Design of a cascade observer for a model of bacterial batch culture with nutrient recycling

Abstract

A mathematical model of microbial growth on a single limited substrate in batch culture is proposed as an extension of the Monod's one. This model takes into account cell mortality, non-viable cell accumulation and cell recycling. We consider that only substrate concentration and total biomass are measured on-line. The parameters of the model are not identifiable at steady state, but we propose a design of an observer that reconstructs both parameters and state variable with a practical convergence, from any initial condition away from the equilibrium. The observer is built as a coupling of two non-linear observers in cascade with different time scales.