Parameter Calibration and Experiment of Main Stem Model of Red Pepper Cluster Based on Discrete Element Method

In order to solve the problem of lack of accurate model for discrete element simulation of pepper stems in the current research and development of mechanized picking devices for red pepper, and to improve the accuracy and reliability of discrete element method in guiding the design and optimization of mechanized picking manipulators for red pepper, this paper takes the stems of red pepper cluster picking and clamping as the object, uses the Hertz-Mindlin with bonding contact model in EDEM to establish a discrete element bonding model of red pepper stems and calibrate its parameters. Physical shear tests were carried out on the stems to determine the ultimate shear load (6.272N) and ultimate displacement (1.552mm) of the stems. Based on this, Placket burman, steepest climbing and Box-Behnken tests were designed to determine the optimal combination of bonding parameters of the stem model: normal contact stiffness X ₁ is 1.156×10 ⁸ N.m ^-3 , tangential contact stiffness X ₂ is 1.2×10 ⁷ N.m ^-3 , critical normal stress X ₃ is 5×10 ⁷ Pa, critical tangential stress X ₄ is 1.2×10 ⁷ Pa and bonding radius X ₅ is 1.418mm. The calibration results were used for verification, showing that the relative errors of the simulation ultimate load and ultimate displacement to the physical test were 0.52% and 2.58%, respectively. The torque tester was used to verify the stems, and the error of the verification test was 4.17%, which verified the reliability of the calibration method and provided a reliable discrete element model for mechanized picking of red pepper.