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Chrstos, Jeffrey P.
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Development of a Vehicle Model/Simulation Evaluation Tool

SAE International Journal of Commercial Vehicles

RealTime Technologies, Inc.-Richard Romano
Systems Technology, Inc.-J. Gavin Howe, Jeffrey P. Chrstos
  • Journal Article
  • 2008-01-0778
Published 2008-04-14 by SAE International in United States
As part of the evaluation of vehicle simulation models, a vehicle dynamics engineer typically desires to compare simulation results to test data from actual vehicles and/or results from known, or higher fidelity simulations. Depending on the type of model, several types of tests and/or maneuvers may need to be compared. For military vehicles, there is the additional requirement to run specific types of maneuvers for vehicle model evaluations to ensure that the vehicle complies with procurement requirements. A thorough evaluation will run two different categories of tests/maneuvers. The first category consists of laboratory type tests that include weight distribution, kinematics and compliance, steering ratio, and other static measures. The second category consists of dynamic maneuvers that include handling, drive train, braking, ride, and obstacle types. In this paper, a process for proper evaluation of vehicle simulation models is presented. A method for evaluating simulation results from different simulation programs is also presented.
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Further Analysis of Potential Road/Terrain Characterization Rating Metrics

Systems Technology, Inc.-J. Gavin Howe, Dong-Chan Lee, Jeffrey P. Chrstos, Ole Balling, Thomas T. Myers, R. Wade Allen
U.S. Army TARDEC-David J. Gorsich, Alexander Reid
Published 2005-11-01 by SAE International in United States
The U.S. Army uses the root mean square and power spectral density of elevation to characterize road/terrain (off-road) roughness for durability. This paper describes research aimed toward improving these metrics. The focus is on taking previously developed metrics and applying them to mathematically generated terrains to determine how each metric discerns the relative roughness of the terrains from a vehicle durability perspective. Multiple terrains for each roughness level were evaluated to determine the variability for each terrain rating metric. One method currently under consideration is running a relatively simple, yet vehicle class specific, model over a given terrain and using predicted vehicle response(s) to classify or characterize the terrain.
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Analysis of Potential Road/Terrain Characterization Rating Metrics

Systems Technology, Inc.-J. Gavin Howe, Dong-Chan Lee, Jeffrey P. Chrstos, Thomas T. Myers, R. Wade Allen
U.S. Army TARDEC-David J. Gorsich, Alexander Reid
Published 2004-10-26 by SAE International in United States
The U.S. Army uses the root mean square and power spectral density of elevation to characterize road/terrain (off-road) roughness for durability. This paper describes research aimed toward improving these metrics. The focus is on taking previously developed metrics and applying them to mathematically generated terrains to determine how each metric discerns the relative roughness of the terrains from a vehicle durability perspective. Multiple terrains for each roughness level were evaluated to determine the variability for each terrain rating metric. One method currently under consideration is running a relatively simple, yet vehicle class specific, model over a given terrain and using predicted vehicle response(s) to classify or characterize the terrain.
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Tire Modeling for Off-Road Vehicle Simulation

Systems Technology, Inc.-Chi-Ying Liang, R. Wade Allen, Theodore J. Rosenthal, Jeffrey P. Chrstos
TACOM / TARDEC-Patrick Nunez
Published 2004-05-04 by SAE International in United States
A tire/terrain interaction model is presented to support the dynamic simulation of off-road ground vehicle. The model adopts a semi-empirical approach that is based on curve fits of soil data combined with soil mechanics theories to capture soil compaction, soil shear deformation, and soil passive failure that associate with off-road driving. The resulting model allows the computation of the tire forces caused by terrain deformation in longitudinal and lateral direction. This model has been compared with experimental data and shown reasonable prediction of the tire/terrain interaction.
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Driver/Vehicle Modeling and Simulation

