Application of End-Point Control and Trajectory Tracking to Batch Processes

Abstract

Batch processing has grown in importance in recent years as the interest in producing high value-added materials has increased. To help ensure stringent product quality metrics are met, batch processes have become increasingly instrumented. Advanced instruments, such as NIR, Raman and other spectral devices are now common place in the pharmaceutical industry. In this paper it is shown how measurements from spectral devices can be used within a feedback control framework to improve product quality. Two specific control systems are applied; one is used to ensure that the final spectral measurement from the end-point of the batch meets target specifications, while the other regulates features within the spectral measurement throughout the batch. The relative merits of each of the proposed control systems are demonstrated through their application to a simulated chemical batch reactor. The case study shows that the end-point controller is able to track set point changes but cannot maintain product quality in the presence of a disturbance. In contrast the trajectory tracking controller is able to reject disturbances but cannot be implemented to track unseen set-point changes.