The conformability is yet a challenge for most soft robotic grippers due to the continuous motion and deformation of these machines under external force. Herein, inspired by the movement mechanism of human fingers, we propose a novel tendon-driven soft robotic finger with a preprogrammed bending configuration and a human finger like sequential motion that can be obtained by matching the stiffness gradient of the finger joints with three-dimensional (3D) printing technology. The contents of this article are organized as follows. First, the effect of the anisotropy caused by 3D printing filling direction on the mechanical property is investigated by tensile test. Then, kinematic, stiffness, and fingertip trajectory models are established to analyze the influence of the cross-section thickness and width on the bending and bearing capacity of the finger joint. Furthermore, several experiments are conducted on a self-built experimental platform to evaluate the advantages of sequential motion induced by stiffness gradients. Results reveal that soft robotic fingers with sequential motion show excellent conformability on the object surfaces with various curvatures and outperform nonsequential motion fingers with larger envelop range. Without changing motion trajectories of the fingertip, the deformability of the finger can be tuned by adjusting only the stiffness of the joint. Besides, a two-finger gripper is developed, which presents the capability of grasping objects with different shapes and weights in practical applications. The sequential motion mechanism proposed in this study shows promising potential in soft grippers and robotic design.

中文翻译：

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基于肌腱驱动机制的具有顺序运动的仿生软机器人手指

由于这些机器在外力作用下会持续运动和变形，因此对于大多数软机器人夹持器来说，顺应性仍然是一个挑战。在此，受人类手指运动机制的启发，我们提出了一种新颖的肌腱驱动软机器人手指，具有预编程的弯曲配置和类似人类手指的顺序运动，可以通过将手指关节的刚度梯度与三维匹配来获得(3D) 打印技术。本文的内容组织如下。首先，通过拉伸试验研究了3D打印填充方向引起的各向异性对力学性能的影响。然后，运动学，刚度，建立指尖轨迹模型，分析断面厚度和宽度对指关节弯曲承载力的影响。此外，在一个自建的实验平台上进行了几个实验，以评估由刚度梯度引起的顺序运动的优势。结果表明，具有顺序运动的软机器人手指在具有各种曲率的物体表面上表现出出色的顺应性，并且优于具有更大包络范围的非顺序运动手指。在不改变指尖运动轨迹的情况下，仅通过调整关节的刚度就可以调整手指的变形能力。此外，还开发了一种双指夹持器，在实际应用中具有抓取不同形状和重量物体的能力。