Design and Operating-Parameter Optimization of a Precision Seeder for Chinese Yam Based on Automatic Seed Distribution and Chain-Driven Metering

A precision seeder for elongated Chinese yam seed segments was developed by integrating automatic seed distribution with chain-driven metering. The design was based on measured seed segment properties, including mean length, width, thickness, equivalent diameter, density, moisture content, intrinsic mechanical properties, and seed-seed/seed-steel contact parameters. A seed-layer stress model, sprocket-conveying stability condition, seed-dropping trajectory equation, and plant-spacing equation were used to determine the main structural parameters and to select operating speed, seed-dropping height, and seed-box slope angle as optimization variables. Box–Behnken response surface optimization predicted the best parameter combination as an operating speed of 0.20 m s−1, a seed-dropping height of 0.14 m, and a seed-box slope angle of 26.18°, with predicted qualified-seeding, multiple-seeding, and missed-seeding indices of 86.45%, 5.16%, and 8.40%, respectively. Field validation using the rounded seed-box slope angle of 26° produced mean qualified-seeding, multiple-seeding, and missed-seeding indices of 86.16%, 5.13%, and 8.71%, respectively. The results demonstrate a practical design route for oriented precision seeding of elongated tuber segments.