Optimal Operation with Changing Active Constraint Regions using Classical Advanced Control

Abstract

With ”classical advanced control” we mean the control structures that are commonly used in industry for multivariable control. These have been in use for at least 50 years, but surprisingly there is little literature published on how to design such structures in a systematic manner. We present a design procedure to assure optimal operation when active constraint changes occur. In this paper, we focus on input saturation. We suggest to use a priority list of constraints as an important first step of the presented design procedure. We also discuss how to handle input saturation using split range control, valve position control (input resetting), and selectors. As a case study, we consider optimal operation and a priority list of constraints for a cooler with temperature and flow control, and evaluate alternative classical advanced control implementations that maintain optimality.