Optimal controller design using discrete linear model for a four tank benchmark process

Abstract

This paper deals with implementation of an optimal linear controller for a laboratory liquid four-tank system. A discrete linear model is used for modeling a class of MIMO nonlinear systems. It is shown that this model can identify these nonlinear systems with any desired accuracy, as a result the designed controller is accurate. The global stability condition is studied. The advantage of the proposed method against other controllers is its simplicity in design, there is no need for physical equations of the nonlinear system, and it is more accurate than other proposed linear methods. We present a step-by-step description of all steps leading towards the derivation and implementation of such a controller. The proposed method is tested on an experimental four tank benchmark process.

Keywords: Discrete Taylor series expansion; Discrete linear optimal controller; Four-tank system; Nonlinear systems.