A nonlinear observer design for an activated sludge wastewater treatment process

Boulaïd Boulkroune (1) , Mohamed Darouach (1) , Michel Zasadzinski (1) , Serge Gillé (2) , David Fiorelli (2)

1 CRAN - Centre de Recherche en Automatique de Nancy
2 LTI - Laboratoire des Technologies Industrielles

This paper treats the problem of estimating simultaneously the state and the unknown inputs of a class of nonlinear discrete-time systems. An observer design method for nonlinear Lipschitz discrete-time systems is proposed. By assuming that the linear part of this class of systems is time-varying, the state estimation problem of nonlinear system is transformed into a state estimation problem for LPV system. The stability analysis is performed using a Lyapunov function that leads to the solvability of linear matrix inequalities (LMIs). Performances of the proposed observer are shown through the application to an activated sludge process model.

Mots clés: Activated sludge; wastewater treatment process; Lyapunov function; Lipschitz singular discrete-time systems; nonlinear systems; unknown inputs; LPV approach

Domaines: Automatique / Robotique

Boulaïd Boulkroune, Mohamed Darouach, Michel Zasadzinski, Serge Gillé, David Fiorelli. A nonlinear observer design for an activated sludge wastewater treatment process. Journal of Process Control, 2009, 19 (9), pp.1558-1565. ⟨10.1016/j.jprocont.2009.07.017⟩. ⟨hal-00422417⟩