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152 Multibody Systems Approach to Vehicle Dynamics
Upper bushes (mounts)
Upper wishbone
(control arm)
Upper ball joint
(bushes on rear)
Spring
Damper
Wheel knuckle
(stub axle) (kingpin)
Lower bushes (mounts)
Road wheel
Lower wishbone
(control arm)
Connection to rack
(body on rear)
Fig. 4.14
Track rod
(tie rod on rear)
Double wishbone suspension system
Lower ball joint
(bushes on rear)
Track rod end
the rigid bodies will not be required. This information would be required,
however, if the model is to be used for a dynamic analysis predicting the
response of the suspension to inputs at the tyre contact patch.
The modelling of the connections between the suspension links will also
depend on the type of vehicle and whether the suspension is for the front or
rear of the vehicle. On the front of the vehicle the connections between the
control arms and the wheel knuckle would be modelled using spherical
joints to represent the ball joints used here. On the rear these connections
are more likely to include the compliance effects of rubber bushes. On a
racing car where ride comfort is not an issue the suspension model is likely
to be rigidly jointed throughout. Not shown in Figure 4.14 are the bump
and rebound stops that would need to be included when considering situations
where the wheel loads are severe enough to generate contact with
these force elements.
The other type of suspension system that is very common on road
vehicles is the McPherson strut system as illustrated in Figure 4.15. The
main difference between this system and the double wishbone system is
the absence of an upper control arm and the combination of the spring and the
damper into a single main strut, the body of which is the major component
in the system.
4.3 Quarter vehicle modelling approaches
One of the earliest documented applications of the MSC.ADAMS program
by the automotive industry (Orlandea and Chace, 1977) was the use of
the software to analyse suspension geometry. This approach is now well