CN107607998A - A kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method and system - Google Patents

A kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method and system Download PDF

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CN107607998A
CN107607998A CN201710874077.5A CN201710874077A CN107607998A CN 107607998 A CN107607998 A CN 107607998A CN 201710874077 A CN201710874077 A CN 201710874077A CN 107607998 A CN107607998 A CN 107607998A
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CN107607998B (en
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于晓辉
张鹏
李新波
孙晓东
石屹然
张志成
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Jilin University
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Jilin University
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Abstract

The present invention discloses a kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method and system.This method includes：Obtain the Magnetic Resonance data at N number of moment；The Magnetic Resonance data at 1 moment of preceding 1 moment of N and rear N are taken to form two observation vectors respectively；Two observation vectors are merged, form observing matrix；Computing is carried out to observing matrix with reference to total least square method and invariable rotary parametric method, obtains rotation operator；Rotation operator is the function of average attenuation time；The average attenuation time is calculated by rotation operator；Using the average attenuation time, form of the Magnetic Resonance data conversion into sinusoidal signal plus noise will be surveyed；Fast Fourier transform is carried out to sinusoidal signal and obtains initial amplitude.Method and system disclosed by the invention, improve the extraction accuracy of parameter.

Description

A kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method and system
Technical field
The present invention relates to Magnetic Resonance field, believes more particularly to a kind of nuclear magnetic resonance water detector magnetic resonance response Number parameter extracting method and system.
Background technology
Water resource shortage is a significant problem in worldwide.In the 45th, the whole world Davos world of 2015 Issued on Economic Forum《Global risk report in 2015》Point out, load of the people to flood, arid, water pollution and insufficient water Sorrow has been over the worry to nuclear weapon or global disease, and water crisis has been global first Risks factor.
Nuclear magnetic resonance underground water Detection Techniques, it is a kind of lossless detection technology of direct look for water.With traditional exploring subsurface The geophysical method of water is compared, and there is nuclear magnetic resonance underground water Detection Techniques high-resolution, high efficiency, informative to conciliate The advantages that uniqueness.1996, the commercialization version i.e. method for the first nuclear magnetic resonance underground water Detection Techniques in the world of being born The nuclear magnetic induction system (NUMIS, Nuclearmagnetic induction system) that geologic survey office of state develops.China has Unit is closed using the French NUMIS and NUMIS boughtplus(NUMISplusThe NUMIS upgrade versions released for France in 1999) Multiple water shortage provinces such as the Inner Mongol and area have carried out related experiment, wherein NUMIS detection depth capacitys are 100 meters, NUMISplusFor 150 meters, and underground water is successfully found, has promoted the development of China's nuclear magnetic resonance underground water Detection Techniques.Mesh Before, Jilin University of China has voluntarily developed model JLMRS nuclear magnetic resonance water detector, has also reached in performance indications French NUMIS technical merit.
The general principle of nuclear magnetic resonance water detector is to make the hydrogen in underground water to underground water excitation energy by transmitting coil Energy level transition occurs for proton electron outside nucleus, is then received when electron outside nucleus is moved back from high level to low-lying level and released with receiving coil again The energy put, so as to obtain magnetic resonance response (Magnetic Resonance Sounding, MRS) signal, rung by the magnetic resonance Induction signal can inverting obtain the relevant information of underground water.
The complex signal model of nuclear magnetic resonance water detector Magnetic Resonance is as follows：
Wherein, n is sampling instant, E0For initial amplitude, the size and underground water content of initial amplitude are directly proportional, also include The information such as underground reservoir depth, thickness, unit volume water content.T2For average attenuation time (also referred to as relaxation time), put down Equal die-away time reflects the information of underground reservoir average pore.The initial phase of Magnetic ResonanceReflect and contain The conductance of water layer, is a constant, ω0=2 π fl(flFor your frequency of Rameau) be earth's magnetic field angular frequency.It will need to only extract Initial amplitude E0With average die-away time T2The two parameters, underground water content, depth, aqueous can just be obtained by carrying out inverting The information such as layer porosity.Because itself sensitivity of nuclear magnetic resonance water detector is higher, the useful signal pole of Magnetic Resonance Its is faint, is highly prone to the interference from the natural noise such as the man-made noises such as power line and iron ore rock layers.How from noise Magnetic Resonance in extract initial amplitude E0With average die-away time T2The two parameters are just asked as a key Topic.
The extraction for the parameter of the Magnetic Resonance of nuclear magnetic resonance water detector is improved using first de-noising more at present Signal to noise ratio, then carry out the strategy of curve parameter fitting.The noise-eliminating method of use have a lot, as the addition method, digital filtering, small echo, Adaptive-filtering, Higher Order Cumulants etc., after denoising Processing, the signal to noise ratio of the Magnetic Resonance of nuclear magnetic resonance water detector Necessarily lifted, recycle the NUMERICAL MATCH METHOD FORs such as linear fit, nonlinear fitting, fit magnetic resonance response curve, after And obtain the parameter of water detector Magnetic Resonance.
