阅读说明：本技术 一种基于u型槽结构的fbg二维加速度传感器及其测量方法 (A kind of FBG two dimension acceleration sensor and its measurement method based on U-type groove structure ) 是由 魏莉 姜达洲 李恒春 余玲玲 于 2019-08-14 设计创作，主要内容包括：本发明提供一种基于U型槽结构的FBG二维加速度传感器及其测量方法,包括上壳体和下壳体、位于上下壳体中部的芯体和若干光纤、光栅,所述芯体包括上下依次连接的上部惯性体,中部主体和下部底座,芯体的中部主体上下分别开设有两对背向设置的U型槽结构,上下两对U型槽的开口方向垂直,底座和上下两对U型槽的轴线位置开有竖直设置的方形通孔,惯性体和底座周向外表面都均匀地开设有四个光纤槽,四根光纤通过施加一定的预应力安装到光纤槽内,四根光纤内均刻有光栅,四根光栅处于相邻两两垂直的方向,方便用于检测两个垂直方向上的振动。该传感器具有温度补偿的效果、精确测量合加速度、抗电磁干扰、结构简单、体积小、分布式测量等优点。(The present invention provides a kind of FBG two dimension acceleration sensor and its measurement method based on U-type groove structure, including upper housing and lower case, core and several optical fiber in the middle part of upper-lower casing, grating, the core includes upper and lower sequentially connected top coasting body, mid-section body and lower base, the mid-section body of core offers two pairs of U-type groove structures backwards to setting respectively up and down, the opening direction of upper and lower two pairs of U-type grooves is vertical, the axial location of pedestal and upper and lower two pairs of U-type grooves is provided with the square through hole being vertically arranged, coasting body and pedestal circumferential exterior surface are all equably opened up there are four optical fiber duct, four optical fiber are by applying in certain installed under prestressing to optical fiber duct, grating is carved in four optical fiber, four gratings are in adjacent direction perpendicular to each other, the vibration being conveniently used in two vertical direction of detection.The sensor has many advantages, such as that the effect of temperature-compensating, precise measurement resultant acceleration, electromagnetism interference, structure be simple, small in size, distributed measurement.)

1. a kind of FBG two dimension acceleration sensor based on U-type groove structure, including upper housing and lower case, it is located at upper-lower casing The core at middle part and several optical fiber, grating, it is characterised in that: the core includes upper and lower sequentially connected top coasting body, in Portion's main body and lower base, the mid-section body of core offer respectively up and down two pairs backwards to setting U-type groove structures, upper and lower two pairs The opening direction of U-type groove is vertical, and the axial location of pedestal and upper and lower two pairs of U-type grooves is provided with the square through hole being vertically arranged, lower casing Body is cooperated by the square hole in the long square column and pedestal on its internal axis to be fixed, and upper housing and lower case are solid by screw thread Fixed, there are four aperture, coasting body and pedestal circumferential exterior surfaces all equably to open up there are four optical fiber duct for the surface setting of upper housing, By applying in certain installed under prestressing to optical fiber duct, optical fiber is pierced by four optical fiber by the aperture on upper housing surface, and four Grating is carved in optical fiber, grating is in gap between coasting body and pedestal, and it is vertical two-by-two that four gratings are in adjacent two Direction, be conveniently used for detection two vertical direction on vibration.

2. a kind of FBG two dimension acceleration sensor based on U-type groove structure as described in claim 1, it is characterised in that: in order to Further such that core is fixed with lower case, four threaded holes matched are respectively equipped on the lower case bottom and pedestal, The two is connected and fixed by screw.

3. a kind of FBG two dimension acceleration sensor based on U-type groove structure as described in claim 1, it is characterised in that: described Core is made using 304 stainless steel materials.

4. a kind of FBG two dimension acceleration sensor based on U-type groove structure as described in claim 1, it is characterised in that: described Core is an integral molding structure, and wherein coasting body includes the tapered rotary table of upper cylindrical body and lower section retracted downward, core middle part Main body upper end is connected with tapered rotary table bottom, and lower end is connected with pedestal.

5. a kind of FBG two dimension acceleration sensor based on U-type groove structure as described in claim 1, it is characterised in that: described Optical fiber is further fixed after being embedded in optical fiber duct by colloid 4.

