Search Results

The characteristics, functionality, limitations, and applications of mid-level driving simulators are reviewed and discussed. For this paper a mid-level simulator is defined as one which has a large roadway scene display typically comprising animated computer graphics, it may have a motion system or be fixed base, it should have a dedicated cab with a steering feel system and interactive controls and displays, it has a parametrically configurable vehicle dynamics model, data acquisition is provided for, and the simulator is intended to be used for driver behavior research and vehicle or highway research and development studies. Possible simulator sickness issues are discussed, and categories of mid-level driving simulator applications are noted. Approximately 20 different contemporary driving simulators are included in the survey.

Interactive driving simulation is attractive for a variety of applications, including screening, training and licensing, due to considerations of safety, control and repeatability. However, widespread dissemination of these applications will require modest cost simulator systems. Low cost simulation is possible given the application of PC level technology, which is capable of providing reasonable fidelity in visual, auditory and control feel cuing. This paper describes a PC based simulation with high fidelity vehicle dynamics, which provides an easily programmable visual data base and performance measurement system, and good fidelity auditory and steering torque feel cuing. This simulation has been used in a variety of applications including screening truck drivers for the effects of fatigue, research on real time monitoring for driver drowsiness and measurement of the interference effect of in-vehicle IVHS tasks on driving performance.

The physical forces applied to vehicle inertial dynamics derive primarily from the tires. These forces have a profound effect on handling. Tire force modeling therefore provides a critical foundation for overall vehicle dynamics simulation. This paper will describe the role tire characteristics play in handling, and will discuss modeling requirements for appropriately simulating these effects. Tire input and output variables will be considered in terms of their relationship to vehicle handling. General computational requirements will be discussed. An example tire model will be described that allows for efficient computational procedures and provides responses over the full range of vehicle maneuvering conditions.

A combined biodynamic and vehicle model is used to assess the vibration and performance of a human operator performing driving and other tasks. The other tasks include reaching, pointing and tracking by the driver and/or passenger. This analysis requires the coordinated use of separate and mature software programs for anthropometrics, vehicle dynamics, biodynamics, and systems analysis. The total package is called AVB-DYN, an acronym for Anthropometrics, Vehicle, and Bio-DYNamics. The objectives and architecture are discussed, and then a preliminary version of this package is demonstrated in an example where a HMMWV (High Mobility Multipurpose Wheeled Vehicle) operator is performing a driving task.

A combined biodynamic and vehicle model is used to assess the vibration and performance of a human operator performing driving and other tasks. The other tasks include reaching, pointing and tracking by the driver and/or passenger. This analysis requires the coordinated use of separate and mature software programs for anthropometrics, vehicle dynamics, biodynamics, and systems analysis. The total package is called AVB-DYN, an acronym for Anthropometrics, Vehicle and Bio-DYNamics. The biodynamic component of AVB-DYN is described, and then compared with an experiment that studied human operator in-vehicle reaching performance using the U.S. Army TACOM Ride Motion Simulator.

Typically, driver interactions with in-vehicle devices such as navigation systems have been accomplished using a visual-manual interface. As a result of recent advances in technology, voice activated interfaces are being introduced, which reduce or eliminate the need for manual inputs and related visual scanning. This paper compares driver use of contemporary examples of the 2 different types of interface for several types of navigation destination entry tasks based on over-the-road evaluations. These data include glance behavior, HMI interactions (manual inputs, etc.), driver/vehicle response and performance including lane deviations, and subjective ratings. In general, the results show that, for a given task, the example contemporary voice activated systems result in fewer glances, shorter glance durations, fewer entry steps, improved driver/vehicle performance, and improved subjective ratings for ease of task accomplishment and mental workload.

A Grade Severity Rating System (GSRS) was developed as a means for reducing the incidence and severity of truck accidents on downgrades. The ultimate result is a roadside sign at the top of each hill. The sign is tailored to the individual hill and gives a recommended maximum speed (to be held constant for the entire grade descent) for each of several truck weight ranges. This concept represents a major step forward in terms of grade descent safety because it tells the driver what to do directly, rather than giving him information which still requires evaluation under different loading conditions.

Full-scale vehicle response tests were conducted on five vehicles using a crosswind disturbance test facility capable of providing a 35 mph wind over a nominal 120 ft test length. The vehicles were a Honda Accord, Chevrolet station wagon, Ford Econoline van, VW Microbus, and Ford pickup/camper. Results showed that passenger cars, station wagons, and most vans have virtually no crosswind sensitivity problems, whereas the VW Microbus, the pickup/camper (in winds higher than 35 mph), and cars pulling trailers do have potential problems. Key vehicle parameters dictating this yaw response sensitivity are the distance between the aerodynamic and tire force centers, tire restoring moment (including understeer gradient), and the basic aerodynamic side forces. A simple analytical relationship in these terms was developed to predict steady-state yaw rate in steady winds.

Models have been developed to describe the dynamic response and performance of drivers, vehicles, and driver-vehicle systems; and recent experiments have provided some quantification and refinement. This paper summarizes the theory and the data, and attempts to provide part of the transition between properties of the human and the assessment of safety performance in driving. The model and data shown emphasize steering or directional control situations. Simulation experiments with random crosswind gust disturbances were used to measure driver-vehicle describing functions for a number of driver subjects and experimental replications. The results are consistent with previous data and show good repeatability within subjects on successive runs. Interpretation of the data in terms of the driver-vehicle model indicates that the driver's outputs can be explained in simplest terms as functions of lateral position and heading.

