Dual encoder robot for accurate Robotic Friction Stir Welding for 3D aeronautic components
By Mario Guillo (Institut MAUPERTUIS), Guillaume Even (STELIA Aerospace), Marc Douilly (STELIA Aerospace)

The present study proposes the use of an industrial serial robot to reduce the investment cost and to increase the process flexibility of Friction Stir Welding (FSW). The robot has a big advantage for 3D aeronautic components, as it could weld in multiple positions and orientations. However, the robot stiffness is not sufficient. Due to high process forces tool deviations appear and lead to poor welding quality. In this paper, a dual loop control force/position is used to compensate the robot tool deviation in real-time. Unlike classical industrial robots, a second position control loop with secondary encoders is used in order to compensate in dynamic the robot tool deviations (position and orientation). Moreover, the second position control loop is combined with the force control loop which control the forging force. The relevance of the proposed method is done on a complex 3D path, the accuracy is improved about 70% compared to the same robot without the dual encoder system.