CN107748734B - Analytic-empirical mode decomposition method - Google Patents
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Abstract
The invention discloses an analytic-empirical mode decomposition method, which comprises the following steps: s1, screening the original signals through an empirical mode decomposition method to obtain n IMF components and 1 residual amount; and S2, processing the IMF components through an analytic mode decomposition algorithm, and then reconstructing the mode according to a certain rule. The invention provides a screening termination criterion based on an effective data segment aiming at the problem of the screening termination criterion of empirical mode decomposition, provides an analysis-empirical mode decomposition method aiming at the mode confusion phenomenon, carries out analysis mode decomposition on the modes with mode confusion, and finally reconstructs the modes. The analytic-empirical mode decomposition method can effectively inhibit mode confusion, and has short decomposition time and higher method execution efficiency.
Description
Technical Field
The invention relates to an analytic-empirical mode decomposition method.
Background
Empirical Mode Decomposition (EMD) is a self-adaptive signal processing method which is widely applied, and aiming at the problem of screening termination criteria in the implementation process of empirical mode decomposition, the screening termination criteria based on an effective data segment is provided and compared with the traditional screening termination criteria, the new screening criteria avoid the influence of end point effect, and the accuracy of empirical mode decomposition is improved. Aiming at the mode confusion phenomenon, an analytic-empirical mode decomposition method is provided, the modes which have mode confusion in the empirical mode decomposition are subjected to analytic mode decomposition, and the modes are reconstructed, so that the mode confusion of each order of modes is obviously smaller than the empirical mode decomposition. Compared with the existing main improvement method of empirical mode decomposition, namely the ensemble average empirical mode decomposition method, the method provided by the invention can effectively inhibit mode aliasing as the ensemble average empirical mode decomposition method. However, the method has more obvious effect of inhibiting mode confusion and has higher execution efficiency.
The Empirical Mode Decomposition (EMD) method is based on the local characteristic time scale of a signal, and can decompose a complex signal into the sum of a limited number of Intrinsic Mode functions (IMF for short), each Intrinsic Mode Function represents an Intrinsic vibration Mode of an original signal, and the stable Intrinsic Mode functions are analyzed to extract the characteristic information of the signal.
Empirical mode decomposition has attracted considerable attention from the advent of numerous scholars. The method is widely applied to the fields of economics, biomedicine, engineering science and the like, but has some defects, mainly including Mode aliasing (Mode Mixing), End Effects (End Effects) and Stop conditions (Stop criterion) of Intrinsic Mode Function (IMF) criterion, overcladding and undercladding phenomena and the like. The empirical mode decomposition has the defects that the further popularization and the use of the empirical mode decomposition are restricted.
The condition for judging the intrinsic mode function in the empirical mode decomposition method is that the average value of the upper envelope line and the lower envelope line of the intrinsic mode function is zero, but in the factual decomposition process, the average value of the envelope lines of the intrinsic mode function components obtained by the empirical mode decomposition cannot be zero due to the interference of cubic spline curve interpolation, the endpoint effect, the influence of the adopted frequency and the like. Therefore, it is necessary to define a stopping criterion of the decomposition process feasible in engineering, i.e. the intrinsic mode function criterion problem of empirical mode decomposition is also called screening stopping criterion problem.
The Mode aliasing refers to that one IMF (intrinsic Mode function) includes a characteristic time scale with a great difference, or similar characteristic time scales are distributed in different IMFs, so that adjacent 2 IMF waveforms are aliased, mutually affected and difficult to recognize.
The mode confusion is an important defect of the EMD, once the mode confusion is generated, the physical meaning of the finally obtained intrinsic mode function component is not clear, the accuracy of signal decomposition is affected, and the application of the mode confusion in engineering is seriously hindered.
In order to solve the problem of mode confusion of empirical mode decomposition, scholars propose some improved methods. Most notably, Huang's proposed Ensemble Empirical Mode Decomposition (EEMD) is the best known method. The method utilizes the statistical characteristic that Gaussian white noise has uniform frequency distribution, so that signals added with the Gaussian white noise have continuity on different scales, and the problem of mode aliasing is solved on a certain scale. However, there are problems such as the number of times of adding white noise and the selection of the magnitude of the added white noise are highly subjective and the method is poorly adaptive. In addition, when the number and amplitude of the added white noise are reasonably selected, the mode confusion of low frequency can be artificially caused while the mode confusion of high frequency is suppressed. Moreover, the overall local mean decomposition method has a complex algorithm and a long program running time.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for resolving modes of modes with mode confusion and finally reconstructing the modes. The analytic-empirical mode decomposition method can effectively inhibit mode confusion, has short decomposition time and higher execution efficiency.
