Parallel decoupling of a high-purity distillation column

The authors present a design technique that can be applied to process control systems with both high and low RGA (relative gain matrix) entries. This technique is called parallel decoupling. The controller is designed on the basis of a nominal process model. It is assumed that the real process contains a bandwidth constraint due to the time delays or right-half plane zeros. For simplicity of exposition this is illustrated by norm-bounded perturbations of the nominal process model. A high-purity distillation column with large RGA entries at all frequencies is used as a design example, and μ-analysis is used to evaluate the quality of the design compared to other methods