A nonlinear Luenberger-type observer with application to catalyst activity estimation

The present work proposes a new approach to the nonlinear observer design problem. Based on the ideas that influenced the development of the linear Luenberger observer theory, the proposed approach develops a nonlinear analogue. The formulation of the observer design problem is realized via a system of first-order linear PDEs, and a rather general set of necessary and sufficient conditions for solvability is derived. Within the proposed design framework, both full-order and reduced-order observers are studied. The performance of the proposed nonlinear observer is evaluated in a batch reactor example, where catalyst deactivation takes place and the problem of catalyst activity estimation becomes truly important for an efficient reactor operation.