| With the continuous improvement of seed cultivation technology and quality, precision seeding technology application is more and more widely, and more strict to the requirement of precision seeding machine, requires both the seed metering device to provide uniform flow and precise hole grain number, affecting the seed sowing depth and the actual planting distance distribution of soil coverer is also put forward higher requirements. Good soil cover quality can not only guarantee the seeds have a suitable sowing depth, increase crop seedling emergence, still can make uniform crop planting distance, daylighting and ventilated to crops and late machine, etc.A new type of disc type covering device which is double disc type covering device has been put forward and designed in this paper in order to further explore the influences of structure and motion parameters of covering device on covering effect. A set of smaller diameter discs are installed inside of the discs based on common double disc type covering device aim at turning the previous one-time covering into two times covering. In the first step, the double disc type covering device uses its inside discs to push a small amount of soil with larger water content and in good condition close to seeds in groove. Then, it utilizes its outside discs to push the remaining soil to cover the surface. Lastly, it completes the covering operation. The change of seeds location caused by strike on seeds from a large number of soil during the one-time covering and the mixed between dry and wet soil can be reduced, even the contacting between the good characteristics of soil and seeds can be ensured though two times covering. Consequently, covering effect has been ensured and the probability of seeds has been improved. So, it contributes to the further development of the precision seeding technology.The 3-D geometrical modeling of double disc type covering device has been established by Solid Works software and it has been imported into ANSYS Workbench through the port between the Solid Works and ANSYS Workbench in this paper. The process of covering has been simulated and analyzed by combining the method of smooth particle hydrodynamics（SPH）. The result shows that the soil disturbance impacted by double disc type covering device is relatively small compared to common disc type covering device. So soil movement is relatively flat during the process of covering. Covering effect of two types of covering devices has been contrastive analyzed through soil tank modeling. The conclusion shows that the impaction on seeds from soil is relatively small during the process of covering of double disc type covering device. Therefore, the seed displacement is relatively small and it is in favor of realizing precision planting. The covering device has a minimum influence on seeds displacement when the inside covering plate edge plane diameter is 305 mm, covering speed 0.85 m/s, and the opening angle of covering device 50°,and the covering effect is the most ideal. Through the analysis of experimental data obtained the mathematical model of seeds displace and soil covering thickness between soil disc diameter, speed and opening angle, provides a theoretical support for the further study of precision seeding.By quadratic polynomial stepwise regression analysis was carried out on the test data, obtained the mathematical model Y1 and Y2 between the displacement of seeds and covering soil thickness and covering soil disc diameter, speed and covering plate opening angle:Y1 =1.914 +0.081 x3 -5.643 x22 -0.00365 x32 +0.0323 x1 x1 +0.00063 x1 x3Y2 = -18.814 +0.755 x1 -64.764 x2 +134.834 x 22-0.0378 x32 -1.293 x1 x2 +5.248 x2 x3Regression model Y1 reflects the relationship between the displacement of seed and factors : covering rate of the secondary and covering plate opening angle of the second order items and negatively correlated with seed displacement; Covering plate covering rate and the diameter of the interaction of the item, disc diameter and covering plate turns the soil interaction angle and negatively correlated with seed displacement.Regression model Y2 reflects the relationship between the thickness of soil and the factors: covering rate of quadratic term and speed of overlying soil interaction with the covering plate angle and thickness of overburden soil were positively correlated; Covering plate opening angle of the secondary and covering plate covering rate and the diameter of the interaction of the item and negatively correlated with thickness of overlying soil.Through the establishment of regression model, established the mathematical relationship between seeds displacement,thickness of soil and covering plate diameter, velocity and opening angle, provides a theoretical support for further study on the performance parameters of soil coverer. |
