Parameter optimization and experiment of vibration seed-uniforming device for hybrid rice based on discrete element method

Hybrid rice requires sparse and precision seeding, and it increases yield by its strong tillering ability. But the existing mechanization planting technology can not meet the planting requirement of hybrid rice, and it is necessary to understand the mechanism of hybrid rice precision seeding technology. This paper studied the vibration seed-uniforming device in the seedling devices of hybrid rice through the theoretical analysis, simulations and experimental setup, in order to clarify the influence of the vibration frequency and amplitude of its V-T type vibration plate on the movement of seeds and the influence of seed flow characteristics on seeding performance in the sowing process, which could lead to an improvement in the seedling performance. Firstly, through the kinetic analysis of individual seed, the seed gliding and jumping conditions on the V-T type vibration plate were obtained, and the amplitude, frequency, and vibrator installation angle of the vibration plate were identified as the 3 key factors that affected the sowing performance. Secondly, to further study the movement principles of seeds on the vibration plate, the working process of the V-T type vibrating plate was simulated using the discrete element method (DEM) analysis software EDEM and the Hertz-Mindlin non-slip model. In the EDEM software, seed particles were modeled as spheres with 10 different diameters, in order to more accurately depict the characteristics of actual hybrid rice seeds. When designing the simulation motion parameters of the V-T type vibrating plate, since the pneumatic vibrator was installed on the center of the V-T type vibration plate, which led to varied vibration parameters across the plate, the vibration frequency and amplitude at different parts of the vibration plate were measured separately and adopted in the model. Next, 8 groups of simulation experiments were designed by varying the amplitude and frequency of the vibration plate, and the successful sowing rate was used as the standard to evaluate sowing performance. The simulation result showed that vibration frequency from 57 to 59 Hz led to the uniform distribution of seeds on the V-T type vibration plate and relatively better sowing performance. To validate the feasibility and accuracy of the simulation result, a single-factor experimental design was implemented. The result indicated a high accuracy for the EDEM simulation of the sowing process using the vibration seed-uniforming device, and a relative error of from 1.15% to 6.19% in the successful sowing rate was shown between the simulation and experimental value. Finally, based on simulation and experimental results, 3 experimental factors, the material choice of the vibration arms, the installation angle of the vibrator and the pneumatic vibrator inlet pressure, were chosen to carry out parameter optimization experiments of vibration seed-uniforming device. The optimal parameter combination was obtained, which was 60Si2Mn as the material of vibration arms, 47.5° as installed angle of vibrator, and 0.26 MPa as the pneumatic vibrator inlet pressure. With this optimal parameter combination, the performance of the vibration seed-uniforming device was improved, and the successful sowing rate was 92.86% and the cavity rate was 1.14%. This study provides a basis for the future research on the improvement of the precision sowing technology of hybrid rice. © 2016, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.