Maneuver analysis methodology to predict vehicle impacts on training lands

Tactical mobility analysis techniques were merged with land management strategies to assess potential impacts of vehicle operations on training areas for rangeland planning and management. A vehicle mobility analysis was performed for a suite of vehicle types using the NATO Reference Mobility Model (NRMM II). Input parameters include terrain information (soil type, slope, vegetation, surface roughness, soil strength), terrain surface condition based on climate (terrain strength, freeze–thaw, moisture content, snow cover), and vehicle specifications (tire, power train, weight on each axle, ground clearance, dimensions, ride). The vehicle performance was spatially mapped over the terrain for different seasons of the year and used to calculate the maneuverable acreage, which was compared to acreage needed for training requirements. This can be related to land capability based on expected training impact (Maneuver Impact Miles, MIM) and Land Condition Curves which link training density to land condition. This methodology can be used to determine the suitability of training lands and the degree of land management or rehabilitation expected. The methodology was applied to the transformation of the Alaska training lands to support a new brigade unit called the Stryker Brigade Combat Team (SBCT3), but is equally useful for other training areas and military units. For summer use, Alaska training lands are capable of supporting four times the projected training requirements. For winter, when the ground is frozen, more than 10 times the area needed was available.     

Quantifying vegetation biomass impacts on vehicle mobility

Soil impacts on vehicle mobility are well known; however, most data are for bare soil or the type and amount of vegetation is not documented. This study summarizes results from experiments to quantify the effect of above ground and below ground vegetation biomass on vehicle performance. Soil–vegetation combinations of three soils and three grasses were used. The vegetation was tested at various growth stages and was also subjected to stressors such as trafficking, burning, and cutting. Vegetation measurements included above ground (leaves and shoots) and below ground (root) biomass weights, lengths, diameters and surface area parameters. The soils were characterized for size distribution, moisture, density and terrain strength for each test condition. Vehicle traction and motion resistance were measured for each soil–grass combination using the CRREL Instrumented Vehicle. Results showed an increase in net traction biomass in sandy soils. For clay soils above ground biomass generally increased resistance while increased root diameter clearly decreased resistance. This study represents the first measurements quantifying the impacts of specific biomass parameters on vehicle mobility. The results will serve to guide new experimental methods, improve datasets, and develop physics-based models for years to come.     

Clarification of vehicle cone index with reference to mean maximum pressure

The US Army developed Vehicle Cone Index (VCI) as a metric for directly quantifying the ability of vehicles to traverse soft-soil terrain. In order to ensure minimum soft-soil performance capabilities for their new military vehicles, the US Army has used VCI for many years as a performance specification. The United Kingdom’s Ministry of Defence (UK MOD) has used the Mean Maximum Pressure (MMP) parameter for many years as a performance specification. It has been demonstrated that the MMP parameter relates to soft-soil performance capabilities, and hence, the UK MOD has ensured minimum performance capabilities for their new military vehicles by using MMP specifications. Both the VCI and MMP specification approaches have served their users well, but fundamental differences in the two specification approaches have produced some misunderstandings concerning what VCI really is and how it relates to MMP. This article clarifies that VCI is a performance metric, not a set of predictive equations, explains how VCI is measured, and compares different methods of predicting VCI for one-pass performance (i.e., VCI₁) of wheeled vehicles in fat clay soils. It is further clarified that MMP should not be compared with VCI but instead with Mobility Index (MI), which is the principal parameter used by the US Army for predicting VCI. Relationships are presented for using MMP to predict VCI₁ for wheeled vehicles in clay, and the resulting relationships allow comparison between MMP and MI in terms of their ability to predict VCI. Seventy-nine VCI₁ performance measurements were used for the comparison, and they demonstrate that MI describes the historical performance data somewhat better than MMP.     

Fundamental study on underwater trafficability for tracked vehicle

In recent years, water disasters have increased in Japan. In water disaster, remote controlled vehicles which work for disaster recovery must run in water environment. Since underwater ground is likely to be soft, the vehicle has a risk of stuck. If a vehicle gets stuck at disaster sites, rescue work is difficult because it is not easily to access to that area. We must make a method for judging whether to run or not. For this purpose, we must quantitatively clarify the relationship between the trafficability and the strength, bearing capacity, etc. of underwater ground. We measured the cone index of underwater ground. From results, we confirmed that fragile layer was formed on the surface layer in underwater ground. We measured drawbar pull of a tracked carrier in test field. As a result, maximum drawbar pull of underwater ground was lower than on the ground. After slip occurs, drawbar pull of underwater ground was smaller than ground significantly.     

