基于现代谱估计理论的工况模态分析

OPERATIONAL MODAL IDENTIFICATION BASED ON MODERN SPECTRAL ESTIMATION

大型结构如涡轮发动机、桥梁和濒海建筑等通常都处于变化非常大的一种工作环境之下 ,承受某种随机的环境激励。这时就需要直接利用工况条件下的响应数据提取模态参数。根据环境激励技术 (NExT)的相关理论 ,线性结构中白噪声响应之间的相关函数与系统的脉冲响应函数具有类似的数学表达形式。本文首先将上述结论推广到复模态中 ,然后采用现代谱理论 ,运用谐波恢复的扩充的Prony方法 ,从相关函数中提取环境激励下的结构的模态参数。该方法由于对实模态和复模态进行了统一的处理 ,因而对于实模态和复模态都适用。通过仿真数值算例表明 ,该辨识方法对于环境激励下的系统辨识是合理有效的。

Latge structures such as turbines,bridges and offshore architectures are usually subjected to uncertain operating environments.In this situation it is obliged to make use of the response directly to extract modal parameters.According to the technique called the Natural Excitation Technique,the correlation functions of responses induced by white noise on linear structures have similar mathematical format as the impulse response functions.This conclusion is demonstrated and extended to the field of complex modes in the paper.Then using the extended Prony Method in the modern spectral analysis,the modal parameters of operational structures can be identified from the correlation functions.The numerical simulation shows that the method is proper and effective to the identification of structures under ambient excitation.