CN101806646A - Intensity demodulation lamp cap torque optical sensor - Google Patents

Abstract

The invention relates to an intensity demodulation type lamp head torque optical fiber sensor. The accuracy of traditional measuring equipment is not high, and it is difficult to realize dynamic online detection. The invention comprises a homogeneous circular rotating shaft, a metal wire, a sensing optical fiber, a lamp head clamp, and a guiding optical fiber. Either end of the homogeneous circular rotating shaft is fixedly connected with the lamp holder and coaxially arranged with the lamp holder, the metal wire and the axial direction of the homogeneous circular rotating shaft are arranged in close contact with the surface of the homogeneous circular rotating shaft at an angle of θ ₁ , and the sensing optical fiber The axial direction of the homogeneous circular shaft is θ ₂ and evenly wound on the surface of the homogeneous circular shaft; the metal wire and the sensing optical fiber form an intersection point on the surface of the homogeneous circular shaft. The invention adopts an all-fiber structure, can work reliably for a long time in a strong electromagnetic interference environment, and has higher precision and lower cost.

Description

A kind of intensity demodulation lamp cap torque optical sensor

Technical field

The invention belongs to measuring technology and sensory field of optic fibre, be specifically related to a kind of intensity demodulation lamp cap torque optical sensor.

Background technology

Country payes attention to the specifications of quality of product safety performance, and in the electrical lighting industry, the safety index of lamp holder physical strength is classified the state compulsion test item as; The detection of lamp holder mechanical strength properties index torque resistant power, national standard explicitly calls for.Along with development of science and technology, the microminiaturization of detection system, intellectuality, networking will become trend, and traditional Static Detection technology will be substituted by new dynamic online measuring technique.

At present the lamp holder torque resistant force transducer that uses is generally strain gauge transducer, and this type of sensor adopts resistance strain gage as sensing element usually, has that sensitivity is lower, precision is not high, has bigger non-linear under the great straining force effect; Shortcomings such as output signal is fainter, antijamming capability is relatively poor.Be accompanied by the widespread use of optical fiber sensing technology, lamp cap torque Fibre Optical Sensor achievement in research of new generation is arisen at the historic moment.

Summary of the invention

It is not high to the objective of the invention is to overcome the traditional measurement equipment precision, is difficult for realizing the defective of dynamic online detection; Providing a kind of can work under strong electromagnetic interference environment reliably and with long-term, simple in structure, and lower-cost intensity demodulation lamp cap torque optical sensor.

The technical solution adopted in the present invention is as follows:

The present invention includes the circular rotating shaft of homogeneous, tinsel, sensor fibre, lamp base fixture, guiding fiber.Any end of the circular rotating shaft of homogeneous fixedly connected with lamp base fixture and with the coaxial setting of lamp base fixture, the diameter of described homogeneous circle rotating shaft is D, length is L, 40mm≤D≤50mm, 100mm≤L≤150mm; Tinsel is oblique to be close to around the home on the circular rotating shaft of homogeneous surface, and tinsel is θ with the axial angle of the circular commentaries on classics of homogeneous ₁, 30 °≤θ ₁≤ 60 °, diameter wiry is d, 0.3mm≤d≤0.4mm; Evenly direction is opposite around the home on the circular rotating shaft of homogeneous surface and with tinsel around the home for sensor fibre, and the axial angle of the circular commentaries on classics of sensor fibre and homogeneous is θ ₂, 40 °≤θ ₂≤ 50 °, the sensor fibre number of turns around the home is n, 5≤n≤10; Described tinsel and sensor fibre form 3～8 point of crossing on the circular rotating shaft of homogeneous surface.

The present invention compared with prior art has the following advantages:

1. employing all optical fibre structure, can be under strong electromagnetic interference environment reliably and with long-term work;

2. direct output intensity signal only needs simple opto-electronic conversion can obtain the lamp cap torque value; It is fast to measure response, the demodulation techniques maturation;

3. simple in structure, than strain gauge transducer, have higher precision and lower cost;

4. help realizing dynamic online detection, can promote microminiaturization, the intellectuality and networked of detection system.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 measures the embodiment synoptic diagram for lamp cap torque.

Among the figure: 1, the circular rotating shaft of homogeneous, 2, steel wire, 3, multimode optical fiber, 4, lamp base fixture, 5, guiding fiber, 6, light source, 7, detector, 8, light fixture.

