Passenger cars -- Free-steer behaviour

ISO 17288-1:2011 specifies an open-loop test method for determining the free control stability of a passenger car as defined in ISO 3833, by measurement of the transient behaviour following steering release, starting from a steady-state cornering status.

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STANDARD 17288-1
Second edition
Passenger cars — Free-steer
behaviour —
Part 1:
Steering-release open-loop test method
Voitures particulières — Comportement volant libre —
Partie 1: Méthode d'essai en boucle ouverte avec relâchement du
Reference number
ISO 17288-1:2011(E)
ISO 2011
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ISO 17288-1:2011(E)
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© ISO 2011

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ii © ISO 2011 – All rights reserved
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ISO 17288-1:2011(E)

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

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the

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 3.

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 part of ISO 17288 may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 17288-1 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 17288-1:2002), of which it constitutes a minor


ISO 17288 consists of the following parts, under the general title Passenger cars — Free-steer behaviour :

⎯ Part 1: Steering-release open-loop test method
⎯ Part 2: Steering-pulse open-loop test method
© ISO 2011 – All rights reserved iii
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ISO 17288-1:2011(E)

The main purpose of this part of ISO 17288 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 interactions 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


Since this test method 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


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 this test method for regulation purposes

will require proven correlation between test results and accident statistics.
iv © ISO 2011 – All rights reserved
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Passenger cars — Free-steer behaviour —
Part 1:
Steering-release open-loop test method
1 Scope

This part of ISO 17288 specifies an open-loop test method for determining the free control stability of a

passenger car as defined in ISO 3833, by measurement of the transient behaviour following steering release,

starting from a steady-state cornering status.

NOTE The open-loop manoeuvre specified in this part of ISO 17288 is not representative of normal driving

conditions, but is nonetheless useful for obtaining a measure of vehicle transient behaviour.

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 3833, Road vehicles — Types — Terms and definitions
ISO 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary

ISO 15037-1:2006, Road vehicles — Vehicle dynamics test methods — Part 1: General conditions for

passenger cars
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 3833 and ISO 8855 apply.

4 Principle

This test is intended for evaluating the ability of a vehicle to return to a straight path following steering-wheel

release from a steady-state turn.

The initial conditions are defined by a steady-state circular motion. During the test, the driver releases the

steering wheel. The steering-wheel angle and the vehicle response are measured and recorded. From the

recorded signals, characteristic values are calculated.
© ISO 2011 – All rights reserved 1
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ISO 17288-1:2011(E)
5 Variables
5.1 Reference system
The provisions given in ISO 15037-1:2006, 3.1, apply.
5.2 Measurement
Measure the following variables (see ISO 8855):
⎯ longitudinal velocity (v );
⎯ lateral acceleration (a );
⎯ yaw velocity (ψ );
⎯ steering-wheel angle (δ ).
6 Measuring e

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