Control of coupled liquid tank system using different methods

The model of tank systems frequently used in the process control is represented by the coupled tank system. Controlling liquid levels is a significant control issue that arises in a variety of industrial applications, including heating boilers, waste treatment systems, power plants, filtration and oil refineries. For this reason, implementing liquid level control is very difficult and costly process. The coupled tank experimental set that produced by the Feedback Instruments Ltd. 33-041S model has been preferred to use due to cost, difficultly, security etc. The 33-041S model consists of five tanks connected to each other by pipes. Reservoir tank has been located at the bottom of the coupled tanks system and it has two submersible pumps. Submersible pumps and pipelines are utilized for supplying fluid flow. The fluid level is measured by four sensors that are located at the bottom of the other four tanks. Controllers that act as strainers are generally used to provide liquid level control. The scope of this study, controllers such as PI (Proportional-Integral) controller, PID (Proportional-Integral-Derivative) controller, phase lag controller, parameter values have been determined that using various methods for control of the liquid level. In this way controllers have been designed. The study has been applied separately to each of the Tank (1) and Tank (2) system. First of all, for both the Tank (1) and Tank (2) systems, linear mathematical models in the Laplace domain have been constructed. Mathematical models have been utilized to construct the designs for the controllers. The Stability Boundary Locus technique, a graphical approach; the Ziegler-Nichols (ZN) technique, a conventional method; and the Genetic Algorithm (GA), a contemporary algorithm-based optimization method, have all been utilized to find the parameters of PI and PID controllers. The root locus technique and Bode diagram techniques, which are conventional methods that enable us to observe them graphically, have been applied in the design of the phase lag controller. The design results have been obtained in simulation and real time in MATLAB/SIMULINK software. The theoretical study has been supported by examining the results obtained. Keywords: PI-PID Controller, Phase Lag Controller, Genetic Algorithm, Ziegler-Nichols, Stability Boundary Locus, Bode Diagram, Root Locus