Outlook of the Dynamic Behavior of Closed-Loop Control through Open-Loop Analysis for Intensified Separation Processes

This work shows a comparative assessment of open-loop and closed-loop processes to select, among a set of alternatives, the best distillation scheme regarding its controllability. A new point of view to assess the controllability using the information from the singular value decomposition (SVD) technique is proposed. In the research, the techniques for comparing the open-loop analysis and closed-loop analysis were standardized. The open-loop controllability index was calculated from the minimum singular value and the condition number of the certain areas in the frequency domain and a simplified index for measuring the singularity in SVD results. The derived controllability index then was compared with the normalized value of the Integral Absolute Error (IAE) of a proportional–integral (PI) controller obtained under closed-loop operation. Several different frequency areas were investigated to calculate the SVD and were used to compare the open-loop and closed-loop behaviors. The selected best distillation scheme was the same despite the chosen approach. Through the simulation study, it is verified that the newly proposed controllability index based on the condition number derived from open-loop responses can be useful to predict the best performance under closed-loop operation. This prediction is suitable to use in an optimization algorithm, because of the structure of the proposed controllability index