Decentralized Robust Controller for Two-Tank Liquid Flow Process with Recycle

In this paper, we propose the improvement of a modern technique for the synthesis of decentralized robust control for two-input, two-output (MIMO) nonlinear systems. interaction, stability analysis, and controller design for the Two-Tank Liquid Flow Process with recycling have been done. The equations of the system are non-linear and have two inputs and two outputs. The Gershgorin bands check the system's interaction and the system's instability is studied by using a generalized Nyquist diagram. The linear model is used, so that it is necessary to consider uncertainty. In a physical system, it is essential to consider several goals; despite the uncertainty, the system should be stable, desire performance without considering the uncertainty, and minimize the disturbance effect, due to the interaction. In the first step, the pre-compensator is used for decoupling. Then, due to the uncertainty and disturbance, the H 2 /H ∞ robust controller is designed to minimize the three conditions of robust stability and nominal performance while minimizing the disturbance effect for each channel. The proposed method, for the synthesis of the decentralized robust nonlinear multivariable control systems, is approved for the two-tank system. The simulation results show the success of the robust decentralized controller with minimum control signal and order.