非線形船体応答のバイスペクトル解析-II. : 非線形復原力変動の影響

概要

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The non-linear ship responses, such as parametric rolling and pure loss of stability, have become the key issues in the research field of ship stability. In order to investigate these non-linear phenomena, it is well known that the higher order spectral analysis should be introduced and the non-linearity must be treated properly. In this paper, the instantaneous bispectral analysis, which is an application of the time-varying coefficient auto-regressive (TVAR) modeling to the higher order spectral analysis, is proposed to investigate the non-linear and non-stationary ship responses with focusing on the skewness of the data. First of all, the non-linear pitching motion and the fluctuating skewness, which were reported in the previous paper, are investigated and simulated using simplified equations of motion for the one-degree of freedom. Secondly, the instantaneous bispectrum is defined as an extension of the instantaneous power spectrum that is based on the TVAR model. The time history data that were obtained during on-board tests are investigated by the instantaneous bispectral analysis, and the phase angle of a peak is followed in the time domain to explain the fluctuating skewness. The effectiveness of the instantaneous bispectra is shown for analyzing the transition of skewness of non-linear ship responses.
社団法人日本航海学会の論文
2008-03-25