Design And Experiment Research Of U-shaped Cavity Type Precision Hill-drop Seed-metering Device For Rice

In this study,in order to improve the problems of precision hill-drop seeding for rice,such as complex structure of the seed-metering device,poor stability of seeding rate,low uniformity of hole spacing and easy damage of rice seeds when planting conventional rice with large sowing rate.A unique U-shaped cavity type precision hill-drop seed-metering device for rice was designed,innovatively puts forward a side filling cavity type seed metering plate which characterized with seed-dropping orifice and seed-filling orifice connected by the cavity.The characteristics of rice seeds material were studied,the key components of the seed-metering device were designed,the mechanical models of the process of seed filling and dropping were constructed,and the main structural parameters of the seeding plate were determined.EDEM software was used to simulate the seeding process of the seed-metering device.The bench test of the seed-metering device was carried out to clarify the suitable structure and working parameters of the seed platter,and the field seeding test of the seed-metering device was carried out.The main research contents are as follows:(1)Three kinds of conventional rice varieties with obvious difference in shape and size which were suitable for dry direct planting in the middle and lower reaches of Yangtze River were selected as follows: Huanghuazhan,Jingliangyou-1177,Tesanai-2.The water content,three-axis size,weight of one thousand seeds,density,angle of repose and sliding friction coefficient were studied,which provided the reference for the structure design of seed-metering device,analysis of seed metering process,construction of virtual simulation particle model and parameter setting.(2)Based on the mechanical characteristics of rice seeds and its agronomy requirements of hill-drop seeding,a unique U-shaped cavity type precision hill-drop seed-metering device for rice was designed.Adopt side filling mode,clear seeds by using the gravity of rice seeds,carry seeds according to the rotation of the cavity,simplify the mechanism of seed-metering device.The process of seed filling and dropping was analyzed theoretically,and the main structural parameters of the seeding plate were determined.The seeding objects was Huanghuazhan,the seed filling performance test was carried out to clarify the main factors affecting the seed filling performance of the seed-metering device.Within the range of test parameters,the precision seeding performance of the seed-metering device was better when the number,length,width and inclination of the seed-filling orifice were 20,10.6 mm,7.6mm and 0 degree,respectively.Correspondingly,the miss-seeding rate,qualified rate of hole number,reseeding rate and seed damage rate were 0.40%,94.00%,5.60% and 0.13%.(3)With the help of discrete element software EDEM,the simulation model of the seed-metering device was established.The sensitivity analysis of the contact parameters of simulated materials affecting the seed platter was carried out,and the contact parameters which had a greater influence on the seed-metering device effect were identified and calibrated.The simulation study of seed arrangement process was carried out to clarify the influence of the structure of stirring tooth and introducing groove on the seed arrangement plate on the seed filling effect.To carry out the simulation and optimization research on the structure parameters of the seed introduction tank,and to clarify the appropriate structure parameters of the seed introduction tank;a single factor simulation test was carried out to clarify the parameters range of suitable working speed and feeding height of the seed-metering device.(4)By means of high-speed camera and JPS 12 type seed-metering device performance test bench,experiments were carried out on the adaptability and uniformity of the seeds with different shapes and sizes,and the suitable structure and working parameters of the seed-metering device for the three varieties were obtained respectively.Seeding uniformity performance test results indicated that the seed-dropping angle very significantly affected the average value and qualified rate of hole diameter,and significantly affected the variation coefficient of hole distance.The suitable seed-dropping angle of seed-metering device was33°.Under the above range of seed-dropping angle,all the average hole diameter were not more than 26.12 mm,all the qualified rate of hole diameter were not less than 97.60%,all the average hole distances were about 140 mm,and all the variation coefficient of hole distance were not more than 7.02%.The results of field experiment showed that qualified rate of hole number,miss-seeding rate and reseeding rate were 90.28%,0.83% and 8.89%,respectively.And the average hole diameter of 46.71 mm,qualified rate of hole diameter of71.67%,average hole distance of 137.21 mm and variation coefficient of hole distance of12.64% were found in the field experiment.All the sowing performance satisfied the general precision direct hill-drop seeding requirement of conventional rice in field.The research result provided a theoretical reference for the simplification design of the mechanical seedmetering device.