Road vehicles -- Heavy commercial vehicles and buses -- Lateral transient response test methods

ISO 14793:2011 specifies test methods for determining the transient response behaviour of heavy commercial vehicles, heavy commercial vehicle combinations, buses and articulated buses, as defined in ISO 3833 for trucks and trailers above 3,5 t and buses above 5 t maximum weight, and in UNECE (United Nations Economic Commission for Europe) and EC vehicle classification, categories M3, N2, N3, O3 and O4.

Véhicules routiers -- Véhicules utilitaires lourds et autobus -- Méthodes d'essai de réponse transitoire latérale

General Information

Status
Published
Publication Date
02-Feb-2011
Current Stage
6060 - International Standard published
Start Date
21-Jan-2011
Completion Date
03-Feb-2011
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INTERNATIONAL ISO
STANDARD 14793
Second edition
2011-02-15
Road vehicles — Heavy commercial
vehicles and buses — Lateral transient
response test methods
Véhicules routiers — Véhicules utilitaires lourds et autobus —
Méthodes d'essai de réponse transitoire latérale
Reference number
ISO 14793:2011(E)
ISO 2011
---------------------- Page: 1 ----------------------
ISO 14793:2011(E)
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© ISO 2011

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Published in Switzerland
ii © ISO 2011 – All rights reserved
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ISO 14793:2011(E)
Contents Page

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

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

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

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

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

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

5 Reference system..................................................................................................................................2

6 Variables.................................................................................................................................................3

7 Measuring equipment ...........................................................................................................................3

7.1 Description.............................................................................................................................................3

7.2 Transducer installation.........................................................................................................................3

7.3 Data processing.....................................................................................................................................3

8 Test conditions ......................................................................................................................................7

8.1 General ...................................................................................................................................................7

8.2 Test track................................................................................................................................................7

8.3 Weather conditions ...............................................................................................................................7

8.4 Test vehicle ............................................................................................................................................8

8.5 Warm-up .................................................................................................................................................9

8.6 Test speed..............................................................................................................................................9

8.7 Lateral acceleration...............................................................................................................................9

8.8 Average longitudinal acceleration.....................................................................................................10

9 Step input .............................................................................................................................................10

9.1 Test procedure.....................................................................................................................................10

9.2 Data analysis........................................................................................................................................10

9.3 Data presentation ................................................................................................................................11

10 Sinusoidal input — One period (see ISO/TR 8725) ..........................................................................12

10.1 Test procedure.....................................................................................................................................12

10.2 Data analysis........................................................................................................................................12

10.3 Data presentation ................................................................................................................................13

11 Random input (see ISO/TR 8726) .......................................................................................................13

11.1 Test procedure.....................................................................................................................................13

11.2 Data analysis........................................................................................................................................14

11.3 Data presentation ................................................................................................................................14

12 Pulse input ...........................................................................................................................................15

12.1 Test procedure.....................................................................................................................................15

12.2 Data analysis........................................................................................................................................15

12.3 Data presentation ................................................................................................................................15

13 Continuous sinusoidal input..............................................................................................................16

13.1 Test procedure.....................................................................................................................................16

13.2 Data analysis........................................................................................................................................16

13.3 Data presentation ................................................................................................................................17

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

Annex B (normative) Test report — Presentation of results........................................................................24

Bibliography......................................................................................................................................................29

© ISO 2011 – All rights reserved iii
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ISO 14793:2011(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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

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.

ISO 14793 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 9, Vehicle

dynamics and road-holding ability.

This second edition cancels and replaces the first edition (ISO 14793:2003), which has been technically

revised.
iv © ISO 2011 – All rights reserved
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ISO 14793:2011(E)
Introduction

The main purpose of this International Standard is to provide repeatable and discriminatory test results.

The dynamic behaviour of a road vehicle is a very important aspect of active vehicle safety. Any given vehicle,

together with its driver and the prevailing environment, constitutes a closed-loop system that is unique. The

task of evaluating the dynamic behaviour is therefore very difficult since the significant interaction of these

driver-vehicle-environment elements is each complex in itself. A complete and accurate description of the

behaviour of the road vehicle must necessarily involve information obtained from a number of different tests.