6. a kind of FBG two dimension acceleration sensor based on U-type groove structure as described in claim 1, it is characterised in that: described Four gratings include two gratings positioned at X-axis line direction: No. 1 grating-#1FBG, No. 3 grating #3FBG, for detecting X-axis The vibration in direction, two gratings positioned at Y-axis line direction: No. 2 grating-#2FBG, No. 4 grating #4FBG, for detecting Y-axis side To vibration.

7. a kind of measurement side of FBG two dimension acceleration sensor based on U-type groove structure as claimed in any one of claims 1 to 6 Method, which is characterized in that comprise the following processes: when measurement, sensor is fixed on to the surface of object under test, and keeps sensor Bottom surface be in a horizontal position, when sensor is by extraneous vibrational excitation, under effect of inertia, the coasting body of sensor Around U-type groove minor rotation, the vertical displacement amount that coasting body generates draws the optical fiber fixed with the optical fiber duct of coasting body It stretches or compresses, cause raster center wave length shift, the drift value of raster center wavelength is measured by (FBG) demodulator, to establish outer Boundary motivates the corresponding relationship of acceleration and raster center wavelength shift, thus obtains the vibration information of vibration acceleration.

Technical field

The invention belongs to mechanical oscillation field of measuring technique, and in particular to a kind of FBG (optical fiber light based on U-type groove structure Grid) two dimension acceleration sensor and its measurement method.

Background technique

Fiber-optic grating sensor receives extensive attention due to its significant advantage, such as convenience and safety, electromagnetism interference, Corrosion-resistant, telemeasurement.Existing fiber grating two-dimensional vibration acceleration sensor mainly has following two categories, first is that spring beam Isostructural acceleration transducer, the transducer sensitivity of the type is small, structure size is bigger than normal, it is difficult to guarantee that all directions are sensitive Spend it is identical so that synthesis total acceleration measurement it is inaccurate；It is fabricated to second is that directlying adopt fiber grating as elastic element Acceleration transducer, small in size although such acceleration transducer structure is simple, the working frequency model of two measurement directions Enclose, sensitivity difference it is larger, and optical fiber itself is more fragile, easy to damage, leads to the less reproducible of sensors with auxiliary electrode.

Summary of the invention

In view of the problems of the existing technology, the technical solution that the present invention uses to solve problems of the prior art It is as follows:

A kind of FBG two dimension acceleration sensor based on U-type groove structure, including upper housing and lower case, it is located at upper lower casing Core and several optical fiber, grating in the middle part of body, it is characterised in that: the core includes upper and lower sequentially connected top coasting body, Mid-section body and lower base, the mid-section body of core offer respectively up and down two pairs backwards to setting U-type groove structures, upper and lower two Vertical to the opening direction of U-type groove, the axial location of pedestal and upper and lower two pairs of U-type grooves is provided with the square through hole being vertically arranged, under Shell is cooperated by the square hole in the long square column and pedestal on its internal axis to be fixed, and upper housing and lower case are solid by screw thread Fixed, there are four aperture, coasting body and pedestal circumferential exterior surfaces all equably to open up there are four optical fiber duct for the surface setting of upper housing, By applying in certain installed under prestressing to optical fiber duct, optical fiber is pierced by four optical fiber by the aperture on upper housing surface, and four Grating is carved in optical fiber, grating is in gap between coasting body and pedestal, and it is vertical two-by-two that four gratings are in adjacent two Direction, be conveniently used for detection two vertical direction on vibration.

In order to be respectively equipped with four matchings on the lower case bottom and pedestal further such that core is fixed with lower case The two is connected and fixed by the threaded hole of conjunction by screw.

The core is made using 304 stainless steel materials.

The core is an integral molding structure, and wherein coasting body includes the tapered circle of upper cylindrical body and lower section retracted downward Platform, core mid-section body upper end are connected with tapered rotary table bottom, and lower end is connected with pedestal.

The optical fiber is further fixed after being embedded in optical fiber duct by colloid 4.

Four gratings include two gratings positioned at X-axis line direction: No. 1 grating-#1FBG, No. 3 grating #3FBG, For detecting the vibration of X-direction, two gratings positioned at Y-axis line direction: No. 2 grating-#2FBG, No. 4 grating #4FBG are used In the vibration of detection Y direction.

