@article{lee_nie_han_2024, title={Automatic and Real-Time Joint Tracking and Three-Dimensional Scanning for a Construction Welding Robot}, volume={150}, ISSN={["1943-7862"]}, url={https://doi.org/10.1061/JCEMD4.COENG-14135}, DOI={10.1061/JCEMD4.COENG-14135}, abstractNote={Although welding is one of the essential steel fabrication processes, the American Welding Society expects that the labor shortage in the United States will reach a deficit of 360,000 welders by 2027. Developing an automatic robotic welding system could potentially alleviate the labor shortage and provide better welding quality. As a first step, this paper designs a system pipeline that can automatically detect different welding joints and plan and track the joints’ trajectory with the initial point alignment in real time. There are rare studies that could achieve automatic initial point alignment in real time because the laser stripe’s deformation is not obvious at the narrow weld. In this study, the target joint’s endpoints were detected once the joint was detected on live video. Then, the joint trajectory was planned, and the robotic arm automatically aligned with the initial point and tracked the planned trajectory while scanning. The results demonstrate the accuracy and effectiveness of the proposed method.}, number={3}, journal={JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT}, author={Lee, Doyun and Nie, Guang-Yu and Han, Kevin}, year={2024}, month={Mar} }
 @article{lee_nie_han_2023, title={Vision-based inspection of prefabricated components using camera poses: Addressing inherent limitations of image-based 3D reconstruction}, volume={64}, ISSN={["2352-7102"]}, url={https://doi.org/10.1016/j.jobe.2022.105710}, DOI={10.1016/j.jobe.2022.105710}, abstractNote={Modular construction can lead to additional cost overruns and delays when a defect is found on the construction site and is not easily repairable. Researchers have developed various methods that use image-based 3D reconstruction for quality assessment, but they have inherent limitations, such as inconsistency and dealing with surfaces with reflectivity and limited visual features. Therefore, this paper presents a vision-based quality assessment method using cameras for prefabricated components by addressing these limitations. Specifically, this paper proposes a novel quality inspection method with sub-millimeter accuracy using cameras focused on leveraging camera poses (as opposed to 3D point clouds that are often not consistent in quality) from the image-based 3D reconstruction. The 3D point estimation by computing triangulation was used for achieving accurate measurement. The proposed method is validated using six different variances and two case studies – an aluminum pipe with a reflective surface and a fabricated concrete column. The results demonstrate the accuracy and effectiveness of the proposed method.}, journal={JOURNAL OF BUILDING ENGINEERING}, author={Lee, Doyun and Nie, Guang-Yu and Han, Kevin}, year={2023}, month={Apr} }