FSDD运行模态参数识别方法中不确定性的计算

UNCERTAINTY CALCULATION IN FREQUENCY SPATIAL DOMAIN DECOMPOSITION MODAL PARAMETERS IDENTIFICATION METHOD

运行模态参数识别是一种只利用响应数据进行模态分析的方法.环境激励条件下获得的识别结果会存在随机不确定性,这种不确定程度可以通过模态参数的统计特性进行描述评价.以运行模态分析中的频域空间域分解方法(FSDD)为研究对象,通过对整个模态识别算法进行摄动分析,确定出模态参数对测量误差的灵敏度,实现了模态参数方差的计算.计算过程分为四步:第一步,响应信号功率谱矩阵中噪声方差的估计;第二步,增强功率谱方差的计算;第三步,极点协方差的计算;第四步,模态参数方差的计算.最后通过一个4自由度仿真算例与张家港桥梁实测算例对所给出的方法进行了验证与应用.

Operational modal parameters identification is a modal analysis method,which only is based upon the response data. The modal parameters obtained from ambient vibration are subject to statistical un- certainty. The uncertainty can be evaluated by its statistical characteristics. Variance calculation in frequen-cy spatial domain decomposition is illustrated based on sensitivity analysis of the algorithm. The calculation flow includes four steps： （1） Estimating covariance of power spectrum density,（2） Calculating variance of enhanced power spectrum density, （3） Calculating poles covariance, （4） Calculating modal parameters vari-ance. Finally,the present method is validated by comparing the computational result of four DOFs system with the experimentally measured results of Zhang-Jia-Gang bridge.