Batch Distillation Control

Optimal control problems in batch distillation have received considerable attention in the literature. In general, control refers to a closed-loop system where the desired operating point is compared to an actual operating point and a knowledge of the dierence (error) is fed back to the system to drive the actual operating point towards the desired one. The purpose of designing a closed-loop control system is to decrease the sensitivity of the plant to external disturbances. Conventional frequency domain techniques can be used to design a controller. However, optimal control problems do not fall under this category. These problems are dened in the time domain, and their solution requires establishing an index of performance for the system and designing the system so as to optimize the selected index. Use of the control function here provides an open-loop control. Since the decision variables that result in optimal performance are time-dependent, this type of control problem is referred to as an optimal control problem. The dynamic nature of these decision variables makes these problems much more dicult to solve compared to normal optimization where the decision variables are scalar.