Simulation and Control of a Multi-Stage Batch Operation with Measurement Constraints

This paper presents the simulation of a multi-stage batch operation, such as sputtering. The objective of the research is to examine the effect of different sampling strategies on the overall control of part-to-part quality, not the control of the continuous processes that occur during each stage. Selection of a sampling strategy is difficult because the measurement system for the operation is constrained in such a way that sampling control variables at each stage simultaneously is not possible. At individual stages, supervisory controllers are implemented to maintain part-to-part quality. Hence, the process and its simulation are completely discrete since it is the behavior of the supervisory loops that are studied. The immediate results of this research indicate that the strategies that repetitively sample every other stage are superior to the other methods considered. Additionally, these results may direct the development of intelligent sampling strategies that will not be static and fixed, but will strategically sample stages in order to better maintain overall product quality.