Rodolpho R. Fonseca, Ivan C. Franco, and Flávio V. da Silva
Fuzzy Logic, Feedforward, Process Control, Bioprocess
Fermentation process is widely used in industries to produce biofuels, beverages, foods and medicines. As example, ethanol is obtained via corn syrup fermentation by Saccharomyces cerevisae, a bioprocess that is thermal sensitive and requires temperature control to maintain microorganism metabolic rate. In a CSTR, the feed stream temperature is normally a load source, affecting process variable control that makes a feedforward control system highly recommended to this case. However, bioprocesses are intrinsically nonlinear processes, becoming very difficult to obtain satisfactory control performance using classic feedforward control. Nevertheless, Fuzzy logic control is indicated to this type of process because results in nonlinear control law. For this reason, this work presents a generic Fuzzy feedforward control strategy developed to be used with a feedback control system in nonlinear processes, aiming load rejection improvement. The results shown that the Fuzzy feedforward feedback control system (4FB) was better than only feedback control to reject feed stream temperature loads in Saccharomyces cerevisae fermentation in a CSTR, being an interesting control strategy for load rejection in nonlinear processes.