor for one-dimensional angle measurement described above, the first guide assembly includes a first guide post disposed in the first rotating part and a second guide post disposed in the second rotating part. Both the first guide post and the second guide post are provided with a first guide groove. In the height direction of the first guide assembly, the first guide groove and the first groove are provided in a one-to-one correspondence. The second guide assembly includes a third guide post disposed on the third rotating part and a fourth guide post disposed on the fourth rotating part. Both the third guide post and the fourth guide post are provided with a second guide groove. In the height direction of the second guide assembly, the second guide groove and the second groove are provided in a one-to-one correspondence.

[0013] Optionally, in the novel fiber Bragg grating sensor for one-dimensional angle measurement described above, the first prestress adjustment component includes: The first screw connector passes through the side wall of the second rotating part and is screwed to the second fixing member; The first sliding groove is provided on the second rotating part and slides in cooperation with the second fixing member; In this process, by screwing the first screw connector along the first direction, the first screw connector slides along the first groove and stretches the first optical fiber. The second prestress adjustment component includes: The second screwed member passes through the side wall of the fourth rotating part and is screwed to the fourth fixing member; The second sliding groove is provided on the fourth rotating part and slides in cooperation with the fourth fixing member; In this process, by screwing the second screw in the first direction, the second screw slides along the second groove and stretches the second optical fiber.

[0014] Optionally, in the novel fiber Bragg grating sensor for one-dimensional angle measurement described above, the first elastic element is a first spring sheet, and the first rotating part is provided with a first abutting component for abutting the two ends of the first spring sheet. The second elastic element is a second spring sheet, and the third rotating part is provided with a second abutting component for abutting both ends of the second spring sheet; or, The first elastic element is a first spring, and the first spring and the first fixing element are disposed in the first receiving cavity, which is fixedly disposed in the first rotating part; The second elastic element is a second spring, and the second spring and the third fixing element are disposed in the second receiving cavity, which is fixedly disposed in the third rotating part.

[0015] This application provides a novel fiber Bragg grating sensor for one-dimensional angle measurement. A first truncated cone is provided in the first rotating part, and a first connector is provided in the second rotating part. The first truncated cone and the first connector are connected by an insertion joint. The first and second rotating parts can rotate relative to each other around the axis of the first truncated cone, avoiding the use of other rotating structures, simplifying the sensor's structure and improving its compactness. In addition to its connection function, the first truncated cone has a first groove on its outer peripheral wall to ensure that the first optical fiber is stably positioned within the groove, preventing the first optical fiber from slipping out of the first truncated cone and causing sensor malfunction. Furthermore, the first truncated cone radially compresses the first optical fiber, causing strain in the fiber Bragg grating mounted on the first optical fiber, which in turn causes a change in the Bragg wavelength of the fiber Bragg grating. This design significantly improves the sensor's compactness. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 A partial structural schematic diagram of the sensor provided in this application; Figure 2 A partial structural schematic diagram of another sensor provided in this application; Figure 3 The overall structural diagram of the sensor provided in this application; Figure 4 A side view of the sensor provided in this application.

[0018] exist Figures 1-4 middle: 1. First rotating part; 2. Second rotating part; 3. First frustum; 4. First optical fiber; 5. Fiber Bragg grating; 6. First fixing member; 7. Second fixing member; 8. First elastic member; 9. First guide post; 10. Second guide post; 11. First screw connector; 12. First slide groove; 13. First abutment assembly; 14. Third rotating part; 15. Fourth rotating part; 16. Second screw connector; 17. Second optical fiber. Detailed Implementation

[0019] This application provides a novel fiber Bragg grating sensor for one-dimensional angle measurement. The sensor uses a first frustum on a first rotating mechanism to not only connect to a second rotating part but also to radially compress a first optical fiber to monitor the angle. This configuration enables the angle sensor to monitor the angle within a limited space, improving the sensor's compactness.

