Three-component FBG vibration sensor and method of use

Abstract

The present application relates to the field of optical fiber sensing technology, especially to a three-component FBG vibration sensor and a use method thereof. The three-component FBG vibration sensor comprises an integrated polymer block and FBG, wherein a three-dimensional coordinate system is constructed with the geometric center of a rectangular base as the origin, the rectangular base has an x-axis surface, a y-axis surface and a z-axis surface; two flexible hinges are connected to the x-axis surface and symmetric about the yoz reference surface; two first mass blocks are connected to the end surface of the flexible hinges, the tail fibers of two FBGs parallel to the x-axis are connected to the surface of each first mass block to form a y-direction and z-direction vibration detection module; a cantilever beam is connected to any y-axis surface, a second mass block is connected to the end surface of the cantilever beam, the tail fiber of an FBG parallel to the y-axis is connected to the surface of the second mass block and the x-axis surface of the rectangular base to form an x-direction vibration detection module. The proposed sensor has the advantages of low mass, no assembly error and strong magnetic resistance, and realizes the sensing characteristics of high sensitivity and high natural frequency under the condition of limited volume.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, and in particular to a three-component FBG vibration sensor and its usage method. Background Technology

[0002] Traditional vibration sensors based on electrical principles are unsuitable for harsh environments such as strong electromagnetic fields, oil contamination, or corrosion. Vibration sensors based on Fiber Bragg Gratings (FBGs) are optical sensing elements formed by introducing periodic refractive index modulation into optical fibers. They have advantages such as resistance to electromagnetic interference, corrosion resistance, and ease of multiplexing multiple sensors, making them suitable for operation in harsh environments.

[0003] Currently, there are two main approaches to solving three-dimensional vibration testing problems based on FBG vibration sensors: One approach involves placing one-dimensional sensors in three mutually orthogonal directions, such as the x, y, and z directions of a Cartesian coordinate system. This approach only requires designing one-dimensional sensors, making the design relatively simple, but it necessitates the simultaneous use of three sensors. Finally, the acceleration vectors in each direction are combined to synthesize the spatial acceleration. Its disadvantages include strict requirements for the assembly and matching of each module, resulting in a large size and complex structure. The other approach is a three-component integrated sensor. This uses a mass block or an integrated mass block combined with the sensor structure to transmit information from each component to the FBG sensor. It enables real-time measurement at the same point, offers high accuracy, and is easy to use.

[0004] The existing three-component FBG vibration sensor has the following drawbacks:

[0005] (1) The design of the mass block of the FBG acceleration vibration sensor is basically made of high-density metal materials (such as steel). However, various metal mass blocks are easily damaged in harsh environments such as strong magnetic fields, humidity, and acid and alkali, and are not suitable for vibration monitoring in particularly harsh environments such as strong magnetic fields, strong corrosion, humidity, and acid and alkali, which affects the performance of the sensor. Therefore, the selection of metal mass blocks weakens the advantages of fiber optic sensors as non-metallic material sensors in adapting to harsh environments and being lightweight.

[0006] (2) The design of FBG acceleration vibration sensors generally uses high-density metal materials (such as steel). Sensors made in this way generally require the processing of multiple parts, and then the parts are assembled by fastening bolts. This assembly method has the problems of high precision requirements and fasteners being prone to loosening, which affects the sensing characteristics.

[0007] (3) Existing low-density non-metallic polymer FBG vibration sensors are all one-dimensional sensors. Simply extending one-dimensional to three-dimensional will be limited by the structure and have a large cross sensitivity, resulting in low test accuracy.

[0008] (4) When the sensor itself is large, if the volume and mass of the object to be measured are small, it is easy to cause the vibration characteristics of the object to be measured to be affected due to the large mass of the sensor itself, thus resulting in a large measurement error.

[0009] (5) All reported multi-dimensional sensors are made of high-density metal materials, which are different from the environmental adaptability of the present invention and are not suitable for vibration monitoring in particularly harsh environments such as strong magnetic fields, strong corrosion, humidity, acid and alkali. Summary of the Invention

[0010] The present invention aims to at least improve one of the technical problems existing in the prior art. To this end, the present invention proposes a three-component FBG vibration sensor and a method of using it.

[0011] A three-component FBG vibration sensor according to a first aspect embodiment of the present invention includes an FBG, wherein the sensor further includes:

[0012] An integrally molded polymer block, the polymer block comprising:

[0013] A rectangular base, wherein a three-dimensional coordinate system is constructed with the geometric center of the rectangular base as the origin, the rectangular base has an x-axis plane, a y-axis plane and a z-axis plane, and a through hole is opened in the x-axis plane;

[0014] Two flexible hinges are connected to the x-axis plane of the base surface and are axially symmetrical about the yoz reference plane. They have two rotational degrees of freedom. One is used to measure the acceleration in the y direction, and the motion is rotation about the z-axis. The other is used to measure the acceleration in the z direction, and the motion is rotation about the y-axis.

[0015] Two first mass blocks are connected to the end face of the flexible hinge, and the pigtail of the FBG parallel to the x-axis is connected to the surface of each first mass block to form a vibration detection module in the y-direction and a vibration detection module in the z-direction.

[0016] A cantilever beam connected to any y-axis plane;

[0017] The second mass block is connected to the end face of the cantilever beam. The FBG pigtail, which is parallel to the y-axis, is connected to the surface of the second mass block and the x-axis plane of the rectangular base to form an x-direction vibration detection module.

[0018] In one possible implementation of the first aspect, the polymer block further includes:

[0019] Two trapezoidal transition blocks have a first connecting end face and a second connecting end face that are parallel to each other. The first connecting end face is adapted to the end face of the flexible hinge, and the second connecting end face is adapted to the end face of the first mass block. The area of ​​the second connecting end face is larger than the area of ​​the first connecting end face.

[0020] In one possible implementation of the first aspect, the entire structure of the polymer block is symmetrical about the xoy reference plane and the yoz reference plane, respectively. There are two reasons for this: firstly, it facilitates the installation of the FBG; secondly, it is to maintain strict consistency between the mode shapes of the sensor in the x, y, and z directions and the directions of the x-axis, y-axis, and z-axis.

[0021] In one possible implementation of the first aspect, viewed from the yoz plane, the width of the first mass block in the z direction is greater than the width of the rectangular base in the z direction, which facilitates the installation of the FBG and avoids interference from the base edge when sensing signals in the y and z directions.

[0022] In one possible implementation of the first aspect, the height of the first mass block is the same as the height of the center of the through hole, and the geometric center of the through hole is located on the y-axis. The FBG passes through the through hole and is connected to the surface of the first mass block.

[0023] In one possible implementation of the first aspect, the surface of the second mass block on which the FBG is mounted lies in the same plane as the x-axis plane of the rectangular base.

