Ship Radiated Noise Of The Chaotic Feature Extraction Method

Underwater targets feature extraction has a very important effect on underwater acoustics. The ship targets recognition can be reached up by the nonlinear time series analysis method of phase reconstruction and chaos feature extraction. In this paper, some work has been done to extract the ship radiated noise signal on the basis of nonlinear methods and chaos theory, the main contribution of the dissertation is as follows:1. The Takens embedding theory is explored and two parameters of reconstruction including the delay time and the minimum embedding dimension are estimated. The delay time of reconstruction is confirmed by the average mutual information method. The minimum embedding dimension of reconstruction is confirmed by the false nearest neighbours method. The concept of information flow among the nonlinear state variable can help understanding the nonlinear essence.2. Nonlinear local project noise reduction on the basis of phase space reconstruction is studied. The principle of this method is to develop the lower time series into the higher phase space and decompose the higher into two orthogonal sub-spaces, then project the sub-space which has little eigenvalues to the eigenvectors which has larger eigenvalues. The nonlinear local project noise reduction method has been improved greatly to recover the origin signal and trajectories of phase space.3. Feature extraction of ship radiated noise signal is explored. It can be learned that correlation dimension can be used to classify the different types of underwater objects; there are positive maximum Lyapunov exponents and h₂ entropy, this indicated that ship radiated noise signals are chaotic.4. The recurrence plots and quantification recurrence analysis on the basis of state space reconstruction are explored. By analyzing the recurrence plots of ship radiated noise and calculating the parameters of quantification recurrence analysis, it can be learned that there are some connections between the recurrence plots of ship radiated noise and the chaos parameter such as correlation dimension; some parameters of quantification recurrence analysis can identify and classify the actual underwater object; recurrence analysis is a new valid nonlinear analyzing tool.