ISO 11012:2009

INTERNATIONAL ISO
STANDARD 11012
First edition
2009-09-15
Heavy commercial vehicles and buses —
Open-loop test methods for the
quantification of on-centre handling —
Weave test and transition test
Véhicules utilitaires lourds et autobus — Méthode d'essai en boucle
ouverte pour mesurer la tenue de route en ligne — Essai de
changement de trajectoire et essai transitoire

Reference number
©
ISO 2009
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©  ISO 2009
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ii © ISO 2009 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms, definitions and symbols .1
3.1 Terms and definitions .1
3.2 Symbols.2
4 Principle .2
5 Variables.2
5.1 Reference system.2
5.2 Variables.3
6 Measuring equipment .3
7 Test conditions.4
8 Test procedure.4
8.1 General .4
8.2 Warm-up .4
8.3 Initial driving condition.4
8.4 Weave test procedure .4
8.5 Transition test procedure .5
9 Data evaluation and presentation of results.5
9.1 General .5
9.2 Time histories .5
9.3 Characteristic values for the weave test.6
9.4 Characteristic values for the transition test .8
Annex A (normative) Test report — General data and test conditions .11
Annex B (informative) Calculating the time delay from sinusoidal data.12
Bibliography.14

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 11012 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 9, Vehicle
dynamics and road-holding ability.
iv © ISO 2009 – All rights reserved

Introduction
The main purpose of this International Standard is to provide repeatable and discriminatory test results.
The dynamic behaviour of a road vehicle is a very important aspect of active vehicle safety. Any given vehicle,
together with its driver and the prevailing environment, constitutes a closed-loop system that is unique. The
task of evaluating the dynamic behaviour is therefore very difficult, since the significant interaction of these
driver-vehicle-environment elements are each complex in themselves. A complete and accurate description of
the behaviour of the road vehicle must necessarily involve information obtained from a number of different
tests.
Since the test method described in this International Standard quantifies only one small part of the complete
vehicle handling characteristics, the results of these tests can only be considered significant for a
correspondingly small part of the overall dynamic behaviour.
Moreover, insufficient knowledge is available concerning the relationship between overall vehicle dynamic
properties and accident avoidance. A substantial amount of work is necessary to acquire sufficient and
reliable data on the correlation between accident avoidance and vehicle dynamic properties in general, and
the results of these tests in particular. Consequently, any application of the test method described in this
International Standard for regulation purposes will require proven correlation between test results and
accident statistics.
INTERNATIONAL STANDARD ISO 11012:2009(E)

Heavy commercial vehicles and buses — Open-loop test
methods for the quantification of on-centre handling — Weave
test and transition test
1 Scope
This International Standard describes two open-loop test methods for determining on-centre handling
characteristics of a vehicle in response to specific types of steering input under closely controlled test
conditions:
⎯ the weave test, and
⎯ the transition test.
This International Standard applies to heavy vehicles, i.e. commercial vehicles, commercial vehicle
combinations, buses and articulated buses as defined in ISO 3833 (trucks and trailers with maximum weight
above 3,5 tonnes and buses and articulated buses with maximum weight above 5 tonnes, in accordance with
ECE and EC vehicle classification, categories M3, N2, N3, O3 and O4).
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 1176, Road vehicles — Masses — Vocabulary and codes
ISO 3833, Road vehicles — Types — Terms and definitions
ISO 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
ISO 15037-2:2002, Road vehicles — Vehicle dynamics test methods — Part 2: General conditions for heavy
vehicles and buses
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1176, ISO 3833, ISO 8855,
ISO 15037-2 and the following apply.
3.1.1
on-centre handling
objective description of the steering feel and steering precision of a vehicle during nominally straight-line
driving and in negotiating large-radius bends at high speeds but low lateral accelerations
3.1.2
ordinate deadband
vertical width of the hysteresis loops at an abscissa value of zero
3.1.3
abscissa deadband
horizontal width of the hysteresis loops at an ordinate value of zero
3.1.4
gradient
ratio of the change in the ordinate to a unit change in the abscissa
3.2 Symbols
For the purposes of this document, the symbols given in ISO 8855 and ISO 15037-2 apply.
4 Principle
On-centre handling represents that part of the straight-line directional stability characteristics of the vehicle
existing at low levels of lateral acceleration, typically not larger than 1 m/s . On-centre handling is concerned
primarily with features that directly influence the driver’s steering input, such as steering-system
characteristics and tyre characteristics. Thus, test schedules for the evaluation of on-centre handling
behaviour seek to minimize other factors that influence the wider aspects of straight-line directional stability,
such as disturbance inputs due to ambient winds and road irregularities.
This International Standard defines two test schedules that involve driving the vehicle in a nominally straight
line at a constant forward speed:
⎯ the weave test examines the response at the outer edge of the hysteretic region (see 8.4);
⎯ the transition test examines the transition from straight-line driving to the edge of the hysteretic region
(see 8.5).
During these tests, driver inputs and vehicle responses are measured and recorded. From the recorded
signals, characteristic values are calculated.
5 Variables
5.1 Reference system
The variables of motion used to describe vehicle behaviour in a test-specific driving situation shall be related
to the intermediate axis system (X, Y, Z) of the first vehicle unit (see ISO 8855).
For the purposes of this International Standard, the location of the reference point shall be in the plane of
symmetry and at the longitudinal and vertical position of the wheel centre of the first axle of the first vehicle
unit at static load and straight-ahead steering.
NOTE This provision overrides the provision of 15037-2.
2 © ISO 2009 – All rights reserved

