On-line control of solid-liquid interface by state feedback

This paper deals with the problem of controlling the solid-liquid interface shape during directional solidification of a molten material inside a Brid gman-Stockbarger furnace. The necessary convective boundary conditions that would achieve the desired interface shape are found using feedback control s. A state-space model of the solidification process is determined by emplo ying a modified finite-element technique to the governing conduction equati on developed using the apparent heat capacity (AHC) formulation. This model is used to design a dynamic controller that would set up a desired interfa ce share at the desired location and translate it at the desired velocity. The proposed controller is implemented on a multizone transparent Bridgman crystal growth furnace. (C) 1999 Elsevier Science B.V. All rights reserved.