Study On Dynamics Character Of Nonlinear Vehicle Suspension System Due To Speed Control Bumps Impact

Speed control humps (SCHs) play an important role in inhibiting traffic accidents caused by over-speeding of vehicle. However, most of SCHs cause rough road more severely. When passing through these SCHs with high-speed, Impulse vibrations and incisive yawp will appeared in the vehicle. These disadvantages may affect the body directly through suspension system, thereby causing some discomfort of passenger and the damage of carry cargo. Thus, these can bring bad effect to the vehicle velocity, ride performance (comfort), safety and handling stability, and make fracture of road surface. This irregular vibration not only damages to vehicle components, but also harms health of passenger. Vehicle suspension system is the necessary device to ensure automotive performance and decrease damage of components. However, there are lots of nonlinear components in the suspension system. Some complicated nonlinear dynamic characteristics appear in the system because of excitation from road surface, such as, bifurcation and chaos. These performances may bring hazard to vehicle, and even can cause disastrous consequence. So it is necessary to research dynamics of realistic vibrations caused by vehicle passing through the SCHs with high speed. The results will help to explain the complicated dynamics of vehicle more clearly and design the control system of suspension more reasonable.These vibrations to vehicle from SCHs were taken as external input conditions. Firstly, an approximated static model description of humps as an excitation is presented by analyzing the setting mode and parameters of SCHs. The correlation function of external excitations is get according to vehicle speed, then, the dynamic model relationship couple with velocity is established. In this paper, the four degree-of- freedom (DOF) half vehicle model is taken as main object, the model is established according to the actual property of spring and damper, we need use the reasonable nonlinear model to express these characteristic. All of these are order to get close to actual vehicle model.When passing the single SCH, to assess the transient performance of vehicle, we can analyze the dynamics of vehicle by using the acceleration responses. However, when the excitation is the continuous shape including period and non-periodic, the chaotic dynamics of suspension system was analyzed by numerical simulation. By adopting these discriminating tools (bifurcation diagram, phase graph, time history, Poincarémap and power spectrum density) to prove the chaos in the system. After that, it is necessary to find the conditions and apply chaotic control ways when the chaos appears, the purpose is that make the chaotic motion eliminate in the system.Research on dynamic characteristic for a nonlinear vehicle model caused by the consecutive speed control humps is of great theoretical value as well as practical application. The results will be conducive to understand dynamic responses for nonlinear vehicle suspension system more deeply, select reasonable parameters for suspension and design the dynamics property of full-vehicle, design and install continuous speed control humps more suitably.