Experimental identification of the static model of an industrial robot for the improvement of friction stir welding operations

Friction stir welding (FSW) is a joining process where the regulation of some technological parameters, like machining forces and tool velocities, is essential to ensure the required product quality. Therefore industrial robots are often equipped with force sensors in order to have a monitoring of the interaction forces between the rotating tool and the sheets metal. Alternatively a mathematical model can indirectly provide information about such forces through current measurements of robot motors. The present work focuses on the experimental identification of the static model of the Tricept HP1, a robot suitable for FSW operations because of its high thrust performance. Gravity and friction contributions are taken into account, while inertial terms are neglected from modeling according to the low speed motion involved in the welding process. The model is conveniently used to investigate the axial force developed during welding of aluminum sheets metal, laying the groundwork for a model-based control of the robot.