Design And Mechanism Analysis Of Ripple Surface Pickup Finger Maize Precision Seed Metering Device

Maize has been the most important grain crop in China with an increasing area in recent decades,which has the ternary structure attribute of “grain-feeding-tradition”.Maize cultivation pattern has great significance to ensure food security,promote animal husbandry industry,increase peasantry income and grain production safety.With the continuous development of Chinese corn industry,it has become the primary task of grain production in China to improve the level of maize yield under the condition of ensure the relative balance of maize planting area.At the same time,it puts forward higher requirements for matching mechanized planting technology.Precision planting is the technique of using precision planter to sow seeds to the predetermined position of soil accurately and quantitatively,which is completed by the comprehensive effects of several operating processes and working parts,such as profiling,furrowing,seeding,soil covering and pressing.Precision seed metering device is the core part of precision planting machine,which directly affects the quality and efficiency of sowing.The research and development of precision seed metering device is of great significance to promote precision planting technology and improve the level of mechanized maize cultivation.Precision seed metering device can be divided into two types based on working principle: mechanical and pneumatic.Mechanical seed metering device which has the characteristics of reliable,convenient operation,installation and maintenance is major seed metering device,which has already been increasingly widespread in China for the advantages of high planting quality.Meanwhile,this kind of seed metering device still has some obvious shortages,such as instability performance and unsuitability for high speed operation.It is also great affected by the shape and size of maize seeds in actual field.These shortages have greatly restricted its expanded application.This paper mainly aimed to make breakthroughs in the core and key technologies of mechanical precision seed metering device.The complete and systematic research of precision planting technology and device for maize has been conducted combining agricultural machinery and agronomy,which can provide a theoretical support and technical reference for improvement and optimization of maize precision seed metering device.Based on referring to large numbers of domestic and international aspects of the basic references of precision seed metering device,this research about optimization design and mechanism analysis of pickup finger maize precision seed metering device was conducted combining the theoretical analysis,discrete element simulation analysis,high-speed photography technology,bench performance experiment,configuration design of prototype and so on.Aim to this subject,the paper mainly studied following six aspects parts,Material properties measurement and parameters calibration of maize seed,Optimization design and analysis of pickup finger maize precision seed metering device,Numerical simulation and analysis on seeding performance of pickup finger maize precision seed metering device based on discrete element method,Analysis and experiment of guiding and dropping migratory mechanism on pickup finger maize precision seed metering device based on high-speed photography,Bench performance experiment of pickup finger maize precision seed metering device,Configuration design and field experiment of pickup finger maize no-tillage precision planter.The main contents of this paper were as follows:(1)Material properties measurement maize seed for planting in cold Northern-ChinaDifferent types maize seeds widely planted in Heilongjiang province were selected as research object,and the basic physical parameters of various types maize seeds were measured such as geometric size distribution,moisture content,1000-grain weight and density.The test bench for measuring friction and mechanical properties was designed and built based on high-speed photography technology.Static friction coefficient,rolling friction coefficient and restitution coefficient between maize seeds and various materials in different conditions were obtained.And then stiffness coefficient and elasticity modulus of various types maize seeds in all directions could be determined by electronic texture analyzer.On this basis,contrast verification test of repose angle and collision test of single maize seed were conducted through virtual calibration method to verify the accuracy and reliability material characteristic parameters.This section could provide an important reference for the precision planting technology,agricultural machinery system modeling and its numerical simulation.(2)Optimization design and analysis of ripple surface pickup finger maize precision seed metering deviceA pickup finger maize precision seed metering device was designed to improve the performance and adaptability of mechanical seed metering device and to meet the requirements of precision planting,which could perform operations of seed-clamping and filling,vibration seed-cleaning,flexible seed-guiding.The overall structure and working principle of the seed metering device were illustrated and analyzed.The optimal design of structural parameters of key components was conducted,such as the ripple surface type pickup finger,seed-filling adjusting mechanism,compound vibration seed-cleaning system and steady migratory seed-guiding system.And then the systematic working mechanism of whole cycle was conducted through theoretical analysis including seed-filling,seed-cleaning,seed-guiding and seed-dropping to analyze main factors which affected the performance of seed metering device.This section could provide a theoretical basis and important reference for seeding performance numerical simulation,high-speed photography measurement,working parameters optimization,bench performance experiment and configuration design of precision planter.