Computer Science – Sound
Scientific paper
Apr 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eaeja....14530r&link_type=abstract
EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #14530
Computer Science
Sound
Scientific paper
As a result of the ESA TRP activity MIDD (Mobile Instrument Deployment Device), an advanced Breadboard Model of a wheeled mobile device for use on planetary surfaces has recently been completed and functionally tested. The vehicle is based on previous mechanical component development work for small wheeled devices performed since 1995 and serves to demonstrate the scientific potential of a 4 kg-class system for supporting surface and subsurface science on a planetary landing mission. Moreover, the device is being extensively used to study general problems of locomotion on regolith-like surface materials and of obstacle negotiation. As payload elements, two spectrometers for mineralogical and elemental studies on surface materials - including rocks - have been foreseen, as well as an acoustic subsurface sounder, a close-up imager and a self-penetrating "Mole" for subsurface measurements and sampling. In addition, a dust removal device was accommodated for preparing rock surfaces for measurements. The mass of the payload, excluding their electronics, amounts to 1.5 kg. Following an accommodation study for the instruments, the vehicle chassis was sized by taking into account planetary surface rock distributions with ground clearance as well as mean straight path constraints, while restricting the number of wheels to four for reasons of simplicity and mass. The two front wheels are mounted on folding levers which allow to contact the soil with the cab and to place the spectrometers and the close-up imager against their targets. Also for operations of the Mole sampling system - reaching depths of more than 1 m and being derived from the "Beagle 2" Mole - , the front wheels are preferably rotated upwards to achieve a larger vehicle base. In order to minimize the stowage volume, a dual wheel configuration was chosen which allows the front wheels to be folded back while overlapping the rear wheels. The folding lever feature also provides a re-righting capability by shifting the center-of-mass, should the vehicle fall on its side. All wheels and the two folding levers are individually driven by brushless DC motors located inside a thermal enclosure in the vehicle cab. Except for the actuators and drive mechanisms, the enclosure houses a central electronics unit which also provides pre-processing of payload data. For the power supply and communications, a tether link to the lander is used, allowing a maximum range of some 20 m. As to the tether type, a flexible printed circuit was chosen which allows efficient packaging of the tether on board the vehicle. The wheel design was based on theoretical and experimental studies on tractive performance of small wheels on planetary soils being one of the subjects of the MIDD activity, involving a dedicated soil channel at DLR. As a result, the vehicle wheels were chosen to be rigid while featuring a wire mesh running surface and chevron-shaped grousers. Mass of a flight unit is projected to be around 2.9 kg, excluding the vehicle payload. The principal design philosophy for MIDD has been: conservative design with sufficient margins (i.e., provision of thermal enclosure for instruments); early component development and realistic environmental testing (mechanism functional testing in Thermal Vacuum; dust sealing test with mechanisms operating in simulated airborne dust environment of Mars).
Bernasconi Marco
Coste Ph.
Haapanala S.
Richter L. L.
Steiner Richard
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