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The Future Combat System Operational Requirements Document requires that manned and unmanned ground vehicles be capable of negotiating gaps 1.5- to 4.0-meters wide. Gaps include both natural and manmade obstacles. Overcoming battlespace gaps requires the ability to effectively conduct four tasks: prediction, definition, avoidance, and defeat. The inability to overcome gaps within the theater of operations will significantly impair the Future Force's responsiveness, agility, and sustainability. Researchers at the US Army Engineer Research and Development Center (ERDC), working in the field of vehicle mobility have developed methods to predict the physical interactions of vehicles with terrain mechanics. This physics-based simulation method uses research conducted at the ERDC to combine historical empirical laboratory and field evaluations with lumped parameter and numerical analysis to develop a simulated environment of the terrain.

Three-dimensional models of real world terrain have application in a variety of tasks, but digitizing a large environment poses constraints on the design of a 3D scanning system. We have developed a Mobile Scanning System that works within these constraints to quickly digitize large-scale real world environments. We utilize a mobile platform to move our sensors past the scene to be digitized - fusing the data from cm-level accuracy laser range scanners, positioning and orientation instruments, and high-resolution video cameras - to provide the mobility and speed required to quickly and accurately model the target scene.

A methodology has been developed to generate military vehicle driving cycles for use in vehicle simulation models. This methodology is based upon the mission profile for a vehicle, which is typically given within a vehicle's specifications and lists the types of terrains that the vehicle is likely to encounter. A simplistic vehicle powertrain and road load model and the Bekker vehicle-soil interaction model are used to estimate the vehicle performance over each type of terrain. Two types of driving cycles are generated within a Graphical User Interface developed within MATLAB using the results of the vehicle models: Linear modes driving cycles, and Real-world driving cycles.

One fundamental difficulty in understanding the physics of the off-road traction and in predicting vehicle performance is the variability of the terrain profile and soil parameters. These operating conditions are uniquely defined at a given spatial location and a given time. It is not practically feasible, however, to measure them at a sufficiently large number of points to be able to accurately represent the terrain in models. This renders traditional analysis tools insufficient when dealing with rough deformable terrain. We employ stochastic analysis to capture the uncertain nature of this running support and the corresponding vehicle response. From a finite number of observations the terrain profile and soil properties can be modeled as random processes, with the actual operating conditions viewed as a particular realization of these processes. Soil parameters vary substantially from one type of soil to another.

The 1/8-scale Generic Conventional Model was studied experimentally in two wind tunnels at NASA Ames Research Center. The investigation was conducted at a Mach number of 0.15 over a Reynolds number range from 1 to 6 million. The experimental measurements included total and component forces and moments, surface pressures, and 3-D particle image velocimetry. Two configurations (trailer base flaps and skirts) were compared to a baseline representative of a modern tractor aero package. Details of each configuration provide insight into the complex flow field and the resulting drag reduction was found to be sensitive to Reynolds number.

Aerodynamic drag, lift, and side forces have a profound influence on fuel efficiency, vehicle speed, stability, acceleration and performance. All of these areas benefit from drag reduction and changing the lift force in favor of the operating conditions. The present study simulates the external flow field around a heavy truck with three prototype add-on drag reduction devices using a computational method. The model and the method are selected to be three dimensional and time-dependent. The Reynolds-averaged Navier Stokes equations are solved using a finite volume method. The Renormalization Group (RNG) k-ε model was elected for closure of the turbulent quantities. The run cases were chosen so that the influence of each drag reduction device could be established using a regression model from a Design of Experiments (DOEX) derived test matrix.

An investigation is made to the multiobjective suspension control problem for a heavy off-road vehicle based on mixed H2/H ∞ optimal control synthesis. A design procedure is explained based on a performance trade-off curve in order to solve this problem. In comparison with other control synthesis results we have obtained, it is shown that by combining both techniques into one mixed norm optimization framework, it is possible to exploit the strengths of each norm to provide better performance for the given hydropneumatic suspensions.

The National Highway Traffic Safety Administration (NHTSA) realizes that medium and heavy vehicles have different issues than passenger vehicles with respect to tire pressure monitoring. The NHTSA did not have time during the one year deadline imposed by the Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act to address these complex concerns in its rulemaking.1 This paper explores the unique concerns that accompany commercial vehicle tire pressure monitoring and management that must be considered before a potential regulation for the commercial vehicle industry can be implemented successfully.

