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This paper presents a feedback linearization control technique as applied to a Roll Simulator. The purpose of the Roll Simulator is to reproduce in-field rollovers of ROVs and study occupant kinematics in a laboratory setting. For a system with known parameters, non-linear dynamics and trajectories, the feedback linearization algorithm cancels out the non-linearities such that the closed-loop dynamics behave in a linear fashion. The control inputs are computed values that are needed to attain certain desired motions. The computed values are a form of inverse dynamics or feed-forward calculation. With increasing system eigenvalue, the controller exhibits greater response time. This, however, puts a greater demand on the translational actuator. The controller also demonstrates that it is able to compensate for and reject a disturbance in force level.

This paper presents a methodology for validating vehicle stability and control computer simulations. Validation is defined as showing that, within some specified operating range of the vehicle, a simulation's predictions of a vehicle's responses agree with the actual measured vehicle's responses to within some specified level of accuracy. The method uses repeated experimental runs at each test condition to generate sufficient data for statistical analyses. The acquisition and reduction of experimental data, and the processing path for simulation data, are described. The usefulness of time domain validation for steady state and slowly varying transients is discussed. The importance of frequency domain validation for thoroughly validating a simulation is shown. Both qualitative and quantitative methods for the comparison of the simulation predictions with the actual test measurements are developed.

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).

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.

This research focuses on the development and performance of analytical models to simulate a tractor-semitrailer in straight-ahead braking. The simulations were modified and tuned to simulate full-treadle braking with all brakes functioning correctly, as well as the behavior of the tractor-semitrailer rig under full braking with selected brakes disabled. The models were constructed in TruckSim and based on a tractor-semitrailer used in dry braking performance testing. The full-scale vehicle braking research was designed to define limits for engineering estimates on stopping distance when Class 8 air-braked vehicles experience partial degradation of the foundation brake system. In the full scale testing, stops were conducted from 30 mph and 60 mph, with the combination loaded to 80,000 lbs (gross combined weight or GCW), half payload, and with the tractor-semitrailer unladen (lightly loaded vehicle weight, or LLVW).

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.

This paper presents an evaluation of a complete vehicle dynamics model for a 1998 Chevrolet Malibu to be used for the National Advanced Driving Simulator. Vehicle handling, braking 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 Malibu evaluation covers vehicle directional dynamics that include steady state, transient frequency response, and vehicle longitudinal dynamics composed of acceleration and braking. Also, analyses of the effects of modified tire parameters on vehicle dynamics response is performed. The effects of wind gusts generated by a tractor-trailer and a bus on the Malibu vehicle directional dynamics are analyzed. For the steering system feel, we compare the handwheel torque feedback with the measured data during both high-speed dynamics and in the very low speed tire stick-slip regime.

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.

During Phase VI of the National Highway Traffic Safety Administration's (NHTSA) Light Vehicle Rollover Research Program, three of the twenty-six light vehicles tested exhibited significant response asymmetries with respect to left versus right steer maneuvers. This paper investigates possible vehicle asymmetric characteristics and unintended inputs that may cause vehicle asymmetric response. An analysis of the field test data, results from suspension and steering parameter measurements, and a summary of a computer simulation study are also given.

This paper presents a real-time steering system torque feedback model used in the National Advanced Driving Simulator (NADS). The vehicle model is based on real-time recursive multi-body dynamics augmented with vehicle subsystems models including tires, power train, brakes, aerodynamics and steering. The steering system feel is of paramount importance for the fidelity of the simulator. The driver has to feel the appropriate torque as he/she steers the vehicle. This paper presents a detailed mathematical model of the steering physics from low-speed stick-slip to high-speed states. On-center steering weave handling and aggressive lane change inputs are used to validate the basic mathematical predictions. This validation is objective and open loop, and was done using field experiments.

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]

This study involves two areas of research. The first is the finalization of the Pedestrian Crash Data Study (PCDS) in order to provide detailed information regarding the vehicle/pedestrian accident environment and how it has changed from the interim PCDS information. The pedestrian kinematics, injury contact sources, and injuries were analyzed relative to vehicle geometry. The second area presented is full-scale attempts at reconstruction of two selected PCDS cases using the Polar II pedestrian dummy to determine if the pre-crash motion of the pedestrian and vehicle could somehow be linked to the injuries and vehicle damage documented in the case.

