Displacement measurement of large structures using nonoverlapping field of view multi‐camera systems under six degrees of freedom ego‐motion

Abstract

In this work, a non-overlapping field of view (FOV) multi-camera system (MCS) has been proposed to realize the motion self-compensation, which can be flexibly arranged according to the field situation. The challenges of ensuring a complete fixed measurement platform owing to the self-weight, unexpected collisions, and adjacent engineering constructions have been addressed in this study. MCS can be fixed on an unstable platform and employ two or more correcting cameras, without an overlapping FOV, to measure and compensate the six degrees of freedom (6-DOF) ego-motion of the platform, with high accuracy. The numerical simulation results show that, under the same configuration conditions, the 6-DOF motion estimation accuracy of the proposed method is better than that of the Perspective-n-Points methods, especially for the estimation accuracy of the out-of-plane motion and the roll motion of the camera. The field demonstration has been performed on a suspension bridge, and the results demonstrate that the deflection measurements provided by the proposed MCS are consistent with those provided by the Robotic Total Station. The proposed MCS, which is not restrained by a strictly stable platform, proves to be an effective method to compensate for the errors induced by the platform ego-motion, and it can meet the requirements of the displacement measurement of large structures needing high precision.

A vision monitoring system for multipoint deflection of large‐span bridge based on camera networking

“…Note, the aforementioned vision methods were performed based on the assumption that the camera is fixed in a strictly stable position, which is impractical for long-term monitoring (Shang et al, 2014;Yu et al, 2015). Several researchers tried to compensate the camera motion-induced errors in the long-term monitoring of bridge deflection (Lee et al, 2020;Pan et al, 2016;Yu et al, 2022). For example, Lee et al (2020) proposed a dual-head camera system that can simultaneously measure and correct the ego motion of the observation platform.…”

“…For example, Lee et al (2020) proposed a dual-head camera system that can simultaneously measure and correct the ego motion of the observation platform. Yu et al (2022) proposed a multicamera system composed of multiple correcting cameras and measuring cameras, which can accurately correct the influence of the platform 6-degree-of-freedom ego-motion on the measurement results. However, those methods are not suitable for the large-span bridge.…”

“…Several structural control methods and systems have been proposed to reduce the effect of dynamic load (e.g., traffic, wind, and earthquake) on a bridge (Adeli & Saleh, 1997; Gutierrez Soto & Adeli, 2019; Kim & Adeli, 2005). Meanwhile, large efforts have been devoted to the structural health monitoring, including but not limited to the defect detection (Chun et al., 2022; Sajedi & Liang, 2021; Zhang & Lin, 2022; Zheng et al., 2022), stress or force estimation (Lee & Park, 2011; Tian et al., 2021), and strain or displacement measurement (Hampshire & Adeli, 2000; Park et al., 2007; Yu et al., 2022). As the most direct embodiment of structural health, the deflection of large‐span bridge is an important index for the evaluation of bridge safety and applicability, which can be further used for the bridge properties identification (Amezquita‐Sanchez & Adeli, 2019; Amezquita‐Sanchez, Park, & Adeli, 2017; Perez‐Ramirez et al., 2016; Pezeshki et al., 2023), structural response prediction (Perez‐Ramirez et al., 2019; Ren et al., 2021), and early warning (Bao et al., 2019; Li et al., 2015; Oh et al., 2017; Sousa Tome et al., 2020).…”

“…Yu et al. (2022) proposed a multicamera system composed of multiple correcting cameras and measuring cameras, which can accurately correct the influence of the platform 6‐degree‐of‐freedom ego‐motion on the measurement results. However, those methods are not suitable for the large‐span bridge.…”

Nodes2STRNet for structural dense displacement recognition by deformable mesh model and motion representation

“…Vision-based displacement measurement methods have been proposed for several decades. [1][2][3][4][5][6][7][8][9] At the early stage, the methods required installing artificial targets on structures. Wahbeh et al 10 installed light-emitting diode lights on bridges to measure structural displacement in low-light conditions, such as at night.…”