Calibration and establishment for the discrete element simulation parameters of pepper stem during harvest period

To address the problem of poorly defined mechanical parameters in discrete element simulations of mechanized pepper harvesting, a discrete element model was developed to accurately represent the biomechanical characteristics of pepper stems. This research presents a parameter calibration and optimization approach using both Hertz-Mindlin and Hertz-Mindlin with bonding methods. The basic properties of the pepper stems were determined by mechanical property testing, while the stacking angle was assessed using the cylinder lift technique. The stacking angle and maximum bending damage force were used as evaluation indexes. Significant parameters influencing the model were identified using the Plackett-Burman test, followed by a steepest ascent test to define the central test group. The Central-Composite and Box-Behnken tests were then used to formulate quadratic regression equations and optimal parameter combinations for the significant factors were derived using an optimization solver to validate the accuracy of the model. The results showed that the relative errors between simulated and actual values for the two models under optimal conditions were 0.86% and 1.02%, respectively. The discrete element model of pepper stems closely approximates real-world conditions and reflects the mechanical behavior of pepper stems as they bend and break upon impact during harvesting. This research provides a basic framework for mechanistic analysis of the pepper harvesting process.