IS 11948: AUTOMOTIVE VEHICLES — STEERING EFFORT — METHOD OF EVALUATION

2010·0.93 MB·English

by  Bureau of Indian Standards

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in order to promote transparency and accountability in the working of every public authority,
and whereas the attached publication of the Bureau of Indian Standards is of particular interest
to the public, particularly disadvantaged communities and those engaged in the pursuit of
education and knowledge, the attached public safety standard is made available to promote the
timely dissemination of this information in an accurate manner to the public.
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IS 11948 (2010): AUTOMOTIVE VEHICLES — STEERING EFFORT —
METHOD OF EVALUATION [TED 4: Automotive Braking Systems]
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IS 11948: 2010
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Indian Standard
AUTOMOTIVE VEHICLES — STEERING
EFFORT — METHOD OF EVALUATION
( Second Revision )
ICS 43.040.50
© BIS 2010
B U R E A U O F I N D I A N S T A N D A R D S
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002
November 2010 Price Group 7
Automotive Braking Systems, Vehicle Testing and Performance Evaluation Sectional Committee, TED 4
FOREWORD
This Indian Standard (Second Revision) was adopted by the Bureau of Indian Standards, after the draft finalized
by the Automotive Braking Systems, Vehicle Testing and Performance Evaluation Sectional Committee had been
approved by the Transport Engineering Division Council.
The overall performance of an automotive vehicle is a function of the performance of its various systems and
components. The steering system is one of the main systems that directly contribute to the active safety of the
driver and the other road users.
This standard was first published in 1986 and was first revised in 1999. This revision has been taken up to align
the standard with ECE Regulation 79 — Revision 2 Amendment 2. This revised standard additionally considers
the following:
a) Provisions for trailers and the trailers with hydraulic steering transmissions.
b) Braking performance for vehicles using the same energy source to supply steering equipment and braking
device (see Annex A).
c) Additional provisions for vehicles equipped with auxiliary steering equipment.
d) Special requirements to be applied for the safety aspects of complex electronic vehicle control systems.
For the purpose of deciding whether a particular requirement of this standard is complied with, the final value,
observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS2:1960
‘Rules for rounding off numerical values (revised)’. The number of significant places retained in the rounded off
value should be the same as that of the specified value in this standard.
IS 11948 : 2010
Indian Standard
AUTOMOTIVE VEHICLES — STEERING
EFFORT — METHOD OF EVALUATION
( Second Revision )
1 SCOPE 3.1 Approval of a Vehicle, means the approval of a
vehicle type with regard to its steering equipment.
1.1 This standard specifies the method of evaluation
of steering efforts of automotive vehicles. This standard 3.2 Vehicle Type, means the vehicle, which does not
applies to the steering equipment of vehicles of differ with respect to the manufacturer’s designation
categories M, N and O as defined in IS 14272 of the vehicle type and in essential characteristics,
(Part1):1995 ‘Automotive vehicles — Types — such as type of steering equipment, steering control,
Terminology: Part 1 Three and four wheelers’. steering transmission, steered wheels, and energy
source.
1.2 This standard does not apply to,
3.3 Steering Equipment, means all the equipment the
a) steering equipment with a purely pneumatic
purpose of which is to determine the direction of
transmission;
movement of the vehicle. The steering equipment
b) autonomous steering systems as defined
consists of steering control, steering transmission,
in3.3.3;
steered wheels and the energy supply, if any.
c) full power steering systems fitted to trailers
3.3.1 Steering Control, means the part of the steering
where the energy necessary for operation is
equipment, which controls its operation, it may be
transmitted from the towing vehicle; and
operated with or without direct intervention of the
d) the electrical control of full power steering
driver. For steering equipment in which the steering
systems fitted to trailers, other than additional
forces are provided solely or partly by the muscular
steering equipment as defined in 3.5.2.4.
effort of the driver the steering control includes all
2 REFERENCES parts up to the point where the steering effort is
transformed by mechanical, hydraulic or electrical
The following standards contain provisions, which
means.
through reference in this text, constitute provisions of
the standard. At the time of publication, the edition 3.3.2 Steering Transmission, means all components,
indicated were valid. All standards are subject to which form a functional link between the steering
revision and parties to agreements based on this control and the road wheels. The transmission is
standard are encouraged to investigate the possibility divided into two independent functions.
of applying the most recent editions of the standard
The control transmission and the energy transmission.
indicated below:
Where the term transmission is used alone in this
IS No. Title standard, it means both the control transmission and
the energy transmission. A distinction is drawn between
7079:2008 Automotive vehicles — Brake hose
mechanical, electrical and hydraulic transmission
assemblies for hydraulic braking
systems or combinations thereof, according to the
systems used with non-petroleum
means by which the signals and/or energy is
base brake fluid — Specification
transmitted.
