Fuzzy self-tuning PI controller for bioreactors

Abstract

A fuzzy self-tuned PI controller for regulation of a nonlinear bioreactor is presented. The basic idea is to parameterize Ziegler-Nichols like tuning formula by two parameters α and β and then to use an on-line fuzzy inference mechanism to tune the PI controller parameters k _c and τ _I . The fuzzy self-tuning method takes the process output error as input and the tuning parameters α and β as outputs. Simulation studies on the nonlinear bioreactor model equations show that the present method is superior to that of fixed parameters conventional PI controller (based on transfer function) for both servo and regulatory problems. The present fuzzy logic controller is robust to process parameters uncertainties and to changes in magnitude and direction of the disturbances.