[0024] In one possible implementation of the first aspect, the flexible hinge is an orthogonal composite notch-type flexible hinge with an asymmetrical circular arc cut-out structure on all four sides. Specifically, the notch of the flexible hinge is cut with a circular arc, and the thickness and notch radius of the thinnest part of the flexible hinge in the y and z directions are different, making the structure asymmetrical.

[0025] In one possible implementation of the first aspect, the FBG includes:

[0026] The first FBG pigtail is respectively mounted on the rectangular base and the second mass block, and the first FBG is aligned with the y-axis direction.

[0027] The second FBG passes through the through hole and is connected to the surface of the first mass block. The second FBG is aligned with the x-axis direction.

[0028] The third FBG has its pigtails connected to the surface of the first mass block, and the third FBG is aligned with the x-axis direction.

[0029] In one possible implementation of the first aspect, the through hole is formed on the x-axis plane near the side of the cantilever beam.

[0030] The three-component FBG vibration sensor according to embodiments of the present invention is based on a polymer integrally molded mass block, which has advantages such as low mass, no assembly error, high temperature resistance, strong magnetic resistance, and corrosion resistance. It is not only suitable for vibration monitoring in harsh environments, but also achieves high sensitivity and high natural frequency sensing characteristics within a limited volume. Specifically, the sensor of the present invention uses a low-mass-density polymer, which has the characteristics of low mass and small volume, but still achieves a high level of sensitivity and natural frequency. The use of polymer as the mass block in this invention allows the FBG three-component vibration sensor to be made entirely of non-metallic materials, making it more suitable for vibration testing in harsh environments such as strong magnetic fields, acids and alkalis, and humidity. Through reasonable structural design, the present invention uses a low-density polymer to integrally mold the mass block and sensing structure, effectively avoiding errors caused by assembly and improving the stability of sensor performance. Finally, by optimizing the design of the mass block and sensor structure, a high-sensitivity, high-natural-frequency three-component vibration sensor is realized.

[0031] A method for using a three-component FBG vibration sensor according to a second aspect of the present invention, wherein the three-component FBG vibration sensor is used to measure the object under test, includes the following steps:

[0032] Step S100: The sensitivity of the packaged three-component FBG vibration sensor in the x, y, and z directions is tested to obtain the relationship between the center wavelength offset of the FBG in the x, y, and z directions and the acceleration in each direction, thereby obtaining the sensitivity matrix. The relationship between the acceleration of the sensor in the x, y, and z directions and the change in the center wavelength of the FBG is shown below:

[0033] ,

[0034] in, These represent the changes in the center wavelength of the first FBG, second FBG, and third FBG, respectively. These represent the accelerations applied in the x, y, and z directions, respectively. Let be the sensitivity matrix, where: This represents the sensitivity of the sensor in the x-direction when vibration is applied in the x-direction. This represents the sensitivity to cross-coupling interference in the y direction when acceleration is applied in the x direction. This represents the sensitivity to cross-coupling interference in the z direction when acceleration is applied in the x direction;

[0035] This represents the sensor's cross-coupling interference sensitivity in the x-direction when vibration is applied in the y-direction. This represents the sensitivity perceived in the y-direction when acceleration is applied in the y-direction. This represents the sensitivity to cross-coupling interference in the z direction when acceleration is applied in the x direction;

[0036] This represents the cross-coupling interference sensitivity of the sensor in the x-direction when vibration is applied in the z-direction. This represents the sensitivity to cross-coupling interference in the y direction when acceleration is applied in the z direction. This represents the sensitivity perceived in the z-direction when acceleration is applied in the z-direction;

[0037] Step S200: Fix the surface of the rectangular base (10) away from the cantilever beam (12) to the surface of the object being measured;

[0038] Step S300: When the object under test is subjected to vibration, the center wavelength shift of the three FBGs is collected. , , ;

[0039] Step S400: Based on the sensor sensitivity matrix measured in step S100, the following relationship is established.

[0040] ,

[0041] Acceleration in all directions can be obtained, among which It is the inverse of the sensitivity matrix. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the mechanism of a vibration sensor based on FBG;

[0044] Figure 2 This is an overall schematic diagram of a three-component FBG vibration sensor according to an embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram of the structure of a three-component FBG vibration sensor according to an embodiment of the present invention;

[0046] Figure 4 This is a schematic diagram of the flexible hinge of a three-component FBG vibration sensor according to an embodiment of the present invention;

[0047] Figure 5 This is a schematic diagram of the flexible hinge design of a three-component FBG vibration sensor according to an embodiment of the present invention;

[0048] Figure 6 This is a schematic diagram of the flexible hinge of the three-component FBG vibration sensor according to an embodiment of the present invention from various perspectives.

[0049] Figure label:

[0050] Polymer block 1, FBG2;

[0051] Rectangular base 10, through hole 101, flexible hinge 11, cantilever beam 12, first mass block 13, second mass block 14, trapezoidal platform transition block 15, first connecting end face 151, second connecting end face 152.

[0052] First FBG21, Second FBG22, Third FBG23. Detailed Implementation

[0053] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0054] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0056] The terms "first," "second," "third," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects and not to describe a particular order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, it may include a series of steps or units, or optionally, steps or units not listed, or other steps or units inherent to these processes, methods, products, or devices.

[0057] The accompanying drawings show only the portions relevant to this application, not all of them. Before discussing exemplary embodiments in more detail, it should be noted that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe operations (or steps) as sequential processes, many of these operations may be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations may be rearranged. The process may be terminated when its operation is completed, but may also have additional steps not included in the drawings. The process may correspond to a method, function, procedure, subroutine, subprogram, etc.

[0058] The terms “component,” “module,” “system,” “unit,” etc., used in this specification are used to refer to computer-related entities, hardware, firmware, combinations of hardware and software, software, or software in execution. For example, a unit can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, a thread of execution, a program, and / or distributed between two or more computers. Furthermore, these units can be executed from various computer-readable media on which various data structures are stored. Units can communicate, for example, via local and / or remote processes based on signals having one or more data packets (e.g., data from a second unit interacting with another unit between a local system, a distributed system, and / or a network; for example, the Internet interacting with other systems via signals).

[0059] Vibration sensors have significant applications in health monitoring fields such as earthquake monitoring, geological disaster early warning, power systems, and oil and mine exploration. In many applications, the sensors operate in harsh environments, such as the humid environments of oil and mines and the strong magnetic field environments of power systems. This invention designs a three-component vibration sensor based on a Bragg fiber grating. This acceleration vibration sensor can effectively capture vibration signals in the x, y, and z directions and has advantages such as suitability for various harsh environments, high sensitivity, light weight, and simple manufacturing.

[0060] The mechanism of FBG-based vibration sensors is as follows: Figure 1 As shown. Mass block ,spring and damper It is connected to the outer casing, wherein the lower surface of the outer casing is fixed to the test piece.

[0061] Its sensitivity expression is:

[0062] (1),

[0063] in Indicates the sensitivity of the sensor. The center wavelength of the light reflected by the FBG. For the changing center wavelength, The acceleration applied to the sensor, The elastic modulus of the optical fiber. This represents the cross-sectional area of ​​the optical fiber.

