CN116183960A - FBG acceleration sensor based on bearing and flexible hinge and measuring method - Google Patents
FBG acceleration sensor based on bearing and flexible hinge and measuring method Download PDFInfo
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- CN116183960A CN116183960A CN202310018561.3A CN202310018561A CN116183960A CN 116183960 A CN116183960 A CN 116183960A CN 202310018561 A CN202310018561 A CN 202310018561A CN 116183960 A CN116183960 A CN 116183960A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/03—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses by using non-electrical means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
- G01V1/16—Receiving elements for seismic signals; Arrangements or adaptations of receiving elements
- G01V1/18—Receiving elements, e.g. seismometer, geophone or torque detectors, for localised single point measurements
Abstract
The application is applicable to the technical field of acceleration sensors, and provides an FBG acceleration sensor based on a bearing and a flexible hinge and a measuring method, wherein the FBG acceleration sensor comprises: the device comprises a first mass block, a second mass block, a flexible hinge, a first bearing seat, a second bearing seat and a fiber bragg grating; the first mass block and the second mass block are arranged in parallel and opposite, and the flexible hinge is connected between the two mass blocks; the first bearing seat and the second bearing seat are respectively arranged on the outer side surfaces of the first mass block and the second mass block; the fiber bragg grating comprises a first fiber bragg grating and/or a second fiber bragg grating, wherein the first fiber bragg grating is arranged between the upper ends of the two mass blocks, and/or the second fiber bragg grating is arranged between the lower ends of the two mass blocks. The FBG acceleration sensor based on the bearing and the flexible hinge has high sensitivity, high linearity and high natural frequency, and can realize accurate measurement of medium-high frequency vibration signals.
Description
Technical Field
The application relates to the technical field of acceleration sensors, in particular to an FBG acceleration sensor based on a bearing and a flexible hinge and a measuring method.
Background
The accurate measurement of the medium-high frequency vibration signal (namely the vibration acceleration of the medium-high frequency vibration signal) has important significance for the vibration monitoring of axle boxes of high-speed motor train units, microseism monitoring and the like in many engineering fields. The traditional electric sensor has the defects of easiness in electromagnetic interference, signal attenuation caused by overlong wires, difficulty in application in special environments and the like. The optical fiber Bragg grating (Fiber Bragg Grating, english is called FBG for short, chinese is called fiber grating for short) acceleration sensor adopts a passive sensing element, optical signal transmission is not influenced by factors such as electromagnetism and distance, and the optical fiber Bragg grating acceleration sensor is corrosion-resistant, networking-enabled, easy to realize distributed sensing, and suitable for vibration monitoring in severe environments, so that the optical fiber Bragg grating acceleration sensor is widely focused by scientific researchers.
However, the conventional FBG acceleration sensor has the problems of low sensitivity, low linearity, low natural frequency and the like, and cannot realize accurate measurement of the medium-high frequency vibration signal.
Disclosure of Invention
In view of this, the embodiment of the application provides an FBG acceleration sensor based on a bearing and a flexible hinge and a measurement method thereof, so as to solve the technical problem that the existing acceleration sensor cannot realize accurate measurement of a medium-high frequency vibration signal.
In a first aspect, embodiments of the present application provide an FBG acceleration sensor based on a bearing and a flexible hinge, including: the device comprises a first mass block, a second mass block, a flexible hinge, a first bearing seat, a second bearing seat and a fiber bragg grating.
The first mass block and the second mass block are arranged in parallel and opposite to each other, and the side surfaces of the first mass block and the second mass block, which are close to each other, are inner side surfaces; the first end of the flexible hinge is connected with the inner side surface of the first mass block, and the second end of the flexible hinge is connected with the inner side surface of the second mass block.
The first end of the first bearing seat is connected with the central position of the outer side surface of the first mass block, and the first end of the second bearing seat is connected with the central position of the outer side surface of the second mass block; the first bearing seat and the second bearing seat are respectively provided with a first bearing hole and a second bearing hole, and the axial direction of the bearing holes is vertical to the axial direction of the mass block; the opposite side of the inner side of the mass is the outer side of the mass.
The fiber bragg grating comprises a first fiber bragg grating and/or a second fiber bragg grating; the first fiber bragg grating is arranged between the upper end of the first mass block and the upper end of the second mass block, and/or the second fiber bragg grating is arranged between the lower end of the first mass block and the lower end of the second mass block.
In a possible implementation manner of the first aspect, the FBG acceleration sensor based on the bearing and the flexible hinge further comprises: the first extension rod, the second extension rod, the third extension rod and the fourth extension rod.
The first extension rod and the second extension rod are respectively arranged on the upper surface and the lower surface of the first mass block and extend along the axial direction of the first mass block; the third extension rod and the fourth extension rod are respectively arranged on the upper surface and the lower surface of the second mass block and extend along the axial direction of the second mass block. The first fiber bragg grating is arranged between the free end of the first extension rod and the free end of the third extension rod, and/or the second fiber bragg grating is arranged between the free end of the second extension rod and the free end of the fourth extension rod.
In a possible implementation manner of the first aspect, the FBG acceleration sensor based on the bearing and the flexible hinge further comprises: the device comprises a shell, a third bearing seat and a fourth bearing seat; the center positions of the left inner side surface and the right inner side surface of the shell are respectively provided with a third bearing seat and a fourth bearing seat; the third bearing seat and the fourth bearing seat are respectively provided with a third bearing hole and a fourth bearing hole, and the axial direction of the bearing holes is perpendicular to the axial direction of the shell.
