Multi-flagellated bacteria utilize the hydrodynamic interaction between their filamentary tails, known as flagella, to swim and change their swimming direction in low Reynolds number flow. This interaction, referred to as bundling and tumbling, is often overlooked in simplified hydrodynamic models such as Resistive Force Theories (RFT). However, for the development of efficient and steerable robots inspired by bacteria, it becomes crucial to exploit this interaction. In this paper, we present the construction of a macroscopic bio-inspired robot featuring two rigid flagella arranged as right-handed helices, along with a cylindrical head. By rotating the flagella in opposite directions, the robot's body can reorient itself through repeatable and controllable tumbling. To accurately model this bi-flagellated mechanism in low Reynolds flow, we employ a coupling of rigid body dynamics and the method of Regularized Stokeslet Segments (RSS). Unlike RFT, RSS takes into account the hydrodynamic interaction between distant filamentary structures. Furthermore, we delve into the exploration of the parameter space to optimize the propulsion and torque of the system. To achieve the desired reorientation of the robot, we propose a tumble control scheme that involves modulating the rotation direction and speed of the two flagella. By implementing this scheme, the robot can effectively reorient itself to attain the desired attitude. Notably, the overall scheme boasts a simplified design and control as it only requires two control inputs. With our macroscopic framework serving as a foundation, we envision the eventual miniaturization of this technology to construct mobile and controllable micro-scale bacterial robots.

翻译：多鞭毛细菌利用其丝状尾部（即鞭毛）之间的流体动力学相互作用，在低雷诺数流动中实现游动并改变游动方向。这种被称为“成束”与“翻滚”的相互作用，在简化流体动力学模型（如阻力力理论RFT）中常被忽略。然而，对于开发受细菌启发的、高效且可操控的机器人而言，利用这种相互作用至关重要。本文构建了一台宏观仿生机器人，其具有两个呈右螺旋排列的刚性鞭毛和一个圆柱形头部。通过反向旋转鞭毛，机器人能够通过可重复且可控的翻滚实现自身姿态重新定向。为精确模拟低雷诺数流动下的双鞭毛机构，我们采用了刚体动力学与正则化Stokeslet段方法的耦合。与RFT不同，RSS考虑了远距离丝状结构之间的流体动力学相互作用。此外，我们深入探索参数空间以优化系统的推进力与扭矩。为实现机器人的目标姿态重定向，我们提出了一种翻滚控制方案，通过调节两个鞭毛的旋转方向与速度来实现。该方案实施后，机器人可有效重新定向以达成期望姿态。值得注意的是，该整体方案仅需两个控制输入，因而设计简洁、控制简便。以我们的宏观框架为基础，我们最终期望将该技术微型化，以构建可移动且可控的微观尺度细菌机器人。