Design and Experiment of a Seed-Metering Device Based on the Physical Properties of Cyperus esculentus L. Seeds

The unique material properties of Cyperus esculentus L. seeds present challenges for precision seeding, as no specialized seed-metering device is currently available. In practice, general-purpose planters such as peanut seeders are often adapted for this crop. However, the dry seeds of C. esculentus exhibit an irregular shape, uneven surface texture, significant size variation, and poor flowability, leading to inadequate seed pickup and suboptimal seeding performance in conventional metering devices. To address these issues, two types of seed pickup devices—one with a V-shaped scoop and the other with an arc-shaped scoop—were designed to improve the seed-filling process and enhance seed agitation within the seed pool. A comparative analysis of the material properties of seeds before and after soaking was conducted, and key structural parameters of the scoops were determined based on the post-soaking characteristics. A mechanistic analysis was performed to clarify the operational principles and influencing factors of the scoop-based pickup mechanism. Using EDEM software (2022 version), the motion characteristics of seeds inside the metering device were observed, and the agitating speed of the seed population was compared with and without the scoop devices. Performance comparison experiments were carried out with two scoop types under varying conditions, including metering disc rotation speed, seed size grade (large, medium, and small), and seed moisture state (dry vs. soaked). Simulation results of seed disturbance indicated that the V-shaped scoop significantly enhanced agitation intensity, with a maximum movement velocity 15.8% higher than that of the arc-shaped scoop. The V-shaped scoop demonstrated superior stability and adaptability across different seed sizes, rotation speeds, and moisture conditions. Seed pickup success rates reached 96%, 96%, and 85% for large, medium, and small seeds, respectively. Under high-speed operation (40 r/min), the V-shaped scoop showed a 9% lower miss-seeding rate compared to the arc-shaped scoop.