Unmanned aerial vehicles (UAVs) are often used in mission-critical applications, requiring a critical criterion in flight time. Unfortunately, severe power fluctuations, caused by specific flight patterns, degrade the deliverable capacity of the battery and hamper the flight time. A common approach to mitigating power fluctuations is to employ a hybrid energy storage system using a Li-ion battery with an ultracapacitor (UC). However, the conventional scheme poses inherent problems of low-energy density and power leakage due to the use of the UC and the supplementary hardware required for hybrid storage. In this article, we propose Hydrone, a reconfigurable battery architecture that maximizes the flight time of UAVs, overcoming the previous limitations. Hydrone addresses two key challenges that arise when hybrid energy storage is utilized in UAVs: 1) capacity loss and 2) power leakage. First, the proposed scheme compromises the capacity loss of hybrid storage by using a minimal capacity UC for use as a buffer to counteract the power fluctuations. Second, the power leakage of the hybrid battery is minimized by draining power from the UC only when it is necessary. To this end, the Hydrone architecture provides reconfigurability in hardware and offers two modes of battery operation, i.e., a battery-only mode and a hybrid mode. An appropriate operation is then selected at runtime depending on the flight situation and battery status. To switch modes, we employed a reinforcement learning-based switch control, reflecting the power fluctuation adequately on the flight and battery states. We implemented a hardware prototype to demonstrate the efficiency of Hydrone. Our extensive evaluation shows that the flight time of a UAV is prolonged up to 39% in our experiment setup.

中文翻译：

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Hydrone：无人机应用的可重构储能

无人机 (UAV) 通常用于关键任务应用，需要飞行时间的关键标准。不幸的是，由特定飞行模式引起的严重功率波动会降低电池的可交付容量并阻碍飞行时间。减轻功率波动的一种常见方法是采用混合储能系统，该系统使用带有超级电容器 (UC) 的锂离子电池。然而，由于使用UC和混合存储所需的辅助硬件，传统方案带来了低能量密度和功率泄漏的固有问题。在本文中，我们提出了 Hydrone，一种可重新配置的电池架构，可以最大限度地延长无人机的飞行时间，克服之前的限制。Hydrone 解决了在无人机中使用混合储能时出现的两个关键挑战：1) 容量损失和 2) 功率泄漏。首先，所提出的方案通过使用最小容量 UC 作为缓冲来抵消功率波动，从而降低了混合存储的容量损失。其次，通过仅在必要时从 UC 消耗电力来最大限度地减少混合电池的电力泄漏。为此，Hydrone 架构在硬件上提供可重构性，并提供两种电池操作模式，即纯电池模式和混合模式。然后在运行时根据飞行情况和电池状态选择适当的操作。为了切换模式，我们采用了基于强化学习的切换控制，充分反映了飞行和电池状态的功率波动。我们实现了一个硬件原型来演示 Hydrone 的效率。