Algorithms for passive detection of moving vessels in marine environment

Abstract

In this paper, an investigation on the development of a low-cost passive hydroacoustic system for passive detection of moving vessels to counteract possible collision with an unmanned underwater vehicle is presented. The main goal of this paper is to determine if moving vessels generating hydroacoustic signals/signature are present in the space being searched, and if so, to determine the time delay ΔT between two signals (V1(t) and V2(t)) and consequently to estimate the bearing on the source of the hydroacoustic signals, for example, screw propellers of a moving vessel. The acoustic signals V1(t) and V2(t) have been recorded by a two hydrophones mounted in an unmanned underwater vehicle. In practice, signals V1(t) and V2(t) are heavily corrupted by the additional noise. The noise comes from surrounding environment and from the measurement system errors. Moreover, real signals are often unsteady (nonstationary) and random (stochastic). That is why the different methods have been taken under consideration and the received results have been compared. An analysis has been made for time and frequency domain as well. Due to the planned application of the obstacles detection system in the unmanned underwater vehicle, the algorithm had to be feasible for implementation in digital signal processor.