Since this test method quantifies only one small part of the complete vehicle handling characteristics, the

results of these tests can only be considered significant for a correspondingly small part of the overall dynamic

behaviour.

Moreover, insufficient knowledge is available concerning the relationship between overall vehicle dynamic

properties and accident avoidance. A substantial amount of work is necessary to acquire sufficient and

reliable data on the correlation between accident avoidance and vehicle dynamic properties in general and the

results of these tests in particular. Consequently, any application of this test method for regulation purposes

will require proven correlation between test results and accident statistics.
© ISO 2011 – All rights reserved v
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INTERNATIONAL STANDARD ISO 14793:2011(E)
Road vehicles — Heavy commercial vehicles and buses —
Lateral transient response test methods
1 Scope

This International Standard specifies test methods for determining the transient response behaviour of heavy

commercial vehicles, heavy commercial vehicle combinations, buses and articulated buses, as defined in

ISO 3833 for trucks and trailers above 3,5 t and buses above 5 t maximum weight, and in UNECE (United

Nations Economic Commission for Europe) and EC vehicle classification, categories M3, N2, N3, O3 and O4.

NOTE The open-loop manoeuvres specified in this International Standard are not representative of real driving

conditions, but are nevertheless useful for obtaining measures of vehicle transient behaviour — particularly with respect to

that which the driver experiences — in response to several specific types of steering input under closely controlled test

conditions. For combinations where the response of the last vehicle unit is of importance, see ISO 14791.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.
ISO 1176:1990, Road vehicles — Masses — Vocabulary and codes
ISO 3833:1977, Road vehicles — Types — Terms and definitions

ISO/TR 8725:1988, Road vehicles — Transient open-loop response test method with one period of sinusoidal

input

ISO/TR 8726:1988, Road vehicles — Transient open-loop response test method with pseudo-random steering

input

ISO 8855:1991, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary

ECE Regulation No. 30, Uniform provisions concerning the approval of pneumatic tyres for motor vehicles and

their trailers
3 Terms and definitions

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

3.1
vehicle unit
unit of a vehicle combination which is connected with a yaw-articulation joint
EXAMPLE Tractor, semitrailer, dolly.

NOTE The number of vehicle units is one more than the number of articulation joints.

© ISO 2011 – All rights reserved 1
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ISO 14793:2011(E)
4 Principle

IMPORTANT — The method of data analysis in the frequency domain is based on the assumption that

the vehicle has a linear response. Over the whole range of lateral acceleration this is unlikely to be the

case, the standard method of dealing with such a situation being to restrict the range of the input so

that linear behaviour can be assumed and, if necessary, to perform more than one test at different

ranges of inputs which, together, cover the total range of interest.

The objective of these tests is to determine the transient response of a vehicle. Characteristic values and

functions of both linear and nonlinear behaviour are considered necessary for fully characterizing vehicle

transient response. Linear characteristic values and functions are determined with tests in the frequency

domain and nonlinear characteristic values and functions with tests in the time domain. In the case of vehicle

combinations, it is primarily the response of the first vehicle unit that is evaluated.

Important characteristics in the time domain are
⎯ time lags between steering-wheel angle, lateral acceleration and yaw velocity,
⎯ response times of lateral acceleration and yaw velocity (see 9.2.1),

⎯ lateral acceleration gain (lateral acceleration divided by steering-wheel angle),

⎯ yaw velocity gain (yaw velocity divided by steering-wheel angle), and
⎯ overshoot values (see 9.2.3).
Important characteristics in the frequency domain are the transfer functions of
⎯ lateral acceleration related to steering-wheel angle, and
⎯ yaw velocity related to steering-wheel angle,
expressed as gain and phase functions between input and output variables.

There are several test methods for obtaining these characteristics in the time and frequency domains, as

follows, the applicability of which depends in part on the size of the test track available.

a) time domain:
1) step input;
2) sinusoidal input (one period).
b) frequency domain:
1) random input;
2) pulse input;
3) continuous sinusoidal input.
5 Reference system

The variables of motion used to describe the vehicle behaviour in a test-specific driving situation relate to the

intermediate axis system (X, Y, Z) (see ISO 8855).

