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Technical Paper

Refinements of a Heavy Truck ABS Model

2007-04-16
2007-01-0839
In 2004, a model of a 6s6m ABS controller was developed in order to support NHTSA's efforts in the study of heavy truck braking performance. This model was developed using Simulink and interfaced with TruckSim, a vehicle dynamics software package, in order to create an accurate braking simulation of a 6×4 Peterbilt straight truck. For this study, the vehicle model braking dynamics were improved and the ABS controller model was refined. Also, the controller was made adaptable to ABS configurations other than 6s6m, such as 4s4m and 4s3m. Controller models were finally validated to experimental data from the Peterbilt truck, gathered at NHTSA's Vehicle Research and Test Center (VRTC).
Technical Paper

Evaluation of a Shock Model for Vehicle Simulation

2007-04-16
2007-01-0845
This paper describes the development of a more accurate shock absorber model in order to obtain better vehicle simulation results. Previous shock models used a single spline to represent shock force versus shock velocity curves. These models produced errors in vehicle simulations because the damper characteristics are better represented by the application of a hysteresis loop in the model. Thus, a new damper model that includes a hysteresis loop is developed using Matlab Simulink. The damper characteristics for the new model were extracted from measurements made on a shock dynamometer. The new model better represents experimental shock data. The new shock model is incorporated into two different lumped-parameter vehicle models: one is a three degree-of-freedom vehicle handling model and the other is a seven degree-of-freedom vehicle ride model. The new damper model is compared with the previous model for different shock mileages (different degrees of wear).
Technical Paper

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

2007-04-16
2007-01-0815
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

Automated Steering Controller for Vehicle Testing

2007-08-05
2007-01-3647
Automating road vehicle control can increase the range and reliability of dynamic testing. Some tests, for instance, specify precise steering inputs which human test drivers are only able to approximate, adding uncertainty to the test results. An automated steering system has been developed which is capable of removing these limitations. This system enables any production car or light truck to follow a user-defined path, using global position feedback, or to perform specific steering sequences with excellent repeatability. The system adapts itself to a given vehicle s handling characteristics, and it can be installed and uninstalled quickly without damage or permanent modification to the vehicle.
Technical Paper

Effects of ABS Controller Parameters on Heavy Truck Model Braking Performance

2006-10-31
2006-01-3482
This paper covers research conducted at the National Highway Traffic Safety Administration's Vehicle Research and Test Center (VRTC) examining the performance of semitrailer anti-lock braking systems (ABS). For this study, a vehicle dynamics model was constructed for the combination of a 4×2 tractor and a 48-foot trailer, using TruckSim. ABS models for the tractor and trailer, as well as brake dynamics and surface friction models, were created in Simulink so that the effect of varying ABS controller parameters and configurations on semitrailer braking performance could be studied under extreme braking maneuvers. The longitudinal and lateral performances of this tractor-trailer model were examined for a variety of different trailer ABS controller models, including the 2s1m, 4s2m, and 4s4m configurations. Also, alternative controllers of the same configuration were studied by varying the parameters of the 2s1m controller.
Technical Paper

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

2006-07-04
2006-01-2369
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.
Technical Paper

Advancements in Tire Modeling Through Implementation of Load and Speed Dependent Coefficients

2005-11-01
2005-01-3543
An existing tire model was investigated for additional normal load-dependent characteristics to improve the large truck simulations developed by the National Highway Traffic Safety Administration (NHTSA) for the National Advanced Driving Simulator (NADS). Of the existing tire model coefficients, plysteer, lateral friction decay, aligning torque stiffness and normalized longitudinal stiffness were investigated. The findings of the investigation led to improvements in the tire model. The improved model was then applied to TruckSim to compare with the TruckSim table lookup tire model and test data. Additionally, speed-dependent properties for the NADS tire model were investigated (using data from a light truck tire).
Technical Paper

