Motorcycle and motorcycle-rider kinematics -- Vocabulary

Cinématique relative au motocycle et à son conducteur -- Vocabulaire

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Published
Publication Date
05-Mar-1997
Current Stage
9093 - International Standard confirmed
Start Date
02-Apr-2021
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INTERNATIONAL
IS0
STANDARD
11838
First edition
1997-03-01
Motorcycle and motorcycle-rider
kinematics
- Vocabulary
CSmatique relative au motocycle et ;j son conducteur - Vocabulaire
Reference number
IS0 11838:1997(E)
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IS0 11838:1997(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
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. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
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.
International Standard IS0 11838 was prepared by Technical Committee
lSO/TC 22, Road vehicles, Subcommittee SC 22, Motorcycles.
0 IS0 1997

All rights reserved. Unless otherwise specified, no part of this publication may be

reproduced or utilized in any form or by any means, electronic or mechanical, including

photocopying and microfilm, without permission in writing from the publisher. / Droits de

reproduction reserves. Sauf prescription differente, aucune partie de cette publication ne

peut etre reproduite ni utilisee sous quelque forme que ce soit et par aucun procede,

electronique ou mecanique, y compris la photocopie et les microfilms, sans l’accord ecrit de

I’editeur.
International Organization for Standardization
Case postale 56 l CH-1211 Get-We 20 l Switzerland
Internet
central@iso.ch
x.400 c=ch; a=400net; p=iso; o=isocs; s=central
Printed in Switzerland/lmprime en Suisse
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IS0 11838:1997(E)
INTERNATIONAL STANDARD @ IS0
- Vocabulary
Motorcycle and motorcycle-rider kinematics
1 Scope

1.1 This International Standard specifies symbols, definitions and conventions related to motorcycle and

motorcycle-rider motions and kinematics and to the modelling thereof.

1.2 It does not deal with methods of measurement, nor with the units used in reporting the results, nor with

accuracy.

1.3 The provisions of this International Standard apply to two-wheeled motorcycles as defined in IS0 3833.

1.4 This International Standard does not cover road motorcycles which are controlled by a pedestrian or which

are used for the carriage of goods to the exclusion of persons.

1.5 This International Standard specifies terms, definitions and symbols for the following systems, parts and

aspects:
steering system (clause 3)
suspension system (clause 4)
tyres and wheels (clause 5)
basic principles of axis systems and kinematics (clause 6)
directional dynamics (clause 7)
motorcycle motion characteristics (clause 8)
aerodynamic characteristics of the motorcycle-rider combination (clause 9)
riding postures and behaviours (clause IO)
tests (clause 11).
2 Normative references

The following standards contain provisions which, through reference in this text, constitute provisions of this

International Standard. At the time of publication, the editions indicated were valid. All standards are subject to

revision, and parties to agreements based on this International Standard are encouraged to investigate the

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@ IS0
IS0 11838:1997(E)

possibility o f applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain

national Standa rds.
registers of currently valid Inter
IS0 3833:1977, Road vehicles - Types - Terms and definitions.
- Dimensions of two-wheeled mopeds and motorcycles - Terms and definitions.
IS0 6725:1981, Road vehicles
IS0 6726:1988, Mopeds and motorcycles with two wheels - Masses - Vocabulary.
3 Steering system
3.1 Axis and angles of the steering assembly
3.1.1
steer axis

rotational axis of the steering assembly for steering control which coincides with the axis of the steering stem and

with the axis of the steering head pipe
3.1.2
steer angle

angle of motion of the steering assembly about the steer axis (3.1 .I) which is zero when the front wheel plane is

parallel to the motorcycle longitudinal plane
3.1.3
wheel steer angle

angle formed by the intersection with the road surface plane of the motorcycle longitudinal plane and the front

wheel plane
3.2 Dynamic quantities of the steering assembly
3.2.1
steering velocity
angular velocity of the sprung part of the steering assembly about the zf-axis
3.2.2
steering of the handleba
angular velocity of the handlebars about the zj-j-axis
3.2.3
steer torque
torque about the steer axis (3.1 .I)
3.2.4
steer force

value obtained from dividing the steer torque (3.2.3) and the effective rotational radius of the steering handle

