Cross-country mobility on various snow conditions for validation of a virtual terrain (original) (raw)
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Review of terramechanics models and their applicability to real-time applications
Journal of Terramechanics
ISTVS embarked on a project in 2016 that aims at updating the current ISTVS standards related to nomenclature, definitions, and measurement techniques for modelling, parameterizing, and, respectively, testing and validation of soft soil parameters and vehicle running gear-terrain interaction. As part of this project, a comprehensive literature review was conducted on the parameterization of fundamental terramechanics models. Soil parameters of the empirical models to assess off-road vehicle mobility, and parameters of the models to characterize the response of the terrain interacting with running gears or plates from the existing terramechanics literature and other researchers' reports were identified. This review documents and summarizes the modelling approaches that may be applicable to real-time applications of terramechanics in simulation, as well as in controller design.
Journal of Terramechanics, 2014
This paper investigates the validity of commonly used terramechanics models for lightweight vehicle applications while accounting for experimental variability. This is accomplished by means of cascading uncertainty up to the terminal point of operations measurement. Vehicle-terrain interaction is extremely complex, and thus models and simulation methods for vehicle mobility prediction are largely based on empirical test data. Analytical methods are compared to experimental measurements of key operational parameters such as drawbar force, torque, and sinkage. Models of these operational parameters ultimately depend on a small set of empirically determined soil parameters, each with an inherent uncertainty due to test variability. The soil parameters associated with normal loads are determined by fitting the dimensionless form of Bekker's equation to the data given by the pressure-sinkage test. In a similar approach, the soil parameters associated with shear loads are determined by fitting Janosi and Hanamoto's equation to the data given by the direct shear test. An uncertainty model is used to propagate the soil parameter variability through to the wheel performance based on Wong and Reece. The commonly used analytical model is shown to be inaccurate as the envelope of model uncertainty does not lie within the experimental measures, suggesting that model improvements are required to accurately predict the performance of lightweight vehicles on deformable terrain. BACKGROUND The study of the interaction of wheeled and tracked vehicles with natural terrain is dominated by the discipline of terramechanics. Terramechanics research over the past 50 years has primarily focused on large, heavy military vehicles. A substantial body of terramechanics research has been performed at the U.S. Army Tank Automotive Research, Development, and Engineering Center (TARDEC) and the U.S. Army Engineer Research and Development Center (ERDC) that led to the development of various mobility prediction methodologies including the NATO Reference Mobility Model (NRMM). These methodologies are numerical algorithms for predicting crosscountry vehicle movement at length scales of several meters to several kilometers. They are based on empirical results drawn from years of resource-intensive experimental testing and have been used widely by the military community. However, as a consequence of their empirical nature, while the methods are useful for prediction of large, heavy vehicle mobility, it remains an open question whether they can be reliably used for the prediction of small, lightweight vehicle mobility.
Evaluating planetary digital terrain models—The HRSC DTM test
Planetary and Space Science, 2007
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Updated Standards of the International Society for Terrain-Vehicle Systems
Journal of Terramechanics, 2020
The last version of the ISTVS standards was published in the Journal of Terramechanics in 1977. Since then, the document has not been updated, although new concepts, techniques, testing procedures, and technology have been developed in the last 40 years, which renders some content of the 1977 ISTVS standards outdated and incomplete. The ISTVS identified as a priority the need to develop a set of standards for terminology and testing for modern day research on off-road mobility. This paper, for which the work has been funded in part by ISTVS, is an updated version of the 1977 ISTVS standards and covers a range of aspects in off-road mobility for: vehicles, tires, tracks, soil, wheels, modelling approaches, test methods, and equipment.
Improving engineering models of terramechanics for planetary exploration
Results in Engineering, 2019
This short letter proposes more consolidated explicit solutions for the forces and torques acting on typical rover wheels, that can be used as a method to determine their average mobility characteristics in planetary soils. The closed loop solutions stand in one of the verified methods, but at difference of the previous, observables are decoupled requiring a less amount of physical parameters to measure. As a result, we show that with knowledge of terrain properties, wheel driving performance rely in a single observable only. Because of their generality, the formulated equations established here can have further implications in autonomy and control of rovers or planetary soil characterization.
Journal of Geophysical Research: Planets, 2014
Physical properties of terrains encountered by the Curiosity rover during the first 360 sols of operations have been inferred from analysis of the scour zones produced by Sky Crane Landing System engine plumes, wheel touch down dynamics, pits produced by Chemical Camera (ChemCam) laser shots, rover wheel traverses over rocks, the extent of sinkage into soils, and the magnitude and sign of rover-based slippage during drives. Results have been integrated with morphologic, mineralogic, and thermophysical properties derived from orbital data, and Curiosity-based measurements, to understand the nature and origin of physical properties of traversed terrains. The hummocky plains (HP) landing site and traverse locations consist of moderately to well-consolidated bedrock of alluvial origin variably covered by slightly cohesive, hard-packed basaltic sand and dust, with both embedded and surface-strewn rock clasts. Rock clasts have been added through local bedrock weathering and impact ejecta emplacement and form a pavement-like surface in which only small clasts (<5 to 10 cm wide) have been pressed into the soil during wheel passages. The bedded fractured (BF) unit, site of Curiosity's first drilling activity, exposes several alluvial-lacustrine bedrock units with little to no soil cover and varying degrees of lithification. Small wheel sinkage values (<1 cm) for both HP and BF surfaces demonstrate that compaction resistance countering driven-wheel thrust has been minimal and that rover slippage while traversing across horizontal surfaces or going uphill, and skid going downhill, have been dominated by terrain tilts and wheel-surface material shear modulus values.