ACHORD: communication-aware multi-robot coordination with intermittent connectivity

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksCommunication is an important capability for multi-robot exploration because (1) inter-robot communication (comms) improves coverage efficiency and (2) robot-to-base comms improves situational awareness. Exploring comms-restricted (e.g., subterranean) environments requires a multi-robot system to tolerate and anticipate intermittent connectivity, and to carefully consider comms requirements, otherwise mission-critical data may be lost. In this paper, we describe and analyze ACHORD (Autonomous & Collaborative High-Bandwidth Operations with Radio Droppables), a multi-layer networking solution which tightly co-designs the network architecture and high-level decision-making for improved comms. ACHORD provides bandwidth prioritization and timely and reliable data transfer despite intermittent connectivity. Furthermore, it exposes low-layer networking metrics to the application layer to enable robots to autonomously monitor, map, and extend the network via droppable radios, as well as restore connectivity to improve collaborative exploration. We evaluate our solution with respect to the comms performance in several challenging underground environments including the DARPA SubT Finals competition environment. Our findings support the use of data stratification and flow control to improve bandwidth-usage.Peer ReviewedPostprint (author's final draft

2023 EELS field tests at Athabasca Glacier as an icy moon analogue environment

JPL is developing a versatile and highly intelligent Exobiology Extant Life Surveyor (EELS) robot that would enable access to subsurface oceans and near-surface liquid reservoirs through existing conduits, such as the vents at the south pole of Enceladus or the putative geysers on Europa. A key mobility requirement for future vent exploration missions will be the ability to carefully descend and hold position in the vent to collect and analyze samples while withstanding plume forces without human intervention. Furthermore, this must be accomplished in a highly uncertain environment, requiring versatile hardware and intelligent autonomy. To work towards that goal, we have prototyped the EELS 1.0 and EELS 1.5 robots for horizontal and vertical mobility, respectively, in icy terrain. Autonomous surface mobility of EELS 1.0 was previously validated in a variety of terrain, including snowy mountains, ice rinks, and desert sand. Vertical mobility of EELS 1.5 was developed on laboratory ice walls. This paper presents the first mobility trials for both robots on large-scale, natural icy terrain: the Athabasca Glacier located in Alberta, Canada, a terrestrial analogue to the surfaces and subsurfaces of icy moons. This paper provides a preliminary written record of the test campaign’s four major trials: 1) surface mobility with EELS 1.0, 2) vertical mobility with EELS 1.5, 3) science instrument validation, and 4) terramechanics experiments. During this campaign, EELS 1.5 successfully held position and descended ~1.5 m vertically in an icy conduit and EELS 1.0 demonstrated surface mobility on icy surfaces with undulations and slopes. A miniaturized capillary electrophoresis (CE) instrument built to the form factor of an EELS module was tested in flowing water on the glacier and successfully demonstrated automated sampling and in-situ analysis. Terramechanics experiments designed to better understand the interaction between different ice properties and the screws that propel the robot forwards were performed on horizontal and vertical surfaces. In this paper we report the outcomes of the four tests and discuss their implications for potential future icy missions. The field test also demonstrated EELS’s ability to support Earth science missions. Another potential near-term follow-on could be a technology demonstration on the Moon. This paper is a high level report on the execution of the field test. Data and results will be detailed in subsequent publications