In this article, we propose a soft eel robot design using soft pneumatic actuators that mimic eel muscles. Four pairs of soft actuators are used to construct the eel robot body. Pulse signals with suitable shifting phases are utilized to control delivery of compressed air to the actuators in sequence to create a sinusoidal wave from head to tail of the robot body. A model of hydrodynamic forces acting on an anguilliform swimmer when moving in fluid was built to estimate the thrust force generated by the robot at different tail beat frequencies. Experimental data revealed that the generated thrust force was positively correlated with the beat frequency. Measured data showed that swimming efficiency depended on both generated thrust force and body posture in situ. At the beat frequency of 1.25 Hz, and air pressure at three segments from head to tail of 65, 50, and 30 kPa, respectively, the eel robot body showed the best cost of transport (COT) of 19.21 with velocity of 10.5 cm/s (or 0.198 body length per second [BL/s]), compared to the other's values of operation frequency and air pressure. We also found that control shifting phase strongly affects the swimming speed and COT. The robot body reached the highest velocity at around 19 cm/s (0.36 BL/s) with the COT of 10.72. Obtained result in this research would contribute to development of soft elongated swimming robot and enhance the knowledge on swimming performance of both robot and natural eels.

中文翻译：

---

以鳗鱼为灵感的软体机器人的 Anguilliform 游泳性能

在本文中，我们提出了一种软鳗机器人设计，该机器人使用模拟鳗鱼肌肉的软气动执行器。四对软执行器用于构建鳗鱼机器人本体。具有适当位移相位的脉冲信号用于控制压缩空气按顺序输送到执行器，以产生从机器人身体头部到尾部的正弦波。建立了一个在流体中移动时作用在鳗形游泳者上的水动力模型，以估计机器人在不同尾拍频率下产生的推力。实验数据表明，产生的推力与拍频呈正相关。测量数据表明，游泳效率取决于产生的推力和原位身体姿势. 在 1.25 Hz 的拍频和从头到尾的三个段的气压分别为 65、50 和 30 kPa 时，鳗鱼机器人的身体表现出最佳运输成本 (COT) 为 19.21，速度为 10.5 cm/ s（或每秒 0.198 身体长度 [BL/s]），与其他人的操作频率和气压值相比。我们还发现控制转换阶段强烈影响游泳速度和 COT。机器人本体以 19 cm/s (0.36 BL/s) 左右达到最高速度，COT 为 10.72。本研究取得的成果将有助于开发柔软的细长游泳机器人，提高对机器人和自然鳗鱼游泳性能的认识。