Locomotion as manipulation with ReachBot

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 nongaited legged locomotion that uses internal force control, similar to a multifingered hand, to keep its long, slender booms in tension. Motion planning also depends on finding and executing secure grips on rock features. We used a Monte Carlo simulation to inform gripper design and predict grasp strength and variability. In addition, we used 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.

Navigation Results from Desert Field Tests of the Rocky 7 Mars Rover Prototype

Upcoming missions to the surface of Mars will use mobile robots to traverse long distances from the landing site. To prepare for these missions, the prototype rover, Rocky 7, has been tested in desert field trials conducted with a team of planetary scientists. While several new capabilities have been demonstrated, foremost among these was sun-sensor-based traversal of natural terrain totaling a distance of 1 km. This paper describes navigation results obtained in the field tests, where cross-track error was only 6% of the distance traveled. Comparison with previous results of other planetary rover systems shows this to be a significant improvement. Methods for further improvement are also discussed.

Back-reflection energy-dispersive X-ray diffraction: a novel diffraction technique with almost complete insensitivity to sample morphology

A novel X-ray diffraction (XRD) technique, which exhibits almost complete insensitivity to the morphology of and distance to the sample, is presented for the first time. This technique applies energy-dispersive XRD (EDXRD) in a back-reflection geometry, with 2θ ≃ 180°. Although this geometry leads to low resolution of diffraction peaks and the greatest overlap with fluorescence peaks, it nevertheless yields a combination of properties that are unique in the field of X-ray diffractometry. It is likely that diffraction patterns can be obtained with no or very minimal sample preparation. Furthermore, the intrinsic geometry of the method and the simplicity inherent to EDXRD enables a compact lightweight instrument design, suitable for field-portable or hand-held XRD and X-ray fluorescence analysis. Application to geological and planetary science is emphasized in this paper. The characteristics of the technique are elucidatedviatheoretical considerations and ray-trace modelling, and the simplest possible implementation is described.