Robotic Harvesting of Delicate Fruit: Design and Implementation of an Under-Actuated Disturbance-Resistant Gripper

Abstract

Agricultural harvesting grippers have emerged as a pivotal technology in the evolution of smart agriculture, enhancing efficient fruit collection. Existing grippers frequently fail to accommodate the diverse morphologies of fruits. Moreover, achieving stable grasping under external disturbances, such as natural wind, remains a significant challenge. To mitigate these limitations, we present a novel under-actuated gripper for fruit harvesting, alongside the formulation of innovative harvesting strategies aimed at optimizing both the harvest success rate and fruit integrity. Firstly, a strategy is developed to promote the success rate of harvesting operations under disturbance. The harvesting strategy involves stabilizing the fruit by enclosing the stem, followed by grasping and severing the stem to detach the fruit. Secondly, we propose an auxiliary locking and grasping coupling mechanism, which employs a single actuator to drive all gripper components, thereby reducing both cost and control complexity. Thirdly, a force distribution constraint unit is incorporated to allocate the actuator's power between grasping and shearing actions, enabling regulation of the grasping force to protect the fruit. Finally, the performance of the gripper is assessed through a series of rigorous experiments on fruits with diverse sizes, textures, and surface characteristics, demonstrating its superior efficacy in preserving fruit integrity during real-world harvesting scenarios.