Bsi bs au 230 1989 (1999) iso 7401 1988

BRITISH STANDARD AUTOMOBILE SERIES BS AU 230 1989 ISO 7401 1988 Methods of Test for lateral transient response behaviour of passenger cars [ISO title Road vehicles — Lateral transient response test me[.]

This Bri shStan ard, ha ing

b en pre ared u der the

directonof the Automo ile

Stan ards Policy Commi e ,

waspublished u der the

The folowing BSI references

relate to the work on this

stan ard:

Commi e referenceAUE/15

Draft for comment8 /77 9 DC

The prep ration of this BritishStand rd was entrusted b the Automobi e

Stand ards Pol cy Commit e ( AUE/-) to Tech ical Commit e AUE/ 15, upon

which the fol owing bod ies were represented :

Association of Traier Man facturer

Carav an Club

Dep rtment of Transport

Metropol tan Polce

Motor Ind ustry Resear h Association

National Carav an Cou ci Limited

Society of Motor Man facturer and Tra er Limited

Am endm ents is ued sinc publ cation

Amd No Date of is ue Comments

Fig ure 3 — Sin soid l input ( one period ) — Time histories 13

Fig ure 4 — Random/ pulse input — Harmonic content of

Fig ure 5 — Random/pulse/ contin ous sin soid l input —

Ta le 3 — Sinusoid l input ( one period) — Response d ta

Stand ards Pol cy Commit e and is identical with ISO7 01:19 8 “ R oa d

vehicle — La ter a l tr a nsient r espons te t method s” prep red b Tech ical

Commit e ISO/TC 2 , Roa v ehicles, and publshed b the International

Org anization for Stand rdization ( ISO)

Term inolog y and conventions The text of the International Stand rd has

be n a prov ed as suita le for publcation as a BritishStand rd without

d ev iation Some terminolog y and certain conv entions are not identical with those

used in BritishStand rds; at ention is d rawn especialy to the fol owing

The comma has be n used as a decimal marker In BritishStand ards it is cur ent

practice to use a ful point on the b selne as the decimal marker

W herev er the words “ International Stand rd” a pear,refer ing to this stand rd ,

they should be rea as “BritishStand ard ”

The Tech ical Commit e has rev iewed the prov isions of ISO1 7 , ISO2416 and

ISO3 3 , to which reference is ma e in the text, and has decid ed that they are

ac epta le for use in conju ction with this stand ard

A British Stand ard d oes not purport to includ e al the neces ary prov isions of a

