Bristol Robotics Laboratory, University of Bristol, Bristol BS16 1QY, UK
Bristol Robotics Laboratory, University of Bristol, Bristol BS16 1QY, UK.
J R Soc Interface. 2018 Nov 21;15(148):20180301. doi: 10.1098/rsif.2018.0301.
Swimming is employed as a form of locomotion by many organisms in nature across a wide range of scales. Varied strategies of shape change are employed to achieve fluidic propulsion at different scales due to changes in hydrodynamics. In the case of microorganisms, the small mass, low Reynolds number and dominance of viscous forces in the medium, requires a change in shape that is non-invariant under time reversal to achieve movement. The family of unicellular flagellates evolved a characteristic type of locomotion called euglenoid movement to overcome this challenge, wherein the body undergoes a giant change in shape. It is believed that these large deformations enable the organism to move through viscous fluids and tiny spaces. The ability to drastically change the shape of the body is particularly attractive in robots designed to move through constrained spaces and cluttered environments such as through the human body for invasive medical procedures or through collapsed rubble in search of survivors. Inspired by the euglenoids, we present the design of EuMoBot, a multi-segment soft robot that replicates large body deformations to achieve locomotion. Two robots have been fabricated at different sizes operating with a constant internal volume, which exploit hyperelasticity of fluid-filled elastomeric chambers to replicate the motion of euglenoids. The smaller robot moves at a speed of [Formula: see text] body lengths per cycle (20 mm min or 2.2 cycles min) while the larger one attains a speed of [Formula: see text] body lengths per cycle (4.5 mm min or 0.4 cycles min). We show the potential for biomimetic soft robots employing shape change to both replicate biological motion and act as a tool for studying it. In addition, we present a quantitative method based on elliptic Fourier descriptors to characterize and compare the shape of the robot with that of its biological counterpart. Our results show a similarity in shape of 85% and indicate that this method can be applied to understand the evolution of shape in other nonlinear, dynamic soft robots where a model for the shape does not exist.
游泳是自然界中许多生物在广泛的尺度上使用的一种运动形式。由于水动力的变化，不同尺度下采用了不同的形状变化策略来实现流体推进。对于微生物来说，由于质量小、雷诺数低以及介质中粘性力的主导地位，需要改变形状，使其在时间反转下不保持不变，从而实现运动。单细胞鞭毛虫家族进化出了一种特有的运动方式，称为眼虫运动，以克服这一挑战，其中身体经历了巨大的形状变化。人们认为，这些大变形使生物能够在粘性流体和微小空间中移动。能够剧烈改变身体形状的能力在设计用于通过受限空间和杂乱环境移动的机器人中特别有吸引力，例如通过人体进行侵入性医疗程序或通过倒塌的瓦砾寻找幸存者。受眼虫的启发，我们提出了 EuMoBot 的设计，这是一种多节软机器人，能够复制大的身体变形以实现运动。已经制造了两个不同尺寸的机器人，它们的内部体积保持不变，利用充满流体的弹性体腔的超弹性来复制眼虫的运动。较小的机器人以每周期[Formula: see text]个身体长度的速度移动（20 毫米分钟或 2.2 个周期分钟），而较大的机器人以每周期[Formula: see text]个身体长度的速度移动（4.5 毫米分钟或 0.4 个周期分钟）。我们展示了采用形状变化的仿生软机器人既可以复制生物运动，又可以作为研究它的工具的潜力。此外，我们提出了一种基于椭圆傅里叶描述符的定量方法，用于描述和比较机器人与生物对应物的形状。我们的结果表明形状的相似度为 85%，表明该方法可用于理解不存在形状模型的其他非线性、动态软机器人中形状的演变。
