Identification and control of an industrial polymerisation process

This paper deals with the application of identification and control to an industrial polymerisation process. The final control objective in the present process is to obtain a polymer of a viscosity as homogeneous as possible. The process is characterized by two key inputs : the catalyst feed rate and the air flow rate in the reactor. The first input is the control input, and the second plays indeed the role of a disturbance. The model identification (e.g. (Ljung, 1987) also put in evidence a drift in the gain of the transfer function between the polymer viscosity and the catalyst feed rate. The drift is due to the coating of the reactor with high viscosity polymer. The identified model is used to design a predictive controller with feedforward action of the air flow rate. The present study covers all aspects from the model structure and parameter identification to the control design and control performance evaluation.