Design of PID controller for the modified quadruple-tank process using inverted decoupling technique

This paper presents the approach to design PID controller for a modified quadruple-tank process using inverted decoupling technique. In case of non-minimum phase, TITO system, such as modified quadruple-tank process which can´t be controlled by PID controller with standard decoupling technique because the system can´t be stabled by saturating manipulate signal. With the proposed method, The inverted decoupling controllers, decreasing the cross coupling between inputs and outputs, transform TITO plant transfer function model into SISO form so that SISO controller for each SISO model can be designed by Root Locus Technique easily and efficiently. PID controller with inverted decoupling can stabilize an unstable non-minimum-phase system and minimize several undesirable influences from an interaction in TITO process. The results from control system design can be illustrated by the experiments.