Fast Extremum Seeking for Bioreactors using a Variable Structure Control Approach

A novel extremum seeking technique to maximize biogas production in a second order bioreactor model is proposed. The strategy is a switched control, with only two input values, which drives system trajectories to the optimal operating point by using only the measurement of the biogas production rate. For tuning the control law the knowledge of neither the reaction rate nor the system parameters is needed, and only an upper bound estimate of the reaction rate is required. In contrast to the classical Extremum-Seeking strategies, the control strategy proposed here does not assume a quasi-stationary behavior of the plant, and is therefore able to attain the optimal operating point very fast.