ISO 12021-1:1996
(Main)Road vehicles — Sensitivity to lateral wind — Part 1: Open-loop test method using wind generator input
Road vehicles — Sensitivity to lateral wind — Part 1: Open-loop test method using wind generator input
Gives an open-loop test method to determine the sensitivity to lateral wind of a vehicle by means of a wind generator. It applies to passenger cars as defined in ISO 3833, passenger car-trailer combinations and light trucks.
Véhicules routiers — Sensibilité au vent latéral — Partie 1: Méthode en boucle ouverte avec génération de vent
General Information
Relations
Standards Content (Sample)
INTERNATIONAL
IS0
STANDARD
12021-1
First edition
1996-08-I 5
Road vehicles - Sensitivity to lateral
wind -
Part 1:
Open-loop test method using wind generator
input
V6hicules routiers
- SensibiW au vent la t&al -
Pat-tie 1: M&hode en boucle ouverte avec g&n&ration de vent
Reference number
IS0 12021-1:1996(E)
---------------------- Page: 1 ----------------------
IS0 12021=1:1996(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide fed-
eration of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for
which a technical committee has been established has the right to be rep-
resented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. IS0 col-
laborates closely with the International Electrotechnical Commission (IEC)
on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are cir-
culated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 12021-I was prepared by Technical Committee
lSO/TC 22, Road vehicles, Subcommittee SC 9, Vehicle dynamics and
road-holding ability.
IS0 12021 will consist of the following parts, under the general title Road
vehicles - Sensitivity to lateral wind
Part 7: Open-loop test method using wind generator input
Part 2: Semi open-loop test method using natural wind input
Annexes A and B form an integral part of this part of IS0 12021.
0 IS0 1996
All rights reserved. Unless otherwise specified, no part of this publication may be repro-
duced or utilized in any form or by any means, electronic or mechanical, including photo-
copying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
---------------------- Page: 2 ----------------------
IS0 12021=1:1996(E)
@ IS0
Introduction
The dynamic behaviour of road vehicles is a most important part of active
vehicle safety. Any given vehicle, together with its driver and the prevailing
environment, forms a unique closed-loop system. The task of evaluating
dynamic behaviour is therefore very difficult because of the significant in-
teraction of the driver, vehicle and road elements, each of which is in itself
complex. A complete and accurate description of the behaviour of the road
vehicle must necessarily involve information obtained from a number of
tests of different types.
The results of the test described in this part of IS0 12021 quantify only a
small part of the whole handling field. Hence, the results of a test can be
considered significant only for a correspondingly small part of the overall
dynamic behaviour.
Moreover, insufficient knowledge is available concerning the relationship
between accident risk and the dynamic characteristics evaluated by the
test described in this part of IS0 12021. A substantial amount of effort is
necessary to acquire sufficient and reliable data on the correlation be-
tween accident risk and the characteristics of vehicle dynamics in general
and the results of this test in particular.
Therefore, it is not possible to use this method and test results for regu-
lation purposes at present. The best that can be expected is that the sensi-
tivity to lateral wind test is used as one among many other mostly
transient tests, which together cover the field of vehicle dynamic
behaviour.
---------------------- Page: 3 ----------------------
This page intentionally left blank
---------------------- Page: 4 ----------------------
IS0 12021-1:1996(E)
INTERNATIONAL STANDARD o IsO
- Sensitivity to lateral wind -
Road vehicles
Part 1:
Open-loop test method using wind generator input
3 Principle
1 Scope
The purpose of this test method is to determine ve-
This part of IS0 12021 specifies an open-loop test
hicle sensitivity to lateral wind by which the vehicle
method to determine the sensitivity to lateral wind of
motion is disturbed.
a vehicle by means of a wind generator. It applies to
passenger cars as defined in IS0 3833, passenger
This method requires the measurement of vehicle be-
car-trailer combinations and light trucks. Its applica-
haviour under a lateral wind condition. The vehicle be-
bility to motorcycles is yet to be investigated.
haviour can be characterized by several measures.
The test conditions specified in this test method are
In this test method the vehicle is initially driven along
not representative of real driving conditions but are
a straight path and its response to a crosswind input
useful to obtain measures of vehicle dynamic re-
of a wind generator is then measured. The steering-
sponse to lateral wind.
wheel is held fixed during most of the test.
