On-line Accurate 3D Positioning Solution for Robotic Large-Scale Assembly Using a Vision System and a 6Dof Tracking Unit

Assembly operations in aerospace industry are time consuming and need high accuracy. Robotic assembly is a good solution to increase the productivity. However this solution is limited to the poor accuracy of industrial robots. External sensors could be added to improve the robotic assembly cells accuracy. In this context, the 3D positioning of large-scale parts has become a subject of significant interest. In this paper, an on-line accurate 3D positioning system is proposed. This 3D positioning unit is constituted of a vision system (scanner) “KEYENCE LJ-V7200”, a 6Dof tracking system (Leica AT-960 + T-Mac TMC-30B). This unit has been installed at the end-effector of a robot manipulator (LBR-iiwa 14kg). Different methods, previously presented in the literature, have been used to identify position and orientation of the vision system's TCP (tool center point). Some modifications were applied on the identification methods in order to increase the accuracy of the results. The mean accuracy obtained of an object's 3D positioning, in the workspace of the LBR-iiwa robot, is ±0.16mm. Experimental tests were carried out to validate the TCP determination method in different robot configuration. The results of the proposed online solution were compared with a basic solution, without tracking system to highlight the improvement of accuracy thanks to the on-line solution.