(3)Numerical simulation and analysis on seeding performance of pickup finger maize precision seed metering deviceIn order to study the motion characteristics of maize seed and the influences of rotational speed and size grade on seeding performance,this paper took the pickup finger maize precision seed metering device was as research object to explore seed-clamping and seed-filling mechanism.The dynamical clamping models of pickup seed finger were established based on its working principle.On this basis,the optimization design of structural parameters of pickup seed finger was conducted.The discrete element method(DEM)model of pickup finger precision seed metering device and the seeding performance experiments of numerical simulation were established by the discrete element software EDEM.The rotational speed and the size grade were selected as experimental factors,and the qualified index,replay index,missing index and variation coefficient were selected as experimental indexes.The mainly reasons of reply-seeding and miss-seeding on different size grades of corn grains were researched.On this basis,the experimental prototype of seed metering device was manufactured.The simulation results showed that as the rotational speed was between 15r/min and 45r/min,with the increase of rotational speed,the seeding quantity had a decreasing trend to all size grades of maize seeds,and the seeding quantity of big flat maize seed was best,that of big round maize seed was better,and that of small round maize seed was worst.(4)Analysis and experiment of guiding and dropping migratory mechanism on pickup finger maize precision seed metering deviceIn order to improve the guiding migration performance of pickup finger maize precision seed metering device,the steady migratory mechanism of guiding-seed system was studied.The kinematics and dynamics models of guiding-seed and dropping-seed processes were established based on its working principle.The influences of various factors on dropping trajectory and migration stability were analyzed.A kind of dropping trajectory measuring test platform was designed and built referred to the theory of mirror reflection.And then the three-dimensional space velocities of the falling maize seed were measured and analyzed by high-speed photography and target tracking technology.The single factor tests for factors including the rotational speed and the tilt angle were carried out and the corresponding regression equations were obtained by analysis.Experimental results showed that as the rotational speed was between 15r/min and 45r/min,the tilt angle was 0o,the horizontal displacements of trajectories of frontal and profile dropping seed increased with the increasing of the rotational speed and the seeding variation coefficient decreased with the rotational speed.As the rotational speed was greater than 35r/min,the trajectories and landing positions of corn grains was gradually discrete and the seeding variation coefficient had significantly increased.Its horizontal displacements of frontal trajectory were stabilities within the range of(12.9~14.3)mm,the horizontal displacements of profile trajectory were stabilities within the range of(3.7~4.8)mm,and the average variation coefficient was 15.13%.The dropping seed angle decreased with the increasing of the tilt angle under the rotational speed was 30r/min and the tilt angle was between-12o and 12o.This section could provide guidance and direction for the research of mechanical precision seed metering device and its matching seed tube.(5)Bench performance experiment of pickup finger maize precision seed metering deviceIn order to improve the seeding performance of pickup finger maize precision seed metering device and to obtain the best operation parameters,bench performance experiment was carried out by JPS-12 type seed metering device performance test-bed.Seeding performance optimization experiment(single factor rule experiment and multi-factor optimization experiment)and seeding performance comparison experiment(suitability experiment of various types maize seeds,performance comparison experiment of various seed metering devices and vibration adaptability experiment)were conducted with the rotational speed of seed metering device,tilt angle of seed metering device and wire diameter of spring as experimental factors,and the qualified index,replay index,missing index and variation coefficient as experimental indexes.Based on experimental data,a mathematical model was built by Design-expert 6.0.10 software.The results showed that,the qualified index was 88.90% and variation coefficient was 16.56% under the conditions of 38.92r/min rotational speed,0o tilt angle,and 0.90 mm wire diameter respectively,which could meet the requirements of precision planting.(6)Configuration design and field experiment of pickup finger maize no-tillage precision planterIn order to solve the problem of poor adaptability,low working efficiency,easily blocked opener,and easily burnt seedling with the vertical fertilizer of traditional planting machine,the pickup finger maize no-tillage precision planter was configuration designed based on mechanized conservation technology,in view of meeting the agronomic requirements of rice planting in the northeast region of China.The structural parameters of key components were optimal conducted,such as fertilizer opener assembly,opposed-piston grass dividing and stubble cutting device,double disc opener with synchronous limited depth assembly and V-compacting device.Field performance experiment was carried out,and test results showed that,the opposed-piston grass dividing and stubble cutting device could separate the grass and straws away from the seeding line,effectively protecting the opener from being blocked and avoiding seed spilled on straw.With the forward speed of precision planter less than 9km/h,the qualified index was greater than 80.95%,which satisfy the maize agronomy requirement.