某无人机横向圆柱排气式气囊着陆装置缓冲过程研究

Simulation of Bi-cylindrical Airbag Cushioning System for Pilotless Aircraft

排气式气囊作为一类有效缓冲装置,在诸多回收领域广泛使用。通过设计适当气囊尺寸和排气孔大小可以实现对回收对象的过载和接地速度的有效控制,从而避免反弹和侧翻现象的发生。文章以某无人机圆柱排气式气囊为对象,研究了该类气囊的仿真分析方法。首先从理论角度出发,将气囊缓冲阶段分为封闭压缩和排气释放两个阶段,基于气体状态方程和动力学推导了横向圆柱型排气气囊模型的运动微分方程,并给出了相应的计算方法;然后,采用大型有限元仿真分析技术,实现了该类气囊结构和着陆过程的数学和力学建模,获得全向式缓冲气囊着陆的动态过程仿真。最后对比两种模型与试验在样机重心处的过载与速度变化曲线。研究结果表明,文章提出的理论近似模型能够较好的反映该类排气式气囊的着陆缓冲特性,相比有限元模型,可以兼顾分析精度与效率,这为后续气囊系统的改进设计提供了可靠的分析工具。

Vented airbag, which can be deployed with a more targeted arrangement due to its deterministic impact load direction, is commonly used in modern unmanned aerial vehicles（UAVs）, manned spacecraft, and heavy cargo airdrops. A vented airbag of suitable size and vent hole dimension can keep overload within an allowed range, control touchdown speed of recovery object, and prevent bouncing by properly designed airbag. A simulation analysis method of a cylindrical air bag for UAV is studied in this paper. Firstly, the landing process of airbag is decomposed into adiabatic compression and release of landing shock energy; the differential equation of cylindrical gas-filled bag is presented theoretically based on the ideal gas state equation and dynamic equation. Then, landing mathematic and mechanical models are established by use of modern FEM analysis, and the simulation process is developed. Finally, the simulation results and the test data are compared in terms of important parameters including dynamic process of whole airbag to cushion the landing and overload analysis of important structural parts. The results show that the theoretical approximation model, as a tool for improving the design of airbag, can better balance the accuracy and efficiency of simulation analysis.