Heavy commercial vehicles and buses -- Vehicle dynamics simulation and validation -- Steady-state circular driving behavior

This document specifies a method for comparing simulation results from a vehicle model to measured test data for an existing vehicle according to steady-state circular driving tests as specified in ISO 14792. The comparison is made for the purpose of validating the vehicle model for this type of test. This document applies to heavy vehicles, including commercial vehicles, commercial vehicle combinations, buses and articulated buses as defined in ISO 3833 (trucks and trailers with a maximum weight above 3,5 tonnes and buses and articulated buses with a maximum weight above 5 tonnes, according to ECE and EC vehicle classification, categories M3, N2, N3, O3 and O4).

Véhicules utilitaires lourds et autobus -- Simulation et validation dynamique des véhicules -- Tenue de route en régime permanent sur trajectoire circulaire

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Status
Published
Publication Date
10-Dec-2019
Current Stage
6060 - International Standard published
Start Date
18-Nov-2019
Completion Date
11-Dec-2019
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ISO 19585:2019 - Heavy commercial vehicles and buses -- Vehicle dynamics simulation and validation -- Steady-state circular driving behavior
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INTERNATIONAL ISO
STANDARD 19585
First edition
2019-12
Heavy commercial vehicles and
buses — Vehicle dynamics simulation
and validation — Steady-state circular
driving behavior
Véhicules utilitaires lourds et autobus — Simulation et validation
dynamique des véhicules — Tenue de route en régime permanent sur
trajectoire circulaire
Reference number
ISO 19585:2019(E)
ISO 2019
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ISO 19585:2019(E)
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© ISO 2019

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Published in Switzerland
ii © ISO 2019 – All rights reserved
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ISO 19585:2019(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

6 Simulation model parameters and requirements ............................................................................................................. 3

6.1 General ........................................................................................................................................................................................................... 3

6.2 Basic vehicle parameters — Mass and geometry...................................................................................................... 3

6.3 Estimated vehicle parameters ................................................................................................................................................... 3

6.3.1 Height of the centre of gravity .............................................................................................................................. 4

6.3.2 Tyre lateral force characteristics ....................................................................................................................... 4

6.3.3 Suspension kinematics and compliance properties .......................................................................... 5

6.3.4 Steering system ................................................................................................................................................................. 5

6.4 Additional model requirements ............................................................................................................................................... 6

6.4.1 Powertrain ............................................................................................................................................................................. 6

6.4.2 Chassis stiffness ................................................................................................................................................................ 6

6.4.3 Cabin suspension ............................................................................................................................................................. 6

6.4.4 Active braking systems and other active systems ............................................................................... 6

6.4.5 Driver Control ..................................................................................................................................................................... 7

7 Physical tests ............................................................................................................................................................................................................ 7

7.1 General ........................................................................................................................................................................................................... 7

7.2 Test methods ............................................................................................................................................................................................. 7

7.2.1 Constant radius test with slowly increasing velocity ....................................................................... 8

7.2.2 Constant speed test with slowly increasing steering wheel angle ........................................ 8

7.3 Evaluation of test results ................................................................................................................................................................ 8

7.3.1 Characteristic curves .................................................................................................................................................... 8

7.3.2 Curve fitting .......................................................................................................................................................................... 8

7.3.3 Gradient values ...................................................................... .........................................................................................10

8 Simulation ................................................................................................................................................................................................................11

8.1 General ........................................................................................................................................................................................................11

8.2 Data recording ......................................................................................................................................................................................11

8.3 Documentation ....................................................................................................................................................................................11

9 Comparison of simulation and physical tests ......................................................................................................................11

9.1 Documentation ....................................................................................................................................................................................11

9.2 Calculation of boundary points..............................................................................................................................................11

9.3 Comparison of gradient values ..............................................................................................................................................14

9.4 Validation process .............................................................................................................................................................................14

Annex A (informative) Principle for comparing simulation and test results ..........................................................16

© ISO 2019 – All rights reserved iii
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ISO 19585:2019(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 2019 – All rights reserved
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ISO 19585:2019(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 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 2019 – All rights reserved v
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INTERNATIONAL STANDARD ISO 19585:2019(E)
Heavy commercial vehicles and buses — Vehicle dynamics
simulation and validation — Steady-state circular driving
behavior
1 Scope

This document specifies a method for comparing simulation results from a vehicle model to measured

test data for an existing vehicle according to steady-state circular driving tests as specified in ISO 14792.

