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原文传递 Novel Vision Sensor for Remote Measurement of Bridge Displacement.

题名：	Novel Vision Sensor for Remote Measurement of Bridge Displacement.
作者：	Feng, M. Q.
关键词：	Bridge Displacement, Bridge sites
摘要：	Bridge dynamic responses can reveal significant information about the structural health condition. This project develops a camera-based computer vision sensor system for accurate remote measurement of multipoint bridge displacements in outdoor environments. The vision sensor tracks the movement of natural targets on the structure from a convenient remote location without accessing the bridge toinstallation at bridge sites and thus the cost of the equipment and operation is much lower than conventional sensors. In addition, the measurement points can be easily altered in post processing of the video. However, outdoor conditions such as changes in illumination and background, heat haze-induced image distortions, and camera vibration can cause significant measurement errors. To overcome these challenges, this project develops innovative algorithms and methods including (1) a gradient-based template matching algorithm for robust tracking of “natural” markers (such as rivets on a bridge), integrated with a subpixel technique for enhancing image resolution required for multipoint measurement; (2) a heat haze filtering technique based on detection and statistical characterization of heat haze-induced image distortions; and (3) a practical vibration cancellation method based on simultaneous measurement of displacements of the target structure and a stationary point. In addition, this project proposes a practical calibration method to convert image pixel displacements into physical displacements. This project is executed in two stages. Stage 1 focuses on developing the algorithms, techniques and methods to systematically address all sources of environmental noise that deteriorate image quality and measurement accuracy. Extensive laboratory tests are carried out to validate the effectiveness of the developed algorithms and techniques using simulated environmental noise including low-lighting, shadowing, heat haze, and change in illuminating light and background conditions. In Stage 2, the algorithms developed in Stage 1 are integrated into a software package and fieldBridge Displacement tests are carried in three bridges including two long-span steel bridges, the Manhattan Bridge and the Williamsburg Bridge, and a short-span concrete bridge, the Jamboree Bridge. The remote, real-time and multipoint measurement capabilities of the vision sensor system developed in this study are further validated in presence of various sources of field environmental noise including heat haze and camera vibration. In addition, this project demonstrates, through a laboratory experiment, the use of the vision sensor system for structural dynamic tests, modal analysis, and damage detection, by simultaneously measuring a dense array of displacements at extremely low cost. In the future, the system can be further developed for permanent installation at bridge sites to enable long-term continuous monitoring of structural integrity and safety.
报告类型：	科技报告