Dynamic Analysis Of Vehicle Shimmy System With Clearance And Flexibility Factors Of Steering Mechanism

Front wheel shimmy is defined as the phenomenon when the car driving in the flat straight road, the vibration of the steering wheel vibrating continually around Kingpin in a certain extent and frequency. It is not only harmful for the maneuverability and driving safety, but also performs negative influence on power performance and fuel economy performance. Because of the negative influence and widespread in many model, it cause the common concern in and out the sea.There are many factors which make impact on the wheel shimmy, such as the tire characteristics and body structure parameters. The previous studies of our team show that the clearance in the steering trapezoid of steering system has a great influence on the response of wheel shimmy. In fact, the impact forces caused by the clearance make the elastic deformation of the bar, the influence of that can not be ignored, so it is necessary to study the combined effect of clearance and flexibility factors made on the wheel shimmy.In this dissertation, the steering trapezoid set is simplified as a horizontal four-bar linkage, in which the clearance exists between the left steering knuckle arm and steering tie rod, and the bars are all the elastic rod. Simulation model is established using matlab/simulink software. On this basis, the influence of clearance and flexibility factors together on the wheel shimmy system is analyzed, other factors'impact are also studied, and the measures are given in response. Details are as follows.The dynamic model of rigid four-bar linkage which exist clearance is established, no only the influence of the clearance factor made on the linkage movement is analyzed, but also get the incentive forces of the elastic linkage. On the basis, the dynamic model of the elastic linkage is established using the finite element method, through comparison with the rigid system, the result shows that considering the flexibility the dynamic response of linkage improve, the impact force decrease much, and the clearance causing the chaos increase. But the system eventually comes into chaos status.The steering trapezoid set is simplified as a horizontal four-bar linkage, then establishing a 6-DOF dynamic model of rigid wheel shimmy considering the clearance, combined the model of elastic four-bar linkage, the 6-DOF dynamic model of elastic wheel shimmy is derived.According to the dynamic models of the rigid and elastic wheel shimmy system, the corresponding simulation model is established, through simulation and analysis, the comparison was made. The result shows the wheel shimmy system are more stable considering the flexibility factor, flexibility factor can inhibit the harmful impact of clearance, and the rang of clearance is given. The other factors'impact on the wheel shimmy is also studied, such as speed and steering damp, the corresponding range is given.