LQG/LTR Design for the Concentration Process: Use in the Enological Industry

The four-stage evaporator is the core of the process in the manufacture of concentrated grape juice. The dynamic features of this process are very complex due to inputs and outputs constraints, time delays, loop interactions and the persistent unmeasured disturbances that affect it. Therefore, this kind of process requires a robust control in order to assure a stable operation taking into account the changes in the organoleptic properties of the raw material and, to guarantee the quality of the concentrated product. The mathematical model of the evaporator is obtained by application of the mass and energy balances to each effect. A linear model is identified from a nonlinear model. This linear model is used for control design employing an LTR procedure. Simulation studies show that the proposed control design approach is useful and may prove effective in evaporator control, therefore the performance of the two designs for set point tracking and unmeasured rejection are compared.