Page 324 - Automotive Engineering Powertrain Chassis System and Vehicle Body

11.1
Chapter 11.1

Tyre characteristics and vehicle

handling and stability

Hans Pacejka

11.1.1 Introduction the vehicle at higher lateral accelerations. The load de-
pendency of the curves, notably the non-linear relation-
This chapter is meant to serve as an introduction to ve- ship of cornering stiffness with tyre normal load has
hicle dynamics with emphasis on the influence of tyre a considerable effect on the handling characteristic of the
properties. Steady-state cornering behaviour of simple car. For the (quasi) steady-state handling analysis simple
automobile models and the transient motion after small single-track (two-wheel) vehicle models will be used.
and large steering inputs and other disturbances will be Front- and rear-axle effective side force characteristics
discussed. The effects of various shape factors of tyre are introduced to represent effects that result from
characteristics (cf. Fig. 11.1-1) on vehicle handling suspension and steering system design factors such as
properties will be analysed. The slope of the side force F y steering compliance, roll steer and lateral load transfer.
vs slip angle a near the origin (the cornering or side slip Also the effect of possibly applied (moderate) braking
stiffness) is the determining parameter for the basic
linear handling and stability behaviour of automobiles. and driving forces may be incorporated in the effective
The possible offset of the tyre characteristics with re- characteristics. Large braking forces may result in wheel
spect to their origins may be responsible for the occur- lock and possibly large deviations from the undisturbed
rence of the so-called tyre-pull phenomenon. The further path. The application of the handling and stability theory
non-linear shape of the side (or cornering) force charac- to the dynamics of heavy trucks will also be briefly dealt
teristic governs the handling and stability properties of with in the present chapter. Special attention will be

Fig. 11.1-1 Characteristic shape factors (indicated by points and shaded areas) of tyre or axle characteristics that may influence vehicle
handling and stability properties. Slip angle and force and moment positive directions.
Tyre and Vehicle Dynamics; ISBN: 9780750669184
Copyright Ó 2005 Hans Pacejka. All rights of reproduction, in any form, reserved.