Understanding the parameters which influence the tendency for a heavy truck to exhibit rollover is of paramount importance to the trucking industry. Multiple parameters influence the vehicle’s motion, and the ability to determine how each affects the vehicle as a system would be an indispensable tool for the design of such vehicles. To be able to perform such predictions and analysis, models and a computer simulation were created to allow the examination of changes in design parameters in such vehicles. The vehicle model was originally developed by Law [1] and presented in Law and Janajreh [2]. The model was extended further by Lawson [3, 4] to include (a) the effects of the torsional compliance of both the tractor and trailer, and (b) tanker trailers with various levels of liquid fill. In the present paper, both the tractor and trailer compliances were studied independently to determine their influences on the rollover stability of the vehicle.

As a result of increased demand on the range of cargo types that U.S. military tactical trucks must transport, the effect of variations in the mass properties of the cargo on the roll stability of the trucks has become a serious issue. Vehicle dynamics experiments were conducted to obtain roll stability measurements for a tactical cargo truck hauling a broad range of rigid cargo loadings. A simple statics analysis for roll stability and the data obtained during the vehicle dynamics experiments were used to evaluate the relationship between the roll stability of the truck and the mass properties of the cargo. The results of the evaluation demonstrated that roll stability, quantified as the lateral acceleration at the wheel-liftoff threshold, can be accurately characterized as a function of: (1) the lateral center of gravity over the vertical center of gravity and (2) the longitudinal center of gravity over the wheelbase length.

This paper introduces a concept of predictive active safety by means of a full redundant architecture with the driver, from the perception of the environment to the vehicle controllers. The bottleneck of the current driver-vehicle association will be analyzed first. Then a virtual driver and the safety envelope of the different maneuvers will be described. A decision control will be presented that it matches the driver's command in this safety envelope. It is designed to give adequate feedback to the driver and can safely perform the command to the optimum of the chosen maneuver.

Several mechanical demining machines employ flails as the key mechanism for neutralizing landmines. Typically, flail systems consist of a rotating drum with a series of long chains with masses attached at the end. These masses strike and mill the ground that detonates and/or fragment buried landmines. Despite flail-based technology existing for several years in the demining field, minimal studies regarding the interaction with soil have been conducted. Three chain flail systems were evaluated in the soil bin at various rotational speeds. High speed videography of single pass operations indicated that a consistent and repeatable cleared path was not obtainable. This validated the need for multiple passes to effectively clear a minefield. The results were compared with the Mine Hammer mechanism that had consistent impacts on the surface. The load distribution at the various depths was recorded and the magnitude of the impulses calculated varied with depth and level of soil compaction.

An antipersonnel landmine neutralizing mechanism, called the Mine Hammer, was designed with a prototype developed by the Agriculture and Bioresource Engineering Department, University of Saskatchewan and Defence Research and Development Canada -- Suffield. The Mine Hammer technology combined flail mechanisms and agriculture tillage interaction mechanics. The prototype was retrofitted to be powered by a 78.4 kW tractor and was field evaluated in August 2002. The test plots represented gravel road, prairie clay soil with stubble and full stand of Kochia weed for vegetation and simulated tree stump terrains. Dummy or mechanical replicas of antipersonnel landmines were placed at 0, 25, 50, 100 and 200mm depths. The Mine Hammer triggered and/or fragmented the replica landmines. Its mechanical neutralization effectiveness over the five test plots was 97%. The Mine Hammer produced a two layer overburden consisting of a loose till above a dense, compact soil layer.

To provide good vehicle control in critical cornering, it is important to be able to sense the point of critical cornering. Even if the point of critical cornering is exceeded, it is possible to control the vehicle when drift control is good. As such, a compromise exists between the sensing of critical cornering and drift control. Experiments using a driving simulator were performed on different subjects to investigate this trade-off. It was found that the driver was able to sense the point of critical cornering easily from the change in body slip angle, and to control drift easily with a large body slip angle, in which the tire can attain a high cornering force. When the roll rigidity was low, however, drift control deteriorated although the sensing of critical cornering improved. Therefore, a moderate level of roll rigidity or roll rigidity control is desired to achieve a balance between these two factors.