A kind of measurement method of the FBG two dimension acceleration sensor based on U-type groove structure, which is characterized in that including as follows Sensor: when measurement, being fixed on the surface of object under test, and the bottom surface of sensor is kept to be in a horizontal position by process, when When sensor is by extraneous vibrational excitation, under effect of inertia, the coasting body of sensor is used to around U-type groove minor rotation Property the vertical displacement amount that generates of body to occur to stretch with the fixed optical fiber of the optical fiber duct of coasting body or compression, cause in grating Heart wave length shift, the drift value of raster center wavelength is measured by (FBG) demodulator, to establish in dynamic excitation acceleration and grating Thus the corresponding relationship of heart wavelength shift obtains the vibration information of vibration acceleration.

The present invention has the advantage that

The vibrating sensors such as the present invention resilient beam-type, fiber Bragg grating type different from the past, present invention employs U-type groove knots Structure improves sensitivity while with high intrinsic frequency as elastic element, in selected frequency range, respectively to spirit Sensitivity is identical, being capable of precise measurement two-phase acceleration；The configuration of the present invention is simple is easy to using fiber grating as sensing element It realizes telemetering, has many advantages, such as electromagnetism interference, small in size, distributed measurement, also have the effect of temperature-compensating.

Detailed description of the invention

Fig. 1 is the overall structure diagram of inventive sensor；

Fig. 2 is the structural schematic diagram of core in inventive sensor；

Fig. 3 be in Fig. 1 core-fiber grating in X-direction stress deformation schematic diagram；

Fig. 4 is the scale diagrams of U-type groove on the upside of core in Fig. 1；

Fig. 5 be in Fig. 1 core-fiber grating in Y direction stress deformation schematic diagram；

Fig. 6 is the scale diagrams of U-type groove on the downside of core in Fig. 1；

In figure: 1- optical fiber；2- upper housing；3- core；4- colloid；5- lower case；6- grating；3-1. coasting body；3-2. light Fine slot；U-type groove on the upside of 3-3.；U-type groove on the downside of 3-4.；3-5 pedestal；3-6 square hole.

Specific embodiment

Below with reference to the embodiments and with reference to the accompanying drawing the technical solutions of the present invention will be further described, such as Fig. 1- Shown in 6, a kind of FBG two dimension acceleration sensor based on U-type groove structure, including upper housing 2 and lower case 5, it is located at upper lower casing Core 3 and several optical fiber, grating in the middle part of body, core 3 include upper and lower sequentially connected top coasting body 3-1, mid-section body and Lower base 3-5, the mid-section body of core 3 offer two pairs of U-type groove structures backwards to setting respectively up and down, and upper and lower two pairs U-shaped The opening direction of slot is vertical, and the axial location of pedestal 3-5 and upper and lower two pairs of U-type grooves is provided with the square through hole 3-6 being vertically arranged, under Shell 5 is cooperated by the square hole 3-6 in the long square column and pedestal 3-5 on its internal axis to be fixed, upper housing 2 and lower case 5 It is threadably secured, there are four apertures for the surface setting of upper housing 2, and coasting body 3-1 and pedestal 3-5 circumferential exterior surface are all equably It opens up there are four optical fiber duct 3-2, four optical fiber 1 are passed through by applying 3-2 in certain installed under prestressing to optical fiber duct, optical fiber 1 The aperture on 2 surface of upper housing is pierced by, and grating is carved in four optical fiber, and grating 6 is between coasting body 3-1 and pedestal 3-5 Gap, four gratings 6 are in adjacent two direction perpendicular to each other, the vibration being conveniently used in two vertical direction of detection.

In order to be respectively equipped with 4 phases on 5 bottom of lower case and pedestal 3-5 further such that core 3 and lower case 5 are fixed The two is connected and fixed by the threaded hole of cooperation by screw.

Core is made using 304 stainless steel materials.Core is an integral molding structure, and wherein coasting body includes upper cylindrical body With the tapered rotary table of lower section retracted downward, core mid-section body upper end is connected with tapered rotary table bottom, and lower end is connected with pedestal.

Optical fiber is further fixed after being embedded in optical fiber duct by colloid 4.

Four gratings include two gratings positioned at X-axis line direction: No. 1 grating-#1FBG, No. 3 grating #3FBG are used for The vibration of X-direction is detected, two gratings positioned at Y-axis line direction: No. 2 grating-#2FBG, No. 4 grating #4FBG, for examining Survey the vibration of Y direction.

