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Technical Paper

Vehicle to Vehicle Interaction Maneuvers Choreographed with an Automated Test Driver

Modern passenger cars are being equipped with advanced driver assistance systems such as lane departure warning, collision avoidance systems, adaptive cruise control, etc. Testing for operation and effectiveness of these warning systems involves interaction between vehicles. While dealing with multiple moving vehicles, obtaining discriminatory results is difficult due to the difficulty in minimizing variations in vehicle separation and other parameters. This paper describes test strategies involving an automated test driver interacting with another moving vehicle. The autonomous vehicle controls its state (including position and speed) with respect to the target vehicle. Choreographed maneuvers such as chasing and overtaking can be performed with high accuracy and repeatability that even professional drivers have difficulty achieving. The system is also demonstrated to be usable in crash testing.
Technical Paper

Vehicle and Occupant Response in Heavy Truck to Passenger Car Sideswipe Impacts

There have been a number of papers written about the dynamic effects of low speed front to rear impacts between motor vehicles during the last several years. This has been an important issue in the field of accident analysis and reconstruction because of the frequency with which the accidents occur and the costs of injuries allegedly associated with them. Sideswipe impacts are another, often minor, type of motor vehicle impact that generate a significant number of injury claims. These impacts are difficult to analyze for a number of reasons. First, there have been very few studies in the literature describing the specific dynamic effects of minor sideswipe impacts on the struck vehicles and their occupants. Those that have been performed have focused on the impact of two passenger cars.
Technical Paper

Vehicle Characterization Through Pole Impact Testing, Part II: Analysis of Center and Offset Center Impacts

The severity of an impact in terms of the acceleration in the occupant compartment is dependent not only on the change in vehicle velocity, but also the time for the change in velocity to occur. These depend on the geometry and stiffness of both the striking vehicle and struck object. In narrow-object frontal impacts, impact location can affect the shape and duration of the acceleration pulse that reaches the occupant compartment. In this paper, the frontal impact response of a full-sized pickup to 10 mile per hour and 20 mile per hour pole impacts at the centerline and at a location nearer the frame rails is compared using the acceleration pulse shape, the average acceleration in the occupant compartment, and the residual crush. A bilinear curve relating impact speed to residual crush is developed.
Technical Paper

Vehicle Characterization Through Pole Impact Testing, Part I: Vehicle Response in Terms of Acceleration Pulses

The shape of an acceleration pulse in an impact is not only affected by the change in velocity, but also by the geometry and stiffness of the both the striking vehicle and the struck object. In this paper, the frontal crash performance of a full-size pickup is studied through a series of impact tests with a rigid pole and with a flat barrier. Each rigid pole test is conducted at one of four locations across the front of the vehicle and at impact speeds of 10 mph, 20 mph, or 30 mph. The flat barrier tests are conducted at 10 mph, 15 mph, 20 mph, and 30 mph. The vehicle crush and acceleration pulses resulting from the pole tests are compared to those resulting from the barrier tests. The severity of pole impacts and the severity of flat barrier impacts are compared based on peak accelerations and pulse durations of the occupant compartment.
Technical Paper

Validation and Enhancement of a Heavy Truck Simulation Model with an Electronic Stability Control Model

Validation was performed on an existing heavy truck vehicle dynamics computer model with roll stability control (RSC). The first stage in this validation was to compare the response of the simulated tractor to that of the experimental tractor. By looking at the steady-state gains of the tractor, adjustments were made to the model to more closely match the experimental results. These adjustments included suspension and steering compliances, as well as auxiliary roll moment modifications. Once the validation of the truck tractor was completed for the current configuration, the existing 53-foot box trailer model was added to the vehicle model. The next stage in experimental validation for the current tractor-trailer model was to incorporate suspension compliances and modify the auxiliary roll stiffness to more closely model the experimental response of the vehicle. The final validation stage was to implement some minor modifications to the existing RSC model.
Technical Paper

Two Dimensional Thoracic Modeling Considerations

There is currently a considerable effort being devoted to the development of anthropomorphic test devices for the measurement of thoracic side impact response. Both the SID and EUROSID have been proposed as viable candidates for this test device. In addition, the thorax of the three year old Fart 572 has been shown to be useful in simulating side impact while used in the frontal orientation. This apparent anomaly suggests that the intuitive differences between the frontal and side geometries of the thorax may not be significant. To date, all useable thoracic models have been unidirectional. For the most part, these have been frontal models. This paper discusses some of the difficulties inherent in the development of a two dimensional thoracic model and ways these difficulties can be addressed. Based on these considerations, a single thoracic impact model is proposed for simulation of both frontal and lateral impact without adjustment of model parameters for impact direction.
Technical Paper

