CN113313102B - Random resonance chaotic small signal detection method based on variant differential evolution algorithm - Google Patents
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Abstract
The invention discloses a random resonance chaotic small signal detection method based on a variant differential evolution algorithm. In order to verify the feasibility of the algorithm, low-frequency and high-frequency small signal input simulation experiments are respectively carried out, and in the low-frequency small signal detection experiment, the output signal-to-noise ratio chaos variable-step-size firefly algorithm is averagely improved by 1.98 dB; in a high-frequency small signal detection experiment, small signals at a low-frequency section corresponding to the high-frequency small signals can be accurately recovered, and the existence of the high-frequency small signals is further deduced; simulation experiments are carried out on the actually measured sea clutter data, and the experimental results show that the method can effectively detect the small chaotic signals submerged in the sea clutter background.
Description
Technical Field
The invention belongs to the field of chaotic small signal detection, and particularly relates to a random resonance chaotic small signal detection method based on a variant differential evolution algorithm.
Background
The research direction of the weak signal detection method can not only start from the small signal itself and search the difference between the small signal and background noise to verify the existence of the small signal, but also start from the background noise and realize the enhancement of the small signal by utilizing a stochastic resonance means to obtain the small signal, and the detection method can also be researched by combining the stochastic resonance theory for chaotic small signals under the background of strong sea clutter.
Theory of stochastic resonance is represented by Benzi]A mathematical analysis method is proposed by people in the research of climate problem of periodic change in the age of glaciers, and is used for qualitatively describing solar revolution eccentricityThe alternating phenomenon of the cold and hot climatic periods of the earth caused by the periodic variation of the rate. Afterwards, the stochastic resonance theory is widely varied and applied to various fields such as physics, chemistry, signal processing and the like, and researchers at home and abroad obtain abundant research results in the field of weak signal detection. In 1998, when Frank researches weak electric field and magnetic field signals, Frank utilizes a stochastic resonance theory to improve the signal-to-noise ratio by increasing the chaotic power spectral density of the weak signals so as to realize the detection of the weak signals; aditya in 2003 proposed a quantized stochastic resonance detector suitable for detecting weak sinusoidal signals in noise with detection performance superior to that of matched filters; in 2001, Wang Li ya et al put forward a basic method for detecting weak signals by stochastic resonance, and have a prospect on the application prospect in the field of mechanical fault diagnosis; the Wenxison et al put forward a mechanical fault early detection method based on stochastic resonance in 2009, and have profound influence on fault diagnosis and prediction theory development; in 2018, when a rehong tablet and the like are used for researching a weak signal detection method under a sea clutter background, a self-adaptive stochastic resonance weak signal detection method is provided, the multi-parameter optimization of a Duffing oscillator stochastic resonance system is realized, and the detection performance is improved. How to find the optimization algorithm of the multi-parameter synchronous tuning of the Duffing oscillator stochastic resonance system becomes a breakthrough of the stochastic resonance chaotic small signal detection method under the background of sea clutter.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the defect that the traditional stochastic resonance small signal detection method cannot synchronously adjust and optimize multiple parameters, the stochastic resonance chaotic small signal detection method based on the variant differential evolution algorithm is provided, and stochastic resonance is realized to obtain high-frequency and low-frequency small signals submerged in strong noise.
The invention adopts the following technical scheme: the random resonance chaotic small signal detection method based on the variant differential evolution algorithm comprises the following steps:
firstly, performing phase space reconstruction on a sea clutter signal x (n) to be detected by adopting a C-C method, and determining the delay time of a phase space;
step two, establishing chaotic small signals and noise signalsObtaining the core parameters of the system based on the delay time by using the Duffing oscillator stochastic resonance equation under the combined action、、;
Thirdly, utilizing a variant differential evolution algorithm to carry out pair on core parameters influencing the effect of the stochastic resonance detection、、Optimizing according to the obtained core parameters of the system、、And (3) carrying out stochastic resonance output on the input signal, and analyzing the spectral characteristics of the output signal to obtain the chaotic small signal.
