Research On The Application Of Acoustic Vector Sensor And Array On Underwater Small Carrier

With the constant development of acoustic vector sensor(AVS),its application on small underwater carrier has increasingly drawn more and more attentions.However,the receiving characteristics of each channel of the AVS are distorted by the scattering of the carrier,thus affecting the validity of further processing results,which has greatly constrained its application on small underwater carrier.In order to reduce the scattering influences of carrier on the receiving characteristics of AVS,and further enable the measurement validity of AVS or AVS A(acoustic vector sensor array),the researches of the AVS or AVS A application on the carrier are investigated in this paper.The key contributions are:1.Aiming at the problem that the current researches mainly focus on the scattering influences of single boundary condition(absolute rigid,soft or spherical shell,infinite cylinders that can be solved by analytic method)baffles on the measuring of AVS,the scattering influences of double layer shell on the measuring results of AVS are calculated using FEM(finite element method)coupling BEM(boundary element method).The changing relationships between AVS installation position,the density of buoyancy materials and the receiving characteristics of AVS are analyzed.For low frequency incident wave,the directivity of AVS outside the carrier presents peak value due to the diffracted wave,while the directivity of AVS inside the buoyancy materials comparatively keeps well.With the frequency increasing,the scattered wave of buoyancy materials between the inner and external shells grows,thus distorting the directivity of AVS inside the materials.Besides,when the density of the buoyancy materials grows,the Young’s Modulus also goes up,which enhances the elastic vibration and results in greater influences of sound scattering on the directivity of AVS.2.The researches in existence mainly focus on the scattering influences of different baffles on the measuring results of AVS,while rare studies have been done to decrease such influences.In this paper the method of covering sound absorption material on small underwater carrier is proposed,and the influences of its acoustic parameters(the depth of the material,the loss modulus and the covering position)on the acoustic characteristics of the carrier are analyzed.Further,the receiving characteristics of AVS installed on the carrier are compared before and after covering sound absorption material.The results show that the right part of AVS directivity is improved after covering absorption material,especially for the fan-shaped region near the undersurface.The experimental results carried out in the tank prove the validity of the simulation.3.The receiving characteristics of each channel of AVS are distorted when installed on the carrier,resulting in the DOA estimation inaccuracy,and even causes severe error when the scattering wave is large.In this paper,the changing relationships between the incident wave frequency,the installation positon of AVS,the distance from AVS to the carrier,the acoustic characteristics of the carrier and the DOA estimation accuracy of the AVS are analyzed.To improve the DOA estimation accuracy further,the inversion method is proposed which is based on calculating the measured directions using prior knowledge such as incident frequency,the real target direction and the acoustic characteristics of the carrier,and then the mapping relationship from the measured directions to real target directions are built,and at last the measured direction is mapped to real target direction in practical measuring.For the problem that the changing curve between measured direction and real target direction is not monotonic,the effective measures to enable the usability of inversion method are given.4.The scattering of small underwater carrier will distort the receiving characteristics of each channel of AVS A,thus affecting the DOA estimation performance of the array.In this paper,the signal receiving model of the array under the influences of sound scattering is built,and the influences of amplitude gain and phase deviation on conventional beam-forming,MVDR and MUSIC algorithm are analyzed.Since the influences of sound scattering on the array are different when the target is at different directions,the changing relationships between DOA estimation performance and target directions are analyzed.The results show that the changes of amplitude gain and phase deviation of the each channel are small when the target is near the normal direction of the array.As the target moves toward the array abeam direction of the array,the amplitude gain and phase deviation become large and the DOA estimation performance declines and even loses efficacy.Aiming at such phenomenon,the inversion calibration method is proposed which calculates the array manifold vector at different incident waves with the prior knowledge such as the carrier acoustic characteristics,the installing position of the array,the number of the array and array interval,and then scans the target with the calculated array manifold vector.The theoretical analysis and simulation prove that the method is effective to estimate the direction of the target.