The purpose of the invention is realized by the following technical scheme: an analytical-empirical mode decomposition method, comprising the steps of:
s1, screening the original signals through an empirical mode decomposition method to obtain n IMF components and 1 residual amount;
and S2, processing the IMF components through an analytic mode decomposition algorithm, and reconstructing the mode.
Further, the step S1 includes the following sub-steps:
s11, determining all maximum points and minimum points of original signal x (t), fitting upper and lower envelope curves of the maximum points by cubic spline curve, ensuring the interval between the upper and lower envelope curves of signal x (t), calculating local mean value of the upper and lower envelope curves, and recording as m1；
S12, calculating the difference h between the signal x (t) and the local mean value1(t)：
h1(t)＝x(t)-m1 (1)；
S13, judgment h1(t) whether or not a condition for establishing the IMF can be satisfied; if not, h is1(t) repeating steps S11 and S12 as a new original signal until h1(t) satisfying a condition that IMF is established;
s14, order C1(t)＝h1(t)，C1(t) is the first IMF component obtained by decomposition;
s15, mixing C1(t) is separated from the signal x (t) and the resulting residual signal is noted: r is1(t)＝x(t)-C1(t)；
S16, mixing1(t) repeating steps S11-S15 as new original signal, and performing n finite cycles to obtain n IMF components and 1 residual rn(t); namely:
the original signal x (t) is:
wherein, Ci(t) denotes the i-th intrinsic mode function component, rn(t) is called residual function.
Further, in step S16, the cycle number n is calculated by using a screening termination criterion based on the valid data segment, and the specific operation method includes: when intrinsic mode function Cn(t) stopping the cycle when the following conditions are met:
in the formula (I), the compound is shown in the specification,
is represented by CnAnd (t) in the effective section of the upper and lower envelope mean curves, delta represents a deviation threshold value, and the value range is 0.01-0.1.
Further, the step S2 includes the following sub-steps:
s21, sequentially recording the n intrinsic mode function components obtained by calculation in the step S1 as IMF1(t)～IMFn(t)；
For IMF1(t) performing fast Fourier transform on the component to obtain an amplitude spectrum thereof, and determining a boundary frequency f from the amplitude spectrumb1(ii) a For IMF1(t) performing analytical mode decomposition from the boundary frequency fb1The decomposition yields two signals c1(t) and
c1(t) represents IMF1(ii) a correction component of (t),
is c1(t) a residual component; namely:
s22, mixing
Addition to IMF2(t) obtaining an updated IMF2(t) as
To pair
Performing fast Fourier transform to obtain
And determining the boundary frequency f from the amplitude spectrumb2(ii) a To pair
Performing analytic mode decomposition with the boundary frequency fb2To obtain c2(t) and
wherein, c2(t) is
The correction component of (a) is,
is c2(t) a residual component; namely:
s23, removing IMFn(t) repeating the operations of steps S21 and S22 for all intrinsic mode function components except for (t);
s24 for IMFn(t) performing the following operations: will be provided with
Addition to IMFnIn (t), obtaining IMF* n(t) for IMF* n(t) performing fast Fourier transform and plotting the amplitude spectrum thereof, determining the demarcation frequency fbk(ii) a For IMF* n(t) performing analytical mode decomposition from the boundary frequency fbkObtain a signal cn(t) and
namely:
will be provided with
Added to the residual function rn(t) obtaining the final residual error, denoted as vn(t)。
The invention has the beneficial effects that:
1. the invention provides an analysis-empirical mode decomposition method aiming at the mode confusion phenomenon existing in empirical mode decomposition, and the analysis mode decomposition is carried out on the modes with mode confusion, and finally the modes are reconstructed. The analytic-empirical mode decomposition method can effectively inhibit mode confusion, and has short decomposition time and higher method execution efficiency.
2. Aiming at the problem of the inherent modal function screening termination criterion of empirical mode decomposition, the invention provides the effective data segment-based screening termination criterion, compared with the traditional screening termination criterion, the result of empirical mode decomposition obtained by using the screening termination criterion of the invention is more accurate.
