ISO 22140:2021
(Main)Passenger cars — Validation of vehicle dynamics simulation — Lateral transient response test methods
Passenger cars — Validation of vehicle dynamics simulation — Lateral transient response test methods
This document specifies methods for comparing computer simulation results from a vehicle mathematical model to measured test data for an existing vehicle according to ISO 7401. The comparison is made for the purpose of validating the simulation tool for this type of test when applied to variants of the tested vehicle. It is applicable to passenger cars as defined in ISO 3833.
Voitures particulières — Validation de la simulation de la dynamique du véhicule — Méthodes d'essai de réponse transitoire latérale
General Information
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INTERNATIONAL ISO
STANDARD 22140
First edition
2021-06
Passenger cars — Validation of vehicle
dynamics simulation — Lateral
transient response test methods
Voitures particulières — Validation de la simulation de la dynamique
du véhicule — Méthodes d'essai de réponse transitoire latérale
Reference number
ISO 22140:2021(E)
©
ISO 2021
---------------------- Page: 1 ----------------------
ISO 22140:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
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
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 22140:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Variables . 3
6 Simulation tool requirements . 3
6.1 General . 3
6.2 Mass and inertia . 3
6.3 Tires . 3
6.4 Suspensions . 4
6.5 Steering system . 4
6.6 Aerodynamics . 4
6.7 Brake system . 4
6.8 Powertrain . 5
6.9 Active control system (ESC system, active roll control, etc.) . 5
6.10 Data acquisition . 5
6.11 Driver controls . 5
7 Physical testing. 5
7.1 General . 5
7.2 Measuring equipment . 5
7.3 Test conditions . 5
7.4 Filtering of measured data . 6
7.5 Test methods . 6
7.5.1 Step input . 6
7.5.2 Sinusoidal input — One period . 7
7.5.3 Random input . 8
7.5.4 Pulse input. 8
7.5.5 Continuous sinusoidal input . 9
8 Simulation .10
8.1 General .10
8.2 Data recording and processing .10
8.3 Simulation method .10
8.3.1 Step input .10
8.3.2 Sinusoidal input — One period .10
8.3.3 Random input .11
8.3.4 Pulse input.11
8.3.5 Continuous sinusoidal input .12
9 Comparison between simulation and physical test results .13
9.1 Step input .13
9.2 Sinusoidal input — One period .15
9.3 Random input, pulse, and continuous sinusoidal input .17
9.3.1 General.17
9.3.2 Calculation of boundary point .17
9.3.3 Tolerance for frequency function .18
9.3.4 Validation criteria .19
10 Documentation .20
Bibliography .21
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ISO 22140:2021(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.
iv © ISO 2021 – All rights reserved
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ISO 22140:2021(E)
Introduction
The main purpose of this document is to provide a repeatable and discriminatory method for comparing
simulation results to measured test data from a physical vehicle for a specific type of test.
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 necessarily involves information obtained
from a number of different tests.
Since this test method quantifies only one small part of the complete vehicle handling characteristics,
the validation method associated with this test can only be considered significant for a correspondingly
small part of the overall dynamic behaviour.
© ISO 2021 – All rights reserved v
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INTERNATIONAL STANDARD ISO 22140:2021(E)
Passenger cars — Validation of vehicle dynamics
simulation — Lateral transient response test methods
1 Scope
This document specifies methods for comparing computer simulation results from a vehicle
mathematical model to measured test data for an existing vehicle according to ISO 7401. The comparison
is made for the purpose of validating the simulation tool for this type of test when applied to variants of
the tested vehicle.
It is applicable to passenger cars as defined in ISO 3833.
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 1176:1990, Road vehicles — Masses — Vocabulary and codes
ISO 2416, Passenger cars — Mass distribution
ISO 3833, Road vehicles — Types — Terms and definitions
ISO 7401:2011, Road vehicles — Lateral transient response test methods — Open-loop test methods
ISO 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
ISO 15037-1:2019, 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 1176, ISO 2416, ISO 3833,
ISO 8855 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
simulation
calculation of motion variables of a vehicle from equations in a mathematical model of the vehicle
system
3.2
simulation tool
simulation (3.1) environment including software, model, input data, and hardware in the case of
hardware in the loop simulation
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ISO 22140:2021(E)
4 Principle
Open-loop test methods specified in ISO 7401 are used to determine the lateral transient response of
passenger cars in time and frequency domain as defined in ISO 3833.