NOTE - The effec tive rotational radius of the steering handle is the distance between the

axis (3.1 .I ) and the centre
point of the steering
handlegrip projected on the plane perpendicular to the steer axis.
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0 IS0 IS0 11838:1997(E)
3.2.5
steady state steer torque

torque applied to the steering handle in order to maintain the motion of the motorcycle-rider combination in a given

state

NOTE - When the motorcycle-rider combination is turning, this torque is classified as positive steer torque (3.2.5.1),

neutral steer torque (325.2) or negative steer torque (3.2.5.3).
3.2.5.1
positive steer torque

lied in the direction equal to that in which the motorcyc le-rider combination is

steady state steer torque (3.2.5) app
turning
3.2.5.2
neutral steer torque

amount of steady state steer torque (3.2.5) equal to zero, required when the motorcycle-rider combination is

turning
3.2.5.3
negative steer torque

steady state steer torque (3.2.5) applied in the direction opposite to that in which the motorcycle-rider combi-

nation is turning
3.2.6
steady state steer force

value obtained from dividing the steady state steer torque (3.2.5) and the effective rotational radius of the

steering handle
3.2.7
stiffness of the steering assembly

resistance against the deformation caused by the loads applied to the steering assembly

NOTE - There are torsional and bending stiffnesses.
3.2.8
friction torque of the steering assembly

torque about the steer axis (3.1 .I) required to initiate the motion of the steering assembly which does not include

the friction between the tyre and the road surface
3.2.9
damping torque of the steering assembly

damping torque about the steer axis (3.1 .I) at a certain steering velocity (32.1) which does not include the

damping between the tyre and the road surface
3.2.10
moment of inertia of the steering assembly

moment of inertia of the steering assembly about the steering axis (3.1 .I) under defined load conditions

3.3
Steering characteristics of the steering assembly
3.3.1
steering under stationary conditions

steering operation of the motorcycle-rider combination under stationary conditions

3.3.2
counter steering

positive action on the steering handle in order to compensate (cancel out) the change in the state of the motorcycle

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IS0 11838:1997(E)
3.3.3
disturbed steer

very short and quick rotation of the steering handle caused by an outside disturbance

3.3.4
loss of control in steering
uncontrollable rotation of the steering handle caused by a disturbance
4 Suspension system
4.1 Suspension geometry
4.1.1
wheel plane
centre plane of the wheel which is perpendicular to the wheel spin axis
4.1.2
wheel centre
intersection of the wheel spin axis and the wheel plane (4.1 .I)
4.1.3
front and rear wheel alignment

position of the front and the rear wheel planes relative to some reference frame planes

4.1.4
steering system alignment
relation between the wheel(s) and the body or the road surface

This term is often applied to the fork off-set (4.1.8), castor (4.1.7), castor angle (4.1.6).

NOTE -
4.1.5
alignment variation

displacements and deformations of the suspension system caused by forces applied to the wheels

4.1.6
castor angle
SEE IS0 6725:1981,6.12.
4.1.7
castor
SEE IS0 6725:1981,6.11.
4.1.8
fork off-set
distance between the steering shaft centreline and the front wheel spin axis
4.1.9
vertical wheel travel

vertical distance between the wheel spin axis position when the suspension is fully stretched and when it is fully

compressed according to the manufacturer’s indication
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4.1.10
spring and/or damper stroke

displacement between the spring and/or damper unit positions when fully stretched and when fully compressed

according to the manufacturer’s indication
4.2 Suspension dynamic rates
4.2.1
suspension rate

increase of ground contacting load necessary to approximate the wheel spin axis and the sprung mass projected on

the vertical line passing through the wheel centre by the unit distance under the designated load

