Unknown inputs observer applied to an alternating activated sludge process

This work deals with the design of an unknown inputs observer for MIMO nonlinear hybrid systems. It consists in a switching between different observer to a simultaneous estimate of the unavailable states and inputs. A nonlinear reduced model of an alternating activated sludge process, which is decomposed on an aerobic phase and an anoxic phase, is presented. They are the results of a nitrification and de-nitrification phases. The principal goal of the observer is directed to cure the problem of unavailable input of the influent ammonia concentration and non-measured states of every sub-model. Simulation results verify the effectiveness of the proposed hybrid observers.