In time domain:
— step input;
— sinusoidal input (one period).
In frequency domain:
— random input;
— pulse input;
— continuous sinusoidal input.
The test characterizes transient response behaviour of a vehicle. Characteristic values and functions in
time and frequency domains are considered necessary for characterizing vehicle transient response.
Important characteristics in time domain are
— time lags between steering-wheel angle, lateral acceleration and yaw velocity,
— response times of lateral acceleration and yaw velocity,
— lateral acceleration gain (lateral acceleration divided by steering-wheel angle),
— yaw velocity gain (yaw velocity divided by steering-wheel angle), and
— over-shoot values.
Important characteristics in frequency domain are the frequency responses, i.e. amplitudes and phases
of:
— lateral acceleration related to steering-wheel angle;
— yaw velocity related to steering-wheel angle.
Within this document, the purpose of the test is to demonstrate that a vehicle simulation tool can
predict the vehicle behaviour within specified tolerances. A vehicle simulation tool is used to simulate a
specific existing vehicle running through the open-loop tests specified in ISO 7401.
The existing vehicle is physically tested at least three times to allow the test data to be compared with
the simulation results.
For time domain, response comparison is made between measured and simulated characteristic values
using tolerances of percent errors specified in this document.
For frequency domain, response comparison is made between measured and simulated characteristic
functions of amplitudes and phases using tolerances specified in this document. Simulation results
are used to define boundaries for frequency response curves, and the data from physical testing are
overlaid to see if the measurements fall within the acceptable ranges.
NOTE 1 This document can be used for different purposes. Depending on the purpose of the validation, only
parts of the validation requirements can be met.
NOTE 2 Tolerance requirements can differ for applications, thus different tolerance values can be agreed
between parties involved depending on the applications.
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ISO 22140:2021(E)
5 Variables
The following variables shall be measured from physical testing, and applying the measured steering-
wheel angle and longitudinal velocity as simulation input, yaw velocity and lateral acceleration are
computed:
— steering-wheel angle, δ ;
H
— yaw velocity, ψ ;
— lateral acceleration, a ;
Y
— longitudinal velocity, v .
X
The following optional variables may be measured from physical testing, and obtained from a
simulation tool:
— roll angle,φ ;
— sideslip angle, β;
— lateral velocity, v ;
Y
.
— steering-wheel torque, M
H
6 Simulation tool requirements
6.1 General
The simulation tool used to predict behaviour of a vehicle of interest shall include a mathematical model
capable of calculating variables of interest (see Clause 5) for the test procedures being simulated. In this
document, the mathematical model is used to simulate an open-loop test series as specified in ISO 7401
and provide calculated values of the characteristic variables and functions of interest.
The simulation tool shall be able to cover the lateral acceleration level of time domain tests where
2.
lateral acceleration value starts from the nominal value of 4,0 m/s
The procedure for obtaining input data from experiments may differ for simulation tools, however,
the input data shall not be manipulated for better correlation. Nonetheless, adaptation of input data to
actual testing conditions such as road friction should be allowed.
6.2 Mass and inertia
The mathematical model should include all masses, such as the chassis, engine, payloads, unsprung
masses, etc. The value of the mass, the location of the centre of mass, and moments and products of
inertia are essential properties of the vehicle for the tests covered in this document.
Vehicles with significant torsional frame compliance require a more detailed representation that
includes frame-twist effects that occur in extreme manoeuvres.
6.3 Tires
The vertical, lateral, and longitudinal forces and aligning and overturning moments where each tire
contacts the ground provide the main actions on the vehicle. The fidelity of the prediction of vehicle
movement depends on the fidelity of the calculated tire forces and moments. Differences between
the tire force and moment measurements used for the model and those used in vehicle testing can
be expected due to different wear and aging histories. Although it is difficult to account for these
differences, it is important to acknowledge and understand them.
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ISO 22140:2021(E)
Large lateral slip angles and camber angles can occur under the conditions covered in this document.
