Working Mechanism Analysis And Experimental Research On Two-stage Double Vibration Rice Precision Seeder

Hybrid rice is a high-yield rice variety with good quality.It has been widely cultivated in China.To ensure high tiller ability and high yield production,the cultivation of hybrid rice requires sparse and precise seeding.The existing rice mechanical sowing techniques are hard to satisfy the requirements for the low and precise seeding rate of hybrid rice.High-yield cultivation techniques are not compatible with superior varieties,and the high-yield advantages of hybrid rice cannot be fully utilized.As a result,the cultivation of hybrid rice is very labor intensive,which restricts the development of rice planting mechanization in China.Therefore,it is urgent to study the mechanism of precision sowing techniques for hybrid rice,so as to achieve the technical requirements for precision sowing of hybrid rice and increase the level of mechanized cultivation of hybrid rice.In this paper,the precision seeding mechanism of two-stage double vibration rice precision seeder for rice seeds was studied.The electromagnetic vibrator and pneumatic vibrator were used for vibration.Based on the theory of discrete element method and vibration mechanism,the flowing and feeding process of rice seeds under the action of the cross diversion seeds box and the spiral scoop-type grooved wheel were analyzed.The distribution pattern of rice seeds in T-type plate was studied,and a continuous queuing model of seeds in the vibrating plates was established.The uniform distribution and orderly queuing conditions of rice seeds in the seed-uniforming device under vibration were proposed.The experimental parameters and working performances of the seed-supplying and seed-uniforming device were optimized by the experimental study.Based on a two-stage double vibration rice precision seeder,a direct-seeding device for hybrid rice was developed,and the experimental study on the direct-seeding of hybrid rice was conducted,which provided a new device for the development of rice direct-seeding technology.The main research contents and conclusions are as follows:?1?The structure and working principle of the two-stage double vibration rice precision seeder were systematically analyzed,and the relationship between the multilayer cross diversion plates with spiral spoon-type grooved wheel structure and rice seed flow was constructed.The rice seeds movement theory model under the pneumatic vibration of the seed-uniforming device were set up.The two-stage double vibration precision seeding process under the electromagnetic vibration and pneumatic vibration has been created for seed-supplying and seed-uniforming.Secondly,based on the theory of granular particle mechanics and infinite slit hole arches in silos,the influence of cross diversion type vibration seeds boxes on the flowing and filling process of rice seeds was investigated.Thirdly,The vibrating seeding performance test was used to optimize the pneumatic vibratoras thevibratingsourceforthe seed-uniformingdevice.The single-degree-of-freedom forced vibration system model for the seed-uniforming device under the pneumatic vibrator and the theoretical movement model of rice seeds in the vibrated plate were constructed to analyze the beating and sliding conditions of rice seeds.At last,The vibration frequency,amplitude of vibrated plate and the angle of seeds trough plates were determined as the main factor that affected the flow characteristics and seeding performance of rice seeds.The above conclusions provided the theoretical basis for analyzing the working mechanism of the precision seeder.?2?The key parameters of the discrete elements for rice buds were calibrated.The discrete elements characteristics of the rice buds were firstly analyzed,and the discrete element model of rice bud was constructed,which laid the foundation for the discrete element simulation of the rice precision seeder.The internal wall collapse method,sidewall collapse method and gravity balance method were used to simulate and test the friction angle of rice seeds.Then,the regression analysis was used to establish the ternary regression relationship of the following factors,including the coefficient of static friction between bud seeds and stainless plate,coefficient of static friction between bud seeds,coefficient of rolling friction between bud seeds,the three friction angles of rice bud seeds.The measured results of rice seeds frictional angles were used as the correction index to solve the regression equation,and the contact parameters of rice seeds under different water content conditions were calibrated.The verification test showed that the simulated error after parameter calibration was less than 2.75%,and the calibration model could be used for multiple rice varieties such as Guodao No.1,Hengfengyou 1179,Huayouyou 1179,Huahang No.38 and Huahang No.31.The discrete elements for rice buds provides theoretical basis for dynamic simulation of precision seeding process.?3?The software EDEM was used to simulate the working process of the quantitative seed-supplying device.The flowing characteristics of rice seeds in the vibrated seeds box were described using the cloud map of rice seeds speed distribution,disconnection of seed layers,retention of local seeds,and bulkiness of seeds.Then,The seed-supplying posture,compressive force,and distribution uniformity of the rice seeds in the spiral grooved wheel,the spiral scoop-type grooved wheel and the cell wheal were analyzed.The spiral scoop-type grooved wheel was determined as the best seeding performance.At last,The cloud map of rice seeds speed distribution in the seeds box was plotted using Python programming,and the flow characteristics of the rice seeds during the seed-supplying process were described by the breakage time of different seed layers,the area of retention of local seeds,and the bulkiness of the seeds.It is clarified that periodic small amplitude vibration of the vibrated plate had an effect on relieving funnel flow,stabilizing the flow rate and the distribution density of rice seeds.Combined with the seed performance test,it was found that the electromagnetic vibration could increase the frequency of seed-supplying by 3.64%to 5.52%and improve the seed stability by 1.33%to 2.47%,which optimized the seed-supplying performance.?4?The none-sliding Hertz-Mindlin contact model based on the discrete element method was used to analyze the vibration seeding mechanism of the seed-uniforming device.The distribution of the rice seeds on the T-type plate and the discipline of seeds ordered queuing on the trough plate were firstly explored by using the counting grid and the area dividing grid.Then the structure and working parameters of the precision seeder were optimized combined with the experimental study.The connection with the theoretical model of rice seeds movement was established through the simulation analysis of the vibrating and homogenizing process for single rice seed,then the movement regularity of rice seed in the process of seed-uniforming was verified.The distribution and flowing characteristics of rice seeds under different vibration intensity were studied.the air pressure value of the pneumatic vibrator with better seeding performance was determined to be 0.24to 0.28MPa.Nine different types of trough plates were designed among which the V-90°,V-105°,V-120°and U₁ type trough plate were optimized by analyzing the limiting effect,the uniformity of the flow velocity and the orderly queuing status of the rice seeds through various angles of the slots.Through the sowing performance tests,the best sowing performance was 93.91%for the qualified index and 0.94%for the hole index by using the V-120°grooved and 0.26MPa air pressure.The qualified index was 96.10%and the hole index was 0 when sowing conventional rice with 0.28MPa.?5?The two-stage double vibration rice direct-seeding device was developed,and experimental research was conducted on the direct-seeding performance of the hybrid rice precision seeds with low seeding rate,which provided a new device for the development of rice direct-seeding technology.The precise direct-seeding process for hybrid rice was sowed through the hole-forming mechanism and the seed-feeding tube.The cavity performance was improved effectively by using the thin-corner elbow seed-feeding tube to reduce the seeding speed.The direct sowing test was conducted.The results showed that the qualified index of seeding with direct-seeding device could reach 90.00%,the missing sowing index was less than 4.0%,the qualified index of hole spacing was 91.33%,the coefficient of variation of seedlings for seedling in hole was less than 7.10%,the coefficient of variation of seeding in drill was less than 7.89%,and the average rate of injury was0.67%.The sowing uniformity of the precision direct-seedling device was good,which could basically satisfy the agronomic requirements for direct-seeding of hybrid rice.This study provides research foundation for development of high efficient precision direct-seeding equipment for hybrid rice.