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Modelling and assembly of the full vehicle 333
road will therefore be directly related to the roll angle of the vehicle. Spring
and damper forces act between the suspensions and the body. Such suspensions
have been used on early road vehicles, notably the Lancia
Lambda (1908–1927), where it was termed ‘sliding pillar’.
The front wheel knuckles are modelled as separate parts connected to the
lumped suspension parts by revolute joints. The steering motion required
for each manoeuvre is achieved by applying time dependent rotational
motion inputs about these joints. Each road wheel is modelled as a part
connected to the suspension by a revolute joint. The lumped mass model is
shown schematically in Figure 6.7.
6.4.3 Equivalent roll stiffness model
This model is developed from the lumped mass model by treating the front
and rear suspensions as rigid axles connected to the body by revolute
joints. The locations of the joints for the two axles are their respective ‘roll
centres’ as described in Chapter 4. A torsional spring is located at the front
and rear roll centres to represent the roll stiffness of the vehicle. The determination
of the roll stiffness of the front and rear suspensions required an
investigation as described in the following section. The equivalent roll stiffness
model is shown schematically in Figure 6.8.
REV
Torsional
spring damper
Rear axle
Torsional spring
damper
REV
Front axle and
wheel knuckles
Fig. 6.8
Equivalent roll stiffness model approach