Further, in the step one, the C-C phase space reconstructing step includes:
step 1.1, dividing the sea clutter signals x (N), N =1,2,.. and N to be detected into t disjoint time rows with the length of N/t, and calculating the statistic S (m, N, r, tau) of each subsequence
In the formula,is the firstThe correlation integral of the sub-sequences is,is the length of the data set and,is the search radius in the reconstruction space; m is the embedding dimension, τ is the time delay;
step 1.2, local maximum separationZero point or for all radiiThe points in time at which the difference from each other is minimal. Selecting two radii with maximum and minimum corresponding valuesThe difference is defined as
According to the principle of statistics,is taken fromIn a ratio of (A) to (B),is the mean square of a time seriesThe difference, the equation is as follows:
in the formula,is the mean of the statistics of all sub-sequences, and,、is a statistic defined according to the Brock-Decchert-Scheinkman BDS statistics,is the delta of the statistic of the sub-sequence,for a new indicator of determining the width of the embedding window,the corresponding point of the global minimum value is the width of the embedding window.
Further, the second step includes:
step 2.1, the Duffing oscillator stochastic resonance equation system under the combined action of a chaotic small signal and a noise signal is as follows:
wherein,in order to output the signal for the system,in order to achieve a damping ratio,in order to be a function of the potential,in order to input the signals to the system,is an average value of 0 and a noise intensity ofThe white gaussian noise of (a) is,representing the shock function;
step 2.2, solving a formula according to a quadratic equation of unity to calculate a potential functionComprises three extreme points ofThe system critical value at this time is calculated as;
Step 2.3, if and only if the input signal amplitudeWhen the signal, the noise and the system reach a matching cooperative relationship, partial energy of the noise signal is transferred to the signal, the signal enhancement is realized, namely, the signal enters a stochastic resonance state, and at the moment, the formula (4) is simplified as follows:
equation (5) is the stochastic resonance system of a typical second-order Duffing vibrator, and the parameters、、To determine the core parameters of the Duffing vibrator stochastic resonance system.
Further, the detection method further comprises:
step four, utilizing a variant differential evolution algorithm to carry out pair on core parameters influencing the effect of the stochastic resonance detection、、Optimization is carried out, so that the bistable stochastic resonance system of the Duffing vibrator has the best signal detection effect.
Further, the third step includes:
step 3.1, initializing parameters, setting the initial population quantity asNPThe maximum number of iterations isGSecond, the dimension of the space variable isDCreating an initial populationRandomly generating 0 th generationiThe individual isjDimension dereferencing:
wherein,represents the firstiThe upper and lower limits of the value of the individual,is represented by (A)D,NP) Random numbers uniformly distributed in the interval;
step 3.2, calculating an objective function, wherein for a second-order Duffing oscillator stochastic resonance system, the signal-to-noise ratio of an output signal changes along with the change of system parameters, the signal-to-noise ratio can reflect the enhancement level of the system to chaotic small signals, and the objective function is as follows:
in the formula (7), the reaction mixture is,in order to output a signal for the stochastic resonance system,signal-to-noise ratio of the output signal for the system;
and 3.3, performing mutation operation, namely performing mutation operation on the individuals by adopting a differential strategy, randomly selecting two parent individuals different from the individuals to be mutated, performing differential scaling on the two parent individuals, and synthesizing the two parent individuals with the individuals to obtain:
wherein,Frepresents an adaptive mutation operator and is characterized in that,representing iterationsgThe next generationiThe number of the individuals is small,is the value of the objective function that the optimal individual is,the value of the objective function of the current individual,is the value of the maximum objective function,is the minimum objective function value. The values of all individuals of the population are required to meet boundary conditions in the whole variation process, namely
Step 3.4, crossover operation, pair iterationgLast individualAnd variant individualsAnd (3) performing cross calculation:
in the formula (11), the reaction mixture is,crin order to be a cross-over factor,is composed ofThe intersection of the differential evolution algorithm is different from the intersection of each individual in the genetic algorithm;
step 3.5, selection operation, differential evolution algorithm utilizes greedy algorithm to carry out selection operation
Step 3.6, updating the objective function value, calculating the signal-to-noise ratio of the output signal of the system according to the system parameter optimized by the current iteration times, comparing the signal-to-noise ratio output by the last iteration, and if the signal-to-noise ratio is smaller, performing a round of iteration optimization again; otherwise, outputting the optimizing parameter、、;
Step 3.7, outputting the optimal stochastic resonance, and when the iteration times reach the highest iteration timesGOutputting the stochastic resonance system parameters of the second-order Duffing oscillator corresponding to the maximum objective function value、、And carrying out stochastic resonance output on the input signal according to the obtained optimal parameter value, and analyzing the spectral characteristics of the output signal.