In a possible implementation manner of the first aspect, the FBG acceleration sensor based on the bearing and the flexible hinge further comprises: a first bearing and a second bearing; the first bearing, the first bearing seat and the third bearing seat are matched, and the second bearing, the second bearing seat and the fourth bearing seat are matched; the first mass block is fixed in the shell through a first bearing, a first bearing seat and a third bearing seat, and the second mass block is fixed in the shell through a second bearing, a second bearing seat and a fourth bearing seat; the first mass can rotate around the axial direction of the first bearing, and the second mass can rotate around the axial direction of the second bearing.
In a possible implementation manner of the first aspect, when the number of the first fiber gratings is two or more, each first fiber grating is disposed in parallel between an upper end of the first mass block and an upper end of the second mass block; when the number of the second fiber gratings is two or more, each second fiber grating is arranged in parallel between the lower end of the first mass block and the lower end of the second mass block; the number of the first fiber gratings is the same as or different from the number of the second fiber gratings.
In a possible implementation manner of the first aspect, the upper surface and the lower surface of the flexible hinge are provided with arc-shaped grooves, and the two grooves are symmetrical to each other.
In a possible implementation manner of the first aspect, the first mass and the second mass simultaneously rotate around the axial direction of the first bearing and the axial direction of the second bearing, respectively, when excited by external vibrations; correspondingly, the first fiber bragg grating is compressed or stretched, and/or the second fiber bragg grating is stretched or compressed.
In a second aspect, an embodiment of the present application provides a method for measuring an FBG acceleration sensor based on a bearing and a flexible hinge, which is applied to the FBG acceleration sensor based on a bearing and a flexible hinge as in any one of the first aspects; when vibration is generated outside, the first mass block and the second mass block simultaneously rotate around the axial direction of the first bearing and the axial direction of the second bearing respectively; accordingly, the first fiber grating is compressed or stretched, axial strain is generated to cause the change of the center wavelength of the first fiber grating, and/or the second fiber grating is stretched or compressed, axial strain is generated to cause the change of the center wavelength of the second fiber grating.
The measuring method comprises the following steps: acquiring related parameters of the central wavelength of the first fiber bragg grating and/or related parameters of the central wavelength of the second fiber bragg grating; and determining the vibration acceleration according to the related parameters of the center wavelength of the first fiber grating and/or the related parameters of the center wavelength of the second fiber grating.
In a possible implementation manner of the second aspect, the related parameter of the central wavelength of the first fiber grating is a central wavelength variation of the first fiber grating, and the related parameter of the central wavelength of the second fiber grating is a central wavelength variation of the second fiber grating; determining the vibration acceleration according to the related parameter of the center wavelength of the first fiber grating and/or the related parameter of the center wavelength of the second fiber grating comprises the following steps: determining the vibration acceleration according to the central wavelength variation of the first fiber bragg grating and/or the central wavelength variation of the second fiber bragg grating based on a calculation formula of the first vibration acceleration; the first vibration acceleration is calculated as:
a＝(∑|Δλ 1 |+∑|Δλ 2 |)/S 0
wherein a is vibration acceleration, deltalambda 1 For the central wavelength variation of each first fiber grating, delta lambda 2 S is the central wavelength variation of each second fiber bragg grating 0 The sensitivity is preset; when the fiber bragg grating only comprises the first fiber bragg grating, the related parameter of the second fiber bragg grating is zero; when the fiber grating only comprises the second fiber grating, the relevant parameter of the first fiber grating is zero.
In a possible implementation manner of the second aspect, the related parameter of the central wavelength of the first fiber grating includes the central wavelength of the first fiber grating and the initial central wavelength of the first fiber grating, and the related parameter of the central wavelength of the second fiber grating includes the central wavelength of the second fiber grating and the initial central wavelength of the second fiber grating; the initial center wavelength of the first fiber grating is the center wavelength when the first fiber grating does not vibrate, and the initial center wavelength of the second fiber grating is the center wavelength when the second fiber grating does not vibrate; determining the vibration acceleration according to the related parameter of the center wavelength of the first fiber grating and/or the related parameter of the center wavelength of the second fiber grating comprises the following steps: determining the vibration acceleration according to the central wavelength of the first fiber grating and the initial central wavelength of the first fiber grating and/or the central wavelength of the second fiber grating and the initial central wavelength of the second fiber grating based on a calculation formula of the second vibration acceleration; the second vibration acceleration is calculated as:
a＝[(∑λ 1 -∑λ 2 )-(∑λ 1B -∑λ 2B )]/S 0
wherein a is vibration acceleration, lambda 1 Lambda is the center wavelength of each first fiber grating 2 Is the center wavelength lambda of each second fiber grating 1B For the initial center wavelength lambda of each first fiber grating 2B For the initial center wavelength of each second fiber grating, S 0 The sensitivity is preset; when the fiber bragg grating only comprises the first fiber bragg grating, the related parameter of the second fiber bragg grating is zero; when the fiber grating only comprises the second fiber grating, the relevant parameter of the first fiber grating is zero.
It will be appreciated that the advantages of the second aspect may be found in the relevant description of the first aspect, and will not be described in detail herein.
According to the FBG acceleration sensor and the measuring method based on the bearing and the flexible hinge, the single flexible hinge is used for connecting the two mass blocks, and the fiber bragg grating structure and the double-bearing structure are adopted, so that the sensitivity and the linearity of the FBG acceleration sensor can be improved, the natural frequency is improved, the accurate measurement of medium-high frequency vibration signals is realized, meanwhile, the temperature influence is eliminated, and the frequency measuring range of the FBG acceleration sensor is increased.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required for the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic structural diagram of an FBG acceleration sensor based on a bearing and a flexible hinge according to an embodiment of the present application;
FIG. 2 is a schematic structural diagram of an FBG acceleration sensor based on bearings and flexible hinges according to a further embodiment of the present application;
FIG. 3 is a schematic flow chart of a measurement method of an FBG acceleration sensor based on a bearing and a flexible hinge according to an embodiment of the present application;
FIG. 4 is a schematic diagram of the working principle and structure of an FBG acceleration sensor based on bearings and flexible hinges according to an embodiment of the present application;
fig. 5 is a schematic diagram of the natural frequency and sensitivity of the FBG acceleration sensor according to an embodiment of the present application as a function of each structural parameter.
