CN110598544A - Nuclear pulse signal denoising method based on sparse decomposition - Google Patents

Nuclear pulse signal denoising method based on sparse decomposition Download PDF

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CN110598544A
CN110598544A CN201910720845.0A CN201910720845A CN110598544A CN 110598544 A CN110598544 A CN 110598544A CN 201910720845 A CN201910720845 A CN 201910720845A CN 110598544 A CN110598544 A CN 110598544A
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pulse signal
decomposition
nuclear
signals
overcomplete
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赵修良
贺三军
孙娜
赵健为
刘丽艳
周超
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University of South China
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    • G06F18/21—Design or setup of recognition systems or techniques; Extraction of features in feature space; Blind source separation
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    • G06F18/2136—Feature extraction, e.g. by transforming the feature space; Summarisation; Mappings, e.g. subspace methods based on sparsity criteria, e.g. with an overcomplete basis
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2218/00—Aspects of pattern recognition specially adapted for signal processing
    • G06F2218/02—Preprocessing
    • G06F2218/04—Denoising
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2218/00—Aspects of pattern recognition specially adapted for signal processing
    • G06F2218/08—Feature extraction

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Abstract

The invention discloses a nuclear pulse signal denoising method based on sparse decomposition, which comprises the following steps: firstly, partitioning a nuclear pulse signal to be processed into M sections with the length of N to obtain M data blocks; secondly, generating an overcomplete atomic dictionary D with a corresponding size according to the length N of the data block obtained by the block processing and a nuclear pulse signal overcomplete atomic dictionary construction method; step three, setting an OMP algorithm iteration termination condition; selecting atoms which are most matched with the nuclear signals from the overcomplete atom dictionary D for each frame data block, performing OMP decomposition on the data blocks independently, finishing the decomposition when an iteration termination condition is met, and representing the signals by linear combination of the selected atoms which are most matched to obtain a frame of denoised signals; and step five, recombining the M frames of denoised signals obtained in the step four to obtain denoised nuclear pulse signals. The method is accurate and efficient, simple in steps, reasonable in design and convenient to implement.

