蜂蝇悬停和前飞时的动稳定性

Dynamic flight stability of a model dronefly in hovering and forward flight

悬停和前飞是昆虫常用的两种飞行状态,研究昆虫在这两种状态下的动稳定性问题对昆虫飞行动力学研究工作具有重要意义.基于"平均模型"和小扰动线化的思想,给出了昆虫绕平衡点处纵向和横向的小扰动运动方程;通过计算流体力学方法获得气动导数,并利用特征模态分析法求解运动方程,研究了蜂蝇悬停和前飞时的动稳定性.结果证明,悬停时纵向和横向扰动运动均存在不稳定模态,悬停是不稳定的;前飞时,纵向扰动运动的不稳定模态的倍幅期较悬停时减小,其纵向不稳定性逐渐增强,而横向不稳定性较悬停时减弱,趋于较弱或中性的稳定;前飞是不稳定的.

Insects usually keep hovering or forward flight. Thus the dynamic stability of the two types of flight is significant to study the insect flight. The dynamic flight stability of a model dronefly in hovering and forward flight was studied. On the basis of an averaged model and the small disturbance theory,the linearized equations of longitudinal and lateral motion were given. The method of computational fluid dynamics was used to compute the aerodynamic derivatives and the eigenvalue and eigenvector analysis was applied to solve the equations of motion. The experiment results reveal that at hovering,the longitudinal and lateral disturbed motion both includes the unstable mode,therefore hovering is unstable. At forward flight,for the longitudinal motion,the time for initial disturbances to double for the unstable mode is decreasing,and the instability of the longitudinal motion is increasing; the instability of the lateral motion decreases to a weakly or neutrally stable mode. The forward flight of dronefly is unstable.