Passenger cars -- Power-off reaction of a vehicle in a turn -- Open-loop test method

ISO 9816:2018 specifies open-loop test methods to determine the reactions of a vehicle in a turn to a sudden drop in motive power resulting from release of the accelerator pedal. It applies to passenger cars as defined in ISO 3833.

Voitures particulières -- Réponse d'un véhicule à un lever de pied en virage -- Méthode d'essai en boucle ouverte

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Status
Published
Publication Date
19-Apr-2018
Current Stage
6060 - International Standard published
Start Date
24-Mar-2018
Completion Date
20-Apr-2018
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INTERNATIONAL ISO
STANDARD 9816
Third edition
2018-04
Passenger cars — Power-off reaction
of a vehicle in a turn — Open-loop
test method
Voitures particulières — Réponse d'un véhicule à un lever de pied en
virage — Méthode d'essai en boucle ouverte
Reference number
ISO 9816:2018(E)
ISO 2018
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ISO 9816:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018

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

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below or ISO’s member body in the country of the requester.
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Email: copyright@iso.org
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Published in Switzerland
ii © ISO 2018 – All rights reserved
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ISO 9816:2018(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 2

5 Variables ....................................................................................................................................................................................................................... 2

5.1 Reference system .................................................................................................................................................................................. 2

5.2 Variables to be measured ............................................................................................................................................................... 2

6 Measuring equipment ..................................................................................................................................................................................... 3

6.1 Description ................................................................................................................................................................................................. 3

6.2 Transducers installations .............................................................................................................................................................. 3

6.3 Data processing ...................................................................................................................................................................................... 3

7 Test conditions ....................................................................................................................................................................................................... 3

8 Test method ............................................................................................................................................................................................................... 3

8.1 Warm-up....................................................................................................................................................................................................... 3

8.2 Initial driving condition .................................................................................................................................................................. 4

8.2.1 General...................................................................................................................................................................................... 4

8.2.2 Initial driving condition — Constant-radius method ....................................................................... 4

8.2.3 Initial driving condition — Constant-speed method ........................................................................ 4

8.3 Power-off procedure .......................................................................................................................................................................... 5

9 Data evaluation and presentation of results ........................................................................................................................... 5

9.1 General ........................................................................................................................................................................................................... 5

9.2 Time histories .......................................................................................................................................................................................... 5

9.3 Initial point in time t ...................................................................................................................................................................... 5

9.4 Characteristic values .......................................................................................................................................................................... 6

Annex A (normative) Test report — General data .................................................................................................................................. 9

Annex B (normative) Presentation of results...........................................................................................................................................10

Bibliography .............................................................................................................................................................................................................................23

© ISO 2018 – All rights reserved iii
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ISO 9816:2018(E)
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. 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. 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 on 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 WTO

principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary

information.

This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 33,

Vehicle dynamics and chassis components.

This third edition of ISO 9816 cancels and replaces the second edition (ISO 9816:2006) which has been

technically revised. The main changes compared to the previous edition are as follows:

— an update was made regarding alternative powertrain systems.
iv © ISO 2018 – All rights reserved
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ISO 9816:2018(E)
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 must 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.

© ISO 2018 – All rights reserved v
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INTERNATIONAL STANDARD ISO 9816:2018(E)
Passenger cars — Power-off reaction of a vehicle in a turn
— Open-loop test method
1 Scope

This document specifies open-loop test methods to determine the reactions of a vehicle in a turn to a

sudden drop in motive power resulting from release of the accelerator pedal. It applies to passenger

cars as defined in ISO 3833.

The open-loop manoeuvre specified in this test method is not representative of real driving conditions,

but is useful to obtain measures of a vehicle’s power-off behaviour resulting from specific types of

control inputs under closely controlled test conditions.
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 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary

ISO 15037-1:2018 , 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 8855, ISO 15037-1 and the

following 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

For the purposes of this document, the terms and definitions given in the general conditions given in,

and the following terms and definitions shall apply.
3.1
power-off

vehicle operating condition where the vehicle is in gear and the accelerator pedal is fully released,

especially when initiated by a sudden release of the accelerator pedal
3.2
instant of power-off initiation
moment in time when a rapid release of the accelerator pedal is initiated
1) Under preparation. Stage at time of publication: ISO/DIS.
© ISO 2018 – All rights reserved 1
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ISO 9816:2018(E)
4 Principle

The purpose of this test procedure is to determine the effect of a sudden initiation of a power-off

condition on the course holding and directional behaviour of a vehicle, initially operating in steady-

state circular motion.

