Multi-rate nonlinear state estimation in a polymerization reactor

A new multi-rate nonlinear observer design method is presented. It can use a nonlinear process model in the estimator design directly, without any linear approximation. The multi-rate nonlinear state observer is easy to design and implement and is computationally efficient. The implementation and performance of the observer design method are shown by a polymerization reactor in which free-radical solution polymerization of styrene takes place. The initiator concentration and the three leading moments of the molecular weight distribution (MWD) of the polymer product are estimated continuously from (i) the frequent measurements of the reactor temperature, jacket temperature and the reacting-mixture density and (ii) the infrequent and delayed measurements of the leading moments of the MWD.