This document describes a fuzzy logic based intelligent air conditioning system. It discusses the history of air conditioners, how they operate by using refrigerants in a cooling process, and defines fuzzy logic as dealing with partial truth values between completely true and completely false. It outlines linguistic variables for the system including user temperature, temperature difference, and occupancy. Membership functions are defined for the input and output variables. Finally, it presents the Mamdani fuzzy rule base and discusses a microcontroller, sensors, and hardware implementation of the system.

1. FUZZY LOGIC BASED INTELLIGENT AIR
CONDITIONING SYSTEM
U.ROSHINI T.RAHUL
3RD YEAR –INSTRUMENTATION AND CONTROL ENGINEERING
SRI MANAKULA VINAYAGAR ENGINEERING COLLEGE
PUDUCHERRY.

2. HISTORY OF AIR CONDITIONER
 In 1902, the first modern electrical air
conditioning unit was invented by Willis
Carrier in Buffalo, New York. After
graduating from Cornell University, Carrier
found a job at the Buffalo Forge Company,
then he started experimenting with air
conditioning
 The 2nd-century Chinese inventor Ding
Huan (ft. 180)of the Han Dynasty invented
a rotary fan for air conditioning, with
seven wheels 3 m (9.8 ft.) in diameter and
manually powered.
 In Ancient Rome, water from aqueducts
was circulated through the walls of
certain houses to cool them.
WILLIS CARRIER

3. OPERATIONOF AIR-CONDITIONER
 Air Conditioners are Heat Exchangers.
 They take in warm room air, then blow it over
the cooling coils and back into the room.
 Important elements of AC.

4.  The key element of the air conditioner is the
REFRIGERENT that flows constantly through its
mechanisms.
 The REFRIGERENT becomes liquid and gives off heat
when it is compressed.
 It becomes a gas and absorbs heat when the pressure
is removed.
 The fan blows the air over the cooling coils containing
the refrigerant fluid.
 The warm air reacts with the refrigerant and in the
process refrigerant vaporizes.
 The cooled air is blown back into the room.
 The vaporized refrigerant moves to the compressor,
which pumps it under pressure to the condenser coils.
 The refrigerant is returned to the cooling coil as a
liquid.
OPERATIONOF AIR-CONDITIONER.CONTD

5. DEFINITIONOF FUZZY LOGIC
Boolean FUZZY
(crisp)
Fuzzy logic is a superset of Boolean
(conventional) logic that handles the
concept of partial truth, which is truth
values between "completely true" and
"completely false”.
Fuzzy logic is multivalued. It deals with
degrees of membership and degrees of
truth.
Fuzzy logic uses the continuum of logical
values between 0 (completely false) and 1
(completely true).

6. Examples:
 For example, let a 100 ml glass contain 30 ml of water.
Then we may consider two concepts: Empty and Full.
In boolean logic there are two options for answer i.e.
either the glass is half full or glass is half empty.
 In fuzzy concept one might define the glass as being
0.7 empty and 0.3 full.
100 ml
30ml

7. LINGUISTIC VARIABLES
INPUT VARIABLES
1. USER TEMPERATURE LOW, MEDIUM, HIGH.
2. TEMPERATURE DIFFERENCE NEGETIVE, ZERO, POSITIVE, LARGE.
3. OCCUPANCY LOW, MEDIUM, HIGH.
OUTPUT VARIABLES
1. FAN SPEED LOW, MEDIUM, FAST.
2. COMPRESSOR SPEED OFF, LOW, MEDIUM, FAST.
3. FIN DIRECTION TOWARDS,MIDDLE, AWAY.

8. INPUT VARIABLE – USER TEMPERATURE
User temperature is the
temperature provided by
the use through
controller or thermostat.
The range of this
thermostat should vary
between 18*C and 30*C.
so, the user se the
temperature accordingly

9. INPUT MEMBERSHIP FUNCTIONS
USER TEMPERATURE
LOW,
µ(LOW) : 1 0’C≤X≤22’C≤
-X+25/3 22’C≤X≤25’C
0 25’C≤X≤30’C
MEDIUM,
µ(MED): 0 0’C ≤X ≤22’C
X-22/3 22’C ≤X ≤25’C
-X+28/3 25’C ≤X ≤28’C
0 28’C ≤X ≤30’C
µ(HIGH): 0 0’C≤X ≤25’C
X-25/3 25’C≤X≤28’C
1 28’C≤X≤30’C
[0 25)
(22 28)
(25 30]
HIGH,

