PhD Thesis - Cranfield University

Chapter 4
4.1 Vehicle Longitudinal Dynamics
For any mission profile, an electric road vehicle is subjected to forces that the onboard
propulsion system has to overcome in order to propel or retard the vehicle. These forces are
composed of several components as illustrated in Figure 4.1 .The effort to overcome these
forces by transmitting power via the vehicle drive wheels and tyres to the ground is known
as the total tractive effort or total tractive force (F TR).
F TR
F AD
v xT
CoG
mg
F la
F gxT
F roll
Figure 4.1 Vehicle longitudinal forces representation
The total tractive force expressed as a composition of forces is,
TR
la
gxT
roll
AD
100
β
Centroid of
vertical forces
Rotation
mg
mg
F roll (per wheel)
F = F + F + F + F
(4.1)
where F la is the linear acceleration force, F gxT is the gravitational force acting on the vehicle
on non-horizontal roads, F roll is the rolling resistance force, and F AD is the aerodynamic drag
force.