A new automobile rigid multi-body dynamics model and its stability analysis

With the suspension system taken into account, a new two-axle automobile multi-body dynamics model is developed with Roberson-Wittenburg method in this paper. In the model, there are 6DOF such as lateral, yaw, sprung mass roll, sprung mass vertical, axle roll and axle vertical. On this base, the automobile stability is analyzed further by Hurwitz theorem. It is resulted that an automobile nice stable ride performance would be proved and the two follow necessary conditions: the product of the square of rear bearing spring effective range and rear suspension single side spring constant should be more than the product of the square of front bearing spring effective range and front suspension single side spring constant; the mass hold by rear axle and the severity of front wheel deflection should be more than the mass hold by front axle and the severity of rear wheel deflection. The two conditions complement the deduced condition from classic 2DOF automobile handling stability model. It has great influence for study automobile handling stability and the structure of suspension system.