Soft pneumatic actuators (SPAs) are widely studied and applied in the field of soft robotics. To expand their applications, the SPAs should be purpose-built to generate application-specific complex motions with multiple degrees of freedom. This article describes a new SPA consisting of a series of internal chambers with the same helix angle arranged in a row, which could generate bending and twisting motions simultaneously. The trajectory of the helical actuator was analyzed through the finite element method (FEM) by changing the angle of the chambers and the actuator length. We employed a three-dimensional printing method to directly fabricate the thin-walled and airtight helical actuators without applying any postfabrication process. The recorded trajectory of the actuator and the measured blocking force on the tipping point were compared with the corresponding simulation results from the FEM. The actuation behavior of the helical actuator has been compared with that of the actuator with zero chamber angle, but with the same size (i.e., a normal bending actuator generating a two-dimensional trajectory). It is found that the proposed helical actuator (with a maximum 2.10 N blocking force) had a higher mechanical output (or efficiency) than the normal bending actuator (with a maximum 1.19 N blocking force) under the same pressure input. We fabricated a soft helical actuator as the fingers of a four-finger gripper to grasp complex-shaped items. Furthermore, another four-finger gripper made of a hybrid actuator consisting of a half of the angled chambers and a half of the nonangled chambers was constructed to demonstrate that the proposed design and fabrication technique could be employed to establish application- and function-specific soft robotic systems.

中文翻译：

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仿生三维打印螺旋软气动执行器及其表征。

软气动执行器（SPA）在软机器人领域得到了广泛的研究和应用。为了扩展它们的应用，SPA 应该专门用于生成具有多个自由度的应用特定的复杂运动。本文介绍了一种新的 SPA，它由一系列具有相同螺旋角的内腔排列成一排，可以同时产生弯曲和扭转运动。通过改变腔室的角度和执行器长度，通过有限元方法 (FEM) 分析了螺旋执行器的轨迹。我们采用 3D 打印方法直接制造薄壁和气密螺旋致动器，而无需应用任何后加工工艺。将记录的执行器轨迹和在临界点上测量的阻塞力与 FEM 的相应模拟结果进行比较。已经将螺旋致动器的致动行为与具有零腔角但尺寸相同的致动器（即，产生二维轨迹的正常弯曲致动器）的致动行为进行了比较。结果表明，在相同的压力输入下，所提出的螺旋执行器（最大 2.10 N 阻塞力）比普通弯曲执行器（最大 1.19 N 阻塞力）具有更高的机械输出（或效率）。我们制造了一个软螺旋致动器作为四指夹持器的手指来抓取复杂形状的物品。此外，