The tire model shall cover the entire range of slip (lateral and longitudinal), inclination angle relative
to the ground, and load that occur in the tests being simulated. The tire lateral force reduction at high
slip angles is a critical characteristic that shall be comprehended by the tire testing and modelling. The
effect of combined tire lateral and longitudinal slip on forces and moments shall also be modelled.
The surface friction coefficient between the tire and ground is an important property for the limit
friction conditions that can be encountered in tests.
The simulated tests take place on a flat homogenous surface; detailed tire models that handle uneven
surfaces are not needed. If the test surface has inclination for water drainage, this should be included in
the simulation.
6.4 Suspensions
The properties of the suspensions that determine how the tire is geometrically located, oriented, and
loaded against the ground shall be represented properly in order for the tire model to generate the
correct tire forces and moments. The suspension properties also determine how active and reactive
forces and moments from the tires are transferred to the sprung mass.
The suspension properties should include change of location and orientation of the wheel due to
suspension vertical deflection, steering, and compliance due to applied load as would be measured in a
physical system in kinematics and compliance (K&C) tests.
The model shall cover the full nonlinear range encountered in the tests for springs, jounce and rebound
bumpers, and auxiliary roll moments due to anti-roll bars and other sources of roll stiffness.
Rate-dependent forces such as shock absorbers are significant and shall cover the range of suspension
jounce and rebound rate encountered in the tests.
6.5 Steering system
The steering system interacts with the suspensions to determine how the tire is oriented on the ground.
The test requires that either a robot or driver provides steering wheel control. The model should include
kinematical and compliance relationships needed to calculate the road wheel angles from the steering-
wheel angle.
The model should include the effects of active control systems, if applicable in the test.
If a robot controller provides the steering, the model does not need to predict the associated steering-
wheel torque for this document. However, it should be recognized that inadequate steering robot torque
capacity can result in steering inputs that do not match the intended angle. This can be a source of
discrepancy between simulation and test results.
6.6 Aerodynamics
The model should include aerodynamic effects that influence tire load and overall vehicle drag for
speeds up to 120 km/h.
6.7 Brake system
If the brakes are not engaged during the testing, then the brake system is not needed. However, if an
active controller engages that uses the brakes to control the vehicle during the test covered in this
document (see 6.9), then the vehicle brake model shall include the actuators and response properties
that affect the controlled vehicle response.
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ISO 22140:2021(E)
6.8 Powertrain
In the open-loop steering manoeuvre covered in this document, the standard speed is 100 km/h, and
other test speeds of interest may be used (preferably in 20 km/h steps). The model should include the
drag on the driven wheels, as needed to replicate this behaviour. Inertial effects that influence the
wheel spin dynamics during any intervention by active control system shall be included.
Other aspects of powertrain behaviour that are important for other kinds of tests (engine power,
dynamic responses to throttle, shifting and clutch behaviour) are probably not needed for constant
speed of the tests; however, if a chassis control system engages, then any aspects of the powertrain that
influence the controller behaviour shall be included in the powertrain model.
6.9 Active control system (ESC system, active roll control, etc.)
Any electronic control system that engages in the physical vehicle for the open-loop test manoeuvre
covered in this document shall be included in the simulated version.
Physical controllers and/or mechanical components may be linked to the simulated vehicle by hardware
in the loop.
The control system model shall include actuators that are not already part of the vehicle brake model
(see 6.7), transfer delays, and control logic.
The transmission behaviour of the signal quality and the time delay should be included in the model.
6.10 Data acquisition
Procedures for extracting signals from the simulation should mimic the procedures used to obtain
signals from the physical vehicle for the variables listed in Clause 5. For example, sensor location,
orientation, data processing including filtering, in the simulation should match the physical test setup.
6.11 Driver controls
The test methods described in Clause 7 require control of steering and speed. The simulation tool
shall be capable of applying the driver controls (steering, throttle, gear selection) measured from the
selected test method.
7 Physical testing
7.1 General
An existing vehicle of interest shall be tested using test procedures specified in ISO 7401, where five
test methods are defined; step input and one period sinusoidal input test for time domain, and random
input, pulse input, and continuous sinusoidal input test for frequency domain. These test methods are
optional, but at least one of each domain type shall be performed.
