Performance Research And Development Of Underwater Acoustic Vector Sensor

While locating the underwater target by acoustic waves,scalar hydrophone can only measue the scalar parameter "sound pressure",but acoustic vector sensor can measure the vector parameter "particle velocity" in underwater acoustic field.Compared with the scalar hydrophone,vector sensor can detect the distance and the direction of targets at the same time,and have the advantages of restraining isotropic noise and smaller volume when forming array.In recent years,with the increasing level of muffling of ships and submarines,and the trend of diversification of measurement platforms(such as autonomous underwater vehicles,sonar buoys,towed line arrays,etc.),there is a higher demand for the comprehensive performance of acoustic vector sensors,such us measuring weaker acoustic signals,mounted on smaller measuring platforms and suspension method.Through analysis and design of the built-in vibration sensor,the purpose of increasing sensitivity and reducing volume is achieved.The integrated suspension system is designed,which has higher security compared with traditional discrete suspension system.The main research contents and results are as follows:1.The research of increasing the sensitivity of acoustic vector sensor.Through the sensitivity research and structural design of piezoelectric accelerometer with cantilever structure,the sensitivity of the accelerometer is increased.The sensitivity of the acoustic vector sensor is increased,because the the sensitivity of acoustic vector sensor is proportional to the sensitivity of its built-in acceleration sensor unit.The mathematical model of the acceleration sensor unit is established by the bending formula of Euler-Bernoulli beam combined with piezoelectric equation,electromechanical analogy and finite element simulation.Based on the mathematical model,the influence of geometry,material parameters and rigidity of fixed end on the sensitivity and upper limit frequency of the accelerometer is analyzed.Samples of piezoelectric accelerometer with cantilever structure are made and their performances are tested,which verifies the accuracy of the research results.Through increasing the height of tip mass and the thickness of metal beam,compared with the accelerometer without tip mass,the sensitivity of the accelerometer is increased by 12%and the contour volume isn't changed,which makes the sensitivity of the acoustic vector sensor increased by more than 12%.2.The research of decreasing the volume of acoustic vector sensor.Through the research and structural design of piezoelectric accelerometer with disc structure,the mass of the accelerometer is decreased.The volume of the acoustic vector sensor is decreased,because the the volume of acoustic vector sensor is proportional to the mass of its built-in acceleration sensor unit.Based on the mathematical model of accelerometer with disc structure,three orthogonal acceleration components are decoupled from its deformation under acceleration excitation in arbitrary direction in space.The influences of the geometric parameters and the fixed end on the sensitivity and upped limit frequencies of accelerometer are analyzed.Samples of piezoelectric accelerometer with disc structure are made and its performances are tested,which verifies the accuracy of the research results.The mass of the accelerometer is decreased by 10%,which makes the volume of the acoustic vector sensor decreased by 10%.3.The research of the integrated simulation method of acoustic vector sensor.Based on the research of acceleration sensor unit,the integrated simulation model of acoustic vector sensor including other components is established.The influence of the overall structure of underwater acoustic vector sensor on its performance is quantitatively analyzed.Sample of underwater acoustic vector sensor is fabricated,and the sensitivity amplitude-frequency characteristics are tested.The acoustic vector sensors are designed,which sensitivity is-180dB(@1kHz,re 1V/uPa)and the overall size is 50mm*65mm.4.The research of integrated suspension system design.The finite element model of acoustic vector sensor with integrated suspension system is established and the influence of geometrical and material parameters on its sensitivity and upper limit frequency is analyzed.The idea of parameter optimization is given.The design scheme of acoustic vector sensor with integrated suspension system is given.The scheme has the advantages of simple structure and low process requirement.