Driver response and performance can be quantified by observing the stimulus-response environment. Yet the driver's inherent adaptability allows him to have seemingly adequate performance in potentially hazardous driving situations even though he may be operating near the acceptable safety limits. Physiological measures of the driver's internal state can provide further quantification of his performance level and can give a measure of his workload or safety performance margin. Measures of driver physiological and control responses have been made under gust disturbance conditions with the subject's car operating at various speeds. The experimental techniques and data are described, and correlations between the situational parameters and driver stress and control response are shown.

This paper presents the results of aerodynamic measurements made on six full scale vehicles in a large cross section wind tunnel. The vehicles included a sports car, subcompact sedan, intermediate-sized sedan, two vans, and a full-sized station wagon. Criteria for the selection of the wind tunnel facility is described. Aerodynamic data is then presented as non-dimensional lateral and longitudinal coefficients for yaw angles between +40 to -180 deg. Results are compared to previous model and full scale tests.

This paper highlights the results of a program to study the effects of truck aerodynamics, splash, and spray. The approach has involved state of the art review and assessment, analysis, laboratory tests, model scale wind tunnel experiments, full scale tests, cost effectiveness analysis, and field evaluations. This paper summarizes the latter activities. The emphasis has been on devices fixed to trucks which can modify the air flow properties around the truck and reduce the formation and propagation of splash and spray as experienced by adjacent motorists. Such devices have been conceptualized, developed as prototypes, and tested under full scale and over the road conditions.

The results of a wind tunnel study and a computer simulation are used to determine the effects of aerodynamics on the lateral-directional stability and crosswind response of passenger car/utility trailer combinations. Single and tandem axle utility trailer configurations, with and without drag reducing add-on aerodynamic fairings, were considered with both sedan and station wagon tow cars. Results showed that including aerodynamic terms in the six degree of freedom model reduces the trailer tow angle stability and damping by a few percent. More importantly, the random crosswind response, expressed in terms of tow car yaw velocity, was amplified about 20 to 30 percent when a drag reducing device was added to the trailer.

This paper reviews and expands previously published driver steering control models. The driver model is structured to control vehicle heading angle and lane position. Field test data are used to validate model structure. The closed-loop stability of the driver/vehicle system is analyzed using a two degree of freedom vehicle dynamics approximation. This analysis is used to develop constraints among the various driver model parameters and their dependence on vehicle characteristics. Driver/vehicle model approximations are also used to explore the effects of driver behavior on steering performance.

The driver's ability to control the lateral position of an automobile is dependent on his perception of the command path (roadway) to be followed. This perception is affected by both the configuration of road markings and other features, and the visibility of these elements. As visibility decreases, the driver's preview of the commanded path is reduced. Theory indicates that driver performance should degrade with reduced preview and configurational parameters which characterize the intermittent nature of delineation (e.g., dashed lines). This paper describes a simulation experiment in which driver behavior and driver/vehicle system performance were measured over a range of visibility and configuration parameter variations. Driver dynamic response and noise (remnant) were reliably affected by variations in visibility and configuration. These effects were also reflected in system performance measures such as lane deviations.

For almost twenty years, researchers have attempted to develop an in-vehicle system which would prevent an impaired driver from operating his or her motor vehicle. These systems have ranged from breath testers to psychomotor tests, and have prevented operation of the vehicle by such methods as preventing the vehicle from starting or alerting drivers, and the police through alarm systems. This paper discusses the background leading to an in-vehicle system which was built and tested. We also discuss the system and its components, and present the results of two tests involving convicted drunk drivers. While the primary purpose of this project was to determine the feasibility of this type of system, the results of the two tests show promise for the reduction of impaired driving trips.

This paper presents test methods and modeling procedures for identifying the directional handling characteristics of vehicles over the full maneuvering range from straight running to limit cornering and/or braking. The test procedures are designed to validate steady-state and dynamic response performance. The model parameters are derived from simple static tests of vehicle properties and tire parameters identified from tire machine tests. Current steady-state field test procedures validate the model response under cornering only conditions. Model analysis then extrapolates vehicle response under combined cornering and braking conditions. Some discussion is devoted to potential braking in a turn transient testing for more complete model validation.

This paper presents an analysis of driver/vehicle performance over a range of maneuvering conditions including accident avoidance scenarios involving vehicle limit performance handling. Driver behavior is considered in the same dynamic analysis terms as vehicle response in order to give appropriate closed-loop measures of total system maneuvering capability and handling stability. A driver control structure is developed along with closed-loop system stability constraints on model parameters over a wide range of vehicle maneuvering conditions. Example simulation runs are presented for several accident avoidance scenarios.

Handling and stability problems are typically revealed under limit performance maneuvering conditions where tires are pushed to high slip angles under high normal loading conditions. This paper reviews vehicle dynamics handling and stability models relative to tire characteristics and examines tire testing data obtained under normal and extreme maneuvering conditions. Tire data is normalized according to design characteristics in order to reveal basic maneuvering behavior that is relatively independent of size and construction. Computer simulation analysis is used to demonstrate the influence of tire characteristics on handling and stability.

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.