ISO 7975:2019
(Main)Passenger cars — Braking in a turn — Open-loop test method
Passenger cars — Braking in a turn — Open-loop test method
This document specifies an open-loop test procedure to examine the effect of braking on course holding and directional behaviour of a vehicle. Specifically, the method determines how the steady-state circular response of a vehicle is altered by a braking action only. This document is applicable to passenger cars as defined in ISO 3833 and to light trucks. The open-loop manoeuvre specified in this test method is not representative of real driving conditions but is useful to obtain measures of vehicle braking behaviour resulting from control inputs under closely controlled test conditions.
Voitures particulières — Freinage en virage — Méthode d'essai en boucle ouverte
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INTERNATIONAL ISO
STANDARD 7975
Fourth edition
2019-04
Passenger cars — Braking in a turn —
Open-loop test method
Voitures particulières — Freinage en virage — Méthode d'essai en
boucle ouverte
Reference number
©
ISO 2019
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Variables . 2
5.1 Reference system . 2
5.2 Variables to be measured . 2
6 Measuring equipment . 2
6.1 Description . 2
6.2 Transducers and their installation . 3
6.3 Data processing . 3
7 Test conditions . 3
8 Test methods . 3
8.1 Run-in program for newly installed brakes (pads/shoes) . 3
8.2 Warm-up. 3
8.3 Brake temperature . 4
8.4 Initial driving condition . 4
8.5 Performance of the braking procedure . 4
8.6 General test description . 5
9 Data evaluation and presentation of results . 5
9.1 General . 5
9.2 Time histories . 5
9.3 Braking action . 5
9.3.1 Reference point in time, t . 5
9.3.2 Definition of times and requirements for standard evaluation . 6
9.3.3 Mean longitudinal acceleration, −a . 6
X
9.3.4 Mean longitudinal acceleration, −a , until time t . 7
n
Xt,
n
9.4 Evaluation of characteristic values . 7
Annex A (normative) Presentation of results.11
Bibliography .22
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 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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document was prepared by ISO/TC 22, Road vehicles, Subcommittee SC 33, Vehicle dynamics and
chassis components.
This fourth edition cancels and replaces the third edition (ISO 7975:2006), which has been technically
revised. The main changes compared to the previous edition are as follows:
— recognizing regenerative braking and active control systems.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved
Introduction
The main purpose of this document 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 will necessarily involve information
obtained from a number of different tests.
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 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. If this test method is used for regulation
purposes, the correlation between test results and accident statistics should be checked.
INTERNATIONAL STANDARD ISO 7975:2019(E)
Passenger cars — Braking in a turn — Open-loop test
method
1 Scope
This document specifies an open-loop test procedure to examine the effect of braking on course holding
and directional behaviour of a vehicle. Specifically, the method determines how the steady-state circular
response of a vehicle is altered by a braking action only. This document is applicable to passenger cars
as defined in ISO 3833 and to light trucks.
The open-loop manoeuvre specified in this test method is not representative of real driving conditions
but is useful to obtain measures of vehicle braking behaviour resulting from control inputs under
closely controlled test conditions.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 4138, Passenger cars — Steady-state circular driving behaviour — Open-loop test methods
ISO 15037-1:2019, Road vehicles — Vehicle dynamics test methods — Part 1: General conditions for
passenger cars
ISO 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8855 and ISO 15037-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
4 Principle
The purpose of this test is to examine the effect of braking on course holding and directional behaviour
of a vehicle. Specifically, the method determines how the steady-state circular response of a vehicle is
altered by braking action only.
The initial conditions are defined by constant longitudinal velocity and by a circle with a given radius,
as specified by the constant-radius test method of ISO 4138. The steering-wheel angle required for
the steady-state circular run shall be constantly maintained during the entire test. During the test,
the driver input and the vehicle response are measured and recorded. From the recorded signals,
characteristic values are calculated.
5 Variables
5.1 Reference system
The reference system specified in ISO 15037-1 shall apply.
5.2 Variables to be measured
The following variables shall be determined:
— moment of brake application (t );
— steering-wheel angle (δ );
H
— lateral acceleration (a );
Y
— longitudinal acceleration (a );
X
— longitudinal velocity (v );
X
— yaw velocity (dψ/dt); and
— sideslip angle (β and/or lateral velocity (v ).