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Figures 1-4 As shown, this application provides a novel fiber Bragg grating 5 sensor for one-dimensional angle monitoring, comprising: a first rotating mechanism, including a first rotating part 1 and a second rotating part 2, the first rotating part 1 being provided with a first frustum 3, and the second rotating part 2 being provided with a first connector that is plugged into and connected to the first frustum 3, and the first rotating part 1 and the second rotating part 2 being able to rotate relative to each other around the axis of the first frustum 3; a first optical fiber 4, on which a fiber Bragg grating 5 is provided; and a first fixing mechanism, including a first fixing member 6 disposed on the first rotating part 1 and a second fixing member 7 disposed on the second rotating part 2, the first frustum 3 being located on the first fixing member. Between the first fixing member 6 and the second fixing member 7, both the first fixing member 6 and the second fixing member 7 are used to fix the first optical fiber 4, and the first optical fiber 4 located between the first fixing member 6 and the second fixing member 7 is always in a taut state; wherein, the first truncated cone 3 has a first groove, and a part of the first optical fiber 4 is located in the first groove. When the first rotating part 1 and the second rotating part 2 rotate relative to each other, the first optical fiber 4 located between the first fixing member 6 and the second fixing member 7 is radially squeezed by the first truncated cone 3, so that the first optical fiber 4 is stretched, thereby causing the grating pitch of the fiber Bragg grating 5 to change, and thus causing the Bragg wavelength of the fiber Bragg grating 5 to change.

[0022] Specifically, the first rotating part 1 and the second rotating part 2 are connected by an insertion joint, avoiding the use of other rotating structures, simplifying the sensor structure, improving the sensor's compactness, and making the sensor applicable to various scenarios, especially those requiring small angle sensors. The insertion structure consists of a first frustum 3 in the first rotating part 1 and a first insertion member in the second rotating part 2. The first insertion member includes, but is not limited to, a protrusion such as a cylindrical body, or a groove. The bottom of the first frustum 3 is provided with a groove for rotatably engaging with the protrusion, or a protrusion for rotatably engaging with the groove. The outer peripheral wall of the first frustum 3 is also provided with a first groove to ensure that the first optical fiber 4 is locally and stably located within the first groove, preventing the first optical fiber 4 from slipping out of the first frustum 3 and causing sensor malfunction. At the same time, the first optical fiber 4 located between the first fixing member 6 and the second fixing member 7 is always in a taut state, improving the detection sensitivity. In addition, the first optical fiber 4 is stretched by the relative rotation of the first rotating part 1 and the second rotating part 2, which causes the grating pitch of the fiber Bragg grating 5 to change, thereby causing the Bragg wavelength of the fiber Bragg grating 5 to change. The demodulator measures the Bragg wavelength of the fiber Bragg grating 5 and then obtains the angle of the sensor, which is the angle to be measured.

[0023] In summary, the angle sensor has a simple and reliable monitoring principle and a compact structure.

[0024] It should be noted that the first fixing member 6 and the first optical fiber 4 are fixed together, and the second fixing member 7 and the second optical fiber 17 are fixed together, using AB glue.

[0025] It should also be noted that the sensor has a compact overall structure, making it easy to mass-produce and install, and thus possesses high commercial potential. Dimensions (L*W*H): 108mm*40mm*26mm.

[0026] In addition, the novel fiber Bragg grating 5 sensor for one-dimensional angle monitoring also includes a second rotation mechanism, which comprises a third rotation part 14 and a fourth rotation part 15. The third rotation part 14 is provided with a second frustum, and the fourth rotation part 15 is provided with a second connector that is inserted and connected to the second frustum. The third rotation part 14 and the fourth rotation part 15 can rotate relative to each other around the axis of the second frustum. A second optical fiber 17 is provided with a fiber Bragg grating 5. A second fixing mechanism includes a third fixing member provided on the third rotation part 14 and a fourth fixing member provided on the fourth rotation part 15. The second frustum is located between the third fixing member and the fourth fixing member. Between the third and fourth fixing members, the second optical fiber 17 is always in a tensioned state. The second truncated cone has a second groove, and a portion of the second optical fiber 17 is located in the second groove. When the first rotating mechanism and the second rotating mechanism rotate relative to each other, one of the first optical fiber 4 and the second optical fiber 17 is stretched, and the other is relaxed, so that the grating pitch of the fiber Bragg grating of the stretched optical fiber (one of the first optical fiber 4 and the second optical fiber 17) becomes longer, and the grating pitch of the fiber Bragg grating of the relaxed optical fiber (the other of the first optical fiber 4 and the second optical fiber 17) becomes shorter.

[0027] It should be noted that the third fixing member and the second optical fiber 17 are fixed by AB glue, as are the fourth fixing member and the second optical fiber 17; the second plug can be a protrusion or a groove, and a corresponding groove or protrusion is provided at the bottom of the second frustum.