NOTE 1 The test conditions in this test method do not
Two methods for finding the lateral deviation are pro-
simulate natural wind conditions. However, the wind vel-
posed
ocity proposed here is representative of fairly severe wind
conditions occurring naturally.
- a direct method by means of direct measurement
or with a dye-trail left on the road surface, and
- an indirect method by means of a computation
from on-board-measured vehicle motions.
2 Normative references
The following standards contain provisions which,
through reference in this text, constitute provisions of
4 Reference system
this part of IS0 12021. At the time of publication, the
editions indicated were valid. All standards are subject
The variables of motion used to describe the effect of
to revision, and parties to agreements based on this
lateral wind on course holding and directional behav-
part of IS0 12021 are encouraged to investigate the
iour of the vehicle relate to the intermediate axis sys-
possibility of applying the most recent editions of the
tem (X, Y, 2) as defined in IS0 8855.
standards indicated below. Members of IEC and IS0
maintain registers of currently valid International Stan-
dards.
5 Variables
IS0 1176:1990, Road vehicles - Masses - Vocabu-
The following variables corresponding to the terms
lary and codes.
and definitions of IS0 8855 shall be measured:
IS0 3833:1977, Road vehicles - Types - Terms and
- yaw velocity, y?;
definitions.
- lateral acceleration, a~;
IS0 8855:1991, Road vehicles - Vehicle dynamics
- steering-wheel angle, &;
and road-holding ability - Vocabulary.
---------------------- Page: 5 ----------------------
@ IS0
IS8 12021-1:1996(E)
- longitudinal velocity, vX; 6.2 Transducer installation
The transducers shall be installed according to the
It is optional to measure the additional variables:
manufacturer’s instructions, where such instructions
exist, so that the variables corresponding to the terms
- lateral deviation, y;
and definitions of IS0 8855 can be determined.
- roll angle, c;p;
If the transducer does not measure the variable di-
- sideslip angle, p; rectly, appropriate transformations into the reference
system shall be carried out.
- lateral velocity, vY.
6.2.ll Lateral deviation
The variables listed in this clause are not intended to
The lateral deviation may be measured either by direct
comprise a complete list.
measurement using appropriate instrumentation or by
means of a dye-trail, or by means of a computational
method (see 10.5). The dye-trail shall be made on the
test track by means of a water jet. The water outlet
should be 0,OZ m above the track surface. Elastic tube
may be used to extend this outlet.
6 Measuring equipment
The water jet should be positioned as close as poss-
ible to the z-axis of the intermediate axis system. If
6.1 Description
this is not the case, a correction can be applied to
achieve values within the tolerance for lateral accel-
The variables selected from those listed in clause 5
eration.
shall be measured by means of appropriate trans-
ducers. Their time histories shall be recorded on a
multi-channel recorder having a time base. This is not
6.3 Data processing
obligatory for lateral deviation, which can be measured
directly after the test has been completed.
The frequency range relevant to this test is between
0 Hz and the maximum utilized frequencyf,,, = 5 Hz.
The typical operating ranges of the variables and rec-
According to the chosen data processing method,
ommended maximum errors of the combined trans-
analog or digital data processing, the stipulations given
ducers and the recording system are shown in table 1.
in 6.3.1 or 6.32 shall be observed.
Table 1 -Typical operating ranges of the variables and recommended maximum errors of transducers
and recording system
Variable Range of variable
Steering-wheel angle - 30” to + 30” *) + lo, but resolution < 0,3’
Longitudinal velocity 0 m/s to 40 m/s + 0,4 m/s
Lateral deviation k 0,02 m
Roll angle - IO” to + IO0
Sideslip angle - 5” to + 5”
Lateral velocity -10m/sto+10m/s
k 0,4 m/s
NOTES
1 These values are tentative and provisional until more data are available.
2 Transducers for some of the listed variables are not widely available and are not in general use. Many such instruments
are developed by users. If any system error exceeds the recommended maximum value, this and the actual maximum error
shall be stated in the test report (see annex A).
*) Assuming a conventional steering system
2
---------------------- Page: 6 ----------------------
@ IS0 IS0 12021=1:1996(E)
6.3.1 Analog data processing ensure that time delay differences lie within the re-
quired accuracy fo r time measurements.
