A Nonlinear Process with Variable Parameters and Long Deadtime: Sliding Mode and Linear Algebra Controller's Comparison.

This paper presents the design, simulation, and comparison of different control techniques applied to control a mixing tank's temperature with variable parameters and dominant delay time. The process consists of mixing two fluids inside a tank with variable liquid volume. The cold inlet flow is manipulated through a control valve, and it is mixed with a hot inlet flow to obtain an outlet flow with the desired temperature. The aim of controlling the tank is to have a constant liquid temperature inside it, and it must also maintain that temperature by introducing hot flow disturbancesW1(t). A classic PI controller will be compared with two advanced control techniques, such as Sliding Mode Control and Linear Algebra, based on First Order Plus Dead Time (FOPDT) models. These models capture the essential dynamics of several industrial processes simplifying controller design and tuning. Using ISE and ISU performance indexes, the mixing tank is subj ected to reference changes and disturbances to analyze the controller's performance.