Fuzzy

Scott Lancaster

Fuzzy Logic Controllers
by Scott Lancaster
•Description

of Fuzzy Logic •What Fuzzy Logic Controllers Are Used for •How Fuzzy Controllers Work •Controller Examples

FuzzyLogic by Lotfi Zadeh
• Professor at University of California • First proposed in 1965 as a way to process imprecise data • Its usefulness was not seen until more powerful computers and controllers wereavailable

Fuzzy Flight

1

Scott Lancaster

Basic Concept of Fuzzy Logic
• Zadeh – “Attempt to mimic human control logic” • Do away with crisp sets, Boolean, true/false, etc. • Allow forfractions, partial data, imprecise data • Fuzzify the data you have • How red is this? ½? ¾? 1?
RGB value 150/255

What Is a Fuzzy Controller?
• Simply put, it is fuzzy code designed to controlsomething, usually mechanical. • They can be in software or hardware and can be used in anything from small circuits to large mainframes.

Fuzzy Flight

2

Scott Lancaster

Currently Used FuzzyControllers

F-117 Flight Control System

Camcorder - Stabilization

Lifting Bodies

http://iridia.ulb.ac.be/~famimo/

Fuzzy Flight

3

Scott Lancaster

Why Should We Use FuzzyControllers?
• Very robust • Can be easily modified • Can use multiple inputs and outputs sources • Much simpler than its predecessors (linear algebraic equations) • Very quick and cheaper to implementConstructing a Fuzzy Controller

Create the membership values (fuzzify). 2. Specify the rule table. 3. Determine your procedure for defuzzifying the result.
1.

Fuzzy Flight

4

ScottLancaster

Create the Membership Value
• First we have to fuzzify the data or create membership values for the data and put them into fuzzy sets. Put simply, we have to divide each set of data intoranges. The Y value will always be on a range of 0 to 1 (theoretically 0 to 100%). The X will be an arbitrary range that we determine

• • •

Membership for Inverted Pendulum
• Typically a fuzzy...