Drawings
FIG. 1 is a time domain diagram of a simulated signal x (t) and two component components used in a verification test (one);
FIG. 2 is a decomposition result diagram of a verification test (one) employing a cycle termination criterion based on valid data segments;
FIG. 3 is a graph of the decomposition results of the cycle termination criteria proposed by Huang in the validation test (one);
FIG. 4 is a time domain plot of a vibration signal for verifying a gear tooth break fault used in test (II);
FIG. 5 is a diagram of a first intrinsic mode function component of vibration signal analysis-empirical mode decomposition for a gear tooth breakage fault;
FIG. 6 is a time domain waveform of the simulated signal x (t) used in the verification test (III);
FIG. 7 is a graph of empirical mode decomposition results of simulation signals from a verification test (III);
FIG. 8 is a graph of the simulated signal ensemble-averaged empirical mode decomposition results of the verification test (III);
FIG. 9 is a graph of simulated signal analysis-empirical mode decomposition results for verification test (III);
FIG. 10 is a time domain plot of a rotor fault signal used in the validation test (IV);
FIG. 11 shows a partial mean decomposition of a rotor fault signal;
fig. 12 shows the result of the rotor fault signal analysis-empirical mode decomposition.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
The invention discloses an analytic-empirical mode decomposition method, which comprises the following steps:
s1, screening the original signals through an empirical mode decomposition method to obtain n IMF components and 1 residual amount; empirical mode decomposition is a "sieving" process; screening out the component with minimum extreme value time characteristic scale, screening out the component with larger characteristic scale until the component with minimum extreme value time characteristic scale is screened outThe component with the largest characteristic dimension is screened out. That is, empirical mode decomposition yields an intrinsic mode function component C1，C2The average frequency of … … is gradually reduced. The method specifically comprises the following substeps:
s11, determining all maximum points and minimum points of original signal x (t), fitting upper and lower envelope curves of the maximum points by cubic spline curve, ensuring the interval between the upper and lower envelope curves of signal x (t), calculating local mean value of the upper and lower envelope curves, and recording as m1；
S12, calculating the difference h between the signal x (t) and the local mean value1(t)：
h1(t)＝x(t)-m1 (1)；
S13, judgment h1(t) whether or not a condition for establishing the IMF can be satisfied; if not, h is1(t) repeating steps S11 and S12 as a new original signal until h1(t) satisfying a condition that IMF is established;
s14, order C1(t)＝h1(t)，C1(t) is the first IMF component obtained by decomposition;
s15, mixing C1(t) is separated from the signal x (t) and the resulting residual signal is noted: r is1(t)＝x(t)-C1(t)；
S16, mixing1(t) repeating steps S11-S15 as new original signal, and performing n finite cycles to obtain n IMF components and 1 residual rn(t); namely:
the original signal x (t) is:
wherein, Ci(t) denotes the i-th intrinsic mode function component, rn(t) is called residual function.
The above-mentioned loop process of step S16 is when rn(t) is oneThe loop terminates when the function is monotonic, but in the actual decomposition process when r isnWhen the (t) satisfies the monotonic function condition, the number of cycles is often very large, and the number of intrinsic mode function components finally obtained by decomposition will be large. From a large number of experiments of empirical mode decomposition, it is found that most of the final components obtained by empirical mode decomposition are false intrinsic mode function components, and have no substantial physical significance.
The stopping criterion of the decomposition process proposed by Huang is achieved by limiting the size of the standard deviation between 2 adjacent IMF components, by an iteration threshold SdTo control the number of siftings. SdIs defined as:
in the formula: t is the time length of the signal; h isk(t)，hk-1(t) is the two adjacent IMF components in the decomposition process; when S isdAnd stopping the circulation when the range of 0.2-0.3 is satisfied.
It is very important to determine a reasonable iteration threshold, if the threshold is too small, the calculation amount will be greatly increased, and finally, the obtained intrinsic mode function component is meaningless. If the threshold is too large, it will be difficult to satisfy the decomposition result of the intrinsic mode function condition.
The screening termination criteria defined by Huang are in most cases more effective. It also presents some problems. As can be seen from formula (3), when h iskWhen (t) is 0, the resulting iteration threshold will be an indeterminate value if it is clearly inappropriate to use it as a screening criterion. In addition, the screening termination criterion does not fully consider the influence of the endpoint effect, and the final decomposition result has a large error after the distorted endpoint data is used. In many cases, the end-point effect of empirical mode decomposition is relatively significant, and even if some method is taken to suppress the end-point effect, the end-point effect is still present.
