Modelling and temperature control of electrical heat treatment furnaces

This thesis addresses different kinds of control strategy applications for electrical heat treatment furnaces. First, a dynamic model of an electrical heat treatment furnace has been developed to describe its termal behavior, and the state equations have been obtained in the standard matrix form. Then, system parameters of the furnaces used in the numerical calculations have been determined. Three different values of thickness of the insulation layer have been considered to investigate the effect of insulation on the system behavior. Since determination of the equivalent thermal resistance between the inner furnace wall and the processed material is difficult, three different values of it have been used. The calculations were carried out for two different mass values of the processed material. Algorithms have been developed to perform on-off, PID, optimum, and reduced-order state observer based optimal control methods. Numerical simulations have been carried out to bring temperature of the processed material from the environment temperature to a final reference temperature by using each of the control methods. Results have been presented by performance charts which summarize the control accuracy and the transient response features. Time response of the system output and other relevant variables have been presented in graphical form. Performance charts and graphics obtained from simulations have shown that the reduced-order state observer based optimal control is as good as the optimal control in which all the state variables are employed, and provides much better control accuracy, relative stability and speed of response compared to the other proposed control methods.Key words: Electrical heat treatment furnaces, Temperature control, On-off control, PID control, Optimum control, Reduced order observer.