Research On Passive Localization Of Very Low Frequency Vector Sensor Based On Subsurface Buoy

Vector hydrophone can simultaneously and colocatedly measure the acoustic pressure and three orthogonal components of particle velocity,which may provide more complete sound field information compared with the traditional sound pressure hydrophone.With the development of vector hydrophone and vector signal processing technology,the application research based on vector hydrophone and vector signal processing has become more and more important.Subsurface buoy is a kind of commonly used underwater working platform.The subsurface buoy system in which a vector hydrophone is carried can long-term monitor marine environment noise field and provide data for marine science research.This dissertation is on background of the application of very low frequency vector sensor based on subsurface buoy.After reviewing the research on sea floor parameter inversion technique,matched field processing theory,bearings-only passive localization theory and the status of vector hydrophone research,this dissertation focuses on the target passive location technology,sea floor parameter inversion technique,matched field localization based on single vector hydrophone and bearings-only passive localization theory is researched.Firstly,the geoacoustic inversion based on very low frequency acoustic field interference structure is studied.The fundamental principle of geoacoustic inversion is given,and then the cost functions applied to geoacoustic inversion based on normal mode cutoff frequency and space interference distance are constructed of which the sensitivity is analyzed.By using short time FFT and "f-k," time-frequency analysis,blast pulse signal and ship radiation noise is used for getting normal mode cutoff frequency and space interference distance.The result of geoacoustic inversion is verified through sound source experiments of different depth.On foundation of the geoacoustic inversion,the matched field passive source location of single vector hydrophone is studied.For simple-frequency signal,ambiguity function can be constructed by using active intensity and reactive intensity.The peaks of this ambiguity function correspond to possible source locations.By searching sound level,the target source level can be got.The influence of parameter mismatch(receiving depth,sediment density,sediment sound speed,etc.)on simple-frequency signal single vector hydrophone matched field localization is simulated and analyzed.The feasibility of the method is verified by the sea trial data.For broadband signal,an improved Bartlett processor which can both reduce the side lobe numbers and improve the main lobe intensity is proposed.The influence of parameter mismatch on broadband signal single vector hydrophone matched field localization is simulated and analyzed.The feasibility of the method is verified through sound source experiments data and ship radiation noise.Bearings-only passive localization based on multiple subsurface buoys is studied.Starting with the bearings-only passive positioning system principle,the location precision of the two subsurface-buoy system based on the vector hydrophone is analyzed.Mathematical expressions for Geometrical Dilution of Precision(GDOP)are derived under this condition,and the observability analysis is given.Combined with the application conditions of vector hydrophones and subsurface-buoys,the selections of simulation parameters are given.The impacts of the base length,direction errors,station position errors and target position on the positioning accuracy are studied.Taking four-station system for example,the positioning accuracy and applicable conditions of regular triangle arrangement,rhombus arrangement and"Y"arrangement are analyzed.The analysis of bearings-only passive localization is verified by use of sea trial data.