For SdIn the step S16, the loop is calculated by using the screening termination criteria based on the valid data segmentsThe number n, the valid segment, is the remaining segment excluding the two-end-point distorted segment. The influence of the endpoint effect on the screening criterion is fully considered in the criterion, and only the data of the effective data segment is used as the basis for calculating the iteration threshold, so that the influence of the empirical mode decomposition endpoint effect is avoided. The specific operation method in the step comprises the following steps: when intrinsic mode function Cn(t) stopping the cycle when the following conditions are met:
in the formula (I), the compound is shown in the specification,
is represented by CnAnd (t) in the effective section of the upper and lower envelope mean curves, delta represents a deviation threshold value, and the value range is 0.01-0.1.
Verification test (one); the application of the cycle termination criteria of the present invention in the empirical mode decomposition method is illustrated by a simulation signal and compared to the proposed criteria of n.e. huang. The expression of the simulation signal x (t) is:
x(t)＝x1(t)+x2(t),t∈[0,1] (5)
x1(t)＝(1+0.5sin(2π*4t))*2cos(2π*80t),x2(t)＝sin(2π*24t) (6)
the simulation signal x (t) is composed of x1(t) and x2(t) the two components. The simulated signal and the two component components are shown in figure 1. The results of empirical mode decomposition using the loop termination criteria proposed by the present invention are shown in fig. 2. The results of empirical mode decomposition using the termination criteria proposed by Huang are shown in FIG. 3. Comparing FIGS. 1, 2 and 3, it can be seen that the component C obtained by using the loop termination criteria of the present invention1Component imf derived from the termination criteria set forth in Huang1Are all relatively close to the ideal result x1(t)，C2And imf2Are all relatively close to the ideal result x2(t) which illustrates that empirical mode decomposition will fit this in the original signal regardless of which screening termination criterion is usedTwo components x1(t) and x2(t) accurately isolated. However, C1Curve ratio imf near the two end points of (A)1Is closer to the ideal curve x1(t)，C2Curve ratio imf near the two end points of (A)2Is closer to the ideal curve x2(t), which shows that the results are more accurate than those of empirical mode decomposition using the loop termination criteria proposed by the present invention.
Verification test (ii): FIG. 4 shows a gear vibration signal upon a broken tooth fault. The number of teeth of the gear is z-75, the modulus m-2, and the frequency f-n2And 60 is approximately equal to 13.6Hz, the vibration signal is decomposed by adopting an empirical mode decomposition method, and the screening termination condition of the empirical mode decomposition method adopts the criterion provided by the invention. The final result of the decomposition is 5 intrinsic mode function components imf1,imf2,…imf5。imf1Containing a large amount of information about gear failure, imf1Analysis was performed, imf1Is shown in fig. 5. From the 1 st intrinsic mode function component imf1The obvious modulation characteristic can be seen in the waveform of (1), the period T of the modulation wave is 0.074s, the frequency is approximately 13.6Hz, and the frequency is exactly equal to the rotating frequency of the fault gear. The empirical mode method based on the cycle termination criterion of the effective data segment provided by the invention can be used for accurately resolving the fault information of the actual gear vibration signal.
S2, processing the IMF components through an analytic mode decomposition algorithm, and reconstructing a mode; aiming at the mode confusion phenomenon of empirical mode decomposition, the analytic-empirical mode decomposition method is provided, the analytic mode decomposition method is used for decomposing the modes of the empirical mode decomposition method with mode confusion, and then the modes are reconstructed, so that the mode confusion phenomenon is reduced to a great extent.
