High Mobility Multipurpose Wheeled Vehicle Research Articles

Computational investigation of the effect of up-armouring on the reduction in occupant injury or fatality in a prototypical high-mobility multi-purpose wheeled vehicle subjected to mine blast

A comprehensive finite-element-based computational investigation of the ability of different measures (e.g. up-armouring, seat cushion, or seat belt restraint system) to protect the occupant(s) of a prototypical high-mobility multi-purpose wheeled vehicle in the event of an anti-vehicle mine detonation under the vehicle's front right wheel is carried out. While assessing the effectiveness of these protective measures, different injury criteria had to be defined and/or employed, their values calculated (during the initial response stage of the blast event), and compared with the limiting values corresponding to the critical levels of injury. The efficacies are compared both when these measures are implemented in isolation and in the presence of other protective measures with respect to specific injuries.

Reliability-Based Design Optimization for Durability of Ground Vehicle Suspension System Components

The effect of materials processing- and component manufacturing-induced uncertainties in material properties and component shape and size on the reliability of component performance is investigated. Specifically, reliability of a suspension system component from a high-mobility multipurpose wheeled vehicle which typically can fail under low-cycle strain-based fatigue conditions is analyzed. Toward that end, the most advanced reliability-based design optimization methods available in the literature were combined with the present understanding of low-cycle fatigue durability and applied to the component in question. This entailed intricate integration of several computational tools such as multibody vehicle dynamics, finite-element simulations, and fatigue strain-life assessment/prediction techniques. The results obtained clearly revealed the importance of consideration of material property uncertainties in attaining vehicle performance of critical structural components in complex systems (e.g., a vehicle).

Model reduction in vehicle dynamics using importance analysis

Previous work by the authors developed a novel model reduction method, namely importance analysis, that offered a unique set of properties: concurrent dynamic and kinematic reduction, applicability to nonlinear systems, preservation of realisation, and trajectory dependence. This paper investigates the utility of importance analysis as a model reduction tool within the context of vehicle dynamics. To this end, a high-fidelity model of a High Mobility Multipurpose Wheeled Vehicle (HMMWV) is considered, and this model is reduced for three different scenarios. Reduction is achieved in both dynamics and kinematics while preserving the original definition and interpretation of state variables and parameters. Furthermore, the resulting reduced models are very different in terms of complexity, containing only what is necessary for their respective scenarios, and providing important insight and computational savings. The conclusion is that importance analysis can be an invaluable reduction tool in vehicle dynamics, offering the aforementioned unique set of properties.

Influence of turning radius on wheeled military vehicle induced rut formation

A rut is a depression or groove formed into the ground by the travel of wheels and tracks. Ruts can cause severe influences on soil and vegetation, and reduce vehicle mobility. In this paper, rut depth and rut width were used as the main indicators to quantify a rut. A new indicator, rut index, was proposed, combining rut depth and rut width. A Light Armored Vehicle (LAV) and a High Mobility Multi-purpose Wheeled Vehicle (HMMWV) were used for testing the influence of turning radius on rut depth, rut width and rut index. The LAV and the HMMWV were operated in spiral patterns at different speeds. Differential GPS data for the vehicles were collected every second during the spiral. Rut measurements were manually taken every 4–7 m along each of the spiral tracks. The results of field tests indicate that rut depth, rut width and rut index increase with the decrease of turning radius, especially when turning radius is less than 20 m. Velocity influences rut formation for the LAV but not HMMWV.

Computational investigation of blast survivability and off-road performance of an up-armoured high-mobility multi-purpose wheeled vehicle

Since ballistic and blast survivability and off-road handling and stability of military vehicles, such as the high-mobility multi-purpose wheeled vehicle (HMMWV), are two critical vehicle performance aspects, they both (including the delicate balance between them) have to be considered when a new vehicle is being designed or an existing vehicle retrofitted (e.g. up-armoured). Finite-element-based transient non-linear dynamics and multi-body longitudinal dynamics computational analyses were employed, relatively, in the present work to address the following two specific aspects of the performance of an HMMWV: first, the ability of the vehicle to survive detonation of a landmine shallow buried into sand underneath the right wheel of the vehicle and, second, the ability of the vehicle to withstand a simple straight-line brake manoeuvre during off-road travel without compromising its stability and safety of its occupants. Within the first analysis, the kinematic and structural responses (including large-scale rotation and deformation, buckling, plastic yielding, failure initiation, fracture, and fragmentation) of the HMMWV to the detonation of a landmine were analysed computationally using the general-purpose transient non-linear dynamics analysis software ABAQUS/Explicit. The second analysis was carried out using Simpack, a general-purpose multi-body dynamics program, and the main purpose of this analysis was to address the vehicle stability during the off-road travel. The same sand model was used in both types of analysis. Finally, the computational results obtained are compared with general field-test observations and data in order to judge the physical soundness and fidelity of the present approach.

