Online Estimation and Adaptive Temperature Control of Polymerization Reactor

The temperature control of a semi-batch polymerization reactor described by Chylla and Haase, a control engineering benchmark problem is considered. The process is nonlinear and time varying in nature. There is significant change in heat transfer coefficient, during a batch due to changes in the viscosity of the polymer and also from batch to batch due to surface fouling. Also change in ambient temperature during summer and winter makes the temperature control of this process a challenging task. The conventional cascade control provides robust operation, but often lacks in control performance concerning the required strict temperature tolerances. Hence an adaptive control design by employing a self tuning cascade with feed forward control concept is proposed in this paper to provide excellent control. This design calculates a trajectory for the cooling jacket temperature in order to follow a predefined trajectory of the reactor temperature. The reaction heat as well as the heat transfer coefficient required for the proposed controller is estimated online by using Unscented Kalman Filter (UKF). Simulation results under model uncertainties show the effectiveness of the proposed adaptive control concept.