Design, Analysis, and Experiment of an Automatic Lettuce-Harvesting Mechanism

Abstract The global reduction in agricultural labor owing to rural depopulation and an aging workforce necessitates advancements in agricultural automation. This paper presents the design, optimization, and experimental validation of an innovative automatic lettuce-harvesting robot tailored to address the challenges posed by variable lettuce sizes, irregular shapes, and complex harvesting environments. The robot integrates three primary functional modules: root-cutting, leaf-removal, and adaptive transfer mechanisms. Employing a six-bar linkage for leaf removal, the mechanism achieves superior adaptability, durability, and precision while minimizing design complexity. The transfer system, featuring dual-layer toothed belts and self-adjusting spring mechanisms, ensures the stability and efficiency of lettuce of varying sizes. The system's performance was enhanced through systematic kinematic and dynamic modeling, followed by Monte Carlo-based parametric optimization. Experimental evaluation of the prototype validated the robot's operational effectiveness, achieving a root-cutting success rate of 98%, a leaf-removal completion rate of over 97%, and the ability to complete the full process of handling 29 lettuces per minute in a laboratory setting. This study advances the field of agricultural robotics by offering scalable solutions for efficient lettuce harvesting and potential adaptation to other crops, laying the foundation for sustainable automation in precision agriculture.