CN109186490A - A kind of 3D shape sensing measuring method and device based on multi-core optical fiber - Google Patents
A kind of 3D shape sensing measuring method and device based on multi-core optical fiber Download PDFInfo
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- CN109186490A CN109186490A CN201811104988.0A CN201811104988A CN109186490A CN 109186490 A CN109186490 A CN 109186490A CN 201811104988 A CN201811104988 A CN 201811104988A CN 109186490 A CN109186490 A CN 109186490A
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- G—PHYSICS
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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- G01B11/255—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures for measuring radius of curvature
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Abstract
The invention discloses a kind of 3D shape sensing measuring method and device based on multi-core optical fiber, belongs to optical fiber shape sensing measurement technical field.The present invention changes front and back fiber grating Prague central wavelength according to multi-core optical fiber shape, calculate the maximum strain of fiber grating and the curvature and windup-degree of fiber grating cross section position, curvature and windup-degree interpolation are carried out to multi-core optical fiber, it is shown using after the progress 3D shape reconstruct of three-dimensionalreconstruction algorithm in computer, realizes multi-core optical fiber 3D shape sensing measurement.The measuring device includes computer, optical fiber grating sensing analyzer and multi-core optical fiber fan-in fan-out modular, the present invention is using the measurement strain of all optical fibre structure combination fiber grating, by the distance and quantity that change two neighboring fiber grating, measurement accuracy can be improved, the multi-core optical fiber of use, installation error is eliminated, later maintenance is conducive to and is changed the outfit, reliability is higher.
Description
Technical field
The invention belongs to optical fiber shape sensing measuring method and systems technology fields, and in particular to one kind is based on multi-core optical fiber
3D shape sensing measuring method and device.
Background technique
3D shape sensing measurement is the shape measure to flexible flexible object, in aerospace, medical instrument, stone
The fields such as exploration activity, robot search and rescue have huge development potentiality.Due to the structuring of measuring instrument and point of testing principle
From reasons such as property, traditional method carries out 3D shape using the non-contact opticals detection technique such as laser scanning, machine vision
Sensing measurement is difficult to carry out in some occasions, such as in having electromagnetic interference or inflammable easily fried adverse circumstances, is based on electric signal
The 3D shape sensor of measurement is very restricted, or even can not be worked；When robot searches and rescues, large-scale instrument and equipment
The scene of the accident can not be quickly transported to；In aerospace field, heavy instrument can not carry out aircraft or spacecraft non-contact
Formula detection.
This just needs the strain measurement method using contact, and traditional resistance strain gage lead is more, weight is big, anti-electromagnetism
Interference performance is poor, and carries out Multipoint strain gauging using fiber grating, wiring is simple, fatigue life length, electromagnetism interference, can be with
It realizes composite inner heeling-in, there is the advantage that can not be substituted.
The measurement that a piece single-core fiber grating can only be strained cannot measure 3D shape, can only pass through acquisition
Multiple strain values calculate curvature, and then reconstruct two-dimensional shapes.But multifiber grating can be surveyed by measurement in a closed series
Multiple strain values of the same position are measured, and then reconstruct 3D shape.2014, Shen Lin was bravely equal by 4 FBG (fiber grating)
Sensor array is respectively placed on substrate mutually in the position at 90 ° of angles, each spatial point is by orthogonal both direction
Two FBG array measurements, realizing optical fiber shape sensing, (referring to bibliography: Shen Linyong, Xiao Hai, Qian Jinwu etc. are peeped in intelligence
The shape similarity metric and method for visualizing of mirror study [J] Chinese journal of scientific instrument, 2014 (12): 2725-2730).But this method
It is very complicated when sensor is installed and is arranged, and installation error can be generated.
Summary of the invention
In order to solve above-mentioned problems of the prior art, easily and reliably realize that high-precision three-dimensional shape sensing is surveyed
Amount, the present invention propose a kind of 3D shape sensing measuring method and device based on multi-core optical fiber.