Description

Nuclear pulse signal denoising method based on sparse decomposition
Technical Field
The invention belongs to the field of signal processing, and particularly relates to a nuclear pulse signal denoising method of a nuclear measurement system based on sparse decomposition.
Background
The nuclear measurement system of the nuclear power plant is used for measuring the neutron flux level of a reactor, providing reactor power information for operating personnel, a protection system and a power regulation system, and playing an extremely important role in ensuring the safe and stable operation of the reactor. The nuclear measurement system is used as a weak signal processing system and is easily influenced by different types of interference noise, so that system signals are abnormal.
With the rapid development of scientific technology, the collection, acquisition, processing and analysis methods of nuclear signals are continuously innovated and developed, and particularly, the application of digital technology greatly improves the collection and processing methods of nuclear physical data, so that the nuclear signals can be more efficiently processed and analyzed compared with the traditional nuclear electronics system. In order to improve the signal-to-noise ratio of nuclear signals output by a nuclear measurement system of the reactor and weaken environmental and system electronics interference noise, a certain signal processing method can be adopted to extract target signals from aliasing signals.
In recent years, various algorithms are widely applied to denoising of nuclear signals, and good effects are achieved, such as wavelet threshold denoising and empirical mode decomposition. However, the denoising effect of wavelet threshold denoising is related to the selection of the mother wavelet basis, the threshold and the decomposition layer number, but the selection of the mother wavelet basis and the decomposition layer number depends on human experience, and has subjectivity, randomness and no self-adaptability. Although the empirical mode decomposition has adaptivity, the empirical mode decomposition has a high waveform distortion rate due to problems of mode aliasing, spurious modes, endpoint effects and the like.
In summary, the existing algorithm still lacks an effective solution to the problem of how to efficiently denoise the nuclear pulse signal of the nuclear measurement system.
Disclosure of Invention
The invention aims to provide a nuclear pulse signal denoising method based on sparse decomposition aiming at the defects of the prior art, the method utilizes a sparse theory method to denoise signals, sparsely represents the signals by utilizing the sparsity of the signals, and reconstructs the signals into original signals, so that the method is accurate and efficient, has simple steps, reasonable design and convenient implementation.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a nuclear pulse signal denoising method based on sparse decomposition is characterized by comprising the following steps:
firstly, partitioning a nuclear pulse signal to be processed into M sections with the length of N to obtain M data blocks;
secondly, generating an overcomplete atomic dictionary D with a corresponding size according to the length N of the data block obtained by the block processing and a nuclear pulse signal overcomplete atomic dictionary construction method;
step three, setting an OMP algorithm iteration termination condition;
selecting atoms which are most matched with the nuclear signals from the overcomplete atom dictionary D for each frame data block, performing OMP decomposition on the data blocks independently, finishing the decomposition when an iteration termination condition is met, and representing the signals by linear combination of the selected atoms which are most matched to obtain a frame of denoised signals;
and step five, recombining the M frames of denoised signals obtained in the step four to obtain denoised nuclear pulse signals.
As a preferred mode, in the method for constructing the overcomplete atom dictionary of the nuclear pulse signal, the basic definition of an atom is as follows:
wherein the content of the first and second substances,representing a gaussian window function; γ ═ (s, u, v, w) is an atomic time-frequency parameter; s is a scale factor; u is a displacement factor; v is a frequency factor; w is the phase factor.
Furthermore, discretization processing is carried out on the atom time-frequency parameters.
In a preferred embodiment, in the discretization processing method,
γ＝(aj,pajΔu,ka-jΔv,iΔw)，
wherein a is 2; Δ u ═ 21/; Δ v ═ pi; Δ w ═ pi/6; 0<j<log2N；0≤P≤N*2-j+1；0≤k≤2j+1；0≤i≤12。
Preferably, in the fourth step, the atom that best matches the nuclear signal y is selected in the overcomplete atom dictionary D by using an orthogonal projection methodSo that the following holds:
the kernel signal y is decomposed into two parts, a component on the best atom and a residual,wherein R is1Is a residual, R1Is an atomThe part remaining after matching yDividing;
to R1Repeatedly advancing typeThe decomposition process of (1).
Further, the method also comprises the step of utilizing an orthogonalization method to pair the matched atoms at each step of the decompositionAnd performing orthogonalization processing.
Compared with the prior art, the method has the advantages of accuracy, high efficiency, simple steps, reasonable design and convenient realization: the OMP algorithm is utilized to decompose and reconstruct the nuclear signals, the signal-to-noise ratio of the nuclear signals can be effectively improved, the denoising effect is achieved, and the method has the advantages of accuracy and reasonable design through experimental verification; the block processing method can greatly improve the speed of sparse decomposition, and solves the problems of overlarge overcomplete dictionary and large sparse decomposition calculation amount.
Drawings
FIG. 1 is a flow chart of an embodiment of the present invention.
FIG. 2 is a flow chart of the OMP algorithm employed in the present invention.
Fig. 3 is a block diagram of a signal processing system using the method of the present invention.
Detailed Description
As shown in fig. 1-2, an embodiment of the present invention includes:
(1) and carrying out block processing on the nuclear pulse signal to be processed. Because the size of the overcomplete atom dictionary adopted in the sparse decomposition process depends on the length of the signal to be processed, the larger the length of the signal to be processed is, the larger the number of atoms contained in the dictionary is, the larger the calculation amount of the decomposition algorithm in the atom matching process is, and the calculation speed is also reduced. In order to solve the problem, by taking the idea of blocking in image processing as a reference, the acquired signal data is subjected to Block decomposition processing, and one frame of Block data is only a part of a complete data sequence.
(2) And constructing a corresponding time-frequency atom dictionary by the nuclear signal characteristics. And generating an overcomplete atomic dictionary D with a corresponding size according to the length of the Block data Block in the blocking processing and a nuclear pulse signal overcomplete atomic dictionary construction method so as to be called when signal decomposition is carried out.
(3) And carrying out OMP decomposition on each frame of Block data Block independently, setting the current iteration stop update accumulated times N to be 1, setting an OMP algorithm iteration stop condition, continuing decomposition if the stop condition is not met, finishing decomposition of one frame of Block data if the stop condition is met, representing a signal by using the linear combination of the selected optimal atoms every time, and obtaining a frame of denoised signal. And starting the next frame data processing after finishing the processing of one frame data.
(4) And (4) performing the inverse operation of the step (1), and recombining each frame of Block data Block after the independent processing to restore the original data length.
Specifically, the invention comprises the following two parts:
firstly, constructing an over-complete atom dictionary conforming to the characteristics of nuclear signals
According to the uncertainty principle, the Gabor atoms have excellent time-frequency characteristics, and can effectively reveal the characteristics of signals. The invention utilizes the characteristic design of Gabor atoms to construct a Gabor atom overcomplete dictionary for signal decomposition processing, and the basic definition of the atoms is expressed as follows:
in the formula:representing a gaussian window function; γ ═ (s, u, v, w) is an atomic time-frequency parameter; s is a scale factor; u is a displacement factor; v is a frequency factor; w is the phase factor.
The number of atoms in the dictionary directly influences the signal representation effect, and in order to meet the requirements on redundancy and diversity of the atom dictionary, the atom time-frequency parameters are subjected to discretization treatment as follows:
γ＝(aj,pajΔu,ka-jΔv,iΔw)
wherein a is 2;Δu＝21/；Δv＝π；Δw＝π/6；0<j<log2N；0≤P≤N*2-j+1；0≤k≤2j+1；0≤i≤12。
n is the number of sampling points of a frame signal for performing sparse decomposition processing, and in order to overcome the problem of excessive storage and calculation when the dictionary is too large, the kernel pulse signal data is properly partitioned.
Secondly, signal decomposition and reconstruction are realized by utilizing OMP algorithm
The process is to decompose the kernel signal on an over-complete atom dictionary by using a sparse decomposition algorithm, namely, the process of atom selection from the dictionary is carried out, and then the kernel signal is represented by linear combination of optimal atoms. The OMP algorithm of the nuclear signal sparse decomposition comprises the following steps:
step 1: and (5) initializing the setting. Importing an original nuclear signal y, and carrying out blocking processing on the original nuclear signal y; importing the over-complete atom dictionary D obtained by construction; parameter setting order residual error R0Y, the number of iterations is N.
Step 2: and performing signal sparse decomposition loop iteration by utilizing an OMP algorithm. Firstly, the atom which is most matched with the nuclear signal y is selected from the selected overcomplete dictionary D by utilizing an orthogonal projection methodSo that it satisfies the following conditions:
at this time, the nuclear pulse signal can be decomposed into two parts of a component and a residual on the optimal atom, namely
In the formula, R1Is an atomThe part left after matching y is called R1Is the residual error. For the residue after the best matchDifference R1Continuously repeating the above stepsThe decomposition process of (1).
Matching atoms in each step of decomposition by Gram-Schmidt orthogonalization methodPerforming orthogonalization to increase convergence rate and avoid residual error in atomUnnecessary components are introduced in the up-projection. The specific process is as follows:
order toAccording to the formulaSelected best matching atomsOrthogonalizing the same.
After N iterations, the output signal y is decomposed,
and step 3: and reconstructing the signal by using the linear combination of the optimal atoms selected by each decomposition, and finally splicing the reconstructed data.
Fig. 3 is a block diagram of a signal processing system using the method of the present invention.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (6)

