Fractional PI Control for Coupled-Tank MIMO System

In this paper, the system models of a multivariable process, the coupled-tank system, are obtained by the Identification Toolbox of Matlab from a pair of priori input/output data. Decoupling techniques are the suitable choice for most industrial processes wherein the interactions between process variables are significant. Therefore, in this work, simplified decoupling is suggested for a two-input, two-output (TITO) process and then an approach of controller design for multi-loop systems is proposed. A fractional order PI (FOPI) controller is adopted to solve the problems of level control of the decoupled system. The tuning rules are analytically derived using the frequency domain approach. In this paper, an appropriate frequency range is suggested in determining the controller parameters based on the rules which was firstly proposed by Vu and Lee. The obtained controller is compared with another well-known method to show improved performance and also implemented using Real-Time Window Target of Matlab to substantiate our proposed method in a real application.