Soft robots have attracted much attention in recent years owing to their high adaptability. Long articulated soft robots enable diverse operations, and tip-extending robots that navigate their environment through growth are highly effective in robotic search applications. Robots that extend from the tip can lengthen their body without friction from the environment. However, the flexibility of the thin membrane inhibits the retraction motion of the tip due to buckling. Two methods have been proposed to resolve this issue; increasing the pressure of the internal fluid to reinforce rigidity, and mounting an actuator at the tip. The disadvantage of the former is that the increase is limited by the membrane pressure resistance, while the second method leads to robot complexity. In this letter, we present a tip-retraction mechanism with a hydrostatic skeleton that can prevent buckling and takes advantage of the friction from the external environment. Water is used as the internal fluid to increase ground pressure with the environment, which is different from the conventional methods that use pneumatic. We explore the failure pattern of the retraction motion and propose solutions by using a hydrostatic skeleton robot. Additionally, we develop a prototype robot that successfully retracts by using the proposed methodology. Our solution can contribute to the advancement of mechanical design in the soft robotics field with applications to soft snakes and manipulators.

中文翻译：

---

带静压骨架的软圆环机器人的回缩机构

近年来，软体机器人因其高适应性而备受关注。长关节软机器人能够实现多样化的操作，通过生长在环境中导航的尖端延伸机器人在机器人搜索应用中非常有效。从尖端伸出的机器人可以在不受环境摩擦的情况下拉长身体。然而，由于屈曲，薄膜的柔韧性抑制了尖端的缩回运动。已经提出了两种方法来解决这个问题；增加内部流体的压力以增强刚性，并在尖端安装一个执行器。前者的缺点是增加受到膜压阻力的限制，而第二种方法导致机器人的复杂性。在这封信中，我们提出了一种带有静压骨架的尖端回缩机制，可以防止屈曲并利用外部环境的摩擦。使用水作为内部流体以增加与环境的地面压力，这与使用气动的常规方法不同。我们探索了缩回运动的故障模式，并通过使用静液压骨架机器人提出了解决方案。此外，我们开发了一个原型机器人，通过使用所提出的方法成功收回。我们的解决方案有助于软机器人领域机械设计的进步，并将其应用于软蛇和机械手。使用水作为内部流体以增加与环境的地面压力，这与使用气动的常规方法不同。我们探索了缩回运动的故障模式，并通过使用静液压骨架机器人提出了解决方案。此外，我们开发了一个原型机器人，通过使用所提出的方法成功收回。我们的解决方案有助于软机器人领域机械设计的进步，并将其应用于软蛇和机械手。使用水作为内部流体以增加与环境的地面压力，这与使用气动的常规方法不同。我们探索了缩回运动的故障模式，并通过使用静液压骨架机器人提出了解决方案。此外，我们开发了一个原型机器人，通过使用所提出的方法成功收回。我们的解决方案有助于软机器人领域机械设计的进步，并将其应用于软蛇和机械手。