(third revision)
14272 Automotive vehicles — Types — 3.3.2.1 Control transmission, means all components
(Part 1):1995 Terminology: Part 1 Three and four by means of which signals are transmitted for control
wheelers of the steering equipment.
ISO 2575 : 2004 Road vehicles — Symbols for
3.3.2.2 Energy transmission, means all components
controls, indicators and tell-tales
by means of which the energy required for control/
3 DEFINITIONS Standard of the steering function of the wheels is
transmitted.

For the purposes of this standard the following
definitions shall apply. 3.3.3 Autonomous Steering System, means a system
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IS 11948 : 2010
that incorporates a function within a complex electronic source is stored, for example, a pressurized fluid
control system that causes the vehicle to follow a reservoir or vehicle battery.
defined path or to alter its path in response to signals
3.3.6.3 Storage reservoir, means that part of the
initiated and transmitted from off-board the vehicle.
energy supply in which the operating medium is stored
The driver will not necessarily be in primary control
at or near to the atmospheric pressure, for example a
of the vehicle.
fluid reservoir.
3.3.4 Advanced Driver Assistance Steering System,
means a system, additional to the main steering system, 3.4 Steering Parameters
that provides assistance to the driver in steering the
3.4.1 Steering Control Effort, means the force applied
vehicle but in which the driver remains at all times in
to the steering control in order to steer the vehicle.
primary control of the vehicle. It comprises one or both
of the following functions: 3.4.2 Steering Time, means the period of time from
the beginning of the movement of the steering control
3.3.4.1 Automatically commanded steering function,
to the moment at which the steered wheels have reached
means the function within a complex electronic control
a specific steering angle.
system where actuation of the steering system can result
from automatic evaluation of signals initiated on-board 3.4.3 Steering Angle, means the angle between the
the vehicle, possibly in conjunction with passive projection of a longitudinal axis of the vehicle and the
infrastructure features, to generate continuous control line of intersection of the wheel plane (being the central
action in order to assist the driver in following a plane of the wheel, normal to the axis around which it
particular path, in low speed manoeuvring or parking rotates) and the road surface.
operations.
3.4.4 Steering Forces, mean all the forces operating in
3.3.4.2 Corrective steering function, means the the steering transmission.
discontinuous control function within a complex
3.4.5 Mean Steering Ratio, means the ratio of the
electronic control system whereby, for a limited
angular displacement of the steering control to the
duration, changes to the steering angle of one or more
mean of the swept steering angle of the steered wheels
wheels may result from the automatic evaluation of
signals initiated on-board the vehicle, in order to for a full lock-to-lock turn.
maintain the basic desired path of the vehicle or to
3.4.6 Turning Circle, means the circle within which
influence the vehicle’s dynamic behaviour. Systems
are located the projections onto the ground plane of
that do not themselves positively actuate the steering
all the points of the vehicle, excluding the external
system but that, possibly in conjunction with passive
mirrors and the front direction indicators, when the
infrastructure features, simply warn the driver of a
vehicle is driven in a circle.
deviation from the ideal path of the vehicle, or of an
unseen hazard, by means of a tactile warning 3.4.7 Nominal Radius of Steering Control, means in
transmitted through the steering control, are also the case of a steering wheel the shortest dimension from
considered to be corrective steering. its centre of rotation to the outer edge of the rim. In
the case of any other form of control it means the
3.3.5 Steered Wheels, means the wheels the alignment
distance between its centre of rotation and the point at
of which may be altered directly or indirectly in relation
which the steering effort is applied. If more than one
to the longitudinal axis of the vehicle in order to
such point is provided, the one requiring the greatest
determine the direction of movement of the vehicle.
effort shall be used.
(The steered wheels include the axis around which they
are rotated in order to determine the direction of
3.5 Types of Steering Equipment
movement of the vehicle.)
