Abstract: Previous research showed that the clearance of the movement pair can considerably influence the dynamic response of the mechanism. As a result, it can be deduced that the clearance of the steering mechanism also can have great influences on the steering wheel shimmy system. Therefore, the steering trapezium is simplified as a linkage mechanism, and the influences of the clearance on the steering wheel shimmy system are discussed. The 6-DOF dynamic model of steering wheel shimmy with consideration of movement pair clearance of steering mechanism is established with Lagrange equations. Based on this model, examples with different clearance of the movement pair are analyzed with 4-order Runge-Kutta method in order to evaluate the effect of the clearance on the dynamic behavior of the vehicle shimmy system. Simulation results show that the clearance is an important factor in inducing the chaotic motion of the vehicle shimmy system, so it should be considered adequately in the modeling process of shimmy system. With the increase of the clearance, the system experiences the variations from periodic motion, to quasi-periodic motion, and further to chaos state. The correlative conclusions can provide theoretical basis for effective control of the steering wheel shimmy.

Key words: Clearance, Nonlinear, Steering mechanism, Steering wheel shimmy