A Simulation Calculation Research On Front Wheel Shimmy For Automobile

Vehicle steering system shimmy is a very especially complex vibration. Though the world boasts the 50-year's history of study on vehicle steering wheel shimmy, and many valuable articles have been published meanwhile, the problem of shimmy is still not solved thoroughly. At present, a lot of vehicle types in the home market more or less have the phenomenon of shimmy. So we have a simulation research on shimmy by computer software and have a study on the effect of system parameters on shimmy, which may offer theory guidance for suppressing shimmy.The problem of front wheel shimmy of automobile with dependent suspension is presented in this paper. With the CA10 automobile as research object, for the first time, this paper offers a systematic and comprehensive study of different mechanism of the front wheel shimmy and the influence of sensitive factors on shimmy for different vibration system model. The main research contents are as follows:For the shimmy mathematical model of 3 free degrees of the ordinary CA10 automobile, we have had a study on the influence of different parameters on forced shimmy and on self-excited shimmy and also had a study on the phenomena with the two types of shimmy appearing by using MATLAB software. The simulation results show that a forced shimmy of the truck, with frequency of 4.25Hz, occurs at vehicle speed of 46 km/h.With the CA10 tank truck as research object, considering the greater influence of the vibration above suspension on the movement of front wheel and front bridge, it has researched the mathematical model of 5 free degrees, and the simulation calculation studies of forced shimmy and self-excited shimmy are also completed. The simulation results show that a forced shimmy of the tank truck, with frequency of 4.1 HZ , occurs at vehicle speed of 45 km/h.For the shimmy mathematical model of 3 and 5 free degrees, the numerical simulation calculation results show that the right and left front wheels vibrate with nearly equal angle amplitude and in same phase when shimmy occurs. Those sensitive parameters making system have negative damping and occur self-excited shimmy are horizontal pulling lever rigidity, tire sideslip rigidity, steering gear rigidity and damping, kingpin equivalent damping, kingpin caster angle, tire drag. And wheel center distance, tire side rigidity, vehicle wheel unbalanced mass, tire vertical rigidity, and distance from kingpin center to the vertical central line plane of tire have great influence on shimmy, but they don't make the system have negative damping. And horizontal pulling lever damping, suspension damping and rigidity have very small influence on shimmy. For the same automobile, the vibration degree or even the type of front wheel shimmy will change with the changing of the whole automobile constructs.The end is the summary of this paper and the outlook of the future research. In a word, font wheel shimmy is a problem subject to many factors and variables. Through the systematic research of the shimmy of CA10 automobile, we can offer direct theory guidance to reduce or eliminate the shimmy of all kinds of vehicle.