地面系留对直升机动力响应的影响

 建立了系留状态下直升机旋翼/机体耦合非线性动力学模型，无铰旋翼简化为当量铰刚性桨叶模型，假定机体是刚性体并受起落架和系留索的约束，系留索静态时松弛并只能承受拉力。采用数值仿真研究了系留对模型旋翼地面共振的影响，对初始扰动和旋翼转速对系统动力学行为的影响也进行了仿真研究。对于无系留的模型旋翼来说，在任何转速下没有出现不稳定现象；地面系留时系统会呈现稳定响应、极限环以及大幅值振荡等非线性动力学行为，大幅值振荡将使系留索、接头和支持结构承受破坏性动力载荷。

Ground Mooring Effects on Helicopter Dynamic Response

Helicopter rotor/fuselage coupled nonlinear dynamic model is presented in case of ground mooring.The hingeless rotor is simplified as equivalent hinged rigid blade model.The airframe is assumed to be rigid and restrained with landing gears and mooring ropes.The mooring ropes can only withstand tension force and will be released in static situation.Numerical simulation is used to study the effects of ground mooring on the model-scale rotor/pylon ground resonance.The effects of perturbations and rotor speed on system dynamic behaviors are also simulated.For a model-scale rotor/pylon free from ground mooring,no instability exists at each rotor speed.For the case of pylon ground mooring,nonlinear dynamic behaviors,such as stable responses,stable limit cycle and high amplitude oscillation may apparent.High amplitude oscillations will cause the mooring rope,pin and pylon structure to be subjected to destructive dynamic loads.