Extrusion under material uncertainty with pressure-based closed-loop feedback control in robotic concrete additive manufacturing

Abstract

One of the main challenges in extrusion-based robotic concrete additive manufacturing process is material uncertainty under pressure which leads to geometric inaccuracies. Here, a real-time pressure-based closed-loop feedback control system is developed to address the geometric fidelity challenges that arise from the material uncertainty under extrusion. A robotic extrusion process is instrumented with a load sensor and assessed with and without activation of the pressure-based controller. The reliability and robustness of a pressure-based closed-loop control system is examined by introducing single- and double-perturbation of the extrusion and assessing the recovery of the geometry (width, height) of the extruded filaments to a baseline reference. The developed control system reacts to retrieve and maintain geometric fidelity among all experiments and repetitions, thereby highlighting the utility of pressure as a feedback parameter to handle material uncertainty that is common in extrusion-based robotic manufacturing process. Future directions include evaluating the control system in unseen conditions. • Changes in back pressure result in geometric inaccuracies in an extrusion process. • A pressure-based closed-loop control system is developed to enhance geometric fidelity. • The reliability and robustness of the control system are evaluated. • Pressure can be used as an upstream, material-sensitive variable in feedback control. • The control system demonstrates improved long-term geometric fidelity.