摘要
针对该课题组自主开发研制的ZGM-7自动化穴盘苗嫁接机中出现的钢针顶起穴盘苗失败现象,该文在EDEM离散元分析软件中利用ECM粘结力弹塑性接触模型作为颗粒接触模型并建立多种不同材料属性的复杂颗粒模型来模拟真实的育苗基质,进而研究钢针与育苗基质的作用关系。并以顶起过程中的穴盘苗基质底面最大顶起高度作为指标参数,分析了不同钢针长度、不同钢针径粗、不同顶起速度条件下顶起穴盘苗的工作情况。利用响应曲面法设计并执行仿真和实际试验,仿真分析结果与试验结果得到了很好地验证,变化趋势基本一致,数值结果误差在0.7%~7.2%;钢针直径和顶起速度对指标参数影响显著,且存在显著的交互作用。以育苗基质底面竖直成功顶起的理论最大顶起高度144 mm为优化目标,利用Design_expert软件得到仿真优化参数结果:钢针直径2.28 mm,钢针长度12.28 mm,顶起速度0.09 m/s。仿真优化参数下进行试验,顶起机构顶起穴盘苗成功率高达95.3%,优化效果显著。该研究结果极大地提高了钢针顶起穴盘苗的运行效果,同时为钢针顶起离散基质等类似问题提供参考。
The jacking mechanism of ZGM-7 automatic tray-seedling grafting machine developed by our research group has failure problems in the process of jacking seedling by needle. For solving those failure problems, the software EDEM (enhanced discrete/distinct element method) is used in the research of the process of jacking seedling by needle in this paper. The Edinburgh elastic-plastic cohesion model (ECM) is chosen as particle contact model and a variety of complex particle models with various material properties are established to simulate the realistic seedling substrate in the software EDEM. Furthermore, the relationship between the mechanism and the seedling substrate is studied in simulation. It takes the maximum jacking height of the bottom of seedling substrate as index parameter and analyzes the principles how the different factors, including needle diameter, needle length and jacking speed, influence the process of jacking seedling by needle. The simulation and experimental tests are designed and performed by response surface methodology. The actual experimental result is consistent with the simulation result. The both results show that needle diameter and jacking speed have a significant influence on the maximum jacking height of the bottom of seedling substrate, and the interaction between needle diameter and jacking speed is significant. The maximum jacking height of the bottom of seedling substrate increases monotonically and then slowly decreases monotonically with the increasing of needle diameter in the test level. The maximum jacking height of the bottom of seedling substrate increases monotonically with the increasing of jacking speed in the test level. The maximum jacking height of the bottom of seedling substrate increases with the increasing of jacking speed, when the needle diameter is large. The maximum jacking height of the bottom of seedling substrate decreases with the increasing of the needle diameter, when the jacking speed is small. The maximum jacking height of the bottom of seedling substrate gradually increases and then decreases with the increasing of the diameter of steel needle, when the jacking speed is large. The error between simulation and experiment result is only 0.7%-7.2%. Among those errors, larger errors only exist in phenomenon of dropping and crooking seedling substrate. The realistic seedling substrate has a root system, which prevents the insertion of needle. Thus, the seedling substrate is easier to be dropped and crooked early. However, the error when vertically jacking seedling substrate is less than 2.1% in simulation and experiment. The successful maximum jacking height of the bottom of seedling substrate is 144 mm, which is proposed as the optimization target. The software Design-Expert is used to optimize the simulation results within test level. The optimal parameters of the simulation result are needle diameter of 2.28 mm, needle length of 12.28 mm and jacking speed of 0.09 mm/s. The simulation optimization parameters are applied to the actual mechanism. It's found that the effect of simulation optimization is significant and the success rate of jacking seedlings is 95.3%. This study greatly improves the operation effect of jacking mechanism of ZGM-7 automatic plug-seedling grafting machine, and it provides reference for the similar problems like jacking up the discrete matrix by needle. Meantime, the reliability of simulation results has been proved in this paper. So, the experimental results can be replaced by simulation results, which will reduce actual test workload significantly and shorten the equipment development cycle obviously. The method in this paper achieves a good simulation effect, which can be applied to other similar complicated environments.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2017年第21期29-35,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金(51675011)-盆花移栽机筑模成穴机构多因素作用优化设计方法研究
关键词
农业机械
嫁接
优化
穴盘苗
钢针
顶起
响应曲面法
EDEM
agricultural machinery
grafting
optimization
enhanced discrete element method
seedling
needle
jacking
response surface methodology