The Development of a Heavy Truck ABS Model

2005-04-11
2005-01-0413
This paper discusses the improvement of a heavy truck anti-lock brake system (ABS) model currently used by the National Highway Traffic Safety Administration (NHTSA) in conjunction with multibody vehicle dynamics software. Accurate modeling of this complex system is paramount in predicting real-world dynamics, and significant improvements in model accuracy are now possible due to recent access to ABS system data during on-track experimental testing. This paper focuses on improving an existing ABS model to accurately simulate braking under limit braking maneuvers on high and low-coefficient surfaces. To accomplish this, an ABS controller model with slip ratio and wheel acceleration thresholds was developed to handle these scenarios. The model was verified through testing of a Class VIII 6×4 straight truck. The Simulink brake system and ABS model both run simultaneously with TruckSim, with the initialization and results being acquired through Matlab.
Technical Paper

Experimental Evaluation of Fishhook Maneuver Performance of a Kinetic Suspension System

2005-04-11
2005-01-0392
Kinetic Pty Ltd and Tenneco Automotive have developed a passive suspension system called a Kinetic system. The motivation for the design of the system is discussed, and the function of the system is explained. The system improves handling, stability, and ride by passively decoupling roll stiffness from articulation stiffness and roll damping from bounce damping. Improved stability is evaluated by conducting NHTSA's Roll Rate Feedback Fishhook tests on a small SUV equipped with the Kinetic system. Results of the testing are presented, and benefits to rollover are discussed.
Technical Paper

Integration of an Adaptive Control Strategy on an Automated Steering Controller

2005-04-11
2005-01-0393
This paper describes an adaptive control strategy for improving the steering response of an automated vehicle steering controller. In order to achieve repeatable dynamic test results, precise steering inputs are necessary. This strategy provides the controller tuning parameters optimized for a particular vehicle's steering system. Having the capability to adaptively tune the steering controller for any vehicle installation provides an easy method for obtaining precise steering inputs for a wide range of vehicles, from small off-road utility vehicles to passenger vehicles to heavy trucks. The S.E.A. Ltd. Automated Steering Controller (ASC) is used exclusively in conducting this research. By recording the torque input to the steering system by the steering controller and the resulting steering angle during only a single test, the ASC is able to characterize the steering system of the test vehicle and create a computer model with appropriate parameters.
Technical Paper

Pole and Vehicle Energy Absorption in Lateral Oblique Impacts with Rigid and Frangible Poles

2008-04-14
2008-01-0170
Many vehicle-to-pole impacts occur when a vehicle leaves the roadway due to oversteer and loss of control in a lateral steering maneuver. Such a loss of control typically results in the vehicle having a significant component of lateral sliding motion as it crosses the road edge, so that impacts with objects off of the roadway often occur to the side of the vehicle. The response of the vehicle to this impact depends on the characteristics of the impacted object, the characteristics of the vehicle in the impacted zone, and the speed and orientation of the vehicle. In situations where the suspension or other stiff portions of a vehicle contacts a wooden pole, it is not uncommon for the pole to fracture. When this occurs, reconstruction of the accident is complicated by the need to evaluate both the energy absorbed by the vehicle as well as the energy absorbed by the pole.
Technical Paper

The Impact of Worn Shocks on Vehicle Handling and Stability

2006-04-03
2006-01-0563
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

Coefficients of Restitution for Low and Moderate Speed Impacts with Non-Standard Impact Configurations

2001-03-05
2001-01-0891
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. Several of these papers have discussed the importance of the coefficient of restitution in the accelerations and speed changes that the vehicles undergo in such impacts. These discussions often include data showing the measured restitution for impacts involving various bumper types and closing speeds. However, in most of these studies, the impacts are controlled so that direct bumper to bumper impacts occur. This paper will present the results of several rear impact tests with non-standard impact configurations.
Technical Paper

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

2001-03-05
2001-01-0900
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

A Validation Study of Vehicle Dynamics Simulations for Heavy Truck Handling Maneuvers

