NONLINEAR ESTIMATION OF SPECIFIC GROWTH-RATE FOR AEROBIC FERMENTATIONPROCESSES

The specific growth rate of the biomass, a very important parameter of almost every fermentation process, cannot be measured directly or est imated from related variables, as the concentrations of biomass, subst rates, or products, due to the lack of reliable and cheap sensors. In this article a stable adaptive estimator of the specific growth rate i s designed for those aerobic processes where the measurement of the ox ygen uptake rate is available on-line. This particular approach can be applied also for other reaction rates if the model of the process sat isfies some very general assumptions, which make the dynamics of the m easured reaction rate a nonlinear function only of two unknown paramet ers, the specific growth rate and its time derivative. With respect to a previous similar approach, the new estimator has one additional par ameter and a different nonlinear structure. From the analysis of the d ynamics of the estimation error, a tuning criterion is derived, by whi ch the two different algorithms can be compared under similar conditio ns. Simulation results show a good performance of both estimators for various kind of processes and disturbances. (C) 1995 John Wiley & Sons , Inc.