The location of the origin of the vehicle axis system (X , Y , Z ) is the reference point and shall be thus

V V V
defined.
2 © ISO 2011 – All rights reserved
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ISO 14793:2011(E)
6 Variables
The following variables shall be determined:
⎯ yaw velocity, ψ ;
⎯ lateral acceleration, a ;
⎯ steering-wheel angle, δ ;
⎯ longitudinal velocity, v .
The following variables may be determined:
⎯ lateral deviation, y;
⎯ roll angle at relevant points, ϕ;
⎯ steering-wheel torque, M ;
⎯ sideslip angle, β.

These variables, all but lateral deviation defined in ISO 8855, are not intended to comprise a complete list.

7 Measuring equipment
7.1 Description

The variables to be determined in accordance with Clause 6 shall be measured by means of appropriate

transducers. Their time histories shall be recorded on a multi-channel recording system having a time base.

The typical operating ranges and recommended maximum errors of the transducers and the recording system

are given in Table 1.
7.2 Transducer installation

The transducers shall be installed so that the variables corresponding to the terms and definitions of ISO 8855

can be determined.

If the transducer does not measure the variable directly, appropriate transformations into the reference system

shall be carried out.
7.3 Data processing
7.3.1 General

The frequency range relevant for this test is between 0 Hz and the maximum utilized frequency of f = 2 Hz.

max

Depending on the data processing method chosen (analog or digital data processing) the provisions of 7.3.2

or 7.3.3 shall be observed.

For lighter trucks it may be necessary to increase f to 3 Hz. In this case, the following requirements

max
concerning the frequency f may be modified correspondingly.
max
7.3.2 Analog data processing

The bandwidth of the entire, combined transducer/recording system shall be no less than 8 Hz.

© ISO 2011 – All rights reserved 3
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ISO 14793:2011(E)

In order to execute the necessary filtering of signals, low-pass filters of order four or higher shall be employed.

The width of the passband (from 0 Hz to frequency f at −3 dB) shall be not less than 9 Hz. Amplitude errors

shall be less than ± 0,5 % in the relevant frequency range of 0 Hz to 2 Hz. All analog signals shall be

processed with filters having phase characteristics sufficiently similar to ensure that time delay differences due

to filtering lie within the required accuracy for time measurement.

NOTE During analog filtering of signals with different frequency contents, phase shifts can occur. Therefore, a digital

data processing method, as described in 7.3.3, is preferable.

Table 1 — Variables, their typical operating ranges and recommended maximum errors

Variable Range Recommended maximum error of
combined transducer and recorder system
Yaw velocity − 50°/s to + 50°/s ± 0,5°/s
2 2 2
Lateral acceleration − 15 m/s to + 15 m/s ± 0,15 m/s
Steering-wheel angle − 360° to + 360° ± 2° for angles < 180°
± 4° for angles > 180°
Longitudinal velocity 0 m/s to 35 m/s ± 0,35 m/s
Roll angle − 15° to + 15° ± 0,15°
Side slip angle − 10° to + 10° ± 0,3°
Lateral velocity − 10 m/s to + 10 m/s ± 0,1 m/s
Steering-wheel torque
without power steering − 50 N·m to + 50 N⋅m ± 0,5 N⋅m
with power steering − 20 N·m to + 20 N⋅m ± 0,2 N⋅m

Transducers for some of the listed variables are not widely available and are not in general use. Many such instruments

are developed by users. If any system error exceeds the recommended maximum value, this and the actual maximum

error shall be stated under general data in the test report (see Annex A).
7.3.3 Digital data processing
7.3.3.1 General considerations

Preparation of analog signals includes consideration of filter amplitude attenuation and sampling rate in order

to avoid aliasing errors, and filter phase lags and time delays. Sampling and digitizing considerations include

presampling amplification of signals so as to minimize digitizing errors, the number of bits per sample, the

number of samples per cycle, sample and hold amplification, and timewise spacing of samples.

