Since the birth of bio-inspired flapping-wing micro air vehicles, a controversial topic, i.e., whether and to what extent a flapping wing can outperform conventional micro rotors, has existed in the field of micro-to pico-scale unmanned aircraft. However, instead of answering this debate, an alternative idea that combines the flapping-wing and rotary-wing layouts was proposed and has been extensively studied over the last ten years. By merging bionic features of flapping wings into micro rotors, this novel layout, i.e., flapping rotary wing (FRW), can maintain autorotation with no driving torque and achieve both a superb lift generation and a moderate efficiency at a Reynolds number between 10 and 10, presenting an additional choice for micro air vehicles when facing a task to balance the payload and energy cost. As the first review of FRW, this paper overviews the concept, bionic features, aerodynamic principles, and development of flyable prototypes since 2010, from fundamental aerodynamic mechanisms to key points in prototype design, including wing structure, actuator, transmission system, energy source, etc. The advantages and disadvantages of this novel layout over conventional flapping wings and micro rotors are discussed. Four challenging directions are then suggested to improve the flight performance of this layout and thus boost its application in military and civilian fields.

中文翻译：

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扑翼旋转翼：一种新颖的低雷诺数布局，将仿生特征融入微型转子


自从仿生扑翼微型飞行器诞生以来，扑翼能否以及在多大程度上优于传统微型旋翼，在微型至皮级无人机领域就一直存在着一个颇具争议的话题。然而，并没有回答这个争论，而是提出了一种结合扑翼和旋转翼布局的替代想法，并在过去十年中得到了广泛的研究。通过将扑翼的仿生特征融合到微型旋翼中，这种新颖的布局，即扑翼旋转翼（FRW），可以在没有驱动扭矩的情况下保持自转，并在雷诺数10至10之间实现卓越的升力产生和适度的效率，在面临平衡有效载荷和能源成本的任务时，为微型飞行器提供了额外的选择。作为FRW的首次综述，本文概述了自2010年以来可飞原型机的概念、仿生特征、气动原理和发展情况，从基础气动机构到原型设计的关键点，包括机翼结构、执行机构、传动系统、能源、讨论了这种新颖布局相对于传统扑翼和微型旋翼的优点和缺点。然后提出了四个具有挑战性的方向，以提高该布局的飞行性能，从而促进其在军事和民用领域的应用。