Design and Analyse of Structured H-infinity Controller for Level Control of Nonlinear Quadruple Tank Systems

Industrial process systems operate by interacting with each other to fulfil an essential industrial task. The majority of processes have nonlinear dynamics and multiple-input multiple-output systems which make them even more difficult to design control schemes. In industrial process applications, level control is one of the important problems. This study computes a structured H-infinity controller for the level control of a nonlinear quadruple tank system. This study aims to design a simple (low-order) robust controller and compare its performance to the performance of the classical Proportional-Integral-Derivative (PID) controller. PID controllers are mostly used in industrial processes due to their simplicity of implementation. However, PID controllers have some disadvantages. One of these disadvantages is that PID controllers offer lower robustness than robust control schemes when the industrial process operates in the presence of disturbances. Simulations are conducted in MATLAB\Simulink environment. Furthermore, the performance of the proposed controller is compared with the PID controller in terms of error-dependent performance indices and time-domain specifications. The simulation results have shown that the proposed controller provides robust set-point tracking, good disturbance rejection, and handling of the parametric uncertainty properties for nonlinear quadruple tank systems in industrial processes.