LQ Digital Control of Coupled Liquid Level Equal Atmospheric Tanks – Design and Simulation VLADIMÍR BOBÁL, STANISLAV TALAŠ and MAREK KUBALČÍK Department of Process Control

The flow coupled liquid level control systems are extensively used e. g. in chemical processes and refineries in the petrochemical industry. These processes are characterized by high-order dynamic behaviour or large time constants and time-delays. Time-delays (dead time) are mainly caused by the duration needed to transport mass, energy or information. In many cases time-delay is caused by the effect produced by the accumulation of a large number of low-order systems. One of the possibilities to control such processes is their approximation by lower-order model with time-delay. The contribution is focused on the design of the control of a set of equal liquid cylinder atmospheric tanks. The designed digital control algorithm is based on approximation of high-order process by a second-order model with time-delay. The controller algorithms use the digital modification of the linear quadratic (LQ) Smith predictor (SP). The LQ criterion was combined with pole assignment principle. These algorithms were successfully verified in simulated conditions in the MATLAB/SIMULINK programme environment. Key-Words: Set of atmospheric tanks, Flow liquid level control, Time-delay system, Smith predictor, LQ digital control.