Research On Fuzzy PID Control System Of Temperature For Electric Boiler

Temperature control is a topic full of new meanings in industry, to different control object, there are different methods and modes. But it is difficult to control well because of characteristics of the temperature itself, such as its great inertia, serious time-lag and the difficulty to establish an accurate mathematical model of the object. A duty in this thesis is to study a kind of appropriate control method to the temperature of the electric boiler. Its'technology requirements are: regulating time must be short, overshoot must be small and the control system must be stable.The method of the electric boiler control is studied deeply by the thesis. The first is PID control. Principle of temperature PID controller is to control the object by the linear combination of temperature deviation's proportional, integral and derivative. The control key is the parameter adjustment. The parameter is adjusted by methods of Ziegler-Nichols, Chien-Hrones and artifical tuning in this thesis. The second method is fuzzy control. The fuzzy control theory is studied and the electric boiler fuzzy controller structure is determined. The fuzzy control rule table is established through analysing the characteristic of the electric boiler temperature in the thesis.In this thesis, the PID control system and fuzzy control system are simulated by using Simulink and fuzzy logic tools in MATLAB. Experimental results illustrate that the PID control is used in the system, regulating time and overshoot always can not achieve the specification .When fuzzy control is used, regulating time and overshoot always can achieves the specification, but system cause steady-state error. So it comes to a new method of combining them together. The patameters of Kp, Ki and Kd are adjust by fuzzy inference. Experimental results illustrate that the fuzzy PID parameters controller achieved the system performance index. The method of fuzzy PID control is a ideal method.In this thesis, basing on the request of the electric boiler heating system to the controller, a temperature controller of the electric boiler is designed, in which the PIC16F877A is used. Its performance include: temperature gathering, algorithm realization, warning, etc. the hardware circuit is designed and the corresponding procedure flow chart is also designed. Such as main program flow chart, Fuzzy PID working flow chart and temperature collection flow chart.