共轴式直升机地面共振非线性仿真

Nonlinear Simulation on Ground Resonance of Coaxial Helicopter

建立了共轴式直升机旋翼/机体耦合的非线性动力学模型。在不考虑桨叶减摆器和起落架非线性因素的前提下,通过求解某模型直升机不同转速时桨叶摆振和机体运动的时域响应,确定了该直升机发生地面共振的转速范围,并与特征值分析确定的共振转速范围进行了对比验证。最后,分别采用非线性动力学模型和线性化模型对不同转速时的上、下旋翼桨叶摆振和机体运动响应进行了动态仿真计算,发现:在稳定区内,系统非线性因素的影响不大;在不稳定区,非线性系统与线性化系统的响应特性呈现显著差异,且非线性系统将出现极限环现象。

A nonlinear dynamics model is built for analyzing dynamic stability of coaxial helicopter. In the case of ignoring the nonlinear aspects of lag damper and landing gear, the range of rotation speed of ground resonance is confirmed by calculating the time domain response of blade lag and airframe motion with different rotation speeds. Then it is compared with the result calculated by eigenvalue method. Fi- nally, the time domain responses of blade lag and airframe motion with different rotation speeds are re- spectively calculated by the nonlinear dynamics model and the linearization model. The results show that the nonlinear aspects have little effect on blade lag and airframe motion in stable area, but in unstable area, the response has a significant difference between the nonlinear system and the linear system, and the nonlinear system appears limit cycle phenomenon.