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158 Multibody Systems Approach to Vehicle Dynamics
spherical joint at one end and a universal joint at the other end to constrain
unwanted spin of the push rod about its own axis. The bell crank is attached
to the chassis with a revolute joint, the rotation about which is resisted by
the spring damper unit. It can be noted that it is not really necessary to
model the spring damper as rigid bodies. The definition of the forces generated
will be sufficient to simulate the handling of the full vehicle.
4.4 Determination of suspension system characteristics
The suspension design process discussed at the beginning of this chapter
has been summarized in Table 4.1 by six areas in which the suspension
performance can be assessed. Ultimately the quality of the design will be
judged on the performance of the full vehicle, but an early assessment of
the suspension design as an individual unit is essential. In order to quantify
the performance of the suspension system a range of characteristics may be
determined through simulation of a single suspension system or quarter
vehicle model. During this chapter it will be shown that a single suspension
system can be analysed in a number of ways that will provide information
to support the six suspension design activities that have been identified.
It should also be noted, however, that while the emphasis in this book is to
explain the function and modelling of suspension systems using quarter
models, customized software such as ADAMS/Car and ADAMS/Chassis
extend the modelling as stated to a half vehicle model analysed using a virtual
test rig, an example of which is shown in Figure 4.20.
Such a system also allows the additional incorporation of roll bars and a
steering system to investigate the cross coupling of left and right suspension
systems through roll bar compliance and the effects of steering inputs
in isolation or in combination with suspension movement.
Fig. 4.20 Use of virtual test rig to analyse a half vehicle suspension model
(provided courtesy of MSC.Software)