Benjamin Shamah

Technology and Field Demonstration of Robotic Search for Antarctic Meteorites

Meteorites are the only significant source of material from other planets and asteroids, and therefore are of immense scientific value. Antarctica’s frozen and pristine environment has proven to be the best place on earth to harvest meteorite specimens. The lack of melting and surface erosion keep meteorite falls visible on the ice surface in pristine condition for thousands of years. In this article, we describe the robotic technologies and field demonstration that enabled the first discovery of Antarctic meteorites by a robot. Using a novel autonomous control architecture, specialized science sensing, combined manipulation and visual servoing, and Bayesian classification, the Nomad robot found and classified five indigenous meteorites during an expedition to the remote site of Elephant Moraine in January 2000. This article first overviews Nomad’s mechatronic systems and details the control architecture that governs the robot’s autonomy and classifier that enables the autonomous interpretation of scientific data. It then focuses on the technical results achieved during field demonstrations at Elephant Moraine. Finally, the article discusses the benefits and limitations of robotic autonomy in science missions. Science autonomy is shown as a capable and expandable architecture for exploration and in situ classification. Inefficiencies in the existing implementation are explained with a focus on important lessons that outline future work.

The Science Autonomy System of the Nomad robot

The Science Autonomy System (SAS) is a hierarchical control architecture for exploration and in situ science that integrates sensing, navigation, classification and mission planning. The Nomad robot demonstrated the capabilities of the SAS during a January 2000 expedition to Elephant Moraine, Antarctica where it accomplished the first meteorite discoveries made by a robot. In the paper, the structure and functionality of the three-tiered SAS are detailed. Results and lessons learned are presented with a focus on important future research.

Robotic Antarctic meteorite search: outcomes

Automation of the search for and classification of Antarctic meteorites offers a unique case for early demonstration of robotics in a scenario analogous to geological exploratory missions to other planets and to the Earths extremes. Moreover, the discovery of new meteorite samples is of great value because meteorites are the only significant source of extraterrestrial material available to scientists. In this paper we focus on the primary outcomes and technical lessons learned from the first field demonstration of autonomous search and in situ classification of Antarctic meteorites by a robot. Using a novel autonomous control architecture, specialized science sensing, combined manipulation and visual servoing, and Bayesian classification, the Nomad robot classified five indigenous meteorites during an expedition to the remote site of Elephant Moraine in January 2000. Nomads expedition proved the rudiments of science autonomy and exemplified the merits of machine learning techniques for autonomous geological classification in real-world settings. On the other hand, the expedition showcased the difficulty in executing reliable robotic deployment of science sensors and a limited performance in the speed and coverage of autonomous search.

First experiment in sun-synchronous exploration

Sun-synchronous exploration is accomplished by reasoning about sunlight: where the Sun is in the sky, where and when shadows will fall, and how much power can be obtained through various courses of action. In July 2001 a solar-powered rover, named Hyperion, completed two sun-synchronous exploration experiments in the Canadian high arctic (75/spl deg/N). Using knowledge of orbital mechanics, local terrain, and expected power consumption, Hyperion planned a sun-synchronous route to visit designated sites while obtaining the necessary solar power for continuous 24-hour operation. Hyperion executed its plan and returned to its starting location with batteries fully charged after traveling more than 6 kilometers in barren, Mars-analog terrain. We describe the concept of sun-synchronous exploration. We overview the design of the robot Hyperion and the software system that enables it to operate sun-synchronously. We then discuss results from analysis of our first experiment in sun-synchronous exploration and conclude with observations.

Field validation of Nomad's robotic locomotion

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 Nomads innovative locomotion design which features four-wheel/all-wheel drive locomotion, a reconfigurable chassis, electronically coordinated steering, pivot-arm suspension, and body motion averaging. Nomads locomotion was configured through systematic analysis and simulations of the robots predicted performance in a variety of terrain negotiation scenarios. Experimental work with a single wheel apparatus was sued to determine the effect of repeated traffic and tread pattern on power draw. Field test before and during the Atacama traverse demonstrated Nomads 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 Nomads terrain performance. Because of Nomads 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 Nomads mobility configuration, and reports on experimental data gathered during locomotion testing.

Steering and control of a passively articulated robot

The need for light weight yet highly mobile robotic platforms is driven by the limitation of available power. With unlimited energy, surface exploration missions could survive for months or years and greatly exceed their current productivity. The Sun-Synchronous Navigation project is developing long-duration solar-powered robot exploration through research in planning techniques and low-mass robot configurations. Hyperion is a rover designed and built for experiments in sun-synchronous exploration. This paper details Hyperions steering mechanism and control, which features 4-wheel independent drive and an innovative passively articulated steering joint for locomotion.