UNKNOWN INPUT OBSERVERS DESIGN FOR A CLASS OF NONLINEAR SYSTEMS - APPLICATION TO BIOCHEMICAL PROCESSES

A general theoretical framework that allows a simultaneous estimation of the reaction rates and the non measured component concentrations in biochemical reactors is proposed. Two main features of the proposed approach are worth to be mentioned. The first one lies in the fact that the reaction rates are treated as unknown inputs and they are simultaneously estimated with the component concentrations (the state variables). The second one is related to the gain of the proposed observers which involves a design function that has to satisfy a mild condition which is given. Different expressions of such a function are proposed. Of particular interest, it is shown that high gain like observers and sliding mode like observers can be derived by considering particular expressions of the design function. The performance of the proposed observers is highlighted in simulation through an example dealing with a chemical reactor.