4.2.2
ride rate

increase of ground contacting load necessary to approximate the road plane and the sprung mass projected on the

vertical line passing through the wheel centre by the unit distance under the designated load

4.2.3
link ratio of spring and/or damper

ratio of the vertical wheel travel (4.1.9) and the spring and/or damper stroke (4.1. IO)

NOTES

1 The link ratio can be more or less than 1, d epending on the location and the way of geometrical linking of the spring and/or

damper in relation to the position of the wheel axis.
2 The link ratio can be a function of the wheel travel.
4.2.4
damping characteristics

relation between the damping force occurring at the damper unit and the damper piston speed

NOTE - The sign is positive when the damper is compressed, it is negative when the damper is stretched.

5 Tyres and wheels
5.1
Tyre axis system and variables
5.1.1
conventional centre of tyre contact

intersection of the wheel plane and the vertical projection of the spin axis of the wheel onto the road plane

5.1.2
geometrical centre of tyre contact
geometrical centre of the contact area between the tyre and the road plane
5.1.3
effective centre of tyre contact
centre of pressures in the contact area of the tyre and the road plane
NOTES

When the wheel is cambered, the effective centre of tyre contact can be displaced in the direction of the camber.

2 The effective centre of tyre contact may not be the geometrical centre of tyre contact (5.1.2) area due to distortion of the

tyre produced by applied forces.
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5.1.4
camber angle
angle between the vertical and the wheel plane
5.1.5
tyre slip angle

angle between the xt-axis and the direction of wheel travel in the conventional centre of tyre contact (5.1 .I)

See figure 2.
5.1.6
slip ratio
(driving)
2)t)(cos a - Utc
*tc
5.1.7
slip ratio
(braking)
Z)t,COS a - I&
utxcos a
where
is the forward velocity of the conventional centre of the wheel;
Vtx

utc is the peripheral velocity of the conventional centre of tyre contact (5.1 .I) in reference to the centre of

the wheel;
a is the tyre slip angle (5.1.5).
5.2 Forces applied to tyres and their coefficients
5.2.1
tyre vertical load
zt-component of the force applied from the road plane to the tyre
5.2.2
tyre lateral force
yt-component of the force applied from the road plane to the tyre
5.2.3
tyre longitudinal force
xt-component of the force applied from the road plane to the tyre
5.2.4
tyre vertical stiffness

variation in the vertical load required to shift the distance between the conventional centre of tyre contact (5.1 .I )

and the wheel centre (41.2) in the vertical direction by the length, with the camber angle (5.1.4) being zero

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@ IS0 IS0 11838:1997(E)
5.2.5
tyre lateral stiffness

variation in the tyre lateral force (5.2.2) required to vary the wheel centre (4.1.2) in the yt-direction by the length

relative to the supporting surface, with the camber angle (5.1.4) being zero and a specified tyre vertical load

(5.2.1) being applied
5.2.6
driving force

positive tyre longitudinal force (5.2.3) caused by application of driving torque in the xt-direction

5.2.7
braking force

negative tyre longitudinal force (5.2.3) caused by application of braking torque in the yt-direction

5.2.8
conicity force

tyre lateral force (5.2.2) which changes sign [with respect the horizontal tyre axis system (6.2.2)] with a change

in direction of rotation when the tyre slip angle (5.1.5) and the camber angle (5.1.4) are zero

5.2.9
plysteer force

tyre lateral force (5.2.2) which does not change sign [with respect to the horizontal tyre axis system (6.2.2)] with

a change in direction of rotation when the tyre slip angle (5.1.5) and the camber angle (5.1.4) are zero

5.2.10
camber force
camber thrust

tyre lateral force (5.2.2) applied to the tyre having some camber angle (5.1.4) when the tyre slip angle (5.1.5)

is zero and the plysteer force (5.2.9) and conicity force (5.2.8) have been subtracted

