Working characteristics of vertical shallow-basin type seed-metering device based on high-speed photography and virtual simulation

Abstract: Vertical shallow-basin type seed-metering device is a mechanical precision seed-metering device. Its structure is based on the traditional vertical composite plate seed-metering device, and it can utilize the gravity, centrifugal force and interaction force between the seeds as the composite filling force to fill seeds, which solves the question of single filling force of traditional vertical composite plate seed-metering device. Based on the mechanism research of filling seeds, the author utilized the discrete element simulation analysis software EDEM (engineering discrete element method) and the physical prototype test to verify if vertical shallow-basin type seed-metering device had good working performance at high working speed. Generally, there was a certain model hypothesis in the existing research, for example, in the process of theoretical analysis, mechanical model had a certain simplification and assumption, in the EDEM simulation, there was the particle model assumptions, and meanwhile the discrete element simulation had not the phenomenon of knocking on a seed caused by the vibration of the machine under the actual working condition. Therefore, in order to observe and analyze the working condition and working mechanism more actually and intuitionally in the internal of vertical shallow-basin type seed-metering device, as well as the motion state of seeds in the cavity of seed-metering device, the paper utilized the high-speed photography technology to shoot the working process of the device at different rotational speed of seed shaft, and at the same time, the paper used the EDEM to simulate the working process, used the post-processing module of EDEM to label the particle, and made the analysis on the working process. Combined with 2 kinds of image analysis technologies, the results showed that to ensure the reliability in the process of cleaning seeds, the folding angle of seed plate of vertical shallow-basin type seed-metering device should be at the range of 67°-90°; meanwhile, to avoid hurting the seeds that was caused by the phenomenon of towing seeds in the process of cleaning seeds, the height of seed layer should ensure that there was a distance of 3-4 times of seed diameter between seed layer and protecting-seed device; in the process of throwing seeds, in order to ensure the uniformity and the quality, the smooth finish of the hole should be ensured and the size of throwing-seed mouth should be 16 mm×30 mm. The simulation and physical prototype showed that the trajectory of throwing seeds was a parabola curve, which was relevant with the rotational speed and whose open mouth became bigger with the increasing of rotational speed; the seed-throwing angle was positively associated with the rotational speed. The research provides the reference and basis for refining the design of vertical shallow-basin type seed-metering device and revising the relevant structure parameters to improve the working performance and ability of the device at high working speed.