Reference numerals:
1: a first mass; 2: a second mass; 3: a flexible hinge; 4: a first bearing seat; 5: a second bearing seat; 6: a first fiber grating; 7: a second fiber bragg grating; 8: a first extension rod; 9: a second extension rod; 10: a third extension rod; 11: a fourth extension bar; 12: a housing; 13: a third bearing seat; 14: a fourth bearing housing; 15: a first bearing; 16: and a second bearing.
Detailed Description
The present application will be more clearly described with reference to the following specific examples. The following examples will assist those skilled in the art in further understanding the function of the present application, but are not intended to limit the present application in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the spirit of the present application. These are all within the scope of the present application.
It should be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It should also be understood that the term "and/or" as used in this specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
In the description of this application and the claims that follow, the terms "first," "second," "third," etc. are used merely to distinguish between descriptions and should not be construed to indicate or imply relative importance.
Reference in the specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise.
Furthermore, references to "a plurality of" in the examples of this application should be interpreted as two or more.
Fig. 1 is a schematic structural diagram of an FBG acceleration sensor based on a bearing and a flexible hinge according to an embodiment of the present application. As shown in fig. 1, the FBG acceleration sensor based on the bearing and the flexible hinge (hereinafter abbreviated as FBG acceleration sensor) includes: the mass block comprises a first mass block 1, a second mass block 2, a flexible hinge 3, a first bearing seat 4, a second bearing seat 5 and a fiber bragg grating.
The first mass block 1 and the second mass block 2 are arranged in parallel and opposite, and the side surfaces of the first mass block 1 and the second mass block 2, which are close to each other, are inner side surfaces. The first end of the flexible hinge 3 is connected with the inner side surface of the first mass block 1, and the second end of the flexible hinge 3 is connected with the inner side surface of the second mass block 2.
The first end of the first bearing seat 4 is connected with the central position of the outer side surface of the first mass block 1, and the first end of the second bearing seat 5 is connected with the central position of the outer side surface of the second mass block 2; the first bearing seat 4 and the second bearing seat 5 are respectively provided with a first bearing hole and a second bearing hole, and the axial direction of the bearing holes is vertical to the axial direction of the mass block; the opposite side of the inner side of the mass is the outer side of the mass.
The fibre gratings comprise a first fibre grating 6 and/or a second fibre grating 7. The first fiber bragg grating 6 is disposed between the upper end of the first mass block 1 and the upper end of the second mass block 2, and/or the second fiber bragg grating 7 is disposed between the lower end of the first mass block 1 and the lower end of the second mass block 2 (fig. 1 is an example in which the fiber bragg grating includes the first fiber bragg grating 6 and the second fiber bragg grating 7).
Alternatively, the flexible hinge 3 may be a straight round flexible hinge, the upper and lower surfaces of the flexible hinge 3 are both provided with arc grooves, and the two grooves are symmetrical to each other, and the groove curve is a conical curve. Illustratively, the first and second ends of the flexible hinge 3 may connect the center position of the inner side of the first mass 1 and the center position of the inner side of the second mass 2, respectively, but are not limited to the center positions of the inner sides of the masses. When not excited by external vibration, the axial direction of the mass block is parallel to the vertical direction.
By connecting two mass blocks by adopting a single flexible hinge 3, the sensitivity of the FBG acceleration sensor can be improved, and the problems of reduced linearity and reduced natural frequency of the FBG acceleration sensor caused by a multi-hinge structure are avoided. The two mass blocks are connected through the single flexible hinge 3, so that when the two mass blocks are excited by external vibration, the two mass blocks can vibrate up and down at the same time and cannot rotate in the same direction in a low-order mode, and the FBG acceleration sensor has a wide frequency measurement range. The dual-fiber grating structure is adopted, so that the axial strain directions of the two fiber gratings are opposite, the sensitivity of the FBG acceleration sensor can be improved, and meanwhile, the temperature influence is eliminated. The dual fiber grating structure refers to a fiber grating including both the first fiber grating 6 and the second fiber grating 7.
Optionally, when the number of the first fiber gratings 6 is two or more, each first fiber grating 6 is disposed in parallel between the upper end of the first mass block 1 and the upper end of the second mass block 2. When the number of the second fiber gratings 7 is two or more, each second fiber grating 7 is arranged in parallel between the lower end of the first mass block 1 and the lower end of the second mass block 2. The number of first fiber gratings 6 is the same as or different from the number of second fiber gratings 7.
Illustratively, when the fiber grating includes only the first fiber grating 6, and the fiber grating includes both the first fiber grating 6 and the second fiber grating 7, the first fiber grating 6 is at least one. When the fiber grating includes only the second fiber grating 7, and the fiber grating includes both the first fiber grating 6 and the second fiber grating 7, the second fiber grating 7 is at least one.
Optionally, referring to fig. 1, the FBG acceleration sensor based on the bearing and the flexible hinge further includes: a first extension rod 8, a second extension rod 9, a third extension rod 10 and a fourth extension rod 11.