The Vocabulary of Accident Reconstruction

Vehicular accidents occur in everyday life. Their degree of severity is often perceived by the general public based on the amount of human bodily injuries sustained. Nevertheless, accident reconstructionists measure the degree of severity of vehicular accidents by calculating terms that are called Collision Parameters. The principal objective of this paper is to describe the significance of the Collision Parameters and explain the vocabulary of accident reconstruction. A non-mathematical approach is utilized to provide a thorough understanding for the general public.
Technical Paper

The Use of Single Moving Vehicle Testing to Duplicate the Dynamic Vehicle Response From Impacts Between Two Moving Vehicles

The Federal Side Impact Test Procedure prescribed by FMVSS 214, simulates a central, orthogonal intersection collision between two moving vehicles by impacting the side of the stationary test vehicle with a moving test buck in a crabbed configuration. While the pre- and post-impact speeds of the vehicles involved in an accident can not be duplicated using this method, closing speeds, vehicle damage, vehicle speed changes and vehicle accelerations can be duplicated. These are the important parameters for the examination of vehicle restraint system performance and the prediction of occupant injury. The acceptability of this method of testing is not as obvious for the reconstruction of accidents where the impact is non-central, or the angle of impact is not orthogonal. This paper will examine the use of crash testing with a single moving vehicle to simulate oblique or non-central collisions between two moving vehicles.
Technical Paper

The Measurement of Static Rollover Metrics

This paper describes and compares three methods of estimating the static rollover threshold of passenger cars and light trucks. The Static Stability Factor (SSF), Side Pull Ratio (SPR), and Tilt Table Ratio (TTR) “metrics” are described and methods of measuring each are presented. The comparison of the three metrics is limited to the accuracy, repeatability, and ease of the measurements, and does not attempt to compare their ability to predict real world rollover accident involvement. The results of the comparison have shown that the three metrics are very closely related. Based on this, the rollover accident predictive power of each metric is expected to be similar. However, the ease and accuracy of the TTR measurement make it the most useful of the three. DURING THE 1980's, the use of light trucks and multi-purpose vehicles for basic transportation increased considerably. By 1990, domestic full-size pickup trucks were regularly among the top five passenger vehicles sold.
Technical Paper

Suspension Parameter Measurement Using Side-Pull Test To Enhance Modeling of Vehicle Roll

This paper describes a new laboratory test facility for measuring suspension parameters that affect rollover. The Side-Pull mechanism rolls the test vehicle through a cable attached rigidly at its center of gravity (CG). Changes in wheel camber and wheel steer angles are measured as a function of body roll angle. The roll test simulates a steady-state cornering. Thus, both compliance and kinematic forces are fed simultaneously to the vehicle as they would be applied in a real cornering situation. The lateral load transfer, and roll angle as a function of simulated lateral acceleration is determined. The Side-Pull Roll Measurement has advantages over the conventional roll tests where the rolling force couple is applied vertically. The Side-Pull mechanism rolls the vehicle in a unrestricted way with horizontal forces applied at the tire / pad contact and the CG location. Thus, the measurements take into account coupling of compliance with roll.
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.
Technical Paper

Spot Weld Failure Analysis for Accident Reconstruction

Adequacy of resistance spot welds in low carbon steels in relation to structural integrity can become an issue in the reconstruction of automotive accidents. Because formation of a plug (or button or slug) in a peel test is used as a quality control criterion for welds, it is sometimes assumed conversely that a weld which failed is defective if no plug is present. Spot welds do not necessarily form a plug when fractured. Fracture behavior of spot welds both by overload and fatigue is reviewed. Then techniques for examination of field failures are discussed. Finally two case histories are discussed.
Technical Paper

Simulation Results from a Model of a Tractor Trailer Vehicle Equipped with Roll Stability Control

In 2007, a software model of a Roll Stability Control (RSC) system was developed based on test data for a Volvo tractor at NHTSA's Vehicle Research and Test Center (VRTC). This model was designed to simulate the RSC performance of a commercially available Electronic Stability Control (ESC) system. The RSC model was developed in Simulink and integrated with the available braking model (TruckSim) for the truck. The Simulink models were run in parallel with the vehicle dynamics model of a truck in TruckSim. The complete vehicle model including the RSC system model is used to simulate the behavior of the actual truck and determine the capability of the RSC system in preventing rollovers under different conditions. Several simulations were performed to study the behavior of the model developed and to compare its performance with that of an actual test vehicle equipped with RSC.
Technical Paper

Simplified MADYMO Model of the IHRA Head-form Impactor

Interest in pedestrian head injury has prompted a need to measure the potential of head injury resulting from vehicular impacts. A variety of head impactors have been developed to fulfill this measurement need. A protocol has been developed by the International Harmonization Research Activity (IHRA) to use head impactor measurements to predict head injury. However, the effect of certain characteristics of the various head impactors on the measurement procedure is not well understood. This includes the location of the accelerometers within the head-form and testing the head-form under the variety of conditions necessary to establish its global performance. To address this problem, a simple model of the IHRA head-form has been developed. This model was created using MADYMO© and consists of a solid sphere with a second sphere representing the vinyl covering. Stiffness and damping characteristics of the vinyl covering were determined analytically from drop test data of an IHRA head-form.
Technical Paper

