Robust Feedback Control of Melt Pool Area in Laser Powder Bed Fusion Via Sliding Mode Design

Abstract Laser powder bed fusion (LPBF) is a metal additive manufacturing process that uses a high-power laser to melt a predefined shape in a bed of metal powder, layer by layer. The size of the melted pool throughout the process can significantly affect the mechanical properties of the final part; too small of a melt pool may result in poor fusion, too large will cause porosity. The size of the melt pool is governed by inherently complex multiphysical interactions. Complex models have been developed and simplified in the literature, and in this paper, a nonlinear first-order single state energy transfer model is used to simulate the size of the melt pool transverse surface area. The error is defined as the difference between the melt pool area and a desirable reference value, and a sliding mode control (SMC) law is developed to use input laser power to drive the system to a zero-error manifold in finite time. Since the model used takes advantage of potentially unrealistic geometrical assumptions about the melt-pool shape, the control law is further developed to be robust to inaccuracies and real-time changes in the system parameters related to this assumption. The performance of the controller is compared with other control strategies in the presence of bounded parameter uncertainty.