考虑机体动力特性的前起落架摆振分析
Simulation of Nose Landing Gear Shimmy with Flexible Airframe Considered

以某型客机为对象，研究了飞机滑跑时前起落架的摆振稳定性问题。首先建立了考虑机体动力特性的起落架摆振动力学方程组，之后将某型客机参数带入方程组求解得到了该型机前起落架滑跑临界阻尼、临界速度及发生摆振的频率范围。研究结果表明，该机滑跑时出现的摆振失稳问题为减摆器阻尼不够而引起的轮胎型摆振，且该摆振与机体振动模态形成了耦合共振，可以通过增大减摆阻尼避免此问题。同时，还研究了机体结构弹性、轮胎刚度对起落架摆振特性的影响规律。起落架摆振临界速度、最大临界阻尼值及摆振频率随着轮胎扭转及侧向刚度的增大而增大；而机体弹性使飞机起落架的摆振频率更低，且摆振稳定区变小，更易发生摆振现象。因此在研究现代新型大型客机起落架摆振稳定性问题时，不能忽略机体动力特性的影响。
Shimmy stability of the nose landing gear of an aircraft is studied in this paper. Firstly, Shimmy model was built considering the dynamic characteristics of the airframe. Then the critical damping, critical velocity and frequency range of the shimmy are obtained by introducing relevant parameters into the shimmy model. The research shows that the problem of shimmy is a tire type shimmy caused by insufficient damping of dampers and brings coupled resonance with the vibration mode of the airframe, which can be avoided by increasing the damping of the shimmy. At the same time, the influence of airframe dynamics and tire stiffness on the shimmy characteristics of the landing gear is also studied. With the increase of tire torsion and lateral stiffness, the critical velocity, maximum critical damping value and shimmy frequency of the landing gear increase. However, the elasticity of the airframe makes the frequency of the aircraft landing gear lower and the stable region of the shimmy smaller, so that the phenomenon of shimmy is more likely to occur. Therefore, the influence of airframe dynamic characteristics can not be ignored when studying the shimmy stability of the landing gear of a modern large passenger aircraft