The Research Of Position Control After Seed Contacting Soil In The Process Of Soil Covering And Rolling With Precision Seeder

The quality of precision seeding is comprehensively determined by theperformance of the five main working parts comprising of copying, trenching,metering, soil covering and rolling. The structure and performance issues of any partwill affect the overall quality of precision seeding operations. However, the researchon the above five parts were attached different importance in the past. A largenumber of literature data indicated that early research of precision seedingtechnology mainly focused on the ability to provide a uniform seed flow, whichresulted in the metering device’ quality and performance is superior to other parts inthe five major parts of precision seeding and its technical theory was also in theleading position. Until1990s, the experimental study of the other main workingparts has been paid more attention gradually, which developed the precision seedingtheory. The quality of precision seeding has also been greatly improved and theprecision seeding technology has gained rapid popularization subsequently.However, there is still lack thorough and systematic study in soil covering androlling parts. Neither fully considers the type characteristics, optimization of thestructure and motion parameters of soil covering and rolling parts, nor attaches moreimportance to the machining quality, which lead that precision seeder realized onlyprecision metering but failed to achieve precision seeding.Given the current theoretical and experimental problems on soil covering androlling parts in the existing research of the precision seeder, soil covering and rollingparts which greatly affect the status of soil flow after seed contacting soil and thedegree of soil compaction were taken as the study object. And then the position afterseed contacting soil and the thickness of soil covering were studied thoroughly andsystematically in this paper. The eight-shaped coverer, double-disc coverer andsqueeze-type coverer were made with organic glass and a variable force seedlingsroller with pressure sensor was also designed and developed. The seed leveldisplacement and thickness influenced by the structure motion parameters of threecovers during the soil covering process were analyzed through uniform experimentaldesign method and high-speed camera system. The influence of actual sowing depth and displacement changes caused by different pressure with roller was studiedthrough orthogonal experimental design method, the related mathematical modelswere developed and the best coverer type, structure motion parameters and pressureswere optimized. The simulation analyses of the state of soil movement and seedmotion in the process of covering and rolling were done using the SPH method inLS-DYNA software. The virtual manufacturing and motion simulation of unit coverand roller of precision seeder were studied with Solidworks software and the designaccuracy and efficiency were improved.This paper is part of the Specialized Research Fund for Doctoral Program ofHigher Institution （20040183024）, the Program of Science and TechnologyDepartment of Jilin Province （200405045） and the earmarked fund for ModernAgro-industry Technology Research System（CARS-01-33）, the main contents are asfollows：1. Three different types of soil covers comprising of eight-shaped coverer,double-disc coverer and squeeze-type coverer were developed.The angle, height,width and the front and back position of the covering components can be adjusted,so that the parameters are easy to be optimized. This structure can realize trials tomeasure the position after seed contacting soil in different conditions. Thesimulation models of three types of the soil cover and roller were developed usingSolidworks software and three different soil cover were made with transparentorganic glass in order to observing the motion state of the soil flow and seedsconveniently.2. The test of soil covering with three-type covers was accomplished on the soilbin tester based on high-speed camera technology and regression models of the seeddisplacement and the soil thickness were established under different conditionsusing the uniform experimental design method.The regression model of the seeds’ displacement of the eight-shaped coverer inthe soil is:The regression model shows that the primary and secondary factors affectingthe seed displacement of the eight-shaped coverer during the covering process werethe interaction of the field angle and the forward velocity of machine, the forwardvelocity of machine, the interaction of field angle and inclination angle, field angle and inclination angle in sequence.The regression model of the soil covering thickness of the eight-shapedcoverer in the soil is:The regression model shows that the primary and secondary factors affectingthe covering thickness of the eight-shaped coverer during the covering processwere the field angle, the interaction of field angle and inclination angle, theinteraction of covering device’s field angle and the forward velocity of machine, theinclination angle in sequence.The regression model of the seed displacement of the double-disc soil cover inthe soil is:The regression model shows that the primary and secondary factors affectingthe seed