Thermal Modeling and Control of a Capsule Welding Machine

This Master Thesis has been developed in collaboration with the IMA group. Its objective is to study an existing machine for coffee capsules production and to propose an alternative temperature controller for the welding process. In fact, one of the main issues of the apparatus is the difficult regulation of the temperature, because of its changing working conditions. Problems of high thermal inertia make the system not able to react quickly to the control action, especially at the beginning of the welding phase, creating difficulties in all the system and affecting the quality of the final product. This thesis has this structure: In Chapter 1 the mechanical structure of the machine is analyzed, empathizing the main aspects of the welding apparatus. Moreover, the electrical and electronic hardware is described, in order to realize how the control architecture of the welding apparatus works. In Chapter 2 models for simulation and control of the welding apparatus are developed, with the objective of obtaining a lumped parameter representation of it. Then, some simulations with Matlab/Simulink are carried out in order to check the behavior of the model. Techniques of Physical Modeling and System Identification are exploited together in order to obtain a realistic model of the heat transmission. The modeling phase is concluded in Chapter 3 where the obtained lumped parameter model is validated. Chapter 4 has the goal of analyzing and synthesizing an optimal control algorithm for the temperature regulation of the welding apparatus, with emphasis on the predictability and robustness of the control action in presence of varying working conditions. Chapter 5 is aimed at implementing the control algorithm in a commercial hardware. Then, the control software is validated in the machine, in order to verify its real effectiveness. Finally, Chapter 6 exhibits the conclusions and the further developments that are related to the study carried out in this thesis.