温室劣苗基质离散元仿真参数标定

穴盘育苗中劣质钵苗会影响后期种苗移栽成活率，现有机械式剔除存在颗粒散落遗漏现象，而气吸式剔除方式则可以很好地弥补这一缺陷。为解析钵苗基质气吸式剔除的机理，本文开展离散元仿真的参数标定试验。选取100 g基质进行粒径分布检测，采用漏斗静置，基于图像处理获取基质两侧实际堆积角，通过Plackett-Burman实验确定影响基质堆积角的4个因素；通过最陡爬坡实验确定显著因素最大响应区域；依据Box-Behnken实验建立二阶回归模型并求解最佳参数组合。结果表明，在不显著因素取中间值时，当基质颗粒-颗粒碰撞恢复系数为0.142、基质颗粒-颗粒滚动摩擦因数为0.097、基质颗粒-不锈钢静摩擦因数为0.223和基质JKR表面能为2.325 J/m²时，所得仿真堆积角φ为33.4°,与实际堆积角θ为34.19°的相对误差为2.31%,满足试验需求，所得标定参数可用于钵苗基质的离散元仿真。

Calibration of Discrete Element Simulation Parameters for Greenhouse Inferior Seedling Substrate

The presence of inferior bowl seedlings in hole tray seedling cultivation would affect the survival rate of later seeding transplantation. It is urgent to clean the substrate of these holes. The existing mechanical removal methods often have the phenomenon of particle scattering and omission, while the air suction removal method can effectively compensate for this defect. In order to analyze the mechanism of air suction removal of bowl seedling substrate, parameter calibration experiments for discrete element simulation research were conducted. Totally 100g of matrix was selected for particle size distribution detection and then a funnel was used to stand still. Based on image processing, the actual stacking angle on both sides of the matrix was obtained, the average value was calculated which was used as the response value. Through the Plackett-Burman experiment to screen for four significant factors that affected the stacking angle of the matrix. The maximum response area of significant factors was determined through the steepest climbing experiment. A second-order regression model was establish based on the Box-Behnken experiment and solved for the optimal parameter combination. The results showed that on the premise of taking the intermediate value of insignificant factors, when the matrix particle-particle collision coefficient of restitution A was 0.142, the matrix particle-particle rolling friction coefficient C was 0.097, the matrix particle-stainless steel static friction factor E was 0.223 and the matrix JKR surface energy G was 2.325J/m2, the simulated stacking angle was 33.4°, and the relative error with the actual stacking angle of 34.19° was 2.31%. The research result can meet the experimental requirements, and the obtained calibration parameters can be used for discrete element simulation of bowl seedling matrix.