Heavy commercial vehicles and buses — Test method for steering effort measurement when manoeuvring at low speed or with stationary vehicle

This document specifies a test method for steering effort measurement when manoeuvring a vehicle at low speed or with the vehicle stationary. It is mainly applicable to trucks having a mass exceeding 3,5 tonnes and buses and articulated buses having a mass exceeding 5 tonnes, according to ECE and EC vehicle classification, i.e. categories M3, N2, N3. This document can also be applicable to trucks having a mass not exceeding 3,5 tonnes and buses and articulated buses having a mass not exceeding 5 tonnes, i.e. categories M2, N1.

Véhicule utilitaires lourds et autobus — Méthode d’essai pour la mesure des efforts de direction lors de braquage à basse vitesse ou sur place

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ISO 22139:2022 - Heavy commercial vehicles and buses — Test method for steering effort measurement when manoeuvring at low speed or with stationary vehicle Released:5/11/2022
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INTERNATIONAL ISO
STANDARD 22139
First edition
2022-05
Heavy commercial vehicles and
buses — Test method for steering
effort measurement when
manoeuvring at low speed or with
stationary vehicle
Véhicule utilitaires lourds et autobus — Méthode d’essai pour la
mesure des efforts de direction lors de braquage à basse vitesse ou sur
place
Reference number
ISO 22139:2022(E)
© ISO 2022
---------------------- Page: 1 ----------------------
ISO 22139:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

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.
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Email: copyright@iso.org
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Published in Switzerland
© ISO 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 22139:2022(E)
Contents Page

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

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

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

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

4 Principle ........................................................................................................................................................................................................................ 4

5 Variables ....................................................................................................................................................................................................................... 4

6 Measuring equipment .................................................................................................................................................................................... 5

6.1 Description ................................................................................................................................................................................................. 5

6.2 Transducer installations ................................................................................................................................................................ 5

6.3 Data processing...................................................................................................................................................................................... 5

7 Test conditions .......................................................................................................................................................................................................6

7.1 General ........................................................................................................................................................................................................... 6

7.2 Test track when manoeuvring at low speed ................................................................................................................. 6

7.3 Test track with stationary vehicle......................................................................................................................................... 6

7.4 Test vehicle ................................................................................................................................................................................................. 6

7.4.1 General data ................................... ........................................................................................................ ................................. 6

7.4.2 Operating components .................................................................................................................................................. 6

7.4.3 Tyres and rims ...................................................................................................................................................................... 6

7.4.4 Vehicle loading conditions ......................................................................................................................................... 6

8 Test procedure .......................................................................................................................................................................................................7

8.1 Preparation of test vehicle ........................................................................................................................................................... 7

8.2 Warm-up ...................................................................................................................................................................................................... 7

8.3 Measurement with a stationary vehicle .......................................................................................................................... 7

8.4 Measurement when manoeuvring at low speed ....................................................................................................... 8

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

9.1 Time histories ......................................................................................................................................................................................... 9

9.2 Maximum steering-wheel torque vs. steering-wheel speed ....................................................................... 10

9.3 Catch up steering-wheel speed ............................................................................................................................................. 11

9.4 Cartesian coordinates ................................................................................................................................................................... 11

9.5 Maximum steering-wheel torque (M and M ) ................................................................................ 11

HmaxL HmaxR

9.6 Steering-wheel work when steering OUT (W and W ) ...........................................................12

H OutL H OutR

9.7 Steering-wheel torque when steering IN (M and M ) ........................................................................13

H 0L H 0R

9.8 Steering work when steering IN (W and W ) ........................................................................................ 14

H InL H InR

9.9 Steering return ability .................................................................................................................................................................. 15

9.9.1 Remaining steering-wheel angle (δ and δ ) ...................................................................15

H remL H remR
9.9.2 Steering-wheel speed when returning to steering-wheel straight forward

position .................................................................................................................................................................................... 16

9.10 Steering-wheel torque variation ∆M / M ...................................................................................... 16

Hmax Hmax (%)

Annex A (normative) Test report — General data .............................................................................................................................18

Annex B (normative) Test report — Test conditions .......................................................................................................................21

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

iii
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ISO 22139:2022(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 (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 Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 33,

Vehicle dynamics and chassis components.

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.
© ISO 2022 – All rights reserved
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INTERNATIONAL STANDARD ISO 22139:2022(E)
Heavy commercial vehicles and buses — Test method for
steering effort measurement when manoeuvring at low
speed or with stationary vehicle
1 Scope

This document specifies a test method for steering effort measurement when manoeuvring a vehicle

at low speed or with the vehicle stationary. It is mainly applicable to trucks having a mass exceeding

3,5 tonnes and buses and articulated buses having a mass exceeding 5 tonnes, according to ECE and EC

vehicle classification, i.e. categories M3, N2, N3.