Cross-country mobility on various snow conditions for validation of a virtual terrain

Realistic simulation of on- and off-road vehicle performance in all weather conditions is needed by the U.S. Army for virtual training of personnel on existing vehicles, and for new vehicle design. The virtual test site is a computer simulation representing an actual terrain defined as having spatially distributed terramechanics properties and terrain interaction with vehicles. We developed a virtual test site for Ethan Allen Firing Range (EAFR) in northern Vermont. The virtual test site for EAFR is composed of terramechanics properties including spatially distributed snow depth and density, soil type, drainage class, slope, and vegetation type. Snow depth and density were spatially distributed with regard to elevation, slope, and aspect using a surface energy balance approach. This paper evaluates whether the terramechanics representation of a virtual test site is improved by adding spatially distributed snow and soil properties, rather than using uniform properties. The evaluation was accomplished by conducting a cross-country vehicle performance analysis using the North Atlantic Treaty Organization (NATO) Reference Mobility Model (NRMM) to validate the new algorithms for realistic spatial distribution of snow properties. The results showed that the percentage of No-Go areas for uniform snow is lower than the distributed snow by 4% for the CIV (CRREL Instrumented Vehicle), 8% for the HMMWV (High Mobility Multipurpose Wheeled Vehicle), and 5% for the Stryker vehicle. For both light vehicles, approximately 12% of the No-Go areas are classified as such because of slopes ⩾29%. These results imply that spatial distribution of snow properties provides realistic vehicle response as opposed to having the snow properties distributed uniformly throughout the entire terrain. This represents an improvement over previous versions of the terramechanics properties.

Development of a Scaled Vehicle With Longitudinal Dynamics of an HMMWV for an ITS Testbed

This paper applies Buckingham's pi theorem to the problem of building a scaled car whose longitudinal and power-train dynamics are similar to those of a full-size high-mobility multipurpose wheeled vehicle (HMMWV). The scaled vehicle uses hardware-in-the-loop (HIL) simulation to capture some of the scaled HMMWV dynamics physically, and simulates the remaining dynamics onboard in real time. This is performed with the ultimate goal of testing cooperative collision avoidance algorithms on a testbed comprising a number of these scaled vehicles. Both simulation and experimental results demonstrate the validity of this HIL-based scaling approach.

Tire Force and Terrain Disturbance Measurements During Turning Maneuvers

A proof-of-concept study to link vehicle performance measures to associated terrain disturbance was performed with the intent to improve terrain impact prediction methods. Field tests to assess terrain disturbance during turning maneuvers were completed on dry and wet, grassy fields and slopes in northern Vermont. The vehicle tests consisted of a series of spiral maneuvers at two speeds, and serpentine maneuvers on slopes, to comprise a range of turning radii, upslope and downslope turns, and velocity. The CRREL instrumented vehicle (CIV) and a military high-mobility multipurpose wheeled vehicle (HMMWV) were instrumented to measure linear accelerations, angular and linear velocity, wheel forces, speeds, and location. The terrain was fully characterized for soil type, wetness, shear strength, and vegetation cover prior to testing. The disturbance created by the vehicle was measured using the cumulative impact width method based on disturbed width and impact severity. Results show increased disturbance for the wetter soil, but generally the impacts were low because of sufficient terrain strength for these two vehicles. Nonetheless, correlations were found between the measured horizontal forces, accelerations and yaw rates, and the terrain disturbance; most significantly, increased lateral tire-terrain interface forces resulted in increased cumulative impact width. Additionally, the vehicle lateral force, accerlation, and yaw rate that were directly measured are comparable with those calculated from the global positioning system (GPS) data, illustrating the potential of the much simpler measurements for this purpose.

Engine-in-the-loop study of the stochastic dynamic programming optimal control design for a hybrid electric HMMWV

This paper presents a Stochastic Dynamic Programming (SDP) methodology for automatic generation of an implementable hybrid control strategy, and addresses engine soot emissions during controller development by using an advanced Engine-In-the-Loop (EIL) setup. Coupling the real engine with the virtual driveline/vehicle enables application of fast analysers to characterise the impact of transients on engine emissions. The benefits of using the EIL for establishing driveability and soot emissions constraints, and subsequent application of the constraints for refining the SDP strategy is demonstrated through a study of a virtual parallel-hybrid system for the High-Mobility Multipurpose Wheeled Vehicle with a V8 6L engine.

