摘要
针对高空长航时太阳能无人机的超柔性机翼气动弹性变形明显,与飞行动力学响应耦合,常规分析方法会引起较大误差的特点。本文首先采用拉格朗日方程建立了能够反映超柔性特性的结构/飞行耦合动力学模型;然后结合气动弹性引起的结构变形、全机构型变化和气动导数变化,采用根轨迹法深入分析超柔性太阳能无人机的纵向稳定性;最后研究了气动弹性变形对纵向飞行控制律的影响规律,提出了改进方案并进行了仿真验证。发现超柔性太阳能无人机的纵向特征根随机翼刚度变化很明显,尤其当刚度较小时将会出现短周期和一弯模态耦合、长周期不稳定等不利现象;采用刚性或静气动弹性模型设计得到的控制律增益偏小,同时控制机翼变形和飞行姿态可以得到更平滑的控制效果。
The structure of the wing of High Altitude Long Endurance （HALE） Unmanned Aerial Vehicle （UAV） is highly flexible. The aeroelasticity and flight dynamics are highly coupled. This influences the flight safety seriously. In the stage of conceptual design, it is necessary to research the characteristics of flight dynamics and control thoroughly for highly flexible wing. In this paper, the Lagrangian method is employed to model the motion of rigidwing UAV, the same configuration with static aeroelastic deformation and highly flexiblewing UAV. The longitudinal characteristics of flight dynamics and control are compared and it is found that, while considering the static deformation only, owing to the becoming large of the pitch moment of inertia, the stability derivatives of the pitch axis are reduced and the damp and frequency of short period mode are obviously reduced. The frequency of phugoid changes little but the damping of it is also obviously reduced. It can be found that the longitudinal characteristic roots changed as wing stiffness varies. Particularly, when the stiffness is very small, the short period mode and the first bend mode are coupled and the phugoid is unstable. The pitch rate and the pitch angle feedback gains are smaller than flexible model. Therefore, relatively great adjustment should be made to fulfill the requirement of aeroelastic UAVs. To better reduce the disturbance of angle of attack and normal acceleration, the elevon should be employed to suppress the deformation of wing.
出处
《西北工业大学学报》
EI
CAS
CSCD
北大核心
2015年第4期573-579,共7页
Journal of Northwestern Polytechnical University
基金
国家自然科学基金(11202162)
陕西省科技统筹创新工程计划项目(2015KTCQ01-78)资助
关键词
超柔性无人机
气动弹性
耦合
稳定性
机翼变形抑制
aeroelasticity, angle of attack, angular velocity, computer software, conceptual design, damping, degrees of freedom （mechanics）, eigenvalues and eigenfuctions, feedback, flexible wings, flight dynamics, longitudinal control, matrix algebra, modal analysis, rigid wings, solar energy, stability, stiffness, unmanned aerial vehicles （UAV）
coupled, highly flexible UAV, suppression of wing deformation
