Dem-Based Modeling and Contact Parameter Calibration of Hazelnuts

To address the lack of contact parameters in designing hazelnut harvesting machinery, this study measured the physical properties of hazelnuts through experiments and obtained a 3D model via scanning. A DEM model was established accordingly. Contact parameters between hazelnuts and steel were calibrated through physical and simulated tests, yielding a restitution coefficient of 0.31, static friction of 0.39, and rolling friction of 0.04. Using the relative error of repose angle as the response variable and hazelnut–hazelnut contact parameters as factors, a quadratic regression model was developed by steepest ascent and Central Composite tests. The optimal contact parameters of hazelnuts were 0.11 (restitution), 0.21 (static friction), and 0.04 (rolling friction), with a 1.84% error.