On-line estimation of biomass concentration and non stationary parameters for aerobic bioprocesses

The biomass concentration, a very important state variable of almost every bioprocess, cannot often be measured directly or estimated from related variables, such as the concentrations of substrates or products, due to the lack of reliable and cheap sensors. In this paper, a stable observer of biomass concentration is designed for those aerobic processes where the measurement of oxygen uptake rate is available on-line. This particular approach can also be applied for other reaction rates if the model of the process satisfies some very general assumptions, which make the dynamics of the biomass growth rate and the biomass concentration a linear function only of this unknown parameter and this state variable. With respect to a previous similar approach, the new observer has a different linear structure, which allows a simple tuning procedure. A comparison between the two different algorithms under similar conditions is realized.