The comparison is made for the purpose of validating the vehicle model for this type of test.

This document applies to heavy vehicles, including commercial vehicles, commercial vehicle

combinations, buses and articulated buses as defined in ISO 3833 (trucks and trailers with a maximum

weight above 3,5 tonnes and buses and articulated buses with a maximum weight above 5 tonnes,

according to ECE and EC vehicle classification, categories M3, N2, N3, O3 and O4).

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 14792, Road vehicles — Heavy commercial vehicles and buses — Steady-state circular tests

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

ISO 15037-2:2002, Road vehicles — Vehicle dynamics test methods — Part 2: General conditions for heavy

vehicles and buses

ISO 19364, Passenger cars — Vehicle dynamic simulation and validation — Steady-state circular driving

behaviour
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 3833, ISO 8855, ISO 15037-2,

ISO 19364 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
vehicle configuration
fundamental vehicle characteristic influencing the vehicle dynamics
EXAMPLE Number of axles, axle types, number and type of the vehicle units.

Note 1 to entry: An example of axle types can be independent suspension or rigid axle.

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ISO 19585:2019(E)
3.3
basic vehicle parameters

parameters not subject to model fitting, which are directly and accurately measurable on the test vehicle

EXAMPLE Masses and dimensions.
3.4
estimated vehicle parameters

parameters that may be used for model fitting, which are typically hard to be determined

EXAMPLE Mass moment of inertia and tyre characteristics.
3.5
vehicle model validity range

basic vehicle parameters (3.3) which may be changed if the type of vehicle combination and tyre type

are maintained

Note 1 to entry: For example, when wheel base is modified some of the estimated parameters may need to be

updated accordingly.
4 Principle

The open-loop test methods defined in ISO 14792 are used to determine the steady-state circular

driving behaviour of heavy commercial vehicles and buses as defined in ISO 3833.

Within this document, the purpose of the test is to demonstrate that a vehicle model can predict the

vehicle behaviour within specified tolerances. The vehicle model is used to simulate a specific existing

vehicle which is also tested physically, using one of the steady-state test methods specified in ISO 14792

for both test and simulation. For single vehicle units, alternatively consider a test with constant vehicle

velocity and slowly increasing steer or a test with constant turning radius and slowly increasing vehicle

velocity. Measurement results are used to define reference curves and tolerance boundaries, and

the respective simulation results are overlaid to analyse the deviation between physical testing and

simulation.

The validation process shall be repeated when changing the vehicle configuration, resulting in a

fundamental change of the structure of the vehicle model, for example when simulating a three-axle

vehicle instead of a two-axle vehicle or when simulating a vehicle combination instead of a single vehicle

unit. For one vehicle configuration, it is recommended to repeat the process of comparing simulation

and measurement results at least once for a change in basic vehicle parameters, for example for a

different loading condition or a different wheelbase, to validate the robustness of the vehicle model.

5 Variables

The variables of motion used to describe the behaviour of the vehicle shall be related to the reference

axis system (X, Y, Z) of the first vehicle unit (see ISO 8855). For the purpose of this document, the

reference point shall be the centre of gravity of the first vehicle unit. This provision overrides the similar

provision of ISO 15037-2. Measurement requirements shall be taken from ISO 14792 and ISO 15037-2.

The variables that shall be determined for compliance with this document are:
— longitudinal velocity, v ;
— steering-wheel angle, δ ;
— lateral acceleration, a ;
— roll angle of first vehicle unit, φ.
It is recommended that the following variables are also determined:
— steering-wheel torque, M ;
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ISO 19585:2019(E)
— yaw velocity, ψ ;
— sideslip angle, β;
— lateral acceleration of the cabin of the first vehicle unit, a ;
y,C
— lateral acceleration of the axles, a ;
— cabin roll angle of the first vehicle unit, φ ;
— roll angle(s) of the towed vehicle unit(s) at relevant points, φ ;
— articulation angle(s) between the vehicle units, Δψ.
6 Simulation model parameters and requirements
6.1 General

The vehicle model used to predict the behaviour of a vehicle of interest shall include a mathematical

model capable of calculating variables of interest for the test procedures being simulated. In this

document, the vehicle model is used to simulate one of the steady-state cornering test methods

described in 7.2 and provide calculated values of the variables of interest, see Clause 5.