2001-03-05
2001-01-0139
This paper deals with the ongoing efforts at The Vehicle Research and Test Center (VRTC) in East Liberty, Ohio in promoting the safe operation of heavy trucks. The associated research evaluated two vehicle dynamics simulations for their accuracy in predicting tractor-trailer handling metrics. The goals of the research were threefold: 1. Establish a generic “benchmark” parametric data set for the three-axle truck/two-axle trailer vehicle 2. Demonstrate the accuracy of experimental data that was collected for the tractor-trailer vehicle of this study 3. Demonstrate the accuracy of two vehicle simulations by comparing their predicted responses to experimentally observed vehicle responses and metrics.
Technical Paper

Measured Vehicle Center-of-Gravity Locations - Including NHTSA's Data Through 2008 NCAP

2010-04-12
2010-01-0086
This paper is a printed listing of public domain vehicle center-of-gravity (CG) location measurements conducted on behalf of the National Highway Traffic Safety Administration (NHTSA). This paper is an extension of the 1999 SAE paper titled “Measured Vehicle Inertia Parameters - NHTSA's Data Through November 1998” ( 1 ). The previous paper contained data for 496 vehicles. This paper includes data for 528 additional vehicles tested as part of NHTSA's New Car Assessment Program (NCAP) for year 2001 through year 2008 ( 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ). The previous data included center-of-gravity location and mass moments-of-inertia for nearly all of the entries. The NCAP involves only the CG location measurements; so the vehicles listed in this paper do not have inertia data. This paper provides a brief discussion of the entries provided in the tabular listings as well as the accuracy of CG height measurements.
Technical Paper

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

2010-04-12
2010-01-0098
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

Vehicle Dynamics Modeling and Validation of the 2003 Ford Expedition with ESC using CarSim

2009-04-20
2009-01-0452
The paper discusses the development of a vehicle dynamics model and model validation of the 2003 Ford Expedition in CarSim. The accuracy of results obtained from simulations depends on the realism of the model which in turn depends on the measured data used to define the model parameters. The paper describes the tests used to measure the vehicle data and also gives a detailed account of the methodology used to determine parameters for the CarSim Ford Expedition model. The vehicle model was validated by comparing simulation results with experimental testing. Bounce and Roll tests in CarSim were used to validate the suspension and steering kinematics and compliances. Field test data of the Sine with Dwell maneuver was used for the vehicle model validation. The paper also discusses the development of a functional electronic stability control system and its effect on vehicle handling response in the Sine with Dwell maneuver.
Technical Paper

Vehicle Dynamics Modeling and Validation for the 2003 Ford Expedition with ESC using ADAMS View

2009-04-20
2009-01-0453
The paper discusses the development of a model of the 2003 Ford Expedition using ADAMS View and its validation with experimental data. The front and rear suspensions are independent double A-arm type suspensions modeled using rigid links and ideal joints. The suspension springs and shock absorbers are modeled as force elements. The plots comparing the experimental tests and the simulation results are shown in this paper. Quasi-static roll and bounce tests are used to validate the suspension characteristics of the model while the Sine with Dwell and Slowly Increasing Steer maneuvers are used to validate the vehicle handling and tire-road interaction characteristics of the model. This paper also details the incorporation of an ESC model, originally developed by Kinjawadekar et al. [2] for CarSim, with the ADAMS model. The ESC is modeled in Simulink and co-simulated with the ADAMS vehicle model. Plots validating the ESC model with experimental data are also included.
Technical Paper

Repeatability and Bias Study on the Vehicle Inertia Measurement Facility (VIMF)

2009-04-20
2009-01-0447
Representative vehicle inertial characteristics are important parameters for the development of motor vehicles and the proper operation of on-board systems. The Vehicle Inertia Measurement Facility (VIMF) measures vehicle center of gravity location, principal moments of inertia, and the roll/yaw product of inertia. It is important to understand the VIMF’s accuracy and repeatability, as well as the underlying methodology and assumptions, when performing tests or using the results of the test. This study reports on a repeatability analysis performed at the lower and upper limits of the VIMF. Each test performed is a complete drive-on/drive-off test. The test sequence involves the repeatability evaluation of several different machine configurations. Ten complete tests are performed for each vehicle. To better address the possibility of measurement bias, the design and verification of a calibration fixture for inertial characteristics is presented.
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