As a preferred embodiment of the present application, the detection method further comprises: step four, obtaining the optimal system parameters by using a variant differential evolution algorithm、、And analyzing the detection effect of the stochastic resonance chaotic small signals under the optimal parameters, comparing the time-frequency characteristics of the input and output signals of the stochastic resonance system of the Duffing oscillator, and judging whether the chaotic small signals submerged in the sea clutter background can be detected.
Has the advantages that: the method adopts a variant differential evolution algorithm optimization algorithm, and can ensure the occurrence probability of the variation at the initial stage of iteration, maintain the diversity of the population and prevent premature convergence by adding the self-adaptive variation operator; the optimal solution can be protected in the later iteration stage, the global search capability is improved, the system optimal parameter of the stochastic resonance system is found by utilizing the variant differential evolution algorithm, the speed is high, the accuracy is high, and the requirement of high-precision matching of the system parameter can be met. In order to verify the feasibility of the algorithm, high-frequency and low-frequency small signal detection is carried out, the found optimal parameters are substituted into a two-dimensional Duffing oscillator stochastic resonance system to realize stochastic resonance, the high-frequency and low-frequency small signals under the non-Gaussian noise background are detected, the output signal-to-noise ratio is improved, and the detection precision of the high-frequency and low-frequency small signals is enhanced.
In order to verify the practicability of the algorithm, a chaos small target detection experiment based on the random resonance theory under the sea clutter background is carried out, wherein #54 sea clutter collected by an IPIX radar contains target signal data, and a target data interval is as follows: the primary target is 8 and the secondary target is 7: 10. The sea clutter data containing the target replaces the input signal of the stochastic resonance system of the Duffing oscillator, and the system optimized by the variant differential evolution algorithm outputs the system parameter corresponding to the maximum signal-to-noise ratio、、The existence of the chaotic small signal can be judged in the output signal spectrogram.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flow chart of a stochastic resonance chaotic small signal detection method based on a variant differential evolution algorithm according to the present invention;
FIG. 2 is a schematic diagram of the convergence of random system parameters optimized by a variant differential evolution algorithm;
FIG. 3 is a diagram of the parameter analysis results of a stochastic resonance system of a low-frequency small-signal variant differential evolution algorithm;
(a) inputting a signal diagram; (b) inputting a signal spectrogram; (c) outputting a signal diagram; (d) outputting a signal spectrogram;
FIG. 4 is a diagram of the parameter analysis results of the stochastic resonance system of the high-frequency small-signal variant differential evolution algorithm;
(a) inputting a signal diagram; (b) inputting a signal spectrogram; (c) outputting a signal diagram; (d) outputting a signal spectrogram;
FIG. 5 is a diagram of the detection effect of a stochastic resonance chaotic small signal under a sea clutter background;
(a) inputting a signal diagram; (b) inputting a signal spectrogram; (c) outputting a signal diagram; (d) and outputting a signal spectrogram.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings and implementation.
The method applies the variant differential evolution algorithm to the parameter synchronous optimization of the stochastic resonance system, and by adding the self-adaptive mutation operator, the probability of occurrence of mutation can be ensured at the initial stage of iteration, the population diversity is maintained, and premature convergence is prevented; the optimal solution can be protected in the later iteration stage, and the global search capability is improved. Bistable stochastic resonance system parameters of variant pair Duffing vibrator、、Optimizing, setting the signal-to-noise ratio of the system output signal as an objective function,
in order to verify the effectiveness of the detection method, low-frequency and high-frequency small signal simulation experiments are respectively carried out; in order to ensure the practicability of the detection method, an experiment is carried out by utilizing the actually measured sea clutter signal.
