Operational modal analysis of a rotating structure under ambient excitation using a tracking continuously scanning laser Doppler vibrometer system
Operational modal analysis of a rotating structure under ambient excitation using a tracking continuously scanning laser Doppler vibrometer system
复制标题
DOI：
10.1016/j.ymssp.2020.107367
复制
发表时间：
2021-05
影响因子：
8.4
通讯作者：
L. Lyu;Wei-dong Zhu
中科院分区：
文献类型：
--
作者：
L. Lyu;Wei-dong Zhu
连续扫描激光多普勒测振仪（CSLDV）系统通过使其激光光斑沿结构表面的路径沿着连续扫描，能够快速获得空间密集的振动测量。本文提出了一种新的工作模态分析（OMA）的旋转结构的基础上严格的旋转梁振动理论，图像处理方法和数据处理方法称为提升法。提出了一种新的跟踪CSLDV（TCSLDV）系统，用于跟踪和扫描旋转结构，通过图像处理确定旋转结构的实时位置，使TCSLDV系统能够跟踪旋转结构上随时间变化的扫描路径。提升方法可以将原始TCSLDV测量值转换为多个虚拟测量点处的测量值，就好像它们是由附接到这些测量点的换能器测量的一样。通过计算和分析虚拟测量点处测量值之间具有非负时间延迟的相关函数，可以确定具有恒定速度的旋转结构的模态参数，包括阻尼固有频率、无阻尼模态振型和模态阻尼比，以及具有恒定或指定时变旋转速度的结构的操作偏转形状（ODS）。利用TCSLDV系统对OMA方法进行了实验研究，成功地估计了不同恒速旋转风扇叶片的模态参数和ODS，以及非恒速旋转风扇叶片的ODS。
A continuously scanning laser Doppler vibrometer (CSLDV) system is capable of rapidly obtaining spatially dense vibration measurement by continuously sweeping its laser spot along a path on a structure surface. This paper presents a new operational modal analysis (OMA) method for a rotating structure based on a rigorous rotating beam vibration theory, an image processing method, and a data processing method called the lifting method. A novel tracking CSLDV (TCSLDV) system was developed in this work to track and scan a rotating structure, and the real-time position of the rotating structure can be determined by image processing so that the TCSLDV system is capable of tracking a time-varying scan path on the rotating structure. The lifting method can transform raw TCSLDV measurement into measurements at multiple virtual measurement points as if they were measured by transducers attached to these measurement points. Modal parameters of the rotating structure with a constant speed, including damped natural frequencies, undamped mode shapes, and modal damping ratios, and operating deflection shapes (ODSs) of the structure with a constant or prescribed time-varying rotation speed can be determined by calculating and analyzing correlation functions with non-negative time delays among measurements at virtual measurement points. Experimental investigation is conducted using the TCSLDV system to study the OMA method with which modal parameters and ODSs of a rotating fan blade with different constant speeds, as well as an ODS of the rotating fan blade with a non-constant speed, are successfully estimated.