Alternative Control Methods for Continuous Ultrasonic Welding of Thermoplastic Composites

Abstract

Closed-loop control is a method for regulating a process in the presence of disturbances and uncertainties. Continuous ultrasonic welding of thermoplastic composites is a process with the potential to improve aerospace manufacturing but is not yet fully understood and produces variable weld quality. This thesis investigates the usefulness of different sensor options for a closed-loop control of this process. Using a data-driven approach, the plant’s dynamics and uncertainties are identified and used to design a closed-loop controller. The controller is tested on a 6-axis industrial robot equipped with an ultrasonic welding tool and compared to a baseline open-loop controller. The results show that the closed-loop controller can improve certain aspects of the welding process, such as preventing a low weld quality along the entire weld seam caused by consistently high temperatures