Robustness analysis and control of a pilot-scale distillation column

A pilot-scale distillation column has been connected to an industrial Distributed Control System (ABB MOD 300). The connection of this DCS to a VAX-cluster through Ethernet Gateway facilitates data-collection from the column. This set-up has been used to investigate different control strategies as well as advanced operational techniques. This paper considers the preliminary study of the robustness analysis of this pilot-scale distillation column. Using a combination of plant data and non-linear simulations, both a nominal column model and an associated model uncertainty are identified. This information is used to carry out a complete analysis of robust stability and performance for the case where a (Ziegler-Nichols tuned) multiloop control scheme is employed. To perform robustness analysis of the control, both structured and highly structured uncertainty characterization approaches are used and it is shown that the latter case provides less conservative results. (C) 1997 Elsevier Science Ltd.