Fuzzy Logic Process

1
Fuzzy Logic Process
Crisp Input
2
Solar Pool Heater Example

• suppose we measure the pool water temp and the
  wind speed and we want to adjust the valve that
  sends water to the solar panels
• we have two input parameters temp wind_speed
• we have one output parameter change_in_valve

3
Solar Pool Heater Example

• set up membership functions for the inputs
• for each input, decide on how many categories
  there will be and decide on their membership
  functions

4
Solar Pool Heater Example

• set up membership functions for the output(s)
• for each output, decide on how many categories
  there will be and decide on their membership
  functions

5
Solar Pool Heater Example

• set up the rules
• if (temp is hot) AND (wind_speed is calm)then
  (change_in_valve is big_negative)
• if (temp is warm) OR (wind_speed is brisk)
• then (change_in_valve is small_negative)
• if (temp is nominal) OR (temp is warm)then
  (change_in_valve is no_change)

6
Solar Pool Heater Example

• temp 87F, wind_speed 9 mph
• fuzzify the inputs

7
Solar Pool Heater Example
cold
nominal
warm
cool
hot
0
0.6
0.35
0
0

• fire the rules
• if (temp is hot) AND (wind_speed is calm)then
  (change_in_valve is big_negative)
• if (temp is warm) AND (wind_speed is brisk)
• then (change_in_valve is small_negative)
• if (temp is nominal) OR (temp is warm)then
  (change_in_valve is no_change)

calm
strong
brisk
0.4
0
0.55
8
Solar Pool Heater Example
bigneg.
nochange
smallpos.
bigpos.
smallneg.
0.6
0
0
0
0.55

• fire the rules
• if (temp is hot) AND (wind_speed is calm)then
  (change_in_valve is big_negative)
• if (temp is warm) OR (wind_speed is brisk)
• then (change_in_valve is small_negative)
• if (temp is nominal) OR (temp is warm)then
  (change_in_valve is no_change)

9
Solar Pool Heater Example
bigneg.
nochange
smallpos.
bigpos.
smallneg.

• defuzzify the output(s)

0.6
0
0
0
0.55
big neg sm. neg. no ch. sm. pos.
big pos.
-10 -5 0 5
10 degrees
change_in_valve - 1.29 degrees