Dynamic modeling and characteristics study of airdrop folding multi-body aircraft

空投折叠型多体飞行器动力学建模及投放特性研究

¹ School of Astronautics, Northwestern Polytechnical University, Xi'an 710072, China
² School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China
³ National Key Laboratory of Aircraft Configuration Design, Xi'an 710072, China

Received: 21 November 2024

Abstract

In the processes of launch, development and fall at high altitude without initial velocity, the dynamics model of a folding multi-body aircraft shows the characteristics of a multi-rigid body and multi-degree of freedom. The relative motion of each rigid body of the multi-body aircraft has mutual flow field interference, resulting in unsteady flow phenomenon. Therefore, the multi-body dynamic model of a two-body aircraft is established based on the absolute coordinate method. The unsteady vortex lattice method is derived under absolute coordinates. The multi-body dynamics coupling model that considers unsteady effects is obtained under the absolute coordinate system. Based on the multi-body dynamics coupling model and the unsteady vortex lattice method, the influence of three factors on the dynamic behavior of the drop and development processes is analyzed. The factors include initial folding angle, joint stiffness coefficient and joint damping coefficient. According to the convergence condition of the folding angle, the normal launch and development of the multi-body aircraft can be judged. Finally, the safe launch envelopes of the three factors are drawn. The simulation results are compared with the experimental data, verifying that the coupling model established in this paper can accurately describe the dynamic characteristics of the multi-body aircraft in its launch process. The paper provides technical basis for subsequent high-altitude launch research.

摘要

空投折叠型多体飞行器在高空无初速投放-展开-下落过程中, 其动力学模型会呈现多刚体、多自由度的特点, 且多体飞行器各刚体间的相对运动存在相互的流场干扰, 会产生非定常流动现象。因此, 基于绝对坐标方法建立了两体飞行器的多体动力学模型, 并推导出了绝对坐标下的非定常涡格法, 得到了绝对坐标系下考虑非定常效应的多体动力学耦合模型。在多体动力学与非定常涡格法耦合模型的基础上, 分析初始折叠角、连接刚度系数以及连接阻尼系数对投放-展开过程动力学行为的影响。通过折叠角收敛条件, 判断多体飞行器能否正常投放展开, 并绘制了关于3种影响因素的安全投放包线。将仿真结果与实验数据进行对比, 从而验证了所建立的耦合模型能够准确描述多体飞行器在投放-展开过程中的动力学特性, 为后续的高空投放研究积累了技术基础。