Depending on the way the steering forces are produced,
3.3.6 Energy Supply, includes those parts of the steering
the following types of equipment are distinguished:
equipment, which provide it with energy, regulate that
energy and where appropriate, process and store it. It 3.5.1 For Motor Vehicles
also includes any storage reservoirs for the operating
3.5.1.1 Main steering system, means the steering
medium and the return lines, but not the vehicle’s
equipment of a vehicle, which is mainly responsible
engine or its drive to the energy source.
for determining the direction of travel. It may
3.3.6.1 Energy source, means the part of the energy comprise:
supply, which provides the energy in the required form.
3.5.1.1.1 Manual steering equipment, in which the
3.3.6.2 Energy reservoir, means that part of the ene rgy steering forces result solely from the muscular effort
supply in which the energy provided by the energy of the driver.
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IS 11948 : 2010
3.5.1.1.2 Power assisted steering equipment, in which 3.5.3 Steering Equipment
the steering forces result from both the muscular effort
Depending on the arrangement of the steered wheels,
of the driver and the energy supply (supplies). Steering
the following types of steering equipment are
equipment in which the steering forces result solely,
distinguished:
from one or more energy supplies when the equipment
is intact, but in which the steering forces can be 3.5.3.1 Front-wheel steering equipment, in which only
provided by the muscular effort of the driver alone if the wheels of the front axle(s) are steered. This includes
there is a fault in the steering (integrated power all wheels which are steered in the same direction.
systems), is also considered to be power assisted
3.5.3.2 Rear-wheel steering equipment, in which only
steering equipment.
the wheels of the rear axle(s) are steered. This includes
all wheels which are steered in the same direction.
3.5.1.1.3 Full-power steering equipment, in which the
steering forces are provided solely by one or more 3.5.3.3 Multi-wheel steering equipment, in which the
energy supplies. wheels of one or more of each of the front and the rear
axle(s) are steered.
3.5.1.2 Self-tracking steering equipment, means a
system designed to create a change of steering angle 3.5.3.3.1 All-wheel steering equipment, in which all
on one or more wheels only when acted upon by forces the wheels are steered.
and/or moments applied through the tyre to road
3.5.3.3.2 Buckle steering equipment, in which the
contact.
movement of chassis parts relative to each other is
3.5.1.3 Auxiliary steering equipment (ASE), means a directly produced by the steering forces.
system in which the wheels on axle(s) of vehicles of
3.6 Types of Steering Transmission
Categories M and N are steered in addition to the
wheels of the main steering equipment in the same or Depending on the way the steering forces are
opposite direction to those of the main steering transmitted, the following types of steering
equipment and/or the steering angle of the front and/or transmission are distinguished:
the rear wheels may be adjusted relative to vehicle
3.6.1 Purely Mechanical Steering Transmission, means
behaviour.
a steering transmission in which the steering forces
3.5.2 For Trailers are transmitted entirely by mechanical means.
3.5.2.1 Self-tracking steering equipment, means a 3.6.2 Purely Hydraulic Steering Transmission, means
system designed to create a change of steering angle a steering transmission in which the steering forces,
on one or more wheels only when acted upon by forces somewhere in the transmission, are transmitted only
and/or moments applied through the tyre to road by hydraulic means.
contact.
3.6.3 Purely Electric Steering Transmission, means a
steering transmission in which the steering forces,
3.5.2.2 Articulated steering, means equipment in which
somewhere in the transmission, are transmitted only
the steering forces are produced by a change in
through electric means.
direction of the towing vehicle and in which the
movement of the steered trailer wheels is firmly linked 3.6.4 Hybrid Steering Transmission, means a steering
to the relative angle between the longitudinal axis of transmission in which part of the steering forces are
the towing vehicle and that of the trailer. transmitted through one and the other part through
another of the above mentioned means. However, in
3.5.2.3 Self-steering, means equipment in which the
the case where any mechanical part of the transmission
steering forces are produced by a change in direction
is designed only to give position feedback and is too
of the towing vehicle and in which the movement of
weak to transmit the total sum of the steering forces,
the steered trailer wheels is firmly linked to the relative
this system shall be considered to be purely hydraulic
angle between the longitudinal axis of the trailer frame
or purely electric steering transmission.
or a load replacing it and the longitudinal axis of the
sub-frame to which the axle(s) is (are) attached. 3.7 Electric Control Line
3.5.2.4 Additional steering equipment, means a system, Means the electrical connection which provides the
independent of the main steering system, by which the steering control function to the trailer. It comprises the
steering angle of one or more axle(s) of the steering electrical wiring and connector and includes the parts
system can be influenced selectively for manoeuvr ing for data communication and the electrical energy
purposes. supply for the trailer control transmission.
