ISO/TR 13487:1997 道路車両のブレーキング—完全に発達した平均減速度の定義に関する考慮事項 | ページ 2

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 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 main task of technical committees is to prepare International Standards, but in exceptional circumstances a technical committee may propose the publication of a Technical Report of one of the following types:

• type 1, when the required support cannot be obtained for the publication of an International Standard, despite repeated efforts;
• type 2, when the subject is still under technical development or where for any other reason there is the future but not immediate possibility of an agreement on an International Standard;
• type 3, when a technical committee has collected data of a different kind from that which is normally published as an International Standard ("state of the art", for example).

Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether they can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to be reviewed until the data they provide are considered to be no longer valid or useful.

ISO/TR 13487, which is a Technical Report of type 3, was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 2, Brake systems and equipment.

Introduction

ECE Regulation No. 13"Uniform Provisions Concerning the Approval of Vehicles of Categories M, N and О with Regard to Braking" determines the minimum legal braking performance for new road vehicles at the time of type-approval.

This braking performance is specified in terms of"stopping distance" and in terms of"mean fully developed deceleration" (mfdd).

The 08 series of amendments to ECE-R13 requires that both the above parameters must be fulfilled; furthermore, the 08 series of amendments prescribes the method of calculating the mean fully developed deceleration.

The chosen method of calculating the mfdd is based on the work done in ISO/ТС 22/SC 2 Working Groups 6 and 10.

For this reason, it is useful to summarize the background information on this subject in this ISO Technical Report, by describing the physical fundamentals and the connection between stopping distance and mfdd; this will enable the persons responsible for determining the braking performance to analyse the results of testing, which are never exactly reproducible.

Because the legislative text does not stipulate the measuring equipment nor specific measuring procedures, this Technical Report may indicate alternative solutions to the Technical Services and to the manufacturers of measuring equipment; it will also address prospective computer-supported possibilities. In addition, the transition between different systems of units will be facilitated by this contribution.

The prospective legislative text will concede alternative methods of measuring the mfdd; these are explicitly explained in this Technical Report.

The report clearly indicates that in addition to the exact solutions for the mfdd (see equations 16 and 29), certain approximations (see equations 30, 31 and 33) are also permissible within the required accuracy, as documented by theoretical considerations and corresponding practical measurements with a vehicle.

For this reason, equation 31 was developed for computer-aided and equation 33 for graphical evaluations.

Symbols

Symbol	Unit	Description
a (s)	m/s2	distance-dependent deceleration
a (t)	m/s2	time-dependent deceleration
	m/s2	representative constant deceleration
	m/s2	absolute value of
аB, aE	m/s2	decelerations at the beginning and end of evaluation range on the linear approximate solution for a (t)
aF (t)	m/s2	analytically given deceleration path with temporal drop
ai, ai	m/s2	individual deceleration values
aL(t)	m/s2	linear approximate solution for a (t)
amax	m/s2	maximum value in a time-dependent deceleration path
ams	m/s2	distance-related mean deceleration
ams1, ams2 ams3	m/s2	examples of different distance-related mean deceleration
ãms	m/s2	approximate value for the distance-related mean deceleration in accordance with Equation (33)
amsN	m/s2	numerical approximate value for the distance-related mean deceleration in accordance with Equation (31)
amt	m/s2	time-related mean deceleration
ãmt	m/s2	approximate value for the time-related mean deceleration in accordance with Equation (34)
aR (t)	m/s2	analytically given deceleration path with temporal rise
a1 (s), a2 (s), a3 (s)	m/s2	different distance-dependent deceleration paths
a1 (t), a2 (t), a3 (t)	m/s2	different time-dependent deceleration paths
dm	m/s2	mfdd according toECE Regulation No. 13
ds	m	distance differential
dt	s	time differential
dv	m/s	speed differential
mfdd	m/s2	mean fully developed deceleration
s	m	distance
sB, sE	m	distances at the start and end of evaluation range
sD	m	braking distance during the period of mfdd
sF (t)	m	distance path during the analytically given deceleration aF (t)
si	m	individual distance values
sR	m	braking distance during response time and pressure build-up time pressure build-up time
sR (t)	m	distance path during the analytically given deceleration аR (t)
s1, s2, s3	m	braking distances with different deceleration paths
s1 (t), s2 (t), s3 (t)	m	different distance paths
T	s	total braking time
t, ti	s	time
tB, tE	s	points in time for the start and end of the evaluation range
tR	s	sum of response time and pressure build-up time
tS	s	time at the end of a stop
t1	s	point in time at which the deceleration takes on the value 1/2 amax at first time
t2	s	point in time at which the deceleration takes on the value 1/2 amax at last time
v	km/h	test speed
v (t)	m/s, km/h	variable speed
vB, vE	m/s	speeds at the start and end of evaluation range
vF (t)	m/s	speed path during the analytically given deceleration aF (t)
vi	m/s	individual speed values
vR (t)	m/s	speed path during the analytically given deceleration aR (t)
v0	m/s, km/h	initial speed
v1 (t), v2 (t), v3 (t)	m/s	different speed paths
Δ amsN, Δ ãms	%	related differences of mean decelerations (Tables 5 and 6)
Δ ãmt, Δ ãmsN
Δt	s	time increment
τ	s	time