Considerations for additional phaseless digital filtering include the selection of passbands and stopbands, and

the attenuation and allowable ripple in each, as well as correction of anti-alias filter phase lags. Each of these

factors shall be considered so that an overall data-acquisition accuracy of ± 0,5 % is achieved.

7.3.3.2 Aliasing errors

In order to avoid uncorrectable aliasing, the analog signals shall be appropriately filtered before sampling and

digitizing. The order of the filters used and their passband shall be chosen according to both the required

flatness in the relevant frequency range and the sampling rate. The minimum filter characteristics and

sampling rate shall be such that

⎯ within the relevant frequency range of 0 Hz to f = 2 Hz the attenuation is less than the resolution of the

max
data acquisition system, and

⎯ at one-half the sampling rate (i.e. the Nyquist or “folding” frequency) the magnitudes of all frequency

components of signal and noise are reduced to less than the system resolution.
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ISO 14793:2011(E)

For 12-bit data acquisition systems with a resolution of 0,05 % the filter attenuation shall be less than 0,05 %

to 2 Hz, and the attenuation shall be greater than 99,95 % at all frequencies greater than one-half the

sampling frequency.
NOTE For a Butterworth filter the attenuation is given by
⎛⎞f
max
and
⎛⎞f
⎝⎠0
where
n is the order of the filter;
f is the relevant frequency range (2 Hz);
max
f is the filter cut-off frequency;
f is the Nyquist or “folding” frequency;
f is the sampling frequency = 2 × f
s N
For example, for a fourth-order filter:
⎯ for A = 0,999 5, f = 2,37 × f = 4,74 Hz;
0 max
⎯ for A = 0,000 5, f = 2 × (6,69 × f ) = 63,4 Hz.
7.3.3.3 Phase shifts and time delays for anti-aliasing filtering

Excessive analog filtering shall be avoided, and all filters shall have sufficiently similar phase characteristics to

ensure that time delay differences lie within the required accuracy for the time measurement.

Phase shifts are especially significant when measured variables are multiplied together to form new variables.

This is because, while amplitudes multiply, phase shifts and associated time delays add. Phase shifts and

time delays are reduced by increasing f . Whenever equations describing the presampling filters are known, it

is practical to remove their phase shifts and time delays by simple algorithms performed in the frequency

domain.

NOTE In the frequency range in which the filter amplitude characteristics remain flat, the phase shift, ϕ, of a

Butterworth filter can be approximated by
ϕ = 81° (f/f ) for 2nd order,
⎯ ϕ = 150° (f/f ) for 4th order,
⎯ ϕ = 294° (f/f ) for 8th order.
The time delay for all filter orders is t = (ϕ/360°) × (1/f )
© ISO 2011 – All rights reserved 5
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ISO 14793:2011(E)
7.3.3.4 Data sampling and digitizing

At 2 Hz the signal amplitude changes by up to 1,25 %/ms. To limit dynamic errors caused by changing analog

inputs to 0,1 %, sampling or digitizing time shall be less than 80 × 10 s. All pairs or sets of data samples to

be compared shall be taken simultaneously or over a sufficiently short time period.

In order not to exceed an amplitude error of 0,5 % in the relevant frequency range from zero to f , the

max
sampling rate, f , shall be at least 30 f .
s max
7.3.3.5 Data acquisition system requirements

The data acquisition system shall have a resolution of 12 bits or more (± 0,05 %) and an accuracy of

2 LSB ± 0,1 %. Anti-aliasing filters shall be of order four or higher and the relevant frequency range shall be

from 0 Hz to f .
max

For fourth-order filters, f shall be greater than 2,37 f if phase errors are subsequently adjusted in digital data

0 max

processing, and greater than 5 f otherwise; data sampling frequency f shall be greater than 13,4 f .

max s 0

For filters of orders other than the fourth order, f and f shall be selected for adequate flatness and prevention of

0 s
alias error.

Amplification of the signal before digitizing shall be such that in the digitizing process the additional error is less

than 0,2 %. Sampling and digitizing time for each data channel sampled shall be less than 80 × 10 s.

