PhD defense "Contributions to the control of the vertical gradient freeze crystal growth process on the basis if distributed parameter systems" by Mr. Stefan Ecklebe

The present work is dedicated to the design of model-based tracking control of the Vertical-Gradient-Freeze crystal growth process. This is a modern method for growing single crystals, the basis for almost all integrated electronic circuits. Herein, the successive solidification of the melt into a single crystal is achieved by suitable control of the heaters available as actuators in the system. As the entire temperature distribution in the system is of interest for the control, the process is a representative of the so-called distributed parameter systems, in which the variables under consideration are not concentrated in a few points but are spatially distributed. The thesis deals with the modeling of the process which leads to a boundary value problem with a free boundary - the so-called Stefan problem. In order to obtain a simulation model, an approximation using the finite element method is presented in addition to a method based on power series. With the help of an analytical solution, the approximations are subsequently examined with regard to their accuracy. In the main part of the thesis, different concepts for the design of tracking controls are considered, including a flatness-based and a model-predictive design from the group of early lumping designs, as well as a boundary value feedback and two backstepping-based controllers as representatives of late lumping methods. Finally, simulation studies are used to compare the presented designs and discuss their suitability for various applications.

It is possible to join the defence via Video (no additional Software required, runs in all standard web browsers): BigBlueButton-Link