A New Magneto-rheological Fluid Damper for High-mobility Multi-purpose Wheeled Vehicle (HMMWV)

This study focuses on the design, development, and testing of a new magnetorheological fluid (MRF) damper for high-mobility multi-purpose wheeled vehicle (HMMWV). The new damper is designed to provide controllability while keeping the same geometrical dimensions as the original equipment manufacturer (OEM) damper. To design a fail-safe MRF damper, MRF behavior is simulated using the Bingham Plastic model, and the magnetic field distribution is obtained by a three-dimensional electromagnetic finite element analysis. A fail-safe MRF damper is referred to one which retains a minimum damping capacity comparable to that of OEM damper in the event of a power supply or electronic system failure. The proposed MRF damper is designed to achieve non-symmetrical force characteristics with different force responses at rebound and compression phases. Theoretical predictions and experimental results are presented for the force—displacement and force— velocity behaviors of the damper under different input motions, various magnetic fields, and different MR fluids.

Modeling and Simulation of Various Hybrid-Electric Configurations of the High-Mobility Multipurpose Wheeled Vehicle (HMMWV)

Although hybrid-electric vehicles have been studied mainly with the aim of increasing fuel economy, little has been done in order to improve both fuel economy and performance. However, vehicular-dynamic-performance characteristics such as acceleration and climbing ability are of prime importance in military vehicles such as the high-mobility multipurpose wheeled vehicle (HMMWV). This paper concentrates on the models that describe hybridized HMMWV vehicles and the simulation results of those models. Parallel and series configurations have been modeled using the advanced-vehicle-simulator software developed by the National Renewable Energy Laboratory. Both a retrofit approach and a constant-power approach have been tested, and the results are compared to the conventional model results. In addition, the effects of using smaller engines than the existing ones in hybrid HMMWV drive trains have been studied, and the results are compared to the data collected from an actual implementation of such a vehicle. Moreover, the integrated-starter/alternator (ISA) configuration has been considered, and the results were encouraging

Modeling of a Series Hybrid Electric High-Mobility Multipurpose Wheeled Vehicle

In an effort to reduce fuel costs and gas emissions, the U.S. Army is looking into replacing their diesel high-mobility multipurpose wheeled vehicle (HMMWV) with hybrid electric vehicles. The aim of this paper is to present the simulation of the series hybrid electric HMMWV based on a multidomain model using Ansoft Simplorer. Emphasis is placed on the vehicle's transient response to desired speeds dictated by drive cycles based on an urban dynamometer driving schedule and SAE J227a Schedule D. Also included in this paper were the vehicle's responses to hill climbing up to 60% grade

Design parameterization and tool integration for CAD-based mechanism optimization

This paper presents an open and integrated tool environment that enables engineers to effectively search, in a CAD solid model form, for a mechanism design with optimal kinematic and dynamic performance. In order to demonstrate the feasibility of such an environment, design parameterization that supports capturing design intents in product solid models must be available, and advanced modeling, simulation, and optimization technologies implemented in engineering software tools must be incorporated. In this paper, the design parameterization capabilities developed previously have been applied to support design optimization of engineering products, including a High Mobility Multi-purpose Wheeled Vehicle (HMMWV). In the proposed environment, Pro/ENGINEER and SolidWorks are supported for product model representation, DADS (Dynamic Analysis and Design System) is employed for dynamic simulation of mechanical systems including ground vehicles, and DOT (Design Optimization Tool) is included for a batch mode design optimization. In addition to the commercial tools, a number of software modules have been implemented to support the integration; e.g., interface modules for data retrieval, and model update modules for updating CAD and simulation models in accordance with design changes. Note that in this research, the overall finite difference method has been adopted to support design sensitivity analysis.

Sliding mode based powertrain control for efficiency improvement in series hybrid-electric vehicles

This study involves the improvement of overall efficiency in series hybrid-electric vehicles (SHEVs) by restricting the operation of the engine to the optimal efficiency region, using a control strategy based on two chattering-free sliding mode controllers (SMCs). One of the designed SMCs performs engine speed control, while the other controls the engine/generator torque, together achieving the engine operation in the optimal efficiency region of the torque-speed curve. The control strategy is designed for application on a SHEV converted from a standard high mobility multipurpose wheeled vehicle (HMMWV) and simulated by using the Matlab-based PNGV Systems Analysis Toolkit (PSAT). The performance of the control strategy is compared with that of the original PSAT model, which utilizes PI controllers, a feedforward term for the engine torque, and comprehensive maps for the engine, generator and power converter (static only), which constitute the auxiliary power unit (APU). In this study, in spite of the simple modeling approach taken to model the APU and the optimal efficiency region, an improved performance has been achieved with the new SMC based strategy in terms of overall efficiency, engine efficiency, fuel economy, and emissions. The control strategy developed in this work is the first known application of SMC to SHEVs, and offers a simple, effective and modular approach to problems related to SHEVs

Thermal signature characteristics of vehicle/terrain interaction disturbances: implications for battlefield vehicle classification.

