Feedback linearizing controller coupled to an Unscented Kalman filter for lactic acid regulation

This paper deals with the development of a control law for the regulation of the lactic acid concentration in its biotechnological production process. The studied system consists in a continuous bioreactor using wheat flour as raw material. Three reactions take place at the same time in the bioreactor: the gluten hydrolysis, the maltose saccharification and the glucose fermentation. This paper considers the optimization of the two last reactions. The optimal set point that maximizes the bioprocess productivity is first determined. Then, a state feedback linearizing controller is developed to maintain the lactic acid concentration at this optimal set point. Nevertheless, knowledge of all states variables is required for this kind of control law. Since the sole online measurement is the lactic acid concentration, robust and efficient estimators of the non-measured states have to be developed. In this paper, an Unscented Kalman filter (UKF) is proposed to estimate the biomass and substrates concentrations in the bioreactor and is then coupled with the feedback linearizing control law. Numerical simulations have been carried out to assess the control law performance.