Micro thrust measurement experiment and pressure field evolution of bionic robotic fish with harmonic actuation of macro fiber composites

Dongyi Hu; Junqiang Lou; Tehuan Chen; Yiling Yang; Chao Xu; Hairong Chen; Yuguo Cui

摘要

The design and realization of underwater bionic robots actuated by smart materials have attracted growing attention in recent years. The experimental acquisition of the dynamic thrust force is crucial for the development of underwater robots. A simple micro thrust measurement system based on a decoupled lever mechanism is designed for a macro fiber composite (MFC)-actuated bionic robotic fish. The pressure field distribution and evolution associated with the thrust variation induced by the oscillating caudal fin of the robotic fish are visualized using computational fluid dynamics (CFD) technologies. A miniature MFC-actuated robotic fish that mimics the koi fish is designed. A simple decoupled lever mechanism with excellent linearity, high precision and resolution, and the ability to minimize the interference from the lateral force is proposed. Calibration results indicate that the output sensitivity of the designed measurement apparatus is 5.48 mN/V. The dynamic variations in the micro thrust generated by the robotic fish at different actuation levels are effectively captured using the proposed measurement system. Experimental results show that the MFC-actuated robotic fish obtains a maximum mean thrust of-2.95 mN in the case of the greatest tip oscillating velocity, which is consistent with Lighthill's elongated-body theory. Moreover, for the robotic fish, the maximum instant thrust grows with an increase in the oscillating frequency. The maximum instant drag first decreases, and then increases as the actuation frequency increases. It reaches its minimum value of 0.37 mN in the case of the maximum oscillating velocity. In contrast, the variation behavior of the thrust pattern/oscillating period is the reverse to that of the maximum instant drag, and it obtains a maximum of 85.7%. The propulsion performance indexes of the robotic fish in the CFD simulations match those of experimental results for different oscillating cases. Furthermore, the distribution and evolution mechanisms of the steady pressure fields around the oscillating robotic fish are revealed. The CFD simulations demonstrate that the variations in the instant thrust could be fully determined by the distributions and intensities of the concentrated pressure regions induced by the oscillating caudal fin. The cycle-averaged velocity fields around the caudal fin are closely related to the mean thrust generated by the MFC-actuated robotic fish. Accordingly, these results may be helpful in the development of underwater bionic robots actuated by smart actuators.

机译：智能材料驱动的水下仿生机器人的设计和实现近年来引起了不断增长的关注。对动态推力的实验性获取对水下机器人的发展至关重要。基于去耦杠杆机构的简单微推力测量系统设计用于宏观纤维复合材料（MFC） - 制定的仿生机械鱼。使用计算流体动力学（CFD）技术可视化与机器人鱼的振荡尾鳍引起的推力变化相关的压力场分布和演变。设计了模仿KOI鱼的微型MFC驱动的机器人鱼。提出了一种具有优异的线性，高精度和分辨率的简单解耦杆机构，以及最小化来自横向力的干扰的能力。校准结果表明，设计的测量装置的输出灵敏度为5.48mn / v。使用所提出的测量系统有效地捕获由不同致动水平处产生的机器人鱼类产生的微推力的动态变化。实验结果表明，MFC致动的机器人鱼类在最大的尖端振荡速度的情况下获得-2.95 MN的最大平均推力，这与灯灰的细长体理论一致。此外，对于机器人鱼，最大瞬间推力随着振荡频率的增加而增长。最大即时拖动首先减小，然后随着致动频率的增加而增加。在最大振荡速度的情况下，它在最小值为0.37mn。相反，推力图案/振荡周期的变化行为是与最大立即拖动的变化行为，并且最多获得85.7％。 CFD仿真中机器人鱼的推进性能指标与不同振荡案件的实验结果相匹配。此外，揭示了振荡机器人鱼周围的稳态压力场的分布和演化机制。 CFD模拟表明，瞬间推力的变化可以完全由振荡尾鳍引起的浓缩压力区域的分布和强度确定。尾鳍周围的循环平均速度场与MFC驱动的机器人鱼类产生的平均推力密切相关。因此，这些结果可能有助于开发由智能执行器致动的水下仿生机器人。

Micro thrust measurement experiment and pressure field evolution of bionic robotic fish with harmonic actuation of macro fiber composites

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