Present invention firstly provides a kind of 3D shape sensing measuring method based on multi-core optical fiber, the method specifically include
Step:
Step 1: measuring multi-core optical fiber respectively before and after shape change in every fibre core by optical fiber grating sensing analyzer
Fiber grating Prague central wavelength；Include at least three fibre cores in the multi-core optical fiber, includes at least two on every fibre core
Above fiber grating.
Step 2: according to measured multi-core optical fiber before and after shape change fiber grating Prague center in every fibre core
Wavelength calculates the maximum strain of fiber grating in every fibre core of multi-core optical fiber；
Step 3: calculating the curvature and windup-degree of fiber grating cross section position；
Step 4: carrying out curvature and windup-degree interpolation to multi-core optical fiber using space curve theory and interpolation theory, ask
Obtain the curvature and windup-degree of multiple measurement positions between two neighboring fiber grating cross section in multi-core optical fiber；
Step 5: carrying out 3D shape reconstruct to multi-core optical fiber using three-dimensionalreconstruction algorithm；
Step 6: the multi-core optical fiber of reconstruct is shown in a computer, realize that multi-core optical fiber 3D shape sensing is surveyed
Amount.
The present invention also provides a kind of 3D shape sense measuring device based on multi-core optical fiber, described device include: to calculate
Machine, optical fiber grating sensing analyzer, multi-core optical fiber fan-in fan-out modular and multi-core optical fiber, optical fiber grating sensing analyzer issue
Detection light enter multi-core optical fiber by multi-core optical fiber fan-in fan-out modular, detect light by fiber grating and reflect to form narrowband
Light, narrow band light pass through multi-core optical fiber fan-in fan-out modular again and return in optical fiber grating sensing analyzer, optical fiber grating sensing point
Analyzer finds out multi-core optical fiber every section of fiber grating Prague in every fibre core before and after the shape change by the demodulation to narrow band light
Central wavelength, and it is sent to computer；Then fiber grating cross section position in multi-core optical fiber is calculated in a computer
Curvature and windup-degree；Using space curve theory and interpolation theory to multi-core optical between two adjacent fiber grating cross sections
Fibre carries out Curvature Interpolation and windup-degree interpolation, acquires the curvature and torsion of multiple measurement positions on every fibre core in multi-core optical fiber
Angle；3D shape reconstruct is carried out to multi-core optical fiber using three-dimensionalreconstruction algorithm；The multi-core optical fiber 3D shape of reconstruct is being counted
It is shown in calculation machine, realizes multi-core optical fiber 3D shape sensing measurement.
The advantages and positive effects of the present invention are:
1, the multi-core optical fiber that the present invention uses can choose three cores, four cores, seven cores etc., and multi-core optical according to the actual situation
Fibre can have multiple fiber gratings inside a fibre core, do not need the installation and splicing that carry out multifiber, eliminate
Installation error is conducive to later maintenance and changes the outfit, and reliability is higher.
2, the present invention, can according to actual needs, by changing two neighboring optical fiber light using fiber grating measurement strain
The distance of grid improves measurement accuracy, and the quantity by changing fiber grating changes distance sensing, the reflection of fiber grating
The signal signal that Rayleigh scattering, Brillouin scattering and Raman scattering return than in the prior art is stronger.
3, the present invention uses optical fiber grating sensing analyzer, and measuring principle is simple, not complicated demodulating system and structure
And special device, thus advantage of lower cost, and higher resolution ratio can be obtained.
4, transducing part of the invention is all optical fibre structure, and electromagnetism interference, anti-fatigue life are long, wiring is simple, can be with
Realize composite inner heeling-in.
5, the present invention carries out Curvature Interpolation and windup-degree interpolation between two neighboring fiber grating, by discrete curvature
Data and windup-degree serialization, improve the fitting precision of 3D shape.