[0028] Specifically, the first and second rotating mechanisms have identical construction and dimensions, and are symmetrically arranged about their horizontal contact points. The only difference between them is the fiber optic cable placement. If the first fiber 4 is located on the first side of the first frustum 3, the second fiber 17 is located on the second side of the second frustum. With the first and second sides opposite each other, when the first and second rotating mechanisms rotate synchronously (or when the sensor rotates to one side), one of the first fiber 4 and the second fiber 17 is stretched, while the other is relaxed. Furthermore, the prestress adjustments of the first fiber 4 and the second fiber 17 are identical. At this time, the first fiber 4 and the second fiber 17 are subjected to forces of equal magnitude but opposite directions. The changes in the fiber optic cables are consistent, but the stretching of one fiber and the relaxation of the other cause their Bragg wavelengths to drift in opposite directions. In other words, the symmetrical differential design fundamentally eliminates the influence of temperature on the measurement results, with a temperature error of less than 1%, eliminating the need for additional temperature compensation sensors or complex algorithms.

[0029] like Figure 4As shown, the first optical fiber 4 and the second optical fiber 17 located at the same end (e.g., the left end) are connected in series, and one of the first optical fiber 4 and the second optical fiber 17 located at the other end (e.g., the right end) is connected to the demodulator. The demodulator can measure the Bragg wavelength of the fiber Bragg grating 5 in the first optical fiber 4 and the second optical fiber 17 respectively, thereby obtaining the angle change of the sensor in this application.

[0030] It should be noted that the FBG located in the first optical fiber 4 and the FBG located in the second optical fiber 17 in this application have similar Bragg wavelengths.

[0031] The first rotating part 1 is located on top of the third rotating part 14, and the second rotating part 2 is located on top of the fourth rotating part 15. The first rotating part 1, the second rotating part 2, the third rotating part 14, and the fourth rotating part 15 together form a sealed cavity. The sealed cavity is provided with through holes that match the first optical fiber 4 and the second optical fiber 17. Specifically, the first rotating part 1, the second rotating part 2, the third rotating part 14, and the fourth rotating part 15 each include a chassis and a sidewall protruding from the chassis. After the different rotating parts are assembled, the sidewalls can be sealed and fitted together, thus the chassis and the sidewalls together form a sealed cavity.

[0032] The positional relationship between the first rotating part 1 and the third rotating part 14 is not limited to the first rotating part 1 being located on top of the third rotating part 14; it is also possible that the third rotating part 14 is located on top of the first rotating part 1. Similarly, the positional relationship between the second rotating part 2 and the fourth rotating part 15 is not limited to the second rotating part 2 being located on top of the fourth rotating part 15; it is also possible that the fourth rotating part 15 is located on top of the second rotating part 2. The first rotating part 1 and the third rotating part 14 can be inserted together. For example, the side walls of the first rotating part 1 and the third rotating part 14 can be inserted together, and the side walls of the second rotating part 2 located on the fourth rotating part 15 can be inserted together. Alternatively, the side walls of the first rotating part 1 and the third rotating part 14 can be fitted together, and the side walls of the second rotating part 2 and the fourth rotating part 15 can be fitted together. The chassis of the first rotating part 1 and the third rotating part 14, as well as the chassis of the second rotating part 2 and the fourth rotating part 15, can be connected by bolts.

[0033] It should be noted that there is sealant between the through hole in the sealed cavity and the first optical fiber 4 and the second optical fiber 17. Specifically, in order to enable the first optical fiber 4 and the second optical fiber 17 to be successfully stretched, a protective sleeve is provided between the first optical fiber 4 and the second optical fiber 17 and the through hole. The protective sleeve is bonded to the through hole, and the first optical fiber 4 and the second optical fiber 17 can move relative to the protective sleeve. The first rotating mechanism and the second rotating mechanism are connected by bolts. Specifically, there is a sealing gasket between the bolt and the chassis to seal the sensor.

[0034] It should also be noted that the through-hole design facilitates the routing of optical fibers (first optical fiber 4 and second optical fiber 17) for connection to the demodulator.

[0035] In one example, the chassis and sidewalls of the first rotating part 1, the second rotating part 2, the third rotating part 14, and the fourth rotating part 15 are all made of metal to provide mechanical support and environmental protection.

[0036] In summary, the sensor is encapsulated in a fully sealed shell, effectively isolating it from environmental factors such as moisture and dust, thus improving the sensor's reliability and durability.