The initial conditions are defined by constant longitudinal velocity and by a circular path with a given

radius. The power-off disturbance is introduced by a sudden release of the accelerator pedal. The

steering-wheel angle required for the steady-state circular run is then 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.
The test may be performed using two alternative test methods:

1. A constant-radius test method, where the initial conditions are defined by driving on a fixed-radius

circular path and lateral acceleration is incrementally increased in the test runs by increasing the

initial test speed;

2. A constant-speed test method, where the initial conditions are defined by a constant test speed and

lateral acceleration is incrementally increased in the test runs by increasing the initial steer angle,

resulting in operation on successively smaller initial path radii.

The constant-radius test method has the advantage of requiring only one test arc, and therefore

demands less testing space than the constant-speed test. The test course is similar to curves on rural

roads or exit ramps from high-speed roadways. The test method includes varying initial engine speed,

and thus, varying deceleration due to engine braking. For both test methods, the initial steering-wheel

angle will change as lateral acceleration increases. The constant-radius test method demands some

driver skill, as the test driver must establish initial steady-state cornering conditions, while following

the fixed-radius path.

The constant-speed test method maintains a constant initial engine speed, and thus, a constant

deceleration due to engine braking at power-off. The deceleration achieved in practice depends on the

test conditions and car properties: among others, the combination of engine speed and gear needed

for the chosen longitudinal velocity. This test method may be performed using either a series of

fixed-radius arcs or a series of fixed steering-wheel angles, with no constraint on vehicle path. The

unconstrained-path method places low demands on driver skill, as the requirement to maintain a fixed

initial path is not present. The disadvantage of this test method is that a large test surface is required,

particularly if high initial test speeds are to be evaluated.

The test results from the two test methods are not comparable, except for the same combination of

initial path radius and speed.
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:
— instant of power-off initiation, t ;
— steering-wheel angle, δ ;
— yaw angle, ψ, or yaw velocity, ψ ;
— longitudinal velocity, v ;
2 © ISO 2018 – All rights reserved
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ISO 9816:2018(E)
— lateral acceleration; a ;
— sideslip angle, β, or lateral velocity, v .
In addition, the following variables may be determined:
— longitudinal acceleration, a .

The variables are defined in ISO 8855, except the instant of accelerator pedal release t , which is the

instant at which the accelerator pedal is released (see 8.3). The variables are not intended to comprise

a complete list.
6 Measuring equipment
6.1 Description

The variables selected for test purposes shall be measured by means of appropriate transducers.

Their time histories shall be recorded by a multi-channel recording system having a time base. Typical

operating ranges and recommended maximum errors of the transducer and recording system are

as specified in ISO 15037-1:2006 and Table 1. In the context of this document, these values should be

considered as provisional until more experience and data are available.
6.2 Transducers installations
The requirements of ISO 15037-1 shall apply.
6.3 Data processing
The requirements and specifications of ISO 15037-1 shall be followed.
7 Test conditions

Limits and specifications for the ambient and the vehicle test conditions established in ISO 15037-1

shall be followed.

In addition, for standard test conditions, the adjustment and condition of the engine and drive train

(especially the differentials, clutches, locks, free-wheel shifts, engine idle-calibration) shall correspond

to the vehicle manufacturer’s specifications.
Table 1 — Typical operating ranges and recommended maximum errors for recorded
variables — Additions and exceptions to ISO 15037-1
Recommended maximum error
Variable Typical operating range of the combined transducer
and recorder system
Instant of power-off initiation — 0,05 s
Yaw angle −180° to 180° ±2°

NOTE Increased measuring accuracy be desirable for computation of some of the charac

...

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