Vision-based sensing, when utilized in conjunction with camera-equipped unmanned aerial vehicles (UAVs), has recently emerged as an effective sensing technique in a variety of civil engineering applications (e.g., construction monitoring, conditional assessment, and post-disaster reconnaissance). However, the use of these non-intrusive sensing techniques for extracting the dynamic response of structures has been restricted due to the perspective and scale distortions or image misalignments caused by the movement of the UAV and its on-board camera during flight operations. To overcome these limitations, a vision-based analysis methodology is proposed in the present study for extracting the dynamic response of structures using unmanned aerial vehicle (UAV) aerial videos. Importantly, geo-referenced targets were strategically placed on the structures and the background (stationary) region to enhance the robustness and accuracy related to image feature detection. Image processing and photogrammetric techniques are adopted in the analysis procedures first to recover the camera motion using the world-to-image correspondences of the background (stationary) targets and subsequently to extract the dynamic structural response by reprojecting the image feature of the (moving) targets attached to the structures to the world coordinates. The displacement tracking results are validated using the responses of two full-scale test structures measured by analog displacement sensors during a sequence of shake table tests. The high level of precision (less than 3 mm root-mean-square errors) of the vision-based structural displacement results demonstrates the effectiveness of the proposed UAV displacement tracking methodology. Additionally, the limitations and potential solutions associated with the proposed methodology for monitoring the dynamic responses of real structures are discussed.

中文翻译：

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使用基于无人机视觉的技术监测全尺寸结构的地震反应

基于视觉的传感与配备摄像头的无人机 (UAV) 结合使用时，最近已成为各种土木工程应用（例如，施工监控、条件评估和灾后侦察）中的有效传感技术. 然而，由于无人机及其机载摄像头在飞行操作期间的移动引起的透视和比例失真或图像错位，这些用于提取结构动态响应的非侵入式传感技术的使用受到限制。为了克服这些限制，本研究提出了一种基于视觉的分析方法，用于使用无人机 (UAV) 航拍视频提取结构的动态响应。重要的，地理参考目标被战略性地放置在结构和背景（静止）区域上，以增强与图像特征检测相关的鲁棒性和准确性。在分析过程中首先采用图像处理和摄影测量技术，使用背景（静止）目标的世界到图像的对应关系恢复相机运动，然后通过重新投影（移动）目标的图像特征来提取动态结构响应附加到结构到世界坐标的目标。在一系列振动台测试期间，使用模拟位移传感器测量的两个全尺寸测试结构的响应来验证位移跟踪结果。基于视觉的结构位移结果的高精度（小于 3 毫米均方根误差）证明了所提出的无人机位移跟踪方法的有效性。此外，还讨论了与所提出的用于监测真实结构动态响应的方法相关的局限性和潜在解决方案。