[0064] Vibration is a vector quantity, and a three-dimensional vibration sensor is needed to detect vibration information in all directions. Currently, there are two solutions for solving three-dimensional vibration testing problems based on FBG vibration sensors: One is to place a one-dimensional sensor in three mutually orthogonal directions, such as the x, y, and z directions of a Cartesian coordinate system. This solution only requires designing a one-dimensional sensor, making the design relatively simple, but it requires the simultaneous use of three sensors. Finally, the acceleration vectors in each direction are synthesized into spatial acceleration. Its disadvantages include strict requirements for the assembly and matching of each module, large size, and complex structure. The other solution is a three-component integrated sensor, which uses a mass block or an integrated mass block combined with the sensor structure to transmit the information of each component to the FBG sensor. It can achieve real-time measurement at the same point, has high accuracy, and is easy to use.

[0065] The performance improvement of existing three-component integrated sensors is limited by many factors. First, as shown in equation (1), the sensitivity of the three-component integrated vibration sensor of FBG is proportional to the mass of the mass block. Therefore, in order to achieve higher sensitivity, the mass block in the sensor must be either large in volume or made of high-density metal materials, such as manganese 65, tantalum, stainless steel, etc. Large-volume sensors are limited by space in installation and have limited use. Moreover, various metal mass blocks are easily damaged in harsh environments such as strong magnetic fields, humidity, and acid and alkali, which affects the performance of the sensor. Therefore, their use itself weakens the advantages of fiber optic sensors as non-metallic material sensors in adapting to harsh environments and being lightweight. On the other hand, the use of metal blocks puts high demands on their precision machining and assembly, especially for three-component sensors. Existing three-component FBG sensors with metal material as mass blocks often require the separate machining of each component and then precision assembly. For example, the conventional assembly method is to connect the parts with fasteners such as screws. Therefore, the achievement of the sensor's performance indicators is affected by the machining accuracy and assembly level of each component, and the performance may be affected by the loosening of the fasteners in the connection parts during vibration sensing. Finally, although there have been reports on the development of FBG vibration sensors using low-density non-metallic polymers, these are all one-dimensional sensors. Simply extending one-dimensional sensors to three-dimensional ones is subject to structural limitations and has significant cross-sensitivity, resulting in low testing accuracy.

[0066] To address the above problems, this invention proposes a three-component FBG vibration sensor. Based on a polymer integrally molded mass block, it boasts advantages such as low mass, no assembly errors, high pressure resistance, strong magnetic field resistance, and corrosion resistance. It is suitable not only for vibration monitoring in harsh environments but also for achieving high sensitivity and a high operating frequency within a limited volume. First, the sensor of this invention achieves high sensitivity and natural frequency while using low-mass, low-density polymers and a small volume. Second, the use of polymer material for the mass block allows the FBG three-component vibration sensor to be made entirely of non-metallic materials, making it more suitable for vibration testing in harsh environments such as strong magnetic fields, acids and alkalis, and humidity. Third, through a rational structural design, the invention uses low-density polymer materials to integrally mold the mass block and sensing structure, effectively avoiding errors caused by assembly and improving the stability of sensor performance. Finally, by optimizing the design of the mass block and sensor structure, a three-component sensor with high sensitivity and a high natural frequency is achieved.

[0067] For details, please refer to the following examples.

[0068] Example 1

[0069] See Figure 2 and Figure 3 As shown, the three-component FBG vibration sensor of this embodiment includes FBG2, which further includes:

[0070] An integrally molded polymer block 1, the polymer block 1 comprising:

[0071] A rectangular base 10, wherein a three-dimensional coordinate system is constructed with the geometric center of the rectangular base 10 as the origin, the rectangular base 10 has an x-axis plane, a y-axis plane and a z-axis plane, and a through hole 101 is provided on the x-axis plane;

[0072] Two flexible hinges 11 are respectively connected to the x-axis plane and are symmetrical about the yoz reference plane, with two rotational degrees of freedom. One is used to measure the acceleration in the y direction, and its motion is rotation about the z-axis. The other is used to measure the acceleration in the z direction, and its motion is rotation about the y-axis.

[0073] Two first mass blocks 13 are respectively connected to the end face of the flexible hinge 11 away from the x-axis plane, and the pigtail of the FBG parallel to the x-axis is connected to the surface of each first mass block 13 to form a y-direction vibration detection module and a z-direction vibration detection module.

[0074] Cantilever beam 12 is connected to any y-axis plane;

[0075] The second mass block 14 is connected to the end face of the cantilever beam 12 away from the y-axis plane. The pigtail of the FBG parallel to the y-axis is connected to the surface of the second mass block 14 and the x-axis plane of the rectangular base 10 to form an x-direction vibration detection module.

[0076] It should be noted that both the first mass block 13 and the second mass block 14 are rectangular mass blocks, and the two first mass blocks 13 have identical structures and are symmetrically positioned with respect to the yoz reference plane. There are two reasons for this: firstly, to ensure the symmetry of the sensor's mode shapes in the x, y, and z directions, allowing the second FBG 22 and the third FBG 23 to better sense vibration signals from the y and z directions. Secondly, under the same acceleration, asymmetrical mass blocks on both sides would increase the axial bending of the FBG, thus increasing the bending loss of the optical fiber and negatively impacting the stability of the FBG sensor signal. The symmetrical mass block structure avoids this problem. Furthermore, the rectangular mass block structure can be combined with the characteristics of a biaxial flexible hinge to form a structure capable of withstanding vibrations under different loads. In contrast, the combination of a cylindrical mass block and a biaxial flexible hinge would cause stress concentration due to the discontinuous structure.

[0077] It should be noted that the polymer block 1 further includes:

[0078] Two trapezoidal transition blocks 15 have a first connecting end face 151 and a second connecting end face 152 that are parallel to each other. The first connecting end face 151 is adapted to the end face of the flexible hinge 11, and the second connecting end face 152 is adapted to the end face of the first mass block 13. The area of ​​the second connecting end face 152 is larger than the area of ​​the first connecting end face 151, which can increase the sensitivity of the sensor.

[0079] It should be noted that this embodiment differs from the cylindrical mass block and the frustum-shaped transition block in that the trapezoidal transition block can effectively integrate with the biaxial flexible hinge characteristics, exhibiting efficient dynamic characteristics along the y-axis and z-axis, and forming a three-component vibration sensor with the mass block connected to the cantilever beam. In contrast, using a cylindrical mass block and a frustum-shaped transition block would result in multi-axis dynamic characteristics, which is inconsistent with the three-component vibration sensor of this invention.

[0080] It should be noted that the entire structure of the polymer block 1 is symmetrical about the xoy reference plane and the yoz reference plane, for two reasons: firstly, to facilitate the installation of the FBG, and secondly, to maintain strict consistency between the mode shapes of the sensor in the x, y, and z directions and the directions of the x-axis, y-axis, and z-axis.