[0037] Furthermore, both the first and second truncated cones include multiple stacked and coaxially arranged cylindrical structures with different outer diameters, and each cylindrical structure has a groove on its outer peripheral wall. Based on the different target objects to be monitored and the different accuracy requirements of the sensor, a cylindrical structure with a suitable outer diameter can be selected. Moreover, to ensure reliable compression of the optical fiber by the cylindrical structure, each cylindrical structure is provided with a groove, thereby improving the practicality and versatility of the sensor.

[0038] It should be noted that the larger the radius of the cylindrical structure, the higher the sensitivity, but the smaller the measurement range.

[0039] In an optional embodiment, the novel fiber Bragg grating 5 sensor for one-dimensional angle monitoring further includes: a first prestress adjustment component disposed on the first rotation mechanism, which adjusts the prestress of the first optical fiber 4 disposed between the first fixing member 6 and the second fixing member 7, so that the first optical fiber 4 is always in a taut state during the rotation of the first rotation mechanism; and a second prestress adjustment component disposed on the second rotation mechanism, which adjusts the prestress of the first optical fiber 4 disposed between the third fixing member and the fourth fixing member, so that the second optical fiber 17 is always in a taut state during the rotation of the second rotation mechanism. The first and second prestress adjustment components can have the same or different configurations. The prestress adjustment is used to apply and maintain a constant initial prestress on the optical fiber, ensuring the stability of the initial measurement state and the required stress range. For example, initially applying a prestress of 1 nm to the fiber Bragg grating keeps it taut throughout the required angle range. Compared to traditional methods of applying prestress using external components such as weights, this makes the adjustment of the sensor's prestress more convenient.

[0040] By using a prestress adjustment assembly (first prestress adjustment assembly and second prestress adjustment assembly) in conjunction with a stepped frustum (first frustum and second frustum) to dynamically stretch the optical fiber (first optical fiber 4 and second optical fiber 17), the axial strain of the fiber grating can be precisely controlled, thereby achieving high-precision and repeatable tuning of its Bragg wavelength.

[0041] In an optional embodiment, the novel fiber Bragg grating 5 sensor for one-dimensional angle monitoring further includes: a first elastic element 8 disposed between the first frustum 3 and the first fixing member 6 or the second fixing member 7, the first elastic element 8 being configured to compensate for a portion of the elongation of the first optical fiber 4 when it is stretched; and a second elastic element disposed between the second frustum and the third fixing member or the fourth fixing member, the second elastic element being configured to compensate for a portion of the elongation of the second optical fiber 17 when it is stretched. The elastic elements include, but are not limited to, sheet springs or spring sheets. The inclusion of the elastic elements increases the sensor's angle monitoring range.

[0042] In addition, this application utilizes the conversion principle of "disc radial extrusion - fiber axial tension" to replace the traditional bending strain principle of pendulum, equal strength beam, etc., and is equipped with an elastic structure to achieve a wider range of linear measurement (±15°). The prestress adjustment device can be used with a stepped frustum to adjust the required initial stress.

[0043] In an optional embodiment, the first rotating mechanism is provided with a first guiding component to guide the first optical fiber 4 located in the first groove to extend towards the positions of the first fixing member 6 and the second fixing member 7, respectively; the second rotating mechanism is provided with a second guiding component to guide the second optical fiber 17 located in the second groove to extend towards the positions of the third fixing member and the fourth fixing member, respectively. The first guiding component and the second guiding component may be a guide post, a guide block, etc.

[0044] The guide component can effectively constrain and guide the direction of the first optical fiber 4 and the second optical fiber 17 in the groove, ensuring that the optical fiber extends accurately to the corresponding fixing position and avoiding assembly errors caused by improper offset or bending.

[0045] Furthermore, the first guiding assembly includes a first guide post 9 disposed in the first rotating part 1 and a second guide post 10 disposed in the second rotating part 2. Both the first guide post 9 and the second guide post 10 are provided with first guide grooves, and the first guide grooves are arranged one-to-one with the first grooves in the height direction of the first guiding assembly. The second guiding assembly includes a third guide post disposed in the third rotating part 14 and a fourth guide post disposed in the fourth rotating part 15. Both the third guide post and the fourth guide post are provided with second guide grooves, and the second guide grooves are arranged one-to-one with the second grooves in the height direction of the second guiding assembly. The guiding assembly is a guide post, and the guide post has a smooth shape without sharp edges to avoid damage to the optical fiber. At the same time, both the first guide post 9 and the second guide post 10 are provided with guide grooves, thus improving the guiding capability of the optical fiber. Each guide post is provided with multiple guide grooves, and the height of the guide groove on each guide post corresponds one-to-one with the height of the groove on the frustum (first frustum 3 and second frustum), thus improving the consistency of guidance.

