船舶结构运行模态参数辨识研究(英文)

Study on Operational Modal Parameters Identification of Ship Structures

运行模态分析是仅基于结构运行状态下的响应来提取结构模态参数的一种方法,通常假设环境激励为白噪声进行分析。实际上,船舶航行过程所受激励十分复杂,不能简单地假设为白噪声激励,由主机和螺旋桨等产生的确定频率激励同样存在。因此,航行中船舶所受激励可以假设为白噪声和简谐激励同时存在。进一步讨论了运行模态技术在船舶结构振动分析中应用的可行性和前景。研究使用带阻数字滤波技术滤除激励中的简谐成分来提高结构真实模态的辨识精度。讨论了自互功率谱密度法,并研究使用此方法提取同时受白噪声和简谐激励作用的简支梁的模态参数。实验结果表明该方法能够较准确地识别出同时受白噪声和简谐激励的结构模态参数。这对于分析航行中船舶有害振动结构的模态特征,并实施有效的减振优化措施具有很广泛的实际意义。

Operational modal analysis is a procedure which allows extracting modal parameters from a structure only based on response data under ambient excitation.It is based on the assumption that input to the structure is stationary white noise.In this paper,the application feasibility of operational modal analysis on ship structures is discussed.And band stop filter is proposed to filter the obvious harmonic energy to improve the identification precision of real modes.Then the auto-cross spectrum density method is discussed and verified by a simply supported beam experiment with white noise and harmonic excitations.This method is testified to be effective to identify the natural frequencies and operating deflection shapes.So it isfeasible and significant to identify modal parameters of ship structures under ambient excitations.