Research On Underwater Location Method Based On VIF Sound Field Characteristics Of Target

Hydroacoustic positioning technology plays an extremely important role in both military and civilian activities,and is an important part of our country’s construction of a maritime power and strengthening of coastal defense.our country has an extremely wide continental shelf,making target positioning and tracking in shallow seas particularly important.In addition,with the development of submarine stealth technology and ship vibration and noise reduction technology to this day,high-frequency radiated noise can be better suppressed,but the noise reduction effect is not obvious for the stronger penetration of low-frequency noise.Therefore,studying the propagation law of VLF acoustic signals in the ocean is of great significance for improving the detection ability of underwater acoustic equipment,and then for target detection and positioning.In response to this demand,this paper has carried out a study on the characteristics and positioning of the VLF sound field in a shallow sea environment.It has important practical value for passive positioning in shallow seas.The main research contents are(1)Sound field characteristics of Pekeris model with elastic seabedThe pekeris model with elastic seafloor and elastic seafloor is established.The normal mode method and fast field method are used to solve the model.The characteristics of acoustic vector field are analyzed.The theoretical and simulation results show that the propagation laws of sound pressure and horizontal vibration velocity are basically the same,while the propagation laws of sound pressure and vertical vibration velocity are quite different.The vertical wave impedance obtained by the combination of the two methods fluctuates greatly with distance contains more abundant sound field information.(2)Location method based on Bayesian theoryThe vertical wave impedance obtained by the joint processing of the vibration velocity field of the Pekeris model of the elastic seabed and the sound pressure is used to estimate the position of the sound source.The estimation process is regarded as a nonlinear Bayesian estimation solution process,and PSO-PF and ASSA are used to solve the problem.Among them: the introduction of particle swarm algorithm can solve the problem of poor performance of the particle filter method when the initial value is absent.In addition,it can greatly reduce the number of particles and save computing power.The adaptive simplex simulated annealing algorithm combined with simple downhill can solve the problem that the local convergence ability of simulated annealing is not strong.Comparing PSO-PF and ASSA as positioning estimators,simulation shows that both algorithms can locate sound sources more accurately.Among them,ASSA is limited to the speed of simplex contraction,which is slightly slower than PSO-PF,but has higher accuracy.(3)Experimental data processing verificationThe positioning method proposed in this paper is verified with the help of an experimental result in Qingdao.The selected methods are the particle filter algorithm optimized by particle swarm and the adaptive simplex simulated annealing algorithm.The results show that both methods can estimate the sound source target position,which proves the accuracy of the method proposed in this paper.