Embodiment

Below in conjunction with accompanying drawing the present invention is further described:

As shown in Figure 1, a kind of intensity demodulation lamp cap torque optical sensor comprises the circular rotating shaft 1 of homogeneous, steel wire 2, multimode optical fiber 3, lamp base fixture 4, guiding fiber 5.The circular rotating shaft 1 of homogeneous is round section, the equally distributed rotating shaft of quality.Lamp base fixture 4 is fixedlyed connected by the right-hand member of the circular rotating shaft of nut and homogeneous, in order to fixing lamp holder; It is 45mm that its diameter of organic glass (perhaps can select aluminium alloy for use) is adopted in the circular rotating shaft of homogeneous, and length is 150mm.Axially being 45 ° and sticking on the circular rotating shaft of the homogeneous surface with seccotine 504 of the circular rotating shaft of steel wire (perhaps can select phosphorus copper wire for use) and homogeneous, the diameter of steel wire (perhaps can select phosphorus copper wire for use) is 0.35mm; The circular rotating shaft of multimode optical fiber and homogeneous axially be 45 ° with tinsel around the home the hand of spiral be oppositely around the home on the circular rotating shaft of homogeneous surface, the two ends of optical fiber stick on the homogeneous circle rotating shaft surface with seccotine 504; The number of turns around the home of multimode optical fiber is 6; Steel wire and multimode optical fiber form 6 point of crossing on the circular rotating shaft of homogeneous surface.

As shown in Figure 2, the light that light source 6 sends is transferred to multimode optical fiber 3 through guiding fiber 5, is detected device 7 and receives.When lamp base fixture 4 is not rotated by external force, so multimode optical fiber 3 can not produce little bending with steel wire 2 contact positions owing to be subjected to the shearing strain of the circular rotating shaft 1 of homogeneous.So the transmission light intensity that detector 7 receives does not change.

When light fixture 8 at up time needle force F ₁Drive when rotating down, drive the circular rotating shaft 1 of homogeneous simultaneously by lamp base fixture 4 and rotate.This moment, the other end in the circular rotating shaft 1 of homogeneous applied a reacting force F ₂Keep circular rotating shaft 1 relative fixed of homogeneous, the circular rotating shaft 1 of homogeneous makes multimode optical fiber 3 and steel wire 2 contact positions produce little bending because of producing shearing strain everywhere.The moment of torsion difference that lamp holder applies, the micro curving rate peak value of pulse of optical fiber, wide variety difference cause through the optical power loss of multimode optical fiber 3 also different thus.The effect of this moment of torsion makes and is modulated by the light intensity of multimode optical fiber.By measuring the variation of multimode optical fiber 3 its transmitted intensities of little curved back, just can obtain the torque value of lamp holder.

Lamp cap torque measuring principle of the present invention is: produced by torsional interaction little when curved when the multimode optical fiber in the homogeneous rotating shaft around the home, represents the multimode optical fiber axial coordinate with ξ, then curvature function C _f(ξ) be:

$C_f\left(\mathrm{\ξ}\right)={\mathrm{\Σ}}_{n=1}^N{C}_n\left(\mathrm{\ξ}\right)=A_n\exp [-2^2{(\mathrm{\ξ}-{\mathrm{\ξ}}_n)}^2/W_n^2]---\left(1\right)$

C in the formula _f(ξ) multimode optical fiber n of expression is little curved, and N is the total little curved number (being that multimode optical fiber was counted with intersecting of steel wire) of the multimode optical fiber in rotating shaft around the home; A _n, ξ _nBe respectively curvature peak value of pulse and peak; W _nIt is the pulse width that curvature value is reduced to the 1/e place of peak value.

For the gradient shape optical fiber of Refractive Index Profile o parameter alpha=2 (multimode optical fiber a kind of), microbending loss I is:

I＝3.9J″(Δβ)/δ (2)

δ is the refractive index contrast of fibre core and covering in the formula, and Δ β is the poor of two-mode transmission; " (Δ β) is the power spectrum density of micro curving rate impulse function to J; Suppose that adjacent little curved interval is greater than curvature pulse width, then J in the multimode optical fiber " (Δ β)) be expressed as:

$J^{\′\′}\left(\mathrm{\Δ\β}\right)\≈[\mathrm{\πN}{\left(\sqrt{\stackrel{\‾}{A^2}}\right)}^2{\stackrel{\‾}{W}}^2/4]\exp [-{\left(\mathrm{\Δ\β}\right)}^2{\stackrel{\‾}{W}}^2/8]---\left(3\right)$