The technical scheme is as follows:
(1) performing phase space reconstruction on the sea clutter signals x (n) to be detected by adopting a C-C method, and determining the core parameter embedding dimension and delay time of the phase space;
(2) the detection of the chaotic small signal is realized by utilizing the capability that the bistable stochastic resonance system of the Duffing vibrator can match with the small signal in the collaborative chaotic state, background noise and the system;
(3) using a variant differential evolution algorithm to influence system parameters of a stochastic resonance detection effect、、Optimizing to ensure that the bistable stochastic resonance system of the Duffing vibrator has the best signal detection effect;
(4) optimal system parameters obtained by using variant differential evolution algorithm、、And analyzing the detection effect of the stochastic resonance chaotic small signals under the optimal parameters, comparing the time-frequency characteristics of the input and output signals of the stochastic resonance system of the Duffing oscillator, and judging whether the chaotic small signals submerged in the sea clutter background can be detected.
As shown in FIG. 1, the invention provides a random resonance chaotic small signal detection method based on a variant differential evolution algorithm, which comprises the following steps:
(1) performing phase space reconstruction on the sea clutter signals x (n) to be detected by adopting a C-C method, and determining the core parameter embedding dimension and delay time of the phase space;
(1.1) dividing the sea clutter signals x (N), N =1, 2.. and N to be detected into t disjoint time columns, rounding the time columns with the length of N/t, and calculating the statistic S (m, N, r, tau) of each subsequence
In the formula,is the firstThe correlation integral of the sub-sequences is,is the length of the data set and,for the search radius in reconstruction space, m is the embedding dimension, τ is the time delay;
(1.2) local maximum separation can be removedZero point of (2) or for all search radiiThe points in time at which the difference from each other is minimal. Selecting two radii with maximum and minimum corresponding valuesThe difference is defined as
Wherein,u,vthe sequence representing the parameter represents any unknown in the range and, according to statistical principles,mthe value is between 2 and 5 and,is taken from the value ofAndin the above-mentioned manner,is the mean square error of the time series, the equation is as follows:
in the formula,is the mean of the statistics of all sub-sequences, and,、is a statistic defined according to the Brock-Decchert-Scheinkman BDS statistics,is the delta of the statistic of the sub-sequence,for a new indicator of determining the width of the embedding window,the corresponding point of the global minimum value is the width of the embedding window.
(2) The detection of the chaotic small signal is realized by utilizing the capability that the bistable stochastic resonance system of the Duffing vibrator can match with the small signal in the collaborative chaotic state, background noise and the system;
(2.1) the Duffing oscillator stochastic resonance equation system under the combined action of a chaotic small signal and a noise signal is as follows:
wherein,in order to output the signal for the system,in order to achieve a damping ratio,in order to be a function of the potential,in order to input the signals to the system,is white gaussian noise with an average value of 0 and a noise intensity of 0,representing the shock function.
(2.2) solving according to a quadratic equation of one elementSolving the formula can calculate a potential functionComprises three extreme points ofDefining the barrier height of the potential function as. If the pole of the potential function is equal to the inflection point, the system critical value is calculated as,、Are parameters.
(2.3) if and only if the input signal amplitudeWhen the signal, the noise and the system reach a matching cooperative relationship, partial energy of the noise signal is transferred to the signal, the signal enhancement is realized, namely the signal enters a stochastic resonance state, and at the moment, the formula (4) can be simplified into the following steps:
formula (5) is a stochastic resonance system of a typical second-order Duffing vibrator, and parameters are obtained by analyzing the formula、、In order to determine the core parameters of the Duffing vibrator stochastic resonance system, the following optimization algorithm is laid.
