Article

Road crown, tire, and suspension effects on vehicle straight-ahead motion

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Abstract

During normal operating conditions, a motor vehicle is constantly subjected to a variety of forces, which can adversely affect its straight-ahead motion performance. These forces can originate both from external sources such as wind and road and from on-board sources such as tires, suspension, and chassis configuration. One of the effects of these disturbances is the phenomenon of vehicle lateral-drift during straight-ahead motion. This paper examines the effects of road crown, tires, and suspension on vehicle straight-ahead motion. The results of experimental studies into the effects of these on-board and external disturbances are extremely sensitive to small changes in test conditions and are therefore difficult to guarantee repeatability. This study was therefore conducted by means of computer simulation using a full vehicle model. The purpose of this paper is to gain further understanding of the straight-ahead maneuver from simulation results, some aspects of which may not be obtainable from experimental study. This paper also aims to clarify some of the disputable arguments on the theories of vehicle straight-ahead motion found in the literature. Tire residual aligning torque, road crown angle, scrub radius and caster angle in suspension geometry, were selected as the study variables. The effects of these variables on straight-ahead motion were evaluated from the straight-ahead motion simulation results during a 100m run in free control mode. Examination of vehicle behavior during straight-ahead motion under a fixed control mode was also carried out in order to evaluate the validity of several disputable arguments on vehicle pull theory, found in the literature. Finally, qualitative comparisons between the simulation results and the test results were made to support the validity of the simulation results.

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... However, due to increasing suspension compliance they are dependent on the load case as well [1] [5] [8]. Although they are regarded as lever arms referring to steering torque, they are also used for studying vehicle behavior, such as straight-line behavior [9] [10] [11]. ...
... This is important, for example, to further analyze and evaluate vehicle straight-line behavior, as [5] already refers to. Though several authors have already studied the influence of the suspension system on straightline behavior, they have only analyzed it with reference to characteristic values resulting from the kinematic steering axis, which characterize steering feedback, such as scrub radius and caster trail [10] [11] [12] [13]. Characteristic values describing wheel movement, such as toe behavior, and thus vehicle motion have yet to be considered. ...
... The second method is to estimate the lateral shift of the vehicle in the same conditions, without any interference of the costumer on the wheel. (LEE et al., 2005). ...
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