NOTE This document does not define all the details of the testing procedure. Clause 7 describes the parts of
the test procedure that are typically simulated.
7.2 Measuring equipment
Specification for measuring equipment, installation and data processing shall be in accordance with
ISO 7401:2011, Clause 8.
7.3 Test conditions
General test conditions shall be in accordance with ISO 7401:2011, Clause 9.
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ISO 22140:2021(E)
Tests shall be carried out with the design loading condition where the total vehicle mass shall consist
of the complete vehicle kerb mass (code: ISO-M06) in accordance with ISO 1176:1990, 4.6, plus the
masses of the driver and the instrumentation. The mass of the driver and the instrumentation shall not
exceed 150 kg. The load distribution shall be equivalent to that of two occupants in the front seats, in
accordance with ISO 2416. (see ISO 7401:2011, 9.2.2).
NOTE ISO 7401 requires testing with both the design and maximum loading conditions. However, since
minimum loading condition represents more realistic driving situation, validation is performed with the design
loading condition.
The warm-up procedures specified in ISO 15037-1:2019, 6.1 shall apply.
The test speed is defined as the nominal value of the longitudinal velocity. The standard test speed is
100 km/h. Other test speeds of interest may be used (preferably in 20 km/h steps).
7.4 Filtering of measured data
Raw measurements of steering-wheel angle, yaw velocity, lateral acceleration, longitudinal velocity,
and other optional variables shall be filtered and conditioned as specified in ISO 15037-1.
7.5 Test methods
7.5.1 Step input
7.5.1.1 Test procedure
Test procedure specified in ISO 7401:2011, 10.1 shall apply. Take data for both left and right turns. All
data shall be taken in one direction followed by all data in the other direction. Alternatively, take data
successively in each direction for each acceleration level, from the lowest to the highest level, this being
preferable with respect to tyre wear and symmetrical vehicle stress. Record the method chosen in the
test report (see ISO 7401:2011, Annex A).
Perform all test runs at least three times.
7.5.1.2 Data analysis
Response time, peak response time, and overshoot values specified in ISO 7401:2011, 10.2 shall be
calculated.
ISO 7401 does not specify how to determine peak or steady-state values. One method to determine
steady-state values would be averaging for 3 s after steady-state is estimated to be reached. Method
used for measured data shall be applied
...
INTERNATIONAL ISO
STANDARD 22140
First edition
Passenger cars — Validation of vehicle
dynamics simulation — Lateral
transient response test methods
Voitures particulières — Validation de la simulation de la dynamique
du véhicule — Méthodes d'essai de réponse transitoire latérale
PROOF/ÉPREUVE
Reference number
ISO 22140:2021(E)
©
ISO 2021
---------------------- Page: 1 ----------------------
ISO 22140:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
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
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 22140:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Variables . 3
6 Simulation tool requirements . 3
6.1 General . 3
6.2 Mass and inertia . 3
6.3 Tires . 3
6.4 Suspensions . 4
6.5 Steering system . 4
6.6 Aerodynamics . 4
6.7 Brake system . 4
6.8 Powertrain . 5
6.9 Active control system (ESC system, active roll control, etc.) . 5
6.10 Data acquisition . 5
6.11 Driver controls . 5
7 Physical testing. 5
7.1 General . 5
7.2 Measuring equipment . 5
7.3 Test conditions . 5
7.4 Filtering of measured data . 6
7.5 Test methods . 6
7.5.1 Step input . 6
7.5.2 Sinusoidal input — One period . 7
7.5.3 Random input . 8
7.5.4 Pulse input. 8
7.5.5 Continuous sinusoidal input . 9
8 Simulation .10
8.1 General .10
8.2 Data recording and processing .10
8.3 Simulation method .10
8.3.1 Step input .10
8.3.2 Sinusoidal input — One period .10
8.3.3 Random input .11
8.3.4 Pulse input.11
8.3.5 Continuous sinusoidal input .12
9 Comparison between simulation and physical test results .13
9.1 Step input .13
9.2 Sinusoidal input — One period .15
9.3 Random input, pulse, and continuous sinusoidal input .17
9.3.1 General.17
9.3.2 Calculation of boundary point .17
9.3.3 Tolerance for frequency function .18
9.3.4 Validation criteria .19
10 Documentation .20
Bibliography .21
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ISO 22140:2021(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.
iv PROOF/ÉPREUVE © ISO 2021 – All rights reserved
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ISO 22140:2021(E)
Introduction
The main purpose of this document is to provide a repeatable and discriminatory method for comparing
simulation results to measured test data from a physical vehicle for a specific type of test.
