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首页> 外文期刊>International journal of non-linear mechanics >Response and instability prediction of helicopter dynamics on the ground
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Response and instability prediction of helicopter dynamics on the ground

机译：地面直升机动力的响应和不稳定性预测

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In helicopters with hinged blades an unstable dynamical phenomenon known as ground resonance may occur during take-off and landing and lead to the total destruction of the aircraft. Predicting the phenomenon is necessary to determine the stability of periodical equations of motion. The instability boundaries can be easily obtained for isotropic rotor configurations through multi-blade coordinate transformation once the periodic terms are eliminated. However, Floquet's theory is commonly used to treat the periodic motion equations when introducing the asymmetric effects of spring or damper aging or rotor rupture (anisotropic rotors). In additional, it is known that when treated as parametric excitations, periodic terms may lead to instability in dynamical systems under parametric resonances. In this paper a helicopter in contact with the ground is considered as a parametrically excited system and the equations are treated analytically by applying the method of multiple scales (MMS). A stability analysis verifies the existence of parametric instabilities by first order sets of equations for an isotropic rotor configuration. The results are compared and validated with those obtained by using Floquet's Theory. Moreover, the amplitude responses of the aircraft at equilibrium in the remaining resonant cases are studied. The results are then compared with those obtained from the time response analysis.
机译：在带有铰接叶片的直升机中，在起飞和降落期间可能会发生称为地面共振的不稳定动力现象，并导致飞机的全部毁坏。预测这种现象对于确定运动周期方程的稳定性是必要的。一旦消除了周期项，就可以通过多叶片坐标变换轻松获得各向同性转子配置的不稳定性边界。但是，当引入弹簧或阻尼器老化或转子破裂（各向异性转子）的非对称效应时，Floquet的理论通常用于处理周期运动方程。另外，已知当被视为参数激励时，周期项可能导致动态系统在参数谐振下的不稳定性。在本文中，与地面接触的直升机被视为参数激励系统，并且通过应用多尺度（MMS）方法对方程进行解析处理。稳定性分析通过各向同性转子配置的一阶方程组验证参数不稳定性的存在。将结果与使用Floquet理论获得的结果进行比较和验证。此外，研究了在其余共振情况下飞机处于平衡状态时的振幅响应。然后将结果与从时间响应分析获得的结果进行比较。

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