contract User of British Stand rd s are responsible for their cor ect a plcation

Com pl anc with a British Standard does not ofitself confer im m unity

f om leg al o l g ations

Cros - referenc

Inte national Stand rd Cor esp nding BritishStand rd

ISO413 :19 2 BS AU18 :19 3 Method o te t fr stea d y sta te cor ner ing

beha viour f r r oa d vehicle

( Id entical

Sum mary of pag es

This document comprises a f ont cov er, an insid e font cov er, p g esi andi ,

p g es1 to16, an inside b ck cov er and a b ck cov er

This stand rd has be n up ated ( se copy rig ht d ate) an ma hav e ha

amendments incorporated This wi l be indicated in the amendment ta le on the

inside f ont cov er

0 Introduction

0.1 General

The roa -hold ing a i ty of a road v ehicle is a most

important p rt of activ e v ehicle safety Any g iv en

v ehicle, together with its driv er and the prev ai ing

env ironment, forms a u iq ue closed -lo p sy stem

The task of ev aluating road -holding a i ity is

therefore v ery dificult because of the sig nificant

interaction of these driv er-v ehicle-road elements,

each of which is in itself complex A complete an

ac urate d es ription of the behav iour of the road

v ehicle must neces ari y inv olv e information

obtained f om a n mber of tests of d iferent ty pes

Because they q uantify only a smal p rt of the whole

hand ling field, the results of these tests can only be

considered sig nificant for a cor espond ing ly smal

p rt of the overal v ehicle handl ng behav iour

More v er, nothing is k own a out the relationship

betwe n the results of these tests and ac id ent

av oid nce Consid era le work is neces ary to

acq uire suficient and rela le d ta on the

cor elation betwe n handl ng properties in g eneral,

an ac ident av oid nce

It is therefore not pos ible to use these procedures

and test results for reg ulation purposes at the

moment The best that can be ex ected is that the

transient response tests are used as some among

many other mostly transient tests, which tog ether

cover the field of v ehicle dy namic behav iour

Final y , the role of the ty res is important an results

ma be strong ly influenced b the ty pe and

condition of ty res

0.2 Obje t of tests

The primary object of these tests is to d etermine the

transient response behav iour of a v ehicle

Characteristic v alues and fu ctions in the time

d omain and f eq uency d omain are considered

neces ary to characteriz the transient response of

v ehicles

Important c iteria in the time domain are:

— time lag s betwe n ste ring -whe l ang le,

lateral ac eleration and y aw v elocity ;

— response times of lateral ac eleration and y aw

v elocity ( se 6.1.1);

— lateral ac eleration g ain ( lateral ac eleration

d iv ided b ste ring -whe l ang le);

— y aw v elocity g ain ( y aw v elocity d iv id ed b

ste ring -whe l ang le);

— ov er ho t v alues ( se 6.1.3);

— v ehicle TB factor ( se 7.1.1.2)

The c iteria lsted a ov e show some cor elation with

subjectiv e ev aluation during road driv ing

Important c iteria in the feq uency domain are the

f eq uency responses of

— lateral ac eleration related to ste ring -whe l

ang le;

— y aw v elocity related to ste ring -whe l ang le;

— phase betwe n input and output fu ctions

There are sev eral test methods to obtain these

c iteria, the a plca i ty of which depends in p rt

on the siz of the test track av ai a le, in the domains

of time and feq uency :

— contin ous sin soid al input

These test methods are optional At least one of each

d omain ty pe shal be per ormed The method s

chosen shal be indicated in the g eneral d ta

presentation ( se Annex A) and in the presentation

of test results ( se Annex B)

It is neces ary to measure

— ste ring -whe l ang le;

— v ehicle rol ang le;

— ste ring -whe l torq ue

The v aria les lsted are not intended to comprise a

complete lst

NOT Strictly sp aking , test results b sed on lateral

ac eleraton should not b used for comp rison ofthe

p rormance of diferent v hicles This is b cause lateral

ac eleraton, as precisely defined,is me sured at rig ht ang les to

the v hicle x-a is

As refer ed to an a is system defined as folows:

a is sys em : Rig ht-han orthog onal a is system fix d in the v hicle such that is orig in is at the centre of g ra iy of the v ehicle

Thex½-a is is long itu inal forward, the y½-a is is lateral an the z ½-a is is v rtcal upwards

To o erome this dificulty, lateral aceleraton ma b cor ected

for v ehicle sideslip ang le, which g iv s the quant y “centrip tal

ac eleraton” Howe er, the e tent of this corecton is not likely

to e ce d a few p r ent an can g eneraly b neg lected

1 Scope and field ofappl cation

This International Stand rd specifies test methods

to d etermine transient response behav iour: it

a ples to p s eng er car as defined in ISO3 3

The measurement of stea y -state properties is

defined in ISO413

The open- o p mano uv res specified in these test

method s are not representativ e of real d riv ing

cond itions but are useful to obtain measures of

v ehicle transient behav iour in response to sev eral

specific ty pes of ste ring input u der closely

controled test conditions

NOT I is imp rtant to rememb r that the method of data

analy sis in the fe uency domain is b sed on the as umpton that

the v hicle has a line r resp nse Ov r the whole rang e of lateral

ac eleraton this ma not b the case; the stan ard method of

de ling wih such a siuaton is to restrict the rang e of the input

so that line r b hav iour can b as umed,an if neces ary to

p rorm more than one test at diferent rang es of inputs which

tog ether co er the total input rang e that is of interest

2 Ref rences

ISO1 7 , R oa d vehicle — Weights — Voca bula r y

ISO2416, Pa ss nger ca r s — Loa d d istr ibut on

ISO3 3 , R oa d vehicle — Type — Ter ms a nd

d efini ions

ISO413 , R oa d vehicle — Stea d y sta te cir cula r te t

pr oc d ur e

ISO/TR8 25, R oa d vehicle — Tr a nsient open-lo p

r espons te t pr oc d ur e wih one per iod o sin soid a l

input

ISO/TR8 26, R oa d vehicle — La ter a l tr a nsient

r espons te t pr oc d ur e — Expla na tor y r epor t on the

r a nd om ste r ing input method

4)