5.2 Variables
When using these test methods, the following variables shall be determined for the first vehicle unit:
a) steering-wheel angle, δ ;
H
b) steering-wheel torque, M ;
H
c) yaw velocity, dψ/dt;
d) longitudinal velocity, ν ;
X
e) lateral acceleration at the reference point, a .
Y
It is also recommended that the following variable be determined:
⎯ steering-wheel angular velocity, dδ /dt .
H
The listed variables are defined in ISO 8855.
In order to acquire a deeper understanding of the vehicle behaviour, it may be desirable to determine motions
of various components within the steering system, especially for vehicles with more than one steering axle.
6 Measuring equipment
The measuring equipment shall be in accordance with ISO 15037-2.
Table 1 shows typical operating ranges and recommended maximum errors of the combined transducer and
recording system, which are not given in ISO 15037-2.
NOTE It is advisable that care be taken to ensure that friction or inertia added to the system by steering machines or
steering transducers does not improperly influence the measurement of steering-wheel torque.
Table 1 — Typical operating ranges and maximum errors of variables not listed in ISO 15037-2
Recommended maximum error
Variable Typical operating range
of combined system
Steering-wheel angle ± 80° ± 0,5°
Steering-wheel torque in case of power steering ± 10 Nm ± 0,1 Nm
Yaw velocity ± 10°/s ± 0,1°/s
2 2
Lateral acceleration ± 5 m/s ± 0,05 m/s
Steering wheel angular velocity ± 100°/s ± 1°/s

7 Test conditions
Specifications for test conditions shall be in accordance with ISO 15037-2 together with the additional
specifications listed below.
a) The lateral gradient of the test surface should not exceed 1 % over any distance greater than or equal to
the vehicle track.
b) Special attention should be paid to the condition of the tyres, axle alignments and the steering system to
ensure that the vehicle does not lead or pull when operating on a level surface.
c) During a test, the ambient wind velocity shall not exceed 5 m/s when measured at a height above ground
of not less than 1 m. Ideally the maximum ambient wind velocity should not exceed 1,5 m/s. If this cannot
be achieved, then conditions where there is significant wind gusting should be avoided, i.e. testing should
be avoided in conditions where changes in wind velocity exceed a range of 1,5 m/s. In the event that the
ambient velocity exceeds 1,5 m/s or the range of gusting exceeds 1,5 m/s or both, the vehicle should be
tested in a direction such that the ambient wind is a tail wind.
8 Test procedure
8.1 General
The weave test requires a test track of approximately 1 000 m length and 20 m width for standard test
conditions. The transition test requires less length but approximately 40 m width.
The vehicle is driven at a nominally constant longitudinal velocity. The standard test velocity is 80 km/h. Other
velocities may be used. The test velocity should preferably be decremented or incremented by steps of
10 km/h. For each test run, the average longitudinal velocity shall be maintained within a tolerance of ± 2 km/h
of the selected speed. A deviation of vehicle longitudinal velocity of ± 3 km/h from the selected longitudinal
velocity is permissible. In addition, variation in the position of the accelerator pedal shall be kept to a minimum
consistent with maintaining vehicle longitudinal velocity within required limits.
It is preferable that the steering inputs for these tests be made with a steering machine.
Details shall be recorded in the test report (see Annex A).
8.2 Warm-up
See ISO 15037-2.
8.3 Initial driving condition
The initial driving condition shall be as described in ISO 15037-2 for the steady-state straight-ahead run. The
allowable variations for yaw velocity should be used rather than those for lateral acceleration.
In the time interval, starting no later than time t and ending at time t (see ISO 15037-2:2002, 7.2), the
1 2
steering wheel shall be held fixed within ± 3°. If possible, the steering wheel should be subject to zero input
torque. At time t , the steering input specified in 8.4 and 8.5 shall be applied.
8.4 Weave t
...