5.2.11
cornering force

horizontal component, in the direction perpendicular to the direction of wheel travel, of the force applied from the

road plane to the wheel having some tyre slip angle (5.1.5) when the camber angle (5.1.4) is zero

See figure 2.
5.2.12
tyre side force

tyre lateral force (5.2.2) when the camber angle (5.1.4) is zero and the plysteer force (5.2.9) and conicity force

(5.2.8) have been subtracted
See figure 2.
5.2.13
tractive force

component of the tyre force vector in the direction of wheel travel of the effective centre of tyre contact (5.1.3)

is equal to the tyre lateral force (5.2.2) times the sine of the tyre slip angle (5.1.5) plus the tyre longitudinal

force (5.2.3) times the cosine of the tyre slip angle (5.1.5)
5.2.14
drag force
negative tractive force (5.2.13)
See figure 2.
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IS0 11838:1997(E) @ IS0
5.2.15
rolling resistance

force opposite to the direction of wheel heading mainly resulting from deformation of a rolling tyre

5.2.16
rolling resistance coefficient
ratio between the rolling resistance and the tyre vertical load (5.2.1)
5.2.17
camber stiffness

rate of change of tyre lateral force (5.2.2) with respect to the change in camber angle (5.1.4) usually evaluated

at zero camber angle and at zero tyre slip angle (5.1.5)
5.2.18
camber stiffness coefficient

ratio of camber stiffness (5.2.17) of a free straight-rolling tyre to the tyre vertical load (5.2.1)

5.2.19
cornering stiffness

rate of change of tyre lateral force (5.2.2) with respect to the change in tyre slip angle (5.1.5), usually evaluated

at zero tyre slip angle and at zero camber angle (5.1.4)
5.2.20
cornering stiffness coefficient

ratio of cornering stiffness (5.2.19) of a free straight-rolling tyre to the tyre vertical load (5.2.1)

5.2.21
pneumatic trail

horizontal distance between the point of action of the tyre side force (5.2.12) and the conventional centre of tyre

contact (5.1.1)

NOTE - This is a way of defining the aligning torque relative to the tyre side force (5.2.12).

5.2.22
tyre lag

delay that occurs in the change of the tyre lateral force (5.2.2) resulting from a change in tyre slip angle (5.1.5)

or camber angle (5.1.4)
5.2.23
relaxation length
distance covered during the tyre lag (5.2.22)

NOTE - Normally, the relaxation length is defined as the distance rolled by the tyre until a value of 63,2 % of the normal

value of tyre lateral force (5.2.2) is obtained when the tyre slip angle (5.1.5) and/or the camber angle (5.1 A) change(s) in

steps from zero.
5.3 Moments applied to tyres
5.3.1
overturning moment
component about q-axis of moments applied from the road plane to the tyres
5.3.2
rolling resistance moment

component of the tyre moment vector about the yt-axis resulting from the rolling resistance (5.2.15)

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@ IS0 SO 11838:1997(-- El
5.3.3
camber torque
;ome camber an

component about the zt-axis of moments applied from the road plane to the wheel having ‘9

(5.1.4) when the tyre slip angle (5.1.5) is zero
5.3.4
aligning torque
component of the tyre moment vector tending to rotate the tyre about the q-axis
5.4 Phenomena related with tyres
5.4.1
standing wave

phenomenon that occurs when the tyre peripheral speed exceeds a given peripheral velocity while it is rotating

at a high speed

caused by the tyre contact tend to remain wi recovery even after the deformed portions of the

NOTE - Deformations thout

tyre have left the road s urface, which results in steady standing waves on th e tyre surface.

