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Modelling and analysis of suspension systems 159
A more detailed discussion of suspension analysis methods, such as those
used to investigate body isolation issues, will follow later in this chapter
but using a virtual rig such as this the following are typical of some of the
analyses performed:
(i) The wheels may be moved vertically relative to the vehicle body
through a defined bump–rebound travel distance. For the half model
shown in Figure 4.20 the vertical movement may involve single, opposite
or parallel wheel travel representing ride or roll motions for the
vehicle. The measured outputs allow the analyst to consider, depending
on the model used, aspects of kinematic and compliant wheel
plane control.
(ii) Lateral force and aligning torque may be applied at the tyre contact
path allowing measurement, for example, of the resulting toe angle
change and lateral deflection of the wheel (compliant wheel plane
control).
In addition to the above basic types of analysis it is also possible to use an
MBS suspension model to consider wheel envelopes where under the full
range of suspension travel and steering inputs an envelope mapped by the
outer surface of the tyre can be developed allowing the clearance with surrounding
vehicle structure to be checked.
In practice this has been achieved by using the wheel centre position, orientation
and tyre geometry from the MBS simulation as input to a CAD
system where the clearances can be checked. An example of the graphic
visualization of a wheel envelope, for vertical wheel travel only, using
superimposed animation frames is shown in Figure 4.21.
Fig. 4.21 Superimposed animation frames giving visual indication of
wheel envelope