Soft pneumatic actuators are used to steer soft growing "vine" robots while being flexible enough to undergo the tip eversion required for growth. They also meet the requirements to steer soft growing vine robots through challenging terrain. In this study, we compared the performance of three types of pneumatic actuators in terms of their ability to perform eversion, bending, dynamic motion, and force: the pouch motor, the cylindrical pneumatic artificial muscle (cPAM), and the fabric pneumatic artificial muscle (fPAM). The pouch motor is advantageous for prototyping due to its simple manufacturing process. The cPAM exhibits superior bending behavior and produces the highest forces, while the fPAM actuates fastest and everts at the lowest pressure. We evaluated a similar range of dimensions for each actuator type. Larger actuators can produce more significant deformations and forces, but smaller actuators inflate more quickly and require a lower eversion pressure. Since vine robots are lightweight, the effect of gravity on the functionality of different actuators is minimal. We developed a new analytical model that predicts the pressure-to-bending behavior of vine robot actuators. Using the actuator results, we designed and demonstrated a 4.8 m long vine robot equipped with highly maneuverable 60x60 mm cPAMs in a three-dimensional obstacle course. The vine robot was able to move around sharp turns, travel through a passage smaller than its diameter, and lift itself against gravity.

翻译：软体气动执行器可用于引导软体生长式"藤蔓"机器人，同时保持足够的柔性以承受生长所需的尖端外翻动作。它们也满足通过复杂地形引导软体生长式藤蔓机器人的要求。本研究比较了三种气动执行器在外翻性能、弯曲能力、动态运动和力输出方面的表现：囊式电机（pouch motor）、圆柱形气动人工肌肉（cPAM）和织物气动人工肌肉（fPAM）。囊式电机因其制造工艺简单而利于原型开发；cPAM展现出更优的弯曲性能并产生最大力输出；fPAM则具有最快驱动速度且能在最低压力下实现外翻。我们对每种执行器类型评估了相似的尺寸范围。较大尺寸的执行器能产生更显著的形变和力输出，但较小尺寸的执行器充气更快且所需外翻压力更低。由于藤蔓机器人重量轻，重力对不同执行器功能的影响极小。我们建立了新的解析模型，可预测藤蔓机器人执行器的压力-弯曲行为。基于执行器测试结果，设计并演示了一台搭载高度可操控的60×60毫米cPAM的4.8米长藤蔓机器人，其在三维障碍赛道中成功完成急转弯、穿越直径小于自身的通道以及对抗重力抬升等动作。