Inversion Of Sound Velocity Profile And Waves Based On Multi-beam Echo Sounding

Considering complex and changeable ocean environment,efficiently and conveniently obtaining the ocean environmental parameters is one of the key research directions in ocean science.Sound speed profile(SSP)determined by hydrological parameters is a critical fundamental data for the application of ocean acoustic technology.Point measuring instruments,such as conventional Sound Velocity Profile(SVP)and Conductivity-Temperature-Depth Instrument(CTD),have low efficiency and limited coverage.However,hydroacoustic method using echo data to estimate hydrological parameter has the advantages of rapid observation and wide coverage,and has a broad application prospect.Therefore,inversion methodology for SSP and relevant hydrological parameters,which combines the sound propagation model and the observation data,has gradually aroused concerns from academia and industry.Since the accuracy of Multibeam Echo Sounder(MBES)is greatly affected by the accuracy of the sound speed profile,and measured time of arrival(TOA)and degree of arrival(DOA)cover the SSP information,this thesis proposes a novel experimental idea of inverted MBES: The MBES is fixed upside down,and the acoustic wave is emitted to the sea surface and the corresponding echo is received.The intersection of the transmitting and receiving beams forms beam footprints,TOA and DOA are obtained by the system.The SSP and the sea surface waves are retrieved by the redundancy between multiple measured values.This thesis realizes SSP inversion algorithm based on inverted MBES.The proposed inversion method takes the actual TOA and DOA measured by system as true value,and combines the principles of multi-beam bathymetry,sound ray tracking,and sea surface modeling to perform sound ray inverse tracking to calculate the estimated TOA and DOA when the sound speed profile changes.Genetic algorithm is used to search the SSP information and sea height change information represented by the empirical orthogonal function simultaneously and find the global optimal solution to minimize the difference between the actual TOA and the estimated TOA,and finally get SSP and sea surface waves.Based on new experimental idea and inversion algorithm,this thesis completes the design,integration and landing of the test system.The design of the overall architecture and installation scheme of the inverted MBES system is proposed.According to the inversion algorithm and the related requirements of the multi-beam system,the appropriate auxiliary equipment is selected and the design of the power module and the data forwarding module is completed.The design of system control and data acquisition software under the new experimental idea is completed as well considering the communication protocol and data format of each device.Two sea trials are conducted in the thesis using the inverted MBES system.These two experiments verify the effectiveness of the inversion system and the system-control and data-acquisition software,while the proposed inversion algorithm is utilized to process and analyze the collected data.The feasibility and effectiveness of the inversion algorithm are verified,and the impact of different factors on the accuracy of the inversion algorithm is analyzed according to the estimation results in different experimental scenarios.