Environmental Engineering Reference
In-Depth Information
influences the decision of the destination for the empty tote is the full status
of the tote stackers. However, the distance to the tote stackers should also be
considered. There is no reason to send it to the other end of the system, if a
stacker is nearby, unless the other is empty.
Each stacker monitors its full status as a simple ratio between the current
and maximum number of totes in the stacker. By a standard hedge (Negnevitsky
2005) the ratio is converted into a priority s i for requesting extra totes:
2 r i
0
r i < 1 / 2
s i
=
r i ) 2
1
where r i is the full-ratio for the i th stacker. A plot of the function is shown in
Figure 3.19.
The priority is used to scale the dynamic route length to each tote stacker, so a
nearly empty stacker will have a very short route length or value in the decision,
whereas a full stacker will have its full route length:
v i
1
2 ( 1
1 / 2
r i
s i
where d i is the dynamic distance (requested from the RouteAgent) to the stacker
from the decision point.
=
d i
×
11.6.2 Overtaking Urgent Bags
Consider a typical layout of a discharging area in Figure 3.20. The bottom lane
is a fast-forward transport line, the middle a slower lane with the dischargers
and the upper lane is the return path. A diverter (in the bottom lane) has the
option to detour nonurgent to the middle lane to give way for urgent baggage in
the transport line, but with no queues in the system all totes should follow the
shortest path. When the routes merge again at the mergers in the middle lane,
1
0.8
0.6
0.4
0.2
0.2
0.4
0.6
0.8
1
Full Ratio
Figure 3.19
Plot of ETS priority function
Search WWH ::




Custom Search