Research of complex modal parameters extraction of a multi-degree-of-freedom structure based on similarity search

• Published in: Ocean engineering Vol. 108; pp. 307 - 314
• Main Authors: Tang, Da, Sun, Xu, Yue, Qianjin, Shi, Zhongmin, Feng, Jiaguo
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2015
• Subjects: Complex modal; Dynamical systems; Dynamics; Extraction; Free vibration; Genetic algorithm; Genetic algorithms; Loads (forces); Marine; Matching pursuit; Mathematical models; Mode superposition principle; Searching; Similarity; Mode superposition principle; Genetic algorithm; Free vibration; Complex modal; Matching pursuit
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2015.07.060

We present a method for the extraction of modal parameters that could be useful for the parameter identification of complex structural dynamic modes of multi degree of freedom systems that may be subject to environmental load excitations. The approach is linear and in this sense it operates on the basis of the principles suggested by the so-called Rayleigh superposition method. This atoms which have the form of free vibration are constructed. The method combined with MP (Matching Putsuit) and GA (Genetic Algorithm). MP is borrowed to extract every most similar atom to the random decrement of the structure response to identify modal parameters. GA is used to speed up this process. The method is applied on the analysis of model experiments for an FPSO single point mooring system and results are compared against real monitoring data. It is shown that the method is capable of extracting successfully modal characteristics such as complex modal frequency, damping ratio and mode shapes. •A method for extracting modal parameters based on similarity search is proposed.•We chose free vibration attenuation functions as the dictionary atoms.•Real modal parameters of FPSO are studied by this method for similarity search.•Overall characteristics of structure like mode shapes can be obtained by the method in this paper.