CN111488801A - Ship classification method based on vibration noise identification - Google Patents
Ship classification method based on vibration noise identification Download PDFInfo
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Abstract
The invention discloses a ship classification method based on vibration noise identification, which comprises the following steps: 1. collecting ship vibration noise and converting the ship vibration noise into a time domain signal; 2. carrying out improved set empirical mode decomposition on the ship vibration signal; 3. performing Hilbert-Huang transformation on the signals subjected to modal decomposition; 4. hilbert spectrum analysis of ship radiation noise; 5. extracting ship noise features; 6. classifying the ship noise characteristics by using a ship classifier based on a support vector machine; 7. verifying the accuracy of the ship classification result, and if the accuracy is correct, finishing the ship classification; and if not, entering the ship classifier to reclassify again. The invention realizes a ship classification method based on vibration noise identification, and provides a new way for marine traffic managers, scientific researchers and military personnel to obtain ship types.
Description
Technical Field
The invention relates to the technical field of ship type identification, in particular to a ship classification method based on vibration noise identification.
Background
Ship vibration noise feature identification is one of the very leading issues in underwater acoustic signal processing. When a ship passes by, the sonar can realize the sensing, classification, tracking and positioning of the ship through the processing and recognition of the ship vibration noise signals, and has important significance for guaranteeing the ship navigation safety, the marine traffic management, the national defense safety and the like. The ship radiation noise generation mechanism is complex and influenced by the complex marine environment, so that the ship radiation noise generation mechanism has non-smooth and non-linear characteristics. The traditional signal processing methods such as time domain waveform feature extraction, frequency domain spectrum analysis, wavelet transformation in a time-frequency domain and the like have limitations when processing the problems, can not well extract the features of the ship radiation noise signals, and further can not accurately identify and classify ships.
In recent years, a large amount of research has been carried out by scholars at home and abroad on a ship classification method based on acoustic features, and certain results have been obtained, wherein the method based on the Hilbert-Huang transform has prominent advantages in processing the problems. A time-frequency analysis method combining Bark wavelet analysis and Hilbert-Huang transform is proposed in reference [1] (WangShuguang, ZengXiang. robust underserver noise targets classification of an automatic analysis [ J ]. Applied Acoustics,78:68-76.) to classify ships; the method for extracting the complexity characteristic of the radiation noise of the ship based on the multi-scale arrangement entropy is provided on the basis of the ensemble empirical mode decomposition by using a reference document [2] (the philosophy, Liyaan. the ship radiation noise complexity characteristic extraction research [ J ] vibration and impact, 2019,38(12): 225-. The feasibility of the Hilbert-Huang transform and the improved method thereof for extracting and classifying ship noise features is proved by the method, but the method is classified based on single features and does not comprehensively consider information such as energy, frequency, noise amplitude and the like.
Disclosure of Invention
The invention aims to overcome the defects of the technology and provide a ship classification method based on vibration noise identification.
In order to achieve the purpose, the invention adopts the following technical scheme: a ship classification method based on vibration noise identification is characterized by comprising the following steps:
7, verifying the accuracy of the ship classification result, and if the accuracy is correct, finishing the ship classification; and if not, entering the ship classifier to reclassify again.
Preferably, in step 1, the ship vibration noise is acquired from underwater by using sonar and hydrophone equipment.
Preferably, in step 2, a spurious component in the signal is removed by a method of calculating a Permutation Entropy (PE), and a main Intrinsic Mode Function (IMF) component is screened out, so as to suppress the modal aliasing phenomenon.
Preferably, in step 3, the instantaneous frequency of each order of IMF is solved using a hilbert-yellow transform, thereby obtaining an amplitude-time-frequency representation of the signal, i.e. a hilbert spectrum, and the hilbert marginal spectrum is obtained by calculating the integral of the hilbert spectrum over the entire period.
Preferably, in step 4, each type of ship radiation noise is decomposed into a series of IMF components with different numbers and different oscillation periods through MEEMD, and the normalized energy of each IMF component and the correlation coefficient between the IMF component and the original noise signal are obtained.
Preferably, the correlation coefficient represents the similarity between the IMF component and the original noise signal, the IMF component with a larger correlation coefficient has a high similarity with the original noise signal and should have more energy, the IMF component with the highest correlation coefficient is selected as the ship noise characteristic component, which is called the strongest IMF component, and 4 characteristic parameters, namely the strongest IMF component energy, the strongest IMF average amplitude, the strongest IMF average instantaneous frequency and the strongest IMF center frequency, are adopted.
Preferably, the extracted 4 kinds of feature parameters are converted into feature vectors and input into the SVM for vessel classification and identification, and the SVM classification result is compared with the actual value. If the classification is correct, finishing the ship classification; otherwise, the signal is input into the SVM for reclassification.
