Page 66 - Designing Autonomous Mobile Robots : Inside the Mindo f an Intellegent Machine

Thinking More Clearly Through Fuzzy Logic

Now if we were to read the voltage out of the summing amplifier with an A/D (ana-
log to digital) converter instead of feeding it to the hardware comparator, then we
could consider this signal to be proportional to the intrusion threat. We could compare
this threat level to software thresholds and perform all alarm processing in software.
Better yet, if we moved back to reading the outputs of the two signal amplifiers, and
perform the gain balancing, summing, and thresholding in software, then we have
created a true fuzzy logic intrusion detector. What could be simpler?

Trapezoidal fuzzy logic

The simplest form of fuzzy logic is a linear technique referred to as trapezoidal fuzzy
logic. This technique allows a mere handful of variables to determine the contribu-
tion functions of each channel.

Threat
Contribution

P2 P3
80 PIR

P2 / P3
60 MW

40

20

P0 P1 P1 Signal
Strength
20% 40% 60% 80% 100%

Figure 4.3. Trapezoidal fuzzy logic

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