A New Kind Of Method For The Optimizated Design Of Combination Inner-cell Corn Precision Seed Metering Device

This paper forces on Combination Inner-Cell Corn Precision Seed Metering Device, anew type of corn precision seed metering device, In-depth research of irregular shapeparticles, corn seeds modeling method, the complex structure of mechanical parts, meteringdevice modeling method, DEM calculation of the irregular shape of the particles, simulationanalysis on the design and working process are conducted on the working platformintegrated by CAE software base on DEM developed independently by the research groupand Pro/ENGINEER software. After that, the results acquired by experiments of seedmetering device are analyzed contrastively in order to establish a new kind of method for theoptimization design of corn precision seed metering device based on the discrete elementmethod. The main research works and results are as follows.1) Test analysis is conducted on the physico-mechanical properties of corn seed.Ping’an18, Jifeng218and Changdan228corn seeds are selected as the experiment samplesand then test is made on physico-mechanical parameters of these samples including size ofthree axes, rigidity coefficient, thousand grain weights, collision coefficient of restitution,coefficient of kinetic and static friction and density of pellet. Besides, analysis is also madethe influences of seed varieties, seed moisture content and other relevant factors on collisionrestitution, rigidity, friction and other coefficients, which offers parameter basis for thesimulation analysis of the working process of seed metering device.2) The general particle modeling methods are reviewed in this part, and then, five kindsof ball filling modeling method for irregular shape particle are summarized. Research isconducted on the modeling approach of irregular particles represented by corn seed. Basedon Ping’an18, Jifeng218and Changdan228corn seeds, a modeling method of corn seedparticles is proposed according to the shape features by three-dimensional scanner. In Pro/ENGINEER software environment, modeling method of manually filling spheres isestablished; based on the point cloud and triangle mesh surface, automatic ball particlesfilling algorithm is realized. A more refined corn seed particle model is completed.Furthermore, the model character is analyzed so that the method of the particle centroidcalculating and axes of inertia calculating are acquired. At the end of this part, the reliabilityof the model is verified by some simple cases, laying the foundation for follow-upsimulation of this paper.3) The boundary3D Pro/ENGINEER models is proposed, its3D discrete elementanalytical model is posed. On the basis of the further development on Pro/ENGINEERsoftware, in-depth research is done on identification and reading, eliminating redundancy,setting virtual boundary, motion, binding of material property, data storage and other problems of regular surface（applying graphic method) that contact with particle material inboundary Pro/ENGINEER physical model, more than ten kinds of regular surfaces model ofdiscrete element method including Plane, spherical, cylindrical surface, conical surface,surface of the spherical cap, round table and ball countertops are established, in the end, thegeneration of3D discrete element analytical model from3D Pro/ENGINEER physicalmodel of combination inner-cell corn precision seed metering device is realized.4) Research is made on that ball combination method of irregular particles is utilized tobuild the analytical model of the irregular particle of corn seed, including irregular particleneighbor searching method, contact judgment method, contact overlapping solving method,contact force computing method and particle motion computing method, and also thediscrete element computing method of irregular particles is established basically.5) Bench test of working process of combination inner-cell corn precision seedmetering device is conducted. Transparency organic glass is utilized to develop theexperimental prototype of combination inner-cell precision seed metering device and thenthree kinds of corn seeds (Ping’an18, Jifeng218and Changdan228corn seeds)and differentseed metering wheel rotate speeds(26.82r/min、39.33r/min、51.96r/min) are selected toconduct bench test of combination inner-cell corn precision seed metering device on theperformance test bench of PSJ seed metering device. Besides, high speed video system andblasting analysis software are applied to analyze the working process and performance ofseed metering device deeply. Three corn seeds’ single grain rate, double grain rate and holerate are acquired at three kinds of wheel rotate speed; three corn seeds’ clear seeds startingangle, clear seeds ending angle and seed surface tilt angle are analyzed at three kinds ofwheel rotate speed; furthermore, the trajectory of the seed and resultant velocity areanalyzed.6) Pro/ENGINEER software is used to design the3D physical model of combinationinner-cell corn precision seed metering device. Boundary modeling module developedindependently by the research group is applied to establish the3D discrete element analyticalmodel through reading the data of3D physical model of seed metering device. Simulationanalysis is conducted on the working process and performance of combination inner-cellcorn precision seed metering device through the discrete element simulation moduledeveloped independently by the research group and then the result of simulation analysisincluding the seeding performance indicators, clear seed angle, cast seed angle, the seedsurface tilt angle, the trajectory of seed, and the resultant velocity, with the data of bench testof seed metering device are contrasted. The results show that:①Under three kinds of speed,the maximum error of single grain rate and double grain rate is9.89%in simulation and test;②The simulation values of clear seed starting angle and clear seed ending angle are smallerthan experimental values, its absolute maximum error is8.49°,19.8°respectively, its relativemaximum error is12.38%;③Little difference between simulation and experimental valuesof casting angle, its absolute maximum error is2.78°, relative maximum error is14.11%;④Little difference between filling seed trajectory and casting seed trajectory in simulationand experiment, its relative error is less;⑤Value of seed resultant velocity in simulation and experiment is similar(in0.1unit),its relative error is almost less than10%, the varietytrend of simulation and experiment value is almost same;⑥Taking corn seed Changdan228for example, the effects of the simulation results of three different corn seed particle modelsare analyzed under three different stiffness coefficients(300、3000、30898N/m), threedifferent coefficients of friction and three different particle module methods.In summary, although a little errors exist between simulation and experiment results,but the variety trend is similar and little difference between simulation and experimentvalues. From these, the feasibility and effectiveness of analysis on the corn seed meteringdevice through DEM and self-developed CAE software is verified. A kind of new method foroptimized simulation design is realized.