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IS 11948 : 2010
4 CONSTRUCTION PROVISIONS 4.1.6.1 Whenever the automatically commanded
steering function becomes operational, this shall be
4.1 General Provisions
indicated to the driver and the control action shall be
4.1.1 The steering equipment shall ensure easy and safe automatically disabled if the vehicle speed exceeds the
handling of the vehicle up to its maximum design speed set limit of 10 km/h by more than 20 percent or the
or in case of a trailer up to its technically permitted signals to be evaluated are no longer being received.
maximum speed. There must be a tendency to self- Any termination of control shall produce a short but
distinctive driver warning by a visual signal and either
centre when tested in accordance with 5.2 with the
an acoustic signal or by imposing a tactile warning
intact steering equipment. The vehicle shall meet the
signal on the steering control.
requirements of 5.2 in the case of motor vehicles and
of 5.3 in the case of trailers. If a vehicle is fitted with 4.1.7 Steering Transmission
an auxiliary steering system (ASE), it shall also meet
4.1.7.1 Adjustment devices for steering geometry must
the requirements of Annex B. Trailers equipped with
be such that after adjustment a positive connection can
hydraulic steering transmissions shall also comply with
be established between the adjustable components by
Annex C.
appropriate locking devices.
4.1.2 It must be possible to travel along a straight
4.1.7.2 Steering transmission, which can be
section of road without unusual steering correction
disconnected to cover different configurations of a
by the driver and without unusual vibration in the
vehicle (for example on extendable semi-trailers), must
steering system at the maximum design speed of the
have locking devices, which ensure positive relocation
vehicle.
of components; where locking is automatic, there must
4.1.3 The direction of operation of the steering control be an additional safety lock which is operated
shall correspond to the intended change of direction manually.
of the vehicle and there shall be a continuous
4.1.8 Steered Wheels
relationship between the steering control deflection and
the steering angle. These requirements do not apply to The steered wheels shall not be solely the rear wheels.
systems that incorporate an automatically commanded This requirement does not apply to semi-trailers.
or corrective steering function, or to auxiliary steering
4.1.9 Energy Supply
equipment. These requirements may also not
The same energy supply may be used for the steering
necessarily apply in the case of full power steering
equipment and other systems. However in the case of
when the vehicle is stationary and when the system is
a failure in any system which shares the same energy
not energized.
supply steering shall be ensured in accordance with
4.1.4 The steering equipment shall be designed, the relevant failure conditions of 4.3.
constructed and fitted in such a way it is capable of
4.1.10 Control Systems
withstanding the stresses arising during normal
operation of the vehicle, or combination of vehicles. The requirements of Annex D shall be applied to the
The maximum steering angle shall not be limited by safety aspects of electronic vehicle control systems that
any part of the steering transmission unless specifically provide or form part of the control transmission of the
designed for this purpose. Unless otherwise specified, steering function including advanced driver assistance
it will be assumed that for the purpose of this standard, steering systems. However, systems or functions, that
not more than one failure can occur in the steering use the steering system as the means of achieving a
equipment at any one time and two axles on one bogie higher level objective, are subject to Annex D only
shall be considered as one axle. insofar as they have a direct effect on the steering
system. If such systems are provided, they shall not be
4.1.5 The effectiveness of the steering equipment,
deactivated during type approval testing of the steering
including the electrical control lines, shall not be
system.
adversely affected by magnetic or electric fields.
