【導讀】對于時變系統(tǒng)，如果能夠很好地采用模糊控制器進行調節(jié)，其控制結果的。穩(wěn)定性和活力性都會有改善。但是，如果調節(jié)效果不好，執(zhí)行器會因為周期振蕩影響使用壽命，特別是調節(jié)器是閥門的場合，就必須考慮這個問題。為了解決這個問題，出現(xiàn)了很多模糊控制。本文提出的方法采用一個固定的初始域，這樣相當程度上簡化了模糊控制的設定。文中分析了振蕩的原因并分析如何抑制這種振蕩的各種方法，最后，還給出一。善了控制的實時性。模糊控制器的一個主要缺陷就是調整的參數太多。制性能接近于任何一種PID控制。集的個數，映射規(guī)則，基本模糊控制器的參數和不同的算法組合等。選定模糊推理及解模糊的方法。的優(yōu)點，因為它大大簡化實際過程的調整?？刂瓶梢酝ㄟ^改變采樣時間而不改變定義域的范圍實現(xiàn)調整。所用的最小最大模糊推理的影響。但是造成振蕩的另一個可

　　

【正文】 results can be seen in Fig. 10. Fig. 12 shows the time responses with three different settings. Solid line uses the same adjustment as previously described simulation but inference method is ProdMax. Dashdot dot line represents the simulation with 3 membership functions, inference MinMax and defuzzification using triangular membership functions with COG method. Dashanddot line shows simulation results with 3 membership functions, inference MinMax and defuzzification using singletons. When the singletons are used they are placed into the vertex of original fuzzy membership functions. The influence of disturbance with small amplitude of which acts at the input of the system is shown in Fig. 13. 10 Fuzzy controller is generally inclinable to oscillation with relatively small amplitude. The origin of this oscillation is not only incorrect tuning of the parameters but also the inference method MinMax. The oscillations are considerably eliminated when the ProdMax inference method is employed and singletons for defuzzification are used. Another potential source of oscillations is wrong implementation of inference engine. Shift of the vertex point of middle membership function just for on the normalized universe (illustrated in Fig. 15) causes the limit cycles to appear (see results in Fig. 14) without any other external intervention. The initial deviation is caused by PD controller and the oscillations by PI controller. When the singleton membership functions are used instead of triangular ones the described phenomena of oscillations disappear. Following the results in Fig. 14 it can be seen that the singletons as an output membership functions give at the beginning higher oscillation but after the time they disappear (dashed line). Triangular membership functions with COG defuzzification give after short transient response steady limit cycle. Note the nonzero steady state error in both cases. As a consequence we can say that there is a difference between defuzzification using singletons and triangular membership functions even if the COG method is used. 4. CONCLUSION For the fuzzy PID controller setting it is necessary to determine universe ranges and perform tens or hundreds simulation experiments until the acceptable values are found. A retrieval of optimal parameters is very difficult, because the setting is dependent on big amount of other parameters. Method with the unified universe range, stated in this article, considerably simplifies setting of fuzzy PI/PD/PID controllers. It allows approximate adjustment of controller39。s parameters according to wellknown methods for PID controller synthesis. If the universe has nonlinear membership function layout then the results can have better behaviour than the classical PID controller. The fuzzy PID controller can be programmed like a unified block in industrial controller and therefore work consumed on a implementation to the particular control system can be shortened.