CN103673895B - Fiber Bragg Grating FBG micro-displacement sensor and measuring method thereof - Google Patents

Abstract

The invention discloses a kind of Fiber Bragg Grating FBG micro-displacement sensor and measuring method thereof, this fiber Bragg grating sensor is by column type inner casing, shell forms, on four symmetry directions between inner casing and shell, place four stainless steel flexible sheets, the place of flexible sheet and housing contacts is welded and fixed, utilize the pressure of four flexible sheets that shell is fixed on inner casing, on four flexible sheets, be all stained with Fiber Bragg Grating FBG, fiber grating horizontal positioned, inner casing is fixed, shell is subject to the effect that outside micrometric displacement changes, shell and inner casing relative position change, the generation deformation of diaphragm, drive Bragg grating generation deformation above, Fiber Bragg Grating FBG wavelength drifts about. because the deformation of four diaphragms is different, can judge by analyzing the wave length shift situation of four Bragg gratings the size and Orientation of change in displacement.

Description

Fiber Bragg Grating FBG micro-displacement sensor and measuring method thereof

Technical field

The invention belongs to technical field of optical fiber sensing, especially relate to a kind of column type Fiber Bragg Grating FBG micro-displacement sensor,Belong to fiber optic sensing device.

Background technology

Fiber Bragg Grating FBG micro-displacement sensor is the strain sensitive characteristic according to Bragg grating, when Bragg grating is subject to axleTo effects of strain, the space periodic of grating (being grating pitch) changes, and bragg reflection wavelength will change, logicalCross measuring that spectroanalysis instrument can centering heart wavelength shift, can detect thus the size of change in displacement. Due to lightFine Bragg grating sensor has not only been inherited the various advantages of Fibre Optical Sensor, as simple in structure, volume is little, lightweight, anti-Disturb, anticorrosive etc., also there is the advantage such as Wavelength-encoding, wavelength-division multiplex.

Existing fiber grating displacement sensor can only detect the size of displacement, but displacement is vector, and existing size, also hasDirection, this just not only needs to detect the size of displacement, and the while also will reflect the sensor of the direction of displacement generation.

Summary of the invention

Technical problem to be solved by this invention is: a kind of Fiber Bragg Grating FBG micro-displacement sensor and measuring method thereof are provided,The present invention takes the mode that inside and outside shell is nested against one another and differential measurement combines, and has not only improved sensing sensitivity, and canJudge the direction that displacement occurs simultaneously.

The technical solution adopted in the present invention is: a kind of Fiber Bragg Grating FBG micro-displacement sensor, comprise shell, inner casing, inShell is arranged on enclosure, is also provided with Fiber Bragg Grating FBG between inner casing and shell.

Further, shell and inner casing all adopt cylindrical.

Further, Fiber Bragg Grating FBG is arranged on flexible sheet.

Further, flexible sheet adopts stainless steel, and places on four symmetry directions between inner casing and shell.

Further, Fiber Bragg Grating FBG is around inner casing, and parallel with inner casing bottom surface.

Further, flexible sheet contacts with inner casing, and is welded on shell.

The measuring method of Fiber Bragg Grating FBG micro-displacement sensor, comprising:

Shell is subject to from the horizontal by θ angle, and size is after the displacement effect of h, by the cloth of detection fiber Bragg gratingGlug wavelength vertical direction drift value Δ λ_MN, horizontal direction drift value Δ λ_PQ, calculate respectively flexible sheet vertical direction and changeMeasure MN, horizontal direction variable quantity PQ, then calculate the size of h and θ according to following formula:

$\left\{\begin{array}{c}h=\sqrt{{\mathrm{MN}}^2+{\mathrm{PQ}}^2}\\ \mathrm{\θ}=\arctan \frac{\mathrm{MN}}{\mathrm{PQ}}\end{array}\right.$

Further, the Δ λ obtaining by detection_MN、Δλ_PQ, the method for calculating MN, PQ is according to following two formulas:

MN=1/3.5*Δλ_MN

PQ=1/3.5*Δλ_PQ

Wherein, Δ λ_MN、Δλ_PQUnit be mm, the unit of MN, PQ is nm.