6, the present invention finally carries out difference processing to test data, and fiber arrangement is straight line (nothing by same root multi-core optical fiber
Bending) when, fiber grating Prague central wavelength is measured as substrate, then optical fiber is put into certain 3D shape, measure shape
This fiber grating Prague central wavelength and substrate are done difference, just by fiber grating Prague central wavelength after shape change
Fiber grating Prague central wavelength knots modification can be obtained, to reduce the shadows such as light source fluctuation, temperature fluctuation, fiber manufacturing error
It rings, improves stability and measurement accuracy.It is measured and is strained using optical fiber grating sensing analyzer, compared with the prior art middle optical time domain
Reflectometer and probe beam deflation instrument distributed measuring system, volume is smaller, and structure is simple, and measurement is easy, and cost is lower, more
It is with practical value.
Detailed description of the invention
Fig. 1 is 3D shape sensing measuring method flow chart provided by the invention；
Fig. 2 is that three core fibres shape provided by the invention changes pre-structure schematic diagram；
Fig. 3 is structural schematic diagram after three core fibres shape provided by the invention changes；
Fig. 4 is fiber grating cross-sectional view in three core fibre provided by the invention；
Fig. 5 is reconstruction method of three-dimensional shape schematic diagram in the present invention；
Fig. 6 is the structural schematic diagram of the 3D shape sense measuring device provided by the invention based on multi-core optical fiber；
Fig. 7 is that three core fibre of the embodiment of the present invention is in circular helix status diagram；
Fig. 8 is the 3D shape reconstruct image of three core fibre of the embodiment of the present invention.
Specific embodiment
Below in conjunction with drawings and examples, the present invention is described in further detail: the present embodiment is with skill of the present invention
Implemented under premised on art scheme, gives detailed embodiment, but protection scope of the present invention is not limited to following implementations
Example.
The present invention provides a kind of 3D shape sensing measuring method and device based on multi-core optical fiber, when the shape of multi-core optical fiber
When shape changes, the inside of multi-core optical fiber can generate bending, i.e. the side of multi-core optical fiber neutral axis can be stretched, that is, be drawn
Stress, the other side can be compressed, i.e., by compression, therefore the fiber grating (FBG) for being located at neutral axis two sides will receive stretching
Or compress, the pitch for the fiber grating for being stretched or compressing can increase or reduce accordingly, i.e. the screen periods of fiber grating
It can be decreased or increased, fiber grating Prague central wavelength that fiber grating is reflected back can be decreased or increased, and pass through fiber grating
Sensing analysis instrument measures multi-core optical fiber shape and changes front and back fiber grating Prague central wavelength.And the strain that fiber grating is subject to
It is proportional to the knots modification of fiber grating Prague central wavelength of fiber grating reflection, when fiber grating Prague in every fibre core
When central wavelength is detected, the strain that the fiber grating in every fibre core of multi-core optical fiber is subject to can be based on the light of measurement
Fine grating Bragg central wavelength calculates, and then calculates the curvature and windup-degree of fiber grating cross section position.Benefit
Curvature Interpolation and windup-degree interpolation are carried out to multi-core optical fiber with space curve theory and interpolation theory, acquire phase in multi-core optical fiber
The curvature and windup-degree of multiple measurement positions between adjacent two fiber grating cross sections；Using three-dimensionalreconstruction algorithm to multi-core optical
Fibre carries out 3D shape reconstruct；The multi-core optical fiber of reconstruct is shown in a computer, realizes that multi-core optical fiber 3D shape passes
Sensed quantity.
The shape sensor that multi-core optical fiber is bonded relative to more single-core fibers has better data stability and accurate
Property, also not dependent on measured structure, use is more flexible and convenient, becomes the 3-d shape measurement means of more potentiality.
