Analysis of dynamic stability of nonlinear suspension

Abstract

The vehicle is excited by the road surface while traveling. The vehicle suspensions play a significant role not only in damping out the vibrations created due to the excitation but also in maintaining the stability of the entire system. In this article, the dynamic stability of nonlinear suspension under this excitation is analyzed. The mathematic model for the suspension is established, the nonlinear vibration caused by sprung mass vibration is solved and frequency curves are obtained. Both the characteristics of the stable solution and the related parameters affecting the unstable region are analyzed. The numeric solution reveals the existence of a critical excitation value. When the excitation is within this critical value, the sprung mass vibration is stable; when the excitation is greater than the critical value, an unstable frequency band with the jumping phenomenon is observed. Under the same excitation acceleration, a decrease in damping coefficient results in an increase in both the amplitude and unstable frequency band, all falling into the unstable region which is getting larger. The increase in nonlinear stiffness of spring leads to the same maximum vibration amplitude shifting to the right and a larger unstable frequency band falling into the downward movement unstable region. All these indicate that there exists mutation in the amplitude of vehicle vibration, which endangers the stability of the vehicle while traveling.