EELS: Towards Autonomous Mobility in Extreme Terrain with a Versatile Snake Robot with Resilience to Exteroception Failures

The discovery of ocean worlds such as Enceladus,Titan, and Europa motivates the development of resilient andadaptive autonomous mobility systems to enable the next era ofspace exploration. To explore these environments, we proposeExobiology Extant Life Surveyor (EELS): the first large-scale(4 lm long with 400 Nm peak torque) snake robot. The largescaleachieved by using a screw-based active skin mechanism todecouple motion and shape control. Autonomous mobility forsuch a system remains an open problem due to its many Degreesof Freedom (DoFs), complex terrain interactions, and intermittentlocalization failures in GPS-denied perceptually degradedenvironments. We propose NEO, an autonomy architecture forversatile robot for mobility in unknown extreme environments.In particular, we discuss the resilience capabilities of NEOthat achieves closed-loop tracking performance by leveragingexteroception when available but can also operate with proprioceptiononly, leading to resiliency against localization failuresvia graceful degradation in performance rather than unsafebehaviors. Furthermore, we also implement classical shapebasedgaits, such as sidewinding. A quantitative hardwareevaluation of exteroceptive leader-follower gait is performedindoors on synthetic ice along with qualitative results of fielddeployment of the proprioceptive leader-follower in extremeenvironments of icy and sandy terrains with mobility-stressingelements such as trenches, undulations, and steep slopes. Wepresent a set of lessons learned from field deployments with asummary of challenges and open research problems.Video: www.rohanthakker.in/eels-neo-autonomy.html