The first extension rod 8 and the second extension rod 9 are respectively arranged on the upper surface and the lower surface of the first mass block 1 and extend along the axial direction of the first mass block 1; the third extension rod 10 and the fourth extension rod 11 are respectively disposed on the upper surface and the lower surface of the second mass block 2, and extend along the axial direction of the second mass block 2. The first fiber grating 6 is arranged between the free end of the first extension rod 8 and the free end of the third extension rod 10, and the second fiber grating 7 is arranged between the free end of the second extension rod 9 and the free end of the fourth extension rod 11.
Illustratively, the first fiber grating 6 and the second fiber grating 7 apply a first pre-stress and a second pre-stress, respectively, when set. Specifically, the first fiber bragg grating 6 is stuck between the free ends of the first extension rod 8 and the third extension rod 10 in a two-point encapsulation mode, the second fiber bragg grating 7 is stuck between the free ends of the second extension rod 9 and the fourth extension rod 11 in a two-point encapsulation mode, and the first prestress and the second prestress are respectively applied when the first fiber bragg grating 6 and the second fiber bragg grating 7 are stuck, so that the chirp effect is avoided, and the first prestress can be the same as the second prestress or different from the second prestress.
Alternatively, when the number of the first fiber gratings 6 is two or more, each of the first fiber gratings 6 is disposed in parallel between the free end of the first extension rod 8 and the free end of the third extension rod 10. When there are two or more second fiber gratings 7, each second fiber grating 7 is disposed in parallel between the free end of the second extension rod 9 and the free end of the fourth extension rod 11.
Optionally, referring to fig. 2, the FBG acceleration sensor based on the bearing and the flexible hinge may further include: a housing 12, a third bearing housing 13 and a fourth bearing housing 14.
The center positions of the left and right inner sides of the housing 12 are respectively provided with a third bearing seat 13 and a fourth bearing seat 14. The third bearing seat 13 and the fourth bearing seat 14 are respectively provided with a third bearing hole and a fourth bearing hole, and the axial direction of the bearing holes is perpendicular to the axial direction of the shell 12.
The axial direction of the housing 12 is parallel to the vertical direction.
Optionally, referring to fig. 2, the FBG acceleration sensor based on the bearing and the flexible hinge may further include: a first bearing 15 and a second bearing 16.
The first bearing 15, the first bearing seat 4 and the third bearing seat 13 are matched, and the second bearing 16, the second bearing seat 5 and the fourth bearing seat 14 are matched. The first mass 1 is fixed in the housing 12 by a first bearing 15, a first bearing seat 4 and a third bearing seat 13, and the second mass 2 is fixed in the housing 12 by a second bearing 16, a second bearing seat 5 and a fourth bearing seat 14.
Illustratively, the first mass 1 is capable of micro-rotation about the axis of the first bearing 15 and the second mass 2 is capable of micro-rotation about the axis of the second bearing 16. The first bearing 15 and the second bearing 16 may be deep groove ball bearings. The sensitivity of the FBG acceleration sensor can be improved by adopting a single flexible hinge 3 to connect two mass blocks and adopting a double-bearing structure.
Alternatively, the first mass 1 and the second mass 2 rotate simultaneously around the axial direction of the first bearing 15 and the axial direction of the second bearing 16, respectively, when excited by external vibrations. Accordingly, the first fiber grating 6 is compressed or stretched, and/or the second fiber grating 7 is stretched or compressed. When the fiber gratings include the first fiber grating 6 and the second fiber grating 7, if the first fiber grating 6 is compressed, the second fiber grating 7 is stretched, and if the first fiber grating 6 is stretched, the second fiber grating 7 is compressed. The fiber grating generates axial strain so as to cause the central wavelength of the fiber grating to change, and then the vibration acceleration can be determined according to the relation between the vibration acceleration and the related parameters of the central wavelength of the fiber grating, namely the medium-high frequency vibration signal is determined.
According to the FBG acceleration sensor based on the bearing and the flexible hinge, the two mass blocks are connected through the single flexible hinge, and the sensitivity and the linearity of the FBG acceleration sensor can be improved through the fiber bragg grating structure and the double-bearing structure, the natural frequency is improved, the accurate measurement of the medium-high frequency vibration signal is realized, meanwhile, the temperature influence is eliminated, and the frequency measurement range of the FBG acceleration sensor is increased.
Fig. 3 is a schematic flow chart of a measurement method of an FBG acceleration sensor based on a bearing and a flexible hinge according to an embodiment of the present application. As shown in fig. 3, the above measuring method is applied to an FBG acceleration sensor based on a bearing and a flexible hinge, and includes:
And 102, determining vibration acceleration according to the related parameters of the center wavelength of the first fiber grating and/or the related parameters of the center wavelength of the second fiber grating.
The FBG acceleration sensor based on the bearing and the flexible hinge is provided by any embodiment of the application.
In step 101, the obtaining of the parameter related to the central wavelength of the first fiber bragg grating or the parameter related to the central wavelength of the second fiber bragg grating refers to obtaining the central wavelength of the first fiber bragg grating when the fiber bragg grating includes only the first fiber bragg grating, and obtaining the central wavelength of the second fiber bragg grating when the fiber bragg grating includes only the second fiber bragg grating. Similarly, in step 102, the vibration acceleration is determined according to the related parameter of the center wavelength of the first fiber bragg grating or the related parameter of the center wavelength of the second fiber bragg grating, which means that when the fiber bragg grating includes only the first fiber bragg grating, the vibration acceleration is determined according to the related parameter of the center wavelength of the first fiber bragg grating, and when the fiber bragg grating includes only the second fiber bragg grating, the vibration acceleration is determined according to the related parameter of the center wavelength of the second fiber bragg grating.
