Abstract
In view of the problem that the features of ship-radiated noise are difficult to extract and inaccurate, a novel method based on variational mode decomposition (VMD), multi-scale permutation entropy (MPE) and a support vector machine (SVM) is proposed to extract the features of ship-radiated noise. In order to eliminate mode mixing and extract the complexity of the intrinsic mode function (IMF) accurately, VMD is employed to decompose the three types of ship-radiated noise instead of Empirical Mode Decomposition (EMD) and its extended methods. Considering the reason that the permutation entropy (PE) can quantify the complexity only in one scale, the MPE is used to extract features in different scales. In this study, three types of ship-radiated noise signals are decomposed into a set of band-limited IMFs by the VMD method, and the intensity of each IMF is calculated. Then, the IMFs with the highest energy are selected for the extraction of their MPE. By analyzing the separability of MPE at different scales, the optimal MPE of the IMF with the highest energy is regarded as the characteristic vector. Finally, the feature vectors are sent into the SVM classifier to classify and recognize different types of ships. The proposed method was applied in simulated signals and actual signals of ship-radiated noise. By comparing with the PE of the IMF with the highest energy by EMD, ensemble EMD (EEMD) and VMD, the results show that the proposed method can effectively extract the features of MPE and realize the classification and recognition for ships.
Highlights
Ships are important equipment in the marine field
By comparing with the permutation entropy (PE) of the intrinsic mode function (IMF) with the highest energy by Empirical Mode Decomposition (EMD), ensemble EMD (EEMD) and variational mode decomposition (VMD), the results show that the proposed method can effectively extract the features of multi-scale permutation entropy (MPE) and realize the classification and recognition for ships
Ambient noise, which is constituted by contributions from numerous natural and anthropogenic sources, has made it difficult to extract the features of ships that can reflect properties of the ship from the ship-radiated noise [1,2]
Summary
Ships are important equipment in the marine field. Ship-radiated noise can reflect some important physical properties of ships, so the research of ship-radiated noise is of great significance. Feature extraction of ship-radiated noise is one of the key problems in the field of underwater acoustic signal processing and plays a significant role in research and practical application. Many studies have extracted features of signals by PE combining VMD, EMD, or EEMD in the fields of medicine [23,24,25], fault diagnosis [26,27,28,29,30], and underwater acoustic signal processing [31]. Research in [15] extracts the energy difference between the high- and low-frequency characteristics from different ship-radiated noise signals by EEMD. In this paper, based on the above analysis, a new method for feature extraction of ship-radiated noise is presented by taking advantage of the VMD and MPE. The outline of this paper is as follows: Section 1 is the introduction; Section 2 is the basic theory of VMD and MPE; in Section 3, the review of the proposed method for feature extraction of ship-radiated noise is presented; in Section 4, the proposed method is applied to simulation experimental data; in Section 5, the proposed method is applied to ship-radiated noise signals; and, Section 6 is the conclusion
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