直升机旋翼非线性等效阻尼的识别

 带黏弹减摆器的直升机自激振动具有非线性特性。为了识别摆振后退型的非线性等效阻尼,并提高阻尼的识别精度,提出了一种新的阻尼识别方法,根据多桨叶坐标变换得到后退型摆振的余弦和正弦分量的自由衰减响应,直接形成其衰减包络线,利用该包络线来识别等效阻尼的非线性特性。通过精度分析和实例计算表明,该方法避免了频率因素对阻尼识别的影响,因而提高了摆振后退型等效阻尼的识别精度。最后根据直升机地面共振模拟数据,对摆振后退型等效阻尼进行了识别。

Nonlinear Equivalent Damping Identification for Helicopter Rotor

Nonlinear characteristics are observed in self-excitation of helicopter with elastomeric lag dampers implemented. In order to identify accurately the nonlinear equivalent damping levels of regressive lead-lag motion, a new method of damping identification is presented. Numerical multi-blade coordinate transformation (NMCT) performs transient decaying responses of regressive lead-lag motion in forms of cosine and sine components, which can directly perform the decaying envelope curves. The envelope curves can be applied to estimate the equivalent damping levels. The equivalent damping levels vary with regressive lag amplitude arising from nonlinear lag damper introduced. The present approach appears to exclude the influence of vibratory frequency on damping identifications, and therefore improves the equivalent damping accuracy. This method is successfully applied in regressive lead-lag equivalent damping identifications from helicopter ground resonance simulated responses.