Study on Analysis of Non-stationary Ship Motion Data

船舶参数横摇等非线性响应已成为船舶稳性研究领域的关键问题。1998年后巴拿马型集装箱船事故发生后，国际海事组织（IMO）在对完整稳性规范进行修订的同时，大力开展了时域试验和理论研究，其主要目的是发展船舶非平稳响应谱结构分析的新技术。研究工作从理论和实验的角度持续了三年。主要研究结果如下：1.理论结果：研究了随浪中的非线性纵摇运动及其脉动偏度。考虑到波浪与船体之间的几何相位关系是导致脉动偏度的主要原因，采用简化的单自由度运动方程模拟了这一现象，并提出了基于时变系数自回归（TVAR）建模和瞬时功率谱分析扩展的瞬时双谱分析方法。该方法对船舶非线性响应偏态的过渡分析具有较好的效果。最后，应用三谱分析方法确定了参数轧制的特征.实验结果：利用训练船Shioji-maru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，通过加载自制的控制单元、运动传感器和RS232 C无线通信单元，制作了1/40自航船模，进行了船舶大幅运动数据的测量。

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.