考虑间隙特性的起落架摆振非线性分岔分析

Nonlinear Bifurcation Analysis of Landing Gear Shimmy Considering Freeplay

采用考虑结构间隙、支柱弹性、轮胎变形、支柱前倾角、垂直载荷等影响因素的非线性摆振分析模型,利用分岔分析方法,研究间隙对摆振平衡点的影响,以及支柱扭转阻尼和间隙值对摆振振幅的影响。分岔计算得到系统的单参数分岔图、双参数分岔图以及扭转角幅值随速度变化曲线。研究结果表明,当前起落架系统出现扭转间隙时,飞机滑跑的临界稳定速度会大大降低,并且临界稳定速度不随间隙变化。同时发现,支柱扭转角振幅随间隙值增大而增大,随扭转阻尼增大而减小。研究结论可为间隙型摆振的发生机理和防摆设计提供研究途径。

A nonlinear landing gear shimmy model is constructed,which includes the freeplay,elasticity of strut,tire deflection,vertical loads and positive rake angle. Through bifurcation analysis,the effect of freeplay on neutral equilibrium position( Hopf point) and the influence of torsional damping of strut and gap value to shimmy amplitude are analyzed. The single-parameter bifurcation diagram,double-parameter bifurcation diagram and the variation curve of torsional angle along with speed are obtained. Simulation results show that it will greatly reduce the critical stability of the aircraft when the nose landing gear system has the freeplay. And the critical stability speed will not change with the gap value. At the same time,the torsional angle of the strut increases with the increase of the gap value,and decreases with the increase of torsional damping. The research conclusions provide a new approach to reveal the mechanism of land gear shimmy phenomenon with freeplay,and to prevent the occurrence of shimmy.