MathLab, SISSA-International School for Advanced Studies , Trieste, Italy .
Soft Robot. 2018 Aug;5(4):410-424. doi: 10.1089/soro.2017.0099. Epub 2018 May 15.
Interest in the design of bioinspired robotic microswimmers is growing rapidly, motivated by the spectacular capabilities of their unicellular biological templates. Predicting the swimming speed and efficiency of such devices in a reliable way is essential for their rational design, and to optimize their performance. The hydrodynamic simulations needed for this purpose are demanding and simplified models that neglect nonlocal hydrodynamic interactions (e.g., resistive force theory for slender, filament-like objects that are the typical propulsive apparatus for unicellular swimmers) are commonly used. We show through a detailed case study of a model robotic system consisting of a spherical head powered by a rotating helical flagellum that (a) the errors one makes in the prediction of swimming speed and efficiency by neglecting hydrodynamic interactions are never quite acceptable and (b) there are simple ways to correct the predictions of the simplified theories to make them more accurate. We also formulate optimal design problems for the length of the helical flagellum giving maximal energetic efficiency, maximal distance traveled per motor turn, or maximal distance traveled per unit of work expended, and exhibit optimal solutions.
人们对仿生机器人微型游泳者的设计越来越感兴趣,这主要是受到其单细胞生物模板惊人能力的推动。为了实现其合理设计和优化性能,可靠地预测此类设备的游泳速度和效率至关重要。为此目的所需的水动力模拟要求很高,并且通常使用简化模型来忽略非局部水动力相互作用(例如,对于细长的线状物体(即单细胞游泳者的典型推进装置),采用阻力理论)。我们通过对由旋转螺旋鞭毛驱动的球形头部的模型机器人系统的详细案例研究表明,(a)通过忽略水动力相互作用来预测游泳速度和效率时所犯的错误从未完全可以接受,并且(b)有简单的方法可以纠正简化理论的预测,以使其更准确。我们还为使能量效率最大化、每个电机旋转行驶的最大距离或每个单位功行驶的最大距离制定了螺旋鞭毛长度的最佳设计问题,并展示了最佳解决方案。