Study on Analysis of Non-stationary Ship Motion Data

船舶的非线性响应，如参数横摇等，已成为船舶稳定性研究领域的关键问题。1998年发生的巴拿马型集装箱船事故后，在时域上进行了大量的实验和理论研究，国际海事组织完整稳性规则的修订工作正在进行中。本研究的主要目的是开发分析船舶非平稳响应谱结构的新技术。研究工作从理论和实验的角度持续了三年。结果总结如下：1。理论结果：研究了后续海域的非线性俯仰运动及其波动偏度。由于波浪与船体之间的几何相位关系可以被认为是波动偏度的主要原因，因此采用简化的单自由度运动方程和基于时变系数自回归（TVAR）模型和瞬时功率谱分析的扩展的瞬时双谱分析来模拟波动偏度现象。结果表明，该方法在分析船舶非线性响应的偏度转换时是有效的。最后，应用三谱分析方法对参数轧制特性进行了验证。实验结果：利用Shioji-maru训练船进行了船上测量，并与日本海岸警卫队合作，利用野岛角的雷达波观测系统获得了可靠的波浪数据。在此基础上，通过加载自制控制单元、运动传感器和RS232C无线通信单元组成1/40比例的自推进模型船，测量船舶的大振幅运动数据。

The non-linear ship responses, such as parametric rolling, have become the key issues in the research field of ship stability. After an accident of a post-Panamax container ship happened in 1998, the experimental and theoretical studies in the time domain are carried out vigorously and revision of the Intact Stability Code of the International Maritime Organization (IMO) is now under way.The main objective of this research is development of new techniques for analyzing the spectral structure of non-stationary ship responses. The research work was continued for three years from the theoretical and experimental viewpoints. The results are summarized below:1. Theoretical results: The non-linear pitching motion in following seas and its fluctuating skewness were investigated. Since the geometrical phase-relationship between waves and ship's hull can be considered as the main cause of the fluctuating skewness, the phenomenon was simulated by using simplified equations of motion for a single-degree-of-freedom and the instantaneous bispectral analysis, which is based on Time-varying coefficient autoregressive (TVAR) modeling and an extension of the instantaneous power spectral analysis, was proposed. The effectiveness of the proposed method was shown for analyzing the transition of skewness of non-linear ship responses. Finally, the characteristics of the parametric rolling were confirmed by applying the tri-spectral analysis.2. Experimental results: On board measurements were carried out using the training ship Shioji-maru and the radar wave observation system at Nojima cape was used to obtain reliable wave data in corporation with Japan Coast Guard. Furthermore, a 1/40 scale self propulsive model ship was made up by loading the hand-made control unit, motion sensor and RS232C wireless communication unit to measure the large amplitude ship motion data.