Research On Pneumatic-mechanical Compound Peanut Precision Seed-metering Device

In response to the problems of low adsorption rate,high wind pressure demand and high missed seeding index when sowing large-diameter seeds such as peanuts by the air suction precision seed-metering device.This paper was based on the method of“mechanical disturbance+pneumatic and mechanical coordination of seed extraction+block air flow to unload the seed+mechanical carrying seed+self-weight seeding”,a pneumatic-mechanical compound peanut precision seed-metering device was innovatively designed.This structure uses V-shaped bumps to disturb,position and holds the seeds,and coordinate with the negative pressure of the work,could effectively improve the filling performance and the eligibility index of peanut single seed precision seeding.On this basis,in order to further reduce the working negative pressure of the metering device and improve the seed filling performance and seed cleaning effect,the structure of the metering disc had been optimized,improved and tested.The curve-shaped seed guide track and the self-cleaning bulge were integrated into the metering plate,and a self-cleaning structure of driving and guiding was developed.（1）Taking the commonly used variety"Si Lihong"peanut seeds in Xinjiang area as the research object,the material characteristics such as the three-axis size,sliding friction angle,rolling friction angle and natural angle of repose of the seeds were studied.According to the test,the peanut seeds were divided into three shapes and sizes:ellipsoid,spherical and flat according to the shape difference,which provided a theoretical basis for the design of the structural parameters of the pneumatic-mechanical compound peanut precision seed-metering device.（2）Explain the structure of the metering device and its working principle.The metering device was divided into seed filling area I,seed clearing area II,seed discharging area III,seed carrying area IV,seeding area V and transition zone VI.The structural parameters of the key parts of the seed-metering device were optimized.The diameter of the seed-metering disc was 165 mm;the number of holes was 10,and the diameter was 5 mm.the V-angle was 90°.The force and trajectory of the seed during the seeding process were analyzed,and the factors that affected the vacuum of the negative pressure chamberΔP for adsorbing the seeds were clarified.In the unloading area,the angleθ₁for the seeds to slide smoothly was71°.In the seeding area,the maximum angleβ_maxto achieve smooth seeding was 70°.To ensure that the seeds fall into the duckbill mechanism accurately,the angleδ₃to achieve precise seeding was 17.5°.（3）The simulation analysis of seed disturbance performance of 4 kinds of structure seeding discs was carried out,and the results showed that the seed disturbance mechanism had a significant impact on the kinetic energy of seeds,and the ring-groove double-V-shaped bump of the P₄disc had the best seed disturbance effect.The seeding performance test of the ring-groove double-V-shaped bump structure seeding plate was carried out,the results showed that the seed-metering device had the same effect on the three shapes and sizes of the seeds,the rotating speed of the seeding disk and the working negative pressure were the test factors.The precision seed-metering device had good adaptability.Among them,the seeding performance for spherical seeds was the best,and the seeding qualified index was 94.2%.The mixed unclassified seeds were selected,and the two-factor five-level quadrature orthogonal rotation center combination test was carried out,and the test result was:When the rotation speed of the seeding disk was24 r/min and the working negative pressure was 4.2 k Pa,the qualified index reach 94.1%,the multiple-seeding index was 4.0%,the missed seeding index was 1.9%,and the damage index was only0.48%.Field verification tests under three speed levels had been carried out.The results showed that when the tractor travels at 1.8 km/h（corresponding to the seed-metering speed of 25 r/min）,the seed-metering device had the best seeding performance and the seeding qualified index was 92.9%,the multiple-seeding index was 4.0%,the missed seeding index was 3.1%,and the damage rate was 0.6%,which met the requirements for peanut precision seeding.（4）Based on the principle of steepest drop line,the structure of the curved seed guide track of the optimized seeding disc was designed,and the genetic algorithm was used to solve the steepest drop line curve L;the coordinates of the key points of the self-clearing bulge curve were determined,and the curve equation of the self-clearing bulge was obtained by using Matlab software;the indoor The bench test had determined the optimal parameter combination of the optimized seeder in the range of 3 operating speed ranges,and it is concluded that when the speed of the seeder disk was 18.4 r/min and the working negative pressure was 1.1 k Pa,the seeding the qualified index reach 96.4%,the multiple-seeding index was 1.9%,the missed seeding index was 1.7%,and the damage rate was only 0.33%.