3.1 Description

Those of the v aria les lsted in0.2 which are

selected for test purposes shal be monitored, using

a propriate transd ucer , and the d ata shal be

record ed on a multichan el recorder with a time

b se The normal operating rang es and

recommended ma imum er or of the

transd ucer/ recording sy stem are as shown in

Ta le 1

NOT Some of the transd cer listed are neiher widely

a aila le nor in g eneral use.Many such instruments are

dev elo ed b user If any sy stem eror e ce ds the ma imum

v lues recommen ed, this fact an the actual ma imum eror

shal b stated in the g eneral data ( se Anne A)

The v lues inTa le 1 are tentatv an pro isional u tl more

e p rience is av aila le To cov er al the tests outlined in this

Internatonal Stan ard,the minimum o eral b n width of the

entre me surement system inclu ing transd cer an recorder

shal b 8Hz If dig itzaton is p rormed,i shal b at a rate

suficient for the re uired analysis

3.2 Instal ation

Transducer instal ation an orientation wi v ary

ac ord ing to the ty pe of instrumentation used

Howev er, if a transd ucer do s not measure the

req uired v aria le d irectly , a propriate cor ections

for lnear an ang ular d isplacement shal be mad e

to its sig nals so as to obtain the req uired lev el of

ac uracy

3.2.1 Ste ring-whe l angle

A transducer shal be instal ed as specified b the

man facturer so as to obtain the ste ring -whe l

ang le relativ e to the sprung mas

3.2.2 Lateral ac eleration

A transducer shal be instal ed as specified b the

man facturer an mou ted either

a) on the sprung mas at the whole v ehicle centre

of g rav ity an alg ned with the v ehicle y-a is In

this case, it wi measure “ side ac eleration” an

its output shal be cor ected for the component of

g rav ity on the transd ucer a is due to both the

v ehicle rol ang le an any track sur ace

incl nation; or

b) on the spru g mas at any position and alg ned

p ral el to the v ehicle y-a is In this case, its

output shal be cor ected for its position relativ e

to the centre of g rav ity , which wi l g iv e “ sid e

ac eleration”, which in turn shal be cor ected for

the component of g rav ity on the transducer a is

due to both v ehicle rol ang le an any track

surace inclnation

3.2.3 Yaw velocit y

A transducer shal be instal ed as specified b the

man facturer with its a is al g ned with or p ralel

to the v ehicle z-a is

3.2.4 Side l p angle

A transducer shal be instal ed as specified b the

man facturer so as to determine sid eslp ang le at

the centre of g rav ity I it d oes not measure d irectly

at the centre of g rav ity , an a propriate cor ection

shal be ma e Its output shal also be cor ected for

rol motion influences

Sideslp ang le can be calculated f om coincident

measurements of other v aria les, for ex ample, y aw,

lateral and long itudinal v elocity at any point on the

v ehicle

4)

At present at the stag e of draft

Table 1 — Varia les

The v ehicle point to which the output of the

transd ucer

)

is refer ed shal be ind icated in the

g eneral d ta presentation ( se Annex A)

3.2.5 Fo ward velocity

A v elocity transd ucer shal be instal ed as specified

b the man facturer I it is not al g ned so as to

operate in the x-z plane, and p ral el to the test

track surace, its output shal be cor ected for any

l near or angular d isplacement f om this

3.2.6 Lateral velocit y

A v elocity transd ucer shal be instal ed as specified

b the man facturer I it is not al g ned so as to

operate in the y-z plane, and p ral el to the test

track surace, its output shal be cor ected for any

l near or ang ular d isplacement fom this, especial y

for rol motion influences

The v ehicle point to which the output of the

transducer

)

is refer ed shal be ind icated in the

g eneral d ta presentation ( se Annex A)

