Four-wheel drive vehicles have recently become widely used for
their enhanced safety in a variety of road conditions on the
highway and snowy, wet, and gravel-covered roads.
It is well known that four-wheel drive vehicles are superior in
maneuverability to two-wheel drive vehicles. We have attempted to
explain this superiority by theoretical as well as experimental
methods.
This paper deals with the theoretical approach in determining
the difference in movements between two-wheel and four-wheel drive
vehicles during cornering with varying tire-to-road-surface
friction coefficients and wheel loads. Experiments were carried out
on paved and snowy roads using the two types of vehicles. As a
result, it has been verified quantitatively that the four-wheel
drive vehicle provides higher stability with greater variations in
friction coefficients and wheel loads, though the difference is
only marginal under a steady state.
This paper also reports on the new suspension system developed
to implement enhanced characteristic levels of a normal passenger
car (vibration, ride comfort, steering stability and control, etc.)
without sacrificing the unique features of the four-wheel drive
system.