Search Results

The military aviation services pay a phenomenal price due to turbine engine stall. Several of the major factors which comprise a substantial portion of the total price are presented. Included are weapon system development time, operational limitations, field maintenance problems, overhaul costs and accident rates. Also presented, in a general fashion, are several technical approaches to the solution of turbine engine stall. Fundamental research and orderly development of basic engine components, power control systems, and airframe and installation factors are discussed. Emphasis is placed on the need for tighter control of production tolerances and the requirement for united efforts in the integration of components into a complete system.

This paper describes a system which includes several subsystems forming a gun recoil injury-monitoring simulator. These subsystems include: a motion simulator, motion capture system, mannequin with integrated data acquisition, and combat vehicle dynamics model. Motion data from these subsystems provides vehicle and human factors engineers with valuable information about the occupant response to gun fire events. The final system has been successfully utilized recently on a gun fire program that enabled vehicle designers to determine results of their concept design. The simulation design exceeded performance expectations and can be used on future vehicle design iterations.

Until recently, U.S. government efforts to dramatically reduce emissions, greenhouse gases and vehicle fuel consumption have primarily focused on passenger car applications. Similar aggressive reductions need to be extended to heavy vehicles such as delivery trucks, buses, and motorhomes. However, the wide range of torques, speeds, and powers that such vehicles must operate under makes it difficult for any current powertrain system to provide the desired improvements in emissions and fuel economy. Hybrid electric powertrains provide the most promising, near-term technology that can satisfy these requirements. This paper highlights the configuration and benefits of a hybrid electric powertrain capable of operating in either a parallel or series mode. It describes the hybrid electric components in the system, including the electric motors, power electronics and batteries.

Variant modeling techniques have been developed to allow systems engineers to model multiple similar variants in a product line as a single variant model. In this paper, we expand on this past work to explore the extent to which variant modeling in SysML can be applied to a broad range of dissimilar systems, covering the entire domain of ground vehicles, in single reference architecture model. Traditionally, a system’s structure is decomposed into subsystems and components. However, this method is found to be ineffective when modeling variants that are functionally similar but structurally different. We propose to address this challenge by first decomposing the system not only by subsystem but also by high-level function. This pattern is particularly useful for situations where two variants perform the same function, but one variant performs the function using one subsystem, whereas the other variant performs the same function using one or more different subsystems.

In line with the need to provide improved components for vehicle applications, the U.S. Army Tank-Automotive Command is currently preparing a detailed technical plan covering materials research and development as related to automotive, tank, and allied equipment. The plan includes (1) establishing and analyzing future systems requirements with regard to design criteria, application, and environment, and (2) determining and outlining the major areas of material development and needs, including characteristics and properties based on the original analysis and requirements. It is hoped that with the successful completion of this plan for setting up a long range research and development program, it will be possible to obtain an accurate forecast of future materials requirements for Army vehicles.

As part of the Army Test and Evaluation Command (ATEC) the Metrology and Simulation Division at the U.S. Army Yuma Proving Ground (USAYPG) has the mission to measure and record the detrimental effects of firing conventional and experimental munitions on gun crews under live fire testing. In order to provide a safer environment for soldiers and to comply with national and international military specifications, the Measurements and Simulation Branch of the Metrology and Simulation Division at The U.S. Army Yuma Proving Ground has developed a mobile system to quantitatively analyze and record the level of toxicity present in the crew compartment of a variety of military vehicles. The system is housed in a medium sized van that is self-contained with the exception of its power source.

Brake Fluid, Silicone (BFS, MIL-B-46176), which was developed by the U.S. Army Belvoir Research, Development and Engineering Center (BRDEC) in conjunction with industry, was approved in 1980 for retrofit of all U.S. Army vehicles. The approved method for conversion was a flush-and-fill procedure. This method, however, will leave residual polyglycol fluid in brake systems due to the following interdependent reasons: (a) The geometry of the wheel cylinders (bleeders at the top), (b) the immiscibility of the two fluids, and (c) the lower density of the silicone. A project in this Laboratory resulted in the development of a method which is effective in the complete removal of all polyglycol fluid. The method involves the use of an intermediate fluid (2-ethylhexanol, 2-EH) whose properties are such that a reversal of the phases is induced. This method is thus based on the existence of an isopycnic tie line in the phase diagram of the binary phase system.