An Analytical Mode Decomposition (AMD) method can separate harmonic components of each frequency band from a signal, and the principle of the method is as follows:
signal x0(t) from the dividing frequency fbThe decomposition is carried out in two parts: a fast varying signal xf(t) and a slowly varying signal xs(t)：
x0(t)＝xf(t)+xs(t) (7)
The corresponding Fourier transforms are respectively denoted as Xf(ω)、Xs(ω) that do not overlap in frequency band. Respectively to cos (2 pi f)bt)·x0(t) and sin (2 π f)bt)·x0(t) performing Hilbert transform to obtain:
H[cos(2πfbt)·x0(t)]＝xs(t)·H[cos(2πfbt)]+cos(2πfbt)·H[xf(t)] (8)
H[sin(2πfbt)·x0(t)]＝xs(t)·H[sin(2πfbt)]+sin(2πfbt)·H[xf(t)] (9)
deriving x from the above formulaf(t) and xsThe calculation method of (t) is as follows:
xs(t)＝sin(2πfbt)·H[cos(2πfbt)·x0(t)]-cos(2πfbt)·H[sin(2πfbt)·x0(t)] (10)
xf(t)＝x0(t)-xs(t) (11)。
the step S2 specifically includes the following sub-steps:
s21, sequentially recording the n intrinsic mode function components obtained by calculation in the step S1 as IMF1(t)～IMFn(t)；
For IMF1(t) performing fast Fourier transform on the component to obtain an amplitude spectrum thereof, and determining a boundary frequency f from the amplitude spectrumb1(ii) a For IMF1(t) performing analytical mode decomposition from the boundary frequency fb1The decomposition yields two signals c1(t) and
c1(t) represents IMF1(ii) a correction component of (t),
is c1(t) a residual component; namely:
s22, mixing
Addition to IMF2(t) obtaining an updated IMF2(t) as
To pair
Performing fast Fourier transform to obtain
And determining the boundary frequency f from the amplitude spectrumb2(ii) a To pair
Performing analytic mode decomposition with the boundary frequency fb2To obtain c2(t) and
wherein, c2(t) is
The correction component of (a) is,
is c2(t) a residual component; namely:
s23, removing IMFn(t) repeating the operations of steps S21 and S22 for all intrinsic mode function components except for (t);
s24 for IMFn(t) carrying out the following operationsThe method comprises the following steps: will be provided with
Addition to IMFnIn (t), obtaining IMF* n(t) for IMF* n(t) performing fast Fourier transform and plotting the amplitude spectrum thereof, determining the demarcation frequency fbk(ii) a For IMF* n(t) performing analytical mode decomposition from the boundary frequency fbkObtain a signal cn(t) and
namely:
will be provided with
Added to the residual function rn(t) obtaining the final residual error, denoted as vn(t)。
Verification test (iii): in order to prove the effectiveness and the advantages of the analytic-empirical mode decomposition method, the overall average empirical mode decomposition method and the analytic-empirical mode decomposition method are adopted to decompose the simulation signals respectively, and the decomposition results are compared.
The simulation signals x (t) are:
x(t)＝x1(t)+x2(t)+x3(t)；t∈[0,1] (15)
x2(t)＝2cos(60πt)；x3(t)＝2.5cos(28πt)；t∈[0,1] (17)
the simulated signal is shown in fig. 6. The results of the empirical mode decomposition are shown in fig. 7. As can be seen from FIG. 7, the resulting modal aliasing is more severe, the first oneMode C1(t) aliasing the high frequency intermittent signal with a 30Hz sinusoidal signal; second mode C2(t), the 30Hz sinusoidal signal is aliased with the 14Hz sinusoidal signal; the third and fourth modes are spurious intrinsic mode function components. The ensemble average empirical mode decomposition method has an ensemble average number N of 30, a noise amplitude of 0.01 times the standard deviation of the original signal, and the result of the ensemble average empirical mode decomposition is imf1、imf2、imf3、imf4As shown in fig. 8. The results of the analytical-empirical mode decomposition are shown in fig. 9. During the program run, the run times (6 run times) for the three methods were recorded, as shown in table 1. In table 1, EMD represents the empirical mode decomposition method, EEMD represents the ensemble average empirical mode decomposition method, and AEMD represents the analysis-empirical mode decomposition method.
TABLE 1 three methods run time (units s)
| Method | For the first time | For the second time | The third time | Fourth time | Fifth time | The sixth time |
| EMD | 1.3988 | 1.3860 | 1.3930 | 1.3846 | 1.3820 | 1.3940 |
| EEMD | 41.4875 | 44.8383 | 44.1800 | 42.8480 | 43.2321 | 44.024 |
| AEMD | 1.4027 | 1.3832 | 1.3843 | 1.3934 | 1.3880 | 1.3848 |
By comparing the decomposition results of the three methods, it can be found that both the ensemble empirical mode decomposition and the analytical empirical mode decomposition can suppress mode confusion, but the analytical empirical mode decomposition effect is better than that of the ensemble empirical mode decomposition method. By comparing the decomposition times of the three methods, it can be seen that the runtime of the analytical-empirical mode decomposition method is significantly lower than that of the ensemble average empirical mode decomposition method, and is similar to that of the empirical mode method. Therefore, the analytic-empirical mode decomposition has certain advantages.
