Mobile Robot for Exploring Cold Liquid/Solid Environments
- Thursday, 16 November 2006
This tethered robot could float, swim, crawl, and sample environmental materials.
The Planetary Autonomous Amphibious Robotic Vehicle (PAARV), now at the prototype stage of development, was originally intended for use in acquiring and analyzing samples of solid, liquid, and gaseous materials in cold environments on the shores and surfaces, and at shallow depths below the surfaces, of lakes and oceans on remote planets. The PAARV also could be adapted for use on Earth in similar exploration of cold environments in and near Arctic and Antarctic oceans and glacial and sub-glacial lakes.
The PAARV design is based partly on the design of prior ice-penetrating exploratory robots and partly on the designs of drop sondes heretofore used on Earth for scientific and military purposes. Like a sonde, the PAARV is designed to be connected to a carrier vehicle (e.g., a balloon, aircraft, or vessel in a terrestrial setting) by a tether, through which the carrier vehicle would provide power and would relay data communications between the PAARV and an external or remote control station. Like a sonde, the PAARV could be lowered from the carrier vehicle into an ocean or lake environment to be explored. Unlike a sonde, the PAARV would be capable of swimming and of crawling along the bottom, and crawling out of the ocean or lake and moving to a designated site of scientific interest on the shore.
As now envisioned, the fully developed PAARV (see figure) would include an upper sonde segment and a lower sonde segment. Protruding from the lower sonde segment would be two assemblies containing both lifting surfaces (for control of attitude during descent and swimming) and crawler tracks. These assemblies could be rotated to align them parallel, perpendicular, or at an oblique angle with respect to the longitudinal axis of the lower sonde segment. Also protruding from the lower sonde segment, at a point above the center of gravity, would be a thruster for swimming.
The upper sonde segment would be cylindrical, approximately 30 cm in diameter and 20 cm high. This segment would contain a tether management and actuation subsystem; buoyancy-control chambers; a subsystem of pumps, actuators, and valves; a chamber holding compressed gas; and a chamber containing a heater. The upper sonde segment would be attached to the lower sonde segment via a single-joint actuator that effects rotation about an axis perpendicular to the longitudinal axes of the sonde segments.
The lower sonde segment would be approximately 60 cm long and 15 cm in diameter. Either a general-purpose radioisotope heat source or a mass of phase-change heat-storage material would be located in the nose (lower and outer end) of the lower sonde segment to keep instruments warm in the cold environment. The sonde would have a dual-walled shell with insulation to reduce the loss of heat. The heat source in the nose also would serve as ballast to maintain stability like that of a traditional ocean buoy.
When the PAARV was initially lowered from the carrier vehicle, the upper and lower sonde segments and the lifting surface/crawler-track assemblies would be aligned collinearly so that the PAARV would float in a nominal vertical orientation like a buoy. Once the buoyancy chambers started to fill, the tether would be paid out from the top sonde segment as the PAARV descended. Upon arrival at a depth designated for swimming, the thruster would be activated and relative alignments of the upper and lower sonde segments and the lifting-surface/ crawler-track assemblies varied as needed for steering. Upon contact with the bottom, the lower sonde segment and the lifting-surface/crawler-track assemblies would be turned to a nominally horizontal orientation with the upper sonde segment in a nominally vertical orientation, and the crawler tracks would then be activated.
A sampling needle could be extended from the lower side of the lower sonde segment into the bottom of the ocean or lake, where it would adsorb bottom material. The needle would then be retracted, then heated to desorb the material for analysis by instruments in the lower sonde segment. The data from the analyses would be relayed to the external control station via the tether.
Once the bottom sampling was complete, the PAARV would increase its buoyancy by displacing liquid from the buoyancy-control chambers and would reel the tether back in. An onboard guidance, navigation, and control system coupled with acoustic range sensors would enable the vehicle to move slowly toward shore as it ascended. Upon contact with ascending slope, the crawler tracks would be rotated to the angle of the slope and the crawler tracks would be activated. Once out of the water, the PAARV would crawl to a location of interest designated by coordinates provided by cameras on the carrier vehicle or an aircraft overhead. The sampling process would be repeated at the location of interest.
This work was done by Charles Bergh and Wayne Zimmerman of Caltech for NASA’s Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Machinery/Automation category. NPO-40731
This Brief includes a Technical Support Package (TSP).
Mobile Robot for Exploring Cold Liquid/Solid Environments (reference NPO-40731) is currently available for download from the TSP library.
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