Thermal emissivity spectra (8-14 microm) of track impressions/background were determined in conjunction with operation of six military vehicle types, T-72 and M1 Tanks, an M2 Bradley Fighting Vehicle, a 5-ton truck, a D7 tractor, and a High Mobility Multipurpose Wheeled Vehicle (HMMWV), over diverse soil surfaces to determine if vehicle type could be related to track thermal signatures. Results suggest soil compaction and fragmentation/pulverization are primary parameters affecting track signatures and that soil and vehicle/terrain-contact type determine which parameter dominates. Steel-tracked vehicles exert relatively low ground-contact pressure but tend to fragment/pulverize soil more so than do rubber-tired vehicles, which tend mainly to compact. In quartz-rich, lean clay soil tracked vehicles produced impressions with spectral contrast of the quartz reststrahlen features decreased from that of the background. At the same time, 5-ton truck tracks exhibited increased contrast on the same surface, suggesting that steel tracks fragmented soil while rubber tires mainly produced compaction. The structure of materials such as sand and moist clay-rich river sediment makes them less subject to further fragmentation/pulverization; thus, compaction was the main factor affecting signatures in these media, and both tracked and wheeled vehicles created impressions with increased spectral contrast on these surfaces. These results suggest that remotely sensed thermal signatures could differentiate tracked and wheeled vehicles on terrain in many areas of the world of strategic interest. Significant applications include distinguishing visually/spectrally identical lightweight decoys from actual threat vehicles.

Modeling hybrid electric HMMWV power system performance

The Defense Advanced Research Projects Agency (DARPA) and the US Army Tank and Automotive Command (TACOM) have sponsored the testing of two High Mobility Multi-purpose Wheeled Vehicles (HMMWVs) which were converted in 1996 from production mechanical drive configuration to hybrid electric drive architectures. This paper describes the performance modeling of these two hybrid electric HMMWV vehicles using simulation components derived from a standard vehicle performance toolbox and presents simulation output demonstrating the general behavior of these implementations of hybrid electric drive. These models are compared with preliminary test data from the manufacturers and show good agreement. Validation of these codes with more extensive testing in winter is expected to enhance the credibility of the dynamic modeling tools for predictive use on future combat vehicles.

Numerical Methods for High-Speed Vehicle Dynamic Simulation

Recent developments in numerical methods for high-speed vehicle dynamic simulation in the multiuniversity Automotive Research Center sponsored by the U.S. Army Tank-Automotive Research, Development, and Engineering Center are summarized and illustrated. The prior state-of-the-art is reviewed, and computational developments focusing on both computer-aided engineering applications with stiff equations and driver-in-the-loop real-time vehicle system simulation are presented. To illustrate gains achieved in computational efficiency and reliability, realistic handling models of the Army's High Mobility Multipurpose Wheeled Vehicle are simulated and compared to results obtained using previous methods. A demonstration of two orders of magnitude speed-up for stiff vehicle models characteristic of those employed by vehicle developers in computer-aided engineering is presented. Achievement of real-time simulation on computing platforms integral to emerging driving simulators that are establishing new capabilities for virtual proving ground simulation is presented.

A Multilevel Product Model for Simulation-Based Design of Mechanical Systems

This paper presents a multilevel product model that supports Simulation-Based Design (SBD) of mechanical systems, from pre liminary to detailed design stages The pnmary goal of the SBD is to achieve product designs featuring better performance and greater du rability and reliability through computer-based modeling, engineering analysis, and design trade-off. A Computer-Aided Design (CAD) model combined with engineering parameters and mathematical equations that simulate physical behavior of the mechanical system constitute its product model for SBD. For preliminary design, improvement of system performance, including dynamics and human factors, is usually the primary focus A CAD model with reasonably accurate physical parameters, such as mass properties of major components or assemblies, is defined as the base definition of the product model for SBD. A number of simulation models are derived from the base definition to sup port simulation of the mechanical system performance A parametric study can be conducted to search for design alternatives using dimen sion parameters created in the parameterized CAD model. The CAD model and base definition are then refined from the preliminary design stage to support intermediate designs. Intermediate designs will primarily focus on product subsystem performance. A product model is evolved by refining geometric representation of mechanical components in CAD, and expanding product assembly into parts and sub assemblies for further engineering analysis Component designs for performance, such as fatigue, mechanical reliability, and structural per formance, as well as maintainability are the primary focus in the detailed design stage. A detailed product model evolved from that of the previous design is needed In the detailed design stage, a systematic design trade-off method supports design improvement. A High Mobil ity Multi-Purpose Wheeled Vehicle (HMMWV) is employed to illustrate and demonstrate the proposed product model.