This document can also be applicable to trucks having a mass not exceeding 3,5 tonnes and buses and

articulated buses having a mass not exceeding 5 tonnes, i.e. categories M2, N1.
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 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary

ISO 15037-2, Road vehicles — Vehicle dynamics test methods — Part 2: General conditions for heavy

vehicles and buses
3 Terms and definitions

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

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
rim offset
distance of a rim from its hub mounting surface to the centreline of the wheel

Note 1 to entry: A positive rim offset is when the hub mounting surface is more toward the outside of the

centreline of the wheel.
3.2
catch up

point when the steering-wheel torque abruptly increases while increasing the steering-wheel speed

Note 1 to entry: (See Figure 3).

Note 2 to entry: On a hydraulic or an electric-hydraulic system this is usually the point when the steering servo

fluid pump reaches the limit when the fluid flow is no longer sufficient to give the required output torque to turn

the steering wheel.
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ISO 22139:2022(E)
3.3
catch up steering-wheel torque limit
predetermined level of steering-wheel torque limit for the specific application

Note 1 to entry: The catch-up steering-wheel torque limit level corresponds to the torque when a driver

depending on application is no longer able to apply or is no longer comfortable with the torque needed to turn the

steering-wheel. (See Figure 3).
3.4
steering-wheel straight forward position
steering-wheel angle resulting in vehicle zero course angle
Note 1 to entry: See Figure 1.
3.5
maximum steering-wheel angles
HmaxL
HmaxR

steering-wheel angles (left and right) that due to mechanically limitations are the maximum that can

be reached in the steering system

Note 1 to entry: In order not to overload the steering components when reaching the maximum steering wheel

angles, vehicles with power steering system are equipped with a mechanism for lowering the boost torque before

reaching the maximum steering wheel angles e.g. a hydraulic relief pressure valve. (See Figure 1 and 8.1).

3.6
maximum steering-wheel angles range of interest
H maxroiL
H maxroiR

range of steering wheel angles (left and right) of interest for the test and that are used while collecting

data
Note 1 to entry: See Figure 1 and 8.1.
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ISO 22139:2022(E)
Key
X steering-wheel angle δ (°)
Y steering-wheel torque M (Nm)
δ steering-wheel straight forward position (°)
δ maximum steering-wheel angles in right direction (°)
HmaxR
δ maximum steering-wheel angles range of interest in right direction (°)
H maxroiR
δ maximum steering-wheel angles in left direction (°)
HmaxL
δ maximum steering-wheel angles range of interest in left direction (°)
H maxroiL
Figure 1 — Maximum steering wheel angles and
maximum steering wheel angles range of interest
3.7
remaining steering wheel angles
H remL
H remR

left and right steering-wheel angles when steering-wheel torque changes sign and is passing zero after

reversing the steering-wheel inwards towards the steering-wheel straight forward position (3.4)

Note 1 to entry: See Figure 8.
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ISO 22139:2022(E)
3.8
steering-wheel work
work needed to turn the steering-wheel between two defined steering-wheel angles
Note 1 to entry: See Figures 5 and 7.
3.9
steering-wheel return ability

ability of the steering-wheel to return towards the steering-wheel straight forward position (3.4) without

applying any torque to the steering-wheel
Note 1 to entry: See 9.9.
3.10
steering-wheel torque variation
Hmax
Hmax
variation in steering-wheel torque

Note 1 to entry: The variation can result, e.g. from non-optimum phasing of steering column intermediate shaft

universal joints.
Note 2 to entry: See 9.10.
4 Principle

The purpose of the test method is to objectively evaluate and quantify the driver’s perception of the

steering feel and effort while manoeuvring a vehicle at low speed or with the vehicle stationary.

The method is not intended to specify how to measure and evaluate mechanical or electrical properties

in a steering system, e.g. pressure, flow, temperature, electrical current.

The driver’s perception is quantified by calculating and evaluating characteristics parameters from the

measured variables.
The main characteristic parameters are:
— steering-wheel torque;
— steering-wheel work;
— steering-wheel return ability;
— steering-wheel torque variation.
See Clause 9 for detailed characteristic parameters.
5 Variables
The following variables shall be determined:
— steering-wheel angle δ (°);
— steering-wheel torque M (Nm);
— steering-wheel speed dδ /dt (°/s).

If not directly available, the steering-wheel speed may be calculated from the time signal of steering

wheel angle, i.e. dδ /dt.
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ISO 22139:2022(E)
6 Measuring equipment
6.1 Description
The measuring equipment shall be in accordance with ISO 15037-2.

The variables listed in Clause 5 shall be monitored using appropriate transducers and the data shall

be recorded on a multi-channel recorder with time base. Typical operating ranges and recommended

maximum errors of the combined transducer and recording system are shown in Table 1.