Mobility assessment for combat vehicles is often a great challenge for the military due to various subjective attributes. The attributes' characteristics vary significantly depending on the vehicle type and its operating environments such as terrain, weather, and human factors. A clear definition and relationship between multiple attributes including human factors is necessary to assess mobility. To the best of authors' knowledge, many existing mobility assessment techniques use complex analytical methods and focus on individual attributes. In this paper, for the first time, the authors propose a novel approach to define vehicle mobility and its influencing attributes using qualitative linguistic fuzzy variables, which are defined as having values between 0 and 1. The authors also propose a fuzzy logic mobility (FLM) model and a simulation approach to assess a combat vehicle's mobility.

The objective of the Integrated Chassis Controllers (ICC) is to combine multiple actuators and dynamics controllers to maximize the overall vehicle performance at all driving conditions. It is well known that there are two methods that can be used to develop an ICC. The first is a centralized method, where all the actuators are considered in one controller to ensure a harmonic integration between different actuators. The second method is called decentralized integration, where each actuator is considered in a separate controller and a low-level controller is used to coordinate the operation of the controllers. In this paper, the second method is used to develop a decentralized ICC using a novel controller coordinator based on Genetic Programming (GP). The GP is used to integrate torque vectoring and active rear steering controllers of an 8x8 combat vehicle. The controller is utilized to enhance the lateral stability of the vehicle in various driving conditions.

A design evaluation is presented for four different propulsion system approaches for a Direct Support Fighter in the 15,000 to 20,000 pound class. This includes three different arrangements for composite lift engine and main propulsion arrangements and one lift fan and wing arrangement. For a given payload range the factors considered are take-off weight, performance under single engine failure conditions, STOL performance, and cost. The results indicate that vectoring the cruise engine for lift is not necessarily optimum. V/STOL vehicles can be designed to sustain altitude after a single engine failure, for a small weight penalty. Reducing the number of lift engines has an insignificant effect on overall weapon system cost.

Vehicle motions can adversely affect the ability of a driver or occupant to quickly and accurately push control buttons located in many advanced vehicle control, navigation and communications systems. A pilot study was conducted using the U.S. Army Tank Automotive and Armaments Command (TACOM) Ride Motion Simulator (RMS) to assess the effects of vertical ride motion on the kinematics of reaching. The RMS was programmed to produce 0.5 g and 0.8 g peak-to-peak sinusoidal inputs at the seat-sitter interface over a range of frequencies. Two participants performed seated reaching tasks to locations typical of in-vehicle controls under static conditions and with single-frequency inputs between 0 and 10 Hz. The participants also held terminal reach postures during 0.5 to 32 Hz sine sweeps. Reach kinematics were recorded using a 10-camera VICON motion capture system. The effects of vertical ride motion on movement time, accuracy, and subjective responses were assessed.

This paper presents the operations research, systems analysis, and cost-effectiveness procedures used in comparing a new system concept with relatively conventional off-road Army vehicles. The combination of these procedures is indicative of the work that must be considered in the development of new off-road systems. Of particular importance is the analysis of the wheel performance when it is off-loaded by a supplementary air cushion. Although much remains to be done in developing such procedures, it is concluded that until actual vehicles become available for operational testing, the procedures adopted will provide useful indications of the costs and effectiveness to be expected.

This paper summarizes a study of the applicability of electric drive trains to heavy-duty vehicles, with emphasis on military use. Presently used power transmission systems are compared with electrical systems considering design, performance, and maintenance factors. The comparison is supplemented by a cost-effectiveness analysis using mining, manufacturing, and military vehicle data. It is concluded that feasibility of electric propulsion systems for heavy-duty applications has been well established; that d-c systems are cost effective, and a-c systems are potentially cost effective; further, that the time is ripe for development programs on a-c drives to reach operational availability in the late seventies.

