Dynamic Simulation In Pool For Acoustic Characteristics Of Target And Disturb

In this thesis, a project of hardware-in-the-loop pool simulation system for the underwater target acoustic echo sound and disturb signals is presented. This system will be helpful for the research on the homing torpedo acoustic signal processing, especially on the abstraction method for the dynamic characteristics of the target echo sound received by the torpedo.In this thesis, the research on underwater target acoustic scattering is concentrated on three areas. First, the mathematical model and a numerical solve method are established for the echoed sounds, which is produced by the complex underwater targets in the shallow water. Second, the influence on the echo sound characteristics and the received signal structure, which is introduced by the relative movement between the target and the torpedo, is researched using numerical method. Finally, a dynamic pool simulation method for the underwater targets echo sound and disturb signal is presented.In the shallow water, the target echo sound structure will become complex because of the influence of the sea bottom and surface reflection. Even though the reflection times on the interface are no more than twice, one reflecting highlight in the infinite space will be turned into six highlights in the shallow water channel.In order to model the acoustic target scattering in the shallow water, first, the target with any kind of shape, such as a submarine, is modeled by geometric drawing software. Then the target strength is deduced based on the modified Kirchhoff approximation. And finally, an algorithm to predict the echoed sound signal is established using the planar element method and the indirect frequency-domain method. Using a certain submarine as the target, the target strength and the target's echo strength in near field, echo-to-reverberation ratio of bottom and surface and the echoed sound structure are calculated.To simulate the echoed sound signal characteristics of moving target, theechoed signal can be derived effectively with the planar element method.A project of hardware-in-the-loop pool simulation system is presented in this thesis. Using this system, the acoustic homing torpedo received signals can be simulated dynamically. Based on the highlight model, this system can simulate the time delay, signal strength, Doppler frequency shift and the signal arrival of azimuth for the torpedo receive signal effectively, which are caused by the target movement in the shallow water channel.It is anticipated that the results of this thesis will promote the research on the signal processing for acoustic homing torpedo.