Research On Bionic MEMS Three-Dimensional Vector Hydrophone For Suppressing In-plane Vibration Interference

Due to the prevention of the enemy's sea power,the traditional detection ships,antisubmarine aircraft and submarines have some limitations in detecting and positioning the enemy's submarines.The unmanned underwater vehicle(UUV)has the characteristics of low cost,small size,flexible operation and wide range of activities,which can supplement the shortcomings of traditional detection platform and become the focus of Naval Research in various countries.Acoustic wave is still a form of long-distance transmission under water.Hydrophone can convert acoustic signal into electrical signal.Hydrophone is the key component of underwater detection.Compared with scalar hydrophone,vector hydrophone can measure vector information in sound field and suppress isotropic noise in environment,which is the future development direction.The higher the frequency of sound wave is,the faster the attenuation rate is in the water.With the requirement for the detection distance of submarine,the working frequency of hydrophone is getting lower and lower.Small platforms such as UUV will inevitably be affected by the impact of waves,currents and other external shocks when they work,and the hydrophone can suppress the vibration interference is the basis of its practical application.In order to realize the accurate positioning of submarine,the hydrophone should be able to measure the acoustic signal in three-dimensional space.Considering the limited carrying capacity of UUV,the hydrophone should be a single integrated three-dimensional MEMS hydrophone.The piezoresistive bionic MEMS vector hydrophone proposed by North University of China based on the bionic principle has the characteristics of small size,low cost and good low frequency response.It has good application prospects in sonar system.However,the bionic MEMS vector hydrophone currently developed cannot simultaneously measure threedimensional spatial acoustic wave and suppress vibration interference.In order to solve this problem,a monolithic integrated bionic three-dimensional vector hydrophone based on MEMS is proposed,which can suppress in-plane vibration interference.(1)A bionic MEMS three-dimensional vector hydrophone for suppressing in-plane vibration interference was proposed.The hydrophone is a "cilia-supporting block-eight-beam" structure.The cilia can sense the acoustic signals in X and Y directions,and the supporting block can sense the acoustic signals in Z directions.Through encapsulation,the X/Y direction acoustic signal can be applied to cilia but not to support blocks.However,the X/Y direction vibration disturbance to the hydrophone can be applied to both cilia and support blocks.The bending moments of the cilia and the support block can cancel each other,thus reducing the stress on the piezo-resistor on the beam surface and effectively reducing the output signal of the hydrophone subjected to vibration interference.(2)Mathematical models of bionic MEMS three-dimensional vector hydrophone for suppressing in-plane vibration and noise were established.Mathematical models of the longitudinal stress of the beam were established when the hydrophone is subjected to X/Y and Z direction acoustic and vibration signals.Mathematical models for solving the first three natural frequencies of hydrophones were established.(3)Finite element simulations of bionic three-dimensional vector hydrophone for suppressing in-plane vibration interference.The effects of beam length,width,thickness,cilia radius and height,length and thickness of support block on hydrophone performance were simulated and analyzed.Considering the influence of different structure parameters on the performance of hydrophone,specific structure parameters of hydrophone were designed.The static,modal,harmonic and transient responses of the designed hydrophone and the traditional hydrophone were simulated.The accuracy of mathematical models was verified.(4)The fabrication of a bionic three-dimensional vector hydrophone for suppressing inplane vibration and noise.The influence of different process parameters on the processing results was analyzed,and the processing flow and process parameters of hydrophone chip were designed and then the integration of cilia and chip was completed.(5)Measurements of a bionic three-dimensional vector hydrophone for suppressing in-plane vibration and noise.The results of standing wave bucket test show that the acoustic sensitivity of X,Y and Z channels is-182 dB,-187 dB and-160dB(0dB = 1V/uPa)at 400 Hz,and the concave depth is 34 dB,35dB and 33 dB,respectively.The shaking table test results show that the vibration sensitivity of the hydrophone designed in this paper is reduced by about 92% at 100 Hz compared with that of the hydrophone with the traditional structure.The experimental results show that the hydrophone designed in this paper can effectively suppress the influence of in-plane vibration interference when the hydrophone is disturbed by both sound signals and vibration interference.