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 necessarily involves information obtained
from a number of different tests.
Since this test method quantifies only one small part of the complete vehicle handling characteristics,
the validation method associated with this test can only be considered significant for a correspondingly
small part of the overall dynamic behaviour.
© ISO 2021 – All rights reserved PROOF/ÉPREUVE v
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INTERNATIONAL STANDARD ISO 22140:2021(E)
Passenger cars — Validation of vehicle dynamics
simulation — Lateral transient response test methods
1 Scope
This document specifies methods for comparing computer simulation results from a vehicle
mathematical model to measured test data for an existing vehicle according to ISO 7401. The comparison
is made for the purpose of validating the simulation tool for this type of test when applied to variants of
the tested vehicle.
It is applicable to passenger cars as defined in ISO 3833.
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 1176:1990, Road vehicles — Masses — Vocabulary and codes
ISO 2416, Passenger cars — Mass distribution
ISO 3833, Road vehicles — Types — Terms and definitions
ISO 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
ISO 15037-1:2019, Road vehicles — Vehicle dynamics test methods — Part 1: General conditions for
passenger cars
ISO 7401:2011, Road vehicles — Lateral transient response test methods — Open-loop test methods
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1176, ISO 2416, ISO 3833,
ISO 8855 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
simulation
calculation of motion variables of a vehicle from equations in a mathematical model of the vehicle system
3.2
simulation tool
simulation (3.1) environment including software, model, input data, and hardware in the case of
hardware in the loop simulation
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ISO 22140:2021(E)
4 Principle
Open-loop test methods specified in ISO 7401 are used to determine the lateral transient response of
passenger cars in time and frequency domain as defined in ISO 3833.
In time domain:
— step input;
— sinusoidal input (one period).
In frequency domain:
— random input;
— pulse input;
— continuous sinusoidal input.
The test characterizes transient response behaviour of a vehicle. Characteristic values and functions in
time and frequency domains are considered necessary for characterizing vehicle transient response.
Important characteristics in time domain are
— time lags between steering-wheel angle, lateral acceleration and yaw velocity,
— response times of lateral acceleration and yaw velocity,
— lateral acceleration gain (lateral acceleration divided by steering-wheel angle),
— yaw velocity gain (yaw velocity divided by steering-wheel angle), and
— over-shoot values.
Important characteristics in frequency domain are the frequency responses, i.e. amplitudes and
phases of:
— lateral acceleration related to steering-wheel angle;
— yaw velocity related to steering-wheel angle.
Within this document, the purpose of the test is to demonstrate that a vehicle simulation tool can
predict the vehicle behaviour within specified tolerances. A vehicle simulation tool is used to simulate a
specific existing vehicle running through the open-loop tests specified in ISO 7401.
The existing vehicle is physically tested at least three times to allow the test data to be compared with
the simulation results.
For time domain, response comparison is made between measured and simulated characteristic values
using tolerances of percent errors specified in this document.
For frequency domain, response comparison is made between measured and simulated characteristic
functions of amplitudes and phases using tolerances specified in this document. Simulation results
are used to define boundaries for frequency response curves, and the data from physical testing are
overlaid to see if the measurements fall within the acceptable ranges.
NOTE 1 This document can be used for different purposes. Depending on the purpose of the validation, only
parts of the validation requirements can be met.
NOTE 2 Tolerance requirements can differ for applications, thus different tolerance values can be agreed
between parties involved depending on the applications.
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ISO 22140:2021(E)
5 Variables
The following variables shall be measured from physical testing, and applying the measured steering-
wheel angle and longitudinal velocity as simulation input, yaw velocity and lateral acceleration are
computed:
— steering-wheel angle, δ ;
H
— yaw velocity, ψ ;
— lateral acceleration, a ;
Y
— longitudinal velocity, v .