displacement of the double-disc coverer during the covering process werethe interaction of field angle and inclination angle, the inclination angle, the forwardvelocity of machine, the field angle, the interaction of the inclination angle and thespeed of operation in sequence.The regression model of the soil covering thickness of the double-disc soilcover in the soil is:The regression model shows that the primary and secondary factors affectingthe covering thickness of the double-disc coverer during the covering process insequence were the interaction of field angle and inclination angle, the interaction ofthe inclination angle and the speed of operation, the interaction of the inclinationangle and the speed of machine, the interaction of the field angle and the operatingspeed, the inclination angle, the field angle, finally, the operating speed.The regression model of the seeds’ displacement of the extrusion soil cover inthe soil is:The regression model shows that the primary and secondary factors affecting the seed displacement of the squeeze-type coverer during the covering process insequence were the interaction of the field angle and the operating speed, theoperating speed.The regression model of the soil covering thickness of the extrusion soilcover in the soil is:After the optimization of the above regression models, the optimumexperimental levels of the three types of soil cover are derived and the squeeze–typecover is defined as the optimal one. The optimal trial level is where the forwardvelocity of machine X1=4km/h, the inclination angle of the covering disc X2=30°,In this condition, the seed minimal displacement is△Y₁=0.0075m, the soilthickness△Y₂=0.0389m.The regression model shows that the primary and secondary factors affectingthe covering thickness of the squeeze-type coverer during the covering process insequence were the field angle, the operating speed, finally, the interaction of thefield angle and the operating speed.3、Based on the smooth particle hydrodynamics method（SPH）, The dynamicssimulation for soil motion status, seed’s displacement, covering thickness and theactual sowing depth were finished during the soil covering process with the soilcoverer. The measurement of soil physical parameters and mechanical parameterswas completed. The simulation results and the test results are consistent with eachother. seed displacement error of the eight covering process is Y₁=0.002m,covering thickness error is Y₂=0.012m; seed’s displacement error of the doubleround type covering process is Y₁=0.0068m, covering thickness error isY₂=0.003m. These results showed that using SPH to do simulation on contactingparts of the precision seeder is feasible.4、A variable force seedlings roller realizing that the rolling pressure fromquantitative regulation to stepless regulation was developed. The variable forceseedlings roller was developed making use of the Solidworks parametric modelingsoftware. Rolling pressure test system also were constituted using S-shaped sensor,digital display, computer and the tractor hydraulic components, which could realizethe rolling pressure from quantitative regulation to steptless regulation.5、Experimental study of the variable force seedlings roller was conducted. Theinfluence of rolling pressure and operating speed on the actual planting depth, the Seed displacement change, the firmness of the seedbed soil, germination rate,moisture content and seedling height were systematically analyzed. The orthogonalexperiment results show that the actual sowing depth reduced while the rollingpressure increased, the other test indices increased with the increase of the rollingpressure. Among them, the firmness index of the seedbed soil and seed displacementchange index increase faster with the rolling pressure persistently adding, plantheight decreases with the rolling pressure persistently increasing, and the rest of thetest indices increase slowly with the rolling pressures persistently increasing. Theseed displacement change in the impact of the rolling pressure changes was explored.The results showed that the size of the rolling pressure on seed grain distance changehas little effect, but has a greater impact on covering thickness. The influence ofrolling pressure on all test indices is greater than the influence of the operationspeed.6、The soil model was established using SPH softward and LS-DYNA rollingsimulation system has also been realized based on the SPH/FEM coupling algorithm.Based on the parametric modeling Solidworks software, a variable force seedlingsroller was developed and the motion simulation was carried out with the selection of1600-1800N rolling pressure and6km/h operation speed in the process. Simulationresults and the actual test results are close. The seed displacement error during therolling process is△Y₁=0.003m, the covering thickness error is△Y₂=0.0017m. It shows that the SPH method was feasible to simulate in the rolling process.The structure parameters and motion parameters of soil coverer and roller in theprecision seeder were studied thoroughly and systematically and the SPH methodwas used to do kinematics simulation analysis in this paper. This research provides anew approach to improve the design quality of the precision seeder, and it hasimportant significance for enriching precision seeding theory...