The Research Of Feed Forward Fuzzy PID Control Method Of LCD Glass Furnace Temperature

LCD glass has qualities of good light transmittance,thin thickness,high purity,and there is a extremely high requirement of process temperature.In the control process of the temperature,both settling time and steady-state precision have an influence on the quality of the product.Therefore,the control of LCD glass furnace temperature is more conflict than the control of traditional glass furnace temperature.The control system of LCD glass furnace temperature is a system with the features of typical nonlinear,large lag and difficulty in modeling.The single PID control method was used in traditional LCD glass furnace,and there would be bubbles or stripes in the glass with this control method.The LCD glass furnace was used as the study object in this paper,and the decision was to design an effective control method which can achieve a smaller overshoot,a better stability,a decreased settling time,a reduced steady-state error and can resist the coupling interference effectively.In the choice of heating mode,two kinds of heating methods named burning fuel and electric heating was chose in this paper,and the temperature control circuit of two kinds of heating methods was represented.The traditional PID control method was combined with the fuzzy control method in the study of temperature control method,and a fuzzy PID control algorithm with feed forward was designed when a feed-forward control was added.Smaller steady-state error of PID control and smaller overshoot of fuzzy control was achieved in this kind of control algorithm.When feed-forward link was added in the system,settling time was decreased and steady-state error was reduced when there was a interfering signal.The specific researching contents of this thesis was as follows:(1)The influence of heating mode and temperature control method of LCD glass furnace on the quality of the product was analyzed.(2)The LCD glass production process and the important position of LCD glass furnace temperature control was analyzed.(3)The LCD glass furnace temperature control program was focused on in this paper.The feed-forward and feedback controller structure was designed,and the temperature control block diagram with feed-forward was given.(4)The fuzzy PID control algorithm was studied.The fuzzy PID control algorithm was designed by combining PID control with fuzzy control,and the realization of fuzzy PID control on PLC was completed.(5)The effects of PID control,fuzzy PID control and feed-forward fuzzy PID control on the LCD glass furnace temperature control were analyzed and studied through simulation experiments.The results showed that there were comprehensive advantages of a smaller overshoot,a better stability,and resisting the coupling interference effectively in feed-forward fuzzy PID control method.