In the formula

Be the root mean square of curvature pulse,

Be mean curvature pulse width (persistence length).Merge (2), (3) formula, and utilize relational expression r _fBe the fiber core radius of multimode optical fiber, obtain the microbending loss I of Gaussian curvature pulse correspondence _GFor:

$I_G=(3.06\mathrm{<figure-callout\; id="2"\; label="N\; A"\; filenames="HSA00000077253100011.png,HSA00000077253100012.png"\; state="\{\{state\}\}">N</figure-callout>}\stackrel{}{A^{}}\stackrel{\&OverBar;}{{}^2}{\stackrel{\&OverBar;}{W}}^2/\mathrm{\&delta;})\exp (-\mathrm{\&delta;}{\stackrel{\&OverBar;}{W}}^2/4r_f^2)---\left(4\right)$

From the angle of statistical average, under the little condition of rotating shaft shearing strain γ,

Variation small,

Variation to I _GThe influence of size is better than

So, can suppose

ε is proportional with the optical fiber microstrain, promptly

$\stackrel{\&OverBar;}{W}=\stackrel{\&OverBar;}{W_0}+{(-1)}^{i+1}\mathrm{k\&epsiv;}---\left(5\right)$

K is a scale factor in the formula.The corresponding clockwise direction of symbol i=0 is reversed, and i=1 is corresponding counterclockwise to be reversed.

According to principle of elasticity, under the smaller condition of shearing strain γ, multimode optical fiber strain stress and relative torsional angle

Closely seemingly be expressed as:

Because

With the value of 2/d be suitable, so can think

And N ≈ l ' θ ₂/ s (l ' be is the length of multimode optical fiber around the home, and s is the pitch of multimode optical fiber) merges (4), and (5) get relative microbending loss I with (6) formula _G

Formula (7) is to utilize fiber microbending loss to carry out the basic theories model that relative torsional angle is measured.Three factors are respectively in the formula

K ₁＝(12.24l′cosθ ₁)/(d ²sδ)，K ₂＝(kDsinθ ₂)/(4L)， $K_3=\mathrm{\&delta;}/4{\mathrm{<figure-callout\; id="2"\; label="r\; f"\; filenames="HSA00000077253100011.png,HSA00000077253100012.png"\; state="\{\{state\}\}">r</figure-callout>}}_f^{}$

The expression formula that is obtained relative torsional angle measurement sensitivity by formula (7) is

In the formula

Formula (7) shows, by measuring microbending loss I _G, can get the rotating shaft relative torsional angle

Value.Geometric relationship by the elastic rotation shaft mechanics obtains the difference M that the circular rotating shaft of homogeneous two ends apply moment of torsion:

G is the shear elasticity of the circular rotating shaft of homogeneous in the formula, I _PSecond polar moment of area for the circular rotating shaft of homogeneous.So just can obtain being added on the moment of torsion at homogeneous round section two ends, promptly realize the measurement of moment of torsion.

The light path of optical fiber has been hermetic among the present invention, has anti-electromagnetic interference, high sensitivity and does not disturb the characteristics such as tested scene, is adapted at measuring under the adverse circumstances such as light fixture workshop; Compare traditional lamp cap torque sensor, adopt multimode fibre to be easier to realize dynamically online detection of lamp cap torque as measuring cell, and have higher precision and lower cost.

Claims (1)

1. A kind of intensity demodulation type lamp cap torque optical fiber sensor, comprises homogeneous circular rotating shaft, metal wire, sensing optical fiber, lamp cap clamp, guide optical fiber, it is characterized in that: Any one end of the homogeneous circular shaft is fixedly connected to the lamp holder and arranged coaxially with the lamp holder, the diameter of the homogeneous circular shaft is D, the length is L, 40mm≤D≤50mm, 100mm≤L≤150mm; The metal wire is obliquely placed on the surface of the homogeneous circular shaft, the angle between the metal wire and the axial direction of the homogeneous circular shaft is θ ₁ , 30°≤θ ₁ ≤60°, and the diameter of the metal wire is d , 0.3mm≤d≤0.4mm; the sensing fiber is evenly wound on the surface of the homogeneous circular shaft and is opposite to the winding direction of the metal wire, and the angle between the sensing fiber and the axial direction of the homogeneous circular shaft is θ ₂ , 40°≤θ ₂ ≤50°, the number of turns of the sensing fiber is n, 5≤n≤10; the metal wire and the sensing fiber form 3 to 8 intersection points on the surface of the homogeneous circular shaft .

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