The parameter extraction technical spirit of the Magnetic Resonance of existing nuclear magnetic resonance water detector is to be based on classical signal The strategy of processing.But any noise-eliminating method can only all suppress to noise, and noise can not possibly be completely eliminated, by This necessarily brings error to extraction result, and NUMERICAL MATCH METHOD FOR below can further produce error, and thus two-stage error must The extraction accuracy of the parameter of the Magnetic Resonance of nuclear magnetic resonance water detector can so be reduced.
The content of the invention
It is an object of the invention to provide a kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method and system, Improve the extraction accuracy of the two parameters of average attenuation time and initial amplitude.
To achieve the above object, the invention provides following scheme：
A kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method, including：
Obtain the actual measurement Magnetic Resonance data at N number of moment；
In the actual measurement Magnetic Resonance data, the actual measurement Magnetic Resonance data at N-1 moment before taking The first observation vector is formed, takes the actual measurement Magnetic Resonance data at rear N-1 moment to form the second observation vector；Described The signal subspace of one observation vector is identical with the dimension of the signal subspace of second observation vector；
First observation vector and second observation vector are merged, form observing matrix；
Computing is carried out to the observing matrix with reference to total least square method and invariable rotary parametric method, rotation is obtained and calculates Son；The rotation operator is the signal subspace of second observation vector relative to the letter of first observation vector The space angle in work song space, the rotation operator are the function of average attenuation time；
The average attenuation time is calculated by the rotation operator；The average attenuation time is used to reflect that underground contains The information of water layer average pore；
Using the average attenuation time, by the Magnetic Resonance data conversion of surveying into sinusoidal signal plus noise Form；
Fast Fourier transform is carried out to the sinusoidal signal and obtains initial amplitude, the initial amplitude includes underground water content Information.
Optionally, the combination total least square method and invariable rotary parametric method carry out computing to the observing matrix, Rotation operator is obtained, is specifically included：
Auto-correlation computation is carried out to the observing matrix, obtains the autocorrelation matrix of the observing matrix；
Eigenvalues Decomposition is carried out to the autocorrelation matrix of the observing matrix, obtains two characteristic values；
It is signal subspace characteristic vector to determine the characteristic vector corresponding to the larger characteristic value in described two characteristic values； The signal subspace characteristic vector includes Part I and Part II；The Part I and the first observation vector phase Corresponding, the Part II is corresponding with second observation vector；
Factor matrices ψ is calculated according to the Part I and Part II；The factor matrices ψ is that guarantee makes described second It is multiplied by matrix of the result equal to the Part I of the factor matrices ψ in part；
Eigenvalues Decomposition is carried out to the factor matrices ψ, obtains the rotation operator.
Optionally, it is described that factor matrices ψ is calculated according to the Part I and Part II, specifically include：
By the Part I and Part II construction autocorrelation matrix and singular value decomposition is carried out, obtains left unusual square Battle array；
Factor matrices ψ is calculated using the submatrix of the left singular matrix.
Optionally, it is described that autocorrelation matrix is constructed by the Part I and Part II and carries out singular value decomposition, obtain To left singular matrix, specifically include：
By the Part I and Part II construction autocorrelation matrix, signal subspace autocorrelation matrix is obtained；
Singular value decomposition is carried out to the signal subspace autocorrelation matrix, obtains left singular matrix and right singular matrix； The left singular matrix and the right singular matrix are 2 × 2 dimension matrixes.
Optionally, the submatrix using the left singular matrix calculates factor matrices ψ, specifically includes：
The left singular matrix U is decomposed into four 1 × 1 dimension minor matrixs, respectively the row minor matrix U of the first row one11, first The row minor matrix U of row two12, the row minor matrix U of the second row one21With the row minor matrix U of the second row two22
According to the row minor matrix U of the first row two12With the row minor matrix U of the second row two22Calculate the factor matrices ψ
Ψ=- U12U22 -1。
The invention also discloses a kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extraction system, including：
Acquisition module, for obtaining the actual measurement Magnetic Resonance data at N number of moment；
Observation vector builds module, in the actual measurement Magnetic Resonance data, taking the reality at preceding N-1 moment Survey Magnetic Resonance data and form the first observation vector, take the actual measurement Magnetic Resonance data group at rear N-1 moment Into the second observation vector；The signal subspace of the signal subspace of first observation vector and second observation vector The dimension in space is identical；
Observation vector merging module, for first observation vector and second observation vector to be merged, shape Into observing matrix；
Rotation operator computing module, for reference to total least square method and invariable rotary parametric method to the observing matrix Computing is carried out, obtains rotation operator；The rotation operator is that the signal subspace of second observation vector is relatively described The space angle of the signal subspace of first observation vector, the rotation operator are the function of average attenuation time；
Average attenuation time computing module, for the average attenuation time to be calculated by the rotation operator；It is described The average attenuation time is used for the information for reflecting underground reservoir average pore；
Form transformation module, for utilizing the average attenuation time, the actual measurement Magnetic Resonance data are turned Change the form of sinusoidal signal plus noise into；
Initial amplitude computing module, initial amplitude is obtained for carrying out fast Fourier transform to the sinusoidal signal, it is described Initial amplitude includes underground water content information.
