| More than 90% of rapeseed is concentrated mainly in Yangtze River Basin in China, where is the main produce area of winter rapeseed and is twice or triple cropping area for the crop rotation patterns of paddy and upland, which include rice-rapeseed and rice-rice-rapeseed. The rapeseed is usually sowing after the harvest of rice, when is usually in late October to mid-November, so that it’s too late to sowing rapeseed. As such, most areas take the method of transplanting, especially in triple cropping area. Rapeseed is sowed before the harvest of rice and is transplanted after the harvest of rice. The cropping patterns of transplanting could fully exploit light and temperature conditions before winter to make up for lack of year-round growing season cropping, which is conducive to high yield.Although there are varieties of transplanter, the degree of the functional integration is low. The repeated tillage before the transplanting is easily causing the soil compaction. And most of the ditching parts couldn’t adapt to the heavy clay soil, so that the spread speed of the rape transplanter is slow. In the view of the application of the pneumatic precision planter for rapeseed, a multifunctional rape transplanter was developed, which was attached to the pneumatic precision planter for rapeseed and could realize tillage, fertilizing, ditching and transplanting simultaneously. The main research contents of this paper were conducted as follows:1)Based on the current reality that the level of mechanical transplanting for rape seedling is low and there is a scarce link between characteristics of plant morphological parameters and the traditional design of transplanter, the research on characteristics of plant morphological parameters about 8 hybrid rape varieties for mechanical transplanting was carried out with the LA-S image processing system. The characteristics of rape seedling morphological parameters were measured during 28 to 40 days after sowing, which include seedling height, seedling width, seedling cone angle, root length and root diameter. The distribution and growth difference of rape seedling morphological parameters were analyzed. And the reasonable structure and operating parameters of rapeseed transplanter were pointed out, as follow, the appropriate length of the duckbill-type planting unit is within the range of 170 mm to 270 mm, the appropriate cone angle of the planting unit is within the range of 35o to45o, the minimum height of the planting locus is 260 mm, the maximum opening width of the planting unit is 140 mm, and the planting depth is adjustable within the range of 60 mm to 90 mm. The result showed that there were significant differences between some rape varieties in seedling height, seedling width, seedling cone angle and root length. The characteristics of plant morphological parameters during 28 to 40 days after sowing were subjected to normal or skewed distribution. The growth models of the rape seedling morphological parameters during 28 to 40 days after sowing were established, which indicated that there were positive linear relationship between the characteristics of plant morphological parameters including seedling height, seedling width, root length and root diameter and time, the average correlation coefficient was 0.9736, there were negative linear relationship between seedling cone angle and time, the average correlation coefficient was 0.9818. The study showed that it was better to choose the appropriate rape varieties which were suitable for mechanized transplanting and adjust the transplanting time according to the plant developmental morphology, to achieve the integration of agricultural and agronomic for rape mechanical transplanting. In conclude, the research on characteristics of rape seedling morphological parameters provide useful guidance for the design and optimization of rapeseed transplanter.2)A multifunctional rape pot seedling transplanter was developed, which was attached to the pneumatic precision planter for rapeseed and could realize tillage, fertilizing, ditching and transplanting simultaneously. The structure, working principle and process of the rape transplanter were introduced.3)The technical parameters and performance evaluation were defined, the structure design of the double five-bar transplanting mechanism was completed. In order to seek out the optimal structural parameters, the Three-dimensional solid parametric simulation model of the double five-bar transplanting mechanism based on Pro/E was established. The simulation results show that the transplanting locus with batter verticality and overlap and small cave could adjust to the agricultural requirements for rape transplanting. The transplanting spacing is 300 mm and the height of the transplanting locus is426.5mm. The design of the cam synchronous control system was developed, the synchronous analysis of seedling separating and transplanting was carried out. The phase angle differences between transplanting cam and separating cam were 144o.4)In order to overcome the shortage of traditional analytical method for design of double five-bar transplanting mechanism for rape pot seedling, the working principle and kinematics model was analyzed. Also a multi-objective optimization design model of double five-bar transplanting mechanism was established, which solved by Matlab. And the kinematics characteristics of double five-bar transplanting mechanism were analyzed, which matched the solving result of the multi-objective optimization design model. The consistency verification experiment for the transplanting locus was carried out by the using of high speed photography system. The transplanting spacing and the height of the transplanting locus of the rape pot seedling transplanter which is at the speed of 0.3 meters per second and the transplanting frequency of 60 seedlings per minute are 300 mm. And the cave is less than 0.91 mm with the transplanting depth within the range of 60 to 100 mm. In additions, the vertical width of the transplanting locus is 12.8 mm when the height of the transplanting locus is less than 200 mm. The swinging angle of duck-beak is in the range of-2.3° to 2.3° in the planting stage, and the horizontal velocity of duck-beak is 0.04 meters per second by the lowest point of the transplanting locus which is close to zero. In the falling stage the swinging angle of duck-beak is in the range of-2.4° to 2.2° and the vertical velocity is less than 0.7 meters per second, so that the vertical displacement is small to catch the seedling for duck-beak. The demands of rapeseed mechanized transplanting could be met by the transplanting locus of the double five-bar transplanting mechanism that matches the solving result of the multi-objective optimization design model, which provides the basis for the design of multi-linkage with specific function locus.5)The experiments were carried out, which certified the feasibility of the rape transplanter. The results showed that when the forward speed is 0.95 kilometers per hour and the transplanting frequency was 45 seedlings per minute, the percentage of upright seedlings was 91%, the average transplanting spacing was 370.83 mm, the coefficient of variation of transplanting spacing was 3.05%, the average transplanting depth was 56.41 mm, the qualified index of transplanting depth was 88.64%, the coefficient of variation of transplanting depth was 11.91%. |
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