Sliding Mode Control for Coupled-Tank Liquid Level Control System

This paper presents the mathematical modeling of coupled-tank system and designing of sliding mode control (SMC) for liquid level control in the system. The non-linear single-input single-output (SISO) mathematical model of plant is developed initially. A simulation is carried out using MATLAB/SIMULINK to control the non-linear model of coupled-tank system for a number of different conditions. The commanded inputs such as that of step, random, square, saw tooth and sinusoidal input signals are fed to the system to test the tracking performance of SMC. Some realistic situations are also included in the plant to examine the robustness of controller. The controller showed robustness for disturbance in the plant and produced an appropriate control signals for the sake of controlling the liquid level in the coupled tank system. The tracking performance of SMC is also compared with conventional PID controller in terms of performance index ITAE. The SMC showed excellent tracking results than PID controller for time varying command signals.