[0046] The first prestress adjustment assembly includes: a first screw connector 11, which passes through the side wall of the second rotating part 2 and is screwed to the second fixing member 7; and a first sliding groove 12, which is disposed on the second rotating part 2 and slidably engages with the second fixing member 7. The first screw connector 11 is screwed relative to the second rotating part 2 in a first direction, causing it to slide along the first sliding groove 12 and stretch the first optical fiber 4. The second prestress adjustment assembly includes: a second screw connector 16, which passes through the side wall of the fourth rotating part 15 and is screwed to the fourth fixing member; and a second sliding groove, which is disposed on the fourth rotating part 15 and slidably engages with the fourth fixing member. The second screw connector 16 is screwed in the first direction, causing it to slide along the second sliding groove and stretch the second optical fiber 17. The first optical fiber 4 is glued to the second fixing member 7, and the second optical fiber 17 is glued to the fourth fixing member. The first screw connector 11 and the second screw connector 16 are bolts or screws.

[0047] It can be seen that the above-mentioned prestress adjustment component has a relatively simple structure, and the application of prestress is also relatively simple.

[0048] In an optional embodiment, the first elastic element 8 is a first spring sheet, and the first rotating part 1 is provided with a first abutting component 13 for abutting the two ends of the first spring sheet; the second elastic element is a second spring sheet, and the third rotating part 14 is provided with a second abutting component for abutting the two ends of the second spring sheet.

[0049] The first abutting component 13 is an L-shaped member protruding from the side wall of the first rotating part 1. The end of the first spring abuts against the L-shaped member. The second abutting component has the same structure as the first abutting component 13. The L-shaped member fixes / constrains the spring on one hand, and keeps the spring in a simply supported state on the other hand. Only in a simply supported state can Hooke's Law be well satisfied, and only then can the elastic range be large.

[0050] This configuration, with an L-shaped contact component mounted on the side wall of the rotating part to fit the spring, eliminates the need for additional independent components, resulting in high integration and efficient use of limited space. It is particularly suitable for devices with stringent size requirements, further miniaturizing the sensor.

[0051] Alternatively, the first elastic element 8 is a first spring, which, along with the first fixing element 6, is disposed within the first receiving cavity, which is fixedly disposed within the first rotating part 1; the second elastic element is a second spring, which, along with the third fixing element, is disposed within the second receiving cavity, which is fixedly disposed within the third rotating part 14. Both the first and second receiving cavities are rectangular structures and are used to simultaneously accommodate the spring and the fixing element, further improving the integration of the sensor.

[0052] It should be noted that the first truncated cone 3, the first abutting component 13 and the first fixing component 6 are integrally formed structures, and the second truncated cone, the second abutting component and the third fixing component are integrally formed structures.

[0053] Sensor detection principle: Sensor rotates by angle The length of the arc swept for (1) In the formula, Let be the radius of the frustum.

[0054] The two FBGs will be stretched and compressed respectively, arc length It will be supported by springs and optical fibers respectively. and ,Right now .

[0055] The force analysis of the spring and the optical fiber yields the following derivation formulas: For a spring: Based on Hooke's Law, the force acting on a spring for (2) In the formula, The spring constant, expressed in N. mm-1; This represents the deformation length of the spring, in meters (m).

[0056] For optical fibers: stress in optical fibers It can be expressed by formula (3): (3) In the formula, This represents the cross-sectional area of ​​the optical fiber. , This represents the Young's modulus of the optical fiber. Let be the magnitude of the strain in the optical fiber, and , This refers to the change in the length of the optical fiber. This represents the initial length of the optical fiber.

[0057] Based on formulas (1), (2), and (3), in the force balance system of the spring and the optical fiber, The change in fiber length can be derived. With angle The relation is: (4) So, the strain of the fiber grating for: (5) wavelength offset The relationship between temperature and strain is as follows: (6) In the formula, The initial Bragg wavelength is given in nm. Thermo-optic coefficient; The coefficient of thermal expansion; This is the change in temperature, expressed in °C. The effective photoelastic coefficient is 0.22. Let be the change in strain of FBG.