Illustratively, the first mass and the second mass simultaneously rotate about the axial direction of the first bearing and the axial direction of the second bearing, respectively, when vibration is generated from the outside. Accordingly, the first fiber grating is compressed or stretched, axial strain is generated to cause the change of the center wavelength of the first fiber grating, and/or the second fiber grating is stretched or compressed, axial strain is generated to cause the change of the center wavelength of the second fiber grating. And determining the vibration acceleration according to the related parameters of the center wavelength of the fiber bragg grating.
In one possible implementation, the step 102 may include:
and determining the vibration acceleration according to the central wavelength variation of the first fiber bragg grating and/or the central wavelength variation of the second fiber bragg grating based on a calculation formula of the first vibration acceleration.
The calculation formula of the first vibration acceleration is as follows:
a＝(∑|Δλ 1 |+∑|Δλ 2 |)/S 0 (1)
wherein a is vibration acceleration, deltalambda 1 For the central wavelength variation of each first fiber grating, delta lambda 2 S is the central wavelength variation of each second fiber bragg grating 0 The sensitivity is preset. When the fiber bragg grating only comprises the first fiber bragg grating, the related parameter of the second fiber bragg grating is zero; when the fiber grating only comprises the second fiber grating, the relevant parameter of the first fiber grating is zero.
The central wavelength variation of the first fiber grating and the central wavelength variation of the second fiber grating can be obtained through a fiber grating demodulator. The preset sensitivity is the calibration sensitivity of the FBG acceleration sensor.
It is noted that, as shown in the calculation formula of the first vibration acceleration, when there are two or more first fiber gratings, the amount of change in the center wavelength of each first fiber grating is the sum of the amounts of change in the center wavelength of each first fiber grating. When there are two or more second fiber gratings, the amount of change in the center wavelength of each second fiber grating is the sum of the amounts of change in the center wavelength of each second fiber grating.
In another possible embodiment, the parameters related to the center wavelength of the first fiber grating include the center wavelength of the first fiber grating and the initial center wavelength of the first fiber grating, and the parameters related to the center wavelength of the second fiber grating include the center wavelength of the second fiber grating and the initial center wavelength of the second fiber grating. The step 102 may include:
and determining the vibration acceleration according to the central wavelength of the first fiber grating and the initial central wavelength of the first fiber grating and/or the central wavelength of the second fiber grating and the initial central wavelength of the second fiber grating based on a calculation formula of the second vibration acceleration.
The calculation formula of the second vibration acceleration is as follows:
a＝[(∑λ 1 -∑λ 2 )-(∑λ 1B -∑λ 2B )]/S 0 (2)
wherein a is vibration acceleration, lambda 1 Lambda is the center wavelength of each first fiber grating 2 Is the center wavelength lambda of each second fiber grating 1B For the initial center wavelength lambda of each first fiber grating 2B For the initial center wavelength of each second fiber grating, S 0 The sensitivity is preset. When the fiber bragg grating only comprises the first fiber bragg grating, the related parameter of the second fiber bragg grating is zero; when the fiber grating only comprises the second fiber grating, the relevant parameter of the first fiber grating is zero.
It is noted that, as shown in the calculation formula of the second vibration acceleration, when there are two or more first fiber gratings, the center wavelength of each first fiber grating is the sum of the center wavelengths of the first fiber gratings, and the initial center wavelength of each first fiber grating is the sum of the initial center wavelengths of the first fiber gratings. When the number of the second fiber gratings is two or more, the center wavelength of the second fiber gratings is the sum of the center wavelengths of the second fiber gratings, and the initial center wavelength of the second fiber gratings is the sum of the initial center wavelengths of the second fiber gratings.
The center wavelength of the first fiber grating and the center wavelength of the second fiber grating can be obtained through a fiber grating demodulator and are measured values. The preset sensitivity is the calibration sensitivity of the FBG acceleration sensor. The measuring method can avoid the influence of the temperature on the center wavelength of the fiber bragg grating, further eliminate the influence of the temperature on the calculation of the vibration acceleration, and improve the accuracy of the vibration acceleration.
Alternatively, the sensitivity and frequency measurement range of the FBG acceleration sensor are controlled by the size adjustment of the minimum thickness of the flexible hinge. That is, the sensitivity and frequency measurement range of the FBG acceleration sensor can be adjusted by adjusting the size of the minimum thickness of the flexible hinge. The smaller the minimum thickness of the flexible hinge is, the higher the sensitivity of the FBG acceleration sensor is, but the narrower the corresponding frequency measurement range is. From the foregoing, two symmetrical grooves are formed on the flexible hinge, the groove curves are conic curves, and the minimum thickness of the flexible hinge is the distance between the peaks of the two conic curves.
According to the measuring method of the FBG acceleration sensor based on the bearing and the flexible hinge, the vibration acceleration is obtained and determined according to the relevant parameters of the center wavelength of the fiber bragg grating, so that accurate measurement of medium-high frequency vibration signals can be achieved.
It should be understood that the sequence number of each step in the foregoing embodiment does not mean that the execution sequence of each process should be determined by the function and the internal logic of each process, and should not limit the implementation process of the embodiment of the present application in any way.
In the following, in order to determine the structural parameters of the FBG acceleration sensor, theoretical analysis is performed on the FBG acceleration sensor. The analysis is performed taking 1 number of first fiber gratings and 1 number of second fiber gratings as an example. For convenience of description, the fiber grating is abbreviated as FBG, and the first fiber grating is abbreviated as FBG 1 The second fiber grating is abbreviated as FBG 2 。
FBG 1 With FBG (fiber Bragg Grating) 2 The amount of change in the center wavelength of (c) can be expressed as:
Δλ 1 ＝(1-P e )ε 1 λ 1 +(α f +ξ)ΔTλ 1 (3)
Δλ 2 ＝(1-P e )ε 2 λ 2 +(α f +ξ)ΔTλ 2 (4)
wherein Deltalambda 1 Is FBG (fiber Bragg Grating) 1 The amount of change in the center wavelength of Deltalambda 2 Is FBG (fiber Bragg Grating) 2 The central wavelength variation, P e For effective elastance, ε 1 And epsilon 2 FBG respectively 1 With FBG (fiber Bragg Grating) 2 Lambda of the axial strain of (a) 1 And lambda (lambda) 2 FBG respectively 1 With FBG (fiber Bragg Grating) 2 Center wavelength, alpha f The optical fiber is characterized in that the optical fiber thermal expansion coefficient is xi, the optical fiber material thermal optical coefficient is xi, and the delta T is the temperature variation.