The ship classification method based on the multi-feature noise component has the advantages that the ship classification method based on the multi-feature noise component is realized, the defect that the classification is carried out by means of single feature in the current method is technically made up, and the improvement of the identification accuracy rate is facilitated. The ship classification method based on vibration noise identification can realize underwater identification and hidden detection, provides an effective ship identification, classification and supervision means without influencing water traffic, and has wide application prospects in the fields of marine traffic management, ship navigation safety, national defense safety and the like.
Drawings
FIG. 1 is a flow chart of a ship classification method based on vibration noise identification according to the present invention;
FIG. 2 is a time domain graph of the radiated noise of a ship according to the present invention;
FIG. 3 shows the MEEMD decomposition result of the ship radiation noise of the present invention;
FIG. 4 is a Hilbert-Huang spectrum of the radiated noise of a ship according to the present invention;
fig. 5 is a hilbert marginal spectrum of the radiated noise of the ship of the present invention.
FIG. 6 is a graph comparing normalized energy and correlation coefficient of the ship radiation noise of the present invention.
Detailed Description
Fig. 1 is a ship classification method based on vibration noise identification according to the present invention, and as shown in fig. 1, the method of this embodiment may include:
7, verifying the accuracy of the ship classification result, and if the accuracy is correct, finishing the ship classification; and if not, entering the ship classifier to reclassify again.
Further, the ship vibration noise collection comprises: the equipment such as sonar and hydrophone is used for acquiring the ship vibration noise from the underwater and converting the ship vibration noise into a time domain signal, and a time domain signal diagram of the ship vibration noise is shown in fig. 2.
Further, the improved ensemble empirical mode decomposition of the ship vibration signal includes: and eliminating false components in the signals by a method of calculating the permutation entropy, screening out main intrinsic mode function IMF components, and further inhibiting the mode aliasing phenomenon. The MEEMD algorithm comprises the following specific steps:
(1) adding white noise signal n with zero mean value to original signal x (t)i(t) and-ni(t), obtaining:
wherein the white noise amplitude aiFrom 0.1 to 0.2 times the standard deviation of the original signal.
(2) Are respectively pairedAndperforming EMD decomposition to obtainAndtaking the integrated average to obtain:
where N is the number of samples of the signal x (t) to be analyzed.
(3) Calculating IMF'1(t) a entropy value θ, if θ is greater than the predetermined entropy value θ0Then it is considered as an abnormal signal. The preset arrangement entropy value is obtained through a plurality of experiments according to the researched signal, theta0The value is 0.6.
(4) Repeating the processes of (2) - (3) until IMF'p(t) is not an anomaly signal.
Removing the decomposed first p-1 false components from the original signal, and decomposing the residual signal R (t) to obtain:
wherein C isjAnd (t) and r (t) are respectively an IMF component and a remainder, and m is the number of IMFs obtained by EMD decomposition. The original data sequence is decomposed into the sum of m IMF components and the remainder by the MEEMD method, the remainder represents the average trend of the data, and the MEEMD decomposition result is shown in FIG. 3.
Further, the hilbert-yellow transform is performed on the signal after modal decomposition, and includes: solving the instantaneous frequency of each order of IMF by using Hilbert transform, thereby obtaining an amplitude-time-frequency representation of the signal, namely a Hilbert spectrum; the Hilbert marginal spectrum is obtained by calculating the integral of the Hilbert spectrum over the entire period.
The method comprises the following specific steps:
and performing Hilbert transform on each IMF component obtained by decomposition to obtain:
calculating the instantaneous amplitude a from the analytic signalj(t) and instantaneous frequency fj(t) is:
whereinIs the instantaneous phase. The instantaneous frequency extracts the frequency changing along with time in the signal, and compared with signal processing modes with fixed basis functions, such as Fourier transform, wavelet transform and the like, the method has the advantage of self-adaptive signal analysis. The hilbert spectrum of the signal is obtained by calculation and is expressed as:
the hilbert spectrum is the distribution of instantaneous amplitude on a frequency-time plane, and has good time-frequency aggregation.
Integration of H (ω, t) in the time domain yields the marginal spectrum:
wherein T is the period. The marginal spectrum describes the distribution of the same frequency amplitude or energy superposition value in the frequency domain in the whole time frequency of the signal. Fig. 4-5 are hilbert-spectrum and hilbert marginal spectrum, respectively.
Further, the hilbert spectrum analysis of the ship radiation noise includes: the radiation noise of various ships is decomposed into a series of IMF components with different quantities and oscillation periods through MEEMD. The normalized energy of each IMF component and the correlation coefficient with the original noise signal are found, as shown in fig. 6.
