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22 Multibody Systems Approach to Vehicle Dynamics
Anderson and Hanna (1989) have carried out an interesting study where they
have used two vehicles to make a comparison of three different vehicle
simulation methodologies. They have also made use of the Iltis, a vehicle of
German design, which at that time was the current small utility vehicle
used by the Canadian military. The Iltis was a vehicle that was considered
to have performed well and had very different characteristics to the M-151
Jeep that was the other vehicle in this study. The authors state that the M-
151 vehicle, also used by the Canadian military, had been declared unsafe
due to a propensity for rolling over.
Work has been carried out at the University of Bath (Ross-Martin et al.,
1992) where the authors have compared MSC.ADAMS with their own
hydraulic and simulation package. The results for both programs are compared
with measured vehicle test data provided in this case by Ford. The
Bath model is similar to the Roll Stiffness Model described later in this
book but is based on a force roll centre as described by Dixon (1987). This
requires the vehicle to actually exist so that the model can use measured
inputs obtained through static rig measurements, using equipment of the
type described by Whitehead (1995). The roll-centre model described
in this book is based on a kinematic roll centre derived using a geometric
construction as described in Chapter 4, though there is little to preclude a
force-based prediction by modelling the test rig on which the real vehicle
is measured.
As a guide to the complexity of the models discussed in Ross-Martin et al.
(1992), the Bath model required 91 pieces of information and the
MSC.ADAMS model, although not described in detail, needed 380 pieces
of information. It is also stated in this paper that the MSC.ADAMS model
used 150 sets of non-linear data pairs that suggests detailed modelling of
all the non-linear properties of individual bushes throughout the vehicle.