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Handbook of air conditioning and refrigeration / Shan K

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5.46 CHAPTER FIVE<br />

PL<br />

PS<br />

ZE<br />

NS<br />

NL<br />

Fan speed variation range, %<br />

100<br />

80<br />

60<br />

40<br />

20<br />

0<br />

�20<br />

�32<br />

�40<br />

�60<br />

�80<br />

�100<br />

0 0.5<br />

PL<br />

PS<br />

ZE<br />

NS<br />

NL<br />

Positive large<br />

Positive small<br />

Zero<br />

Negative small<br />

Negative large<br />

1<br />

Centroid<br />

0.5<br />

0.45<br />

0.2<br />

0<br />

If cold,<br />

then<br />

increase<br />

a lot<br />

Cold<br />

Cold<br />

If cool,<br />

then increase<br />

a little<br />

62 66 70 71<br />

Fuzzy sets<br />

<strong>and</strong> negative large), then the production rules, or fuzzy logic rules, can be described as follows:<br />

Cool<br />

Cool<br />

● If the indoor temperature is hot, then the fan speed rises a lot.<br />

If just right,<br />

then do<br />

nothing<br />

Conventional crisp sets<br />

FIGURE 5.23 Fuzzy sets, membership function, <strong>and</strong> fuzzy logic control.<br />

● If the indoor temperature is warm, then the fan speed rises a little.<br />

● If the indoor temperature is just right, then the fan speed stays unchanged.<br />

● If the indoor temperature is cool, then the fan speed reduces a little.<br />

● If the indoor temperature is cold , then fan speed reduces a lot.<br />

1<br />

1<br />

0.5<br />

0<br />

Just<br />

right<br />

If warm,<br />

then<br />

decrease<br />

a little<br />

Warm<br />

If hot,<br />

then<br />

decrease<br />

a lot<br />

74 78 82 86 90<br />

Indoor temperature, �F<br />

Just<br />

right<br />

Warm<br />

62 66 70 74 78 82 86 90<br />

Indoor temperature, �F<br />

Hot<br />

Hot

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