CN100465601C - Pressure-measuring fiber grating process and device - Google Patents

Abstract

The present invention discloses one kind of pressure-measuring fiber grating process and device. After linear conversion of the measured force in a 'piston-liquid-piston' converter in the conversion ratio equal to the upper and the lower piston area ratio, the converted force is transmitted by the lower piston to the fiber grating with relatively small measuring range. The change in force causes the axial strain in the fiber grating, and change of fiber grating in parameters, including Bragg wavelength. After the mathematic model between the pressure and the central wavelength of the grating, measuring the wavelength can obtain the corresponding pressure. The present invention has the advantages of great measurement range, high precision, etc.

Description

The pressure-measuring fiber grating device

Technical field

The present invention relates to a kind of rock pressure [in mine detecting instrument, relate in particular to a kind of wide range, high-precision rock pressure [in mine detecting instrument.

Background technology

In the mining process of colliery, destroyed the mechanical balance in rock mass and coal seam, around getting working face, formed " rock pressure [in mine ", claim again " roof pressure ".Roof accident is exactly that this very easily causes casualties owing to the roof pressure supporting of crushing causes collapsing of tunnel or workplace to emit.Because the casualties number that roof accident causes accounts for about 1/3rd of China's coal-mine industrial accident injures and deaths number, rank first above the gas accident death toll.At present, be used for the key instrument that rock pressure [in mine detects and be divided into mechanical type, fluid pressure type, resistance-strain type, type vibration wire etc. by its principle of work.Mechanical type and fluid pressure type ore deposit press that observation instrument is simple in structure, reliable operation, cost are lower, but have shortcomings such as response speed is slow, precision is not high, volume is big; Resistance strain type sensor is based on tinsel when under external force mechanically deform taking place, its resistance value this resistance strain effect that changes is made, it is sensitiveer, accurate than mechanical type, fluid pressure type sensor, but such sensor exists temperature shortcomings such as sensitivity, long-time stability difference relatively; Vibrating string type sensor succeeds in developing and has obtained application at the beginning of the eighties, it is to utilize string wire under the differential tension effect, detection with this principle realizable force of different fixed frequencies, be that the most frequently used instrument in the detection is pressed in present ore deposit, precision is not high, response speed waits defective more slowly but such sensor still exists.

Summary of the invention

The object of the present invention is to provide a kind of pressure-measuring fiber grating device, it has the high precision of fiber bragg grating pressure sensor and the advantages such as wide range that force conversion system is realized.

Its technical solution is:

Pressure-measuring fiber grating device device comprises pedestal, offer chamber in the pedestal, the top of pedestal offers stepped hole, chamber in stepped hole and the pedestal is communicated with, be provided with upper piston and lower piston in the stepped hole, full of liquid between upper piston and the lower piston, the bottom of stepped hole is provided with elastic membrane, and the lower surface of elastic membrane is provided with fiber grating; It is the optical fiber fixed leg of axis of symmetry that the lower surface of above-mentioned elastic membrane is provided with the axis of stepped hole, and fiber grating is fixed on the optical fiber fixed leg; The lower end of above-mentioned lower piston is a sphere shape.

The cross-sectional area of above-mentioned upper piston is greater than the cross-sectional area of lower piston.

The end face of above-mentioned chamber is the center with the axis of stepped hole, and projection forms a boss downwards, is equipped with the elastic membrane of cylindricality on the boss.

Aforesaid liquid is a hydraulic oil.

Have through hole on the sidewall of above-mentioned chamber.

The invention has the beneficial effects as follows: utilize " piston-liquid-piston " force conversion system to realize by the linear transformation of side force, the conversion ratio is the ratio of the cross-sectional area of upper piston and lower piston, and be sent to fiber grating by the power of lower piston after with transformation of scale, the variation of power makes fiber grating produce axial strain, the parameter that is reflected to fiber grating changes, thereby change the bragg wavelength of fiber grating, can utilize the mathematical model of pressure size and grating Prague centre wavelength then, measure the size of counter stress by the value of measuring wavelength, have the measuring accuracy height, advantages such as range is big.

Description of drawings

Fig. 1 is the structural representation of pressure-measuring fiber grating device of the present invention.

