A high-accuracy pose measurement system for robotic automated assembly in large-scale space

Abstract

Robotic automated assembly in large-scale space is a challenging task both in aerospace engineering and automobile manufacturing industries, which involves several technical metrics, such as accuracy, efficiency as well as stability of the assembly system. In this work, we propose a high-accuracy pose measurement system to tackle this problem. Compared to existing measurement technologies, our system can adequately cover the assembly space and reach a high pose accuracy (<0.2° on rotation and <0.2mm on translation), which meets the requirements of most robotic automated assembly tasks in large-scale space (usually in sub-millimeter). To achieve that, we design a multi-degree-of-freedom measurement platform, which allows the camera to move in the motion space so as to find the best viewpoints to respectively measure the robot end-effector and the assembly target. Another key issue is the localization of the robot end-effector in the assembly space. Traditional calibration methods cannot be applied directly, since the robot and the camera are movable. Hence, we design a practical mechanical tooling which is attached to the sixth axis of the robot. Cubes are uniformly distributed on the tooling, serving for the precise localization of the end-effector. We also propose a novel calibration method to solve the kinematics solution. Moreover, we design a camera-pointcloud collaborative method to effectively compute the accurate 3D coordinates in camera space for sub-pixel marker centers, which can make a significant promotion in measurement accuracy.