Emulating periodic main wing movement of a bird for generating lift and thrust remains a significant challenge in developing a robotic bird. The sequences of main wing motion are comprised of flapping, folding, bending, and twisting. In this paper, we concentrate on the flapping and folding motion, and design two wing mechanisms based on a 4-bar linkage structure: one is only for Flapping Motion (FM) and the other is for simultaneous Flapping and Folding Motion (FFM) during a wing stroke. We derive relationships between length and angle of links to analyze kinematic characteristics of the mechanisms and conduct an optimization to select the length parameters of links that allow maximization of the flapping angle. We run a simulation to confirm the performance of the optimized parameters by examining physical properties, and fabricate two wing mechanisms accordingly. In particular, the folding motion is achieved without using an additional actuator. Force measurements to investigate a lift profile of each mechanism and their quantitative comparison of the performance of both types confirm the benefits of the folding motion in the perspectives of wing frequency and lift. We expect that our kinematic formulation, design procedures, and comparative measurement results can help develop a wing mechanism to create a truly biomimetic robotic bird.

中文翻译：

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机械鸟拍打和折叠翼机构的设计，制造和分析

模拟鸟类的周期性主翼运动以产生升力和推力仍然是开发机器人鸟类的重大挑战。主翼运动的顺序包括拍打，折叠，弯曲和扭曲。在本文中，我们专注于拍打和折叠运动，并基于四连杆机构设计两种机翼机构：一种仅用于拍打运动（FM），另一种用于同时拍打和折叠运动（FFM）。机翼冲程。我们得出链节的长度和角度之间的关系，以分析机构的运动学特征，并进行优化以选择链节的长度参数，以使拍打角度最大化。我们进行了仿真，以通过检查物理属性来确认优化参数的性能，并据此制造两个机翼机构。特别地，无需使用额外的致动器就可以实现折叠运动。力的测量可以研究每种机构的升力曲线，并且可以对两种类型的性能进行定量比较，从而从机翼频率和升力的角度证实了折叠运动的好处。我们希望我们的运动学公式，设计程序和比较的测量结果可以帮助开发一种机翼机制，从而创造出真正的仿生机械鸟。