Torsion Resistant Strain Limiting Layers Enable High Grip Strength of Electrically-Driven Handed Shearing Auxetic Grippers

TL;DR

This paper introduces a torsionally rigid strain limiting layer (TR-SLL) that enhances the payload capacity and grip strength of soft, electrically-driven shearing auxetic (HSA) grippers, enabling them to lift over 5 kg and grasp a wide variety of objects.

Contribution

The study presents a novel TR-SLL design that improves the torsion resistance of HSA grippers, allowing for higher payloads and stronger grips while maintaining softness.

Findings

Enabled lifting of over 5 kg payloads.

Achieved a peak pinch force of 5.8 N.

Successfully grasped 37 out of 43 objects in tests.

Abstract

Soft grippers have demonstrated a strong ability to successfully pick and manipulate many objects. A key limitation to their wider adoption is their inability to grasp larger payloads due to objects slipping out of grasps. We have overcome this limitation by introducing a torsionally rigid strain limiting layer (TR-SLL). This reduces out-of-plane bending while maintaining the gripper's softness and in-plane flexibility. We characterize the design space of the strain limiting layer and Handed Shearing Auxetic (HSA) actuators for a soft gripper using simulation and experiment. The inclusion of the TR-SLL with HSAs enables HSA grippers to be made with a single digit. We found that the use of our TR-SLL HSA gripper enabled pinch grasping of payloads over 1 kg. We demonstrate a lifting capacity of 5 kg when loading using the TR-SLL. We also demonstrate a peak pinch grasp force of 5.8 N, and a peak planar caging force of 14.5 N. Finally, we test the TR-SLL gripper on a suite of 43 YCB objects. We show success on 37 objects demonstrating significant capabilities.