基于离散元法的谷子脱出物建模与参数标定

Discrete Element Method Based Modeling and Parameter Calibration for Millet Threshing Mixture

摘要:

针对谷子联合收获过程中清选环节对多组分异质颗粒缺乏精准建模与参数支撑的问题，本文开展了谷子脱出物建模与参数标定。基于谷子脱出物组成特性，构建了籽粒、谷码和茎秆3类典型颗粒模型，采用离散元方法结合自动填充技术分别进行球体、异形体和圆柱体建模，并通过填充球面数量与形态差异度分析优化建模形态。在颗粒物理参数测定基础上，以休止角为指标，采用Plackett-Burman试验、最陡爬坡法与Box-Behnken响应面优化相结合的参数标定方法，实现了籽粒、谷码、短茎秆接触参数修正，仿真与实际休止角平均误差分别为1.94%、3.72%、1.16%。为验证模型精度，开展高速摄像验证试验，利用TEMA软件提取颗粒轨迹并与仿真结果进行对比，结果显示3类颗粒轨迹重合度均大于0.75，所得平均绝对误差与均方根误差均处于较低水平，说明仿真轨迹在幅值与趋势方面均与实测结果高度一致，验证了模型预测动态行为的精度与可行性。研究结果表明，本文所构建的建模方法与标定参数具备良好的物理一致性与工程适用性，可为谷子清选过程颗粒动力学仿真与机理研究提供支撑。

Abstract:

In order to solve the problem of lack of accurate modeling and parameter support for multi-component heterogeneous particles in the clearing link during the combined millet harvesting process, a research on the modeling and parameter calibration of grain threshing mixture was carried out. Based on the compositional characteristics of millet threshing mixture, three types of typical particle models were constructed for seeds, millet panicle clusters and stalks, and the discrete element method combined with the auto-filling technology was used to model spheres, heteromorphs and cylinders, respectively, and the modeling morphology was optimized through the analysis of the number of filled spherical surfaces and the degree of morphological differences. Based on the determination of physical parameters of particles, using the angle of repose as an index, the parameter calibration method combining Plackett-Burman test, the steepest ascent test and Box-Behnken response surface optimization was adopted to realize the correction of contact parameters of seeds, millet panicle clusters and short stalks, and the average errors of simulation and actual angle of repose were 1.94%, 3.72% and 1.16%, respectively. In order to verify the accuracy of the model, high-speed camera validation tests were carried out, and the particle trajectories were extracted by using TEMA software and compared with the simulation results. The results showed that the overlap of the three types of particle trajectories was greater than 0.75, and the obtained mean absolute error and root mean square error were at a low level, indicating that the simulation trajectories were highly consistent with the measured results in terms of amplitude and trend, which verified the accuracy, and the model constructed was highly consistent with the measured results. The results showed that the modeling method and calibration parameters constructed had good physical consistency and engineering applicability, which can provide effective support for the particle dynamics simulation and mechanism research of millet cleaning process.