[en] This paper deals with the design of a discrete
time nonlinear observer for an anaerobic digestion process.
The designed observer is devoted to a general class of systems,
precisely linear systems, LPV systems with known and bounded
parameters, and nonlinear Lipschitz systems. In order to
ensure stability of the estimation error, a new LMI condition
is proposed. In this LMI, additional decision variables are
included to enhance its feasibility. Indeed, this was possible due
to the use of a suitable reformulation of the Young’s inequality.
Numerical simulations using the investigated two-step anaerobic
digestion model show the effectiveness of the proposed LMI