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Technical Paper

Closed Loop Steering System Model for the National Advanced Driving Simulator

2004-03-08
2004-01-1072
This paper presents the details of the model for the physical steering system used on the National Advanced Driving Simulator. The system is basically a hardware-in-the-loop (steering feedback motor and controls) steering system coupled with the core vehicle dynamics of the simulator. The system's torque control uses cascaded position and velocity feedback and is controlled to provide steering feedback with variable stiffness and dynamic properties. The reference model, which calculates the desired value of the torque, is made of power steering torque, damping function torque, torque from tires, locking limit torque, and driver input torque. The model also provides a unique steering dead-band function that is important for on-center feel. A Simulink model of the hardware/software is presented and analysis of the simulator steering system is provided.
Technical Paper

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

2010-04-12
2010-01-0104
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.
Journal Article

Integration of a Torsional Stiffness Model into an Existing Heavy Truck Vehicle Dynamics Model

2010-04-12
2010-01-0099
Torsional stiffness properties were developed for both a 53-foot box trailer and a 28-foot flatbed control trailer based on experimental measurements. In order to study the effect of torsional stiffness on the dynamics of a heavy truck vehicle dynamics computer model, static maneuvers were conducted comparing different torsional stiffness values to the original rigid vehicle model. Stiffness properties were first developed for a truck tractor model. It was found that the incorporation of a torsional stiffness model had only a minor effect on the overall tractor response for steady-state maneuvers up to 0.4 g lateral acceleration. The effect of torsional stiffness was also studied for the trailer portion of the existing model.
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

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

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

1999-03-01
1999-01-1323
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

Derivation and Validation of New Analytical Planar Models for Simulating Multi-Axle Articulated Vehicles

2004-03-08
2004-01-1784
This paper discusses the derivation and validation of planar models of articulated vehicles that were developed to analyze jackknife stability on low-μ surfaces. The equations of motion are rigorously derived using Lagrange's method, then linearized for use in state-space models. The models are verified using TruckSim™, a popular nonlinear solid body vehicle dynamics modeling package. The TruckSim™ models were previously verified using extensive on-vehicle experimental data [1, 2]. A three-axle articulated model is expanded to contain five axles to avoid lumping the parameters for the drive and semitrailer tandems. Compromises inherent in using the linearized models are discussed and evaluated. Finally, a nonlinear tire cornering force model is coupled with the 5-axle model, and its ability to simulate a jackknife event is demonstrated. The model is shown to be valid over a wide range of inputs, up to and including loss of control, on low-and-medium-μ surfaces.
Technical Paper

Parameter Determination and Vehicle Dynamics Modeling for The National Advanced Driving Simulator of the 2006 BMW 330i

2007-04-16
2007-01-0818
The paper discusses the development of a model for the 2006 BMW 330i for the National Advanced Driving Simulator's (NADS) vehicle dynamics simulation, NADSdyna. The front and rear suspensions are independent strut and link type suspensions modeled using recursive rigid-body dynamics formulations. The suspension springs and shock absorbers are modeled as force elements. The paper includes parameters for front and rear semi-empirical tire models used with NADSdyna. Longitudinal and lateral tire force plots are also included. The NADSdyna model provides state-of-the-art high-fidelity handling dynamics for real-time hardware-in-the-loop simulation. The realism of a particular model depends heavily on how the parameters are obtained from the actual physical system. Complex models do not guarantee high fidelity if the parameters used were not properly measured. Methodologies for determining the parameters are detailed in this paper.
Technical Paper

Model Validation of the 2006 BMW 330i for the National Advanced Driving Simulator

2007-04-16
2007-01-0817
This paper presents an evaluation of a complete vehicle dynamics model for a 2006 BMW 330i to be used for the National Advanced Driving Simulator. Vehicle handling and braking are evaluated and simulation results are compared with experimental field-testing. NADSdyna, the National Advanced Driving Simulator vehicle dynamics software, is used. The BMW evaluation covers vehicle directional dynamics that include steady-state, transient, and frequency domain responses. These evaluations are performed with the DSC (Dynamic Stability and Control) turned off to ensure the principle mechanical properties of the vehicle are properly modeled before enabling the electronic stability system. The evaluation also includes simulation runs with DSC turned on for the J-turn and severe lane change maneuvers.
Technical Paper

Simulator Study of Heavy Truck Air Disc Brake Effectiveness During Emergency Braking

2008-04-14
2008-01-1498
In crashes between heavy trucks and light vehicles, most of the fatalities are the occupants of the light vehicle. A reduction in heavy truck stopping distance should lead to a reduction in the number of crashes, the severity of crashes, and consequently the numbers of fatalities and injuries. This study made use of the National Advanced Driving Simulator (NADS). NADS is a full immersion driving simulator used to study driver behavior as well as driver-vehicle reactions and responses. The vehicle dynamics model of the existing heavy truck on NADS had been modified with the creation of two additional brake models. The first was a modified S-cam (larger drums and shoes) and the second was an air-actuated disc brake system. A sample of 108 CDL-licensed drivers was split evenly among the simulations using each of the three braking systems. The drivers were presented with four different emergency stopping situations.
Technical Paper