A steering machine including driver emergency override functionality is preferred to be used to turn

the steering wheel while collecting data.

The steering machine shall be able to perform triangular wave steering angle input with a steering-

wheel torque, steering-wheel speed and maximum steering wheel angles corresponding to the test

needs.

Care shall be taken to ensure that friction and inertia added to the system by steering machine or

steering transducers does not improperly influence the measurement of steering-wheel torque. For

example, any friction added by the steering-wheel torque sensor shall be estimated and compensated

for if this is not done in the measuring equipment.

The steering input may be done manually without the help of a steering machine but with a risk of loss

of accuracy in the results as it can be hard to maintain a constant steering-wheel speed during the

manoeuvres. See 8.3 and 8.4.

Table 1 — Variables, typical operating ranges and recommended maximum errors. Not listed in

or changed from ISO 15037-2
Recommended maximum error of
Variable Typical operating range the combined transducer and re-
corder system
Vehicle, axle or track mass: Up to 40 000 kg ±0,2 %
Steering-wheel angle ±1 000° ±1°
Steering-wheel torque ±30 Nm ±0,3 Nm
Steering-wheel speed ±600°/s ±2°/s

Transducers for measuring some of the listed variables are not widely available and are not in general use. Some 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 as shown in Annex B.

These transducer ranges are appropriate for the standard test conditions and may not be suitable for non-standard

test conditions.

Steering-wheel speeds above ±600°/s are usually not of interest for a normal driver.

6.2 Transducer installations

The transducers shall be installed according to the manufacturers’ instructions, where such

instructions exist, so that the variables in Clause 5 corresponding to the terms and definitions in

Clause 3 and ISO 8855 can be determined.

If a transducer does not measure a variable directly, appropriate transformations into the specified

reference system shall be carried out. For example, if not directly available the steering-wheel speed

should be calculated from the time signal of steering wheel angle, i.e. dδ /dt.
6.3 Data processing
See Clause 9.
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ISO 22139:2022(E)
7 Test conditions
7.1 General

For each test the surface characteristics, paving material and ground (or ambient) temperature shall be

recorded and documented in the test report. See Annex B.

If possible, the coefficient of friction should be estimated and documented. See Annex B.

7.2 Test track when manoeuvring at low speed

For measurements when manoeuvring the vehicle at low speed a large, smooth, flat and hard asphalt or

concrete area of minimum size of 50 m × 150 m is preferred. Then a complete test while increasing the

steering-wheel speed can be performed without interruption.

However, if this area is not available the test should be adapted and divided into smaller parts.

The lateral gradient of the test surface shall not exceed 2 %.
7.3 Test track with stationary vehicle

For measurements with stationary vehicle the steering effort is quite dependant on the tyre to road

surface friction. It is recommended to perform the test on a surface with a stable coefficient of friction

during the test.

On some surfaces the coefficient of friction can vary with the ground temperature and on some surfaces

the coefficient of friction can change due to, e.g. polishing when steering multiple times at the same

spot.

Due to this the vehicle may have to be moved a little bit between each set of measurements not to

change the coefficient of friction or to damage the tyres and /or the surface.

In stationary tests with vehicles with more than one steerable axle, all steerable axles shall be on the

same type of surface.
7.4 Test vehicle
7.4.1 General data

General data of the test vehicle shall be presented in the test report shown in Annex A.

7.4.2 Operating components

For the standard test conditions, all operating components likely to influence the test results shall

be according to specification. Any deviations from specification shall be noted in the presentation of

general data. See Annex A.
7.4.3 Tyres and rims

For general information regarding tyres used for test purposes, see ISO 15037-1:2019, 6.4.2.

Rim offset can have a significant influence and shall be reported in the test report-general data. See

Annex A.
7.4.4 Vehicle loading conditions
See ISO 15037-1:2019, 6.4.4.
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ISO 22139:2022(E)

Depending on the purpose of the test it may be performed in any load condition of the vehicle even if a

test at maximum design total mass for the vehicle is usually included.
The axle loads shall be documented in the test report-general data. See Annex A.
8 Test procedure
8.1 Preparation of test vehicle
Load the vehicle to the desired axle loads.
Check and adjust tyre pressure to the load.

Find the maximum steering-wheel angles and if applicable choose the maximum steering-wheel angles

range of interest to be used in the measurement.

In many test cases measuring the steering-wheel torque all the way out to maximum steering-wheel

angles is not necessary or even desirable. The reason being that the level of rise in torque when getting

close to maximum steering wheel angles usually is irrelevant for the driver as there is no practical use

to try to steer close to or beyond this point. Also, if using a steering machine to perform the manoeuvre

going all the way out to maximum steering wheel angles can cause unwanted terminations of the

measurements due to the sudden rise in torque exceeding the physical or pre-set torque limit for the

machine.