1. A nuclear pulse signal denoising method based on sparse decomposition is characterized by comprising the following steps:
firstly, partitioning a nuclear pulse signal to be processed into M sections with the length of N to obtain M data blocks;
secondly, generating an overcomplete atomic dictionary D with a corresponding size according to the length N of the data block obtained by the block processing and a nuclear pulse signal overcomplete atomic dictionary construction method;
step three, setting an OMP algorithm iteration termination condition;
selecting atoms which are most matched with the nuclear signals from the overcomplete atom dictionary D for each frame data block, performing OMP decomposition on the data blocks independently, finishing the decomposition when an iteration termination condition is met, and representing the signals by linear combination of the selected atoms which are most matched to obtain a frame of denoised signals;
and step five, recombining the M frames of denoised signals obtained in the step four to obtain denoised nuclear pulse signals.
2. The sparse decomposition-based nuclear pulse signal denoising method of claim 1, wherein in the nuclear pulse signal overcomplete atom dictionary construction method, the basic definition of atoms is as follows:
wherein the content of the first and second substances,representing a gaussian window function; γ ═ (s, u, v, w) is an atomic time-frequency parameter; s is a scale factor; u is a displacement factor; v is a frequency factor; w is the phase factor.
3. The sparse decomposition-based kernel pulse signal denoising method of claim 2, further comprising discretizing the atomic time-frequency parameters.
4. The sparse decomposition-based kernel pulse signal denoising method of claim 3, wherein in the discretization processing method,
γ＝(aj,pajΔu,ka-jΔv,iΔw)，
wherein a is 2; Δ u ═ 21/; Δ v ═ pi; Δ w ═ pi/6; 0<j<log2N；0≤P≤N*2-j+1；0≤k≤2j+1；0≤i≤12。
5. The sparse decomposition-based nuclear pulse signal denoising method of claim 1, wherein in step four, the atom that best matches the nuclear signal y is selected in the overcomplete atom dictionary D by using an orthogonal projection methodSo that the following holds:
the kernel signal y is decomposed into two parts, a component on the best atom and a residual,wherein R is1Is a residual, R1Is an atomThe part remaining after matching y;
to R1Repeatedly advancing typeThe decomposition process of (1).
6. The sparse decomposition-based nuclear pulse signal denoising method of claim 5, further comprising using an orthogonalization method to the matched atoms at each step of decompositionAnd performing orthogonalization processing.
CN201910720845.0A 2019-06-03 2019-08-06 Nuclear pulse signal denoising method based on sparse decomposition Pending CN110598544A (en)

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103176946A (en) * 2013-04-02 2013-06-26 哈尔滨工业大学 Sparse decomposition and denoising method facing block sparse signals

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103176946A (en) * 2013-04-02 2013-06-26 哈尔滨工业大学 Sparse decomposition and denoising method facing block sparse signals

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Application publication date: 20191220