直升机桨叶液压减摆器等效阻尼计算研究

Study on equivalent damping calculation for hydraulic damper of helicopter rotor

直升机桨叶液压减摆器具有强非线性、大阻尼的特点。为了正确评估减摆器的等效阻尼,就旋转桨叶在水平面内的自由摆振运动,采用基于富里叶分析的移动矩形窗、基于希尔贝特(Hilbert)变换和能量平衡的方法对减摆器的等效阻尼进行了计算研究,并就阻尼强弱、衰减对数曲线的拟合等因素对计算结果的影响进行了分析。结果表明,对于线性阻尼和非线性弱阻尼振动系统,包络衰减法和能量平衡法计算等效阻尼能获得较一致的结果,对于非线性强阻尼振动系统来说结果有分散性,应用时须谨慎。

Great amplitude and highly nonlinear damping exists in the hydraulic damper of helicopter rotors. The Fourier series based moving block, the Hilbert transform based technology and the energy balance method are studied in the equivalent damping calculations in terms of the rotating blade lead-lag free oscillations. Influences of the factors, such as the damping amplitude and the logarithmic curve fitting of decaying envelope on estimates are also discussed. The results indicate that, for the linear vibratory or the lightly nonlinear oscillatory systems, the consistent predictions could be obtained with above three deferent equivalent-damping-estimate methods. However the divergence exists in amplitudes of equivalent damping in heavily damped nonlinear oscillatory systems and it needs to be dealt with cautiously.