By taking three core fibres in multi-core optical fiber as an example, the three core fibres shape change pre-structure schematic diagram as shown in Fig. 2,
Fiber grating 1, fiber grating 2 and fiber grating 3 are respectively provided on three fibre cores, when the shape of three core fibre changes,
The inside of three core fibre correspondingly generates strain, and structural schematic diagram after three core fibre shapes change is as shown in figure 3, when described
When three core fibres are bent downwardly, the fiber grating 1 on the upside of the neutral axis of three core fibre can be stretched, i.e., answered by drawing
Power, fiber grating 2 and fiber grating 3 on the downside of the neutral axis of three core fibre can be compressed, i.e., by compression, position
FBG (fiber grating) in the neutral axis two sides of three core fibres is stretched or compresses, correspondingly, the light after being stretched or compressed
The pitch of fine grating will increase or reduce, and therefore, fiber grating periods lambda can correspondingly reduce or increase, fiber grating periods lambda
Change will lead to fiber grating Prague central wavelength that fiber grating is reflected back and change.The shape is every before changing
There are following relationships with the fiber grating period for fiber grating Prague central wavelength in root fibre core:
λB=2neffΛ (1)
In formula (1), Λ is fiber grating period, neffIt is the effective refractive index of fiber grating, λBIt is every before shape changes
Fiber grating Prague central wavelength in fibre core.
A kind of 3D shape sensing measuring method based on multi-core optical fiber provided by the invention, as shown in Figure 1, specifically including
Following steps:
Step 1: measuring multi-core optical fiber respectively before and after shape change in every fibre core by optical fiber grating sensing analyzer
Fiber grating Prague central wavelength；Include at least three fibre cores in the multi-core optical fiber, every fibre core include at least two with
On fiber grating, the length of the distance between fiber grating and each fiber grating determines according to actual use situation.Specifically
Change fiber grating Prague center in preceding every fibre core in shape to measure multi-core optical fiber using optical fiber grating sensing analyzer
Wavelength XBWith multi-core optical fiber after shape change fiber grating Prague central wavelength lambda in every fibre core.
Step 2: according to measured multi-core optical fiber before and after shape change fiber grating Prague center in every fibre core
Wavelength calculates the maximum strain ε of fiber grating in every fibre core of multi-core optical fiber.
The strain stress of fiber grating and the knots modification Δ λ of fiber grating Prague central wavelengthBThere is following relationship:
In formula (2), ε is the maximum strain of fiber grating, and P is the elasto-optical coefficient of fiber grating, Δ λBFor fiber grating cloth
The knots modification of glug central wavelength, Δ λB=λ-λB, λ is fiber grating Prague central wavelength after shape changes.
As it can be seen that the maximum strain ε of fiber grating is proportional to the knots modification Δ λ of fiber grating Prague central wavelengthB。
Step 3: calculating the curvature and windup-degree of fiber grating cross section position.
As shown in figure 4, there are three fiber gratings in each fibre core, in three core fibres by taking three core fibres after straining as an example
One fiber grating cross section of upper interception, each fiber grating in Fig. 4 is since shape change can generate strain, in conjunction with every fibre
The distance r of strain and every fibre core to fiber grating cross section geometric center caused by fiber grating is calculated such as figure in core
The curvature and windup-degree of the position of fiber grating cross section shown in 4, fiber grating cross section position are to survey
Position is measured, by taking three core fibres as an example, there is the establishment of following equation group:
In formula (3), ε1For strain, ε caused by fiber grating in fibre core 12To be answered caused by fiber grating in fibre core 2
Become, ε3For strain, θ caused by fiber grating in fibre core 31For windup-degree；Enabling ε is the maximum of fiber grating cross section in Fig. 4
Strain, ε0It is the axial strain of three core fibres, if fibre core 1, fibre core 2 and 3 position of fibre core point A, B, C respectively, fiber grating
The geometric center of cross section is point O, then defines the angle Δ θ of AO and BO12For the angle between fibre core 1 and fibre core 2, BO and CO's
Angle Δ θ23For the angle between fibre core 2 and fibre core 3, Δ θ12=Δ θ23=120 °.
