Design and testing of maize top-rod precision seed metering device based on DEM-MBD coupling technology

To address the challenges of significant variations in maize seed size and low seed-picking accuracy of the seed-taking component in the seed metering device, a maize top-rod precision seed metering device with an attitude adjustment protrusions was designed based on the agronomic requirements for maize cultivation in Northwest China. This device drives the top-rods to move along a circular trajectory via a roller, and the opening and closing of the top-rods are realized under the control of the top-rod adjustment lever. Thereby, it completes the clamping and fixed-point discharge of seeds, ensuring single-seed picking and stable seeding. Attitude-adjusting protrusions were added to the inner wall of the seed metering device housing to effectively adjust the seed filling posture; they also serve the function of seed cleaning to prevent multi-seed clamping. In this study, the operational performance of the device was investigated under different conditions, including top-rod adjustment position, top-rod adjustment angle, and planter angular velocity. Through DEM-MBD (Discrete Element Method-Multi-Body Dynamics) coupling simulation, the effects of attitude adjustment efficiency and seed size variation on seeding performance were clarified; additionally, bench tests were conducted to optimize and verify the device's performance. The results indicate that the seed metering device equipped with attitude-adjusting protrusions exhibits a higher posture qualification rate, more uniform seed population velocity, and better filling effect. The optimization results based on Design Expert show that the seeding performance is optimal when the top-rod adjustment position is 7.03 mm, the top-rod adjustment angle is 78.86°, and the planter angular velocity is 3.68 rad/s. Under these conditions, the seed qualified rate reaches 97.15 %, while the leakage rate and multiple rate are 2.06 % and 0.79 %, respectively—all meeting national and industrial standards. This study can provide a reference for the design and optimization of mechanical maize precision seed metering devices.