Field Validation of Nomad’s Robotic Locomotion

Abstract

During June and July of 1997, a mobile robot named Nomad traversed 223km in the Atacama Desert of southern Chile via transcontinental teleoperation. This unprecedented accomplishment is primarily attributed to Nomad's innovative locomotion design which features four-wheel/all-wheel drive locomotion, a reconfigurable chassis, electronically coordinated steering, pivot-arm suspension, and body motion averaging. Nomad's locomotion was configured through systematic analysis and simulations of the robot's predicted performance in a variety of terrain negotiation scenarios. Experimental work with a single wheel apparatus was used to determine the effect of repeated traffic and tread pattern on power draw. Field tests before and during the Atacama traverse demonstrated Nomad's substantial terrainability and autonomous navigation capabilities, and validated theoretical performance projections made during its geometric configuration. Most recently, the augmentation of the internal monitoring system with a variety of sensors has enabled a much more comprehensive characterization of Nomad's terrain performance. Because of Nomad's unique steering design a comparison of skid and explicit steering was performed by monitoring wheel torque and power during steady state turns. This paper summarizes the process and metrics of Nomad's mobility configuration, and reports on experimental data gathered during locomotion testing.