Standards related to:

GB/T 12549-2013GB/T 12549-2013

NATIONAL STANDARD OF THE

PEOPLE’S REPUBLIC OF CHINA

ICS 43.040.50

T 23

Replacing GB/T 12549-1990

Terms and definitions for vehicle controllability and stability

ISSUED ON: NOVEMBER 27, 2013

IMPLEMENTED ON: JULY 01, 2014

Issued by: General Administration of Quality Supervision, Inspection and

Quarantine of PRC;

Standardization Administration of PRC.

Table of Contents

Foreword ... 3

1 Scope ... 4

2 Normative references ... 4

3 Steering system ... 4

4 Suspension system ... 7

5 Tires and wheels ... 13

6 Axis systems and motion ... 22

7 Movement characteristics ... 32

8 Characteristics of limit maneuver and abnormal motion ... 40

9 Test and evaluation ... 43

10 Aerodynamics ... 51

Index in English ... 68

Foreword

This standard was drafted in accordance with the rules given in GB/T 1.1-2009 and

GB/T 20000.2-2009.

This standard replaces GB/T 12549-1990 "Terms and definitions for vehicle

controllability and stability".

This standard was formulated with reference to such documents as ISO 8855:1991

"Road vehicles - Vehicle dynamics and road-holding ability - Vocabulary", SAE J670e

"Vehicle dynamics terminology".

This standard is a revision of GB/T 12549-1990 "Terms and definitions for vehicle

controllability and stability". Compared with GB/T 12549-1990, the main changes are

as follows:

- ADD the terminology of vehicle aerodynamics (see Chapter 10);

- ADD the definitions of wheelbase change rate, longitudinal slip rate, wheel linear

free rolling angular velocity, longitudinal slip angular velocity, etc.;

- DELETE the definitions of slip rate, rudder holding force, rudder holding moment,

etc.;

- MODIFY the definitions of Ackerman angle, steering force, kingpin offset,

disturbance response, closed-loop control, total variance, etc.

This standard has collected and screened the automotive aerodynamic terms, which are

used in China for many years. Some terms and symbols in Chapter 10 are coordinated

and consistent with Clause 3.1 Aerodynamic fundamentals in GB/T 16638.1-2008

"Aerodynamics - Concepts quantities and symbols - Part 1: Aerodynamic terms in

common use".

This standard was proposed by the Ministry of Industry and Information Technology of

the People's Republic of China.

This standard shall be under the jurisdiction of the National Automotive Standardization

Technical Committee (SAC/TC 114).

Drafting organization of this standard: China FAW Group Technology Center.

The main drafters of this standard: Huang Chaosheng, Wang Debao, Ma Zhimin, Liu

Minghui, Zhu Hongwei, Ying Guozeng, Wu Zhenxin, Ling Qisheng.

This standard replaces the standard previously issued as follows:

- GB/T 12549-1990.

Terms and definitions for vehicle controllability and stability

1 Scope

This standard specifies the terms and definitions of vehicle controllability and stability.

This standard applies to all types of vehicles.

2 Normative references

The following documents are essential to the application of this document. For the dated

documents, only the versions with the dates indicated are applicable to this document;

for the undated documents, only the latest version (including all the amendments) is

applicable to this standard.

GB/T 3730.3-1992 Motor vehicles and towed vehicles - Dimensions of vehicles -

Terms and definitions

GB/T 6326-2005 Tyre terms and definitions

GB/T 16638.1-2008 Aerodynamics - Concepts quantities and symbols - Part 1:

Aerodynamic terms in common use

3 Steering system

3.1 Angles in steering system

3.1.1

Steer angle

δs

The angle, BETWEEN the vehicle's longitudinal symmetry plane (see 6.1.6) and the

center plane of the steering wheel (see 4.1.1) AND the intersection of the pavement

(see Figure 1).

vehicle steered.

3.2.2

Steering force

When the vehicle is turning, the operating force, which is applied to the steering

wheel, in the same rotation direction as the steering wheel. It is equal to the steering

wheel moment divided by the steering wheel radius.