Any data input into the model should be derived from design data or characteristics measurements of

the relevant components described below. If only input data of a similar component are available (e.g.

tyre characteristics measurements of tyres of a different brand), the validation process described in

this document may serve to identify the unknown component parameters by a parameter variation

within moderate, feasible boundaries.
6.2 Basic vehicle parameters — Mass and geometry

The vehicle model shall include all relevant masses of all vehicle units. The value of the mass and

the location of the centre of mass are essential properties of the vehicle for the tests covered in this

document. Table 1 shows the recommended maximum deviations.

Mathematical models of vehicle combinations shall include a correct representation of the position and

the rotational degrees of freedom of the coupling device(s) between the units.

Table 1 — Recommended maximum input data deviation between vehicle model and test

vehicle for basic vehicle parameters
Recommended maximum error
Vehicle parameter Typical usage range between model and physical
vehicle combination
Axle and coupling positions with front axle
0 m to 100 m ±0,02 m
as reference
Axle loads 0 kg to 15 000 kg ±100 kg
Vehicle unit mass 0 kg to 50 000 kg ±200 kg

To receive an accurate centre of gravity position in the longitudinal direction, each vehicle unit in the vehicle

combination with significant vertical force in joint couplings between units, such as fifth wheel on tractor or converter

dolly, shall also be measured separately on the weighting scale.
6.3 Estimated vehicle parameters

The following model parameters are based on representative data or calculations with expected

variability. As they have substantial influence on the vehicle behaviour during steady-state cornering,

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ISO 19585:2019(E)

they may be adjusted within feasible boundaries for the test vehicle and test conditions during the

validation process.

NOTE Moments and products of inertia have no effect under steady-state conditions, when angular

accelerations are negligible.
6.3.1 Height of the centre of gravity

For heavy commercial vehicles, the characteristic curve of the roll angle versus lateral acceleration

depends largely on the loading condition and the resulting height of the centre of gravity of the

vehicle units.

For the purpose of simulation, the height of the centre of gravity of the laden test vehicle can be

determined from measurement or design data of the unladen vehicle, modified in accordance with

the measured payload geometries and conditions. The loading conditions of the test vehicle shall be

recorded as accurately as possible to ensure that the remaining uncertainty in the height of the centre

of gravity shall lie within the boundaries shown in Table 2.

NOTE The height of the centre of gravity of the laden vehicle will be influenced not only by the mass

and position of the payload but by other associated effects including, but not limited to, suspension and tyre

deflections.
6.3.2 Tyre lateral force characteristics

The vertical, lateral, and longitudinal forces and moments where each tyre contacts the ground provide

the main actions on the vehicle. The simulated vehicle movement depends largely on the accuracy of the

calculated tyre forces and moments.

Large lateral slip angles can occur under the conditions covered in this document. Longitudinal slip

ratios are usually limited to the amounts needed to generate longitudinal forces to maintain a target

speed in the test. The tyre model should cover the entire ranges of slip (lateral and longitudinal),

camber angle relative to the ground, and vertical load that occur in the tests being simulated. The

simulated tests may take place on a flat homogenous surface; detailed tyre models that handle uneven

surfaces are not needed. The surface friction coefficient between the tyre and ground is an important

property for the limit friction conditions that can be encountered in steady-state circular driving tests.

The simulated tests involve conditions that are intended to be steady state; therefore, transient effects

in tyre response (e.g. relaxation length) are not relevant.

Typically, the tyre model applied within the vehicle model uses measurements of the tyre characteristics

on test rigs as a basis for the tyre model parameters. For the validation, tyre measurements of the same

tyres as used on the test vehicle (or, at least, measurements of a tyre with comparable size and wheel

load range) shall be used for parametrizing the tyre model. The validation process may be used for

adjusting the tyre model parameters within feasible boundaries. It is recommended that (on a dry and

even road surface) the deviation of the characteristic curves of the lateral tyre force versus the tyre slip

angle used in the tyre model and the curves of the tyre measurement should not exceed ±25 % for slip

angles below 10° (see Table 2). To avoid this tolerance being used to alter the balance between front

and rear tyre force characteristics, it is recommended that the relative difference between the lateral

force characteristics of the tyres at the front axle and the first driven rear axle of the first vehicle unit

is not modified by more than 20 % during this adjustment process, see also Table 2. For example, if

the cornering stiffness of the tyres of the first axle is increased by 25 %, the cornering stiffness of the

rear axle tyres shall also be increased by at least 5 % to meet this requirement. For this comparison of

characteristic curves of the tyres, curves of at least three wheel loads should be used, covering a wide

range of the wheel loads occurring during the test.

