Page 371 - Understanding Automotive Electronics

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10 DIAGNOSTICS

Figure 10.15
Simple Automobile
Diagnostic Rule Base

FPO

fractional number. These values represent the confidence of the expert who is
responsible for the rule that the given action is true for the specified condition.
Further suppose that the facts known to be true are as shown in Figure
10.16. The controlling mechanism follows step 1 and discovers that only R1 is
in the conflict set. This rule is executed, deriving these additional facts in
performing steps 2 and 3:
Suspect there is no spark.
Suspect too much fuel is reaching the engine.
At step 4, the system returns to step 1 and learns that the conflict set includes
R1, R4, and R6. Since R1 has been executed, it is dropped from the conflict set.
In this simplified example, assume that the conflict is resolved by selecting the
lowest-numbered rule (i.e., R4 in this case). Rule R4 yields the additional facts
after completing steps 2 and 3 that there is a break in fuel line (0.65). The value
0.65 refers to the confidence level of this conclusion.

358 UNDERSTANDING AUTOMOTIVE ELECTRONICS