DEM calibration with two-dimensional look-up table and accuracy evaluation for modelling non-contact wheat seeding

Abstract

Parameter calibration is a key component of the discrete element method (DEM). Limitations on the predictive accuracy of DEM parameters calibrated by in-situ simulation approaches exist but are always ignored by researchers. To determine a DEM parameter combination for accurately predicting the seeding depth in non-contact seeding, under a condition of varying vertical velocities, this study constructed a two-dimensional look-up table (LUT) of seeding depths with DEM parameters as inputs using the in-situ simulation. According to the experimental results of seeding depths in five soil bins with different water content, multiple parameter combinations for each soil bin were found in the LUT with their prediction accuracies higher than 95 % under a fixed seed vertical velocity. Although the vertical velocity was different from it in the calibration, the parameter combinations for each soil bin were expected to have at least one that could accurately predict seeding depth with the same parameter combination. Thus, the experimental results of seeding depth at varying vertical velocities for each soil bin and their simulated results were compared. The results demonstrated strong simulation-experiment correlations (R² > 0.88) for parameter combinations in each soil bin under varying vertical velocities, though the correlation weakened with increasing velocity. Optimal parameter combinations were uniquely identified per soil bin through correlation maximization. The validated DEM parameters showed prediction errors of 2.42–21.23 % related to vertical velocities. This research provides foundational insights for developing real-time pressure adjustment systems in non-contact wheat seeding using spatial soil property databases.