Abstract
Field breeding experiments are small area trials conducted in plots for breeding new crop varieties, which is important to improve crop quality and seed propagation. As a major part of field breeding experiment, plot sowing has a significant impact on the test results. The plot drill machine is a special sowing machine used for field breeding experiment, which can complete supplying, filling, shipping, seeding, and dispensing. Among them, the uniformity of sowing is directly effected by the performance of centrifugal seed dispenser. However, the research of seed dispenser is insufficient, such as the influence of structural parameters, rotational speed and sowing rate on the seeding uniformity, which cannot met the requirements of the breeders and still need to further improved. In order to improve the seeding uniformity of plot seeder, centrifugal seed dispenser was taken as the research object, and motion characteristic was analyzed in the process of centrifugal dispensing seed. According to the analysis of kinematic characteristics, the centrifugal movement of wheat granules was mainly affected by dispenser rotation speed, dispenser angle, and dispenser distance. In this research, the combination of EDEM and experimental verification were used to analyze the influence of various test factors on the uniformity of dispensing seed. When the sowing rate is 1 000, 2 000 and 3 000 seeds, the three-factor and three-level orthogonal test was designed with dispenser rotation speed, dispenser angle, and dispenser distance as test factors, and the variation coefficient of seeding uniformity was used as the test index, to obtain better combination of parameters. Among them, dispenser rotation speed was set at 1 100, 1 250 and 1 400 r/min, dispenser angle was selected 90, 120 and 150°, dispenser distance was choose 17.5, 22.5 and 27.5 mm. The simulation results showed that the order of importance was followed by dispenser rotation speed, dispenser distances and dispenser angle in the case of 2 000 seeds and 3 000 seeds. When the sowing rate was 1 000 seeds, the order of importance was followed by dispenser rotation speed, dispenser angle and dispenser distance. According to the analysis of variance, the dispenser rotation speed has a significant effect on the variation coefficient of seeding uniformity when the sowing rate was 1 000 and 2 000 seeds, and has some effect when the sowing rate was 3 000 seeds. The dispenser angle has a certain significant effect on the variation coefficient of seeding uniformity when the sowing rate was 1 000 and has no effect on other seeding rates. Dispenser distance has a certain effect on the variation coefficient of seeding uniformity when the sowing rate was 1 000 and 2 000 seeds, and has no effect when the sowing rate was 3 000 seeds. The test bench was set up. Under the optimal combination of parameters, test was repeated three times to get the main value of variation coefficient of seeding uniformity. The tests revealed that the better combination of parameters was that the dispenser rotation speed was 1 250 r/min, the dispenser angle was 120° and the dispenser distance was 17.5 mm. When the sowing rate was 1 000, 2 000 and 3 000 seeds, the variation coefficient of seeding uniformity of were 5.18%, 4.45% and 3.98%, respectively, which were 0.36%, 0.14% and 0.55% different from the simulation results, the bench test and simulation test results were basically the same. The grain damage rate were 0.17%, 0.13% and 0.14%, and the grain damage was lower, which reached the requirements of plot sowing. The research results could provide a reference for optimizing structural parameters and improving of seeding performance of centrifugal seed dispenser in plot drill.
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