(3) Using a variant differential evolution algorithm to influence system parameters of a stochastic resonance detection effect、、Optimizing to ensure that the bistable stochastic resonance system of the Duffing vibrator has the best signal detection effect;
(3.1) initializing parameters, setting the number of initial population toNPThe maximum number of iterations isGSecond, the dimension of the space variable isDCreating an initial populationRandomly generating 0 th generationiThe individual isjDimension dereferencing: (6)
wherein,represents the firstiThe upper and lower limits of the value of the individual,is represented by (A)D,NP) Random numbers are uniformly distributed in the interval.
(3.2) calculating an objective function, wherein for a second-order Duffing oscillator stochastic resonance system, the signal-to-noise ratio of an output signal changes along with the change of system parameters, the signal-to-noise ratio can reflect the enhancement level of the system to chaotic small signals, and the objective function is as follows: (7)
in the formula (7), the reaction mixture is,in order to output a signal for the stochastic resonance system,the signal-to-noise ratio of the system output signal.
And (3.3) mutation operation, which is one of the marks distinguished from genetic algorithm, of individuals by adopting a difference strategy. Randomly selecting two parent individuals different from the parent individuals to be mutated, carrying out differential scaling, and synthesizing with the individuals to obtain: (8)
wherein,Frepresents an adaptive mutation operator and is characterized in that,representing iterationsgThe next generationiThe number of the individuals is small,is the value of the objective function that the optimal individual is,the value of the objective function of the current individual,is the value of the maximum objective function,is the minimum objective function value. Species in the whole mutation processThe values of all individuals in the group are required to satisfy boundary conditions, i.e.
(3.4) crossover operation, pair iterationgLast individualAnd variant individualsAnd (3) performing cross calculation: (11)
in the formula (11), the reaction mixture is,crin order to be a cross-over factor,is composed ofThe cross of the differential evolution algorithm is different from the cross of each individual in the genetic algorithm, and only the individuals with the same dimension are crossed.
(3.5) selection operation, the differential evolution algorithm uses greedy algorithm to perform the selection operation
(3.6) updating the objective function value, calculating the signal-to-noise ratio of the output signal of the system according to the system parameter optimized by the current iteration number, comparing the signal-to-noise ratio output by the last iteration, and if the signal-to-noise ratio is smaller, performing a round of iteration optimization again; otherwise, outputting the optimizing parameter、、;
(3.7) outputting the optimal random resonance, and when the iteration times reach the maximum iteration timesGOutputting the stochastic resonance system parameters of the second-order Duffing oscillator corresponding to the maximum objective function value、、And carrying out stochastic resonance output on the input signal according to the obtained optimal parameter value, and analyzing the spectral characteristics of the output signal.
(4) Optimal system parameters obtained by using variant differential evolution algorithm、、Analyzing the detection effect of the stochastic resonance chaotic small signals under the optimal parameters, comparing the time-frequency characteristics of the input and output signals of the stochastic resonance system of the Duffing oscillator, and judging whether the chaotic small signals submerged in the sea clutter background can be detected;
(4.1) to verify the feasibility of the proposed algorithm, a simulation experiment of low frequency small signal input was first performed. Considering that the system parameter is smaller when the stochastic resonance occurs, the population number is setNPIs 50, variable dimensionD10, initial mutation operator0.4, cross causeSeed of Japanese apricotcr0.1, maximum number of iterationsGAt 200, the following low frequency small signals are input:
wherein, the frequency of the small signal is 0.01Hz, the sampling frequency is 5 Hz, and the number of sampling points is 800. Setting the amplitude A =0.1, 0.08, 0.06, 0.04, 0.02 of the low-frequency signal, corresponding to the noise intensity D =0.15, 0.3, 0.45, 0.6, 0.75, forming five groups of input signals 1,2, 3, 4, 5 with gradually decreasing signal-to-noise ratios, and setting the optimization range of the parameters of the optimized output system to be [0.001, 2]The parameter accuracy was 0.001. Taking the input signal amplitude A =0.1 and the noise intensity D =0.15 as an example for detailed description, and searching a system parameter corresponding to the maximum output signal-to-noise ratio of the Duffing oscillator stochastic resonance system under the current input signal characteristic by using a variant differential evolution algorithm、、. And analyzing the time-frequency characteristics of the input and output signals under the optimal system parameters to judge the existence of the chaotic small signals.
