WEBVTT
Kind: captions
Language: en

00:00:14.420 --> 00:00:17.480
Hello everybody.My name is Ying-Jen Cheng.

00:00:17.880 --> 00:00:20.340
I am an assistant professor

00:00:20.500 --> 00:00:27.040
in the department of electrical engineering, National Taipei university.

00:00:27.480 --> 00:00:29.555
Today, I want to introduce

00:00:29.555 --> 00:00:32.065
Fuzzy Logic Control Systems

00:00:32.280 --> 00:00:34.340
and Their Applications.

00:00:35.080 --> 00:00:37.840
This is the outline of today’s course

00:00:37.940 --> 00:00:39.600
including Background,

00:00:40.060 --> 00:00:41.460
Fuzzy Set Theory,

00:00:42.100 --> 00:00:43.680
Fuzzy Logic Controller

00:00:44.480 --> 00:00:46.300
and Applications.

00:00:47.020 --> 00:00:52.000
Now I am going to start with the background of Fuzzy Set Theory.

00:00:52.960 --> 00:01:00.900
Fuzzy Logic was proposed  in 1965  by Zadeh in his paper "Fuzzy Sets".

00:01:01.480 --> 00:01:02.620
We can see here.

00:01:02.880 --> 00:01:03.940
This is Zadeh.

00:01:04.600 --> 00:01:07.920
He just passed away about two years ago.

00:01:08.540 --> 00:01:16.320
At first, fuzzy sets and fuzzy logic were not accepted when proposed by Zadeh.

00:01:16.840 --> 00:01:18.020
We can see here.

00:01:18.420 --> 00:01:20.600
In 1975,

00:01:21.280 --> 00:01:25.080
Zadeh’s colleague offered  his assessment

00:01:25.680 --> 00:01:29.480
“Fuzzy theory is wrong, wrong, and pernicious.

00:01:29.640 --> 00:01:33.820
What we need is more logical thinking, not less.

00:01:34.400 --> 00:01:41.760
The danger of fuzzy logic is that it will encourage the sort of imprecise thinking

00:01:42.280 --> 00:01:45.600
that has brought us so much trouble.

00:01:46.140 --> 00:01:50.060
Fuzzy logic is the cocaine of science.”

00:01:50.660 --> 00:01:51.400
However,

00:01:51.940 --> 00:01:54.960
fuzzy logic was fully accepted

00:01:55.540 --> 00:01:59.400
and implemented in products in Japan.

00:01:59.840 --> 00:02:05.480
The fuzzy logic revived in the US in the late 80s.

00:02:06.560 --> 00:02:10.500
Now I am going to introduce the Fuzzy Set Theory.

00:02:11.260 --> 00:02:19.320
Fuzzy sets and fuzzy logic are based on the way the brain deals with inexact information.

00:02:20.020 --> 00:02:26.160
The way we perceive the world cannot always be defined in true or false.

00:02:26.900 --> 00:02:28.900
We can see this example.

00:02:29.940 --> 00:02:31.320
This is an apple

00:02:31.940 --> 00:02:34.060
and this is an apple core.

00:02:34.640 --> 00:02:35.940
How about this one?

00:02:36.260 --> 00:02:38.820
It is not totally an apple.

00:02:39.200 --> 00:02:42.280
Of course it is not an apple core.

00:02:43.200 --> 00:02:44.380
In this case,

00:02:44.760 --> 00:02:48.520
we can use the concept of fuzzy set theory.

00:02:48.980 --> 00:02:58.340
We can say its membership degree in Apple is 0.8 and in apple core is 0.2.

00:02:59.060 --> 00:03:01.500
Also, we can see this example.

00:03:02.340 --> 00:03:05.400
Assume that your child got a fever

00:03:05.860 --> 00:03:08.940
and you took him to see a doctor.

00:03:09.280 --> 00:03:10.920
The doctor said that

00:03:11.260 --> 00:03:13.460
if he get a strong fever

00:03:13.900 --> 00:03:16.880
please take him to a hospital.

00:03:17.540 --> 00:03:19.900
The doctor also said that

00:03:20.220 --> 00:03:25.980
strong fever means the body temperature is higher than 39 degree.

00:03:26.480 --> 00:03:34.700
So what will you do when the body temperature of your child is 38.8 degree?

00:03:35.540 --> 00:03:38.760
If you use the conventional set theory,

00:03:39.240 --> 00:03:40.860
the membership degree

00:03:41.260 --> 00:03:48.160
in Strong Fever is 0. That means it’s totally not a strong fever.

00:03:49.020 --> 00:03:52.400
Hence you may still watch TV on sofa.

00:03:52.860 --> 00:03:58.000
However, it’s really strange if the child is really yours.

00:03:58.640 --> 00:04:03.800
So in this case, we naturally use the fuzzy set theory.

00:04:04.420 --> 00:04:14.120
The membership degree in strong fever is 0.8 when the body temperature is 38.8 degree.

00:04:14.660 --> 00:04:18.360
Hence you should be ready to go to the hospital.