Model Validation of the 1997 Jeep Cherokee for the National Advanced Driving Simulator

2000-03-06
2000-01-0700
This paper presents an evaluation of a complete vehicle dynamics model for a 1997 Jeep Cherokee to be used for the National Advanced Driving Simulator. Vehicle handling and powertrain dynamics are evaluated and simulation results are compared with experimental field-testing. NADSdyna, the National Advanced Driving Simulator vehicle dynamics software, is used. The Jeep evaluation covers vehicle directional dynamics that include steady state, transient and frequency response, and vehicle longitudinal dynamics that include acceleration and braking.
Technical Paper

Inertia Measurements of Large Military Vehicles

2001-03-05
2001-01-0792
This paper describes the design and operation of a facility for measuring vehicle center-of-gravity height; roll, pitch, and yaw moments of inertia; and roll/yaw cross product of inertia for a broad range of test specimens. The facility is configurable such that it is capable of measuring these properties for light, single axle trailers; long, heavy vehicles; and tank turrets. The design was driven by the need for accurate, repeatable measurement results and the desire to have a single facility capable of making measurements on a broad range of vehicle sizes.
Technical Paper

Parameter Determination and Vehicle Dynamics Modeling for the NADS of the 1998 Chevrolet Malibu

2001-03-05
2001-01-0140
The paper discusses the development of a model for a 1998 Chevrolet Malibu for the National Advanced Driving Simulator’s (NADS) vehicle dynamics simulation, NADSdyna. The Malibu is the third vehicle modeled for the NADS, and this is the third paper dealing with model development. SAE Paper 970564 contains details of the model for the 1994 Ford Taurus and SAE Paper 1999–01-0121 contains details of the model for the 1997 Jeep Cherokee. The front and rear suspensions are independent strut and link type suspensions modeled using recursive rigid body dynamics formulations. The suspension springs and shock absorbers are modeled as elements in the rigid body formulation. To complement the vehicle dynamics for the NADS application, subsystem models that include tire forces, braking, powertrain, aerodynamics, and steering are added to the rigid body dynamics model. The models provide state-of-the-art high fidelity vehicle handling dynamics for real-time simulation.
Technical Paper

Enhancement of Vehicle Dynamics Model Using Genetic Algorithm and Estimation Theory

2003-03-03
2003-01-1281
A determination of the vehicle states and tire forces is critical to the stability of vehicle dynamic behavior and to designing automotive control systems. Researchers have studied estimation methods for the vehicle state vectors and tire forces. However, the accuracy of the estimation methods is closely related to the employed model. In this paper, tire lag dynamics is introduced in the model. Also application of estimation methods in order to improve the model accuracy is presented. The model is developed by using the global searching algorithm, a Genetic Algorithm, so that the model can be used in the nonlinear range. The extended Kalman filter and sliding mode observer theory are applied to estimate the vehicle state vectors and tire forces. The obtained results are compared with measurements and the outputs from the ADAMS full vehicle model. [15]
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

Vehicle Dynamics Modeling for the National Advanced Driving Simulator of a 1997 Jeep Cherokee

1999-03-01
1999-01-0121
This paper discusses the development of the 1997 Jeep Cherokee model for the National Advanced Driving Simulator's planned vehicle dynamics software, NADSdyna. Recursive rigid body formalism called the Real Time Recursive Dynamics (RTRD) developed by the University of Iowa is used to model the front and rear suspension mechanisms. To complement vehicle dynamics for simulator applications, subsystems that include tires, aerodynamics, powertrain, brake, and steering are added to the rigid body dynamics model. These models provide high fidelity driving realism to simulate severe handling maneuvers in real time. The soundness of the model does not only depend on the mathematics of the model, but also on the validity of the parameters. Therefore, this paper discusses thoroughly the methodology of parameters estimation. A generic model of cruise control is included.
Technical Paper

Effects of Loading on Vehicle Handling

1998-02-23
980228
This paper explores the effects of changes in vehicle loading on vehicle inertial properties (center-of-gravity location and moments of inertia values) and handling responses. The motivation for the work is to gain better understanding of the importance vehicle loading has in regard to vehicle safety. A computer simulation is used to predict the understeer changes for three different vehicles under three loading conditions. An extension of this loading study includes the effects of moving occupants, which are modeled for inclusion in the simulation. A two-mass model for occupants/cargo, with lateral translational and rotational degrees of freedom, has been developed and is included in the full vehicle model. Using the simulation, the effects that moving occupants have on vehicle dynamics are studied.
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

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

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.
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