Industrial robot trajectory measurement by target tracking and 3D coordinate measurement in large-scale assembly cell

Abstract. Ensuring precise and accurate six-degree-of-freedom (6 DoF) positioning of industrial robots is crucial in large-scale automotive and aerospace assembly cells, where even slight positional errors can compromise product quality and production efficiency. Traditional laser tracker–based methods commonly require multiple trackers to acquire complete 6 DoF measurements, leading to high costs and constraints such as limited measurement range, line-of-sight restrictions, and declining accuracy in large workspaces. This study presents a low-cost approach that combines pre-characterized target tracking with photogrammetry to overcome these limitations. By mounting a specially designed target artifact on a robot’s end effector and capturing images from multiple high-resolution cameras, the proposed system performs camera calibration and multi-view triangulation to calculate the artifact’s three-dimensional (3D) position and orientation. Preliminary results validate the method’s efficacy, showing that the edges of spherical targets can be accurately fitted in three dimensions. In the next phase of research, the corrected pose data from the vision system will be transmitted back to the robot, enabling a closed-loop feedback control strategy. Comprehensive validation trials will further quantify the system’s accuracy and robustness, laying the groundwork for broader adoption in large-scale industrial assembly applications.