Control of gliding in a flying snake-inspired n-chain model
Control of gliding in a flying snake-inspired n-chain model
复制标题
受飞蛇启发的 n 链模型中的滑翔控制
DOI：
10.1088/1748-3190/aa8c2f
复制
发表时间：
2017
影响因子：
3.4
通讯作者：
J. Socha
中科院分区：
文献类型：
--
作者：
Farid Jafari;S. Tahmasian;S. Ross;J. Socha
金蛇属的飞蛇具有高度动态的滑行行为，其主要表现形式是向身体后方发送的侧波形式的波动。据推测，由此产生的质量和空气动力分布的高振幅周期性变化有助于蛇滑行轨迹的稳定性。然而，之前的纵向平面二维分析未能揭示波动对俯仰方向稳定性的显着影响。在这项研究中，利用理论模型来研究飞蛇在三个维度上的动力学和稳定性特性。蛇被建模为与旋转接头连接的铰接翼型链。振动控制方法采用高振幅周期性输入在非线性系统中产生理想的稳定运动，波动被视为系统的周期性输入。这是通过直接将关节角度规定为时间的周期函数（运动学波动）或通过假设作用在关节上的周期性扭矩（扭矩波动）来实现的。使用叶片单元理论和先前确定的力系数对空气动力进行建模。结果表明，扭矩波动以及基于线性化的闭环控制可以增加稳定盆的大小。扭矩波动提供的稳定性的有效性是输入的幅度和频率的函数。此外，运动波动为足够大的频率提供了开环稳定性。结果表明，尽管波动对滑行稳定性有明显贡献，但蛇仍需要一定程度的闭环控制。然而，由于闭环控制系统需要围绕被动稳定轨迹工作，波动降低了对复杂闭环控制系统的需求。总的来说，这项研究证明了使用变形的身体而不是对称配对的机翼在滑翔过程中保持稳定性的可能性。
Flying snakes of genus Chrysopelea possess a highly dynamic gliding behavior, which is dominated by an undulation in the form of lateral waves sent posteriorly down the body. The resulting high-amplitude periodic variations in the distribution of mass and aerodynamic forces have been hypothesized to contribute to the stability of the snake’s gliding trajectory. However, a previous 2D analysis in the longitudinal plane failed to reveal a significant effect of undulation on the stability in the pitch direction. In this study, a theoretical model was used to examine the dynamics and stability characteristics of flying snakes in three dimensions. The snake was modeled as an articulated chain of airfoils connected with revolute joints. Along the lines of vibrational control methods, which employ high-amplitude periodic inputs to produce desirable stable motions in nonlinear systems, undulation was considered as a periodic input to the system. This was implemented either by directly prescribing the joint angles as periodic functions of time (kinematic undulation), or by assuming periodic torques acting at the joints (torque undulation). The aerodynamic forces were modeled using blade element theory and previously determined force coefficients. The results show that torque undulation, along with linearization-based closed-loop control, could increase the size of the basin of stability. The effectiveness of the stabilization provided by torque undulation is a function of the amplitude and frequency of the input. In addition, kinematic undulation provides open-loop stability for sufficiently large frequencies. The results suggest that the snakes need some amount of closed-loop control despite the clear contribution of undulation to glide stability. However, as the closed-loop control system needs to work around a passively stable trajectory, undulation lowers the demand for a complex closed-loop control system. Overall, this study demonstrates the possibility of maintaining stability during gliding using a morphing body instead of symmetrically paired wings.