3.2.7 Vehicle r l angle

A transduce shal be instaled as specified b the

man facturer so as to measure the ang le betwe n

the v ehicle y-a is and the track sur ace

3.2.8 Ste ring-whe l t orque

A transducer shal be instaled, as specified b the

man facturer, so as to measure the torque a pled

to the ste ring -whe l a out its a is of rotation

3.2.9 Ste ring machine

I a ste ring machine is used , it shal be instal ed as

specified b the man facturer

All tests shal be car ied out on a u iform hard

sur ace which is f e of contaminants and has no

more than2% g ra ient as measured ov er a distance

betwe n5 and25m in any d irection For stand rd

test cond itions, a smo th dry p v ement of asphalt or

cement conc ete or a hig h-fiction test surace is

recommend ed

For the random input test, the test sur ace shal be

maintained ov er a track of8m minimum width for

a leng th suficient to permit at least3 s ru ning at

the test spe d , in a d ition to the ru -up an

stop ing requirements

The ambient wind spe d shal not exce d7m/s For

test spe ds a ov e3 m/s, a lower ma imum win

spe d is d esira le I the lateral component

ex ce d s4m/s it shal be noted in the g eneral d ta

presentation ( se Annex A)

4.2 Tyres

The tests ma be perormed with ty res in any state

of wear so long as a minimum of1,5mm of tread

d epth remains ov er the whole wid th and

cir umference of the ty res at the end of the tests

( se note)

Howev er, for stand rd ty re conditions, new ty res

shal be used after being ru - n for15 to20 km in

the a propriate position on the test car without

exces iv e har h use, for ex mple braking ,

ac elerating , cornering , hit ing the kerb, etc

Re om m ended m axim um e ror

of the com bined

transduc r/r corde sys em

Ste ring -whe l ang le ±3 0°

a

Assuming a conv ntonal ste ring system

5)

I is recommen ed that the centre of g ra iy or the p int of interecton b twe n a line con ectng the re r whe l centres an

the v ehicle long itu inal median plane is used as a reference p int

Ty res shal be inflated to the pres ure specified b

the v ehicle man facturer for the test v ehicle

config uration The tolerance for set ing the cold

pres ure is±0,0 b r

)

for pres ures up to2,5b r

and±2 % for pres ures a ov e2,5b r

NOT As in certain cases, the tre d de th has a sig nificant

influence on test results, i is recommen ed that i should b

taken into ac ou t when comp ring v hicles or tyres

The width is that p rt of the tyre which contacts the ro d surace

when the v hicle is statonary an the ste red whe ls are in the

straig ht-ahe d p si on

4.3 Operating components

All operating components lkely to influence the

results of this test ( for ex mple, condition and

set ing of shock a sorber , spring s and other

suspension components) shal be inspected to

d etermine whether they me t the man facturer’s

specifications The results of these inspections and

measurements shal be recorded and in p rticular

any dev iations fom man facturer’s specifications

shal be noted in the g eneral d ta presentation

( se Annex A)