6 Basic principles of axis systems and kinematics
6.1 Axis systems
See figure 3.
6.1.1
earth-fixed axis system
ix, y, z)

right-hand orthogonal axis system fixed on the earth, in which the X- and Y-axis are in a horizontal plane and the

Z-axis is directed upwards

The trajectory of the motorcycle is described with respect to this earth fixed axis system.

NOTE -
6.1.2
motorcycle axis system
(XI, y’, 23

right-hand orthogonal axis system which has its origin at the centre of gravity of the motorcycle such that, when

the motorcycle is moving in a straight line on a level road, the x’-axis is substantially horizontal, points forwards and

is parallel to the motorcycle longitudinal plane, the y’-axis points to the rider’s left and the Z’-axis points upwards.

(x’

NOTE - Use the motorcycle-rider combination axis system res, y’res, z’res) which substitutes the motorcycle axis system

in every corresponding definition when considering the motorcycle-rider combination instead of the motorcycle only.

6.2 Horizontal axis systems
6.2.1
horizontal motorcycle axis system
(x, y, 2)

right-hand orthogonal axis system which has its origin at the centre of gravity of the motorcycle and moves

together with the motorcycle body such that the x-y plane is always parallel to the X-Y plane of the earth-fixed axis

system (6.1 .I); the x-axis is the projection of the Y-axis of the motorcycle axis system (6.1.2) on the x-y plane and

points forwards and the z-axis is parallel to the Z-axis of the earth-fixed axis system and points upwards

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@ IS0
IS0 11838:1997(E)
6.2.2
horizontal tyre axis system
Ixt, yt, zt)

right-hand orthogonal axis system which has its origin at the conventional centre of tyre contact (5.1. I); the xt-

axis is the intersection of the wheel plane (4.1 .I) and the road plane with a positive direction forward, the q-axis is

perpendicular to the road plane with a positive direction upward and the yt-axis is in the road plane

In order to differentiate between front and rear horizontal tyre axis systems, indices “f” and “r” are used.

NOTE -
6.3 Component and assembly axis systems

The following component and assembly axis system s are right-hand orthogonal axis sys terns which have an origin

mbly
at the centre of gravity of the component or the asse
6.3.1
steering assembly axis system
(xi”, Yf”l &J)

axis system of the steering assembly in which the &-axis is parallel to the steering head pipe axis and points

upwards and the &-axis points forwards and is parallel to the wheel plane (4.1 .I )

6.3.2
frame fixed axis system
but Yru hl)
horizontal axis system of the frame without the steering assembly
6.3.3
steering assembly sprung part fixed axis system
(xi, y>, Z’f)

assembly axis system which applies to the sprung part of the steering assembly and is parallel to the steering

assembly axis system (6.3.1) and has axes pointing in the same directions
6.3.4
frame sprung part fixed axis system
(Xp yrl ZJ

horizontal assembly axis system which applies to the sprung part of the frame without the steering assembly

6.3.5
motorcycle longitudinal plane

plane that passes through the steering head pipe axis and that is parallel to the rear wheel plane

6.4 Ground contact axes
6.4.1
conventional ground contact axis
(xgo)

axis through both conventional centres of tyre contact (5.1 .I ) of the front and rear tyres; the direction of this axis

is positive in the forward direction of the motorcycle
6.4.2
geometrical ground contact axis
(xss)

axis through both geometrical centres of tyre contact (5.1.2) of the front and rear tyres; the direction of the axes

is positive in the forward direction of the motorcycle
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@ IS0 IS0 11838:1997(E)
6.4.3
effective ground contact axis
(xge)

axis through both effective centres of tyre contact (5.1.3) of the front and rear tyres; the direction of the axis is

positive in the forward direction of the motorcycle
6.4.4
angular orientation of the motorcycle

orientation of the motorcycle axis system (6.12) with respect to the earth-fixed axis system (6.1 .I) which is

given by the following sequence of three angular rotations starting from a condition in which the two sets of axes

are initially aligned:
- yaw rotation, Y, about the aligned z’- and Z-axis;
pitch rotation, 8, about the motorcycle y’-axis;
- roll rotation, @, about the motorcycle Y-axis.
NOTES

1 Roll rotations can also be considered about axes xgO, x99 and +. The respective angles will then be &, og9 and age.

2 Angular rotations are positive if clockwise when looking in the positive direction of the axis about which the rotation occurs.

