Underwater Target Analysis And Software System Design Based On Extraction Of Echo Features

As a mechanical wave,sound waves do not decay that largely underwater as electromagnetic waves and lasers do.Therefore,Sound Navigation and Ranging(SONAR)has been an effective carrier for signal propagation and becomes widely used in underwater detection.Its main functions include target localization and recognition.However,the lack of core equipment(such as high-power amplifiers and transducer,etc.)and supporting technologies(such as highly precise and real-time technologies,etc.)makes SONAR unable to achieve long-distance underwater detection currently.This thesis has mainly made some related design and verified experiments on the latter issue which focuses on detection software,and some specific work has been done as follows:1)The target strength simulation models for common underwater targets,especially hypothetical military targets have been built.Based on the mathematical models of all kinds of ideal geometric target strength that have been explored,this thesis has summarized the various types of underwater targets,which include military targets(such as submarines,mines and torpedoes,etc.)and aquatic products(such as varieties of fish,etc.).Using COMSOL Multiphysics(one kind of Finite Element Method(FEM)in multi-physics),a type of hypothetical military target strength has been modeled.As the absorbing coefficient of acoustic materials was increasing,the trend of target strength has been studied.The simulation results could make prediction and estimation,and guide the design of experiment in actual.2)Two simulation models of the echo acoustic scattering of a target baffle have both been built,which were from frequency domain and transient state in TwoDimensional(2D)acoustic field.This thesis has established two simulation models of the baffle’s echo acoustic scattering from both frequency domain and transient state in 2D acoustic field.The steady-state and dynamic diagram of the Sound Pressure Level(SPL)distribution have been both drawn.The simulation results could be used as reference for the experimental design and site selection.3)The design of underwater target analysis software system has been effectively developed for complex environment in lakes.Based on Lab VIEW,this thesis has developed an underwater target analysis software system for small lake experiments.There have been two key technologies used to complete existing requirement in this software,which were the echo ranging algorithm based on highly precise peak capturing and the target strength modeling method.Finally,the experimental results and practical application have proved that the proposed prototype could be feasible,and the designed functions could be effective.