4.2 Special Provisions for Trailers
4.1.6 Advanced driver assistance steering systems shall
only be approved in accordance with this standard 4.2.1 Trailers (with the exception of semi-trailers and
where the function does not cause any deterioration in centre-axle trailers) which have more than one axle
the performance of the basic steering system. In with steered wheels and semi-trailers and centre-axle
addition they shall be designed such that the driver trailers which have at least one axle with steered wheels
may, at any time and by deliberate action, override the must fulfil the conditions given in 5.3. However, for
function. trailers with self-tracking steering equipment a test
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IS 11948 : 2010
under 5.3 is not necessary if the axle load ratio between first subsequent application shall comply with the
the un-steered and the self-tracking axles equals or requirements of A-3.
exceeds 1.6 under all loading conditions. However for
4.3.1.6 In the case of trailers the requirements of 4.2.2
trailers with self-tracking steering equipment, the axle
and 5.3.4.1 shall also be met when there is a failure in
load ratio between un-steered or articulated steered
the steering system.
axles and friction-steered axles shall be at least 1 under
all loading conditions. 4.3.2 Power Assisted Steering Systems
4.2.2 If the towing vehicle of a vehicle combination is 4.3.2.1 Should the engine stop or a part of the
driving straight ahead, the trailer and towing vehicle transmission fail, with the exception of those parts
must remain aligned. If alignment is not retained listed in 4.3.1.1. there shall be no immediate changes
automatically, the trailer must be equipped with a in steering angle. As long as the vehicle is capable of
suitable adjustment facility for maintenance. being driven at a speed greater than 10 km/h the
requirements given in 5, relating to a system with a
4.3 Failure Provisions and Performance
failure, shall be met.
4.3.1 General
4.3.3 Full Power Steering Systems
4.3.1.1 For the purposes of this standard, the steered
4.3.3.1 The system shall be designed such that the
wheels, the steering control and all mechanical parts
vehicle cannot be driven indefinitely at speeds above10
of the steering transmission shall not be regarded as
km/h where there is any fault which requires operation
liable to breakage if they are amply dimensioned, are
of the warning signal referred to in 4.4.2.1.
readily accessible for maintenance, and exhibit safety
features at least equal to those prescribed for other 4.3.3.2 In case of a failure within the control
essential components (such as the braking system) of transmission, with the exception of those parts listed
the vehicle. Where the failure of any such part would in 4.1.4, it shall still be possible to steer with the
be likely to result in loss of control of the vehicle, that performance laid down in 7 for the intact steering
part must be made of metal or of a material with system.
equivalent characteristics and must not be subject to
4.3.3.3 In the event of a failure of the energy source of
significant distortion in normal operation of the steering
the control transmission, it shall be possible to carry
system.
out at least 24 ‘figure of eight’ manoeuvres, where each
4.3.1.2 The requirements of 4.1.2, 4.1.3 and 5.2.1 shall loop of the figure is 40 m diameter at 10 km/h speed
also be satisfied with a failure in the steering equipment and at the performance level given for an intact system
as long as the vehicle can be driven with the speeds in 5. The test manoeuvres shall begin at an energy
required in the respective clauses. In this case 4.1.3 storage level given in 4.3.3.5.
shall not apply for full power steering systems when
4.3.3.4 In the event of a failure within the energy
the vehicle is stationary.
transmission, with the exception of those parts listed
4.3.1.3 Any failure in a transmission other than purely in 4.3.1.1, there shall not be any immediate changes
mechanical must clearly be brought to the attention of
in steering angle. As long as the vehicle is capable of
the vehicle driver as given in 4.4.
being driven at a speed greater than 10 km/h the
4.3.1.4 In the case where the braking system of the requirements of 5 for the system with a failure shall
vehicle shares the same energy source as the steering be met after the completion of at least 25 ‘figure of
system and this energy source fails, the steering system eight’ manoeuvres at 10 km/h minimum speed, where
shall have priority and shall be capable of meeting the each loop of the figure is 40 m diameter. The test
requirements of 4.3.2 and 4.3.3 as applicable. In manoeuvres shall begin at an energy storage level
addition the braking performance on the first given in 4.3.3.5.
subsequent application shall not drop below the
4.3.3.5 The energy level to be used for the tests referred
prescribed service brake performance, as given in
to in 4.3.3.3 and 4.3.3.4 shall be the energy storage
Annex A.
level at which a failure is indicated to the driver. In the
4.3.1.5 In the case where the braking system of the case of electrically powered systems subject to
vehicle shares the same energy supply as the steering AnnexD, this level shall be the worst case situation
system and there is a failure in the energy supply, the outlined by the manufacturer in the documentation
steering system shall have priority and shall be capable submitted in connection with Annex D and shall take
of meeting the requirements of 4.3.2 and4.3.3 as into account the effects of, for example temperature

applicable. In addition the braking performance on the and ageing on battery performance.
5