Constrained output feedback control of a multivariable polymerization reactor

A multivariable nonlinear control strategy which accounts for unmeasured state variables and input constraints is developed for the free-radical polymerization of methyl methacrylate in a continuous stirred tank reactor. Monomer concentration and reactor temperature are controlled using a technique which combines nonlinear input–output decoupling and linear model predictive control. Input constraints are handled explicitly by applying linear model predictive control to the constrained linear system obtained after feedback linearization and constraint transformation. Unmeasured initiator and solvent concentrations are accounted for by treating the live polymer concentration as an unknown parameter which is estimated on-line. The performance of the control strategy is compared to other nonlinear control techniques through closed-loop simulations.