Fuzzy Logic Control Systems

Hello everybody.My name is Ying-Jen Cheng. I am an assistant professor in the department of electrical engineering, National Taipei university. Today, I want to introduce Fuzzy Logic Control Systems and Their Applications. This is the outline of today’s course including Background, Fuzzy Set Theory, Fuzzy Logic Controller and Applications. Now I am going to start with the background of Fuzzy Set Theory. Fuzzy Logic was proposed in 1965 by Zadeh in his paper “Fuzzy Sets”. We can see here. This is Zadeh. He just passed away about two years ago. At first, fuzzy sets and fuzzy logic were not accepted when proposed by Zadeh. We can see here. In 1975, Zadeh’s colleague offered his assessment “Fuzzy theory is wrong, wrong, and pernicious.

What we need is more logical thinking, not less. The danger of fuzzy logic is that it will encourage the sort of imprecise thinking that has brought us so much trouble. Fuzzy logic is the cocaine of science.” However, fuzzy logic was fully accepted and implemented in products in Japan. The fuzzy logic revived in the US in the late 80s. Now I am going to introduce the Fuzzy Set Theory. Fuzzy sets and fuzzy logic are based on the way the brain deals with inexact information. The way we perceive the world cannot always be defined in true or false. We can see this example. This is an apple and this is an apple core. How about this one?

It is not totally an apple. Of course it is not an apple core. In this case, we can use the concept of fuzzy set theory. We can say its membership degree in Apple is 0.8 and in apple core is 0.2. Also, we can see this example. Assume that your child got a fever and you took him to see a doctor. The doctor said that if he get a strong fever please take him to a hospital. The doctor also said that strong fever means the body temperature is higher than 39 degree. So what will you do when the body temperature of your child is 38.8 degree? If you use the conventional set theory, the membership degree in Strong Fever is 0.

That means it’s totally not a strong fever. Hence you may still watch TV on sofa. However, it’s really strange if the child is really yours. So in this case, we naturally use the fuzzy set theory. The membership degree in strong fever is 0.8 when the body temperature is 38.8 degree. Hence you should be ready to go to the hospital.