Making manned and remotely-controlled wheeled and tracked vehicles easier to drive, especially off-road, is of great interest to the U.S. Army. If vehicles are easier to drive (especially closed hatch) or if they are driven autonomously, then drivers could perform additional tasks (e.g., operating weapons or communication systems), leading to reduced crew sizes. Further, poorly driven vehicles are more likely to get stuck, roll over, or encounter mines or improvised explosive devices, whereby the vehicle can no longer perform its mission and crew member safety is jeopardized. HMI technology and systems to support human drivers (e.g., autonomous driving systems, in-vehicle monitors or head-mounted displays, various control devices (including game controllers), navigation and route-planning systems) need to be evaluated, which traditionally occurs in mission-specific (and incomparable) evaluations.

This paper addresses the problem of quantifying the cross-country speed capability of military vehicles. While numerous tests have been run to evaluate various aspects of cross-country speed, such as obstacle crossing capability and maximum speed over a specified standard course, quantitative evaluation of the total man-machine system has only been superficially attempted. Recognizing the complex interactions of the man-machine system within various environments, the project was designed specifically to allow separation of various factors in order to determine the relative cross-country performance of vehicles. Two separate tests were established. The first test determined the relative cross-country performance of nine different vehicles by utilizing 18 drivers and 27 test courses in three varied terrains for a total of 563 test runs.

There is a need for high efficiency radiators in liquid cooled military vehicles. It is obvious that the new system should be better than the current Al radiators in terms of thermal performance, military robustness, size, weight and easiness of mass production. For the last ten to fifteen years, a search for new materials has been ongoing. One of the best current candidates is a pitch-based carbon foam that exhibits a superior thermal performance, but with inferior mechanical performance. While developing carbon foam systems, with the intent of overcoming its seriously low mechanical strength, it was also discovered that another serious concern emerged, namely the difficulty in joining, bonding and sealing the carbon foam to the same, or dissimilar material, such as metal or ceramic. This paper presents results of our first stage effort in strengthening carbon foam under an SBIR program funded by the National Automotive Center (NAC) at TACOM, Warren, MI.

The popularity of CAN (Controller Area Network) in the production vehicles is well established. As a result, CAN has been developed for use in many non-automotive applications. This gave rise to the development of an open higher layer CAN protocol known as DeviceNet. With the popularity of DeviceNet for Automation Systems, this technology has drastically decreased in cost. Although DeviceNet is quite complex to develop, it easier to implement than SAE J1939 due to the large number of commercial off-the-shelf product that is available. Also, there are many configuration and diagnostic tools available by the same means. There are more than 300 vendors of DeviceNet product. Researchers at the University of Warwick have built a vehicle demonstrator using CAN/DeviceNet modules. This paper will illustrate the ease of vehicle system integration utilising this popular technology.

The application of fluid power technology in the United States is widespread, seeing use in industries as diverse as dentistry, military vehicles, and mining. Fluid power is also attracting interest in hybrid vehicle applications, which require an energy storage component. While most hydraulic energy storage is accomplished using hydraulic accumulators, energy storage flywheels also provide an attractive alternative for use in mobile hydraulic systems. The main difference between the system architectures proposed in literature has been whether to include distinct, separate hydraulic pump/motors for the engine and the flywheel. Previous studies have compared the various topographies to traditional drivetrains, using both numerical simulation and experimentation, with favorable results.

System Safety Engineering techniques are frequently used to discover and correct potential hazards in military equipment. MIL-S-38130 and MIL-STD-882 require the use of systems methodology for assuring that designed hardware can be used operationally with an acceptable degree of safety. The System Safety techniques and methodology discussed here are applied to a military program but the same techniques and methodology are applicable to any operational unit. The techniques and methodology developed for the military can yield many dividends when applied anywhere that a hazardous operation may exist. The CVA (aircraft carrier) incident/accident rate, coupled with the severity of recent aircraft carrier accidents, is unacceptable (to the Navy) for efficient carrier operation, as well as being costly from both personnel and equipment viewpoints.

Approximately 2500 tests of the ability of wheeled military vehicles to climb slopes of loose sand were conducted on a variety of beach and dune sands. Test procedures and techniques are described briefly. The strength of the sand on the slopes was measured by means of a cone penetrometer. The slope-climbing performance of each of the five sizes of vehicles tested is shown to be determined principally by the strength of the sand and by tire size and inflation pressure. The effect of each of these variables on performance is discussed briefly. An empirical method employing firm-surface tire-print data, wheel load, and sand strength is presented as a means of predicting the sand slope-climbing capability of conventional all-wheel-drive vehicles.