6.4.5
rolling
banking

angular rotation of the motorcycle or of the motorcycle-rider combination about the x’axis or &,-axis respectively

NOTE - Rolling can also be considered about the axes +, X~~ and +, as defined in 6.4.5.1, 6.4.5.2 and 6.4.5.3.

6.4.5.1
conventional rolling
rolling (6.4.5) about the xg,-axis
6.4.5.2
geometrical rolling
rolling (6.4.5) about the xgg-axis
6.4.5.3
effective rolling
rolling (6.4.5) about the xge-axis
6.4.6
pitching

angular rotation of the motorcycle or of the motorcycle-rider combination about the y’-axis or &,-axis respectively

6.4.7
yawing

angular rotation of the motorcycle or of the motorcycle-rider combination about the Z’-axis or &,-axis respectively

6.5 Motorcycle masses and weight distribution
6.5.1
motorcycle mass
mass of the motorcycle under a given loading condition
NOTE - Some particular conditions of motorcycle mass are defined in IS0 6726.
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IS0 11838:1997(E)
6.5.2
sprung mass
mass correspo nding to the load sup ported by the suspension

In cases where some of the masses of the propeller shaft, roller chain, suspension system, steering system,

NOTE -

braking system, etc., constitute the sprung mass, such masses should be added to the corresponding masses according to

the structure of the motorcycle.
6.5.3
unsprung mass

mass which corres pond s to the difference between motorcycle mass and sprung mass

6.5.4
weight distribution ratio

percentage of weight distribu ted to each axle under well-defined loading conditions

6.6 Moments of inertia
6.6.1
moment of inertia

sum of the products of the elements of mass and the squares of their distances from an axis

NOTE - This axis may be the axis that passes through the centre of gravity of the motorcycle, the assembly or the

component.

of inertia about the axes of the motorcycle axis system (6.12) are indicated by &it, ‘yyt

EXAMPLE - Moments
or &I.
6.6.2
product of inertia
sum of the products of the elements of mass and their distances from two axes

The two axes should be clearly stipulated and indices used to indicate which axes are relevant.

NOTE -
EXAMPLE - Product of inertia about x’-axis and z’-axis is indicated by IZkf.
6.7 Motion variables
6.7.1
pitch angle

angle formed between the +-axis and the X-Y plane, which is positive when the +axis is moving clockwise about

the Y-axis seen in the positive sense of the Y-axis
6.7.2
yaw angle

angle formed between the x,,-axis projection on the road plane and the X-axis, which is positive when the +,-axis

projection on the road plane is moving clockwise about the Z-axis seen in the positive sense of the Z-axis

6.7.3
course angle

angle between the horizontal motorcycle speed and the X-axis which is positive when the motorcycle velocity on

the road plane is moving clockwise about the Z-axis seen in the positive sense of the Z-axis

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@ IS0 IS0 11838:1997(E)
6.7.4
motorcycle sideslip angle

angle between the horizontal motorcycle speed and the motorcycle x-axis, which is equivalent to the difference

between the course angle and the yaw angle
6.7.5
roll angle
bank angle

angle between the Y-2’ plane and the X-Z plane which is positive for a right turn (clockwise as seen by the rider)

NOTE - Other roll angles can be considered as the angles formed by the plane through the xgo or xgg or xge-axis and the

motorcycle centre of gravity and the z-axis, these are defined in 6.7.5.1, 6.7.5.2 and 6.7.5.3.