NOTE 1 It can be necessary to consider the tyre side force characteristics for slip angles up to 10° if, during the

physical tests, the nonlinear tyre force range is reached.
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ISO 19585:2019(E)

NOTE 2 When representing the twin tyres on the rear axle of heavy commercial vehicles by a single tyre in

the simulation model, the tyre force characteristics of the single tyres are the same as those of twin tyres but the

correct track width for twin tyres is parametrized in the model.
6.3.3 Suspension kinematics and compliance properties

The properties of the suspensions that determine how the tyre is geometrically located, oriented, and

loaded against the ground shall be represented properly in the vehicle model in order for the tyre model

to generate the correct tyre forces and moments. The suspension properties also determine how active

and reactive forces and moments from the tyres are transferred to the sprung mass.

The suspension properties should include change of location and orientation of the wheel due to

suspension deflection and applied load as would be measured in a physical system in kinematics and

compliance (K&C) tests. The K&C properties should not be altered during the validation process.

The vehicle model used for the steady-state cornering tests, shall cover the full range of springs and

auxiliary roll moments due to anti-roll bars and other sources of roll stiffness (including the torsional

frame stiffness for trucks). Rate-dependent forces such as those produced by shock absorbers are not

relevant in steady-state conditions.

During the validation process, the stiffness characteristics of springs and anti-roll bars shall be taken

from measurement or design data and should not be altered by more than the corresponding production

tolerances of the components, see Table 2.

NOTE 1 The vehicle model can cover the K&C properties either by a measurement-based approach or by

detailed suspension modelling. For detailed modelling, the results of K&C simulation and K&C measurement are

compared before conducting the entire vehicle simulation. If the vehicle tested for K&C properties is not the same

vehicle tested for handling performance, vehicle-to-vehicle variation in suspension geometry and compliance

may result in significant differences in K&C properties such as ride, roll, and compliance steer and camber.

NOTE 2 Conventional modelling of leaf springs typically under-represents the amount of auxiliary roll

stiffness that leaf spring torsional rate provides.
6.3.4 Steering system

The vehicle model shall include kinematic and compliance relationships (including non-linear effects)

between the steering wheel angle and the road wheel angles. Steering system damping and friction

are not relevant in steady-state conditions and can be neglected. For compensation of a constant offset

between the measured and the simulated curve of the steering wheel angle versus lateral acceleration,

the parameters of the steering system giving the overall steering ratio may be adapted to meet the

measured curve for low lateral accelerations (see Table 2).

NOTE 1 The steering system geometry can cause different Ackermann steering angles for left- and right-hand

steer. This effect is represented correctly in the simulation model.

NOTE 2 Wear in steering system components, particularly a power steering gear, can result in significant

changes in steering friction that affect the magnitude and linearity of steering compliance and thereby lateral

force and aligning torque compliance steer.
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ISO 19585:2019(E)

Table 2 — Recommended maximum deviation between initial estimated vehicle parameters

and validated estimated vehicle parameters
Recommended maximum varia-
Estimated vehicle parameter
tion range
Centre of gravity height ±10 %
Tyre lateral force vs. sideslip angle (for angles <10°) ±25 %
Relative difference of tyre lateral force vs. sideslip angle between front and
±20 %
first driven rear axle of the first vehicle unit
Stiffness of suspension components (for first vehicle unit) ±10 %
Overall steering gear ratio (for constant offset) ±5 %

Other model parameters with influence on the driving behaviour during steady-state cornering may also be varied

during the validation process.

The tolerances for tyre lateral force mainly serve to compensate for differences between measurements of the tyre

characteristics on test rigs and the tyre behaviour on the real road in the physical test status, including tyre wear, tyre

temperature, variations in inflation pressure, and others. It is recommended that the simulation use tyre force and moment

properties measured on the same make and model tyre(s) with a wear state and date of manufacture similar to those fitted

to the test vehicle and at the same tyre pressure(s).
6.4 Additional model requirements

The following model parameters may have additional influence on the vehicle behaviour during steady-

state cornering and should therefore be included in the simulation model.
6.4.1 Powertrain

In the steady-state steering manoeuvre, motive power is applied as needed to achieve the vehicle target

lateral acceleration. The transfer of drive torque to the wheels
...

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