AGV Parking in Parallel Buffers

N4 supports parking AGVs in parallel buffers (PBs). When considering PBs for parking an AGV, the Parking Decker considers the following conditions:

Distance from the AGV location to the PB slot.
Whether it is an Entry QC parallel buffer and the AGV is at QC.

If an AGV is at the QC, the Parking Decker should not select the QC's Entry PB as the parking destination.

Whether the PB slot is active or inactive.

An active PB is a PB that is within the PB range of at least one active QC work queue (WQ).

It is possible to park in an active PB if:

The AGV location is known; and
The traffic level in the PB range (to which the PB belongs) is acceptable. For more information, see Traffic regimes (on page 1).

Whether the PB slot is already occupied by an AGV.
Whether there is already a drive instruction (DI) to the PB slot.

If an AGV is evicted from its current location, it will be parked into the closest available parallel buffer.

If you do not want to use parallel buffers for parking AGVs, you can use the steps provided in the following sections in the N4 Automation Configuration Guide to disable parking in parallel buffers:

Disable parking in parallel buffer (Basic mode)
Disable parking in parallel buffer (Advanced mode)

Scenario Setup for Parking in Parallel Buffers

The following sections are based on a scenario with two PB ranges:

Entry PB: From PBen1 - PBen3
Exit PB: From PBex1 - PBex3
Inactive PB: PBinFar and PBinClose
If an AGV is at the QC, either PBinFar or PBinClose is farther (in terms of drive time and not distance) from the AGV location than any active PB.
If an AGV is at a waterside transfer point (WSTP), PBinFar is farthest from the AGV location than any active PB and PBinClose is closest to the AGV location than any active PB.
PBen3 and PBex3 are occupied by AGVs.
All the other PBs are available, unless specified otherwise.

AGV is at the QC

In this case:

Active Exit PBs are preferred.
Inactive PBs are allowed.
Active Entry PBs are not allowed.

The following table displays the suggested and selected PBs in this scenario (on page 1).

	PBs Suggested by the AGV Scheduler	Reason for the selection	PB Selected by the Parking Decker
1	PBen1 (active Entry) and PBex1 (active Exit)	PBen1 is in the Entry zone and an AGV at the QC should not go there.	PBex1
2	PBen1 (active Entry) and PBinFar (inactive)	PBen1 is in the Entry zone and an AGV at the QC should not go there.	PBinFar
3	PBinFar (inactive) and PBex3 (active Exit)	PBex3 is occupied (see Scenario Setup (on page 1) above)	PBinFar
4	PBinFar (inactive) and PBex1 (active Exit)	It is closer.	PBex1
5	PBinFar (inactive) and PBex1 (active Exit)	Traffic in the PB Exit range is too high.	PBinFar (PBex2 is occupied)

AGV is at the WSTP

In this case:

Inactive PBs are allowed.
Active PBs are allowed if the AGV is at the waterside.

The following table displays the suggested and selected PBs in this scenario (on page 1).

	PBs Suggested by the AGV Scheduler	Reason for the selection	PB Selected by the Parking Decker
1	PBen1 (active Entry) and PBex1 (active Exit)	Both are active PBs.	Parking Decker selects the PB that is closest.
2	PBinFar (inactive) and PBex1 (active Exit)	PBex1 is in the Exit zone and an AGV at the WSTP should not go there.	Parking Decker selects the PB that is closest.
3	PBen1 (active Entry) and PBinFar (inactive)	PBen1 is an active PB.	PBinFar (even though it is farther than PBen1)
4	PBinFar (inactive) and PBinClose (inactive)	It is closer.	PBinClose

AGV is at the PB

In this case:

Inactive PBs are allowed.
Active PBs are allowed.

The following table displays the suggested and selected PBs in this scenario (on page 1).

	PBs Suggested by the AGV Scheduler	Reason for the selection	PB Selected by the Parking Decker
1	The AGV's current location is in the list of PBs suggested for parking.	The AGV is Idle and is in an inactive PB.	AGV stays in its position.
2	The AGV's current location is in the list of PBs suggested for parking.	The AGV is Idle, is in an active PB, but the traffic is low.	AGV stays in its position.
3	The AGV's current location is in the list of PBs suggested for parking.	Although the AGV is Idle and was most likely parked at the current location as part of a previous order but now due to some reasons the AGV is in a PB range with high traffic.	AGV leaves.
4	The AGV's current location is not in the list of PBs suggested for parking.	The AGV is Idle and is in an inactive PB.	AGV leaves.

AGV Location is Unknown

In this case:

Inactive PBs are allowed.
Active PBs are not allowed.

The following table displays the suggested and selected PBs in this scenario (on page 1).

	PBs Suggested by the AGV Scheduler	Reason for the selection	PB Selected by the Parking Decker
1	PBen2 (active Entry), PBinFar (inactive), and PBex2 (active Exit)	An AGV at an unknown location cannot use active PBs because it may have to travel in a direction opposite to the traffic direction in the active PB.	PBinFar
2	PBen2 (active Entry), PBinFar (inactive), and PBex2 (active Exit)	PBinFar is occupied by another AGV.	Parking Decker fails to Deck.