近年来多旋翼无人飞行器(UAV)成为了小型无人飞行器发展的热门领域,而学界对于多旋翼飞行器飞行力学建模与飞行力学特性分析的研究还相对较少.针对相关研究需求,基于传统旋翼模型,建立了适用于多旋翼无人飞行器的飞行力学模型,并利用此模型对多旋翼无人飞行器悬停模态特性进行了初步分析,结果显示多旋翼飞行器模态稳定性明显弱于传统直升机,且横向Phugoid模态取代了荷兰滚模态.随后利用弱耦合系统理论与纵向模态简化模型,对多旋翼建模过程中的旋翼旋转自由度(DOF)动态特性、入流模型和旋翼气动力矩的建模必要性进行了研究.分析表明,旋翼旋转自由度的动态特性在飞控增稳条件下对全机特性有着重要影响,入流分布对刚性旋翼的俯仰、滚转气动力矩有着决定性作用,而旋翼气动力矩是决定多旋翼悬停模态的重要因素,这三者在多旋翼建模分析中不能忽略.%The multi-rotor unmanned aerial vehicle (UAV) is one of the popular configurations in the UAV industry for small UAVs.However,research on the modeling of multi-rotor vehicles and its characteristics regarding flight mechanics is still limited.A flight mechanics model for multi-rotor UAV is developed based on a classical helicopter model,and is used for the initial analyses of the hovering modes of a multi-rotor UAV.The results show that the dynamic stability of a multi-rotor vehicle is lower than that of a conventional helicopter,and the Dutch-roll mode is replaced by the lateral Phugoid mode.Based on the weakly-coupled system theory and simplified longitudinal equation of motion,the impacts of different modeling elements on multi-rotor modeling are analyzed,including the rotor rotation degree of freedom (DOF),the rotor inflow model and the rotor aerodynamic moments.It is shown that the rotor rotation DOF has large impacts on the flight mechanics characteristics of a multi-rotor vehicle with stability augmentation system.For a rigid rotor,the inflow distribution is one of the definitive factors for the rotor pitch and roll aerodynamic moments,which play an important role in the hovering modes of a multi-rotor vehicle.Therefore,all these three elements should be considered in the modeling and flight mechanics analyses for multi-rotor vehicles.
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