Abstract
A hybrid model of vehicle vibration when the vehicle is moving on a bad road is proposed . This considers, as well as the usual kinematic excitation on unsprung mass the presence of the free vibration mode of the vehicle which is taken into account as an additional disturbing force acting on the sprung mass. In this way, some experimentally observed phenomena of vehicle dynamics, such as the parametric dependence of vibration upon the excitation amplitude related to the static deflection of the vehicle, and the antiresonance effects on the upper spring mass, could be analytically described.