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This paper describes validation work carried out for two vehicle dynamics computer simulation programs. One program, referred to as VDANL (Vehicle Dynamics Analysis NonLinear), is intended to simulate passenger cars, vans and light trucks. The second program simulates All Terrain Vehicles (ATVs) and is referred to as NLATV (NonLinear ATV). The programs have been checked out and validated for a variety of maneuvering conditions and a broad range of vehicles. The programs run on IBM-PC/MS DOS compatible computers, and numerical methods have been used to give numerically stable solutions with reasonable computational speed over a broad range of maneuvering situations.

Automatic and four wheel steering control laws are often developed from the performance point of view to optimize rapid response. Under linear tire operating conditions (i.e., maneuvering at less than .5g's) both performance and safety conditions can be simultaneously met. Under severe operating conditions, such as might be encountered during crash avoidance maneuvering, tire characteristics can change dramatically and induce directional dynamic instability and spinout. The challenge in automatic and four wheel steering system design is to achieve a compromise between performance and safety. This paper will describe analyses carried out with a validated vehicle dynamics computer simulation that shed some light on the vehicle and control characteristics that influence tradeoffs between performance and safety. The computer simulation has been validated against field test data from twelve vehicles including passenger cars, vans, pickup trucks and utility vehicles.

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.

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 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.

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.