| The wake generated by dynamic target motion in sea surface or layered seawater is one of the main motion features of dynamic targets in the ocean.The study of the electromagnetic scattering characteristics and identification and positioning of the dynamic target's wake in the complex ocean environment plays an important role in the field of target recognition and characteristic parameter inversion.It plays an important role in target recognition and feature parameter inversion.This paper studies the distribution characteristics of Kelvin wakes and internal wave wakes generated by dynamic targets under a two-dimensional rough sea background,and proposes a sea wake identification and detection method based on feature selection verification method : regarding the large-scale rough sea surface,the wake superposition is regarded as the change of local sea surface wave energy,and the wake division recognition and detection are realized by extracting and comparing the mean value of the feature difference of the correlation function;when the size of the wake distribution is close to the size of the sea surface,based on the influence of the wake on the electromagnetic scattering characteristics of the sea surface,the feature selection verification method is used to extract and quantify the change characteristics of the electromagnetic scattering characteristics,and the law of the electromagnetic scattering characteristics of the rough sea surface before and after the superimposed wakes with the characteristic parameters is obtained,so as to realize the identification and detection of the wakes.The main work content is as follows:(1)The two-dimensional sea-spectrum model and the directional spectral function are studied.Combining the characteristic expression of sea surface anisotropy by the directional distribution function,and comprehensively considering the computational complexity of the directional distribution function,a comparison and evaluation method of the directional distribution functions with different wave ratios under typical sea conditions is proposed.It provides an effective theoretical basis for the selection of the direction distribution function when modeling the two-dimensional rough sea surface.(2)The generation mechanism of random rough sea surface and dynamic target wake is studied.The geometric models of the two-dimensional large-scale rough sea surface,the Kelvin wake of the sea surface ship and the internal wave wake in the layered seawater are obtained by geometric modeling calculation.The relationship between sea surface and wake and sea surface modeling parameters,hull operating parameters and hull structure parameters are analyzed,and the law of sea surface wave height and wake changing with the above parameters is discussed.(3)The partition recognition and detection methods of Kelvin wake and internal wave wake under the background of large-scale rough sea surface are studied.First,the wake is regarded as the change of local sea surface wave energy in the large-scale rough sea surface,the rough sea surface is divided into regions,and the Radon transform is used to extract the detection amount of the correlation function of the sea surface in each region.Then the feature selection verification method is used to extract and compare the feature differences of the detected quantities,and the average value of the regional sea surface feature differences and their change characteristics are obtained.And based on the mapping relationship between the change of the mean value of the feature difference and the sea surface wind speed,ship sailing speed and other parameters,a method and applicable conditions for realizing dynamic target wake recognition using the partition detection method are proposed.(4)The electromagnetic scattering characteristics of the two-dimensional rough sea surface before and after superimposed wakes are studied.Based on the two-scale method,the influence of sea surface wind speed,wind direction,hull structure size and ship sailing speed on the backward electromagnetic scattering characteristics of rough sea is compared and analyzed.When the rough sea surface is superimposed with wakes of similar distribution area,the feature selection verification method is used to compare the changes of the sea surface backscattering coefficient,and the change characteristics are extracted and quantified,so that the impact of dynamic target wakes on the rough sea surface electromagnetic scattering can be systematically evaluated.Through the feature selection verification method,the influence of wakes on the electromagnetic scattering characteristics of the sea surface is numerically quantified and rated,and the influence of typical parameters such as sea surface wind speed and ship sailing speed on the evaluation level is comprehensively considered,and the applicable conditions for using electromagnetic scattering characteristics to realize wake identification are determined.This paper proposes two dynamic target generation wake recognition methods based on feature selection verification methods under different superposition conditions: one is to compare the mean value of the difference between the subregional sea surface feature selection,and realize the identification and detection of the large-size rough sea surface superimposed wake through the calculation of the comparison value parameter;one is to systematically evaluate and quantify the influence of wakes on the backscattering coefficient of the sea surface,and realize the identification and detection of wakes that are similar in size to the sea surface to be measured according to the FSV evaluation level.The recognition results of the two methods are affected by parameters such as sea surface wind speed and ship sailing speed.The calculation results show that under suitable parameter conditions,both methods can intuitively and accurately realize the wake identification. |
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