ISSUES IN THE APPLICATION OF NONLINEAR ESTIMATION FOR IMPROVING PRODUCT QUALITY CONTROL IN BATCH AND SEMI-BATCH PROCESSES

摘要

Inferential control techniques offer an attractive approach to overcome batch-to-batch variations in product quality. In order to calculate effective control moves, inferential techniques must have accurate on-line estimates of the key process states based on available secondary measurements. The focus of this paper is on the problem of nonlinear estimation of batch processes because of its importance to the inferential control approach. First, some of the important issues in applying nonlinear estimation techniques to batch and semi-batch processes are outlined. Then, methods for improving the estimation of initial batch conditions and the speed of convergence of the state estimates are considered. A practical example process, the nylon 6,6 autoclave reactor, is included to provide the physical motivations for many of the issues examined and to demonstrate the effectiveness of techniques proposed to address these issues. Finally, some areas where future research is needed to improve the effectiveness of the inferential approach are indicated.