Robust control of thermal manufacturing processes

• Main Author: Μιχαήλ, Χρήστος
• Other Authors: Michail, Christos
• Language: English
• Published: 2021
• Subjects: Additive manufacturing; Robust control; Process control; Manufacturing processes; Digital twin; Finite element method; Linear matrix inequality; Προσθετική παραγωγή; Σθεναρός σχεδιασμός ελεγκτή; Θερμικές κατεργασίες; Πεπερασμένα στοιχεία

The thermal-based manufacturing processes such the welding and Additive Manufacturing (AM) processes are lacking on the efficiency of process control. This study arrives to bridge the gap of optimization in the control using linear matrix inequalities as an innovative method in this field. The study proposed two methodologies of controllers, the first one (a) employs a robust control through quadratic optimization using two dynamic output feedback controller of H-Infinity and H2, an observer-based controller using two gain of state-feedback and an observer-gain to synthesize a closed-loop feedback and a second one (b) using polytopic uncertainties due to structural variation in the powder material through a robust model predictive control. All the controllers are compared with a classical fine-tuned Proportional-Integral-Derivative (PID) for the single-input-single-output dynamical system. A Laser-based Powder Bed Fusion (LPBF) AM process is developed using Finite Element Method (FEM) for a single track of titanium alloy to construct a polynomial model through AutoRegressive (ARX) method. The response of proposed robust controllers via LMIs are compared with typical metrics of step response, such as the settling time and the rise time. The results of the (a) first developed controllers show the dominant of the proposed controller in comparison with a PID, which conclude that the latter’s metrics are approximately twice of the proposed ones. The results from the (b) polytopic uncertain system in the material properties shows the good agreement in the tracking response. At last, all the developed controllers can be adopted in a Digital Twin-based controller for their robustness under the uncertainties and the efficiency against the tracking response.