CONTROL OF OSCILLATING MICROBIAL CULTURES DESCRIBED BY POPULATION BALANCE MODELS

Nonlinear feedback control laws are derived which attenuate undesired oscillations or induce synchrony in microbial cultures described by po pulation balance models. The population balance model is solved using a finite difference method. A model suitable for controller design is obtained by expressing the population balance equations in terms of mo ments of the cell age distribution. Oscillations are damped, and the c ulture is forced to a desired equilibrium point by designing a feedbac k linearizing controller which manipulates dilution rate and feed subs trate concentration and regulates cell number concentration and substr ate concentration. An approximate equilibrium solution to the populati on balance equations is used to determine setpoint values for the two controlled variables. Cell synchrony is induced by designing a feedbac k linearizing controller which manipulates feed substrate concentratio n and regulates substrate concentration to an oscillatory trajectory o f a predetermined period. The performance of the nonlinear controllers is evaluated through closed-loop simulations.