In order to analyze the effect of different factors on the bouncing and rolling distance of soybeans at the time of seed throwing, tests and discrete element method (DEM) are employed to analyze test soil and three representative soybean varieties. The parameters between soybean seed particles and soil particles are calibrated by means of a piling test and simulation. A seed throwing test apparatus is improved to analyze the effects of seed throwing height, soil plane inclination angle and collision orientation on the bouncing and rolling distance of soybean seeds. The effect of relative seed throwing speed on the bouncing and rolling distance of soybean seeds is analyzed using a computer vision seeding test bench. On this basis, the above-mentioned test procedure is simulated and compared with the test results. The results showed that the bouncing distance of the soybean seed particles was not significant. The rolling distance had a certain randomness when the seed throwing height was different. When the inclination of the soil plane became larger, the rolling distance increased and when the sphericity of the soybean seed particles was high, the effect of different collision orientations was not obvious if sphericity was low. The rolling distance was the shortest when colliding in the horizontal orientation and the longest when colliding in the vertical orientation. The larger the relative seed throwing speed, the larger the rolling distance of the soybean seed particles.

In order to establish a Discrete Element Method (DEM) model of soil particles, the soil in the laboratory soil bin was used as the research object. The soil texture was determined to be sandy loam by sieving, and the shape of the soil particles was analyzed by an image particle analyzer to establish a geometric model of the soil particles. The Edinburgh Elasto-Plastic Adhesion (EEPA) model was chosen as the contact model for the soil particle simulation analysis, and the accuracy of the model selection was determined by texture tests. The parameters in the contact model played a crucial role in the results of the simulation. Test methods were used to obtain parameters for the soil particles that were easy to measure. For parameters that could not be measured in the contact model, a direct shear test was used as the calibration test, and after screening the sensitive parameters using the PB test, the response surface method was used to calibrate the sensitive parameters. The accuracy of the calibration results was verified by comparing the simulation and test results of the direct shear test under different loadings.

The discrete element method has become a common method for analyzing the contact interaction between particulate materials and between particles and mechanical components. It has been widely used in agricultural engineering and other fields. Taking soybean as an example, soybean seed particles always have contact effects between particles and mechanical components in the process of planting, harvesting, threshing, separation, cleaning, and processing. The discrete element method can be used to obtain information on the contact forces between seed particles and mechanical parts, as well as the velocity and displacement of seed particle motion from a microscopic perspective. This paper summarizes the application of the discrete element method in soybean cultivation and production processes in recent years. This will help future researchers to conduct relevant test studies, develop and improve existing research methods. It can also serve as a guide and reference for the production and processing of other granular materials and the optimization of agricultural machinery components.

In discrete element method (DEM) simulations, accurate simulation parameters are very important. For ellipsoidal soybean seed particles, the rolling friction coefficient between seed particles (RFCP-P) and the rolling friction coefficients between seed particle and boundary (RFCP-B) are difficult to measure experimentally and therefore need to be calibrated. In this paper, soybean seed particles of three varieties with different sphericities were taken as the research objects. Through the simulation analysis of repose angle and self-flow screening, it was shown that the above two parameters needed to be accurately calibrated. In addition, the sensitivity of the RFCP-P and RFCP-B to the angle of repose was analyzed by simulating the repose angle test. The results showed that the RFCP-P had a significant effect on the test results of the repose angle, and the RFCP-B had little effect on the test results of the repose angle. Therefore, the RFCP-P was calibrated using a single-factor test of repose angle, and the RFCP-B was calibrated using the repose angle test with soybean particles mixed with organic glass spheres. The accuracy of the calibration parameters was verified by rotating cylinder test and self-flow screening test.

Soybean seeding monomers can realize the process of opening, seed throwing, covering, and compacting when they work. Due to the complexity of their working process, the relevant process cannot be analyzed by the discrete element method (DEM) alone. The DEM coupled with the multi-rigid body dynamics method (MBD) can solve the above problem, and the simulation analysis of the above process is realized by coupling the EDEM software with RecurDyn software. The changes in the position of soybean seed particles before and after covering and compacting are analyzed. The results show that when the working speed of the seeding monomer increases, the distance along the vertical direction of the soybean seed particles after covering gradually increases, and the distance along the horizontal direction gradually decreases. The effect of different working speeds of seeding monomer on the opening situation and the variation in seed particle positions is studied. The results show that the ditch angle gradually decreases as the working speed of the seeding monomer increases. The distribution of seed particle spacing is also analyzed. The above tests are simulated, and the results show a high agreement between the simulation and test results, proving the accuracy of the coupling method. This paper applies the coupling method for the first time to the simulation of the seeding monomer. This method can be applied not only to the analysis of the sowing process of soybean seeding monomers, but also be applied to the analysis of other machinery working processes, such as the tillage process, the sieving process, the planting and harvesting processes of crops, etc. It also deepens the application of the discrete element method in the field of agriculture.