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操控软体生长式“藤蔓”机器人，同时需保持足够柔性以承受生长所需的顶端外翻。本研究从外翻能力、准静态弯曲、动态运动及力输出四个方面，比较了三种气动执行器的性能：囊式电机、圆柱形气动人工肌肉（cPAM）及织物气动人工肌肉（fPAM）。囊式电机因制造工艺简单而利于原型开发；cPAM展现出更优的弯曲性能且输出力最大；fPAM响应速度最快且能在最低压力下实现外翻。我们评估了每种执行器的尺寸范围：较大执行器可产生更显著的形变与力输出，但较小执行器充气更快且外翻压力更低。由于藤蔓机器人自重轻，重力对不同执行器功能的影响可忽略。我们提出了一种新型解析模型，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，我们设计并验证了一台配备高机动性60×60 mm cPAM的4.8米长藤蔓机器人，其在三维障碍赛道中可实现急转弯、穿越小于自身直径的通道及抵抗重力自主抬升。