FUZZY-LOGIC CONTROL OF AN UNSTABLE BIOLOGICAL REACTOR

In the present work, we employ a fuzzy logic controller (FLC) to contr ol the unstable state of a nonlinear biological reaction. The state va riable vectors consist of cell density and substrate concentration. Th e dilution rate is used as a manipulated variable to control the react ion dynamics. An analytic form of FLC employing Zadeh AND logic along with Center of Mass defuzzification method is considered. Simulations reveal that for servo response test, the FLC shows satisfactory perfor mance for natural unsteady states for which a conventional PI controll er is known to fail. Further simulations also show that the FLC gives satisfactory regulatory response and is relatively insensitive to the deviations in model parameters.