An optimal operation strategy for a bioprocess: robustness evaluation

This paper investigates the influence of parameter uncertainty in the reaction rate function on the efficiency of a bang-bang control strategy for a microorganism's growth process. The bang-bang controller is developed to drive the bioreactor from an initial state to a small neighbourhood (target set) of the optimal steady state, while maximizing the productivity. Once the target set is reached, the control effort is switched to the optimal dilution rate, which allows the process to converge to the optimum. This simple control strategy uses a model of the process i) to determine when the switching in the control effort must occur, ii) to determine which initial states will lead the system to an optimal steady state, and iii) to predict the optimal equilibrium point. For certain kinetic coefficients of the model a wide region in the process's kinetic coefficients space is identified, for which the bang-bang control will perform reasonably. Moreover, the productivity of the process will be higher than the one predicted by the model in almost the entire robustness region