In many cases the absolute values of the maximum steering-wheel angles range of interest left and right

will be equal. For example, ±600 (°) as in examples in 9.5 to 9.10.

If there is a special interest in the behaviour of the system close to maximum steering-wheel angles, the

measurement could be extended to these angles.

If available, activate the steering machine steering-wheel torque limit. This is the limit when the

machine automatically stops the tests. It is recommended to set the value to a maximum of (30 to

40) Nm not to get too high forces in the machine attachment and also to have an automatic stop of the

test when torque values become too high to be of any interest to measure, i.e. too high of a torque for a

driver to handle.
Higher steering-wheel torque limit values can be used for special test cases.

As the servo fluid temperature in a hydraulic steering system can have a significant influence on the

performance of the steering system it is recommended to have control of the temperature and report it

together with the corresponding test results.
8.2 Warm-up

All relevant vehicle components shall be warmed up prior to the test in order to achieve a temperature

representative for the purpose of the test.
8.3 Measurement with a stationary vehicle

The engine should normally be at idle speed, but the engine speed may be increased to check any change

in performance.
The parking brake shall be released, and no foot brake applied.

Use the steering machine to give input on the steering-wheel starting at steering-wheel straight

forward position and then performing complete cycles of triangular waves at constant steering-wheel

speed going to maximum steering-wheel angles range of interest right, then to the maximum left and

back to the maximum right again at a constant turning speed starting at 30 (°/s).

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ISO 22139:2022(E)

In this position increase steering-wheel speed to 60 (°/s) and going to the maximum left and back to

maximum right again.

Continue in the same way while increasing the steering-wheel speed in 30 (°/s) increments until

reaching the catch-up steering-wheel torque limit or when reaching the pre-set steering machine

torque limit or when reaching a decided maximum steering-wheel speed, e.g. 120 (°/s).

Depending on the specific test and test object other ranges and increments of turning speeds may be

used.
The tests can be repeated with either parking or foot brake, or both, applied.

Make sure not to exceed maximum temperatures specified by the manufacturer as this can damage the

system.

If the steering input is done by hand, it is very important to keep a constant steering-wheel speed

throughout the test and a minimum of five consistent test runs shall be made where the time histories

are checked.

The test runs for which the control criteria steering-wheel speed are best met shall be selected for data

analysis.
8.4 Measurement when manoeuvring at low speed

This test can be done at any chosen engine r/min but will typically start with engine at idle, e.g. 600 r/

min and then the test should be repeated with increased engine speeds e.g. (800, 1 000, 1 200 and

1 400) r/min. Other engine speeds can be used depending on vehicle and test purpose.

Choose a gear to keep the vehicle speed between 5 km/h and 10 km/h at the chosen engine r/min.

The exact vehicle speed is not very critical for the result as long as the speed is between 5 km/h and

10 km/h which is for making sure that when performing the manoeuvres, no significant dynamic side

forces are acting on the tyres and that the vehicle dynamic yaw behaviour is not influencing the result

in a significant way.

With the vehicle placed at the end of the test surface area, start driving at steering-wheel straight

forward position while keeping the engine speed constant at the chosen r/min.

Use the steering machine to give input on the steering-wheel starting at steering-wheel straight forward

position and then perform complete cycles of triangular waves with constant steering-wheel speed

going to the maximum steering-wheel angles range of interest right, then to the maximum left and back

to maximum right again at a constant turning speed starting at 120 (°/s). In this position increase to

180 (°/s) going to the maximum left and back to maximum right again. Continue in the same way while

increasing the steering-wheel speed in 60 (°/s) increments until reaching the catch-up steering-wheel

torque limit or when reaching the pre-set steering machine torque limit or when reaching a decided

maximum steering-wheel speed, e.g. 600 (°/s).

Depending on the specific test and test object other ranges and increments of turning speeds may be

used.
The test can be repeated while reversing the vehicle at low speed.

If the steering input is done by hand, it is very important to keep a constant steering-wheel speed.

A minimum of five consistent test runs at each steering-wheel speed shall be made where the time

histories are checked. The test runs for which the control criteria steering-wheel speed is best met

shall be selected for data analysis.

Performing the test at higher vehicle speeds (>10 km/h) may be done if for some reason this is of

interest, but it has to be taken into consideration that with increasing vehicle speeds the dynamic yaw

behaviour of the vehicle, for example, under/over steering and the corresponding time delays between

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ISO 22139:2022(E)

time signals will have increasingly influence on the test results, e.g. between steering-wheel speed and

steering-wheel torque time signals.

Especially when comparing steering characteristics between vehicles with different specifications

or when changing the load case on a specific vehicle it is important to understand if any

...

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