3.2.3

Friction force of steering system

The minimum steering force, which is necessary to initiate angular displacement of

the steering wheels. It does not include the friction between the wheels and the

pavement.

3.2.4

Forward efficiency

The ratio -- of rocker shaft or rack's output power TO steering shaft's input power.

3.2.5

Steering system stiffness

When the steering knuckle is fixed, the ratio -- of the torque increment input by the

steering wheel TO the angular displacement increment it produces.

3.2.6

Moment of inertia of steering system

The equivalent moment of inertia, which converts the moving parts of the steering

system and the steering wheel to the rotating body, which rotates around the steering

shaft (or kingpin).

4 Suspension system

4.1 Suspension geometry

4.1.1

Wheel plane

For a single wheel, the wheel plane is the plane, which is equidistant from the inner

edge of the wheel rim, on both sides.

For double wheel, the wheel plane is the plane, which is equidistant from the inner

rim of the outer wheel rim AND the outer rim of the inner wheel rim.

[GB/T 3730.3-1992, definition 2.2] (see Figure 4)

4.1.2

Wheel center

The intersection, between the wheel plane and the wheel centerline of rotation.

[GB/T 3730.3-1992, definition 2.3] (see Figure 1)

4.1.3

Wheel alignment

The angular relationship, between the wheel and the body (or pavement), namely

the general term of the inclination of the steering kingpin (see 4.1.9), the caster angle

of the steering kingpin (see 4.1.6), the camber angle (see 4.1.8), the toe-in (see 4.1.4).

4.1.4

Toe-in

When the end point of the horizontal diameter of the inner contour line of the wheel

rim, at both ends of the same axis, is taken as the vertex of the isosceles trapezoid,

the difference between the lengths of the front and rear base sides of the isosceles

trapezoid is the toe-in. When the front base of the trapezoid is smaller than the back

base, the toe-in is positive; otherwise, it is negative. The angle between the

horizontal diameter of the wheel and the Y plane is the toe angle.

[GB/T 3730.3-1992, definition 3.28]

4.1.5

Toe angle

According to the provisions of 4.1.4.

4.1.6

Caster angle

The angle, between the projection of the centerline of the steering kingpin on the

4.1.9

Kingpin inclination

In a plane perpendicular to both the Y and X planes, the acute angle, which is formed

by the projection of the axis of the real or imaginary kingpin, on this plane, AND

the line which is perpendicular to the X plane.

[GB/T 3730.3-1992, definition 3.26]

4.1.10

Kingpin offset

The length of the projection of the line, which connects the intersection of the

kingpin's extension line and the pavement AND the center of tire contact (see 5.1.1),

on the Y'-axis (see 5.1.2). If the center of tire contact is outside the intersection of

the kingpin's extension line and the pavement relative to the vehicle body, the

kingpin offset is positive; otherwise, it is negative.

Note: Rewrite GB/T 3730.3-1992, definition 3.27.

4.1.11

Lateral slip

The lateral slip value of the straight-running tire, per unit travel distance, which is

measured on the lateral slip test bench. It is expressed in m/km, mm/m.

4.1.12

Wheelbase

The distance, between two planes that pass through point A or (B) of two adjacent

wheels on the same side of the vehicle AND are perpendicular to the Y and X planes,

respectively.

[GB/T 3730.3-1992, definition 3.4.1]

The distance, between the two planes that pass the semitrailer's tow pin axis and the

center of the semitrailer wheel AND are perpendicular to the Y and X planes,

respectively.

[GB/T 3730.3-1992, definition 3.4.2]

4.1.13

Track

Distance between points A and B, on both ends of the wheel, on the same axis.

[GB/T 3730.3-1992, definition 3.5]

4.1.14

Track rate

When the left and right wheels move up and down synchronously, as relative to the

sprung mass (see 6.2.2), the rate of change of the wheel track, as relative to the wheel

runout height.

