As a non-contact and full-field testing method, high-speed camera-based modal analysis has become a feasible and acknowledged approach. However, extracting small displacements from noisy images has experienced high level of difficulty, especially in high frequency range. This paper proposes a novel adaptive spatial filtering (beamforming) algorithm to extract the displacement signals using high-speed camera. In the proposed algorithm, one pixel is considered as a sensor measuring displacement and a set of pixels are therefore taken as the elements of sensor array. Then, an adaptive spatial filtering acting on this sensor array is proposed. The proposed approach mainly includes three steps. Firstly, a set of pixels are selected to compose a sensor array according to signal to distortion and noise (SINAD). Secondly, a node/antinode searching scheme is proposed based on sinusoid-based piecewise functions, which works as an adaptive filter to match mode shape and enhance modal displacement. Finally, the output of spatial filtering is adopted as the system response for the identification of modal parameters. To validate the performance of the proposed method, simulation and experiment studies are conducted based on measuring the vibration model properties of a free-free beam, which includes a comparison with LK optical flow method and conventional accelerometer-based method. The results show that the SNR of estimated displacement and computational efficiency is significantly improved without using additional sensors. The proposed method paves a way for broadening the applications of using high-speed camera for full-field vibration measurements.

作为一种非接触式全场测试方法，基于高速相机的模态分析已成为一种可行且公认的方法。然而，从嘈杂的图像中提取小位移遇到了很大的困难，尤其是在高频范围内。本文提出了一种新的自适应空间滤波（波束成形）算法来使用高速相机提取位移信号。在所提出的算法中，一个像素被视为测量位移的传感器，因此一组像素被视为传感器阵列的元素。然后，提出了一种作用于该传感器阵列的自适应空间滤波。所提出的方法主要包括三个步骤。首先，根据信噪比（SINAD）选择一组像素组成传感器阵列。其次，提出了基于正弦分段函数的节点/波腹搜索方案，该方案用作自适应滤波器以匹配模态形状并增强模态位移。最后，采用空间滤波的输出作为模态参数识别的系统响应。为了验证所提出方法的性能，基于测量自由梁的振动模型特性进行了仿真和实验研究，其中包括与 LK 光流方法和基于传统加速度计的方法的比较。结果表明，在不使用额外传感器的情况下，估计位移的信噪比和计算效率得到了显着提高。所提出的方法为扩大使用高速相机进行全场振动测量的应用铺平了道路。