The gas–solid flow of mixed seeds of oat and vetch in the air-blowing venturi tube was simulated numerically by means of a coupling approach of the discrete element method (DEM) and computational fluid dynamics (CFD). In the gas–solid coupling model, EDEM software was used to depict the discrete particle phase, and ANSYS Fluent software was used to describe the continuous gas phase. The effects of the seed entry angle and inlet air velocity on the uniformity of mixed seed supply were studied and analyzed from the angle of airflow field variation and mixed seeds movement characteristics. The simulation results showed that the seeding angle has a great influence on the seed movement in the tube and affects the pressure and velocity gradient of the airflow field. If the seed insertion angle is too large, the number of collisions between the seed and the tube wall will increase, and the phenomenon of seeds retention and disordered jumping will occur. The inlet air velocity mainly affects the outlet air velocity and seed velocity and has little effect on the change in airfield. With the increase in inlet air velocity, the greater the velocity and force of the seeds, the closer the mixed seeds collide with the wall to the outlet pipe. At high inlet airflow velocity, there is a great disparity in the movement speed between the seeds, resulting in uneven spacing between the seeds. The results showed that under the conditions of 60° seed entry angle and 35~40 m/s inlet air velocity, the airflow field distribution in the tube was uniform and the seed movement was continuous and uniform.

To analyze the interaction between the surface soil and the soil-contacting component (65 Mn) in the camellia oleifera forest planting area in Changsha City, Hunan, China, in this study, we conducted discrete element calibration using physical and simulation tests. The chosen contact model was Hertz–Mindlin with JKR cohesion, with the soil repose angle as the response variable. The repose angle of the soil was determined to be 36.03° based on the physical tests. The significant influencing factors of the repose angle determined based on the Plackett–Burman test were the soil–soil recovery coefficient, soil–soil rolling friction coefficient, soil-65 Mn static friction coefficient, and surface energy of soil for the JKR model. A regression model for the repose angle was developed using the Box–Behnken response surface optimization method to identify the best parameter combination. The optimal parameter combination for the JKR model was determined as follows: surface energy of soil: 0.400, soil–soil rolling friction coefficient: 0.040, soil-65 Mn static friction coefficient: 0.404, and soil–soil recovery coefficient: 0.522. The calibrated discrete element parameters were validated through experiments on the repose angle and steel rod insertion. The results indicated that the relative errors obtained from the two verification methods were 2.44% and 1.71%, respectively. This research offers fundamental insights for understanding the interaction between soil and soil-contacting components and optimizing their design.

Method for the posture control of bionic mechanical wheel-legged vehicles in hilly and mountainous areas

With the benefits of small turning radius and high trafficability, the articulated steering half-track tractor had been widely utilized in orchard and small spaced farmland. To study the dynamic performance of the articulated steering half-track tractor and provide a model basis for studying the path tracking control, an accurate multi-body dynamic model of the tractor was required. In this study, the crucial parameters in the dynamic model construction of the tractor were investigated. Firstly, the topology model of the components of the half-track tractor was built by RecurDyn, in which the movement subs and driver functions were given. Secondly, considering the difference of dynamic characteristic of the articulated steering tractor with respect to different pavement hardnesses, the soft and hard pavement models were constructed by employing the harmonic superposition method. Finally, the simulations of the half-track tractor under straight-line and swerve had been conducted on the two types of pavements, and the simulation results were compared with the experimental and theoretical results. The results indicated that the average speed error of the dynamic model on hard pavement and farmland soft pavement were 2.7% and 2.1% compared with the real tractor tests. At the same time, the straight-line driving offset errors of the dynamic model on the two pavements were 1.6% and 3.8% for the front wheels and the rear wheels offset errors were 3.9% and 2.4%, respectively. Furthermore, the turning radius error under front wheel steering was 8.2% and the error under articulated steering was 5.3%. It is proved that the established dynamic model had high accuracy, which provides an efficient approach to analyze the dynamic features of the half-track tractor. Keywords: articulated steering, half-track tractor, multi-body dynamics, model verification, real tractor test DOI: 10.25165/j.ijabe.20231606.8165 Citation: Zhou B C, Chen S Y, Hu J N, You Y, Wang D C, Zhang Q. Multi-body dynamics modeling and test of an articulated steering half-track tractor. Int J Agric & Biol Eng, 2023; 16(6): 124–133.

Pre-sowing treatment of seeds by plasma can improve seed vigor and promote seed germination and growth. To solve the problems of low processing volume and uneven treatment in plasma seed treatment devices, according to the process scheme of medium-blocking discharge plasma seed treatment, a medium-blocking discharge vibration-uniform material plasma seed treatment device was designed, the structure and working principle of the vibration-uniform material device were systematically analyzed, and the mathematical model of seed force was established. According to electromagnetic vibration theory, the seed sorting and conveying principles were analyzed in the lower trough, and the relevant parameters were selected and calculated. Using EDEM discrete element simulation software, a numerical simulation of alfalfa seed feeding and vibration-uniform material process was carried out. A three-factor, three-level orthogonal test was established. The results showed that the vibration amplitude and groove shape significantly affected the coefficient of variation of seed uniformity on the groove during the seed feeding and vibration-uniform material processes, and the groove wheel speed had a certain effect on the coefficient of variation of uniformity. The main order of factors affecting the uniformity of seed spreading was vibration amplitude B > notch shape C > speed A. The optimal speed was 35 r/min, the optimal notch shape was circular, and the optimal vibration amplitude was 0.55 mm.