Physical parameter measurement and discrete element simulation parameter calibration with fresh Rhizoma polygonati

Abstract This study is aimed to solve the parameter shortage during discrete element method (DEM) simulation in mechanized deseeding of fresh Rhizoma polygonati, and to calibrate DEM simulation parameters of fresh R. polygonati using physical measurement and simulation trials. First, the physical properties of fresh R. polygonati from picking to 15 days of stacking, and the contact parameters between fresh R. polygonati and different materials along with the prolonging of stacking days were measured through physical experiments. Based on the physical test results, the parameters significantly affecting the repose angle of fresh R. polygonati were screened out via Plackett-Burman test. The collision recovery coefficient, static friction coefficient, and rolling friction coefficient between fresh R. polygonati fruits all significantly affected the repose angle of fresh R. polygonati. On basis of Plackett-Burman test, a steepest ascent test was designed to further clarify the ranges of the significant parameters. Targeting at the actual repose angle of fresh R. olygonati (27.23°), we conducted Box-Behnken test and obtained the optimal parameter combination for DEM simulation of fresh R. polygonati. Verification tests showed the relative errors between the simulated values and measured values of repose angle in fresh R. polygonati were less than 3%, which proves the DEM simulation parameters are reliable.