[0081] It should be noted that, viewed from the yoz plane, the width of the first mass block 13 in the z-direction is greater than the width of the rectangular base 10 in the z-direction. This facilitates the installation of the FBG and avoids interference from the base edge when sensing signals in the y and z directions. It is worth mentioning that if the above conditions are not met, the third FBG 23 cannot be installed properly due to the influence of the rectangular base 10. Proper installation here means that the FBG cannot maintain a vertically stretched state and will be affected by the rectangular base 10 during vibration. Specifically, when the FBG is installed on the accelerometer, a certain prestress is applied to maintain its stretched state. When the accelerometer senses vibration signals, the FBG can be considered to be undergoing minute vibrations. Therefore, the width of the first mass block 13 in the z-direction is greater than the width of the rectangular base 10 in the z-direction, i.e., a thickness of several millimeters is reserved so that the FBG will not touch the base 10 during vibration. This ensures that when sensing signals in the y and z directions, there will be no additional force from touching the base edge.

[0082] It should be noted that the height of the first mass block 13 is the same as the height of the geometric center of the through hole 101, and the center of the through hole 101 is located on the y-axis. The FBG passes through the through hole 101 and is connected to the surface of the first mass block 13.

[0083] It should be noted that the surface of the second mass block 14 on which the FBG is installed is in the same plane as the x-axis plane of the rectangular base 10.

[0084] It should be noted that the flexible hinge 11 is a co-orthogonal composite notch type flexible hinge, with its four sides exhibiting an asymmetrical arc-cut structure. Specifically, the notch of this flexible hinge is cut using an arc, and the thickness and notch radius differ at the thinnest point of the flexible hinge in the y and z directions, resulting in an asymmetric structure. The flexible hinge 11 possesses numerous advantages, including no gaps, no lubrication, no mechanical friction, high sensitivity, high energy conversion efficiency, and high displacement resolution. Unlike cylindrical flexible hinges, the flexible hinge described in this invention is a co-orthogonal composite notch type flexible hinge, forming a biaxial flexible hinge, while a cylindrical flexible hinge would form a multiaxial flexible hinge, which contradicts the design objectives.

[0085] From another perspective, the flexible hinge 11 is a co-orthogonal composite notch type flexible hinge, which is a biaxial flexible hinge with an arc-shaped notch. To match the three-component sensing characteristics involved in this invention, a biaxial flexible hinge is used in the y and z directions. This structure differs from cylindrical multiaxial flexible hinges and can effectively identify the vibration magnitude of the object under test in the y and z directions. Simultaneously, the flexible hinge 11 is a co-orthogonal composite notch type flexible hinge, which is an asymmetric arc-shaped notch type flexible hinge. This asymmetry is mainly reflected in the difference in the thickness of the thinnest part of the flexible hinge and the radius of the arc-shaped notch in the y and z directions. The difference in the thickness of the flexible hinge in the two directions directly affects the sensor's withstand strength limit in the y and z directions. By designing different thicknesses, measurements can be performed under vibration environments of varying intensities. The radius of the arc-shaped notch in the y and z directions is also an important parameter directly affecting the sensor's sensitivity and natural frequency in the y and z directions. Appropriate radius sizes can be used to adapt to vibration measurement environments with different vibration intensities and frequency ranges.

[0086] It should be noted that the FBG includes:

[0087] The first FBG21 is mounted on the rectangular base 10 and the second mass block 14 respectively. The first FBG21 is aligned with the y-axis direction.

[0088] The second FBG22 passes through the through hole 101 and is connected to the surface of the first mass block 13. The second FBG22 is aligned with the x-axis direction.

[0089] The third FBG23 has its pigtails connected to the surface of the first mass block 13, and the third FBG23 is aligned with the x-axis direction.

[0090] It should be noted that the cantilever beam 12 is a long and thin cantilever beam. The surface of the second mass block 14, on which the first FBG21 is mounted, is in the same plane as the x-axis plane of the rectangular base 10. This is to ensure that the first FBG21, after installation, is parallel to the yoz plane and perpendicular to the x-axis, so as to effectively sense vibration information in the x-direction. Since the flexible hinge requires a large mass block to exert its advantages, if a flexible hinge with an additional large mass block structure is used here, it will inevitably cause the first FBG21 to be non-parallel to the yoz plane or the overall volume to be too large. Furthermore, since the sensitivity of a short and thick cantilever beam structure is low, a compromise of a long and thin cantilever beam structure is chosen to balance the above two points, which ensures high sensitivity and avoids the problem of excessive volume.

[0091] It should be noted that the through hole 101 is opened on the x-axis plane near the side of the cantilever beam 12.

[0092] The three-component FBG vibration sensor according to embodiments of the present invention is based on a polymer integrally molded mass block, which has advantages such as low mass, no assembly error, high temperature resistance, strong magnetic field resistance, and corrosion resistance. It is not only suitable for vibration monitoring in harsh environments, but also achieves high sensitivity and high natural frequency sensing characteristics within a limited volume. Specifically, the sensor of the present invention uses a low mass density polymer block, which has the characteristics of low mass and small volume, but still achieves a high level of sensitivity and natural frequency. The use of polymer as the mass block in this invention allows the FBG three-component vibration sensor to be made entirely of non-metallic materials, making it more suitable for vibration testing in harsh environments such as strong magnetic fields, acids and alkalis, and humidity. Through reasonable structural design, the present invention uses a polymer mass block, integrally molding the mass block and the sensing structure, effectively avoiding errors caused by assembly and improving the stability of sensor performance. Finally, by optimizing the design of the mass block and sensor structure, a three-component sensor with high sensitivity and high natural frequency is realized.

[0093] This embodiment provides the design steps for a flexible hinge, including the following:

[0094] The geometry of the flexible hinge 11 is as follows Figure 4 As shown, the flexible hinge 11 is a co-position orthogonal composite notch type flexible hinge. Its structural feature is an asymmetric circular arc notch type flexible hinge. Its two side-view rectangular end faces are respectively connected to the x-axis plane of the rectangular base 10 and the smaller rectangular surface of the trapezoidal transition block 15. The flexible hinge 11 can be obtained by cutting a cuboid through a cylinder.

[0095] Step 1: [Imagine a circle with radius r] z The central axis of the cylinder is parallel to the y-axis, and it is moved inward along the z-axis of the cuboid to cut it off until the arc surface of the cylinder intersects the two vertices of the xoz plane of the cuboid. The cut is then complete. After cutting off both sides, its top view is as follows. Figure 5 As shown in (a) of the diagram.

[0096] Step 2: [The text abruptly ends here, seemingly incomplete.] y The central axis of the cylinder is parallel to the z-axis, and it is moved inward along the y-axis of the cuboid to cut it off until the arc surface of the cylinder intersects the two vertices of the xoy plane of the cuboid. The cutting is complete when both sides are cut off. The front view after cutting off both sides is as follows. Figure 5 As shown in (b) in the figure, a flexible hinge structure can be obtained.

