Adaptive and H∞ control of a strong acid — Strong base system

pH neutralization is recognized as a difficult control problem in terms of practical control. The difficulties arise from high process nonlinearity and from changes in the pH characteristics due to changes in influent concentration. Various techniques have been developed to control the process pH. This paper considers both adaptive and H_∞ controllers for pH regulation and mainly emphasize on the simulation study of a strong acid-strong base pH process and its controls. The adaptive controller under consideration is a combined feedback-feed forward controller while the H_∞ controller is a feedback controller. For random input disturbance with large variations, H_∞ controller outperforms the adaptive controller. But for step disturbance the adaptive controller shows good response. Simulation results confirm that a robust control of the process is achievable for both adaptive and H_∞ controllers.