Simulation and Optimization Experiment of Seven-Link Planting Mechanism Based on Discrete Element Method and Multibody Dynamics (DEM–MBD) Coupling

To address issues in traditional vegetable transplanter planting mechanisms such as poor hole-forming quality and low seedling uprightness, a seven-bar linkage planting mechanism with posture compensation of seedling entering soil was designed. By establishing a mathematical model of the planting mechanism and developing visual auxiliary optimization software, the optimal mechanism parameters for the best planting trajectory were determined. A DEM–MBD (Discrete Element Method and Multibody Dynamics) coupling simulation model of planting mechanism-soil-seedlings was established. The planting frequency, opening width, and opening time of the planter were used as factors, and the soil backflow and seedling uprightness were used as evaluation indicators. A quadratic regression orthogonal rotation combination simulation test was carried out. The regression model was established using Design-Expert 12.0 software to analyze the influence of various factors on the indicators. Response surface methodology was simultaneously applied for comprehensive optimization of the influencing factors. The optimal parameter combination obtained was as follows: planting frequency 57 plants/min, opening width 48.5 mm, opening time 0.76 s, corresponding to a soil backflow of 0.67 and seedling uprightness of 80.35°. Field tests were conducted to verify the following mechanism: the soil backflow was 0.64, and the seedling uprightness was 78.49°, which were 4.47% and 2.31% different from the regression model optimization results, respectively. The error variation was small, indicating that the simulation results were effective and the mechanism design was reasonable. This study provides a reference for the development of high-quality and efficient vegetable transplanters.