Embodiment

Below in conjunction with accompanying drawing the present invention is described in further detail, as shown in Figure 1, make a kind of piston-liquid-piston machine structure of fixed fiber grating sensing part, this physical construction comprises pedestal 1, offer chamber 2 in the pedestal 1, the top of pedestal 1 offers the stepped hole 3 that communicates with chamber 2, be provided with upper piston 4 and lower piston 5 in the stepped hole 3, the cross-sectional area of upper piston 4 is greater than the cross-sectional area of lower piston 5, be full of hydraulic oil 6 between upper piston 4 and the lower piston 5, the lower end of lower piston 5 is a sphere shape, the end face of chamber 2 is the center with the axis of stepped hole 3, projection forms a boss 21 downwards, is equipped with the elastic membrane 7 of cylindricality on the boss 21, and the lower end of lower piston 5 can contact with springform 7; Scribe fiber grating, and fiber grating passive temperature compensation method studied, produce only to pressure-sensitive high precision, highly sensitive fiber grating 9, it is two optical fiber fixed legs 8 of axis of symmetry that the lower surface of springform 7 is provided with the axis of stepped hole 3, be fixed with fiber grating 9 between two optical fiber fixed legs 8, fiber grating 9 passes the through hole 10 that is opened on pedestal 1 sidewall and links to each other with the outside.

Principle according to " piston-liquid-piston " line of force conversion is acted on the upper piston by measuring pressure, establishes the applied pressure F on the upper piston ₁, piston I area S ₁, process liquid is with pressure $P=\frac{F_1}{{\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="C200710014559E00051.png"\; state="\{\{state\}\}">S</figure-callout>}}_1}$ Pass to lower piston, set the directed force F on the piston ₂, valve piston area S ₂, ${\mathrm{<figure-callout\; id="2"\; label="F"\; filenames="C200710014559E00051.png"\; state="\{\{state\}\}">F</figure-callout>}}_2=P\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="C200710014559E00051.png"\; state="\{\{state\}\}">S</figure-callout>}}_2=\frac{S_2}{S_1}{\mathrm{<figure-callout\; id="1"\; label="F"\; filenames="C200710014559E00051.png"\; state="\{\{state\}\}">F</figure-callout>}}_1=\mathrm{<figure-callout\; id="1"\; label="K\; F"\; filenames="C200710014559E00051.png"\; state="\{\{state\}\}">K</figure-callout>}{F}_{}{}_1,(K<1)$ , the variable effect of lower piston power is to the strain of fiber grating.Fiber grating centre wavelength is strict linear with the variation of strain, and it is as follows to change formula:

${\mathrm{\&Delta;\&lambda;}}_B=2\mathrm{n\&Lambda;}[1-\left(\frac{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="C200710014559E00051.png"\; state="\{\{state\}\}">n</figure-callout>}}^2}{2}\right)[p_{12}-v(p_{11}+p_{12})]]\mathrm{\&epsiv;}={\mathrm{\&lambda;}}_B{K}_{\mathrm{\&epsiv;}}\mathrm{\&epsiv;}$ , K in the formula _εBe the temperature control and the strain sensitivity of fiber grating, p ₁₁And p ₁₂Be the elasto-optical coefficient of fiber optic materials, ε is the size that acts on the stress on the grating.Therefore, had linear relationship by measuring pressure and fiber grating centre wavelength.By this linear relationship, set up the mathematical model of pressure and fiber grating bragg wavelength relation, promptly pressure is to the coded modulation model of fiber grating centre wavelength.By to tunable fiber F-P filters demodulate method, the edge filter demodulation method, optical signal processing methods such as matched fiber grating demodulation by filter and electric signal demodulation method etc. carry out systematic analysis, work out the optimal demodulation scheme of the large range high precision fiber bragg grating pressure sensor that is fit to ore deposit pressure detection, and produce the fiber grating signal demodulating system.By the relation of optical fiber Bragg wavelength change and pressure, and the ratio of the area of two-piston, calculate the size of testing pressure.

Claims (5)

1, a kind of pressure-measuring fiber grating device, comprise pedestal, offer chamber in the pedestal, the top of pedestal offers stepped hole, chamber in stepped hole and the pedestal is communicated with, and is provided with upper piston and lower piston in the stepped hole, full of liquid between upper piston and the lower piston, the bottom of stepped hole is provided with elastic membrane, it is characterized in that: the lower surface of described elastic membrane is provided with fiber grating; It is the optical fiber fixed leg of axis of symmetry that the lower surface of above-mentioned elastic membrane is provided with the axis of stepped hole, and fiber grating is fixed on the optical fiber fixed leg; The lower end of described lower piston is a sphere shape.

2, pressure-measuring fiber grating device according to claim 1, it is characterized in that: the cross-sectional area of described upper piston is greater than the cross-sectional area of lower piston.

3, pressure-measuring fiber grating device according to claim 1 is characterized in that: the end face of described chamber is the center with the axis of stepped hole, and projection forms a boss downwards, is equipped with the elastic membrane of cylindricality on the boss.

4, pressure-measuring fiber grating device according to claim 1 is characterized in that: described liquid is hydraulic oil.

5, pressure-measuring fiber grating device according to claim 1 is characterized in that: have through hole on the sidewall of described chamber.

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