Reference system decoupling for multivariable control

Abstract

A new method for controlling multivariable processes is presented. The method, which we call reference system decoupling, features a single tuning constant per loop, complete interaction compensation (when there are no nonminimum phase elements present), and offset free performance in the presence of modeling errors. In the absence of modeling errors the tuning constants specify the closed-loop set-point trajectories, while in the presence of modeling errors they are adjusted to maintain robustness. The method is illustrated with two simulation examples. One is a distillation system studied widely in the literature, and the second involves multiple flash drums operating in parallel at an industrial site. A comparison of the results with PI (proportional-integral) control, with decoupling, shows the excellent capability of reference system decoupling for servo and regulatory control of multivariable processes. © 1991 American Chemical Society.