10. INPUTVARIABLE– TEMPERATURE DIFFERENCE

11. INPUT MEMBERSHIP FUNCTIONS
TEMPERATURE DIFFERENCE
µ(ZERO)(X): X+1 -1C ≤X ≤0’C
-X+1 0’C ≤X ≤1’C
0 1’C ≤X ≤3’C
µ(POS)(X) : 0 -1’C ≤X ≤O’C
X 0’C ≤X ≤1’C
-X+2 1’C ≤X ≤2’C
0 2’C ≤X ≤3’C
µ(LARGE)(X): 0 1’C ≤X ≤1’C
X-1 1’C ≤X ≤2’C
1 2’C ≤ X ≤3’C
µ(NEG)(X): -X -1’C ≤X ≤0’C
0 0’C ≤X ≤3’C
[-1 0)
(-1 1)
(0 2)
(1, 3]
NEGETIVE
ZERO
POSITIVE
LARGE

12. INPUTVARIABLE– OCCUPANCY
Occupancy is number of
people exposed to a/c.
The range of people will
decide the level of
occupancy as low ,
medium or high.
Accordingly the range of
requirement can be
decided for an optimum
cooling and power
consumption

13. INPUT MEMBERSHIP FUNCTIONS
OCCUPANCY
µ(MED)(X): 0 0 ≤X ≤2
X-2/3 2 ≤X ≤5
-X+8/3 5 ≤X ≤8
0 8 ≤X ≤10
µ(HIGH)(X): 0 0 ≤X ≤5
X-5/3 5 ≤X ≤8
1 8 ≤X ≤10
µ(LOW)(X): 1 0 ≤X ≤2
-X+5/3 2 ≤X ≤5
0 5 ≤X ≤10
[0 5)
(2 8)
(5 10]
LOW
MEDIUM
HIGH

14. OUTPUT VARIABLE – FAN SPEED

15. OUTPUT MEMBERSHIP FUNCTION
TEMPERATURE DIFFERENCE
µ(ZERO)(X): X+1 -1C ≤X ≤0’C
-X+1 0’C ≤X ≤1’C
0 1’C ≤X ≤3’C
µ(POS)(X) : 0 -1’C ≤X ≤O’C
X 0’C ≤X ≤1’C
-X+2 1’C ≤X ≤2’C
0 2’C ≤X ≤3’C
µ(LARGE)(X): 0 1’C ≤X ≤1’C
X-1 1’C ≤X ≤2’C
1 2’C ≤ X ≤3’C
µ(NEG)(X): -X -1’C ≤X ≤0’C
0 0’C ≤X ≤3’C
[-1 0)
(-1 1)
(0 2)
(1, 3]
NEGETIVE
ZERO
POSITIVE
LARGE

16. OUTPUT VARIABLE –COMPRESSOR SPEED

17. OUTPUT MEMBERSHIP FUNCTION
COMPRESSOR SPEED
µ(LOW)(X): 0 0 ≤X ≤30
X-30/15 30 ≤X ≤45
-X+65/20 45 ≤X ≤65
0 65 ≤X ≤100
µ(MED)(X): 0 0 ≤X ≤45
X-45/20 45 ≤X ≤65
-X+80/15 65 ≤X ≤80
0 80 ≤X ≤100
µ(FAST)(X): 0 0 ≤ X ≤ 65
X-65/15 65 ≤X ≤ 80
1 80 ≤ X ≤ 100
[30 65)
(45 80)
(65 100]
LOW
MEDIUM
FAST
µ(OFF)(X): 1 0 ≤X ≤30
-X+45/15 30 ≤X ≤45
0 45 ≤X ≤100
OFF
[0, 45)

18. OUTPUT VARIABLE – FIN DIRECTION

19. OUTPUT MEMBERSHIP FUNCTION
µ(TOWARDS)(X): 1 0 ≤X ≤20
-X+45/25 20 ≤X ≤45
0 45 ≤X ≤90
µ(AWAY)(X): 0 0 ≤X ≤45
X-45/25 45 ≤X ≤70
1 70 ≤X ≤90
[0 45)
(45 90]
µ(NO OP)(X): 0 0 ≤X ≤20
X-20/25 20 ≤X ≤45
-X+70/25 45 ≤X ≤55
0 55 ≤X ≤90
TOWARDS
AWAY
NO OPERATION
(20 55)
FIN DIRECTION

20. MAMDANI MODEL-FUZZY RULES
USER
TEMPERATURE
OCCUPANCY TEMPERATURE
DIFFERENCE
FAN SPEED COMPRESSOR
SPEED
FAN DIRECTION
LOW AND LOW AND NEGETIVE THEN MEDIUM AND OFF AND AWAY
LOW AND LOW AND ZERO THEN FAST AND OFF AND NO OPERATION
LOW AND LOW AND POSITIVE THEN MEDIUM AND LOW AND TOWARDS
LOW AND LOW AND HIGH THEN FAST AND LOW AND TOWARDS
LOW AND MEDIUM AND NEGETIVE THEN FAST AND MEDIUM AND TOWARDS
LOW AND MEDIUM AND ZERO THEN MEDIUM AND FAST AND NO OPERATION
LOW AND MEDIUM AND POSITIVE THEN FAST AND MEDIUM AND TOWARDS
LOW AND MEDIUM AND HIGH THEN MEDIUM AND FAST AND TOWARDS
LOW AND HIGH AND NEGETIVE THEN LOW AND FAST AND TOWARDS
LOW AND HIGH AND ZERO THEN MEDIUM AND FAST AND NO OPERATION
LOW AND HIGH AND POSITIVE THEN MEDIUM AND FAST AND TOWARDS
LOW AND HIGH AND HIGH THEN FAST AND FAST AND TOWARDS

