AN INTERVAL OBSERVER FOR NON-MONOTONE SYSTEMS: APPLICATION TO AN INDUSTRIAL ANAEROBIC DIGESTION PROCESS

This article proposes a new class of observers in order to estimate unmeasured variables of a biotechnological process. The observer is developed on the basis of interval estimates, which provide guaranteed upper and lower bounds of the unknown variables. The proposed method exploits monotonicity properties of the error dynamics. A bundle of observers is generated by appropriately varying the observer gains. The method is applied to a real industrial anaerobic digestion plant, for the estimation of the key variables on the basis of the available measurements of the methane flow rate.