| Temperature is one of the main parameters controlled in the industrial process control,for example in the metallurgy industry,machinery industry,food industry,chemicalindustry,print industry and the petroleum-processing industry etc., various kinds of heatersand reactors are extensively used. But it is very difficult to control temperature well becauseof some characteristics of the temperature itself. For example temperature's inertia is great,it's time-lag is serious and it is difficult to establish accurate mathematical model of theobject. This paper is to study an adapt control method to control the temperature of theelectric oven, the technology demand of control method is: the regulating time must beshort, the overshoot must be zero and steady-state error must be in ±1℃. For the electric oven, there are many control methods to be selected. The first is the PID method. It is simple and easily realized. In most cases, it can meetthe control demand. At present, in all of the control methods in use, the PID method stillaccounts for over 80 percent. It has the advantage to eliminate the steady-state error. Itsefficiency depends on it parameters. In terms of those control objects whose models arecomplicated or are established difficultly, the PID method has very great limitation. Moreover,because of the conflict between quickness and the small overshoot, PID control cannot meetcontrol demand. Second method can be fuzzy control, because it has the advantage of quickness, itsrobustness is very good and it needn't to know the object's mathematical model. But becauseits theory is not very perfect, the control quality cannot be expected in advance. And it cancause easily steady-state error because it is restricted by limited grades of the fuzzy rules. This paper analyses the advantages and disadvantages of the PID control and fuzzycontrol and comes to the method of combining them together. This method can get theadvantages of them and avoid the disadvantages of them. In this paper it is fuzzy self-tuningPID control method in which KPand KI of PID controller are adjusted by fuzzy control rules. In the paper stimulations of PID control,fuzzy control and fuzzy self-tuning PIDcontrol are done by MATLAB. And then the fuzzy self-tuning PID control method is selected,because it can meet the control demands and it's anti-interference ability is very strong.Moreover, simulation results show that: it's robustness is good because very good controlresult that the regulating time is short, the overshoot is zero and the steady-error is very littlecan be obtained, for first-order inertia and time-lag model. In the paper AT89S52 is used as controller, Pt100 is used as temperature sensor, andICL7135 is used as A/D converter, because of it's precision being high and anti-interferenceability being strong. Performance unit is composed of photoelectrical coupler MOC3061 andTRIACS BTA20.Man-machine circuit is composed of buttons, LED and warning unit, etc.While the hardware circuit is designed, the corresponding procedure flow chart is alsodesigned.
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