6.7.5.1
conventional roll angle
@go
-axis and the motorcycle centre of gravity, which is positive for a right turn
angle between the plane through the xgo
(clockwise as seen by the rider)
6.7.5.2
geometrical roll angle

angle between the plane through the xgg -axis and the motorcycle centre of gravity, which is positive for a right turn

(clockwise as seen by the rider)
6.7.5.3
effective roll angle

angle between the plane through the xge -axis and the motorcycle centre of gravity, which is positive for a right turn

(clockwise as seen by the rider)
6.7.6
resultant roll angles

angles formed by the planes through either the xgo or xgg or Xge -axis and the motorcycle-rider combination’s centre

of gravity and the z-axis; these are called respectively conventional (@go,res), geometrical (@gg,res) and effective

(@ge,res) resultant force angle
6.7.7
speed of the centre of gravity

velocity vector which has its origin at the centre of gravity of a component, an assembly or a motorcycle

6.7.8
horizontal motorcycle speed

horizontal component of the speed of the centre of gravity of the motorcycle frame

6.7.9
motorcycle velocity

iector quantity expressing the velocity of a point in the motorcycle relative to the earth-fixed axis system (6.1 .I),

of which the following motion variables are components of this vector, resolved with respect to the moving

motorcycle axis system (6.12)
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IS0 11838:1997(E)
6.7.9.1
longitudinal velocity

magnitude of the component of the velocity vector of a point in the motorcycle in the Y-direction

6.7.9.2
side velocity
vY'

magnitude of the component of the velocity vector of a point in the motorcycle in the y’-direction

6.7.9.3
normal velocity
vZ'

magnitude of the component of the velocity vector of a point in the motorcycle in the z’-direction

6.7.9.4
forward velocity

magnitude of the component of the velocity vector of a point in the motorcycle perpendicular to the y-axis and

parallel to the x-axis
6.7.9.5
lateral velocity

magnitude of the component of the velocity vector of a point in the motorcycle perpendicular to the x-axis and

parallel to the y-axis
6.7.9.6
vertical velocity

magnitude of the component of the velocity vector of a point in the motorcycle parallel to the z-axis

6.7.9.7
roll velocity
bank velocity
angular velocity about the x,-axis

NOTE - Other roll velocities can be considered as the angular velocities about either the xgo or xgg or xge-axis, these are

defined in 6.7.9.7.1, 6.7.9.7.2 and 6.7.9.7.3.
6.7.9.7.1
conventional roll velocity
@go
angular velocity about the xgo-axis
6.7.9.7.2
geometrical roll velocity
@ss
angular velocity about the xgg-axis
6.7.9.7.3
effective roll velocity
angular velocity about the xge-axis
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IS0 11838:1997(E)
@ IS0
6.7.9.8
pitch velocity
angular velocity about the y’-axis
6.7.9.9
yaw velocity
angular velocity about the z-axis
6.7.10
acceleration vector of the centre of gravity

acceleration vector with its origin at the centre of gravity of a component, an assembly or a motorcycle

6.7.11
motorcycle acceleration

vector quantity expressing the acceleration of a point in the motorcycle relative to the earth-fixed axis system

(6.1 .I) of which the following motion variables are components of this vector, resolved with respect to the

motorcycle axis system (6.12)
6.7.11.1
longitudinal acceleration
ax’
eration vector of a point in the motorcycle in the S-direction
magnitude of the component of the acce
6.7.11.2
side acceleration
aY'

magnitude of the component of the acce eration vector of a point in the motorcycle in the y’-direction

6.7.11.3
normal acceleration
a,’

magnitude of the component of the acceleration vector of a point in the motorcycle in the $direction

6.7.11.4
forward acceleration

magnitude of the component of the acceleration vector of a point in the motorcycle perpendicular to the y-axis and

parallel to the road plane
6.7.11.5
lateral acceleration

magnitude of the component of the acceleration vector of a point in the motorcycle perpendicular to the x-axis and

paralle
...

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