结构全场工作模态分析的计算机视觉测振方法
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O329

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国 家 自 然 科 学 基 金 资 助 项 目(52005522,12072378);深 圳 市 科 技 计 划 项 目(RCYX20210706092137055, ZDSYS20210623091808026)


Full-field structural modal analysis based on visual vibrometry
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    摘要:

    介绍了一种基于计算机视觉的结构模态参数辨识方法,对于连续、长时间的采样视频,该方法通过设置局部 “虚拟”测点、放大视频切片的处理方式,保证了测量结果的精度和分辨率,同时显著提高了数据处理效率。该方法 具体步骤包括:拍摄被测结构在外激励下响应历程的一段视频;通过图像边缘检测算法在结构边缘处设置若干“虚 拟”测点;通过光流法提取测点的表观运动响应,并利用随机子空间法辨识结构的模态参数;依次截取与每一阶模态 对应的整周期运动视频,通过运动放大算法获得结构的全场工作模态振型。开展了模型飞机的单频振动试验,结果 表明视觉测振的频率误差小于频率分辨率。开展了悬臂梁的模态分析试验,利用相机和激光多普勒测振仪同时进 行动力学响应测量,结果显示提出的视觉方法与激光多普勒测振仪对悬臂梁结构前五阶模态频率的测量误差不超 过 0.35%,阻尼比的测量误差不超过 14.6%,两者振型的 MAC 值高于 94%,测量结果基本吻合。

    Abstract:

    This paper introduces a method of structural modal parameter identification based on visual vibrometry. For continuous and long time sampling video, this method ensures the accuracy and resolution of measurement results by setting local “virtual” measurement points and enlarging video slices, and significantly improves the data processing efficiency. It includes several steps: recording a video of the test structure under external excitations; Setting a series of “virtual measurement points” at the edge of the structure by using edge detection algorithm; Extracting apparent motions of “virtual measuring points” using optical flow methods, and then identifying natural frequencies and modal damping ratios using the stochastic subspace method; Estimating the full-field operational mode shapes of the structure by applying motion magnification to cropped videos. Two real-life tests are conducted to validate the procedure: firstly, vibration test of a model aircraft excited by a single sinusoidal input is used, where the response peak appears in the same frequency with the known-input. Secondly, operational modal analysis of a cantilevered beam is conduct‐ ed using visual vibrometry, in which the first five modal parameters are estimated and compared to the measurement results using a Scanning Laser Doppler Vibrometer. It is shown that the maximum relative discrepancies of the natural frequencies and damping ra‐ tios are only 0.35% and 14.6%, respectively, and the modal shapes are also observed in excellent correlation.

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王路倩,王振宇,王 兴.结构全场工作模态分析的计算机视觉测振方法[J].振动工程学报,2024,37(2):226~236.[WANG Lu-qian, WANG Zhen-yu, WANG Xing. Full-field structural modal analysis based on visual vibrometry[J]. Journal of Vibration Engineering,2024,37(2):226~236.]

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