Advantage of the present invention: in order to realize the measurement of all directions micrometric displacement in plane, designed a kind of novel column type optical fiberBragg grating micro-displacement sensor, it adopts the column type inner core mode nested with shell, and simple in structure, inner casing is fixed, outerShell produces change in displacement and acts on inner casing, due to the symmetry of cylinder, can effectively experience the displacement of all directions in plane. WithTime introduced differential measurement method, two fiber gratings, as fiber grating pair, change according to two fiber grating reflection wavelengthsDifference not only can detect the size of displacement, can also judge the direction of displacement.

Brief description of the drawings

Fig. 1 is overall structure schematic diagram of the present invention.

Fig. 2 is cross sectional representation of the present invention.

Fig. 3 is stainless steel flexible sheet structural representation of the present invention.

Fig. 4 is the schematic diagram of embodiment of the present invention measuring method.

Description of reference numerals:

1-cylindrical shell 2-cylinder inner casing 3-stainless steel flexible sheet 4-Bragg grating (FBG)

Detailed description of the invention

This fiber Bragg grating sensor is by column type inner casing, and shell forms, four symmetry directions between inner casing and shellFour stainless steel flexible sheets of upper placement, the place of flexible sheet and housing contacts is welded and fixed, and utilizes the pressure of four flexible sheetsPower is fixed on shell on inner casing, is all stained with Fiber Bragg Grating FBG, fiber grating horizontal positioned, inner casing on four flexible sheetsFixing, shell is subject to the effect that outside micrometric displacement changes, and shell and inner casing relative position change, the generation deformation of diaphragm,Drive Bragg grating generation deformation above, Fiber Bragg Grating FBG wavelength drifts about. Because the deformation of four diaphragms is different,Can judge by analyzing the wave length shift situation of four Bragg gratings the size and Orientation of change in displacement.

Below in conjunction with concrete enforcement, the present invention is described in further detail.

The invention provides one and there is higher sensitivity, and can judge the column type optical fiber Bragg of displacement generation directionOptical grating micro-displacement pickup. Technical scheme of the present invention comprises: cylindrical inner casing, and the cylinder blanket matching with inner casing,On four symmetry directions between inner casing and shell, place four stainless steel flexible sheets.

In such scheme, together with being pressed on by four stainless steel flexible sheets between inner casing and shell.

In such scheme, optical fiber is close to and is surrounded on cylindrical inner casing, is parallel to inner casing bottom surface, is placed between shell and inner casing.

In such scheme, four stainless steel flexible sheets and column type housing contacts part are welded and fixed.

Be described in further detail the present invention below in conjunction with drawings and Examples. What Fig. 1 provided is column type Fiber Bragg Grating FBG micrometric displacementSensor construction schematic diagram.

Embodiment:

Column type Fiber Bragg Grating FBG micro-displacement sensor, it comprises cylindrical shell 1, cylinder inner casing 2, stainless steel elasticityDiaphragm 3 and Fiber Bragg Grating FBG 4 are placed 4 stainless steel bombs on four symmetry directions between inner casing 2 and shell 1Property diaphragm 3, stainless steel flexible sheet 3 is welded and fixed with shell 1 contact portion, cylinder inner casing 2 is by 4 stainless steel bombsProperty diaphragm is pressed in shell 1, is all stained with the Fiber Bragg Grating FBG 4 that sensing is used on stainless steel flexible sheet 3.

In the present embodiment, Fiber Bragg Grating FBG 4 sticks on the center of stainless steel flexible sheet 3, and inner casing and shell are logicalCross flexible sheet and be coupled mutually, on 4 mutual symmetrical vertical inwalls that are welded on shell of stainless steel flexible sheet, noRust steel flexible sheet produces deformation under the change in displacement of shell, acts on Fiber Bragg Grating FBG, and two pairs of fiber gratings formDifferential measurement, a fiber grating is subject to strain aggravation, and another fiber grating is subject to strain to be weakened, and adopts differential structure,The difference changing by two fiber grating reflection wavelengths not only can detect the size of displacement, can also judge change in displacementDirection, sensitivity is the twice of single-sensor.

