Intermittent sliding locomotion of a two-link body
Intermittent sliding locomotion of a two-link body
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二连杆机构的间歇滑动运动
DOI：
10.1103/physreve.101.052613
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发表时间：
2020
影响因子：
2.4
通讯作者：
Puritz, Connor
中科院分区：
文献类型：
--
作者：
Alben, Silas;Puritz, Connor
我们研究了通过周期性地改变两个连杆机构的链接角来实现有效间歇运动的可能性。我们发现滑动摩擦系数的各向异性比是一个关键参数，而解与摩擦系数的大小有简单的标度关系。在各向异性摩擦的情况下，有效的运动包括在低阻力状态下滑行，以及快速和不对称的动力和恢复行程。随着各向异性的减小，爆裂和海岸运动转变为具有长的动力冲程和短的恢复冲程的运动，并且每个运动的链接角速度大致恒定。这些运动是在分别由两个参数和五个参数描述的正弦和幂规律运动的空间中看到的。与对称功率和恢复行程的情况相比，允许占空比变化大大提高了运动的效率。只有当摩擦力非常各向异性时，才允许动力和恢复冲程的凹度进一步变化才能进一步提高效率。在各向同性摩擦附近，发现了各种具有更复杂波形的最佳有效运动。许多最优的正弦运动和幂定律运动类似于我们在更一般的周期函数(截断的傅立叶级数)空间中通过优化搜索找到的运动。当我们增加阻力对速度的幂定律依赖性时，最优运动变得更平滑、更慢、效率更低，尤其是在接近各向同性的摩擦中。
We study the possibility of efficient intermittent locomotion for two-link bodies that slide by changing their interlink angle periodically in time. We find that the anisotropy ratio of the sliding friction coefficients is a key parameter, while solutions have a simple scaling dependence on the friction coefficients' magnitudes. With very anisotropic friction, efficient motions involve coasting in low-drag states, with rapid and asymmetric power and recovery strokes. As the anisotropy decreases, burst-and-coast motions change to motions with long power strokes and short recovery strokes, and roughly constant interlink angle velocity on each. These motions are seen in the spaces of sinusoidal and power-law motions described by two and five parameters, respectively. Allowing the duty cycle to vary greatly increases the motions' efficiency compared to the case of symmetric power and recovery strokes. Allowing further variations in the concavity of the power and recovery strokes improves the efficiency further only when friction is very anisotropic. Near isotropic friction, a variety of optimally efficient motions are found with more complex waveforms. Many of the optimal sinusoidal and power-law motions are similar to those that we find with an optimization search in the space of more general periodic functions (truncated Fourier series). When we increase the resistive force's power-law dependence on velocity, the optimal motions become smoother, slower, and less efficient, particularly near isotropic friction.