Design of an Air-Assisted Mechanical Seed-Metering Device for Millet (Setaria Italica) Based on Experiments and Simulation Analysis

: In this study, an air-assisted mechanical seed-metering device for millet (Setariaitalica) was developed. The discrete element method (DEM) and response surface method (RSM) were used to research the influences of the side length, depth, and oblique angle of the shaped hole on the seeding performance (quality, multiples, and miss indices) of the seed-metering device, and the parameters of the shaped hole were optimized. Furthermore, after determining the size of the shaped hole, the influence of negative pressure on the quality index was studied under the condition of the higher rotational speed of the seed-sowing wheel. At the rotational speed of 20 r/min, the optimal values of the side length, depth, and oblique angle of the shaped hole were found to be 3.55 mm, 2.1 mm, and 109°, which resulted in a quality index of 94%. The optimal parameters were consistent with the simulated values and bench test values, with a relative deviation of 5.05%. Moreover, under the condition of a rotational speed of 40 r/min, the application of appropriate negative pressure to the seeds was found to promote seed entry into the shaped hole, thus significantly reducing the miss index and increasing the quality index. At the negative pressure of − 90 Pa, the quality index was found to exceed 90%. These results provide a theoretical basis for future studies on a seed-metering device for millet (Setaria italica).