Concrete measuring method is as follows:

What detect due to Bragg grating on two flexible sheets of symmetry is unidirectional change in displacement, for the side analyzingJust, can only analyze the variation relation of two perpendicular diaphragms. As shown in the figure, while not being subjected to displacement, the center of circle of inside and outside shell is O point,If shell is subject to from the horizontal by θ angle, size is the displacement effect of h, and the center of circle of shell moves to O ' point, vertical directionThe intersection point A point of diameter and shell upper end moves to A ' point, and the intersection points B point of horizontal direction diameter and shell left end moves to B ' point.While not being subjected to displacement, inner casing and upper horizontal diaphragm are tangential on M point. Shell is subject to after displacement effect, if without inner casing squeezing action, MPoint moves to M ' point. Because inner casing is fixed, diaphragm edge and shell are fixed, diaphragm flexes and be still tangential on M point with inner casing.What measure is micrometric displacement, and M point is still near the center of diaphragm, and Bragg grating sticks near diaphragm center, can be similar to and recognizeFor the effect that now Bragg grating is subject to is that variation MN in vertical direction causes, wherein N is bending upper horizontal diaphragmThe intersection point of two edges line and vertical direction diameter.

In like manner, while not being subjected to displacement, inner casing and left vertical diaphragm are tangential on P point. Shell is subject to after displacement effect, if without inner casingSqueezing action, P point moves to P' point. Variation PQ in horizontal direction can be detected by the Bragg grating on the diaphragm of the left side, itsMiddle Q is bending left vertical diaphragm two edges line and the intersection point of horizontal direction diameter.

Finally utilize fiber Bragg grating (FBG) demodulator, according to the drift value Δ λ of the bragg wavelength recording_MN(vertical direction) and Δ λ_PQ(waterSquare to) calculate respectively MN, PQ. Wherein, fiber Bragg grating (FBG) demodulator can not directly record the variation of displacement, can only be anti-Reflect the variation of all directions wavelength value, in experiment, record change in displacement and the Δ λ of MN, PQ direction_MNWith Δ λ_PQThere is linear closingSystem, i.e. MN(mm)=(1/3.5) Δ λ_MN（nm），PQ（mm）=（1/3.5）Δλ_PQ(nm). Vertical direction and levelThe variable quantity that Bragg grating in direction detects be respectively displacement in the vertical direction with horizontal direction on component, like this canDetect the size of h and θ by the MN that detects and PQ. Can obtain:

$\left\{\begin{array}{c}h=\sqrt{{\mathrm{MN}}^2+{\mathrm{PQ}}^2}\\ \mathrm{\θ}=\arctan \frac{\mathrm{MN}}{\mathrm{PQ}}\end{array}\right.$

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all in spirit of the present invention and formerAny amendment of doing, be equal to and replace and improvement etc., within all should being included in protection scope of the present invention.

Claims (2)

1. the measuring method of Fiber Bragg Grating FBG micro-displacement sensor, is characterized in that comprising:

Described micro-displacement sensor comprises shell (1), inner casing (2), and inner casing (2) is arranged on shell (1) inside, inner casing (2)And between shell (1), be also provided with Fiber Bragg Grating FBG (4); Shell (1) and inner casing (2) all adopt cylindrical; Optical fiber clothGlug grating (4) is arranged on flexible sheet (3); Flexible sheet (3) adopts stainless steel, and at inner casing (2) and shell(1) on four symmetry directions between, place; Fiber Bragg Grating FBG (4) is around inner casing (2), and with inner casing (2) bottom surfaceParallel; Flexible sheet (3) contacts with inner casing (2), and is welded on shell (1);

Shell (1) is subject to from the horizontal by θ angle, and size is after the displacement effect of h, by detection fiber Bragg grating(4) bragg wavelength vertical direction drift value Δ λ_MN, horizontal direction drift value Δ λ_PQ, calculate respectively flexible sheet (3)Vertical direction variable quantity MN, horizontal direction variable quantity PQ, wherein M inner casing (2) and upside flexible sheet when not being subjected to displacement(3) point of contact, N is bending upside flexible sheet (3) two edges line and the intersection point of vertical direction diameter, P does not occurThe point of contact of inner casing when displacement (2) and left side flexible sheet (3), Q be bending left side flexible sheet (3) two edges line withThe intersection point of horizontal direction diameter, then calculates the size of h and θ according to following formula:

$\left\{\begin{array}{c}h=\sqrt{{\mathrm{MN}}^2+{\mathrm{PQ}}^2}\\ \mathrm{\θ}=\arctan \frac{MN}{PQ}\end{array}\right..$

2. method according to claim 1, is characterized in that: the Δ λ obtaining by detection_MN、Δλ_PQ, calculating MN,The method of PQ is according to following two formulas:

MN＝1/3.5*Δλ_MN

PQ＝1/3.5*Δλ_PQ

Wherein, Δ λ_MN、Δλ_PQUnit be nm, the unit of MN, PQ is nm.