Calibration of contact parameters for complex shaped fruits based on discrete element method: The case of pod pepper (Capsicum annuum)

The discrete element parameters of pod pepper (Capsicum annuum) were calibrated for the future numerical optimisation for a pod pepper harvester. A group of discrete element method (DEM) models for pod pepper was established through reverse engineering reconstruction technology to simulate the formation of repose angle. The intrinsic parameters and some contact parameters of pod pepper were obtained through direct measurement. The measured repose angle of pod pepper was determined through bench tests of the cylinder lifting method. Based on these parameters and the DEM simulations, the contact parameters of pod pepper that were difficult to measure directly were calibrated through response surface methodology (RSM). These parameters included: static friction coefficient between pod pepper and pod pepper 0.21, rolling friction coefficient between pod pepper and pod pepper 0.10. These optimal parameters were applied to simulate the formation of pod peppers' repose angle in the two verification tests, and the relative errors between the verification repose angle and the measured repose angle were both within 3.35%. The results showed that the calibration methods for pod pepper were suitable to guide the parameter calibration of other irregular shaped crops.(c) 2022 IAgrE. Published by Elsevier Ltd. All rights reserved.