Controlling the Sequence of Task Groups

Overriding the next Task Group

The WMS may explicitly select a task group with the openbin method. This is not recommended during normal
operation. AutoStore plans a flow of bins to a port, and overriding the plan in the last minute will cause a
performance penalty. The planned bins may already be moved to the port and may need to be moved away.

The use case of explicitly selecting a task group with openbin is when the WMS wants to continue on a
suspended task group. In this case, the openbin will immediately follow the openport. When a user logs out
(closes the port) in the middle of a task group, the WMS normally specifies that the current task group shall be
suspended. (If the task group is not suspended, the task group could be selected and continued on another
port.) To continue on the task group on the same port when the user logs in, the WMS can explicitly select the
suspended task group.

Implementing Cut-Off Time

A warehouse may have different cut-off times during a day, and the different task groups may be targeting
specific deadlines. A normal prioritization concept would be to set the task groups' req_time equal to their
deadline. This would give the task groups with the earliest deadline highests priority, and would in many cases
be the preferred solution. But in order to optimize the total throughput, it is still allowed to pick task groups with
later deadlines.

To fully prioritize picking of the upcoming deadline, it is possible to specify that a port only selects task groups
with req_time equal to or lower than a specified cut-off time.

The port's req_time limit (see Select Requirements on page 24) is set by using the req_time parameter in the
openport method.

Synchronizing with the Task Group Sequence

Sometimes, the WMS needs to synchronize external processes, for instance package machines, with the task
groups that are being picked in the port. In these use cases, the WMS does not need to decide the exact
sequence of task groups at the ports, but the WMS needs visibility into the exact sequence of task group
sequence that AutoStore will deliver.

The method getnexttaskgroups (see Get Next Task Groups on page 53) returns information about which task
groups will be delivered to a port. The same information is available from Log Publisher. Different processes
and installations may need different length of visibility into the future. Sometimes the WMS only needs to know
the next task group half a minute in advance, while in other cases the WMS may need to know the upcoming
task groups many minutes in advance. Therefore, it is possible to configure this length of visibility per port.

Please note that AS Router should not change/optimize the published information, so configuring a long lookahead horizon may have a performance impact (depending on the length). However, this should normally not
be a problem and compared to explicitly overriding the sequence from the WMS side it is probably better to let
AutoStore decide the sequence.

Specifying a Strict Sequence of Task Groups

Some use cases may require the WMS to specify the sequence of the task groups at ports, for example in
order to consolidate bins from different ports or grids within a limited time interval.

With the introduction of port mode SEQUENCE, it is possible to specify the exact sequence of task group to
be delivered at the ports.

Port Mode SEQUENCE

When a port is opened in the special port mode SEQUENCE, the WMS can specify the exact sequence of
task groups to be delivered. (This is similar to the Port Queue concept of the Bin Interface, but the sequence
feature in Task Interface operates on task groups instead of bins.) In order to benefit from the AutoStore
optimizations, this feature should only be used when it is required, and only for the ports that require a specific
sequence of task groups.

At the same time, some ports can be opened in mode SEQUENCE while other ports can operate in the
standard OPEN mode.

The WMS specifies the sequence of task groups to be delivered by using the methods setportsequence and
appendportsequence.

To avoid conflicts between the sequences specified by the WMS and the normal delivery of task groups to
ports in the other modes (e.g. OPEN/SWAP/AUTO), the WMS must use different set if categories for the task
groups used in mode SEQUENCE than for the task groups used in the other port modes. There are also other
limitations for the task groups that are used in a sequence.

The following rules apply:
▪ openport (mode OPEN/AUTO/SWAP) with a list of categories is rejected if another Port's sequence already
includes a task group with same category as one of the listed categories.
▪ setportsequence/appendportsequence is rejected if another port is opened (mode OPEN/AUTO/SWAP)
with same category as any of the specified task groups.
▪ Task groups that shall be used in a port's sequence cannot have a shipment property.
▪ A task group cannot be added to different ports' sequence at the same time.
▪ Updating a task group (updatetaskgroup) that belongs to a port's sequence is not allowed.
▪ Adding tasks (addtask) to a task group that belongs to a port's sequence is allowed (standard rules apply).
▪ Cancelling a task group (cancel_taskgroup) will remove it from the port's sequence.
▪ closeport clears the port's sequence.
▪ openport with mode SEQUENCE shall not specify any categories or content parameters.

The SEQUENCE feature should be used with caution. Consider if the standard port mode can be used (e.g.
looking into the port sequence instead of specifying it, or using cutoff restriction on the port).
Consider the following guidelines when using the SEQUENCE feature:

▪ Unprepared task groups will cause waiting in port and wasted performance. Use Log Publisher (alterntively
getbinlocation) to check the preparation state of the bins before adding the task group to a port's sequence
queue.
▪ Use long enough sequence queues to allow AutoStore to plan for the bin delivery. (10-15 minutes of
operation.)
▪ Avoid bin conflicts between ports. Do not plan same bin to arrive on different ports at the same time.
▪ If alternative ports can be used for a task group, consider the travelling distance between port and bins.