LMI-based H2 Control of Vertical Nonlinear Coupled-tank System

This study deals with the design and implementation of an H ₂ controller for a vertical nonlinear coupled-tank system. As in the last decades, the chemical industries' processes have been more complicated, the need for robust and powerful controllers is increased. According to the nonlinear properties of these processes, the performance of some of the classical and common controllers, such as Proportional Integral control, is decreased in terms of response time and tracking accuracy. Therefore, to improve some disadvantages of these types of controllers, and make the system robust against the exogenous inputs such as disturbance and sensor noise, the H ₂ control methodology is proposed as an alternative method to control the liquid level of a nonlinear coupled-tank framework. On the other hand, as the H ₂ norm minimizes the Root Mean Square of the signal's energy in all frequencies, the system output and the control signal will be improved. To overcome some mathematical difficulties of the design procedure such as singularity, the Linear Matrix Inequalities (LMI) is used. The simulation and experimental results are compared with the PI+feedforward controller in terms of the design objectives and the acceptable results are obtained.