Environmental Engineering Reference
In-Depth Information
Merger
Dischargers
Return path
Fast-forward transport lane
Diverter
Figure 3.20
Area of the BHS layout with indication of diverters, mergers, and dischargers
that lane will give higher priority to totes from the merging leg with the most
urgent baggage.
Urgency is a constructed function, which gives high priority to urgent totes and
negative priority to totes where remaining time to departure exceeds a threshold.
⎧
⎨
1
t
j
2
t
j
<U
T
u
j
=
1
⎩
t
j
2
U
T
2
)
j
U
T
)
2
(
−
+
2
U
T
t
j
−
≥
U
T
(U
max
−
where
U
max
is the full window size of the allocated discharger. If the tote's
remaining time exceeds this value, it should go to EBS.
U
T
is the threshold
value, which is set to 20 minutes, as no tote should be considered urgent if it
has more than 20 minutes left before the discharger closes.
3
t
j
is the remaining
time for the
j
th tote. The graph is plotted in Figure 3.21.
The urgency factor is converted to a scale factor for the dynamic route lengths
of alternatives routes. Then the principle of simple modification of the route
Priority
1
0.5
Min
25
50
75
100
125
150
175
−
0.5
−
1
Figure 3.21
Urgency function for totes
3
When the discharger closes the tote becomes a rush bag, but the threshold of 20 minutes is
independent of the 20 minutes time limit for rush bags, so in total a tote is considered nonurgent
if it has more than 40 minutes left to departure.
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