Self tuning PID control of semi-batch polymerization reactors using genetic algorithm

viSELF TUNING PID CONTROL OF SEMI-BATCHPOLYMERIZATION REACTORS USING GENETIC ALGORITHM(M.Sc. Thesis)Sevtap KARAKURTGAZI UNIVERSITYINSTITUTE OF SCIENCE AND TECHNOLOGYJanuary 2007ABSTRACTPolymers are used in variety of growing fields in our daily life. The mainobjective in polymerization processes is to produce polymer of desired quality.Molecular weight and molecular weight distribution of the polymer are the mostimportant quality variables due to their effect on the processability. Since thesevariables are strongly influenced by the reactor process conditions, in order toobtain a product at desired quality, reactor process conditions must beoptimized and controlled. In semi-batch polymerization reactors, due tochanging monomer concentration, the reaction rate varies with the time andnon-linearly. The heat transfer characteristics change by the large changes inthe viscosity of the polymer solution over the reaction and by the environmentalconditions like temperature. These factors complicate the automatic control ofpolymerization processes. In this study, considering operational constraints,optimum reactor temperature for the desired conversion and molecular weightin minimum time was tried to track using self-tuning PID controller. Tuningparameters of controller were obtained by using Genetic Algorithm. Geneticalgorithm is an optimization method used for the solution of problems that aredifficult or impossible to solve by conventional methods. The fitness function forgenetic algorithm was chosen to be integral of the absolute value of error(IAE).viiThe results show that self-tuning PID controller with genetic algorithm controlsthe temperature of the polymerization reactor very well.Science Code : 912.1.084Key Words : Genetic Algorithm, Self-tuning PID control, Semi-batchpolymerization reactorsPage Number : 92Adviser : Prof. Dr. Sebahat ERDOĞAN