Hardware-in-the-loop control of additive manufacturing processes using temperature feedback

Laser-based additive manufacturing is a technology for the production of freeform metallic parts. In order to produce parts with high quality, it is important for the manufacturing processes to be controllable with a high degree of precision. Current additive manufacturing systems attempt to reach this goal by carefully tuning the operational parameters, often in combination with a feedback control system. These systems are based on low order, empirical models of the process, which may limit the performance that can be achieved. This paper introduces a control system based on a high order physical heat conduction model of the melt pool dynamics. The control system serves as a framework which can be applied to many laser material processes in which high precision is required, such as laser cladding and selective laser melting. The controller is able to regulate the melt pool size by modulating the laser power using a number of surface temperature measurements as the feedback signal. A hardware-in-the-loop (HIL) system was built to enable safe and cost-effective testing of the controller hardware in different simulation environments. The HIL setup includes a real-time image processing module for extracting the required temperature information from hyperspectral data generated by detailed numerical simulations of the melt pool dynamics. Hyperspectral measurements are performed on a laser cladding system to validate the simulation results.