Hybrid System Model of Microextrusion-Based Direct-Write Additive Manufacturing

Flowrate control in Direct-Write (DW) Additive Manufacturing (AM) continues to be a challenge due to a capacitative energy storage in the system and the absence of suitable flowrate sensors at the micro-scale. Lack of precise control leads to an excess or a lack of ink while printing, resulting in manufacturing defects. The incorporation of a pressure sensor and a feedback controller is a potential approach for precisely controlling the flowrate. However, in the case where the ink loses contact with the pressure sensor, there will be an abrupt loss in feedback signal, which could potentially result in instability in the closed loop. In this paper, we present a hybrid model that represents the continuous dynamics of microextrusion with discrete switching between three different modes that captures the presence or loss of a sensed pressure. The simulation results demonstrate that the model captures the continuous dynamics of microextrusion while switching between three discrete modes: normal printing mode, retracted ink leading edge mode, and loss of pressure signal mode. The hybrid model presented here paves the way for switched controller synthesis to create stable feedback controllers.