Hovering flapping wing flight is intrinsically unstable in most cases and requires active flight stabilization mechanisms. This paper explores the passive stability enhancement with the addition of top and bottom sails, and the capability to predict the stability from a very simple model decoupling the roll and pitch axes. The various parameters involved in the dynamical model are evaluated from experiments. One of the findings is that the damping coefficient of a bottom sail (located in the flow induced by the flapping wings) is significantly larger than that of a top sail. Flight experiments have been conducted on a flapping wing robot of the size of a hummingbird with sails of various sizes and the observations regarding the flight stability correlate quite well with the predictions of the dynamical model. Twelve out of 13 flight experiments are in agreement with stability predictions.

中文翻译：

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悬停扑翼双翼机器人帆被动稳定性增强

在大多数情况下，悬停扑翼飞行本质上是不稳定的，需要主动的飞行稳定机制。本文探讨了通过添加顶部和底部帆来增强被动稳定性，以及从一个非常简单的模型将横滚轴和俯仰轴解耦来预测稳定性的能力。动力学模型中涉及的各种参数通过实验进行评估。研究结果之一是底部帆的阻尼系数（位于由扑翼引起的流动中）明显大于顶部帆的阻尼系数。已经在蜂鸟大小的扑翼机器人上进行了飞行实验，其帆具有各种尺寸，飞行稳定性的观察结果与动力学模型的预测非常相关。