A low-cost and flexible solution for one-shot cooperative robotic drilling of aeronautic stack materials

In this paper, a general architecture for robotized cooperative drilling of hybrid metal/Carbon Fibre Reinforced Polymer (CFRP) aeronautic stacks is presented. The main objectives are to reduce non-added value operations as dismantling, deburring, cleaning and to improve hole quality by reducing the occurrence of delamination and inter-laminar cracking. The approach to achieve such targets is the adoption of a one-shot drilling automatized system based on low cost cooperative robots. The proposed technology consists in a general robot architecture and a cooperative drilling process using only standard low-cost robots and off-the shelf components. A first robot is in charge of drilling the hybrid stack, while a second manipulator ensures the right clamping force between the parts of the stack. Both robots are equipped with force control capabilities to control the generalized forces raising during the interaction with the stack. In this perspective, thanks to the adoption of a fuzzy inference system, the tuning of the force controllers might be carried out by operators that have knowledge of the drilling process but not of control system technology. Such feature makes the solution appealing for industrial production environments. The approach is experimentally validated on a cell with two Comau SmartSix robots drilling an aluminium-carbon fibre stack.