[0097] To provide sufficient theoretical basis for the research and design of the three-component FBG vibration sensor, this embodiment discloses the theoretical analysis results in the x, y, and z directions. The fixed frequency and sensitivity in each direction in this embodiment are as follows:

[0098] The natural frequency of the entire system in the x-direction and sensitivity They are respectively:

[0099] (4)

[0100] (5)

[0101] in, The initial strain generated by the first FBG21 is due to the influence of gravity or fiber pretension on the cantilever beam when it is initially at rest. The stiffness of the optical fiber in the first FBG21. Let be the stiffness of the cantilever beam. The equivalent mass of the cantilever beam and the second mass block. The effective elastic-optical coefficient of the optical fiber. Let x be the effective length of the fiber in the x-direction of the first FBG21. Let be the length of the first connecting surface 151 and the second connecting surface 152 in the x direction.

[0102] Natural frequency in the y direction Sensitivity formula:

[0103] (6)

[0104] (7)

[0105] In the formula, Let be the stiffness of the biaxial flexible hinge rotating in the y-direction. This refers to the stiffness of the fiber in the second FBG. (If inserted...) Figure 3 As shown, The length of the first mass block in the y-direction is given, and the effective lengths of the optical fibers in the second FBG22 and the third FBG23 are given. , Let be the distance from the center of the flexible hinge to the center of mass of the mass block. The equivalent mass of the flexible hinge and the first mass block.

[0106] The same method can be used to obtain the natural frequency of the entire system in the z-direction. and sensitivity They are respectively:

[0107] (8)

[0108] (9)

[0109] in, Let be the stiffness of the biaxial flexible hinge rotating in the z-direction. The stiffness of the third FBG23 optical fiber. Let be the width of the first mass block in the z-direction.

[0110] This embodiment provides the following specific implementation examples:

[0111] The integrated polymer material block is formed by photopolymerization of methacrylic acid monomers, photoinitiators, and additives at 405 nm using a 3D printer for 10 minutes. It has an elastic modulus of 2.29737 GPa, a density of 1359.6 kg / m3, and a Poisson's ratio of 0.35.

[0112] A three-dimensional coordinate system is established with the geometric center of the rectangular base, and the dimensions of each component are as follows:

[0113] 1. The rectangular base 10 has a length of 11mm in the x direction, 30mm in the y direction, and 18mm in the z direction;

[0114] 2. The second mass block 14 has a length of 11 mm in the x direction, 9 mm in the y direction, and 18 mm in the z direction;

[0115] 3. The cantilever beam 12 has a length of 1.9 mm in the x-direction, 25 mm in the y-direction, and 18 mm in the z-direction;

[0116] 4. The first mass block 13 has a length of 13.5 mm in the x direction, 18 mm in the y direction, and 27 mm in the z direction;

[0117] 5. The thickness of the flexible hinge 11 at its thinnest point in the y-direction is t. y =2.69mm, the thinnest part in the z direction is t z =4.87mm; the radii of the cutting circles are r y =7.5mm, r z =4.4mm; the central axis of the flexible hinge 11 along the x-direction coincides with the central axis of the base along the x-direction;

[0118] 6. The flexible hinge 11 has a length of 8mm in the x-direction, 5mm in the y-direction, and 10mm in the z-direction;

[0119] 7. The overall geometric dimensions of the device are 70mm×27mm×64mm, and the length of the FBG is less than 1cm.

[0120] The performance of the three-dimensional FBG vibration sensor in this embodiment is compared with that of existing three-dimensional FBG acceleration vibration sensors, and the following experimental statistics are shown in Table 1:

[0121] Table 1: Performance Comparison of Three-Dimensional FBG Accelerometer Vibration Sensors

[0122]

[0123] The analysis of Comparative Example 1 is as follows:

[0124] ① The sensor in Comparative Example 1 is assembled using fastening bolts. The sensor is composed of multiple tiny parts and fastening bolts, making the assembly extremely complex. Under prolonged vibration, the sensor is prone to nonlinear vibration due to loosening of the fastening bolts, causing nonlinear changes in the resonance characteristics. For example, due to nonlinear effects, the actual natural frequency is less than the designed natural frequency, which is a fraction of the original natural frequency, resulting in a significant reduction in the sensor's operating frequency.

[0125] The present invention is made of polymer material using one-piece molding technology, and there is no problem of loose fasteners.

[0126] ② In Comparative Example 1, the sensor is made of metal. Because metal has high density, it weakens the advantage of fiber optic sensors as non-metallic FBG material sensors in terms of light weight. When measuring vibration, it is easy to have measurement errors due to its own weight.

[0127] The polymer material used in this invention possesses advantages such as corrosion resistance, moisture resistance, and resistance to strong magnetic interference, which are well-matched with the corrosion resistance, moisture resistance, and resistance to strong magnetic interference characteristics of fiber optic sensors. Furthermore, due to the low density of polymers, this invention is lightweight and less prone to measurement errors caused by weight.

[0128] The analysis of Comparative Example 2 is as follows:

[0129] ① The sensor in Comparative Example 2 is assembled using fastening bolts. The sensor is assembled using multiple tiny parts and fastening bolts, making the assembly extremely complex. Under prolonged vibration, the sensor is prone to nonlinear vibration caused by the loosening of the fastening bolts. This leads to nonlinear changes in the resonance characteristics. For example, due to nonlinear effects, the actual natural frequency is less than the designed natural frequency, and is a fraction of the original natural frequency, resulting in a significant reduction in the sensor's operating frequency.

[0130] This invention is made using polymer materials and integral molding technology, thus eliminating the problem of loose fasteners.

[0131] ② In Comparative Example 2, the sensor is made of metal. Because metal has high density, it weakens the advantage of fiber optic sensors as non-metallic FBG material sensors in terms of light weight. When measuring vibration, it is easy to have measurement errors due to its own weight.

[0132] The polymer material used in this invention possesses advantages such as corrosion resistance, moisture resistance, and resistance to strong magnetic interference, which are well-matched with the corrosion resistance, moisture resistance, and resistance to strong magnetic interference characteristics of fiber optic sensors. Furthermore, due to the low density of polymers, this invention is lightweight and less prone to measurement errors caused by weight.

[0133] ③ The hinge of the sensor in Comparative Example 2 is too weak, which makes it prone to fatigue fracture, and the machining accuracy of the vibration pickup structure is difficult to guarantee.

[0134] The present invention has performed a strength analysis on the accelerometer, and it can measure normally within the test range, without this problem.

[0135] The analysis of Comparative Example 3 is as follows:

[0136] ① The sensor in Comparative Example 3 is assembled using fastening bolts. The sensor is assembled with multiple tiny parts and fastening bolts, making the assembly extremely complex. Under prolonged vibration, the sensor is prone to nonlinear vibration caused by the loosening of the fastening bolts. This leads to nonlinear changes in the resonance characteristics. For example, due to nonlinear effects, the actual natural frequency is less than the designed natural frequency, and is a fraction of the original natural frequency, resulting in a significant reduction in the sensor's operating frequency.

