CHORD: Distributed Data-Sharing via Hybrid ROS 1 and 2 for Multi-Robot Exploration of Large-Scale Complex Environments

A well-structured and reliable communication system is key to the successful operations of multi-robot systems. In this letter, we present our design and implementation of a multi-robot communication architecture CHORD (Collaborative High-bandwidth Operations with Radio Droppables) based on two popular robotics middleware, ROS 1 and ROS 2. We discuss the benefit and best practices of combining two different frameworks that share the same spirit and show its performance from large-scale real-world experiments. The proposed system is developed as part of Team CoSTAR's effort for the DARPA Subterranean (SubT) Challenge. The system has been field-proved and demonstrated in the Urban Circuit event, where team CoSTAR won first place. To our knowledge, this work is the first real-world demonstration of a ROS 2-based multi-robot system in such large-scale extreme environments. From the significant improvement of the communication performance and the ease of transition from existing ROS 1 systems, this work encourages wider adoption of ROS 2 in field robotics applications.