Cascade Hybrid Control for Anaerobic Digestion Systems*

AbstractA cascade hybrid controller is proposed to guarantee the operational stability of anaerobic digestion systems and at the same time to assure a satisfactory remotion. The effluent chemical oxygen demand (COD) concentration and the dilution rate are taken respectively as the regulated and the manipulated variables. This controller is composed by a continuous inner loop which controls the concentration of volatile fatty acids and updates its reference at each sampling period according to the available discrete information of the COD, enhancing the robustness of the closed-loop with respect of influent disturbances. The performance of the proposed control scheme is illustrated via numerical simulations and compared with a discrete controller which only uses the COD information.