Optionally, the rotation operator computing module, is specifically included：
Auto-correlation computation submodule, for carrying out auto-correlation computation to the observing matrix, obtain the observing matrix Autocorrelation matrix；
The First Eigenvalue decomposes submodule, for carrying out Eigenvalues Decomposition to the autocorrelation matrix of the observing matrix, obtains To two characteristic values；
Characteristic vector determination sub-module, for determining the Characteristic Vectors corresponding to the larger characteristic value in described two characteristic values Measure as signal subspace characteristic vector；The signal subspace characteristic vector includes Part I and Part II；Described first Part is corresponding with first observation vector, and the Part II is corresponding with second observation vector；
Factor matrices calculating sub module, for calculating factor matrices ψ according to the Part I and Part II；It is described because Matrix number ψ is the matrix that the result for ensureing to make the Part II be multiplied by the factor matrices ψ is equal to the Part I；
Second Eigenvalue decomposes submodule, for carrying out Eigenvalues Decomposition to the factor matrices ψ, obtains the rotation and calculates Son.
Optionally, the factor matrices calculating sub module, is specifically included：
Singular value decomposition unit, for constructing autocorrelation matrix by the Part I and Part II and carrying out singular value Decompose, obtain left singular matrix；
Factor matrices computing unit, for calculating factor matrices ψ using the submatrix of the left singular matrix.
Optionally, the singular value decomposition unit, is specifically included：
Auto-correlation subelement, for the Part I and the Part II to be constructed into autocorrelation matrix, obtain signal Subspace autocorrelation matrix；
Singular value decomposition subelement, for carrying out singular value decomposition to the signal subspace autocorrelation matrix, obtain a left side Singular matrix and right singular matrix；The left singular matrix and the right singular matrix are 2 × 2 dimension matrixes.
Optionally, the factor matrices computing unit, is specifically included：
Matrix decomposition subelement, for by the left singular matrix U be decomposed into four 1 × 1 dimension minor matrixs, respectively first The row minor matrix U of row one11, the row minor matrix U of the first row two12, the row minor matrix U of the second row one21With the row minor matrix U of the second row two22
Factor matrices computation subunit, for according to the row minor matrix U of the first row two12Small square is arranged with second row two Battle array U22Calculate the factor matrices ψ
Ψ=- U12U22 -1。
According to specific embodiment provided by the invention, the invention discloses following technique effect：One kind disclosed by the invention In the technical scheme of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method and system, the preceding N-1 moment is utilized Magnetic Resonance data form the first observation vector and the Magnetic Resonance data at rear N-1 moment composition second is seen Invariable rotary relation between direction finding amount, rotation operator is determined, and utilizes rotation operator and the relation between the average attenuation time, Rotation operator is calculated so as to extract the average attenuation time with reference to total least square method and invariable rotary parametric method, is realized and is being gone The average attenuation time is directly calculated while except noise, the precision of parameter extraction is improved, reduces operand.
Brief description of the drawings
In order to illustrate more clearly about the embodiment of the present invention or technical scheme of the prior art, below will be to institute in embodiment The accompanying drawing needed to use is briefly described, it should be apparent that, drawings in the following description are only some implementations of the present invention Example, for those of ordinary skill in the art, without having to pay creative labor, can also be according to these accompanying drawings Obtain other accompanying drawings.
Fig. 1 is the method flow of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention Figure；
Fig. 2 is that the calculating rotation of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention is calculated The method flow diagram of submethod；
Fig. 3 is the calculating factor square of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention The method flow diagram of battle array method；
Fig. 4 is to extract averagely to decline in nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention Subtract the emulation experiment curve of time parameter；The curve that wherein (a) partly changes for the average of average attenuation time with signal to noise ratio, (b) curve partly changed for the variance of average attenuation time with signal to noise ratio；
Fig. 5 is to extract initially to shake in nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention The emulation experiment curve of width parameter；The curve that wherein (a) partly changes for the average of initial amplitude with signal to noise ratio, (b) is partly The curve that the variance of initial amplitude changes with signal to noise ratio；
Fig. 6 is the system architecture of nuclear magnetic resonance water detector Magnetic Resonance parameter extraction system embodiment of the present invention Figure.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clear, complete Site preparation describes, it is clear that described embodiment is only part of the embodiment of the present invention, rather than whole embodiments.It is based on Embodiment in the present invention, those of ordinary skill in the art are obtained every other under the premise of creative work is not made Embodiment, belong to the scope of protection of the invention.
When two parameters of most critical are average attenuations in the Magnetic Resonance x (n) that nuclear magnetic resonance water detector obtains Between T2With initial amplitude E0.The present invention uses total least square (TLS, Total least squares) and invariable rotary parameter Method (ESPRIT, Estimating Signal Parameter via Rotational Invariance Techniques) carries Take average die-away time T2, initial amplitude is calculated using fast Fourier transform (FFT, Fast FourierTransformation) E0。
In the actual measurement Magnetic Resonance data x (n) that nuclear magnetic resonance water detector obtains, white Gaussian can be typically attached with Noise η (n), then survey Magnetic Resonance data x (n) and be expressed as：
X (n)=s (n)+η (n) (2)
Wherein n is sampling instant, and s (n) is to remove the true Magnetic Resonance after noise；E0For initial amplitude, The size of the initial amplitude is directly proportional to underground water content, also contains underground reservoir depth, thickness, unit volume water content Etc. information；T2For average attenuation time, also referred to as relaxation time, the average attenuation time reflects underground reservoir average pore Information；For initial phase, the initial phase reflects the conductance in water-bearing layer, is a constant；ω0For the angular frequency in earth's magnetic field Rate, ω0=2 π fl, flFor Rameau that frequency.
