Extended Kalman Filter Controller: First Principles Models to Neural Networks

Extended Kalman filters (EKF) have been widely employed for state and parameter estimation in chemical engineering systems. Gao et al. [Gao, F., Wang, F. and Li, M. (1999 Gao , F. , Wang , F. , and Li , M. (1999) . A neural-network-based nonlinear controller using an extended Kalman filter , Ind. Eng. Chem. Res. , 38 , 2345 – 2349 [CROSSREF] [CSA] [Crossref], [Web of Science ®] , [Google Scholar]). Ind. Eng. Chem. Res., 38 , 2345–2349] have proposed the use of EKF for control computation using a neural network representation of the system in a discrete-time framework. In the present study, an EKF controller is proposed in a continuous time framework with models incorporating different levels of process knowledge. The problem of process-model mismatch is handled by incorporating EKF-based state and/or parameter estimation along with control computation. A batch reactor temperature control problem for a highly exothermic reaction between maleic anhydride and hexanol to form hexyl monoester of maleic acid is considered as a test bed to evaluate the performance of the proposed control schemes. Three different models are considered, namely the first principles model, a reduced-order process model, and an artificial neural network (ANN) model for formulation of the control schemes. The performance of the proposed control scheme using first principles model is compared to that of generic model control, and a similar performance is achieved. The present study illustrates the usefulness of the proposed control schemes and can be easily extended to general chemical engineering systems.