Dynamic considerations in the synthesis of self-optimizing control structures

This work builds on our prior results to develop novel control structure design principles for integrated plants featuring multiple time scale dynamics. Specifically, the concept of self-optimizing control can be used to identify the variables that must be controlled to achieve acceptable economic performance during plant operation. This approach does not, however, provide guidelines on control structure design and control loop tuning; a detailed controllability and dynamic analysis is generally needed to this end. In this work, we employ a singular perturbation-based framework, which accounts for the time scale separation present in the open loop dynamics of integrated plants, to identify the available controlled and manipulated variables in each time scale. The resulting controller design procedure thus accounts for both economic optimality and dynamic performance. The developed concepts are sub-sequently successfully applied on a reactor-separator process with recycle and purge.