The bandwidth of the e ntire combined tra nsducer/
no less than 8 H Z. Additional filtering shall be avoided in the data acqui-
reco Irding system shall be
sition string.
Low-pass filters with order four or higher shall be
Amplification of the signal shall be such that, in re-
employed to filter the signals. The width of the pass-
- 3 dB shall not be less than lation to the digitizing process, the additional error is
band frequency f. at
8 Hz. Amplitude errors shall be less than It 0,5 % in less than 0,2 %.
the relevant frequency range of 0 Hz to 5 Hz. All ana-
log signals shall be processed with filters having suf-
6.3.2.2 Digitizing
ficiently similar phase characteristics to ensure that
time delay differences due to filtering shall lie within
The sampling ratef, shall be at least twice the highest
the required accuracy for time measurement.
frequency after filtering. In practice the sample fre-
quency is usually chosen to be appropriate to the or-
NOTE 2 During analog filtering of signals with different
frequency contents, phase shifts can occur. Therefore a der of the filters used and to the resolution of the
data processing method, as described in 6.3.2, is prefer-
digitizing process (see note 3).
able.
NOTE 3 As examples, fS 3 9f0 for four pole butterworth
filters and fS 3 3,8fo for eight pole butterworth filters, both
6.3.2 Digital data processing
at 12 bits resolution.
6.3.2.1 Preparation of analog signals
6.3.2.3 Digital filtering
In order to avoid aliasing, the analog signals shall be
filtered correspondingly before digitizing. In this case
For the filtering of sampled data in the data evaluation,
low-pass filters with order four or higher shall be em-
phaseless (zero phase shift) digital filters shall be used
ployed. The width of passband frequency (fo at
with the following characteristics (see figure 1):
- 3 dB) shall be:
- passband range, 3 0 Hz to > 5 Hz;
- start of stopband, 2 10 Hz and s 15 Hz;
The amplitude error of the anti-aliasing filter shall not
- filter gain in the passband, 1 + 0,005
exceed + 0,5 % in the usable frequency range. All
(100 % If: 0,5 %)*
I
analog signals shall be processed with anti-aliasing fil-
ters having sufficient similar phase characteristics to
- filter gain in the stopband, s 0,Ol (G 1 %).
n
Passband
Stopband
0
0
!
Frequency, Hz
Figure 1 - Required characteristics of phaseless digital filters
3
---------------------- Page: 7 ----------------------
@ IS0
IS0 120214:1996(E)
not exceed 3 m/s regardless of the wind direction.
7 Test conditions
The standard test condition of a dry road surface
should be used. However, a wet road with no measur-
Limits and specifications for the ambient wind and
able water depth may be used.
vehicle test conditions are established in 7.1 to 7.3,
and shall be maintained during the test. Any devi-
ations shall be specified in the test report (see Weather conditions shall be recorded in the test re-
annex A), including individual diagrams for the pres- port (see annex A).
entation of results (see annex B).
7.1 Test track
7.3 Test vehicle
All tests shall be carried out on a uniform hard road
surface which is free of contaminants. The gradient,
7.3.1 Pyres
as measured over the full width of the track in the lat-
eral direction and over a distance of at least 50 m in
It is recommended that new tyres are fitted on the
the longitudinal direction, shall be < 2,5 %.
test vehicle in the approriate position. They shall be
It is recommended that the track has either a smooth run in for at least 150 km on the test vehicle without
surface (asphalt or concrete) or a high friction surface. excessively harsh use, for example braking, accelerat-
ing, cornering, hitting the kerb, etc. They shall have a
The test surface shall be at least 5 m wide, from at
tread depth of at least 90 % of the original value and
least 100 m before to 100 m after the wind zone (see
shall have been manufactured not more than one year
figure 2). The width of the track after the wind zone
before the tests.
shall be at least 7 m.
The tests may also be performed with tyres in any
Increased run-off area should be provided in addition
state of wear providing that at the end of the tests
to the specified test surface.
they retain a minimum of I ,5 mm of tread depth
across the whole tread breadth and around the whole
circumference of the tyre.
7.2 Weather conditions
NOTE 4 Tread breadth is the width of that part of the tread
During the time frame of the experiment, ambient
which, with the tyre correctly inflated, contacts the road in
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.