ISO 8855:2011
(Main)Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
ISO 8855:2011 defines the principal terms used for road vehicle dynamics. The terms apply to passenger cars, buses and commercial vehicles with one or more steered axles, and to multi-unit vehicle combinations.
Véhicules routiers — Dynamique des véhicules et tenue de route — Vocabulaire
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INTERNATIONAL ISO
STANDARD 8855
Second edition
2011-12-15
Road vehicles — Vehicle dynamics and
road-holding ability — Vocabulary
Véhicules routiers — Dynamique des véhicules et tenue de route —
Vocabulaire
Reference number
©
ISO 2011
© ISO 2011
The reproduction of the terms and definitions contained in this International Standard is permitted in teaching manuals, instruction
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that no modifications are made to the terms and definitions; that such reproduction is not permitted for dictionaries or similar publications
offered for sale; and that this International Standard is referenced as the source document.
With the sole exceptions noted above, no other part of this publication may be reproduced or utilized in any form or by any means,
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Published in Switzerland
ii © ISO 2011 – All rights reserved
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Axis system.1
3 Vehicle unit.5
4 Vehicle geometry and masses.6
5 Vehicle motion variables .8
5.1 Linear motion variables .8
5.2 Angular motion variables .10
5.3 Terms relating to vehicle trajectory measures.14
6 Forces and moments .15
6.1 Forces.15
6.2 Moments.16
7 Suspension and steering geometry .16
7.1 Steer and camber angles .16
7.2 Steering-axis geometry.20
8 Kinematics and compliances.23
8.1 Kinematics.23
8.2 Compliances.25
9 Ride and roll stiffness.25
10 Tyres.26
10.1 Tyre geometry.26
10.2 Tyre forces and moments.27
10.3 Terms relating to tyre measures.28
11 Input types and control modes.30
11.1 Input types.30
11.2 Control modes .30
12 Responses.31
12.1 General response types.31
12.2 Equilibrium and stability.31
12.3 Lateral response measures.32
12.4 Understeer and oversteer measures .33
Annex A (informative) Comments on terms and definitions .37
Bibliography.39
Alphabetical index.40
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
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International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 8855 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 9, Vehicle
dynamics and road-holding ability.
This second edition cancels and replaces the first edition (ISO 8855:1991), which has been technically
revised. It also incorporates the Addendum ISO 8855:1991/Add.1:1992.
iv © ISO 2011 – All rights reserved
Introduction
This International Standard defines terms appertaining to road vehicle dynamics, principally for use by design,
simulation and development engineers in the automotive industries. This second edition has been prepared in
response to a requirement to update the first, and to harmonize its contents with that of the comparable
standard published by SAE International (SAE J670:JAN2008). This revision extends the scope to include
provision for separate tyre and wheel axis systems, inclined and non-uniform road surfaces, tyre forces and
moments, multiple unit commercial vehicles, and two-axle vehicles possessed of four-wheel steer geometry.
The vocabulary contained in this International Standard has been developed from the previous edition, and
SAE J670, in order to facilitate accurate and unambiguous communication of the terms and definitions
employed in the test, analysis and general description of the lateral, longitudinal, vertical and rotational
dynamics of road vehicles.
INTERNATIONAL STANDARD ISO 8855:2011(E)
Road vehicles — Vehicle dynamics and road-holding ability —
Vocabulary
1 Scope
This International Standard defines the principal terms used for road vehicle dynamics. The terms apply to
passenger cars, buses and commercial vehicles with one or more steered axles, and to multi-unit vehicle
combinations.
2 Axis system
2.1
reference frame
geometric environment in which all points remain fixed with respect to each other at all times
2.2
inertial reference frame
Newtonian reference frame
reference frame (2.1) that is assumed to have zero linear and angular acceleration and zero angular velocity
NOTE In Newtonian physics, the Earth is assumed to be an inertial reference frame.
2.3
axis system
set of three orthogonal directions associated with X, Y and Z axes
GGG
NOTE A right-handed axis system is assumed throughout this International Standard, where: Z=×XY .
