FUZZY SELF-TUNING PI-CONTROLLER FOR BIOREACTORS

A fuzzy self-tuned PI controller for regulation of a nonlinear bioreac tor is presented. The basic idea is to parameterize Ziegler-Nichols li ke tuning formula by two parameters alpha and beta and then to use an on-line fuzzy inference mechanism to tune the PI Controller parameters k(epsilon) and tau(I). The fuzzy self-tuning method takes the process output error as input and the tuning parameters alpha and beta as out puts. Simulation studies on the nonlinear bioreactor model equations s how that the present method is superior to that of fixed parameters co nventional PI controller (based on transfer function) for both servo a nd regulatory problems. The present fuzzy logic controller is robust t o process parameters uncertainties and to changes in magnitude and dir ection of the disturbances.