4.4 Vehicle lo ding conditions

4.4.1 G eneral conditions

In no case shal the man facturer’s ma imum total

mas and the man facturer’s ma imum a le load ,

both as d efined in ISO1 7 , be exce ded The

complete v ehicle kerb mas as defined in ISO1 7

shal be reg ard ed as the minimum mas

Care shal be taken to g iv e minimum er or in the

location of the centre of g ra ity and in the v alues of

the moments of inertia as comp red to the load ing

cond itions of the v ehicle in normal use

4.4.2 Minimum loading conditions

The total v ehicle mas for the minimum loa ing

condition shal consist of the complete v ehicle kerb

mas ( se 4.4.1), plus the mas es of the driv er an

instrumentation The load distribution shal be

equiv alent to that prod uced b two oc up nts in the

f ont seats

4.4.3 Max imum loading conditions

For the ma imum loa ing cond ition, the total mas

of a fuly la en v ehicle shal consist of the complete

v ehicle kerb mas ( se 4.4.1), plus 6 kg for each

seat in the p s eng er comp rtment, and the

ma imum lug g ag e mas eq ualy distributed ov er

the lug g ag e comp rtment ac ording to ISO2416

Loa ing of the p s eng er comp rtment shal be

such that the actual whe l load s are eq ual to those

obtained b loa ing each seat with6 kg ac ord ing

to ISO2416 The mas of the driv er and

instrumentation shal be includ ed in the v ehicle

mas

5 Test method

5.1 Tyre warm -up

The ty res shal be warmed up prior to the tests b a

procedure equiv alent to driv ing5 0m at a lateral

ac eleration of3m/s

2

( left and rig ht turn each) or to

driv ing at the test spe d for a d istance of10km

5.2 Test spe d

All tests shal be carr ied out at a test spe d

of8 km/h ( d epending on v ehicle ca a i ity ) I

hig her or lower test spe ds are selected they shal be

in20km/h steps

5.3 Ste ring - whe l ang le am pl tude

The ste ring -whe l ang le ampltude shal be

determined b stea y -state driv ing on a cir le the

rad ius of which g iv es the preselected lateral

ac eleration at the req uired test spe d

5.4 Step input

The v ehicle shal be dr iv en at the test spe d ( se 5.2)

in a straig ht lne Starting f om0±0,5°/s y aw

v elocity eq ui brium condition, a ste ring input

shal be a pl ed as ra idly

7)

as pos ible to a

preselected v alue and maintained at that v alue for

sev eral second s or unti the measured v ehicle

motion v aria les reach a stea y state No chang e in

throt le position shal be ma e, ev en thoug h spe d

ma dec ease

Data shal be taken for both left and rig ht turns.All

the d ta ma be taken in one d irection folowed b

al the d ata in the other d irection As an alternativ e,

d ata ma be taken suc es iv ely in each d irection for

each ac eleration lev el g oing f om the lowest to the

hig hest The method chosen shal be noted in the

g eneral d ata

Data shal be taken throug h the d esired rang e of

ste ring inputs and response v aria le outputs

7)

De en ing on the lateral aceleraton desired an the e istng v ehicle p rameter Values b twe n2 0°/ s an 5 0°/ s are

considered suia le for the turning sp ed of the ste ring -whe l

The req uired lateral ac eleration lev el is4m/ s

are recommend ed

All test ru s shal be per ormed at least thre times

5.5 Sinusoidal input (one perio )

The v ehicle shal be driv en at the test spe d ( se 5.2)

in a straig ht l ne Starting f om0±0,5°/s y aw

v elocity eq ui ibrium cond ition, one ful period

sin soid al ste ring -whe l input shal be a pl ed

with a ste ring f equency of0,5Hz Optional

ste ring fequency of1 Hz is recommended The

al owa le ampl tude er or comp red to the true sine

wav e is±5% of the fir t peak v alue

Req uired lateral ac eleration lev el is4m/ s

up to the a hesion l mit ( se ISO/TR8 25) are

recommend ed No chang e in throt le position shal

be ma e, ev en thoug h spe d ma dec ease

Data shal be taken for both left and rig ht turns All

the d ata ma be taken in one direction fol owed b

al the d ta in the other d irection As an alternativ e,

d ata ma be taken suc es iv ely in each direction for

each ac eleration lev el g oing fom the lowest to the

hig hest The method chosen shal be noted in the

g eneral d ta presentation ( se Annex A)

All test ru s shal be per ormed at least thre times

in ord er to obtain mean v alues and stand ard

d ev iations

5.6 Random input

Test ru s shal be mad e b driv ing the v ehicle at the

req uired test spe d ( se 5.2) and making contin ous

inputs to the ste ring -whe l up to pred etermined

lmits of ste ring -whe l ampl tude ( se 5.3) This

l mit is d etermined ac ord ing to5.3 for a lateral

ac eleration lev el within the rang e in which the

v ehicle exhibits lnear behav iour ( se the note to

clause1) The recommend ed v alue of lateral

Any mechanical l mitations of ste ring -whe l ang le

shal not be used because of their efect on the

harmonic content of the input It is also important

that the input is contin ous because periods of

relativ e inactiv ity wi l seriously red uce the

sig nal/ noise ratio

In order to ensure ad eq uate hig h-f equency content,

the input must be energ etic; to ensure enoug h total

d ta, at least1 min of d ata is d esira le u les

ind icated confidence lmits permit a shorter time

Idealy , this should be a contin ous ru , but

practical considerations ma prev ent this for two

reasons Fir tly , the test track ma not be

suficiently long to permit a contin ous ru of such

a leng th at the req uired lateral ac eleration an

secondly , the computer used to analy se the d ta

ma not be larg e enoug h to hand le al the d ta at

one g o In either case, it is permis ible to use a

n mber of shorter ru s of at least3 s duration:

