An investigation on the Resonances and Chaotic Behavior of a Nonlinear Vehicle Suspension System

In recent years، more attention has been paid on intelligent vehicle suspension systems equipped with magneto-rheological dampers. In order to investigate nonlinear vehicle dynamics، in the majority of the researches، a quarter-car model with one or two degrees of freedom is used. In such simple models، one can only study the bounce motion of sprung and unsprung masses. In this paper، in order to consider more realistic model for vehicle suspension system، a nonlinear half car model with four degrees of freedom is employed. Frequency response diagrams of the model have been obtained. In order to identify the region of excitation frequency in which the system has chaotic behavior، the bifurcation and Poincare maps are used. Results show that near the heave and pitch natural frequencies، the system forced response has been changed considerably and new unstable region has been appeared in frequency diagrams. Moreover، results show that in comparison with quarter car model، the resonant frequency of pitch motion intensifies the chaotic response.