The present work focuses on a comparative study of the performance of Fuzzy and conventional PID controllers applied to temperature control in the bromelain precipitation process from aqueous extract of pineapple wastes. A quantitative analysis of process nonlinearities was performed based on process reaction curves methodology. Different sensitivity to control actions was detected at different batch times. The conventional controller was tuned by applying Ziegler-Nichols equations to the process parameters obtained at the beginning of the experiment, followed by fine tuning based on trial-and-error procedure. Using the knowledge obtained from the reaction curves analysis, the Fuzzy controller tuning consisted in changing the universe of discourse, the rule base and the support sets of membership functions. It was observed that the Fuzzy controller outperformed the PID, showing the smallest value of integral of time multiplied by absolute of the error (ITAE), a great recovery of enzymatic activity and the smallest consumption of electric energy for the system refrigeration.
Fuzzy controller; PID controller; Bromelain; Fieldbus
