Study Of Interval-Valued Fuzzy Control

People had studied fuzzy systems theory for several years and had made very great achievements, especially on the automatic controlled field. But there were some problems about fuzzy theory, for example, it was difficult to make sure fuzzy variable membership function, and its information was simple. The systematic precision became low and the dynamic characteristics became bad as results of fuzzy simplification of information. In order to improve the control precision of system, people increased quantization progression. In result control rules would be added and response of systems would be slow. Turksen proposed the interval-valued fuzzy sets in 1986. The membership function of interval-valued fuzzy sets was easier to assure than that of the fuzzy sets. And its membership function contained not only the positive information of variable but also the negative information that accorded with the life. So the interval-valued fuzzy sets was a intelligent theory imitating the brain visually. The author applied the interval-valued fuzzy sets theory to the control field to design controller for progressing the fuzzy control technology. Two interval-valued fuzzification methods that were the key of the design were proposed in the paper: the definition method and the expressions meathod. The interval-valued fuzzy controllers were designed using several interval-valued fuzzy reasonings on the basis of control rules from the boiler model. The effect of interval-valued fuzzy controller was compared with that of fuzzy controller on Matlab. The thesis was classified into three chapters and the contents were outlined as follows: In chaper 1,an introduction was fist given to the background of fuzzy control. Then the development of interval-valued fuzzy theory was reviewed. Finally, the main achievement and arrangement of the thesis were conclued. In chapter 2, an introduction was first given to the basis concepts of fuzzy control. Then its general principle and theoretical basis of fuzzy control were discussed. Finally, a discussion was given to its general structure and basic analysis methods. In chaper 3, interval-valued fuzzy theory and interval-valued fuzzy control were studied. Fist, the interval-valued fuzzy defination and three interval-valued fuzzy reasonings were introduced. Then the interval-valued fuzzy controller was designed and was tested in the lab.