The use of second order sliding modes, namely the generalized super-twisting algorithm or one of its variants, is illustrated for two applications in bioprocesses. Both the theoretical framework and some practical aspects are discussed. Two applications are considered: the design of a variable-gain super-twisting observer to robustly estimate the reaction rate in a bioreactor, and the proposal of a pseudo-super-twisting controller that maximizes the product output rate for a simplified model of a bioprocess. The case studies are the on-line estimation of the nitrogen quota in a microalgae bioreactor, and the maximization of biogas production during anaerobic wastewater treatment.
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