Wherein the FBG is excited by external vibration 1 With FBG (fiber Bragg Grating) 2 One tensile and one compressive, FBG 1 With FBG (fiber Bragg Grating) 2 The central wavelength variation of (a) is equal in magnitude and opposite in direction, namely epsilon 1 ＝|-ε 2 |＝ε。FBG 1 With FBG (fiber Bragg Grating) 2 Is similar in center wavelength, i.e. lambda 1 ≈λ 2 ＝λ。
The total wavelength variation Δλ of the fiber grating is expressed as:
Δλ＝Δλ 1 -Δλ 2 ＝2(1-P e )λε (5)
when the masses (including the first mass and the second mass) are excited by the vertical vibratory acceleration, there is, according to newton's second law:
F＝Kx m ＝M e a (6)
where K is the system stiffness (i.e., the system equivalent total stiffness), x m For displacement of the mass M e Is equivalent mass of a system, wherein the system refers to a vibration system of the whole FBG acceleration sensor structure.
When the vibration acceleration direction is upward, the mass block rotates downwards relative to the bearing due to inertia, and when the rotation angle of the mass block is theta according to moment balance, the mass block receives the elastic force F in the vertical direction of the flexible hinge h And the tensile force F transmitted to the mass center of the mass block by the fiber bragg grating in the vertical direction f And rotation occurs as shown in fig. 4 (a). F is due to small rotation angle h And F f Considered as a force in the vertical direction, the resultant force is F, i.e., F in equation (6).
Referring to fig. 4 (a) and 4 (b), the displacement of the first mass and the FBG will be described as an example 1 The tensile lengths of (a) are respectively approximated as:
x m ＝L 1 θ (7)
x f ＝Lθ (8)
wherein x is f Is FBG (fiber Bragg Grating) 1 Is L 1 L is the horizontal distance from the center of the first bearing to the center of mass of the first mass, L is the center of mass of the first mass to the FBG 1 And θ is the rotation angle of the first mass (i.e., the distance from the mass center to the end of the extension rod). The displacement of the second mass and the FBG 2 Can be referred to the displacement of the first mass and the FBG 1 Is not described in detail herein.
The rotation rigidity of the flexible hinge and the rigidity of the FBG are respectively as follows:
wherein k is h For rotational stiffness, k, of the flexible hinge f For the stiffness of FBG, s=r/t, E is the material elastic modulus (here 304 stainless steel elastic modulus), R is the cutting radius of the flexible hinge, which is a straight round flexible hinge, t is the minimum thickness of the flexible hinge, i is the depth of the flexible hinge, E f The elastic modulus of FBG (namely the elastic modulus of the optical fiber), A f The cross-sectional area of the FBG (i.e. the cross-sectional area of the fiber), y is the length of the FBG, i.e. the separation of the two masses.
According to the moment balance, there is
F f L 1 ＝2k f x f L (12)
Wherein F is h For the mass block to receive the elastic force of the flexible hinge in the vertical direction, F f The FBG is transmitted to the pulling force of the mass center in the vertical direction.
The system stiffness K is:
the total moment of inertia J of the mass and the upper and lower extension rods is:
wherein m and m b The mass is the mass of the mass block and the mass of the extension rod (the extension rod comprises a first extension rod, a second extension rod, a third extension rod and a fourth extension rod), h is the mass block height, and b is the mass block length.
Obtained by conservation of mechanical energy
As can be seen from the equation (13) and the equation (15), the natural frequency f of the FBG acceleration sensor is:
when external vibration acceleration acts on the mass block, a moment balance equation of the mass block and the flexible hinge is as follows:
from equation (8) and equation (17), the single FBG strain (i.e., axial strain of FBG) ε is:
as can be seen from equation (17), the sensitivity of the FBG acceleration sensor is:
wherein lambda is B Is the center wavelength of the FBG (lambda 1 Or lambda 2 ) The sensitivity of the FBG acceleration sensor is the single-gate sensitivity of the FBG acceleration sensor, and the total sensitivity of the FBG acceleration sensor is the superposition of the two single-gate sensitivities, namely 2S. As can be seen from equation (19), the natural frequency f of the FBG acceleration sensor and the sensitivity S of the FBG acceleration sensor are limited to each other, and increasing f or S will cause another parameter to decrease.
In summary, the structural parameters that have a great influence on the natural frequency of the FBG acceleration sensor and the sensitivity of the FBG acceleration sensor are as follows: the length of the FBG (i.e., the effective length of the fiber) y, the cutting radius R of the flexible hinge, the minimum thickness t of the flexible hinge, the depth i of the flexible hinge, the mass length b, the mass width c, the mass height h, and the mass centroid to extension rod end distance L. A schematic diagram of the natural frequency and sensitivity of the FBG acceleration sensor as a function of various structural parameters is shown in fig. 5. Referring to fig. 5, the natural frequency and sensitivity of the FBG acceleration sensor are changed in opposite directions with the increase of each structural parameter except for the effective length y of the optical fiber, i.e., the natural frequency and sensitivity of the FBG acceleration sensor are mutually limited.
