An out-put only modal parameter identification method based on variational mode decomposition (VMD) is developed for civil structure identifications. The recently developed VMD technique is utilized to decompose the f...An out-put only modal parameter identification method based on variational mode decomposition (VMD) is developed for civil structure identifications. The recently developed VMD technique is utilized to decompose the free decay response (FDR) of a structure into to modal responses. A novel procedure is developed to calculate the instantaneous modal frequencies and instantaneous modal damping ratios. The proposed identification method can straightforwardly extract the mode shape vectors using the modal responses extracted from the FDRs at all available sensors on the structure. A series of numerical and experimental case studies are conducted to demonstrate the efficiency and highlight the superiority of the proposed method in modal parameter identification using both free vibration and ambient vibration data. The results of the present method are compared with those of the empirical mode decomposition-based method, and the superiorities of the present method are verified. The proposed method is proved to be efficient and accurate in modal parameter identification for both linear and nonlinear civil structures, including structures with closely spaced modes, sudden modal parameter variation, and amplitude-dependent modal parameters, etc.展开更多
考虑轴承故障初期具有特征信号微弱、易受噪声干扰以及非线性强等特点。基于分形盒维数提出改进变分模态分解提取轴承故障信号非线性信息方法(Improved Variational Mode Decomposition for Nonlinear Features Extraction,IVMD-NFE)。...考虑轴承故障初期具有特征信号微弱、易受噪声干扰以及非线性强等特点。基于分形盒维数提出改进变分模态分解提取轴承故障信号非线性信息方法(Improved Variational Mode Decomposition for Nonlinear Features Extraction,IVMD-NFE)。又因非线性信号的多测度性,采用多重分形去趋势波动分析(Multifractal Detrended Fluctuation Analysis,MF-DFA)法,研究各故障信号的多重分形特征。以滚动轴承实验数据为研究对象,采用IVMD-NFE与MF-DFA方法对轴承初期信号进行故障分析与诊断。结果表明:采用IVMD-NFE方法提取的信号可较大程度滤除噪声且具有更低的分形盒维数,提取的非线性特征更具代表性;轴承故障信号呈现多重分形特征,外圈故障的奇异指数α;最大,非线性最强,保持架故障时α;最小,非线性最弱,说明通过数据复杂度可较好反应轴承运行状态,而采用VMD或直接对原始信号进行处理的方法,未能提取有效非线性特征,导致故障区分失败。展开更多
文摘An out-put only modal parameter identification method based on variational mode decomposition (VMD) is developed for civil structure identifications. The recently developed VMD technique is utilized to decompose the free decay response (FDR) of a structure into to modal responses. A novel procedure is developed to calculate the instantaneous modal frequencies and instantaneous modal damping ratios. The proposed identification method can straightforwardly extract the mode shape vectors using the modal responses extracted from the FDRs at all available sensors on the structure. A series of numerical and experimental case studies are conducted to demonstrate the efficiency and highlight the superiority of the proposed method in modal parameter identification using both free vibration and ambient vibration data. The results of the present method are compared with those of the empirical mode decomposition-based method, and the superiorities of the present method are verified. The proposed method is proved to be efficient and accurate in modal parameter identification for both linear and nonlinear civil structures, including structures with closely spaced modes, sudden modal parameter variation, and amplitude-dependent modal parameters, etc.
