A robust non‐linear feedback control strategy for a class of bioprocesses

This study proposes a multiple‐input/multiple‐output robust approach to the control of bioprocesses based on a cascaded‐loop strategy. The internal loop is a classical input‐to‐output feedback linearising controller which is obtained from the nominal dynamics of the bioprocess. Then, the outer loop is designed based on the internal model principle to obtain zero steady‐state tracking error (and disturbance rejection) for constant signals while ensuring the robust stability of the overall closed‐loop system. In addition, a robust Luenberger‐like observer is proposed to estimate unmeasured state variables for the feedback linearising control law. The approach is applied to the simultaneous control of biomass and substrate concentrations in a perfusion/chemostat bioreactor, where the simulation results demonstrate the effectiveness of the proposed control strategy.