Soft pneumatic actuators are used to steer soft growing "vine" robots while being flexible enough to undergo the tip eversion required for growth. In this study, we compared the performance of three types of pneumatic actuators in terms of their ability to perform eversion, quasi-static bending, dynamic motion, and force output: 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 range of dimensions for each actuator type. Larger actuators can produce more significant deformations and forces, but smaller actuators inflate faster and can evert at a lower pressure. Because 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：软体气动执行器用于引导软体生长“藤蔓”机器人转向，同时兼具足够的柔韧性以承受生长所需的尖端外翻。本研究比较了三种类型气动执行器在外翻能力、准静态弯曲、动态运动及力输出方面的性能：囊式电机、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有利于原型制作。cPAM表现出更优的弯曲行为且输出力最大，而fPAM驱动速度最快且能在最低压力下实现外翻。我们对每种执行器类型的多种尺寸进行了评估。较大执行器能产生更显著的变形和力，但较小执行器充气更快且能在更低压力下外翻。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。我们开发了一个新的解析模型，用于预测藤蔓机器人执行器的压力-弯曲行为。基于执行器研究结果，我们设计并展示了一台4.8米长的藤蔓机器人，配备高度灵活的60x60毫米cPAM，在三维障碍赛道中完成演示。该藤蔓机器人能绕过急转弯、穿过直径小于自身尺寸的通道，并克服重力自行抬升。