hav ing calculated the power spectral densities for

each ru , they can then be av erag ed The av erag ing

fu ction used shal be noted in the g eneral d ta

presentation ( se Annex A)

5.7 Pulse input

The v ehicle shal be d riv en at the test spe d ( se 5.2)

in a straig ht l ne Starting f om0±0,5°/ s y aw

v elocity eq ui ibrium cond ition, a triang ular

wav eform ste ring -whe l input shal be a pled

folowed b 3 to5s neutral ste ring -whe l position

The pulse width of0,3 to0,5s is required Eforts

shal be ma e to minimiz the ov er ho t of

ste ring -whe l ang le input The ampl tude of

ste ring -whe l ang le is determined ac ording to5.3

for a lateral ac eleration lev el of4m/s

2

The test shal be per ormed at least thr ee times

5.8 Continuous sinusoid l input

The v ehicle shal be d riv en at the test spe d ( se 5.2)

in a straig ht l ne Starting f om0±0,5°/ s y aw

v elocity equi ibrium condition, at least thre periods

of sin soid al ste ring -whe l input shal be a pled

with the predetermined ste ring -whe l ang le

ampl tude ( se 5.3) and f eq uency

The required lateral ac eleration lev el is4m/s

The ste ring f equency shal be inc eased in steps

It is recommended that the feq uency rang e cov ered

is up to4Hz

6 Da ta analysis

6.1 Step input

6.1.1 Re pons t ime

The transient response d ta red uction shal be

car ied out as folows: the orig in for each response is

that time when the ste ring -whe l ang le chang e

is5 % completed This is the reference point fom

which al response time d ta are measured

Response time is th s defined as the time,measured

f om this reference, for a v ehicle transient response

fir t to reach9 % of its new stead y -state v alue

( se Fig ure 1)

6.1.2 Peak re pons time

The peak response time is the time,measured f om

the orig in for a v ehicle transient response to reach

its peak v alue

8)

( se Fig ure 1)

6.1.3 O versho t value

The ov er ho t v alues are calculated as a ratio:

diference ofpeak v alue min s stead y -state

v alue/stead y -state v alue

6.2 Sinusoidal input (one perio )

6.2.1 G eneral

The test results ma be sensitiv e to the method of

d ta proces ing It is therefore recommend ed that

the procedure g iv en in ISO/TR8 25 be used

6.2.2 Lateral ac eleration

Lateral ac eleration in this test is d efined as the

fir t peak v alue of the lateral ac eleration cor ected

for v ehicle rol ang le at the v ehicle centre of g rav ity

6.2.3 Yaw velocit y

Yaw v elocity in this test is defined as the fir t peak

v alue of the y aw v elocity

6.2.4 Time lags

The time lag s betwe n the v aria les ste ring -whe l

ang le, lateral ac eleration and y aw v elocity are

calculated for the fir t and second peaks b means

of c os -cor elation of the fir t and secon halfwav es

respectiv ely ( positiv e and neg ativ e p rts ofthe time

history )

6.2.5 Lateral ac eleration g in

Lateral ac eleration g ain per unit ofste ring -whe l

ang le is calculated as the ratio betwe n the lateral

ac eleration ac ord ing to6.2.2 and the

cor esponding ste ring -whe l ang le ma imum

ampltude

6.2.6 Yaw velocity g in

Yaw v elocity g ain per u it of ste ring -whe l ang le is

calculated as the ratio betwe n the y aw v elocity

ac ording to6.2.3 an the cor esponding

ste ring -whe l ang le ma imum ampl tude

6.3 Random input

6.3.1 G eneral

The d ta proces ing can be car ied out most ra idly

b using a multi chan el real time analy ser, or b

using a computer with the a propriate software

( se ISO/TR8 26)

