ComputerAided_Design_Engineering_amp_Manufactur.pdf
ComputerAided_Design_Engineering_amp_Manufactur.pdf
ComputerAided_Design_Engineering_amp_Manufactur.pdf
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TABLE 8.1 Summary of the Rules<br />
Conditions of Generations PP Rule TT Rule<br />
A. cycles created — TT.2<br />
B. no cycles created — —<br />
B.1 only one of ng and nj in a cycle from PP.1<br />
— TT.0<br />
B.2 exclusive PP.2 TT.0<br />
B.3 concurrent PP.0 —<br />
B.3.1 neither ng nor nj in<br />
a cycle from PP.1<br />
— TT.4<br />
B.3.2 both ng and nj in<br />
a cycle from PP.1<br />
— TT.3<br />
B.4 sequential or cyclic PP.1 (PG)<br />
TT.1 (PG)<br />
PP.2 (IG)<br />
TT.4 (IG)<br />
(0) PP.0 If pg pj , then signal “forbidden, delete the � ” and return.<br />
(1) PP.1 if<br />
(2) PP.2<br />
, signal “a pure PP generation;” otherwise signal “an interactive PP generation.”<br />
(a) PP.2.1 Generate a TP-path from a transition of NP to a place of each in .<br />
(b) PP.2.2 Generate a virtual PSP, a PT-path, from a place of each in to the transition<br />
of NP.<br />
w<br />
�g � �j tk pj �j Cjg pg �g Cgj n˙ g<br />
Note that some generations may require the application of more than one rule. For instance, a backward<br />
IG may need both Rules TT.2 and TT.4. Note also the partial dual relationship between the TT and PP<br />
rules. Replacing transitions with places (and vice versa) reversing each arc in Rule TT.4, we obtain Rule<br />
PP.2. The rules are summarized in Table 8.1.<br />
Section 8.6 demonstrates the application of these rules to an automated manufacturing system. Note<br />
that during each application of a rule, more than one new PSP may be generated; we call such a generation<br />
a macro generation. Otherwise, it is a singular generation.<br />
In the remainder of this chapter, all nets mentioned refer to nets synthesized using the rules presented<br />
above.<br />
Below, we explain the rules starting with the rules that forbid generations. Forbidden TT and PP<br />
generations come from synchronic and concurrency mismatches, respectively, which cause uncoordinated<br />
actions. For a TT generation, a single parameter, the synchronic distance between tg and tj , can unify<br />
all cases of the structural relationships between and .<br />
n g<br />
Definition: Synchronic Mismatch: A TT generation causes a synchronic mismatch of , where<br />
1 w<br />
( dgj)<br />
denotes the synchronic distance between tg and tj and N (NP).<br />
1<br />
d gj<br />
Definition: Concurrency Mismatch: A PP generation causes a concurrency mismatch if ( pg � pj ) and �<br />
a p � P, p � pg , and ¬ (p � pj ).<br />
There are three possible synchronic distances: 1, �, and the integers in between. A TT generation<br />
should not alter the synchronic distance between tg and tj . But a TT-path implies a synchronic distance<br />
of 1 between tg and tj . Thus, if the synchronic distance between tg and tj is 1 prior to the generation,<br />
the TT generation will not alter the reachable markings of N . If ( ) can fire infinitely often without<br />
firing , then the NP will get unbounded tokens (become nonlive due to deficiency of tokens).<br />
In terms of structural relationship, �� for the following cases: (1) � , (2) and/or is in a cycle<br />
generated earlier using the PP rule, (3) ↔ or � , such that , and/or , and , and<br />
(4) tg and are in two separate PNs. For cases (1) and part of (2) where only one of and is in a<br />
cycle, the generation is chosen to be forbidden to make Rule TT.0. The rest of the cases need additional<br />
generations to make Rules TT.3 and TT.4.<br />
1<br />
tg tj tj ( tg) dgj tg tj tg tj tg tj tg tj �tx tg tx tj tx tg tj tg tj n j<br />
1 w<br />
dgj � dgj