In order to meet the test requirements of the medium-high frequency vibration signals, the FBG acceleration sensor should have a wider frequency measurement range and higher sensitivity. As can be seen from fig. 5 (a), the natural frequency of the FBG acceleration sensor (hereinafter referred to as natural frequency) and the sensitivity of the FBG acceleration sensor (hereinafter referred to as sensitivity) decrease as the effective length y of the optical fiber increases. For the flexible hinge, the parameter value of the flexible hinge mainly influences the rigidity and the natural frequency of the system, and the cutting radius R of the flexible hinge is half of the width between the two mass blocks because the width between the two mass blocks is equal to the effective length of the optical fiber. As is clear from fig. 5 (b), the natural frequency increases with the minimum thickness t of the flexible hinge, but the error of the rigidity of the flexible hinge is large when t/R >0.85, and the error is 10 to 20% when 0.25 < t/R < 0.85. As can be seen from fig. 5 (c), the natural frequency increases with the depth i of the flexible hinge, but the increase of the depth i of the flexible hinge results in an increase of the processing difficulty, and the test requirement cannot be met when the depth i of the flexible hinge is smaller.
As for the mass, as is clear from (d) in fig. 5 and (e) in fig. 5, the influence of the mass width c and the mass height h on the sensitivity is larger than the influence on the natural frequency, and therefore the mass width c and the mass height h should be as large as possible to increase the sensitivity, but too large may affect the overall size. As can be seen from fig. 5 (f), the mass block length b should be as small as possible to increase the natural frequency while the sensitivity and the natural frequency are both considered, but not smaller than 4mm, otherwise the package is not firm. As can be seen from fig. 5 (g), when the mass centroid to extension rod end distance L < 20mm, the natural frequency does not change much with an increase in L, but the sensitivity increases rapidly with an increase in L. When 20mm < L < 35mm, the natural frequency decreases with increasing L, and the sensitivity slowly increases with increasing L. When L > 35mm, the natural frequency decreases rapidly as L increases, and the sensitivity begins to decrease slowly as L increases. In conclusion, the structural parameters of the FBG acceleration sensor can be determined according to the theoretical analysis, so that the FBG acceleration sensor has a higher frequency measurement range and higher sensitivity. The structural parameters of the FBG acceleration sensor are determined according to the theoretical analysis, so that the theoretical natural frequency of the FBG acceleration sensor is 3667.7Hz, and the theoretical sensitivity (namely single-gate sensitivity) is 16.10pm/g.
The above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention, and are intended to be included in the scope of the present invention.
Claims (10)
1. An FBG acceleration sensor based on bearings and flexible hinges, characterized by comprising: the device comprises a first mass block, a second mass block, a flexible hinge, a first bearing seat, a second bearing seat and a fiber bragg grating;
the first mass block and the second mass block are arranged in parallel and opposite to each other, and the side surfaces of the first mass block and the second mass block, which are close to each other, are inner side surfaces; the first end of the flexible hinge is connected with the inner side surface of the first mass block, and the second end of the flexible hinge is connected with the inner side surface of the second mass block;
the first end of the first bearing seat is connected with the center position of the outer side surface of the first mass block, and the first end of the second bearing seat is connected with the center position of the outer side surface of the second mass block; the first bearing seat and the second bearing seat are respectively provided with a first bearing hole and a second bearing hole, and the axial direction of the bearing holes is perpendicular to the axial direction of the mass block; the opposite side surface of the inner side surface of the mass block is the outer side surface of the mass block;
the fiber bragg grating comprises a first fiber bragg grating and/or a second fiber bragg grating; the first fiber bragg grating is arranged between the upper end of the first mass block and the upper end of the second mass block, and/or the second fiber bragg grating is arranged between the lower end of the first mass block and the lower end of the second mass block.
2. The FBG acceleration sensor based on bearings and flexible hinges according to claim 1, characterized in that it further comprises: the first extension rod, the second extension rod, the third extension rod and the fourth extension rod;
the first extension rod and the second extension rod are respectively arranged on the upper surface and the lower surface of the first mass block and extend along the axial direction of the first mass block; the third extension rod and the fourth extension rod are respectively arranged on the upper surface and the lower surface of the second mass block and extend along the axial direction of the second mass block;
the first fiber bragg grating is arranged between the free end of the first extension rod and the free end of the third extension rod, and/or the second fiber bragg grating is arranged between the free end of the second extension rod and the free end of the fourth extension rod.
3. The FBG acceleration sensor based on bearings and flexible hinges according to claim 1, characterized in that it further comprises: the device comprises a shell, a third bearing seat and a fourth bearing seat;
the center positions of the left inner side surface and the right inner side surface of the shell are respectively provided with a third bearing seat and a fourth bearing seat;
the third bearing seat and the fourth bearing seat are respectively provided with a third bearing hole and a fourth bearing hole, and the axial direction of the bearing holes is perpendicular to the axial direction of the shell.
4. The FBG acceleration sensor based on bearings and flexible hinges according to claim 3, characterized in that it further comprises: a first bearing and a second bearing;
the first bearing, the first bearing seat and the third bearing seat are matched, and the second bearing, the second bearing seat and the fourth bearing seat are matched;
the first mass block is fixed in the shell through the first bearing, the first bearing seat and the third bearing seat, and the second mass block is fixed in the shell through the second bearing seat, the second bearing seat and the fourth bearing seat; the first mass can rotate around the axial direction of the first bearing, and the second mass can rotate around the axial direction of the second bearing.
