A nonlinear observer for semidetectable chemical reactions with application to kinetic-rate-constant estimation

In this paper we develop a nonlinear observer to estimate the concentration of reactants in a kinetic network when kinetic rate constants are unknown. When kinetic rate constants are unknown a steady-state error is present in the observer states. We thus develop an augmented observer that accounts for this steady-state error. We demonstrate this technique on numerical examples of increasing complexity, starting with a nominal case and then off-nominal cases, where input and output noise corrupt the available measurements, and finally when a kinetic rate constant evolves periodically over time with unknown dynamics.