Elham Sareban - Khorasan Institute of Higher Education;
Amir Aminian - Khorasan Institute of Higher Education;
Seyyed Kamaloddin Mousavi Mashhadi - Iran University of Science and Technology, Faculty of Electric Engineering;

The interactions between input/output variables are a common phenomenon and the main obstacle encountered in the design of multi-loop controllers for interacting multivariable processes. In this study, A H∞ robust controller for a 24-tray separating a mixture of methanol and water is proposed. The idea has favorable controls on control targets (rise time, settling time, overshoot and undershoot, the interaction between input and output) and help on stability of the system output. Using the principles of modern control the other two controllers designed. The first design method is LQG/LTR, that proper eigenvalue for closed loop LQG designed and then in LTR method these eigenvalues with adjusting of gain in LQR method will be re-adjusted. The other method is decoupling that a PI-controller is combined with this case. Finally we applied robust controller H∞ that the setting of controller in this method is higher than LQG/LTR method. For robust stability, using of dynamic output feedback, robust controllers H2 and H∞ for a class of indefinite linear systems is proposed. Uncertainties are of limited norm. The simulation results are employed to demonstrate obtained results in proposed method (H∞)have best time characteristics and in face with uncertainties has better reacts than other controllers.

Control targets, H∞ Robust controller, LQG/LTR controller, Decoupling, Uncertainty