X
The following optional variables may be measured from physical testing, and obtained from a
simulation tool:
— roll angle,φ ;
— sideslip angle, β;
— lateral velocity, v ;
Y
.
— steering-wheel torque, M
H
6 Simulation tool requirements
6.1 General
The simulation tool used to predict behaviour of a vehicle of interest shall include a mathematical model
capable of calculating variables of interest (see Clause 5) for the test procedures being simulated. In this
document, the mathematical model is used to simulate an open-loop test series as specified in ISO 7401
and provide calculated values of the characteristic variables and functions of interest.
The simulation tool shall be able to cover the lateral acceleration level of time domain tests where
2.
lateral acceleration value starts from the nominal value of 4,0 m/s
The procedure for obtaining input data from experiments may differ for simulation tools, however,
the input data shall not be manipulated for better correlation. Nonetheless, adaptation of input data to
actual testing conditions such as road friction should be allowed.
6.2 Mass and inertia
The mathematical model should include all masses, such as the chassis, engine, payloads, unsprung
masses, etc. The value of the mass, the location of the centre of mass, and moments and products of
inertia are essential properties of the vehicle for the tests covered in this document.
Vehicles with significant torsional frame compliance require a more detailed representation that
includes frame-twist effects that occur in extreme manoeuvres.
6.3 Tires
The vertical, lateral, and longitudinal forces and aligning and overturning moments where each tire
contacts the ground provide the main actions on the vehicle. The fidelity of the prediction of vehicle
movement depends on the fidelity of the calculated tire forces and moments. Differences between
the tire force and moment measurements used for the model and those used in vehicle testing can
be expected due to different wear and aging histories. Although it is difficult to account for these
differences, it is important to acknowledge and understand them.
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Large lateral slip angles and camber angles can occur under the conditions covered in this document.
The tire model shall cover the entire range of slip (lateral and longitudinal), inclination angle relative
to the ground, and load that occur in the tests being simulated. The tire lateral force reduction at high
slip angles is a critical characteristic that shall be comprehended by the tire testing and modelling. The
effect of combined tire lateral and longitudinal slip on forces and moments shall also be modelled.
The surface friction coefficient between the tire and ground is an important property for the limit
friction conditions that can be encountered in tests.
The simulated tests take place on a flat homogenous surface; detailed tire models that handle uneven
surfaces are not needed. If the test surface has inclination for water drainage, this should be included in
the simulation.
6.4 Suspensions
The properties of the suspensions that determine how the tire is geometrically located, oriented, and
loaded against the ground shall be represented properly in order for the tire model to generate the
correct tire forces and moments. The suspension properties also determine how active and reactive
forces and moments from the tires are transferred to the sprung mass.
The suspension properties should include change of location and orientation of the wheel due to
suspension vertical deflection, steering, and compliance due to applied load as would be measured in a
physical system in kinematics and compliance (K&C) tests.
The model shall cover the full nonlinear range encountered in the tests for springs, jounce and rebound
bumpers, and auxiliary roll moments due to anti-roll bars and other sources of roll stiffness.
Rate-dependent forces such as shock absorbers are significant and shall cover the range of suspension
jounce and rebound rate encountered in the tests.
6.5 Steering system
The steering system interacts with the suspensions to determine how the tire is oriented on the ground.
The test requires that either a robot or driver provides steering wheel control. The model should include
kinematical and compliance relationships needed to calculate the road wheel angles from the steering-
wheel angle.
The model should include the effects of active control systems, if applicable in the test.
If a robot controller provides the steering, the model does not need to predict the associated steering-
wheel torque for this document. However, it should be recognized that inadequate steering robot torque
capacity can result in steering inputs that do not match the intended angle. This can be a source of
discrepancy between simulation and test results.
6.6 Aerodynamics
The model should include aerodynamic effects that influence tire load and overall vehicle drag for
speeds up to 120 km/h.
