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Journal Article

The Design of a Suspension Parameter Identification Device and Evaluation Rig (SPIDER) for Military Vehicles

This paper describes the mechanical design of a Suspension Parameter Identification Device and Evaluation Rig (SPIDER) for wheeled military vehicles. This is a facility used to measure quasi-static suspension and steering system properties as well as tire vertical static stiffness. The machine operates by holding the vehicle body nominally fixed while hydraulic cylinders move an “axle frame” in bounce or roll under each axle being tested. The axle frame holds wheel pads (representing the ground plane) for each wheel. Specific design considerations are presented on the wheel pads and the measurement system used to measure wheel center motion. The constraints on the axle frames are in the form of a simple mechanism that allows roll and bounce motion while constraining all other motions. An overview of the design is presented along with typical results.
Journal Article

Validation of Real Time Hardware in the Loop Simulation for ESC Testing with a 6×4 Tractor and Trailer Models

The tractor trailer models discussed in this paper were for a real-time hardware-in-the-loop (HIL) simulation to test heavy truck electronic stability control (ESC) systems [1]. The accuracy of the simulation results relies on the fidelity and accuracy of the vehicle parameters used. However in this case where hardware components are part of the simulation, their accuracy also affects the proper working of the simulation and ESC unit. Hence both the software and hardware components have to be validated. The validation process discussed in this paper is divided into two sections. The first section deals with the validation of the TruckSim vehicle model, where experimental data is compared with simulation results from TruckSim. Once the vehicle models are validated, they are incorporated in the HIL simulation and the second section discusses the validation of the whole HIL system with ESC.
Journal Article

Vehicle Coast Analysis: Typical SUV Characteristics

Typical factors that contribute to the coast down characteristics of a vehicle include aerodynamic drag, gravitational forces due to slope, pumping losses within the engine, frictional losses throughout the powertrain, and tire rolling resistance. When summed together, these reactions yield predictable deceleration values that can be related to vehicle speeds. This paper focuses on vehicle decelerations while coasting with a typical medium-sized SUV. Drag factors can be classified into two categories: (1) those that are caused by environmental factors (wind and slope) and (2) those that are caused by the vehicle (powertrain losses, rolling resistance, and drag into stationary air). The purpose of this paper is to provide data that will help engineers understand and model vehicle response after loss of engine power.
Technical Paper

Development and Implementation of a Path-Following Algorithm for an Autonomous Vehicle

This paper describes the development and implementation of an accurate and repeatable path-following algorithm focused ultimately on vehicle testing. A compact, lightweight, and portable hardware package allows easy installation and negligible impact on the vehicle mass, even for the smallest automobile. Innovative features include the ability to generate a smooth, evenly-spaced path vector regardless the quality of the given path. The algorithm proposed in this work is suitable for testing in a controlled environment. The system was evaluated in simulation and performed well in road tests at low speeds.
Technical Paper

The Impact of Worn Shocks on Vehicle Handling and Stability

The intent of this research is to understand the effects worn dampers have on vehicle stability and safety through dynamic model simulation. Dampers, an integral component of a vehicle's suspension system, play an important role in isolating road disturbances from the driver by controlling the motions of the sprung and unsprung masses. This paper will show that a decrease in damping leads to excessive body motions and a potentially unstable vehicle. The concept of poor damping affecting vehicle stability is well established through linear models. The next step is to extend this concept for non-linear models. This is accomplished through creating a vehicle simulation model and executing several driving maneuvers with various damper characteristics. The damper models used in this study are based on splines representing peak force versus velocity relationships.
Technical Paper

MADYMO Modeling of the IHRA Head-form Impactor

The International Harmonization Research Activities Pedestrian Safety Working Group (IHRA PSWG) has proposed design requirements for two head-forms for vehicle hood (bonnet) impact testing. This paper discusses the development of MADYMO models representing the IHRA adult and child head-forms, validation of the models against laboratory drop tests, and assessment of the effect of IHRA geometric and mass constraints on the model response by conducting a parameter sensitivity analysis. The models consist of a multibody rigid sphere covered with a finite element modeled vinyl skin. The most important part in developing the MADYMO head-form models was to experimentally determine the material properties of the energy-absorbing portion of the head-form (vinyl skin) and incorporate these properties into MADYMO using a suitable material model. Three material models (linear isotropic, viscoelastic, hyperelastic) were examined.
Technical Paper

Pole Impact Speeds Derived from Bilinear Estimations of Maximum Crush for Body-On-Frame Constructed Vehicles

Accident reconstructionists use several different approaches to determine vehicle equivalent impact speed from damage due to narrow object impacts. One method that is used relates maximum crush to equivalent impact speed with a bilinear curve. In the past, this model has been applied to several passenger cars with unibody construction. In this paper, the approach is applied to a body-on-frame vehicle. Several vehicle-to-rigid pole impact tests have been conducted on a full-size pickup at different speeds and impact locations: centrally located across the vehicle's front and outside the frame rail. A bilinear model relating vehicle equivalent impact speed to maximum crush is developed for the impact locations. These results are then compared to results obtained from other body-on-frame vehicles as well as unibody vehicles. Other tests such as impacts on the frame rail and barrier impacts are also presented. Limitations to this bilinear approach are discussed.
Technical Paper

The Design of a Vehicle Inertia Measurement Facility

This paper describes the design of a vehicle inertia measurement facility (VIMF): a facility used to measure vehicle center of gravity position; vehicle roll, pitch, and yaw mass moments of inertia; and vehicle roll/yaw mass product of inertia. The rationale for general design decisions and the methods used to arrive at the decisions are discussed. The design is inspired by the desire to have minimal measurement error and short test time. The design was guided by analytical error analyses of the contributions of individual system errors to the overall measurement error. A National Highway Traffic Safety Administration (NHTSA) database of center of gravity position and mass moment of inertia data for over 300 vehicles was used in conjunction with the error analyses to design various VIMF components, such as the roll and yaw spring sizes.
Technical Paper

An Experimental Determination of the Strain History, Deflection Behavior, and Material Properties of a Composite material Rooftop for a Multipurpose Vehicle Part III

Composite material roof structures for multipurpose vehicles are comprised of a composite shell molded without metal frames as in most automobile rooftops. This paper experimentally analyzes the roof structure performance for a static uniformly distributed load over the roof surface and examines the tensile properties, effects of high temperatures and sound absorption characteristics of the random, chopped glass fiber reinforced epoxy resin material. The roof performance includes the load-strain history and the load-deflection behavior of the structure.
Technical Paper

On the Optimum Design of Composite Roof Structures

The roof structures of light utility vehicles are often comprised of a single composite shell without the usual steel or aluminum frames found on conventional passenger automobiles. This study analyzes the geometry of such structures in relation to their performance during rollover accident and roof intrusion. For a given set of material properties and roof impact velocity, their exists an optimum value of roof stiffness that would minimize the impact energy, manifested in a rollover accident, that would be transmitted to the occupant compartment. This work shows the effects of various geometric parameters on the amount of elastic strain energy that can be absorbed during deformation of the rooftop. The optimum roof geometry was determined to minimize the possibility of, if not the severity of, occupant injury.
Technical Paper

Sub-System and Full System Testing to Assess Side Impact Safety

A study is being conducted in which both component level and full scale crash tests are being compared. This report documents the approach selected for component level testing and the matrix selected for full scale crash testing. The hardware that was fabricated to conduct the component tests is shown and discussed. The component test results to date are discussed as to repeatability, durability and ability to discriminate between levels of safety.