Fuzzy Logic
C HAPTER S EVENTEEN
FUZZY LOGIC
Slumber not in the tents of your fathers. The world is advancing. Advance with it. —Giuseppe Mazzini
Industrial Text & Video Company 1-800-752-8398 www.industrialtext.com
SECTION 5
Advanced PLC Topics and Networks
Fuzzy Logic
CHAPTER 17
C HAPTER H IGHLIGHTS
Fuzzy logic provides PLCs with the ability to make “reasoned” decisions about a process. In this chapter, we will introduce you to the basics of fuzzy logic, including fundamental concepts and historical origins. We will demonstrate how fuzzy logic can be used in practical applications to provide realtime, logical control of a process. When you finish this chapter, you will have learned about the advanced applications of PLCs. You will then be ready to learn how to connect PLCs through local area networks.
17-1 I NTRODUCTION TO F UZZY L OGIC
Fuzzy logic is a branch of artificial intelligence that deals with reasoning algorithms used to emulate human thinking and decision making in machines. These algorithms are used in applications where process data cannot be represented in binary form. For example, the statements “the air feels cool” and “he is young” are not discrete statements. They do not provide concrete data about the air temperature or the person’s age (i.e., the air is at 65°F or the boy is 12 years old). Fuzzy logic interprets vague statements like these so that they make logical sense. In the case of the cool air, a PLC with fuzzy logic capabilities would interpret both the level of coolness and its relationship to warmth to ascertain that “cool” means somewhere between hot and cold. In straight binary logic, hot would be one discrete value (e.g., logic 1) and cold would be the other (e.g., logic 0), leaving no value to represent a cool temperature (see Figure 17-1).
Hot
1
Cold 0
Figure 17-1. Binary logic representation of a discrete temperature value.
In contrast to binary logic, fuzzy logic can be thought of as gray logic,
FUZZY LOGIC
Slumber not in the tents of your fathers. The world is advancing. Advance with it. —Giuseppe Mazzini
Industrial Text & Video Company 1-800-752-8398 www.industrialtext.com
SECTION 5
Advanced PLC Topics and Networks
Fuzzy Logic
CHAPTER 17
C HAPTER H IGHLIGHTS
Fuzzy logic provides PLCs with the ability to make “reasoned” decisions about a process. In this chapter, we will introduce you to the basics of fuzzy logic, including fundamental concepts and historical origins. We will demonstrate how fuzzy logic can be used in practical applications to provide realtime, logical control of a process. When you finish this chapter, you will have learned about the advanced applications of PLCs. You will then be ready to learn how to connect PLCs through local area networks.
17-1 I NTRODUCTION TO F UZZY L OGIC
Fuzzy logic is a branch of artificial intelligence that deals with reasoning algorithms used to emulate human thinking and decision making in machines. These algorithms are used in applications where process data cannot be represented in binary form. For example, the statements “the air feels cool” and “he is young” are not discrete statements. They do not provide concrete data about the air temperature or the person’s age (i.e., the air is at 65°F or the boy is 12 years old). Fuzzy logic interprets vague statements like these so that they make logical sense. In the case of the cool air, a PLC with fuzzy logic capabilities would interpret both the level of coolness and its relationship to warmth to ascertain that “cool” means somewhere between hot and cold. In straight binary logic, hot would be one discrete value (e.g., logic 1) and cold would be the other (e.g., logic 0), leaving no value to represent a cool temperature (see Figure 17-1).
Hot
1
Cold 0
Figure 17-1. Binary logic representation of a discrete temperature value.
In contrast to binary logic, fuzzy logic can be thought of as gray logic,