Truck & Off-Highway Engineering - April 2022 - 15

MODELING & SIMULATION FEATURE
NG-NRMM terramechanics modeling.
To understand what an end-to-end mobility solver
would require, the group focused on key attributes such
as methodologies, tool choices, input/output needs and
stochastics. For instance, they identified scale-invariant
terrain descriptions for representing topographic map
data (obtained at various scales) within a suitable multibody
dynamic simulator that will enable automated
analysis of regions of interest, given heterogeneous
map data products as inputs. The group also was able
to identify efficient, automated, parallelizable experimental
design methods (i.e., sampling methods) for
extracting metrics of interest from a multibody dynamic
simulator. These included mobility-related metrics and
auxiliary metrics that can yield rich statistical mobilityrelated
outputs in a computationally efficient manner,
allowing the use of modern high-performance computing
(HPC) resources.
ET-148 looked at the use of compact representations
of vehicle dynamics (i.e., response surface methods or
other approximation methods) within a multibody dynamic
simulator, with a goal of further reducing computational
cost that will yield an update to classical
" Speed-Made-Good " or " GO/NOGO " maps. They are
respectively defined as the effective maximum possible
vehicle straight-line running speed from one location
to another, and regions where the vehicle can
and cannot traverse. In addition, a benchmarking exercise
was conducted to understand the capabilities of
physics-based tools available from commercial software
developers.
The ET determined that a desirable set of new NGNRMM
requirements would encompass certain traits
(see table). At the conclusion of the study, the committee
felt confident that an adequate set of new requirements
had been defined and that the necessary
TRUCK & OFF-HIGHWAY ENGINEERING
tools were available. The time was right to develop an improved vehicle
mobility modeling capability appropriate to the needs of NATO
nations, and they recommended the formation of a research task
group (RTG) to develop a new NG-NRMM methodology.
Developing game-changing capabilities
The follow-on, three-year RTG (AVT-248) started work in January
2016 to research and develop an updated mobility modeling methodology
that could yield a new paradigm for ground vehicles with the
possibility to model and simulate complex off-road vehicle maneuvers
in high fidelity anywhere in the world. The new RTG was organized
around seven working groups: GIS terrain/mobility mapping,
simple terramechanics, complex terramechanics, intelligent vehicles,
uncertainty treatment, verification/validation (V&V), and data gaps/
operational readiness. The RTG was able to develop an NG-NRMM
prototype approach that included many of the desired attributes envisioned
by the ET, such as the integration of GIS-based terrain data
and implementation of mobility mapping metrics into mobility simulation
software.
The RTG also was able to identify and implement vehicle-terrain
interaction models - i.e., terramechanics models that balance fidelity
with computational efficiency, which may be semi-empirical, or fully
analytical, such as those based on discrete elements - and integrate
those terramechanics models into modern vehicle dynamic simulation
software. The goal was to place the physics-based mobility software
at the center of the geospatial terrain data and soil maps so
that mobility performance metrics such as GO/NOGO maps could be
derived. This mobility metric can be used in the acquisition process
and in operational planning as is done today using NRMM.
The group also was able to implement efficient, automated tools
that enable the use of HPC techniques and develop in-situ and realtime
measurement tools to identify required terrain parameters.
Further, the RTG identified the type and form of desired responses, to
yield rich mobility predictions and useful auxiliary outputs that included
April 2022 15
U.S. ARMY
Truck & Off-Highway Engineering - April 2022

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