ANGEL: A Novel Gripper for Versatile and Light-touch Fruit Harvesting

TL;DR

This paper presents ANGEL, a lightweight, soft, cable-driven gripper inspired by drawstrings, designed for gentle, versatile fruit harvesting with minimal bruising and damage, adaptable to various fruit sizes, and validated through experiments on tomatoes.

Contribution

Introduction of a novel, simple, and adaptable soft gripper design that reduces mechanical complexity and damage during fruit harvesting.

Findings

0% immediate damage rate on tomatoes

Less than 9% bruising after five days

Effective for fruits of varying sizes

Abstract

Fruit harvesting remains predominantly a labor-intensive process, motivating the development of research for robotic grippers. Conventional rigid or vacuum-driven grippers require complex mechanical design or high energy consumption. Current enveloping-based fruit harvesting grippers lack adaptability to fruits of different sizes. This paper introduces a drawstring-inspired, cable-driven soft gripper for versatile and gentle fruit harvesting. The design employs 3D-printed Thermoplastic Polyurethane (TPU) pockets with integrated steel wires that constrict around the fruit when actuated, distributing pressure uniformly to minimize bruising and allow versatility to fruits of varying sizes. The lightweight structure, which requires few components, reduces mechanical complexity and cost compared to other grippers. Actuation is achieved through servo-driven cable control, while motor feedback provides autonomous grip adjustment with tunable grip strength. Experimental validation shows that, for tomatoes within the gripper's effective size range, harvesting was achieved with a 0% immediate damage rate and a bruising rate of less than 9% after five days, reinforcing the gripper's suitability for fruit harvesting.