21. USER
TEMPERATURE
OCCUPANCY TEMPERATURE
DIFFERENCE
FAN SPEED COMPRESSOR
SPEED
FAN DIRECTION
MEDIUM AND LOW AND NEGETIVE THEN MEDIUM AND OFF AND AWAY
MEDIUM AND LOW AND ZERO THEN MEDIUM AND OFF AND NO OPERATION
MEDIUM AND LOW AND POSITIVE THEN LOW AND MEDIUM AND TOWARDS
MEDIUM AND LOW AND HIGH THEN MEDIUM AND MEDIUM AND TOWARDS
MEDIUM AND MEDIUM AND NEGETIVE THEN MEDIUM AND MEDIUM AND TOWARDS
MEDIUM AND MEDIUM AND ZERO THEN MEDIUM AND MEDIUM AND NO OPERATION
MEDIUM AND MEDIUM AND POSITIVE THEN MEDIUM AND FAST AND TOWARDS
MEDIUM AND MEDIUM AND HIGH THEN FAST AND FAST AND TOWARDS
MEDIUM AND HIGH AND NEGETIVE THEN MEDIUM AND MEDIUM AND TOWARDS
MEDIUM AND HIGH AND ZERO THEN FAST AND MEDIUM AND NO OPERATION
MEDIUM AND HIGH AND POSITIVE THEN FAST AND FAST AND TOWARDS
MEDIUM AND HIGH AND HIGH THEN MEDIUM AND FAST AND TOWARDS

22. USER
TEMPERATURE
OCCUPANCY TEMPERATURE
DIFFERENCE
FAN SPEED COMPRESSOR
SPEED
FAN
DIRECTION
HIGH AND LOW AND NEGETIVE THEN FAST AND OFF AND AWAY
HIGH AND LOW AND ZERO THEN LOW AND LOW AND NO OPERATION
HIGH AND LOW AND POSITIVE THEN MEDIUM AND MEDIUM AND TOWARDS
HIGH AND LOW AND HIGH THEN FAST AND MEDIUM AND TOWARDS
HIGH AND MEDIUM AND NEGETIVE THEN FAST AND LOW AND TOWARDS
HIGH AND MEDIUM AND ZERO THEN FAST AND MEDIUM AND NO OPERATION
HIGH AND MEDIUM AND POSITIVE THEN FAST AND FAST AND TOWARDS
HIGH AND MEDIUM AND HIGH THEN FAST AND FAST AND TOWARDS
HIGH AND HIGH AND NEGETIVE THEN FAST AND MEDIUM AND TOWARDS
HIGH AND HIGH AND ZERO THEN FAST AND MEDIUM AND NO OPERATION
HIGH AND HIGH AND POSITIVE THEN FAST AND FAST AND TOWARDS
HIGH AND HIGH AND HIGH THEN FAST AND FAST AND TOWARDS

23. BLOCK DIAGRAM
MICROCONTROLLER
(PIC16F877A)
ADC
PWM
TEMPERATURE
SENSOR
POWER SUPPLY
HEAD COUNTER
SENSOR
MOTOR DRIVER
CIRCUIT
DC MOTOR

24. MC &PIN DETAILS
 Flash memory 8KB
 SRAM (Data Memory)
 Watch Dog timer
 3Timers
 2CCP Module
 2serial
Communication
ports(MSSP,USART)

25. OTHER COMPONENTS

26. HARDWARE IMPLEMENTATION

27. CONCLUSION
Previous Air conditioning system which were used to simply cool
the rooms now can perform a variety of functions. By adding
intelligence to the Air conditioning system we do not have to worry
about the cooling process.
In future we will come up with a device that implements the
Fuzzy Logic Controller in An embedded system which can be used
fro increasing the efficiency of Air conditioners.

28. REFERENCES
Fuzzy logic with engineering applications by TIMOTHY J.ROSE
http://www.sciencedirect.com/science/article/pii/S1364032104001200
http://aptnk.in/profile/papers/Fuzzy-Logic-Control-of-Air-Conditioners.pdf
http://reference.wolfram.com/applications/fuzzylogic/Manual/10.html