Controlling The Sequence Of Task Groups

Overview

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AutoStore may occasionally deliver lower-priority tasks to maximize throughput.

In practice, it is often better to keep the ports actively working—delivering a lower-priority task group—rather than waiting for the highest-priority task group, which may be temporarily unavailable (e.g., if the bin is in use at another port or has not yet been prepared).

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When AS Router is used:

• AS Router uses req_time to order and prioritize task groups in a regular system.
• AS Router’s planning logic differs significantly from AS Planner, as it evaluates multiple internal metrics.
• As a result, req_time is considered during planning, but it is not a strict or forcing parameter.
• A task group with an older req_time will typically be planned before one with a newer req_time.
• Task group selection is a trade-off between several factors. Requested time is intuitively the most important one, while other factors (e.g. prepare state, port conflicts) are considered temporary constraints.
• AS Router also makes an effort to prioritize preparation of bins belonging to the earliest requested task group that still has unprepared bins.

Overriding The Next Task Group

The WMS can explicitly select a task group using the openbin method. However, this is not recommended during normal operation, as AutoStore plans a flow of bins to each port. Overriding this plan at the last moment can result in a performance penalty, since bins may have already been moved to the port and might need to be relocated.

Resume A Suspended Task Group

The primary use case for explicitly selecting a task group with openbin is when the WMS needs to resume a previously suspended task group, which was suspended using closeport with the parameter suspend_taskgroup set to true. In such cases, openbin is executed immediately after openport.

For example, when an operator logs out (closes the port) in the middle of a task group, the WMS typically suspends the current task group. If the task group is not suspended, it could be selected and continued on another port. To continue the task group on the same port when the user logs back in, the WMS can explicitly select the suspended task group using openbin.

Implementing Cut-Off Time

A warehouse may have different cut-off times throughout the day, and various task groups may target specific deadlines. A standard prioritization approach is to set each task group’s req_time equal to its deadline. This ensures that task groups with the earliest deadlines receive the highest priority, which is often the preferred solution. However, to optimize overall throughput, AutoStore may still pick task groups with later deadlines.

To strictly prioritize task groups with upcoming deadlines, a port can be configured to select only those task groups whose req_time is equal to or earlier than a specified cut-off time.

The port’s req_time limit is set using the corresponding parameter in the openport method.

Synchronizing With The Task Group Sequence

In some cases, the WMS needs to synchronize external processes—such as packaging machines—with the task groups being picked at a port. In these scenarios, the WMS does not need to determine the exact sequence of task groups at the ports, but it does require visibility into the sequence AutoStore will deliver.

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Even if it is technically possible, avoid repeatedly requesting ad-hoc bins. Doing so will disrupt the internal queue, preventing AutoStore from maintaining proper visibility into what task should be prepared.

The getnexttaskgroups method provides information about which task groups will be delivered to a port. The same information is also available via Log Publisher. Different processes and installations may require different lengths of visibility into upcoming task groups. For example, the WMS may only need to know the next task group 30 seconds in advance, while in other cases it may need visibility several minutes ahead. This look-ahead period can be configured individually for each port.

It is important to note that the AS Router should not modify or optimize the published information.

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Configuring a long look-ahead horizon may have performance impact, depending on its length.

However, this is generally not a concern, and allowing AutoStore to manage the sequence is usually preferable to having the WMS explicitly override it.

Specifying A Strict Sequence Of Task Groups

Certain use cases may require the WMS to enforce the exact sequence of task groups at the ports—for example, to consolidate bins from different ports or grids within a limited time window.

With the introduction of port mode SEQUENCE, it is now possible to specify the precise order in which task groups are delivered to the ports.

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The port mode SEQUENCE requires the April 2023 software release.

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 the Task Interface operates on task groups rather than individual bins.

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Ports in SEQUENCE mode cannot have any category or content code parameters!

To take full advantage of AutoStore optimizations, SEQUENCE mode should only be used when required, and only for ports that need a specific task group order. Other ports can simultaneously operate in standard modes, such as OPEN, AUTO, or SWAP.

The WMS specifies the task group sequence using the setportsequence and appendportsequence methods.

Important Considerations And Limitations

To avoid conflicts between task group sequences in SEQUENCE mode and normal delivery in other port modes, the following rules apply:

• Category conflicts:
  • openport (mode OPEN/AUTO/SWAP) specifying categories is rejected if another port’s sequence already includes a task group with the same category.
  • setportsequence / appendportsequence is rejected if another port is open in OPEN/AUTO/SWAP mode with any of the specified categories.
• Shipment restriction: Task groups used in a port sequence cannot have a shipment property.
• Exclusive assignment: A task group cannot be added to multiple ports’ sequences simultaneously.
• Updating restrictions:
  • updatetaskgroup is not allowed for task groups in a port sequence.
  • Adding tasks (addtask) to a task group in a sequence is allowed, following standard rules.
  • Cancelling a task group (cancel_taskgroup) removes it from the port sequence.
• Port operations:
  • closeport clears the port’s sequence.
  • openport with mode SEQUENCE must not specify categories or content parameters.

Guidelines For Using SEQUENCE Mode

The sequence feature should be used with caution. Consider whether standard port modes or cut-off restrictions could achieve the same result before enforcing SEQUENCE. Additional recommendations include:

• Check preparation state: Unprepared task groups can cause waiting at the port and reduce performance. Use Log Publisher or getbinlocation to verify bin readiness before adding task groups to the sequence.
• Plan sufficiently long sequences: Allow AutoStore 10–15 minutes of operation to effectively plan bin deliveries.
• Avoid bin conflicts: Do not schedule the same bin to arrive at multiple ports simultaneously.
• Consider travel distance: If alternative ports can be used for a task group, optimize for shortest travel distance between bins and port.