7.3.3.6 Digital filtering

For filtering of sampled data in data evaluation, phaseless (zero-phase-shift) digital filters shall be used, in

accordance with the following (see Figure 1):
⎯ the passband shall range from 0 Hz to 2 Hz;
⎯ the stopband shall begin at < 6 Hz;
⎯ the filter gain in the passband shall be 1 ± 0,005 (100 ± 0,5) %;
⎯ the filter gain in the stopband shall be u 0,01 (u 1 %);
⎯ the filter gain shall fall within the unshaded area of Figure 1.
6 © ISO 2011 – All rights reserved
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ISO 14793:2011(E)
X frequency, in Hz
Y filter gain
Passband.
Stopband.
Figure 1 — Required characteristics of phaseless digital filters
8 Test conditions
8.1 General

Limits and specifications for the ambient wind and vehicle test conditions in accordance with 8.3 and 8.4 shall

be maintained throughout the test. Any deviations shall be shown in the test report (see Annex A), including

the individual diagrams of the presentation of results (see Annex B).
8.2 Test track

All standard tests shall be carried out on a smooth, clean, dry and uniform paved road surface. The gradient of

the paved surface shall not exceed 2,5 % in any direction when measured over any distance greater than or

equal to the vehicle track. In addition, for tests concerned with damping of combination vehicles, the gradient

of the test surface shall not exceed 1 % along the path of the vehicle as measured over any distance of 25 m

or more. For each test the road surface conditions and paving material shall be recorded in the test report

(see Annex A).
8.3 Weather conditions
During the measurements, ambient wind velocity shall not exceed 5 m/s.

For each test procedure, weather conditions shall be recorded in the test report (see Annex A).

Since, in certain cases, ambient temperature can have a significant influence on test results, it should be

taken into account when making comparisons between vehicles.
© ISO 2011 – All rights reserved 7
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ISO 14793:2011(E)
8.4 Test vehicle
8.4.1 General data

Appropriate general data on the test vehicle or vehicle unit shall be presented in the test report in accordance

with Annex A.
8.4.2 Tyres

For the standard test conditions, new tyres shall be fitted on the test vehicle according to the vehicle

manufacturer's specifications. They shall have a tread depth of at least 90 % of the original value in the

principal grooves within 0,75 of the tread breadth (in accordance with specifications for tread-wear indicators

given in ECE Regulation No. 30), shall have been stored in accordance with the manufacturer's

recommendation and shall not have been manufactured more than two years prior to the test. The date of

manufacture shall be noted in the test report (see Annex A).

NOTE The tread breadth is the width of that part of the tread which, with the tyre correctly inflated, is in contact with

the road in normal straight-line driving.

If not otherwise specified by the tyre manufacturer, the tyres shall be run in for at least 150 km on the test

vehicle or an equivalent vehicle without excessively harsh use such as severe braking, acceleration, cornering

or hitting the kerb. After running in, the tyres shall be maintained at the same position on the vehicle

throughout the tests.

Tyres shall be inflated to the pressure specified by the vehicle manufacturer for the test vehicle configuration.

The tolerance for setting the cold inflation pressure is ± 2 %.

Inflation pressure and tread depth before tyre warm-up and after completion of the test shall be recorded in

the test report (see Annex A).

The tests may also be performed with tyres in any state of wear as well as with retreaded or regrooved tyres.

The details shall be recorded in the test report (see Annex A). As tread depth or uneven tread wear can have

a significant influence on test results, these should be taken into account when making comparisons between

vehicles or between tyres.
8.4.3 Other operating components

For the standard test conditions, any operating component likely to influence the results of a test (e.g. shock

absorbers, springs and other suspension components and suspension geometry) shall be as specified by the

manufacturer. Any deviations from the manufacturer's specification shall be recorded in the test report

(see Annex A).

Levelling systems of the chassis and cabin suspension which affect the response behaviour inappropriately

should be disabled during steady-state and step-input tests.
8.4.4 Vehicle loading conditions
8.4.4.1 General
The maximum design total mass (Code: ISO-M07) and the m
...

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