If three core fibres only influence by bending when shape changes, the axial strain ε of three core fibres0=0, fiber grating is horizontal
The relationship of maximum strain ε and curvature k caused by section are as follows:
ε=- kr (4)
In formula (4), the distance of fibre core 1, fibre core 2 and fibre core 3 to fiber grating cross section geometric center O are r.Therefore right
There is following equation establishment respectively in three fibre cores:
ε1=-krsin (θ1) (5)
ε2=-krsin (θ1+Δθ12) (6)
ε3=-krsin (θ1+Δθ12+Δθ23) (7)
First curvature and the first windup-degree are obtained according to equation (5) and equation (6) solution, according to equation (6) and equation
(7) it is solved in and obtains torsion and the second windup-degree, solved according to equation (5) and equation (7) and obtain third curvature and the
Three windup-degrees are averaged first, second, and third curvature to obtain the 4th curvature；By described first, second
It is averaged to obtain the 4th windup-degree with third windup-degree.Using the 4th curvature and the 4th windup-degree as current
The curvature and windup-degree of fiber grating cross section.The windup-degree θ1AO is expressed as to answer with fiber grating cross section maximum
Angle between changing direction.
Similarly, other positions fiber grating cross section in three core fibres is calculated according to above method, obtains three
The curvature and windup-degree of all fiber grating cross sections position in core fibre.
Step 4: carrying out curvature and windup-degree interpolation to multi-core optical fiber using space curve theory and interpolation theory, ask
Obtain the curvature and windup-degree of multiple measurement positions between two neighboring fiber grating cross section in multi-core optical fiber.
By taking three core fibres as an example, due to the different fiber grating cross sections acquired by step 3 be in three core fibres from
Dissipate distribution, and the fiber grating limited amount in every fibre core, it is therefore desirable to two neighboring fiber grating cross section
Curvature and windup-degree find out the curvature and windup-degree of the corresponding insertion measurement position in more insertion points using interpolation method, obtain
More dense curvature and windup-degree data are obtained, to carry out the reconstruct of three core fibre 3D shapes.The interpolation method of step 4 uses
Linear interpolation method, by taking Curvature Interpolation as an example, it is assumed that the curvature between two neighboring measurement position is linear homogeneous variation, is enabled
The curvature of+1 measurement position of pth is kp+1, the curvature of p-th of measurement position is kp, p=1,2 ..., m-1, m is fiber grating
The quantity of cross section；E interpolation point is shared among the two measurement positions, the corresponding insertion of each interpolation point measures position
It sets, then three core fibres between the two measurement positions are divided into e+1 sections, at this point, the corresponding insertion of j-th of interpolation point of insertion
The curvature k of measurement positionjAre as follows:
It is corresponding that each interpolation point after linear interpolation is found out between two fiber grating cross sections of arbitrary neighborhood by formula (6)
Insertion measurement position curvature.Similarly find out the windup-degree of the corresponding insertion measurement position of each interpolation point.
Step 5: carrying out 3D shape reconstruct to multi-core optical fiber using three-dimensionalreconstruction algorithm.
For the reconstruct of 3D shape described in step 5 specifically, by taking three core fibres as an example, existing circular arc splicing method can only
The reconstruct of two-dimensional shapes is carried out, there is significant limitation, therefore, the present invention uses the Three-dimensional Gravity of based drive orthogonal frame
Structure algorithm, this three-dimensionalreconstruction algorithm is realized by translation transformation matrix and rotational transformation matrix.