In order to facilitate the understanding of the purposes, features and advantages of the present invention, it is below in conjunction with the accompanying drawings and specific real Applying mode, the present invention is further detailed explanation.
Fig. 1 is the method flow of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention Figure.
Referring to Fig. 1, the nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method, including：
Step 1：Obtain the actual measurement Magnetic Resonance data at N number of moment, respectively x (n1)、x(n2)、…、x(nN), N value is defined as n successively1、n2、…、nN, then
Step 2：In the actual measurement Magnetic Resonance data, the actual measurement magnetic resonance response letter at N-1 moment before taking Number forms the first observation vector X, takes the actual measurement Magnetic Resonance data at rear N-1 moment to form the second observation vector Y；Then
Wherein,Expression is defined as；There is translation relation, W between first observation vector X and the second observation vector YxFor White Gaussian noise in first observation vector X, WyFor the white Gaussian noise in the second observation vector X；A is direction vector, comprising Frequency and the information of average die-away time；Γ is width phase information matrix, and the width phase information matrix is to contain amplitude and phase The matrix of information, width phase information matrix only have an element γ,
Rotation operator Φ is defined, i.e.,
Then have
It can be seen that the first observation vector X and the second observation vector Y are seen into dimension identical signal subspace by first The signal subspace of direction finding amount X and the second observation vector Y understands that the second observation vector Y revolves relative to the first observation vector X Rotation operator Φ is turned, and rotation operator Φ is average attenuation time T2Function.The present invention is exactly to utilize the second observation Invariable rotary relation extraction average attenuation time T of vector and the first observation vector2。
Step 3：The first observation vector X and the second observation vector Y are merged, form observing matrix Z；
Wherein
For direction matrix, WzFor noise matrix；Observing matrix Z, direction matrixWith noise matrix WzIt is 2 × (N-1) Dimension.
Step 4：Computing is carried out to the observing matrix Z with reference to total least square method and invariable rotary parametric method, obtained Rotation operator.
Fig. 2 is that the calculating rotation of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention is calculated The method flow diagram of submethod.
Referring to Fig. 2, the step 4 specifically includes：
Step 401：Auto-correlation computation is carried out to the observing matrix Z, obtains the autocorrelation matrix R of the observing matrixzz；
Wherein I is unit matrix, σ2For the variance of white Gaussian noise.
Auto-correlation computation equally is carried out to width phase information matrix Γ, obtains width phase information matrix Γ autocorrelation matrix RΓΓ, RΓΓ=E { Γ ΓH}。
Step 402：To the autocorrelation matrix R of the observing matrixzzEigenvalues Decomposition is carried out, obtains two eigenvalue λs1With λ2；I.e.
Wherein λiIt is characterized value, eiIt is characterized value λiCorresponding characteristic vector；I is characterized sequence number corresponding to value；ΛsTo be right Angular moment battle array；EsIt is characterized value λ1Corresponding characteristic vector, ENIt is characterized value λ2Corresponding characteristic vector；
With reference to formula (15) and formula (16), because Magnetic Resonance is simple component, then eigenvalue λ1＞ λ2, then There is λ1=Λs, λ2=σ2, eigenvalue λ1Corresponding characteristic vector Es=[e1] open into signal subspace, eigenvalue λ2Corresponding feature Vector EN=[e2] open into noise subspace, the noise subspace and eigenvalue λ1Corresponding characteristic vector EsThe signal subspace opened Space has orthogonality relation.It means that existence anduniquess, it is nonsingular 1 × 1 dimension non-singular matrix T, set up following formula：
Step 403：Determine the larger eigenvalue λ in described two characteristic values1Corresponding characteristic vector EsIt is empty for signal subspace Between characteristic vector；The signal subspace characteristic vector includes Part I ExWith Part II Ey；The Part I ExWith institute It is corresponding to state the first observation vector X, the Part II EyIt is corresponding with the second observation vector Y；
Specially：Can be by E by the rotational invariance of observation vectorsIt is decomposed into ExAnd EyTwo parts, the first observation is corresponded to respectively Vectorial X and the second observation vector Y；I.e.
Wherein ExAnd EyIt is 1 × 1 dimension matrix.
Step 404：According to the Part I ExWith the Part II EyCalculate factor matrices ψ；The factor matrices ψ To ensure to make the Part II EyThe result for being multiplied by the factor matrices ψ is equal to the Part I ExMatrix, i.e., using total Body least square method seeks equation Ey=ExΨ solution.
Fig. 3 is the calculating factor square of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention The method flow diagram of battle array method.
