• comfort
• fuel cell
• in-wheel motor
• mass ratio
• ride
• unsprung mass

The present thesis work is part of the feasibility study of a lightweight fuel-cell urban
vehicle named Hyrban. The vehicle mounts four wheel hub electric motors instead
of a traditional single motor on the chassis. This causes a sensible increase of the
unsprung-to-sprung mass ratio of the car. The aim of the thesis then, has been
to investigate the effects of this imbalance, in particular pointing out the attention
on the comfort behaviour. Through a frequency analysis of simple models it has
been possible to define and evaluate the variation of the comfort index to the mass
ratio increase and for various damping coefficients. It yielded not only that the
comfort index gets worse as the mass ratio increases, but also that it is less sensitive
to its change when the damping coefficient is lower than the optimal value. The
last one is variable relatively to the mass ratio, while the total mass and the bounce frequency are assumed to be constant. Other two performance indices have
been evaluate about the mass ratio: the suspension working space and the dynamic
tyre load. Representing physical limits to the suspension design, as a matter of fact
they influence the comfort, even if indirectly. Finally, among various suspension
solutions aimed to improve the comfort, only switchable dampers are regarded to
be a feasible solution for a vehicle with limited amount of space and power.