[0137] This invention is made using polymer materials and integral molding technology, thus eliminating the problem of loose fasteners.

[0138] ② The sensor in Comparative Example 3 is made of metal. Because metal has high density, it weakens the advantage of fiber optic sensors as non-metallic FBG material sensors in terms of light weight. When measuring vibration, it is easy to have measurement errors due to its own weight.

[0139] The polymer material used in this invention possesses advantages such as corrosion resistance, moisture resistance, and resistance to strong magnetic interference, which are well-matched with the corrosion resistance, moisture resistance, and resistance to strong magnetic interference characteristics of fiber optic sensors. Furthermore, due to the low density of polymers, this invention is lightweight and less prone to measurement errors caused by weight.

[0140] The analysis of Comparative Example 4 is as follows:

[0141] ① The sensor in Comparative Example 4 is assembled using fastening bolts. The sensor is assembled with multiple tiny parts and fastening bolts, making the assembly extremely complex. Under prolonged vibration, the sensor is prone to nonlinear vibration caused by the loosening of the fastening bolts. This leads to nonlinear changes in the resonance characteristics. For example, due to nonlinear effects, the actual natural frequency is less than the designed natural frequency, and is a fraction of the original natural frequency, resulting in a significant reduction in the sensor's operating frequency.

[0142] This invention is made using polymer materials and integral molding technology, thus eliminating the problem of loose fasteners.

[0143] ②Comparative Example 4 uses 5 FBGs, but too many FBGs make the sensor more susceptible to damage. This invention uses only 3 FBGs.

[0144] ③ The sensors in Comparative Example 4 have sensitivities of 9.7 / 10.13 / 7.45 pm / g in three directions, respectively. The sensitivity is too low to be suitable for testing scenarios with minute vibrations.

[0145] The sensor of this invention has sensitivities of 57.03 / 128.16 / 60.49 pm / g in three directions, which can better measure scenarios with minute vibrations.

[0146] ④ The sensor in Comparative Example 4 is made of metal. Because metal has high density, it weakens the advantage of fiber optic sensors as non-metallic FBG material sensors in terms of light weight. When measuring vibration, it is easy to have measurement errors due to its own weight.

[0147] The polymer material used in this invention possesses advantages such as corrosion resistance, moisture resistance, and resistance to strong magnetic interference, which are well-matched with the corrosion resistance, moisture resistance, and resistance to strong magnetic interference characteristics of fiber optic sensors. Furthermore, due to the low density of polymers, this invention is lightweight and less prone to measurement errors caused by weight.

[0148] The analysis of Comparative Example 5 is as follows:

[0149] ① The sensor in Comparative Example 5 is assembled using fastening bolts. The sensor is assembled with multiple tiny parts and fastening bolts, making the assembly extremely complex. Under prolonged vibration, the sensor is prone to nonlinear vibration caused by the loosening of the fastening bolts. This leads to nonlinear changes in the resonance characteristics. For example, due to nonlinear effects, the actual natural frequency is less than the designed natural frequency, and is a fraction of the original natural frequency, resulting in a significant reduction in the sensor's operating frequency.

[0150] This invention is made using polymer materials and integral molding technology, thus eliminating the problem of loose fasteners.

[0151] ② The sensor in Comparative Example 5 is made of metal. Because metal has high density, it weakens the advantage of fiber optic sensors as non-metallic FBG material sensors in terms of light weight. When measuring vibration, it is easy to have measurement errors due to its own weight.

[0152] The polymer material used in this invention possesses advantages such as corrosion resistance, moisture resistance, and resistance to strong magnetic interference, which are well-matched with the corrosion resistance, moisture resistance, and resistance to strong magnetic interference characteristics of fiber optic sensors. Furthermore, due to the low density of polymers, this invention is lightweight and less prone to measurement errors caused by weight.

[0153] ③Comparative Example 5 uses 6 FBGs, but too many FBGs will cause them to be more easily damaged. This invention uses only 3 FBGs, which provides better safety.

[0154] The analysis of Comparative Example 6 is as follows:

[0155] ① The sensor in Comparative Example 6 is assembled using fastening bolts. The sensor is assembled using multiple tiny parts and fastening bolts, making the assembly extremely complex. Under prolonged vibration, the sensor is prone to nonlinear vibration caused by the loosening of the fastening bolts. This leads to nonlinear changes in the resonance characteristics. For example, due to nonlinear effects, the actual natural frequency is less than the designed natural frequency, and is a fraction of the original natural frequency, resulting in a significant reduction in the sensor's operating frequency.

[0156] This invention is made using polymer materials and integral molding technology, thus eliminating the problem of loose fasteners.

[0157] ② The sensor in Comparative Example 6 is made of metal. Due to the high density of metal, it weakens the advantage of fiber optic sensors as non-metallic FBG material sensors in terms of light weight. When measuring vibration, it is easy to have measurement errors due to its own weight.

[0158] The polymer material used in this invention possesses advantages such as corrosion resistance, moisture resistance, and resistance to strong magnetic interference, which are well-matched with the corrosion resistance, moisture resistance, and resistance to strong magnetic interference characteristics of fiber optic sensors. Furthermore, due to the low density of polymers, this invention is lightweight and less prone to measurement errors caused by weight.

[0159] ③ The comparative example 6 uses 6 FBGs. Too many FBGs will make the sensor more susceptible to damage. The maximum detectable acceleration is 3g, which is not suitable for testing high-intensity vibrations.

[0160] This invention uses only 3 FBGs to perform strength analysis on the accelerometer. It can withstand 10g of acceleration in three test directions without damage, which provides better safety compared to other methods.

[0161] The analysis of Comparative Example 7 is as follows:

[0162] ① The sensor in Comparative Example 7 is assembled using fastening bolts. The sensor is assembled with multiple tiny parts and fastening bolts, making the assembly extremely complex. Under prolonged vibration, the sensor is prone to nonlinear vibration caused by the loosening of the fastening bolts. This leads to nonlinear changes in the resonance characteristics. For example, due to nonlinear effects, the actual natural frequency is less than the designed natural frequency, which is a fraction of the original natural frequency, resulting in a significant reduction in the sensor's operating frequency.

[0163] This invention is made using polymer materials and integral molding technology, thus eliminating the problem of loose fasteners.

[0164] ② In Comparative Example 1, the sensor is made of metal. Because metal has high density, it weakens the advantage of fiber optic sensors as non-metallic FBG material sensors in terms of light weight. When measuring vibration, it is easy to have measurement errors due to its own weight.

[0165] The polymer material used in this invention possesses advantages such as corrosion resistance, moisture resistance, and resistance to strong magnetic interference, which are well-matched with the corrosion resistance, moisture resistance, and resistance to strong magnetic interference characteristics of fiber optic sensors. Furthermore, due to the low density of polymers, this invention is lightweight and less prone to measurement errors caused by weight.

