Gongpu Wang, Jiwen Peng, Guangyu Xue, Baoliang Peng, Yanhua Zhang, Lianglong Hu, Haiyang Shen
To mitigate the high skin-damage rates and substantial harvest losses typical of mechanized fresh sweet-potato harvesting, we developed a lightweight, integrated harvester featuring a low-damage conveying-separating mechanism. Guided by machinery-agronomy integration and informed by planting patterns, harvesting practices, and crop traits, we selected key structural parameters and introduced several innovations: a chain-rod elevating conveyor with alternating straight and concave rods, a passive vibrating wheel to enhance soil separation, and a rubber-coated secondary conveyor for gentle handling. A three-factor, three-level Box-Behnken design was used to optimize conveyor chain speed, conveyor inclination angle, and forward travel speed. Quadratic regression models for tuber injury rate, skin damage rate, and soil content were fitted and analyzed via response surfaces. Results showed that conveyor speed, conveyor angle, and their interaction exerted highly significant effects on injury rate, with forward speed also significant; conveyor speed and angle had highly significant effects on skin damage, whereas forward speed was not significant; and conveyor speed and angle had highly significant effects on soil content, with forward speed significant. Response-surface optimization identified an operating combination of conveyor speed 0.45 m·s-1, conveyor angle 30°, and forward speed 0.25 m·s-1. Field validation at these settings yielded an injury rate of 0.94%, a skin-damage rate of 0.97%, and a soil-content rate of 76.56%, with model-measurement relative errors below 3% for all indices. These findings demonstrate that the proposed conveying-separating mechanism substantially reduces mechanical damage and skin peeling, enabling low-loss, high-quality harvest of fresh sweet potatoes and providing a technical reference for the design of dedicated fresh-market harvesters.