(4.2) to further verify the feasibility of the variant differential evolution algorithm to optimize the stochastic resonance small signal detection method, the input signal amplitude a =0.2, the noise intensity D =2.1, and the signal frequencyHigh frequency small signal, sampling frequencyThe number of sampling points is 800, and the carrier frequency is set by combining the heterodyne stochastic resonance theoryAnd the low-frequency signal component output after frequency mixing meets the adiabatic approximate theoretical requirement, and a high-frequency small signal detection experiment is carried out.
Detecting the high-frequency small signal under the stochastic resonance system by utilizing a variant differential evolution algorithm to obtain a system parameter corresponding to the maximum signal-to-noise ratio of the output signal、、And judging the existence of the high-frequency small signal by utilizing a heterodyne stochastic resonance recovery principle.
(4.3) in order to verify the practicability of the variant differential evolution algorithm, performing a chaotic small target detection experiment based on a random resonance theory under a sea clutter background, wherein #54 sea clutter collected by an IPIX radar contains target signal data, and a target data interval: the primary target is 8 and the secondary target is 7: 10. The sea clutter data containing the target replaces the input signal of the stochastic resonance system of the Duffing oscillator, and the system optimized by the variant differential evolution algorithm outputs the system parameter corresponding to the maximum signal-to-noise ratio、、And analyzing the time-frequency characteristics of the input and the output of the system to judge the existence of the small signal.
In order to illustrate the effectiveness of the method, the sea clutter data is subjected to chaotic phase space reconstruction to establish actual measurement data. In order to verify the feasibility of the algorithm, a low-frequency small signal detection experiment is firstly carried out, and low-frequency small signal mixed noise is used as Duffing vibrationAfter the input signal of the sub-stochastic resonance system is optimized by the system parameters through the variant difference algorithm, the output signal of the system is obtained and the time-frequency characteristic of the output signal is analyzed to verify the detection effect of the chaotic small signal, for example, the amplitude of the input signal A =0.1 and the noise intensity D =0.15, for example, in the figure 2, the variant difference evolution algorithm obtains the optimal parameters of the current input signal of the system through 33 times of iterative optimization, namely, the optimal parameters are respectively,,In this case, the signal-to-noise ratio of the output signal is 10.710dB at most, which is 29.391dB higher than the input signal-to-noise ratio (-18.681dB), the stochastic resonance diagram of the variant differential evolution algorithm of fig. 3 under the optimal parameters is shown, fig. 3 (a) is the input signal diagram, it can be seen that the chaotic small signal is buried in the noise, and as shown in fig. 3 (b), the spectral characteristics cannot be seen. However, by analyzing the output signal (c) in fig. 3, the outline of the signal can be briefly seen, and then analyzing the spectral characteristics (d) in fig. 3, the small signal can be obviously observed to be enhanced, and the small signal at 0.01Hz can be directly judged.
In order to further verify the feasibility of the small-signal detection method for optimizing stochastic resonance by using the variant differential evolution algorithm, it is considered that in the adiabatic approximation theory, the input signal is required to have low amplitude, low frequency and low noise intensity, but the input signal in practical engineering application may often be a high-frequency small signal with higher frequency, and for this problem, the heterodyne stochastic resonance can be used for solving.
Input signal amplitude a =0.2, noise intensity D =2.1, signal frequencyHigh frequency small signal, sampling frequencyThe number of sampling points is 800, and the carrier frequency is set by combining the heterodyne stochastic resonance theoryAnd the low-frequency signal component output after frequency mixing meets the adiabatic approximate theoretical requirement, and a high-frequency small signal detection experiment is carried out.
