Research On Key Technologies Of Integrated Acoustic Detection Of Seabed Topography Geomorphology And Subbottom Profile

Submarine resource survey and investigation,sediment classification,and research on the genesis and evolution of seabed sediments are inseparable from the effective acquisition of features information such as seabed topography,geomorphology,and subbottom profiling.Due to the limitation of acoustic detection technology,different seabed features information requires asynchronous measurement by corresponding multiple acoustic devices.The time-varying and space-varying complexity of the marine environment makes it difficult or even impossible to fuse the seabed features data obtained by asynchronous measurements with different instruments,which seriously affects the progress of scientific research based on seabed features information.This paper is based on the parametric array sound source theory and researches on the integrated acoustic detection technology of seabed features.The core idea is: based on sharing a set of innovatively designed and manufactured combined acoustic arrays,specialized electronic systems and targeted seabed reaction The signal processing method of directional scattering realizes synchronous and common-point acoustic detection of features information such as seabed topography,geomorphology,and subbottom profiling.Research on the key technologies related to the integrated detection of seabed features through three aspects: the characteristics of the phase-controlled parametric array sound source of the integrated detection,the design of the integrated system sonar array and the processing of the seabed features echo signal.Provide technology for the development and application of related systems support.Research has been carried out on the influence of the phase-controlled emission of the sound source in the phase-controlled parametric subbottom profile detection on the difference frequency sound conversion rate in the parametric sound field and the oblique incidence of the parametric sound beam on the seabed.First,the Khokhlov–Zabolotskaya–Kuznetsov(KZK)equation describing nonlinear sound propagation in Cartesian coordinates is derived,and its time-domain finite difference calculation model is constructed based on the idea of operator splitting;secondly,the concept of equivalent parametric sound source is introduced.The phase-controlled parametric sound field is equivalent to the natural directivity sound field of the virtual parametric sound source under certain inclined boundary conditions.Solve the problem that the finite difference calculation model is difficult to directly calculate the entire phase-controlled parametric sound field due to the deviation of the sound wave propagation direction;again,the oblique incident parametric sound field calculation model is established,and the sound field calculation model after the parametric sound beam is incident on the new medium is deduced The calculation parameters in the need to undergo a re-determined transformation formula;finally,the SES2000 standard parametric subbottom profiler is used as the parametric sound source to carry out numerical calculations and tank experiments to verify the correctness of the proposed phase-controlled parametric sound field model and oblique incident parametric sound field model.The seabed features integrated detection sonar array is the key to the realization of the seabed features integrated detection technology.Based on the current mainstream multi-beam sonar and parametric sonar's parameters,combined with the research results of phase-controlled parametric sound field characteristics,technical indicators for subsea integrated detection sonar are proposed.Based on the parametric emission array platform,a dual-channel wide-coverage phase-controlled emission method is proposed,so that the parametric acoustic array can be used as a phase-controlled radiation subbottom profiling detection sound source and has the ability to radiate multi-beam wide-coverage sector detection sound sources.On this basis,an integrated detection combined array consisting of a parametric array,a primary frequency receiving linear array and a two-dimensional vector hydrophone is proposed.Among them,the parametric array is used as a multi-beam sound source and a subbottom profiler's parametric sound transmitting array,and the corresponding seabed topography,geomorphology echo signals and subbottom formation echo signals are received and collected by the original frequency receiving linear array and the two-dimensional vector hydrophone respectively.Combining the integrated detection technical indicators,complete the design parameter estimation of the entire integrated array,and pass the integrated array obtained by the outsourcing process through the pool experiment to test its sound source performance.The characteristic extraction research is carried out on the collected various seabed scattering echo signals.For multi-beam echo signals,the multi-beam multi-subarray coherent algorithm is used to realize the DOA(Direction of Arrival),TOA(Time of Arrival)and the corresponding echo intensity estimation of the multi-beam echo signals scattered on the sea floor.Comprehensive analysis of various factors that affect the intensity of multi-beam echo acoustic signals,and correcting the intensity of the seabed echo signal to obtain backscattering intensity data that can directly reflect the seabed topography.For subbottom ground echo signals,it is proposed to use pulse compression technology to extract the envelope of the seabed subbottom ground profile.Aiming at the problem that the signal-to-noise of the echo signal from the oblique detection direction is lower than that in the vertical direction during phase-controlled subbottom profiling detection,the two-dimensional vector hydrophone beamforming technology is used to achieve consistent reception and spatial filtering of the target echo direction.The path of the echo signal is corrected to obtain accurate subbottom formation depth information.In order to obtain the sound velocity information of the sediments,a multi-angle backscattered sound propagation model of the inclined seafloor is proposed,and the sound velocity of the first sediments is estimated based on the time delay information of the echo signal.Finally,a set of integrated detection sonar principle prototypes that can simultaneously detect seabed topography,geomorphology and subbottom formation profiles are implemented.Construct the entire integrated detection sonar system and introduce the various modules of the system.Aiming at the problem of possible mutual interference between multi-beam sound sources and subbottom profiling detection sound sources during the detection process,an integrated detection control flow sequence is designed to separate the above two detection signals in the time domain.Through the sea test,the integrated detection function of the seabed topography,geomorphology and shallow formation profile of the sonar system was tested to verify the effectiveness of the integrated detection technology of seabed features.