As shown in figure 5, in figure, O0With OnFor the geometric center of the measurement position at both ends on three core fibres, three core fibres pass through
After Curvature Interpolation and windup-degree interpolation, (including the corresponding survey in fiber grating cross section position of all measurement positions is chosen
Measure position and the corresponding insertion measurement position of interpolation point) i.e. in the geometry of any one measurement position in n+1 measurement position
The heart is point Oi, i=0,2 ..., n-1.It will point OiThe kinetic coordinate system a at placeibiciA translation transformation is completed along three core fibres,
Obtain adjacent measurement position midpoint Oi+1Kinetic coordinate system ai+1bi+1ci+1, point Oi+1In kinetic coordinate system aibiciIn position
dai、dbi、dciIt is as follows:
In formula (7), kiFor point OiThe curvature of place fiber grating cross section, αiThe circular arc O for being ds for arc lengthi Oi+1Institute is right
The central angle answered, αi=ki*ds.It is hereby achieved that kinetic coordinate system aibiciTo kinetic coordinate system ai+1bi+1ci+1Coordinate become
Change matrix Ri+1:
In formula (8), θiFor point Oi+1Relative to point OiWindup-degree.Note fixed coordinate system xyz is A, kinetic coordinate system
aibiciFor Wi, kinetic coordinate system ai+1bi+1ci+1For Wi+1, then:
Wi+1=Ri+1Wi=Ri+1TiA (9)
In formula (9), TiFor kinetic coordinate system WiTo the transformation matrix of fixed coordinate system A, transformation matrix is equal to two coordinate systems
Between translation transformation matrix and rotational transformation matrix product.
Using above-mentioned formula, iteration is calculated, and calculates coordinate of each measurement position at fixed coordinate system xyz, real
The 3D shape reconstruct of existing multi-core optical fiber.
Step 6: the multi-core optical fiber of reconstruct is shown in a computer, realize that multi-core optical fiber 3D shape sensing is surveyed
Amount.
The present invention also provides a kind of 3D shape sense measuring device based on multi-core optical fiber, as shown in fig. 6, the three-dimensional
Shape sense measuring device includes: computer, optical fiber grating sensing analyzer (model RT8000L), multi-core optical fiber fan-in fan
Module and multi-core optical fiber out, the detection light that optical fiber grating sensing analyzer issues enter by multi-core optical fiber fan-in fan-out modular
To multi-core optical fiber, light is detected by fiber grating and reflects to form narrow band light, narrow band light passes through multi-core optical fiber fan-in fan-out modular again and returns
It returns in optical fiber grating sensing analyzer, optical fiber grating sensing analyzer is found out multi-core optical fiber and existed by the demodulation to narrow band light
Shape changes every section of fiber grating Prague central wavelength in the every fibre core in front and back, and is sent to computer, then in computer
The curvature and windup-degree of fiber grating cross section position in middle calculating multi-core optical fiber；Two adjacent fiber gratings are transversal
Curvature Interpolation and windup-degree interpolation are carried out to multi-core optical fiber using space curve theory and interpolation theory between face, acquire multicore
In optical fiber on every fibre core multiple measurement positions curvature and windup-degree；Three are carried out to multi-core optical fiber using three-dimensionalreconstruction algorithm
Tie up Shape Reconstruction；The multi-core optical fiber 3D shape of reconstruct is shown in a computer, realizes that multi-core optical fiber 3D shape passes
Sensed quantity.
Embodiment: three symmetrical fibre cores of three core fibres are connected to fiber grating using FC type optical fiber connector and are passed
It on three channels for feeling analyzer, is specially connected using metallic sheath, is fastened using thread, optical fiber grating sensing analyzer passes
Detection light out enters three core fibres by three core fibre fan-in fan-out modulars.Diagonal line first by three core fibres along paper is consolidated
It is fixed, it is preferably fixed on the diagonal line of the paper of 21cm × 29.7cm, three core fibres is enabled to be tested when being in straight configuration, and
It stores three core fibres and changes fiber grating Prague central wavelength in preceding every fibre core in shape；Then three core fibres will be fixed with
Paper roll at cylindrical shape, it is preferable that drum diameter 6.8cm, as shown in fig. 7, three core fibres is enabled to be in helix state when progress
Test, optical fiber grating sensing analyzer measure three core fibres cardiac wave in fiber grating Prague in every fibre core after shape change
Long incoming computer storage.