Systems Technology, Inc.-R. Wade Allen, Jeffrey P. Chrstos, Bimal L. Aponso, Dongchan Lee
Published 2002-05-07 by SAE International in United States
This paper describes the driver/vehicle modeling aspects of a computer simulation that can respond to highway engineering descriptions of roadways. The driver model interacts with a complete vehicle dynamics model that has been described previously. The roadway path is described in terms of horizontal and vertical curvature and cross slopes of lanes, shoulders, side slopes and ditches. Terrain queries are made by the vehicle dynamics to locate tires on the roadway cross-section, and to define vehicle path and road curvature at some distance down the road. The driver model controls steering to maintain lateral lane position. Speed is maintained at a speed limit on tangents, and decreased as needed to maintain safe lateral acceleration. Because the bandwidth of longitudinal (speed) control is much lower than lateral/directional (steering) control, the driver model looks further ahead for speed control than for steering.The paper considers numerous examples of the path and speed control ability of the driver model in response to horizontal and vertical curvature. The driver model must slow down, and brake if necessary, to avoid excessive…
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Vehicle Dynamics and Simulation 2001

JPC Engineering-Jeffrey P. Chrstos
National Highway Traffic Safety Administration-W. Riley Garrott
  • Special Publication (SP)
  • SP-1602
Published 2001-03-05 by SAE International in United States
These papers demonstrate the broad range of vehicle dynamics research currently underway to better understand handling, braking, control, lateral stability, and rollover characteristics of cars and light trucks, and the force and momentum generating capabilities of tires.
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Vehicle and Tire Modeling for DynamicAnalysis and Real-Time Simulation

Systems Technology. Inc-R. Wade Allen, Theodore J. Rosenthal, David H. Klyde, Jeffrey P. Chrstos
Published 2000-05-01 by SAE International in United States
This paper reviews the development and application of a computer simulation for simulating ground vehicle dynamics including steady state tire behavior. The models have been developed over the last decade, and include treatment of sprung and unsprung masses, suspension characteristics and composite road plane tire forces. The models have been applied to single unit passenger cars, trucks and buses, and articulated tractor/trailer vehicles. The vehicle model uses composite parameters that are relatively easy to measure. The tire model responds to normal load, camber angle and composite tire patch slip, and its longitudinal and lateral forces interact with an equivalent friction ellipse formulation. The tire model can represent behavior on both paved and off-road surfaces. Tire model parameters can be automatically identified given tire force and moment test data. The vehicle and tire models have been validated against real world test data, and can be used to analyze handling and stability including limit performance maneuvering. The models are efficient enough to run in real-time on Intel Pentium class PCs, and have been used in driving simulations…
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Vehicle Dynamics and Simulation 1999

Jeffrey P. Chrstos, W. Riley Garrott, Gary J. Heydinger
  • Special Publication (SP)
  • SP-1445
Published 1999-03-01 by SAE International in United States
The papers in this book demonstrate the broad range of vehicle dynamics research currently underway to better understand these characteristocs of cars and light trucks: handling; braking; control; latera stability; and rollover.
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A Low Cost PC Based Driving Simulator for Prototyping and Hardware-In-The-Loop Applications

JPC Engineering-Jeffrey P. Chrstos
Systems Technology, Inc.-R. Wade Allen, Theodore J. Rosenthal, Bimal L. Aponso, David H. Klyde, Fritz G. Anderson, Jeffrey R. Hogue
Published 1998-02-23 by SAE International in United States
This paper describes a low cost, PC based driving simulation that includes a complete vehicle dynamics model (VDM), photo realistic visual display, torque feedback for steering feel and realistic sound generation. The VDM runs in real-time on Intel based PCs. The model, referred to as VDANL (Vehicle Dynamics Analysis, Non-Linear) has been developed and validated for a range of vehicles over the last decade and has been previously used for computer simulation analysis. The model's lateral and longitudinal dynamics have 17 degrees of freedom for a single unit vehicle and 33 degrees of freedom for an articulated vehicle. The model also includes a complete drive train including engine, transmission and front and rear drive differentials, and complete, power assisted braking and steering systems. A comprehensive tire model (STIREMOD) generates lateral and longitudinal forces and aligning torque based on normal load, camber angle and horizontal (lateral and longitudinal) slip. The tire model correctly simulates saturation and can represent off-road behavior including plowing in soft soil at high sideslip angles. The articulated vehicle can simulate tractor/trailer rigs,…
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Vehicle Dynamics and Simulation, 1998

W. Riley Garrott, Jeffrey P. Chrstos, Gary J. Heydiner
  • Special Publication (SP)
  • SP-1361
Published 1998-02-13 by SAE International in United States
Topics covered in this publication include: simulation models; driving simulators; the vehicle/driver system; simulation predictions to study and verify vehicle responses; modeling and simulation of 6x6 military trucks; and the Chevrolet C5 Corvette vehicle dynamic control system.