GOALI: Hybrid Control of Continuous Casting for Whale and Crack Prevention

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The research effort supported by this award is aimed at preventing two major problems in continuous thin-slab steel casting: internal and surface cracks and whales ? bulges of the solidifying steel shell. A model-based spray cooling control system will be created to track, under disturbances and process model uncertainty, temperature profiles designed to satisfy quality constraints. Control of moving solidification front position will be addressed by developing theory of hybrid state estimation and control for systems with moving boundaries, applicable to a number of processes. The research approach progresses from the development of a controller/state estimator system for an idealized configuration to the real caster which has constrained spray-nozzle actuation, unmodelled process dynamics, and unreliable pyrometer measurements. Deliverables include fundamental control-theoretic results, controller and state estimator synthesis and analysis tools, software/hardware demonstration and validation on an industrial caster at Nucor Steel, an offline educational process control and visualization tool, documentation of research results in publications, and engineering student education.Once completed, the results of this research will offer widely applicable, cost-effective control systems capable of accomplishing sophisticated spray cooling control tasks in continuous thin slab steel casting. This research will have broad impact across the entire industry due to quality improvement, (through fewer defects), energy savings (through yield improvement and lower reheating costs), better safety (from improved steel quality, and fewer breakouts and whale-defects), and competitiveness (by enabling the casting of new steel products). Improving spray cooling control to achieve even a one percent reduction in yield loss would save about $100 million per year (based on the roughly 100 million tons of steel produced each year in the U.S. and $100 per ton net cost of scrapping). Development of novel observation and control tools - sensor fusion with unreliable sensors and control of systems with moving boundaries - will address problems encountered in many other manufacturing processes. The research and educational infrastructure will be significantly enhanced through student involvement, industry and international collaborations, and broad dissemination of new knowledge.