[0166] In summary, the main differences between this invention and existing technologies can be summarized as follows:

[0167] The three-component acceleration vibration sensor of this invention employs co-positioned orthogonal composite notch-type flexible hinges on both sides of a rectangular base. This is an asymmetric arc-cut structure, distinct from cylindrical flexible hinge structures that are thinner in the middle and thicker at both ends. The mass blocks connected to both sides of the biaxial arc-cut flexible hinge via trapezoidal transition blocks are cuboid structures, unlike cylindrical structures. This structure allows the flexible hinge to better capture vibrations from both the y and z directions; while cylindrical flexible hinge structures are sensitive to multi-axis vibrations and therefore cannot meet the requirements of three-component vibration sensing. The three-component acceleration vibration sensor of this invention uses a long cantilever beam structure for the elastic body sensing vibration in the x-direction. This structure differs from flexible hinges in that flexible hinges typically require a large mass block to achieve their advantages. Since the FBG (Fast-Induced Gear) measuring the x-direction must be orthogonal to the x-axis, the second mass block at the top should not be too large, otherwise the rectangular base would be too bulky, making it difficult to control the sensor's size. Furthermore, while a short, thick cantilever beam structure can significantly reduce the sensor's size, it sacrifices too much sensitivity in the x-direction. Therefore, a compromise is made with a long, thin cantilever beam structure, ensuring high sensitivity and low cross-interference in the x-direction while also considering the sensor's size design. Currently, existing FBG acceleration vibration sensor designs primarily use metal materials, leading to assembly difficulties due to numerous components, and issues such as loosening and interference between fastening bolts and parts. This invention uses polymer materials and 3D printing technology, facilitating integrated sensor structure design and significantly reducing the impact of component assembly on performance. Unlike most current sensors made of high-density metal materials such as manganese 65, tantalum, and stainless steel, the performance of metal mass blocks is affected by harsh environments such as strong magnetic fields, humidity, and acid / alkali conditions. Their use inherently weakens the advantages of fiber optic sensors as non-metallic materials, making them suitable for harsh environments and lightweight. The polymer material used in this invention possesses advantages such as corrosion resistance, moisture resistance, and resistance to strong magnetic interference, which better match the corrosion resistance, moisture resistance, and resistance to strong magnetic interference characteristics of fiber optic sensors. Therefore, sensors made of this material are suitable for vibration monitoring in harsher environments. Existing sensors made of non-metallic composite materials are all one-dimensional sensors, unsuitable for vibration environments requiring omnidirectional monitoring. The three-component accelerometer sensor described in this invention can perform omnidirectional measurements in harsh environments. Compared with existing three-dimensional accelerometer FBG vibration sensors, this invention leverages the advantages of polymer materials, not only accurately measuring vibration signals in three dimensions in harsher environments but also achieving natural frequencies and sensitivities in the x, y, and z directions comparable to steel materials while achieving low cross-interference sensitivity. Example 2

[0168] A method for using a three-component FBG vibration sensor according to a second aspect of the present invention, wherein the three-component FBG vibration sensor is used to measure the object under test, includes the following steps:

[0169] Step S100: The sensitivity of the packaged three-component FBG vibration sensor in the x, y, and z directions is tested to obtain the relationship between the center wavelength offset of the FBG in the x, y, and z directions and the acceleration in each direction, thereby obtaining the sensitivity matrix. The relationship between the acceleration of the sensor in the x, y, and z directions and the change in the center wavelength of the FBG is shown below:

[0170] ,

[0171] in, These represent the changes in the center wavelength of the first FBG, second FBG, and third FBG, respectively. These represent the accelerations applied in the x, y, and z directions, respectively. Let be the sensitivity matrix, where: This represents the sensitivity of the sensor in the x-direction when vibration is applied in the x-direction. This represents the sensitivity to cross-coupling interference in the y direction when acceleration is applied in the x direction. This represents the sensitivity to cross-coupling interference in the z direction when acceleration is applied in the x direction;

[0172] This represents the sensor's cross-coupling interference sensitivity in the x-direction when vibration is applied in the y-direction. This represents the sensitivity perceived in the y-direction when acceleration is applied in the y-direction. This represents the sensitivity to cross-coupling interference in the z direction when acceleration is applied in the x direction;

[0173] This represents the cross-coupling interference sensitivity of the sensor in the x-direction when vibration is applied in the z-direction. This represents the sensitivity to cross-coupling interference in the y direction when acceleration is applied in the z direction. This represents the sensitivity perceived in the z-direction when acceleration is applied in the z-direction;

[0174] Step S200: Fix the surface of the rectangular base (10) away from the cantilever beam (12) to the surface of the object being measured;

[0175] Step S300: When the object under test is subjected to vibration, the center wavelength shift of the three FBGs is collected. , , ;

[0176] Step S400: Based on the sensor sensitivity matrix measured in step S100, the following relationship is established.

[0177]

[0178] Acceleration in all directions can be obtained, among which It is the inverse of the sensitivity matrix.

[0179] It should be noted that this embodiment also provides a test method for determining the relationship between the vibration amplitude and the change in the center wavelength of the FBG in the x, y, and z directions based on the sensor described in step S100. Specifically, when the vibration direction is parallel to the x-direction, the change in the center wavelength of the FBG in the x, y, and z directions is measured to obtain the sensor's response in the x-direction. and the cross-coupling interference response in the y and z directions. , (All are normalized sensitivities). When the vibration direction is parallel to the y-direction, the sensor's response in the y-direction can be obtained by measuring the change in the center wavelength of the FBG in the x, y, and z directions. and the cross-coupling interference response in the x and z directions. , (All are normalized sensitivities). When the vibration direction is parallel to the z-direction, the sensor's response in the z-direction can be obtained by measuring the change in the center wavelength of the FBG in the x, y, and z directions. and the cross-coupling interference response in the x and y directions. , (All are normalized sensitivities). The sensitivity coefficients obtained from the tests... , , , , , , , , Substituting the relationship between the vibration amplitude of the sensor in the x, y, and z directions and the change in the center wavelength of the FBG described in step S100, the specific parameters in this embodiment are as follows:

[0180]

[0181] It should be noted that, based on the relationship between the vibration amplitude of the sensor in each direction and the change in the center wavelength of the FBG measured in step S100, the relationship described in step S100 can be transformed into the following decoupling relationship of the accelerometer:

[0182]

[0183] The decoupling relationship of the accelerometer in this embodiment is specifically expressed as follows:

[0184]

[0185] It should be noted that, based on the relationship between the acceleration of the sensor in the x, y, and z directions measured in step S100 and the change in the center wavelength of the FBG, the decoupling relationship of the acceleration sensor mentioned in step S400 can be obtained, and the vibration of the object under test can be measured based on the decoupling relationship of the sensor.

