nexus_transporter

This package provides a pure virtual interface Transporter to be implemented to integrate a transportation system into Nexus.

Libraries that implement the Transporter class can be loaded through pluginlib at runtime by the TransporterNode. Two reference implementations of Transporter are provided.

Mock transporter

The mock transporter simulates a simple conveyor belt and has the following parameters:

• x_increment The distance in meters between stations.
• destinations An ordered list of named stations.
• speed Speed in m/s of the conveyor belt.

The plugin will then simulate a conveyor with a list of destinations, equally spaced by x_increment, moving at a fixed speed.

RMF transporter

The RMF transporter provides an interface to a running RMF instance. The plugin will create a composed task with a series of pickup / dropoffs based on the requested itinerary and assess its feasibility by checking that the requested destinations are present in the building map published by Open-RMF. The time estimate is temporarily hardcoded to a fixed value. and estimate Itinerary duration by submitting a task with the dry run feature, which allow it to request to the Open-RMF task planner what’s the estimate for a specific task without actually starting it. The node also uses the Transporter::handle_signal interface to signal AMRs when they can resume their itinerary. Specifically, when an AMR reaches its last destination and it is marked as a pickup, the transportation request will be marked as complete and Open-RMF will begin publishing an DispenserRequest and wait for a matching DispenserResponse. As soon as the transporter’s handle_signal function receives the pickup signal, the matching DispenserResponse message will be published and the AMR will be released and complete its task.

Future work

• Move from using the building map to using the dry run feature of the task bidding system to assess feasibility and calculate task completion time estimates.
• Move from hardcoded pickup final phase to a dropoff .
• Implement workcells with multiple input / output stations and use them for transportation requests.

Changelog for package nexus_transporter

0.1.1 (2023-11-20)

0.1.0 (2023-11-06)

• Provides the nexus_transporter_node which interfaces with transportation systems to move material across a flowline.
• Provides the Transporter API for users to integrate transportation systems.