Build Height Control in Directed Energy Deposition Using a Model-Based Feed-Forward Controller

Control of deposition geometry is critical for repair and fabrication of complex components through directed energy deposition (DED). However, current limited sensing technology is often one of the bottlenecks that make it difficult to implement a real-time, measurement-feedback control of build geometry. Hence, this paper proposes to implement the control trajectories from a model-based, simulated-output feedback controller (where the controller uses simulated rather than measured outputs for feedback) as a feed-forward controller in a real DED process. We illustrate the effectiveness of such feed-forward implementation of a model-based, simulated-output feedback controller in the height control of a L-shaped structure via varying laser power in a DED process. Experimental validation shows that by applying the proposed feed-forward controller for laser power, the resulting build has (30%–50%) increased accuracy in achieving the target build height than applying laser with constant power or experience-based, hatch-dependent laser power. Results in this paper indicate that applying a simulated-output feedback controller could be a practical alternative for the control of DED (or other additive manufacturing processes) before the sensing technologies are matured enough to support real-time, measurement-feedback controller.