Verification test (iv): fig. 10 is a vibration signal of a rotor rub fault. The rotating speed of the rotor is controlled by an input motor, and the rotating speed of the rotor is set to be 300 r/min. And the displacement sensor is horizontally arranged and used for measuring a vibration signal of the rotor with local rubbing fault. The sensor sampling frequency was set to 8 kHz. The vibration signal was decomposed using a modified method of empirical mode decomposition, local mean, and the results are shown in fig. 11. The results of the decomposition using the analytical-empirical mode decomposition of the present invention are shown in fig. 12. Comparing fig. 11 and fig. 12, it can be seen that the result mode confusion of the local mean method is more serious, and the mode confusion of the analysis empirical mode decomposition result is weaker, which indicates that the analysis empirical mode can suppress the mode confusion, and has a certain practical value for analyzing the rotor vibration signal.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.
Claims (2)
1. An analytical-empirical mode decomposition method, comprising the steps of:
s1, screening the original signals through an empirical mode decomposition method to obtain n IMF components and 1 residual amount; the original signal is a gear vibration signal with a broken tooth fault or a rotor rubbing fault; the method comprises the following substeps:
s11, determining all maximum points and minimum points of original signal x (t), fitting upper and lower envelope curves of the maximum points by cubic spline curve, ensuring the interval between the upper and lower envelope curves of signal x (t), calculating local mean value of the upper and lower envelope curves, and recording as m1；
S12, calculating the difference h between the signal x (t) and the local mean value1(t)：
h1(t)＝x(t)-m1 (1)；
S13, judgment h1(t) whether or not a condition for establishing the IMF can be satisfied; if not, h is1(t) repeating steps S11 and S12 as a new original signal until h1(t) satisfying a condition that IMF is established;
S14、let C1(t)＝h1(t)，C1(t) is the first IMF component obtained by decomposition;
s15, mixing C1(t) is separated from the signal x (t) and the resulting residual signal is noted: r is1(t)＝x(t)-C1(t)；
S16, mixing1(t) repeating steps S11-S15 as new original signal, and performing n finite cycles to obtain n IMF components and 1 residual rn(t); namely:
the original signal x (t) is:
wherein, Ci(t) denotes the i-th intrinsic mode function component, rn(t) is called residual function;
s2, processing the IMF components through an analytic mode decomposition algorithm, and reconstructing a mode; the method comprises the following substeps:
s21, sequentially recording the n intrinsic mode function components obtained by calculation in the step S1 as IMF1(t)～IMFn(t)；
For IMF1(t) performing fast Fourier transform on the component to obtain an amplitude spectrum thereof, and determining a boundary frequency f from the amplitude spectrumb1(ii) a For IMF1(t) performing analytical mode decomposition from the boundary frequency fb1The decomposition yields two signals c1(t) and
c1(t) represents IMF1(ii) a correction component of (t),
is c1(t) a residual component; namely:
s22, mixing
Addition to IMF2(t) obtaining an updated IMF2(t) as IMF2 *(t); for IMF2 *(t) performing fast Fourier transform to obtain IMF2 *(t) amplitude spectrum and determining the dividing frequency f from the amplitude spectrumb2(ii) a For IMF2 *(t) performing analytical mode decomposition from the boundary frequency fb2To obtain c2(t) and
wherein, c2(t) is IMF2 *(ii) a correction component of (t),
is c2(t) a residual component; namely:
s23, removing IMFn(t) repeating the operations of steps S21 and S22 for all intrinsic mode function components except for (t);
s24 for IMFn(t) performing the following operations: will be provided with
Addition to IMFnIn (t), obtaining IMF* n(t) for IMF* n(t) performing fast Fourier transform and plotting the amplitude spectrum thereof, determining the demarcation frequency fbk(ii) a For IMF* n(t) performing analytical mode decomposition from the boundary frequency fbkObtain a signal cn(t) and
namely:
will be provided with
Added to the residual function rn(t) obtaining the final residual error, denoted as vn(t)。
2. The method according to claim 1, wherein the step S16 is performed by using a screening termination criterion based on the valid data segment to calculate the number of cycles n, and the specific operation method is as follows: when intrinsic mode function Cn(t) stopping the cycle when the following conditions are met:
in the formula (I), the compound is shown in the specification,
is represented by CnAnd (t) in the effective section of the upper and lower envelope mean curves, delta represents a deviation threshold value, and the value range is 0.01-0.1.
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