By three core fibres in straight configuration and helix state in every fibre core fiber grating Prague central wavelength into
Row difference can obtain the knots modification Δ λ of fiber grating Prague central wavelength in every fibre coreB, and then can calculate every
It is in place in each fiber grating cross section institute can to find out three core fibres by solve system of equation for the strain stress that a fiber grating generates
The curvature k and windup-degree θ set1, then in conjunction with Curvature Interpolation and torsion angle interpolation, with three-dimensionalreconstruction algorithm to multi-core optical fiber into
The reconstruct of row 3D shape, obtains 3D shape reconstruct image shown in Fig. 8.The present invention success it can be seen from Fig. 8 and Fig. 7 comparison
Ground realizes the 3D shape sensing measurement based on multi-core optical fiber, and the configuration of the present invention is simple, installs and easy to detect, practical
Property is strong, at low cost, has broad application prospects.
It above are only the preferable specific embodiment of the present invention, protection scope of the present invention is with the protection model of claims
Subject to enclosing.
Claims (6)
1. a kind of 3D shape sensing measuring method based on multi-core optical fiber, which is characterized in that the method specifically includes step:
Step 1: measuring multi-core optical fiber optical fiber in every fibre core before and after shape change respectively by optical fiber grating sensing analyzer
Grating Bragg central wavelength；
Step 2: according to measured multi-core optical fiber before and after shape change cardiac wave in fiber grating Prague in every fibre core
It is long, calculate the maximum strain of fiber grating in every fibre core of multi-core optical fiber；
Step 3: calculating the curvature and windup-degree of fiber grating cross section position；
Step 4: carrying out Curvature Interpolation and windup-degree interpolation to multi-core optical fiber using space curve theory and interpolation theory, ask
Obtain the curvature and windup-degree of multiple measurement positions between the two neighboring fiber grating cross section of multi-core optical fiber；
Step 5: carrying out 3D shape reconstruct to multi-core optical fiber using three-dimensionalreconstruction algorithm；
Step 6: the multi-core optical fiber of reconstruct is shown in a computer, multi-core optical fiber 3D shape sensing measurement is realized.
2. the 3D shape sensing measuring method based on multi-core optical fiber as described in claim 1, which is characterized in that the multicore
It include at least three fibre cores in optical fiber, every fibre core includes at least two fiber grating.
3. the 3D shape sensing measuring method based on multi-core optical fiber as described in claim 1, which is characterized in that step 3 tool
Body calculating process are as follows:
By taking three core fibres after straining as an example, there are three fiber gratings in each fibre core, and an optical fiber is intercepted on three core fibres
Grating cross section, each fiber grating is since shape change can generate strain, in conjunction with caused by fiber grating in every fibre core
The distance r of strain and every fibre core to fiber grating cross section geometric center calculates fiber grating cross section position
There are the establishment of following equation group in curvature and windup-degree, fiber grating cross section position:
In formula, ε1、ε2And ε3Strain, θ caused by fiber grating in respectively three fibre cores1For the torsion of fiber grating cross section
Angle；Enabling ε is the maximum strain of fiber grating cross section, ε0It is the axial strain of three core fibres, if fibre core 1, fibre core 2 and fibre core
The geometric center of 3 positions point A, B, C respectively, fiber grating cross section are point O, then define the angle Δ θ of AO and BO12For fibre
The angle Δ θ of angle between core 1 and fibre core 2, BO and CO23For the angle between fibre core 2 and fibre core 3, Δ θ12=Δ θ23=
120°；
If three core fibres only influence by bending when shape changes, the axial strain ε of three core fibres0=0, fiber grating cross section
The relationship of generated maximum strain ε and curvature k are as follows:
ε=- kr
In formula, the distance of fibre core 1, fibre core 2 and fibre core 3 to fiber grating cross section geometric center O are r；Therefore for three
Fibre core has following equation establishment respectively:
ε1=-krsin (θ1)
ε2=-krsin (θ1+Δθ12)
ε3=-krsin (θ1+Δθ12+Δθ23)
According in three equations on three fibre cores of any two equation solution fiber grating curvature and windup-degree, and calculate flat
Mean value, curvature and windup-degree as current optical fiber grating cross section；
Similarly, other positions fiber grating cross section in three core fibres is calculated according to above method, obtains three core light
The curvature and windup-degree of all fiber grating cross sections position in fibre.
