基于DEM-MBD耦合的咖啡采摘过程仿真与试验

Simulation and Experiment of Coffea Picking Process Based on DEM-MBD Coupling

摘要:

针对咖啡机械采摘过程中因作业参数不准确导致采摘质量偏低的问题，利用离散元软件EDEM构建采收期小粒咖啡带果枝条离散元柔性模型，通过对比果实-果柄拉伸分离力和枝条三点弯曲折断力的仿真与试验结果，验证模型设置参数的准确性;采用EDEM-Recurdyn耦合的方法构建小粒咖啡带果枝条与振动式采摘装置互作的离散元模型，通过单因素仿真试验分析小粒咖啡采摘过程中采摘装置的作业参数对采摘质量的影响规律，确定了各作业参数范围。以振频、调幅机构倾角和振动时间为试验因素，采净率、采熟率、枝条损伤率为试验指标，进行三因素五水平的二次回归正交旋转组合仿真试验，结果表明：因素对采净率和采熟率影响由大到小为振频、振动时间和调幅机构倾角，对损伤率影响由大到小为振动时间、振幅和调幅机构倾角，参数优化得到当振频为64 Hz、倾角为40°、振动时间为1.5 s时，采摘效果最佳。在优化作业参数下进行田间采摘试验，得到采净率、采熟率、枝条损伤率平均值分别为92.54%、95.47%和5.01%，与仿真试验结果相对误差分别为4.23%、3.39%、6.37%，验证了仿真试验的可靠性，为咖啡采摘机作业参数研究及结构优化提供理论依据和技术参考。

Abstract:

In view of the low picking quality caused by inaccurate operating parameters in the mechanical picking process of coffea, the discrete element simulation software EDEM was used to construct the discrete element flexible model of Arabica coffea fruit-bearing branches in harvesting time, the accuracy of the model setup parameters was verified by comparing the simulation and actual test results of fruit-stalk tensile separation force and branch three-point bending fracture force. The EDEM-Recurdyn coupling method was used to construct the simulation model of Arabica coffea fruitbearing branches interacting with a vibratory picking device, the influence regularity of the operating parameters of the picking device on the picking quality during the picking process was analyzed by means of a single factor simulation test, and the operating parameters value range were defined. The quadratic regression orthogonal rotation combination simulation test of three factors and five levels was carried out with vibration frequency, inclination angle of the amplitude adjustment mechanism and vibration time as the test factors, and picking clean rate, picking ripening rate, and branch damage rate were used as the test indexes. The results showed that the importance of the effect of each factor on each test index in descending order was the vibration frequency, the vibration time and the inclination angle of the amplitude adjustment mechanism. The best picking effect was obtained through parameter optimization when the vibration frequency was 64 Hz, the inclination angle was 40 °, and the vibration time was 1.5 s. The field-picking test was conducted under the optimized operating parameters. The mean values of 92.54%，95.47% and 5.01% were obtained for the picking clean rate, picking ripening rate and branch damage rate, respectively, and the relative errors with the simulation test were 4.23%，3.39%, and 6.37%, respectively, which verified the reliability of the simulation test, and provided a theoretical basis and technical references for the study of the operating parameters and the optimization of the structure of the coffee picking machine.