A kind of measurement method of the FBG two dimension acceleration sensor based on U-type groove structure, comprises the following processes: when measurement, Sensor is fixed on to the surface of object under test, and the bottom surface of sensor is kept to be in a horizontal position, when sensor is by outer When the vibrational excitation on boundary, under effect of inertia, around U-type groove minor rotation, coasting body generates perpendicular the coasting body of sensor Straight displacement to occur to stretch or compress with the fixed optical fiber of the optical fiber duct of coasting body, causes raster center wave length shift, The drift value of raster center wavelength is measured by (FBG) demodulator, to establish dynamic excitation acceleration and raster center wavelength shift Corresponding relationship, thus obtain the vibration information of vibration acceleration.

Measuring principle of the invention is as follows:

One, sensors X axis sensitivity

When sensor is vibrated acceleration a in X-direction_XWhen, coasting body is around upside U-type groove structure minor rotation； In the sensor, U-type groove structure can be considered as a kind of circular hinges structure, and the rigidity theory according to hinge arrangement calculates public Formula, hinge arrangement are much larger than the rotational stiffness along its width along the rotational stiffness of thickness, ignore downside U-type groove structure along X-axis side To vibration influence that upside U-type groove is rotated, the stress deformation figure of sensor is as shown in Figure 3.Sensor-based system is in inertia force, hinge Meet equalising torque, expression formula under chain restoring force, optical fiber pulling force effect are as follows:

ma_xd₁-2k₁θ₁-k_f(Δl₃-Δl₁)r₁=0 (1)

In formula, m is the quality of coasting body；a_XFor the vibration acceleration of sensors X axis direction；d₁For coasting body mass center to upper hinge The distance of chain center of rotation；k₁It is hinge around the rotational stiffness of Y-axis；θ₁It is coasting body around hinge angle of rotation；k_fFor the rigid of optical fiber Spend coefficient；Δl₁、Δl₃The deflection of grating #1FBG, #3FBG span respectively in X-direction；r₁For cylindrical body in coasting body Radius.

By Fig. 3, Fig. 4 it is found that in X-direction grating #1FBG, #3FBG span deflection Δ l₁、Δl₃Expression formula point Not are as follows:

Δl₁=l [cos (θ₁+φ)-cos(φ)] (2)

Δl₃=l [cos (φ-θ₁)-cos(φ)] (3)

Simultaneous (2), (3) formula have

Δl₃-Δl₁=2lsin (θ₁)φ (4)

In formula, l be coasting body on optical fiber fixed point to upper hinge center of rotation distance；φ is that optical fiber is fixed on coasting body Point arrives the connecting line of upper hinge center of rotation and the angle of core-center axis.

When the span amount of being deformed of fiber grating, the corresponding dependent variable Δ of grating #1FBG, #3FBG in X-direction ε₁、Δε₃Expression formula are as follows:

In formula, l₁、l₃The spacing of grating #1FBG, #3FBG in coasting body and pedestal optical fiber duct respectively in X-direction.

The structure size figure of sensors X axis direction is as shown in figure 3, set the density of material of core as ρ, the quality m of coasting body Are as follows:

M=m₁+m₂ (7)

m₁=π r₁ ²eρ (8)

In formula, r₁For the radius of cylindrical body in coasting body；r₂For the bottom surface radius of rotary table in coasting body；E is circle in coasting body The height of cylinder；h₁For the height of rotary table in coasting body；m₁For the quality of the cylindrical body of coasting body；m₂For the matter of the rotary table of coasting body Amount.

Three formulas above simultaneous it is found that coasting body mass center to upper hinge center of rotation distance are as follows:

In formula, d₂For the distance of rotary table mass center to its bottom surface, expression formula are as follows:

R₁For the cut radius of upper hinge, elastic element of the hinge as the sensor, stiffness characteristics are to sensor Performance has a great impact, and the rigidity of hinge can be calculated according to pertinent literature, i.e., are as follows:

In formula, q_mFor the central angle of hinge；E is the elasticity modulus of flexible hinge material；B is the width of hinge；R is hinge Cut radius；f₂For intermediate variable, expression formula are as follows:

In formula, i=R/t, t are the thickness of hinge arrangement.

The spacing l of grating #1FBG, #3FBG in X-direction in coasting body and pedestal optical fiber duct₁、l₃It is equal, expression formula Are as follows:

l_f=l₁=l₃=h₁+2R₁+h₂+2R₂ (14)

In formula, l_fFor the spacing of fiber grating both ends fixed point on core；h₂For the thickness of connector in core；R₂For The cut radius of lower hinge.

