Bokeh-based target tracking for structural dynamic monitoring: A novel approach in variable lighting conditions

Abstract

The application of Computer Vision (CV) techniques in Structural Dynamic Monitoring (SDM) eliminates the need for sensor installation and calibration, providing reliable monitoring results. However, conventional CV methods typically require time-intensive supervised pre-processing steps such as pattern extraction and machine learning. This paper introduces a novel Bokeh-effect-based target object tracking method for SDM that forgoes the need for such pre-processing, allowing for unsupervised, real-time, non-contact monitoring. This method, adaptable for diverse lighting conditions and employing consumer-grade cameras and computers, creates circles around target objects positioned beyond the depth of field of the camera lens, then detects and tracks the movement of these circles to facilitate structural dynamic monitoring. The proposed method is applied to a wind tunnel experiment on bridge girder sections to verify its accuracy and reliability, and the result is validated with the measurement from LASER transducers in the same wind tunnel experiment. This innovative approach advances efficient SDM by offering rapid response and real-time non-contact tracking capability with a high tolerance for target objects under regular and low-light conditions while avoiding the complexities linked with the pre-processing inherent in other supervised CV detection methods.