[0058] Combining equation (5), the FBG wavelength shift can be obtained. With rotation angle The relationship is: (7) When the sensors are working, FBG1 and FBG2 generate equal and opposite axial strains, that is... If two FBGs are placed in the same temperature environment, then the strain caused by temperature is approximately equal. From formula (7), the relationship between the change in sensor wavelength difference and the rotation angle is derived as follows: (8) In the formula, , This refers to the wavelength offset of FBG1 and FBG2; , These are the initial Bragg wavelengths for FBG1 and FBG2.

[0059] If two FBG , recorded as Then formula (8) can be rewritten as follows: (9) It can be seen that the change in wavelength difference between the two fiber gratings is related to the rotation angle. The sensitivity exhibits a linear relationship at any angle, meaning it is related to the radius r of the frustum and the spring constant k. Therefore, by adjusting the radius of the frustum and the spring constant, the sensitivity and the range of measurement angles can be adjusted.

[0060] The rotation angle is calculated based on the change in the Bragg wavelength of the FBG measured by the demodulator and then on the formula (9).

[0061] It should be noted that the wavelengths of the two FBGs change in opposite directions; that is, one FBG is relaxed while the other is stretched. This can be understood as the wavelengths of the two FBGs changing in opposite directions, with one changing positively and the other changing negatively.

[0062] The optimized structural design of this application achieves a high sensitivity of 150 pm / °, and when combined with a high-resolution demodulation device, the resolution can reach 0.01°.

[0063] This angle sensor can be used for monitoring deep slope displacement, which is often a precursor to landslides. Monitoring deep displacement is of great significance for predicting slope deformation.

[0064] This angle sensor can also be used to monitor roadbed / foundation settlement. By burying the angle sensor in the roadbed or foundation, the amount of stratified settlement and uneven deformation at different depths can be monitored.

[0065] This angle sensor can also be used for robot joint angle feedback. Installed at the rotary joints of industrial or collaborative robots, it serves as a high-precision joint angle sensor, providing real-time position feedback and improving the accuracy and smoothness of motion control. The anti-interference capabilities of fiber optics are a significant advantage here. For example, because the core structure of the sensor is a frustum of a cone and the center of the rotation point coincides with the center of the frustum, this structure can be integrated into various critical internal components, such as finger joints, knee joints, and elbow joints. Combined with a sealed design, stable angle monitoring can be achieved.

[0066] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0067] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0068] It should also be noted that in the apparatus, equipment, and housing of this application, the components or steps can be disassembled and / or reassembled. These disassemblies and / or reassemblies should be considered as equivalent solutions of this application.

[0069] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0070] It should be understood that the qualifiers “first,” “second,” “third,” “fourth,” “fifth,” and “sixth” used in the description of the embodiments of this application are only used to more clearly illustrate the technical solutions and are not intended to limit the scope of protection of this application.

