The mobility of military vehicles plays a key role in operation. The ability to reach the desired area in war theatre represents the most important condition for a successful accomplishment of the mission for military vehicles. The offroad vehicles face a broad spectrum of terrains to cross. These terrains differ by geometry and the soil characteristics.
NATO References Mobility Model (NRMM) software is based on empirical relationship between the terrain characteristics, running conditions and vehicles design. The paper presents the main results of a comparative mobility analysis for M1 and HMMWV vehicles obtained using NRMM.
Introduction:
There are numerous scientific attempts to describe the traction of vehicles on soft soils in direct correlation with the soils characteristics.
A large amount of papers have developed analytical approaches based on Bekker’s equations. The last developments of the analytical models deals with the detailed study of the design influence on traction characteristics.
The complexity of the phenomena occurring within the terrain – vehicle interface leaved enough room for the development of empirical methods for evaluation of the vehicle mobility. The first successful attempts includes the work of US Army specialized laboratories. Considerable efforts were made in order to set up empirical relations who cover the current design diversity of the vehicle; finally, the mathematical relations were implemented into NATO Reference Mobility Modelling (NRMM) software.
NRMM is a large scale digital simulation, which predicts the on-road and crosscountry performance of a vehicle in a global sense. The measure of performance is speedmade-good and percent of an area denied due to immobilization.
NRMM is used in the development of requirements, cost-performance analyses, as an evaluation tool, in support of contract selections and to support other mobility studies.
NRMM is an engineering model (constructive type) which marries the engineering characterization of the vehicle (power train, running gear, suspension, mass and inertial properties and geometry) with the engineering characterization of the terrain (slopes, soil strength, obstacle geometry, surface roughness, and vegetation density). It is an analytical simulation model which predicts the vehicle’s maximum attainable speed cross-country and on-road for a specified geographic region and environmental condition (wet season, rainfall, snow), and defines within the geographic region areas of immobilization and the reasons for such situation. Meanwhile, this model is based on empiric relations experimentally validated for al large variety of vehicles in terms of size, weight and running gear type.
Author: Ticusor CIOBOTARU
Source: Leonardo Electronic Journal of Practices and Technologies
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