2.4
coordinate system
numbering convention used to assign a unique ordered trio (x, y, z) of values to each point in a reference
frame (2.1), and which consists of an axis system (2.3) plus an origin point
2.5
ground plane
horizontal plane in the inertial reference frame (2.2), normal to the gravitational vector
2.6
road surface
surface supporting the tyre and providing friction necessary to generate shear forces in the road plane (2.7)
NOTE The surface may be flat, curved, undulated or of other shape.
2.7
road plane
plane representing the road surface (2.6) within the tyre contact patch
NOTE 1 For an uneven road, a different road plane may exist at each tyre contact patch.
NOTE 2 For a planar road surface, the road plane is coincident with the road surface. For road surfaces with surface
contours having a wavelength similar to or less than the size of the tyre contact patch, as in the case of many ride events,
it is intended that an equivalent road plane be determined. Determination of the equivalent road plane is dependent on the
requirements of the analysis being performed. The equivalent road plane may not be coincident with the actual road
surface at the contact centre (4.1.4).
2.7.1
road plane elevation angle
λ
angle from the normal projection of the X axis on to the ground plane (2.5) to the X axis
T T
2.7.2
road plane camber angle
η
angle from the normal projection of the Y axis on to the ground plane (2.5) to the Y axis
T T
2.8
earth-fixed axis system
(X , Y , Z )
E E E
axis system (2.3) fixed in the inertial reference frame (2.2), in which the X and Y axes are parallel to the
E E
ground plane (2.5), and the Z axis points upward and is aligned with the gravitational vector
E
NOTE The orientation of the X and Y axes is arbitrary and is intended to be based on the needs of the analysis or test.
E E
2.9
earth-fixed coordinate system
(x , y , z )
E E E
coordinate system (2.4) based on the earth-fixed axis system (2.8) with an origin that is fixed in the
ground plane (2.5)
NOTE The location of the origin is generally an arbitrary point defined by the user.
2.10
vehicle axis system
(X , Y , Z )
V V V
axis system (2.3) fixed in the reference frame (2.1) of the vehicle sprung mass (4.12), so that the X axis is
V
substantially horizontal and forwards (with the vehicle at rest), and is parallel to the vehicle's longitudinal plane
of symmetry, and the Y axis is perpendicular to the vehicle's longitudinal plane of symmetry and points to the
V
left with the Z axis pointing upward
V
See Figure 1.
NOTE 1 For multi-unit combinations a separate vehicle axis system may be defined for each vehicle unit (3.1)
(see Figure 2).
NOTE 2 The symbolic notation (X , Y , Z ), (X , Y , Z ), …, (X , Y , Z ) may be assigned to the vehicle
V,1 V,1 V,1 V,2 V,2 V,2 V,n V,n V,n
axis systems of a multi-unit combination with n vehicle units (3.1).
2.11
vehicle coordinate system
(x , y , z )
V V V
coordinate system (2.4) based on the vehicle axis system (2.10) with the origin located at the vehicle
reference point (2.12)
2.12
vehicle reference point
point fixed in the vehicle sprung mass (4.12)
NOTE The vehicle reference point may be defined in a variety of locations, based on the needs of the analysis or test.
Commonly used locations include the total vehicle centre of gravity, the sprung mass centre of gravity, the mid-wheelbase
(4.2) point at the height of the centre of gravity, and the centre of the front axle. For multi-unit combinations, a vehicle
reference point may be defined for each vehicle unit (3.1).
2 © ISO 2011 – All rights reserved
2.13
intermediate axis system
(X, Y, Z)
axis system (2.3) whose X and Y axes are parallel to the ground plane (2.5), with the X axis aligned with the
vertical projection of the X axis on to the ground plane (2.5)
V
See Figure 1.
NOTE 1 For multi-unit combinations, a separate intermediate axis system may be defined for each vehicle unit (3.1).
NOTE 2 The intermediate axi
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