[论文解读] Towards a New Paradigm of UAV Safety

Juan-Pablo Afman, Laurent Ciarletta+4 more|arXiv (Cornell University)|Mar 24, 2018

Fault Detection and Control SystemsEngineering参考文献 15被引用 18

一句话总结

本文提出一种机械式主动切割系统（OABBS），通过瞬间切断多旋翼无人机的螺旋桨以减少升力，实现对失控飞行的无人机的安全终止，使其能够进行受控下降。该系统确保了确定性、不可恢复的着陆，最大限度降低撞击动能和附带损伤，实验验证表明其在真实失控无人机事件中有效缓解了坠毁风险。

ABSTRACT

With the rising popularity of UAVs in the civilian world, we are currently witnessing and paradim shift in terms of operational safety of flying vehicles. Safe and ubiquitous human-system interaction shall remain the core requirement but those prescribed in general aviation are not adapted for UAVs. Yet we believe it is possible to leverage the specific aspects of unmanned aviation to meet acceptable safety requirements. We start this paper with by discussing the new operational context of civilian UAVs and investigate the meaning of safety in light of this new context. Next, we explore the different approaches to ensuring system safety from an avionics point of view. Subsets of operational requirements such as geofencing or mechanical systems for termination or impact limitation can easily be implemented. These are presented with the goal of limiting the collateral damages of a system failure. We then present some experimental results regarding two of the major problems with UAVs. With actual impacts, we demonstrate how dangerous uncontrolled crashes can be. Furthermore, with the large number of runaway drone experiences during civilian operations, the risk is even higher as they can travel a long way before crashing. We provide data on such a case where the software controller is working, keeping the UAV in the air, but the operator is unable to actually control the system. It should be terminated! Finally, after having analyzed the context and some actual solutions, based on a minimal set of requirement and our own experience, we are proposing a simple mechanical based safety system. It unequivocally terminates the flight in the most efficient way by instantly removing parts of the propellers leaving a minimal lifting surface. It takes advantage of what controllability may remain but with a deterministic ending: a definite landing.

研究动机与目标

• 为应对民用无人机日益增长的安全风险，特别是失控飞行或‘失控’无人机的情况。
• 将安全范式从通用航空中的‘无坠毁飞行’转变为成本效益更高的‘可安全坠毁’设计。
• 开发一种低成本、机械坚固的解决方案，确保飞行终止，且无需依赖昂贵的软件验证或复杂的航电系统。
• 通过真实飞行数据和原型验证，证明机械系统可在民用无人机中有效缓解坠毁风险。

提出的方法

• 设计并原型化一种最优主动制动系统（OABBS），采用伺服电机快速部署刀片，将螺旋桨切割至预定长度。
• 将OABBS集成至四旋翼无人机的机臂中，使其激活后能干净地切断螺旋桨，减少升力，同时保留一定程度的可控性以实现下降引导。
• 确保系统不可逆：一旦激活，无人机无法在不更换螺旋桨的情况下恢复至正常飞行状态。
• 利用佐治亚理工学院Afman气动力学实验室的真实飞行数据，分析失控无人机事件，验证该系统的需求。
• 将OABBS与未来可能的智能降落伞系统结合，以增强下降控制和撞击安全性。
• 根据关键安全标准评估系统性能：激活速度、不可逆性，以及限制下降速度和撞击动能的能力。

实验结果

研究问题

• RQ1 如何重新定义无人机安全，使其在民用应用中优先考虑地面安全而非无坠毁飞行？
• RQ2 何种机械设计可实现快速、不可逆的飞行终止，从而最小化撞击动能和附带损伤？
• RQ3 低成本、基于硬件的系统是否能在可靠性与成本效益方面超越以软件为核心的安全部方案？
• RQ4 现实世界中的失控无人机事件如何证明确定性、不可恢复终止机制的必要性？
• RQ5 在螺旋桨被切断后，残余的可控性在多大程度上可被用于引导无人机避开人员和建筑物？

主要发现

• 来自佐治亚理工学院Afman气动力学实验室的真实飞行数据显示，失控四旋翼无人机因电磁干扰导致非指令性油门输入，造成无人机失控爬升并漂移100码后坠毁。
• OABBS系统成功将螺旋桨切割至特定长度，显著降低升力，即使在全油门状态下也能实现受控下降，从而最大限度减少撞击动能。
• 该系统不可逆：一旦激活，无人机必须更换螺旋桨才能恢复飞行，确保不会发生虚假恢复。
• 在多种螺旋桨类型上均实现了干净切割，证实了切割机构的机械可行性与一致性。
• 系统允许一定程度的受控下降，使无人机在飞行末期能够避开人员和建筑物。
• OABBS提供了一种确定性的硬件解决方案，避免了传统航空领域所需的高昂软件验证与认证成本。