| Seeding is an important part of improving corn yield,and corn precision seeders with profiling function are widely used.At low operating speed,the seed guide can effectively ensure the uniformity of seed spacing,but at high operating speed,the role of the seed guide gradually weakens and the uniformity of seed spacing gradually deteriorates.In response to the problems that seeds and seed guide tubes collide and bounce under high speed operation,resulting in lower sowing qualification rate and poor spacing uniformity,a paddle belt seed guide device is designed to meet the needs of high speed precision sowing operation and improve spacing uniformity,which can effectively restrain the freedom of seeds during seeding,precisely control the trajectory of seed transport and reduce the collision and bounce phenomenon during seeding.The main findings of the paper are as follows.The main research contents and conclusions of the paper are as follows:(1)To design an electrically driven paddle belt type precision seed guide device for high speed operation,the overall structure and key components of the device are designed based on the structure of the seeding unit and corn seed size parameters.The paddle type synchronous belt is composed of paddles on the outside of the synchronous belt,the length,width and thickness of the paddles are 11 mm,11mm and 1mm respectively,the spacing between the paddles is 15 mm,and there are 79 seed delivery chambers composed of two adjacent paddles.And the kinetic and kinematic analysis of the key positions of seeds incorporated into the seed area and seeds cast out of the seed area during the seed guiding process was carried out,and the mathematical model was established to analyze the factors affecting the seed guiding performance of the device mainly including the paddle belt speed,the operating speed of the machine,the height of the seed guiding device from the ground and the influence of the installation angle of the seed guiding device.(2)The simulation analysis of seed delivery and seed dropping process of the seed guide device was carried out based on the discrete element simulation software EDEM.The simulation test was carried out by selecting the paddle spacing as the test factor and using the pass rate,reseeding rate,omission rate and coefficient of variation as the evaluation indexes to investigate the influence of paddle spacing on the seed guide performance of the device and further determine the structural parameters of the paddle belt.At the same time,the seed transport trajectory in the seed guide device was observed by combining high-speed camera technology,and the causes of reseeding and omission in the seed guide process were analyzed,and the simulation test was verified by high-speed camera test.The simulation results are reliable.(3)Bench tests were conducted on the factors affecting the operational performance of the seed guide.The number of empty chambers between two adjacent seeds in the paddle belt,the operating speed,the tilt angle of the seed guide and the height above the ground were selected as the test factors,and single-factor tests were conducted with the pass rate,reseeding rate,omission rate and coefficient of variation as the evaluation indexes to clarify the influence pattern of each factor on the performance indexes.The number of empty chambers between two adjacent seeds in the paddle belt,the tilt angle of the seed guide and the ground clearance height were selected as the test factors,and the pass rate,reseeding rate,omission rate and coefficient of variation were used as the evaluation indexes to conduct a three-factor,five-level quadratic orthogonal rotational combination test at the machine operating speed of 14 km/h.The order of influence on the evaluation indexes was obtained by the contribution rate method.The response surface analysis was conducted by Design-Expert12 software to determine the better interval of each factor,and the regression equation of the evaluation index was optimized by using the software optimization module,and the best performance of the seed guide was obtained when the number of seed spacing chambers was 5.16,the installation angle of the seed guide was79.40°,and the height of the device was 31.84 mm from the ground.The pass rate was 98.49%,the reseeding rate was 0.48%,the omission rate was 1.03%,and the coefficient of variation was6.80%.The results of the validation test were less inaccurate than the optimized results and met the requirements of precision seeding.(4)To comprehensively evaluate the performance of the paddle-belt seed guide in the field,a field comparison test was conducted between the paddle-belt seed guide and the conventional seed guide tube.The test results showed that under the conditions of high-speed sowing(12km/h-16km/h),compared with the seed guide,the sowing pass rate of the paddle belt seed guide was significantly improved,and the reseeding rate,omission rate and grain spacing variation coefficient were significantly reduced,and the performance of the paddle belt seed guide was better than that of the seed guide,which could better ensure the consistency and uniformity of grain spacing. |
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