Service Trial of Waste Vegetable Oil as a Diesel Fuel Supplement

This paper presents the results of actual in service testing of a diesel fuel supplement, specifically a 20-80% blend of waste vegetable oil and diesel No. 1. Tests are presented illustrating the effects of smoke readings, viscosity, specific gravity, and mileage with the 20-80 blend. Coupled with these results was the actual diesel engine tear down. The bus engine inspection included the head, piston heads, injectors, rings, and intake ports. The results of this in service test indicate that a diesel engine without any modification will run successfully on a blend of 20% waste vegetable oil and 80% diesel fuel without damage to the engine parts. Additionally only a diesel No. 1 blend was found to be satisfactory in cold weather unless measures are taken to prevent filter plugging. Finally, the results of this study indicate that the use of waste soybean oil as a diesel fuel extender is a viable short term energy solution based on economics as well as engine performance.
Journal Article

Semitrailer Torsional Stiffness Data for Improved Modeling Fidelity

Vehicle dynamics models employed in heavy truck simulation often treat the semitrailer as a torsionally rigid member, assuming zero deflection along its longitudinal axis as a moment is applied to its frame. Experimental testing, however, reveals that semitrailers do twist, sometimes enough to precipitate rollover when a rigid trailer may have remained upright. Improving the model by incorporating realistic trailer roll stiffness values can improve assessment of heavy truck dynamics, as well as an increased understanding of the effectiveness of stability control systems in limit handling maneuvers. Torsional stiffness measurements were conducted by the National Highway Traffic Safety Administration (NHTSA) for eight semitrailers of different types, including different length box vans, traditional and spread axle flat beds, and a tanker.
Technical Paper

Scenario Regeneration using a Hardware-in-the-loop Simulation Platform to Study ABS and ESC Performance Benefits

This study was performed to showcase the possible applications of the Hardware-in-the-loop (HIL) simulation environment developed by the National Highway Traffic Safety Administration (NHTSA), to test heavy truck crash avoidance safety systems. In this study, the HIL simulation environment was used to recreate a simulation of an actual accident scenario involving a single tractor semi-trailer combination. The scenario was then simulated with and without an antilock brake system (ABS) and electronic stability control (ESC) system to investigate the crash avoidance potential afforded by the tractor equipped with the safety systems. The crash scenario was interpreted as a path-following problem, and three possible driver intended paths were developed from the accident scene data.
Technical Paper

Review of Pedestrian Safety Research in the United States

Pedestrian vehicle accidents account for a considerable proportion of all automobile related injuries and deaths each year. Due to the large difference in mass between the pedestrian and the vehicle, pedestrian injury reduction is a formidable task. In spite of these difficulties, world attention is beginning to focus on pedestrian injuries and methods to quantitatively evaluate a vehicle for its pedestrian injury potential. This paper reviews the status of work in the United States on devices and methods for measuring pedestrian impact response. Where data is available test device response is summarized. The state of pedestrian accident research is also reviewed in the light of national and International interest in reducing pedestrian injuries.
Technical Paper

Response of the 6-Month-Old CRABI in Forward Facing and Rear Facing Child Restraints to a Simulated Real World Impact

It is commonly recommended to use infant/child restraints in the rear seat, and that until an infant reaches certain age, weight and height criteria, the infant restraint should be placed rear facing. This paper will describe the injuries suffered by an infant that was restrained in a forward-facing child seat placed in the front passenger seating position during a real world collision. Based on this collision, a full-scale vehicle to barrier impact test was performed. For this test, two 6-month-old CRABI dummies were used in identical child restraints. One of the restraints was placed in the front passenger seat in a forward facing configuration, and the other was placed in the right rear seating position in a rear-facing configuration. This paper provides a detailed discussion of the results of this test, including comparisons of the specific kinematics for both the restraint/child dummy configurations.
Technical Paper

Response of Neck Muscles to Rear Impact in the Presence of Bracing

In this research, cervical muscle behavior in rear impact accidents was investigated. Specifically, cervical muscle forces and muscle lengthening velocities were investigated with respect to cervical injuries. Variation of the onset time for muscle activation, variation of muscle activation level and variation of rear impact pulses were considered. The human body simulation computer program, MADYMO and anthropometric numerical human model were used to evaluate the neck. The factors mentioned above were examined with specific data being obtained from several different literature sources. Cervical muscles were separated into three groups, the sternocleidomastoideus, the flexor muscle group and the extensor muscle group. Longuscolli and spleniuscapitis were selected to represent the flexor muscle and extensor muscle groups respectively. The values and trends of the muscle forces and lengthening velocities are investigated in each muscle group.