It is k that optical fiber, which can see a rigidity as, in sensor structure_fSpring exists in conjunction with optical fiber axial direction stiffness coefficient and optical fiber The relationship of both ends fixed endpoint spacing, can obtain on core

In formula, E_fFiber-draw elasticity modulus；A_fFor cross section of optic fibre area.

According to the drift value of fiber bragg grating center wavelength and strain and the relationship of temperature, expression formula are as follows:

Wherein, λ is the central wavelength of grating；Δ λ is the central wavelength drift value of grating；p_eElasto-optical coefficient, α for optical fiber_f Thermal expansion coefficient, ξ for optical fiber_fThermo-optical coeffecient, Δ t for optical fiber are temperature variation, and ε is the dependent variable of grating.

When vibration acceleration of the sensor by X-direction, by (16) it is found that #1FBG is at temperature and effect of vibration Its expression formula are as follows:

In formula, Δ λ₁For No. 1 grating #1FBG at temperature and effect of vibration wherein heart wavelength shift；Δ t is environment temperature The variable quantity of degree, ε₁For the dependent variable of No. 1 grating #1FBG.Similarly, for #3FBG, expression formula are as follows:

In formula, Δ λ₃No. 3 grating #3FBG central wavelength drift values when to have temperature and vibration acceleration；Δ t is environment temperature The variable quantity of degree, ε₃For the dependent variable of No. 3 grating #3FBG.

Due to λ₁3 > > Δ λ of ≈ λ₁、Δλ₃, simultaneous (17), (18) formula have:

Δλ₃-Δλ₁=λ₃(1-p_e)(Δε₃-Δε₁) (19)

Simultaneous (4), (5), (6) and (19) can obtain,

Δl₃-Δl₁=λ₃(1-p_e)(ε₃-ε₁)=2lsin (θ₁)φ (20)

In formula, l be coasting body on optical fiber fixed point to upper hinge center of rotation distance；Due to θ₁Value very little, take θ₁≈ sin(θ₁)=r₁/ l,

In the vibrational excitation by X-axis, simultaneous (1), (20) formula, the sensitivity of sensors X axis direction are as follows:

From (19), (20) and (21) formula it is known that sensor relative to single optical grating, the sensor is not only The self compensation of temperature may be implemented, and sensitivity may be implemented and double.

Two, sensor Y-axis sensitivity

When vibration acceleration of the sensor by Y direction, the stress deformation figure of sensor and the structure of Y-axis positive direction Size as shown in figs.5 and 6, torque equilibrium equation are as follows:

Ma_Yd₃-2k₂ψ-k_f(Δl₄-Δl₂)r₁=0 (22)

In formula, M be coasting body, connector, U-type groove total quality；k₂It, can for the Equivalent Rotational rigidity of downside U-type groove It is obtained by (12), (13) formula, is the angle of rotation of downside U-type groove, Δ l₂、Δl₄It is respectively No. 2 grating #2FBG, No. 4 in Y direction The variable quantity of grating #4FBG fiber lengths between coasting body and pedestal.

L ' is distance of the optical fiber fixed endpoint to downside U-type groove center of rotation on coasting body, expression formula are as follows:

In formula, R₂For the cut radius of downside U type slot.

When sensor is when Y direction is vibrated acceleration excitation, coasting body, upside U-type groove and connector are under Side U-type groove minor rotation, distance of the mass center relative to downside U-type groove center of rotation are as follows:

In formula, d₂It expires the distance of bottom surface for the mass center of rotary table part in coasting body；m₅For upper and lower sides U-type groove and connector Equivalent mass, expression formula are as follows:

According to the derivation process of sensors X axis direction sensitivity, sensor Y direction sensitivity are as follows:

In formula, λ₂For central wavelength of No. 2 grating #2FBG after applying certain prestressing force.From above formula it is found that sensor exists For Y direction there are when vibration acceleration, measurement result is unrelated with temperature change.

Protection scope of the present invention is not limited to the above embodiments, it is clear that those skilled in the art can be to this hair It is bright to carry out various changes and deformation without departing from scope and spirit of the present invention.If these changes and deformation belong to power of the present invention In the range of benefit requirement and its equivalent technologies, then including the intent of the present invention also includes these changes and deforms.