Y
Strictly speaking, test results based on lateral acceleration should not be used for comparison of the
performance of different vehicles. This is because lateral acceleration is measured at right angles to
the intermediate X-axis and not perpendicular to the vehicle path. To overcome this difficulty, lateral
acceleration can be corrected for vehicle sideslip angle, which gives the centripetal acceleration.
However, the extent of this correction is not likely to exceed a few percent and ma
...
INTERNATIONAL ISO
STANDARD 7975
Fourth edition
2019-04
Passenger cars — Braking in a turn —
Open-loop test method
Voitures particulières — Freinage en virage — Méthode d'essai en
boucle ouverte
Reference number
©
ISO 2019
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Variables . 2
5.1 Reference system . 2
5.2 Variables to be measured . 2
6 Measuring equipment . 2
6.1 Description . 2
6.2 Transducers and their installation . 3
6.3 Data processing . 3
7 Test conditions . 3
8 Test methods . 3
8.1 Run-in program for newly installed brakes (pads/shoes) . 3
8.2 Warm-up. 3
8.3 Brake temperature . 4
8.4 Initial driving condition . 4
8.5 Performance of the braking procedure . 4
8.6 General test description . 5
9 Data evaluation and presentation of results . 5
9.1 General . 5
9.2 Time histories . 5
9.3 Braking action . 5
9.3.1 Reference point in time, t . 5
9.3.2 Definition of times and requirements for standard evaluation . 6
9.3.3 Mean longitudinal acceleration, −a . 6
X
9.3.4 Mean longitudinal acceleration, −a , until time t . 7
n
Xt,
n
9.4 Evaluation of characteristic values . 7
Annex A (normative) Presentation of results.11
Bibliography .22
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 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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document was prepared by ISO/TC 22, Road vehicles, Subcommittee SC 33, Vehicle dynamics and
chassis components.
This fourth edition cancels and replaces the third edition (ISO 7975:2006), which has been technically
revised. The main changes compared to the previous edition are as follows:
— recognizing regenerative braking and active control systems.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved
Introduction
The main purpose of this document 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 will necessarily involve information
obtained from a number of different tests.
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 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. If this test method is used for regulation
purposes, the correlation between test results and accident statistics should be checked.
INTERNATIONAL STANDARD ISO 7975:2019(E)
Passenger cars — Braking in a turn — Open-loop test
method
1 Scope
This document specifies an open-loop test procedure to examine the effect of braking on course holding
and directional behaviour of a vehicle. Specifically, the method determines how the steady-state circular
response of a vehicle is altered by a braking action only. This document is applicable to passenger cars
as defined in ISO 3833 and to light trucks.
The open-loop manoeuvre specified in this test method is not representative of real driving conditions
but is useful to obtain measures of vehicle braking behaviour resulting from control inputs under
closely controlled test conditions.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 4138, Passenger cars — Steady-state circular driving behaviour — Open-loop test methods
ISO 15037-1:2019, Road vehicles — Vehicle dynamics test methods — Part 1: General conditions for
passenger cars
ISO 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8855 and ISO 15037-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
4 Principle
The purpose of this test is to examine the effect of braking on course holding and directional behaviour
of a vehicle. Specifically, the method determines how the steady-state circular response of a vehicle is
altered by braking action only.
The initial conditions are defined by constant longitudinal velocity and by a circle with a given radius,
as specified by the constant-radius test method of ISO 4138. The steering-wheel angle required for
the steady-state circular run shall be constantly maintained during the entire test. During the test,
the driver input and the vehicle response are measured and recorded. From the recorded signals,
characteristic values are calculated.
5 Variables
5.1 Reference system
The reference system specified in ISO 15037-1 shall apply.
5.2 Variables to be measured
The following variables shall be determined:
— moment of brake application (t );
— steering-wheel angle (δ );
H
— lateral acceleration (a );
Y
— longitudinal acceleration (a );
X
— longitudinal velocity (v );
X
— yaw velocity (dψ/dt); and
— sideslip angle (β and/or lateral velocity (v ).
Y
Strictly speaking, test results based on lateral acceleration should not be used for comparison of the
performance of different vehicles. This is because lateral acceleration is measured at right angles to
the intermediate X-axis and not perpendicular to the vehicle path. To overcome this difficulty, lateral
acceleration can be corrected for vehicle sideslip angle, which gives the centripetal acceleration.
However, the extent of this correction is not likely to exceed a few percent and ma
...
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