| With the extension and application of technology for conservation tillage, precision sowing technology had become the main trends of planter. Performance of the planter mainly depended on the seed metering device. Maize seeds metering device was parted into mechanical and pneumatic according to the principle. Pneumatic precision seed metering device was in the majority in abroad, but it was restricted in domestic for its complex structure and high price. The mechanical metering device was more used in domestic but there were some problems with it such as being strict with the size of seeds and high damage to seeds. Moreover, performance of the seed metering device was related to its drive mechanism. As drive mechanism of the seed metering device, high sliding of the ground wheel directly affected the precision of sowing. Aimed at above problems and based on the Patents of Utility Model of Precision Seed Metering Device for Planter (Patent No.200920021268.2) and Ground Wheel for Planter (Petent No. 200920021269.2), a new precision seed metering device for pelleted maize seeds was designed on the basis of materials characteristics of pelleted maize. Meanwhile, its structure parameters were optimized and factors affecting sowing performance were studied. Furthermore, drive mechanism of seed metering device was analyzed and a new ground wheel was designed in this paper, interaction and force betweetn the wheel and soil were also analyzed, and these provided good technical supports for developing better planter.1) Seeds pelleted experiments were conducted with the familiar maize seeds in Shandong Province.Then granular materials characteristics of pelleted maize seeds such as the size distribution, angle of repose and thousand kernel weight were analyzed,and this provided a basisi for structural design of seed metering device.2) In correlation to the available mechanical seed metering devices, a seed metering device was designed in this paper. The metering plate was conical and there were leading slots at both sides of cell. An angle was set between the metering plate and horizontal plane to ensure the process of seed-filling and seed-cleaning, by force analysis of the seed at the edge of seed box, the angle was determined as 30°.3) Seed-filling and seed-cleaning process was studied, by force analysis of single seed among the seeds group, the seed's relative limiting speed was obtained. The metering axis's limiting rotary speed were studied on the condition that the seed not overfying the cell. On the basis of average diameter of pelleted seeds and combined with reliability principle, diameter of the cell was determined. By force analysis between the seeds and seed-cleaning device, on the condition that seed was cleaned from the cell, the angle between the leading slot and undersurface of the metering plate was determined as 45°. In this paper, BP artificial neural network was used to predict performance of the seed metering device and establish model for precision metering. By internet training and measurement, the results showed that the predicted value and trial value had good conformity. And this provided basis for optimum design of structure and working parameters and reduced the experimental time and cost.4) By analysis of the structure and principle, combined with the metering performance artificial neural network model, the factors chosen in this paper were the rotary speed of metering axis, diameter of the cell and cone angle of the metering plate. The experiments were conducted with Quadratic-orthogonal-rotation-combination design. According to calculation methods of the metering performance indexes by GB6973-2005, Single (precision)Seeder Experimental Method, experiments on metering performance were conducted on the JPS-12 seed metering device test bench. The regression equations of single index(S), missed index(M), double index(D) were obtained to discuss the effect of structure parameters on the metering performance indexes. By analysis of the regression equations of metering performance indexes, it was concluded that the rotary speed of the metering axis and cone angle of the moving plate had distinct effect on the metering performance indexes, and the diameter of cell had less effect on the performance index. The seed metering device's best rotary speed was 12～14r/min, diameter of cell was 15～15.5mm, cone angle of moving plate was 23～26°.5)In order to solve the problem of seeds missing due to sliding of ground wheel, a planetary geared anti-sliding ground wheel for planter was designed in correlation to the available drive device of metering device. A six-angle star wheel with anti-sliding tooth was added to the ground wheel. The anti-sliding tooth would mesh with the hole on the wheel rim and stick out of it to enhance the tracking, and this could effectively clear the soil glue to the wheel and prevent the straw from winding on the anti-sliding tooth. Furthermore, the meshing location could be changed according to the different work states of planter and this could reduce the running resistance.6)Force on the wheel was analyzed then factors affecting running ability of ground wheel were found. Furthermore, the wheel's running resistance(Rx), reaction of support(Ry) and depression value(z0) in the soft soil were derived. From the analysis, it could be concluded that the conditions of the soil, diameter and width of the wheel, vertical load and traction were the factors affecting sliding of the ground wheel. Combined with the available ground wheel's structure parameters, layout of the meshing hole on the wheel trim and structure of the star wheel were determined.7)According to computational method of sliding of the ground wheel, a sliding test system based on the technologies of sensor and single-chip microcomputer was presented in this paper. The photoelectric switch and rotary encoder were used to test the practical and theoretical distances respectively. The single-chip microcomputer Atmega16 was used to count the number of impulse from the photoelectric switch and rotary encoder, then the sliding was calculated and displayed on the LCD which could help driver of the planter realize the working conditions timely.8)Sliding test experiments were conducted in the indoor soil bin. Firstly, comparative experiments on power consumption and sliding were conducted with different kinds of ground wheels. It was found that the ground wheel presented in this paper had minor sliding with little distinction in power consumption. Secondly, using this ground wheel as object of study, experiments were conducted to study the effects of straw coverage amount on sliding with different straw covered on the ground. It was found that sliding would increase with more straw covered on the ground and the sliding was minor when the straw coverage amount was 200～251kg/m2. Lastly, with the straw coverage amount, the effects of the soil's moisture content and rigidity on sliding were studied and it was found that the sliding was minor with 10～15% moisture content in the soil.9)Experiments were arranged with quadratic-orthogonal-rotation-combination to optimize the structure parameters. In this paper, the factors chosen were diameter and width of the wheel, vertical load on the wheel and the length of the anti-sliding tooth, then the regression equation was obtained to study the effects of all factors on sliding of the ground wheel. By analysis of the regression equation, it was found that the length of the anti-sliding tooth, diameter of the wheel and vertical load were the remarkable factors affecting the sliding and the width of wheel had little effect on sliding. On the consider of little sliding, the best parameters combination could be achieved when the diameter of wheel was 650mm, the vertical load on wheel was 200kg and the length of anti-sliding tooth was 30mm. This provided theoretical basis for determination of the parameters for the planter.
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