A Simulation Study of the Self-excited Shimmy for Automobiles with Dependent Suspension

The influences of tie-rod stiffness, kingpin caster angle, steering gear stiffness, tire cornering stiffness, tire drag, steering gear damping and equivalent damping of wheel around kingpin on the self-excited front wheel shimmy are presented by numeric simulation. It is shown that the front wheel shimmy may be induced when these parameter values vary. However vehicle speed is also one of those factors to cause shimmy. With certain values of these parameters and vehicle speed, initial excitation may lead to stable vibration, namely self-excited front wheel shimmy or unstable motion. Different from the case of forced shimmy, change in the frequencies of self-excited shimmy is not in agreement with change in driving speed.