[0071] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A novel fiber Bragg grating sensor for one-dimensional angle measurement, characterized in that, include: The first rotating mechanism includes a first rotating part and a second rotating part. The first rotating part is provided with a first frustum, and the second rotating part is provided with a first connector that is plugged into and connected to the first frustum. The first rotating part and the second rotating part can rotate relative to each other around the axis of the first frustum. The first optical fiber is equipped with a fiber Bragg grating; The first fixing mechanism includes a first fixing member disposed on the first rotating part and a second fixing member disposed on the second rotating part. The first truncated cone is located between the first fixing member and the second fixing member. Both the first fixing member and the second fixing member are used to fix the first optical fiber, and the first optical fiber located between the first fixing member and the second fixing member is always in a tensioned state. The first truncated cone has a first groove, and a portion of the first optical fiber is located in the first groove. When the first rotating part and the second rotating part rotate relative to each other, the first optical fiber located between the first fixing member and the second fixing member is radially squeezed by the first truncated cone, causing the first optical fiber to be elongated, thereby causing the grating pitch of the fiber Bragg grating to change, and thus causing the Bragg wavelength of the fiber Bragg grating to change. It also includes a second rotating mechanism, which includes a third rotating part and a fourth rotating part. The third rotating part is provided with a second frustum, and the fourth rotating part is provided with a second connector that is plugged into and connected to the second frustum. The third rotating part and the fourth rotating part can rotate relative to each other around the axis of the second frustum. The second optical fiber is equipped with a fiber Bragg grating; The second fixing mechanism includes a third fixing member disposed on the third rotating part and a fourth fixing member disposed on the fourth rotating part. The second truncated cone is located between the third fixing member and the fourth fixing member. Both the third fixing member and the fourth fixing member are used to fix the second optical fiber, and the second optical fiber located between the third fixing member and the fourth fixing member is always in a tensioned state. The second truncated cone has a second groove, and a portion of the second optical fiber is located in the second groove. When the first rotating mechanism and the second rotating mechanism rotate relative to each other, one of the first optical fiber and the second optical fiber is stretched, and the other is relaxed. The first rotating part is located on top of the third rotating part, the second rotating part is located on top of the fourth rotating part, and the first rotating part, the second rotating part, the third rotating part and the fourth rotating part surround to form a sealed cavity, wherein the sealed cavity is provided with through holes that match the first optical fiber and the second optical fiber; Both the first frustum and the second frustum include multiple stacked and coaxially arranged cylindrical structures, the outer diameters of the multiple cylindrical structures are different, and the outer peripheral wall of each cylindrical structure is provided with a groove; Also includes: A first prestress adjustment component is provided on the first rotating mechanism. The first prestress adjustment component is used to adjust the prestress of the first optical fiber provided between the first fixing member and the second fixing member, so that the first optical fiber is always in a taut state during the rotation of the first rotating mechanism. A second prestress adjustment component is provided on the second rotating mechanism. The second prestress adjustment component is used to adjust the prestress of the second optical fiber provided between the third fixing member and the fourth fixing member, so that the second optical fiber is always in a taut state during the rotation of the second rotating mechanism. Also includes: A first elastic member is disposed between the first frustum and the first fixing member or the second fixing member, the first elastic member being configured to compensate for part of the elongation of the first optical fiber when the first optical fiber is stretched. A second elastic member is disposed between the second frustum and the third or fourth fixing member, the second elastic member being configured to compensate for a portion of the elongation of the second optical fiber when the second optical fiber is stretched.

2. The novel fiber Bragg grating sensor for one-dimensional angle measurement according to claim 1, characterized in that, The first rotating mechanism is provided with a first guide component for guiding the first optical fiber located in the first groove, so that the first optical fiber extends to the first fixing position and the second fixing position respectively. The second rotating mechanism is provided with a second guide component for guiding the second optical fiber located in the second groove, so that the second optical fiber extends to the third fixing position and the fourth fixing position respectively.

3. The novel fiber Bragg grating sensor for one-dimensional angle measurement according to claim 2, characterized in that, The first guide assembly includes a first guide post disposed in the first rotating part and a second guide post disposed in the second rotating part. Both the first guide post and the second guide post are provided with a first guide groove. In the height direction of the first guide assembly, the first guide groove and the first groove are provided in a one-to-one correspondence. The second guide assembly includes a third guide post disposed on the third rotating part and a fourth guide post disposed on the fourth rotating part. Both the third guide post and the fourth guide post are provided with a second guide groove. In the height direction of the second guide assembly, the second guide groove and the second groove are provided in a one-to-one correspondence.

4. The novel fiber Bragg grating sensor for one-dimensional angle measurement according to claim 1, characterized in that, The first prestress adjustment component includes: The first screw connector passes through the side wall of the second rotating part and is screwed to the second fixing member; The first sliding groove is provided on the second rotating part and slides in cooperation with the second fixing member; In this process, by screwing the first screw connector along the first direction, the first screw connector slides along the first groove and stretches the first optical fiber. The second prestress adjustment component includes: The second screwed member passes through the side wall of the fourth rotating part and is screwed to the fourth fixing member; The second sliding groove is provided on the fourth rotating part and slides in cooperation with the fourth fixing member; In this process, by screwing the second screw in the first direction, the second screw slides along the second groove and stretches the second optical fiber.

5. The novel fiber Bragg grating sensor for one-dimensional angle measurement according to claim 1, characterized in that, The first elastic element is a first spring sheet, and the first rotating part is provided with a first abutting component for abutting the two ends of the first spring sheet; The second elastic element is a second spring sheet, and the third rotating part is provided with a second abutting component for abutting both ends of the second spring sheet; or, The first elastic element is a first spring, and the first spring and the first fixing element are disposed in the first receiving cavity, which is fixedly disposed in the first rotating part; The second elastic element is a second spring, and the second spring and the third fixing element are disposed in the second receiving cavity, which is fixedly disposed in the third rotating part.

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