8)

In some instances, system damping ma b so hig h that a p ak v lue can ot b determined If this ocur , data she ts should

b marked ac ording ly

Fig ure 1 — Response tim e and peak response tim e

6.3.2 Prel minar analy sis

The record ed time history of forward v elocity shal

be d isplay ed and ex mined v isualy to ensure that it

is within5% of the nominal v alue

A Fourier analy sis shal be ma e of the

ste ring -whe l ang le time history , and the result

shal be d isplay ed as a g ra h of the input lev el

relativ e to that at the lowest feq uency v er us

f eq uency as shown inFig ure 4 ( se Annex B,

clauseB.3)

This g ra h shal be ex mined v isualy to ensure

a equate fequency content The recommend ed

ratio betwe n ma imum and minimum

ste ring -whe l angle shal not be g reater

than4 : 1( 12dB).I the ratio is g reater,the results

ma be d is ard ed or, if used, the extent of the ratio

shal be noted in the g eneral d ta presentation

( se Annex A)

6.3.3 Furt her pr c s ing

The d ta shal then be proces ed using a propriate

equipment to prod uce the trans er fu ction

ampl tude and phase information tog ether with the

coherence fu ction for the fol owing combinations of

input and output v aria les:

— lateral ac eleration per u it of ste ring -whe l

6.4.2 Prel minar analy sis

The record ed time history of long itudinal v elocity

shal be display ed and ex mined visual y to ensure

that it is within5% of the nominal v alue

NOT Althoug h i is desira le to ha e such data so that the

zero reference b fore stering an the zero reference after the

ste ring p raton b come the same, the line con ectng the p int

of ini aton of chang es an the p int of completon of chang es

shal b made as zero reference, if the zero references b fore an

after the chang es d ifer fom one another

A Fourier analy sis shal be ma e of the

ste ring -whe l ang le time history , an the result

shal be display ed as a g ra h of the input lev el

relativ e to that at the lowest feq uency v er us

f eq uency as shown inFig ure 4 ( se Annex B,

clauseB.3)

6.4.3 Furt her pr c s ing ( se 6.3.3)

The trans er fu ctions of at least thre test ru s

shal be av erag ed

6.5 Continuous sinusoidal input

6.5.1 Ste ring-whe l angle ampl tude

Ste ring -whe l ang le ampltude is defined as the

mean v alue of the ampltudes fol owing the fir t

period

All ampltud es shal be taken during the mano uv re

when the v ehicle is in a period ic stead y -state

condition

6.5.2 Lat eral ac eleration ampl tude

Lateral ac eleration ampltude is d efined as the

mean v alue of the ampltudes fol owing the fir t

period

All ampltud es shal be taken during the mano uv re

when the v ehicle is in a period ic stead y -state

condition

6.5.3 Yaw velocit y ampl tude

Yaw v elocity ampltude is defined as the mean v alue

of the ampltud es folowing the fir t period

All ampltud es shal be taken during the mano uv re

when the v ehicle is in a period ic stead y -state

condition

6.5.4 Lateral ac eleration gain

Lateral ac eleration g ain per u it of ste ring -whe l

ang le is calculated as the ratio betwe n lateral

ac eleration ampl tude ac ording to6.5.2 and the

ste ring -whe l ang le ampl tude ac ord ing to6.5.1

6.5.5 Yaw velocity gain

Yaw v elocity g ain per u it of ste ring-whe l ang le is

calculated as the ratio betwe n y aw v elocity

ampl tude ac ording to6.5.3 an the ste ring -whe l

ang le ampl tude ac ording to6.5.1

6.5.6 Phas angle

Phase ang les betwe n the ste ring -whe l ang le and

the v aria les lateral ac eleration an y aw v elocity

shal be determined f om the time histories after the

fir t period when the v ehicle is in a period ic

stea y -state condition

7 Data pr sentation

General d ata shal be presented as shown on the

summary form g iv en inAnnex A

Time histories ofv aria les used in d ata reduction

shal be plot ed I a curv e is fit ed to any set of d ta,

the method ofcurv e fit ing shal be d es ribed in the

results presentation in ac ord ance withAnnex B