Detecting the high-frequency small signal under the stochastic resonance system by utilizing a variant differential evolution algorithm to obtain a system parameter corresponding to the maximum signal-to-noise ratio of the output signal、、Are respectively as,,And the maximum signal-to-noise ratio under the current condition is output, namely 3.54dB, which is improved by 26.76dB compared with the input signal-to-noise ratio (-23.22 dB). Fig. 4 is an optimized stochastic resonance chart in the case of inputting a high-frequency small signal, and from the analysis of (a) and (b) in fig. 4, no high-frequency small signal submerged in a strong noise background can be observed in the time-frequency characteristic chart of the input signal. However, the outline of the input signal can be clearly seen in the output signal diagram (c) in fig. 4, and the frequency analysis of the outline results in the output signal spectrogram (d) in fig. 4, so that the small signal is obviously enhanced, and the judgment is madeThe small signal is calculated according to the heterodyne stochastic resonance recovery principleAnd further deducing that the enhanced frequency represents that the input frequency is 20Hz, which shows that the Duffing oscillator stochastic resonance system optimized by the variant differential evolution algorithm can detect a high-frequency small signal.
In order to verify the practicability of the variant differential evolution algorithm, a chaos small target detection experiment based on the random resonance theory under the sea clutter background is carried out, wherein #54 sea clutter collected by an IPIX radar contains target signal data, and a target data interval is as follows: the primary target is 8 and the secondary target is 7: 10. The sea clutter data containing the target replaces the input signal of the stochastic resonance system of the Duffing oscillator, and the system optimized by the variant differential evolution algorithm outputs the system parameter corresponding to the maximum signal-to-noise ratio、、Are respectively as,,The output signal-to-noise ratio is 22.47dB, which is 83.50dB higher than the signal-to-noise ratio (-55.03dB) of the input signal, the detection effect of the chaotic small random resonance signal under the background of the sea clutter is shown in fig. 5, wherein (a) and (b) in fig. 5 are time-frequency characteristic diagrams of the input signal, which cannot analyze the existence of the chaotic small signal, after the optimized stochastic resonance system, the chaotic small signal profile submerged under the background of the sea clutter can be drawn out in a hidden way in (c) in fig. 5, and the spectral peak appearing at the position with the frequency of 0.01632 can be clearly identified in (d) in fig. 5, which represents the position where the spectral peak appearsChaotic small signals exist, and the effect of experimental research is achieved.
Those skilled in the art will recognize that in one or more of the examples described above, the functions described herein may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer.
The above-mentioned embodiments, objects, technical solutions and advantages of the present application are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present application, and are not intended to limit the scope of the present application, and any modifications, equivalent substitutions, improvements and the like made on the basis of the technical solutions of the present application should be included in the scope of the present application.
Claims (4)
1. The random resonance chaotic small signal detection method based on the variant differential evolution algorithm is characterized by comprising the following steps of:
firstly, performing phase space reconstruction on a sea clutter signal x (n) to be detected by adopting a C-C method, and determining the delay time of a phase space;
establishing a Duffing oscillator stochastic resonance equation under the combined action of the chaotic small signal and the noise signal, and obtaining the core parameters of the system based on the delay time、、;
Thirdly, utilizing a variant differential evolution algorithm to carry out pair on core parameters influencing the effect of the stochastic resonance detection、、Optimizing according to the obtained core parameters of the system、、The value of (3) is to perform stochastic resonance output on an input signal, and analyze the spectral characteristics of the output signal to obtain a chaotic small signal;
the third step comprises:
step 3.1, initializing parameters, setting the initial population quantity asNPThe maximum number of iterations isGSecond, the dimension of the space variable isDCreating an initial populationRandomly generating 0 th generationiThe individual isjDimension dereferencing:
wherein,represents the firstiThe upper and lower limits of the value of the individual,is represented by (A)D,NP) Random numbers uniformly distributed in the interval;
step 3.2, calculating an objective function, wherein for a second-order Duffing oscillator stochastic resonance system, the signal-to-noise ratio of an output signal changes along with the change of system parameters, the signal-to-noise ratio can reflect the enhancement level of the system to chaotic small signals, and the objective function is as follows:
in the formula (7), the reaction mixture is,in order to output a signal for the stochastic resonance system,signal-to-noise ratio of the output signal for the system;
