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Modelling and assembly of the full vehicle 331
V
X
β
V y
cm
V x
Y
Fig. 6.6
Body slip angle
(iv)
(v)
(vi)
Pitch angle
Yaw rate
Roll rate
Another measure often determined during test or simulation is the body
slip angle, . This is the angle of the vehicle velocity vector measured from
a longitudinal axis through the vehicle as shown in Figure 6.6. The components
of velocity of the vehicle mass centre V x and V y , measured in vehicle
body reference frame, can be used to readily determine this.
6.4 Suspension system representation
6.4.1 Overview
In Chapter 4 the modelling and analysis of the suspension system was considered
in isolation. In this section the representation of the suspension as
a component of the full vehicle system model will be considered. As stated
the use of powerful multibody systems analysis programs often results in
modelling the suspension systems as installed on the actual vehicle. In the
following discussion a vehicle modelled with the suspension represented in
this manner is referred to as a ‘Linkage model’.
Before the advent of computer simulation classical vehicle dynamicists
needed to simplify the modelling of the vehicle to a level where the formulation
of the equations of motion was manageable and the solution was
amenable with the computational tools available at the time. Such an
approach encouraged efficiency with the analyst identifying the modelling
issues that were important in representing the problem in hand. The use of
modern software need not discourage such an approach. The following
sections summarize four vehicle models, one of which is based on modelling
the suspension linkages with three other models that use alternative
simplified implementations. All four models have been used to simulate
a double lane change manoeuvre (Blundell, 2000) and are compared in
Case study 7 at the end of this chapter. The four models described here