Auto Tuning Applied to Distillation Column Based on Armax Model Parameter Estimation

An auto-tuning procedure for PID controllers based on model ARMAX is the main subject of this paper. Such a model has been used in the on-line controller parameters estimation through the relay method, resulting in a smaller deviation between the model and process variables when utilized a normalized regression matrix. The procedure was applied to an Aspen Plus Dynamics (R) model of Naphtha Treatment Unit. The Aspen model takes into account the main control structures and the principal observed disturbances. The procedure has been developed in Visual Basic for Applications programming language, making possible a real-time connection with the Aspen model. The on-line identification of the ARMAX model was made using the RELS (PR), thereby allowing the estimation of the controllers parameters from classical tuning procedures in closed loop. With the use of this strategy, the updating of the controllers parameters has been possible, promoting a superior performance of the control structure.