動画情報を用いた道路柱状構造物の固有振動数の推定と異常検知の可能性

Abstract

本研究の目的は，撮像装置から取得される動画を用いた道路柱状構造物の固有振動数の推定と異常検知である．実物大柱状構造物を用いて，動画から推定される固有振動数の精度検証を行う．また損傷シナリオとしてアンカーボルト緩解時の計測を実施し，固有振動数低下による異常検知の可能性を検討する．振動抽出には撮影動画の画角全体に処理を施し，特定の周波数帯域のみ拡大させる Phase-based motion magnification 法を適用し，特徴点の追跡により振動波形を抽出する．検討の結果，固有振動数推定値は精度に課題が残る一方で，損傷時の推定値の低下が確認され異常検知の可能性が示された．また撮影動画の背景情報が推定に影響を与える可能性を考慮し，CNN を応用した背景除去手法を導入し，動画処理後の動画に適用することで振動抽出精度向上の可能性について検討を行った．

This study is intended to discuss the feasibility of the frequency identification and anomaly detection of highway pole structures from video footage. The accuracy of the identified frequencies from video footage is investigated through a laboratory experiment on a full-scale pole structure. Loosening anchor bolt conditions are considered as a damage scenario. In order to extract vibration modes of the pole structure, this study applies Phase-based motion magnification method which processes to the whole image frame and expands the designated frequency bands. Then, vibration waves are extracted by tracking the featured points in the image frame. Although the accuracy of estimated frequency identified from the vibration modes extracted from the video footage still needs improvement, the decreasing tendency of the frequency due to the damage scenario was observed. This study also investigates ways to remove background in the video image for the purpose of reducing influences of noise and improving identification accuracy.