| In this thesis,a rice seed-oriented filling method and seeding control were proposed to solve the problems of poor population precision separation and difficulty in precise adjustment of seeding control caused by the disorderly filling of rice seeds in the traditional rice seeding process of light and simple mechanized hill-drop seeding.Adjustment strategy,constructing a seed filling model of variable stacking of rice seeds and a mechanical model of the rice seed delivery process,and elucidating the key structural parameters of the orificegroove combination hole;utilizing the discrete EDEM simulation method,a high-speed camera,and image target tracking technology;clarifying the dredging and orientation process of rice seeds in the filling area;conducting the bench test and field test of the variably stacked rice seed delivery system.The main research contents are as follows:(1)Based on the physical and mechanical characteristics of rice seeds and the agronomic requirements for planting precision hill-drop seeding,a oriented filling type rice precision hill-drop seeding metering device is designed that uses orifice-groove combined holes for quantitative filling and analyzes the seeding holes and V-shaped grooves theoretically.The most crucial intrinsic factors are the combined hole-slot relative height,slanted cavity,and others.The best structural parameters of the seeding hole are the width of the largest seeding hole,which is 6.8-7.6 mm,and the width of the smallest seeding hole,which is 4.6-5.2 mm,as determined by the pre-test of seeding performance.The seeding rate of the seed metering device is obviously high.In the condition of low-frequency vibration,the reseeding rate of the seed metering device increased greatly to 85%,while the qualified rate decreased significantly and the missed seeding rate decreased little.The seeding performance of the seed meter was primarily impacted by the low-frequency vibration.(2)Using the discrete element software EDEM,a simulation model of the seed metering device was developed,and numerical simulation analysis of seed filling was conducted on three types of orifice plate styles and three types of guiding teeth,respectively,and the following ranking of disturbance intensity was determined: guiding tooth and introduction groove plate > guiding tooth plate > smooth plate;linear plate > rice-like plate > arcs plate;The average orientation rate of rice seeds in the observation area was steady and went towards 85% after the construction of a visual test bench.Various vibration circumstances positively influenced the orientation process of rice seeds in the hole-filling region,and the frequency distribution of the attitude angle of rice seeds tended to be concentrated within30°.(3)Divide the rice seed filling area and analyze the rice seed-oriented filling process by means of numerical simulation analysis;A full factorial simulation analysis is done on the V-groove inclination angle and the orifice attitude angle.The optimal seed-filling performance of the seed meter is achieved when the orientation angle of the V-shaped groove is 54° and the orientation angle of the shape orifice is 0°.The current qualifying rate,missseeding rate,and reseeding rate were 91%,3%,and 6%,respectively.The compressive force exerted on rice seeds during filling,transporting,and sowing is always less than 0.04 Newtons,which is far less than the maximum load rice seeds can support.(4)Perform experimental study on the seeding performance of the seed metering device,conduct the comparison test of the orifice plate and the comparison test with or without the introduction groove,and determine the optimal combination of the hole plate’s structural paramete rs;When the width of the large orifice is 7 mm and the width of the small orifice is 5 mm,according to the findings of the two-factor test,the seed metering device has good seeding performance under low-frequency vibration and no vibration situations,and the seeding is qualified.The rate is essentially higher than 90%;The results of the speed adaptability test and the variety adaptability test indicate the following: at the general forward speed of the direct seeding machine,the qualified rate of seeding in each group at different speeds is greater than 85 percent;the effective length and size of the seed metering device are both greater than 85%;and the seed damage rate of each variety does not exceed0.16%.When Huanghua Zhanshi was planted in large holes,the field seeding qualified rate was 90.21%,the missed seeding rate was 1.07%,the reseeding rate was 8.73%,the average hole diameter was 49.69 millimeters,and the average hole distance was 138.62 millimeters.The coefficient of distance variation was 11.57%.The qualified rate of field seeding was86.65%,the missed seeding rate was 5.87%,the reseeding rate was 7.75%,the average hole diameter was 42.33 mm,and the average hole distance was 203.78 mm when Fengliangyou3948 was seeded in small holes.The coefficient of variation of hole spacing is 11.55%,and all evaluation indicators satisfy the planting standards for dry hill-drop direct seeding with precision in the field. |
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