4. the 3D shape sensing measuring method based on multi-core optical fiber as described in claim 1, which is characterized in that step 4 is adopted
With linear interpolation method, enabling the curvature of+1 measurement position of pth is kp+1, the curvature of p-th of measurement position is kp, p=1,
2 ..., m-1, m are the quantity of fiber grating cross section；E interpolation point, each interpolation point are shared among the two measurement positions
Corresponding to an insertion measurement position, then three core fibres between the two measurement positions are divided into e+1 sections, at this point, insertion
The curvature k of the corresponding insertion measurement position of j-th of interpolation pointjAre as follows:
Wherein, j=1,2,3...e；The song of measurement position between two fiber grating cross sections of arbitrary neighborhood is found out by above formula
Rate；Similarly find out the windup-degree of each measurement position.
5. the 3D shape sensing measuring method based on multi-core optical fiber as described in claim 1, which is characterized in that in step 5
The 3D shape reconstruct is specifically, assume O0With OnFor the geometric center of the measurement position at both ends on three core fibres, multi-core optical
Fibre chooses the geometric center point O of any one measurement position after Curvature Interpolation and torsion angle interpolationi, i=0,2 ..., n-
1；It will point OiThe kinetic coordinate system a at placeibiciA translation transformation is completed along multi-core optical fiber, is obtained in adjacent measurement position
Point Oi+1Kinetic coordinate system ai+1bi+1ci+1, point Oi+1In kinetic coordinate system aibiciIn position dai、dbi、dciIt is as follows:
In formula, kiFor point OiThe curvature of place fiber grating cross section, αiThe circular arc O for being ds for arc lengthi Oi+1The corresponding center of circle
Angle, αi=ki*ds；Thus kinetic coordinate system a is obtainedibiciTo kinetic coordinate system ai+1bi+1ci+1Transformation matrix of coordinates Ri+1:
In formula, θiFor point Oi+1Relative to point OiWindup-degree；Note fixed coordinate system xyz is A, kinetic coordinate system aibiciFor Wi,
Kinetic coordinate system ai+1bi+1ci+1For Wi+1, then:
Wi+1=Ri+1Wi=Ri+1TiA
In formula, TiFor kinetic coordinate system WiTo the transformation matrix of fixed coordinate system A；
Using above-mentioned formula, iteration is calculated, and calculates coordinate of each measurement position at fixed coordinate system xyz, is realized more
The 3D shape of core fibre reconstructs.
6. a kind of 3D shape sense measuring device based on multi-core optical fiber, which is characterized in that described device include: computer,
Optical fiber grating sensing analyzer, multi-core optical fiber fan-in fan-out modular and multi-core optical fiber, what optical fiber grating sensing analyzer issued
Detection light enters multi-core optical fiber by multi-core optical fiber fan-in fan-out modular, detects light by fiber grating and reflects to form narrow band light,
Narrow band light passes through multi-core optical fiber fan-in fan-out modular again and returns in optical fiber grating sensing analyzer, optical fiber grating sensing analyzer
By the demodulation to narrow band light, multi-core optical fiber every section of fiber grating Prague center in every fibre core before and after the shape change is found out
Wavelength, and it is sent to computer；Then the curvature of fiber grating cross section position in multi-core optical fiber is calculated in a computer
And windup-degree；Between two adjacent fiber grating cross sections using space curve theory and interpolation theory to multi-core optical fiber into
Row Curvature Interpolation and windup-degree interpolation acquire the curvature and torsion angle of multiple measurement positions on every fibre core in multi-core optical fiber
Degree；3D shape reconstruct is carried out to multi-core optical fiber using three-dimensionalreconstruction algorithm；The multi-core optical fiber 3D shape of reconstruct is being calculated
It is shown in machine, realizes multi-core optical fiber 3D shape sensing measurement.
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