5. The FBG acceleration sensor based on bearings and flexible hinges according to claim 1, characterized in that when the number of the first fiber gratings is two or more, each first fiber grating is disposed in parallel between the upper end of the first mass block and the upper end of the second mass block;
when the number of the second fiber gratings is two or more, each second fiber grating is arranged in parallel between the lower end of the first mass block and the lower end of the second mass block;
the number of the first fiber gratings is the same as or different from the number of the second fiber gratings.
6. The FBG acceleration sensor based on bearings and flexible hinges according to claim 1, characterized in that the upper and lower surfaces of the flexible hinges are provided with arc-shaped grooves, and the two grooves are symmetrical to each other.
7. The FBG acceleration sensor based on bearings and flexible hinges according to claim 4, characterized in that the first mass and the second mass simultaneously rotate around the axial direction of the first bearing and the axial direction of the second bearing, respectively, when being excited by external vibrations;
correspondingly, the first fiber bragg grating is compressed or stretched, and/or the second fiber bragg grating is stretched or compressed.
8. A measuring method of an FBG acceleration sensor based on a bearing and a flexible hinge, characterized in that it is applied to the FBG acceleration sensor based on a bearing and a flexible hinge as claimed in any one of claims 1 to 7; when vibration is generated outside, the first mass block and the second mass block simultaneously rotate around the axial direction of the first bearing and the axial direction of the second bearing respectively; correspondingly, the first fiber bragg grating is compressed or stretched to generate axial strain to cause the central wavelength of the first fiber bragg grating to change, and/or the second fiber bragg grating is stretched or compressed to generate axial strain to cause the central wavelength of the second fiber bragg grating to change;
the measuring method comprises the following steps:
acquiring related parameters of the central wavelength of the first fiber bragg grating and/or related parameters of the central wavelength of the second fiber bragg grating;
and determining vibration acceleration according to the related parameters of the central wavelength of the first fiber grating and/or the related parameters of the central wavelength of the second fiber grating.
9. The method for measuring the FBG acceleration sensor based on the bearing and the flexible hinge according to claim 8, wherein the parameter related to the central wavelength of the first fiber grating is the central wavelength variation of the first fiber grating, and the parameter related to the central wavelength of the second fiber grating is the central wavelength variation of the second fiber grating;
the determining the vibration acceleration according to the related parameter of the center wavelength of the first fiber bragg grating and/or the related parameter of the center wavelength of the second fiber bragg grating comprises the following steps:
determining vibration acceleration according to the central wavelength variation of the first fiber bragg grating and/or the central wavelength variation of the second fiber bragg grating based on a calculation formula of the first vibration acceleration;
the calculation formula of the first vibration acceleration is as follows:
a＝(∑Δλ 1 +∑Δλ 2 )/S 0
wherein a is vibration acceleration, deltalambda 1 For the central wavelength variation of each first fiber grating, delta lambda 2 S is the central wavelength variation of each second fiber bragg grating 0 The sensitivity is preset; when the fiber bragg grating only comprises the first fiber bragg grating, the related parameter of the second fiber bragg grating is zero; when the fiber grating only comprises the second fiber grating, the relevant parameter of the first fiber grating is zero.
10. The method for measuring an FBG acceleration sensor based on a bearing and a flexible hinge according to claim 8, wherein the related parameter of the center wavelength of the first fiber grating comprises the center wavelength of the first fiber grating and the initial center wavelength of the first fiber grating, and the related parameter of the center wavelength of the second fiber grating comprises the center wavelength of the second fiber grating and the initial center wavelength of the second fiber grating; the initial center wavelength of the first fiber bragg grating is the center wavelength when the first fiber bragg grating does not vibrate, and the initial center wavelength of the second fiber bragg grating is the center wavelength when the second fiber bragg grating does not vibrate;
the determining the vibration acceleration according to the related parameter of the center wavelength of the first fiber bragg grating and/or the related parameter of the center wavelength of the second fiber bragg grating comprises the following steps:
determining vibration acceleration according to a calculation formula of second vibration acceleration and/or according to the central wavelength of the first fiber grating and the initial central wavelength of the first fiber grating and/or the central wavelength of the second fiber grating and the initial central wavelength of the second fiber grating;
the second vibration acceleration is calculated by the following formula:
a＝[(∑λ 1 -∑λ 2 )-(∑λ 1B -∑λ 2B )]/S 0
wherein a is vibration acceleration, lambda 1 Lambda is the center wavelength of each first fiber grating 2 Is the center wavelength lambda of each second fiber grating 1B For the initial center wavelength lambda of each first fiber grating 2B For the initial center wavelength of each second fiber grating, S 0 The sensitivity is preset; when the fiber bragg grating only comprises the first fiber bragg grating, the related parameter of the second fiber bragg grating is zero; when the fiber grating only comprises the second fiber grating, the relevant parameter of the first fiber grating is zero.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117191179A (en) * | 2023-08-15 | 2023-12-08 | 北京信息科技大学 | Triaxial vibration sensor adopting double-four-core FBGs |
| CN117191180A (en) * | 2023-08-15 | 2023-12-08 | 北京信息科技大学 | Miniaturized triaxial fiber bragg grating vibration sensor |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117191179A (en) * | 2023-08-15 | 2023-12-08 | 北京信息科技大学 | Triaxial vibration sensor adopting double-four-core FBGs |
| CN117191180A (en) * | 2023-08-15 | 2023-12-08 | 北京信息科技大学 | Miniaturized triaxial fiber bragg grating vibration sensor |
| CN117191179B (en) * | 2023-08-15 | 2024-03-15 | 北京信息科技大学 | Triaxial vibration sensor adopting double-four-core FBGs |
| CN117191180B (en) * | 2023-08-15 | 2024-03-15 | 北京信息科技大学 | Miniaturized triaxial fiber bragg grating vibration sensor |
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