| The common drill planter or large row spacing hole planter have large soil disturbance,large seed consumption,large sowing row spacing and poor seed distribution uniformity in the field,which are difficult to meet the agronomic requirements of narrow-row-dense-planting.The narrow-row-dense-planting crops precision planting lack suitable seeding machinery.Based on the motion principle of planetary gear train,this paper designed a kind of planet-wheel dibbling full-constrained seed guiding device matching with multi-row parallel pneumatic needle seed metering device and determined the structural parameters of the seed guiding device.Combined with a 16-row multi-row parallel pneumatic needle seed metering device,a narrow-row-dense-planting precision planter that can realize ridging,precision seeding,orderly guiding and coating soil was developed.The overall structure and working principle of the planter and the transmission scheme of the whole machine were designed.The seeding bench experiment was carried out to obtain the optimal combination of seeding parameters.The working performance of the planter was verified by field experiment,and the optimization and improvement of the machine and the versatility of the whole machine were studied.The main research contents and results are as follows:(1)Overall design and analysis of narrow-row-dense-planting precision planter.Through understanding the agronomic requirements and technical difficulties of narrow-row-dense-planting crops planting,a narrow-row-dense-planting precision planter was designed,which can complete the operation of ridging,precision seeding,orderly guiding and coating soil at one time.The overall structure,working principle,main technical parameters and operating state of the planter were described.The driving system of the planter was analyzed,and the relationship between seeding distance and driving device diameter,total transmission ratio,radial hole number of seed metering device and slip coefficient was calculated and the number of teeth of driving sprocket,seed guiding sprocket and seed metering sprocket were determined.The relationship between the forward speed of planter and the rotation speed of seed metering device was calculated.When the rotation speed of seed metering device is 12.00～18.00r/min,the corresponding forward speed of planter is 0.10～0.15m/s.(2)Design and experiment of pneumatic needle seed metering system.Based on the24-row pneumatic needle seed metering device,a 16-row pneumatic needle seed metering device was improved and designed.The structure and working principle of seed metering device was described,and the design and selection of pneumatic system were carried out.The triaxial dimensions,spherical degree and 1000-grain weight of cherry radish,spinach and American ginseng seeds were measured and analyzed.The diameter of needle hole of cherry radish,spinach and American ginseng seeds were determined by theoretical calculation and single factor experiment.According to the single factor experiment analysis of cherry radish seeds,the level range of orthogonal experiment factors were determined.The three factors and five levels quadratic regression orthogonal rotation combination experiment of cherry radish seeds was carried out.The regression model was established,significance analysis,influence effect analysis and parameter optimization were carried out,and the primary and secondary order of factors affecting the qualified index,multiple index and missing index were determined.The optimized parameters were determined as follows: rotation speed of seed metering device 12.00～18.20r/min,negative pressure-1.80～-2.90 kPa,and positive pressure 1.20 kpa.When the rotation speed of seed metering device was 15.00r/min,the negative pressure was-2.50 kPa,and the positive pressure was 1.20 kPa,the qualified index was 91.9%,the multiple index was 4.6% and the missing index was 3.5%.(3)Study on seed arrangement adaptability of pneumatic needle seed metering device.The single factor experiment was carried out on the negative pressure of seed suction and the positive pressure of seed unloading,and the negative pressure and the positive pressure range were determined.The rotation speed of seed metering device was set at 15.00r/min,and the two factors and three levels all-factor experiment of the negative pressure and positive pressure were carried out.The optimal parameters combination of spinach seeds were determined as follows: rotation speed of seed metering device 15.00r/min,negative pressure-3.00 kPa,and positive pressure 1.50 kpa.Under the optimal parameter combination,the qualified index was 91.9%,the multiple index was 3.7% and the missing index was 4.4%.A validation experiment was carried out on the optimal parameters combination of American ginseng for accelerating germination.When the rotation speed of seed metering device was set at 15.00r/min,the negative pressure of seed suction was-4.40 kpa,and the positive pressure of seed unloading was2.90 kpa.The qualified index,multiple index and missing index were 90.8%,5.7% and3.5% respectively,which were consistent with the previous experiment results.It was determined that the seed metering device had good adaptability to the three typical special-shaped seeds of cherry radish,spinach and American ginseng with small size,medium size and large size.(4)Design of planet-wheel dibbling full-constrained seed guiding device.Based on the motion principle of planetary gear train,a planet-wheel dibbling full-constrained seed guiding device matching pneumatic needle seed metering device was designed.The structure and working principle of seed guiding device was described.Through mechanism analysis,the parameters of sun wheel,idler wheel and planet wheel in planetary gear train were determined.The theoretical analysis and high-speed photography experiment of seed unloading process were carried out to determine the horizontal displacement and influencing factors of seed unloading trajectory.The results showed that: The horizontal displacements of American ginseng,cherry radish and spinach seeds in the front and back directions mainly distributed within ±10mm,and the opening size of the inserting apparatus was determined to be 12mm×28mm.The theory and simulation analysis of seed guiding trajectory were carried out to determine the motion law of inserting apparatus and the low-position zero-speed dropping condition.According to the theoretical and simulation analysis of the guide trajectory,the motion law of inserting apparatus and low-position zero-speed seed dropping conditions were defined.According to the theoretical and simulation analysis results,the relation curve between the cam angle and the pendulum angle of the inserting apparatus was determined.Based on the inversion method,the profile of the dropping control cam was designed.(5)Field experiment and improved design of narrow-row-dense-planting precision planter.The soil parameters were measured,the results were as follows: the soil type was sandy loam,with 14.75% soil water content and 261.96 kpa soil firmness.Under the working conditions of negative pressure of seed suction of-4.50 kpa,positive pressure of seed unloading of 3.00 kpa,and operation speed of 0.54km/h,field sowing experiment of American ginseng was carried out.The results showed that: The seeding effect of this planter was good,the qualified index of seed per hole was 86.2%,the multiple index was4.4%,the seed-missing index was 9.4%,the qualified index of seed depth was 92.8%,and the qualified index of hole distance was 93.9%,which meet the agronomy requirements of American ginseng planting.The structure,working principle and main technical parameters of the improved narrow-row-dense-planting precision planter were described,and the trial production and processing of the improved scheme was carried out. |