Further, the extraction of the ship noise features comprises: the IMF component with a larger correlation coefficient has a higher similarity to the original noise signal and should also carry more energy. And selecting the IMF component with the highest correlation coefficient as the ship noise characteristic component, namely the strongest IMF component. 4 characteristic parameters of strongest IMF component energy, strongest IMF average amplitude, strongest IMF average instantaneous frequency and strongest IMF center frequency are adopted. Further, let the strongest IMF component include N samples, after Hilbert transform, the instantaneous amplitude of the nth sample is anInstantaneous frequency of fnThen the instantaneous energy of the pointThe strongest IMF component QmaxIs defined as:
mean amplitude a of the strongest IMFmeanIs defined as:
strongest IMF mean instantaneous frequency fmeanIs defined as:
further, the ship classifier based on the support vector machine comprises: 4 kinds of extracted ship radiation noise characteristics, namely Qmax、amean、fmean、And converting the characteristic vectors into characteristic vectors, inputting the characteristic vectors into the SVM, and performing ship classification and identification.
Further, the classification result verification includes: and comparing the SVM classification result with the actual value. If the classification is correct, finishing the ship classification; otherwise, the signal is input into the SVM for reclassification.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (7)
1. A ship classification method based on vibration noise identification is characterized by comprising the following steps:
step 1, collecting ship vibration noise, and converting the ship vibration noise into a time domain signal;
step 2, carrying out improved set empirical mode decomposition on the ship vibration signal;
step 3, performing Hilbert-Huang transformation on the signals subjected to modal decomposition;
step 4, Hilbert spectrum analysis of ship radiation noise;
step 5, extracting ship noise characteristics;
step 6, classifying the ship noise characteristics by using a ship classifier based on a support vector machine;
7, verifying the accuracy of the ship classification result, and if the accuracy is correct, finishing the ship classification; and if not, entering the ship classifier to reclassify again.
2. The ship classification method based on vibration noise identification according to claim 1, wherein in step 1, ship vibration noise is acquired from underwater by using sonar and hydrophone equipment.
3. The method of claim 1, wherein in step 2, false components in the signals are removed by calculating a Permutation Entropy (PE), and a main Intrinsic Mode Function (IMF) component is selected to suppress modal aliasing.
4. The method of claim 1, wherein in step 3, the instantaneous frequency of each IMF is solved by using Hilbert-Huang transform to obtain the amplitude-time-frequency representation of the signal, i.e. Hilbert spectrum, and the Hilbert marginal spectrum is obtained by calculating the integral of the Hilbert spectrum over the whole period.
5. The ship classification method based on vibration noise identification according to claim 1, wherein in step 4, each ship radiation noise is decomposed into a series of IMF components with different numbers and different oscillation periods through MEEMD, and the normalized energy of each IMF component and the correlation coefficient between the normalized energy and the original noise signal are obtained.
6. The ship classification method based on vibration noise identification according to claim 5, wherein the correlation coefficient represents the similarity degree between the IMF component and the original noise signal, the IMF component with the larger correlation coefficient has the high similarity degree with the original noise signal and should have more energy, the IMF component with the highest correlation coefficient is selected as the ship noise characteristic component, which is called the strongest IMF component, and 4 characteristic parameters including the strongest IMF component energy, the strongest IMF average amplitude, the strongest IMF average instantaneous frequency and the strongest IMF center frequency are adopted.
7. The ship classification method based on vibration noise recognition of claim 6, wherein the extracted 4 feature parameters are converted into feature vectors and input into SVM for ship classification recognition, and the SVM classification result is compared with an actual value. If the classification is correct, finishing the ship classification; otherwise, the signal is input into the SVM for reclassification.
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CN112525467A (en) * | 2020-11-26 | 2021-03-19 | 山东科技大学 | Impact damage area identification method and device suitable for cantilever beam |
CN112651385A (en) * | 2021-01-18 | 2021-04-13 | 西北工业大学青岛研究院 | Magnetic anomaly multi-feature information extraction method based on Hilbert-Huang transform |
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CN112183280A (en) * | 2020-09-21 | 2021-01-05 | 西安交通大学 | Underwater sound target radiation noise classification method and system based on EMD and compressed sensing |
CN112525467A (en) * | 2020-11-26 | 2021-03-19 | 山东科技大学 | Impact damage area identification method and device suitable for cantilever beam |
CN112525467B (en) * | 2020-11-26 | 2022-09-13 | 山东科技大学 | Impact damage area identification method and device suitable for cantilever beam |
CN112651385A (en) * | 2021-01-18 | 2021-04-13 | 西北工业大学青岛研究院 | Magnetic anomaly multi-feature information extraction method based on Hilbert-Huang transform |
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CN113189624A (en) * | 2021-04-30 | 2021-07-30 | 中山大学 | Adaptive classification multipath error extraction method and device |
CN113189624B (en) * | 2021-04-30 | 2023-10-03 | 中山大学 | Self-adaptive classification multipath error extraction method and device |
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