Search Results

This paper presents the results from an experimental project involving the full-scale testing of vehicles in a variety of maneuvers. The maneuvers include tripped rollover maneuvers resulting from impacts of eight test vehicles with both soil and curb pavement discontinuities. The reduced data from experimental tests form the impact condition variables which are augmented with vehicle design parameters in the analysis of results. The data are analyzed in datasets created according to such criteria as maneuver type, maneuver result, and type of terrain discontinuity. These results are investigated on the basis of mean values and coefficients of correlation. Results throughout the study support the conclusion that soil-tripped rollover maneuvers are qualitatively different than curb-tripped rollover maneuvers.

Computer simulations are frequently used to investigate vehicle motion in various maneuvers. Although a wide range of maneuvers and types of vehicle motion can presently be simulated by computer, most current vehicle dynamics simulations do not model vehicle behavior once a roadway or roadside barrier is encountered by a vehicle or once vehicle rollover occurs. If the forces generated through such vehicle body and terrain interactions can be accurately modelled, then computer simulation capabilities can be extended to include post-barrier-impact and post-rollover vehicle motion. This paper describes the development of a vehicle-terrain impact model. The terrain is modelled to represent a roadway, either level or sloped, as well as roadside hazards such as curbs, ditches, and guard rails.

A reliable dynamic measure to predict vehicle rollover under various conditions must be developed in order to quantitatively analyze the rollover propensities of vehicles. Several efforts have been made and are introduced in this paper on the development of such a dynamic measure of vehicle rollover stability. The position of the axis about which a vehicle rolls over (rollover axis) must be determined prior to developing a vehicle rollover propensity measure. For this reason, an investigation into the central axis concept was first performed. However, as shown in the paper, the unpredictability of the central axis position of the vehicle leads to the analyses of three other possible rollover axes. Investigations into the kinetic and potential energies of the vehicle system and its components have resulted in the modification and the extension of a previously developed energy based function called Rollover Prevention Energy Reserve (RPER).

This paper describes the development and validation of an advanced microcomputer based simulation developed to investigate the complex dynamic responses of light vehicles in a variety of maneuvers. These maneuvers include cornering with braking or acceleration as well as vehicle skidding, spinning, and rolling over. A three-dimensional, non-linear vehicle dynamic model having eight degrees-of-freedom is generated according to user specifications. Multiple masses are connected through suspension elements to properly account for vehicle forward, lateral, vertical, roll, pitch, and yaw directional dynamics. To build an accurate model, any one of 8 different commonly used front suspension systems can be employed in conjunction with any one of 19 different rear independent, semi-independent, and dependent suspension systems. The capability of implementing various suspension systems allows the utilization of important kinematic and dynamic effects of these suspensions on vehicle response.

Recently, a great deal of attention has been focused on the development of four wheel steering systems (4WS) for passenger vehicles in order to enhance their handling properties. At high speeds vehicle response can be enhanced by steering the rear wheels in the same direction as those in the front, while at low speeds vehicle maneuverability can be enhanced by turning front and rear wheels in opposite directions. Much of the current theoretical literature explores various methods which can be employed to control the steer angle of the rear wheels. The results of these papers are usually based on analysis of the classic two degree of freedom linear bicycle model. This paper presents the development of a vehicle model which is capable of simulating the dynamic behavior of a passenger car and includes many important effects ignored by the two degree freedom bicycle model.

A variety of suspensions are used in light vehicles and they affect dynamics of vehicles in various ways. The components of lateral and longitudinal weight transfers, which depend upon suspension design, influence the wheel normal loads, tire characteristics, and tire-roadway limits of adhesion which in consequence determine vehicle stability. Modeling procedures for nonlinear kinematic and dynamic analysis of 25 commonly used light vehicle suspensions have been developed and applied to investigate the spatial movement of vehicle roll axis. A nonlinear tire model based on a friction ellipse concept and capable of accepting CALSPAN tire data has been developed to compute cornering forces as functions of slip angle variables, normal loads, tire adhesion characteristics and skid numbers.