PLASMA SPRAY PROCESS ADVANCED CONTROL SYSTEM DESIGN: EXPERIMENTAL AND MODELING ANALYSIS OF PLASMA SPRAY NONLINEARITIES

Plasma spray is a high-throughput, economical and low environmental impact coating process that can be used to meet the demanding performance requirements for turbines, pumps, and emerging biomedical applications and solid oxide fuel cells. However, current plasma spray process capabilities are limited by its significant process variations which pose challenges for engineering coating structure for advanced applications as well as optimizing process yield and economics. This dissertation investigates the critical issues needed to develop an advanced plasma spray process control system that can compensate for these process variations, including: characterization of different fluctuations observed in plasma spray process, development an understanding of the sources of the dominant variations, the dominant torch input-output dynamics and nonlinear behaviors of the process, and the control sensing requirements for detecting these variations.