Referring to Fig. 3, the step 404 specifically includes：
Step 4041：By the Part I ExWith the Part II EyConstruct autocorrelation matrix RsAnd carry out singular value Decompose, obtain left singular matrix U；Realized especially by procedure below：
Make Ψ=T-1Φ T, then can obtain：
Ey=ExT-1Φ T=ExΨ (19)
In view of Part I E described in equation both sidesxWith the Part II EyBoth sides error, using singular value point Solution combines total least square method, and the Part I and the Part II are constructed into autocorrelation matrix, obtains signal subspace sky Between autocorrelation matrix, and to the signal subspace autocorrelation matrix carry out singular value decomposition, obtain left singular matrix and the right side be strange Different matrix；The left singular matrix and the right singular matrix are 2 × 2 dimension matrixes, then
Wherein, S is singular value matrix, and U is left singular matrix, and V is right singular matrix, and S, U and V are 2 × 2 dimension matrixes.
Step 4042：Factor matrices ψ is calculated using the submatrix of the left singular matrix；
The left singular matrix U is decomposed into four 1 × 1 dimension minor matrixs, respectively the row minor matrix U of the first row one11, first The row minor matrix U of row two12, the row minor matrix U of the second row one21With the row minor matrix U of the second row two22
According to the row minor matrix U of the first row two12With the row minor matrix U of the second row two22Calculate the factor matrices ψ
Ψ=- U12U22 -1 (22)
Step 405：Eigenvalues Decomposition is carried out to the factor matrices ψ, obtains the rotation operator Φ.
From formula (19), rotation operator Φ is factor matrices ψ characteristic value, as long as therefore being carried out to factor matrices ψ Eigenvalues Decomposition, gained characteristic value are rotation operator Φ.
Step 5：The calculated value of average attenuation time is calculated by the rotation operator ΦDuring with the average attenuation Between calculated valueReflect the information of underground reservoir average pore；
From formula (10), rotation operator Φ is average attenuation time T2Function, therefore only require to obtain rotation operator Φ can be obtained by the calculated value of average attenuation timeI.e.
And rotation operator can be utilized to calculate the angular frequency in earth's magnetic field, obtain the calculated value of earth's magnetic field angular frequencyI.e.
In practice, when detecting underground water with nuclear magnetic resonance technique, the actual value ω of the angular frequency in earth's magnetic field0It is known , therefore pass through the calculated value of contrastively magnetic field angular frequencyWith the actual value ω of earth's magnetic field angular frequency0Can checking test As a result accuracy.
Step 6：Using the average attenuation time, the actual measurement Magnetic Resonance data x (n) is converted into sine The form of signal plus noise；
The calculated value of the average attenuation time obtained in steps of 5It is the actual value T of average attenuation time2Approximation. In practice, the actual value T of average attenuation time2It can not obtain, computational methods provided by the invention can make averagely to decline Subtract the calculated value of timeCloser to the actual value T of average attenuation time2.The step 6 of the present invention is actually using flat The calculated value of equal die-away timeThe form that Magnetic Resonance data x (n) is converted into sinusoidal signal plus noise, tool will be surveyed Body is：
It is multiplied by simultaneously in the equal sign both sides of formula (2)It can obtain
Now, actual measurement Magnetic Resonance data are converted into the form of sinusoidal signal plus noise.
Step 7：Fast Fourier transform is carried out to the sinusoidal signal and obtains initial amplitude；The initial amplitude is used to reflect Underground water content information.
The principle of sinusoidal signal amplitude is calculated using fast Fourier transform, fast Fourier transform is carried out to formula (25), can To obtain initial amplitude.Specially：
Obtain the real part of the sinusoidal signal；
Fast Fourier transform is carried out to the real part of the sinusoidal signal, obtains the calculated value of initial amplitude.
In a kind of technical scheme of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method disclosed by the invention, The first observation vector and the magnetic resonance response at rear N-1 moment are formed using the Magnetic Resonance data at preceding N-1 moment Signal data forms the invariable rotary relation between the second observation vector, determines rotation operator, and using rotation operator and averagely Relation between die-away time, it is average so as to extract to calculate rotation operator with reference to total least square method and invariable rotary parametric method Die-away time, compared with existing parameter extracting method, it is not necessary to by first de-noising the two steps of extracting parameter again, but The average attenuation time is directly calculated while removing noise, the precision of parameter extraction is improved, reduces operand.
Emulation experiment is carried out to the method that the average attenuation time is extracted in this embodiment of the invention below：
Take Magnetic Resonance data parameters：Initial amplitude E0=300nv, average attenuation time T2=10, Rameau You are frequency f0=2326Hz, initial phaseSample frequency fs=10000Hz, sampling number N=30000.
White Gaussian noise is added, takes different signal to noise ratio to repeat 100 experiments.
Table 1 is to extract averagely to decline in nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention Subtract the experimental result form of the emulation experiment of time parameter.
The experimental result table of the emulation experiment of the average attenuation time parameter of table 1
Fig. 4 is to extract averagely to decline in nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention Subtract the emulation experiment curve of time parameter；The curve that wherein (a) partly changes for the average of average attenuation time with signal to noise ratio, (b) curve partly changed for the variance of average attenuation time with signal to noise ratio.
