Locomotion as Manipulation with ReachBot

TL;DR

ReachBot is a novel robot designed for exploring inaccessible lunar and Martian terrains, using extendable booms and microspine grippers for manipulation and locomotion in confined spaces like lava tubes.

Contribution

The paper introduces ReachBot, a new robot architecture with extendable booms and a contact-based locomotion planner, validated through field testing in a lava tube environment.

Findings

ReachBot can find multiple secure grasp points on rock surfaces.

The contact-before-motion planner effectively enables non-gaited locomotion.

Field tests demonstrate ReachBot’s capability in realistic lava tube conditions.

Abstract

Caves and lava tubes on the Moon and Mars are sites of geological and astrobiological interest but consist of terrain that is inaccessible with traditional robot locomotion. To support the exploration of these sites, we present ReachBot, a robot that uses extendable booms as appendages to manipulate itself with respect to irregular rock surfaces. The booms terminate in grippers equipped with microspines and provide ReachBot with a large workspace, allowing it to achieve force closure in enclosed spaces such as the walls of a lava tube. To propel ReachBot, we present a contact-before-motion planner for non-gaited legged locomotion that utilizes internal force control, similar to a multi-fingered hand, to keep its long, slender booms in tension. Motion planning also depends on finding and executing secure grips on rock features. We use a Monte Carlo simulation to inform gripper design and predict grasp strength and variability. Additionally, we use a two-step perception system to identify possible grasp locations. To validate our approach and mechanisms under realistic conditions, we deployed a single ReachBot arm and gripper in a lava tube in the Mojave Desert. The field test confirmed that ReachBot will find many targets for secure grasps with the proposed kinematic design.