基于离散元仿真的马铃薯收获机集薯装袋过程研究

Bagging Process of Potato Harvester Based on EDEM

摘要:

为保证收获机作业效率的同时，降低马铃薯收获机在集薯装袋过程的伤薯率，设计了一种集薯卸袋装置，并基于离散元仿真研究马铃薯在该装置上的碰撞过程和受力情况。该装置可完成集薯、装袋、卸袋工序，保证作业过程不停机，提高机器作业效率。通过理论分析获取了升降液压缸的受力关系式并确定了升降液压缸的选型及布置形式。分析了薯块碰撞过程，获取了碰撞应力的关系表达式，并确定了应力的影响因素为箱壁与水平面的夹角和法向冲击速度;通过分析计算得到了集薯箱的结构参数范围，结合集薯卸袋装置的工作需求设计了相应的液压系统。为验证所选工作和结构参数范围的合理性及集薯装袋过程中马铃薯的受力情况，通过测定马铃薯的物料特性，赋予相应部件运动属性，进行离散元仿真试验。利用堆积角验证了颗粒模型的准确性并进行了相应的单因素仿真试验，选取各时间步颗粒所受最大力及各阶段所受力均值作为评价指标。通过分析仿真试验结果，明确了各因素对马铃薯颗粒受力的影响规律，并对工作顺序进行了相应的仿真试验，确定了马铃薯收获机集薯装袋的顺序。仿真试验结果表明，先集薯后装袋的伤薯率为1.07%、先装袋后集薯的伤薯率为3.04%。并通过田间试验验证先集薯后装袋工作顺序的正确性，田间试验结果表明，先集薯后装袋的整机作业伤薯率为2.59%，低于先装袋后集薯的整机作业伤薯率（3.71%）。

Abstract:

In order to ensure the efficiency of harvester and reduce the damage rate of potato harvester during bagging process, a kind of bagging unloading device was designed, and the collision process and stress of the potato on the device were studied based on discrete element simulation. The device can complete the processes of cache collection, bag loading and bag unloading, ensure the working process without stopping, and improve the working efficiency of the machine. Through theoretical analysis, the force relation of lifting hydraulic cylinder was obtained and the type selection and layout of lifting hydraulic cylinder were determined. The collision process of potato block was analyzed, the relation expression of the collision stress was obtained, and the influencing factors of the stress were determined as the angle between the box wall and the horizontal plane and the normal impact velocity. Through analysis and calculation, the range of structural parameters of the collecting potato box was obtained, and the corresponding hydraulic system was designed according to the working requirements of the unloading bag device of the collecting potato. In order to verify the rationality of the selected work and the range of structural parameters and the stress of the potato in the bagging process, the discrete element simulation test was carried out by measuring the material characteristics of the potato and giving the motion properties of the corresponding components. The accuracy of the particle model was verified by the stacking angle and the corresponding single factor simulation test was carried out. The maximum force of the particles at each time step and the mean value of the forces at each stage were selected as the evaluation index.By analyzing the simulation test results, the influence of various factors on the force on potato particles was clarified, and corresponding simulation tests were conducted on the working sequence.The order of potato harvesting and bagging was determined. The simulation test results showed that the damage rate of potatoes collected first and then bagged was 1.07%, and the damage rate of potatoes collected first and then bagged was 3.04%. And the correctness of the working sequence of the first collecting potatoes and then bagging was verified through field experiments. The field experiment results showed that the potato damage rate during the whole machine operation of first collecting potatoes and then bagging was 2.59%, which was lower than that of the potato damage rate（3.71%） during the whole machine operation of the first bagging and then collecting potatoes.