Referring to table 1 and Fig. 4, from simulation result as can be seen that when additive gaussian white noise, the embodiment in the present invention Method can effectively extract average attenuation time parameter.When signal to noise ratio is higher than -5dB, extraction accuracy and extraction stability are all fine. As signal to noise ratio reduces, extraction performance has declined, but the range of decrease is not quickly.When signal to noise ratio is -10dB, the average attenuation of extraction The mean value error of time is 0.12%, and the variance of the average attenuation time of extraction is 0.03.Even if work as signal to noise ratio as little as -20dB When, the error of the average of the average attenuation time of extraction is also only 0.47%, and the variance of the average attenuation time of extraction is 0.25, Still within the acceptable range.
Emulation experiment is carried out to the method that initial amplitude is extracted in this embodiment of the invention below：
Take Magnetic Resonance data parameters：Initial amplitude E0=300nv, average attenuation time T2=10, Rameau You are frequency f0=2326Hz, initial phaseSample frequency fs=10000Hz, sampling number N=30000.
The points that selection carries out fast Fourier transform are NF=5000, now spectral resolution beCalculating resolution isAnd Rameau that frequency f0=2326Hz, both Be the integral multiple of spectral resolution, be the integral multiple of calculating resolution again, thus in theory fast Fourier transform method in amplitude It is no error in terms of extraction, extraction error is mainly derived from extraction error and the influence of noise of average attenuation time.
Additive gaussian white noise, different signal to noise ratio are taken to repeat 100 experiments.
Table 2 is to extract initially to shake in nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention The experimental result form of the emulation experiment of width parameter.
The experimental result table of the emulation experiment of the initial amplitude parameter of table 2
Fig. 5 is to extract initially to shake in nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method embodiment of the present invention The emulation experiment curve of width parameter；The curve that wherein (a) partly changes for the average of initial amplitude with signal to noise ratio, (b) is partly The curve that the variance of initial amplitude changes with signal to noise ratio.
Referring to table 2 and Fig. 5, from simulation result as can be seen that when additive gaussian white noise, fast Fourier transform method can Effectively to extract initial amplitude parameter, extraction accuracy and stability are all preferable.
Fig. 6 is the system architecture of nuclear magnetic resonance water detector Magnetic Resonance parameter extraction system embodiment of the present invention Figure.
Referring to Fig. 6, the nuclear magnetic resonance water detector Magnetic Resonance parameter extraction system, including：
Acquisition module 801, for obtaining the actual measurement Magnetic Resonance data at N number of moment；
Observation vector builds module 802, in the actual measurement Magnetic Resonance data, taking the preceding N-1 moment Actual measurement Magnetic Resonance data form the first observation vector, take the actual measurement Magnetic Resonance number at rear N-1 moment According to forming the second observation vector；The letter of the signal subspace of first observation vector and second observation vector The dimension in work song space is identical；
Observation vector merging module 803, for first observation vector and second observation vector to be merged, Form observing matrix；
Rotation operator computing module 804, for reference to total least square method and invariable rotary parametric method to the observation Matrix carries out computing, obtains rotation operator；The rotation operator is that the signal subspace of second observation vector is relative The space angle of the signal subspace of first observation vector, the rotation operator are the function of average attenuation time；
Average attenuation time computing module 805, for the average attenuation time to be calculated by the rotation operator；Institute State information of the average attenuation time for reflecting underground reservoir average pore；
Form transformation module 806, for utilizing the average attenuation time, by the actual measurement Magnetic Resonance data It is converted into the form of sinusoidal signal plus noise；
Initial amplitude computing module 807, initial amplitude is obtained for carrying out fast Fourier transform to the sinusoidal signal, institute State initial amplitude and include underground water content information.
The rotation operator computing module 804, is specifically included：
Auto-correlation computation submodule, for carrying out auto-correlation computation to the observing matrix, obtain the observing matrix Autocorrelation matrix；
The First Eigenvalue decomposes submodule, for carrying out Eigenvalues Decomposition to the autocorrelation matrix of the observing matrix, obtains To two characteristic values；
Characteristic vector determination sub-module, for determining the Characteristic Vectors corresponding to the larger characteristic value in described two characteristic values Measure as signal subspace characteristic vector；The signal subspace characteristic vector includes Part I and Part II；Described first Part is corresponding with first observation vector, and the Part II is corresponding with second observation vector；
Factor matrices calculating sub module, for calculating factor matrices ψ according to the Part I and Part II；It is described because Matrix number ψ is the matrix that the result for ensureing to make the Part II be multiplied by the factor matrices ψ is equal to the Part I；
Second Eigenvalue decomposes submodule, for carrying out Eigenvalues Decomposition to the factor matrices ψ, obtains the rotation and calculates Son.
The factor matrices calculating sub module, is specifically included：
Singular value decomposition unit, for constructing autocorrelation matrix by the Part I and Part II and carrying out singular value Decompose, obtain left singular matrix；
Factor matrices computing unit, for calculating factor matrices ψ using the submatrix of the left singular matrix.
The singular value decomposition unit, is specifically included：
Auto-correlation subelement, for the Part I and the Part II to be constructed into autocorrelation matrix, obtain signal Subspace autocorrelation matrix；
Singular value decomposition subelement, for carrying out singular value decomposition to the signal subspace autocorrelation matrix, obtain a left side Singular matrix and right singular matrix；The left singular matrix and the right singular matrix are 2 × 2 dimension matrixes.