The following has been understood for the change in the steer characteristic and the amount of perspiration in the drift cornering when not only visual information but also body sensory information is added. When body sensory information joins visual information as for the driver, it has been understood that the amount of perspiration increases overall and can do the drift control continuing with a moderate tension. In the drive only of visual information, the driver comes to arrive easily at spin because the drift control is difficult. And, it has been understood that the amount of perspiration increases greatly compared with the case to give body sensory information, and becomes the one with a very high risk. Moreover, the driver can control an adequate drift compared with driving only visual information in feed back body sensory information on the roll angle to the steer.

In this study, a compliant control strategy is developed, which makes the application of position based control strategies practicable for electric power assisted steering systems. In order to do this, an additional virtual degree of freedom is added to the system, which is stimulated by the torque exerted on the steering wheel by the driver and the pinion position. The electro-actuator modeled on the second pinion of the steering gear is then commanded to position the pinion to the virtual system position using a traditional position control strategy. Thus, a compliance behavior is established that can be varied depending on the vehicle states and environmental conditions to improve the vehicle dynamics and safety of the passenger.

The emerging business imperative of frequent new product introduction in market throws up challenge to shorten testing and evaluation time. Advanced test facilities and statistical tools have a greater role in reducing the evaluation cycle time. Considering limitations of field testing, a need was felt to simulate field condition in the laboratory i.e., ‘Bringing field to lab’. In this paper, an effort is made to explain the concept of ‘Bringing field to lab’ and the approach towards accomplishing it. The methodology developed for assessing effectiveness of laboratory tests i.e., ‘Power of Lab’ is shared. Various means of accelerating the tests and verifying field to lab correlation are explained. In quest to pursue the vision of ‘Bringing field to lab’ program, a new test facility has been developed to evaluate tractor i.e., Three-Poster Test System. Features of this test system, along with it’s role in ‘Bringing field to lab’, are shared along with the test results obtained.

A wind tunnel experiment has been conducted to determine the changes in drag and side force due to the presence and position of cab extenders on a model of a commercial tractor-trailer truck. The geometric variables investigated are the cab extenders angle of incidence, the tractor-trailer spacing and the yaw angle of the vehicle. Three cab extender angles were tested-0°, 15° (out) and -15° (in) with respect to the side of the tractor. The cab and trailer models have the same width and height. The minimum drag coefficient was found for the tractor and trailer combination when the cab extenders were set to 0° angle of incidence with respect to the headwind. This result holds for all yaw angles with moderate gap spacing between the tractor and trailer. This study suggests that commercial tractor-trailer trucks can benefit from adjustable cab extender settings; 0° when using a trailer and -15° when no trailer is used.

The RTV900 utility vehicle with tractor technology features the first Variable Hydro Transmission (VHT) with auxiliary hydraulics, power steering and wet disc brakes. The VHT comes equipped with a servo-type variable capacity pump, linked in parallel with fixed capacity and variable capacity motors on the same axle. This variable motor enables an increased driving force with auto-deceleration. Additionally, the RTV900 uses hydraulic power steering that is commonly used on tractors. The RTV900's power steering decreases heavy kickback in rough terrain and allows the operator to maneuver and drive the machine with minimal effort. Wet disk brakes resolve the problems of mud and water that can infect dry-type brakes, improving safety and reliability in bad road conditions. With its sealed VHT components, power steering and wet disk brakes, the RTV900 will provide farmers, vineyards, nurseries, orchards and golf courses increased power, lower maintenance costs and easy, safe operation.

The 4200 Hybrid Electric Vehicle is a Class 5-6 medium duty chassis usable in a variety of short range applications. The vision for this vehicle concept is a self contained hybrid diesel-electric vehicle with range and performance similar to a diesel-only vehicle along with improved fuel efficiency. The hydraulic steering system is an ideal candidate for energy savings due to its continuously running on-engine pump component. Electrically powered hydraulic steering (EPHS) pumps, along with a Column Drive electric assist unit, replace the conventional engine driven pump. The Column Drive masks any switching transients in the flow from the EPHS units and provides steering feel tuning. The system offers the benefits of improved on-center handling, increased returnability, speed proportional assist, and cross-wind compensation.