Anthropomorphic Twisted String-Actuated Soft Robotic Gripper with Tendon-Based Stiffening

TL;DR

This paper introduces a novel soft robotic gripper driven by twisted string actuators, featuring tunable stiffness and high force output, inspired by the human hand, achieving superior grasping performance.

Contribution

The paper presents a new soft gripper design using twisted string actuators with antagonistic tendons for tunable stiffness, enhancing force and dexterity.

Findings

Achieved a maximum grasping force of 72 N, 13 times its own weight.

Recreated 31 of 33 grasps in the Feix GRASP taxonomy.

Demonstrated comparable or superior performance to existing soft grippers.

Abstract

Realizing high-performance soft robotic grippers is challenging because of the inherent limitations of the soft actuators and artificial muscles that drive them, including low force output, small actuation range, and poor compactness. Despite advances in this area, realizing compact soft grippers with high dexterity and force output is still challenging. This paper explores twisted string actuators (TSAs) to drive a soft robotic gripper. TSAs have been used in numerous robotic applications, but their inclusion in soft robots has been limited. The proposed design of the gripper was inspired by the human hand. Tunable stiffness was implemented in the fingers with antagonistic TSAs. The fingers' bending angles, actuation speed, blocked force output, and stiffness tuning were experimentally characterized. The gripper achieved a score of 6 on the Kapandji test and recreated 31 of the 33 grasps of the Feix GRASP taxonomy. It exhibited a maximum grasping force of 72 N, which was almost 13 times its own weight. A comparison study revealed that the proposed gripper exhibited equivalent or superior performance compared to other similar soft grippers.