The factor matrices computing unit, is specifically included：
Matrix decomposition subelement, for by the left singular matrix U be decomposed into four 1 × 1 dimension minor matrixs, respectively first The row minor matrix U of row one11, the row minor matrix U of the first row two12, the row minor matrix U of the second row one21With the row minor matrix U of the second row two22
Factor matrices computation subunit, for according to the row minor matrix U of the first row two12Small square is arranged with second row two Battle array U22Calculate the factor matrices ψ
Ψ=- U12U22 -1。
In a kind of technical scheme of nuclear magnetic resonance water detector Magnetic Resonance parameter extraction system disclosed by the invention, The first observation vector and the magnetic resonance response at rear N-1 moment are formed using the Magnetic Resonance data at preceding N-1 moment Signal data forms the invariable rotary relation between the second observation vector, determines rotation operator, and using rotation operator and averagely Relation between die-away time, it is average so as to extract to calculate rotation operator with reference to total least square method and invariable rotary parametric method Die-away time, compared with existing parameter extracting method, it is not necessary to by first de-noising the two steps of extracting parameter again, but The average attenuation time is directly calculated while removing noise, the precision of parameter extraction is improved, reduces operand.
Each embodiment is described by the way of progressive in this specification, what each embodiment stressed be and other The difference of embodiment, between each embodiment identical similar portion mutually referring to.For system disclosed in embodiment For, because it is corresponded to the method disclosed in Example, so description is fairly simple, related part is said referring to method part It is bright.
Specific case used herein is set forth to the principle and embodiment of the present invention, and above example is said It is bright to be only intended to help the method and its core concept for understanding the present invention；Meanwhile for those of ordinary skill in the art, foundation The thought of the present invention, in specific embodiments and applications there will be changes.In summary, this specification content is not It is interpreted as limitation of the present invention.

Claims (10)

  1. A kind of 1. nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method, it is characterised in that including：
    Obtain the actual measurement Magnetic Resonance data at N number of moment；
    In the actual measurement Magnetic Resonance data, the actual measurement Magnetic Resonance data composition at N-1 moment before taking First observation vector, the actual measurement Magnetic Resonance data at rear N-1 moment are taken to form the second observation vector；Described first sees The signal subspace of direction finding amount is identical with the dimension of the signal subspace of second observation vector；
    First observation vector and second observation vector are merged, form observing matrix；
    Computing is carried out to the observing matrix with reference to total least square method and invariable rotary parametric method, obtains rotation operator；Institute State the signal subspace that rotation operator is opened for the signal subspace of second observation vector relative to first observation vector The space angle in space, the rotation operator are the function of average attenuation time；
    The average attenuation time is calculated by the rotation operator；The average attenuation time is used to reflect underground reservoir The information of average pore；
    Using the average attenuation time, the shape by the actual measurement Magnetic Resonance data conversion into sinusoidal signal plus noise Formula；
    Fast Fourier transform is carried out to the sinusoidal signal and obtains initial amplitude, the initial amplitude is believed comprising underground water content Breath.
  2. 2. a kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method according to claim 1, its feature It is, the combination total least square method and invariable rotary parametric method carry out computing to the observing matrix, obtain rotation and calculate Son, specifically include：
    Auto-correlation computation is carried out to the observing matrix, obtains the autocorrelation matrix of the observing matrix；
    Eigenvalues Decomposition is carried out to the autocorrelation matrix of the observing matrix, obtains two characteristic values；
    It is signal subspace characteristic vector to determine the characteristic vector corresponding to the larger characteristic value in described two characteristic values；It is described Signal subspace characteristic vector includes Part I and Part II；The Part I is relative with first observation vector Should, the Part II is corresponding with second observation vector；
    Factor matrices ψ is calculated according to the Part I and Part II；The factor matrices ψ is that guarantee makes the Part II The result for being multiplied by the factor matrices ψ is equal to the matrix of the Part I；
    Eigenvalues Decomposition is carried out to the factor matrices ψ, obtains the rotation operator.
  3. 3. a kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method according to claim 2, its feature It is, it is described that factor matrices ψ is calculated according to the Part I and Part II, specifically include：
    By the Part I and Part II construction autocorrelation matrix and singular value decomposition is carried out, obtains left singular matrix；
    Factor matrices ψ is calculated using the submatrix of the left singular matrix.
  4. 4. a kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method according to claim 3, its feature It is, it is described that autocorrelation matrix is constructed by the Part I and Part II and carries out singular value decomposition, obtain left unusual square Battle array, is specifically included：
    By the Part I and Part II construction autocorrelation matrix, signal subspace autocorrelation matrix is obtained；
    Singular value decomposition is carried out to the signal subspace autocorrelation matrix, obtains left singular matrix and right singular matrix；It is described Left singular matrix and the right singular matrix are 2 × 2 dimension matrixes.