[0186] It should be noted that the test method for the relationship between the vibration amplitude of the three-component accelerometer in the x, y, and z directions and the change in the center wavelength of the FBG in step S100 is as follows: When the vibration direction is parallel to the x-direction, test the response in the x-direction, and the cross-coupling interference response in the y and z directions. Using the sensitivity in the x-direction as 1, normalize the sensitivity in the y and z directions to obtain the sensitivity matrix. , , The coefficients of and . Using the same method, the remaining coefficients in the formula relating the vibration amplitude of the sensor in the x, y, and z directions to the change in the center wavelength of the FBG can be obtained. , , , , , .

[0187] It should be noted that, for ease of understanding, the following supplementary explanation is provided: In this embodiment, the measured acceleration sensitivity of the sensor in the x, y, and z directions is 57.03 pm / g, 128.16 pm / g, and 60.49 pm / g, respectively. Regarding the specific explanation of each parameter in the decoupling equation of the acceleration sensor in this embodiment, assuming the sensor is only subjected to vibration from the x direction, the y and z directions are... , No response, then based on the sensitivity in the x-direction... You can get Thus, the acceleration in the x-direction is obtained. If the sensor receives a vibration signal from an unknown direction in three-dimensional space, it will cause acceleration in all three directions of the sensor. , , The change in the center wavelength results in a waveform in the x, y, and z directions containing coupled cross-interference. To obtain the true acceleration vibration signal input, it is necessary to decouple again according to the sensitivity decoupling relationship described in this embodiment.

[0188] In the description of this invention, 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," "axial," "radial," and "circumferential" 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 invention 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 the invention.

[0189] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0190] Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The reference to "embodiment" herein means that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily indicate the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0191] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A three-component FBG vibration sensor, comprising an FBG, characterized in that, Also includes: An integrally molded polymer block (1), the polymer block (1) comprising: A rectangular base (10) is provided, wherein a three-dimensional coordinate system is constructed with the geometric center of the rectangular base (10) as the origin. The rectangular base (10) has an x-axis surface, a y-axis surface and a z-axis surface, and a through hole (101) is provided on the x-axis surface. Two flexible hinges (11) are connected to the x-axis plane and are symmetrical about the yoz reference plane. They have two rotational degrees of freedom. One is used to measure the acceleration in the y direction and the motion is rotation around the z axis. The other is used to measure the acceleration in the z direction and the motion is rotation around the y axis. The flexible hinge (11) is a co-position orthogonal composite notch type flexible hinge. The four sides are as a whole asymmetrical arc notch structure. Specifically, the notch of the flexible hinge is cut with an arc. The thickness and notch radius of the thinnest part of the flexible hinge in the y and z directions are different, which makes the structure asymmetrical. Two first mass blocks (13) are connected to the end face of the flexible hinge (11) respectively. The pigtail of the FBG parallel to the x-axis is connected to the surface of each first mass block (13) to form a vibration detection module in the y-direction and a vibration detection module in the z-direction. Cantilever beam (12), connected to any y-axis plane; The second mass block (14) is connected to the end face of the cantilever beam (12), and the FBG tail fiber parallel to the y-axis is connected to the surface of the second mass block (14) and the x-axis surface of the rectangular base (10) to form an x-direction vibration detection module. Two trapezoidal transition blocks (15) have a first connecting end face (151) and a second connecting end face (152) that are parallel to each other, wherein the first connecting end face (151) is adapted to the end face of the flexible hinge (11), and the second connecting end face (152) is adapted to the end face of the first mass block (13), and the area of ​​the second connecting end face is greater than the area of ​​the first connecting end face.

2. The three-component FBG vibration sensor according to claim 1, characterized in that, The entire structure of the polymer block (1) is symmetrical about the xoy reference plane and the yoz reference plane, respectively.

3. The three-component FBG vibration sensor according to claim 1, characterized in that, Viewed from the yoz plane, the width of the first mass block (13) in the z direction is greater than the width of the rectangular base (10) in the z direction.

4. The three-component FBG vibration sensor according to claim 1, characterized in that, The height of the first mass block (13) is the same as the height of the geometric center of the through hole (101), and the geometric center of the through hole (101) is located on the y-axis. The FBG passes through the through hole (101) and connects to the surface of the first mass block (13).

5. The three-component FBG vibration sensor according to claim 1, characterized in that, The surface of the second mass block (14) on which the FBG is mounted is in the same plane as the x-axis plane of the rectangular base (10).

6. The three-component FBG vibration sensor according to claim 1, characterized in that, The FBG includes: The first FBG (21) has its pigtails mounted on a rectangular base (10) and a second mass block (14), respectively. The axial direction of the first FBG (21) is consistent with the y-axis direction. The second FBG (22) passes through the through hole (101) and is connected to the surface of the first mass block (13). The axial direction of the second FBG (22) is consistent with the x-axis direction. The third FBG (23) has its pigtails connected to the surface of the first mass block (13), and the axial direction of the third FBG (23) is consistent with the x-axis direction.

7. The three-component FBG vibration sensor according to claim 1, characterized in that, The through hole (101) is located on the x-axis surface near the side of the cantilever beam (12).

8. A method of using a three-component FBG vibration sensor, characterized in that, Measuring an object using a three-component FBG vibration sensor as described in any one of claims 1 to 7 includes the following steps: Step S100: The sensitivity of the packaged three-component FBG vibration sensor in the x, y, and z directions is tested to obtain the relationship between the center wavelength offset of the FBG in the x, y, and z directions and the acceleration in each direction, thereby obtaining the sensitivity matrix. The relationship between the acceleration of the sensor in the x, y, and z directions and the change in the center wavelength of the FBG is shown below: ， in, These represent the changes in the center wavelength of the first FBG, second FBG, and third FBG, respectively. These represent the accelerations applied in the x, y, and z directions, respectively. Let be the sensitivity matrix, where: This represents the sensitivity of the sensor in the x-direction when vibration is applied in the x-direction. This represents the sensitivity to cross-coupling interference in the y direction when acceleration is applied in the x direction. This represents the sensitivity to cross-coupling interference in the z direction when acceleration is applied in the x direction; This represents the sensor's cross-coupling interference sensitivity in the x-direction when vibration is applied in the y-direction. This represents the sensitivity perceived in the y-direction when acceleration is applied in the y-direction. This represents the sensitivity to cross-coupling interference in the z direction when acceleration is applied in the x direction; This represents the cross-coupling interference sensitivity of the sensor in the x-direction when vibration is applied in the z-direction. This represents the sensitivity to cross-coupling interference in the y direction when acceleration is applied in the z direction. This represents the sensitivity perceived in the z-direction when acceleration is applied in the z-direction; Step S200: Fix the surface of the rectangular base (10) away from the cantilever beam (12) to the surface of the object being measured; Step S300: When the object under test is subjected to vibration, the center wavelength shift of the three FBGs is collected. , , ; Step S400: Based on the sensor sensitivity matrix measured in step S100, the following relationship is established. ， Acceleration in all directions can be obtained, among which It is the inverse of the sensitivity matrix.

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