Discrete-time nonlinear observer-based estimators for the on-line estimation of the kinetic rates in bioreactors

Simple discrete-time estimators which allow the on-line estimation of the kinetic rates from the measurements of components' concentrations inside a bioreactor are proposed. In fact, the proposed estimators are obtained by a direct forward Euler discretization of continuous-time estimators. The design of the estimators in the continuous as well as in the discrete-time does not require or assume any model for the kinetic rates. One of the main characteristics of these estimators lies in the easiness of their calibration. We here emphasize on the performances of the discrete version of these estimators, whose stability and convergence are proved under the same conditions as in the continuous case with an additional mild assumption on the sampling time. Simulation and real-life experiments results corresponding to the discrete estimation are given. The accuracy of the obtained estimates as well as the easiness of the estimators' implementation do constitute reliable and powerful arguments for their use, in particular in adaptive control schemes.