  5. 5. a kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extracting method according to claim 3, its feature It is, the submatrix using the left singular matrix calculates factor matrices ψ, specifically includes：
    The left singular matrix U is decomposed into four 1 × 1 dimension minor matrixs, respectively the row minor matrix U of the first row one11, the first row two Row minor matrix U12, the row minor matrix U of the second row one21With the row minor matrix U of the second row two22
    <mrow> <mi>U</mi> <mo>=</mo> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <msub> <mi>U</mi> <mn>11</mn> </msub> </mtd> <mtd> <msub> <mi>U</mi> <mn>12</mn> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>U</mi> <mn>21</mn> </msub> </mtd> <mtd> <msub> <mi>U</mi> <mn>22</mn> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>;</mo> </mrow>
    According to the row minor matrix U of the first row two12With the row minor matrix U of the second row two22Calculate the factor matrices ψ
    Ψ=- U12U22 -1。
  6. A kind of 6. nuclear magnetic resonance water detector Magnetic Resonance parameter extraction system, it is characterised in that including：
    Acquisition module, for obtaining the actual measurement Magnetic Resonance data at N number of moment；
    Observation vector builds module, in the actual measurement Magnetic Resonance data, taking the actual measurement magnetic at preceding N-1 moment Resonance response signal data forms the first observation vector, takes the actual measurement Magnetic Resonance data composition the at rear N-1 moment Two observation vectors；The signal subspace of the signal subspace of first observation vector and second observation vector Dimension it is identical；
    Observation vector merging module, for first observation vector and second observation vector to be merged, formed and seen Survey matrix；
    Rotation operator computing module, for being carried out with reference to total least square method and invariable rotary parametric method to the observing matrix Computing, obtain rotation operator；The rotation operator is the signal subspace relatively described first of second observation vector The space angle of the signal subspace of observation vector, the rotation operator are the function of average attenuation time；
    Average attenuation time computing module, for the average attenuation time to be calculated by the rotation operator；It is described average Die-away time is used for the information for reflecting underground reservoir average pore；
    Form transformation module, for utilize the average attenuation time, by it is described actual measurement Magnetic Resonance data conversion into The form of sinusoidal signal plus noise；
    Initial amplitude computing module, initial amplitude is obtained for carrying out fast Fourier transform to the sinusoidal signal, it is described initial Amplitude includes underground water content information.
  7. 7. a kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extraction system according to claim 6, its feature It is, the rotation operator computing module, specifically includes：
    Auto-correlation computation submodule, for carrying out auto-correlation computation to the observing matrix, obtain the observing matrix from phase Close matrix；
    The First Eigenvalue decomposes submodule, for carrying out Eigenvalues Decomposition to the autocorrelation matrix of the observing matrix, obtains two Individual characteristic value；
    Characteristic vector determination sub-module, for determining that the characteristic vector corresponding to the larger characteristic value in described two characteristic values is Signal subspace characteristic vector；The signal subspace characteristic vector includes Part I and Part II；The Part I Corresponding with first observation vector, the Part II is corresponding with second observation vector；
    Factor matrices calculating sub module, for calculating factor matrices ψ according to the Part I and Part II；The factor square Battle array ψ is the matrix that the result for ensureing to make the Part II be multiplied by the factor matrices ψ is equal to the Part I；
    Second Eigenvalue decomposes submodule, for carrying out Eigenvalues Decomposition to the factor matrices ψ, obtains the rotation operator.
  8. 8. a kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extraction system according to claim 7, its feature It is, the factor matrices calculating sub module, specifically includes：
    Singular value decomposition unit, for constructing autocorrelation matrix by the Part I and Part II and carrying out singular value point Solution, obtains left singular matrix；
    Factor matrices computing unit, for calculating factor matrices ψ using the submatrix of the left singular matrix.
  9. 9. a kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extraction system according to claim 8, its feature It is, the singular value decomposition unit, specifically includes：
    Auto-correlation subelement, for the Part I and the Part II to be constructed into autocorrelation matrix, obtain signal subspace sky Between autocorrelation matrix；
    Singular value decomposition subelement, for carrying out singular value decomposition to the signal subspace autocorrelation matrix, obtain left unusual Matrix and right singular matrix；The left singular matrix and the right singular matrix are 2 × 2 dimension matrixes.
  10. 10. a kind of nuclear magnetic resonance water detector Magnetic Resonance parameter extraction system according to claim 8, its feature It is, the factor matrices computing unit, specifically includes：
    Matrix decomposition subelement, for the left singular matrix U to be decomposed into four 1 × 1 dimension minor matrixs, respectively the first row one Row minor matrix U11, the row minor matrix U of the first row two12, the row minor matrix U of the second row one21With the row minor matrix U of the second row two22
    <mrow> <mi>U</mi> <mo>=</mo> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <msub> <mi>U</mi> <mn>11</mn> </msub> </mtd> <mtd> <msub> <mi>U</mi> <mn>12</mn> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>U</mi> <mn>21</mn> </msub> </mtd> <mtd> <msub> <mi>U</mi> <mn>22</mn> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>;</mo> </mrow>
    Factor matrices computation subunit, for according to the row minor matrix U of the first row two12With the row minor matrix U of the second row two22 Calculate the factor matrices ψ
    Ψ=- U12U22 -1。
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