4569846498

Modelling and assembly of the full vehicle 335
6.4.4 Swing arm model
This model is developed from the equivalent roll stiffness mass model by
using revolute joints to allow the suspensions for all four wheels to ‘swing’
relative to the vehicle body rather than using the suspensions linked on
an axle. The revolute joints are located at the instant centres of the actual
suspension linkage assembly. These positions are found by modelling the
suspensions separately as described in Chapter 4. The swing arm model has
an advantage over the roll centre model in that it allows the wheels to
change camber angle independently of each other and relative to the vehicle
body. The swing arm model is shown schematically in Figure 6.9. Although
in the sketch the swing arms are shown with an axis parallel to the vehicle
axis this need not be so in general. Also, although in the sketch the swing
arms are shown as a ‘plausible’ mechanical arrangement (i.e. not overlapping)
this also need not be so; in general contact between elements is not
modelled for vehicle dynamics studies and in general the instant centres are
widely spaced and not necessarily within the physical confines of the vehicle
body. The swing arm model has the advantage over the equivalent roll stiffness
model in that the heave and pitch ride behaviour can be included.
6.4.5 Linkage model
The model based on linkages as shown in Figure 6.10 is the model that
most closely represents the actual vehicle. This sort of vehicle model is the
Fig. 6.10
Linkage model ‘as is’ approach