基于时域缩放ERA方法的工作模态辨识技术

研究了基于时域缩放选带,使用振动模态特征系统实现算法(eigensystem realization algorithm,ERA)的工作模态辨识技术.分析了ERA环境激励模态辨识方法的理论,给出了时域缩放选带技术和真实模态挑选技术的方法以及工作流程.通过算例研究了采用时域缩放技术的ERA工作模态辨识方法.研究结果表明:使用该方法可以有效地辨识出结构的模态,且可以采用滑动时间窗的方法获得模态随时间的变化结果;用于辨识的数据长度需要包含所需识别模态的6～8周期;阻尼辨识结果的偏差随阻尼比理论值变大而变小,对于理论值从1％～5％,辨识偏差从175％减小至10％;一阶和二阶阻尼比辨识结果偏差基本一致;振型辨识结果MAC值均在0.99以上.

Study on the Operational Mode Identification Based on ERA with the ZOOM Method

Based on the ZOOM method,the operational mode identification was investigated under ambient excitation based on ERA method.Firstly,the theory of the ERA method was introduced.Secondly,the strategy for decomposition and implementation was put forward,including the ZOOM method and the modes' filtration method.At last,an example as studied,where the cantilever beam was built and the white noise exciting was added.It is found that the mode can be realized by using the method,and the variety of the mode with the time can be present by using the sliding time window.A longer time period is most likely needed to capture at least 6 ～ 8 cycles of the mode for operational mode identification.The warp of the damping ratio identification becomes smaller as the theoretical value increases,where the warp changes from 175％ to 10％ as the theoretical value increases from 1％ to 5％.The warps of the firstly and secondly order damping ratio identification are basically consistent.And the MAC of the model shape is all above 0.99.