The study of the influence of the pneumatic defects on the vehicle’s dynamics
H. Shraim, M. Ouladsine, H. Noura and M. El Adel
LSIS UMR 6168
Domaine Universitaire st Jérôme
Av escadrille de Normandie Niemen
13397 Marseille Cedex 20
Tél : (33) (0)491056062 - Email : mustapha.ouladsine@lsis.org
Abstract
Ever since, in the study of the dynamics of the vehicle, the influence of the inflation pressure of the tire on the longitudinal and the side forces, the radius of the tire and the surface of contact with the ground has rarely been approached and studied in the literature. The principle goal of this paper relates to the modeling of the behavior of all these forces in terms of the inflation pressure of the tire.
I- Introduction
During the last decades, it was noticed that many accidents of vehicles were caused by failures of tires. Thus the study of the components which influence the forces caused by the interaction between the tire and the ground as well as friction is very important to specify the principal causes of these failures. This study makes it possible to give an important automatic preview for the dynamics of the vehicle making it possible to stabilize its trajectory or to maintain the safety for the driver in the case of sudden occurrences of these failures. Many works were carried out in the field of the modelisation of the tires and they cover models from simplest one aiming to explain the basic behavior of the tire to models based on the finite elements approximations which make it possible to view with high precision the behavior of the tire [1-7].
The motivation of this paper is to treat the effects of the inflation pressure on the variation of lateral and longitudinal forces which influence the total stability of the vehicle. Another objective is to determine the accepted limits of the inflation pressure that the tire should not exceed in order to maintain a reliable operation. This paper is organized as the following:
The second section deals with the definition and the principle of construction of the tire arriving to the structures that are used in the last decades which are the diagonal structure girdled diagonal structure, Radial structure. Section III deals with the modelisation of the wheel and the forces that are generated due to the contact with the ground. In this section, we define and express the effect of the inflation pressure on these forces and on the variation of the radius of the wheel. Simulation results are given in section IV.
II- Definition and principle of construction
The tire, which is the only part in contact with the ground, constitutes one of the essential parts of the vehicle. All the interaction forces between the ground and the vehicle are thus transmitted through this small surface. The choice of the model of the tire influences the calculation of these forces. Therefore, the modeling of these efforts is essential for the dynamic behavior of the vehicle.
The tire is a mechanical structure, covered with rubber, consisted of cables orderly distributed (placed) according to a specified structure so that they give it certain mechanical properties which are necessary for it’s good behavior. One of the important roles of the tire is to maintain under a nearly constant pressure a certain volume of air, which has as a role to support the vertical load.
The tire is the element of interface between the vehicle and the ground; it hardly influences the behavior of the vehicle. Its capacity to transmit efforts is thus of primary importance for a good behavior. Its damping coefficients absorb the vibratory requests generated by the road.
Tires vary according to their structure; we distinguish many types of the tires:
Diagonal structure:
It is a structure in which the various “napes” are crushed alternatively ones on the others, this tire has a good rigidity and can become deformed without damaged under the rim. The inconvenient of this tire is that it heats quickly, and this heating causes a great variation of the coefficient of friction.
Girdled diagonal structure:
This structure is identical to the preceding one with a light evolution in mounting, a girdled part limits the frontal deformation but without solving all the problems of heating.
Radial structure:
In this structure, the tire is stabilized by a belt made up of several crossed (90°) napes, and the structure also includes cables laid out in right arches. This
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