  Safe long-term deployment of a fleet of mobile robots requires reliable and
secure two-way communication channels between individual robots and remote
human operators for supervision and tasking. Existing open-source solutions to
this problem degrade in performance in challenging real-world situations such
as intermittent and low-bandwidth connectivity, do not provide security control
options, and can be computationally expensive on hardware-constrained mobile
robot platforms. In this paper, we present Robofleet, a lightweight open-source
system which provides inter-robot communication, remote monitoring, and remote
tasking for a fleet of ROS-enabled service-mobile robots that is designed with
the practical goals of resilience to network variance and security control in
mind.
  Robofleet supports multi-user, multi-robot communication via a central
server. This architecture deduplicates network traffic between robots,
significantly reducing overall network load when compared with native ROS
communication. This server also functions as a single entrypoint into the
system, enabling security control and user authentication. Individual robots
run the lightweight Robofleet client, which is responsible for exchanging
messages with the Robofleet server. It automatically adapts to adverse network
conditions through backpressure monitoring as well as topic-level priority
control, ensuring that safety-critical messages are successfully transmitted.
Finally, the system includes a web-based visualization tool that can be run on
any internet-connected, browser-enabled device to monitor and control the
fleet.
  We compare Robofleet to existing methods of robotic communication, and
demonstrate that it provides superior resilience to network variance while
maintaining performance that exceeds that of widely-used systems.