A four-state field evaluation of the Boeing Landing Suitability Index (BLSI) for automatically mapping candidate aircraft operating sites in natural terrain from LANDSAT TM data

The Boeing Landing Suitability Index (BLSI) is a computer algorithm designed at Bowling Green State University for The Boeing Company for the purpose of mapping candidate aircraft operating sites of different “runway” lengths in natural terrain from LANDSAT TM data. Four LANDSAT TM frames (each 115 miles × 115 miles in area) from parts of California, New Mexico, South Dakota, and Louisiana (with annual rainfalls averaging approximately 3.5, 7, 17, and 53 in., respectively, though the Louisiana frame was collected during a drought year that had 28 in. of annual rainfall) were entered as inputs to the BLSI algorithm, which identified pixels in each of the frames that were sufficiently flat, treeless, and absent of surface water to land an aircraft on them, present weather conditions permitting, and perform off-loading, on-loading, and take-off operations. Adjustments were made to the algorithm for differences in annual rainfall. Although no attempt was made before these field trips to force BLSI to map surface firmness, the California Bearing Ratio (CBR) was measured in the field on-site and off-site with dynamic cone penetrometers by a contractor for the Air Force Research Lab (Tyndall AFB in Florida) for several of these candidate aircraft operating sites. We found that all of the sites selected by BLSI that were visited in the field were suitably flat for landing and had no surface water or trees on them (except for one small tree that was younger than the LANDSAT frame employed for that region). Fortunately, most of these candidate aircraft operating sites found by BLSI had firmer ground than their immediate surroundings, as measured from the dynamic cone penetrometers. Our field observations support the hypothesis that BLSI is primarily mapping very subtle, local topographic highs. Such a subtle topographic high, which may rise only few feet from the middle to the edge of a candidate aircraft operating site, usually has a hard pan beneath it, owing to its relatively better drainage, compared with its immediate surrounds. This may account for its greater firmness, compared to its surrounds. Because the slopes are so small and the feature is slightly convex upward, there are no gullies on candidate aircraft operating sites. This causes the subtle topographic highs to be very flat and without rocks, unlike higher-sloped regions, where water in gullies tend to wash rocks. This seems the most reasonable explanation for why a pixel size as gross as 28.5 m (LANDSAT TM bands 1–5 and 7) is adequate to map such features. BLSI displayed as a continuous-toned image has potential for mapping areas of highest trafficability for wheeled vehicles, with lower BLSI values (shown as purple or blue areas) having the greatest trafficability.     

The applicability of the MMP concept in specifying off-road mobility for wheeled and tracked vehicles

A review is given of the use of mean maximum pressure (MMP) in specifying off-road performance of vehicles. The need to quote a single mobility criterion which is unbiased in favour of either wheeled or tracked vehicles is recognised. The difficulties which researchers have encountered in developing expressions for MMP for both wheeled and tracked vehicles which correctly describe their relative performance are highlighted. Predictions of MMP for wheeled vehicles are compared with ground pressure measurements for a number of vehicles and it is shown that the MMP parameter does not actually represent the ground pressure accurately. Finally it is argued that the only safe route for the specifier is to quote a range of soil types, conditions and gradients on which the vehicle is to operate. This shifts the responsibility to the designer but also clears the way for innovative design, beyond the constraints of the MMP formulae.     

Prediction of trafficability for tracked vehicle on broken soil: real size tests

Full-scale tests were carried out within the broader framework of a study of an operational mechanical mine clearance system. This system is made up of a tracked machine pushing a mine clearance plow that scarifies the soil to approximately 30 cm depth. This study examines the capacity of the tractor to move on a disturbed soil. This paper presents motion resistance tests and drawbar pull tests on four types of soil. The soils have been chosen to be scientifically representative of the broad distribution on our planet: a sand (frictional soil), a silt (cohesive soil), a silty gravel (coarse-grained soil), and a silty sand (cohesive soil). The tests are performed in two configurations: on compacted soils and on soils scarified with an experimental plow. The results of each test condition are described. The effects of the soil type, its state, and the speed of the tested vehicle are presented. Using these results and, in addition, full-scale tests of scarification, we present an operational analysis determining the mobility of a tracked vehicle on broken soil. This method makes it possible to calculate the maximum speed of a mechanical mine clearance system for the whole range of soils tested.     

Rapid stabilization of thawing soils: field experience and application

Thawing soils can severely restrict vehicle travel on unpaved surfaces. However, a variety of materials and construction techniques can be used to stabilize thawing soils to reduce immobilization problems. The US Engineer Research and Development Center's Army Cold Regions Research and Engineering Laboratory (CRREL) and the Wisconsin National Guard evaluated several stabilization techniques in a field demonstration project during spring thaw at Fort McCoy, Wisconsin, in 1995. Additional tests on chemical stabilizing techniques were conducted at CRREL's Frost Effects Research Facility. The results of these test programs were reduced to a decision matrix for stabilizing thawing ground, and used during the deployment of US troops in Bosnia during January and February of 1996. The soil frost and moisture conditions expected during this time frame were predicted using MIDFROCAL (MIDwest FROst CALculator). This paper is an overview of the stabilization techniques evaluated and their recommended application based on the expected soil frost conditions and traffic requirements. Although the experiments were performed with military vehicles in mind, the techniques are suitable for many civilian applications such as forestry, construction, mining, and oil exploration.     

An optimum design method for robotic tracked-vehicles operating over fresh concrete during straight-line motion

This paper addresses the general problem of the design of tracked base travel systems for special purpose vehicles and/or robotic machines that may be required to move over weak surfaces or over a lightly bonded terrain composed of fresh concrete. For the special case of a vehicle travelling on a very soft fresh concrete during construction, the paper presents detailed comparative studies of the tractive performance of several tracked vehicles with alternative slump values and mean contact pressure configurations. To complete these studies a detailed simulation-analytical method was used. From this, it was established that the simulation analysis method is useful for predicting land locomotion performance of specially designed small tracked vehicles running over fresh concrete of different consistencies during driving and braking action. This work was done for straight-line motion. Some possibilities for the real-time optimum control method of the tractive and braking performance of automated and robotic vehicles are also outlined.