4.2 Suspension system mechanics

4.2.1

Suspension vertical stiffness

Under a certain load state, the change in the vertical load of the wheel, which is

corresponding to the unit displacement of the sprung center of mass, as relative to

the center of the wheel, in the vertical direction.

4.2.2

Suspension longitudinal stiffness

The change in longitudinal force at the wheel center, which is corresponding to a

unit displacement of the wheel center, as relative to the sprung center of mass, in the

longitudinal [x-axis (see 6.1.3) direction].

4.2.3

Suspension transverse stiffness

The change in the lateral force at the wheel center, which is corresponding to a unit

displacement of the wheel center, as relative to the sprung center of mass, in the

transverse [y-axis (see 6.1.3) direction].

4.2.4

Ride rate

Under a certain load state, the change in the vertical load of the wheel, which is

corresponding to the unit displacement of the sprung center of mass, as relative to

the ground, in the vertical direction.

4.2.5

[GB/T 6326-2005, definition 9.12.9]

5.1.5

Static loaded radius

The vertical distance, from the center of the axle to the support plane of a static tire,

under vertical load.

[GB/T 6326-2005, definition 9.1.2]

5.1.6

Dynamic loaded radius

The vertical distance, from the center of the axle to the support plane, when the tire

is running under load AND the inclination angle is zero.

[GB/T 6326-2005, definition 9.12.10]

5.1.7

Rolling circumference

Under specified conditions, the distance, that the tire center moves, in one full circle.

[GB/T 6326-2005, definition 9.2.1]

5.1.8

Rolling radius

The value, which is obtained by dividing the rolling circumference of a tire by 2π.

[GB/T6326-2005, definition 9.2.2]

5.1.9

Free rolling wheel

The rolling wheel, which is only subject to a vertical load, without driving moment

(see 5.3.5) or braking moment (see 5.3.6).

5.1.10

Wheel rotation speed of straight free-rolling wheel

The rotational angular velocity of a free-rolling wheel rolling, along a straight line,

under the conditions of zero slip angle and zero camber angle.

5.1.11

Longitudinal slip angular velocity

The difference, between the wheel roll angular velocity and the wheel rotation speed

of straight free-rolling wheel.

Note: The above two angular velocities are measured, when the velocity components

of the wheel center along the X' axis are the same.

5.1.12

Longitudinal slip

The ratio -- of the longitudinal slip angular velocity TO the wheel rotation speed of

straight free-rolling wheel.

5.2 Tire forces

5.2.1

Vertical force of tire

The component along the Z' axis of the force, which acts on the tire by the pavement

(see Figure 4).

5.2.2

Lateral force of tire

The component of the force, which acts on the tire by the pavement, in the direction

of the Y' axis (see Figure 4).

5.2.3

Longitudinal force of tire

The component along the X' axis of the force, which acts on the tire by the pavement

(see Figure 4).

5.2.4

Radial stiffness

The change in the vertical load of the tire, which is corresponding to the unit

displacement of the center of the wheel, as relative to the ground plane of the tire,

in the vertical direction.

5.2.5

5.2.12

Cornering drag

When the wheel camber angle is zero, in order to maintain the slip angle, the

horizontal component of the force, which acts on the wheel by the pavement, along

the opposite direction of travel of the center of tire contact (see Figure 5).

5.2.13

Resistance force of drag

When the wheel camber angle is zero, in order to maintain the slip angle, the

longitudinal force acting on the wheel by the pavement (see Figure 5).

5.2.14

Tractive force

The component in the forward direction of the force vector, which acts on the center

of the tire contact by the pavement. It is equal to the lateral force multiplied by the

sine of the slip angle PLUS the longitudinal force multiplied by the cosine of the

slip angle.

5.2.15

Drag force

It is equal to negative traction.

5.3 Tire moments

5.3.1

Overturning moment of tire

The component of the moment vector, which acts on the tire by the pavement, to

rotate the tire about the X' axis (see Figure 4).

5.3.2

Rolling resistance moment

The component of the moment vector, which acts on the tire by the pavement, to

rotate the tire about the Y' axis (see Figure 4).

5.3.3

Aligning torque

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