Reducing weight and increasing lift have been an important goal of using flapping wing micro air vehicles (FWMAVs). However, FWMAVs with mechanisms to limit the angle of attack (α) artificially by active force cannot meet specific requirements. This study applies a bioinspired model that passively imitates insects’ pitching wings to resolve this problem. In this bionic passive pitching model, the wing root is equivalent to a torsional spring. α obtained by solving the coupled dynamic equation is similar to that of insects and exhibits a unique characteristic with two oscillated peaks during the middle of the upstroke/downstroke under the interaction of aerodynamic, torsional, and inertial moments. Excess rigidity or flexibility deteriorates the aerodynamic force and efficiency of the passive pitching wing. With appropriate torsional stiffness, passive pitching can maintain a high efficiency while enhancing the average lift by 10% than active pitching. This observation corresponds to a clear enhancement in instantaneous force and a more concentrated leading edge vortex. This phenomenon can be attributed to a vorticity moment whose component in the lift direction grows at a rapid speed. A novel bionic control strategy of this model is also proposed. Similar to the rest angle in insects, the rest angle of the model is adjusted to generate a yaw moment around the wing root without losing lift, which can assist to change the attitude and trajectory of a FWMAV during flight. These findings may guide us to deal with various conditions and requirements of FWMAV designs and applications.

中文翻译：

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仿生拍击翼微型飞机被动俯仰模型的空气动力学性能。

减轻重量和增加升力已经成为使用襟翼微型飞行器（FWMAV）的重要目标。但是，具有通过主动力人为限制攻角（α）的机制的FWMAV无法满足特定要求。这项研究采用了一种受生物启发的模型，该模型可以被动地模仿昆虫的俯仰翅膀来解决这个问题。在这种仿生的被动俯仰模型中，机翼根部等效于扭转弹簧。α通过求解耦合动力学方程得到的结果与昆虫相似，并且在空气动力，扭转和惯性力矩的相互作用下，在上冲程/下冲程的中途表现出独特的特征，即两个振荡峰。过多的刚性或柔韧性会降低被动式俯仰翼的空气动力和效率。具有适当的扭转刚度，被​​动俯仰可以保持较高的效率，同时将平均升力比主动俯仰提高10％。该观察结果对应于瞬时力的明显增强和更集中的前缘涡旋。该现象可归因于涡旋力矩，其在升力方向上的分量以快速增长。还提出了该模型的新型仿生控制策略。与昆虫的静止角度相似，调整模型的休息角，以在不损失升力的情况下在机翼根部产生偏航力矩，这可以在飞行过程中帮助改变FWMAV的姿态和轨迹。这些发现可能指导我们应对FWMAV设计和应用的各种条件和要求。