The Mars Exploration Rovers (MERs), Spirit and Opportunity, far exceeded their original drive distance expectations and have traveled, at the time of this reporting, a combined 29 kilometers across the surface of Mars. The Rover Sequencing and Visualization Program (RSVP), the current program used to plan drives for MERs, is only a kinematic simulator of rover movement. Therefore, rover response to various terrains and soil types cannot be modeled. Although sandbox experiments attempt to model rover-terrain interaction, these experiments are time-intensive and costly, and they cannot be used within the tactical timeline of rover driving. Imaging techniques and hazard avoidance features on MER help to prevent the rover from traveling over dangerous terrains, but mobility issues have shown that these methods are not always sufficient.
ARTEMIS, a dynamic modeling tool for MER, allows planned drives to be simulated before commands are sent to the rover. The deformable soils component of this model allows rover-terrain interactions to be simulated to determine if a particular drive path would take the rover over terrain that would induce hazardous levels of slip or sink. When used in the rover drive planning process, dynamic modeling reduces the likelihood of future mobility issues because high-risk areas could be identified before drive commands are sent to the rover, and drives planned over these areas could be rerouted.
The ARTEMIS software consists of several components. These include a preprocessor, Digital Elevation Models (DEMs), Adams rover model, wheel and soil parameter files, MSC Adams GUI (commercial), MSC Adams dynamics solver (commercial), terramechanics subroutines (FORTRAN), a contact detection engine, a soil modification engine, and output DEMs of deformed soil. The preprocessor is used to define the terrain (from a DEM) and define the soil parameters for the terrain file. The Adams rover model is placed in this terrain. Wheel and soil parameter files can be altered in the respective text files. The rover model and terrain are viewed in Adams View, the GUI for ARTEMIS. The Adams dynamics solver calls terramechanics subroutines in FORTRAN containing the Bekker-Wong equations. These subroutines use contact and soil modification engines to produce the simulation of rover movement over deformable soils, viewed in Adams View.
New drive techniques could be tested in ARTEMIS to avoid wasting limited time and energy during real-time drives. Extrication techniques can also be developed using ARTEMIS without sandbox testing. These uses of dynamic modeling are not limited to Martian vehicles, and ARTEMIS would have similar benefits for lunar vehicles. ARTEMIS could potentially be modified to dynamically simulate the movement of any vehicle over deformable soil.
This work was done by Brian P. Trease and Randel A. Lindemann of Caltech; Raymond E. Arvidson, Keith Bennett, Lauren P. Van Dyke, and Feng Zhou of the Washington University at St. Louis; and Karl Iagnemma and Carmine Senatore of MIT for NASA’s Jet Propulsion Laboratory.
This Brief includes a Technical Support Package (TSP).
Adams-Based Rover Terramechanics and Mobility Simulator — ARTEMIS
(reference NPO-47781) is currently available for download from the TSP library.
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