and 3.3, performing mutation operation, namely performing mutation operation on the individuals by adopting a differential strategy, randomly selecting two parent individuals different from the individuals to be mutated, performing differential scaling on the two parent individuals, and synthesizing the two parent individuals with the individuals to obtain:
wherein,Frepresents an adaptive mutation operator and is characterized in that,representative stackSubstitute for Chinese traditional medicinegThe next generationiThe number of the individuals is small,is the value of the objective function that the optimal individual is,the value of the objective function of the current individual,is the value of the maximum objective function,is the minimum objective function value; the values of all individuals of the population are required to meet boundary conditions in the whole variation process, namely
Step 3.4, crossover operation, pair iterationgLast individualAnd variant individualsAnd (3) performing cross calculation:
in the formula (11), the reaction mixture is,crin order to be a cross-over factor,is composed ofIs randomly adjustedThe crossing of the differential evolution algorithm is different from the crossing of each individual in the genetic algorithm;
step 3.5, selection operation, differential evolution algorithm utilizes greedy algorithm to carry out selection operation
Step 3.6, updating the objective function value, calculating the signal-to-noise ratio of the output signal of the system according to the system parameter optimized by the current iteration times, comparing the signal-to-noise ratio output by the last iteration, and if the signal-to-noise ratio is smaller, performing a round of iteration optimization again; otherwise, outputting the optimizing parameter、、;
Step 3.7, outputting the optimal stochastic resonance, and when the iteration times reach the highest iteration timesGOutputting the stochastic resonance system parameters of the second-order Duffing oscillator corresponding to the maximum objective function value、、And carrying out stochastic resonance output on the input signal according to the obtained optimal parameter value, and analyzing the spectral characteristics of the output signal.
2. The stochastic resonance chaotic small signal detection method based on the variant differential evolution algorithm according to claim 1, wherein in the first step, the C-C phase space reconstruction step comprises:
step 1.1, dividing the sea clutter signals x (N), N =1,2,.. and N to be detected into t disjoint time rows with the length of N/t, and calculating the statistic S (m, N, r, tau) of each subsequence
In the formula,is the firstThe correlation integral of the sub-sequences is,is the length of the data set and,is the search radius in the reconstruction space; m is the embedding dimension, τ is the time delay;
step 1.2, local maximum separationZero point or for all radiiSelecting the time point with the minimum difference, and selecting the radius with the maximum and minimum corresponding valuesThe difference is defined as
u,vAny unknown number within the sequence range representing the parameter is determined, according to statistical principles,is taken fromIn a ratio of (A) to (B),is the mean square error of the time series, the equation is as follows:
in the formula,is the mean of the statistics of all sub-sequences, and,、is a statistic defined according to the Brock-Decchert-Scheinkman BDS statistics,is the delta of the statistic of the sub-sequence,for a new indicator of determining the width of the embedding window,the global minimum value point of (1) corresponds to the width of the embedding window。
3. The random resonance chaotic small signal detection method based on the variant differential evolution algorithm according to claim 1, wherein the second step comprises:
step 2.1, the Duffing oscillator stochastic resonance equation system under the combined action of a chaotic small signal and a noise signal is as follows:
wherein,in order to output the signal for the system,in order to achieve a damping ratio,in order to be a function of the potential,in order to input the signals to the system,is an average value of 0 and a noise intensity ofThe white gaussian noise of (a) is,representing the shock function;
step 2.2, solving a formula according to a quadratic equation of unity to calculate a potential functionComprises three extreme points ofThe system critical value at this time is calculated as;
Step 2.3, if and only if the input signal amplitudeWhen the signal, the noise and the system reach a matching cooperative relationship, partial energy of the noise signal is transferred to the signal, the signal enhancement is realized, namely, the signal enters a stochastic resonance state, and at the moment, the formula (4) is simplified as follows:
4. The random resonance chaotic small signal detection method based on the variant differential evolution algorithm according to claim 1, characterized in that the detection method further comprises: step four, obtaining the optimal system parameters by using a variant differential evolution algorithm、、And analyzing the detection effect of the stochastic resonance chaotic small signals under the optimal parameters, comparing the time-frequency characteristics of the input and output signals of the stochastic resonance system of the Duffing oscillator, and judging whether the chaotic small signals submerged in the sea clutter background can be detected.
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