一种分析滑橇式起落架直升机"地面共振"的方法

针对滑橇式起落架直升机，提供了一种“地面共振”动力稳定性分析的方法。首先，针对滑橇式起落架在承受直升机重量与旋翼升力时产生大变形的特点，逐级用有限元法计算其刚度和变形，并通过与地面库伦摩擦系数的比较，判断滑橇式起落架与地面接触的橇筒所受摩擦力的大小以及与地面产生的相对运动；其次，考虑滑橇式起落架与直升机相连阻尼器的作用，将有限元计算弹性刚度的方法拓展到适用于复刚度的计算；最后，根据直升机旋翼桨毂不同的结构形式，用桨叶振动模态法对滑橇式起落架的直升机进行“地面共振”动力稳定性分析，并通过算例得到验证。工程实例分析结果表明，本文方法具有物理概念清晰、运用方便的特点，能适用于各种旋翼结构形式的滑橇式起落架直升机的“地面共振”分析。

Analytical Method of Ground Resonance for Helicopters with Ski Landing Gears

An analytical method of ground resonance dynamic stability countering the helicopters with ski landing gears is provided. Firstly, according to the characteristic of ski landing gears having large deformation acted by helicopter weight and rotor thrust, the stiffness and the deformation of landing gear are calculated using finite element method step by step. Through comparison of Coulomb friction coefficient, the friction forces on ski applied by ground and relative motion between ski and ground can be determined. Secondly, considered the function of dampers mounted between landing gears and the airframe, the finite element method for computing elastic stiffness of landing gear is extended to be adapted to complex stiffness calculation. Finally, the analysis of the ground resonance dynamic stability of helicopters with ski landing gears is preformed by using blade vibration modal method and considering different rotor hub configurations. Analytical method is verified by examples. Results of engineering examples show that the method has a clear physical conception and is convenient for use. It can be adapted to analyze the ground resonance of helicopters with ski landing gears and different rotor hub configurations.