Development of Marker-Free Night-Vision Displacement Sensor System by Using Image Convex Hull Optimization.

Insub Choi,Junhee Kim,Jisang Jang

doi:10.3390/s18124151

Abstract

Vision-based displacement sensors (VDSs) have the potential to be widely used in the structural health monitoring field, because the VDSs are generally easier to install and have higher applicability to the existing structures compared to the other conventional displacement sensors. However, the VDS also has disadvantages, in that ancillary markers are needed for extracting displacement data and data reliability is significantly lowered at night. In this study, a night vision displacement sensor (NVDS) was proposed to overcome the aforementioned two limitations. First, a non-contact NVDS system is developed with the installation of the infrared (IR) pass filter. Since it utilizes the wavelength of the infrared region and it is not sensitive to the change of a visible ray, it can precisely extract the shape information of the structure even at night. Second, a technique to extract the feature points from the images without any ancillary marker was formulated through an image convex hull optimization. Finally, the experimental tests of a three-story scaled model were performed to investigate the effectiveness of proposed NVDS at night. The results demonstrate that the NVDS has sufficiently high accuracy even at night and it can precisely measure the dynamic characteristics such as mode shapes and natural frequencies of the structure. The proposed system and formulation would extend the applicability of vision sensor not only into night-time measure but also marker-free measure.

Highlights

In the modern communities, where there are a high population and a high building density in the downtown areas, it is becoming more important than ever to identify and evaluate the status of the existing buildings
The purpose of this study is to propose a night vision displacement sensor (NVDS), which is marker-less Vision-based displacement sensors (VDSs) optimized for nighttime
This chapter chapteranalyzes analyzesthe thereliability reliability dynamic displacement obtained from the NVDS

Summary

Introduction

In the modern communities, where there are a high population and a high building density in the downtown areas, it is becoming more important than ever to identify and evaluate the status of the existing buildings. The displacement data are said to be useful for quickly and intuitively evaluating the status of a building through a comparison with the allowable displacement at the design stage. It has been widely utilized in the system identification (SI) technique, which evaluates the status of a building by determining its dynamic characteristics, or in the damage assessment technique, which evaluates the building damage [1,2,3,4,5]. It is important to acquire the displacement data, which are raw data containing the behavior information of a structure for evaluating its status

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Conclusion