Dynamic Analysis And Evaluation Of Vehicle Shimmy Control With Reclaiming Energy Steering Damper

Due to the hazard of shimmy on many aspects such as the power、stability control of the vehicle and the service life of vehicle components, many researches have been done on the mechanism and control of shimmy, and lots of achievements are acquired. As a result of the complexity of the problem, it’s still difficult to solve the problem in particle with these theories. In this study, dynamic response of vehicle shimmy with the dynamic unbalance of front wheel is analyzed. On the other hand, the possibility of the application of reclaiming energy damper in the steering system is estimated, and the dynamic response of shimmy with reclaiming energy damper is analyzed. Through these works the theoretical basis for the control of shimmy is provided.In this study, a3-DOF dynamic model of vehicle shimmy is established, in which the external excitation of dynamic unbalance of front wheel is considered. Based on phase plane method, Poincae mapping method, combined with power spectrum and bifurcation analyze, the dynamic response of vehicle shimmy system with the excitation of dynamic unbalance is analyzed, and the characteristics of frequency components of the vibration response are systematically analyzed. The results show that, in the shimmy response, it usually contains self-excited vibration and forced vibration at the same time, and the proportion of the two components is mainly depended on the speed of vehicle and the magnitude of the excitation of dynamic unbalance. The characteristics of shimmy with the external excitation of dynamic unbalance are quite different from self-excited vibration, so it should be considered in the modeling process of shimmy system. With increment of the excitation of dynamic unbalance, the vibration experiences the variations from domination of self-excited vibration, which is caused by system structure itself, to forced vibration, which is caused by external excitation. As a result, the system experiences the variations from quasi-periodic motion to periodic motion under certain vehicle speed range. The correlative conclusions can provide theoretical basis for effective control of the steering wheel shimmy.Based on the3-DOF dynamic model of vehicle shimmy with the excitation of dynamic unbalance and combining the mechanical properties of motor and ball screw, the shimmy model with reclaiming energy damper was established. Under the restrict of hand force on steering wheel, the lead of ball screw and external resistors are matched for the optimization of shimmy control, and the dynamic response of the shimmy system is analyzed with the matched parameters. The results show that, since the application of the reclaiming energy damper, the amplitude of shimmy is significantly reduced, moreover, the solution of the function of the wheel movement is changed a lot too. The quasi-periodic motion and the jump of shimmy amplitude appeared under some certain speed turns to periodic motion. The easier motion characteristic is helpful to the control of vehicle shimmy.