Modular Field Robots for Extraterrestrial Exploration

Abstract

Modular design methodology enables rapid reconfigurability for functional changes, robustness to failures and space utilisation for transportation. In the case of planetary exploration robots, there is promise in modular robots that are able to reconfigure themselves for exploration of unknown terrains. This paper presents a design and controller architecture for modular field robots that can be rapidly assembled in a variety of functional configurations. A key challenge of building a functional robot out of modular units is the ability to seamlessly add, remove and replace individual units to enable functional improvements as well as adapt to terrain requirements. We present a representative modular wheel design and a distributed controller architecture able to create a range of bespoke multi-wheeled configurations capable of traversal on a variety of terrains during simulated failure scenarios. The self-contained wheeled unit has energy, computation communication, and actuation modules and does not require any modification or physical customization in the field during deployment enabling a seamless plug and play behaviour. The hierarchical control structure runs a body controller node that decomposes a whole body motion requested from a higher level planner to generate a sequence of actuation goals for each of the modules, while a local controller node running on each of the modules ensures that the desired actuation is adapted to the configuration, load and terrain characteristics.

Enabling robustness to failure with modular field robots

“…(C) ICR located between both sets of wheels produces differential drive or skid steer. Image reproduced from Cordie et al (2019a) .…”

“…(B) Followed by the failure of a module in the three-wheeled platform. Image reproduced from Cordie et al (2019a) .…”

“…The contribution of this work is the validation of the robustness framework first described in the position paper presented at the International Astronautical Congress ( Cordie et al, 2019a) . This validation includes simulated deployments of robots to failure paired with field experiments in two environments and analysis of the resulting data.…”

“…All of the WLMRs mentioned above would suffer the same fate as Spirit if a wheel became stuck. In this work, we have implemented and tested the work proposed in the paper by Cordie et al (2019a) , allowing a robot to reconfigure and adapt to failure. This adaptation combines the reconfigurability of the WLMRs with the noted ability of modular reconfigurable robots (MRRs) to degrade gracefully ( Yim et al, 2007; Murata and Kurokawa, 2007) .…”

“…The NMRS contains homogeneous two degrees of freedom (DOF) modular wheels, or NeWheels, capable of independent or collaborative operation, combining one or more NeWheels with a dumb body using clamps and adaptors ( Cordie et al, 2016 and Cordie et al, 2019b) . The basis of the strategy explored was proposed by Cordie et al (2019a); it involves internally reconfiguring the robot’s controller or locomotion reconfigurability and ejecting failed modules to adapt to failure.…”