Inspired by the dexterous handling ability of an elephant's trunk, we propose a pneumatic actuator that generates diverse bending and extension motions in a flexible arm. The actuator consists of two flexible tubes. Each flexible tube is restrained by a single string with variable length and tilt angle. Even if a single tube can perform only three simple types of motions (bending, extension, and helical), a variety of complex bending patterns can be created by arranging a pair of tubes in parallel and making the restraint variable. This performance takes advantage of the effect of the superposition of forces by arranging two tubes to constructively interfere with each other. This paper described six resulting pose patterns. First, the configuration and operating principle are described, and the fabrication method is explained. Next, two mathematical models and four finite element method-based analyses are introduced to predict the tip position changes in five motion patterns. All the models were validated through experiments. Finally, we experimentally demonstrated that the prototype SEMI-TRUNK can realize the action of grabbing a bottle and pouring water, verifying the effectiveness of the proposed method.

翻译：受象鼻灵巧操作能力的启发，我们提出一种能在柔性臂中生成多样化弯曲与伸缩运动的气动执行器。该执行器由两根柔性管构成，每根柔性管通过单根可变长度和倾斜角度的绳索约束。尽管单根管仅能实现三种简单运动类型（弯曲、伸缩与螺旋运动），但通过将一对管子平行排列并使约束参数可变，即可生成多种复杂弯曲模式。该性能利用了两根管子结构干涉的力叠加效应。本文描述了由此产生的六种姿态模式。首先阐述构型与工作原理，说明制造方法；随后引入两种数学模型和四种基于有限元方法的分析模型，用于预测五种运动模式下末端位置变化。所有模型均通过实验验证。最后，我们通过实验证明原型机SEMI-TRUNK可实现抓取水瓶并倒水的动作，验证了所提方法的有效性。