Computer simulations are popular for modeling vehicle system dynamics. However, further refinement of the vehicle dynamic model is required for extensive use in the automotive industry. In this paper, the model refining procedure is illustrated by developing reliable kinematic models verified with laboratory test results; instrument test data; and a mathematical optimization method. More specifically, simple kinematic models are developed for reduced computation times using ADAMS. They are tuned by the gradient-based optimization technique using the results from a laboratory testing facility, which includes the compliance effect in order to use the kinematic models in dynamic simulations. Also the Magic Formula tire model is developed using the optimization method and tire property data for the STI (Systems Technology, Incorporated) tire model.

This paper presents the development of a real-time vehicle dynamics model of the heavy tractor-trailer combination used in the National Advanced Driving Simulator. The model includes multi-body dynamics of the tractor and trailer chassis, suspension, and steering mechanisms. The rigid body model is formulated using recursive multi-body dynamics code. This model is augmented with subsystem models that include tires, leaf springs, brakes, steering system, and aerodynamic drag. This paper also presents parameter measurement and estimations used to set up the model. Also included are models for brake fade, steering torque resistance, and defective tires.

This paper evaluates the heavy tractor-trailer handling dynamics model used in the National Advanced Driving Simulator. The comparison between simulation and experiments were done using lane change, slowly increasing steer, pulse steer, step steer, and straight-line braking maneuvers. The paper discusses tractor-trailer instrumentation and the results of field experiments.

This paper discusses the importance of having an adequate model for the dynamic response characteristics of tire lateral force to steering inputs. Computer simulation and comparison with experimental results are used to show the importance of including appropriate tire dynamics in simulation tire models to produce accurate predictions of vehicle dynamics. Improvements made to the tire dynamics model of an existing vehicle stability and control simulation, the Vehicle Dynamics Analysis, Non-Linear (VDANL) simulation, are presented. Specifically, the improvements include changing the simulation's tire dynamics from first-order system tire side force lag dynamics to second-order system tire slip angle dynamics. A second-order system representation is necessary to model underdamped characteristics of tires at high speeds. Lagging slip angle (an input to the tire model) causes all slip angle dependent tire force and moment outputs to be lagged.

The goal of this research was to find vehicle characteristics which may contribute to steering maneuver induced rollover accidents. This work involved studying vehicle handling dynamics using the Vehicle Dynamics Analysis, Non-Linear (VDANL) computer simulation. The simulation was used to predict vehicle responses while performing 28 different steering induced maneuvers for each of 51 vehicles. Various measures of vehicle response (metrics), such as response times, percent overshoots, etc., were computed for each vehicle from simulation predictions. These vehicle directional response metrics were analyzed in an attempt to identify vehicle characteristics that might be good predictor/explanatory variables for vehicle rollover propensity. The metrics were correlated, using the Statistical Analysis System (SAS) software and logistic regression, with single vehicle accident data from the state of Michigan for the years 1986 through 1988.

This paper presents the results of an in-depth study of the measurement of occupant kinematic response on the S-E-A Roll Simulator. This roll simulator was built to provide an accurate and repeatable test procedure for the evaluation of occupant protection and restraint systems during roll events within a variety of occupant compartments. In the present work this roll simulator was utilized for minimum-energy, or threshold type, rollover events of recreational off-highway vehicles (ROVs). Input profiles for these tests were obtained through a separate study involving autonomous full vehicle tests [1]. During simulated roll events anthropomorphic test device (ATD) responses were measured using on-board high speed video, an optical three-dimensional motion capture system (OCMS) and an array of string potentiometers.

There exists a fairly extensive set of tire force measurements performed on dry pavement. But in order to develop a low-coefficient of friction tire model, a set of tire force measurements made on wet pavement is required. Using formulations and parameters obtained on dry roads, and then reducing friction level to that of a wet road is not sufficient to model tire forces in a high fidelity simulation. This paper describes the process of more accurately modeling low coefficient tire forces on the National Advanced Driving Simulator (NADS). It is believed that the tire model improvements will be useful in many types of NADS simulations, including ESC and other advanced vehicle technology studies. In order to produce results that would come from a road surface that would be sufficiently slippery, a set of tires were shaved to 4/32 inches and sent to a tire-testing lab for measurement.

This paper presents results from recent studies on using pulse inputs to generate simulated and experimental frequency responses. The purpose of the paper is to disseminate information on the application of pulse testing methods, and to compare the results with frequency response results obtained using other methods. Frequency responses were generated from a vehicle handling dynamics simulation, from full-scale vehicle handling tests, and from dynamic tire tests. The requirements on the input pulses used to drive the systems under study are discussed, including pulse size, shape, and duration, and the corresponding pulse frequency content and power spectral densities. Pulse testing is generally faster and cheaper than the alternative test methods, and for the case of full-scale vehicle testing, requires much less test area.