基于离散单元分析与物场分析的盆花移栽手爪优化

Improvement of transplanting manipulator for potted flower based on discrete element analysis and Su-field analysis

该文针对盆花移栽作业过程中出现的移栽手爪提取基质不完整的现象,基于离散单元分析方法,利用EDEM(enhanced discrete element method)软件建立起机构(移栽手爪)、作用对象(带有根系的盆花基质)、作用条件(花盆)间的离散元仿真模型,对手爪钢针的插入和提离过程进行离散元仿真分析,确定基质断层为提取基质不完整的原因,并通过对基质提离过程进行受力分析发现,导致基质发生断层现象的根本原因是基质提离总阻力大于基质内部所能提供的最大凝聚力。鉴于如上分析,利用物场分析方法提出在原有系统中添加揉盆机构的解决方案,通过对揉盆机构工作过程进行离散元仿真分析发现,在揉盆机构的作用下基质与花盆之间产生了缝隙,使花盆对基质由于粘附作用产生的摩擦阻力降低,减小了基质提离总阻力,证明在工作过程中揉盆机构可以通过减小基质提离总阻力来解决基质断层问题。分别对添加揉盆机构前后的样机进行3组100盆的花苗移栽试验,移栽手爪完整提取基质成功率从84.67%提升到97.67%。该研究将EDEM离散单元分析与物场分析方法结合应用在机构优化设计过程,可以为盆间自动化移栽领域的设备研制与开发提供参考。

In the process of planting Anthurium andraeanum,people need to transplant the seedling from small pot to big pot to get more growth space.This work will not only spend much time,but also increase the cost of planting.Our research group has finished a design of the transplanting machine to realize the automatic transplanting of Anthurium andraeanum.However,during the usage of the machine,we found that the transplanting manipulator cannot take out the soil matrix completely from the small pot sometimes.Once the incomplete soil matrix is watered after the transplanting,the seedling will tilt.It will lead to the difficulty of sale.So taking out the soil matrix completely from the small pot will be one of the most critical technical problems in the transplanting mechanical system for potted anthurium.Operation objects can be regarded as rigid body in the traditional mechanism design,however,the potted soil matrix,as the operation object of transplanting manipulator,belongs to the discrete body,although the potted matrix can be condensed as a certain shape under the limitation of the pot.In the process of sinking the needle into the soil matrix and taking it out,it is hard to keep the original stable shape and take out the matrix completely due to the lack of the cohesion of matrix itself and the adhesion effect between the pot and matrix.This condition will lead to the failure of transplanting.Based on the discrete element analysis method,this paper established discrete element simulation model among mechanism（transplanting manipulator）,action object（matrix with rootstock）,and action condition（pots） by EDEM（enhanced discrete element method） software to analyze the whole process of transplanting.In the simulation,we found that when the transplanting manipulator takes out the soil matrix,a fault happens inside the soil matrix.After the analysis for this simulation phenomenon,we knew that when the total resistance force is greater than the maximum cohesive force that soil matrix can offer,the matrix will be broken and become the incomplete matrix.According to the above analysis,we started to use the Su-Field analysis method to solve this problem.By using the component analysis and functional model,the transplanting mechanical system was known more,and we focused the key point on the harmful adhesion effect between small pot and soil matrix.With the help of Su-Field model and standard solution,we fully analyzed the resources of the mechanical system and translated the Su-Field model into the solution of pot pressing mechanism finally.And for this solution,we also done the discrete element simulation by EDEM and found that the pot pressing mechanism can make a crack and reduce the friction between the soil matrix and pot.With the reduction of friction in this way,the total resistance force cannot be greater than the maximum cohesive force that soil matrix can offer most of the time.It will effectively avoid the appearance of incomplete soil matrix.So the solution of pot pressing mechanism is reasonable and feasible.On the basis of the solution,we done the optimization for the original transplanting mechanical system.The transplanting experiment of 3 groups of pots（100 pots each group） was carried out respectively for the transplanting manipulator before and after the optimization.We found that the success rate of taking out soil matrix completely is improved from 84.67%to 97.67%.In this study,the discrete element analysis and Su-Field analysis method in TRIZ（theory of inventive problem solving） are combined to apply to the mechanism optimization design process,which can provide reference for the research and development of automated transplanting equipment about potted plant.