• 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 define 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.