Nonlinear observer design for process monitoring

The present work proposes a systematic nonlinear observer design framework for process monitoring. The objective is to accurately monitor key process variables associated with process safety or product quality, by designing a model-based nonlinear observer that directly utilizes the available inform ation coming from continuous-time on-line process output measurements. The nonlinear observer possesses a state-dependent gain which is computed from the solution of a system of first-order linear partial differential equatio ns (PDEs). Depending on whether the process operates in continuous or batch made, a different mathematical treatment and solution scheme for the syste m of PDEs is needed. Within the proposed design framework, both full-order and reduced-order observers are studied. Finally, the performance of the pr oposed observer is evaluated in two chemical-engineering examples: (1) a ca talytic batch reactor where the objective is to accurately estimate the cat alyst activity and (2) an exothermic CSTR that exhibits steady-state multip licity and the heat released by the reaction needs to be closely monitored.