ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Neural network model predictive control of a styrene polymerization plant: online testing using an electronic worksheet

Brunno F. Santos, Manuela S. Leite, Flávio V. Silva, and Ana M. F. Fileti

School of Chemical Engineering, University of Campinas, Av. Albert Einstein 500, 13083-852 Campinas, SP, Brazil

E-mail: frattini@feq.unicamp.br

Abstract: The batch styrene polymerization process presents transient and nonlinear temperature behavior. In this work, manual control and open loop experiments were carried out in order to build a process knowledge database. Initially, a cascade feedback control loop was implemented by manipulating the thyristor unit of the electrical heater in the thermal fluid tank. Aiming at the MPC development, algebraic equations of a neural network and its adjusted parameters were implemented in an electronic worksheet. Every five seconds, the worksheet was updated with measurements (reactor temperature, thermal fluid temperature and thyristor position) by means of the OLE for the Process Control protocol (OPC). The one-step-ahead temperature prediction was then employed in the objective function of the worksheet solver which used Visual Basic Applications programming. The manipulated variable action was then calculated and sent to the process. A hybrid controller (cascade feedback and MPC) outperformed the pure strategies since the time-integral performance indexes, IAE and ITAE, were reduced by around 22 % and 32 %, respectively. Methodology for the Model Predictive Control presented in this study was considered feasible because the solver of Microsoft Office Excel (2007) is very friendly, easy to understand and ready to implement using VBA

Keywords: predictive control – artificial neural networks – styrene polymerization – electronic worksheet

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-012-0165-z

Chemical Papers 66 (7) 654–663 (2012)