6.7 Brake system
If the brakes are not engaged during the testing, then the brake system is not needed. However, if an
active controller engages that uses the brakes to control the vehicle during the test covered in this
document (see 6.9), then the vehicle brake model shall include the actuators and response properties
that affect the controlled vehicle response.
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6.8 Powertrain
In the open-loop steering manoeuvre covered in this document, the standard speed is 100 km/h, and
other test speeds of interest may be used (preferably in 20 km/h steps). The model should include the
drag on the driven wheels, as needed to replicate this behaviour. Inertial effects that influence the
wheel spin dynamics during any intervention by active control system shall be included.
Other aspects of powertrain behaviour that are important for other kinds of tests (engine power,
dynamic responses to throttle, shifting and clutch behaviour) are probably not needed for constant
speed of the tests; however, if a chassis control system engages, then any aspects of the powertrain that
influence the controller behaviour shall be included in the powertrain model.
6.9 Active control system (ESC system, active roll control, etc.)
Any electronic control system that engages in the physical vehicle for the open-loop test manoeuvre
covered in this document shall be included in the simulated version.
Physical controllers and/or mechanical components may be linked to the simulated vehicle by hardware
in the loop.
The control system model shall include actuators that are not already part of the vehicle brake model
(see 6.7), transfer delays, and control logic.
The transmission behaviour of the signal quality and the time delay should be included in the model.
6.10 Data acquisition
Procedures for extracting signals from the simulation should mimic the procedures used to obtain
signals from the physical vehicle for the variables listed in Clause 5. For example, sensor location,
orientation, data processing including filtering, in the simulation should match the physical test setup.
6.11 Driver controls
The test methods described in Clause 7 require control of steering and speed. The simulation tool
shall be capable of applying the driver controls (steering, throttle, gear selection) measured from the
selected test method.
7 Physical testing
7.1 General
An existing vehicle of interest shall be tested using test procedures specified in ISO 7401, where five
test methods are defined; step input and one period sinusoidal input test for time domain, and random
input, pulse input, and continuous sinusoidal input test for frequency domain. These test methods are
optional, but at least one of each domain type shall be performed.
NOTE This document does not define all the details of the testing procedure. Clause 7 describes the parts of
the test procedure that are typically simulated.
7.2 Measuring equipment
Specification for measuring equipment, installation and data processing shall be in accordance with
ISO 7401:2011, Clause 8.
7.3 Test conditions
General test conditions shall be in accordance with ISO 7401:2011, Clause 9.
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Tests shall be carried out with the design loading condition where the total vehicle mass shall consist
of the complete vehicle kerb mass (code: ISO-M06) in accordance with ISO 1176:1990, 4.6, plus the
masses of the driver and the instrumentation. The mass of the driver and the instrumentation shall not
exceed 150 kg. The load distribution shall be equivalent to that of two occupants in the front seats, in
accordance with ISO 2416. (see ISO 7401:2011, 9.2.2).
NOTE ISO 7401 requires testing with both the design and maximum loading conditions. However, since
minimum loading condition represents more realistic driving situation, validation is performed with the design
loading condition.
The warm-up procedures specified in ISO 15037-1:2019, 6.1 shall apply.
The test speed is defined as the nominal value of the longitudinal velocity. The standard test speed is
100 km/h. Other test speeds of interest may be used (preferably in 20 km/h steps).
7.4 Filtering of measured data
Raw measurements of steering-wheel angle, yaw velocity, lateral acceleration, longitudinal velocity,
and other optional variables shall be filtered and conditioned as specified in ISO 15037-1.
7.5 Test methods
7.5.1 Step input
7.5.1.1 Test procedure
Test procedure specified in ISO 7401:2011, 10.1 shall apply. Take data for both left and right turns. All
data shall be taken in one direction followed by all data in the other direction. Alternatively, take data
successively in each direction for each acceleration level, from the lowest to the highest level, this being
preferable with respect to tyre wear and symmetrical vehicle stress. Record the method chosen in the
test report (see ISO 7401:2011, Annex A).
Perform all test runs at least three times.
7.5.1.2 Data analysis
Response time, peak response time, and overshoot values specified in ISO 7401:2011, 10.2 shall be
calculated.
ISO 7401 does not specify how to determine peak or steady-state values. One method to determine
steady-state values
...
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