A novel high-precision citrus harvesting robotic system for controlled stem length: Design, validation, and field evaluation

Labor shortages and stringent quality standards in citrus harvesting necessitate robotic systems capable of detaching fruit while maintaining precise control of residual stem length. This study presents a high-precision robotic system centered on a novel end-effector that achieves millimeter-level residual stem-length control through the integration of a compliant three-finger gripper, servo-actuated shears, and a dual-axis YZ positioning stage. Unlike existing citrus harvesting solutions that rely on pulling, vibration, or coarse cutting, the proposed design enables fine shear placement and controlled cutting using embedded sensing and an Arduino-based controller, with closed-loop alignment provided by limit-switch, pressure, and current feedback to ensure adaptive gripping. Field experiments conducted on 142 citrus samples evaluated harvesting accuracy, reliability, and speed under semi-manual operation, in which fruit selection and gross positioning were performed by a human operator, while gripping, shear alignment, cutting, and release were executed autonomously by the end-effector subsystem. The system achieved a 99.3% end-effector detachment success rate with zero fruit damage and an average residual stem length of 0.81 mm, with 73.9% of samples meeting the study’s precision target of residual stem length ≤ 1.0 mm. The average cycle time of 10.79 s reflects a deliberate trade-off prioritizing precision over speed. These results demonstrate that combining compliant actuation with coordinated multi-axis positioning enables repeatable, high-quality stem cutting and damage-free fruit handling. Future work will focus on full system integration, reducing cycle time through faster actuation and optimized robotic arm motion, and improving perception robustness for orchard environments.